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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * INET     An implementation of the TCP/IP protocol suite for the LINUX
  *      operating system.  INET is implemented using the  BSD Socket
  *      interface as the means of communication with the user level.
  *
  *      The User Datagram Protocol (UDP).
  *
  * Authors: Ross Biro
  *      Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
  *      Arnt Gulbrandsen, <agulbra@nvg.unit.no>
  *      Alan Cox, <alan@lxorguk.ukuu.org.uk>
  *      Hirokazu Takahashi, <taka@valinux.co.jp>
  *
  * Fixes:
  *      Alan Cox    :   verify_area() calls
  *      Alan Cox    :   stopped close while in use off icmp
  *                  messages. Not a fix but a botch that
  *                  for udp at least is 'valid'.
  *      Alan Cox    :   Fixed icmp handling properly
  *      Alan Cox    :   Correct error for oversized datagrams
  *      Alan Cox    :   Tidied select() semantics.
  *      Alan Cox    :   udp_err() fixed properly, also now
  *                  select and read wake correctly on errors
  *      Alan Cox    :   udp_send verify_area moved to avoid mem leak
  *      Alan Cox    :   UDP can count its memory
  *      Alan Cox    :   send to an unknown connection causes
  *                  an ECONNREFUSED off the icmp, but
  *                  does NOT close.
  *      Alan Cox    :   Switched to new sk_buff handlers. No more backlog!
  *      Alan Cox    :   Using generic datagram code. Even smaller and the PEEK
  *                  bug no longer crashes it.
  *      Fred Van Kempen :   Net2e support for sk->broadcast.
  *      Alan Cox    :   Uses skb_free_datagram
  *      Alan Cox    :   Added get/set sockopt support.
  *      Alan Cox    :   Broadcasting without option set returns EACCES.
  *      Alan Cox    :   No wakeup calls. Instead we now use the callbacks.
  *      Alan Cox    :   Use ip_tos and ip_ttl
  *      Alan Cox    :   SNMP Mibs
  *      Alan Cox    :   MSG_DONTROUTE, and 0.0.0.0 support.
  *      Matt Dillon :   UDP length checks.
  *      Alan Cox    :   Smarter af_inet used properly.
  *      Alan Cox    :   Use new kernel side addressing.
  *      Alan Cox    :   Incorrect return on truncated datagram receive.
  *  Arnt Gulbrandsen    :   New udp_send and stuff
  *      Alan Cox    :   Cache last socket
  *      Alan Cox    :   Route cache
  *      Jon Peatfield   :   Minor efficiency fix to sendto().
  *      Mike Shaver :   RFC1122 checks.
  *      Alan Cox    :   Nonblocking error fix.
  *  Willy Konynenberg   :   Transparent proxying support.
  *      Mike McLagan    :   Routing by source
  *      David S. Miller :   New socket lookup architecture.
  *                  Last socket cache retained as it
  *                  does have a high hit rate.
  *      Olaf Kirch  :   Don't linearise iovec on sendmsg.
  *      Andi Kleen  :   Some cleanups, cache destination entry
  *                  for connect.
  *  Vitaly E. Lavrov    :   Transparent proxy revived after year coma.
  *      Melvin Smith    :   Check msg_name not msg_namelen in sendto(),
  *                  return ENOTCONN for unconnected sockets (POSIX)
  *      Janos Farkas    :   don't deliver multi/broadcasts to a different
  *                  bound-to-device socket
  *  Hirokazu Takahashi  :   HW checksumming for outgoing UDP
  *                  datagrams.
  *  Hirokazu Takahashi  :   sendfile() on UDP works now.
  *      Arnaldo C. Melo :   convert /proc/net/udp to seq_file
  *  YOSHIFUJI Hideaki @USAGI and:   Support IPV6_V6ONLY socket option, which
  *  Alexey Kuznetsov:       allow both IPv4 and IPv6 sockets to bind
  *                  a single port at the same time.
  *  Derek Atkins <derek@ihtfp.com>: Add Encapulation Support
  *  James Chapman       :   Add L2TP encapsulation type.
  */
 
 #define pr_fmt(fmt) "UDP: " fmt
 
 #include <linux/bpf-cgroup.h>
 #include <linux/uaccess.h>
 #include <asm/ioctls.h>
 #include <linux/memblock.h>
 #include <linux/highmem.h>
 #include <linux/types.h>
 #include <linux/fcntl.h>
 #include <linux/module.h>
 #include <linux/socket.h>
 #include <linux/sockios.h>
 #include <linux/igmp.h>
 #include <linux/inetdevice.h>
 #include <linux/in.h>
 #include <linux/errno.h>
 #include <linux/timer.h>
 #include <linux/mm.h>
 #include <linux/inet.h>
 #include <linux/netdevice.h>
 #include <linux/slab.h>
 #include <net/tcp_states.h>
 #include <linux/skbuff.h>
 #include <linux/proc_fs.h>
 #include <linux/seq_file.h>
 #include <net/net_namespace.h>
 #include <net/icmp.h>
 #include <net/inet_hashtables.h>
 #include <net/ip_tunnels.h>
 #include <net/route.h>
 #include <net/checksum.h>
 #include <net/xfrm.h>
 #include <trace/events/udp.h>
 #include <linux/static_key.h>
 #include <linux/btf_ids.h>
 #include <trace/events/skb.h>
 #include <net/busy_poll.h>
 #include "udp_impl.h"
 #include <net/sock_reuseport.h>
 #include <net/addrconf.h>
 #include <net/udp_tunnel.h>
 #if IS_ENABLED(CONFIG_IPV6)
 #include <net/ipv6_stubs.h>
 #endif
 
 struct udp_table udp_table __read_mostly;
 EXPORT_SYMBOL(udp_table);
 
 long sysctl_udp_mem[3] __read_mostly;
 EXPORT_SYMBOL(sysctl_udp_mem);
 
 atomic_long_t udp_memory_allocated ____cacheline_aligned_in_smp;
 EXPORT_SYMBOL(udp_memory_allocated);
 DEFINE_PER_CPU(int, udp_memory_per_cpu_fw_alloc);
 EXPORT_PER_CPU_SYMBOL_GPL(udp_memory_per_cpu_fw_alloc);
 
 #define MAX_UDP_PORTS 65536
 #define PORTS_PER_CHAIN (MAX_UDP_PORTS / UDP_HTABLE_SIZE_MIN)
 
 static int udp_lib_lport_inuse(struct net *net, __u16 num,
                    const struct udp_hslot *hslot,
                    unsigned long *bitmap,
                    struct sock *sk, unsigned int log)
 {
     struct sock *sk2;
     kuid_t uid = sock_i_uid(sk);
 
     sk_for_each(sk2, &hslot->head) {
         if (net_eq(sock_net(sk2), net) &&
             sk2 != sk &&
             (bitmap || udp_sk(sk2)->udp_port_hash == num) &&
             (!sk2->sk_reuse || !sk->sk_reuse) &&
             (!sk2->sk_bound_dev_if || !sk->sk_bound_dev_if ||
              sk2->sk_bound_dev_if == sk->sk_bound_dev_if) &&
             inet_rcv_saddr_equal(sk, sk2, true)) {
             if (sk2->sk_reuseport && sk->sk_reuseport &&
                 !rcu_access_pointer(sk->sk_reuseport_cb) &&
                 uid_eq(uid, sock_i_uid(sk2))) {
                 if (!bitmap)
                     return 0;
             } else {
                 if (!bitmap)
                     return 1;
                 __set_bit(udp_sk(sk2)->udp_port_hash >> log,
                       bitmap);
             }
         }
     }
     return 0;
 }
 
 /*
  * Note: we still hold spinlock of primary hash chain, so no other writer
  * can insert/delete a socket with local_port == num
  */
 static int udp_lib_lport_inuse2(struct net *net, __u16 num,
                 struct udp_hslot *hslot2,
                 struct sock *sk)
 {
     struct sock *sk2;
     kuid_t uid = sock_i_uid(sk);
     int res = 0;
 
     spin_lock(&hslot2->lock);
     udp_portaddr_for_each_entry(sk2, &hslot2->head) {
         if (net_eq(sock_net(sk2), net) &&
             sk2 != sk &&
             (udp_sk(sk2)->udp_port_hash == num) &&
             (!sk2->sk_reuse || !sk->sk_reuse) &&
             (!sk2->sk_bound_dev_if || !sk->sk_bound_dev_if ||
              sk2->sk_bound_dev_if == sk->sk_bound_dev_if) &&
             inet_rcv_saddr_equal(sk, sk2, true)) {
             if (sk2->sk_reuseport && sk->sk_reuseport &&
                 !rcu_access_pointer(sk->sk_reuseport_cb) &&
                 uid_eq(uid, sock_i_uid(sk2))) {
                 res = 0;
             } else {
                 res = 1;
             }
             break;
         }
     }
     spin_unlock(&hslot2->lock);
     return res;
 }
 
 static int udp_reuseport_add_sock(struct sock *sk, struct udp_hslot *hslot)
 {
     struct net *net = sock_net(sk);
     kuid_t uid = sock_i_uid(sk);
     struct sock *sk2;
 
     sk_for_each(sk2, &hslot->head) {
         if (net_eq(sock_net(sk2), net) &&
             sk2 != sk &&
             sk2->sk_family == sk->sk_family &&
             ipv6_only_sock(sk2) == ipv6_only_sock(sk) &&
             (udp_sk(sk2)->udp_port_hash == udp_sk(sk)->udp_port_hash) &&
             (sk2->sk_bound_dev_if == sk->sk_bound_dev_if) &&
             sk2->sk_reuseport && uid_eq(uid, sock_i_uid(sk2)) &&
             inet_rcv_saddr_equal(sk, sk2, false)) {
             return reuseport_add_sock(sk, sk2,
                           inet_rcv_saddr_any(sk));
         }
     }
 
     return reuseport_alloc(sk, inet_rcv_saddr_any(sk));
 }
 
 /**
  *  udp_lib_get_port  -  UDP/-Lite port lookup for IPv4 and IPv6
  *
  *  @sk:          socket struct in question
  *  @snum:        port number to look up
  *  @hash2_nulladdr: AF-dependent hash value in secondary hash chains,
  *                   with NULL address
  */
 int udp_lib_get_port(struct sock *sk, unsigned short snum,
              unsigned int hash2_nulladdr)
 {
     struct udp_hslot *hslot, *hslot2;
     struct udp_table *udptable = sk->sk_prot->h.udp_table;
     int    error = 1;
     struct net *net = sock_net(sk);
 
     if (!snum) {
         int low, high, remaining;
         unsigned int rand;
         unsigned short first, last;
         DECLARE_BITMAP(bitmap, PORTS_PER_CHAIN);
 
         inet_get_local_port_range(net, &low, &high);
         remaining = (high - low) + 1;
 
         rand = prandom_u32();
         first = reciprocal_scale(rand, remaining) + low;
         /*
          * force rand to be an odd multiple of UDP_HTABLE_SIZE
          */
         rand = (rand | 1) * (udptable->mask + 1);
         last = first + udptable->mask + 1;
         do {
             hslot = udp_hashslot(udptable, net, first);
             bitmap_zero(bitmap, PORTS_PER_CHAIN);
             spin_lock_bh(&hslot->lock);
             udp_lib_lport_inuse(net, snum, hslot, bitmap, sk,
                         udptable->log);
 
             snum = first;
             /*
              * Iterate on all possible values of snum for this hash.
              * Using steps of an odd multiple of UDP_HTABLE_SIZE
              * give us randomization and full range coverage.
              */
             do {
                 if (low <= snum && snum <= high &&
                     !test_bit(snum >> udptable->log, bitmap) &&
                     !inet_is_local_reserved_port(net, snum))
                     goto found;
                 snum += rand;
             } while (snum != first);
             spin_unlock_bh(&hslot->lock);
             cond_resched();
         } while (++first != last);
         goto fail;
     } else {
         hslot = udp_hashslot(udptable, net, snum);
         spin_lock_bh(&hslot->lock);
         if (hslot->count > 10) {
             int exist;
             unsigned int slot2 = udp_sk(sk)->udp_portaddr_hash ^ snum;
 
             slot2          &= udptable->mask;
             hash2_nulladdr &= udptable->mask;
 
             hslot2 = udp_hashslot2(udptable, slot2);
             if (hslot->count < hslot2->count)
                 goto scan_primary_hash;
 
             exist = udp_lib_lport_inuse2(net, snum, hslot2, sk);
             if (!exist && (hash2_nulladdr != slot2)) {
                 hslot2 = udp_hashslot2(udptable, hash2_nulladdr);
                 exist = udp_lib_lport_inuse2(net, snum, hslot2,
                                  sk);
             }
             if (exist)
                 goto fail_unlock;
             else
                 goto found;
         }
 scan_primary_hash:
         if (udp_lib_lport_inuse(net, snum, hslot, NULL, sk, 0))
             goto fail_unlock;
     }
 found:
     inet_sk(sk)->inet_num = snum;
     udp_sk(sk)->udp_port_hash = snum;
     udp_sk(sk)->udp_portaddr_hash ^= snum;
     if (sk_unhashed(sk)) {
         if (sk->sk_reuseport &&
             udp_reuseport_add_sock(sk, hslot)) {
             inet_sk(sk)->inet_num = 0;
             udp_sk(sk)->udp_port_hash = 0;
             udp_sk(sk)->udp_portaddr_hash ^= snum;
             goto fail_unlock;
         }
 
         sk_add_node_rcu(sk, &hslot->head);
         hslot->count++;
         sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
 
         hslot2 = udp_hashslot2(udptable, udp_sk(sk)->udp_portaddr_hash);
         spin_lock(&hslot2->lock);
         if (IS_ENABLED(CONFIG_IPV6) && sk->sk_reuseport &&
             sk->sk_family == AF_INET6)
             hlist_add_tail_rcu(&udp_sk(sk)->udp_portaddr_node,
                        &hslot2->head);
         else
             hlist_add_head_rcu(&udp_sk(sk)->udp_portaddr_node,
                        &hslot2->head);
         hslot2->count++;
         spin_unlock(&hslot2->lock);
     }
     sock_set_flag(sk, SOCK_RCU_FREE);
     error = 0;
 fail_unlock:
     spin_unlock_bh(&hslot->lock);
 fail:
     return error;
 }
 EXPORT_SYMBOL(udp_lib_get_port);
 
 int udp_v4_get_port(struct sock *sk, unsigned short snum)
 {
     unsigned int hash2_nulladdr =
         ipv4_portaddr_hash(sock_net(sk), htonl(INADDR_ANY), snum);
     unsigned int hash2_partial =
         ipv4_portaddr_hash(sock_net(sk), inet_sk(sk)->inet_rcv_saddr, 0);
 
     /* precompute partial secondary hash */
     udp_sk(sk)->udp_portaddr_hash = hash2_partial;
     return udp_lib_get_port(sk, snum, hash2_nulladdr);
 }
 
 static int compute_score(struct sock *sk, struct net *net,
              __be32 saddr, __be16 sport,
              __be32 daddr, unsigned short hnum,
              int dif, int sdif)
 {
     int score;
     struct inet_sock *inet;
     bool dev_match;
 
     if (!net_eq(sock_net(sk), net) ||
         udp_sk(sk)->udp_port_hash != hnum ||
         ipv6_only_sock(sk))
         return -1;
 
     if (sk->sk_rcv_saddr != daddr)
         return -1;
 
     score = (sk->sk_family == PF_INET) ? 2 : 1;
 
     inet = inet_sk(sk);
     if (inet->inet_daddr) {
         if (inet->inet_daddr != saddr)
             return -1;
         score += 4;
     }
 
     if (inet->inet_dport) {
         if (inet->inet_dport != sport)
             return -1;
         score += 4;
     }
 
     dev_match = udp_sk_bound_dev_eq(net, sk->sk_bound_dev_if,
                     dif, sdif);
     if (!dev_match)
         return -1;
     if (sk->sk_bound_dev_if)
         score += 4;
 
     if (READ_ONCE(sk->sk_incoming_cpu) == raw_smp_processor_id())
         score++;
     return score;
 }
 
 static u32 udp_ehashfn(const struct net *net, const __be32 laddr,
                const __u16 lport, const __be32 faddr,
                const __be16 fport)
 {
     static u32 udp_ehash_secret __read_mostly;
 
     net_get_random_once(&udp_ehash_secret, sizeof(udp_ehash_secret));
 
     return __inet_ehashfn(laddr, lport, faddr, fport,
                   udp_ehash_secret + net_hash_mix(net));
 }
 
 static struct sock *lookup_reuseport(struct net *net, struct sock *sk,
                      struct sk_buff *skb,
                      __be32 saddr, __be16 sport,
                      __be32 daddr, unsigned short hnum)
 {
     struct sock *reuse_sk = NULL;
     u32 hash;
 
     if (sk->sk_reuseport && sk->sk_state != TCP_ESTABLISHED) {
         hash = udp_ehashfn(net, daddr, hnum, saddr, sport);
         reuse_sk = reuseport_select_sock(sk, hash, skb,
                          sizeof(struct udphdr));
     }
     return reuse_sk;
 }
 
 /* called with rcu_read_lock() */
 static struct sock *udp4_lib_lookup2(struct net *net,
                      __be32 saddr, __be16 sport,
                      __be32 daddr, unsigned int hnum,
                      int dif, int sdif,
                      struct udp_hslot *hslot2,
                      struct sk_buff *skb)
 {
     struct sock *sk, *result;
     int score, badness;
 
     result = NULL;
     badness = 0;
     udp_portaddr_for_each_entry_rcu(sk, &hslot2->head) {
         score = compute_score(sk, net, saddr, sport,
                       daddr, hnum, dif, sdif);
         if (score > badness) {
             result = lookup_reuseport(net, sk, skb,
                           saddr, sport, daddr, hnum);
             /* Fall back to scoring if group has connections */
             if (result && !reuseport_has_conns(sk, false))
                 return result;
 
             result = result ? : sk;
             badness = score;
         }
     }
     return result;
 }
 
 static struct sock *udp4_lookup_run_bpf(struct net *net,
                     struct udp_table *udptable,
                     struct sk_buff *skb,
                     __be32 saddr, __be16 sport,
                     __be32 daddr, u16 hnum, const int dif)
 {
     struct sock *sk, *reuse_sk;
     bool no_reuseport;
 
     if (udptable != &udp_table)
         return NULL; /* only UDP is supported */
 
     no_reuseport = bpf_sk_lookup_run_v4(net, IPPROTO_UDP, saddr, sport,
                         daddr, hnum, dif, &sk);
     if (no_reuseport || IS_ERR_OR_NULL(sk))
         return sk;
 
     reuse_sk = lookup_reuseport(net, sk, skb, saddr, sport, daddr, hnum);
     if (reuse_sk)
         sk = reuse_sk;
     return sk;
 }
 
 /* UDP is nearly always wildcards out the wazoo, it makes no sense to try
  * harder than this. -DaveM
  */
 struct sock *__udp4_lib_lookup(struct net *net, __be32 saddr,
         __be16 sport, __be32 daddr, __be16 dport, int dif,
         int sdif, struct udp_table *udptable, struct sk_buff *skb)
 {
     unsigned short hnum = ntohs(dport);
     unsigned int hash2, slot2;
     struct udp_hslot *hslot2;
     struct sock *result, *sk;
 
     hash2 = ipv4_portaddr_hash(net, daddr, hnum);
     slot2 = hash2 & udptable->mask;
     hslot2 = &udptable->hash2[slot2];
 
     /* Lookup connected or non-wildcard socket */
     result = udp4_lib_lookup2(net, saddr, sport,
                   daddr, hnum, dif, sdif,
                   hslot2, skb);
     if (!IS_ERR_OR_NULL(result) && result->sk_state == TCP_ESTABLISHED)
         goto done;
 
     /* Lookup redirect from BPF */
     if (static_branch_unlikely(&bpf_sk_lookup_enabled)) {
         sk = udp4_lookup_run_bpf(net, udptable, skb,
                      saddr, sport, daddr, hnum, dif);
         if (sk) {
             result = sk;
             goto done;
         }
     }
 
     /* Got non-wildcard socket or error on first lookup */
     if (result)
         goto done;
 
     /* Lookup wildcard sockets */
     hash2 = ipv4_portaddr_hash(net, htonl(INADDR_ANY), hnum);
     slot2 = hash2 & udptable->mask;
     hslot2 = &udptable->hash2[slot2];
 
     result = udp4_lib_lookup2(net, saddr, sport,
                   htonl(INADDR_ANY), hnum, dif, sdif,
                   hslot2, skb);
 done:
     if (IS_ERR(result))
         return NULL;
     return result;
 }
 EXPORT_SYMBOL_GPL(__udp4_lib_lookup);
 
 static inline struct sock *__udp4_lib_lookup_skb(struct sk_buff *skb,
                          __be16 sport, __be16 dport,
                          struct udp_table *udptable)
 {
     const struct iphdr *iph = ip_hdr(skb);
 
     return __udp4_lib_lookup(dev_net(skb->dev), iph->saddr, sport,
                  iph->daddr, dport, inet_iif(skb),
                  inet_sdif(skb), udptable, skb);
 }
 
 struct sock *udp4_lib_lookup_skb(const struct sk_buff *skb,
                  __be16 sport, __be16 dport)
 {
     const struct iphdr *iph = ip_hdr(skb);
 
     return __udp4_lib_lookup(dev_net(skb->dev), iph->saddr, sport,
                  iph->daddr, dport, inet_iif(skb),
                  inet_sdif(skb), &udp_table, NULL);
 }
 
 /* Must be called under rcu_read_lock().
  * Does increment socket refcount.
  */
 #if IS_ENABLED(CONFIG_NF_TPROXY_IPV4) || IS_ENABLED(CONFIG_NF_SOCKET_IPV4)
 struct sock *udp4_lib_lookup(struct net *net, __be32 saddr, __be16 sport,
                  __be32 daddr, __be16 dport, int dif)
 {
     struct sock *sk;
 
     sk = __udp4_lib_lookup(net, saddr, sport, daddr, dport,
                    dif, 0, &udp_table, NULL);
     if (sk && !refcount_inc_not_zero(&sk->sk_refcnt))
         sk = NULL;
     return sk;
 }
 EXPORT_SYMBOL_GPL(udp4_lib_lookup);
 #endif
 
 static inline bool __udp_is_mcast_sock(struct net *net, struct sock *sk,
                        __be16 loc_port, __be32 loc_addr,
                        __be16 rmt_port, __be32 rmt_addr,
                        int dif, int sdif, unsigned short hnum)
 {
     struct inet_sock *inet = inet_sk(sk);
 
     if (!net_eq(sock_net(sk), net) ||
         udp_sk(sk)->udp_port_hash != hnum ||
         (inet->inet_daddr && inet->inet_daddr != rmt_addr) ||
         (inet->inet_dport != rmt_port && inet->inet_dport) ||
         (inet->inet_rcv_saddr && inet->inet_rcv_saddr != loc_addr) ||
         ipv6_only_sock(sk) ||
         !udp_sk_bound_dev_eq(net, sk->sk_bound_dev_if, dif, sdif))
         return false;
     if (!ip_mc_sf_allow(sk, loc_addr, rmt_addr, dif, sdif))
         return false;
     return true;
 }
 
 DEFINE_STATIC_KEY_FALSE(udp_encap_needed_key);
 void udp_encap_enable(void)
 {
     static_branch_inc(&udp_encap_needed_key);
 }
 EXPORT_SYMBOL(udp_encap_enable);
 
 void udp_encap_disable(void)
 {
     static_branch_dec(&udp_encap_needed_key);
 }
 EXPORT_SYMBOL(udp_encap_disable);
 
 /* Handler for tunnels with arbitrary destination ports: no socket lookup, go
  * through error handlers in encapsulations looking for a match.
  */
 static int __udp4_lib_err_encap_no_sk(struct sk_buff *skb, u32 info)
 {
     int i;
 
     for (i = 0; i < MAX_IPTUN_ENCAP_OPS; i++) {
         int (*handler)(struct sk_buff *skb, u32 info);
         const struct ip_tunnel_encap_ops *encap;
 
         encap = rcu_dereference(iptun_encaps[i]);
         if (!encap)
             continue;
         handler = encap->err_handler;
         if (handler && !handler(skb, info))
             return 0;
     }
 
     return -ENOENT;
 }
 
 /* Try to match ICMP errors to UDP tunnels by looking up a socket without
  * reversing source and destination port: this will match tunnels that force the
  * same destination port on both endpoints (e.g. VXLAN, GENEVE). Note that
  * lwtunnels might actually break this assumption by being configured with
  * different destination ports on endpoints, in this case we won't be able to
  * trace ICMP messages back to them.
  *
  * If this doesn't match any socket, probe tunnels with arbitrary destination
  * ports (e.g. FoU, GUE): there, the receiving socket is useless, as the port
  * we've sent packets to won't necessarily match the local destination port.
  *
  * Then ask the tunnel implementation to match the error against a valid
  * association.
  *
  * Return an error if we can't find a match, the socket if we need further
  * processing, zero otherwise.
  */
 static struct sock *__udp4_lib_err_encap(struct net *net,
                      const struct iphdr *iph,
                      struct udphdr *uh,
                      struct udp_table *udptable,
                      struct sock *sk,
                      struct sk_buff *skb, u32 info)
 {
     int (*lookup)(struct sock *sk, struct sk_buff *skb);
     int network_offset, transport_offset;
     struct udp_sock *up;
 
     network_offset = skb_network_offset(skb);
     transport_offset = skb_transport_offset(skb);
 
     /* Network header needs to point to the outer IPv4 header inside ICMP */
     skb_reset_network_header(skb);
 
     /* Transport header needs to point to the UDP header */
     skb_set_transport_header(skb, iph->ihl << 2);
 
     if (sk) {
         up = udp_sk(sk);
 
         lookup = READ_ONCE(up->encap_err_lookup);
         if (lookup && lookup(sk, skb))
             sk = NULL;
 
         goto out;
     }
 
     sk = __udp4_lib_lookup(net, iph->daddr, uh->source,
                    iph->saddr, uh->dest, skb->dev->ifindex, 0,
                    udptable, NULL);
     if (sk) {
         up = udp_sk(sk);
 
         lookup = READ_ONCE(up->encap_err_lookup);
         if (!lookup || lookup(sk, skb))
             sk = NULL;
     }
 
 out:
     if (!sk)
         sk = ERR_PTR(__udp4_lib_err_encap_no_sk(skb, info));
 
     skb_set_transport_header(skb, transport_offset);
     skb_set_network_header(skb, network_offset);
 
     return sk;
 }
 
 /*
  * This routine is called by the ICMP module when it gets some
  * sort of error condition.  If err < 0 then the socket should
  * be closed and the error returned to the user.  If err > 0
  * it's just the icmp type << 8 | icmp code.
  * Header points to the ip header of the error packet. We move
  * on past this. Then (as it used to claim before adjustment)
  * header points to the first 8 bytes of the udp header.  We need
  * to find the appropriate port.
  */
 
 int __udp4_lib_err(struct sk_buff *skb, u32 info, struct udp_table *udptable)
 {
     struct inet_sock *inet;
     const struct iphdr *iph = (const struct iphdr *)skb->data;
     struct udphdr *uh = (struct udphdr *)(skb->data+(iph->ihl<<2));
     const int type = icmp_hdr(skb)->type;
     const int code = icmp_hdr(skb)->code;
     bool tunnel = false;
     struct sock *sk;
     int harderr;
     int err;
     struct net *net = dev_net(skb->dev);
 
     sk = __udp4_lib_lookup(net, iph->daddr, uh->dest,
                    iph->saddr, uh->source, skb->dev->ifindex,
                    inet_sdif(skb), udptable, NULL);
 
     if (!sk || udp_sk(sk)->encap_type) {
         /* No socket for error: try tunnels before discarding */
         if (static_branch_unlikely(&udp_encap_needed_key)) {
             sk = __udp4_lib_err_encap(net, iph, uh, udptable, sk, skb,
                           info);
             if (!sk)
                 return 0;
         } else
             sk = ERR_PTR(-ENOENT);
 
         if (IS_ERR(sk)) {
             __ICMP_INC_STATS(net, ICMP_MIB_INERRORS);
             return PTR_ERR(sk);
         }
 
         tunnel = true;
     }
 
     err = 0;
     harderr = 0;
     inet = inet_sk(sk);
 
     switch (type) {
     default:
     case ICMP_TIME_EXCEEDED:
         err = EHOSTUNREACH;
         break;
     case ICMP_SOURCE_QUENCH:
         goto out;
     case ICMP_PARAMETERPROB:
         err = EPROTO;
         harderr = 1;
         break;
     case ICMP_DEST_UNREACH:
         if (code == ICMP_FRAG_NEEDED) { /* Path MTU discovery */
             ipv4_sk_update_pmtu(skb, sk, info);
             if (inet->pmtudisc != IP_PMTUDISC_DONT) {
                 err = EMSGSIZE;
                 harderr = 1;
                 break;
             }
             goto out;
         }
         err = EHOSTUNREACH;
         if (code <= NR_ICMP_UNREACH) {
             harderr = icmp_err_convert[code].fatal;
             err = icmp_err_convert[code].errno;
         }
         break;
     case ICMP_REDIRECT:
         ipv4_sk_redirect(skb, sk);
         goto out;
     }
 
     /*
      *      RFC1122: OK.  Passes ICMP errors back to application, as per
      *  4.1.3.3.
      */
     if (tunnel) {
         /* ...not for tunnels though: we don't have a sending socket */
         if (udp_sk(sk)->encap_err_rcv)
             udp_sk(sk)->encap_err_rcv(sk, skb, iph->ihl << 2);
         goto out;
     }
     if (!inet->recverr) {
         if (!harderr || sk->sk_state != TCP_ESTABLISHED)
             goto out;
     } else
         ip_icmp_error(sk, skb, err, uh->dest, info, (u8 *)(uh+1));
 
     sk->sk_err = err;
     sk_error_report(sk);
 out:
     return 0;
 }
 
 int udp_err(struct sk_buff *skb, u32 info)
 {
     return __udp4_lib_err(skb, info, &udp_table);
 }
 
 /*
  * Throw away all pending data and cancel the corking. Socket is locked.
  */
 void udp_flush_pending_frames(struct sock *sk)
 {
     struct udp_sock *up = udp_sk(sk);
 
     if (up->pending) {
         up->len = 0;
         up->pending = 0;
         ip_flush_pending_frames(sk);
     }
 }
 EXPORT_SYMBOL(udp_flush_pending_frames);
 
 /**
  *  udp4_hwcsum  -  handle outgoing HW checksumming
  *  @skb:   sk_buff containing the filled-in UDP header
  *          (checksum field must be zeroed out)
  *  @src:   source IP address
  *  @dst:   destination IP address
  */
 void udp4_hwcsum(struct sk_buff *skb, __be32 src, __be32 dst)
 {
     struct udphdr *uh = udp_hdr(skb);
     int offset = skb_transport_offset(skb);
     int len = skb->len - offset;
     int hlen = len;
     __wsum csum = 0;
 
     if (!skb_has_frag_list(skb)) {
         /*
          * Only one fragment on the socket.
          */
         skb->csum_start = skb_transport_header(skb) - skb->head;
         skb->csum_offset = offsetof(struct udphdr, check);
         uh->check = ~csum_tcpudp_magic(src, dst, len,
                            IPPROTO_UDP, 0);
     } else {
         struct sk_buff *frags;
 
         /*
          * HW-checksum won't work as there are two or more
          * fragments on the socket so that all csums of sk_buffs
          * should be together
          */
         skb_walk_frags(skb, frags) {
             csum = csum_add(csum, frags->csum);
             hlen -= frags->len;
         }
 
         csum = skb_checksum(skb, offset, hlen, csum);
         skb->ip_summed = CHECKSUM_NONE;
 
         uh->check = csum_tcpudp_magic(src, dst, len, IPPROTO_UDP, csum);
         if (uh->check == 0)
             uh->check = CSUM_MANGLED_0;
     }
 }
 EXPORT_SYMBOL_GPL(udp4_hwcsum);
 
 /* Function to set UDP checksum for an IPv4 UDP packet. This is intended
  * for the simple case like when setting the checksum for a UDP tunnel.
  */
 void udp_set_csum(bool nocheck, struct sk_buff *skb,
           __be32 saddr, __be32 daddr, int len)
 {
     struct udphdr *uh = udp_hdr(skb);
 
     if (nocheck) {
         uh->check = 0;
     } else if (skb_is_gso(skb)) {
         uh->check = ~udp_v4_check(len, saddr, daddr, 0);
     } else if (skb->ip_summed == CHECKSUM_PARTIAL) {
         uh->check = 0;
         uh->check = udp_v4_check(len, saddr, daddr, lco_csum(skb));
         if (uh->check == 0)
             uh->check = CSUM_MANGLED_0;
     } else {
         skb->ip_summed = CHECKSUM_PARTIAL;
         skb->csum_start = skb_transport_header(skb) - skb->head;
         skb->csum_offset = offsetof(struct udphdr, check);
         uh->check = ~udp_v4_check(len, saddr, daddr, 0);
     }
 }
 EXPORT_SYMBOL(udp_set_csum);
 
 static int udp_send_skb(struct sk_buff *skb, struct flowi4 *fl4,
             struct inet_cork *cork)
 {
     struct sock *sk = skb->sk;
     struct inet_sock *inet = inet_sk(sk);
     struct udphdr *uh;
     int err;
     int is_udplite = IS_UDPLITE(sk);
     int offset = skb_transport_offset(skb);
     int len = skb->len - offset;
     int datalen = len - sizeof(*uh);
     __wsum csum = 0;
 
     /*
      * Create a UDP header
      */
     uh = udp_hdr(skb);
     uh->source = inet->inet_sport;
     uh->dest = fl4->fl4_dport;
     uh->len = htons(len);
     uh->check = 0;
 
     if (cork->gso_size) {
         const int hlen = skb_network_header_len(skb) +
                  sizeof(struct udphdr);
 
         if (hlen + cork->gso_size > cork->fragsize) {
             kfree_skb(skb);
             return -EINVAL;
         }
         if (datalen > cork->gso_size * UDP_MAX_SEGMENTS) {
             kfree_skb(skb);
             return -EINVAL;
         }
         if (sk->sk_no_check_tx) {
             kfree_skb(skb);
             return -EINVAL;
         }
         if (skb->ip_summed != CHECKSUM_PARTIAL || is_udplite ||
             dst_xfrm(skb_dst(skb))) {
             kfree_skb(skb);
             return -EIO;
         }
 
         if (datalen > cork->gso_size) {
             skb_shinfo(skb)->gso_size = cork->gso_size;
             skb_shinfo(skb)->gso_type = SKB_GSO_UDP_L4;
             skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(datalen,
                                  cork->gso_size);
         }
         goto csum_partial;
     }
 
     if (is_udplite)                  /*     UDP-Lite      */
         csum = udplite_csum(skb);
 
     else if (sk->sk_no_check_tx) {           /* UDP csum off */
 
         skb->ip_summed = CHECKSUM_NONE;
         goto send;
 
     } else if (skb->ip_summed == CHECKSUM_PARTIAL) { /* UDP hardware csum */
 csum_partial:
 
         udp4_hwcsum(skb, fl4->saddr, fl4->daddr);
         goto send;
 
     } else
         csum = udp_csum(skb);
 
     /* add protocol-dependent pseudo-header */
     uh->check = csum_tcpudp_magic(fl4->saddr, fl4->daddr, len,
                       sk->sk_protocol, csum);
     if (uh->check == 0)
         uh->check = CSUM_MANGLED_0;
 
 send:
     err = ip_send_skb(sock_net(sk), skb);
     if (err) {
         if (err == -ENOBUFS && !inet->recverr) {
             UDP_INC_STATS(sock_net(sk),
                       UDP_MIB_SNDBUFERRORS, is_udplite);
             err = 0;
         }
     } else
         UDP_INC_STATS(sock_net(sk),
                   UDP_MIB_OUTDATAGRAMS, is_udplite);
     return err;
 }
 
 /*
  * Push out all pending data as one UDP datagram. Socket is locked.
  */
 int udp_push_pending_frames(struct sock *sk)
 {
     struct udp_sock  *up = udp_sk(sk);
     struct inet_sock *inet = inet_sk(sk);
     struct flowi4 *fl4 = &inet->cork.fl.u.ip4;
     struct sk_buff *skb;
     int err = 0;
 
     skb = ip_finish_skb(sk, fl4);
     if (!skb)
         goto out;
 
     err = udp_send_skb(skb, fl4, &inet->cork.base);
 
 out:
     up->len = 0;
     up->pending = 0;
     return err;
 }
 EXPORT_SYMBOL(udp_push_pending_frames);
 
 static int __udp_cmsg_send(struct cmsghdr *cmsg, u16 *gso_size)
 {
     switch (cmsg->cmsg_type) {
     case UDP_SEGMENT:
         if (cmsg->cmsg_len != CMSG_LEN(sizeof(__u16)))
             return -EINVAL;
         *gso_size = *(__u16 *)CMSG_DATA(cmsg);
         return 0;
     default:
         return -EINVAL;
     }
 }
 
 int udp_cmsg_send(struct sock *sk, struct msghdr *msg, u16 *gso_size)
 {
     struct cmsghdr *cmsg;
     bool need_ip = false;
     int err;
 
     for_each_cmsghdr(cmsg, msg) {
         if (!CMSG_OK(msg, cmsg))
             return -EINVAL;
 
         if (cmsg->cmsg_level != SOL_UDP) {
             need_ip = true;
             continue;
         }
 
         err = __udp_cmsg_send(cmsg, gso_size);
         if (err)
             return err;
     }
 
     return need_ip;
 }
 EXPORT_SYMBOL_GPL(udp_cmsg_send);
 
 int udp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 {
     struct inet_sock *inet = inet_sk(sk);
     struct udp_sock *up = udp_sk(sk);
     DECLARE_SOCKADDR(struct sockaddr_in *, usin, msg->msg_name);
     struct flowi4 fl4_stack;
     struct flowi4 *fl4;
     int ulen = len;
     struct ipcm_cookie ipc;
     struct rtable *rt = NULL;
     int free = 0;
     int connected = 0;
     __be32 daddr, faddr, saddr;
     __be16 dport;
     u8  tos;
     int err, is_udplite = IS_UDPLITE(sk);
     int corkreq = READ_ONCE(up->corkflag) || msg->msg_flags&MSG_MORE;
     int (*getfrag)(void *, char *, int, int, int, struct sk_buff *);
     struct sk_buff *skb;
     struct ip_options_data opt_copy;
 
     if (len > 0xFFFF)
         return -EMSGSIZE;
 
     /*
      *  Check the flags.
      */
 
     if (msg->msg_flags & MSG_OOB) /* Mirror BSD error message compatibility */
         return -EOPNOTSUPP;
 
     getfrag = is_udplite ? udplite_getfrag : ip_generic_getfrag;
 
     fl4 = &inet->cork.fl.u.ip4;
     if (up->pending) {
         /*
          * There are pending frames.
          * The socket lock must be held while it's corked.
          */
         lock_sock(sk);
         if (likely(up->pending)) {
             if (unlikely(up->pending != AF_INET)) {
                 release_sock(sk);
                 return -EINVAL;
             }
             goto do_append_data;
         }
         release_sock(sk);
     }
     ulen += sizeof(struct udphdr);
 
     /*
      *  Get and verify the address.
      */
     if (usin) {
         if (msg->msg_namelen < sizeof(*usin))
             return -EINVAL;
         if (usin->sin_family != AF_INET) {
             if (usin->sin_family != AF_UNSPEC)
                 return -EAFNOSUPPORT;
         }
 
         daddr = usin->sin_addr.s_addr;
         dport = usin->sin_port;
         if (dport == 0)
             return -EINVAL;
     } else {
         if (sk->sk_state != TCP_ESTABLISHED)
             return -EDESTADDRREQ;
         daddr = inet->inet_daddr;
         dport = inet->inet_dport;
         /* Open fast path for connected socket.
            Route will not be used, if at least one option is set.
          */
         connected = 1;
     }
 
     ipcm_init_sk(&ipc, inet);
     ipc.gso_size = READ_ONCE(up->gso_size);
 
     if (msg->msg_controllen) {
         err = udp_cmsg_send(sk, msg, &ipc.gso_size);
         if (err > 0)
             err = ip_cmsg_send(sk, msg, &ipc,
                        sk->sk_family == AF_INET6);
         if (unlikely(err < 0)) {
             kfree(ipc.opt);
             return err;
         }
         if (ipc.opt)
             free = 1;
         connected = 0;
     }
     if (!ipc.opt) {
         struct ip_options_rcu *inet_opt;
 
         rcu_read_lock();
         inet_opt = rcu_dereference(inet->inet_opt);
         if (inet_opt) {
             memcpy(&opt_copy, inet_opt,
                    sizeof(*inet_opt) + inet_opt->opt.optlen);
             ipc.opt = &opt_copy.opt;
         }
         rcu_read_unlock();
     }
 
     if (cgroup_bpf_enabled(CGROUP_UDP4_SENDMSG) && !connected) {
         err = BPF_CGROUP_RUN_PROG_UDP4_SENDMSG_LOCK(sk,
                         (struct sockaddr *)usin, &ipc.addr);
         if (err)
             goto out_free;
         if (usin) {
             if (usin->sin_port == 0) {
                 /* BPF program set invalid port. Reject it. */
                 err = -EINVAL;
                 goto out_free;
             }
             daddr = usin->sin_addr.s_addr;
             dport = usin->sin_port;
         }
     }
 
     saddr = ipc.addr;
     ipc.addr = faddr = daddr;
 
     if (ipc.opt && ipc.opt->opt.srr) {
         if (!daddr) {
             err = -EINVAL;
             goto out_free;
         }
         faddr = ipc.opt->opt.faddr;
         connected = 0;
     }
     tos = get_rttos(&ipc, inet);
     if (sock_flag(sk, SOCK_LOCALROUTE) ||
         (msg->msg_flags & MSG_DONTROUTE) ||
         (ipc.opt && ipc.opt->opt.is_strictroute)) {
         tos |= RTO_ONLINK;
         connected = 0;
     }
 
     if (ipv4_is_multicast(daddr)) {
         if (!ipc.oif || netif_index_is_l3_master(sock_net(sk), ipc.oif))
             ipc.oif = inet->mc_index;
         if (!saddr)
             saddr = inet->mc_addr;
         connected = 0;
     } else if (!ipc.oif) {
         ipc.oif = inet->uc_index;
     } else if (ipv4_is_lbcast(daddr) && inet->uc_index) {
         /* oif is set, packet is to local broadcast and
          * uc_index is set. oif is most likely set
          * by sk_bound_dev_if. If uc_index != oif check if the
          * oif is an L3 master and uc_index is an L3 slave.
          * If so, we want to allow the send using the uc_index.
          */
         if (ipc.oif != inet->uc_index &&
             ipc.oif == l3mdev_master_ifindex_by_index(sock_net(sk),
                                   inet->uc_index)) {
             ipc.oif = inet->uc_index;
         }
     }
 
     if (connected)
         rt = (struct rtable *)sk_dst_check(sk, 0);
 
     if (!rt) {
         struct net *net = sock_net(sk);
         __u8 flow_flags = inet_sk_flowi_flags(sk);
 
         fl4 = &fl4_stack;
 
         flowi4_init_output(fl4, ipc.oif, ipc.sockc.mark, tos,
                    RT_SCOPE_UNIVERSE, sk->sk_protocol,
                    flow_flags,
                    faddr, saddr, dport, inet->inet_sport,
                    sk->sk_uid);
 
         security_sk_classify_flow(sk, flowi4_to_flowi_common(fl4));
         rt = ip_route_output_flow(net, fl4, sk);
         if (IS_ERR(rt)) {
             err = PTR_ERR(rt);
             rt = NULL;
             if (err == -ENETUNREACH)
                 IP_INC_STATS(net, IPSTATS_MIB_OUTNOROUTES);
             goto out;
         }
 
         err = -EACCES;
         if ((rt->rt_flags & RTCF_BROADCAST) &&
             !sock_flag(sk, SOCK_BROADCAST))
             goto out;
         if (connected)
             sk_dst_set(sk, dst_clone(&rt->dst));
     }
 
     if (msg->msg_flags&MSG_CONFIRM)
         goto do_confirm;
 back_from_confirm:
 
     saddr = fl4->saddr;
     if (!ipc.addr)
         daddr = ipc.addr = fl4->daddr;
 
     /* Lockless fast path for the non-corking case. */
     if (!corkreq) {
         struct inet_cork cork;
 
         skb = ip_make_skb(sk, fl4, getfrag, msg, ulen,
                   sizeof(struct udphdr), &ipc, &rt,
                   &cork, msg->msg_flags);
         err = PTR_ERR(skb);
         if (!IS_ERR_OR_NULL(skb))
             err = udp_send_skb(skb, fl4, &cork);
         goto out;
     }
 
     lock_sock(sk);
     if (unlikely(up->pending)) {
         /* The socket is already corked while preparing it. */
         /* ... which is an evident application bug. --ANK */
         release_sock(sk);
 
         net_dbg_ratelimited("socket already corked\n");
         err = -EINVAL;
         goto out;
     }
     /*
      *  Now cork the socket to pend data.
      */
     fl4 = &inet->cork.fl.u.ip4;
     fl4->daddr = daddr;
     fl4->saddr = saddr;
     fl4->fl4_dport = dport;
     fl4->fl4_sport = inet->inet_sport;
     up->pending = AF_INET;
 
 do_append_data:
     up->len += ulen;
     err = ip_append_data(sk, fl4, getfrag, msg, ulen,
                  sizeof(struct udphdr), &ipc, &rt,
                  corkreq ? msg->msg_flags|MSG_MORE : msg->msg_flags);
     if (err)
         udp_flush_pending_frames(sk);
     else if (!corkreq)
         err = udp_push_pending_frames(sk);
     else if (unlikely(skb_queue_empty(&sk->sk_write_queue)))
         up->pending = 0;
     release_sock(sk);
 
 out:
     ip_rt_put(rt);
 out_free:
     if (free)
         kfree(ipc.opt);
     if (!err)
         return len;
     /*
      * ENOBUFS = no kernel mem, SOCK_NOSPACE = no sndbuf space.  Reporting
      * ENOBUFS might not be good (it's not tunable per se), but otherwise
      * we don't have a good statistic (IpOutDiscards but it can be too many
      * things).  We could add another new stat but at least for now that
      * seems like overkill.
      */
     if (err == -ENOBUFS || test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) {
         UDP_INC_STATS(sock_net(sk),
                   UDP_MIB_SNDBUFERRORS, is_udplite);
     }
     return err;
 
 do_confirm:
     if (msg->msg_flags & MSG_PROBE)
         dst_confirm_neigh(&rt->dst, &fl4->daddr);
     if (!(msg->msg_flags&MSG_PROBE) || len)
         goto back_from_confirm;
     err = 0;
     goto out;
 }
 EXPORT_SYMBOL(udp_sendmsg);
 
 int udp_sendpage(struct sock *sk, struct page *page, int offset,
          size_t size, int flags)
 {
     struct inet_sock *inet = inet_sk(sk);
     struct udp_sock *up = udp_sk(sk);
     int ret;
 
     if (flags & MSG_SENDPAGE_NOTLAST)
         flags |= MSG_MORE;
 
     if (!up->pending) {
         struct msghdr msg = {   .msg_flags = flags|MSG_MORE };
 
         /* Call udp_sendmsg to specify destination address which
          * sendpage interface can't pass.
          * This will succeed only when the socket is connected.
          */
         ret = udp_sendmsg(sk, &msg, 0);
         if (ret < 0)
             return ret;
     }
 
     lock_sock(sk);
 
     if (unlikely(!up->pending)) {
         release_sock(sk);
 
         net_dbg_ratelimited("cork failed\n");
         return -EINVAL;
     }
 
     ret = ip_append_page(sk, &inet->cork.fl.u.ip4,
                  page, offset, size, flags);
     if (ret == -EOPNOTSUPP) {
         release_sock(sk);
         return sock_no_sendpage(sk->sk_socket, page, offset,
                     size, flags);
     }
     if (ret < 0) {
         udp_flush_pending_frames(sk);
         goto out;
     }
 
     up->len += size;
     if (!(READ_ONCE(up->corkflag) || (flags&MSG_MORE)))
         ret = udp_push_pending_frames(sk);
     if (!ret)
         ret = size;
 out:
     release_sock(sk);
     return ret;
 }
 
 #define UDP_SKB_IS_STATELESS 0x80000000
 
 /* all head states (dst, sk, nf conntrack) except skb extensions are
  * cleared by udp_rcv().
  *
  * We need to preserve secpath, if present, to eventually process
  * IP_CMSG_PASSSEC at recvmsg() time.
  *
  * Other extensions can be cleared.
  */
 static bool udp_try_make_stateless(struct sk_buff *skb)
 {
     if (!skb_has_extensions(skb))
         return true;
 
     if (!secpath_exists(skb)) {
         skb_ext_reset(skb);
         return true;
     }
 
     return false;
 }
 
 static void udp_set_dev_scratch(struct sk_buff *skb)
 {
     struct udp_dev_scratch *scratch = udp_skb_scratch(skb);
 
     BUILD_BUG_ON(sizeof(struct udp_dev_scratch) > sizeof(long));
     scratch->_tsize_state = skb->truesize;
 #if BITS_PER_LONG == 64
     scratch->len = skb->len;
     scratch->csum_unnecessary = !!skb_csum_unnecessary(skb);
     scratch->is_linear = !skb_is_nonlinear(skb);
 #endif
     if (udp_try_make_stateless(skb))
         scratch->_tsize_state |= UDP_SKB_IS_STATELESS;
 }
 
 static void udp_skb_csum_unnecessary_set(struct sk_buff *skb)
 {
     /* We come here after udp_lib_checksum_complete() returned 0.
      * This means that __skb_checksum_complete() might have
      * set skb->csum_valid to 1.
      * On 64bit platforms, we can set csum_unnecessary
      * to true, but only if the skb is not shared.
      */
 #if BITS_PER_LONG == 64
     if (!skb_shared(skb))
         udp_skb_scratch(skb)->csum_unnecessary = true;
 #endif
 }
 
 static int udp_skb_truesize(struct sk_buff *skb)
 {
     return udp_skb_scratch(skb)->_tsize_state & ~UDP_SKB_IS_STATELESS;
 }
 
 static bool udp_skb_has_head_state(struct sk_buff *skb)
 {
     return !(udp_skb_scratch(skb)->_tsize_state & UDP_SKB_IS_STATELESS);
 }
 
 /* fully reclaim rmem/fwd memory allocated for skb */
 static void udp_rmem_release(struct sock *sk, int size, int partial,
                  bool rx_queue_lock_held)
 {
     struct udp_sock *up = udp_sk(sk);
     struct sk_buff_head *sk_queue;
     int amt;
 
     if (likely(partial)) {
         up->forward_deficit += size;
         size = up->forward_deficit;
         if (size < (sk->sk_rcvbuf >> 2) &&
             !skb_queue_empty(&up->reader_queue))
             return;
     } else {
         size += up->forward_deficit;
     }
     up->forward_deficit = 0;
 
     /* acquire the sk_receive_queue for fwd allocated memory scheduling,
      * if the called don't held it already
      */
     sk_queue = &sk->sk_receive_queue;
     if (!rx_queue_lock_held)
         spin_lock(&sk_queue->lock);
 
 
     sk->sk_forward_alloc += size;
     amt = (sk->sk_forward_alloc - partial) & ~(PAGE_SIZE - 1);
     sk->sk_forward_alloc -= amt;
 
     if (amt)
         __sk_mem_reduce_allocated(sk, amt >> PAGE_SHIFT);
 
     atomic_sub(size, &sk->sk_rmem_alloc);
 
     /* this can save us from acquiring the rx queue lock on next receive */
     skb_queue_splice_tail_init(sk_queue, &up->reader_queue);
 
     if (!rx_queue_lock_held)
         spin_unlock(&sk_queue->lock);
 }
 
 /* Note: called with reader_queue.lock held.
  * Instead of using skb->truesize here, find a copy of it in skb->dev_scratch
  * This avoids a cache line miss while receive_queue lock is held.
  * Look at __udp_enqueue_schedule_skb() to find where this copy is done.
  */
 void udp_skb_destructor(struct sock *sk, struct sk_buff *skb)
 {
     prefetch(&skb->data);
     udp_rmem_release(sk, udp_skb_truesize(skb), 1, false);
 }
 EXPORT_SYMBOL(udp_skb_destructor);
 
 /* as above, but the caller held the rx queue lock, too */
 static void udp_skb_dtor_locked(struct sock *sk, struct sk_buff *skb)
 {
     prefetch(&skb->data);
     udp_rmem_release(sk, udp_skb_truesize(skb), 1, true);
 }
 
 /* Idea of busylocks is to let producers grab an extra spinlock
  * to relieve pressure on the receive_queue spinlock shared by consumer.
  * Under flood, this means that only one producer can be in line
  * trying to acquire the receive_queue spinlock.
  * These busylock can be allocated on a per cpu manner, instead of a
  * per socket one (that would consume a cache line per socket)
  */
 static int udp_busylocks_log __read_mostly;
 static spinlock_t *udp_busylocks __read_mostly;
 
 static spinlock_t *busylock_acquire(void *ptr)
 {
     spinlock_t *busy;
 
     busy = udp_busylocks + hash_ptr(ptr, udp_busylocks_log);
     spin_lock(busy);
     return busy;
 }
 
 static void busylock_release(spinlock_t *busy)
 {
     if (busy)
         spin_unlock(busy);
 }
 
 int __udp_enqueue_schedule_skb(struct sock *sk, struct sk_buff *skb)
 {
     struct sk_buff_head *list = &sk->sk_receive_queue;
     int rmem, delta, amt, err = -ENOMEM;
     spinlock_t *busy = NULL;
     int size;
 
     /* try to avoid the costly atomic add/sub pair when the receive
      * queue is full; always allow at least a packet
      */
     rmem = atomic_read(&sk->sk_rmem_alloc);
     if (rmem > sk->sk_rcvbuf)
         goto drop;
 
     /* Under mem pressure, it might be helpful to help udp_recvmsg()
      * having linear skbs :
      * - Reduce memory overhead and thus increase receive queue capacity
      * - Less cache line misses at copyout() time
      * - Less work at consume_skb() (less alien page frag freeing)
      */
     if (rmem > (sk->sk_rcvbuf >> 1)) {
         skb_condense(skb);
 
         busy = busylock_acquire(sk);
     }
     size = skb->truesize;
     udp_set_dev_scratch(skb);
 
     /* we drop only if the receive buf is full and the receive
      * queue contains some other skb
      */
     rmem = atomic_add_return(size, &sk->sk_rmem_alloc);
     if (rmem > (size + (unsigned int)sk->sk_rcvbuf))
         goto uncharge_drop;
 
     spin_lock(&list->lock);
     if (size >= sk->sk_forward_alloc) {
         amt = sk_mem_pages(size);
         delta = amt << PAGE_SHIFT;
         if (!__sk_mem_raise_allocated(sk, delta, amt, SK_MEM_RECV)) {
             err = -ENOBUFS;
             spin_unlock(&list->lock);
             goto uncharge_drop;
         }
 
         sk->sk_forward_alloc += delta;
     }
 
     sk->sk_forward_alloc -= size;
 
     /* no need to setup a destructor, we will explicitly release the
      * forward allocated memory on dequeue
      */
     sock_skb_set_dropcount(sk, skb);
 
     __skb_queue_tail(list, skb);
     spin_unlock(&list->lock);
 
     if (!sock_flag(sk, SOCK_DEAD))
         sk->sk_data_ready(sk);
 
     busylock_release(busy);
     return 0;
 
 uncharge_drop:
     atomic_sub(skb->truesize, &sk->sk_rmem_alloc);
 
 drop:
     atomic_inc(&sk->sk_drops);
     busylock_release(busy);
     return err;
 }
 EXPORT_SYMBOL_GPL(__udp_enqueue_schedule_skb);
 
 void udp_destruct_sock(struct sock *sk)
 {
     /* reclaim completely the forward allocated memory */
     struct udp_sock *up = udp_sk(sk);
     unsigned int total = 0;
     struct sk_buff *skb;
 
     skb_queue_splice_tail_init(&sk->sk_receive_queue, &up->reader_queue);
     while ((skb = __skb_dequeue(&up->reader_queue)) != NULL) {
         total += skb->truesize;
         kfree_skb(skb);
     }
     udp_rmem_release(sk, total, 0, true);
 
     inet_sock_destruct(sk);
 }
 EXPORT_SYMBOL_GPL(udp_destruct_sock);
 
 int udp_init_sock(struct sock *sk)
 {
     skb_queue_head_init(&udp_sk(sk)->reader_queue);
     sk->sk_destruct = udp_destruct_sock;
     return 0;
 }
 EXPORT_SYMBOL_GPL(udp_init_sock);
 
 void skb_consume_udp(struct sock *sk, struct sk_buff *skb, int len)
 {
     if (unlikely(READ_ONCE(sk->sk_peek_off) >= 0)) {
         bool slow = lock_sock_fast(sk);
 
         sk_peek_offset_bwd(sk, len);
         unlock_sock_fast(sk, slow);
     }
 
     if (!skb_unref(skb))
         return;
 
     /* In the more common cases we cleared the head states previously,
      * see __udp_queue_rcv_skb().
      */
     if (unlikely(udp_skb_has_head_state(skb)))
         skb_release_head_state(skb);
     __consume_stateless_skb(skb);
 }
 EXPORT_SYMBOL_GPL(skb_consume_udp);
 
 static struct sk_buff *__first_packet_length(struct sock *sk,
                          struct sk_buff_head *rcvq,
                          int *total)
 {
     struct sk_buff *skb;
 
     while ((skb = skb_peek(rcvq)) != NULL) {
         if (udp_lib_checksum_complete(skb)) {
             __UDP_INC_STATS(sock_net(sk), UDP_MIB_CSUMERRORS,
                     IS_UDPLITE(sk));
             __UDP_INC_STATS(sock_net(sk), UDP_MIB_INERRORS,
                     IS_UDPLITE(sk));
             atomic_inc(&sk->sk_drops);
             __skb_unlink(skb, rcvq);
             *total += skb->truesize;
             kfree_skb(skb);
         } else {
             udp_skb_csum_unnecessary_set(skb);
             break;
         }
     }
     return skb;
 }
 
 /**
  *  first_packet_length - return length of first packet in receive queue
  *  @sk: socket
  *
  *  Drops all bad checksum frames, until a valid one is found.
  *  Returns the length of found skb, or -1 if none is found.
  */
 static int first_packet_length(struct sock *sk)
 {
     struct sk_buff_head *rcvq = &udp_sk(sk)->reader_queue;
     struct sk_buff_head *sk_queue = &sk->sk_receive_queue;
     struct sk_buff *skb;
     int total = 0;
     int res;
 
     spin_lock_bh(&rcvq->lock);
     skb = __first_packet_length(sk, rcvq, &total);
     if (!skb && !skb_queue_empty_lockless(sk_queue)) {
         spin_lock(&sk_queue->lock);
         skb_queue_splice_tail_init(sk_queue, rcvq);
         spin_unlock(&sk_queue->lock);
 
         skb = __first_packet_length(sk, rcvq, &total);
     }
     res = skb ? skb->len : -1;
     if (total)
         udp_rmem_release(sk, total, 1, false);
     spin_unlock_bh(&rcvq->lock);
     return res;
 }
 
 /*
  *  IOCTL requests applicable to the UDP protocol
  */
 
 int udp_ioctl(struct sock *sk, int cmd, unsigned long arg)
 {
     switch (cmd) {
     case SIOCOUTQ:
     {
         int amount = sk_wmem_alloc_get(sk);
 
         return put_user(amount, (int __user *)arg);
     }
 
     case SIOCINQ:
     {
         int amount = max_t(int, 0, first_packet_length(sk));
 
         return put_user(amount, (int __user *)arg);
     }
 
     default:
         return -ENOIOCTLCMD;
     }
 
     return 0;
 }
 EXPORT_SYMBOL(udp_ioctl);
 
 struct sk_buff *__skb_recv_udp(struct sock *sk, unsigned int flags,
                    int *off, int *err)
 {
     struct sk_buff_head *sk_queue = &sk->sk_receive_queue;
     struct sk_buff_head *queue;
     struct sk_buff *last;
     long timeo;
     int error;
 
     queue = &udp_sk(sk)->reader_queue;
     timeo = sock_rcvtimeo(sk, flags & MSG_DONTWAIT);
     do {
         struct sk_buff *skb;
 
         error = sock_error(sk);
         if (error)
             break;
 
         error = -EAGAIN;
         do {
             spin_lock_bh(&queue->lock);
             skb = __skb_try_recv_from_queue(sk, queue, flags, off,
                             err, &last);
             if (skb) {
                 if (!(flags & MSG_PEEK))
                     udp_skb_destructor(sk, skb);
                 spin_unlock_bh(&queue->lock);
                 return skb;
             }
 
             if (skb_queue_empty_lockless(sk_queue)) {
                 spin_unlock_bh(&queue->lock);
                 goto busy_check;
             }
 
             /* refill the reader queue and walk it again
              * keep both queues locked to avoid re-acquiring
              * the sk_receive_queue lock if fwd memory scheduling
              * is needed.
              */
             spin_lock(&sk_queue->lock);
             skb_queue_splice_tail_init(sk_queue, queue);
 
             skb = __skb_try_recv_from_queue(sk, queue, flags, off,
                             err, &last);
             if (skb && !(flags & MSG_PEEK))
                 udp_skb_dtor_locked(sk, skb);
             spin_unlock(&sk_queue->lock);
             spin_unlock_bh(&queue->lock);
             if (skb)
                 return skb;
 
 busy_check:
             if (!sk_can_busy_loop(sk))
                 break;
 
             sk_busy_loop(sk, flags & MSG_DONTWAIT);
         } while (!skb_queue_empty_lockless(sk_queue));
 
         /* sk_queue is empty, reader_queue may contain peeked packets */
     } while (timeo &&
          !__skb_wait_for_more_packets(sk, &sk->sk_receive_queue,
                           &error, &timeo,
                           (struct sk_buff *)sk_queue));
 
     *err = error;
     return NULL;
 }
 EXPORT_SYMBOL(__skb_recv_udp);
 
 int udp_read_skb(struct sock *sk, skb_read_actor_t recv_actor)
 {
     int copied = 0;
 
     while (1) {
         struct sk_buff *skb;
         int err, used;
 
         skb = skb_recv_udp(sk, MSG_DONTWAIT, &err);
         if (!skb)
             return err;
 
         if (udp_lib_checksum_complete(skb)) {
             __UDP_INC_STATS(sock_net(sk), UDP_MIB_CSUMERRORS,
                     IS_UDPLITE(sk));
             __UDP_INC_STATS(sock_net(sk), UDP_MIB_INERRORS,
                     IS_UDPLITE(sk));
             atomic_inc(&sk->sk_drops);
             kfree_skb(skb);
             continue;
         }
 
         WARN_ON_ONCE(!skb_set_owner_sk_safe(skb, sk));
         used = recv_actor(sk, skb);
         if (used <= 0) {
             if (!copied)
                 copied = used;
             kfree_skb(skb);
             break;
         } else if (used <= skb->len) {
             copied += used;
         }
 
         kfree_skb(skb);
         break;
     }
 
     return copied;
 }
 EXPORT_SYMBOL(udp_read_skb);
 
 /*
  *  This should be easy, if there is something there we
  *  return it, otherwise we block.
  */
 
 int udp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int flags,
         int *addr_len)
 {
     struct inet_sock *inet = inet_sk(sk);
     DECLARE_SOCKADDR(struct sockaddr_in *, sin, msg->msg_name);
     struct sk_buff *skb;
     unsigned int ulen, copied;
     int off, err, peeking = flags & MSG_PEEK;
     int is_udplite = IS_UDPLITE(sk);
     bool checksum_valid = false;
 
     if (flags & MSG_ERRQUEUE)
         return ip_recv_error(sk, msg, len, addr_len);
 
 try_again:
     off = sk_peek_offset(sk, flags);
     skb = __skb_recv_udp(sk, flags, &off, &err);
     if (!skb)
         return err;
 
     ulen = udp_skb_len(skb);
     copied = len;
     if (copied > ulen - off)
         copied = ulen - off;
     else if (copied < ulen)
         msg->msg_flags |= MSG_TRUNC;
 
     /*
      * If checksum is needed at all, try to do it while copying the
      * data.  If the data is truncated, or if we only want a partial
      * coverage checksum (UDP-Lite), do it before the copy.
      */
 
     if (copied < ulen || peeking ||
         (is_udplite && UDP_SKB_CB(skb)->partial_cov)) {
         checksum_valid = udp_skb_csum_unnecessary(skb) ||
                 !__udp_lib_checksum_complete(skb);
         if (!checksum_valid)
             goto csum_copy_err;
     }
 
     if (checksum_valid || udp_skb_csum_unnecessary(skb)) {
         if (udp_skb_is_linear(skb))
             err = copy_linear_skb(skb, copied, off, &msg->msg_iter);
         else
             err = skb_copy_datagram_msg(skb, off, msg, copied);
     } else {
         err = skb_copy_and_csum_datagram_msg(skb, off, msg);
 
         if (err == -EINVAL)
             goto csum_copy_err;
     }
 
     if (unlikely(err)) {
         if (!peeking) {
             atomic_inc(&sk->sk_drops);
             UDP_INC_STATS(sock_net(sk),
                       UDP_MIB_INERRORS, is_udplite);
         }
         kfree_skb(skb);
         return err;
     }
 
     if (!peeking)
         UDP_INC_STATS(sock_net(sk),
                   UDP_MIB_INDATAGRAMS, is_udplite);
 
     sock_recv_cmsgs(msg, sk, skb);
 
     /* Copy the address. */
     if (sin) {
         sin->sin_family = AF_INET;
         sin->sin_port = udp_hdr(skb)->source;
         sin->sin_addr.s_addr = ip_hdr(skb)->saddr;
         memset(sin->sin_zero, 0, sizeof(sin->sin_zero));
         *addr_len = sizeof(*sin);
 
         BPF_CGROUP_RUN_PROG_UDP4_RECVMSG_LOCK(sk,
                               (struct sockaddr *)sin);
     }
 
     if (udp_sk(sk)->gro_enabled)
         udp_cmsg_recv(msg, sk, skb);
 
     if (inet->cmsg_flags)
         ip_cmsg_recv_offset(msg, sk, skb, sizeof(struct udphdr), off);
 
     err = copied;
     if (flags & MSG_TRUNC)
         err = ulen;
 
     skb_consume_udp(sk, skb, peeking ? -err : err);
     return err;
 
 csum_copy_err:
     if (!__sk_queue_drop_skb(sk, &udp_sk(sk)->reader_queue, skb, flags,
                  udp_skb_destructor)) {
         UDP_INC_STATS(sock_net(sk), UDP_MIB_CSUMERRORS, is_udplite);
         UDP_INC_STATS(sock_net(sk), UDP_MIB_INERRORS, is_udplite);
     }
     kfree_skb(skb);
 
     /* starting over for a new packet, but check if we need to yield */
     cond_resched();
     msg->msg_flags &= ~MSG_TRUNC;
     goto try_again;
 }
 
 int udp_pre_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
 {
     /* This check is replicated from __ip4_datagram_connect() and
      * intended to prevent BPF program called below from accessing bytes
      * that are out of the bound specified by user in addr_len.
      */
     if (addr_len < sizeof(struct sockaddr_in))
         return -EINVAL;
 
     return BPF_CGROUP_RUN_PROG_INET4_CONNECT_LOCK(sk, uaddr);
 }
 EXPORT_SYMBOL(udp_pre_connect);
 
 int __udp_disconnect(struct sock *sk, int flags)
 {
     struct inet_sock *inet = inet_sk(sk);
     /*
      *  1003.1g - break association.
      */
 
     sk->sk_state = TCP_CLOSE;
     inet->inet_daddr = 0;
     inet->inet_dport = 0;
     sock_rps_reset_rxhash(sk);
     sk->sk_bound_dev_if = 0;
     if (!(sk->sk_userlocks & SOCK_BINDADDR_LOCK)) {
         inet_reset_saddr(sk);
         if (sk->sk_prot->rehash &&
             (sk->sk_userlocks & SOCK_BINDPORT_LOCK))
             sk->sk_prot->rehash(sk);
     }
 
     if (!(sk->sk_userlocks & SOCK_BINDPORT_LOCK)) {
         sk->sk_prot->unhash(sk);
         inet->inet_sport = 0;
     }
     sk_dst_reset(sk);
     return 0;
 }
 EXPORT_SYMBOL(__udp_disconnect);
 
 int udp_disconnect(struct sock *sk, int flags)
 {
     lock_sock(sk);
     __udp_disconnect(sk, flags);
     release_sock(sk);
     return 0;
 }
 EXPORT_SYMBOL(udp_disconnect);
 
 void udp_lib_unhash(struct sock *sk)
 {
     if (sk_hashed(sk)) {
         struct udp_table *udptable = sk->sk_prot->h.udp_table;
         struct udp_hslot *hslot, *hslot2;
 
         hslot  = udp_hashslot(udptable, sock_net(sk),
                       udp_sk(sk)->udp_port_hash);
         hslot2 = udp_hashslot2(udptable, udp_sk(sk)->udp_portaddr_hash);
 
         spin_lock_bh(&hslot->lock);
         if (rcu_access_pointer(sk->sk_reuseport_cb))
             reuseport_detach_sock(sk);
         if (sk_del_node_init_rcu(sk)) {
             hslot->count--;
             inet_sk(sk)->inet_num = 0;
             sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
 
             spin_lock(&hslot2->lock);
             hlist_del_init_rcu(&udp_sk(sk)->udp_portaddr_node);
             hslot2->count--;
             spin_unlock(&hslot2->lock);
         }
         spin_unlock_bh(&hslot->lock);
     }
 }
 EXPORT_SYMBOL(udp_lib_unhash);
 
 /*
  * inet_rcv_saddr was changed, we must rehash secondary hash
  */
 void udp_lib_rehash(struct sock *sk, u16 newhash)
 {
     if (sk_hashed(sk)) {
         struct udp_table *udptable = sk->sk_prot->h.udp_table;
         struct udp_hslot *hslot, *hslot2, *nhslot2;
 
         hslot2 = udp_hashslot2(udptable, udp_sk(sk)->udp_portaddr_hash);
         nhslot2 = udp_hashslot2(udptable, newhash);
         udp_sk(sk)->udp_portaddr_hash = newhash;
 
         if (hslot2 != nhslot2 ||
             rcu_access_pointer(sk->sk_reuseport_cb)) {
             hslot = udp_hashslot(udptable, sock_net(sk),
                          udp_sk(sk)->udp_port_hash);
             /* we must lock primary chain too */
             spin_lock_bh(&hslot->lock);
             if (rcu_access_pointer(sk->sk_reuseport_cb))
                 reuseport_detach_sock(sk);
 
             if (hslot2 != nhslot2) {
                 spin_lock(&hslot2->lock);
                 hlist_del_init_rcu(&udp_sk(sk)->udp_portaddr_node);
                 hslot2->count--;
                 spin_unlock(&hslot2->lock);
 
                 spin_lock(&nhslot2->lock);
                 hlist_add_head_rcu(&udp_sk(sk)->udp_portaddr_node,
                              &nhslot2->head);
                 nhslot2->count++;
                 spin_unlock(&nhslot2->lock);
             }
 
             spin_unlock_bh(&hslot->lock);
         }
     }
 }
 EXPORT_SYMBOL(udp_lib_rehash);
 
 void udp_v4_rehash(struct sock *sk)
 {
     u16 new_hash = ipv4_portaddr_hash(sock_net(sk),
                       inet_sk(sk)->inet_rcv_saddr,
                       inet_sk(sk)->inet_num);
     udp_lib_rehash(sk, new_hash);
 }
 
 static int __udp_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
 {
     int rc;
 
     if (inet_sk(sk)->inet_daddr) {
         sock_rps_save_rxhash(sk, skb);
         sk_mark_napi_id(sk, skb);
         sk_incoming_cpu_update(sk);
     } else {
         sk_mark_napi_id_once(sk, skb);
     }
 
     rc = __udp_enqueue_schedule_skb(sk, skb);
     if (rc < 0) {
         int is_udplite = IS_UDPLITE(sk);
         int drop_reason;
 
         /* Note that an ENOMEM error is charged twice */
         if (rc == -ENOMEM) {
             UDP_INC_STATS(sock_net(sk), UDP_MIB_RCVBUFERRORS,
                     is_udplite);
             drop_reason = SKB_DROP_REASON_SOCKET_RCVBUFF;
         } else {
             UDP_INC_STATS(sock_net(sk), UDP_MIB_MEMERRORS,
                       is_udplite);
             drop_reason = SKB_DROP_REASON_PROTO_MEM;
         }
         UDP_INC_STATS(sock_net(sk), UDP_MIB_INERRORS, is_udplite);
         kfree_skb_reason(skb, drop_reason);
         trace_udp_fail_queue_rcv_skb(rc, sk);
         return -1;
     }
 
     return 0;
 }
 
 /* returns:
  *  -1: error
  *   0: success
  *  >0: "udp encap" protocol resubmission
  *
  * Note that in the success and error cases, the skb is assumed to
  * have either been requeued or freed.
  */
 static int udp_queue_rcv_one_skb(struct sock *sk, struct sk_buff *skb)
 {
     int drop_reason = SKB_DROP_REASON_NOT_SPECIFIED;
     struct udp_sock *up = udp_sk(sk);
     int is_udplite = IS_UDPLITE(sk);
 
     /*
      *  Charge it to the socket, dropping if the queue is full.
      */
     if (!xfrm4_policy_check(sk, XFRM_POLICY_IN, skb)) {
         drop_reason = SKB_DROP_REASON_XFRM_POLICY;
         goto drop;
     }
     nf_reset_ct(skb);
 
     if (static_branch_unlikely(&udp_encap_needed_key) && up->encap_type) {
         int (*encap_rcv)(struct sock *sk, struct sk_buff *skb);
 
         /*
          * This is an encapsulation socket so pass the skb to
          * the socket's udp_encap_rcv() hook. Otherwise, just
          * fall through and pass this up the UDP socket.
          * up->encap_rcv() returns the following value:
          * =0 if skb was successfully passed to the encap
          *    handler or was discarded by it.
          * >0 if skb should be passed on to UDP.
          * <0 if skb should be resubmitted as proto -N
          */
 
         /* if we're overly short, let UDP handle it */
         encap_rcv = READ_ONCE(up->encap_rcv);
         if (encap_rcv) {
             int ret;
 
             /* Verify checksum before giving to encap */
             if (udp_lib_checksum_complete(skb))
                 goto csum_error;
 
             ret = encap_rcv(sk, skb);
             if (ret <= 0) {
                 __UDP_INC_STATS(sock_net(sk),
                         UDP_MIB_INDATAGRAMS,
                         is_udplite);
                 return -ret;
             }
         }
 
         /* FALLTHROUGH -- it's a UDP Packet */
     }
 
     /*
      *  UDP-Lite specific tests, ignored on UDP sockets
      */
     if ((up->pcflag & UDPLITE_RECV_CC)  &&  UDP_SKB_CB(skb)->partial_cov) {
 
         /*
          * MIB statistics other than incrementing the error count are
          * disabled for the following two types of errors: these depend
          * on the application settings, not on the functioning of the
          * protocol stack as such.
          *
          * RFC 3828 here recommends (sec 3.3): "There should also be a
          * way ... to ... at least let the receiving application block
          * delivery of packets with coverage values less than a value
          * provided by the application."
          */
         if (up->pcrlen == 0) {          /* full coverage was set  */
             net_dbg_ratelimited("UDPLite: partial coverage %d while full coverage %d requested\n",
                         UDP_SKB_CB(skb)->cscov, skb->len);
             goto drop;
         }
         /* The next case involves violating the min. coverage requested
          * by the receiver. This is subtle: if receiver wants x and x is
          * greater than the buffersize/MTU then receiver will complain
          * that it wants x while sender emits packets of smaller size y.
          * Therefore the above ...()->partial_cov statement is essential.
          */
         if (UDP_SKB_CB(skb)->cscov  <  up->pcrlen) {
             net_dbg_ratelimited("UDPLite: coverage %d too small, need min %d\n",
                         UDP_SKB_CB(skb)->cscov, up->pcrlen);
             goto drop;
         }
     }
 
     prefetch(&sk->sk_rmem_alloc);
     if (rcu_access_pointer(sk->sk_filter) &&
         udp_lib_checksum_complete(skb))
             goto csum_error;
 
     if (sk_filter_trim_cap(sk, skb, sizeof(struct udphdr))) {
         drop_reason = SKB_DROP_REASON_SOCKET_FILTER;
         goto drop;
     }
 
     udp_csum_pull_header(skb);
 
     ipv4_pktinfo_prepare(sk, skb);
     return __udp_queue_rcv_skb(sk, skb);
 
 csum_error:
     drop_reason = SKB_DROP_REASON_UDP_CSUM;
     __UDP_INC_STATS(sock_net(sk), UDP_MIB_CSUMERRORS, is_udplite);
 drop:
     __UDP_INC_STATS(sock_net(sk), UDP_MIB_INERRORS, is_udplite);
     atomic_inc(&sk->sk_drops);
     kfree_skb_reason(skb, drop_reason);
     return -1;
 }
 
 static int udp_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
 {
     struct sk_buff *next, *segs;
     int ret;
 
     if (likely(!udp_unexpected_gso(sk, skb)))
         return udp_queue_rcv_one_skb(sk, skb);
 
     BUILD_BUG_ON(sizeof(struct udp_skb_cb) > SKB_GSO_CB_OFFSET);
     __skb_push(skb, -skb_mac_offset(skb));
     segs = udp_rcv_segment(sk, skb, true);
     skb_list_walk_safe(segs, skb, next) {
         __skb_pull(skb, skb_transport_offset(skb));
 
         udp_post_segment_fix_csum(skb);
         ret = udp_queue_rcv_one_skb(sk, skb);
         if (ret > 0)
             ip_protocol_deliver_rcu(dev_net(skb->dev), skb, ret);
     }
     return 0;
 }
 
 /* For TCP sockets, sk_rx_dst is protected by socket lock
  * For UDP, we use xchg() to guard against concurrent changes.
  */
 bool udp_sk_rx_dst_set(struct sock *sk, struct dst_entry *dst)
 {
     struct dst_entry *old;
 
     if (dst_hold_safe(dst)) {
         old = xchg((__force struct dst_entry **)&sk->sk_rx_dst, dst);
         dst_release(old);
         return old != dst;
     }
     return false;
 }
 EXPORT_SYMBOL(udp_sk_rx_dst_set);
 
 /*
  *  Multicasts and broadcasts go to each listener.
  *
  *  Note: called only from the BH handler context.
  */
 static int __udp4_lib_mcast_deliver(struct net *net, struct sk_buff *skb,
                     struct udphdr  *uh,
                     __be32 saddr, __be32 daddr,
                     struct udp_table *udptable,
                     int proto)
 {
     struct sock *sk, *first = NULL;
     unsigned short hnum = ntohs(uh->dest);
     struct udp_hslot *hslot = udp_hashslot(udptable, net, hnum);
     unsigned int hash2 = 0, hash2_any = 0, use_hash2 = (hslot->count > 10);
     unsigned int offset = offsetof(typeof(*sk), sk_node);
     int dif = skb->dev->ifindex;
     int sdif = inet_sdif(skb);
     struct hlist_node *node;
     struct sk_buff *nskb;
 
     if (use_hash2) {
         hash2_any = ipv4_portaddr_hash(net, htonl(INADDR_ANY), hnum) &
                 udptable->mask;
         hash2 = ipv4_portaddr_hash(net, daddr, hnum) & udptable->mask;
 start_lookup:
         hslot = &udptable->hash2[hash2];
         offset = offsetof(typeof(*sk), __sk_common.skc_portaddr_node);
     }
 
     sk_for_each_entry_offset_rcu(sk, node, &hslot->head, offset) {
         if (!__udp_is_mcast_sock(net, sk, uh->dest, daddr,
                      uh->source, saddr, dif, sdif, hnum))
             continue;
 
         if (!first) {
             first = sk;
             continue;
         }
         nskb = skb_clone(skb, GFP_ATOMIC);
 
         if (unlikely(!nskb)) {
             atomic_inc(&sk->sk_drops);
             __UDP_INC_STATS(net, UDP_MIB_RCVBUFERRORS,
                     IS_UDPLITE(sk));
             __UDP_INC_STATS(net, UDP_MIB_INERRORS,
                     IS_UDPLITE(sk));
             continue;
         }
         if (udp_queue_rcv_skb(sk, nskb) > 0)
             consume_skb(nskb);
     }
 
     /* Also lookup *:port if we are using hash2 and haven't done so yet. */
     if (use_hash2 && hash2 != hash2_any) {
         hash2 = hash2_any;
         goto start_lookup;
     }
 
     if (first) {
         if (udp_queue_rcv_skb(first, skb) > 0)
             consume_skb(skb);
     } else {
         kfree_skb(skb);
         __UDP_INC_STATS(net, UDP_MIB_IGNOREDMULTI,
                 proto == IPPROTO_UDPLITE);
     }
     return 0;
 }
 
 /* Initialize UDP checksum. If exited with zero value (success),
  * CHECKSUM_UNNECESSARY means, that no more checks are required.
  * Otherwise, csum completion requires checksumming packet body,
  * including udp header and folding it to skb->csum.
  */
 static inline int udp4_csum_init(struct sk_buff *skb, struct udphdr *uh,
                  int proto)
 {
     int err;
 
     UDP_SKB_CB(skb)->partial_cov = 0;
     UDP_SKB_CB(skb)->cscov = skb->len;
 
     if (proto == IPPROTO_UDPLITE) {
         err = udplite_checksum_init(skb, uh);
         if (err)
             return err;
 
         if (UDP_SKB_CB(skb)->partial_cov) {
             skb->csum = inet_compute_pseudo(skb, proto);
             return 0;
         }
     }
 
     /* Note, we are only interested in != 0 or == 0, thus the
      * force to int.
      */
     err = (__force int)skb_checksum_init_zero_check(skb, proto, uh->check,
                             inet_compute_pseudo);
     if (err)
         return err;
 
     if (skb->ip_summed == CHECKSUM_COMPLETE && !skb->csum_valid) {
         /* If SW calculated the value, we know it's bad */
         if (skb->csum_complete_sw)
             return 1;
 
         /* HW says the value is bad. Let's validate that.
          * skb->csum is no longer the full packet checksum,
          * so don't treat it as such.
          */
         skb_checksum_complete_unset(skb);
     }
 
     return 0;
 }
 
 /* wrapper for udp_queue_rcv_skb tacking care of csum conversion and
  * return code conversion for ip layer consumption
  */
 static int udp_unicast_rcv_skb(struct sock *sk, struct sk_buff *skb,
                    struct udphdr *uh)
 {
     int ret;
 
     if (inet_get_convert_csum(sk) && uh->check && !IS_UDPLITE(sk))
         skb_checksum_try_convert(skb, IPPROTO_UDP, inet_compute_pseudo);
 
     ret = udp_queue_rcv_skb(sk, skb);
 
     /* a return value > 0 means to resubmit the input, but
      * it wants the return to be -protocol, or 0
      */
     if (ret > 0)
         return -ret;
     return 0;
 }
 
 /*
  *  All we need to do is get the socket, and then do a checksum.
  */
 
 int __udp4_lib_rcv(struct sk_buff *skb, struct udp_table *udptable,
            int proto)
 {
     struct sock *sk;
     struct udphdr *uh;
     unsigned short ulen;
     struct rtable *rt = skb_rtable(skb);
     __be32 saddr, daddr;
     struct net *net = dev_net(skb->dev);
     bool refcounted;
     int drop_reason;
 
     drop_reason = SKB_DROP_REASON_NOT_SPECIFIED;
 
     /*
      *  Validate the packet.
      */
     if (!pskb_may_pull(skb, sizeof(struct udphdr)))
         goto drop;      /* No space for header. */
 
     uh   = udp_hdr(skb);
     ulen = ntohs(uh->len);
     saddr = ip_hdr(skb)->saddr;
     daddr = ip_hdr(skb)->daddr;
 
     if (ulen > skb->len)
         goto short_packet;
 
     if (proto == IPPROTO_UDP) {
         /* UDP validates ulen. */
         if (ulen < sizeof(*uh) || pskb_trim_rcsum(skb, ulen))
             goto short_packet;
         uh = udp_hdr(skb);
     }
 
     if (udp4_csum_init(skb, uh, proto))
         goto csum_error;
 
     sk = skb_steal_sock(skb, &refcounted);
     if (sk) {
         struct dst_entry *dst = skb_dst(skb);
         int ret;
 
         if (unlikely(rcu_dereference(sk->sk_rx_dst) != dst))
             udp_sk_rx_dst_set(sk, dst);
 
         ret = udp_unicast_rcv_skb(sk, skb, uh);
         if (refcounted)
             sock_put(sk);
         return ret;
     }
 
     if (rt->rt_flags & (RTCF_BROADCAST|RTCF_MULTICAST))
         return __udp4_lib_mcast_deliver(net, skb, uh,
                         saddr, daddr, udptable, proto);
 
     sk = __udp4_lib_lookup_skb(skb, uh->source, uh->dest, udptable);
     if (sk)
         return udp_unicast_rcv_skb(sk, skb, uh);
 
     if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb))
         goto drop;
     nf_reset_ct(skb);
 
     /* No socket. Drop packet silently, if checksum is wrong */
     if (udp_lib_checksum_complete(skb))
         goto csum_error;
 
     drop_reason = SKB_DROP_REASON_NO_SOCKET;
     __UDP_INC_STATS(net, UDP_MIB_NOPORTS, proto == IPPROTO_UDPLITE);
     icmp_send(skb, ICMP_DEST_UNREACH, ICMP_PORT_UNREACH, 0);
 
     /*
      * Hmm.  We got an UDP packet to a port to which we
      * don't wanna listen.  Ignore it.
      */
     kfree_skb_reason(skb, drop_reason);
     return 0;
 
 short_packet:
     drop_reason = SKB_DROP_REASON_PKT_TOO_SMALL;
     net_dbg_ratelimited("UDP%s: short packet: From %pI4:%u %d/%d to %pI4:%u\n",
                 proto == IPPROTO_UDPLITE ? "Lite" : "",
                 &saddr, ntohs(uh->source),
                 ulen, skb->len,
                 &daddr, ntohs(uh->dest));
     goto drop;
 
 csum_error:
     /*
      * RFC1122: OK.  Discards the bad packet silently (as far as
      * the network is concerned, anyway) as per 4.1.3.4 (MUST).
      */
     drop_reason = SKB_DROP_REASON_UDP_CSUM;
     net_dbg_ratelimited("UDP%s: bad checksum. From %pI4:%u to %pI4:%u ulen %d\n",
                 proto == IPPROTO_UDPLITE ? "Lite" : "",
                 &saddr, ntohs(uh->source), &daddr, ntohs(uh->dest),
                 ulen);
     __UDP_INC_STATS(net, UDP_MIB_CSUMERRORS, proto == IPPROTO_UDPLITE);
 drop:
     __UDP_INC_STATS(net, UDP_MIB_INERRORS, proto == IPPROTO_UDPLITE);
     kfree_skb_reason(skb, drop_reason);
     return 0;
 }
 
 /* We can only early demux multicast if there is a single matching socket.
  * If more than one socket found returns NULL
  */
 static struct sock *__udp4_lib_mcast_demux_lookup(struct net *net,
                           __be16 loc_port, __be32 loc_addr,
                           __be16 rmt_port, __be32 rmt_addr,
                           int dif, int sdif)
 {
     struct sock *sk, *result;
     unsigned short hnum = ntohs(loc_port);
     unsigned int slot = udp_hashfn(net, hnum, udp_table.mask);
     struct udp_hslot *hslot = &udp_table.hash[slot];
 
     /* Do not bother scanning a too big list */
     if (hslot->count > 10)
         return NULL;
 
     result = NULL;
     sk_for_each_rcu(sk, &hslot->head) {
         if (__udp_is_mcast_sock(net, sk, loc_port, loc_addr,
                     rmt_port, rmt_addr, dif, sdif, hnum)) {
             if (result)
                 return NULL;
             result = sk;
         }
     }
 
     return result;
 }
 
 /* For unicast we should only early demux connected sockets or we can
  * break forwarding setups.  The chains here can be long so only check
  * if the first socket is an exact match and if not move on.
  */
 static struct sock *__udp4_lib_demux_lookup(struct net *net,
                         __be16 loc_port, __be32 loc_addr,
                         __be16 rmt_port, __be32 rmt_addr,
                         int dif, int sdif)
 {
     unsigned short hnum = ntohs(loc_port);
     unsigned int hash2 = ipv4_portaddr_hash(net, loc_addr, hnum);
     unsigned int slot2 = hash2 & udp_table.mask;
     struct udp_hslot *hslot2 = &udp_table.hash2[slot2];
     INET_ADDR_COOKIE(acookie, rmt_addr, loc_addr);
     const __portpair ports = INET_COMBINED_PORTS(rmt_port, hnum);
     struct sock *sk;
 
     udp_portaddr_for_each_entry_rcu(sk, &hslot2->head) {
         if (inet_match(net, sk, acookie, ports, dif, sdif))
             return sk;
         /* Only check first socket in chain */
         break;
     }
     return NULL;
 }
 
 int udp_v4_early_demux(struct sk_buff *skb)
 {
     struct net *net = dev_net(skb->dev);
     struct in_device *in_dev = NULL;
     const struct iphdr *iph;
     const struct udphdr *uh;
     struct sock *sk = NULL;
     struct dst_entry *dst;
     int dif = skb->dev->ifindex;
     int sdif = inet_sdif(skb);
     int ours;
 
     /* validate the packet */
     if (!pskb_may_pull(skb, skb_transport_offset(skb) + sizeof(struct udphdr)))
         return 0;
 
     iph = ip_hdr(skb);
     uh = udp_hdr(skb);
 
     if (skb->pkt_type == PACKET_MULTICAST) {
         in_dev = __in_dev_get_rcu(skb->dev);
 
         if (!in_dev)
             return 0;
 
         ours = ip_check_mc_rcu(in_dev, iph->daddr, iph->saddr,
                        iph->protocol);
         if (!ours)
             return 0;
 
         sk = __udp4_lib_mcast_demux_lookup(net, uh->dest, iph->daddr,
                            uh->source, iph->saddr,
                            dif, sdif);
     } else if (skb->pkt_type == PACKET_HOST) {
         sk = __udp4_lib_demux_lookup(net, uh->dest, iph->daddr,
                          uh->source, iph->saddr, dif, sdif);
     }
 
     if (!sk || !refcount_inc_not_zero(&sk->sk_refcnt))
         return 0;
 
     skb->sk = sk;
     skb->destructor = sock_efree;
     dst = rcu_dereference(sk->sk_rx_dst);
 
     if (dst)
         dst = dst_check(dst, 0);
     if (dst) {
         u32 itag = 0;
 
         /* set noref for now.
          * any place which wants to hold dst has to call
          * dst_hold_safe()
          */
         skb_dst_set_noref(skb, dst);
 
         /* for unconnected multicast sockets we need to validate
          * the source on each packet
          */
         if (!inet_sk(sk)->inet_daddr && in_dev)
             return ip_mc_validate_source(skb, iph->daddr,
                              iph->saddr,
                              iph->tos & IPTOS_RT_MASK,
                              skb->dev, in_dev, &itag);
     }
     return 0;
 }
 
 int udp_rcv(struct sk_buff *skb)
 {
     return __udp4_lib_rcv(skb, &udp_table, IPPROTO_UDP);
 }
 
 void udp_destroy_sock(struct sock *sk)
 {
     struct udp_sock *up = udp_sk(sk);
     bool slow = lock_sock_fast(sk);
 
     /* protects from races with udp_abort() */
     sock_set_flag(sk, SOCK_DEAD);
     udp_flush_pending_frames(sk);
     unlock_sock_fast(sk, slow);
     if (static_branch_unlikely(&udp_encap_needed_key)) {
         if (up->encap_type) {
             void (*encap_destroy)(struct sock *sk);
             encap_destroy = READ_ONCE(up->encap_destroy);
             if (encap_destroy)
                 encap_destroy(sk);
         }
         if (up->encap_enabled)
             static_branch_dec(&udp_encap_needed_key);
     }
 }
 
 /*
  *  Socket option code for UDP
  */
 int udp_lib_setsockopt(struct sock *sk, int level, int optname,
                sockptr_t optval, unsigned int optlen,
                int (*push_pending_frames)(struct sock *))
 {
     struct udp_sock *up = udp_sk(sk);
     int val, valbool;
     int err = 0;
     int is_udplite = IS_UDPLITE(sk);
 
     if (optlen < sizeof(int))
         return -EINVAL;
 
     if (copy_from_sockptr(&val, optval, sizeof(val)))
         return -EFAULT;
 
     valbool = val ? 1 : 0;
 
     switch (optname) {
     case UDP_CORK:
         if (val != 0) {
             WRITE_ONCE(up->corkflag, 1);
         } else {
             WRITE_ONCE(up->corkflag, 0);
             lock_sock(sk);
             push_pending_frames(sk);
             release_sock(sk);
         }
         break;
 
     case UDP_ENCAP:
         switch (val) {
         case 0:
 #ifdef CONFIG_XFRM
         case UDP_ENCAP_ESPINUDP:
         case UDP_ENCAP_ESPINUDP_NON_IKE:
 #if IS_ENABLED(CONFIG_IPV6)
             if (sk->sk_family == AF_INET6)
                 up->encap_rcv = ipv6_stub->xfrm6_udp_encap_rcv;
             else
 #endif
                 up->encap_rcv = xfrm4_udp_encap_rcv;
 #endif
             fallthrough;
         case UDP_ENCAP_L2TPINUDP:
             up->encap_type = val;
             lock_sock(sk);
             udp_tunnel_encap_enable(sk->sk_socket);
             release_sock(sk);
             break;
         default:
             err = -ENOPROTOOPT;
             break;
         }
         break;
 
     case UDP_NO_CHECK6_TX:
         up->no_check6_tx = valbool;
         break;
 
     case UDP_NO_CHECK6_RX:
         up->no_check6_rx = valbool;
         break;
 
     case UDP_SEGMENT:
         if (val < 0 || val > USHRT_MAX)
             return -EINVAL;
         WRITE_ONCE(up->gso_size, val);
         break;
 
     case UDP_GRO:
         lock_sock(sk);
 
         /* when enabling GRO, accept the related GSO packet type */
         if (valbool)
             udp_tunnel_encap_enable(sk->sk_socket);
         up->gro_enabled = valbool;
         up->accept_udp_l4 = valbool;
         release_sock(sk);
         break;
 
     /*
      *  UDP-Lite's partial checksum coverage (RFC 3828).
      */
     /* The sender sets actual checksum coverage length via this option.
      * The case coverage > packet length is handled by send module. */
     case UDPLITE_SEND_CSCOV:
         if (!is_udplite)         /* Disable the option on UDP sockets */
             return -ENOPROTOOPT;
         if (val != 0 && val < 8) /* Illegal coverage: use default (8) */
             val = 8;
         else if (val > USHRT_MAX)
             val = USHRT_MAX;
         up->pcslen = val;
         up->pcflag |= UDPLITE_SEND_CC;
         break;
 
     /* The receiver specifies a minimum checksum coverage value. To make
      * sense, this should be set to at least 8 (as done below). If zero is
      * used, this again means full checksum coverage.                     */
     case UDPLITE_RECV_CSCOV:
         if (!is_udplite)         /* Disable the option on UDP sockets */
             return -ENOPROTOOPT;
         if (val != 0 && val < 8) /* Avoid silly minimal values.       */
             val = 8;
         else if (val > USHRT_MAX)
             val = USHRT_MAX;
         up->pcrlen = val;
         up->pcflag |= UDPLITE_RECV_CC;
         break;
 
     default:
         err = -ENOPROTOOPT;
         break;
     }
 
     return err;
 }
 EXPORT_SYMBOL(udp_lib_setsockopt);
 
 int udp_setsockopt(struct sock *sk, int level, int optname, sockptr_t optval,
            unsigned int optlen)
 {
     if (level == SOL_UDP  ||  level == SOL_UDPLITE)
         return udp_lib_setsockopt(sk, level, optname,
                       optval, optlen,
                       udp_push_pending_frames);
     return ip_setsockopt(sk, level, optname, optval, optlen);
 }
 
 int udp_lib_getsockopt(struct sock *sk, int level, int optname,
                char __user *optval, int __user *optlen)
 {
     struct udp_sock *up = udp_sk(sk);
     int val, len;
 
     if (get_user(len, optlen))
         return -EFAULT;
 
     len = min_t(unsigned int, len, sizeof(int));
 
     if (len < 0)
         return -EINVAL;
 
     switch (optname) {
     case UDP_CORK:
         val = READ_ONCE(up->corkflag);
         break;
 
     case UDP_ENCAP:
         val = up->encap_type;
         break;
 
     case UDP_NO_CHECK6_TX:
         val = up->no_check6_tx;
         break;
 
     case UDP_NO_CHECK6_RX:
         val = up->no_check6_rx;
         break;
 
     case UDP_SEGMENT:
         val = READ_ONCE(up->gso_size);
         break;
 
     case UDP_GRO:
         val = up->gro_enabled;
         break;
 
     /* The following two cannot be changed on UDP sockets, the return is
      * always 0 (which corresponds to the full checksum coverage of UDP). */
     case UDPLITE_SEND_CSCOV:
         val = up->pcslen;
         break;
 
     case UDPLITE_RECV_CSCOV:
         val = up->pcrlen;
         break;
 
     default:
         return -ENOPROTOOPT;
     }
 
     if (put_user(len, optlen))
         return -EFAULT;
     if (copy_to_user(optval, &val, len))
         return -EFAULT;
     return 0;
 }
 EXPORT_SYMBOL(udp_lib_getsockopt);
 
 int udp_getsockopt(struct sock *sk, int level, int optname,
            char __user *optval, int __user *optlen)
 {
     if (level == SOL_UDP  ||  level == SOL_UDPLITE)
         return udp_lib_getsockopt(sk, level, optname, optval, optlen);
     return ip_getsockopt(sk, level, optname, optval, optlen);
 }
 
 /**
  *  udp_poll - wait for a UDP event.
  *  @file: - file struct
  *  @sock: - socket
  *  @wait: - poll table
  *
  *  This is same as datagram poll, except for the special case of
  *  blocking sockets. If application is using a blocking fd
  *  and a packet with checksum error is in the queue;
  *  then it could get return from select indicating data available
  *  but then block when reading it. Add special case code
  *  to work around these arguably broken applications.
  */
 __poll_t udp_poll(struct file *file, struct socket *sock, poll_table *wait)
 {
     __poll_t mask = datagram_poll(file, sock, wait);
     struct sock *sk = sock->sk;
 
     if (!skb_queue_empty_lockless(&udp_sk(sk)->reader_queue))
         mask |= EPOLLIN | EPOLLRDNORM;
 
     /* Check for false positives due to checksum errors */
     if ((mask & EPOLLRDNORM) && !(file->f_flags & O_NONBLOCK) &&
         !(sk->sk_shutdown & RCV_SHUTDOWN) && first_packet_length(sk) == -1)
         mask &= ~(EPOLLIN | EPOLLRDNORM);
 
     /* psock ingress_msg queue should not contain any bad checksum frames */
     if (sk_is_readable(sk))
         mask |= EPOLLIN | EPOLLRDNORM;
     return mask;
 
 }
 EXPORT_SYMBOL(udp_poll);
 
 int udp_abort(struct sock *sk, int err)
 {
     lock_sock(sk);
 
     /* udp{v6}_destroy_sock() sets it under the sk lock, avoid racing
      * with close()
      */
     if (sock_flag(sk, SOCK_DEAD))
         goto out;
 
     sk->sk_err = err;
     sk_error_report(sk);
     __udp_disconnect(sk, 0);
 
 out:
     release_sock(sk);
 
     return 0;
 }
 EXPORT_SYMBOL_GPL(udp_abort);
 
 struct proto udp_prot = {
     .name           = "UDP",
     .owner          = THIS_MODULE,
     .close          = udp_lib_close,
     .pre_connect        = udp_pre_connect,
     .connect        = ip4_datagram_connect,
     .disconnect     = udp_disconnect,
     .ioctl          = udp_ioctl,
     .init           = udp_init_sock,
     .destroy        = udp_destroy_sock,
     .setsockopt     = udp_setsockopt,
     .getsockopt     = udp_getsockopt,
     .sendmsg        = udp_sendmsg,
     .recvmsg        = udp_recvmsg,
     .sendpage       = udp_sendpage,
     .release_cb     = ip4_datagram_release_cb,
     .hash           = udp_lib_hash,
     .unhash         = udp_lib_unhash,
     .rehash         = udp_v4_rehash,
     .get_port       = udp_v4_get_port,
     .put_port       = udp_lib_unhash,
 #ifdef CONFIG_BPF_SYSCALL
     .psock_update_sk_prot   = udp_bpf_update_proto,
 #endif
     .memory_allocated   = &udp_memory_allocated,
     .per_cpu_fw_alloc   = &udp_memory_per_cpu_fw_alloc,
 
     .sysctl_mem     = sysctl_udp_mem,
     .sysctl_wmem_offset = offsetof(struct net, ipv4.sysctl_udp_wmem_min),
     .sysctl_rmem_offset = offsetof(struct net, ipv4.sysctl_udp_rmem_min),
     .obj_size       = sizeof(struct udp_sock),
     .h.udp_table        = &udp_table,
     .diag_destroy       = udp_abort,
 };
 EXPORT_SYMBOL(udp_prot);
 
 /* ------------------------------------------------------------------------ */
 #ifdef CONFIG_PROC_FS
 
 static struct sock *udp_get_first(struct seq_file *seq, int start)
 {
     struct sock *sk;
     struct udp_seq_afinfo *afinfo;
     struct udp_iter_state *state = seq->private;
     struct net *net = seq_file_net(seq);
 
     if (state->bpf_seq_afinfo)
         afinfo = state->bpf_seq_afinfo;
     else
         afinfo = pde_data(file_inode(seq->file));
 
     for (state->bucket = start; state->bucket <= afinfo->udp_table->mask;
          ++state->bucket) {
         struct udp_hslot *hslot = &afinfo->udp_table->hash[state->bucket];
 
         if (hlist_empty(&hslot->head))
             continue;
 
         spin_lock_bh(&hslot->lock);
         sk_for_each(sk, &hslot->head) {
             if (!net_eq(sock_net(sk), net))
                 continue;
             if (afinfo->family == AF_UNSPEC ||
                 sk->sk_family == afinfo->family)
                 goto found;
         }
         spin_unlock_bh(&hslot->lock);
     }
     sk = NULL;
 found:
     return sk;
 }
 
 static struct sock *udp_get_next(struct seq_file *seq, struct sock *sk)
 {
     struct udp_seq_afinfo *afinfo;
     struct udp_iter_state *state = seq->private;
     struct net *net = seq_file_net(seq);
 
     if (state->bpf_seq_afinfo)
         afinfo = state->bpf_seq_afinfo;
     else
         afinfo = pde_data(file_inode(seq->file));
 
     do {
         sk = sk_next(sk);
     } while (sk && (!net_eq(sock_net(sk), net) ||
             (afinfo->family != AF_UNSPEC &&
              sk->sk_family != afinfo->family)));
 
     if (!sk) {
         if (state->bucket <= afinfo->udp_table->mask)
             spin_unlock_bh(&afinfo->udp_table->hash[state->bucket].lock);
         return udp_get_first(seq, state->bucket + 1);
     }
     return sk;
 }
 
 static struct sock *udp_get_idx(struct seq_file *seq, loff_t pos)
 {
     struct sock *sk = udp_get_first(seq, 0);
 
     if (sk)
         while (pos && (sk = udp_get_next(seq, sk)) != NULL)
             --pos;
     return pos ? NULL : sk;
 }
 
 void *udp_seq_start(struct seq_file *seq, loff_t *pos)
 {
     struct udp_iter_state *state = seq->private;
     state->bucket = MAX_UDP_PORTS;
 
     return *pos ? udp_get_idx(seq, *pos-1) : SEQ_START_TOKEN;
 }
 EXPORT_SYMBOL(udp_seq_start);
 
 void *udp_seq_next(struct seq_file *seq, void *v, loff_t *pos)
 {
     struct sock *sk;
 
     if (v == SEQ_START_TOKEN)
         sk = udp_get_idx(seq, 0);
     else
         sk = udp_get_next(seq, v);
 
     ++*pos;
     return sk;
 }
 EXPORT_SYMBOL(udp_seq_next);
 
 void udp_seq_stop(struct seq_file *seq, void *v)
 {
     struct udp_seq_afinfo *afinfo;
     struct udp_iter_state *state = seq->private;
 
     if (state->bpf_seq_afinfo)
         afinfo = state->bpf_seq_afinfo;
     else
         afinfo = pde_data(file_inode(seq->file));
 
     if (state->bucket <= afinfo->udp_table->mask)
         spin_unlock_bh(&afinfo->udp_table->hash[state->bucket].lock);
 }
 EXPORT_SYMBOL(udp_seq_stop);
 
 /* ------------------------------------------------------------------------ */
 static void udp4_format_sock(struct sock *sp, struct seq_file *f,
         int bucket)
 {
     struct inet_sock *inet = inet_sk(sp);
     __be32 dest = inet->inet_daddr;
     __be32 src  = inet->inet_rcv_saddr;
     __u16 destp   = ntohs(inet->inet_dport);
     __u16 srcp    = ntohs(inet->inet_sport);
 
     seq_printf(f, "%5d: %08X:%04X %08X:%04X"
         " %02X %08X:%08X %02X:%08lX %08X %5u %8d %lu %d %pK %u",
         bucket, src, srcp, dest, destp, sp->sk_state,
         sk_wmem_alloc_get(sp),
         udp_rqueue_get(sp),
         0, 0L, 0,
         from_kuid_munged(seq_user_ns(f), sock_i_uid(sp)),
         0, sock_i_ino(sp),
         refcount_read(&sp->sk_refcnt), sp,
         atomic_read(&sp->sk_drops));
 }
 
 int udp4_seq_show(struct seq_file *seq, void *v)
 {
     seq_setwidth(seq, 127);
     if (v == SEQ_START_TOKEN)
         seq_puts(seq, "   sl  local_address rem_address   st tx_queue "
                "rx_queue tr tm->when retrnsmt   uid  timeout "
                "inode ref pointer drops");
     else {
         struct udp_iter_state *state = seq->private;
 
         udp4_format_sock(v, seq, state->bucket);
     }
     seq_pad(seq, '\n');
     return 0;
 }
 
 #ifdef CONFIG_BPF_SYSCALL
 struct bpf_iter__udp {
     __bpf_md_ptr(struct bpf_iter_meta *, meta);
     __bpf_md_ptr(struct udp_sock *, udp_sk);
     uid_t uid __aligned(8);
     int bucket __aligned(8);
 };
 
 static int udp_prog_seq_show(struct bpf_prog *prog, struct bpf_iter_meta *meta,
                  struct udp_sock *udp_sk, uid_t uid, int bucket)
 {
     struct bpf_iter__udp ctx;
 
     meta->seq_num--;  /* skip SEQ_START_TOKEN */
     ctx.meta = meta;
     ctx.udp_sk = udp_sk;
     ctx.uid = uid;
     ctx.bucket = bucket;
     return bpf_iter_run_prog(prog, &ctx);
 }
 
 static int bpf_iter_udp_seq_show(struct seq_file *seq, void *v)
 {
     struct udp_iter_state *state = seq->private;
     struct bpf_iter_meta meta;
     struct bpf_prog *prog;
     struct sock *sk = v;
     uid_t uid;
 
     if (v == SEQ_START_TOKEN)
         return 0;
 
     uid = from_kuid_munged(seq_user_ns(seq), sock_i_uid(sk));
     meta.seq = seq;
     prog = bpf_iter_get_info(&meta, false);
     return udp_prog_seq_show(prog, &meta, v, uid, state->bucket);
 }
 
 static void bpf_iter_udp_seq_stop(struct seq_file *seq, void *v)
 {
     struct bpf_iter_meta meta;
     struct bpf_prog *prog;
 
     if (!v) {
         meta.seq = seq;
         prog = bpf_iter_get_info(&meta, true);
         if (prog)
             (void)udp_prog_seq_show(prog, &meta, v, 0, 0);
     }
 
     udp_seq_stop(seq, v);
 }
 
 static const struct seq_operations bpf_iter_udp_seq_ops = {
     .start      = udp_seq_start,
     .next       = udp_seq_next,
     .stop       = bpf_iter_udp_seq_stop,
     .show       = bpf_iter_udp_seq_show,
 };
 #endif
 
 const struct seq_operations udp_seq_ops = {
     .start      = udp_seq_start,
     .next       = udp_seq_next,
     .stop       = udp_seq_stop,
     .show       = udp4_seq_show,
 };
 EXPORT_SYMBOL(udp_seq_ops);
 
 static struct udp_seq_afinfo udp4_seq_afinfo = {
     .family     = AF_INET,
     .udp_table  = &udp_table,
 };
 
 static int __net_init udp4_proc_init_net(struct net *net)
 {
     if (!proc_create_net_data("udp", 0444, net->proc_net, &udp_seq_ops,
             sizeof(struct udp_iter_state), &udp4_seq_afinfo))
         return -ENOMEM;
     return 0;
 }
 
 static void __net_exit udp4_proc_exit_net(struct net *net)
 {
     remove_proc_entry("udp", net->proc_net);
 }
 
 static struct pernet_operations udp4_net_ops = {
     .init = udp4_proc_init_net,
     .exit = udp4_proc_exit_net,
 };
 
 int __init udp4_proc_init(void)
 {
     return register_pernet_subsys(&udp4_net_ops);
 }
 
 void udp4_proc_exit(void)
 {
     unregister_pernet_subsys(&udp4_net_ops);
 }
 #endif /* CONFIG_PROC_FS */
 
 static __initdata unsigned long uhash_entries;
 static int __init set_uhash_entries(char *str)
 {
     ssize_t ret;
 
     if (!str)
         return 0;
 
     ret = kstrtoul(str, 0, &uhash_entries);
     if (ret)
         return 0;
 
     if (uhash_entries && uhash_entries < UDP_HTABLE_SIZE_MIN)
         uhash_entries = UDP_HTABLE_SIZE_MIN;
     return 1;
 }
 __setup("uhash_entries=", set_uhash_entries);
 
 void __init udp_table_init(struct udp_table *table, const char *name)
 {
     unsigned int i;
 
     table->hash = alloc_large_system_hash(name,
                           2 * sizeof(struct udp_hslot),
                           uhash_entries,
                           21, /* one slot per 2 MB */
                           0,
                           &table->log,
                           &table->mask,
                           UDP_HTABLE_SIZE_MIN,
                           64 * 1024);
 
     table->hash2 = table->hash + (table->mask + 1);
     for (i = 0; i <= table->mask; i++) {
         INIT_HLIST_HEAD(&table->hash[i].head);
         table->hash[i].count = 0;
         spin_lock_init(&table->hash[i].lock);
     }
     for (i = 0; i <= table->mask; i++) {
         INIT_HLIST_HEAD(&table->hash2[i].head);
         table->hash2[i].count = 0;
         spin_lock_init(&table->hash2[i].lock);
     }
 }
 
 u32 udp_flow_hashrnd(void)
 {
     static u32 hashrnd __read_mostly;
 
     net_get_random_once(&hashrnd, sizeof(hashrnd));
 
     return hashrnd;
 }
 EXPORT_SYMBOL(udp_flow_hashrnd);
 
 static int __net_init udp_sysctl_init(struct net *net)
 {
     net->ipv4.sysctl_udp_rmem_min = PAGE_SIZE;
     net->ipv4.sysctl_udp_wmem_min = PAGE_SIZE;
 
 #ifdef CONFIG_NET_L3_MASTER_DEV
     net->ipv4.sysctl_udp_l3mdev_accept = 0;
 #endif
 
     return 0;
 }
 
 static struct pernet_operations __net_initdata udp_sysctl_ops = {
     .init   = udp_sysctl_init,
 };
 
 #if defined(CONFIG_BPF_SYSCALL) && defined(CONFIG_PROC_FS)
 DEFINE_BPF_ITER_FUNC(udp, struct bpf_iter_meta *meta,
              struct udp_sock *udp_sk, uid_t uid, int bucket)
 
 static int bpf_iter_init_udp(void *priv_data, struct bpf_iter_aux_info *aux)
 {
     struct udp_iter_state *st = priv_data;
     struct udp_seq_afinfo *afinfo;
     int ret;
 
     afinfo = kmalloc(sizeof(*afinfo), GFP_USER | __GFP_NOWARN);
     if (!afinfo)
         return -ENOMEM;
 
     afinfo->family = AF_UNSPEC;
     afinfo->udp_table = &udp_table;
     st->bpf_seq_afinfo = afinfo;
     ret = bpf_iter_init_seq_net(priv_data, aux);
     if (ret)
         kfree(afinfo);
     return ret;
 }
 
 static void bpf_iter_fini_udp(void *priv_data)
 {
     struct udp_iter_state *st = priv_data;
 
     kfree(st->bpf_seq_afinfo);
     bpf_iter_fini_seq_net(priv_data);
 }
 
 static const struct bpf_iter_seq_info udp_seq_info = {
     .seq_ops        = &bpf_iter_udp_seq_ops,
     .init_seq_private   = bpf_iter_init_udp,
     .fini_seq_private   = bpf_iter_fini_udp,
     .seq_priv_size      = sizeof(struct udp_iter_state),
 };
 
 static struct bpf_iter_reg udp_reg_info = {
     .target         = "udp",
     .ctx_arg_info_size  = 1,
     .ctx_arg_info       = {
         { offsetof(struct bpf_iter__udp, udp_sk),
           PTR_TO_BTF_ID_OR_NULL },
     },
     .seq_info       = &udp_seq_info,
 };
 
 static void __init bpf_iter_register(void)
 {
     udp_reg_info.ctx_arg_info[0].btf_id = btf_sock_ids[BTF_SOCK_TYPE_UDP];
     if (bpf_iter_reg_target(&udp_reg_info))
         pr_warn("Warning: could not register bpf iterator udp\n");
 }
 #endif
 
 void __init udp_init(void)
 {
     unsigned long limit;
     unsigned int i;
 
     udp_table_init(&udp_table, "UDP");
     limit = nr_free_buffer_pages() / 8;
     limit = max(limit, 128UL);
     sysctl_udp_mem[0] = limit / 4 * 3;
     sysctl_udp_mem[1] = limit;
     sysctl_udp_mem[2] = sysctl_udp_mem[0] * 2;
 
     /* 16 spinlocks per cpu */
     udp_busylocks_log = ilog2(nr_cpu_ids) + 4;
     udp_busylocks = kmalloc(sizeof(spinlock_t) << udp_busylocks_log,
                 GFP_KERNEL);
     if (!udp_busylocks)
         panic("UDP: failed to alloc udp_busylocks\n");
     for (i = 0; i < (1U << udp_busylocks_log); i++)
         spin_lock_init(udp_busylocks + i);
 
     if (register_pernet_subsys(&udp_sysctl_ops))
         panic("UDP: failed to init sysctl parameters.\n");
 
 #if defined(CONFIG_BPF_SYSCALL) && defined(CONFIG_PROC_FS)
     bpf_iter_register();
 #endif
 }