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 /* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
 /* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of version 2 of the GNU General Public
  * License as published by the Free Software Foundation.
  */
 #ifndef _UAPI__LINUX_BPF_H__
 #define _UAPI__LINUX_BPF_H__
 
 #include <linux/types.h>
 #include <linux/bpf_common.h>
 
 /* Extended instruction set based on top of classic BPF */
 
 /* instruction classes */
 #define BPF_JMP32   0x06    /* jmp mode in word width */
 #define BPF_ALU64   0x07    /* alu mode in double word width */
 
 /* ld/ldx fields */
 #define BPF_DW      0x18    /* double word (64-bit) */
 #define BPF_ATOMIC  0xc0    /* atomic memory ops - op type in immediate */
 #define BPF_XADD    0xc0    /* exclusive add - legacy name */
 
 /* alu/jmp fields */
 #define BPF_MOV     0xb0    /* mov reg to reg */
 #define BPF_ARSH    0xc0    /* sign extending arithmetic shift right */
 
 /* change endianness of a register */
 #define BPF_END     0xd0    /* flags for endianness conversion: */
 #define BPF_TO_LE   0x00    /* convert to little-endian */
 #define BPF_TO_BE   0x08    /* convert to big-endian */
 #define BPF_FROM_LE BPF_TO_LE
 #define BPF_FROM_BE BPF_TO_BE
 
 /* jmp encodings */
 #define BPF_JNE     0x50    /* jump != */
 #define BPF_JLT     0xa0    /* LT is unsigned, '<' */
 #define BPF_JLE     0xb0    /* LE is unsigned, '<=' */
 #define BPF_JSGT    0x60    /* SGT is signed '>', GT in x86 */
 #define BPF_JSGE    0x70    /* SGE is signed '>=', GE in x86 */
 #define BPF_JSLT    0xc0    /* SLT is signed, '<' */
 #define BPF_JSLE    0xd0    /* SLE is signed, '<=' */
 #define BPF_CALL    0x80    /* function call */
 #define BPF_EXIT    0x90    /* function return */
 
 /* atomic op type fields (stored in immediate) */
 #define BPF_FETCH   0x01    /* not an opcode on its own, used to build others */
 #define BPF_XCHG    (0xe0 | BPF_FETCH)  /* atomic exchange */
 #define BPF_CMPXCHG (0xf0 | BPF_FETCH)  /* atomic compare-and-write */
 
 /* Register numbers */
 enum {
     BPF_REG_0 = 0,
     BPF_REG_1,
     BPF_REG_2,
     BPF_REG_3,
     BPF_REG_4,
     BPF_REG_5,
     BPF_REG_6,
     BPF_REG_7,
     BPF_REG_8,
     BPF_REG_9,
     BPF_REG_10,
     __MAX_BPF_REG,
 };
 
 /* BPF has 10 general purpose 64-bit registers and stack frame. */
 #define MAX_BPF_REG __MAX_BPF_REG
 
 struct bpf_insn {
     __u8    code;       /* opcode */
     __u8    dst_reg:4;  /* dest register */
     __u8    src_reg:4;  /* source register */
     __s16   off;        /* signed offset */
     __s32   imm;        /* signed immediate constant */
 };
 
 /* Key of an a BPF_MAP_TYPE_LPM_TRIE entry */
 struct bpf_lpm_trie_key {
     __u32   prefixlen;  /* up to 32 for AF_INET, 128 for AF_INET6 */
     __u8    data[0];    /* Arbitrary size */
 };
 
 struct bpf_cgroup_storage_key {
     __u64   cgroup_inode_id;    /* cgroup inode id */
     __u32   attach_type;        /* program attach type (enum bpf_attach_type) */
 };
 
 union bpf_iter_link_info {
     struct {
         __u32   map_fd;
     } map;
 };
 
 /* BPF syscall commands, see bpf(2) man-page for more details. */
 /**
  * DOC: eBPF Syscall Preamble
  *
  * The operation to be performed by the **bpf**\ () system call is determined
  * by the *cmd* argument. Each operation takes an accompanying argument,
  * provided via *attr*, which is a pointer to a union of type *bpf_attr* (see
  * below). The size argument is the size of the union pointed to by *attr*.
  */
 /**
  * DOC: eBPF Syscall Commands
  *
  * BPF_MAP_CREATE
  *  Description
  *      Create a map and return a file descriptor that refers to the
  *      map. The close-on-exec file descriptor flag (see **fcntl**\ (2))
  *      is automatically enabled for the new file descriptor.
  *
  *      Applying **close**\ (2) to the file descriptor returned by
  *      **BPF_MAP_CREATE** will delete the map (but see NOTES).
  *
  *  Return
  *      A new file descriptor (a nonnegative integer), or -1 if an
  *      error occurred (in which case, *errno* is set appropriately).
  *
  * BPF_MAP_LOOKUP_ELEM
  *  Description
  *      Look up an element with a given *key* in the map referred to
  *      by the file descriptor *map_fd*.
  *
  *      The *flags* argument may be specified as one of the
  *      following:
  *
  *      **BPF_F_LOCK**
  *          Look up the value of a spin-locked map without
  *          returning the lock. This must be specified if the
  *          elements contain a spinlock.
  *
  *  Return
  *      Returns zero on success. On error, -1 is returned and *errno*
  *      is set appropriately.
  *
  * BPF_MAP_UPDATE_ELEM
  *  Description
  *      Create or update an element (key/value pair) in a specified map.
  *
  *      The *flags* argument should be specified as one of the
  *      following:
  *
  *      **BPF_ANY**
  *          Create a new element or update an existing element.
  *      **BPF_NOEXIST**
  *          Create a new element only if it did not exist.
  *      **BPF_EXIST**
  *          Update an existing element.
  *      **BPF_F_LOCK**
  *          Update a spin_lock-ed map element.
  *
  *  Return
  *      Returns zero on success. On error, -1 is returned and *errno*
  *      is set appropriately.
  *
  *      May set *errno* to **EINVAL**, **EPERM**, **ENOMEM**,
  *      **E2BIG**, **EEXIST**, or **ENOENT**.
  *
  *      **E2BIG**
  *          The number of elements in the map reached the
  *          *max_entries* limit specified at map creation time.
  *      **EEXIST**
  *          If *flags* specifies **BPF_NOEXIST** and the element
  *          with *key* already exists in the map.
  *      **ENOENT**
  *          If *flags* specifies **BPF_EXIST** and the element with
  *          *key* does not exist in the map.
  *
  * BPF_MAP_DELETE_ELEM
  *  Description
  *      Look up and delete an element by key in a specified map.
  *
  *  Return
  *      Returns zero on success. On error, -1 is returned and *errno*
  *      is set appropriately.
  *
  * BPF_MAP_GET_NEXT_KEY
  *  Description
  *      Look up an element by key in a specified map and return the key
  *      of the next element. Can be used to iterate over all elements
  *      in the map.
  *
  *  Return
  *      Returns zero on success. On error, -1 is returned and *errno*
  *      is set appropriately.
  *
  *      The following cases can be used to iterate over all elements of
  *      the map:
  *
  *      * If *key* is not found, the operation returns zero and sets
  *        the *next_key* pointer to the key of the first element.
  *      * If *key* is found, the operation returns zero and sets the
  *        *next_key* pointer to the key of the next element.
  *      * If *key* is the last element, returns -1 and *errno* is set
  *        to **ENOENT**.
  *
  *      May set *errno* to **ENOMEM**, **EFAULT**, **EPERM**, or
  *      **EINVAL** on error.
  *
  * BPF_PROG_LOAD
  *  Description
  *      Verify and load an eBPF program, returning a new file
  *      descriptor associated with the program.
  *
  *      Applying **close**\ (2) to the file descriptor returned by
  *      **BPF_PROG_LOAD** will unload the eBPF program (but see NOTES).
  *
  *      The close-on-exec file descriptor flag (see **fcntl**\ (2)) is
  *      automatically enabled for the new file descriptor.
  *
  *  Return
  *      A new file descriptor (a nonnegative integer), or -1 if an
  *      error occurred (in which case, *errno* is set appropriately).
  *
  * BPF_OBJ_PIN
  *  Description
  *      Pin an eBPF program or map referred by the specified *bpf_fd*
  *      to the provided *pathname* on the filesystem.
  *
  *      The *pathname* argument must not contain a dot (".").
  *
  *      On success, *pathname* retains a reference to the eBPF object,
  *      preventing deallocation of the object when the original
  *      *bpf_fd* is closed. This allow the eBPF object to live beyond
  *      **close**\ (\ *bpf_fd*\ ), and hence the lifetime of the parent
  *      process.
  *
  *      Applying **unlink**\ (2) or similar calls to the *pathname*
  *      unpins the object from the filesystem, removing the reference.
  *      If no other file descriptors or filesystem nodes refer to the
  *      same object, it will be deallocated (see NOTES).
  *
  *      The filesystem type for the parent directory of *pathname* must
  *      be **BPF_FS_MAGIC**.
  *
  *  Return
  *      Returns zero on success. On error, -1 is returned and *errno*
  *      is set appropriately.
  *
  * BPF_OBJ_GET
  *  Description
  *      Open a file descriptor for the eBPF object pinned to the
  *      specified *pathname*.
  *
  *  Return
  *      A new file descriptor (a nonnegative integer), or -1 if an
  *      error occurred (in which case, *errno* is set appropriately).
  *
  * BPF_PROG_ATTACH
  *  Description
  *      Attach an eBPF program to a *target_fd* at the specified
  *      *attach_type* hook.
  *
  *      The *attach_type* specifies the eBPF attachment point to
  *      attach the program to, and must be one of *bpf_attach_type*
  *      (see below).
  *
  *      The *attach_bpf_fd* must be a valid file descriptor for a
  *      loaded eBPF program of a cgroup, flow dissector, LIRC, sockmap
  *      or sock_ops type corresponding to the specified *attach_type*.
  *
  *      The *target_fd* must be a valid file descriptor for a kernel
  *      object which depends on the attach type of *attach_bpf_fd*:
  *
  *      **BPF_PROG_TYPE_CGROUP_DEVICE**,
  *      **BPF_PROG_TYPE_CGROUP_SKB**,
  *      **BPF_PROG_TYPE_CGROUP_SOCK**,
  *      **BPF_PROG_TYPE_CGROUP_SOCK_ADDR**,
  *      **BPF_PROG_TYPE_CGROUP_SOCKOPT**,
  *      **BPF_PROG_TYPE_CGROUP_SYSCTL**,
  *      **BPF_PROG_TYPE_SOCK_OPS**
  *
  *          Control Group v2 hierarchy with the eBPF controller
  *          enabled. Requires the kernel to be compiled with
  *          **CONFIG_CGROUP_BPF**.
  *
  *      **BPF_PROG_TYPE_FLOW_DISSECTOR**
  *
  *          Network namespace (eg /proc/self/ns/net).
  *
  *      **BPF_PROG_TYPE_LIRC_MODE2**
  *
  *          LIRC device path (eg /dev/lircN). Requires the kernel
  *          to be compiled with **CONFIG_BPF_LIRC_MODE2**.
  *
  *      **BPF_PROG_TYPE_SK_SKB**,
  *      **BPF_PROG_TYPE_SK_MSG**
  *
  *          eBPF map of socket type (eg **BPF_MAP_TYPE_SOCKHASH**).
  *
  *  Return
  *      Returns zero on success. On error, -1 is returned and *errno*
  *      is set appropriately.
  *
  * BPF_PROG_DETACH
  *  Description
  *      Detach the eBPF program associated with the *target_fd* at the
  *      hook specified by *attach_type*. The program must have been
  *      previously attached using **BPF_PROG_ATTACH**.
  *
  *  Return
  *      Returns zero on success. On error, -1 is returned and *errno*
  *      is set appropriately.
  *
  * BPF_PROG_TEST_RUN
  *  Description
  *      Run the eBPF program associated with the *prog_fd* a *repeat*
  *      number of times against a provided program context *ctx_in* and
  *      data *data_in*, and return the modified program context
  *      *ctx_out*, *data_out* (for example, packet data), result of the
  *      execution *retval*, and *duration* of the test run.
  *
  *      The sizes of the buffers provided as input and output
  *      parameters *ctx_in*, *ctx_out*, *data_in*, and *data_out* must
  *      be provided in the corresponding variables *ctx_size_in*,
  *      *ctx_size_out*, *data_size_in*, and/or *data_size_out*. If any
  *      of these parameters are not provided (ie set to NULL), the
  *      corresponding size field must be zero.
  *
  *      Some program types have particular requirements:
  *
  *      **BPF_PROG_TYPE_SK_LOOKUP**
  *          *data_in* and *data_out* must be NULL.
  *
  *      **BPF_PROG_TYPE_RAW_TRACEPOINT**,
  *      **BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE**
  *
  *          *ctx_out*, *data_in* and *data_out* must be NULL.
  *          *repeat* must be zero.
  *
  *      BPF_PROG_RUN is an alias for BPF_PROG_TEST_RUN.
  *
  *  Return
  *      Returns zero on success. On error, -1 is returned and *errno*
  *      is set appropriately.
  *
  *      **ENOSPC**
  *          Either *data_size_out* or *ctx_size_out* is too small.
  *      **ENOTSUPP**
  *          This command is not supported by the program type of
  *          the program referred to by *prog_fd*.
  *
  * BPF_PROG_GET_NEXT_ID
  *  Description
  *      Fetch the next eBPF program currently loaded into the kernel.
  *
  *      Looks for the eBPF program with an id greater than *start_id*
  *      and updates *next_id* on success. If no other eBPF programs
  *      remain with ids higher than *start_id*, returns -1 and sets
  *      *errno* to **ENOENT**.
  *
  *  Return
  *      Returns zero on success. On error, or when no id remains, -1
  *      is returned and *errno* is set appropriately.
  *
  * BPF_MAP_GET_NEXT_ID
  *  Description
  *      Fetch the next eBPF map currently loaded into the kernel.
  *
  *      Looks for the eBPF map with an id greater than *start_id*
  *      and updates *next_id* on success. If no other eBPF maps
  *      remain with ids higher than *start_id*, returns -1 and sets
  *      *errno* to **ENOENT**.
  *
  *  Return
  *      Returns zero on success. On error, or when no id remains, -1
  *      is returned and *errno* is set appropriately.
  *
  * BPF_PROG_GET_FD_BY_ID
  *  Description
  *      Open a file descriptor for the eBPF program corresponding to
  *      *prog_id*.
  *
  *  Return
  *      A new file descriptor (a nonnegative integer), or -1 if an
  *      error occurred (in which case, *errno* is set appropriately).
  *
  * BPF_MAP_GET_FD_BY_ID
  *  Description
  *      Open a file descriptor for the eBPF map corresponding to
  *      *map_id*.
  *
  *  Return
  *      A new file descriptor (a nonnegative integer), or -1 if an
  *      error occurred (in which case, *errno* is set appropriately).
  *
  * BPF_OBJ_GET_INFO_BY_FD
  *  Description
  *      Obtain information about the eBPF object corresponding to
  *      *bpf_fd*.
  *
  *      Populates up to *info_len* bytes of *info*, which will be in
  *      one of the following formats depending on the eBPF object type
  *      of *bpf_fd*:
  *
  *      * **struct bpf_prog_info**
  *      * **struct bpf_map_info**
  *      * **struct bpf_btf_info**
  *      * **struct bpf_link_info**
  *
  *  Return
  *      Returns zero on success. On error, -1 is returned and *errno*
  *      is set appropriately.
  *
  * BPF_PROG_QUERY
  *  Description
  *      Obtain information about eBPF programs associated with the
  *      specified *attach_type* hook.
  *
  *      The *target_fd* must be a valid file descriptor for a kernel
  *      object which depends on the attach type of *attach_bpf_fd*:
  *
  *      **BPF_PROG_TYPE_CGROUP_DEVICE**,
  *      **BPF_PROG_TYPE_CGROUP_SKB**,
  *      **BPF_PROG_TYPE_CGROUP_SOCK**,
  *      **BPF_PROG_TYPE_CGROUP_SOCK_ADDR**,
  *      **BPF_PROG_TYPE_CGROUP_SOCKOPT**,
  *      **BPF_PROG_TYPE_CGROUP_SYSCTL**,
  *      **BPF_PROG_TYPE_SOCK_OPS**
  *
  *          Control Group v2 hierarchy with the eBPF controller
  *          enabled. Requires the kernel to be compiled with
  *          **CONFIG_CGROUP_BPF**.
  *
  *      **BPF_PROG_TYPE_FLOW_DISSECTOR**
  *
  *          Network namespace (eg /proc/self/ns/net).
  *
  *      **BPF_PROG_TYPE_LIRC_MODE2**
  *
  *          LIRC device path (eg /dev/lircN). Requires the kernel
  *          to be compiled with **CONFIG_BPF_LIRC_MODE2**.
  *
  *      **BPF_PROG_QUERY** always fetches the number of programs
  *      attached and the *attach_flags* which were used to attach those
  *      programs. Additionally, if *prog_ids* is nonzero and the number
  *      of attached programs is less than *prog_cnt*, populates
  *      *prog_ids* with the eBPF program ids of the programs attached
  *      at *target_fd*.
  *
  *      The following flags may alter the result:
  *
  *      **BPF_F_QUERY_EFFECTIVE**
  *          Only return information regarding programs which are
  *          currently effective at the specified *target_fd*.
  *
  *  Return
  *      Returns zero on success. On error, -1 is returned and *errno*
  *      is set appropriately.
  *
  * BPF_RAW_TRACEPOINT_OPEN
  *  Description
  *      Attach an eBPF program to a tracepoint *name* to access kernel
  *      internal arguments of the tracepoint in their raw form.
  *
  *      The *prog_fd* must be a valid file descriptor associated with
  *      a loaded eBPF program of type **BPF_PROG_TYPE_RAW_TRACEPOINT**.
  *
  *      No ABI guarantees are made about the content of tracepoint
  *      arguments exposed to the corresponding eBPF program.
  *
  *      Applying **close**\ (2) to the file descriptor returned by
  *      **BPF_RAW_TRACEPOINT_OPEN** will delete the map (but see NOTES).
  *
  *  Return
  *      A new file descriptor (a nonnegative integer), or -1 if an
  *      error occurred (in which case, *errno* is set appropriately).
  *
  * BPF_BTF_LOAD
  *  Description
  *      Verify and load BPF Type Format (BTF) metadata into the kernel,
  *      returning a new file descriptor associated with the metadata.
  *      BTF is described in more detail at
  *      https://www.kernel.org/doc/html/latest/bpf/btf.html.
  *
  *      The *btf* parameter must point to valid memory providing
  *      *btf_size* bytes of BTF binary metadata.
  *
  *      The returned file descriptor can be passed to other **bpf**\ ()
  *      subcommands such as **BPF_PROG_LOAD** or **BPF_MAP_CREATE** to
  *      associate the BTF with those objects.
  *
  *      Similar to **BPF_PROG_LOAD**, **BPF_BTF_LOAD** has optional
  *      parameters to specify a *btf_log_buf*, *btf_log_size* and
  *      *btf_log_level* which allow the kernel to return freeform log
  *      output regarding the BTF verification process.
  *
  *  Return
  *      A new file descriptor (a nonnegative integer), or -1 if an
  *      error occurred (in which case, *errno* is set appropriately).
  *
  * BPF_BTF_GET_FD_BY_ID
  *  Description
  *      Open a file descriptor for the BPF Type Format (BTF)
  *      corresponding to *btf_id*.
  *
  *  Return
  *      A new file descriptor (a nonnegative integer), or -1 if an
  *      error occurred (in which case, *errno* is set appropriately).
  *
  * BPF_TASK_FD_QUERY
  *  Description
  *      Obtain information about eBPF programs associated with the
  *      target process identified by *pid* and *fd*.
  *
  *      If the *pid* and *fd* are associated with a tracepoint, kprobe
  *      or uprobe perf event, then the *prog_id* and *fd_type* will
  *      be populated with the eBPF program id and file descriptor type
  *      of type **bpf_task_fd_type**. If associated with a kprobe or
  *      uprobe, the  *probe_offset* and *probe_addr* will also be
  *      populated. Optionally, if *buf* is provided, then up to
  *      *buf_len* bytes of *buf* will be populated with the name of
  *      the tracepoint, kprobe or uprobe.
  *
  *      The resulting *prog_id* may be introspected in deeper detail
  *      using **BPF_PROG_GET_FD_BY_ID** and **BPF_OBJ_GET_INFO_BY_FD**.
  *
  *  Return
  *      Returns zero on success. On error, -1 is returned and *errno*
  *      is set appropriately.
  *
  * BPF_MAP_LOOKUP_AND_DELETE_ELEM
  *  Description
  *      Look up an element with the given *key* in the map referred to
  *      by the file descriptor *fd*, and if found, delete the element.
  *
  *      For **BPF_MAP_TYPE_QUEUE** and **BPF_MAP_TYPE_STACK** map
  *      types, the *flags* argument needs to be set to 0, but for other
  *      map types, it may be specified as:
  *
  *      **BPF_F_LOCK**
  *          Look up and delete the value of a spin-locked map
  *          without returning the lock. This must be specified if
  *          the elements contain a spinlock.
  *
  *      The **BPF_MAP_TYPE_QUEUE** and **BPF_MAP_TYPE_STACK** map types
  *      implement this command as a "pop" operation, deleting the top
  *      element rather than one corresponding to *key*.
  *      The *key* and *key_len* parameters should be zeroed when
  *      issuing this operation for these map types.
  *
  *      This command is only valid for the following map types:
  *      * **BPF_MAP_TYPE_QUEUE**
  *      * **BPF_MAP_TYPE_STACK**
  *      * **BPF_MAP_TYPE_HASH**
  *      * **BPF_MAP_TYPE_PERCPU_HASH**
  *      * **BPF_MAP_TYPE_LRU_HASH**
  *      * **BPF_MAP_TYPE_LRU_PERCPU_HASH**
  *
  *  Return
  *      Returns zero on success. On error, -1 is returned and *errno*
  *      is set appropriately.
  *
  * BPF_MAP_FREEZE
  *  Description
  *      Freeze the permissions of the specified map.
  *
  *      Write permissions may be frozen by passing zero *flags*.
  *      Upon success, no future syscall invocations may alter the
  *      map state of *map_fd*. Write operations from eBPF programs
  *      are still possible for a frozen map.
  *
  *      Not supported for maps of type **BPF_MAP_TYPE_STRUCT_OPS**.
  *
  *  Return
  *      Returns zero on success. On error, -1 is returned and *errno*
  *      is set appropriately.
  *
  * BPF_BTF_GET_NEXT_ID
  *  Description
  *      Fetch the next BPF Type Format (BTF) object currently loaded
  *      into the kernel.
  *
  *      Looks for the BTF object with an id greater than *start_id*
  *      and updates *next_id* on success. If no other BTF objects
  *      remain with ids higher than *start_id*, returns -1 and sets
  *      *errno* to **ENOENT**.
  *
  *  Return
  *      Returns zero on success. On error, or when no id remains, -1
  *      is returned and *errno* is set appropriately.
  *
  * BPF_MAP_LOOKUP_BATCH
  *  Description
  *      Iterate and fetch multiple elements in a map.
  *
  *      Two opaque values are used to manage batch operations,
  *      *in_batch* and *out_batch*. Initially, *in_batch* must be set
  *      to NULL to begin the batched operation. After each subsequent
  *      **BPF_MAP_LOOKUP_BATCH**, the caller should pass the resultant
  *      *out_batch* as the *in_batch* for the next operation to
  *      continue iteration from the current point.
  *
  *      The *keys* and *values* are output parameters which must point
  *      to memory large enough to hold *count* items based on the key
  *      and value size of the map *map_fd*. The *keys* buffer must be
  *      of *key_size* * *count*. The *values* buffer must be of
  *      *value_size* * *count*.
  *
  *      The *elem_flags* argument may be specified as one of the
  *      following:
  *
  *      **BPF_F_LOCK**
  *          Look up the value of a spin-locked map without
  *          returning the lock. This must be specified if the
  *          elements contain a spinlock.
  *
  *      On success, *count* elements from the map are copied into the
  *      user buffer, with the keys copied into *keys* and the values
  *      copied into the corresponding indices in *values*.
  *
  *      If an error is returned and *errno* is not **EFAULT**, *count*
  *      is set to the number of successfully processed elements.
  *
  *  Return
  *      Returns zero on success. On error, -1 is returned and *errno*
  *      is set appropriately.
  *
  *      May set *errno* to **ENOSPC** to indicate that *keys* or
  *      *values* is too small to dump an entire bucket during
  *      iteration of a hash-based map type.
  *
  * BPF_MAP_LOOKUP_AND_DELETE_BATCH
  *  Description
  *      Iterate and delete all elements in a map.
  *
  *      This operation has the same behavior as
  *      **BPF_MAP_LOOKUP_BATCH** with two exceptions:
  *
  *      * Every element that is successfully returned is also deleted
  *        from the map. This is at least *count* elements. Note that
  *        *count* is both an input and an output parameter.
  *      * Upon returning with *errno* set to **EFAULT**, up to
  *        *count* elements may be deleted without returning the keys
  *        and values of the deleted elements.
  *
  *  Return
  *      Returns zero on success. On error, -1 is returned and *errno*
  *      is set appropriately.
  *
  * BPF_MAP_UPDATE_BATCH
  *  Description
  *      Update multiple elements in a map by *key*.
  *
  *      The *keys* and *values* are input parameters which must point
  *      to memory large enough to hold *count* items based on the key
  *      and value size of the map *map_fd*. The *keys* buffer must be
  *      of *key_size* * *count*. The *values* buffer must be of
  *      *value_size* * *count*.
  *
  *      Each element specified in *keys* is sequentially updated to the
  *      value in the corresponding index in *values*. The *in_batch*
  *      and *out_batch* parameters are ignored and should be zeroed.
  *
  *      The *elem_flags* argument should be specified as one of the
  *      following:
  *
  *      **BPF_ANY**
  *          Create new elements or update a existing elements.
  *      **BPF_NOEXIST**
  *          Create new elements only if they do not exist.
  *      **BPF_EXIST**
  *          Update existing elements.
  *      **BPF_F_LOCK**
  *          Update spin_lock-ed map elements. This must be
  *          specified if the map value contains a spinlock.
  *
  *      On success, *count* elements from the map are updated.
  *
  *      If an error is returned and *errno* is not **EFAULT**, *count*
  *      is set to the number of successfully processed elements.
  *
  *  Return
  *      Returns zero on success. On error, -1 is returned and *errno*
  *      is set appropriately.
  *
  *      May set *errno* to **EINVAL**, **EPERM**, **ENOMEM**, or
  *      **E2BIG**. **E2BIG** indicates that the number of elements in
  *      the map reached the *max_entries* limit specified at map
  *      creation time.
  *
  *      May set *errno* to one of the following error codes under
  *      specific circumstances:
  *
  *      **EEXIST**
  *          If *flags* specifies **BPF_NOEXIST** and the element
  *          with *key* already exists in the map.
  *      **ENOENT**
  *          If *flags* specifies **BPF_EXIST** and the element with
  *          *key* does not exist in the map.
  *
  * BPF_MAP_DELETE_BATCH
  *  Description
  *      Delete multiple elements in a map by *key*.
  *
  *      The *keys* parameter is an input parameter which must point
  *      to memory large enough to hold *count* items based on the key
  *      size of the map *map_fd*, that is, *key_size* * *count*.
  *
  *      Each element specified in *keys* is sequentially deleted. The
  *      *in_batch*, *out_batch*, and *values* parameters are ignored
  *      and should be zeroed.
  *
  *      The *elem_flags* argument may be specified as one of the
  *      following:
  *
  *      **BPF_F_LOCK**
  *          Look up the value of a spin-locked map without
  *          returning the lock. This must be specified if the
  *          elements contain a spinlock.
  *
  *      On success, *count* elements from the map are updated.
  *
  *      If an error is returned and *errno* is not **EFAULT**, *count*
  *      is set to the number of successfully processed elements. If
  *      *errno* is **EFAULT**, up to *count* elements may be been
  *      deleted.
  *
  *  Return
  *      Returns zero on success. On error, -1 is returned and *errno*
  *      is set appropriately.
  *
  * BPF_LINK_CREATE
  *  Description
  *      Attach an eBPF program to a *target_fd* at the specified
  *      *attach_type* hook and return a file descriptor handle for
  *      managing the link.
  *
  *  Return
  *      A new file descriptor (a nonnegative integer), or -1 if an
  *      error occurred (in which case, *errno* is set appropriately).
  *
  * BPF_LINK_UPDATE
  *  Description
  *      Update the eBPF program in the specified *link_fd* to
  *      *new_prog_fd*.
  *
  *  Return
  *      Returns zero on success. On error, -1 is returned and *errno*
  *      is set appropriately.
  *
  * BPF_LINK_GET_FD_BY_ID
  *  Description
  *      Open a file descriptor for the eBPF Link corresponding to
  *      *link_id*.
  *
  *  Return
  *      A new file descriptor (a nonnegative integer), or -1 if an
  *      error occurred (in which case, *errno* is set appropriately).
  *
  * BPF_LINK_GET_NEXT_ID
  *  Description
  *      Fetch the next eBPF link currently loaded into the kernel.
  *
  *      Looks for the eBPF link with an id greater than *start_id*
  *      and updates *next_id* on success. If no other eBPF links
  *      remain with ids higher than *start_id*, returns -1 and sets
  *      *errno* to **ENOENT**.
  *
  *  Return
  *      Returns zero on success. On error, or when no id remains, -1
  *      is returned and *errno* is set appropriately.
  *
  * BPF_ENABLE_STATS
  *  Description
  *      Enable eBPF runtime statistics gathering.
  *
  *      Runtime statistics gathering for the eBPF runtime is disabled
  *      by default to minimize the corresponding performance overhead.
  *      This command enables statistics globally.
  *
  *      Multiple programs may independently enable statistics.
  *      After gathering the desired statistics, eBPF runtime statistics
  *      may be disabled again by calling **close**\ (2) for the file
  *      descriptor returned by this function. Statistics will only be
  *      disabled system-wide when all outstanding file descriptors
  *      returned by prior calls for this subcommand are closed.
  *
  *  Return
  *      A new file descriptor (a nonnegative integer), or -1 if an
  *      error occurred (in which case, *errno* is set appropriately).
  *
  * BPF_ITER_CREATE
  *  Description
  *      Create an iterator on top of the specified *link_fd* (as
  *      previously created using **BPF_LINK_CREATE**) and return a
  *      file descriptor that can be used to trigger the iteration.
  *
  *      If the resulting file descriptor is pinned to the filesystem
  *      using  **BPF_OBJ_PIN**, then subsequent **read**\ (2) syscalls
  *      for that path will trigger the iterator to read kernel state
  *      using the eBPF program attached to *link_fd*.
  *
  *  Return
  *      A new file descriptor (a nonnegative integer), or -1 if an
  *      error occurred (in which case, *errno* is set appropriately).
  *
  * BPF_LINK_DETACH
  *  Description
  *      Forcefully detach the specified *link_fd* from its
  *      corresponding attachment point.
  *
  *  Return
  *      Returns zero on success. On error, -1 is returned and *errno*
  *      is set appropriately.
  *
  * BPF_PROG_BIND_MAP
  *  Description
  *      Bind a map to the lifetime of an eBPF program.
  *
  *      The map identified by *map_fd* is bound to the program
  *      identified by *prog_fd* and only released when *prog_fd* is
  *      released. This may be used in cases where metadata should be
  *      associated with a program which otherwise does not contain any
  *      references to the map (for example, embedded in the eBPF
  *      program instructions).
  *
  *  Return
  *      Returns zero on success. On error, -1 is returned and *errno*
  *      is set appropriately.
  *
  * NOTES
  *  eBPF objects (maps and programs) can be shared between processes.
  *
  *  * After **fork**\ (2), the child inherits file descriptors
  *    referring to the same eBPF objects.
  *  * File descriptors referring to eBPF objects can be transferred over
  *    **unix**\ (7) domain sockets.
  *  * File descriptors referring to eBPF objects can be duplicated in the
  *    usual way, using **dup**\ (2) and similar calls.
  *  * File descriptors referring to eBPF objects can be pinned to the
  *    filesystem using the **BPF_OBJ_PIN** command of **bpf**\ (2).
  *
  *  An eBPF object is deallocated only after all file descriptors referring
  *  to the object have been closed and no references remain pinned to the
  *  filesystem or attached (for example, bound to a program or device).
  */
 enum bpf_cmd {
     BPF_MAP_CREATE,
     BPF_MAP_LOOKUP_ELEM,
     BPF_MAP_UPDATE_ELEM,
     BPF_MAP_DELETE_ELEM,
     BPF_MAP_GET_NEXT_KEY,
     BPF_PROG_LOAD,
     BPF_OBJ_PIN,
     BPF_OBJ_GET,
     BPF_PROG_ATTACH,
     BPF_PROG_DETACH,
     BPF_PROG_TEST_RUN,
     BPF_PROG_RUN = BPF_PROG_TEST_RUN,
     BPF_PROG_GET_NEXT_ID,
     BPF_MAP_GET_NEXT_ID,
     BPF_PROG_GET_FD_BY_ID,
     BPF_MAP_GET_FD_BY_ID,
     BPF_OBJ_GET_INFO_BY_FD,
     BPF_PROG_QUERY,
     BPF_RAW_TRACEPOINT_OPEN,
     BPF_BTF_LOAD,
     BPF_BTF_GET_FD_BY_ID,
     BPF_TASK_FD_QUERY,
     BPF_MAP_LOOKUP_AND_DELETE_ELEM,
     BPF_MAP_FREEZE,
     BPF_BTF_GET_NEXT_ID,
     BPF_MAP_LOOKUP_BATCH,
     BPF_MAP_LOOKUP_AND_DELETE_BATCH,
     BPF_MAP_UPDATE_BATCH,
     BPF_MAP_DELETE_BATCH,
     BPF_LINK_CREATE,
     BPF_LINK_UPDATE,
     BPF_LINK_GET_FD_BY_ID,
     BPF_LINK_GET_NEXT_ID,
     BPF_ENABLE_STATS,
     BPF_ITER_CREATE,
     BPF_LINK_DETACH,
     BPF_PROG_BIND_MAP,
 };
 
 enum bpf_map_type {
     BPF_MAP_TYPE_UNSPEC,
     BPF_MAP_TYPE_HASH,
     BPF_MAP_TYPE_ARRAY,
     BPF_MAP_TYPE_PROG_ARRAY,
     BPF_MAP_TYPE_PERF_EVENT_ARRAY,
     BPF_MAP_TYPE_PERCPU_HASH,
     BPF_MAP_TYPE_PERCPU_ARRAY,
     BPF_MAP_TYPE_STACK_TRACE,
     BPF_MAP_TYPE_CGROUP_ARRAY,
     BPF_MAP_TYPE_LRU_HASH,
     BPF_MAP_TYPE_LRU_PERCPU_HASH,
     BPF_MAP_TYPE_LPM_TRIE,
     BPF_MAP_TYPE_ARRAY_OF_MAPS,
     BPF_MAP_TYPE_HASH_OF_MAPS,
     BPF_MAP_TYPE_DEVMAP,
     BPF_MAP_TYPE_SOCKMAP,
     BPF_MAP_TYPE_CPUMAP,
     BPF_MAP_TYPE_XSKMAP,
     BPF_MAP_TYPE_SOCKHASH,
     BPF_MAP_TYPE_CGROUP_STORAGE,
     BPF_MAP_TYPE_REUSEPORT_SOCKARRAY,
     BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE,
     BPF_MAP_TYPE_QUEUE,
     BPF_MAP_TYPE_STACK,
     BPF_MAP_TYPE_SK_STORAGE,
     BPF_MAP_TYPE_DEVMAP_HASH,
     BPF_MAP_TYPE_STRUCT_OPS,
     BPF_MAP_TYPE_RINGBUF,
     BPF_MAP_TYPE_INODE_STORAGE,
     BPF_MAP_TYPE_TASK_STORAGE,
     BPF_MAP_TYPE_BLOOM_FILTER,
 };
 
 /* Note that tracing related programs such as
  * BPF_PROG_TYPE_{KPROBE,TRACEPOINT,PERF_EVENT,RAW_TRACEPOINT}
  * are not subject to a stable API since kernel internal data
  * structures can change from release to release and may
  * therefore break existing tracing BPF programs. Tracing BPF
  * programs correspond to /a/ specific kernel which is to be
  * analyzed, and not /a/ specific kernel /and/ all future ones.
  */
 enum bpf_prog_type {
     BPF_PROG_TYPE_UNSPEC,
     BPF_PROG_TYPE_SOCKET_FILTER,
     BPF_PROG_TYPE_KPROBE,
     BPF_PROG_TYPE_SCHED_CLS,
     BPF_PROG_TYPE_SCHED_ACT,
     BPF_PROG_TYPE_TRACEPOINT,
     BPF_PROG_TYPE_XDP,
     BPF_PROG_TYPE_PERF_EVENT,
     BPF_PROG_TYPE_CGROUP_SKB,
     BPF_PROG_TYPE_CGROUP_SOCK,
     BPF_PROG_TYPE_LWT_IN,
     BPF_PROG_TYPE_LWT_OUT,
     BPF_PROG_TYPE_LWT_XMIT,
     BPF_PROG_TYPE_SOCK_OPS,
     BPF_PROG_TYPE_SK_SKB,
     BPF_PROG_TYPE_CGROUP_DEVICE,
     BPF_PROG_TYPE_SK_MSG,
     BPF_PROG_TYPE_RAW_TRACEPOINT,
     BPF_PROG_TYPE_CGROUP_SOCK_ADDR,
     BPF_PROG_TYPE_LWT_SEG6LOCAL,
     BPF_PROG_TYPE_LIRC_MODE2,
     BPF_PROG_TYPE_SK_REUSEPORT,
     BPF_PROG_TYPE_FLOW_DISSECTOR,
     BPF_PROG_TYPE_CGROUP_SYSCTL,
     BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE,
     BPF_PROG_TYPE_CGROUP_SOCKOPT,
     BPF_PROG_TYPE_TRACING,
     BPF_PROG_TYPE_STRUCT_OPS,
     BPF_PROG_TYPE_EXT,
     BPF_PROG_TYPE_LSM,
     BPF_PROG_TYPE_SK_LOOKUP,
     BPF_PROG_TYPE_SYSCALL, /* a program that can execute syscalls */
 };
 
 enum bpf_attach_type {
     BPF_CGROUP_INET_INGRESS,
     BPF_CGROUP_INET_EGRESS,
     BPF_CGROUP_INET_SOCK_CREATE,
     BPF_CGROUP_SOCK_OPS,
     BPF_SK_SKB_STREAM_PARSER,
     BPF_SK_SKB_STREAM_VERDICT,
     BPF_CGROUP_DEVICE,
     BPF_SK_MSG_VERDICT,
     BPF_CGROUP_INET4_BIND,
     BPF_CGROUP_INET6_BIND,
     BPF_CGROUP_INET4_CONNECT,
     BPF_CGROUP_INET6_CONNECT,
     BPF_CGROUP_INET4_POST_BIND,
     BPF_CGROUP_INET6_POST_BIND,
     BPF_CGROUP_UDP4_SENDMSG,
     BPF_CGROUP_UDP6_SENDMSG,
     BPF_LIRC_MODE2,
     BPF_FLOW_DISSECTOR,
     BPF_CGROUP_SYSCTL,
     BPF_CGROUP_UDP4_RECVMSG,
     BPF_CGROUP_UDP6_RECVMSG,
     BPF_CGROUP_GETSOCKOPT,
     BPF_CGROUP_SETSOCKOPT,
     BPF_TRACE_RAW_TP,
     BPF_TRACE_FENTRY,
     BPF_TRACE_FEXIT,
     BPF_MODIFY_RETURN,
     BPF_LSM_MAC,
     BPF_TRACE_ITER,
     BPF_CGROUP_INET4_GETPEERNAME,
     BPF_CGROUP_INET6_GETPEERNAME,
     BPF_CGROUP_INET4_GETSOCKNAME,
     BPF_CGROUP_INET6_GETSOCKNAME,
     BPF_XDP_DEVMAP,
     BPF_CGROUP_INET_SOCK_RELEASE,
     BPF_XDP_CPUMAP,
     BPF_SK_LOOKUP,
     BPF_XDP,
     BPF_SK_SKB_VERDICT,
     BPF_SK_REUSEPORT_SELECT,
     BPF_SK_REUSEPORT_SELECT_OR_MIGRATE,
     BPF_PERF_EVENT,
     BPF_TRACE_KPROBE_MULTI,
     BPF_LSM_CGROUP,
     __MAX_BPF_ATTACH_TYPE
 };
 
 #define MAX_BPF_ATTACH_TYPE __MAX_BPF_ATTACH_TYPE
 
 enum bpf_link_type {
     BPF_LINK_TYPE_UNSPEC = 0,
     BPF_LINK_TYPE_RAW_TRACEPOINT = 1,
     BPF_LINK_TYPE_TRACING = 2,
     BPF_LINK_TYPE_CGROUP = 3,
     BPF_LINK_TYPE_ITER = 4,
     BPF_LINK_TYPE_NETNS = 5,
     BPF_LINK_TYPE_XDP = 6,
     BPF_LINK_TYPE_PERF_EVENT = 7,
     BPF_LINK_TYPE_KPROBE_MULTI = 8,
     BPF_LINK_TYPE_STRUCT_OPS = 9,
 
     MAX_BPF_LINK_TYPE,
 };
 
 /* cgroup-bpf attach flags used in BPF_PROG_ATTACH command
  *
  * NONE(default): No further bpf programs allowed in the subtree.
  *
  * BPF_F_ALLOW_OVERRIDE: If a sub-cgroup installs some bpf program,
  * the program in this cgroup yields to sub-cgroup program.
  *
  * BPF_F_ALLOW_MULTI: If a sub-cgroup installs some bpf program,
  * that cgroup program gets run in addition to the program in this cgroup.
  *
  * Only one program is allowed to be attached to a cgroup with
  * NONE or BPF_F_ALLOW_OVERRIDE flag.
  * Attaching another program on top of NONE or BPF_F_ALLOW_OVERRIDE will
  * release old program and attach the new one. Attach flags has to match.
  *
  * Multiple programs are allowed to be attached to a cgroup with
  * BPF_F_ALLOW_MULTI flag. They are executed in FIFO order
  * (those that were attached first, run first)
  * The programs of sub-cgroup are executed first, then programs of
  * this cgroup and then programs of parent cgroup.
  * When children program makes decision (like picking TCP CA or sock bind)
  * parent program has a chance to override it.
  *
  * With BPF_F_ALLOW_MULTI a new program is added to the end of the list of
  * programs for a cgroup. Though it's possible to replace an old program at
  * any position by also specifying BPF_F_REPLACE flag and position itself in
  * replace_bpf_fd attribute. Old program at this position will be released.
  *
  * A cgroup with MULTI or OVERRIDE flag allows any attach flags in sub-cgroups.
  * A cgroup with NONE doesn't allow any programs in sub-cgroups.
  * Ex1:
  * cgrp1 (MULTI progs A, B) ->
  *    cgrp2 (OVERRIDE prog C) ->
  *      cgrp3 (MULTI prog D) ->
  *        cgrp4 (OVERRIDE prog E) ->
  *          cgrp5 (NONE prog F)
  * the event in cgrp5 triggers execution of F,D,A,B in that order.
  * if prog F is detached, the execution is E,D,A,B
  * if prog F and D are detached, the execution is E,A,B
  * if prog F, E and D are detached, the execution is C,A,B
  *
  * All eligible programs are executed regardless of return code from
  * earlier programs.
  */
 #define BPF_F_ALLOW_OVERRIDE    (1U << 0)
 #define BPF_F_ALLOW_MULTI   (1U << 1)
 #define BPF_F_REPLACE       (1U << 2)
 
 /* If BPF_F_STRICT_ALIGNMENT is used in BPF_PROG_LOAD command, the
  * verifier will perform strict alignment checking as if the kernel
  * has been built with CONFIG_EFFICIENT_UNALIGNED_ACCESS not set,
  * and NET_IP_ALIGN defined to 2.
  */
 #define BPF_F_STRICT_ALIGNMENT  (1U << 0)
 
 /* If BPF_F_ANY_ALIGNMENT is used in BPF_PROF_LOAD command, the
  * verifier will allow any alignment whatsoever.  On platforms
  * with strict alignment requirements for loads ands stores (such
  * as sparc and mips) the verifier validates that all loads and
  * stores provably follow this requirement.  This flag turns that
  * checking and enforcement off.
  *
  * It is mostly used for testing when we want to validate the
  * context and memory access aspects of the verifier, but because
  * of an unaligned access the alignment check would trigger before
  * the one we are interested in.
  */
 #define BPF_F_ANY_ALIGNMENT (1U << 1)
 
 /* BPF_F_TEST_RND_HI32 is used in BPF_PROG_LOAD command for testing purpose.
  * Verifier does sub-register def/use analysis and identifies instructions whose
  * def only matters for low 32-bit, high 32-bit is never referenced later
  * through implicit zero extension. Therefore verifier notifies JIT back-ends
  * that it is safe to ignore clearing high 32-bit for these instructions. This
  * saves some back-ends a lot of code-gen. However such optimization is not
  * necessary on some arches, for example x86_64, arm64 etc, whose JIT back-ends
  * hence hasn't used verifier's analysis result. But, we really want to have a
  * way to be able to verify the correctness of the described optimization on
  * x86_64 on which testsuites are frequently exercised.
  *
  * So, this flag is introduced. Once it is set, verifier will randomize high
  * 32-bit for those instructions who has been identified as safe to ignore them.
  * Then, if verifier is not doing correct analysis, such randomization will
  * regress tests to expose bugs.
  */
 #define BPF_F_TEST_RND_HI32 (1U << 2)
 
 /* The verifier internal test flag. Behavior is undefined */
 #define BPF_F_TEST_STATE_FREQ   (1U << 3)
 
 /* If BPF_F_SLEEPABLE is used in BPF_PROG_LOAD command, the verifier will
  * restrict map and helper usage for such programs. Sleepable BPF programs can
  * only be attached to hooks where kernel execution context allows sleeping.
  * Such programs are allowed to use helpers that may sleep like
  * bpf_copy_from_user().
  */
 #define BPF_F_SLEEPABLE     (1U << 4)
 
 /* If BPF_F_XDP_HAS_FRAGS is used in BPF_PROG_LOAD command, the loaded program
  * fully support xdp frags.
  */
 #define BPF_F_XDP_HAS_FRAGS (1U << 5)
 
 /* link_create.kprobe_multi.flags used in LINK_CREATE command for
  * BPF_TRACE_KPROBE_MULTI attach type to create return probe.
  */
 #define BPF_F_KPROBE_MULTI_RETURN   (1U << 0)
 
 /* When BPF ldimm64's insn[0].src_reg != 0 then this can have
  * the following extensions:
  *
  * insn[0].src_reg:  BPF_PSEUDO_MAP_[FD|IDX]
  * insn[0].imm:      map fd or fd_idx
  * insn[1].imm:      0
  * insn[0].off:      0
  * insn[1].off:      0
  * ldimm64 rewrite:  address of map
  * verifier type:    CONST_PTR_TO_MAP
  */
 #define BPF_PSEUDO_MAP_FD   1
 #define BPF_PSEUDO_MAP_IDX  5
 
 /* insn[0].src_reg:  BPF_PSEUDO_MAP_[IDX_]VALUE
  * insn[0].imm:      map fd or fd_idx
  * insn[1].imm:      offset into value
  * insn[0].off:      0
  * insn[1].off:      0
  * ldimm64 rewrite:  address of map[0]+offset
  * verifier type:    PTR_TO_MAP_VALUE
  */
 #define BPF_PSEUDO_MAP_VALUE        2
 #define BPF_PSEUDO_MAP_IDX_VALUE    6
 
 /* insn[0].src_reg:  BPF_PSEUDO_BTF_ID
  * insn[0].imm:      kernel btd id of VAR
  * insn[1].imm:      0
  * insn[0].off:      0
  * insn[1].off:      0
  * ldimm64 rewrite:  address of the kernel variable
  * verifier type:    PTR_TO_BTF_ID or PTR_TO_MEM, depending on whether the var
  *                   is struct/union.
  */
 #define BPF_PSEUDO_BTF_ID   3
 /* insn[0].src_reg:  BPF_PSEUDO_FUNC
  * insn[0].imm:      insn offset to the func
  * insn[1].imm:      0
  * insn[0].off:      0
  * insn[1].off:      0
  * ldimm64 rewrite:  address of the function
  * verifier type:    PTR_TO_FUNC.
  */
 #define BPF_PSEUDO_FUNC     4
 
 /* when bpf_call->src_reg == BPF_PSEUDO_CALL, bpf_call->imm == pc-relative
  * offset to another bpf function
  */
 #define BPF_PSEUDO_CALL     1
 /* when bpf_call->src_reg == BPF_PSEUDO_KFUNC_CALL,
  * bpf_call->imm == btf_id of a BTF_KIND_FUNC in the running kernel
  */
 #define BPF_PSEUDO_KFUNC_CALL   2
 
 /* flags for BPF_MAP_UPDATE_ELEM command */
 enum {
     BPF_ANY     = 0, /* create new element or update existing */
     BPF_NOEXIST = 1, /* create new element if it didn't exist */
     BPF_EXIST   = 2, /* update existing element */
     BPF_F_LOCK  = 4, /* spin_lock-ed map_lookup/map_update */
 };
 
 /* flags for BPF_MAP_CREATE command */
 enum {
     BPF_F_NO_PREALLOC   = (1U << 0),
 /* Instead of having one common LRU list in the
  * BPF_MAP_TYPE_LRU_[PERCPU_]HASH map, use a percpu LRU list
  * which can scale and perform better.
  * Note, the LRU nodes (including free nodes) cannot be moved
  * across different LRU lists.
  */
     BPF_F_NO_COMMON_LRU = (1U << 1),
 /* Specify numa node during map creation */
     BPF_F_NUMA_NODE     = (1U << 2),
 
 /* Flags for accessing BPF object from syscall side. */
     BPF_F_RDONLY        = (1U << 3),
     BPF_F_WRONLY        = (1U << 4),
 
 /* Flag for stack_map, store build_id+offset instead of pointer */
     BPF_F_STACK_BUILD_ID    = (1U << 5),
 
 /* Zero-initialize hash function seed. This should only be used for testing. */
     BPF_F_ZERO_SEED     = (1U << 6),
 
 /* Flags for accessing BPF object from program side. */
     BPF_F_RDONLY_PROG   = (1U << 7),
     BPF_F_WRONLY_PROG   = (1U << 8),
 
 /* Clone map from listener for newly accepted socket */
     BPF_F_CLONE     = (1U << 9),
 
 /* Enable memory-mapping BPF map */
     BPF_F_MMAPABLE      = (1U << 10),
 
 /* Share perf_event among processes */
     BPF_F_PRESERVE_ELEMS    = (1U << 11),
 
 /* Create a map that is suitable to be an inner map with dynamic max entries */
     BPF_F_INNER_MAP     = (1U << 12),
 };
 
 /* Flags for BPF_PROG_QUERY. */
 
 /* Query effective (directly attached + inherited from ancestor cgroups)
  * programs that will be executed for events within a cgroup.
  * attach_flags with this flag are returned only for directly attached programs.
  */
 #define BPF_F_QUERY_EFFECTIVE   (1U << 0)
 
 /* Flags for BPF_PROG_TEST_RUN */
 
 /* If set, run the test on the cpu specified by bpf_attr.test.cpu */
 #define BPF_F_TEST_RUN_ON_CPU   (1U << 0)
 /* If set, XDP frames will be transmitted after processing */
 #define BPF_F_TEST_XDP_LIVE_FRAMES  (1U << 1)
 
 /* type for BPF_ENABLE_STATS */
 enum bpf_stats_type {
     /* enabled run_time_ns and run_cnt */
     BPF_STATS_RUN_TIME = 0,
 };
 
 enum bpf_stack_build_id_status {
     /* user space need an empty entry to identify end of a trace */
     BPF_STACK_BUILD_ID_EMPTY = 0,
     /* with valid build_id and offset */
     BPF_STACK_BUILD_ID_VALID = 1,
     /* couldn't get build_id, fallback to ip */
     BPF_STACK_BUILD_ID_IP = 2,
 };
 
 #define BPF_BUILD_ID_SIZE 20
 struct bpf_stack_build_id {
     __s32       status;
     unsigned char   build_id[BPF_BUILD_ID_SIZE];
     union {
         __u64   offset;
         __u64   ip;
     };
 };
 
 #define BPF_OBJ_NAME_LEN 16U
 
 union bpf_attr {
     struct { /* anonymous struct used by BPF_MAP_CREATE command */
         __u32   map_type;   /* one of enum bpf_map_type */
         __u32   key_size;   /* size of key in bytes */
         __u32   value_size; /* size of value in bytes */
         __u32   max_entries;    /* max number of entries in a map */
         __u32   map_flags;  /* BPF_MAP_CREATE related
                      * flags defined above.
                      */
         __u32   inner_map_fd;   /* fd pointing to the inner map */
         __u32   numa_node;  /* numa node (effective only if
                      * BPF_F_NUMA_NODE is set).
                      */
         char    map_name[BPF_OBJ_NAME_LEN];
         __u32   map_ifindex;    /* ifindex of netdev to create on */
         __u32   btf_fd;     /* fd pointing to a BTF type data */
         __u32   btf_key_type_id;    /* BTF type_id of the key */
         __u32   btf_value_type_id;  /* BTF type_id of the value */
         __u32   btf_vmlinux_value_type_id;/* BTF type_id of a kernel-
                            * struct stored as the
                            * map value
                            */
         /* Any per-map-type extra fields
          *
          * BPF_MAP_TYPE_BLOOM_FILTER - the lowest 4 bits indicate the
          * number of hash functions (if 0, the bloom filter will default
          * to using 5 hash functions).
          */
         __u64   map_extra;
     };
 
     struct { /* anonymous struct used by BPF_MAP_*_ELEM commands */
         __u32       map_fd;
         __aligned_u64   key;
         union {
             __aligned_u64 value;
             __aligned_u64 next_key;
         };
         __u64       flags;
     };
 
     struct { /* struct used by BPF_MAP_*_BATCH commands */
         __aligned_u64   in_batch;   /* start batch,
                          * NULL to start from beginning
                          */
         __aligned_u64   out_batch;  /* output: next start batch */
         __aligned_u64   keys;
         __aligned_u64   values;
         __u32       count;      /* input/output:
                          * input: # of key/value
                          * elements
                          * output: # of filled elements
                          */
         __u32       map_fd;
         __u64       elem_flags;
         __u64       flags;
     } batch;
 
     struct { /* anonymous struct used by BPF_PROG_LOAD command */
         __u32       prog_type;  /* one of enum bpf_prog_type */
         __u32       insn_cnt;
         __aligned_u64   insns;
         __aligned_u64   license;
         __u32       log_level;  /* verbosity level of verifier */
         __u32       log_size;   /* size of user buffer */
         __aligned_u64   log_buf;    /* user supplied buffer */
         __u32       kern_version;   /* not used */
         __u32       prog_flags;
         char        prog_name[BPF_OBJ_NAME_LEN];
         __u32       prog_ifindex;   /* ifindex of netdev to prep for */
         /* For some prog types expected attach type must be known at
          * load time to verify attach type specific parts of prog
          * (context accesses, allowed helpers, etc).
          */
         __u32       expected_attach_type;
         __u32       prog_btf_fd;    /* fd pointing to BTF type data */
         __u32       func_info_rec_size; /* userspace bpf_func_info size */
         __aligned_u64   func_info;  /* func info */
         __u32       func_info_cnt;  /* number of bpf_func_info records */
         __u32       line_info_rec_size; /* userspace bpf_line_info size */
         __aligned_u64   line_info;  /* line info */
         __u32       line_info_cnt;  /* number of bpf_line_info records */
         __u32       attach_btf_id;  /* in-kernel BTF type id to attach to */
         union {
             /* valid prog_fd to attach to bpf prog */
             __u32       attach_prog_fd;
             /* or valid module BTF object fd or 0 to attach to vmlinux */
             __u32       attach_btf_obj_fd;
         };
         __u32       core_relo_cnt;  /* number of bpf_core_relo */
         __aligned_u64   fd_array;   /* array of FDs */
         __aligned_u64   core_relos;
         __u32       core_relo_rec_size; /* sizeof(struct bpf_core_relo) */
     };
 
     struct { /* anonymous struct used by BPF_OBJ_* commands */
         __aligned_u64   pathname;
         __u32       bpf_fd;
         __u32       file_flags;
     };
 
     struct { /* anonymous struct used by BPF_PROG_ATTACH/DETACH commands */
         __u32       target_fd;  /* container object to attach to */
         __u32       attach_bpf_fd;  /* eBPF program to attach */
         __u32       attach_type;
         __u32       attach_flags;
         __u32       replace_bpf_fd; /* previously attached eBPF
                          * program to replace if
                          * BPF_F_REPLACE is used
                          */
     };
 
     struct { /* anonymous struct used by BPF_PROG_TEST_RUN command */
         __u32       prog_fd;
         __u32       retval;
         __u32       data_size_in;   /* input: len of data_in */
         __u32       data_size_out;  /* input/output: len of data_out
                          *   returns ENOSPC if data_out
                          *   is too small.
                          */
         __aligned_u64   data_in;
         __aligned_u64   data_out;
         __u32       repeat;
         __u32       duration;
         __u32       ctx_size_in;    /* input: len of ctx_in */
         __u32       ctx_size_out;   /* input/output: len of ctx_out
                          *   returns ENOSPC if ctx_out
                          *   is too small.
                          */
         __aligned_u64   ctx_in;
         __aligned_u64   ctx_out;
         __u32       flags;
         __u32       cpu;
         __u32       batch_size;
     } test;
 
     struct { /* anonymous struct used by BPF_*_GET_*_ID */
         union {
             __u32       start_id;
             __u32       prog_id;
             __u32       map_id;
             __u32       btf_id;
             __u32       link_id;
         };
         __u32       next_id;
         __u32       open_flags;
     };
 
     struct { /* anonymous struct used by BPF_OBJ_GET_INFO_BY_FD */
         __u32       bpf_fd;
         __u32       info_len;
         __aligned_u64   info;
     } info;
 
     struct { /* anonymous struct used by BPF_PROG_QUERY command */
         __u32       target_fd;  /* container object to query */
         __u32       attach_type;
         __u32       query_flags;
         __u32       attach_flags;
         __aligned_u64   prog_ids;
         __u32       prog_cnt;
         __aligned_u64   prog_attach_flags; /* output: per-program attach_flags */
     } query;
 
     struct { /* anonymous struct used by BPF_RAW_TRACEPOINT_OPEN command */
         __u64 name;
         __u32 prog_fd;
     } raw_tracepoint;
 
     struct { /* anonymous struct for BPF_BTF_LOAD */
         __aligned_u64   btf;
         __aligned_u64   btf_log_buf;
         __u32       btf_size;
         __u32       btf_log_size;
         __u32       btf_log_level;
     };
 
     struct {
         __u32       pid;        /* input: pid */
         __u32       fd;     /* input: fd */
         __u32       flags;      /* input: flags */
         __u32       buf_len;    /* input/output: buf len */
         __aligned_u64   buf;        /* input/output:
                          *   tp_name for tracepoint
                          *   symbol for kprobe
                          *   filename for uprobe
                          */
         __u32       prog_id;    /* output: prod_id */
         __u32       fd_type;    /* output: BPF_FD_TYPE_* */
         __u64       probe_offset;   /* output: probe_offset */
         __u64       probe_addr; /* output: probe_addr */
     } task_fd_query;
 
     struct { /* struct used by BPF_LINK_CREATE command */
         __u32       prog_fd;    /* eBPF program to attach */
         union {
             __u32       target_fd;  /* object to attach to */
             __u32       target_ifindex; /* target ifindex */
         };
         __u32       attach_type;    /* attach type */
         __u32       flags;      /* extra flags */
         union {
             __u32       target_btf_id;  /* btf_id of target to attach to */
             struct {
                 __aligned_u64   iter_info;  /* extra bpf_iter_link_info */
                 __u32       iter_info_len;  /* iter_info length */
             };
             struct {
                 /* black box user-provided value passed through
                  * to BPF program at the execution time and
                  * accessible through bpf_get_attach_cookie() BPF helper
                  */
                 __u64       bpf_cookie;
             } perf_event;
             struct {
                 __u32       flags;
                 __u32       cnt;
                 __aligned_u64   syms;
                 __aligned_u64   addrs;
                 __aligned_u64   cookies;
             } kprobe_multi;
             struct {
                 /* this is overlaid with the target_btf_id above. */
                 __u32       target_btf_id;
                 /* black box user-provided value passed through
                  * to BPF program at the execution time and
                  * accessible through bpf_get_attach_cookie() BPF helper
                  */
                 __u64       cookie;
             } tracing;
         };
     } link_create;
 
     struct { /* struct used by BPF_LINK_UPDATE command */
         __u32       link_fd;    /* link fd */
         /* new program fd to update link with */
         __u32       new_prog_fd;
         __u32       flags;      /* extra flags */
         /* expected link's program fd; is specified only if
          * BPF_F_REPLACE flag is set in flags */
         __u32       old_prog_fd;
     } link_update;
 
     struct {
         __u32       link_fd;
     } link_detach;
 
     struct { /* struct used by BPF_ENABLE_STATS command */
         __u32       type;
     } enable_stats;
 
     struct { /* struct used by BPF_ITER_CREATE command */
         __u32       link_fd;
         __u32       flags;
     } iter_create;
 
     struct { /* struct used by BPF_PROG_BIND_MAP command */
         __u32       prog_fd;
         __u32       map_fd;
         __u32       flags;      /* extra flags */
     } prog_bind_map;
 
 } __attribute__((aligned(8)));
 
 /* The description below is an attempt at providing documentation to eBPF
  * developers about the multiple available eBPF helper functions. It can be
  * parsed and used to produce a manual page. The workflow is the following,
  * and requires the rst2man utility:
  *
  *     $ ./scripts/bpf_doc.py \
  *             --filename include/uapi/linux/bpf.h > /tmp/bpf-helpers.rst
  *     $ rst2man /tmp/bpf-helpers.rst > /tmp/bpf-helpers.7
  *     $ man /tmp/bpf-helpers.7
  *
  * Note that in order to produce this external documentation, some RST
  * formatting is used in the descriptions to get "bold" and "italics" in
  * manual pages. Also note that the few trailing white spaces are
  * intentional, removing them would break paragraphs for rst2man.
  *
  * Start of BPF helper function descriptions:
  *
  * void *bpf_map_lookup_elem(struct bpf_map *map, const void *key)
  *  Description
  *      Perform a lookup in *map* for an entry associated to *key*.
  *  Return
  *      Map value associated to *key*, or **NULL** if no entry was
  *      found.
  *
  * long bpf_map_update_elem(struct bpf_map *map, const void *key, const void *value, u64 flags)
  *  Description
  *      Add or update the value of the entry associated to *key* in
  *      *map* with *value*. *flags* is one of:
  *
  *      **BPF_NOEXIST**
  *          The entry for *key* must not exist in the map.
  *      **BPF_EXIST**
  *          The entry for *key* must already exist in the map.
  *      **BPF_ANY**
  *          No condition on the existence of the entry for *key*.
  *
  *      Flag value **BPF_NOEXIST** cannot be used for maps of types
  *      **BPF_MAP_TYPE_ARRAY** or **BPF_MAP_TYPE_PERCPU_ARRAY**  (all
  *      elements always exist), the helper would return an error.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * long bpf_map_delete_elem(struct bpf_map *map, const void *key)
  *  Description
  *      Delete entry with *key* from *map*.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * long bpf_probe_read(void *dst, u32 size, const void *unsafe_ptr)
  *  Description
  *      For tracing programs, safely attempt to read *size* bytes from
  *      kernel space address *unsafe_ptr* and store the data in *dst*.
  *
  *      Generally, use **bpf_probe_read_user**\ () or
  *      **bpf_probe_read_kernel**\ () instead.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * u64 bpf_ktime_get_ns(void)
  *  Description
  *      Return the time elapsed since system boot, in nanoseconds.
  *      Does not include time the system was suspended.
  *      See: **clock_gettime**\ (**CLOCK_MONOTONIC**)
  *  Return
  *      Current *ktime*.
  *
  * long bpf_trace_printk(const char *fmt, u32 fmt_size, ...)
  *  Description
  *      This helper is a "printk()-like" facility for debugging. It
  *      prints a message defined by format *fmt* (of size *fmt_size*)
  *      to file *\/sys/kernel/debug/tracing/trace* from DebugFS, if
  *      available. It can take up to three additional **u64**
  *      arguments (as an eBPF helpers, the total number of arguments is
  *      limited to five).
  *
  *      Each time the helper is called, it appends a line to the trace.
  *      Lines are discarded while *\/sys/kernel/debug/tracing/trace* is
  *      open, use *\/sys/kernel/debug/tracing/trace_pipe* to avoid this.
  *      The format of the trace is customizable, and the exact output
  *      one will get depends on the options set in
  *      *\/sys/kernel/debug/tracing/trace_options* (see also the
  *      *README* file under the same directory). However, it usually
  *      defaults to something like:
  *
  *      ::
  *
  *          telnet-470   [001] .N.. 419421.045894: 0x00000001: <formatted msg>
  *
  *      In the above:
  *
  *          * ``telnet`` is the name of the current task.
  *          * ``470`` is the PID of the current task.
  *          * ``001`` is the CPU number on which the task is
  *            running.
  *          * In ``.N..``, each character refers to a set of
  *            options (whether irqs are enabled, scheduling
  *            options, whether hard/softirqs are running, level of
  *            preempt_disabled respectively). **N** means that
  *            **TIF_NEED_RESCHED** and **PREEMPT_NEED_RESCHED**
  *            are set.
  *          * ``419421.045894`` is a timestamp.
  *          * ``0x00000001`` is a fake value used by BPF for the
  *            instruction pointer register.
  *          * ``<formatted msg>`` is the message formatted with
  *            *fmt*.
  *
  *      The conversion specifiers supported by *fmt* are similar, but
  *      more limited than for printk(). They are **%d**, **%i**,
  *      **%u**, **%x**, **%ld**, **%li**, **%lu**, **%lx**, **%lld**,
  *      **%lli**, **%llu**, **%llx**, **%p**, **%s**. No modifier (size
  *      of field, padding with zeroes, etc.) is available, and the
  *      helper will return **-EINVAL** (but print nothing) if it
  *      encounters an unknown specifier.
  *
  *      Also, note that **bpf_trace_printk**\ () is slow, and should
  *      only be used for debugging purposes. For this reason, a notice
  *      block (spanning several lines) is printed to kernel logs and
  *      states that the helper should not be used "for production use"
  *      the first time this helper is used (or more precisely, when
  *      **trace_printk**\ () buffers are allocated). For passing values
  *      to user space, perf events should be preferred.
  *  Return
  *      The number of bytes written to the buffer, or a negative error
  *      in case of failure.
  *
  * u32 bpf_get_prandom_u32(void)
  *  Description
  *      Get a pseudo-random number.
  *
  *      From a security point of view, this helper uses its own
  *      pseudo-random internal state, and cannot be used to infer the
  *      seed of other random functions in the kernel. However, it is
  *      essential to note that the generator used by the helper is not
  *      cryptographically secure.
  *  Return
  *      A random 32-bit unsigned value.
  *
  * u32 bpf_get_smp_processor_id(void)
  *  Description
  *      Get the SMP (symmetric multiprocessing) processor id. Note that
  *      all programs run with migration disabled, which means that the
  *      SMP processor id is stable during all the execution of the
  *      program.
  *  Return
  *      The SMP id of the processor running the program.
  *
  * long bpf_skb_store_bytes(struct sk_buff *skb, u32 offset, const void *from, u32 len, u64 flags)
  *  Description
  *      Store *len* bytes from address *from* into the packet
  *      associated to *skb*, at *offset*. *flags* are a combination of
  *      **BPF_F_RECOMPUTE_CSUM** (automatically recompute the
  *      checksum for the packet after storing the bytes) and
  *      **BPF_F_INVALIDATE_HASH** (set *skb*\ **->hash**, *skb*\
  *      **->swhash** and *skb*\ **->l4hash** to 0).
  *
  *      A call to this helper is susceptible to change the underlying
  *      packet buffer. Therefore, at load time, all checks on pointers
  *      previously done by the verifier are invalidated and must be
  *      performed again, if the helper is used in combination with
  *      direct packet access.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * long bpf_l3_csum_replace(struct sk_buff *skb, u32 offset, u64 from, u64 to, u64 size)
  *  Description
  *      Recompute the layer 3 (e.g. IP) checksum for the packet
  *      associated to *skb*. Computation is incremental, so the helper
  *      must know the former value of the header field that was
  *      modified (*from*), the new value of this field (*to*), and the
  *      number of bytes (2 or 4) for this field, stored in *size*.
  *      Alternatively, it is possible to store the difference between
  *      the previous and the new values of the header field in *to*, by
  *      setting *from* and *size* to 0. For both methods, *offset*
  *      indicates the location of the IP checksum within the packet.
  *
  *      This helper works in combination with **bpf_csum_diff**\ (),
  *      which does not update the checksum in-place, but offers more
  *      flexibility and can handle sizes larger than 2 or 4 for the
  *      checksum to update.
  *
  *      A call to this helper is susceptible to change the underlying
  *      packet buffer. Therefore, at load time, all checks on pointers
  *      previously done by the verifier are invalidated and must be
  *      performed again, if the helper is used in combination with
  *      direct packet access.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * long bpf_l4_csum_replace(struct sk_buff *skb, u32 offset, u64 from, u64 to, u64 flags)
  *  Description
  *      Recompute the layer 4 (e.g. TCP, UDP or ICMP) checksum for the
  *      packet associated to *skb*. Computation is incremental, so the
  *      helper must know the former value of the header field that was
  *      modified (*from*), the new value of this field (*to*), and the
  *      number of bytes (2 or 4) for this field, stored on the lowest
  *      four bits of *flags*. Alternatively, it is possible to store
  *      the difference between the previous and the new values of the
  *      header field in *to*, by setting *from* and the four lowest
  *      bits of *flags* to 0. For both methods, *offset* indicates the
  *      location of the IP checksum within the packet. In addition to
  *      the size of the field, *flags* can be added (bitwise OR) actual
  *      flags. With **BPF_F_MARK_MANGLED_0**, a null checksum is left
  *      untouched (unless **BPF_F_MARK_ENFORCE** is added as well), and
  *      for updates resulting in a null checksum the value is set to
  *      **CSUM_MANGLED_0** instead. Flag **BPF_F_PSEUDO_HDR** indicates
  *      the checksum is to be computed against a pseudo-header.
  *
  *      This helper works in combination with **bpf_csum_diff**\ (),
  *      which does not update the checksum in-place, but offers more
  *      flexibility and can handle sizes larger than 2 or 4 for the
  *      checksum to update.
  *
  *      A call to this helper is susceptible to change the underlying
  *      packet buffer. Therefore, at load time, all checks on pointers
  *      previously done by the verifier are invalidated and must be
  *      performed again, if the helper is used in combination with
  *      direct packet access.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * long bpf_tail_call(void *ctx, struct bpf_map *prog_array_map, u32 index)
  *  Description
  *      This special helper is used to trigger a "tail call", or in
  *      other words, to jump into another eBPF program. The same stack
  *      frame is used (but values on stack and in registers for the
  *      caller are not accessible to the callee). This mechanism allows
  *      for program chaining, either for raising the maximum number of
  *      available eBPF instructions, or to execute given programs in
  *      conditional blocks. For security reasons, there is an upper
  *      limit to the number of successive tail calls that can be
  *      performed.
  *
  *      Upon call of this helper, the program attempts to jump into a
  *      program referenced at index *index* in *prog_array_map*, a
  *      special map of type **BPF_MAP_TYPE_PROG_ARRAY**, and passes
  *      *ctx*, a pointer to the context.
  *
  *      If the call succeeds, the kernel immediately runs the first
  *      instruction of the new program. This is not a function call,
  *      and it never returns to the previous program. If the call
  *      fails, then the helper has no effect, and the caller continues
  *      to run its subsequent instructions. A call can fail if the
  *      destination program for the jump does not exist (i.e. *index*
  *      is superior to the number of entries in *prog_array_map*), or
  *      if the maximum number of tail calls has been reached for this
  *      chain of programs. This limit is defined in the kernel by the
  *      macro **MAX_TAIL_CALL_CNT** (not accessible to user space),
  *      which is currently set to 33.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * long bpf_clone_redirect(struct sk_buff *skb, u32 ifindex, u64 flags)
  *  Description
  *      Clone and redirect the packet associated to *skb* to another
  *      net device of index *ifindex*. Both ingress and egress
  *      interfaces can be used for redirection. The **BPF_F_INGRESS**
  *      value in *flags* is used to make the distinction (ingress path
  *      is selected if the flag is present, egress path otherwise).
  *      This is the only flag supported for now.
  *
  *      In comparison with **bpf_redirect**\ () helper,
  *      **bpf_clone_redirect**\ () has the associated cost of
  *      duplicating the packet buffer, but this can be executed out of
  *      the eBPF program. Conversely, **bpf_redirect**\ () is more
  *      efficient, but it is handled through an action code where the
  *      redirection happens only after the eBPF program has returned.
  *
  *      A call to this helper is susceptible to change the underlying
  *      packet buffer. Therefore, at load time, all checks on pointers
  *      previously done by the verifier are invalidated and must be
  *      performed again, if the helper is used in combination with
  *      direct packet access.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * u64 bpf_get_current_pid_tgid(void)
  *  Description
  *      Get the current pid and tgid.
  *  Return
  *      A 64-bit integer containing the current tgid and pid, and
  *      created as such:
  *      *current_task*\ **->tgid << 32 \|**
  *      *current_task*\ **->pid**.
  *
  * u64 bpf_get_current_uid_gid(void)
  *  Description
  *      Get the current uid and gid.
  *  Return
  *      A 64-bit integer containing the current GID and UID, and
  *      created as such: *current_gid* **<< 32 \|** *current_uid*.
  *
  * long bpf_get_current_comm(void *buf, u32 size_of_buf)
  *  Description
  *      Copy the **comm** attribute of the current task into *buf* of
  *      *size_of_buf*. The **comm** attribute contains the name of
  *      the executable (excluding the path) for the current task. The
  *      *size_of_buf* must be strictly positive. On success, the
  *      helper makes sure that the *buf* is NUL-terminated. On failure,
  *      it is filled with zeroes.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * u32 bpf_get_cgroup_classid(struct sk_buff *skb)
  *  Description
  *      Retrieve the classid for the current task, i.e. for the net_cls
  *      cgroup to which *skb* belongs.
  *
  *      This helper can be used on TC egress path, but not on ingress.
  *
  *      The net_cls cgroup provides an interface to tag network packets
  *      based on a user-provided identifier for all traffic coming from
  *      the tasks belonging to the related cgroup. See also the related
  *      kernel documentation, available from the Linux sources in file
  *      *Documentation/admin-guide/cgroup-v1/net_cls.rst*.
  *
  *      The Linux kernel has two versions for cgroups: there are
  *      cgroups v1 and cgroups v2. Both are available to users, who can
  *      use a mixture of them, but note that the net_cls cgroup is for
  *      cgroup v1 only. This makes it incompatible with BPF programs
  *      run on cgroups, which is a cgroup-v2-only feature (a socket can
  *      only hold data for one version of cgroups at a time).
  *
  *      This helper is only available is the kernel was compiled with
  *      the **CONFIG_CGROUP_NET_CLASSID** configuration option set to
  *      "**y**" or to "**m**".
  *  Return
  *      The classid, or 0 for the default unconfigured classid.
  *
  * long bpf_skb_vlan_push(struct sk_buff *skb, __be16 vlan_proto, u16 vlan_tci)
  *  Description
  *      Push a *vlan_tci* (VLAN tag control information) of protocol
  *      *vlan_proto* to the packet associated to *skb*, then update
  *      the checksum. Note that if *vlan_proto* is different from
  *      **ETH_P_8021Q** and **ETH_P_8021AD**, it is considered to
  *      be **ETH_P_8021Q**.
  *
  *      A call to this helper is susceptible to change the underlying
  *      packet buffer. Therefore, at load time, all checks on pointers
  *      previously done by the verifier are invalidated and must be
  *      performed again, if the helper is used in combination with
  *      direct packet access.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * long bpf_skb_vlan_pop(struct sk_buff *skb)
  *  Description
  *      Pop a VLAN header from the packet associated to *skb*.
  *
  *      A call to this helper is susceptible to change the underlying
  *      packet buffer. Therefore, at load time, all checks on pointers
  *      previously done by the verifier are invalidated and must be
  *      performed again, if the helper is used in combination with
  *      direct packet access.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * long bpf_skb_get_tunnel_key(struct sk_buff *skb, struct bpf_tunnel_key *key, u32 size, u64 flags)
  *  Description
  *      Get tunnel metadata. This helper takes a pointer *key* to an
  *      empty **struct bpf_tunnel_key** of **size**, that will be
  *      filled with tunnel metadata for the packet associated to *skb*.
  *      The *flags* can be set to **BPF_F_TUNINFO_IPV6**, which
  *      indicates that the tunnel is based on IPv6 protocol instead of
  *      IPv4.
  *
  *      The **struct bpf_tunnel_key** is an object that generalizes the
  *      principal parameters used by various tunneling protocols into a
  *      single struct. This way, it can be used to easily make a
  *      decision based on the contents of the encapsulation header,
  *      "summarized" in this struct. In particular, it holds the IP
  *      address of the remote end (IPv4 or IPv6, depending on the case)
  *      in *key*\ **->remote_ipv4** or *key*\ **->remote_ipv6**. Also,
  *      this struct exposes the *key*\ **->tunnel_id**, which is
  *      generally mapped to a VNI (Virtual Network Identifier), making
  *      it programmable together with the **bpf_skb_set_tunnel_key**\
  *      () helper.
  *
  *      Let's imagine that the following code is part of a program
  *      attached to the TC ingress interface, on one end of a GRE
  *      tunnel, and is supposed to filter out all messages coming from
  *      remote ends with IPv4 address other than 10.0.0.1:
  *
  *      ::
  *
  *          int ret;
  *          struct bpf_tunnel_key key = {};
  *
  *          ret = bpf_skb_get_tunnel_key(skb, &key, sizeof(key), 0);
  *          if (ret < 0)
  *              return TC_ACT_SHOT; // drop packet
  *
  *          if (key.remote_ipv4 != 0x0a000001)
  *              return TC_ACT_SHOT; // drop packet
  *
  *          return TC_ACT_OK;       // accept packet
  *
  *      This interface can also be used with all encapsulation devices
  *      that can operate in "collect metadata" mode: instead of having
  *      one network device per specific configuration, the "collect
  *      metadata" mode only requires a single device where the
  *      configuration can be extracted from this helper.
  *
  *      This can be used together with various tunnels such as VXLan,
  *      Geneve, GRE or IP in IP (IPIP).
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * long bpf_skb_set_tunnel_key(struct sk_buff *skb, struct bpf_tunnel_key *key, u32 size, u64 flags)
  *  Description
  *      Populate tunnel metadata for packet associated to *skb.* The
  *      tunnel metadata is set to the contents of *key*, of *size*. The
  *      *flags* can be set to a combination of the following values:
  *
  *      **BPF_F_TUNINFO_IPV6**
  *          Indicate that the tunnel is based on IPv6 protocol
  *          instead of IPv4.
  *      **BPF_F_ZERO_CSUM_TX**
  *          For IPv4 packets, add a flag to tunnel metadata
  *          indicating that checksum computation should be skipped
  *          and checksum set to zeroes.
  *      **BPF_F_DONT_FRAGMENT**
  *          Add a flag to tunnel metadata indicating that the
  *          packet should not be fragmented.
  *      **BPF_F_SEQ_NUMBER**
  *          Add a flag to tunnel metadata indicating that a
  *          sequence number should be added to tunnel header before
  *          sending the packet. This flag was added for GRE
  *          encapsulation, but might be used with other protocols
  *          as well in the future.
  *
  *      Here is a typical usage on the transmit path:
  *
  *      ::
  *
  *          struct bpf_tunnel_key key;
  *               populate key ...
  *          bpf_skb_set_tunnel_key(skb, &key, sizeof(key), 0);
  *          bpf_clone_redirect(skb, vxlan_dev_ifindex, 0);
  *
  *      See also the description of the **bpf_skb_get_tunnel_key**\ ()
  *      helper for additional information.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * u64 bpf_perf_event_read(struct bpf_map *map, u64 flags)
  *  Description
  *      Read the value of a perf event counter. This helper relies on a
  *      *map* of type **BPF_MAP_TYPE_PERF_EVENT_ARRAY**. The nature of
  *      the perf event counter is selected when *map* is updated with
  *      perf event file descriptors. The *map* is an array whose size
  *      is the number of available CPUs, and each cell contains a value
  *      relative to one CPU. The value to retrieve is indicated by
  *      *flags*, that contains the index of the CPU to look up, masked
  *      with **BPF_F_INDEX_MASK**. Alternatively, *flags* can be set to
  *      **BPF_F_CURRENT_CPU** to indicate that the value for the
  *      current CPU should be retrieved.
  *
  *      Note that before Linux 4.13, only hardware perf event can be
  *      retrieved.
  *
  *      Also, be aware that the newer helper
  *      **bpf_perf_event_read_value**\ () is recommended over
  *      **bpf_perf_event_read**\ () in general. The latter has some ABI
  *      quirks where error and counter value are used as a return code
  *      (which is wrong to do since ranges may overlap). This issue is
  *      fixed with **bpf_perf_event_read_value**\ (), which at the same
  *      time provides more features over the **bpf_perf_event_read**\
  *      () interface. Please refer to the description of
  *      **bpf_perf_event_read_value**\ () for details.
  *  Return
  *      The value of the perf event counter read from the map, or a
  *      negative error code in case of failure.
  *
  * long bpf_redirect(u32 ifindex, u64 flags)
  *  Description
  *      Redirect the packet to another net device of index *ifindex*.
  *      This helper is somewhat similar to **bpf_clone_redirect**\
  *      (), except that the packet is not cloned, which provides
  *      increased performance.
  *
  *      Except for XDP, both ingress and egress interfaces can be used
  *      for redirection. The **BPF_F_INGRESS** value in *flags* is used
  *      to make the distinction (ingress path is selected if the flag
  *      is present, egress path otherwise). Currently, XDP only
  *      supports redirection to the egress interface, and accepts no
  *      flag at all.
  *
  *      The same effect can also be attained with the more generic
  *      **bpf_redirect_map**\ (), which uses a BPF map to store the
  *      redirect target instead of providing it directly to the helper.
  *  Return
  *      For XDP, the helper returns **XDP_REDIRECT** on success or
  *      **XDP_ABORTED** on error. For other program types, the values
  *      are **TC_ACT_REDIRECT** on success or **TC_ACT_SHOT** on
  *      error.
  *
  * u32 bpf_get_route_realm(struct sk_buff *skb)
  *  Description
  *      Retrieve the realm or the route, that is to say the
  *      **tclassid** field of the destination for the *skb*. The
  *      identifier retrieved is a user-provided tag, similar to the
  *      one used with the net_cls cgroup (see description for
  *      **bpf_get_cgroup_classid**\ () helper), but here this tag is
  *      held by a route (a destination entry), not by a task.
  *
  *      Retrieving this identifier works with the clsact TC egress hook
  *      (see also **tc-bpf(8)**), or alternatively on conventional
  *      classful egress qdiscs, but not on TC ingress path. In case of
  *      clsact TC egress hook, this has the advantage that, internally,
  *      the destination entry has not been dropped yet in the transmit
  *      path. Therefore, the destination entry does not need to be
  *      artificially held via **netif_keep_dst**\ () for a classful
  *      qdisc until the *skb* is freed.
  *
  *      This helper is available only if the kernel was compiled with
  *      **CONFIG_IP_ROUTE_CLASSID** configuration option.
  *  Return
  *      The realm of the route for the packet associated to *skb*, or 0
  *      if none was found.
  *
  * long bpf_perf_event_output(void *ctx, struct bpf_map *map, u64 flags, void *data, u64 size)
  *  Description
  *      Write raw *data* blob into a special BPF perf event held by
  *      *map* of type **BPF_MAP_TYPE_PERF_EVENT_ARRAY**. This perf
  *      event must have the following attributes: **PERF_SAMPLE_RAW**
  *      as **sample_type**, **PERF_TYPE_SOFTWARE** as **type**, and
  *      **PERF_COUNT_SW_BPF_OUTPUT** as **config**.
  *
  *      The *flags* are used to indicate the index in *map* for which
  *      the value must be put, masked with **BPF_F_INDEX_MASK**.
  *      Alternatively, *flags* can be set to **BPF_F_CURRENT_CPU**
  *      to indicate that the index of the current CPU core should be
  *      used.
  *
  *      The value to write, of *size*, is passed through eBPF stack and
  *      pointed by *data*.
  *
  *      The context of the program *ctx* needs also be passed to the
  *      helper.
  *
  *      On user space, a program willing to read the values needs to
  *      call **perf_event_open**\ () on the perf event (either for
  *      one or for all CPUs) and to store the file descriptor into the
  *      *map*. This must be done before the eBPF program can send data
  *      into it. An example is available in file
  *      *samples/bpf/trace_output_user.c* in the Linux kernel source
  *      tree (the eBPF program counterpart is in
  *      *samples/bpf/trace_output_kern.c*).
  *
  *      **bpf_perf_event_output**\ () achieves better performance
  *      than **bpf_trace_printk**\ () for sharing data with user
  *      space, and is much better suitable for streaming data from eBPF
  *      programs.
  *
  *      Note that this helper is not restricted to tracing use cases
  *      and can be used with programs attached to TC or XDP as well,
  *      where it allows for passing data to user space listeners. Data
  *      can be:
  *
  *      * Only custom structs,
  *      * Only the packet payload, or
  *      * A combination of both.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * long bpf_skb_load_bytes(const void *skb, u32 offset, void *to, u32 len)
  *  Description
  *      This helper was provided as an easy way to load data from a
  *      packet. It can be used to load *len* bytes from *offset* from
  *      the packet associated to *skb*, into the buffer pointed by
  *      *to*.
  *
  *      Since Linux 4.7, usage of this helper has mostly been replaced
  *      by "direct packet access", enabling packet data to be
  *      manipulated with *skb*\ **->data** and *skb*\ **->data_end**
  *      pointing respectively to the first byte of packet data and to
  *      the byte after the last byte of packet data. However, it
  *      remains useful if one wishes to read large quantities of data
  *      at once from a packet into the eBPF stack.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * long bpf_get_stackid(void *ctx, struct bpf_map *map, u64 flags)
  *  Description
  *      Walk a user or a kernel stack and return its id. To achieve
  *      this, the helper needs *ctx*, which is a pointer to the context
  *      on which the tracing program is executed, and a pointer to a
  *      *map* of type **BPF_MAP_TYPE_STACK_TRACE**.
  *
  *      The last argument, *flags*, holds the number of stack frames to
  *      skip (from 0 to 255), masked with
  *      **BPF_F_SKIP_FIELD_MASK**. The next bits can be used to set
  *      a combination of the following flags:
  *
  *      **BPF_F_USER_STACK**
  *          Collect a user space stack instead of a kernel stack.
  *      **BPF_F_FAST_STACK_CMP**
  *          Compare stacks by hash only.
  *      **BPF_F_REUSE_STACKID**
  *          If two different stacks hash into the same *stackid*,
  *          discard the old one.
  *
  *      The stack id retrieved is a 32 bit long integer handle which
  *      can be further combined with other data (including other stack
  *      ids) and used as a key into maps. This can be useful for
  *      generating a variety of graphs (such as flame graphs or off-cpu
  *      graphs).
  *
  *      For walking a stack, this helper is an improvement over
  *      **bpf_probe_read**\ (), which can be used with unrolled loops
  *      but is not efficient and consumes a lot of eBPF instructions.
  *      Instead, **bpf_get_stackid**\ () can collect up to
  *      **PERF_MAX_STACK_DEPTH** both kernel and user frames. Note that
  *      this limit can be controlled with the **sysctl** program, and
  *      that it should be manually increased in order to profile long
  *      user stacks (such as stacks for Java programs). To do so, use:
  *
  *      ::
  *
  *          # sysctl kernel.perf_event_max_stack=<new value>
  *  Return
  *      The positive or null stack id on success, or a negative error
  *      in case of failure.
  *
  * s64 bpf_csum_diff(__be32 *from, u32 from_size, __be32 *to, u32 to_size, __wsum seed)
  *  Description
  *      Compute a checksum difference, from the raw buffer pointed by
  *      *from*, of length *from_size* (that must be a multiple of 4),
  *      towards the raw buffer pointed by *to*, of size *to_size*
  *      (same remark). An optional *seed* can be added to the value
  *      (this can be cascaded, the seed may come from a previous call
  *      to the helper).
  *
  *      This is flexible enough to be used in several ways:
  *
  *      * With *from_size* == 0, *to_size* > 0 and *seed* set to
  *        checksum, it can be used when pushing new data.
  *      * With *from_size* > 0, *to_size* == 0 and *seed* set to
  *        checksum, it can be used when removing data from a packet.
  *      * With *from_size* > 0, *to_size* > 0 and *seed* set to 0, it
  *        can be used to compute a diff. Note that *from_size* and
  *        *to_size* do not need to be equal.
  *
  *      This helper can be used in combination with
  *      **bpf_l3_csum_replace**\ () and **bpf_l4_csum_replace**\ (), to
  *      which one can feed in the difference computed with
  *      **bpf_csum_diff**\ ().
  *  Return
  *      The checksum result, or a negative error code in case of
  *      failure.
  *
  * long bpf_skb_get_tunnel_opt(struct sk_buff *skb, void *opt, u32 size)
  *  Description
  *      Retrieve tunnel options metadata for the packet associated to
  *      *skb*, and store the raw tunnel option data to the buffer *opt*
  *      of *size*.
  *
  *      This helper can be used with encapsulation devices that can
  *      operate in "collect metadata" mode (please refer to the related
  *      note in the description of **bpf_skb_get_tunnel_key**\ () for
  *      more details). A particular example where this can be used is
  *      in combination with the Geneve encapsulation protocol, where it
  *      allows for pushing (with **bpf_skb_get_tunnel_opt**\ () helper)
  *      and retrieving arbitrary TLVs (Type-Length-Value headers) from
  *      the eBPF program. This allows for full customization of these
  *      headers.
  *  Return
  *      The size of the option data retrieved.
  *
  * long bpf_skb_set_tunnel_opt(struct sk_buff *skb, void *opt, u32 size)
  *  Description
  *      Set tunnel options metadata for the packet associated to *skb*
  *      to the option data contained in the raw buffer *opt* of *size*.
  *
  *      See also the description of the **bpf_skb_get_tunnel_opt**\ ()
  *      helper for additional information.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * long bpf_skb_change_proto(struct sk_buff *skb, __be16 proto, u64 flags)
  *  Description
  *      Change the protocol of the *skb* to *proto*. Currently
  *      supported are transition from IPv4 to IPv6, and from IPv6 to
  *      IPv4. The helper takes care of the groundwork for the
  *      transition, including resizing the socket buffer. The eBPF
  *      program is expected to fill the new headers, if any, via
  *      **skb_store_bytes**\ () and to recompute the checksums with
  *      **bpf_l3_csum_replace**\ () and **bpf_l4_csum_replace**\
  *      (). The main case for this helper is to perform NAT64
  *      operations out of an eBPF program.
  *
  *      Internally, the GSO type is marked as dodgy so that headers are
  *      checked and segments are recalculated by the GSO/GRO engine.
  *      The size for GSO target is adapted as well.
  *
  *      All values for *flags* are reserved for future usage, and must
  *      be left at zero.
  *
  *      A call to this helper is susceptible to change the underlying
  *      packet buffer. Therefore, at load time, all checks on pointers
  *      previously done by the verifier are invalidated and must be
  *      performed again, if the helper is used in combination with
  *      direct packet access.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * long bpf_skb_change_type(struct sk_buff *skb, u32 type)
  *  Description
  *      Change the packet type for the packet associated to *skb*. This
  *      comes down to setting *skb*\ **->pkt_type** to *type*, except
  *      the eBPF program does not have a write access to *skb*\
  *      **->pkt_type** beside this helper. Using a helper here allows
  *      for graceful handling of errors.
  *
  *      The major use case is to change incoming *skb*s to
  *      **PACKET_HOST** in a programmatic way instead of having to
  *      recirculate via **redirect**\ (..., **BPF_F_INGRESS**), for
  *      example.
  *
  *      Note that *type* only allows certain values. At this time, they
  *      are:
  *
  *      **PACKET_HOST**
  *          Packet is for us.
  *      **PACKET_BROADCAST**
  *          Send packet to all.
  *      **PACKET_MULTICAST**
  *          Send packet to group.
  *      **PACKET_OTHERHOST**
  *          Send packet to someone else.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * long bpf_skb_under_cgroup(struct sk_buff *skb, struct bpf_map *map, u32 index)
  *  Description
  *      Check whether *skb* is a descendant of the cgroup2 held by
  *      *map* of type **BPF_MAP_TYPE_CGROUP_ARRAY**, at *index*.
  *  Return
  *      The return value depends on the result of the test, and can be:
  *
  *      * 0, if the *skb* failed the cgroup2 descendant test.
  *      * 1, if the *skb* succeeded the cgroup2 descendant test.
  *      * A negative error code, if an error occurred.
  *
  * u32 bpf_get_hash_recalc(struct sk_buff *skb)
  *  Description
  *      Retrieve the hash of the packet, *skb*\ **->hash**. If it is
  *      not set, in particular if the hash was cleared due to mangling,
  *      recompute this hash. Later accesses to the hash can be done
  *      directly with *skb*\ **->hash**.
  *
  *      Calling **bpf_set_hash_invalid**\ (), changing a packet
  *      prototype with **bpf_skb_change_proto**\ (), or calling
  *      **bpf_skb_store_bytes**\ () with the
  *      **BPF_F_INVALIDATE_HASH** are actions susceptible to clear
  *      the hash and to trigger a new computation for the next call to
  *      **bpf_get_hash_recalc**\ ().
  *  Return
  *      The 32-bit hash.
  *
  * u64 bpf_get_current_task(void)
  *  Description
  *      Get the current task.
  *  Return
  *      A pointer to the current task struct.
  *
  * long bpf_probe_write_user(void *dst, const void *src, u32 len)
  *  Description
  *      Attempt in a safe way to write *len* bytes from the buffer
  *      *src* to *dst* in memory. It only works for threads that are in
  *      user context, and *dst* must be a valid user space address.
  *
  *      This helper should not be used to implement any kind of
  *      security mechanism because of TOC-TOU attacks, but rather to
  *      debug, divert, and manipulate execution of semi-cooperative
  *      processes.
  *
  *      Keep in mind that this feature is meant for experiments, and it
  *      has a risk of crashing the system and running programs.
  *      Therefore, when an eBPF program using this helper is attached,
  *      a warning including PID and process name is printed to kernel
  *      logs.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * long bpf_current_task_under_cgroup(struct bpf_map *map, u32 index)
  *  Description
  *      Check whether the probe is being run is the context of a given
  *      subset of the cgroup2 hierarchy. The cgroup2 to test is held by
  *      *map* of type **BPF_MAP_TYPE_CGROUP_ARRAY**, at *index*.
  *  Return
  *      The return value depends on the result of the test, and can be:
  *
  *      * 1, if current task belongs to the cgroup2.
  *      * 0, if current task does not belong to the cgroup2.
  *      * A negative error code, if an error occurred.
  *
  * long bpf_skb_change_tail(struct sk_buff *skb, u32 len, u64 flags)
  *  Description
  *      Resize (trim or grow) the packet associated to *skb* to the
  *      new *len*. The *flags* are reserved for future usage, and must
  *      be left at zero.
  *
  *      The basic idea is that the helper performs the needed work to
  *      change the size of the packet, then the eBPF program rewrites
  *      the rest via helpers like **bpf_skb_store_bytes**\ (),
  *      **bpf_l3_csum_replace**\ (), **bpf_l3_csum_replace**\ ()
  *      and others. This helper is a slow path utility intended for
  *      replies with control messages. And because it is targeted for
  *      slow path, the helper itself can afford to be slow: it
  *      implicitly linearizes, unclones and drops offloads from the
  *      *skb*.
  *
  *      A call to this helper is susceptible to change the underlying
  *      packet buffer. Therefore, at load time, all checks on pointers
  *      previously done by the verifier are invalidated and must be
  *      performed again, if the helper is used in combination with
  *      direct packet access.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * long bpf_skb_pull_data(struct sk_buff *skb, u32 len)
  *  Description
  *      Pull in non-linear data in case the *skb* is non-linear and not
  *      all of *len* are part of the linear section. Make *len* bytes
  *      from *skb* readable and writable. If a zero value is passed for
  *      *len*, then all bytes in the linear part of *skb* will be made
  *      readable and writable.
  *
  *      This helper is only needed for reading and writing with direct
  *      packet access.
  *
  *      For direct packet access, testing that offsets to access
  *      are within packet boundaries (test on *skb*\ **->data_end**) is
  *      susceptible to fail if offsets are invalid, or if the requested
  *      data is in non-linear parts of the *skb*. On failure the
  *      program can just bail out, or in the case of a non-linear
  *      buffer, use a helper to make the data available. The
  *      **bpf_skb_load_bytes**\ () helper is a first solution to access
  *      the data. Another one consists in using **bpf_skb_pull_data**
  *      to pull in once the non-linear parts, then retesting and
  *      eventually access the data.
  *
  *      At the same time, this also makes sure the *skb* is uncloned,
  *      which is a necessary condition for direct write. As this needs
  *      to be an invariant for the write part only, the verifier
  *      detects writes and adds a prologue that is calling
  *      **bpf_skb_pull_data()** to effectively unclone the *skb* from
  *      the very beginning in case it is indeed cloned.
  *
  *      A call to this helper is susceptible to change the underlying
  *      packet buffer. Therefore, at load time, all checks on pointers
  *      previously done by the verifier are invalidated and must be
  *      performed again, if the helper is used in combination with
  *      direct packet access.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * s64 bpf_csum_update(struct sk_buff *skb, __wsum csum)
  *  Description
  *      Add the checksum *csum* into *skb*\ **->csum** in case the
  *      driver has supplied a checksum for the entire packet into that
  *      field. Return an error otherwise. This helper is intended to be
  *      used in combination with **bpf_csum_diff**\ (), in particular
  *      when the checksum needs to be updated after data has been
  *      written into the packet through direct packet access.
  *  Return
  *      The checksum on success, or a negative error code in case of
  *      failure.
  *
  * void bpf_set_hash_invalid(struct sk_buff *skb)
  *  Description
  *      Invalidate the current *skb*\ **->hash**. It can be used after
  *      mangling on headers through direct packet access, in order to
  *      indicate that the hash is outdated and to trigger a
  *      recalculation the next time the kernel tries to access this
  *      hash or when the **bpf_get_hash_recalc**\ () helper is called.
  *  Return
  *      void.
  *
  * long bpf_get_numa_node_id(void)
  *  Description
  *      Return the id of the current NUMA node. The primary use case
  *      for this helper is the selection of sockets for the local NUMA
  *      node, when the program is attached to sockets using the
  *      **SO_ATTACH_REUSEPORT_EBPF** option (see also **socket(7)**),
  *      but the helper is also available to other eBPF program types,
  *      similarly to **bpf_get_smp_processor_id**\ ().
  *  Return
  *      The id of current NUMA node.
  *
  * long bpf_skb_change_head(struct sk_buff *skb, u32 len, u64 flags)
  *  Description
  *      Grows headroom of packet associated to *skb* and adjusts the
  *      offset of the MAC header accordingly, adding *len* bytes of
  *      space. It automatically extends and reallocates memory as
  *      required.
  *
  *      This helper can be used on a layer 3 *skb* to push a MAC header
  *      for redirection into a layer 2 device.
  *
  *      All values for *flags* are reserved for future usage, and must
  *      be left at zero.
  *
  *      A call to this helper is susceptible to change the underlying
  *      packet buffer. Therefore, at load time, all checks on pointers
  *      previously done by the verifier are invalidated and must be
  *      performed again, if the helper is used in combination with
  *      direct packet access.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * long bpf_xdp_adjust_head(struct xdp_buff *xdp_md, int delta)
  *  Description
  *      Adjust (move) *xdp_md*\ **->data** by *delta* bytes. Note that
  *      it is possible to use a negative value for *delta*. This helper
  *      can be used to prepare the packet for pushing or popping
  *      headers.
  *
  *      A call to this helper is susceptible to change the underlying
  *      packet buffer. Therefore, at load time, all checks on pointers
  *      previously done by the verifier are invalidated and must be
  *      performed again, if the helper is used in combination with
  *      direct packet access.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * long bpf_probe_read_str(void *dst, u32 size, const void *unsafe_ptr)
  *  Description
  *      Copy a NUL terminated string from an unsafe kernel address
  *      *unsafe_ptr* to *dst*. See **bpf_probe_read_kernel_str**\ () for
  *      more details.
  *
  *      Generally, use **bpf_probe_read_user_str**\ () or
  *      **bpf_probe_read_kernel_str**\ () instead.
  *  Return
  *      On success, the strictly positive length of the string,
  *      including the trailing NUL character. On error, a negative
  *      value.
  *
  * u64 bpf_get_socket_cookie(struct sk_buff *skb)
  *  Description
  *      If the **struct sk_buff** pointed by *skb* has a known socket,
  *      retrieve the cookie (generated by the kernel) of this socket.
  *      If no cookie has been set yet, generate a new cookie. Once
  *      generated, the socket cookie remains stable for the life of the
  *      socket. This helper can be useful for monitoring per socket
  *      networking traffic statistics as it provides a global socket
  *      identifier that can be assumed unique.
  *  Return
  *      A 8-byte long unique number on success, or 0 if the socket
  *      field is missing inside *skb*.
  *
  * u64 bpf_get_socket_cookie(struct bpf_sock_addr *ctx)
  *  Description
  *      Equivalent to bpf_get_socket_cookie() helper that accepts
  *      *skb*, but gets socket from **struct bpf_sock_addr** context.
  *  Return
  *      A 8-byte long unique number.
  *
  * u64 bpf_get_socket_cookie(struct bpf_sock_ops *ctx)
  *  Description
  *      Equivalent to **bpf_get_socket_cookie**\ () helper that accepts
  *      *skb*, but gets socket from **struct bpf_sock_ops** context.
  *  Return
  *      A 8-byte long unique number.
  *
  * u64 bpf_get_socket_cookie(struct sock *sk)
  *  Description
  *      Equivalent to **bpf_get_socket_cookie**\ () helper that accepts
  *      *sk*, but gets socket from a BTF **struct sock**. This helper
  *      also works for sleepable programs.
  *  Return
  *      A 8-byte long unique number or 0 if *sk* is NULL.
  *
  * u32 bpf_get_socket_uid(struct sk_buff *skb)
  *  Description
  *      Get the owner UID of the socked associated to *skb*.
  *  Return
  *      The owner UID of the socket associated to *skb*. If the socket
  *      is **NULL**, or if it is not a full socket (i.e. if it is a
  *      time-wait or a request socket instead), **overflowuid** value
  *      is returned (note that **overflowuid** might also be the actual
  *      UID value for the socket).
  *
  * long bpf_set_hash(struct sk_buff *skb, u32 hash)
  *  Description
  *      Set the full hash for *skb* (set the field *skb*\ **->hash**)
  *      to value *hash*.
  *  Return
  *      0
  *
  * long bpf_setsockopt(void *bpf_socket, int level, int optname, void *optval, int optlen)
  *  Description
  *      Emulate a call to **setsockopt()** on the socket associated to
  *      *bpf_socket*, which must be a full socket. The *level* at
  *      which the option resides and the name *optname* of the option
  *      must be specified, see **setsockopt(2)** for more information.
  *      The option value of length *optlen* is pointed by *optval*.
  *
  *      *bpf_socket* should be one of the following:
  *
  *      * **struct bpf_sock_ops** for **BPF_PROG_TYPE_SOCK_OPS**.
  *      * **struct bpf_sock_addr** for **BPF_CGROUP_INET4_CONNECT**
  *        and **BPF_CGROUP_INET6_CONNECT**.
  *
  *      This helper actually implements a subset of **setsockopt()**.
  *      It supports the following *level*\ s:
  *
  *      * **SOL_SOCKET**, which supports the following *optname*\ s:
  *        **SO_RCVBUF**, **SO_SNDBUF**, **SO_MAX_PACING_RATE**,
  *        **SO_PRIORITY**, **SO_RCVLOWAT**, **SO_MARK**,
  *        **SO_BINDTODEVICE**, **SO_KEEPALIVE**.
  *      * **IPPROTO_TCP**, which supports the following *optname*\ s:
  *        **TCP_CONGESTION**, **TCP_BPF_IW**,
  *        **TCP_BPF_SNDCWND_CLAMP**, **TCP_SAVE_SYN**,
  *        **TCP_KEEPIDLE**, **TCP_KEEPINTVL**, **TCP_KEEPCNT**,
  *        **TCP_SYNCNT**, **TCP_USER_TIMEOUT**, **TCP_NOTSENT_LOWAT**.
  *      * **IPPROTO_IP**, which supports *optname* **IP_TOS**.
  *      * **IPPROTO_IPV6**, which supports *optname* **IPV6_TCLASS**.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * long bpf_skb_adjust_room(struct sk_buff *skb, s32 len_diff, u32 mode, u64 flags)
  *  Description
  *      Grow or shrink the room for data in the packet associated to
  *      *skb* by *len_diff*, and according to the selected *mode*.
  *
  *      By default, the helper will reset any offloaded checksum
  *      indicator of the skb to CHECKSUM_NONE. This can be avoided
  *      by the following flag:
  *
  *      * **BPF_F_ADJ_ROOM_NO_CSUM_RESET**: Do not reset offloaded
  *        checksum data of the skb to CHECKSUM_NONE.
  *
  *      There are two supported modes at this time:
  *
  *      * **BPF_ADJ_ROOM_MAC**: Adjust room at the mac layer
  *        (room space is added or removed below the layer 2 header).
  *
  *      * **BPF_ADJ_ROOM_NET**: Adjust room at the network layer
  *        (room space is added or removed below the layer 3 header).
  *
  *      The following flags are supported at this time:
  *
  *      * **BPF_F_ADJ_ROOM_FIXED_GSO**: Do not adjust gso_size.
  *        Adjusting mss in this way is not allowed for datagrams.
  *
  *      * **BPF_F_ADJ_ROOM_ENCAP_L3_IPV4**,
  *        **BPF_F_ADJ_ROOM_ENCAP_L3_IPV6**:
  *        Any new space is reserved to hold a tunnel header.
  *        Configure skb offsets and other fields accordingly.
  *
  *      * **BPF_F_ADJ_ROOM_ENCAP_L4_GRE**,
  *        **BPF_F_ADJ_ROOM_ENCAP_L4_UDP**:
  *        Use with ENCAP_L3 flags to further specify the tunnel type.
  *
  *      * **BPF_F_ADJ_ROOM_ENCAP_L2**\ (*len*):
  *        Use with ENCAP_L3/L4 flags to further specify the tunnel
  *        type; *len* is the length of the inner MAC header.
  *
  *      * **BPF_F_ADJ_ROOM_ENCAP_L2_ETH**:
  *        Use with BPF_F_ADJ_ROOM_ENCAP_L2 flag to further specify the
  *        L2 type as Ethernet.
  *
  *      A call to this helper is susceptible to change the underlying
  *      packet buffer. Therefore, at load time, all checks on pointers
  *      previously done by the verifier are invalidated and must be
  *      performed again, if the helper is used in combination with
  *      direct packet access.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * long bpf_redirect_map(struct bpf_map *map, u32 key, u64 flags)
  *  Description
  *      Redirect the packet to the endpoint referenced by *map* at
  *      index *key*. Depending on its type, this *map* can contain
  *      references to net devices (for forwarding packets through other
  *      ports), or to CPUs (for redirecting XDP frames to another CPU;
  *      but this is only implemented for native XDP (with driver
  *      support) as of this writing).
  *
  *      The lower two bits of *flags* are used as the return code if
  *      the map lookup fails. This is so that the return value can be
  *      one of the XDP program return codes up to **XDP_TX**, as chosen
  *      by the caller. The higher bits of *flags* can be set to
  *      BPF_F_BROADCAST or BPF_F_EXCLUDE_INGRESS as defined below.
  *
  *      With BPF_F_BROADCAST the packet will be broadcasted to all the
  *      interfaces in the map, with BPF_F_EXCLUDE_INGRESS the ingress
  *      interface will be excluded when do broadcasting.
  *
  *      See also **bpf_redirect**\ (), which only supports redirecting
  *      to an ifindex, but doesn't require a map to do so.
  *  Return
  *      **XDP_REDIRECT** on success, or the value of the two lower bits
  *      of the *flags* argument on error.
  *
  * long bpf_sk_redirect_map(struct sk_buff *skb, struct bpf_map *map, u32 key, u64 flags)
  *  Description
  *      Redirect the packet to the socket referenced by *map* (of type
  *      **BPF_MAP_TYPE_SOCKMAP**) at index *key*. Both ingress and
  *      egress interfaces can be used for redirection. The
  *      **BPF_F_INGRESS** value in *flags* is used to make the
  *      distinction (ingress path is selected if the flag is present,
  *      egress path otherwise). This is the only flag supported for now.
  *  Return
  *      **SK_PASS** on success, or **SK_DROP** on error.
  *
  * long bpf_sock_map_update(struct bpf_sock_ops *skops, struct bpf_map *map, void *key, u64 flags)
  *  Description
  *      Add an entry to, or update a *map* referencing sockets. The
  *      *skops* is used as a new value for the entry associated to
  *      *key*. *flags* is one of:
  *
  *      **BPF_NOEXIST**
  *          The entry for *key* must not exist in the map.
  *      **BPF_EXIST**
  *          The entry for *key* must already exist in the map.
  *      **BPF_ANY**
  *          No condition on the existence of the entry for *key*.
  *
  *      If the *map* has eBPF programs (parser and verdict), those will
  *      be inherited by the socket being added. If the socket is
  *      already attached to eBPF programs, this results in an error.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * long bpf_xdp_adjust_meta(struct xdp_buff *xdp_md, int delta)
  *  Description
  *      Adjust the address pointed by *xdp_md*\ **->data_meta** by
  *      *delta* (which can be positive or negative). Note that this
  *      operation modifies the address stored in *xdp_md*\ **->data**,
  *      so the latter must be loaded only after the helper has been
  *      called.
  *
  *      The use of *xdp_md*\ **->data_meta** is optional and programs
  *      are not required to use it. The rationale is that when the
  *      packet is processed with XDP (e.g. as DoS filter), it is
  *      possible to push further meta data along with it before passing
  *      to the stack, and to give the guarantee that an ingress eBPF
  *      program attached as a TC classifier on the same device can pick
  *      this up for further post-processing. Since TC works with socket
  *      buffers, it remains possible to set from XDP the **mark** or
  *      **priority** pointers, or other pointers for the socket buffer.
  *      Having this scratch space generic and programmable allows for
  *      more flexibility as the user is free to store whatever meta
  *      data they need.
  *
  *      A call to this helper is susceptible to change the underlying
  *      packet buffer. Therefore, at load time, all checks on pointers
  *      previously done by the verifier are invalidated and must be
  *      performed again, if the helper is used in combination with
  *      direct packet access.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * long bpf_perf_event_read_value(struct bpf_map *map, u64 flags, struct bpf_perf_event_value *buf, u32 buf_size)
  *  Description
  *      Read the value of a perf event counter, and store it into *buf*
  *      of size *buf_size*. This helper relies on a *map* of type
  *      **BPF_MAP_TYPE_PERF_EVENT_ARRAY**. The nature of the perf event
  *      counter is selected when *map* is updated with perf event file
  *      descriptors. The *map* is an array whose size is the number of
  *      available CPUs, and each cell contains a value relative to one
  *      CPU. The value to retrieve is indicated by *flags*, that
  *      contains the index of the CPU to look up, masked with
  *      **BPF_F_INDEX_MASK**. Alternatively, *flags* can be set to
  *      **BPF_F_CURRENT_CPU** to indicate that the value for the
  *      current CPU should be retrieved.
  *
  *      This helper behaves in a way close to
  *      **bpf_perf_event_read**\ () helper, save that instead of
  *      just returning the value observed, it fills the *buf*
  *      structure. This allows for additional data to be retrieved: in
  *      particular, the enabled and running times (in *buf*\
  *      **->enabled** and *buf*\ **->running**, respectively) are
  *      copied. In general, **bpf_perf_event_read_value**\ () is
  *      recommended over **bpf_perf_event_read**\ (), which has some
  *      ABI issues and provides fewer functionalities.
  *
  *      These values are interesting, because hardware PMU (Performance
  *      Monitoring Unit) counters are limited resources. When there are
  *      more PMU based perf events opened than available counters,
  *      kernel will multiplex these events so each event gets certain
  *      percentage (but not all) of the PMU time. In case that
  *      multiplexing happens, the number of samples or counter value
  *      will not reflect the case compared to when no multiplexing
  *      occurs. This makes comparison between different runs difficult.
  *      Typically, the counter value should be normalized before
  *      comparing to other experiments. The usual normalization is done
  *      as follows.
  *
  *      ::
  *
  *          normalized_counter = counter * t_enabled / t_running
  *
  *      Where t_enabled is the time enabled for event and t_running is
  *      the time running for event since last normalization. The
  *      enabled and running times are accumulated since the perf event
  *      open. To achieve scaling factor between two invocations of an
  *      eBPF program, users can use CPU id as the key (which is
  *      typical for perf array usage model) to remember the previous
  *      value and do the calculation inside the eBPF program.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * long bpf_perf_prog_read_value(struct bpf_perf_event_data *ctx, struct bpf_perf_event_value *buf, u32 buf_size)
  *  Description
  *      For en eBPF program attached to a perf event, retrieve the
  *      value of the event counter associated to *ctx* and store it in
  *      the structure pointed by *buf* and of size *buf_size*. Enabled
  *      and running times are also stored in the structure (see
  *      description of helper **bpf_perf_event_read_value**\ () for
  *      more details).
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * long bpf_getsockopt(void *bpf_socket, int level, int optname, void *optval, int optlen)
  *  Description
  *      Emulate a call to **getsockopt()** on the socket associated to
  *      *bpf_socket*, which must be a full socket. The *level* at
  *      which the option resides and the name *optname* of the option
  *      must be specified, see **getsockopt(2)** for more information.
  *      The retrieved value is stored in the structure pointed by
  *      *opval* and of length *optlen*.
  *
  *      *bpf_socket* should be one of the following:
  *
  *      * **struct bpf_sock_ops** for **BPF_PROG_TYPE_SOCK_OPS**.
  *      * **struct bpf_sock_addr** for **BPF_CGROUP_INET4_CONNECT**
  *        and **BPF_CGROUP_INET6_CONNECT**.
  *
  *      This helper actually implements a subset of **getsockopt()**.
  *      It supports the following *level*\ s:
  *
  *      * **IPPROTO_TCP**, which supports *optname*
  *        **TCP_CONGESTION**.
  *      * **IPPROTO_IP**, which supports *optname* **IP_TOS**.
  *      * **IPPROTO_IPV6**, which supports *optname* **IPV6_TCLASS**.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * long bpf_override_return(struct pt_regs *regs, u64 rc)
  *  Description
  *      Used for error injection, this helper uses kprobes to override
  *      the return value of the probed function, and to set it to *rc*.
  *      The first argument is the context *regs* on which the kprobe
  *      works.
  *
  *      This helper works by setting the PC (program counter)
  *      to an override function which is run in place of the original
  *      probed function. This means the probed function is not run at
  *      all. The replacement function just returns with the required
  *      value.
  *
  *      This helper has security implications, and thus is subject to
  *      restrictions. It is only available if the kernel was compiled
  *      with the **CONFIG_BPF_KPROBE_OVERRIDE** configuration
  *      option, and in this case it only works on functions tagged with
  *      **ALLOW_ERROR_INJECTION** in the kernel code.
  *
  *      Also, the helper is only available for the architectures having
  *      the CONFIG_FUNCTION_ERROR_INJECTION option. As of this writing,
  *      x86 architecture is the only one to support this feature.
  *  Return
  *      0
  *
  * long bpf_sock_ops_cb_flags_set(struct bpf_sock_ops *bpf_sock, int argval)
  *  Description
  *      Attempt to set the value of the **bpf_sock_ops_cb_flags** field
  *      for the full TCP socket associated to *bpf_sock_ops* to
  *      *argval*.
  *
  *      The primary use of this field is to determine if there should
  *      be calls to eBPF programs of type
  *      **BPF_PROG_TYPE_SOCK_OPS** at various points in the TCP
  *      code. A program of the same type can change its value, per
  *      connection and as necessary, when the connection is
  *      established. This field is directly accessible for reading, but
  *      this helper must be used for updates in order to return an
  *      error if an eBPF program tries to set a callback that is not
  *      supported in the current kernel.
  *
  *      *argval* is a flag array which can combine these flags:
  *
  *      * **BPF_SOCK_OPS_RTO_CB_FLAG** (retransmission time out)
  *      * **BPF_SOCK_OPS_RETRANS_CB_FLAG** (retransmission)
  *      * **BPF_SOCK_OPS_STATE_CB_FLAG** (TCP state change)
  *      * **BPF_SOCK_OPS_RTT_CB_FLAG** (every RTT)
  *
  *      Therefore, this function can be used to clear a callback flag by
  *      setting the appropriate bit to zero. e.g. to disable the RTO
  *      callback:
  *
  *      **bpf_sock_ops_cb_flags_set(bpf_sock,**
  *          **bpf_sock->bpf_sock_ops_cb_flags & ~BPF_SOCK_OPS_RTO_CB_FLAG)**
  *
  *      Here are some examples of where one could call such eBPF
  *      program:
  *
  *      * When RTO fires.
  *      * When a packet is retransmitted.
  *      * When the connection terminates.
  *      * When a packet is sent.
  *      * When a packet is received.
  *  Return
  *      Code **-EINVAL** if the socket is not a full TCP socket;
  *      otherwise, a positive number containing the bits that could not
  *      be set is returned (which comes down to 0 if all bits were set
  *      as required).
  *
  * long bpf_msg_redirect_map(struct sk_msg_buff *msg, struct bpf_map *map, u32 key, u64 flags)
  *  Description
  *      This helper is used in programs implementing policies at the
  *      socket level. If the message *msg* is allowed to pass (i.e. if
  *      the verdict eBPF program returns **SK_PASS**), redirect it to
  *      the socket referenced by *map* (of type
  *      **BPF_MAP_TYPE_SOCKMAP**) at index *key*. Both ingress and
  *      egress interfaces can be used for redirection. The
  *      **BPF_F_INGRESS** value in *flags* is used to make the
  *      distinction (ingress path is selected if the flag is present,
  *      egress path otherwise). This is the only flag supported for now.
  *  Return
  *      **SK_PASS** on success, or **SK_DROP** on error.
  *
  * long bpf_msg_apply_bytes(struct sk_msg_buff *msg, u32 bytes)
  *  Description
  *      For socket policies, apply the verdict of the eBPF program to
  *      the next *bytes* (number of bytes) of message *msg*.
  *
  *      For example, this helper can be used in the following cases:
  *
  *      * A single **sendmsg**\ () or **sendfile**\ () system call
  *        contains multiple logical messages that the eBPF program is
  *        supposed to read and for which it should apply a verdict.
  *      * An eBPF program only cares to read the first *bytes* of a
  *        *msg*. If the message has a large payload, then setting up
  *        and calling the eBPF program repeatedly for all bytes, even
  *        though the verdict is already known, would create unnecessary
  *        overhead.
  *
  *      When called from within an eBPF program, the helper sets a
  *      counter internal to the BPF infrastructure, that is used to
  *      apply the last verdict to the next *bytes*. If *bytes* is
  *      smaller than the current data being processed from a
  *      **sendmsg**\ () or **sendfile**\ () system call, the first
  *      *bytes* will be sent and the eBPF program will be re-run with
  *      the pointer for start of data pointing to byte number *bytes*
  *      **+ 1**. If *bytes* is larger than the current data being
  *      processed, then the eBPF verdict will be applied to multiple
  *      **sendmsg**\ () or **sendfile**\ () calls until *bytes* are
  *      consumed.
  *
  *      Note that if a socket closes with the internal counter holding
  *      a non-zero value, this is not a problem because data is not
  *      being buffered for *bytes* and is sent as it is received.
  *  Return
  *      0
  *
  * long bpf_msg_cork_bytes(struct sk_msg_buff *msg, u32 bytes)
  *  Description
  *      For socket policies, prevent the execution of the verdict eBPF
  *      program for message *msg* until *bytes* (byte number) have been
  *      accumulated.
  *
  *      This can be used when one needs a specific number of bytes
  *      before a verdict can be assigned, even if the data spans
  *      multiple **sendmsg**\ () or **sendfile**\ () calls. The extreme
  *      case would be a user calling **sendmsg**\ () repeatedly with
  *      1-byte long message segments. Obviously, this is bad for
  *      performance, but it is still valid. If the eBPF program needs
  *      *bytes* bytes to validate a header, this helper can be used to
  *      prevent the eBPF program to be called again until *bytes* have
  *      been accumulated.
  *  Return
  *      0
  *
  * long bpf_msg_pull_data(struct sk_msg_buff *msg, u32 start, u32 end, u64 flags)
  *  Description
  *      For socket policies, pull in non-linear data from user space
  *      for *msg* and set pointers *msg*\ **->data** and *msg*\
  *      **->data_end** to *start* and *end* bytes offsets into *msg*,
  *      respectively.
  *
  *      If a program of type **BPF_PROG_TYPE_SK_MSG** is run on a
  *      *msg* it can only parse data that the (**data**, **data_end**)
  *      pointers have already consumed. For **sendmsg**\ () hooks this
  *      is likely the first scatterlist element. But for calls relying
  *      on the **sendpage** handler (e.g. **sendfile**\ ()) this will
  *      be the range (**0**, **0**) because the data is shared with
  *      user space and by default the objective is to avoid allowing
  *      user space to modify data while (or after) eBPF verdict is
  *      being decided. This helper can be used to pull in data and to
  *      set the start and end pointer to given values. Data will be
  *      copied if necessary (i.e. if data was not linear and if start
  *      and end pointers do not point to the same chunk).
  *
  *      A call to this helper is susceptible to change the underlying
  *      packet buffer. Therefore, at load time, all checks on pointers
  *      previously done by the verifier are invalidated and must be
  *      performed again, if the helper is used in combination with
  *      direct packet access.
  *
  *      All values for *flags* are reserved for future usage, and must
  *      be left at zero.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * long bpf_bind(struct bpf_sock_addr *ctx, struct sockaddr *addr, int addr_len)
  *  Description
  *      Bind the socket associated to *ctx* to the address pointed by
  *      *addr*, of length *addr_len*. This allows for making outgoing
  *      connection from the desired IP address, which can be useful for
  *      example when all processes inside a cgroup should use one
  *      single IP address on a host that has multiple IP configured.
  *
  *      This helper works for IPv4 and IPv6, TCP and UDP sockets. The
  *      domain (*addr*\ **->sa_family**) must be **AF_INET** (or
  *      **AF_INET6**). It's advised to pass zero port (**sin_port**
  *      or **sin6_port**) which triggers IP_BIND_ADDRESS_NO_PORT-like
  *      behavior and lets the kernel efficiently pick up an unused
  *      port as long as 4-tuple is unique. Passing non-zero port might
  *      lead to degraded performance.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * long bpf_xdp_adjust_tail(struct xdp_buff *xdp_md, int delta)
  *  Description
  *      Adjust (move) *xdp_md*\ **->data_end** by *delta* bytes. It is
  *      possible to both shrink and grow the packet tail.
  *      Shrink done via *delta* being a negative integer.
  *
  *      A call to this helper is susceptible to change the underlying
  *      packet buffer. Therefore, at load time, all checks on pointers
  *      previously done by the verifier are invalidated and must be
  *      performed again, if the helper is used in combination with
  *      direct packet access.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * long bpf_skb_get_xfrm_state(struct sk_buff *skb, u32 index, struct bpf_xfrm_state *xfrm_state, u32 size, u64 flags)
  *  Description
  *      Retrieve the XFRM state (IP transform framework, see also
  *      **ip-xfrm(8)**) at *index* in XFRM "security path" for *skb*.
  *
  *      The retrieved value is stored in the **struct bpf_xfrm_state**
  *      pointed by *xfrm_state* and of length *size*.
  *
  *      All values for *flags* are reserved for future usage, and must
  *      be left at zero.
  *
  *      This helper is available only if the kernel was compiled with
  *      **CONFIG_XFRM** configuration option.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * long bpf_get_stack(void *ctx, void *buf, u32 size, u64 flags)
  *  Description
  *      Return a user or a kernel stack in bpf program provided buffer.
  *      To achieve this, the helper needs *ctx*, which is a pointer
  *      to the context on which the tracing program is executed.
  *      To store the stacktrace, the bpf program provides *buf* with
  *      a nonnegative *size*.
  *
  *      The last argument, *flags*, holds the number of stack frames to
  *      skip (from 0 to 255), masked with
  *      **BPF_F_SKIP_FIELD_MASK**. The next bits can be used to set
  *      the following flags:
  *
  *      **BPF_F_USER_STACK**
  *          Collect a user space stack instead of a kernel stack.
  *      **BPF_F_USER_BUILD_ID**
  *          Collect buildid+offset instead of ips for user stack,
  *          only valid if **BPF_F_USER_STACK** is also specified.
  *
  *      **bpf_get_stack**\ () can collect up to
  *      **PERF_MAX_STACK_DEPTH** both kernel and user frames, subject
  *      to sufficient large buffer size. Note that
  *      this limit can be controlled with the **sysctl** program, and
  *      that it should be manually increased in order to profile long
  *      user stacks (such as stacks for Java programs). To do so, use:
  *
  *      ::
  *
  *          # sysctl kernel.perf_event_max_stack=<new value>
  *  Return
  *      The non-negative copied *buf* length equal to or less than
  *      *size* on success, or a negative error in case of failure.
  *
  * long bpf_skb_load_bytes_relative(const void *skb, u32 offset, void *to, u32 len, u32 start_header)
  *  Description
  *      This helper is similar to **bpf_skb_load_bytes**\ () in that
  *      it provides an easy way to load *len* bytes from *offset*
  *      from the packet associated to *skb*, into the buffer pointed
  *      by *to*. The difference to **bpf_skb_load_bytes**\ () is that
  *      a fifth argument *start_header* exists in order to select a
  *      base offset to start from. *start_header* can be one of:
  *
  *      **BPF_HDR_START_MAC**
  *          Base offset to load data from is *skb*'s mac header.
  *      **BPF_HDR_START_NET**
  *          Base offset to load data from is *skb*'s network header.
  *
  *      In general, "direct packet access" is the preferred method to
  *      access packet data, however, this helper is in particular useful
  *      in socket filters where *skb*\ **->data** does not always point
  *      to the start of the mac header and where "direct packet access"
  *      is not available.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * long bpf_fib_lookup(void *ctx, struct bpf_fib_lookup *params, int plen, u32 flags)
  *  Description
  *      Do FIB lookup in kernel tables using parameters in *params*.
  *      If lookup is successful and result shows packet is to be
  *      forwarded, the neighbor tables are searched for the nexthop.
  *      If successful (ie., FIB lookup shows forwarding and nexthop
  *      is resolved), the nexthop address is returned in ipv4_dst
  *      or ipv6_dst based on family, smac is set to mac address of
  *      egress device, dmac is set to nexthop mac address, rt_metric
  *      is set to metric from route (IPv4/IPv6 only), and ifindex
  *      is set to the device index of the nexthop from the FIB lookup.
  *
  *      *plen* argument is the size of the passed in struct.
  *      *flags* argument can be a combination of one or more of the
  *      following values:
  *
  *      **BPF_FIB_LOOKUP_DIRECT**
  *          Do a direct table lookup vs full lookup using FIB
  *          rules.
  *      **BPF_FIB_LOOKUP_OUTPUT**
  *          Perform lookup from an egress perspective (default is
  *          ingress).
  *
  *      *ctx* is either **struct xdp_md** for XDP programs or
  *      **struct sk_buff** tc cls_act programs.
  *  Return
  *      * < 0 if any input argument is invalid
  *      *   0 on success (packet is forwarded, nexthop neighbor exists)
  *      * > 0 one of **BPF_FIB_LKUP_RET_** codes explaining why the
  *        packet is not forwarded or needs assist from full stack
  *
  *      If lookup fails with BPF_FIB_LKUP_RET_FRAG_NEEDED, then the MTU
  *      was exceeded and output params->mtu_result contains the MTU.
  *
  * long bpf_sock_hash_update(struct bpf_sock_ops *skops, struct bpf_map *map, void *key, u64 flags)
  *  Description
  *      Add an entry to, or update a sockhash *map* referencing sockets.
  *      The *skops* is used as a new value for the entry associated to
  *      *key*. *flags* is one of:
  *
  *      **BPF_NOEXIST**
  *          The entry for *key* must not exist in the map.
  *      **BPF_EXIST**
  *          The entry for *key* must already exist in the map.
  *      **BPF_ANY**
  *          No condition on the existence of the entry for *key*.
  *
  *      If the *map* has eBPF programs (parser and verdict), those will
  *      be inherited by the socket being added. If the socket is
  *      already attached to eBPF programs, this results in an error.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * long bpf_msg_redirect_hash(struct sk_msg_buff *msg, struct bpf_map *map, void *key, u64 flags)
  *  Description
  *      This helper is used in programs implementing policies at the
  *      socket level. If the message *msg* is allowed to pass (i.e. if
  *      the verdict eBPF program returns **SK_PASS**), redirect it to
  *      the socket referenced by *map* (of type
  *      **BPF_MAP_TYPE_SOCKHASH**) using hash *key*. Both ingress and
  *      egress interfaces can be used for redirection. The
  *      **BPF_F_INGRESS** value in *flags* is used to make the
  *      distinction (ingress path is selected if the flag is present,
  *      egress path otherwise). This is the only flag supported for now.
  *  Return
  *      **SK_PASS** on success, or **SK_DROP** on error.
  *
  * long bpf_sk_redirect_hash(struct sk_buff *skb, struct bpf_map *map, void *key, u64 flags)
  *  Description
  *      This helper is used in programs implementing policies at the
  *      skb socket level. If the sk_buff *skb* is allowed to pass (i.e.
  *      if the verdict eBPF program returns **SK_PASS**), redirect it
  *      to the socket referenced by *map* (of type
  *      **BPF_MAP_TYPE_SOCKHASH**) using hash *key*. Both ingress and
  *      egress interfaces can be used for redirection. The
  *      **BPF_F_INGRESS** value in *flags* is used to make the
  *      distinction (ingress path is selected if the flag is present,
  *      egress otherwise). This is the only flag supported for now.
  *  Return
  *      **SK_PASS** on success, or **SK_DROP** on error.
  *
  * long bpf_lwt_push_encap(struct sk_buff *skb, u32 type, void *hdr, u32 len)
  *  Description
  *      Encapsulate the packet associated to *skb* within a Layer 3
  *      protocol header. This header is provided in the buffer at
  *      address *hdr*, with *len* its size in bytes. *type* indicates
  *      the protocol of the header and can be one of:
  *
  *      **BPF_LWT_ENCAP_SEG6**
  *          IPv6 encapsulation with Segment Routing Header
  *          (**struct ipv6_sr_hdr**). *hdr* only contains the SRH,
  *          the IPv6 header is computed by the kernel.
  *      **BPF_LWT_ENCAP_SEG6_INLINE**
  *          Only works if *skb* contains an IPv6 packet. Insert a
  *          Segment Routing Header (**struct ipv6_sr_hdr**) inside
  *          the IPv6 header.
  *      **BPF_LWT_ENCAP_IP**
  *          IP encapsulation (GRE/GUE/IPIP/etc). The outer header
  *          must be IPv4 or IPv6, followed by zero or more
  *          additional headers, up to **LWT_BPF_MAX_HEADROOM**
  *          total bytes in all prepended headers. Please note that
  *          if **skb_is_gso**\ (*skb*) is true, no more than two
  *          headers can be prepended, and the inner header, if
  *          present, should be either GRE or UDP/GUE.
  *
  *      **BPF_LWT_ENCAP_SEG6**\ \* types can be called by BPF programs
  *      of type **BPF_PROG_TYPE_LWT_IN**; **BPF_LWT_ENCAP_IP** type can
  *      be called by bpf programs of types **BPF_PROG_TYPE_LWT_IN** and
  *      **BPF_PROG_TYPE_LWT_XMIT**.
  *
  *      A call to this helper is susceptible to change the underlying
  *      packet buffer. Therefore, at load time, all checks on pointers
  *      previously done by the verifier are invalidated and must be
  *      performed again, if the helper is used in combination with
  *      direct packet access.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * long bpf_lwt_seg6_store_bytes(struct sk_buff *skb, u32 offset, const void *from, u32 len)
  *  Description
  *      Store *len* bytes from address *from* into the packet
  *      associated to *skb*, at *offset*. Only the flags, tag and TLVs
  *      inside the outermost IPv6 Segment Routing Header can be
  *      modified through this helper.
  *
  *      A call to this helper is susceptible to change the underlying
  *      packet buffer. Therefore, at load time, all checks on pointers
  *      previously done by the verifier are invalidated and must be
  *      performed again, if the helper is used in combination with
  *      direct packet access.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * long bpf_lwt_seg6_adjust_srh(struct sk_buff *skb, u32 offset, s32 delta)
  *  Description
  *      Adjust the size allocated to TLVs in the outermost IPv6
  *      Segment Routing Header contained in the packet associated to
  *      *skb*, at position *offset* by *delta* bytes. Only offsets
  *      after the segments are accepted. *delta* can be as well
  *      positive (growing) as negative (shrinking).
  *
  *      A call to this helper is susceptible to change the underlying
  *      packet buffer. Therefore, at load time, all checks on pointers
  *      previously done by the verifier are invalidated and must be
  *      performed again, if the helper is used in combination with
  *      direct packet access.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * long bpf_lwt_seg6_action(struct sk_buff *skb, u32 action, void *param, u32 param_len)
  *  Description
  *      Apply an IPv6 Segment Routing action of type *action* to the
  *      packet associated to *skb*. Each action takes a parameter
  *      contained at address *param*, and of length *param_len* bytes.
  *      *action* can be one of:
  *
  *      **SEG6_LOCAL_ACTION_END_X**
  *          End.X action: Endpoint with Layer-3 cross-connect.
  *          Type of *param*: **struct in6_addr**.
  *      **SEG6_LOCAL_ACTION_END_T**
  *          End.T action: Endpoint with specific IPv6 table lookup.
  *          Type of *param*: **int**.
  *      **SEG6_LOCAL_ACTION_END_B6**
  *          End.B6 action: Endpoint bound to an SRv6 policy.
  *          Type of *param*: **struct ipv6_sr_hdr**.
  *      **SEG6_LOCAL_ACTION_END_B6_ENCAP**
  *          End.B6.Encap action: Endpoint bound to an SRv6
  *          encapsulation policy.
  *          Type of *param*: **struct ipv6_sr_hdr**.
  *
  *      A call to this helper is susceptible to change the underlying
  *      packet buffer. Therefore, at load time, all checks on pointers
  *      previously done by the verifier are invalidated and must be
  *      performed again, if the helper is used in combination with
  *      direct packet access.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * long bpf_rc_repeat(void *ctx)
  *  Description
  *      This helper is used in programs implementing IR decoding, to
  *      report a successfully decoded repeat key message. This delays
  *      the generation of a key up event for previously generated
  *      key down event.
  *
  *      Some IR protocols like NEC have a special IR message for
  *      repeating last button, for when a button is held down.
  *
  *      The *ctx* should point to the lirc sample as passed into
  *      the program.
  *
  *      This helper is only available is the kernel was compiled with
  *      the **CONFIG_BPF_LIRC_MODE2** configuration option set to
  *      "**y**".
  *  Return
  *      0
  *
  * long bpf_rc_keydown(void *ctx, u32 protocol, u64 scancode, u32 toggle)
  *  Description
  *      This helper is used in programs implementing IR decoding, to
  *      report a successfully decoded key press with *scancode*,
  *      *toggle* value in the given *protocol*. The scancode will be
  *      translated to a keycode using the rc keymap, and reported as
  *      an input key down event. After a period a key up event is
  *      generated. This period can be extended by calling either
  *      **bpf_rc_keydown**\ () again with the same values, or calling
  *      **bpf_rc_repeat**\ ().
  *
  *      Some protocols include a toggle bit, in case the button was
  *      released and pressed again between consecutive scancodes.
  *
  *      The *ctx* should point to the lirc sample as passed into
  *      the program.
  *
  *      The *protocol* is the decoded protocol number (see
  *      **enum rc_proto** for some predefined values).
  *
  *      This helper is only available is the kernel was compiled with
  *      the **CONFIG_BPF_LIRC_MODE2** configuration option set to
  *      "**y**".
  *  Return
  *      0
  *
  * u64 bpf_skb_cgroup_id(struct sk_buff *skb)
  *  Description
  *      Return the cgroup v2 id of the socket associated with the *skb*.
  *      This is roughly similar to the **bpf_get_cgroup_classid**\ ()
  *      helper for cgroup v1 by providing a tag resp. identifier that
  *      can be matched on or used for map lookups e.g. to implement
  *      policy. The cgroup v2 id of a given path in the hierarchy is
  *      exposed in user space through the f_handle API in order to get
  *      to the same 64-bit id.
  *
  *      This helper can be used on TC egress path, but not on ingress,
  *      and is available only if the kernel was compiled with the
  *      **CONFIG_SOCK_CGROUP_DATA** configuration option.
  *  Return
  *      The id is returned or 0 in case the id could not be retrieved.
  *
  * u64 bpf_get_current_cgroup_id(void)
  *  Description
  *      Get the current cgroup id based on the cgroup within which
  *      the current task is running.
  *  Return
  *      A 64-bit integer containing the current cgroup id based
  *      on the cgroup within which the current task is running.
  *
  * void *bpf_get_local_storage(void *map, u64 flags)
  *  Description
  *      Get the pointer to the local storage area.
  *      The type and the size of the local storage is defined
  *      by the *map* argument.
  *      The *flags* meaning is specific for each map type,
  *      and has to be 0 for cgroup local storage.
  *
  *      Depending on the BPF program type, a local storage area
  *      can be shared between multiple instances of the BPF program,
  *      running simultaneously.
  *
  *      A user should care about the synchronization by himself.
  *      For example, by using the **BPF_ATOMIC** instructions to alter
  *      the shared data.
  *  Return
  *      A pointer to the local storage area.
  *
  * long bpf_sk_select_reuseport(struct sk_reuseport_md *reuse, struct bpf_map *map, void *key, u64 flags)
  *  Description
  *      Select a **SO_REUSEPORT** socket from a
  *      **BPF_MAP_TYPE_REUSEPORT_SOCKARRAY** *map*.
  *      It checks the selected socket is matching the incoming
  *      request in the socket buffer.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * u64 bpf_skb_ancestor_cgroup_id(struct sk_buff *skb, int ancestor_level)
  *  Description
  *      Return id of cgroup v2 that is ancestor of cgroup associated
  *      with the *skb* at the *ancestor_level*.  The root cgroup is at
  *      *ancestor_level* zero and each step down the hierarchy
  *      increments the level. If *ancestor_level* == level of cgroup
  *      associated with *skb*, then return value will be same as that
  *      of **bpf_skb_cgroup_id**\ ().
  *
  *      The helper is useful to implement policies based on cgroups
  *      that are upper in hierarchy than immediate cgroup associated
  *      with *skb*.
  *
  *      The format of returned id and helper limitations are same as in
  *      **bpf_skb_cgroup_id**\ ().
  *  Return
  *      The id is returned or 0 in case the id could not be retrieved.
  *
  * struct bpf_sock *bpf_sk_lookup_tcp(void *ctx, struct bpf_sock_tuple *tuple, u32 tuple_size, u64 netns, u64 flags)
  *  Description
  *      Look for TCP socket matching *tuple*, optionally in a child
  *      network namespace *netns*. The return value must be checked,
  *      and if non-**NULL**, released via **bpf_sk_release**\ ().
  *
  *      The *ctx* should point to the context of the program, such as
  *      the skb or socket (depending on the hook in use). This is used
  *      to determine the base network namespace for the lookup.
  *
  *      *tuple_size* must be one of:
  *
  *      **sizeof**\ (*tuple*\ **->ipv4**)
  *          Look for an IPv4 socket.
  *      **sizeof**\ (*tuple*\ **->ipv6**)
  *          Look for an IPv6 socket.
  *
  *      If the *netns* is a negative signed 32-bit integer, then the
  *      socket lookup table in the netns associated with the *ctx*
  *      will be used. For the TC hooks, this is the netns of the device
  *      in the skb. For socket hooks, this is the netns of the socket.
  *      If *netns* is any other signed 32-bit value greater than or
  *      equal to zero then it specifies the ID of the netns relative to
  *      the netns associated with the *ctx*. *netns* values beyond the
  *      range of 32-bit integers are reserved for future use.
  *
  *      All values for *flags* are reserved for future usage, and must
  *      be left at zero.
  *
  *      This helper is available only if the kernel was compiled with
  *      **CONFIG_NET** configuration option.
  *  Return
  *      Pointer to **struct bpf_sock**, or **NULL** in case of failure.
  *      For sockets with reuseport option, the **struct bpf_sock**
  *      result is from *reuse*\ **->socks**\ [] using the hash of the
  *      tuple.
  *
  * struct bpf_sock *bpf_sk_lookup_udp(void *ctx, struct bpf_sock_tuple *tuple, u32 tuple_size, u64 netns, u64 flags)
  *  Description
  *      Look for UDP socket matching *tuple*, optionally in a child
  *      network namespace *netns*. The return value must be checked,
  *      and if non-**NULL**, released via **bpf_sk_release**\ ().
  *
  *      The *ctx* should point to the context of the program, such as
  *      the skb or socket (depending on the hook in use). This is used
  *      to determine the base network namespace for the lookup.
  *
  *      *tuple_size* must be one of:
  *
  *      **sizeof**\ (*tuple*\ **->ipv4**)
  *          Look for an IPv4 socket.
  *      **sizeof**\ (*tuple*\ **->ipv6**)
  *          Look for an IPv6 socket.
  *
  *      If the *netns* is a negative signed 32-bit integer, then the
  *      socket lookup table in the netns associated with the *ctx*
  *      will be used. For the TC hooks, this is the netns of the device
  *      in the skb. For socket hooks, this is the netns of the socket.
  *      If *netns* is any other signed 32-bit value greater than or
  *      equal to zero then it specifies the ID of the netns relative to
  *      the netns associated with the *ctx*. *netns* values beyond the
  *      range of 32-bit integers are reserved for future use.
  *
  *      All values for *flags* are reserved for future usage, and must
  *      be left at zero.
  *
  *      This helper is available only if the kernel was compiled with
  *      **CONFIG_NET** configuration option.
  *  Return
  *      Pointer to **struct bpf_sock**, or **NULL** in case of failure.
  *      For sockets with reuseport option, the **struct bpf_sock**
  *      result is from *reuse*\ **->socks**\ [] using the hash of the
  *      tuple.
  *
  * long bpf_sk_release(void *sock)
  *  Description
  *      Release the reference held by *sock*. *sock* must be a
  *      non-**NULL** pointer that was returned from
  *      **bpf_sk_lookup_xxx**\ ().
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * long bpf_map_push_elem(struct bpf_map *map, const void *value, u64 flags)
  *  Description
  *      Push an element *value* in *map*. *flags* is one of:
  *
  *      **BPF_EXIST**
  *          If the queue/stack is full, the oldest element is
  *          removed to make room for this.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * long bpf_map_pop_elem(struct bpf_map *map, void *value)
  *  Description
  *      Pop an element from *map*.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * long bpf_map_peek_elem(struct bpf_map *map, void *value)
  *  Description
  *      Get an element from *map* without removing it.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * long bpf_msg_push_data(struct sk_msg_buff *msg, u32 start, u32 len, u64 flags)
  *  Description
  *      For socket policies, insert *len* bytes into *msg* at offset
  *      *start*.
  *
  *      If a program of type **BPF_PROG_TYPE_SK_MSG** is run on a
  *      *msg* it may want to insert metadata or options into the *msg*.
  *      This can later be read and used by any of the lower layer BPF
  *      hooks.
  *
  *      This helper may fail if under memory pressure (a malloc
  *      fails) in these cases BPF programs will get an appropriate
  *      error and BPF programs will need to handle them.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * long bpf_msg_pop_data(struct sk_msg_buff *msg, u32 start, u32 len, u64 flags)
  *  Description
  *      Will remove *len* bytes from a *msg* starting at byte *start*.
  *      This may result in **ENOMEM** errors under certain situations if
  *      an allocation and copy are required due to a full ring buffer.
  *      However, the helper will try to avoid doing the allocation
  *      if possible. Other errors can occur if input parameters are
  *      invalid either due to *start* byte not being valid part of *msg*
  *      payload and/or *pop* value being to large.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * long bpf_rc_pointer_rel(void *ctx, s32 rel_x, s32 rel_y)
  *  Description
  *      This helper is used in programs implementing IR decoding, to
  *      report a successfully decoded pointer movement.
  *
  *      The *ctx* should point to the lirc sample as passed into
  *      the program.
  *
  *      This helper is only available is the kernel was compiled with
  *      the **CONFIG_BPF_LIRC_MODE2** configuration option set to
  *      "**y**".
  *  Return
  *      0
  *
  * long bpf_spin_lock(struct bpf_spin_lock *lock)
  *  Description
  *      Acquire a spinlock represented by the pointer *lock*, which is
  *      stored as part of a value of a map. Taking the lock allows to
  *      safely update the rest of the fields in that value. The
  *      spinlock can (and must) later be released with a call to
  *      **bpf_spin_unlock**\ (\ *lock*\ ).
  *
  *      Spinlocks in BPF programs come with a number of restrictions
  *      and constraints:
  *
  *      * **bpf_spin_lock** objects are only allowed inside maps of
  *        types **BPF_MAP_TYPE_HASH** and **BPF_MAP_TYPE_ARRAY** (this
  *        list could be extended in the future).
  *      * BTF description of the map is mandatory.
  *      * The BPF program can take ONE lock at a time, since taking two
  *        or more could cause dead locks.
  *      * Only one **struct bpf_spin_lock** is allowed per map element.
  *      * When the lock is taken, calls (either BPF to BPF or helpers)
  *        are not allowed.
  *      * The **BPF_LD_ABS** and **BPF_LD_IND** instructions are not
  *        allowed inside a spinlock-ed region.
  *      * The BPF program MUST call **bpf_spin_unlock**\ () to release
  *        the lock, on all execution paths, before it returns.
  *      * The BPF program can access **struct bpf_spin_lock** only via
  *        the **bpf_spin_lock**\ () and **bpf_spin_unlock**\ ()
  *        helpers. Loading or storing data into the **struct
  *        bpf_spin_lock** *lock*\ **;** field of a map is not allowed.
  *      * To use the **bpf_spin_lock**\ () helper, the BTF description
  *        of the map value must be a struct and have **struct
  *        bpf_spin_lock** *anyname*\ **;** field at the top level.
  *        Nested lock inside another struct is not allowed.
  *      * The **struct bpf_spin_lock** *lock* field in a map value must
  *        be aligned on a multiple of 4 bytes in that value.
  *      * Syscall with command **BPF_MAP_LOOKUP_ELEM** does not copy
  *        the **bpf_spin_lock** field to user space.
  *      * Syscall with command **BPF_MAP_UPDATE_ELEM**, or update from
  *        a BPF program, do not update the **bpf_spin_lock** field.
  *      * **bpf_spin_lock** cannot be on the stack or inside a
  *        networking packet (it can only be inside of a map values).
  *      * **bpf_spin_lock** is available to root only.
  *      * Tracing programs and socket filter programs cannot use
  *        **bpf_spin_lock**\ () due to insufficient preemption checks
  *        (but this may change in the future).
  *      * **bpf_spin_lock** is not allowed in inner maps of map-in-map.
  *  Return
  *      0
  *
  * long bpf_spin_unlock(struct bpf_spin_lock *lock)
  *  Description
  *      Release the *lock* previously locked by a call to
  *      **bpf_spin_lock**\ (\ *lock*\ ).
  *  Return
  *      0
  *
  * struct bpf_sock *bpf_sk_fullsock(struct bpf_sock *sk)
  *  Description
  *      This helper gets a **struct bpf_sock** pointer such
  *      that all the fields in this **bpf_sock** can be accessed.
  *  Return
  *      A **struct bpf_sock** pointer on success, or **NULL** in
  *      case of failure.
  *
  * struct bpf_tcp_sock *bpf_tcp_sock(struct bpf_sock *sk)
  *  Description
  *      This helper gets a **struct bpf_tcp_sock** pointer from a
  *      **struct bpf_sock** pointer.
  *  Return
  *      A **struct bpf_tcp_sock** pointer on success, or **NULL** in
  *      case of failure.
  *
  * long bpf_skb_ecn_set_ce(struct sk_buff *skb)
  *  Description
  *      Set ECN (Explicit Congestion Notification) field of IP header
  *      to **CE** (Congestion Encountered) if current value is **ECT**
  *      (ECN Capable Transport). Otherwise, do nothing. Works with IPv6
  *      and IPv4.
  *  Return
  *      1 if the **CE** flag is set (either by the current helper call
  *      or because it was already present), 0 if it is not set.
  *
  * struct bpf_sock *bpf_get_listener_sock(struct bpf_sock *sk)
  *  Description
  *      Return a **struct bpf_sock** pointer in **TCP_LISTEN** state.
  *      **bpf_sk_release**\ () is unnecessary and not allowed.
  *  Return
  *      A **struct bpf_sock** pointer on success, or **NULL** in
  *      case of failure.
  *
  * struct bpf_sock *bpf_skc_lookup_tcp(void *ctx, struct bpf_sock_tuple *tuple, u32 tuple_size, u64 netns, u64 flags)
  *  Description
  *      Look for TCP socket matching *tuple*, optionally in a child
  *      network namespace *netns*. The return value must be checked,
  *      and if non-**NULL**, released via **bpf_sk_release**\ ().
  *
  *      This function is identical to **bpf_sk_lookup_tcp**\ (), except
  *      that it also returns timewait or request sockets. Use
  *      **bpf_sk_fullsock**\ () or **bpf_tcp_sock**\ () to access the
  *      full structure.
  *
  *      This helper is available only if the kernel was compiled with
  *      **CONFIG_NET** configuration option.
  *  Return
  *      Pointer to **struct bpf_sock**, or **NULL** in case of failure.
  *      For sockets with reuseport option, the **struct bpf_sock**
  *      result is from *reuse*\ **->socks**\ [] using the hash of the
  *      tuple.
  *
  * long bpf_tcp_check_syncookie(void *sk, void *iph, u32 iph_len, struct tcphdr *th, u32 th_len)
  *  Description
  *      Check whether *iph* and *th* contain a valid SYN cookie ACK for
  *      the listening socket in *sk*.
  *
  *      *iph* points to the start of the IPv4 or IPv6 header, while
  *      *iph_len* contains **sizeof**\ (**struct iphdr**) or
  *      **sizeof**\ (**struct ipv6hdr**).
  *
  *      *th* points to the start of the TCP header, while *th_len*
  *      contains the length of the TCP header (at least
  *      **sizeof**\ (**struct tcphdr**)).
  *  Return
  *      0 if *iph* and *th* are a valid SYN cookie ACK, or a negative
  *      error otherwise.
  *
  * long bpf_sysctl_get_name(struct bpf_sysctl *ctx, char *buf, size_t buf_len, u64 flags)
  *  Description
  *      Get name of sysctl in /proc/sys/ and copy it into provided by
  *      program buffer *buf* of size *buf_len*.
  *
  *      The buffer is always NUL terminated, unless it's zero-sized.
  *
  *      If *flags* is zero, full name (e.g. "net/ipv4/tcp_mem") is
  *      copied. Use **BPF_F_SYSCTL_BASE_NAME** flag to copy base name
  *      only (e.g. "tcp_mem").
  *  Return
  *      Number of character copied (not including the trailing NUL).
  *
  *      **-E2BIG** if the buffer wasn't big enough (*buf* will contain
  *      truncated name in this case).
  *
  * long bpf_sysctl_get_current_value(struct bpf_sysctl *ctx, char *buf, size_t buf_len)
  *  Description
  *      Get current value of sysctl as it is presented in /proc/sys
  *      (incl. newline, etc), and copy it as a string into provided
  *      by program buffer *buf* of size *buf_len*.
  *
  *      The whole value is copied, no matter what file position user
  *      space issued e.g. sys_read at.
  *
  *      The buffer is always NUL terminated, unless it's zero-sized.
  *  Return
  *      Number of character copied (not including the trailing NUL).
  *
  *      **-E2BIG** if the buffer wasn't big enough (*buf* will contain
  *      truncated name in this case).
  *
  *      **-EINVAL** if current value was unavailable, e.g. because
  *      sysctl is uninitialized and read returns -EIO for it.
  *
  * long bpf_sysctl_get_new_value(struct bpf_sysctl *ctx, char *buf, size_t buf_len)
  *  Description
  *      Get new value being written by user space to sysctl (before
  *      the actual write happens) and copy it as a string into
  *      provided by program buffer *buf* of size *buf_len*.
  *
  *      User space may write new value at file position > 0.
  *
  *      The buffer is always NUL terminated, unless it's zero-sized.
  *  Return
  *      Number of character copied (not including the trailing NUL).
  *
  *      **-E2BIG** if the buffer wasn't big enough (*buf* will contain
  *      truncated name in this case).
  *
  *      **-EINVAL** if sysctl is being read.
  *
  * long bpf_sysctl_set_new_value(struct bpf_sysctl *ctx, const char *buf, size_t buf_len)
  *  Description
  *      Override new value being written by user space to sysctl with
  *      value provided by program in buffer *buf* of size *buf_len*.
  *
  *      *buf* should contain a string in same form as provided by user
  *      space on sysctl write.
  *
  *      User space may write new value at file position > 0. To override
  *      the whole sysctl value file position should be set to zero.
  *  Return
  *      0 on success.
  *
  *      **-E2BIG** if the *buf_len* is too big.
  *
  *      **-EINVAL** if sysctl is being read.
  *
  * long bpf_strtol(const char *buf, size_t buf_len, u64 flags, long *res)
  *  Description
  *      Convert the initial part of the string from buffer *buf* of
  *      size *buf_len* to a long integer according to the given base
  *      and save the result in *res*.
  *
  *      The string may begin with an arbitrary amount of white space
  *      (as determined by **isspace**\ (3)) followed by a single
  *      optional '**-**' sign.
  *
  *      Five least significant bits of *flags* encode base, other bits
  *      are currently unused.
  *
  *      Base must be either 8, 10, 16 or 0 to detect it automatically
  *      similar to user space **strtol**\ (3).
  *  Return
  *      Number of characters consumed on success. Must be positive but
  *      no more than *buf_len*.
  *
  *      **-EINVAL** if no valid digits were found or unsupported base
  *      was provided.
  *
  *      **-ERANGE** if resulting value was out of range.
  *
  * long bpf_strtoul(const char *buf, size_t buf_len, u64 flags, unsigned long *res)
  *  Description
  *      Convert the initial part of the string from buffer *buf* of
  *      size *buf_len* to an unsigned long integer according to the
  *      given base and save the result in *res*.
  *
  *      The string may begin with an arbitrary amount of white space
  *      (as determined by **isspace**\ (3)).
  *
  *      Five least significant bits of *flags* encode base, other bits
  *      are currently unused.
  *
  *      Base must be either 8, 10, 16 or 0 to detect it automatically
  *      similar to user space **strtoul**\ (3).
  *  Return
  *      Number of characters consumed on success. Must be positive but
  *      no more than *buf_len*.
  *
  *      **-EINVAL** if no valid digits were found or unsupported base
  *      was provided.
  *
  *      **-ERANGE** if resulting value was out of range.
  *
  * void *bpf_sk_storage_get(struct bpf_map *map, void *sk, void *value, u64 flags)
  *  Description
  *      Get a bpf-local-storage from a *sk*.
  *
  *      Logically, it could be thought of getting the value from
  *      a *map* with *sk* as the **key**.  From this
  *      perspective,  the usage is not much different from
  *      **bpf_map_lookup_elem**\ (*map*, **&**\ *sk*) except this
  *      helper enforces the key must be a full socket and the map must
  *      be a **BPF_MAP_TYPE_SK_STORAGE** also.
  *
  *      Underneath, the value is stored locally at *sk* instead of
  *      the *map*.  The *map* is used as the bpf-local-storage
  *      "type". The bpf-local-storage "type" (i.e. the *map*) is
  *      searched against all bpf-local-storages residing at *sk*.
  *
  *      *sk* is a kernel **struct sock** pointer for LSM program.
  *      *sk* is a **struct bpf_sock** pointer for other program types.
  *
  *      An optional *flags* (**BPF_SK_STORAGE_GET_F_CREATE**) can be
  *      used such that a new bpf-local-storage will be
  *      created if one does not exist.  *value* can be used
  *      together with **BPF_SK_STORAGE_GET_F_CREATE** to specify
  *      the initial value of a bpf-local-storage.  If *value* is
  *      **NULL**, the new bpf-local-storage will be zero initialized.
  *  Return
  *      A bpf-local-storage pointer is returned on success.
  *
  *      **NULL** if not found or there was an error in adding
  *      a new bpf-local-storage.
  *
  * long bpf_sk_storage_delete(struct bpf_map *map, void *sk)
  *  Description
  *      Delete a bpf-local-storage from a *sk*.
  *  Return
  *      0 on success.
  *
  *      **-ENOENT** if the bpf-local-storage cannot be found.
  *      **-EINVAL** if sk is not a fullsock (e.g. a request_sock).
  *
  * long bpf_send_signal(u32 sig)
  *  Description
  *      Send signal *sig* to the process of the current task.
  *      The signal may be delivered to any of this process's threads.
  *  Return
  *      0 on success or successfully queued.
  *
  *      **-EBUSY** if work queue under nmi is full.
  *
  *      **-EINVAL** if *sig* is invalid.
  *
  *      **-EPERM** if no permission to send the *sig*.
  *
  *      **-EAGAIN** if bpf program can try again.
  *
  * s64 bpf_tcp_gen_syncookie(void *sk, void *iph, u32 iph_len, struct tcphdr *th, u32 th_len)
  *  Description
  *      Try to issue a SYN cookie for the packet with corresponding
  *      IP/TCP headers, *iph* and *th*, on the listening socket in *sk*.
  *
  *      *iph* points to the start of the IPv4 or IPv6 header, while
  *      *iph_len* contains **sizeof**\ (**struct iphdr**) or
  *      **sizeof**\ (**struct ipv6hdr**).
  *
  *      *th* points to the start of the TCP header, while *th_len*
  *      contains the length of the TCP header with options (at least
  *      **sizeof**\ (**struct tcphdr**)).
  *  Return
  *      On success, lower 32 bits hold the generated SYN cookie in
  *      followed by 16 bits which hold the MSS value for that cookie,
  *      and the top 16 bits are unused.
  *
  *      On failure, the returned value is one of the following:
  *
  *      **-EINVAL** SYN cookie cannot be issued due to error
  *
  *      **-ENOENT** SYN cookie should not be issued (no SYN flood)
  *
  *      **-EOPNOTSUPP** kernel configuration does not enable SYN cookies
  *
  *      **-EPROTONOSUPPORT** IP packet version is not 4 or 6
  *
  * long bpf_skb_output(void *ctx, struct bpf_map *map, u64 flags, void *data, u64 size)
  *  Description
  *      Write raw *data* blob into a special BPF perf event held by
  *      *map* of type **BPF_MAP_TYPE_PERF_EVENT_ARRAY**. This perf
  *      event must have the following attributes: **PERF_SAMPLE_RAW**
  *      as **sample_type**, **PERF_TYPE_SOFTWARE** as **type**, and
  *      **PERF_COUNT_SW_BPF_OUTPUT** as **config**.
  *
  *      The *flags* are used to indicate the index in *map* for which
  *      the value must be put, masked with **BPF_F_INDEX_MASK**.
  *      Alternatively, *flags* can be set to **BPF_F_CURRENT_CPU**
  *      to indicate that the index of the current CPU core should be
  *      used.
  *
  *      The value to write, of *size*, is passed through eBPF stack and
  *      pointed by *data*.
  *
  *      *ctx* is a pointer to in-kernel struct sk_buff.
  *
  *      This helper is similar to **bpf_perf_event_output**\ () but
  *      restricted to raw_tracepoint bpf programs.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * long bpf_probe_read_user(void *dst, u32 size, const void *unsafe_ptr)
  *  Description
  *      Safely attempt to read *size* bytes from user space address
  *      *unsafe_ptr* and store the data in *dst*.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * long bpf_probe_read_kernel(void *dst, u32 size, const void *unsafe_ptr)
  *  Description
  *      Safely attempt to read *size* bytes from kernel space address
  *      *unsafe_ptr* and store the data in *dst*.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * long bpf_probe_read_user_str(void *dst, u32 size, const void *unsafe_ptr)
  *  Description
  *      Copy a NUL terminated string from an unsafe user address
  *      *unsafe_ptr* to *dst*. The *size* should include the
  *      terminating NUL byte. In case the string length is smaller than
  *      *size*, the target is not padded with further NUL bytes. If the
  *      string length is larger than *size*, just *size*-1 bytes are
  *      copied and the last byte is set to NUL.
  *
  *      On success, returns the number of bytes that were written,
  *      including the terminal NUL. This makes this helper useful in
  *      tracing programs for reading strings, and more importantly to
  *      get its length at runtime. See the following snippet:
  *
  *      ::
  *
  *          SEC("kprobe/sys_open")
  *          void bpf_sys_open(struct pt_regs *ctx)
  *          {
  *                  char buf[PATHLEN]; // PATHLEN is defined to 256
  *                  int res = bpf_probe_read_user_str(buf, sizeof(buf),
  *                                                ctx->di);
  *
  *              // Consume buf, for example push it to
  *              // userspace via bpf_perf_event_output(); we
  *              // can use res (the string length) as event
  *              // size, after checking its boundaries.
  *          }
  *
  *      In comparison, using **bpf_probe_read_user**\ () helper here
  *      instead to read the string would require to estimate the length
  *      at compile time, and would often result in copying more memory
  *      than necessary.
  *
  *      Another useful use case is when parsing individual process
  *      arguments or individual environment variables navigating
  *      *current*\ **->mm->arg_start** and *current*\
  *      **->mm->env_start**: using this helper and the return value,
  *      one can quickly iterate at the right offset of the memory area.
  *  Return
  *      On success, the strictly positive length of the output string,
  *      including the trailing NUL character. On error, a negative
  *      value.
  *
  * long bpf_probe_read_kernel_str(void *dst, u32 size, const void *unsafe_ptr)
  *  Description
  *      Copy a NUL terminated string from an unsafe kernel address *unsafe_ptr*
  *      to *dst*. Same semantics as with **bpf_probe_read_user_str**\ () apply.
  *  Return
  *      On success, the strictly positive length of the string, including
  *      the trailing NUL character. On error, a negative value.
  *
  * long bpf_tcp_send_ack(void *tp, u32 rcv_nxt)
  *  Description
  *      Send out a tcp-ack. *tp* is the in-kernel struct **tcp_sock**.
  *      *rcv_nxt* is the ack_seq to be sent out.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * long bpf_send_signal_thread(u32 sig)
  *  Description
  *      Send signal *sig* to the thread corresponding to the current task.
  *  Return
  *      0 on success or successfully queued.
  *
  *      **-EBUSY** if work queue under nmi is full.
  *
  *      **-EINVAL** if *sig* is invalid.
  *
  *      **-EPERM** if no permission to send the *sig*.
  *
  *      **-EAGAIN** if bpf program can try again.
  *
  * u64 bpf_jiffies64(void)
  *  Description
  *      Obtain the 64bit jiffies
  *  Return
  *      The 64 bit jiffies
  *
  * long bpf_read_branch_records(struct bpf_perf_event_data *ctx, void *buf, u32 size, u64 flags)
  *  Description
  *      For an eBPF program attached to a perf event, retrieve the
  *      branch records (**struct perf_branch_entry**) associated to *ctx*
  *      and store it in the buffer pointed by *buf* up to size
  *      *size* bytes.
  *  Return
  *      On success, number of bytes written to *buf*. On error, a
  *      negative value.
  *
  *      The *flags* can be set to **BPF_F_GET_BRANCH_RECORDS_SIZE** to
  *      instead return the number of bytes required to store all the
  *      branch entries. If this flag is set, *buf* may be NULL.
  *
  *      **-EINVAL** if arguments invalid or **size** not a multiple
  *      of **sizeof**\ (**struct perf_branch_entry**\ ).
  *
  *      **-ENOENT** if architecture does not support branch records.
  *
  * long bpf_get_ns_current_pid_tgid(u64 dev, u64 ino, struct bpf_pidns_info *nsdata, u32 size)
  *  Description
  *      Returns 0 on success, values for *pid* and *tgid* as seen from the current
  *      *namespace* will be returned in *nsdata*.
  *  Return
  *      0 on success, or one of the following in case of failure:
  *
  *      **-EINVAL** if dev and inum supplied don't match dev_t and inode number
  *              with nsfs of current task, or if dev conversion to dev_t lost high bits.
  *
  *      **-ENOENT** if pidns does not exists for the current task.
  *
  * long bpf_xdp_output(void *ctx, struct bpf_map *map, u64 flags, void *data, u64 size)
  *  Description
  *      Write raw *data* blob into a special BPF perf event held by
  *      *map* of type **BPF_MAP_TYPE_PERF_EVENT_ARRAY**. This perf
  *      event must have the following attributes: **PERF_SAMPLE_RAW**
  *      as **sample_type**, **PERF_TYPE_SOFTWARE** as **type**, and
  *      **PERF_COUNT_SW_BPF_OUTPUT** as **config**.
  *
  *      The *flags* are used to indicate the index in *map* for which
  *      the value must be put, masked with **BPF_F_INDEX_MASK**.
  *      Alternatively, *flags* can be set to **BPF_F_CURRENT_CPU**
  *      to indicate that the index of the current CPU core should be
  *      used.
  *
  *      The value to write, of *size*, is passed through eBPF stack and
  *      pointed by *data*.
  *
  *      *ctx* is a pointer to in-kernel struct xdp_buff.
  *
  *      This helper is similar to **bpf_perf_eventoutput**\ () but
  *      restricted to raw_tracepoint bpf programs.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * u64 bpf_get_netns_cookie(void *ctx)
  *  Description
  *      Retrieve the cookie (generated by the kernel) of the network
  *      namespace the input *ctx* is associated with. The network
  *      namespace cookie remains stable for its lifetime and provides
  *      a global identifier that can be assumed unique. If *ctx* is
  *      NULL, then the helper returns the cookie for the initial
  *      network namespace. The cookie itself is very similar to that
  *      of **bpf_get_socket_cookie**\ () helper, but for network
  *      namespaces instead of sockets.
  *  Return
  *      A 8-byte long opaque number.
  *
  * u64 bpf_get_current_ancestor_cgroup_id(int ancestor_level)
  *  Description
  *      Return id of cgroup v2 that is ancestor of the cgroup associated
  *      with the current task at the *ancestor_level*. The root cgroup
  *      is at *ancestor_level* zero and each step down the hierarchy
  *      increments the level. If *ancestor_level* == level of cgroup
  *      associated with the current task, then return value will be the
  *      same as that of **bpf_get_current_cgroup_id**\ ().
  *
  *      The helper is useful to implement policies based on cgroups
  *      that are upper in hierarchy than immediate cgroup associated
  *      with the current task.
  *
  *      The format of returned id and helper limitations are same as in
  *      **bpf_get_current_cgroup_id**\ ().
  *  Return
  *      The id is returned or 0 in case the id could not be retrieved.
  *
  * long bpf_sk_assign(struct sk_buff *skb, void *sk, u64 flags)
  *  Description
  *      Helper is overloaded depending on BPF program type. This
  *      description applies to **BPF_PROG_TYPE_SCHED_CLS** and
  *      **BPF_PROG_TYPE_SCHED_ACT** programs.
  *
  *      Assign the *sk* to the *skb*. When combined with appropriate
  *      routing configuration to receive the packet towards the socket,
  *      will cause *skb* to be delivered to the specified socket.
  *      Subsequent redirection of *skb* via  **bpf_redirect**\ (),
  *      **bpf_clone_redirect**\ () or other methods outside of BPF may
  *      interfere with successful delivery to the socket.
  *
  *      This operation is only valid from TC ingress path.
  *
  *      The *flags* argument must be zero.
  *  Return
  *      0 on success, or a negative error in case of failure:
  *
  *      **-EINVAL** if specified *flags* are not supported.
  *
  *      **-ENOENT** if the socket is unavailable for assignment.
  *
  *      **-ENETUNREACH** if the socket is unreachable (wrong netns).
  *
  *      **-EOPNOTSUPP** if the operation is not supported, for example
  *      a call from outside of TC ingress.
  *
  *      **-ESOCKTNOSUPPORT** if the socket type is not supported
  *      (reuseport).
  *
  * long bpf_sk_assign(struct bpf_sk_lookup *ctx, struct bpf_sock *sk, u64 flags)
  *  Description
  *      Helper is overloaded depending on BPF program type. This
  *      description applies to **BPF_PROG_TYPE_SK_LOOKUP** programs.
  *
  *      Select the *sk* as a result of a socket lookup.
  *
  *      For the operation to succeed passed socket must be compatible
  *      with the packet description provided by the *ctx* object.
  *
  *      L4 protocol (**IPPROTO_TCP** or **IPPROTO_UDP**) must
  *      be an exact match. While IP family (**AF_INET** or
  *      **AF_INET6**) must be compatible, that is IPv6 sockets
  *      that are not v6-only can be selected for IPv4 packets.
  *
  *      Only TCP listeners and UDP unconnected sockets can be
  *      selected. *sk* can also be NULL to reset any previous
  *      selection.
  *
  *      *flags* argument can combination of following values:
  *
  *      * **BPF_SK_LOOKUP_F_REPLACE** to override the previous
  *        socket selection, potentially done by a BPF program
  *        that ran before us.
  *
  *      * **BPF_SK_LOOKUP_F_NO_REUSEPORT** to skip
  *        load-balancing within reuseport group for the socket
  *        being selected.
  *
  *      On success *ctx->sk* will point to the selected socket.
  *
  *  Return
  *      0 on success, or a negative errno in case of failure.
  *
  *      * **-EAFNOSUPPORT** if socket family (*sk->family*) is
  *        not compatible with packet family (*ctx->family*).
  *
  *      * **-EEXIST** if socket has been already selected,
  *        potentially by another program, and
  *        **BPF_SK_LOOKUP_F_REPLACE** flag was not specified.
  *
  *      * **-EINVAL** if unsupported flags were specified.
  *
  *      * **-EPROTOTYPE** if socket L4 protocol
  *        (*sk->protocol*) doesn't match packet protocol
  *        (*ctx->protocol*).
  *
  *      * **-ESOCKTNOSUPPORT** if socket is not in allowed
  *        state (TCP listening or UDP unconnected).
  *
  * u64 bpf_ktime_get_boot_ns(void)
  *  Description
  *      Return the time elapsed since system boot, in nanoseconds.
  *      Does include the time the system was suspended.
  *      See: **clock_gettime**\ (**CLOCK_BOOTTIME**)
  *  Return
  *      Current *ktime*.
  *
  * long bpf_seq_printf(struct seq_file *m, const char *fmt, u32 fmt_size, const void *data, u32 data_len)
  *  Description
  *      **bpf_seq_printf**\ () uses seq_file **seq_printf**\ () to print
  *      out the format string.
  *      The *m* represents the seq_file. The *fmt* and *fmt_size* are for
  *      the format string itself. The *data* and *data_len* are format string
  *      arguments. The *data* are a **u64** array and corresponding format string
  *      values are stored in the array. For strings and pointers where pointees
  *      are accessed, only the pointer values are stored in the *data* array.
  *      The *data_len* is the size of *data* in bytes - must be a multiple of 8.
  *
  *      Formats **%s**, **%p{i,I}{4,6}** requires to read kernel memory.
  *      Reading kernel memory may fail due to either invalid address or
  *      valid address but requiring a major memory fault. If reading kernel memory
  *      fails, the string for **%s** will be an empty string, and the ip
  *      address for **%p{i,I}{4,6}** will be 0. Not returning error to
  *      bpf program is consistent with what **bpf_trace_printk**\ () does for now.
  *  Return
  *      0 on success, or a negative error in case of failure:
  *
  *      **-EBUSY** if per-CPU memory copy buffer is busy, can try again
  *      by returning 1 from bpf program.
  *
  *      **-EINVAL** if arguments are invalid, or if *fmt* is invalid/unsupported.
  *
  *      **-E2BIG** if *fmt* contains too many format specifiers.
  *
  *      **-EOVERFLOW** if an overflow happened: The same object will be tried again.
  *
  * long bpf_seq_write(struct seq_file *m, const void *data, u32 len)
  *  Description
  *      **bpf_seq_write**\ () uses seq_file **seq_write**\ () to write the data.
  *      The *m* represents the seq_file. The *data* and *len* represent the
  *      data to write in bytes.
  *  Return
  *      0 on success, or a negative error in case of failure:
  *
  *      **-EOVERFLOW** if an overflow happened: The same object will be tried again.
  *
  * u64 bpf_sk_cgroup_id(void *sk)
  *  Description
  *      Return the cgroup v2 id of the socket *sk*.
  *
  *      *sk* must be a non-**NULL** pointer to a socket, e.g. one
  *      returned from **bpf_sk_lookup_xxx**\ (),
  *      **bpf_sk_fullsock**\ (), etc. The format of returned id is
  *      same as in **bpf_skb_cgroup_id**\ ().
  *
  *      This helper is available only if the kernel was compiled with
  *      the **CONFIG_SOCK_CGROUP_DATA** configuration option.
  *  Return
  *      The id is returned or 0 in case the id could not be retrieved.
  *
  * u64 bpf_sk_ancestor_cgroup_id(void *sk, int ancestor_level)
  *  Description
  *      Return id of cgroup v2 that is ancestor of cgroup associated
  *      with the *sk* at the *ancestor_level*.  The root cgroup is at
  *      *ancestor_level* zero and each step down the hierarchy
  *      increments the level. If *ancestor_level* == level of cgroup
  *      associated with *sk*, then return value will be same as that
  *      of **bpf_sk_cgroup_id**\ ().
  *
  *      The helper is useful to implement policies based on cgroups
  *      that are upper in hierarchy than immediate cgroup associated
  *      with *sk*.
  *
  *      The format of returned id and helper limitations are same as in
  *      **bpf_sk_cgroup_id**\ ().
  *  Return
  *      The id is returned or 0 in case the id could not be retrieved.
  *
  * long bpf_ringbuf_output(void *ringbuf, void *data, u64 size, u64 flags)
  *  Description
  *      Copy *size* bytes from *data* into a ring buffer *ringbuf*.
  *      If **BPF_RB_NO_WAKEUP** is specified in *flags*, no notification
  *      of new data availability is sent.
  *      If **BPF_RB_FORCE_WAKEUP** is specified in *flags*, notification
  *      of new data availability is sent unconditionally.
  *      If **0** is specified in *flags*, an adaptive notification
  *      of new data availability is sent.
  *
  *      An adaptive notification is a notification sent whenever the user-space
  *      process has caught up and consumed all available payloads. In case the user-space
  *      process is still processing a previous payload, then no notification is needed
  *      as it will process the newly added payload automatically.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * void *bpf_ringbuf_reserve(void *ringbuf, u64 size, u64 flags)
  *  Description
  *      Reserve *size* bytes of payload in a ring buffer *ringbuf*.
  *      *flags* must be 0.
  *  Return
  *      Valid pointer with *size* bytes of memory available; NULL,
  *      otherwise.
  *
  * void bpf_ringbuf_submit(void *data, u64 flags)
  *  Description
  *      Submit reserved ring buffer sample, pointed to by *data*.
  *      If **BPF_RB_NO_WAKEUP** is specified in *flags*, no notification
  *      of new data availability is sent.
  *      If **BPF_RB_FORCE_WAKEUP** is specified in *flags*, notification
  *      of new data availability is sent unconditionally.
  *      If **0** is specified in *flags*, an adaptive notification
  *      of new data availability is sent.
  *
  *      See 'bpf_ringbuf_output()' for the definition of adaptive notification.
  *  Return
  *      Nothing. Always succeeds.
  *
  * void bpf_ringbuf_discard(void *data, u64 flags)
  *  Description
  *      Discard reserved ring buffer sample, pointed to by *data*.
  *      If **BPF_RB_NO_WAKEUP** is specified in *flags*, no notification
  *      of new data availability is sent.
  *      If **BPF_RB_FORCE_WAKEUP** is specified in *flags*, notification
  *      of new data availability is sent unconditionally.
  *      If **0** is specified in *flags*, an adaptive notification
  *      of new data availability is sent.
  *
  *      See 'bpf_ringbuf_output()' for the definition of adaptive notification.
  *  Return
  *      Nothing. Always succeeds.
  *
  * u64 bpf_ringbuf_query(void *ringbuf, u64 flags)
  *  Description
  *      Query various characteristics of provided ring buffer. What
  *      exactly is queries is determined by *flags*:
  *
  *      * **BPF_RB_AVAIL_DATA**: Amount of data not yet consumed.
  *      * **BPF_RB_RING_SIZE**: The size of ring buffer.
  *      * **BPF_RB_CONS_POS**: Consumer position (can wrap around).
  *      * **BPF_RB_PROD_POS**: Producer(s) position (can wrap around).
  *
  *      Data returned is just a momentary snapshot of actual values
  *      and could be inaccurate, so this facility should be used to
  *      power heuristics and for reporting, not to make 100% correct
  *      calculation.
  *  Return
  *      Requested value, or 0, if *flags* are not recognized.
  *
  * long bpf_csum_level(struct sk_buff *skb, u64 level)
  *  Description
  *      Change the skbs checksum level by one layer up or down, or
  *      reset it entirely to none in order to have the stack perform
  *      checksum validation. The level is applicable to the following
  *      protocols: TCP, UDP, GRE, SCTP, FCOE. For example, a decap of
  *      | ETH | IP | UDP | GUE | IP | TCP | into | ETH | IP | TCP |
  *      through **bpf_skb_adjust_room**\ () helper with passing in
  *      **BPF_F_ADJ_ROOM_NO_CSUM_RESET** flag would require one call
  *      to **bpf_csum_level**\ () with **BPF_CSUM_LEVEL_DEC** since
  *      the UDP header is removed. Similarly, an encap of the latter
  *      into the former could be accompanied by a helper call to
  *      **bpf_csum_level**\ () with **BPF_CSUM_LEVEL_INC** if the
  *      skb is still intended to be processed in higher layers of the
  *      stack instead of just egressing at tc.
  *
  *      There are three supported level settings at this time:
  *
  *      * **BPF_CSUM_LEVEL_INC**: Increases skb->csum_level for skbs
  *        with CHECKSUM_UNNECESSARY.
  *      * **BPF_CSUM_LEVEL_DEC**: Decreases skb->csum_level for skbs
  *        with CHECKSUM_UNNECESSARY.
  *      * **BPF_CSUM_LEVEL_RESET**: Resets skb->csum_level to 0 and
  *        sets CHECKSUM_NONE to force checksum validation by the stack.
  *      * **BPF_CSUM_LEVEL_QUERY**: No-op, returns the current
  *        skb->csum_level.
  *  Return
  *      0 on success, or a negative error in case of failure. In the
  *      case of **BPF_CSUM_LEVEL_QUERY**, the current skb->csum_level
  *      is returned or the error code -EACCES in case the skb is not
  *      subject to CHECKSUM_UNNECESSARY.
  *
  * struct tcp6_sock *bpf_skc_to_tcp6_sock(void *sk)
  *  Description
  *      Dynamically cast a *sk* pointer to a *tcp6_sock* pointer.
  *  Return
  *      *sk* if casting is valid, or **NULL** otherwise.
  *
  * struct tcp_sock *bpf_skc_to_tcp_sock(void *sk)
  *  Description
  *      Dynamically cast a *sk* pointer to a *tcp_sock* pointer.
  *  Return
  *      *sk* if casting is valid, or **NULL** otherwise.
  *
  * struct tcp_timewait_sock *bpf_skc_to_tcp_timewait_sock(void *sk)
  *  Description
  *      Dynamically cast a *sk* pointer to a *tcp_timewait_sock* pointer.
  *  Return
  *      *sk* if casting is valid, or **NULL** otherwise.
  *
  * struct tcp_request_sock *bpf_skc_to_tcp_request_sock(void *sk)
  *  Description
  *      Dynamically cast a *sk* pointer to a *tcp_request_sock* pointer.
  *  Return
  *      *sk* if casting is valid, or **NULL** otherwise.
  *
  * struct udp6_sock *bpf_skc_to_udp6_sock(void *sk)
  *  Description
  *      Dynamically cast a *sk* pointer to a *udp6_sock* pointer.
  *  Return
  *      *sk* if casting is valid, or **NULL** otherwise.
  *
  * long bpf_get_task_stack(struct task_struct *task, void *buf, u32 size, u64 flags)
  *  Description
  *      Return a user or a kernel stack in bpf program provided buffer.
  *      To achieve this, the helper needs *task*, which is a valid
  *      pointer to **struct task_struct**. To store the stacktrace, the
  *      bpf program provides *buf* with a nonnegative *size*.
  *
  *      The last argument, *flags*, holds the number of stack frames to
  *      skip (from 0 to 255), masked with
  *      **BPF_F_SKIP_FIELD_MASK**. The next bits can be used to set
  *      the following flags:
  *
  *      **BPF_F_USER_STACK**
  *          Collect a user space stack instead of a kernel stack.
  *      **BPF_F_USER_BUILD_ID**
  *          Collect buildid+offset instead of ips for user stack,
  *          only valid if **BPF_F_USER_STACK** is also specified.
  *
  *      **bpf_get_task_stack**\ () can collect up to
  *      **PERF_MAX_STACK_DEPTH** both kernel and user frames, subject
  *      to sufficient large buffer size. Note that
  *      this limit can be controlled with the **sysctl** program, and
  *      that it should be manually increased in order to profile long
  *      user stacks (such as stacks for Java programs). To do so, use:
  *
  *      ::
  *
  *          # sysctl kernel.perf_event_max_stack=<new value>
  *  Return
  *      The non-negative copied *buf* length equal to or less than
  *      *size* on success, or a negative error in case of failure.
  *
  * long bpf_load_hdr_opt(struct bpf_sock_ops *skops, void *searchby_res, u32 len, u64 flags)
  *  Description
  *      Load header option.  Support reading a particular TCP header
  *      option for bpf program (**BPF_PROG_TYPE_SOCK_OPS**).
  *
  *      If *flags* is 0, it will search the option from the
  *      *skops*\ **->skb_data**.  The comment in **struct bpf_sock_ops**
  *      has details on what skb_data contains under different
  *      *skops*\ **->op**.
  *
  *      The first byte of the *searchby_res* specifies the
  *      kind that it wants to search.
  *
  *      If the searching kind is an experimental kind
  *      (i.e. 253 or 254 according to RFC6994).  It also
  *      needs to specify the "magic" which is either
  *      2 bytes or 4 bytes.  It then also needs to
  *      specify the size of the magic by using
  *      the 2nd byte which is "kind-length" of a TCP
  *      header option and the "kind-length" also
  *      includes the first 2 bytes "kind" and "kind-length"
  *      itself as a normal TCP header option also does.
  *
  *      For example, to search experimental kind 254 with
  *      2 byte magic 0xeB9F, the searchby_res should be
  *      [ 254, 4, 0xeB, 0x9F, 0, 0, .... 0 ].
  *
  *      To search for the standard window scale option (3),
  *      the *searchby_res* should be [ 3, 0, 0, .... 0 ].
  *      Note, kind-length must be 0 for regular option.
  *
  *      Searching for No-Op (0) and End-of-Option-List (1) are
  *      not supported.
  *
  *      *len* must be at least 2 bytes which is the minimal size
  *      of a header option.
  *
  *      Supported flags:
  *
  *      * **BPF_LOAD_HDR_OPT_TCP_SYN** to search from the
  *        saved_syn packet or the just-received syn packet.
  *
  *  Return
  *      > 0 when found, the header option is copied to *searchby_res*.
  *      The return value is the total length copied. On failure, a
  *      negative error code is returned:
  *
  *      **-EINVAL** if a parameter is invalid.
  *
  *      **-ENOMSG** if the option is not found.
  *
  *      **-ENOENT** if no syn packet is available when
  *      **BPF_LOAD_HDR_OPT_TCP_SYN** is used.
  *
  *      **-ENOSPC** if there is not enough space.  Only *len* number of
  *      bytes are copied.
  *
  *      **-EFAULT** on failure to parse the header options in the
  *      packet.
  *
  *      **-EPERM** if the helper cannot be used under the current
  *      *skops*\ **->op**.
  *
  * long bpf_store_hdr_opt(struct bpf_sock_ops *skops, const void *from, u32 len, u64 flags)
  *  Description
  *      Store header option.  The data will be copied
  *      from buffer *from* with length *len* to the TCP header.
  *
  *      The buffer *from* should have the whole option that
  *      includes the kind, kind-length, and the actual
  *      option data.  The *len* must be at least kind-length
  *      long.  The kind-length does not have to be 4 byte
  *      aligned.  The kernel will take care of the padding
  *      and setting the 4 bytes aligned value to th->doff.
  *
  *      This helper will check for duplicated option
  *      by searching the same option in the outgoing skb.
  *
  *      This helper can only be called during
  *      **BPF_SOCK_OPS_WRITE_HDR_OPT_CB**.
  *
  *  Return
  *      0 on success, or negative error in case of failure:
  *
  *      **-EINVAL** If param is invalid.
  *
  *      **-ENOSPC** if there is not enough space in the header.
  *      Nothing has been written
  *
  *      **-EEXIST** if the option already exists.
  *
  *      **-EFAULT** on failrue to parse the existing header options.
  *
  *      **-EPERM** if the helper cannot be used under the current
  *      *skops*\ **->op**.
  *
  * long bpf_reserve_hdr_opt(struct bpf_sock_ops *skops, u32 len, u64 flags)
  *  Description
  *      Reserve *len* bytes for the bpf header option.  The
  *      space will be used by **bpf_store_hdr_opt**\ () later in
  *      **BPF_SOCK_OPS_WRITE_HDR_OPT_CB**.
  *
  *      If **bpf_reserve_hdr_opt**\ () is called multiple times,
  *      the total number of bytes will be reserved.
  *
  *      This helper can only be called during
  *      **BPF_SOCK_OPS_HDR_OPT_LEN_CB**.
  *
  *  Return
  *      0 on success, or negative error in case of failure:
  *
  *      **-EINVAL** if a parameter is invalid.
  *
  *      **-ENOSPC** if there is not enough space in the header.
  *
  *      **-EPERM** if the helper cannot be used under the current
  *      *skops*\ **->op**.
  *
  * void *bpf_inode_storage_get(struct bpf_map *map, void *inode, void *value, u64 flags)
  *  Description
  *      Get a bpf_local_storage from an *inode*.
  *
  *      Logically, it could be thought of as getting the value from
  *      a *map* with *inode* as the **key**.  From this
  *      perspective,  the usage is not much different from
  *      **bpf_map_lookup_elem**\ (*map*, **&**\ *inode*) except this
  *      helper enforces the key must be an inode and the map must also
  *      be a **BPF_MAP_TYPE_INODE_STORAGE**.
  *
  *      Underneath, the value is stored locally at *inode* instead of
  *      the *map*.  The *map* is used as the bpf-local-storage
  *      "type". The bpf-local-storage "type" (i.e. the *map*) is
  *      searched against all bpf_local_storage residing at *inode*.
  *
  *      An optional *flags* (**BPF_LOCAL_STORAGE_GET_F_CREATE**) can be
  *      used such that a new bpf_local_storage will be
  *      created if one does not exist.  *value* can be used
  *      together with **BPF_LOCAL_STORAGE_GET_F_CREATE** to specify
  *      the initial value of a bpf_local_storage.  If *value* is
  *      **NULL**, the new bpf_local_storage will be zero initialized.
  *  Return
  *      A bpf_local_storage pointer is returned on success.
  *
  *      **NULL** if not found or there was an error in adding
  *      a new bpf_local_storage.
  *
  * int bpf_inode_storage_delete(struct bpf_map *map, void *inode)
  *  Description
  *      Delete a bpf_local_storage from an *inode*.
  *  Return
  *      0 on success.
  *
  *      **-ENOENT** if the bpf_local_storage cannot be found.
  *
  * long bpf_d_path(struct path *path, char *buf, u32 sz)
  *  Description
  *      Return full path for given **struct path** object, which
  *      needs to be the kernel BTF *path* object. The path is
  *      returned in the provided buffer *buf* of size *sz* and
  *      is zero terminated.
  *
  *  Return
  *      On success, the strictly positive length of the string,
  *      including the trailing NUL character. On error, a negative
  *      value.
  *
  * long bpf_copy_from_user(void *dst, u32 size, const void *user_ptr)
  *  Description
  *      Read *size* bytes from user space address *user_ptr* and store
  *      the data in *dst*. This is a wrapper of **copy_from_user**\ ().
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * long bpf_snprintf_btf(char *str, u32 str_size, struct btf_ptr *ptr, u32 btf_ptr_size, u64 flags)
  *  Description
  *      Use BTF to store a string representation of *ptr*->ptr in *str*,
  *      using *ptr*->type_id.  This value should specify the type
  *      that *ptr*->ptr points to. LLVM __builtin_btf_type_id(type, 1)
  *      can be used to look up vmlinux BTF type ids. Traversing the
  *      data structure using BTF, the type information and values are
  *      stored in the first *str_size* - 1 bytes of *str*.  Safe copy of
  *      the pointer data is carried out to avoid kernel crashes during
  *      operation.  Smaller types can use string space on the stack;
  *      larger programs can use map data to store the string
  *      representation.
  *
  *      The string can be subsequently shared with userspace via
  *      bpf_perf_event_output() or ring buffer interfaces.
  *      bpf_trace_printk() is to be avoided as it places too small
  *      a limit on string size to be useful.
  *
  *      *flags* is a combination of
  *
  *      **BTF_F_COMPACT**
  *          no formatting around type information
  *      **BTF_F_NONAME**
  *          no struct/union member names/types
  *      **BTF_F_PTR_RAW**
  *          show raw (unobfuscated) pointer values;
  *          equivalent to printk specifier %px.
  *      **BTF_F_ZERO**
  *          show zero-valued struct/union members; they
  *          are not displayed by default
  *
  *  Return
  *      The number of bytes that were written (or would have been
  *      written if output had to be truncated due to string size),
  *      or a negative error in cases of failure.
  *
  * long bpf_seq_printf_btf(struct seq_file *m, struct btf_ptr *ptr, u32 ptr_size, u64 flags)
  *  Description
  *      Use BTF to write to seq_write a string representation of
  *      *ptr*->ptr, using *ptr*->type_id as per bpf_snprintf_btf().
  *      *flags* are identical to those used for bpf_snprintf_btf.
  *  Return
  *      0 on success or a negative error in case of failure.
  *
  * u64 bpf_skb_cgroup_classid(struct sk_buff *skb)
  *  Description
  *      See **bpf_get_cgroup_classid**\ () for the main description.
  *      This helper differs from **bpf_get_cgroup_classid**\ () in that
  *      the cgroup v1 net_cls class is retrieved only from the *skb*'s
  *      associated socket instead of the current process.
  *  Return
  *      The id is returned or 0 in case the id could not be retrieved.
  *
  * long bpf_redirect_neigh(u32 ifindex, struct bpf_redir_neigh *params, int plen, u64 flags)
  *  Description
  *      Redirect the packet to another net device of index *ifindex*
  *      and fill in L2 addresses from neighboring subsystem. This helper
  *      is somewhat similar to **bpf_redirect**\ (), except that it
  *      populates L2 addresses as well, meaning, internally, the helper
  *      relies on the neighbor lookup for the L2 address of the nexthop.
  *
  *      The helper will perform a FIB lookup based on the skb's
  *      networking header to get the address of the next hop, unless
  *      this is supplied by the caller in the *params* argument. The
  *      *plen* argument indicates the len of *params* and should be set
  *      to 0 if *params* is NULL.
  *
  *      The *flags* argument is reserved and must be 0. The helper is
  *      currently only supported for tc BPF program types, and enabled
  *      for IPv4 and IPv6 protocols.
  *  Return
  *      The helper returns **TC_ACT_REDIRECT** on success or
  *      **TC_ACT_SHOT** on error.
  *
  * void *bpf_per_cpu_ptr(const void *percpu_ptr, u32 cpu)
  *     Description
  *             Take a pointer to a percpu ksym, *percpu_ptr*, and return a
  *             pointer to the percpu kernel variable on *cpu*. A ksym is an
  *             extern variable decorated with '__ksym'. For ksym, there is a
  *             global var (either static or global) defined of the same name
  *             in the kernel. The ksym is percpu if the global var is percpu.
  *             The returned pointer points to the global percpu var on *cpu*.
  *
  *             bpf_per_cpu_ptr() has the same semantic as per_cpu_ptr() in the
  *             kernel, except that bpf_per_cpu_ptr() may return NULL. This
  *             happens if *cpu* is larger than nr_cpu_ids. The caller of
  *             bpf_per_cpu_ptr() must check the returned value.
  *     Return
  *             A pointer pointing to the kernel percpu variable on *cpu*, or
  *             NULL, if *cpu* is invalid.
  *
  * void *bpf_this_cpu_ptr(const void *percpu_ptr)
  *  Description
  *      Take a pointer to a percpu ksym, *percpu_ptr*, and return a
  *      pointer to the percpu kernel variable on this cpu. See the
  *      description of 'ksym' in **bpf_per_cpu_ptr**\ ().
  *
  *      bpf_this_cpu_ptr() has the same semantic as this_cpu_ptr() in
  *      the kernel. Different from **bpf_per_cpu_ptr**\ (), it would
  *      never return NULL.
  *  Return
  *      A pointer pointing to the kernel percpu variable on this cpu.
  *
  * long bpf_redirect_peer(u32 ifindex, u64 flags)
  *  Description
  *      Redirect the packet to another net device of index *ifindex*.
  *      This helper is somewhat similar to **bpf_redirect**\ (), except
  *      that the redirection happens to the *ifindex*' peer device and
  *      the netns switch takes place from ingress to ingress without
  *      going through the CPU's backlog queue.
  *
  *      The *flags* argument is reserved and must be 0. The helper is
  *      currently only supported for tc BPF program types at the ingress
  *      hook and for veth device types. The peer device must reside in a
  *      different network namespace.
  *  Return
  *      The helper returns **TC_ACT_REDIRECT** on success or
  *      **TC_ACT_SHOT** on error.
  *
  * void *bpf_task_storage_get(struct bpf_map *map, struct task_struct *task, void *value, u64 flags)
  *  Description
  *      Get a bpf_local_storage from the *task*.
  *
  *      Logically, it could be thought of as getting the value from
  *      a *map* with *task* as the **key**.  From this
  *      perspective,  the usage is not much different from
  *      **bpf_map_lookup_elem**\ (*map*, **&**\ *task*) except this
  *      helper enforces the key must be an task_struct and the map must also
  *      be a **BPF_MAP_TYPE_TASK_STORAGE**.
  *
  *      Underneath, the value is stored locally at *task* instead of
  *      the *map*.  The *map* is used as the bpf-local-storage
  *      "type". The bpf-local-storage "type" (i.e. the *map*) is
  *      searched against all bpf_local_storage residing at *task*.
  *
  *      An optional *flags* (**BPF_LOCAL_STORAGE_GET_F_CREATE**) can be
  *      used such that a new bpf_local_storage will be
  *      created if one does not exist.  *value* can be used
  *      together with **BPF_LOCAL_STORAGE_GET_F_CREATE** to specify
  *      the initial value of a bpf_local_storage.  If *value* is
  *      **NULL**, the new bpf_local_storage will be zero initialized.
  *  Return
  *      A bpf_local_storage pointer is returned on success.
  *
  *      **NULL** if not found or there was an error in adding
  *      a new bpf_local_storage.
  *
  * long bpf_task_storage_delete(struct bpf_map *map, struct task_struct *task)
  *  Description
  *      Delete a bpf_local_storage from a *task*.
  *  Return
  *      0 on success.
  *
  *      **-ENOENT** if the bpf_local_storage cannot be found.
  *
  * struct task_struct *bpf_get_current_task_btf(void)
  *  Description
  *      Return a BTF pointer to the "current" task.
  *      This pointer can also be used in helpers that accept an
  *      *ARG_PTR_TO_BTF_ID* of type *task_struct*.
  *  Return
  *      Pointer to the current task.
  *
  * long bpf_bprm_opts_set(struct linux_binprm *bprm, u64 flags)
  *  Description
  *      Set or clear certain options on *bprm*:
  *
  *      **BPF_F_BPRM_SECUREEXEC** Set the secureexec bit
  *      which sets the **AT_SECURE** auxv for glibc. The bit
  *      is cleared if the flag is not specified.
  *  Return
  *      **-EINVAL** if invalid *flags* are passed, zero otherwise.
  *
  * u64 bpf_ktime_get_coarse_ns(void)
  *  Description
  *      Return a coarse-grained version of the time elapsed since
  *      system boot, in nanoseconds. Does not include time the system
  *      was suspended.
  *
  *      See: **clock_gettime**\ (**CLOCK_MONOTONIC_COARSE**)
  *  Return
  *      Current *ktime*.
  *
  * long bpf_ima_inode_hash(struct inode *inode, void *dst, u32 size)
  *  Description
  *      Returns the stored IMA hash of the *inode* (if it's avaialable).
  *      If the hash is larger than *size*, then only *size*
  *      bytes will be copied to *dst*
  *  Return
  *      The **hash_algo** is returned on success,
  *      **-EOPNOTSUP** if IMA is disabled or **-EINVAL** if
  *      invalid arguments are passed.
  *
  * struct socket *bpf_sock_from_file(struct file *file)
  *  Description
  *      If the given file represents a socket, returns the associated
  *      socket.
  *  Return
  *      A pointer to a struct socket on success or NULL if the file is
  *      not a socket.
  *
  * long bpf_check_mtu(void *ctx, u32 ifindex, u32 *mtu_len, s32 len_diff, u64 flags)
  *  Description
  *      Check packet size against exceeding MTU of net device (based
  *      on *ifindex*).  This helper will likely be used in combination
  *      with helpers that adjust/change the packet size.
  *
  *      The argument *len_diff* can be used for querying with a planned
  *      size change. This allows to check MTU prior to changing packet
  *      ctx. Providing an *len_diff* adjustment that is larger than the
  *      actual packet size (resulting in negative packet size) will in
  *      principle not exceed the MTU, why it is not considered a
  *      failure.  Other BPF-helpers are needed for performing the
  *      planned size change, why the responsability for catch a negative
  *      packet size belong in those helpers.
  *
  *      Specifying *ifindex* zero means the MTU check is performed
  *      against the current net device.  This is practical if this isn't
  *      used prior to redirect.
  *
  *      On input *mtu_len* must be a valid pointer, else verifier will
  *      reject BPF program.  If the value *mtu_len* is initialized to
  *      zero then the ctx packet size is use.  When value *mtu_len* is
  *      provided as input this specify the L3 length that the MTU check
  *      is done against. Remember XDP and TC length operate at L2, but
  *      this value is L3 as this correlate to MTU and IP-header tot_len
  *      values which are L3 (similar behavior as bpf_fib_lookup).
  *
  *      The Linux kernel route table can configure MTUs on a more
  *      specific per route level, which is not provided by this helper.
  *      For route level MTU checks use the **bpf_fib_lookup**\ ()
  *      helper.
  *
  *      *ctx* is either **struct xdp_md** for XDP programs or
  *      **struct sk_buff** for tc cls_act programs.
  *
  *      The *flags* argument can be a combination of one or more of the
  *      following values:
  *
  *      **BPF_MTU_CHK_SEGS**
  *          This flag will only works for *ctx* **struct sk_buff**.
  *          If packet context contains extra packet segment buffers
  *          (often knows as GSO skb), then MTU check is harder to
  *          check at this point, because in transmit path it is
  *          possible for the skb packet to get re-segmented
  *          (depending on net device features).  This could still be
  *          a MTU violation, so this flag enables performing MTU
  *          check against segments, with a different violation
  *          return code to tell it apart. Check cannot use len_diff.
  *
  *      On return *mtu_len* pointer contains the MTU value of the net
  *      device.  Remember the net device configured MTU is the L3 size,
  *      which is returned here and XDP and TC length operate at L2.
  *      Helper take this into account for you, but remember when using
  *      MTU value in your BPF-code.
  *
  *  Return
  *      * 0 on success, and populate MTU value in *mtu_len* pointer.
  *
  *      * < 0 if any input argument is invalid (*mtu_len* not updated)
  *
  *      MTU violations return positive values, but also populate MTU
  *      value in *mtu_len* pointer, as this can be needed for
  *      implementing PMTU handing:
  *
  *      * **BPF_MTU_CHK_RET_FRAG_NEEDED**
  *      * **BPF_MTU_CHK_RET_SEGS_TOOBIG**
  *
  * long bpf_for_each_map_elem(struct bpf_map *map, void *callback_fn, void *callback_ctx, u64 flags)
  *  Description
  *      For each element in **map**, call **callback_fn** function with
  *      **map**, **callback_ctx** and other map-specific parameters.
  *      The **callback_fn** should be a static function and
  *      the **callback_ctx** should be a pointer to the stack.
  *      The **flags** is used to control certain aspects of the helper.
  *      Currently, the **flags** must be 0.
  *
  *      The following are a list of supported map types and their
  *      respective expected callback signatures:
  *
  *      BPF_MAP_TYPE_HASH, BPF_MAP_TYPE_PERCPU_HASH,
  *      BPF_MAP_TYPE_LRU_HASH, BPF_MAP_TYPE_LRU_PERCPU_HASH,
  *      BPF_MAP_TYPE_ARRAY, BPF_MAP_TYPE_PERCPU_ARRAY
  *
  *      long (\*callback_fn)(struct bpf_map \*map, const void \*key, void \*value, void \*ctx);
  *
  *      For per_cpu maps, the map_value is the value on the cpu where the
  *      bpf_prog is running.
  *
  *      If **callback_fn** return 0, the helper will continue to the next
  *      element. If return value is 1, the helper will skip the rest of
  *      elements and return. Other return values are not used now.
  *
  *  Return
  *      The number of traversed map elements for success, **-EINVAL** for
  *      invalid **flags**.
  *
  * long bpf_snprintf(char *str, u32 str_size, const char *fmt, u64 *data, u32 data_len)
  *  Description
  *      Outputs a string into the **str** buffer of size **str_size**
  *      based on a format string stored in a read-only map pointed by
  *      **fmt**.
  *
  *      Each format specifier in **fmt** corresponds to one u64 element
  *      in the **data** array. For strings and pointers where pointees
  *      are accessed, only the pointer values are stored in the *data*
  *      array. The *data_len* is the size of *data* in bytes - must be
  *      a multiple of 8.
  *
  *      Formats **%s** and **%p{i,I}{4,6}** require to read kernel
  *      memory. Reading kernel memory may fail due to either invalid
  *      address or valid address but requiring a major memory fault. If
  *      reading kernel memory fails, the string for **%s** will be an
  *      empty string, and the ip address for **%p{i,I}{4,6}** will be 0.
  *      Not returning error to bpf program is consistent with what
  *      **bpf_trace_printk**\ () does for now.
  *
  *  Return
  *      The strictly positive length of the formatted string, including
  *      the trailing zero character. If the return value is greater than
  *      **str_size**, **str** contains a truncated string, guaranteed to
  *      be zero-terminated except when **str_size** is 0.
  *
  *      Or **-EBUSY** if the per-CPU memory copy buffer is busy.
  *
  * long bpf_sys_bpf(u32 cmd, void *attr, u32 attr_size)
  *  Description
  *      Execute bpf syscall with given arguments.
  *  Return
  *      A syscall result.
  *
  * long bpf_btf_find_by_name_kind(char *name, int name_sz, u32 kind, int flags)
  *  Description
  *      Find BTF type with given name and kind in vmlinux BTF or in module's BTFs.
  *  Return
  *      Returns btf_id and btf_obj_fd in lower and upper 32 bits.
  *
  * long bpf_sys_close(u32 fd)
  *  Description
  *      Execute close syscall for given FD.
  *  Return
  *      A syscall result.
  *
  * long bpf_timer_init(struct bpf_timer *timer, struct bpf_map *map, u64 flags)
  *  Description
  *      Initialize the timer.
  *      First 4 bits of *flags* specify clockid.
  *      Only CLOCK_MONOTONIC, CLOCK_REALTIME, CLOCK_BOOTTIME are allowed.
  *      All other bits of *flags* are reserved.
  *      The verifier will reject the program if *timer* is not from
  *      the same *map*.
  *  Return
  *      0 on success.
  *      **-EBUSY** if *timer* is already initialized.
  *      **-EINVAL** if invalid *flags* are passed.
  *      **-EPERM** if *timer* is in a map that doesn't have any user references.
  *      The user space should either hold a file descriptor to a map with timers
  *      or pin such map in bpffs. When map is unpinned or file descriptor is
  *      closed all timers in the map will be cancelled and freed.
  *
  * long bpf_timer_set_callback(struct bpf_timer *timer, void *callback_fn)
  *  Description
  *      Configure the timer to call *callback_fn* static function.
  *  Return
  *      0 on success.
  *      **-EINVAL** if *timer* was not initialized with bpf_timer_init() earlier.
  *      **-EPERM** if *timer* is in a map that doesn't have any user references.
  *      The user space should either hold a file descriptor to a map with timers
  *      or pin such map in bpffs. When map is unpinned or file descriptor is
  *      closed all timers in the map will be cancelled and freed.
  *
  * long bpf_timer_start(struct bpf_timer *timer, u64 nsecs, u64 flags)
  *  Description
  *      Set timer expiration N nanoseconds from the current time. The
  *      configured callback will be invoked in soft irq context on some cpu
  *      and will not repeat unless another bpf_timer_start() is made.
  *      In such case the next invocation can migrate to a different cpu.
  *      Since struct bpf_timer is a field inside map element the map
  *      owns the timer. The bpf_timer_set_callback() will increment refcnt
  *      of BPF program to make sure that callback_fn code stays valid.
  *      When user space reference to a map reaches zero all timers
  *      in a map are cancelled and corresponding program's refcnts are
  *      decremented. This is done to make sure that Ctrl-C of a user
  *      process doesn't leave any timers running. If map is pinned in
  *      bpffs the callback_fn can re-arm itself indefinitely.
  *      bpf_map_update/delete_elem() helpers and user space sys_bpf commands
  *      cancel and free the timer in the given map element.
  *      The map can contain timers that invoke callback_fn-s from different
  *      programs. The same callback_fn can serve different timers from
  *      different maps if key/value layout matches across maps.
  *      Every bpf_timer_set_callback() can have different callback_fn.
  *
  *  Return
  *      0 on success.
  *      **-EINVAL** if *timer* was not initialized with bpf_timer_init() earlier
  *      or invalid *flags* are passed.
  *
  * long bpf_timer_cancel(struct bpf_timer *timer)
  *  Description
  *      Cancel the timer and wait for callback_fn to finish if it was running.
  *  Return
  *      0 if the timer was not active.
  *      1 if the timer was active.
  *      **-EINVAL** if *timer* was not initialized with bpf_timer_init() earlier.
  *      **-EDEADLK** if callback_fn tried to call bpf_timer_cancel() on its
  *      own timer which would have led to a deadlock otherwise.
  *
  * u64 bpf_get_func_ip(void *ctx)
  *  Description
  *      Get address of the traced function (for tracing and kprobe programs).
  *  Return
  *      Address of the traced function.
  *
  * u64 bpf_get_attach_cookie(void *ctx)
  *  Description
  *      Get bpf_cookie value provided (optionally) during the program
  *      attachment. It might be different for each individual
  *      attachment, even if BPF program itself is the same.
  *      Expects BPF program context *ctx* as a first argument.
  *
  *      Supported for the following program types:
  *          - kprobe/uprobe;
  *          - tracepoint;
  *          - perf_event.
  *  Return
  *      Value specified by user at BPF link creation/attachment time
  *      or 0, if it was not specified.
  *
  * long bpf_task_pt_regs(struct task_struct *task)
  *  Description
  *      Get the struct pt_regs associated with **task**.
  *  Return
  *      A pointer to struct pt_regs.
  *
  * long bpf_get_branch_snapshot(void *entries, u32 size, u64 flags)
  *  Description
  *      Get branch trace from hardware engines like Intel LBR. The
  *      hardware engine is stopped shortly after the helper is
  *      called. Therefore, the user need to filter branch entries
  *      based on the actual use case. To capture branch trace
  *      before the trigger point of the BPF program, the helper
  *      should be called at the beginning of the BPF program.
  *
  *      The data is stored as struct perf_branch_entry into output
  *      buffer *entries*. *size* is the size of *entries* in bytes.
  *      *flags* is reserved for now and must be zero.
  *
  *  Return
  *      On success, number of bytes written to *buf*. On error, a
  *      negative value.
  *
  *      **-EINVAL** if *flags* is not zero.
  *
  *      **-ENOENT** if architecture does not support branch records.
  *
  * long bpf_trace_vprintk(const char *fmt, u32 fmt_size, const void *data, u32 data_len)
  *  Description
  *      Behaves like **bpf_trace_printk**\ () helper, but takes an array of u64
  *      to format and can handle more format args as a result.
  *
  *      Arguments are to be used as in **bpf_seq_printf**\ () helper.
  *  Return
  *      The number of bytes written to the buffer, or a negative error
  *      in case of failure.
  *
  * struct unix_sock *bpf_skc_to_unix_sock(void *sk)
  *  Description
  *      Dynamically cast a *sk* pointer to a *unix_sock* pointer.
  *  Return
  *      *sk* if casting is valid, or **NULL** otherwise.
  *
  * long bpf_kallsyms_lookup_name(const char *name, int name_sz, int flags, u64 *res)
  *  Description
  *      Get the address of a kernel symbol, returned in *res*. *res* is
  *      set to 0 if the symbol is not found.
  *  Return
  *      On success, zero. On error, a negative value.
  *
  *      **-EINVAL** if *flags* is not zero.
  *
  *      **-EINVAL** if string *name* is not the same size as *name_sz*.
  *
  *      **-ENOENT** if symbol is not found.
  *
  *      **-EPERM** if caller does not have permission to obtain kernel address.
  *
  * long bpf_find_vma(struct task_struct *task, u64 addr, void *callback_fn, void *callback_ctx, u64 flags)
  *  Description
  *      Find vma of *task* that contains *addr*, call *callback_fn*
  *      function with *task*, *vma*, and *callback_ctx*.
  *      The *callback_fn* should be a static function and
  *      the *callback_ctx* should be a pointer to the stack.
  *      The *flags* is used to control certain aspects of the helper.
  *      Currently, the *flags* must be 0.
  *
  *      The expected callback signature is
  *
  *      long (\*callback_fn)(struct task_struct \*task, struct vm_area_struct \*vma, void \*callback_ctx);
  *
  *  Return
  *      0 on success.
  *      **-ENOENT** if *task->mm* is NULL, or no vma contains *addr*.
  *      **-EBUSY** if failed to try lock mmap_lock.
  *      **-EINVAL** for invalid **flags**.
  *
  * long bpf_loop(u32 nr_loops, void *callback_fn, void *callback_ctx, u64 flags)
  *  Description
  *      For **nr_loops**, call **callback_fn** function
  *      with **callback_ctx** as the context parameter.
  *      The **callback_fn** should be a static function and
  *      the **callback_ctx** should be a pointer to the stack.
  *      The **flags** is used to control certain aspects of the helper.
  *      Currently, the **flags** must be 0. Currently, nr_loops is
  *      limited to 1 << 23 (~8 million) loops.
  *
  *      long (\*callback_fn)(u32 index, void \*ctx);
  *
  *      where **index** is the current index in the loop. The index
  *      is zero-indexed.
  *
  *      If **callback_fn** returns 0, the helper will continue to the next
  *      loop. If return value is 1, the helper will skip the rest of
  *      the loops and return. Other return values are not used now,
  *      and will be rejected by the verifier.
  *
  *  Return
  *      The number of loops performed, **-EINVAL** for invalid **flags**,
  *      **-E2BIG** if **nr_loops** exceeds the maximum number of loops.
  *
  * long bpf_strncmp(const char *s1, u32 s1_sz, const char *s2)
  *  Description
  *      Do strncmp() between **s1** and **s2**. **s1** doesn't need
  *      to be null-terminated and **s1_sz** is the maximum storage
  *      size of **s1**. **s2** must be a read-only string.
  *  Return
  *      An integer less than, equal to, or greater than zero
  *      if the first **s1_sz** bytes of **s1** is found to be
  *      less than, to match, or be greater than **s2**.
  *
  * long bpf_get_func_arg(void *ctx, u32 n, u64 *value)
  *  Description
  *      Get **n**-th argument (zero based) of the traced function (for tracing programs)
  *      returned in **value**.
  *
  *  Return
  *      0 on success.
  *      **-EINVAL** if n >= arguments count of traced function.
  *
  * long bpf_get_func_ret(void *ctx, u64 *value)
  *  Description
  *      Get return value of the traced function (for tracing programs)
  *      in **value**.
  *
  *  Return
  *      0 on success.
  *      **-EOPNOTSUPP** for tracing programs other than BPF_TRACE_FEXIT or BPF_MODIFY_RETURN.
  *
  * long bpf_get_func_arg_cnt(void *ctx)
  *  Description
  *      Get number of arguments of the traced function (for tracing programs).
  *
  *  Return
  *      The number of arguments of the traced function.
  *
  * int bpf_get_retval(void)
  *  Description
  *      Get the syscall's return value that will be returned to userspace.
  *
  *      This helper is currently supported by cgroup programs only.
  *  Return
  *      The syscall's return value.
  *
  * int bpf_set_retval(int retval)
  *  Description
  *      Set the syscall's return value that will be returned to userspace.
  *
  *      This helper is currently supported by cgroup programs only.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * u64 bpf_xdp_get_buff_len(struct xdp_buff *xdp_md)
  *  Description
  *      Get the total size of a given xdp buff (linear and paged area)
  *  Return
  *      The total size of a given xdp buffer.
  *
  * long bpf_xdp_load_bytes(struct xdp_buff *xdp_md, u32 offset, void *buf, u32 len)
  *  Description
  *      This helper is provided as an easy way to load data from a
  *      xdp buffer. It can be used to load *len* bytes from *offset* from
  *      the frame associated to *xdp_md*, into the buffer pointed by
  *      *buf*.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * long bpf_xdp_store_bytes(struct xdp_buff *xdp_md, u32 offset, void *buf, u32 len)
  *  Description
  *      Store *len* bytes from buffer *buf* into the frame
  *      associated to *xdp_md*, at *offset*.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * long bpf_copy_from_user_task(void *dst, u32 size, const void *user_ptr, struct task_struct *tsk, u64 flags)
  *  Description
  *      Read *size* bytes from user space address *user_ptr* in *tsk*'s
  *      address space, and stores the data in *dst*. *flags* is not
  *      used yet and is provided for future extensibility. This helper
  *      can only be used by sleepable programs.
  *  Return
  *      0 on success, or a negative error in case of failure. On error
  *      *dst* buffer is zeroed out.
  *
  * long bpf_skb_set_tstamp(struct sk_buff *skb, u64 tstamp, u32 tstamp_type)
  *  Description
  *      Change the __sk_buff->tstamp_type to *tstamp_type*
  *      and set *tstamp* to the __sk_buff->tstamp together.
  *
  *      If there is no need to change the __sk_buff->tstamp_type,
  *      the tstamp value can be directly written to __sk_buff->tstamp
  *      instead.
  *
  *      BPF_SKB_TSTAMP_DELIVERY_MONO is the only tstamp that
  *      will be kept during bpf_redirect_*().  A non zero
  *      *tstamp* must be used with the BPF_SKB_TSTAMP_DELIVERY_MONO
  *      *tstamp_type*.
  *
  *      A BPF_SKB_TSTAMP_UNSPEC *tstamp_type* can only be used
  *      with a zero *tstamp*.
  *
  *      Only IPv4 and IPv6 skb->protocol are supported.
  *
  *      This function is most useful when it needs to set a
  *      mono delivery time to __sk_buff->tstamp and then
  *      bpf_redirect_*() to the egress of an iface.  For example,
  *      changing the (rcv) timestamp in __sk_buff->tstamp at
  *      ingress to a mono delivery time and then bpf_redirect_*()
  *      to sch_fq@phy-dev.
  *  Return
  *      0 on success.
  *      **-EINVAL** for invalid input
  *      **-EOPNOTSUPP** for unsupported protocol
  *
  * long bpf_ima_file_hash(struct file *file, void *dst, u32 size)
  *  Description
  *      Returns a calculated IMA hash of the *file*.
  *      If the hash is larger than *size*, then only *size*
  *      bytes will be copied to *dst*
  *  Return
  *      The **hash_algo** is returned on success,
  *      **-EOPNOTSUP** if the hash calculation failed or **-EINVAL** if
  *      invalid arguments are passed.
  *
  * void *bpf_kptr_xchg(void *map_value, void *ptr)
  *  Description
  *      Exchange kptr at pointer *map_value* with *ptr*, and return the
  *      old value. *ptr* can be NULL, otherwise it must be a referenced
  *      pointer which will be released when this helper is called.
  *  Return
  *      The old value of kptr (which can be NULL). The returned pointer
  *      if not NULL, is a reference which must be released using its
  *      corresponding release function, or moved into a BPF map before
  *      program exit.
  *
  * void *bpf_map_lookup_percpu_elem(struct bpf_map *map, const void *key, u32 cpu)
  *  Description
  *      Perform a lookup in *percpu map* for an entry associated to
  *      *key* on *cpu*.
  *  Return
  *      Map value associated to *key* on *cpu*, or **NULL** if no entry
  *      was found or *cpu* is invalid.
  *
  * struct mptcp_sock *bpf_skc_to_mptcp_sock(void *sk)
  *  Description
  *      Dynamically cast a *sk* pointer to a *mptcp_sock* pointer.
  *  Return
  *      *sk* if casting is valid, or **NULL** otherwise.
  *
  * long bpf_dynptr_from_mem(void *data, u32 size, u64 flags, struct bpf_dynptr *ptr)
  *  Description
  *      Get a dynptr to local memory *data*.
  *
  *      *data* must be a ptr to a map value.
  *      The maximum *size* supported is DYNPTR_MAX_SIZE.
  *      *flags* is currently unused.
  *  Return
  *      0 on success, -E2BIG if the size exceeds DYNPTR_MAX_SIZE,
  *      -EINVAL if flags is not 0.
  *
  * long bpf_ringbuf_reserve_dynptr(void *ringbuf, u32 size, u64 flags, struct bpf_dynptr *ptr)
  *  Description
  *      Reserve *size* bytes of payload in a ring buffer *ringbuf*
  *      through the dynptr interface. *flags* must be 0.
  *
  *      Please note that a corresponding bpf_ringbuf_submit_dynptr or
  *      bpf_ringbuf_discard_dynptr must be called on *ptr*, even if the
  *      reservation fails. This is enforced by the verifier.
  *  Return
  *      0 on success, or a negative error in case of failure.
  *
  * void bpf_ringbuf_submit_dynptr(struct bpf_dynptr *ptr, u64 flags)
  *  Description
  *      Submit reserved ring buffer sample, pointed to by *data*,
  *      through the dynptr interface. This is a no-op if the dynptr is
  *      invalid/null.
  *
  *      For more information on *flags*, please see
  *      'bpf_ringbuf_submit'.
  *  Return
  *      Nothing. Always succeeds.
  *
  * void bpf_ringbuf_discard_dynptr(struct bpf_dynptr *ptr, u64 flags)
  *  Description
  *      Discard reserved ring buffer sample through the dynptr
  *      interface. This is a no-op if the dynptr is invalid/null.
  *
  *      For more information on *flags*, please see
  *      'bpf_ringbuf_discard'.
  *  Return
  *      Nothing. Always succeeds.
  *
  * long bpf_dynptr_read(void *dst, u32 len, struct bpf_dynptr *src, u32 offset, u64 flags)
  *  Description
  *      Read *len* bytes from *src* into *dst*, starting from *offset*
  *      into *src*.
  *      *flags* is currently unused.
  *  Return
  *      0 on success, -E2BIG if *offset* + *len* exceeds the length
  *      of *src*'s data, -EINVAL if *src* is an invalid dynptr or if
  *      *flags* is not 0.
  *
  * long bpf_dynptr_write(struct bpf_dynptr *dst, u32 offset, void *src, u32 len, u64 flags)
  *  Description
  *      Write *len* bytes from *src* into *dst*, starting from *offset*
  *      into *dst*.
  *      *flags* is currently unused.
  *  Return
  *      0 on success, -E2BIG if *offset* + *len* exceeds the length
  *      of *dst*'s data, -EINVAL if *dst* is an invalid dynptr or if *dst*
  *      is a read-only dynptr or if *flags* is not 0.
  *
  * void *bpf_dynptr_data(struct bpf_dynptr *ptr, u32 offset, u32 len)
  *  Description
  *      Get a pointer to the underlying dynptr data.
  *
  *      *len* must be a statically known value. The returned data slice
  *      is invalidated whenever the dynptr is invalidated.
  *  Return
  *      Pointer to the underlying dynptr data, NULL if the dynptr is
  *      read-only, if the dynptr is invalid, or if the offset and length
  *      is out of bounds.
  *
  * s64 bpf_tcp_raw_gen_syncookie_ipv4(struct iphdr *iph, struct tcphdr *th, u32 th_len)
  *  Description
  *      Try to issue a SYN cookie for the packet with corresponding
  *      IPv4/TCP headers, *iph* and *th*, without depending on a
  *      listening socket.
  *
  *      *iph* points to the IPv4 header.
  *
  *      *th* points to the start of the TCP header, while *th_len*
  *      contains the length of the TCP header (at least
  *      **sizeof**\ (**struct tcphdr**)).
  *  Return
  *      On success, lower 32 bits hold the generated SYN cookie in
  *      followed by 16 bits which hold the MSS value for that cookie,
  *      and the top 16 bits are unused.
  *
  *      On failure, the returned value is one of the following:
  *
  *      **-EINVAL** if *th_len* is invalid.
  *
  * s64 bpf_tcp_raw_gen_syncookie_ipv6(struct ipv6hdr *iph, struct tcphdr *th, u32 th_len)
  *  Description
  *      Try to issue a SYN cookie for the packet with corresponding
  *      IPv6/TCP headers, *iph* and *th*, without depending on a
  *      listening socket.
  *
  *      *iph* points to the IPv6 header.
  *
  *      *th* points to the start of the TCP header, while *th_len*
  *      contains the length of the TCP header (at least
  *      **sizeof**\ (**struct tcphdr**)).
  *  Return
  *      On success, lower 32 bits hold the generated SYN cookie in
  *      followed by 16 bits which hold the MSS value for that cookie,
  *      and the top 16 bits are unused.
  *
  *      On failure, the returned value is one of the following:
  *
  *      **-EINVAL** if *th_len* is invalid.
  *
  *      **-EPROTONOSUPPORT** if CONFIG_IPV6 is not builtin.
  *
  * long bpf_tcp_raw_check_syncookie_ipv4(struct iphdr *iph, struct tcphdr *th)
  *  Description
  *      Check whether *iph* and *th* contain a valid SYN cookie ACK
  *      without depending on a listening socket.
  *
  *      *iph* points to the IPv4 header.
  *
  *      *th* points to the TCP header.
  *  Return
  *      0 if *iph* and *th* are a valid SYN cookie ACK.
  *
  *      On failure, the returned value is one of the following:
  *
  *      **-EACCES** if the SYN cookie is not valid.
  *
  * long bpf_tcp_raw_check_syncookie_ipv6(struct ipv6hdr *iph, struct tcphdr *th)
  *  Description
  *      Check whether *iph* and *th* contain a valid SYN cookie ACK
  *      without depending on a listening socket.
  *
  *      *iph* points to the IPv6 header.
  *
  *      *th* points to the TCP header.
  *  Return
  *      0 if *iph* and *th* are a valid SYN cookie ACK.
  *
  *      On failure, the returned value is one of the following:
  *
  *      **-EACCES** if the SYN cookie is not valid.
  *
  *      **-EPROTONOSUPPORT** if CONFIG_IPV6 is not builtin.
  */
 #define __BPF_FUNC_MAPPER(FN)       \
     FN(unspec),         \
     FN(map_lookup_elem),        \
     FN(map_update_elem),        \
     FN(map_delete_elem),        \
     FN(probe_read),         \
     FN(ktime_get_ns),       \
     FN(trace_printk),       \
     FN(get_prandom_u32),        \
     FN(get_smp_processor_id),   \
     FN(skb_store_bytes),        \
     FN(l3_csum_replace),        \
     FN(l4_csum_replace),        \
     FN(tail_call),          \
     FN(clone_redirect),     \
     FN(get_current_pid_tgid),   \
     FN(get_current_uid_gid),    \
     FN(get_current_comm),       \
     FN(get_cgroup_classid),     \
     FN(skb_vlan_push),      \
     FN(skb_vlan_pop),       \
     FN(skb_get_tunnel_key),     \
     FN(skb_set_tunnel_key),     \
     FN(perf_event_read),        \
     FN(redirect),           \
     FN(get_route_realm),        \
     FN(perf_event_output),      \
     FN(skb_load_bytes),     \
     FN(get_stackid),        \
     FN(csum_diff),          \
     FN(skb_get_tunnel_opt),     \
     FN(skb_set_tunnel_opt),     \
     FN(skb_change_proto),       \
     FN(skb_change_type),        \
     FN(skb_under_cgroup),       \
     FN(get_hash_recalc),        \
     FN(get_current_task),       \
     FN(probe_write_user),       \
     FN(current_task_under_cgroup),  \
     FN(skb_change_tail),        \
     FN(skb_pull_data),      \
     FN(csum_update),        \
     FN(set_hash_invalid),       \
     FN(get_numa_node_id),       \
     FN(skb_change_head),        \
     FN(xdp_adjust_head),        \
     FN(probe_read_str),     \
     FN(get_socket_cookie),      \
     FN(get_socket_uid),     \
     FN(set_hash),           \
     FN(setsockopt),         \
     FN(skb_adjust_room),        \
     FN(redirect_map),       \
     FN(sk_redirect_map),        \
     FN(sock_map_update),        \
     FN(xdp_adjust_meta),        \
     FN(perf_event_read_value),  \
     FN(perf_prog_read_value),   \
     FN(getsockopt),         \
     FN(override_return),        \
     FN(sock_ops_cb_flags_set),  \
     FN(msg_redirect_map),       \
     FN(msg_apply_bytes),        \
     FN(msg_cork_bytes),     \
     FN(msg_pull_data),      \
     FN(bind),           \
     FN(xdp_adjust_tail),        \
     FN(skb_get_xfrm_state),     \
     FN(get_stack),          \
     FN(skb_load_bytes_relative),    \
     FN(fib_lookup),         \
     FN(sock_hash_update),       \
     FN(msg_redirect_hash),      \
     FN(sk_redirect_hash),       \
     FN(lwt_push_encap),     \
     FN(lwt_seg6_store_bytes),   \
     FN(lwt_seg6_adjust_srh),    \
     FN(lwt_seg6_action),        \
     FN(rc_repeat),          \
     FN(rc_keydown),         \
     FN(skb_cgroup_id),      \
     FN(get_current_cgroup_id),  \
     FN(get_local_storage),      \
     FN(sk_select_reuseport),    \
     FN(skb_ancestor_cgroup_id), \
     FN(sk_lookup_tcp),      \
     FN(sk_lookup_udp),      \
     FN(sk_release),         \
     FN(map_push_elem),      \
     FN(map_pop_elem),       \
     FN(map_peek_elem),      \
     FN(msg_push_data),      \
     FN(msg_pop_data),       \
     FN(rc_pointer_rel),     \
     FN(spin_lock),          \
     FN(spin_unlock),        \
     FN(sk_fullsock),        \
     FN(tcp_sock),           \
     FN(skb_ecn_set_ce),     \
     FN(get_listener_sock),      \
     FN(skc_lookup_tcp),     \
     FN(tcp_check_syncookie),    \
     FN(sysctl_get_name),        \
     FN(sysctl_get_current_value),   \
     FN(sysctl_get_new_value),   \
     FN(sysctl_set_new_value),   \
     FN(strtol),         \
     FN(strtoul),            \
     FN(sk_storage_get),     \
     FN(sk_storage_delete),      \
     FN(send_signal),        \
     FN(tcp_gen_syncookie),      \
     FN(skb_output),         \
     FN(probe_read_user),        \
     FN(probe_read_kernel),      \
     FN(probe_read_user_str),    \
     FN(probe_read_kernel_str),  \
     FN(tcp_send_ack),       \
     FN(send_signal_thread),     \
     FN(jiffies64),          \
     FN(read_branch_records),    \
     FN(get_ns_current_pid_tgid),    \
     FN(xdp_output),         \
     FN(get_netns_cookie),       \
     FN(get_current_ancestor_cgroup_id), \
     FN(sk_assign),          \
     FN(ktime_get_boot_ns),      \
     FN(seq_printf),         \
     FN(seq_write),          \
     FN(sk_cgroup_id),       \
     FN(sk_ancestor_cgroup_id),  \
     FN(ringbuf_output),     \
     FN(ringbuf_reserve),        \
     FN(ringbuf_submit),     \
     FN(ringbuf_discard),        \
     FN(ringbuf_query),      \
     FN(csum_level),         \
     FN(skc_to_tcp6_sock),       \
     FN(skc_to_tcp_sock),        \
     FN(skc_to_tcp_timewait_sock),   \
     FN(skc_to_tcp_request_sock),    \
     FN(skc_to_udp6_sock),       \
     FN(get_task_stack),     \
     FN(load_hdr_opt),       \
     FN(store_hdr_opt),      \
     FN(reserve_hdr_opt),        \
     FN(inode_storage_get),      \
     FN(inode_storage_delete),   \
     FN(d_path),         \
     FN(copy_from_user),     \
     FN(snprintf_btf),       \
     FN(seq_printf_btf),     \
     FN(skb_cgroup_classid),     \
     FN(redirect_neigh),     \
     FN(per_cpu_ptr),        \
     FN(this_cpu_ptr),       \
     FN(redirect_peer),      \
     FN(task_storage_get),       \
     FN(task_storage_delete),    \
     FN(get_current_task_btf),   \
     FN(bprm_opts_set),      \
     FN(ktime_get_coarse_ns),    \
     FN(ima_inode_hash),     \
     FN(sock_from_file),     \
     FN(check_mtu),          \
     FN(for_each_map_elem),      \
     FN(snprintf),           \
     FN(sys_bpf),            \
     FN(btf_find_by_name_kind),  \
     FN(sys_close),          \
     FN(timer_init),         \
     FN(timer_set_callback),     \
     FN(timer_start),        \
     FN(timer_cancel),       \
     FN(get_func_ip),        \
     FN(get_attach_cookie),      \
     FN(task_pt_regs),       \
     FN(get_branch_snapshot),    \
     FN(trace_vprintk),      \
     FN(skc_to_unix_sock),       \
     FN(kallsyms_lookup_name),   \
     FN(find_vma),           \
     FN(loop),           \
     FN(strncmp),            \
     FN(get_func_arg),       \
     FN(get_func_ret),       \
     FN(get_func_arg_cnt),       \
     FN(get_retval),         \
     FN(set_retval),         \
     FN(xdp_get_buff_len),       \
     FN(xdp_load_bytes),     \
     FN(xdp_store_bytes),        \
     FN(copy_from_user_task),    \
     FN(skb_set_tstamp),     \
     FN(ima_file_hash),      \
     FN(kptr_xchg),          \
     FN(map_lookup_percpu_elem),     \
     FN(skc_to_mptcp_sock),      \
     FN(dynptr_from_mem),        \
     FN(ringbuf_reserve_dynptr), \
     FN(ringbuf_submit_dynptr),  \
     FN(ringbuf_discard_dynptr), \
     FN(dynptr_read),        \
     FN(dynptr_write),       \
     FN(dynptr_data),        \
     FN(tcp_raw_gen_syncookie_ipv4), \
     FN(tcp_raw_gen_syncookie_ipv6), \
     FN(tcp_raw_check_syncookie_ipv4),   \
     FN(tcp_raw_check_syncookie_ipv6),   \
     /* */
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
  * function eBPF program intends to call
  */
 #define __BPF_ENUM_FN(x) BPF_FUNC_ ## x
 enum bpf_func_id {
     __BPF_FUNC_MAPPER(__BPF_ENUM_FN)
     __BPF_FUNC_MAX_ID,
 };
 #undef __BPF_ENUM_FN
 
 /* All flags used by eBPF helper functions, placed here. */
 
 /* BPF_FUNC_skb_store_bytes flags. */
 enum {
     BPF_F_RECOMPUTE_CSUM        = (1ULL << 0),
     BPF_F_INVALIDATE_HASH       = (1ULL << 1),
 };
 
 /* BPF_FUNC_l3_csum_replace and BPF_FUNC_l4_csum_replace flags.
  * First 4 bits are for passing the header field size.
  */
 enum {
     BPF_F_HDR_FIELD_MASK        = 0xfULL,
 };
 
 /* BPF_FUNC_l4_csum_replace flags. */
 enum {
     BPF_F_PSEUDO_HDR        = (1ULL << 4),
     BPF_F_MARK_MANGLED_0        = (1ULL << 5),
     BPF_F_MARK_ENFORCE      = (1ULL << 6),
 };
 
 /* BPF_FUNC_clone_redirect and BPF_FUNC_redirect flags. */
 enum {
     BPF_F_INGRESS           = (1ULL << 0),
 };
 
 /* BPF_FUNC_skb_set_tunnel_key and BPF_FUNC_skb_get_tunnel_key flags. */
 enum {
     BPF_F_TUNINFO_IPV6      = (1ULL << 0),
 };
 
 /* flags for both BPF_FUNC_get_stackid and BPF_FUNC_get_stack. */
 enum {
     BPF_F_SKIP_FIELD_MASK       = 0xffULL,
     BPF_F_USER_STACK        = (1ULL << 8),
 /* flags used by BPF_FUNC_get_stackid only. */
     BPF_F_FAST_STACK_CMP        = (1ULL << 9),
     BPF_F_REUSE_STACKID     = (1ULL << 10),
 /* flags used by BPF_FUNC_get_stack only. */
     BPF_F_USER_BUILD_ID     = (1ULL << 11),
 };
 
 /* BPF_FUNC_skb_set_tunnel_key flags. */
 enum {
     BPF_F_ZERO_CSUM_TX      = (1ULL << 1),
     BPF_F_DONT_FRAGMENT     = (1ULL << 2),
     BPF_F_SEQ_NUMBER        = (1ULL << 3),
 };
 
 /* BPF_FUNC_perf_event_output, BPF_FUNC_perf_event_read and
  * BPF_FUNC_perf_event_read_value flags.
  */
 enum {
     BPF_F_INDEX_MASK        = 0xffffffffULL,
     BPF_F_CURRENT_CPU       = BPF_F_INDEX_MASK,
 /* BPF_FUNC_perf_event_output for sk_buff input context. */
     BPF_F_CTXLEN_MASK       = (0xfffffULL << 32),
 };
 
 /* Current network namespace */
 enum {
     BPF_F_CURRENT_NETNS     = (-1L),
 };
 
 /* BPF_FUNC_csum_level level values. */
 enum {
     BPF_CSUM_LEVEL_QUERY,
     BPF_CSUM_LEVEL_INC,
     BPF_CSUM_LEVEL_DEC,
     BPF_CSUM_LEVEL_RESET,
 };
 
 /* BPF_FUNC_skb_adjust_room flags. */
 enum {
     BPF_F_ADJ_ROOM_FIXED_GSO    = (1ULL << 0),
     BPF_F_ADJ_ROOM_ENCAP_L3_IPV4    = (1ULL << 1),
     BPF_F_ADJ_ROOM_ENCAP_L3_IPV6    = (1ULL << 2),
     BPF_F_ADJ_ROOM_ENCAP_L4_GRE = (1ULL << 3),
     BPF_F_ADJ_ROOM_ENCAP_L4_UDP = (1ULL << 4),
     BPF_F_ADJ_ROOM_NO_CSUM_RESET    = (1ULL << 5),
     BPF_F_ADJ_ROOM_ENCAP_L2_ETH = (1ULL << 6),
 };
 
 enum {
     BPF_ADJ_ROOM_ENCAP_L2_MASK  = 0xff,
     BPF_ADJ_ROOM_ENCAP_L2_SHIFT = 56,
 };
 
 #define BPF_F_ADJ_ROOM_ENCAP_L2(len)    (((__u64)len & \
                       BPF_ADJ_ROOM_ENCAP_L2_MASK) \
                      << BPF_ADJ_ROOM_ENCAP_L2_SHIFT)
 
 /* BPF_FUNC_sysctl_get_name flags. */
 enum {
     BPF_F_SYSCTL_BASE_NAME      = (1ULL << 0),
 };
 
 /* BPF_FUNC_<kernel_obj>_storage_get flags */
 enum {
     BPF_LOCAL_STORAGE_GET_F_CREATE  = (1ULL << 0),
     /* BPF_SK_STORAGE_GET_F_CREATE is only kept for backward compatibility
      * and BPF_LOCAL_STORAGE_GET_F_CREATE must be used instead.
      */
     BPF_SK_STORAGE_GET_F_CREATE  = BPF_LOCAL_STORAGE_GET_F_CREATE,
 };
 
 /* BPF_FUNC_read_branch_records flags. */
 enum {
     BPF_F_GET_BRANCH_RECORDS_SIZE   = (1ULL << 0),
 };
 
 /* BPF_FUNC_bpf_ringbuf_commit, BPF_FUNC_bpf_ringbuf_discard, and
  * BPF_FUNC_bpf_ringbuf_output flags.
  */
 enum {
     BPF_RB_NO_WAKEUP        = (1ULL << 0),
     BPF_RB_FORCE_WAKEUP     = (1ULL << 1),
 };
 
 /* BPF_FUNC_bpf_ringbuf_query flags */
 enum {
     BPF_RB_AVAIL_DATA = 0,
     BPF_RB_RING_SIZE = 1,
     BPF_RB_CONS_POS = 2,
     BPF_RB_PROD_POS = 3,
 };
 
 /* BPF ring buffer constants */
 enum {
     BPF_RINGBUF_BUSY_BIT        = (1U << 31),
     BPF_RINGBUF_DISCARD_BIT     = (1U << 30),
     BPF_RINGBUF_HDR_SZ      = 8,
 };
 
 /* BPF_FUNC_sk_assign flags in bpf_sk_lookup context. */
 enum {
     BPF_SK_LOOKUP_F_REPLACE     = (1ULL << 0),
     BPF_SK_LOOKUP_F_NO_REUSEPORT    = (1ULL << 1),
 };
 
 /* Mode for BPF_FUNC_skb_adjust_room helper. */
 enum bpf_adj_room_mode {
     BPF_ADJ_ROOM_NET,
     BPF_ADJ_ROOM_MAC,
 };
 
 /* Mode for BPF_FUNC_skb_load_bytes_relative helper. */
 enum bpf_hdr_start_off {
     BPF_HDR_START_MAC,
     BPF_HDR_START_NET,
 };
 
 /* Encapsulation type for BPF_FUNC_lwt_push_encap helper. */
 enum bpf_lwt_encap_mode {
     BPF_LWT_ENCAP_SEG6,
     BPF_LWT_ENCAP_SEG6_INLINE,
     BPF_LWT_ENCAP_IP,
 };
 
 /* Flags for bpf_bprm_opts_set helper */
 enum {
     BPF_F_BPRM_SECUREEXEC   = (1ULL << 0),
 };
 
 /* Flags for bpf_redirect_map helper */
 enum {
     BPF_F_BROADCAST     = (1ULL << 3),
     BPF_F_EXCLUDE_INGRESS   = (1ULL << 4),
 };
 
 #define __bpf_md_ptr(type, name)    \
 union {                 \
     type name;          \
     __u64 :64;          \
 } __attribute__((aligned(8)))
 
 enum {
     BPF_SKB_TSTAMP_UNSPEC,
     BPF_SKB_TSTAMP_DELIVERY_MONO,   /* tstamp has mono delivery time */
     /* For any BPF_SKB_TSTAMP_* that the bpf prog cannot handle,
      * the bpf prog should handle it like BPF_SKB_TSTAMP_UNSPEC
      * and try to deduce it by ingress, egress or skb->sk->sk_clockid.
      */
 };
 
 /* user accessible mirror of in-kernel sk_buff.
  * new fields can only be added to the end of this structure
  */
 struct __sk_buff {
     __u32 len;
     __u32 pkt_type;
     __u32 mark;
     __u32 queue_mapping;
     __u32 protocol;
     __u32 vlan_present;
     __u32 vlan_tci;
     __u32 vlan_proto;
     __u32 priority;
     __u32 ingress_ifindex;
     __u32 ifindex;
     __u32 tc_index;
     __u32 cb[5];
     __u32 hash;
     __u32 tc_classid;
     __u32 data;
     __u32 data_end;
     __u32 napi_id;
 
     /* Accessed by BPF_PROG_TYPE_sk_skb types from here to ... */
     __u32 family;
     __u32 remote_ip4;   /* Stored in network byte order */
     __u32 local_ip4;    /* Stored in network byte order */
     __u32 remote_ip6[4];    /* Stored in network byte order */
     __u32 local_ip6[4]; /* Stored in network byte order */
     __u32 remote_port;  /* Stored in network byte order */
     __u32 local_port;   /* stored in host byte order */
     /* ... here. */
 
     __u32 data_meta;
     __bpf_md_ptr(struct bpf_flow_keys *, flow_keys);
     __u64 tstamp;
     __u32 wire_len;
     __u32 gso_segs;
     __bpf_md_ptr(struct bpf_sock *, sk);
     __u32 gso_size;
     __u8  tstamp_type;
     __u32 :24;      /* Padding, future use. */
     __u64 hwtstamp;
 };
 
 struct bpf_tunnel_key {
     __u32 tunnel_id;
     union {
         __u32 remote_ipv4;
         __u32 remote_ipv6[4];
     };
     __u8 tunnel_tos;
     __u8 tunnel_ttl;
     __u16 tunnel_ext;   /* Padding, future use. */
     __u32 tunnel_label;
     union {
         __u32 local_ipv4;
         __u32 local_ipv6[4];
     };
 };
 
 /* user accessible mirror of in-kernel xfrm_state.
  * new fields can only be added to the end of this structure
  */
 struct bpf_xfrm_state {
     __u32 reqid;
     __u32 spi;  /* Stored in network byte order */
     __u16 family;
     __u16 ext;  /* Padding, future use. */
     union {
         __u32 remote_ipv4;  /* Stored in network byte order */
         __u32 remote_ipv6[4];   /* Stored in network byte order */
     };
 };
 
 /* Generic BPF return codes which all BPF program types may support.
  * The values are binary compatible with their TC_ACT_* counter-part to
  * provide backwards compatibility with existing SCHED_CLS and SCHED_ACT
  * programs.
  *
  * XDP is handled seprately, see XDP_*.
  */
 enum bpf_ret_code {
     BPF_OK = 0,
     /* 1 reserved */
     BPF_DROP = 2,
     /* 3-6 reserved */
     BPF_REDIRECT = 7,
     /* >127 are reserved for prog type specific return codes.
      *
      * BPF_LWT_REROUTE: used by BPF_PROG_TYPE_LWT_IN and
      *    BPF_PROG_TYPE_LWT_XMIT to indicate that skb had been
      *    changed and should be routed based on its new L3 header.
      *    (This is an L3 redirect, as opposed to L2 redirect
      *    represented by BPF_REDIRECT above).
      */
     BPF_LWT_REROUTE = 128,
 };
 
 struct bpf_sock {
     __u32 bound_dev_if;
     __u32 family;
     __u32 type;
     __u32 protocol;
     __u32 mark;
     __u32 priority;
     /* IP address also allows 1 and 2 bytes access */
     __u32 src_ip4;
     __u32 src_ip6[4];
     __u32 src_port;     /* host byte order */
     __be16 dst_port;    /* network byte order */
     __u16 :16;      /* zero padding */
     __u32 dst_ip4;
     __u32 dst_ip6[4];
     __u32 state;
     __s32 rx_queue_mapping;
 };
 
 struct bpf_tcp_sock {
     __u32 snd_cwnd;     /* Sending congestion window        */
     __u32 srtt_us;      /* smoothed round trip time << 3 in usecs */
     __u32 rtt_min;
     __u32 snd_ssthresh; /* Slow start size threshold        */
     __u32 rcv_nxt;      /* What we want to receive next     */
     __u32 snd_nxt;      /* Next sequence we send        */
     __u32 snd_una;      /* First byte we want an ack for    */
     __u32 mss_cache;    /* Cached effective mss, not including SACKS */
     __u32 ecn_flags;    /* ECN status bits.         */
     __u32 rate_delivered;   /* saved rate sample: packets delivered */
     __u32 rate_interval_us; /* saved rate sample: time elapsed */
     __u32 packets_out;  /* Packets which are "in flight"    */
     __u32 retrans_out;  /* Retransmitted packets out        */
     __u32 total_retrans;    /* Total retransmits for entire connection */
     __u32 segs_in;      /* RFC4898 tcpEStatsPerfSegsIn
                  * total number of segments in.
                  */
     __u32 data_segs_in; /* RFC4898 tcpEStatsPerfDataSegsIn
                  * total number of data segments in.
                  */
     __u32 segs_out;     /* RFC4898 tcpEStatsPerfSegsOut
                  * The total number of segments sent.
                  */
     __u32 data_segs_out;    /* RFC4898 tcpEStatsPerfDataSegsOut
                  * total number of data segments sent.
                  */
     __u32 lost_out;     /* Lost packets         */
     __u32 sacked_out;   /* SACK'd packets           */
     __u64 bytes_received;   /* RFC4898 tcpEStatsAppHCThruOctetsReceived
                  * sum(delta(rcv_nxt)), or how many bytes
                  * were acked.
                  */
     __u64 bytes_acked;  /* RFC4898 tcpEStatsAppHCThruOctetsAcked
                  * sum(delta(snd_una)), or how many bytes
                  * were acked.
                  */
     __u32 dsack_dups;   /* RFC4898 tcpEStatsStackDSACKDups
                  * total number of DSACK blocks received
                  */
     __u32 delivered;    /* Total data packets delivered incl. rexmits */
     __u32 delivered_ce; /* Like the above but only ECE marked packets */
     __u32 icsk_retransmits; /* Number of unrecovered [RTO] timeouts */
 };
 
 struct bpf_sock_tuple {
     union {
         struct {
             __be32 saddr;
             __be32 daddr;
             __be16 sport;
             __be16 dport;
         } ipv4;
         struct {
             __be32 saddr[4];
             __be32 daddr[4];
             __be16 sport;
             __be16 dport;
         } ipv6;
     };
 };
 
 struct bpf_xdp_sock {
     __u32 queue_id;
 };
 
 #define XDP_PACKET_HEADROOM 256
 
 /* User return codes for XDP prog type.
  * A valid XDP program must return one of these defined values. All other
  * return codes are reserved for future use. Unknown return codes will
  * result in packet drops and a warning via bpf_warn_invalid_xdp_action().
  */
 enum xdp_action {
     XDP_ABORTED = 0,
     XDP_DROP,
     XDP_PASS,
     XDP_TX,
     XDP_REDIRECT,
 };
 
 /* user accessible metadata for XDP packet hook
  * new fields must be added to the end of this structure
  */
 struct xdp_md {
     __u32 data;
     __u32 data_end;
     __u32 data_meta;
     /* Below access go through struct xdp_rxq_info */
     __u32 ingress_ifindex; /* rxq->dev->ifindex */
     __u32 rx_queue_index;  /* rxq->queue_index  */
 
     __u32 egress_ifindex;  /* txq->dev->ifindex */
 };
 
 /* DEVMAP map-value layout
  *
  * The struct data-layout of map-value is a configuration interface.
  * New members can only be added to the end of this structure.
  */
 struct bpf_devmap_val {
     __u32 ifindex;   /* device index */
     union {
         int   fd;  /* prog fd on map write */
         __u32 id;  /* prog id on map read */
     } bpf_prog;
 };
 
 /* CPUMAP map-value layout
  *
  * The struct data-layout of map-value is a configuration interface.
  * New members can only be added to the end of this structure.
  */
 struct bpf_cpumap_val {
     __u32 qsize;    /* queue size to remote target CPU */
     union {
         int   fd;   /* prog fd on map write */
         __u32 id;   /* prog id on map read */
     } bpf_prog;
 };
 
 enum sk_action {
     SK_DROP = 0,
     SK_PASS,
 };
 
 /* user accessible metadata for SK_MSG packet hook, new fields must
  * be added to the end of this structure
  */
 struct sk_msg_md {
     __bpf_md_ptr(void *, data);
     __bpf_md_ptr(void *, data_end);
 
     __u32 family;
     __u32 remote_ip4;   /* Stored in network byte order */
     __u32 local_ip4;    /* Stored in network byte order */
     __u32 remote_ip6[4];    /* Stored in network byte order */
     __u32 local_ip6[4]; /* Stored in network byte order */
     __u32 remote_port;  /* Stored in network byte order */
     __u32 local_port;   /* stored in host byte order */
     __u32 size;     /* Total size of sk_msg */
 
     __bpf_md_ptr(struct bpf_sock *, sk); /* current socket */
 };
 
 struct sk_reuseport_md {
     /*
      * Start of directly accessible data. It begins from
      * the tcp/udp header.
      */
     __bpf_md_ptr(void *, data);
     /* End of directly accessible data */
     __bpf_md_ptr(void *, data_end);
     /*
      * Total length of packet (starting from the tcp/udp header).
      * Note that the directly accessible bytes (data_end - data)
      * could be less than this "len".  Those bytes could be
      * indirectly read by a helper "bpf_skb_load_bytes()".
      */
     __u32 len;
     /*
      * Eth protocol in the mac header (network byte order). e.g.
      * ETH_P_IP(0x0800) and ETH_P_IPV6(0x86DD)
      */
     __u32 eth_protocol;
     __u32 ip_protocol;  /* IP protocol. e.g. IPPROTO_TCP, IPPROTO_UDP */
     __u32 bind_inany;   /* Is sock bound to an INANY address? */
     __u32 hash;     /* A hash of the packet 4 tuples */
     /* When reuse->migrating_sk is NULL, it is selecting a sk for the
      * new incoming connection request (e.g. selecting a listen sk for
      * the received SYN in the TCP case).  reuse->sk is one of the sk
      * in the reuseport group. The bpf prog can use reuse->sk to learn
      * the local listening ip/port without looking into the skb.
      *
      * When reuse->migrating_sk is not NULL, reuse->sk is closed and
      * reuse->migrating_sk is the socket that needs to be migrated
      * to another listening socket.  migrating_sk could be a fullsock
      * sk that is fully established or a reqsk that is in-the-middle
      * of 3-way handshake.
      */
     __bpf_md_ptr(struct bpf_sock *, sk);
     __bpf_md_ptr(struct bpf_sock *, migrating_sk);
 };
 
 #define BPF_TAG_SIZE    8
 
 struct bpf_prog_info {
     __u32 type;
     __u32 id;
     __u8  tag[BPF_TAG_SIZE];
     __u32 jited_prog_len;
     __u32 xlated_prog_len;
     __aligned_u64 jited_prog_insns;
     __aligned_u64 xlated_prog_insns;
     __u64 load_time;    /* ns since boottime */
     __u32 created_by_uid;
     __u32 nr_map_ids;
     __aligned_u64 map_ids;
     char name[BPF_OBJ_NAME_LEN];
     __u32 ifindex;
     __u32 gpl_compatible:1;
     __u32 :31; /* alignment pad */
     __u64 netns_dev;
     __u64 netns_ino;
     __u32 nr_jited_ksyms;
     __u32 nr_jited_func_lens;
     __aligned_u64 jited_ksyms;
     __aligned_u64 jited_func_lens;
     __u32 btf_id;
     __u32 func_info_rec_size;
     __aligned_u64 func_info;
     __u32 nr_func_info;
     __u32 nr_line_info;
     __aligned_u64 line_info;
     __aligned_u64 jited_line_info;
     __u32 nr_jited_line_info;
     __u32 line_info_rec_size;
     __u32 jited_line_info_rec_size;
     __u32 nr_prog_tags;
     __aligned_u64 prog_tags;
     __u64 run_time_ns;
     __u64 run_cnt;
     __u64 recursion_misses;
     __u32 verified_insns;
     __u32 attach_btf_obj_id;
     __u32 attach_btf_id;
 } __attribute__((aligned(8)));
 
 struct bpf_map_info {
     __u32 type;
     __u32 id;
     __u32 key_size;
     __u32 value_size;
     __u32 max_entries;
     __u32 map_flags;
     char  name[BPF_OBJ_NAME_LEN];
     __u32 ifindex;
     __u32 btf_vmlinux_value_type_id;
     __u64 netns_dev;
     __u64 netns_ino;
     __u32 btf_id;
     __u32 btf_key_type_id;
     __u32 btf_value_type_id;
     __u32 :32;  /* alignment pad */
     __u64 map_extra;
 } __attribute__((aligned(8)));
 
 struct bpf_btf_info {
     __aligned_u64 btf;
     __u32 btf_size;
     __u32 id;
     __aligned_u64 name;
     __u32 name_len;
     __u32 kernel_btf;
 } __attribute__((aligned(8)));
 
 struct bpf_link_info {
     __u32 type;
     __u32 id;
     __u32 prog_id;
     union {
         struct {
             __aligned_u64 tp_name; /* in/out: tp_name buffer ptr */
             __u32 tp_name_len;     /* in/out: tp_name buffer len */
         } raw_tracepoint;
         struct {
             __u32 attach_type;
             __u32 target_obj_id; /* prog_id for PROG_EXT, otherwise btf object id */
             __u32 target_btf_id; /* BTF type id inside the object */
         } tracing;
         struct {
             __u64 cgroup_id;
             __u32 attach_type;
         } cgroup;
         struct {
             __aligned_u64 target_name; /* in/out: target_name buffer ptr */
             __u32 target_name_len;     /* in/out: target_name buffer len */
             union {
                 struct {
                     __u32 map_id;
                 } map;
             };
         } iter;
         struct  {
             __u32 netns_ino;
             __u32 attach_type;
         } netns;
         struct {
             __u32 ifindex;
         } xdp;
     };
 } __attribute__((aligned(8)));
 
 /* User bpf_sock_addr struct to access socket fields and sockaddr struct passed
  * by user and intended to be used by socket (e.g. to bind to, depends on
  * attach type).
  */
 struct bpf_sock_addr {
     __u32 user_family;  /* Allows 4-byte read, but no write. */
     __u32 user_ip4;     /* Allows 1,2,4-byte read and 4-byte write.
                  * Stored in network byte order.
                  */
     __u32 user_ip6[4];  /* Allows 1,2,4,8-byte read and 4,8-byte write.
                  * Stored in network byte order.
                  */
     __u32 user_port;    /* Allows 1,2,4-byte read and 4-byte write.
                  * Stored in network byte order
                  */
     __u32 family;       /* Allows 4-byte read, but no write */
     __u32 type;     /* Allows 4-byte read, but no write */
     __u32 protocol;     /* Allows 4-byte read, but no write */
     __u32 msg_src_ip4;  /* Allows 1,2,4-byte read and 4-byte write.
                  * Stored in network byte order.
                  */
     __u32 msg_src_ip6[4];   /* Allows 1,2,4,8-byte read and 4,8-byte write.
                  * Stored in network byte order.
                  */
     __bpf_md_ptr(struct bpf_sock *, sk);
 };
 
 /* User bpf_sock_ops struct to access socket values and specify request ops
  * and their replies.
  * Some of this fields are in network (bigendian) byte order and may need
  * to be converted before use (bpf_ntohl() defined in samples/bpf/bpf_endian.h).
  * New fields can only be added at the end of this structure
  */
 struct bpf_sock_ops {
     __u32 op;
     union {
         __u32 args[4];      /* Optionally passed to bpf program */
         __u32 reply;        /* Returned by bpf program      */
         __u32 replylong[4]; /* Optionally returned by bpf prog  */
     };
     __u32 family;
     __u32 remote_ip4;   /* Stored in network byte order */
     __u32 local_ip4;    /* Stored in network byte order */
     __u32 remote_ip6[4];    /* Stored in network byte order */
     __u32 local_ip6[4]; /* Stored in network byte order */
     __u32 remote_port;  /* Stored in network byte order */
     __u32 local_port;   /* stored in host byte order */
     __u32 is_fullsock;  /* Some TCP fields are only valid if
                  * there is a full socket. If not, the
                  * fields read as zero.
                  */
     __u32 snd_cwnd;
     __u32 srtt_us;      /* Averaged RTT << 3 in usecs */
     __u32 bpf_sock_ops_cb_flags; /* flags defined in uapi/linux/tcp.h */
     __u32 state;
     __u32 rtt_min;
     __u32 snd_ssthresh;
     __u32 rcv_nxt;
     __u32 snd_nxt;
     __u32 snd_una;
     __u32 mss_cache;
     __u32 ecn_flags;
     __u32 rate_delivered;
     __u32 rate_interval_us;
     __u32 packets_out;
     __u32 retrans_out;
     __u32 total_retrans;
     __u32 segs_in;
     __u32 data_segs_in;
     __u32 segs_out;
     __u32 data_segs_out;
     __u32 lost_out;
     __u32 sacked_out;
     __u32 sk_txhash;
     __u64 bytes_received;
     __u64 bytes_acked;
     __bpf_md_ptr(struct bpf_sock *, sk);
     /* [skb_data, skb_data_end) covers the whole TCP header.
      *
      * BPF_SOCK_OPS_PARSE_HDR_OPT_CB: The packet received
      * BPF_SOCK_OPS_HDR_OPT_LEN_CB:   Not useful because the
      *                                header has not been written.
      * BPF_SOCK_OPS_WRITE_HDR_OPT_CB: The header and options have
      *                been written so far.
      * BPF_SOCK_OPS_ACTIVE_ESTABLISHED_CB:  The SYNACK that concludes
      *                  the 3WHS.
      * BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB: The ACK that concludes
      *                  the 3WHS.
      *
      * bpf_load_hdr_opt() can also be used to read a particular option.
      */
     __bpf_md_ptr(void *, skb_data);
     __bpf_md_ptr(void *, skb_data_end);
     __u32 skb_len;      /* The total length of a packet.
                  * It includes the header, options,
                  * and payload.
                  */
     __u32 skb_tcp_flags;    /* tcp_flags of the header.  It provides
                  * an easy way to check for tcp_flags
                  * without parsing skb_data.
                  *
                  * In particular, the skb_tcp_flags
                  * will still be available in
                  * BPF_SOCK_OPS_HDR_OPT_LEN even though
                  * the outgoing header has not
                  * been written yet.
                  */
 };
 
 /* Definitions for bpf_sock_ops_cb_flags */
 enum {
     BPF_SOCK_OPS_RTO_CB_FLAG    = (1<<0),
     BPF_SOCK_OPS_RETRANS_CB_FLAG    = (1<<1),
     BPF_SOCK_OPS_STATE_CB_FLAG  = (1<<2),
     BPF_SOCK_OPS_RTT_CB_FLAG    = (1<<3),
     /* Call bpf for all received TCP headers.  The bpf prog will be
      * called under sock_ops->op == BPF_SOCK_OPS_PARSE_HDR_OPT_CB
      *
      * Please refer to the comment in BPF_SOCK_OPS_PARSE_HDR_OPT_CB
      * for the header option related helpers that will be useful
      * to the bpf programs.
      *
      * It could be used at the client/active side (i.e. connect() side)
      * when the server told it that the server was in syncookie
      * mode and required the active side to resend the bpf-written
      * options.  The active side can keep writing the bpf-options until
      * it received a valid packet from the server side to confirm
      * the earlier packet (and options) has been received.  The later
      * example patch is using it like this at the active side when the
      * server is in syncookie mode.
      *
      * The bpf prog will usually turn this off in the common cases.
      */
     BPF_SOCK_OPS_PARSE_ALL_HDR_OPT_CB_FLAG  = (1<<4),
     /* Call bpf when kernel has received a header option that
      * the kernel cannot handle.  The bpf prog will be called under
      * sock_ops->op == BPF_SOCK_OPS_PARSE_HDR_OPT_CB.
      *
      * Please refer to the comment in BPF_SOCK_OPS_PARSE_HDR_OPT_CB
      * for the header option related helpers that will be useful
      * to the bpf programs.
      */
     BPF_SOCK_OPS_PARSE_UNKNOWN_HDR_OPT_CB_FLAG = (1<<5),
     /* Call bpf when the kernel is writing header options for the
      * outgoing packet.  The bpf prog will first be called
      * to reserve space in a skb under
      * sock_ops->op == BPF_SOCK_OPS_HDR_OPT_LEN_CB.  Then
      * the bpf prog will be called to write the header option(s)
      * under sock_ops->op == BPF_SOCK_OPS_WRITE_HDR_OPT_CB.
      *
      * Please refer to the comment in BPF_SOCK_OPS_HDR_OPT_LEN_CB
      * and BPF_SOCK_OPS_WRITE_HDR_OPT_CB for the header option
      * related helpers that will be useful to the bpf programs.
      *
      * The kernel gets its chance to reserve space and write
      * options first before the BPF program does.
      */
     BPF_SOCK_OPS_WRITE_HDR_OPT_CB_FLAG = (1<<6),
 /* Mask of all currently supported cb flags */
     BPF_SOCK_OPS_ALL_CB_FLAGS       = 0x7F,
 };
 
 /* List of known BPF sock_ops operators.
  * New entries can only be added at the end
  */
 enum {
     BPF_SOCK_OPS_VOID,
     BPF_SOCK_OPS_TIMEOUT_INIT,  /* Should return SYN-RTO value to use or
                      * -1 if default value should be used
                      */
     BPF_SOCK_OPS_RWND_INIT,     /* Should return initial advertized
                      * window (in packets) or -1 if default
                      * value should be used
                      */
     BPF_SOCK_OPS_TCP_CONNECT_CB,    /* Calls BPF program right before an
                      * active connection is initialized
                      */
     BPF_SOCK_OPS_ACTIVE_ESTABLISHED_CB, /* Calls BPF program when an
                          * active connection is
                          * established
                          */
     BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB,    /* Calls BPF program when a
                          * passive connection is
                          * established
                          */
     BPF_SOCK_OPS_NEEDS_ECN,     /* If connection's congestion control
                      * needs ECN
                      */
     BPF_SOCK_OPS_BASE_RTT,      /* Get base RTT. The correct value is
                      * based on the path and may be
                      * dependent on the congestion control
                      * algorithm. In general it indicates
                      * a congestion threshold. RTTs above
                      * this indicate congestion
                      */
     BPF_SOCK_OPS_RTO_CB,        /* Called when an RTO has triggered.
                      * Arg1: value of icsk_retransmits
                      * Arg2: value of icsk_rto
                      * Arg3: whether RTO has expired
                      */
     BPF_SOCK_OPS_RETRANS_CB,    /* Called when skb is retransmitted.
                      * Arg1: sequence number of 1st byte
                      * Arg2: # segments
                      * Arg3: return value of
                      *       tcp_transmit_skb (0 => success)
                      */
     BPF_SOCK_OPS_STATE_CB,      /* Called when TCP changes state.
                      * Arg1: old_state
                      * Arg2: new_state
                      */
     BPF_SOCK_OPS_TCP_LISTEN_CB, /* Called on listen(2), right after
                      * socket transition to LISTEN state.
                      */
     BPF_SOCK_OPS_RTT_CB,        /* Called on every RTT.
                      */
     BPF_SOCK_OPS_PARSE_HDR_OPT_CB,  /* Parse the header option.
                      * It will be called to handle
                      * the packets received at
                      * an already established
                      * connection.
                      *
                      * sock_ops->skb_data:
                      * Referring to the received skb.
                      * It covers the TCP header only.
                      *
                      * bpf_load_hdr_opt() can also
                      * be used to search for a
                      * particular option.
                      */
     BPF_SOCK_OPS_HDR_OPT_LEN_CB,    /* Reserve space for writing the
                      * header option later in
                      * BPF_SOCK_OPS_WRITE_HDR_OPT_CB.
                      * Arg1: bool want_cookie. (in
                      *       writing SYNACK only)
                      *
                      * sock_ops->skb_data:
                      * Not available because no header has
                      * been written yet.
                      *
                      * sock_ops->skb_tcp_flags:
                      * The tcp_flags of the
                      * outgoing skb. (e.g. SYN, ACK, FIN).
                      *
                      * bpf_reserve_hdr_opt() should
                      * be used to reserve space.
                      */
     BPF_SOCK_OPS_WRITE_HDR_OPT_CB,  /* Write the header options
                      * Arg1: bool want_cookie. (in
                      *       writing SYNACK only)
                      *
                      * sock_ops->skb_data:
                      * Referring to the outgoing skb.
                      * It covers the TCP header
                      * that has already been written
                      * by the kernel and the
                      * earlier bpf-progs.
                      *
                      * sock_ops->skb_tcp_flags:
                      * The tcp_flags of the outgoing
                      * skb. (e.g. SYN, ACK, FIN).
                      *
                      * bpf_store_hdr_opt() should
                      * be used to write the
                      * option.
                      *
                      * bpf_load_hdr_opt() can also
                      * be used to search for a
                      * particular option that
                      * has already been written
                      * by the kernel or the
                      * earlier bpf-progs.
                      */
 };
 
 /* List of TCP states. There is a build check in net/ipv4/tcp.c to detect
  * changes between the TCP and BPF versions. Ideally this should never happen.
  * If it does, we need to add code to convert them before calling
  * the BPF sock_ops function.
  */
 enum {
     BPF_TCP_ESTABLISHED = 1,
     BPF_TCP_SYN_SENT,
     BPF_TCP_SYN_RECV,
     BPF_TCP_FIN_WAIT1,
     BPF_TCP_FIN_WAIT2,
     BPF_TCP_TIME_WAIT,
     BPF_TCP_CLOSE,
     BPF_TCP_CLOSE_WAIT,
     BPF_TCP_LAST_ACK,
     BPF_TCP_LISTEN,
     BPF_TCP_CLOSING,    /* Now a valid state */
     BPF_TCP_NEW_SYN_RECV,
 
     BPF_TCP_MAX_STATES  /* Leave at the end! */
 };
 
 enum {
     TCP_BPF_IW      = 1001, /* Set TCP initial congestion window */
     TCP_BPF_SNDCWND_CLAMP   = 1002, /* Set sndcwnd_clamp */
     TCP_BPF_DELACK_MAX  = 1003, /* Max delay ack in usecs */
     TCP_BPF_RTO_MIN     = 1004, /* Min delay ack in usecs */
     /* Copy the SYN pkt to optval
      *
      * BPF_PROG_TYPE_SOCK_OPS only.  It is similar to the
      * bpf_getsockopt(TCP_SAVED_SYN) but it does not limit
      * to only getting from the saved_syn.  It can either get the
      * syn packet from:
      *
      * 1. the just-received SYN packet (only available when writing the
      *    SYNACK).  It will be useful when it is not necessary to
      *    save the SYN packet for latter use.  It is also the only way
      *    to get the SYN during syncookie mode because the syn
      *    packet cannot be saved during syncookie.
      *
      * OR
      *
      * 2. the earlier saved syn which was done by
      *    bpf_setsockopt(TCP_SAVE_SYN).
      *
      * The bpf_getsockopt(TCP_BPF_SYN*) option will hide where the
      * SYN packet is obtained.
      *
      * If the bpf-prog does not need the IP[46] header,  the
      * bpf-prog can avoid parsing the IP header by using
      * TCP_BPF_SYN.  Otherwise, the bpf-prog can get both
      * IP[46] and TCP header by using TCP_BPF_SYN_IP.
      *
      *      >0: Total number of bytes copied
      * -ENOSPC: Not enough space in optval. Only optlen number of
      *          bytes is copied.
      * -ENOENT: The SYN skb is not available now and the earlier SYN pkt
      *      is not saved by setsockopt(TCP_SAVE_SYN).
      */
     TCP_BPF_SYN     = 1005, /* Copy the TCP header */
     TCP_BPF_SYN_IP      = 1006, /* Copy the IP[46] and TCP header */
     TCP_BPF_SYN_MAC         = 1007, /* Copy the MAC, IP[46], and TCP header */
 };
 
 enum {
     BPF_LOAD_HDR_OPT_TCP_SYN = (1ULL << 0),
 };
 
 /* args[0] value during BPF_SOCK_OPS_HDR_OPT_LEN_CB and
  * BPF_SOCK_OPS_WRITE_HDR_OPT_CB.
  */
 enum {
     BPF_WRITE_HDR_TCP_CURRENT_MSS = 1,  /* Kernel is finding the
                          * total option spaces
                          * required for an established
                          * sk in order to calculate the
                          * MSS.  No skb is actually
                          * sent.
                          */
     BPF_WRITE_HDR_TCP_SYNACK_COOKIE = 2,    /* Kernel is in syncookie mode
                          * when sending a SYN.
                          */
 };
 
 struct bpf_perf_event_value {
     __u64 counter;
     __u64 enabled;
     __u64 running;
 };
 
 enum {
     BPF_DEVCG_ACC_MKNOD = (1ULL << 0),
     BPF_DEVCG_ACC_READ  = (1ULL << 1),
     BPF_DEVCG_ACC_WRITE = (1ULL << 2),
 };
 
 enum {
     BPF_DEVCG_DEV_BLOCK = (1ULL << 0),
     BPF_DEVCG_DEV_CHAR  = (1ULL << 1),
 };
 
 struct bpf_cgroup_dev_ctx {
     /* access_type encoded as (BPF_DEVCG_ACC_* << 16) | BPF_DEVCG_DEV_* */
     __u32 access_type;
     __u32 major;
     __u32 minor;
 };
 
 struct bpf_raw_tracepoint_args {
     __u64 args[0];
 };
 
 /* DIRECT:  Skip the FIB rules and go to FIB table associated with device
  * OUTPUT:  Do lookup from egress perspective; default is ingress
  */
 enum {
     BPF_FIB_LOOKUP_DIRECT  = (1U << 0),
     BPF_FIB_LOOKUP_OUTPUT  = (1U << 1),
 };
 
 enum {
     BPF_FIB_LKUP_RET_SUCCESS,      /* lookup successful */
     BPF_FIB_LKUP_RET_BLACKHOLE,    /* dest is blackholed; can be dropped */
     BPF_FIB_LKUP_RET_UNREACHABLE,  /* dest is unreachable; can be dropped */
     BPF_FIB_LKUP_RET_PROHIBIT,     /* dest not allowed; can be dropped */
     BPF_FIB_LKUP_RET_NOT_FWDED,    /* packet is not forwarded */
     BPF_FIB_LKUP_RET_FWD_DISABLED, /* fwding is not enabled on ingress */
     BPF_FIB_LKUP_RET_UNSUPP_LWT,   /* fwd requires encapsulation */
     BPF_FIB_LKUP_RET_NO_NEIGH,     /* no neighbor entry for nh */
     BPF_FIB_LKUP_RET_FRAG_NEEDED,  /* fragmentation required to fwd */
 };
 
 struct bpf_fib_lookup {
     /* input:  network family for lookup (AF_INET, AF_INET6)
      * output: network family of egress nexthop
      */
     __u8    family;
 
     /* set if lookup is to consider L4 data - e.g., FIB rules */
     __u8    l4_protocol;
     __be16  sport;
     __be16  dport;
 
     union { /* used for MTU check */
         /* input to lookup */
         __u16   tot_len; /* L3 length from network hdr (iph->tot_len) */
 
         /* output: MTU value */
         __u16   mtu_result;
     };
     /* input: L3 device index for lookup
      * output: device index from FIB lookup
      */
     __u32   ifindex;
 
     union {
         /* inputs to lookup */
         __u8    tos;        /* AF_INET  */
         __be32  flowinfo;   /* AF_INET6, flow_label + priority */
 
         /* output: metric of fib result (IPv4/IPv6 only) */
         __u32   rt_metric;
     };
 
     union {
         __be32      ipv4_src;
         __u32       ipv6_src[4];  /* in6_addr; network order */
     };
 
     /* input to bpf_fib_lookup, ipv{4,6}_dst is destination address in
      * network header. output: bpf_fib_lookup sets to gateway address
      * if FIB lookup returns gateway route
      */
     union {
         __be32      ipv4_dst;
         __u32       ipv6_dst[4];  /* in6_addr; network order */
     };
 
     /* output */
     __be16  h_vlan_proto;
     __be16  h_vlan_TCI;
     __u8    smac[6];     /* ETH_ALEN */
     __u8    dmac[6];     /* ETH_ALEN */
 };
 
 struct bpf_redir_neigh {
     /* network family for lookup (AF_INET, AF_INET6) */
     __u32 nh_family;
     /* network address of nexthop; skips fib lookup to find gateway */
     union {
         __be32      ipv4_nh;
         __u32       ipv6_nh[4];  /* in6_addr; network order */
     };
 };
 
 /* bpf_check_mtu flags*/
 enum  bpf_check_mtu_flags {
     BPF_MTU_CHK_SEGS  = (1U << 0),
 };
 
 enum bpf_check_mtu_ret {
     BPF_MTU_CHK_RET_SUCCESS,      /* check and lookup successful */
     BPF_MTU_CHK_RET_FRAG_NEEDED,  /* fragmentation required to fwd */
     BPF_MTU_CHK_RET_SEGS_TOOBIG,  /* GSO re-segmentation needed to fwd */
 };
 
 enum bpf_task_fd_type {
     BPF_FD_TYPE_RAW_TRACEPOINT, /* tp name */
     BPF_FD_TYPE_TRACEPOINT,     /* tp name */
     BPF_FD_TYPE_KPROBE,     /* (symbol + offset) or addr */
     BPF_FD_TYPE_KRETPROBE,      /* (symbol + offset) or addr */
     BPF_FD_TYPE_UPROBE,     /* filename + offset */
     BPF_FD_TYPE_URETPROBE,      /* filename + offset */
 };
 
 enum {
     BPF_FLOW_DISSECTOR_F_PARSE_1ST_FRAG     = (1U << 0),
     BPF_FLOW_DISSECTOR_F_STOP_AT_FLOW_LABEL     = (1U << 1),
     BPF_FLOW_DISSECTOR_F_STOP_AT_ENCAP      = (1U << 2),
 };
 
 struct bpf_flow_keys {
     __u16   nhoff;
     __u16   thoff;
     __u16   addr_proto;         /* ETH_P_* of valid addrs */
     __u8    is_frag;
     __u8    is_first_frag;
     __u8    is_encap;
     __u8    ip_proto;
     __be16  n_proto;
     __be16  sport;
     __be16  dport;
     union {
         struct {
             __be32  ipv4_src;
             __be32  ipv4_dst;
         };
         struct {
             __u32   ipv6_src[4];    /* in6_addr; network order */
             __u32   ipv6_dst[4];    /* in6_addr; network order */
         };
     };
     __u32   flags;
     __be32  flow_label;
 };
 
 struct bpf_func_info {
     __u32   insn_off;
     __u32   type_id;
 };
 
 #define BPF_LINE_INFO_LINE_NUM(line_col)    ((line_col) >> 10)
 #define BPF_LINE_INFO_LINE_COL(line_col)    ((line_col) & 0x3ff)
 
 struct bpf_line_info {
     __u32   insn_off;
     __u32   file_name_off;
     __u32   line_off;
     __u32   line_col;
 };
 
 struct bpf_spin_lock {
     __u32   val;
 };
 
 struct bpf_timer {
     __u64 :64;
     __u64 :64;
 } __attribute__((aligned(8)));
 
 struct bpf_dynptr {
     __u64 :64;
     __u64 :64;
 } __attribute__((aligned(8)));
 
 struct bpf_sysctl {
     __u32   write;      /* Sysctl is being read (= 0) or written (= 1).
                  * Allows 1,2,4-byte read, but no write.
                  */
     __u32   file_pos;   /* Sysctl file position to read from, write to.
                  * Allows 1,2,4-byte read an 4-byte write.
                  */
 };
 
 struct bpf_sockopt {
     __bpf_md_ptr(struct bpf_sock *, sk);
     __bpf_md_ptr(void *, optval);
     __bpf_md_ptr(void *, optval_end);
 
     __s32   level;
     __s32   optname;
     __s32   optlen;
     __s32   retval;
 };
 
 struct bpf_pidns_info {
     __u32 pid;
     __u32 tgid;
 };
 
 /* User accessible data for SK_LOOKUP programs. Add new fields at the end. */
 struct bpf_sk_lookup {
     union {
         __bpf_md_ptr(struct bpf_sock *, sk); /* Selected socket */
         __u64 cookie; /* Non-zero if socket was selected in PROG_TEST_RUN */
     };
 
     __u32 family;       /* Protocol family (AF_INET, AF_INET6) */
     __u32 protocol;     /* IP protocol (IPPROTO_TCP, IPPROTO_UDP) */
     __u32 remote_ip4;   /* Network byte order */
     __u32 remote_ip6[4];    /* Network byte order */
     __be16 remote_port; /* Network byte order */
     __u16 :16;      /* Zero padding */
     __u32 local_ip4;    /* Network byte order */
     __u32 local_ip6[4]; /* Network byte order */
     __u32 local_port;   /* Host byte order */
     __u32 ingress_ifindex;      /* The arriving interface. Determined by inet_iif. */
 };
 
 /*
  * struct btf_ptr is used for typed pointer representation; the
  * type id is used to render the pointer data as the appropriate type
  * via the bpf_snprintf_btf() helper described above.  A flags field -
  * potentially to specify additional details about the BTF pointer
  * (rather than its mode of display) - is included for future use.
  * Display flags - BTF_F_* - are passed to bpf_snprintf_btf separately.
  */
 struct btf_ptr {
     void *ptr;
     __u32 type_id;
     __u32 flags;        /* BTF ptr flags; unused at present. */
 };
 
 /*
  * Flags to control bpf_snprintf_btf() behaviour.
  *     - BTF_F_COMPACT: no formatting around type information
  *     - BTF_F_NONAME: no struct/union member names/types
  *     - BTF_F_PTR_RAW: show raw (unobfuscated) pointer values;
  *       equivalent to %px.
  *     - BTF_F_ZERO: show zero-valued struct/union members; they
  *       are not displayed by default
  */
 enum {
     BTF_F_COMPACT   =   (1ULL << 0),
     BTF_F_NONAME    =   (1ULL << 1),
     BTF_F_PTR_RAW   =   (1ULL << 2),
     BTF_F_ZERO  =   (1ULL << 3),
 };
 
 /* bpf_core_relo_kind encodes which aspect of captured field/type/enum value
  * has to be adjusted by relocations. It is emitted by llvm and passed to
  * libbpf and later to the kernel.
  */
 enum bpf_core_relo_kind {
     BPF_CORE_FIELD_BYTE_OFFSET = 0,      /* field byte offset */
     BPF_CORE_FIELD_BYTE_SIZE = 1,        /* field size in bytes */
     BPF_CORE_FIELD_EXISTS = 2,           /* field existence in target kernel */
     BPF_CORE_FIELD_SIGNED = 3,           /* field signedness (0 - unsigned, 1 - signed) */
     BPF_CORE_FIELD_LSHIFT_U64 = 4,       /* bitfield-specific left bitshift */
     BPF_CORE_FIELD_RSHIFT_U64 = 5,       /* bitfield-specific right bitshift */
     BPF_CORE_TYPE_ID_LOCAL = 6,          /* type ID in local BPF object */
     BPF_CORE_TYPE_ID_TARGET = 7,         /* type ID in target kernel */
     BPF_CORE_TYPE_EXISTS = 8,            /* type existence in target kernel */
     BPF_CORE_TYPE_SIZE = 9,              /* type size in bytes */
     BPF_CORE_ENUMVAL_EXISTS = 10,        /* enum value existence in target kernel */
     BPF_CORE_ENUMVAL_VALUE = 11,         /* enum value integer value */
     BPF_CORE_TYPE_MATCHES = 12,          /* type match in target kernel */
 };
 
 /*
  * "struct bpf_core_relo" is used to pass relocation data form LLVM to libbpf
  * and from libbpf to the kernel.
  *
  * CO-RE relocation captures the following data:
  * - insn_off - instruction offset (in bytes) within a BPF program that needs
  *   its insn->imm field to be relocated with actual field info;
  * - type_id - BTF type ID of the "root" (containing) entity of a relocatable
  *   type or field;
  * - access_str_off - offset into corresponding .BTF string section. String
  *   interpretation depends on specific relocation kind:
  *     - for field-based relocations, string encodes an accessed field using
  *       a sequence of field and array indices, separated by colon (:). It's
  *       conceptually very close to LLVM's getelementptr ([0]) instruction's
  *       arguments for identifying offset to a field.
  *     - for type-based relocations, strings is expected to be just "0";
  *     - for enum value-based relocations, string contains an index of enum
  *       value within its enum type;
  * - kind - one of enum bpf_core_relo_kind;
  *
  * Example:
  *   struct sample {
  *       int a;
  *       struct {
  *           int b[10];
  *       };
  *   };
  *
  *   struct sample *s = ...;
  *   int *x = &s->a;     // encoded as "0:0" (a is field #0)
  *   int *y = &s->b[5];  // encoded as "0:1:0:5" (anon struct is field #1,
  *                       // b is field #0 inside anon struct, accessing elem #5)
  *   int *z = &s[10]->b; // encoded as "10:1" (ptr is used as an array)
  *
  * type_id for all relocs in this example will capture BTF type id of
  * `struct sample`.
  *
  * Such relocation is emitted when using __builtin_preserve_access_index()
  * Clang built-in, passing expression that captures field address, e.g.:
  *
  * bpf_probe_read(&dst, sizeof(dst),
  *        __builtin_preserve_access_index(&src->a.b.c));
  *
  * In this case Clang will emit field relocation recording necessary data to
  * be able to find offset of embedded `a.b.c` field within `src` struct.
  *
  * [0] https://llvm.org/docs/LangRef.html#getelementptr-instruction
  */
 struct bpf_core_relo {
     __u32 insn_off;
     __u32 type_id;
     __u32 access_str_off;
     enum bpf_core_relo_kind kind;
 };
 
 #endif /* _UAPI__LINUX_BPF_H__ */