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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.
  *
  *      Implementation of the Transmission Control Protocol(TCP).
  *
  * Authors: Ross Biro
  *      Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
  *      Mark Evans, <evansmp@uhura.aston.ac.uk>
  *      Corey Minyard <wf-rch!minyard@relay.EU.net>
  *      Florian La Roche, <flla@stud.uni-sb.de>
  *      Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
  *      Linus Torvalds, <torvalds@cs.helsinki.fi>
  *      Alan Cox, <gw4pts@gw4pts.ampr.org>
  *      Matthew Dillon, <dillon@apollo.west.oic.com>
  *      Arnt Gulbrandsen, <agulbra@nvg.unit.no>
  *      Jorge Cwik, <jorge@laser.satlink.net>
  *
  * Fixes:
  *      Alan Cox    :   Numerous verify_area() calls
  *      Alan Cox    :   Set the ACK bit on a reset
  *      Alan Cox    :   Stopped it crashing if it closed while
  *                  sk->inuse=1 and was trying to connect
  *                  (tcp_err()).
  *      Alan Cox    :   All icmp error handling was broken
  *                  pointers passed where wrong and the
  *                  socket was looked up backwards. Nobody
  *                  tested any icmp error code obviously.
  *      Alan Cox    :   tcp_err() now handled properly. It
  *                  wakes people on errors. poll
  *                  behaves and the icmp error race
  *                  has gone by moving it into sock.c
  *      Alan Cox    :   tcp_send_reset() fixed to work for
  *                  everything not just packets for
  *                  unknown sockets.
  *      Alan Cox    :   tcp option processing.
  *      Alan Cox    :   Reset tweaked (still not 100%) [Had
  *                  syn rule wrong]
  *      Herp Rosmanith  :   More reset fixes
  *      Alan Cox    :   No longer acks invalid rst frames.
  *                  Acking any kind of RST is right out.
  *      Alan Cox    :   Sets an ignore me flag on an rst
  *                  receive otherwise odd bits of prattle
  *                  escape still
  *      Alan Cox    :   Fixed another acking RST frame bug.
  *                  Should stop LAN workplace lockups.
  *      Alan Cox    :   Some tidyups using the new skb list
  *                  facilities
  *      Alan Cox    :   sk->keepopen now seems to work
  *      Alan Cox    :   Pulls options out correctly on accepts
  *      Alan Cox    :   Fixed assorted sk->rqueue->next errors
  *      Alan Cox    :   PSH doesn't end a TCP read. Switched a
  *                  bit to skb ops.
  *      Alan Cox    :   Tidied tcp_data to avoid a potential
  *                  nasty.
  *      Alan Cox    :   Added some better commenting, as the
  *                  tcp is hard to follow
  *      Alan Cox    :   Removed incorrect check for 20 * psh
  *  Michael O'Reilly    :   ack < copied bug fix.
  *  Johannes Stille     :   Misc tcp fixes (not all in yet).
  *      Alan Cox    :   FIN with no memory -> CRASH
  *      Alan Cox    :   Added socket option proto entries.
  *                  Also added awareness of them to accept.
  *      Alan Cox    :   Added TCP options (SOL_TCP)
  *      Alan Cox    :   Switched wakeup calls to callbacks,
  *                  so the kernel can layer network
  *                  sockets.
  *      Alan Cox    :   Use ip_tos/ip_ttl settings.
  *      Alan Cox    :   Handle FIN (more) properly (we hope).
  *      Alan Cox    :   RST frames sent on unsynchronised
  *                  state ack error.
  *      Alan Cox    :   Put in missing check for SYN bit.
  *      Alan Cox    :   Added tcp_select_window() aka NET2E
  *                  window non shrink trick.
  *      Alan Cox    :   Added a couple of small NET2E timer
  *                  fixes
  *      Charles Hedrick :   TCP fixes
  *      Toomas Tamm :   TCP window fixes
  *      Alan Cox    :   Small URG fix to rlogin ^C ack fight
  *      Charles Hedrick :   Rewrote most of it to actually work
  *      Linus       :   Rewrote tcp_read() and URG handling
  *                  completely
  *      Gerhard Koerting:   Fixed some missing timer handling
  *      Matthew Dillon  :   Reworked TCP machine states as per RFC
  *      Gerhard Koerting:   PC/TCP workarounds
  *      Adam Caldwell   :   Assorted timer/timing errors
  *      Matthew Dillon  :   Fixed another RST bug
  *      Alan Cox    :   Move to kernel side addressing changes.
  *      Alan Cox    :   Beginning work on TCP fastpathing
  *                  (not yet usable)
  *      Arnt Gulbrandsen:   Turbocharged tcp_check() routine.
  *      Alan Cox    :   TCP fast path debugging
  *      Alan Cox    :   Window clamping
  *      Michael Riepe   :   Bug in tcp_check()
  *      Matt Dillon :   More TCP improvements and RST bug fixes
  *      Matt Dillon :   Yet more small nasties remove from the
  *                  TCP code (Be very nice to this man if
  *                  tcp finally works 100%) 8)
  *      Alan Cox    :   BSD accept semantics.
  *      Alan Cox    :   Reset on closedown bug.
  *  Peter De Schrijver  :   ENOTCONN check missing in tcp_sendto().
  *      Michael Pall    :   Handle poll() after URG properly in
  *                  all cases.
  *      Michael Pall    :   Undo the last fix in tcp_read_urg()
  *                  (multi URG PUSH broke rlogin).
  *      Michael Pall    :   Fix the multi URG PUSH problem in
  *                  tcp_readable(), poll() after URG
  *                  works now.
  *      Michael Pall    :   recv(...,MSG_OOB) never blocks in the
  *                  BSD api.
  *      Alan Cox    :   Changed the semantics of sk->socket to
  *                  fix a race and a signal problem with
  *                  accept() and async I/O.
  *      Alan Cox    :   Relaxed the rules on tcp_sendto().
  *      Yury Shevchuk   :   Really fixed accept() blocking problem.
  *      Craig I. Hagan  :   Allow for BSD compatible TIME_WAIT for
  *                  clients/servers which listen in on
  *                  fixed ports.
  *      Alan Cox    :   Cleaned the above up and shrank it to
  *                  a sensible code size.
  *      Alan Cox    :   Self connect lockup fix.
  *      Alan Cox    :   No connect to multicast.
  *      Ross Biro   :   Close unaccepted children on master
  *                  socket close.
  *      Alan Cox    :   Reset tracing code.
  *      Alan Cox    :   Spurious resets on shutdown.
  *      Alan Cox    :   Giant 15 minute/60 second timer error
  *      Alan Cox    :   Small whoops in polling before an
  *                  accept.
  *      Alan Cox    :   Kept the state trace facility since
  *                  it's handy for debugging.
  *      Alan Cox    :   More reset handler fixes.
  *      Alan Cox    :   Started rewriting the code based on
  *                  the RFC's for other useful protocol
  *                  references see: Comer, KA9Q NOS, and
  *                  for a reference on the difference
  *                  between specifications and how BSD
  *                  works see the 4.4lite source.
  *      A.N.Kuznetsov   :   Don't time wait on completion of tidy
  *                  close.
  *      Linus Torvalds  :   Fin/Shutdown & copied_seq changes.
  *      Linus Torvalds  :   Fixed BSD port reuse to work first syn
  *      Alan Cox    :   Reimplemented timers as per the RFC
  *                  and using multiple timers for sanity.
  *      Alan Cox    :   Small bug fixes, and a lot of new
  *                  comments.
  *      Alan Cox    :   Fixed dual reader crash by locking
  *                  the buffers (much like datagram.c)
  *      Alan Cox    :   Fixed stuck sockets in probe. A probe
  *                  now gets fed up of retrying without
  *                  (even a no space) answer.
  *      Alan Cox    :   Extracted closing code better
  *      Alan Cox    :   Fixed the closing state machine to
  *                  resemble the RFC.
  *      Alan Cox    :   More 'per spec' fixes.
  *      Jorge Cwik  :   Even faster checksumming.
  *      Alan Cox    :   tcp_data() doesn't ack illegal PSH
  *                  only frames. At least one pc tcp stack
  *                  generates them.
  *      Alan Cox    :   Cache last socket.
  *      Alan Cox    :   Per route irtt.
  *      Matt Day    :   poll()->select() match BSD precisely on error
  *      Alan Cox    :   New buffers
  *      Marc Tamsky :   Various sk->prot->retransmits and
  *                  sk->retransmits misupdating fixed.
  *                  Fixed tcp_write_timeout: stuck close,
  *                  and TCP syn retries gets used now.
  *      Mark Yarvis :   In tcp_read_wakeup(), don't send an
  *                  ack if state is TCP_CLOSED.
  *      Alan Cox    :   Look up device on a retransmit - routes may
  *                  change. Doesn't yet cope with MSS shrink right
  *                  but it's a start!
  *      Marc Tamsky :   Closing in closing fixes.
  *      Mike Shaver :   RFC1122 verifications.
  *      Alan Cox    :   rcv_saddr errors.
  *      Alan Cox    :   Block double connect().
  *      Alan Cox    :   Small hooks for enSKIP.
  *      Alexey Kuznetsov:   Path MTU discovery.
  *      Alan Cox    :   Support soft errors.
  *      Alan Cox    :   Fix MTU discovery pathological case
  *                  when the remote claims no mtu!
  *      Marc Tamsky :   TCP_CLOSE fix.
  *      Colin (G3TNE)   :   Send a reset on syn ack replies in
  *                  window but wrong (fixes NT lpd problems)
  *      Pedro Roque :   Better TCP window handling, delayed ack.
  *      Joerg Reuter    :   No modification of locked buffers in
  *                  tcp_do_retransmit()
  *      Eric Schenk :   Changed receiver side silly window
  *                  avoidance algorithm to BSD style
  *                  algorithm. This doubles throughput
  *                  against machines running Solaris,
  *                  and seems to result in general
  *                  improvement.
  *  Stefan Magdalinski  :   adjusted tcp_readable() to fix FIONREAD
  *  Willy Konynenberg   :   Transparent proxying support.
  *  Mike McLagan        :   Routing by source
  *      Keith Owens :   Do proper merging with partial SKB's in
  *                  tcp_do_sendmsg to avoid burstiness.
  *      Eric Schenk :   Fix fast close down bug with
  *                  shutdown() followed by close().
  *      Andi Kleen  :   Make poll agree with SIGIO
  *  Salvatore Sanfilippo    :   Support SO_LINGER with linger == 1 and
  *                  lingertime == 0 (RFC 793 ABORT Call)
  *  Hirokazu Takahashi  :   Use copy_from_user() instead of
  *                  csum_and_copy_from_user() if possible.
  *
  * Description of States:
  *
  *  TCP_SYN_SENT        sent a connection request, waiting for ack
  *
  *  TCP_SYN_RECV        received a connection request, sent ack,
  *              waiting for final ack in three-way handshake.
  *
  *  TCP_ESTABLISHED     connection established
  *
  *  TCP_FIN_WAIT1       our side has shutdown, waiting to complete
  *              transmission of remaining buffered data
  *
  *  TCP_FIN_WAIT2       all buffered data sent, waiting for remote
  *              to shutdown
  *
  *  TCP_CLOSING     both sides have shutdown but we still have
  *              data we have to finish sending
  *
  *  TCP_TIME_WAIT       timeout to catch resent junk before entering
  *              closed, can only be entered from FIN_WAIT2
  *              or CLOSING.  Required because the other end
  *              may not have gotten our last ACK causing it
  *              to retransmit the data packet (which we ignore)
  *
  *  TCP_CLOSE_WAIT      remote side has shutdown and is waiting for
  *              us to finish writing our data and to shutdown
  *              (we have to close() to move on to LAST_ACK)
  *
  *  TCP_LAST_ACK        out side has shutdown after remote has
  *              shutdown.  There may still be data in our
  *              buffer that we have to finish sending
  *
  *  TCP_CLOSE       socket is finished
  */
 
 #define pr_fmt(fmt) "TCP: " fmt
 
 #include <crypto/hash.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/types.h>
 #include <linux/fcntl.h>
 #include <linux/poll.h>
 #include <linux/inet_diag.h>
 #include <linux/init.h>
 #include <linux/fs.h>
 #include <linux/skbuff.h>
 #include <linux/scatterlist.h>
 #include <linux/splice.h>
 #include <linux/net.h>
 #include <linux/socket.h>
 #include <linux/random.h>
 #include <linux/memblock.h>
 #include <linux/highmem.h>
 #include <linux/cache.h>
 #include <linux/err.h>
 #include <linux/time.h>
 #include <linux/slab.h>
 #include <linux/errqueue.h>
 #include <linux/static_key.h>
 #include <linux/btf.h>
 
 #include <net/icmp.h>
 #include <net/inet_common.h>
 #include <net/tcp.h>
 #include <net/mptcp.h>
 #include <net/xfrm.h>
 #include <net/ip.h>
 #include <net/sock.h>
 
 #include <linux/uaccess.h>
 #include <asm/ioctls.h>
 #include <net/busy_poll.h>
 
 /* Track pending CMSGs. */
 enum {
     TCP_CMSG_INQ = 1,
     TCP_CMSG_TS = 2
 };
 
 DEFINE_PER_CPU(unsigned int, tcp_orphan_count);
 EXPORT_PER_CPU_SYMBOL_GPL(tcp_orphan_count);
 
 long sysctl_tcp_mem[3] __read_mostly;
 EXPORT_SYMBOL(sysctl_tcp_mem);
 
 atomic_long_t tcp_memory_allocated ____cacheline_aligned_in_smp;    /* Current allocated memory. */
 EXPORT_SYMBOL(tcp_memory_allocated);
 DEFINE_PER_CPU(int, tcp_memory_per_cpu_fw_alloc);
 EXPORT_PER_CPU_SYMBOL_GPL(tcp_memory_per_cpu_fw_alloc);
 
 #if IS_ENABLED(CONFIG_SMC)
 DEFINE_STATIC_KEY_FALSE(tcp_have_smc);
 EXPORT_SYMBOL(tcp_have_smc);
 #endif
 
 /*
  * Current number of TCP sockets.
  */
 struct percpu_counter tcp_sockets_allocated ____cacheline_aligned_in_smp;
 EXPORT_SYMBOL(tcp_sockets_allocated);
 
 /*
  * TCP splice context
  */
 struct tcp_splice_state {
     struct pipe_inode_info *pipe;
     size_t len;
     unsigned int flags;
 };
 
 /*
  * Pressure flag: try to collapse.
  * Technical note: it is used by multiple contexts non atomically.
  * All the __sk_mem_schedule() is of this nature: accounting
  * is strict, actions are advisory and have some latency.
  */
 unsigned long tcp_memory_pressure __read_mostly;
 EXPORT_SYMBOL_GPL(tcp_memory_pressure);
 
 void tcp_enter_memory_pressure(struct sock *sk)
 {
     unsigned long val;
 
     if (READ_ONCE(tcp_memory_pressure))
         return;
     val = jiffies;
 
     if (!val)
         val--;
     if (!cmpxchg(&tcp_memory_pressure, 0, val))
         NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPMEMORYPRESSURES);
 }
 EXPORT_SYMBOL_GPL(tcp_enter_memory_pressure);
 
 void tcp_leave_memory_pressure(struct sock *sk)
 {
     unsigned long val;
 
     if (!READ_ONCE(tcp_memory_pressure))
         return;
     val = xchg(&tcp_memory_pressure, 0);
     if (val)
         NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPMEMORYPRESSURESCHRONO,
                   jiffies_to_msecs(jiffies - val));
 }
 EXPORT_SYMBOL_GPL(tcp_leave_memory_pressure);
 
 /* Convert seconds to retransmits based on initial and max timeout */
 static u8 secs_to_retrans(int seconds, int timeout, int rto_max)
 {
     u8 res = 0;
 
     if (seconds > 0) {
         int period = timeout;
 
         res = 1;
         while (seconds > period && res < 255) {
             res++;
             timeout <<= 1;
             if (timeout > rto_max)
                 timeout = rto_max;
             period += timeout;
         }
     }
     return res;
 }
 
 /* Convert retransmits to seconds based on initial and max timeout */
 static int retrans_to_secs(u8 retrans, int timeout, int rto_max)
 {
     int period = 0;
 
     if (retrans > 0) {
         period = timeout;
         while (--retrans) {
             timeout <<= 1;
             if (timeout > rto_max)
                 timeout = rto_max;
             period += timeout;
         }
     }
     return period;
 }
 
 static u64 tcp_compute_delivery_rate(const struct tcp_sock *tp)
 {
     u32 rate = READ_ONCE(tp->rate_delivered);
     u32 intv = READ_ONCE(tp->rate_interval_us);
     u64 rate64 = 0;
 
     if (rate && intv) {
         rate64 = (u64)rate * tp->mss_cache * USEC_PER_SEC;
         do_div(rate64, intv);
     }
     return rate64;
 }
 
 /* Address-family independent initialization for a tcp_sock.
  *
  * NOTE: A lot of things set to zero explicitly by call to
  *       sk_alloc() so need not be done here.
  */
 void tcp_init_sock(struct sock *sk)
 {
     struct inet_connection_sock *icsk = inet_csk(sk);
     struct tcp_sock *tp = tcp_sk(sk);
 
     tp->out_of_order_queue = RB_ROOT;
     sk->tcp_rtx_queue = RB_ROOT;
     tcp_init_xmit_timers(sk);
     INIT_LIST_HEAD(&tp->tsq_node);
     INIT_LIST_HEAD(&tp->tsorted_sent_queue);
 
     icsk->icsk_rto = TCP_TIMEOUT_INIT;
     icsk->icsk_rto_min = TCP_RTO_MIN;
     icsk->icsk_delack_max = TCP_DELACK_MAX;
     tp->mdev_us = jiffies_to_usecs(TCP_TIMEOUT_INIT);
     minmax_reset(&tp->rtt_min, tcp_jiffies32, ~0U);
 
     /* So many TCP implementations out there (incorrectly) count the
      * initial SYN frame in their delayed-ACK and congestion control
      * algorithms that we must have the following bandaid to talk
      * efficiently to them.  -DaveM
      */
     tcp_snd_cwnd_set(tp, TCP_INIT_CWND);
 
     /* There's a bubble in the pipe until at least the first ACK. */
     tp->app_limited = ~0U;
 
     /* See draft-stevens-tcpca-spec-01 for discussion of the
      * initialization of these values.
      */
     tp->snd_ssthresh = TCP_INFINITE_SSTHRESH;
     tp->snd_cwnd_clamp = ~0;
     tp->mss_cache = TCP_MSS_DEFAULT;
 
     tp->reordering = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_reordering);
     tcp_assign_congestion_control(sk);
 
     tp->tsoffset = 0;
     tp->rack.reo_wnd_steps = 1;
 
     sk->sk_write_space = sk_stream_write_space;
     sock_set_flag(sk, SOCK_USE_WRITE_QUEUE);
 
     icsk->icsk_sync_mss = tcp_sync_mss;
 
     WRITE_ONCE(sk->sk_sndbuf, READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_wmem[1]));
     WRITE_ONCE(sk->sk_rcvbuf, READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_rmem[1]));
 
     sk_sockets_allocated_inc(sk);
 }
 EXPORT_SYMBOL(tcp_init_sock);
 
 static void tcp_tx_timestamp(struct sock *sk, u16 tsflags)
 {
     struct sk_buff *skb = tcp_write_queue_tail(sk);
 
     if (tsflags && skb) {
         struct skb_shared_info *shinfo = skb_shinfo(skb);
         struct tcp_skb_cb *tcb = TCP_SKB_CB(skb);
 
         sock_tx_timestamp(sk, tsflags, &shinfo->tx_flags);
         if (tsflags & SOF_TIMESTAMPING_TX_ACK)
             tcb->txstamp_ack = 1;
         if (tsflags & SOF_TIMESTAMPING_TX_RECORD_MASK)
             shinfo->tskey = TCP_SKB_CB(skb)->seq + skb->len - 1;
     }
 }
 
 static bool tcp_stream_is_readable(struct sock *sk, int target)
 {
     if (tcp_epollin_ready(sk, target))
         return true;
     return sk_is_readable(sk);
 }
 
 /*
  *  Wait for a TCP event.
  *
  *  Note that we don't need to lock the socket, as the upper poll layers
  *  take care of normal races (between the test and the event) and we don't
  *  go look at any of the socket buffers directly.
  */
 __poll_t tcp_poll(struct file *file, struct socket *sock, poll_table *wait)
 {
     __poll_t mask;
     struct sock *sk = sock->sk;
     const struct tcp_sock *tp = tcp_sk(sk);
     int state;
 
     sock_poll_wait(file, sock, wait);
 
     state = inet_sk_state_load(sk);
     if (state == TCP_LISTEN)
         return inet_csk_listen_poll(sk);
 
     /* Socket is not locked. We are protected from async events
      * by poll logic and correct handling of state changes
      * made by other threads is impossible in any case.
      */
 
     mask = 0;
 
     /*
      * EPOLLHUP is certainly not done right. But poll() doesn't
      * have a notion of HUP in just one direction, and for a
      * socket the read side is more interesting.
      *
      * Some poll() documentation says that EPOLLHUP is incompatible
      * with the EPOLLOUT/POLLWR flags, so somebody should check this
      * all. But careful, it tends to be safer to return too many
      * bits than too few, and you can easily break real applications
      * if you don't tell them that something has hung up!
      *
      * Check-me.
      *
      * Check number 1. EPOLLHUP is _UNMASKABLE_ event (see UNIX98 and
      * our fs/select.c). It means that after we received EOF,
      * poll always returns immediately, making impossible poll() on write()
      * in state CLOSE_WAIT. One solution is evident --- to set EPOLLHUP
      * if and only if shutdown has been made in both directions.
      * Actually, it is interesting to look how Solaris and DUX
      * solve this dilemma. I would prefer, if EPOLLHUP were maskable,
      * then we could set it on SND_SHUTDOWN. BTW examples given
      * in Stevens' books assume exactly this behaviour, it explains
      * why EPOLLHUP is incompatible with EPOLLOUT.  --ANK
      *
      * NOTE. Check for TCP_CLOSE is added. The goal is to prevent
      * blocking on fresh not-connected or disconnected socket. --ANK
      */
     if (sk->sk_shutdown == SHUTDOWN_MASK || state == TCP_CLOSE)
         mask |= EPOLLHUP;
     if (sk->sk_shutdown & RCV_SHUTDOWN)
         mask |= EPOLLIN | EPOLLRDNORM | EPOLLRDHUP;
 
     /* Connected or passive Fast Open socket? */
     if (state != TCP_SYN_SENT &&
         (state != TCP_SYN_RECV || rcu_access_pointer(tp->fastopen_rsk))) {
         int target = sock_rcvlowat(sk, 0, INT_MAX);
         u16 urg_data = READ_ONCE(tp->urg_data);
 
         if (unlikely(urg_data) &&
             READ_ONCE(tp->urg_seq) == READ_ONCE(tp->copied_seq) &&
             !sock_flag(sk, SOCK_URGINLINE))
             target++;
 
         if (tcp_stream_is_readable(sk, target))
             mask |= EPOLLIN | EPOLLRDNORM;
 
         if (!(sk->sk_shutdown & SEND_SHUTDOWN)) {
             if (__sk_stream_is_writeable(sk, 1)) {
                 mask |= EPOLLOUT | EPOLLWRNORM;
             } else {  /* send SIGIO later */
                 sk_set_bit(SOCKWQ_ASYNC_NOSPACE, sk);
                 set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
 
                 /* Race breaker. If space is freed after
                  * wspace test but before the flags are set,
                  * IO signal will be lost. Memory barrier
                  * pairs with the input side.
                  */
                 smp_mb__after_atomic();
                 if (__sk_stream_is_writeable(sk, 1))
                     mask |= EPOLLOUT | EPOLLWRNORM;
             }
         } else
             mask |= EPOLLOUT | EPOLLWRNORM;
 
         if (urg_data & TCP_URG_VALID)
             mask |= EPOLLPRI;
     } else if (state == TCP_SYN_SENT && inet_sk(sk)->defer_connect) {
         /* Active TCP fastopen socket with defer_connect
          * Return EPOLLOUT so application can call write()
          * in order for kernel to generate SYN+data
          */
         mask |= EPOLLOUT | EPOLLWRNORM;
     }
     /* This barrier is coupled with smp_wmb() in tcp_reset() */
     smp_rmb();
     if (sk->sk_err || !skb_queue_empty_lockless(&sk->sk_error_queue))
         mask |= EPOLLERR;
 
     return mask;
 }
 EXPORT_SYMBOL(tcp_poll);
 
 int tcp_ioctl(struct sock *sk, int cmd, unsigned long arg)
 {
     struct tcp_sock *tp = tcp_sk(sk);
     int answ;
     bool slow;
 
     switch (cmd) {
     case SIOCINQ:
         if (sk->sk_state == TCP_LISTEN)
             return -EINVAL;
 
         slow = lock_sock_fast(sk);
         answ = tcp_inq(sk);
         unlock_sock_fast(sk, slow);
         break;
     case SIOCATMARK:
         answ = READ_ONCE(tp->urg_data) &&
                READ_ONCE(tp->urg_seq) == READ_ONCE(tp->copied_seq);
         break;
     case SIOCOUTQ:
         if (sk->sk_state == TCP_LISTEN)
             return -EINVAL;
 
         if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV))
             answ = 0;
         else
             answ = READ_ONCE(tp->write_seq) - tp->snd_una;
         break;
     case SIOCOUTQNSD:
         if (sk->sk_state == TCP_LISTEN)
             return -EINVAL;
 
         if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV))
             answ = 0;
         else
             answ = READ_ONCE(tp->write_seq) -
                    READ_ONCE(tp->snd_nxt);
         break;
     default:
         return -ENOIOCTLCMD;
     }
 
     return put_user(answ, (int __user *)arg);
 }
 EXPORT_SYMBOL(tcp_ioctl);
 
 void tcp_mark_push(struct tcp_sock *tp, struct sk_buff *skb)
 {
     TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
     tp->pushed_seq = tp->write_seq;
 }
 
 static inline bool forced_push(const struct tcp_sock *tp)
 {
     return after(tp->write_seq, tp->pushed_seq + (tp->max_window >> 1));
 }
 
 void tcp_skb_entail(struct sock *sk, struct sk_buff *skb)
 {
     struct tcp_sock *tp = tcp_sk(sk);
     struct tcp_skb_cb *tcb = TCP_SKB_CB(skb);
 
     tcb->seq     = tcb->end_seq = tp->write_seq;
     tcb->tcp_flags = TCPHDR_ACK;
     __skb_header_release(skb);
     tcp_add_write_queue_tail(sk, skb);
     sk_wmem_queued_add(sk, skb->truesize);
     sk_mem_charge(sk, skb->truesize);
     if (tp->nonagle & TCP_NAGLE_PUSH)
         tp->nonagle &= ~TCP_NAGLE_PUSH;
 
     tcp_slow_start_after_idle_check(sk);
 }
 
 static inline void tcp_mark_urg(struct tcp_sock *tp, int flags)
 {
     if (flags & MSG_OOB)
         tp->snd_up = tp->write_seq;
 }
 
 /* If a not yet filled skb is pushed, do not send it if
  * we have data packets in Qdisc or NIC queues :
  * Because TX completion will happen shortly, it gives a chance
  * to coalesce future sendmsg() payload into this skb, without
  * need for a timer, and with no latency trade off.
  * As packets containing data payload have a bigger truesize
  * than pure acks (dataless) packets, the last checks prevent
  * autocorking if we only have an ACK in Qdisc/NIC queues,
  * or if TX completion was delayed after we processed ACK packet.
  */
 static bool tcp_should_autocork(struct sock *sk, struct sk_buff *skb,
                 int size_goal)
 {
     return skb->len < size_goal &&
            READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_autocorking) &&
            !tcp_rtx_queue_empty(sk) &&
            refcount_read(&sk->sk_wmem_alloc) > skb->truesize &&
            tcp_skb_can_collapse_to(skb);
 }
 
 void tcp_push(struct sock *sk, int flags, int mss_now,
           int nonagle, int size_goal)
 {
     struct tcp_sock *tp = tcp_sk(sk);
     struct sk_buff *skb;
 
     skb = tcp_write_queue_tail(sk);
     if (!skb)
         return;
     if (!(flags & MSG_MORE) || forced_push(tp))
         tcp_mark_push(tp, skb);
 
     tcp_mark_urg(tp, flags);
 
     if (tcp_should_autocork(sk, skb, size_goal)) {
 
         /* avoid atomic op if TSQ_THROTTLED bit is already set */
         if (!test_bit(TSQ_THROTTLED, &sk->sk_tsq_flags)) {
             NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPAUTOCORKING);
             set_bit(TSQ_THROTTLED, &sk->sk_tsq_flags);
         }
         /* It is possible TX completion already happened
          * before we set TSQ_THROTTLED.
          */
         if (refcount_read(&sk->sk_wmem_alloc) > skb->truesize)
             return;
     }
 
     if (flags & MSG_MORE)
         nonagle = TCP_NAGLE_CORK;
 
     __tcp_push_pending_frames(sk, mss_now, nonagle);
 }
 
 static int tcp_splice_data_recv(read_descriptor_t *rd_desc, struct sk_buff *skb,
                 unsigned int offset, size_t len)
 {
     struct tcp_splice_state *tss = rd_desc->arg.data;
     int ret;
 
     ret = skb_splice_bits(skb, skb->sk, offset, tss->pipe,
                   min(rd_desc->count, len), tss->flags);
     if (ret > 0)
         rd_desc->count -= ret;
     return ret;
 }
 
 static int __tcp_splice_read(struct sock *sk, struct tcp_splice_state *tss)
 {
     /* Store TCP splice context information in read_descriptor_t. */
     read_descriptor_t rd_desc = {
         .arg.data = tss,
         .count    = tss->len,
     };
 
     return tcp_read_sock(sk, &rd_desc, tcp_splice_data_recv);
 }
 
 /**
  *  tcp_splice_read - splice data from TCP socket to a pipe
  * @sock:   socket to splice from
  * @ppos:   position (not valid)
  * @pipe:   pipe to splice to
  * @len:    number of bytes to splice
  * @flags:  splice modifier flags
  *
  * Description:
  *    Will read pages from given socket and fill them into a pipe.
  *
  **/
 ssize_t tcp_splice_read(struct socket *sock, loff_t *ppos,
             struct pipe_inode_info *pipe, size_t len,
             unsigned int flags)
 {
     struct sock *sk = sock->sk;
     struct tcp_splice_state tss = {
         .pipe = pipe,
         .len = len,
         .flags = flags,
     };
     long timeo;
     ssize_t spliced;
     int ret;
 
     sock_rps_record_flow(sk);
     /*
      * We can't seek on a socket input
      */
     if (unlikely(*ppos))
         return -ESPIPE;
 
     ret = spliced = 0;
 
     lock_sock(sk);
 
     timeo = sock_rcvtimeo(sk, sock->file->f_flags & O_NONBLOCK);
     while (tss.len) {
         ret = __tcp_splice_read(sk, &tss);
         if (ret < 0)
             break;
         else if (!ret) {
             if (spliced)
                 break;
             if (sock_flag(sk, SOCK_DONE))
                 break;
             if (sk->sk_err) {
                 ret = sock_error(sk);
                 break;
             }
             if (sk->sk_shutdown & RCV_SHUTDOWN)
                 break;
             if (sk->sk_state == TCP_CLOSE) {
                 /*
                  * This occurs when user tries to read
                  * from never connected socket.
                  */
                 ret = -ENOTCONN;
                 break;
             }
             if (!timeo) {
                 ret = -EAGAIN;
                 break;
             }
             /* if __tcp_splice_read() got nothing while we have
              * an skb in receive queue, we do not want to loop.
              * This might happen with URG data.
              */
             if (!skb_queue_empty(&sk->sk_receive_queue))
                 break;
             sk_wait_data(sk, &timeo, NULL);
             if (signal_pending(current)) {
                 ret = sock_intr_errno(timeo);
                 break;
             }
             continue;
         }
         tss.len -= ret;
         spliced += ret;
 
         if (!timeo)
             break;
         release_sock(sk);
         lock_sock(sk);
 
         if (sk->sk_err || sk->sk_state == TCP_CLOSE ||
             (sk->sk_shutdown & RCV_SHUTDOWN) ||
             signal_pending(current))
             break;
     }
 
     release_sock(sk);
 
     if (spliced)
         return spliced;
 
     return ret;
 }
 EXPORT_SYMBOL(tcp_splice_read);
 
 struct sk_buff *tcp_stream_alloc_skb(struct sock *sk, int size, gfp_t gfp,
                      bool force_schedule)
 {
     struct sk_buff *skb;
 
     skb = alloc_skb_fclone(size + MAX_TCP_HEADER, gfp);
     if (likely(skb)) {
         bool mem_scheduled;
 
         skb->truesize = SKB_TRUESIZE(skb_end_offset(skb));
         if (force_schedule) {
             mem_scheduled = true;
             sk_forced_mem_schedule(sk, skb->truesize);
         } else {
             mem_scheduled = sk_wmem_schedule(sk, skb->truesize);
         }
         if (likely(mem_scheduled)) {
             skb_reserve(skb, MAX_TCP_HEADER);
             skb->ip_summed = CHECKSUM_PARTIAL;
             INIT_LIST_HEAD(&skb->tcp_tsorted_anchor);
             return skb;
         }
         __kfree_skb(skb);
     } else {
         sk->sk_prot->enter_memory_pressure(sk);
         sk_stream_moderate_sndbuf(sk);
     }
     return NULL;
 }
 
 static unsigned int tcp_xmit_size_goal(struct sock *sk, u32 mss_now,
                        int large_allowed)
 {
     struct tcp_sock *tp = tcp_sk(sk);
     u32 new_size_goal, size_goal;
 
     if (!large_allowed)
         return mss_now;
 
     /* Note : tcp_tso_autosize() will eventually split this later */
     new_size_goal = tcp_bound_to_half_wnd(tp, sk->sk_gso_max_size);
 
     /* We try hard to avoid divides here */
     size_goal = tp->gso_segs * mss_now;
     if (unlikely(new_size_goal < size_goal ||
              new_size_goal >= size_goal + mss_now)) {
         tp->gso_segs = min_t(u16, new_size_goal / mss_now,
                      sk->sk_gso_max_segs);
         size_goal = tp->gso_segs * mss_now;
     }
 
     return max(size_goal, mss_now);
 }
 
 int tcp_send_mss(struct sock *sk, int *size_goal, int flags)
 {
     int mss_now;
 
     mss_now = tcp_current_mss(sk);
     *size_goal = tcp_xmit_size_goal(sk, mss_now, !(flags & MSG_OOB));
 
     return mss_now;
 }
 
 /* In some cases, both sendpage() and sendmsg() could have added
  * an skb to the write queue, but failed adding payload on it.
  * We need to remove it to consume less memory, but more
  * importantly be able to generate EPOLLOUT for Edge Trigger epoll()
  * users.
  */
 void tcp_remove_empty_skb(struct sock *sk)
 {
     struct sk_buff *skb = tcp_write_queue_tail(sk);
 
     if (skb && TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq) {
         tcp_unlink_write_queue(skb, sk);
         if (tcp_write_queue_empty(sk))
             tcp_chrono_stop(sk, TCP_CHRONO_BUSY);
         tcp_wmem_free_skb(sk, skb);
     }
 }
 
 /* skb changing from pure zc to mixed, must charge zc */
 static int tcp_downgrade_zcopy_pure(struct sock *sk, struct sk_buff *skb)
 {
     if (unlikely(skb_zcopy_pure(skb))) {
         u32 extra = skb->truesize -
                 SKB_TRUESIZE(skb_end_offset(skb));
 
         if (!sk_wmem_schedule(sk, extra))
             return -ENOMEM;
 
         sk_mem_charge(sk, extra);
         skb_shinfo(skb)->flags &= ~SKBFL_PURE_ZEROCOPY;
     }
     return 0;
 }
 
 
 static int tcp_wmem_schedule(struct sock *sk, int copy)
 {
     int left;
 
     if (likely(sk_wmem_schedule(sk, copy)))
         return copy;
 
     /* We could be in trouble if we have nothing queued.
      * Use whatever is left in sk->sk_forward_alloc and tcp_wmem[0]
      * to guarantee some progress.
      */
     left = sock_net(sk)->ipv4.sysctl_tcp_wmem[0] - sk->sk_wmem_queued;
     if (left > 0)
         sk_forced_mem_schedule(sk, min(left, copy));
     return min(copy, sk->sk_forward_alloc);
 }
 
 static struct sk_buff *tcp_build_frag(struct sock *sk, int size_goal, int flags,
                       struct page *page, int offset, size_t *size)
 {
     struct sk_buff *skb = tcp_write_queue_tail(sk);
     struct tcp_sock *tp = tcp_sk(sk);
     bool can_coalesce;
     int copy, i;
 
     if (!skb || (copy = size_goal - skb->len) <= 0 ||
         !tcp_skb_can_collapse_to(skb)) {
 new_segment:
         if (!sk_stream_memory_free(sk))
             return NULL;
 
         skb = tcp_stream_alloc_skb(sk, 0, sk->sk_allocation,
                        tcp_rtx_and_write_queues_empty(sk));
         if (!skb)
             return NULL;
 
 #ifdef CONFIG_TLS_DEVICE
         skb->decrypted = !!(flags & MSG_SENDPAGE_DECRYPTED);
 #endif
         tcp_skb_entail(sk, skb);
         copy = size_goal;
     }
 
     if (copy > *size)
         copy = *size;
 
     i = skb_shinfo(skb)->nr_frags;
     can_coalesce = skb_can_coalesce(skb, i, page, offset);
     if (!can_coalesce && i >= READ_ONCE(sysctl_max_skb_frags)) {
         tcp_mark_push(tp, skb);
         goto new_segment;
     }
     if (tcp_downgrade_zcopy_pure(sk, skb))
         return NULL;
 
     copy = tcp_wmem_schedule(sk, copy);
     if (!copy)
         return NULL;
 
     if (can_coalesce) {
         skb_frag_size_add(&skb_shinfo(skb)->frags[i - 1], copy);
     } else {
         get_page(page);
         skb_fill_page_desc_noacc(skb, i, page, offset, copy);
     }
 
     if (!(flags & MSG_NO_SHARED_FRAGS))
         skb_shinfo(skb)->flags |= SKBFL_SHARED_FRAG;
 
     skb->len += copy;
     skb->data_len += copy;
     skb->truesize += copy;
     sk_wmem_queued_add(sk, copy);
     sk_mem_charge(sk, copy);
     WRITE_ONCE(tp->write_seq, tp->write_seq + copy);
     TCP_SKB_CB(skb)->end_seq += copy;
     tcp_skb_pcount_set(skb, 0);
 
     *size = copy;
     return skb;
 }
 
 ssize_t do_tcp_sendpages(struct sock *sk, struct page *page, int offset,
              size_t size, int flags)
 {
     struct tcp_sock *tp = tcp_sk(sk);
     int mss_now, size_goal;
     int err;
     ssize_t copied;
     long timeo = sock_sndtimeo(sk, flags & MSG_DONTWAIT);
 
     if (IS_ENABLED(CONFIG_DEBUG_VM) &&
         WARN_ONCE(!sendpage_ok(page),
               "page must not be a Slab one and have page_count > 0"))
         return -EINVAL;
 
     /* Wait for a connection to finish. One exception is TCP Fast Open
      * (passive side) where data is allowed to be sent before a connection
      * is fully established.
      */
     if (((1 << sk->sk_state) & ~(TCPF_ESTABLISHED | TCPF_CLOSE_WAIT)) &&
         !tcp_passive_fastopen(sk)) {
         err = sk_stream_wait_connect(sk, &timeo);
         if (err != 0)
             goto out_err;
     }
 
     sk_clear_bit(SOCKWQ_ASYNC_NOSPACE, sk);
 
     mss_now = tcp_send_mss(sk, &size_goal, flags);
     copied = 0;
 
     err = -EPIPE;
     if (sk->sk_err || (sk->sk_shutdown & SEND_SHUTDOWN))
         goto out_err;
 
     while (size > 0) {
         struct sk_buff *skb;
         size_t copy = size;
 
         skb = tcp_build_frag(sk, size_goal, flags, page, offset, &copy);
         if (!skb)
             goto wait_for_space;
 
         if (!copied)
             TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_PSH;
 
         copied += copy;
         offset += copy;
         size -= copy;
         if (!size)
             goto out;
 
         if (skb->len < size_goal || (flags & MSG_OOB))
             continue;
 
         if (forced_push(tp)) {
             tcp_mark_push(tp, skb);
             __tcp_push_pending_frames(sk, mss_now, TCP_NAGLE_PUSH);
         } else if (skb == tcp_send_head(sk))
             tcp_push_one(sk, mss_now);
         continue;
 
 wait_for_space:
         set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
         tcp_push(sk, flags & ~MSG_MORE, mss_now,
              TCP_NAGLE_PUSH, size_goal);
 
         err = sk_stream_wait_memory(sk, &timeo);
         if (err != 0)
             goto do_error;
 
         mss_now = tcp_send_mss(sk, &size_goal, flags);
     }
 
 out:
     if (copied) {
         tcp_tx_timestamp(sk, sk->sk_tsflags);
         if (!(flags & MSG_SENDPAGE_NOTLAST))
             tcp_push(sk, flags, mss_now, tp->nonagle, size_goal);
     }
     return copied;
 
 do_error:
     tcp_remove_empty_skb(sk);
     if (copied)
         goto out;
 out_err:
     /* make sure we wake any epoll edge trigger waiter */
     if (unlikely(tcp_rtx_and_write_queues_empty(sk) && err == -EAGAIN)) {
         sk->sk_write_space(sk);
         tcp_chrono_stop(sk, TCP_CHRONO_SNDBUF_LIMITED);
     }
     return sk_stream_error(sk, flags, err);
 }
 EXPORT_SYMBOL_GPL(do_tcp_sendpages);
 
 int tcp_sendpage_locked(struct sock *sk, struct page *page, int offset,
             size_t size, int flags)
 {
     if (!(sk->sk_route_caps & NETIF_F_SG))
         return sock_no_sendpage_locked(sk, page, offset, size, flags);
 
     tcp_rate_check_app_limited(sk);  /* is sending application-limited? */
 
     return do_tcp_sendpages(sk, page, offset, size, flags);
 }
 EXPORT_SYMBOL_GPL(tcp_sendpage_locked);
 
 int tcp_sendpage(struct sock *sk, struct page *page, int offset,
          size_t size, int flags)
 {
     int ret;
 
     lock_sock(sk);
     ret = tcp_sendpage_locked(sk, page, offset, size, flags);
     release_sock(sk);
 
     return ret;
 }
 EXPORT_SYMBOL(tcp_sendpage);
 
 void tcp_free_fastopen_req(struct tcp_sock *tp)
 {
     if (tp->fastopen_req) {
         kfree(tp->fastopen_req);
         tp->fastopen_req = NULL;
     }
 }
 
 static int tcp_sendmsg_fastopen(struct sock *sk, struct msghdr *msg,
                 int *copied, size_t size,
                 struct ubuf_info *uarg)
 {
     struct tcp_sock *tp = tcp_sk(sk);
     struct inet_sock *inet = inet_sk(sk);
     struct sockaddr *uaddr = msg->msg_name;
     int err, flags;
 
     if (!(READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_fastopen) &
           TFO_CLIENT_ENABLE) ||
         (uaddr && msg->msg_namelen >= sizeof(uaddr->sa_family) &&
          uaddr->sa_family == AF_UNSPEC))
         return -EOPNOTSUPP;
     if (tp->fastopen_req)
         return -EALREADY; /* Another Fast Open is in progress */
 
     tp->fastopen_req = kzalloc(sizeof(struct tcp_fastopen_request),
                    sk->sk_allocation);
     if (unlikely(!tp->fastopen_req))
         return -ENOBUFS;
     tp->fastopen_req->data = msg;
     tp->fastopen_req->size = size;
     tp->fastopen_req->uarg = uarg;
 
     if (inet->defer_connect) {
         err = tcp_connect(sk);
         /* Same failure procedure as in tcp_v4/6_connect */
         if (err) {
             tcp_set_state(sk, TCP_CLOSE);
             inet->inet_dport = 0;
             sk->sk_route_caps = 0;
         }
     }
     flags = (msg->msg_flags & MSG_DONTWAIT) ? O_NONBLOCK : 0;
     err = __inet_stream_connect(sk->sk_socket, uaddr,
                     msg->msg_namelen, flags, 1);
     /* fastopen_req could already be freed in __inet_stream_connect
      * if the connection times out or gets rst
      */
     if (tp->fastopen_req) {
         *copied = tp->fastopen_req->copied;
         tcp_free_fastopen_req(tp);
         inet->defer_connect = 0;
     }
     return err;
 }
 
 int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size)
 {
     struct tcp_sock *tp = tcp_sk(sk);
     struct ubuf_info *uarg = NULL;
     struct sk_buff *skb;
     struct sockcm_cookie sockc;
     int flags, err, copied = 0;
     int mss_now = 0, size_goal, copied_syn = 0;
     int process_backlog = 0;
     bool zc = false;
     long timeo;
 
     flags = msg->msg_flags;
 
     if ((flags & MSG_ZEROCOPY) && size) {
         skb = tcp_write_queue_tail(sk);
 
         if (msg->msg_ubuf) {
             uarg = msg->msg_ubuf;
             net_zcopy_get(uarg);
             zc = sk->sk_route_caps & NETIF_F_SG;
         } else if (sock_flag(sk, SOCK_ZEROCOPY)) {
             uarg = msg_zerocopy_realloc(sk, size, skb_zcopy(skb));
             if (!uarg) {
                 err = -ENOBUFS;
                 goto out_err;
             }
             zc = sk->sk_route_caps & NETIF_F_SG;
             if (!zc)
                 uarg->zerocopy = 0;
         }
     }
 
     if (unlikely(flags & MSG_FASTOPEN || inet_sk(sk)->defer_connect) &&
         !tp->repair) {
         err = tcp_sendmsg_fastopen(sk, msg, &copied_syn, size, uarg);
         if (err == -EINPROGRESS && copied_syn > 0)
             goto out;
         else if (err)
             goto out_err;
     }
 
     timeo = sock_sndtimeo(sk, flags & MSG_DONTWAIT);
 
     tcp_rate_check_app_limited(sk);  /* is sending application-limited? */
 
     /* Wait for a connection to finish. One exception is TCP Fast Open
      * (passive side) where data is allowed to be sent before a connection
      * is fully established.
      */
     if (((1 << sk->sk_state) & ~(TCPF_ESTABLISHED | TCPF_CLOSE_WAIT)) &&
         !tcp_passive_fastopen(sk)) {
         err = sk_stream_wait_connect(sk, &timeo);
         if (err != 0)
             goto do_error;
     }
 
     if (unlikely(tp->repair)) {
         if (tp->repair_queue == TCP_RECV_QUEUE) {
             copied = tcp_send_rcvq(sk, msg, size);
             goto out_nopush;
         }
 
         err = -EINVAL;
         if (tp->repair_queue == TCP_NO_QUEUE)
             goto out_err;
 
         /* 'common' sending to sendq */
     }
 
     sockcm_init(&sockc, sk);
     if (msg->msg_controllen) {
         err = sock_cmsg_send(sk, msg, &sockc);
         if (unlikely(err)) {
             err = -EINVAL;
             goto out_err;
         }
     }
 
     /* This should be in poll */
     sk_clear_bit(SOCKWQ_ASYNC_NOSPACE, sk);
 
     /* Ok commence sending. */
     copied = 0;
 
 restart:
     mss_now = tcp_send_mss(sk, &size_goal, flags);
 
     err = -EPIPE;
     if (sk->sk_err || (sk->sk_shutdown & SEND_SHUTDOWN))
         goto do_error;
 
     while (msg_data_left(msg)) {
         int copy = 0;
 
         skb = tcp_write_queue_tail(sk);
         if (skb)
             copy = size_goal - skb->len;
 
         if (copy <= 0 || !tcp_skb_can_collapse_to(skb)) {
             bool first_skb;
 
 new_segment:
             if (!sk_stream_memory_free(sk))
                 goto wait_for_space;
 
             if (unlikely(process_backlog >= 16)) {
                 process_backlog = 0;
                 if (sk_flush_backlog(sk))
                     goto restart;
             }
             first_skb = tcp_rtx_and_write_queues_empty(sk);
             skb = tcp_stream_alloc_skb(sk, 0, sk->sk_allocation,
                            first_skb);
             if (!skb)
                 goto wait_for_space;
 
             process_backlog++;
 
             tcp_skb_entail(sk, skb);
             copy = size_goal;
 
             /* All packets are restored as if they have
              * already been sent. skb_mstamp_ns isn't set to
              * avoid wrong rtt estimation.
              */
             if (tp->repair)
                 TCP_SKB_CB(skb)->sacked |= TCPCB_REPAIRED;
         }
 
         /* Try to append data to the end of skb. */
         if (copy > msg_data_left(msg))
             copy = msg_data_left(msg);
 
         if (!zc) {
             bool merge = true;
             int i = skb_shinfo(skb)->nr_frags;
             struct page_frag *pfrag = sk_page_frag(sk);
 
             if (!sk_page_frag_refill(sk, pfrag))
                 goto wait_for_space;
 
             if (!skb_can_coalesce(skb, i, pfrag->page,
                           pfrag->offset)) {
                 if (i >= READ_ONCE(sysctl_max_skb_frags)) {
                     tcp_mark_push(tp, skb);
                     goto new_segment;
                 }
                 merge = false;
             }
 
             copy = min_t(int, copy, pfrag->size - pfrag->offset);
 
             if (unlikely(skb_zcopy_pure(skb) || skb_zcopy_managed(skb))) {
                 if (tcp_downgrade_zcopy_pure(sk, skb))
                     goto wait_for_space;
                 skb_zcopy_downgrade_managed(skb);
             }
 
             copy = tcp_wmem_schedule(sk, copy);
             if (!copy)
                 goto wait_for_space;
 
             err = skb_copy_to_page_nocache(sk, &msg->msg_iter, skb,
                                pfrag->page,
                                pfrag->offset,
                                copy);
             if (err)
                 goto do_error;
 
             /* Update the skb. */
             if (merge) {
                 skb_frag_size_add(&skb_shinfo(skb)->frags[i - 1], copy);
             } else {
                 skb_fill_page_desc(skb, i, pfrag->page,
                            pfrag->offset, copy);
                 page_ref_inc(pfrag->page);
             }
             pfrag->offset += copy;
         } else {
             /* First append to a fragless skb builds initial
              * pure zerocopy skb
              */
             if (!skb->len)
                 skb_shinfo(skb)->flags |= SKBFL_PURE_ZEROCOPY;
 
             if (!skb_zcopy_pure(skb)) {
                 copy = tcp_wmem_schedule(sk, copy);
                 if (!copy)
                     goto wait_for_space;
             }
 
             err = skb_zerocopy_iter_stream(sk, skb, msg, copy, uarg);
             if (err == -EMSGSIZE || err == -EEXIST) {
                 tcp_mark_push(tp, skb);
                 goto new_segment;
             }
             if (err < 0)
                 goto do_error;
             copy = err;
         }
 
         if (!copied)
             TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_PSH;
 
         WRITE_ONCE(tp->write_seq, tp->write_seq + copy);
         TCP_SKB_CB(skb)->end_seq += copy;
         tcp_skb_pcount_set(skb, 0);
 
         copied += copy;
         if (!msg_data_left(msg)) {
             if (unlikely(flags & MSG_EOR))
                 TCP_SKB_CB(skb)->eor = 1;
             goto out;
         }
 
         if (skb->len < size_goal || (flags & MSG_OOB) || unlikely(tp->repair))
             continue;
 
         if (forced_push(tp)) {
             tcp_mark_push(tp, skb);
             __tcp_push_pending_frames(sk, mss_now, TCP_NAGLE_PUSH);
         } else if (skb == tcp_send_head(sk))
             tcp_push_one(sk, mss_now);
         continue;
 
 wait_for_space:
         set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
         if (copied)
             tcp_push(sk, flags & ~MSG_MORE, mss_now,
                  TCP_NAGLE_PUSH, size_goal);
 
         err = sk_stream_wait_memory(sk, &timeo);
         if (err != 0)
             goto do_error;
 
         mss_now = tcp_send_mss(sk, &size_goal, flags);
     }
 
 out:
     if (copied) {
         tcp_tx_timestamp(sk, sockc.tsflags);
         tcp_push(sk, flags, mss_now, tp->nonagle, size_goal);
     }
 out_nopush:
     net_zcopy_put(uarg);
     return copied + copied_syn;
 
 do_error:
     tcp_remove_empty_skb(sk);
 
     if (copied + copied_syn)
         goto out;
 out_err:
     net_zcopy_put_abort(uarg, true);
     err = sk_stream_error(sk, flags, err);
     /* make sure we wake any epoll edge trigger waiter */
     if (unlikely(tcp_rtx_and_write_queues_empty(sk) && err == -EAGAIN)) {
         sk->sk_write_space(sk);
         tcp_chrono_stop(sk, TCP_CHRONO_SNDBUF_LIMITED);
     }
     return err;
 }
 EXPORT_SYMBOL_GPL(tcp_sendmsg_locked);
 
 int tcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t size)
 {
     int ret;
 
     lock_sock(sk);
     ret = tcp_sendmsg_locked(sk, msg, size);
     release_sock(sk);
 
     return ret;
 }
 EXPORT_SYMBOL(tcp_sendmsg);
 
 /*
  *  Handle reading urgent data. BSD has very simple semantics for
  *  this, no blocking and very strange errors 8)
  */
 
 static int tcp_recv_urg(struct sock *sk, struct msghdr *msg, int len, int flags)
 {
     struct tcp_sock *tp = tcp_sk(sk);
 
     /* No URG data to read. */
     if (sock_flag(sk, SOCK_URGINLINE) || !tp->urg_data ||
         tp->urg_data == TCP_URG_READ)
         return -EINVAL; /* Yes this is right ! */
 
     if (sk->sk_state == TCP_CLOSE && !sock_flag(sk, SOCK_DONE))
         return -ENOTCONN;
 
     if (tp->urg_data & TCP_URG_VALID) {
         int err = 0;
         char c = tp->urg_data;
 
         if (!(flags & MSG_PEEK))
             WRITE_ONCE(tp->urg_data, TCP_URG_READ);
 
         /* Read urgent data. */
         msg->msg_flags |= MSG_OOB;
 
         if (len > 0) {
             if (!(flags & MSG_TRUNC))
                 err = memcpy_to_msg(msg, &c, 1);
             len = 1;
         } else
             msg->msg_flags |= MSG_TRUNC;
 
         return err ? -EFAULT : len;
     }
 
     if (sk->sk_state == TCP_CLOSE || (sk->sk_shutdown & RCV_SHUTDOWN))
         return 0;
 
     /* Fixed the recv(..., MSG_OOB) behaviour.  BSD docs and
      * the available implementations agree in this case:
      * this call should never block, independent of the
      * blocking state of the socket.
      * Mike <pall@rz.uni-karlsruhe.de>
      */
     return -EAGAIN;
 }
 
 static int tcp_peek_sndq(struct sock *sk, struct msghdr *msg, int len)
 {
     struct sk_buff *skb;
     int copied = 0, err = 0;
 
     /* XXX -- need to support SO_PEEK_OFF */
 
     skb_rbtree_walk(skb, &sk->tcp_rtx_queue) {
         err = skb_copy_datagram_msg(skb, 0, msg, skb->len);
         if (err)
             return err;
         copied += skb->len;
     }
 
     skb_queue_walk(&sk->sk_write_queue, skb) {
         err = skb_copy_datagram_msg(skb, 0, msg, skb->len);
         if (err)
             break;
 
         copied += skb->len;
     }
 
     return err ?: copied;
 }
 
 /* Clean up the receive buffer for full frames taken by the user,
  * then send an ACK if necessary.  COPIED is the number of bytes
  * tcp_recvmsg has given to the user so far, it speeds up the
  * calculation of whether or not we must ACK for the sake of
  * a window update.
  */
 static void __tcp_cleanup_rbuf(struct sock *sk, int copied)
 {
     struct tcp_sock *tp = tcp_sk(sk);
     bool time_to_ack = false;
 
     if (inet_csk_ack_scheduled(sk)) {
         const struct inet_connection_sock *icsk = inet_csk(sk);
 
         if (/* Once-per-two-segments ACK was not sent by tcp_input.c */
             tp->rcv_nxt - tp->rcv_wup > icsk->icsk_ack.rcv_mss ||
             /*
              * If this read emptied read buffer, we send ACK, if
              * connection is not bidirectional, user drained
              * receive buffer and there was a small segment
              * in queue.
              */
             (copied > 0 &&
              ((icsk->icsk_ack.pending & ICSK_ACK_PUSHED2) ||
               ((icsk->icsk_ack.pending & ICSK_ACK_PUSHED) &&
                !inet_csk_in_pingpong_mode(sk))) &&
               !atomic_read(&sk->sk_rmem_alloc)))
             time_to_ack = true;
     }
 
     /* We send an ACK if we can now advertise a non-zero window
      * which has been raised "significantly".
      *
      * Even if window raised up to infinity, do not send window open ACK
      * in states, where we will not receive more. It is useless.
      */
     if (copied > 0 && !time_to_ack && !(sk->sk_shutdown & RCV_SHUTDOWN)) {
         __u32 rcv_window_now = tcp_receive_window(tp);
 
         /* Optimize, __tcp_select_window() is not cheap. */
         if (2*rcv_window_now <= tp->window_clamp) {
             __u32 new_window = __tcp_select_window(sk);
 
             /* Send ACK now, if this read freed lots of space
              * in our buffer. Certainly, new_window is new window.
              * We can advertise it now, if it is not less than current one.
              * "Lots" means "at least twice" here.
              */
             if (new_window && new_window >= 2 * rcv_window_now)
                 time_to_ack = true;
         }
     }
     if (time_to_ack)
         tcp_send_ack(sk);
 }
 
 void tcp_cleanup_rbuf(struct sock *sk, int copied)
 {
     struct sk_buff *skb = skb_peek(&sk->sk_receive_queue);
     struct tcp_sock *tp = tcp_sk(sk);
 
     WARN(skb && !before(tp->copied_seq, TCP_SKB_CB(skb)->end_seq),
          "cleanup rbuf bug: copied %X seq %X rcvnxt %X\n",
          tp->copied_seq, TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt);
     __tcp_cleanup_rbuf(sk, copied);
 }
 
 static void tcp_eat_recv_skb(struct sock *sk, struct sk_buff *skb)
 {
     __skb_unlink(skb, &sk->sk_receive_queue);
     if (likely(skb->destructor == sock_rfree)) {
         sock_rfree(skb);
         skb->destructor = NULL;
         skb->sk = NULL;
         return skb_attempt_defer_free(skb);
     }
     __kfree_skb(skb);
 }
 
 struct sk_buff *tcp_recv_skb(struct sock *sk, u32 seq, u32 *off)
 {
     struct sk_buff *skb;
     u32 offset;
 
     while ((skb = skb_peek(&sk->sk_receive_queue)) != NULL) {
         offset = seq - TCP_SKB_CB(skb)->seq;
         if (unlikely(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) {
             pr_err_once("%s: found a SYN, please report !\n", __func__);
             offset--;
         }
         if (offset < skb->len || (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)) {
             *off = offset;
             return skb;
         }
         /* This looks weird, but this can happen if TCP collapsing
          * splitted a fat GRO packet, while we released socket lock
          * in skb_splice_bits()
          */
         tcp_eat_recv_skb(sk, skb);
     }
     return NULL;
 }
 EXPORT_SYMBOL(tcp_recv_skb);
 
 /*
  * This routine provides an alternative to tcp_recvmsg() for routines
  * that would like to handle copying from skbuffs directly in 'sendfile'
  * fashion.
  * Note:
  *  - It is assumed that the socket was locked by the caller.
  *  - The routine does not block.
  *  - At present, there is no support for reading OOB data
  *    or for 'peeking' the socket using this routine
  *    (although both would be easy to implement).
  */
 int tcp_read_sock(struct sock *sk, read_descriptor_t *desc,
           sk_read_actor_t recv_actor)
 {
     struct sk_buff *skb;
     struct tcp_sock *tp = tcp_sk(sk);
     u32 seq = tp->copied_seq;
     u32 offset;
     int copied = 0;
 
     if (sk->sk_state == TCP_LISTEN)
         return -ENOTCONN;
     while ((skb = tcp_recv_skb(sk, seq, &offset)) != NULL) {
         if (offset < skb->len) {
             int used;
             size_t len;
 
             len = skb->len - offset;
             /* Stop reading if we hit a patch of urgent data */
             if (unlikely(tp->urg_data)) {
                 u32 urg_offset = tp->urg_seq - seq;
                 if (urg_offset < len)
                     len = urg_offset;
                 if (!len)
                     break;
             }
             used = recv_actor(desc, skb, offset, len);
             if (used <= 0) {
                 if (!copied)
                     copied = used;
                 break;
             }
             if (WARN_ON_ONCE(used > len))
                 used = len;
             seq += used;
             copied += used;
             offset += used;
 
             /* If recv_actor drops the lock (e.g. TCP splice
              * receive) the skb pointer might be invalid when
              * getting here: tcp_collapse might have deleted it
              * while aggregating skbs from the socket queue.
              */
             skb = tcp_recv_skb(sk, seq - 1, &offset);
             if (!skb)
                 break;
             /* TCP coalescing might have appended data to the skb.
              * Try to splice more frags
              */
             if (offset + 1 != skb->len)
                 continue;
         }
         if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) {
             tcp_eat_recv_skb(sk, skb);
             ++seq;
             break;
         }
         tcp_eat_recv_skb(sk, skb);
         if (!desc->count)
             break;
         WRITE_ONCE(tp->copied_seq, seq);
     }
     WRITE_ONCE(tp->copied_seq, seq);
 
     tcp_rcv_space_adjust(sk);
 
     /* Clean up data we have read: This will do ACK frames. */
     if (copied > 0) {
         tcp_recv_skb(sk, seq, &offset);
         tcp_cleanup_rbuf(sk, copied);
     }
     return copied;
 }
 EXPORT_SYMBOL(tcp_read_sock);
 
 int tcp_read_skb(struct sock *sk, skb_read_actor_t recv_actor)
 {
     struct tcp_sock *tp = tcp_sk(sk);
     u32 seq = tp->copied_seq;
     struct sk_buff *skb;
     int copied = 0;
     u32 offset;
 
     if (sk->sk_state == TCP_LISTEN)
         return -ENOTCONN;
 
     while ((skb = tcp_recv_skb(sk, seq, &offset)) != NULL) {
         u8 tcp_flags;
         int used;
 
         __skb_unlink(skb, &sk->sk_receive_queue);
         WARN_ON_ONCE(!skb_set_owner_sk_safe(skb, sk));
         tcp_flags = TCP_SKB_CB(skb)->tcp_flags;
         used = recv_actor(sk, skb);
         consume_skb(skb);
         if (used < 0) {
             if (!copied)
                 copied = used;
             break;
         }
         seq += used;
         copied += used;
 
         if (tcp_flags & TCPHDR_FIN) {
             ++seq;
             break;
         }
     }
     WRITE_ONCE(tp->copied_seq, seq);
 
     tcp_rcv_space_adjust(sk);
 
     /* Clean up data we have read: This will do ACK frames. */
     if (copied > 0)
         __tcp_cleanup_rbuf(sk, copied);
 
     return copied;
 }
 EXPORT_SYMBOL(tcp_read_skb);
 
 void tcp_read_done(struct sock *sk, size_t len)
 {
     struct tcp_sock *tp = tcp_sk(sk);
     u32 seq = tp->copied_seq;
     struct sk_buff *skb;
     size_t left;
     u32 offset;
 
     if (sk->sk_state == TCP_LISTEN)
         return;
 
     left = len;
     while (left && (skb = tcp_recv_skb(sk, seq, &offset)) != NULL) {
         int used;
 
         used = min_t(size_t, skb->len - offset, left);
         seq += used;
         left -= used;
 
         if (skb->len > offset + used)
             break;
 
         if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) {
             tcp_eat_recv_skb(sk, skb);
             ++seq;
             break;
         }
         tcp_eat_recv_skb(sk, skb);
     }
     WRITE_ONCE(tp->copied_seq, seq);
 
     tcp_rcv_space_adjust(sk);
 
     /* Clean up data we have read: This will do ACK frames. */
     if (left != len)
         tcp_cleanup_rbuf(sk, len - left);
 }
 EXPORT_SYMBOL(tcp_read_done);
 
 int tcp_peek_len(struct socket *sock)
 {
     return tcp_inq(sock->sk);
 }
 EXPORT_SYMBOL(tcp_peek_len);
 
 /* Make sure sk_rcvbuf is big enough to satisfy SO_RCVLOWAT hint */
 int tcp_set_rcvlowat(struct sock *sk, int val)
 {
     int cap;
 
     if (sk->sk_userlocks & SOCK_RCVBUF_LOCK)
         cap = sk->sk_rcvbuf >> 1;
     else
         cap = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_rmem[2]) >> 1;
     val = min(val, cap);
     WRITE_ONCE(sk->sk_rcvlowat, val ? : 1);
 
     /* Check if we need to signal EPOLLIN right now */
     tcp_data_ready(sk);
 
     if (sk->sk_userlocks & SOCK_RCVBUF_LOCK)
         return 0;
 
     val <<= 1;
     if (val > sk->sk_rcvbuf) {
         WRITE_ONCE(sk->sk_rcvbuf, val);
         tcp_sk(sk)->window_clamp = tcp_win_from_space(sk, val);
     }
     return 0;
 }
 EXPORT_SYMBOL(tcp_set_rcvlowat);
 
 void tcp_update_recv_tstamps(struct sk_buff *skb,
                  struct scm_timestamping_internal *tss)
 {
     if (skb->tstamp)
         tss->ts[0] = ktime_to_timespec64(skb->tstamp);
     else
         tss->ts[0] = (struct timespec64) {0};
 
     if (skb_hwtstamps(skb)->hwtstamp)
         tss->ts[2] = ktime_to_timespec64(skb_hwtstamps(skb)->hwtstamp);
     else
         tss->ts[2] = (struct timespec64) {0};
 }
 
 #ifdef CONFIG_MMU
 static const struct vm_operations_struct tcp_vm_ops = {
 };
 
 int tcp_mmap(struct file *file, struct socket *sock,
          struct vm_area_struct *vma)
 {
     if (vma->vm_flags & (VM_WRITE | VM_EXEC))
         return -EPERM;
     vma->vm_flags &= ~(VM_MAYWRITE | VM_MAYEXEC);
 
     /* Instruct vm_insert_page() to not mmap_read_lock(mm) */
     vma->vm_flags |= VM_MIXEDMAP;
 
     vma->vm_ops = &tcp_vm_ops;
     return 0;
 }
 EXPORT_SYMBOL(tcp_mmap);
 
 static skb_frag_t *skb_advance_to_frag(struct sk_buff *skb, u32 offset_skb,
                        u32 *offset_frag)
 {
     skb_frag_t *frag;
 
     if (unlikely(offset_skb >= skb->len))
         return NULL;
 
     offset_skb -= skb_headlen(skb);
     if ((int)offset_skb < 0 || skb_has_frag_list(skb))
         return NULL;
 
     frag = skb_shinfo(skb)->frags;
     while (offset_skb) {
         if (skb_frag_size(frag) > offset_skb) {
             *offset_frag = offset_skb;
             return frag;
         }
         offset_skb -= skb_frag_size(frag);
         ++frag;
     }
     *offset_frag = 0;
     return frag;
 }
 
 static bool can_map_frag(const skb_frag_t *frag)
 {
     return skb_frag_size(frag) == PAGE_SIZE && !skb_frag_off(frag);
 }
 
 static int find_next_mappable_frag(const skb_frag_t *frag,
                    int remaining_in_skb)
 {
     int offset = 0;
 
     if (likely(can_map_frag(frag)))
         return 0;
 
     while (offset < remaining_in_skb && !can_map_frag(frag)) {
         offset += skb_frag_size(frag);
         ++frag;
     }
     return offset;
 }
 
 static void tcp_zerocopy_set_hint_for_skb(struct sock *sk,
                       struct tcp_zerocopy_receive *zc,
                       struct sk_buff *skb, u32 offset)
 {
     u32 frag_offset, partial_frag_remainder = 0;
     int mappable_offset;
     skb_frag_t *frag;
 
     /* worst case: skip to next skb. try to improve on this case below */
     zc->recv_skip_hint = skb->len - offset;
 
     /* Find the frag containing this offset (and how far into that frag) */
     frag = skb_advance_to_frag(skb, offset, &frag_offset);
     if (!frag)
         return;
 
     if (frag_offset) {
         struct skb_shared_info *info = skb_shinfo(skb);
 
         /* We read part of the last frag, must recvmsg() rest of skb. */
         if (frag == &info->frags[info->nr_frags - 1])
             return;
 
         /* Else, we must at least read the remainder in this frag. */
         partial_frag_remainder = skb_frag_size(frag) - frag_offset;
         zc->recv_skip_hint -= partial_frag_remainder;
         ++frag;
     }
 
     /* partial_frag_remainder: If part way through a frag, must read rest.
      * mappable_offset: Bytes till next mappable frag, *not* counting bytes
      * in partial_frag_remainder.
      */
     mappable_offset = find_next_mappable_frag(frag, zc->recv_skip_hint);
     zc->recv_skip_hint = mappable_offset + partial_frag_remainder;
 }
 
 static int tcp_recvmsg_locked(struct sock *sk, struct msghdr *msg, size_t len,
                   int flags, struct scm_timestamping_internal *tss,
                   int *cmsg_flags);
 static int receive_fallback_to_copy(struct sock *sk,
                     struct tcp_zerocopy_receive *zc, int inq,
                     struct scm_timestamping_internal *tss)
 {
     unsigned long copy_address = (unsigned long)zc->copybuf_address;
     struct msghdr msg = {};
     struct iovec iov;
     int err;
 
     zc->length = 0;
     zc->recv_skip_hint = 0;
 
     if (copy_address != zc->copybuf_address)
         return -EINVAL;
 
     err = import_single_range(READ, (void __user *)copy_address,
                   inq, &iov, &msg.msg_iter);
     if (err)
         return err;
 
     err = tcp_recvmsg_locked(sk, &msg, inq, MSG_DONTWAIT,
                  tss, &zc->msg_flags);
     if (err < 0)
         return err;
 
     zc->copybuf_len = err;
     if (likely(zc->copybuf_len)) {
         struct sk_buff *skb;
         u32 offset;
 
         skb = tcp_recv_skb(sk, tcp_sk(sk)->copied_seq, &offset);
         if (skb)
             tcp_zerocopy_set_hint_for_skb(sk, zc, skb, offset);
     }
     return 0;
 }
 
 static int tcp_copy_straggler_data(struct tcp_zerocopy_receive *zc,
                    struct sk_buff *skb, u32 copylen,
                    u32 *offset, u32 *seq)
 {
     unsigned long copy_address = (unsigned long)zc->copybuf_address;
     struct msghdr msg = {};
     struct iovec iov;
     int err;
 
     if (copy_address != zc->copybuf_address)
         return -EINVAL;
 
     err = import_single_range(READ, (void __user *)copy_address,
                   copylen, &iov, &msg.msg_iter);
     if (err)
         return err;
     err = skb_copy_datagram_msg(skb, *offset, &msg, copylen);
     if (err)
         return err;
     zc->recv_skip_hint -= copylen;
     *offset += copylen;
     *seq += copylen;
     return (__s32)copylen;
 }
 
 static int tcp_zc_handle_leftover(struct tcp_zerocopy_receive *zc,
                   struct sock *sk,
                   struct sk_buff *skb,
                   u32 *seq,
                   s32 copybuf_len,
                   struct scm_timestamping_internal *tss)
 {
     u32 offset, copylen = min_t(u32, copybuf_len, zc->recv_skip_hint);
 
     if (!copylen)
         return 0;
     /* skb is null if inq < PAGE_SIZE. */
     if (skb) {
         offset = *seq - TCP_SKB_CB(skb)->seq;
     } else {
         skb = tcp_recv_skb(sk, *seq, &offset);
         if (TCP_SKB_CB(skb)->has_rxtstamp) {
             tcp_update_recv_tstamps(skb, tss);
             zc->msg_flags |= TCP_CMSG_TS;
         }
     }
 
     zc->copybuf_len = tcp_copy_straggler_data(zc, skb, copylen, &offset,
                           seq);
     return zc->copybuf_len < 0 ? 0 : copylen;
 }
 
 static int tcp_zerocopy_vm_insert_batch_error(struct vm_area_struct *vma,
                           struct page **pending_pages,
                           unsigned long pages_remaining,
                           unsigned long *address,
                           u32 *length,
                           u32 *seq,
                           struct tcp_zerocopy_receive *zc,
                           u32 total_bytes_to_map,
                           int err)
 {
     /* At least one page did not map. Try zapping if we skipped earlier. */
     if (err == -EBUSY &&
         zc->flags & TCP_RECEIVE_ZEROCOPY_FLAG_TLB_CLEAN_HINT) {
         u32 maybe_zap_len;
 
         maybe_zap_len = total_bytes_to_map -  /* All bytes to map */
                 *length + /* Mapped or pending */
                 (pages_remaining * PAGE_SIZE); /* Failed map. */
         zap_page_range(vma, *address, maybe_zap_len);
         err = 0;
     }
 
     if (!err) {
         unsigned long leftover_pages = pages_remaining;
         int bytes_mapped;
 
         /* We called zap_page_range, try to reinsert. */
         err = vm_insert_pages(vma, *address,
                       pending_pages,
                       &pages_remaining);
         bytes_mapped = PAGE_SIZE * (leftover_pages - pages_remaining);
         *seq += bytes_mapped;
         *address += bytes_mapped;
     }
     if (err) {
         /* Either we were unable to zap, OR we zapped, retried an
          * insert, and still had an issue. Either ways, pages_remaining
          * is the number of pages we were unable to map, and we unroll
          * some state we speculatively touched before.
          */
         const int bytes_not_mapped = PAGE_SIZE * pages_remaining;
 
         *length -= bytes_not_mapped;
         zc->recv_skip_hint += bytes_not_mapped;
     }
     return err;
 }
 
 static int tcp_zerocopy_vm_insert_batch(struct vm_area_struct *vma,
                     struct page **pages,
                     unsigned int pages_to_map,
                     unsigned long *address,
                     u32 *length,
                     u32 *seq,
                     struct tcp_zerocopy_receive *zc,
                     u32 total_bytes_to_map)
 {
     unsigned long pages_remaining = pages_to_map;
     unsigned int pages_mapped;
     unsigned int bytes_mapped;
     int err;
 
     err = vm_insert_pages(vma, *address, pages, &pages_remaining);
     pages_mapped = pages_to_map - (unsigned int)pages_remaining;
     bytes_mapped = PAGE_SIZE * pages_mapped;
     /* Even if vm_insert_pages fails, it may have partially succeeded in
      * mapping (some but not all of the pages).
      */
     *seq += bytes_mapped;
     *address += bytes_mapped;
 
     if (likely(!err))
         return 0;
 
     /* Error: maybe zap and retry + rollback state for failed inserts. */
     return tcp_zerocopy_vm_insert_batch_error(vma, pages + pages_mapped,
         pages_remaining, address, length, seq, zc, total_bytes_to_map,
         err);
 }
 
 #define TCP_VALID_ZC_MSG_FLAGS   (TCP_CMSG_TS)
 static void tcp_zc_finalize_rx_tstamp(struct sock *sk,
                       struct tcp_zerocopy_receive *zc,
                       struct scm_timestamping_internal *tss)
 {
     unsigned long msg_control_addr;
     struct msghdr cmsg_dummy;
 
     msg_control_addr = (unsigned long)zc->msg_control;
     cmsg_dummy.msg_control = (void *)msg_control_addr;
     cmsg_dummy.msg_controllen =
         (__kernel_size_t)zc->msg_controllen;
     cmsg_dummy.msg_flags = in_compat_syscall()
         ? MSG_CMSG_COMPAT : 0;
     cmsg_dummy.msg_control_is_user = true;
     zc->msg_flags = 0;
     if (zc->msg_control == msg_control_addr &&
         zc->msg_controllen == cmsg_dummy.msg_controllen) {
         tcp_recv_timestamp(&cmsg_dummy, sk, tss);
         zc->msg_control = (__u64)
             ((uintptr_t)cmsg_dummy.msg_control);
         zc->msg_controllen =
             (__u64)cmsg_dummy.msg_controllen;
         zc->msg_flags = (__u32)cmsg_dummy.msg_flags;
     }
 }
 
 #define TCP_ZEROCOPY_PAGE_BATCH_SIZE 32
 static int tcp_zerocopy_receive(struct sock *sk,
                 struct tcp_zerocopy_receive *zc,
                 struct scm_timestamping_internal *tss)
 {
     u32 length = 0, offset, vma_len, avail_len, copylen = 0;
     unsigned long address = (unsigned long)zc->address;
     struct page *pages[TCP_ZEROCOPY_PAGE_BATCH_SIZE];
     s32 copybuf_len = zc->copybuf_len;
     struct tcp_sock *tp = tcp_sk(sk);
     const skb_frag_t *frags = NULL;
     unsigned int pages_to_map = 0;
     struct vm_area_struct *vma;
     struct sk_buff *skb = NULL;
     u32 seq = tp->copied_seq;
     u32 total_bytes_to_map;
     int inq = tcp_inq(sk);
     int ret;
 
     zc->copybuf_len = 0;
     zc->msg_flags = 0;
 
     if (address & (PAGE_SIZE - 1) || address != zc->address)
         return -EINVAL;
 
     if (sk->sk_state == TCP_LISTEN)
         return -ENOTCONN;
 
     sock_rps_record_flow(sk);
 
     if (inq && inq <= copybuf_len)
         return receive_fallback_to_copy(sk, zc, inq, tss);
 
     if (inq < PAGE_SIZE) {
         zc->length = 0;
         zc->recv_skip_hint = inq;
         if (!inq && sock_flag(sk, SOCK_DONE))
             return -EIO;
         return 0;
     }
 
     mmap_read_lock(current->mm);
 
     vma = vma_lookup(current->mm, address);
     if (!vma || vma->vm_ops != &tcp_vm_ops) {
         mmap_read_unlock(current->mm);
         return -EINVAL;
     }
     vma_len = min_t(unsigned long, zc->length, vma->vm_end - address);
     avail_len = min_t(u32, vma_len, inq);
     total_bytes_to_map = avail_len & ~(PAGE_SIZE - 1);
     if (total_bytes_to_map) {
         if (!(zc->flags & TCP_RECEIVE_ZEROCOPY_FLAG_TLB_CLEAN_HINT))
             zap_page_range(vma, address, total_bytes_to_map);
         zc->length = total_bytes_to_map;
         zc->recv_skip_hint = 0;
     } else {
         zc->length = avail_len;
         zc->recv_skip_hint = avail_len;
     }
     ret = 0;
     while (length + PAGE_SIZE <= zc->length) {
         int mappable_offset;
         struct page *page;
 
         if (zc->recv_skip_hint < PAGE_SIZE) {
             u32 offset_frag;
 
             if (skb) {
                 if (zc->recv_skip_hint > 0)
                     break;
                 skb = skb->next;
                 offset = seq - TCP_SKB_CB(skb)->seq;
             } else {
                 skb = tcp_recv_skb(sk, seq, &offset);
             }
 
             if (TCP_SKB_CB(skb)->has_rxtstamp) {
                 tcp_update_recv_tstamps(skb, tss);
                 zc->msg_flags |= TCP_CMSG_TS;
             }
             zc->recv_skip_hint = skb->len - offset;
             frags = skb_advance_to_frag(skb, offset, &offset_frag);
             if (!frags || offset_frag)
                 break;
         }
 
         mappable_offset = find_next_mappable_frag(frags,
                               zc->recv_skip_hint);
         if (mappable_offset) {
             zc->recv_skip_hint = mappable_offset;
             break;
         }
         page = skb_frag_page(frags);
         prefetchw(page);
         pages[pages_to_map++] = page;
         length += PAGE_SIZE;
         zc->recv_skip_hint -= PAGE_SIZE;
         frags++;
         if (pages_to_map == TCP_ZEROCOPY_PAGE_BATCH_SIZE ||
             zc->recv_skip_hint < PAGE_SIZE) {
             /* Either full batch, or we're about to go to next skb
              * (and we cannot unroll failed ops across skbs).
              */
             ret = tcp_zerocopy_vm_insert_batch(vma, pages,
                                pages_to_map,
                                &address, &length,
                                &seq, zc,
                                total_bytes_to_map);
             if (ret)
                 goto out;
             pages_to_map = 0;
         }
     }
     if (pages_to_map) {
         ret = tcp_zerocopy_vm_insert_batch(vma, pages, pages_to_map,
                            &address, &length, &seq,
                            zc, total_bytes_to_map);
     }
 out:
     mmap_read_unlock(current->mm);
     /* Try to copy straggler data. */
     if (!ret)
         copylen = tcp_zc_handle_leftover(zc, sk, skb, &seq, copybuf_len, tss);
 
     if (length + copylen) {
         WRITE_ONCE(tp->copied_seq, seq);
         tcp_rcv_space_adjust(sk);
 
         /* Clean up data we have read: This will do ACK frames. */
         tcp_recv_skb(sk, seq, &offset);
         tcp_cleanup_rbuf(sk, length + copylen);
         ret = 0;
         if (length == zc->length)
             zc->recv_skip_hint = 0;
     } else {
         if (!zc->recv_skip_hint && sock_flag(sk, SOCK_DONE))
             ret = -EIO;
     }
     zc->length = length;
     return ret;
 }
 #endif
 
 /* Similar to __sock_recv_timestamp, but does not require an skb */
 void tcp_recv_timestamp(struct msghdr *msg, const struct sock *sk,
             struct scm_timestamping_internal *tss)
 {
     int new_tstamp = sock_flag(sk, SOCK_TSTAMP_NEW);
     bool has_timestamping = false;
 
     if (tss->ts[0].tv_sec || tss->ts[0].tv_nsec) {
         if (sock_flag(sk, SOCK_RCVTSTAMP)) {
             if (sock_flag(sk, SOCK_RCVTSTAMPNS)) {
                 if (new_tstamp) {
                     struct __kernel_timespec kts = {
                         .tv_sec = tss->ts[0].tv_sec,
                         .tv_nsec = tss->ts[0].tv_nsec,
                     };
                     put_cmsg(msg, SOL_SOCKET, SO_TIMESTAMPNS_NEW,
                          sizeof(kts), &kts);
                 } else {
                     struct __kernel_old_timespec ts_old = {
                         .tv_sec = tss->ts[0].tv_sec,
                         .tv_nsec = tss->ts[0].tv_nsec,
                     };
                     put_cmsg(msg, SOL_SOCKET, SO_TIMESTAMPNS_OLD,
                          sizeof(ts_old), &ts_old);
                 }
             } else {
                 if (new_tstamp) {
                     struct __kernel_sock_timeval stv = {
                         .tv_sec = tss->ts[0].tv_sec,
                         .tv_usec = tss->ts[0].tv_nsec / 1000,
                     };
                     put_cmsg(msg, SOL_SOCKET, SO_TIMESTAMP_NEW,
                          sizeof(stv), &stv);
                 } else {
                     struct __kernel_old_timeval tv = {
                         .tv_sec = tss->ts[0].tv_sec,
                         .tv_usec = tss->ts[0].tv_nsec / 1000,
                     };
                     put_cmsg(msg, SOL_SOCKET, SO_TIMESTAMP_OLD,
                          sizeof(tv), &tv);
                 }
             }
         }
 
         if (sk->sk_tsflags & SOF_TIMESTAMPING_SOFTWARE)
             has_timestamping = true;
         else
             tss->ts[0] = (struct timespec64) {0};
     }
 
     if (tss->ts[2].tv_sec || tss->ts[2].tv_nsec) {
         if (sk->sk_tsflags & SOF_TIMESTAMPING_RAW_HARDWARE)
             has_timestamping = true;
         else
             tss->ts[2] = (struct timespec64) {0};
     }
 
     if (has_timestamping) {
         tss->ts[1] = (struct timespec64) {0};
         if (sock_flag(sk, SOCK_TSTAMP_NEW))
             put_cmsg_scm_timestamping64(msg, tss);
         else
             put_cmsg_scm_timestamping(msg, tss);
     }
 }
 
 static int tcp_inq_hint(struct sock *sk)
 {
     const struct tcp_sock *tp = tcp_sk(sk);
     u32 copied_seq = READ_ONCE(tp->copied_seq);
     u32 rcv_nxt = READ_ONCE(tp->rcv_nxt);
     int inq;
 
     inq = rcv_nxt - copied_seq;
     if (unlikely(inq < 0 || copied_seq != READ_ONCE(tp->copied_seq))) {
         lock_sock(sk);
         inq = tp->rcv_nxt - tp->copied_seq;
         release_sock(sk);
     }
     /* After receiving a FIN, tell the user-space to continue reading
      * by returning a non-zero inq.
      */
     if (inq == 0 && sock_flag(sk, SOCK_DONE))
         inq = 1;
     return inq;
 }
 
 /*
  *  This routine copies from a sock struct into the user buffer.
  *
  *  Technical note: in 2.3 we work on _locked_ socket, so that
  *  tricks with *seq access order and skb->users are not required.
  *  Probably, code can be easily improved even more.
  */
 
 static int tcp_recvmsg_locked(struct sock *sk, struct msghdr *msg, size_t len,
                   int flags, struct scm_timestamping_internal *tss,
                   int *cmsg_flags)
 {
     struct tcp_sock *tp = tcp_sk(sk);
     int copied = 0;
     u32 peek_seq;
     u32 *seq;
     unsigned long used;
     int err;
     int target;     /* Read at least this many bytes */
     long timeo;
     struct sk_buff *skb, *last;
     u32 urg_hole = 0;
 
     err = -ENOTCONN;
     if (sk->sk_state == TCP_LISTEN)
         goto out;
 
     if (tp->recvmsg_inq) {
         *cmsg_flags = TCP_CMSG_INQ;
         msg->msg_get_inq = 1;
     }
     timeo = sock_rcvtimeo(sk, flags & MSG_DONTWAIT);
 
     /* Urgent data needs to be handled specially. */
     if (flags & MSG_OOB)
         goto recv_urg;
 
     if (unlikely(tp->repair)) {
         err = -EPERM;
         if (!(flags & MSG_PEEK))
             goto out;
 
         if (tp->repair_queue == TCP_SEND_QUEUE)
             goto recv_sndq;
 
         err = -EINVAL;
         if (tp->repair_queue == TCP_NO_QUEUE)
             goto out;
 
         /* 'common' recv queue MSG_PEEK-ing */
     }
 
     seq = &tp->copied_seq;
     if (flags & MSG_PEEK) {
         peek_seq = tp->copied_seq;
         seq = &peek_seq;
     }
 
     target = sock_rcvlowat(sk, flags & MSG_WAITALL, len);
 
     do {
         u32 offset;
 
         /* Are we at urgent data? Stop if we have read anything or have SIGURG pending. */
         if (unlikely(tp->urg_data) && tp->urg_seq == *seq) {
             if (copied)
                 break;
             if (signal_pending(current)) {
                 copied = timeo ? sock_intr_errno(timeo) : -EAGAIN;
                 break;
             }
         }
 
         /* Next get a buffer. */
 
         last = skb_peek_tail(&sk->sk_receive_queue);
         skb_queue_walk(&sk->sk_receive_queue, skb) {
             last = skb;
             /* Now that we have two receive queues this
              * shouldn't happen.
              */
             if (WARN(before(*seq, TCP_SKB_CB(skb)->seq),
                  "TCP recvmsg seq # bug: copied %X, seq %X, rcvnxt %X, fl %X\n",
                  *seq, TCP_SKB_CB(skb)->seq, tp->rcv_nxt,
                  flags))
                 break;
 
             offset = *seq - TCP_SKB_CB(skb)->seq;
             if (unlikely(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) {
                 pr_err_once("%s: found a SYN, please report !\n", __func__);
                 offset--;
             }
             if (offset < skb->len)
                 goto found_ok_skb;
             if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
                 goto found_fin_ok;
             WARN(!(flags & MSG_PEEK),
                  "TCP recvmsg seq # bug 2: copied %X, seq %X, rcvnxt %X, fl %X\n",
                  *seq, TCP_SKB_CB(skb)->seq, tp->rcv_nxt, flags);
         }
 
         /* Well, if we have backlog, try to process it now yet. */
 
         if (copied >= target && !READ_ONCE(sk->sk_backlog.tail))
             break;
 
         if (copied) {
             if (!timeo ||
                 sk->sk_err ||
                 sk->sk_state == TCP_CLOSE ||
                 (sk->sk_shutdown & RCV_SHUTDOWN) ||
                 signal_pending(current))
                 break;
         } else {
             if (sock_flag(sk, SOCK_DONE))
                 break;
 
             if (sk->sk_err) {
                 copied = sock_error(sk);
                 break;
             }
 
             if (sk->sk_shutdown & RCV_SHUTDOWN)
                 break;
 
             if (sk->sk_state == TCP_CLOSE) {
                 /* This occurs when user tries to read
                  * from never connected socket.
                  */
                 copied = -ENOTCONN;
                 break;
             }
 
             if (!timeo) {
                 copied = -EAGAIN;
                 break;
             }
 
             if (signal_pending(current)) {
                 copied = sock_intr_errno(timeo);
                 break;
             }
         }
 
         if (copied >= target) {
             /* Do not sleep, just process backlog. */
             __sk_flush_backlog(sk);
         } else {
             tcp_cleanup_rbuf(sk, copied);
             sk_wait_data(sk, &timeo, last);
         }
 
         if ((flags & MSG_PEEK) &&
             (peek_seq - copied - urg_hole != tp->copied_seq)) {
             net_dbg_ratelimited("TCP(%s:%d): Application bug, race in MSG_PEEK\n",
                         current->comm,
                         task_pid_nr(current));
             peek_seq = tp->copied_seq;
         }
         continue;
 
 found_ok_skb:
         /* Ok so how much can we use? */
         used = skb->len - offset;
         if (len < used)
             used = len;
 
         /* Do we have urgent data here? */
         if (unlikely(tp->urg_data)) {
             u32 urg_offset = tp->urg_seq - *seq;
             if (urg_offset < used) {
                 if (!urg_offset) {
                     if (!sock_flag(sk, SOCK_URGINLINE)) {
                         WRITE_ONCE(*seq, *seq + 1);
                         urg_hole++;
                         offset++;
                         used--;
                         if (!used)
                             goto skip_copy;
                     }
                 } else
                     used = urg_offset;
             }
         }
 
         if (!(flags & MSG_TRUNC)) {
             err = skb_copy_datagram_msg(skb, offset, msg, used);
             if (err) {
                 /* Exception. Bailout! */
                 if (!copied)
                     copied = -EFAULT;
                 break;
             }
         }
 
         WRITE_ONCE(*seq, *seq + used);
         copied += used;
         len -= used;
 
         tcp_rcv_space_adjust(sk);
 
 skip_copy:
         if (unlikely(tp->urg_data) && after(tp->copied_seq, tp->urg_seq)) {
             WRITE_ONCE(tp->urg_data, 0);
             tcp_fast_path_check(sk);
         }
 
         if (TCP_SKB_CB(skb)->has_rxtstamp) {
             tcp_update_recv_tstamps(skb, tss);
             *cmsg_flags |= TCP_CMSG_TS;
         }
 
         if (used + offset < skb->len)
             continue;
 
         if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
             goto found_fin_ok;
         if (!(flags & MSG_PEEK))
             tcp_eat_recv_skb(sk, skb);
         continue;
 
 found_fin_ok:
         /* Process the FIN. */
         WRITE_ONCE(*seq, *seq + 1);
         if (!(flags & MSG_PEEK))
             tcp_eat_recv_skb(sk, skb);
         break;
     } while (len > 0);
 
     /* According to UNIX98, msg_name/msg_namelen are ignored
      * on connected socket. I was just happy when found this 8) --ANK
      */
 
     /* Clean up data we have read: This will do ACK frames. */
     tcp_cleanup_rbuf(sk, copied);
     return copied;
 
 out:
     return err;
 
 recv_urg:
     err = tcp_recv_urg(sk, msg, len, flags);
     goto out;
 
 recv_sndq:
     err = tcp_peek_sndq(sk, msg, len);
     goto out;
 }
 
 int tcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int flags,
         int *addr_len)
 {
     int cmsg_flags = 0, ret;
     struct scm_timestamping_internal tss;
 
     if (unlikely(flags & MSG_ERRQUEUE))
         return inet_recv_error(sk, msg, len, addr_len);
 
     if (sk_can_busy_loop(sk) &&
         skb_queue_empty_lockless(&sk->sk_receive_queue) &&
         sk->sk_state == TCP_ESTABLISHED)
         sk_busy_loop(sk, flags & MSG_DONTWAIT);
 
     lock_sock(sk);
     ret = tcp_recvmsg_locked(sk, msg, len, flags, &tss, &cmsg_flags);
     release_sock(sk);
 
     if ((cmsg_flags || msg->msg_get_inq) && ret >= 0) {
         if (cmsg_flags & TCP_CMSG_TS)
             tcp_recv_timestamp(msg, sk, &tss);
         if (msg->msg_get_inq) {
             msg->msg_inq = tcp_inq_hint(sk);
             if (cmsg_flags & TCP_CMSG_INQ)
                 put_cmsg(msg, SOL_TCP, TCP_CM_INQ,
                      sizeof(msg->msg_inq), &msg->msg_inq);
         }
     }
     return ret;
 }
 EXPORT_SYMBOL(tcp_recvmsg);
 
 void tcp_set_state(struct sock *sk, int state)
 {
     int oldstate = sk->sk_state;
 
     /* We defined a new enum for TCP states that are exported in BPF
      * so as not force the internal TCP states to be frozen. The
      * following checks will detect if an internal state value ever
      * differs from the BPF value. If this ever happens, then we will
      * need to remap the internal value to the BPF value before calling
      * tcp_call_bpf_2arg.
      */
     BUILD_BUG_ON((int)BPF_TCP_ESTABLISHED != (int)TCP_ESTABLISHED);
     BUILD_BUG_ON((int)BPF_TCP_SYN_SENT != (int)TCP_SYN_SENT);
     BUILD_BUG_ON((int)BPF_TCP_SYN_RECV != (int)TCP_SYN_RECV);
     BUILD_BUG_ON((int)BPF_TCP_FIN_WAIT1 != (int)TCP_FIN_WAIT1);
     BUILD_BUG_ON((int)BPF_TCP_FIN_WAIT2 != (int)TCP_FIN_WAIT2);
     BUILD_BUG_ON((int)BPF_TCP_TIME_WAIT != (int)TCP_TIME_WAIT);
     BUILD_BUG_ON((int)BPF_TCP_CLOSE != (int)TCP_CLOSE);
     BUILD_BUG_ON((int)BPF_TCP_CLOSE_WAIT != (int)TCP_CLOSE_WAIT);
     BUILD_BUG_ON((int)BPF_TCP_LAST_ACK != (int)TCP_LAST_ACK);
     BUILD_BUG_ON((int)BPF_TCP_LISTEN != (int)TCP_LISTEN);
     BUILD_BUG_ON((int)BPF_TCP_CLOSING != (int)TCP_CLOSING);
     BUILD_BUG_ON((int)BPF_TCP_NEW_SYN_RECV != (int)TCP_NEW_SYN_RECV);
     BUILD_BUG_ON((int)BPF_TCP_MAX_STATES != (int)TCP_MAX_STATES);
 
     /* bpf uapi header bpf.h defines an anonymous enum with values
      * BPF_TCP_* used by bpf programs. Currently gcc built vmlinux
      * is able to emit this enum in DWARF due to the above BUILD_BUG_ON.
      * But clang built vmlinux does not have this enum in DWARF
      * since clang removes the above code before generating IR/debuginfo.
      * Let us explicitly emit the type debuginfo to ensure the
      * above-mentioned anonymous enum in the vmlinux DWARF and hence BTF
      * regardless of which compiler is used.
      */
     BTF_TYPE_EMIT_ENUM(BPF_TCP_ESTABLISHED);
 
     if (BPF_SOCK_OPS_TEST_FLAG(tcp_sk(sk), BPF_SOCK_OPS_STATE_CB_FLAG))
         tcp_call_bpf_2arg(sk, BPF_SOCK_OPS_STATE_CB, oldstate, state);
 
     switch (state) {
     case TCP_ESTABLISHED:
         if (oldstate != TCP_ESTABLISHED)
             TCP_INC_STATS(sock_net(sk), TCP_MIB_CURRESTAB);
         break;
 
     case TCP_CLOSE:
         if (oldstate == TCP_CLOSE_WAIT || oldstate == TCP_ESTABLISHED)
             TCP_INC_STATS(sock_net(sk), TCP_MIB_ESTABRESETS);
 
         sk->sk_prot->unhash(sk);
         if (inet_csk(sk)->icsk_bind_hash &&
             !(sk->sk_userlocks & SOCK_BINDPORT_LOCK))
             inet_put_port(sk);
         fallthrough;
     default:
         if (oldstate == TCP_ESTABLISHED)
             TCP_DEC_STATS(sock_net(sk), TCP_MIB_CURRESTAB);
     }
 
     /* Change state AFTER socket is unhashed to avoid closed
      * socket sitting in hash tables.
      */
     inet_sk_state_store(sk, state);
 }
 EXPORT_SYMBOL_GPL(tcp_set_state);
 
 /*
  *  State processing on a close. This implements the state shift for
  *  sending our FIN frame. Note that we only send a FIN for some
  *  states. A shutdown() may have already sent the FIN, or we may be
  *  closed.
  */
 
 static const unsigned char new_state[16] = {
   /* current state:        new state:      action:  */
   [0 /* (Invalid) */]   = TCP_CLOSE,
   [TCP_ESTABLISHED] = TCP_FIN_WAIT1 | TCP_ACTION_FIN,
   [TCP_SYN_SENT]    = TCP_CLOSE,
   [TCP_SYN_RECV]    = TCP_FIN_WAIT1 | TCP_ACTION_FIN,
   [TCP_FIN_WAIT1]   = TCP_FIN_WAIT1,
   [TCP_FIN_WAIT2]   = TCP_FIN_WAIT2,
   [TCP_TIME_WAIT]   = TCP_CLOSE,
   [TCP_CLOSE]       = TCP_CLOSE,
   [TCP_CLOSE_WAIT]  = TCP_LAST_ACK  | TCP_ACTION_FIN,
   [TCP_LAST_ACK]    = TCP_LAST_ACK,
   [TCP_LISTEN]      = TCP_CLOSE,
   [TCP_CLOSING]     = TCP_CLOSING,
   [TCP_NEW_SYN_RECV]    = TCP_CLOSE,    /* should not happen ! */
 };
 
 static int tcp_close_state(struct sock *sk)
 {
     int next = (int)new_state[sk->sk_state];
     int ns = next & TCP_STATE_MASK;
 
     tcp_set_state(sk, ns);
 
     return next & TCP_ACTION_FIN;
 }
 
 /*
  *  Shutdown the sending side of a connection. Much like close except
  *  that we don't receive shut down or sock_set_flag(sk, SOCK_DEAD).
  */
 
 void tcp_shutdown(struct sock *sk, int how)
 {
     /*  We need to grab some memory, and put together a FIN,
      *  and then put it into the queue to be sent.
      *      Tim MacKenzie(tym@dibbler.cs.monash.edu.au) 4 Dec '92.
      */
     if (!(how & SEND_SHUTDOWN))
         return;
 
     /* If we've already sent a FIN, or it's a closed state, skip this. */
     if ((1 << sk->sk_state) &
         (TCPF_ESTABLISHED | TCPF_SYN_SENT |
          TCPF_SYN_RECV | TCPF_CLOSE_WAIT)) {
         /* Clear out any half completed packets.  FIN if needed. */
         if (tcp_close_state(sk))
             tcp_send_fin(sk);
     }
 }
 EXPORT_SYMBOL(tcp_shutdown);
 
 int tcp_orphan_count_sum(void)
 {
     int i, total = 0;
 
     for_each_possible_cpu(i)
         total += per_cpu(tcp_orphan_count, i);
 
     return max(total, 0);
 }
 
 static int tcp_orphan_cache;
 static struct timer_list tcp_orphan_timer;
 #define TCP_ORPHAN_TIMER_PERIOD msecs_to_jiffies(100)
 
 static void tcp_orphan_update(struct timer_list *unused)
 {
     WRITE_ONCE(tcp_orphan_cache, tcp_orphan_count_sum());
     mod_timer(&tcp_orphan_timer, jiffies + TCP_ORPHAN_TIMER_PERIOD);
 }
 
 static bool tcp_too_many_orphans(int shift)
 {
     return READ_ONCE(tcp_orphan_cache) << shift >
         READ_ONCE(sysctl_tcp_max_orphans);
 }
 
 bool tcp_check_oom(struct sock *sk, int shift)
 {
     bool too_many_orphans, out_of_socket_memory;
 
     too_many_orphans = tcp_too_many_orphans(shift);
     out_of_socket_memory = tcp_out_of_memory(sk);
 
     if (too_many_orphans)
         net_info_ratelimited("too many orphaned sockets\n");
     if (out_of_socket_memory)
         net_info_ratelimited("out of memory -- consider tuning tcp_mem\n");
     return too_many_orphans || out_of_socket_memory;
 }
 
 void __tcp_close(struct sock *sk, long timeout)
 {
     struct sk_buff *skb;
     int data_was_unread = 0;
     int state;
 
     sk->sk_shutdown = SHUTDOWN_MASK;
 
     if (sk->sk_state == TCP_LISTEN) {
         tcp_set_state(sk, TCP_CLOSE);
 
         /* Special case. */
         inet_csk_listen_stop(sk);
 
         goto adjudge_to_death;
     }
 
     /*  We need to flush the recv. buffs.  We do this only on the
      *  descriptor close, not protocol-sourced closes, because the
      *  reader process may not have drained the data yet!
      */
     while ((skb = __skb_dequeue(&sk->sk_receive_queue)) != NULL) {
         u32 len = TCP_SKB_CB(skb)->end_seq - TCP_SKB_CB(skb)->seq;
 
         if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
             len--;
         data_was_unread += len;
         __kfree_skb(skb);
     }
 
     /* If socket has been already reset (e.g. in tcp_reset()) - kill it. */
     if (sk->sk_state == TCP_CLOSE)
         goto adjudge_to_death;
 
     /* As outlined in RFC 2525, section 2.17, we send a RST here because
      * data was lost. To witness the awful effects of the old behavior of
      * always doing a FIN, run an older 2.1.x kernel or 2.0.x, start a bulk
      * GET in an FTP client, suspend the process, wait for the client to
      * advertise a zero window, then kill -9 the FTP client, wheee...
      * Note: timeout is always zero in such a case.
      */
     if (unlikely(tcp_sk(sk)->repair)) {
         sk->sk_prot->disconnect(sk, 0);
     } else if (data_was_unread) {
         /* Unread data was tossed, zap the connection. */
         NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTONCLOSE);
         tcp_set_state(sk, TCP_CLOSE);
         tcp_send_active_reset(sk, sk->sk_allocation);
     } else if (sock_flag(sk, SOCK_LINGER) && !sk->sk_lingertime) {
         /* Check zero linger _after_ checking for unread data. */
         sk->sk_prot->disconnect(sk, 0);
         NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTONDATA);
     } else if (tcp_close_state(sk)) {
         /* We FIN if the application ate all the data before
          * zapping the connection.
          */
 
         /* RED-PEN. Formally speaking, we have broken TCP state
          * machine. State transitions:
          *
          * TCP_ESTABLISHED -> TCP_FIN_WAIT1
          * TCP_SYN_RECV -> TCP_FIN_WAIT1 (forget it, it's impossible)
          * TCP_CLOSE_WAIT -> TCP_LAST_ACK
          *
          * are legal only when FIN has been sent (i.e. in window),
          * rather than queued out of window. Purists blame.
          *
          * F.e. "RFC state" is ESTABLISHED,
          * if Linux state is FIN-WAIT-1, but FIN is still not sent.
          *
          * The visible declinations are that sometimes
          * we enter time-wait state, when it is not required really
          * (harmless), do not send active resets, when they are
          * required by specs (TCP_ESTABLISHED, TCP_CLOSE_WAIT, when
          * they look as CLOSING or LAST_ACK for Linux)
          * Probably, I missed some more holelets.
          *                      --ANK
          * XXX (TFO) - To start off we don't support SYN+ACK+FIN
          * in a single packet! (May consider it later but will
          * probably need API support or TCP_CORK SYN-ACK until
          * data is written and socket is closed.)
          */
         tcp_send_fin(sk);
     }
 
     sk_stream_wait_close(sk, timeout);
 
 adjudge_to_death:
     state = sk->sk_state;
     sock_hold(sk);
     sock_orphan(sk);
 
     local_bh_disable();
     bh_lock_sock(sk);
     /* remove backlog if any, without releasing ownership. */
     __release_sock(sk);
 
     this_cpu_inc(tcp_orphan_count);
 
     /* Have we already been destroyed by a softirq or backlog? */
     if (state != TCP_CLOSE && sk->sk_state == TCP_CLOSE)
         goto out;
 
     /*  This is a (useful) BSD violating of the RFC. There is a
      *  problem with TCP as specified in that the other end could
      *  keep a socket open forever with no application left this end.
      *  We use a 1 minute timeout (about the same as BSD) then kill
      *  our end. If they send after that then tough - BUT: long enough
      *  that we won't make the old 4*rto = almost no time - whoops
      *  reset mistake.
      *
      *  Nope, it was not mistake. It is really desired behaviour
      *  f.e. on http servers, when such sockets are useless, but
      *  consume significant resources. Let's do it with special
      *  linger2 option.                 --ANK
      */
 
     if (sk->sk_state == TCP_FIN_WAIT2) {
         struct tcp_sock *tp = tcp_sk(sk);
         if (tp->linger2 < 0) {
             tcp_set_state(sk, TCP_CLOSE);
             tcp_send_active_reset(sk, GFP_ATOMIC);
             __NET_INC_STATS(sock_net(sk),
                     LINUX_MIB_TCPABORTONLINGER);
         } else {
             const int tmo = tcp_fin_time(sk);
 
             if (tmo > TCP_TIMEWAIT_LEN) {
                 inet_csk_reset_keepalive_timer(sk,
                         tmo - TCP_TIMEWAIT_LEN);
             } else {
                 tcp_time_wait(sk, TCP_FIN_WAIT2, tmo);
                 goto out;
             }
         }
     }
     if (sk->sk_state != TCP_CLOSE) {
         if (tcp_check_oom(sk, 0)) {
             tcp_set_state(sk, TCP_CLOSE);
             tcp_send_active_reset(sk, GFP_ATOMIC);
             __NET_INC_STATS(sock_net(sk),
                     LINUX_MIB_TCPABORTONMEMORY);
         } else if (!check_net(sock_net(sk))) {
             /* Not possible to send reset; just close */
             tcp_set_state(sk, TCP_CLOSE);
         }
     }
 
     if (sk->sk_state == TCP_CLOSE) {
         struct request_sock *req;
 
         req = rcu_dereference_protected(tcp_sk(sk)->fastopen_rsk,
                         lockdep_sock_is_held(sk));
         /* We could get here with a non-NULL req if the socket is
          * aborted (e.g., closed with unread data) before 3WHS
          * finishes.
          */
         if (req)
             reqsk_fastopen_remove(sk, req, false);
         inet_csk_destroy_sock(sk);
     }
     /* Otherwise, socket is reprieved until protocol close. */
 
 out:
     bh_unlock_sock(sk);
     local_bh_enable();
 }
 
 void tcp_close(struct sock *sk, long timeout)
 {
     lock_sock(sk);
     __tcp_close(sk, timeout);
     release_sock(sk);
     sock_put(sk);
 }
 EXPORT_SYMBOL(tcp_close);
 
 /* These states need RST on ABORT according to RFC793 */
 
 static inline bool tcp_need_reset(int state)
 {
     return (1 << state) &
            (TCPF_ESTABLISHED | TCPF_CLOSE_WAIT | TCPF_FIN_WAIT1 |
         TCPF_FIN_WAIT2 | TCPF_SYN_RECV);
 }
 
 static void tcp_rtx_queue_purge(struct sock *sk)
 {
     struct rb_node *p = rb_first(&sk->tcp_rtx_queue);
 
     tcp_sk(sk)->highest_sack = NULL;
     while (p) {
         struct sk_buff *skb = rb_to_skb(p);
 
         p = rb_next(p);
         /* Since we are deleting whole queue, no need to
          * list_del(&skb->tcp_tsorted_anchor)
          */
         tcp_rtx_queue_unlink(skb, sk);
         tcp_wmem_free_skb(sk, skb);
     }
 }
 
 void tcp_write_queue_purge(struct sock *sk)
 {
     struct sk_buff *skb;
 
     tcp_chrono_stop(sk, TCP_CHRONO_BUSY);
     while ((skb = __skb_dequeue(&sk->sk_write_queue)) != NULL) {
         tcp_skb_tsorted_anchor_cleanup(skb);
         tcp_wmem_free_skb(sk, skb);
     }
     tcp_rtx_queue_purge(sk);
     INIT_LIST_HEAD(&tcp_sk(sk)->tsorted_sent_queue);
     tcp_clear_all_retrans_hints(tcp_sk(sk));
     tcp_sk(sk)->packets_out = 0;
     inet_csk(sk)->icsk_backoff = 0;
 }
 
 int tcp_disconnect(struct sock *sk, int flags)
 {
     struct inet_sock *inet = inet_sk(sk);
     struct inet_connection_sock *icsk = inet_csk(sk);
     struct tcp_sock *tp = tcp_sk(sk);
     int old_state = sk->sk_state;
     u32 seq;
 
     if (old_state != TCP_CLOSE)
         tcp_set_state(sk, TCP_CLOSE);
 
     /* ABORT function of RFC793 */
     if (old_state == TCP_LISTEN) {
         inet_csk_listen_stop(sk);
     } else if (unlikely(tp->repair)) {
         sk->sk_err = ECONNABORTED;
     } else if (tcp_need_reset(old_state) ||
            (tp->snd_nxt != tp->write_seq &&
             (1 << old_state) & (TCPF_CLOSING | TCPF_LAST_ACK))) {
         /* The last check adjusts for discrepancy of Linux wrt. RFC
          * states
          */
         tcp_send_active_reset(sk, gfp_any());
         sk->sk_err = ECONNRESET;
     } else if (old_state == TCP_SYN_SENT)
         sk->sk_err = ECONNRESET;
 
     tcp_clear_xmit_timers(sk);
     __skb_queue_purge(&sk->sk_receive_queue);
     WRITE_ONCE(tp->copied_seq, tp->rcv_nxt);
     WRITE_ONCE(tp->urg_data, 0);
     tcp_write_queue_purge(sk);
     tcp_fastopen_active_disable_ofo_check(sk);
     skb_rbtree_purge(&tp->out_of_order_queue);
 
     inet->inet_dport = 0;
 
     if (!(sk->sk_userlocks & SOCK_BINDADDR_LOCK))
         inet_reset_saddr(sk);
 
     sk->sk_shutdown = 0;
     sock_reset_flag(sk, SOCK_DONE);
     tp->srtt_us = 0;
     tp->mdev_us = jiffies_to_usecs(TCP_TIMEOUT_INIT);
     tp->rcv_rtt_last_tsecr = 0;
 
     seq = tp->write_seq + tp->max_window + 2;
     if (!seq)
         seq = 1;
     WRITE_ONCE(tp->write_seq, seq);
 
     icsk->icsk_backoff = 0;
     icsk->icsk_probes_out = 0;
     icsk->icsk_probes_tstamp = 0;
     icsk->icsk_rto = TCP_TIMEOUT_INIT;
     icsk->icsk_rto_min = TCP_RTO_MIN;
     icsk->icsk_delack_max = TCP_DELACK_MAX;
     tp->snd_ssthresh = TCP_INFINITE_SSTHRESH;
     tcp_snd_cwnd_set(tp, TCP_INIT_CWND);
     tp->snd_cwnd_cnt = 0;
     tp->window_clamp = 0;
     tp->delivered = 0;
     tp->delivered_ce = 0;
     if (icsk->icsk_ca_ops->release)
         icsk->icsk_ca_ops->release(sk);
     memset(icsk->icsk_ca_priv, 0, sizeof(icsk->icsk_ca_priv));
     icsk->icsk_ca_initialized = 0;
     tcp_set_ca_state(sk, TCP_CA_Open);
     tp->is_sack_reneg = 0;
     tcp_clear_retrans(tp);
     tp->total_retrans = 0;
     inet_csk_delack_init(sk);
     /* Initialize rcv_mss to TCP_MIN_MSS to avoid division by 0
      * issue in __tcp_select_window()
      */
     icsk->icsk_ack.rcv_mss = TCP_MIN_MSS;
     memset(&tp->rx_opt, 0, sizeof(tp->rx_opt));
     __sk_dst_reset(sk);
     dst_release(xchg((__force struct dst_entry **)&sk->sk_rx_dst, NULL));
     tcp_saved_syn_free(tp);
     tp->compressed_ack = 0;
     tp->segs_in = 0;
     tp->segs_out = 0;
     tp->bytes_sent = 0;
     tp->bytes_acked = 0;
     tp->bytes_received = 0;
     tp->bytes_retrans = 0;
     tp->data_segs_in = 0;
     tp->data_segs_out = 0;
     tp->duplicate_sack[0].start_seq = 0;
     tp->duplicate_sack[0].end_seq = 0;
     tp->dsack_dups = 0;
     tp->reord_seen = 0;
     tp->retrans_out = 0;
     tp->sacked_out = 0;
     tp->tlp_high_seq = 0;
     tp->last_oow_ack_time = 0;
     /* There's a bubble in the pipe until at least the first ACK. */
     tp->app_limited = ~0U;
     tp->rack.mstamp = 0;
     tp->rack.advanced = 0;
     tp->rack.reo_wnd_steps = 1;
     tp->rack.last_delivered = 0;
     tp->rack.reo_wnd_persist = 0;
     tp->rack.dsack_seen = 0;
     tp->syn_data_acked = 0;
     tp->rx_opt.saw_tstamp = 0;
     tp->rx_opt.dsack = 0;
     tp->rx_opt.num_sacks = 0;
     tp->rcv_ooopack = 0;
 
 
     /* Clean up fastopen related fields */
     tcp_free_fastopen_req(tp);
     inet->defer_connect = 0;
     tp->fastopen_client_fail = 0;
 
     WARN_ON(inet->inet_num && !icsk->icsk_bind_hash);
 
     if (sk->sk_frag.page) {
         put_page(sk->sk_frag.page);
         sk->sk_frag.page = NULL;
         sk->sk_frag.offset = 0;
     }
     sk_error_report(sk);
     return 0;
 }
 EXPORT_SYMBOL(tcp_disconnect);
 
 static inline bool tcp_can_repair_sock(const struct sock *sk)
 {
     return ns_capable(sock_net(sk)->user_ns, CAP_NET_ADMIN) &&
         (sk->sk_state != TCP_LISTEN);
 }
 
 static int tcp_repair_set_window(struct tcp_sock *tp, sockptr_t optbuf, int len)
 {
     struct tcp_repair_window opt;
 
     if (!tp->repair)
         return -EPERM;
 
     if (len != sizeof(opt))
         return -EINVAL;
 
     if (copy_from_sockptr(&opt, optbuf, sizeof(opt)))
         return -EFAULT;
 
     if (opt.max_window < opt.snd_wnd)
         return -EINVAL;
 
     if (after(opt.snd_wl1, tp->rcv_nxt + opt.rcv_wnd))
         return -EINVAL;
 
     if (after(opt.rcv_wup, tp->rcv_nxt))
         return -EINVAL;
 
     tp->snd_wl1 = opt.snd_wl1;
     tp->snd_wnd = opt.snd_wnd;
     tp->max_window  = opt.max_window;
 
     tp->rcv_wnd = opt.rcv_wnd;
     tp->rcv_wup = opt.rcv_wup;
 
     return 0;
 }
 
 static int tcp_repair_options_est(struct sock *sk, sockptr_t optbuf,
         unsigned int len)
 {
     struct tcp_sock *tp = tcp_sk(sk);
     struct tcp_repair_opt opt;
     size_t offset = 0;
 
     while (len >= sizeof(opt)) {
         if (copy_from_sockptr_offset(&opt, optbuf, offset, sizeof(opt)))
             return -EFAULT;
 
         offset += sizeof(opt);
         len -= sizeof(opt);
 
         switch (opt.opt_code) {
         case TCPOPT_MSS:
             tp->rx_opt.mss_clamp = opt.opt_val;
             tcp_mtup_init(sk);
             break;
         case TCPOPT_WINDOW:
             {
                 u16 snd_wscale = opt.opt_val & 0xFFFF;
                 u16 rcv_wscale = opt.opt_val >> 16;
 
                 if (snd_wscale > TCP_MAX_WSCALE || rcv_wscale > TCP_MAX_WSCALE)
                     return -EFBIG;
 
                 tp->rx_opt.snd_wscale = snd_wscale;
                 tp->rx_opt.rcv_wscale = rcv_wscale;
                 tp->rx_opt.wscale_ok = 1;
             }
             break;
         case TCPOPT_SACK_PERM:
             if (opt.opt_val != 0)
                 return -EINVAL;
 
             tp->rx_opt.sack_ok |= TCP_SACK_SEEN;
             break;
         case TCPOPT_TIMESTAMP:
             if (opt.opt_val != 0)
                 return -EINVAL;
 
             tp->rx_opt.tstamp_ok = 1;
             break;
         }
     }
 
     return 0;
 }
 
 DEFINE_STATIC_KEY_FALSE(tcp_tx_delay_enabled);
 EXPORT_SYMBOL(tcp_tx_delay_enabled);
 
 static void tcp_enable_tx_delay(void)
 {
     if (!static_branch_unlikely(&tcp_tx_delay_enabled)) {
         static int __tcp_tx_delay_enabled = 0;
 
         if (cmpxchg(&__tcp_tx_delay_enabled, 0, 1) == 0) {
             static_branch_enable(&tcp_tx_delay_enabled);
             pr_info("TCP_TX_DELAY enabled\n");
         }
     }
 }
 
 /* When set indicates to always queue non-full frames.  Later the user clears
  * this option and we transmit any pending partial frames in the queue.  This is
  * meant to be used alongside sendfile() to get properly filled frames when the
  * user (for example) must write out headers with a write() call first and then
  * use sendfile to send out the data parts.
  *
  * TCP_CORK can be set together with TCP_NODELAY and it is stronger than
  * TCP_NODELAY.
  */
 void __tcp_sock_set_cork(struct sock *sk, bool on)
 {
     struct tcp_sock *tp = tcp_sk(sk);
 
     if (on) {
         tp->nonagle |= TCP_NAGLE_CORK;
     } else {
         tp->nonagle &= ~TCP_NAGLE_CORK;
         if (tp->nonagle & TCP_NAGLE_OFF)
             tp->nonagle |= TCP_NAGLE_PUSH;
         tcp_push_pending_frames(sk);
     }
 }
 
 void tcp_sock_set_cork(struct sock *sk, bool on)
 {
     lock_sock(sk);
     __tcp_sock_set_cork(sk, on);
     release_sock(sk);
 }
 EXPORT_SYMBOL(tcp_sock_set_cork);
 
 /* TCP_NODELAY is weaker than TCP_CORK, so that this option on corked socket is
  * remembered, but it is not activated until cork is cleared.
  *
  * However, when TCP_NODELAY is set we make an explicit push, which overrides
  * even TCP_CORK for currently queued segments.
  */
 void __tcp_sock_set_nodelay(struct sock *sk, bool on)
 {
     if (on) {
         tcp_sk(sk)->nonagle |= TCP_NAGLE_OFF|TCP_NAGLE_PUSH;
         tcp_push_pending_frames(sk);
     } else {
         tcp_sk(sk)->nonagle &= ~TCP_NAGLE_OFF;
     }
 }
 
 void tcp_sock_set_nodelay(struct sock *sk)
 {
     lock_sock(sk);
     __tcp_sock_set_nodelay(sk, true);
     release_sock(sk);
 }
 EXPORT_SYMBOL(tcp_sock_set_nodelay);
 
 static void __tcp_sock_set_quickack(struct sock *sk, int val)
 {
     if (!val) {
         inet_csk_enter_pingpong_mode(sk);
         return;
     }
 
     inet_csk_exit_pingpong_mode(sk);
     if ((1 << sk->sk_state) & (TCPF_ESTABLISHED | TCPF_CLOSE_WAIT) &&
         inet_csk_ack_scheduled(sk)) {
         inet_csk(sk)->icsk_ack.pending |= ICSK_ACK_PUSHED;
         tcp_cleanup_rbuf(sk, 1);
         if (!(val & 1))
             inet_csk_enter_pingpong_mode(sk);
     }
 }
 
 void tcp_sock_set_quickack(struct sock *sk, int val)
 {
     lock_sock(sk);
     __tcp_sock_set_quickack(sk, val);
     release_sock(sk);
 }
 EXPORT_SYMBOL(tcp_sock_set_quickack);
 
 int tcp_sock_set_syncnt(struct sock *sk, int val)
 {
     if (val < 1 || val > MAX_TCP_SYNCNT)
         return -EINVAL;
 
     lock_sock(sk);
     inet_csk(sk)->icsk_syn_retries = val;
     release_sock(sk);
     return 0;
 }
 EXPORT_SYMBOL(tcp_sock_set_syncnt);
 
 void tcp_sock_set_user_timeout(struct sock *sk, u32 val)
 {
     lock_sock(sk);
     inet_csk(sk)->icsk_user_timeout = val;
     release_sock(sk);
 }
 EXPORT_SYMBOL(tcp_sock_set_user_timeout);
 
 int tcp_sock_set_keepidle_locked(struct sock *sk, int val)
 {
     struct tcp_sock *tp = tcp_sk(sk);
 
     if (val < 1 || val > MAX_TCP_KEEPIDLE)
         return -EINVAL;
 
     tp->keepalive_time = val * HZ;
     if (sock_flag(sk, SOCK_KEEPOPEN) &&
         !((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN))) {
         u32 elapsed = keepalive_time_elapsed(tp);
 
         if (tp->keepalive_time > elapsed)
             elapsed = tp->keepalive_time - elapsed;
         else
             elapsed = 0;
         inet_csk_reset_keepalive_timer(sk, elapsed);
     }
 
     return 0;
 }
 
 int tcp_sock_set_keepidle(struct sock *sk, int val)
 {
     int err;
 
     lock_sock(sk);
     err = tcp_sock_set_keepidle_locked(sk, val);
     release_sock(sk);
     return err;
 }
 EXPORT_SYMBOL(tcp_sock_set_keepidle);
 
 int tcp_sock_set_keepintvl(struct sock *sk, int val)
 {
     if (val < 1 || val > MAX_TCP_KEEPINTVL)
         return -EINVAL;
 
     lock_sock(sk);
     tcp_sk(sk)->keepalive_intvl = val * HZ;
     release_sock(sk);
     return 0;
 }
 EXPORT_SYMBOL(tcp_sock_set_keepintvl);
 
 int tcp_sock_set_keepcnt(struct sock *sk, int val)
 {
     if (val < 1 || val > MAX_TCP_KEEPCNT)
         return -EINVAL;
 
     lock_sock(sk);
     tcp_sk(sk)->keepalive_probes = val;
     release_sock(sk);
     return 0;
 }
 EXPORT_SYMBOL(tcp_sock_set_keepcnt);
 
 int tcp_set_window_clamp(struct sock *sk, int val)
 {
     struct tcp_sock *tp = tcp_sk(sk);
 
     if (!val) {
         if (sk->sk_state != TCP_CLOSE)
             return -EINVAL;
         tp->window_clamp = 0;
     } else {
         tp->window_clamp = val < SOCK_MIN_RCVBUF / 2 ?
             SOCK_MIN_RCVBUF / 2 : val;
         tp->rcv_ssthresh = min(tp->rcv_wnd, tp->window_clamp);
     }
     return 0;
 }
 
 /*
  *  Socket option code for TCP.
  */
 static int do_tcp_setsockopt(struct sock *sk, int level, int optname,
         sockptr_t optval, unsigned int optlen)
 {
     struct tcp_sock *tp = tcp_sk(sk);
     struct inet_connection_sock *icsk = inet_csk(sk);
     struct net *net = sock_net(sk);
     int val;
     int err = 0;
 
     /* These are data/string values, all the others are ints */
     switch (optname) {
     case TCP_CONGESTION: {
         char name[TCP_CA_NAME_MAX];
 
         if (optlen < 1)
             return -EINVAL;
 
         val = strncpy_from_sockptr(name, optval,
                     min_t(long, TCP_CA_NAME_MAX-1, optlen));
         if (val < 0)
             return -EFAULT;
         name[val] = 0;
 
         lock_sock(sk);
         err = tcp_set_congestion_control(sk, name, true,
                          ns_capable(sock_net(sk)->user_ns,
                                 CAP_NET_ADMIN));
         release_sock(sk);
         return err;
     }
     case TCP_ULP: {
         char name[TCP_ULP_NAME_MAX];
 
         if (optlen < 1)
             return -EINVAL;
 
         val = strncpy_from_sockptr(name, optval,
                     min_t(long, TCP_ULP_NAME_MAX - 1,
                           optlen));
         if (val < 0)
             return -EFAULT;
         name[val] = 0;
 
         lock_sock(sk);
         err = tcp_set_ulp(sk, name);
         release_sock(sk);
         return err;
     }
     case TCP_FASTOPEN_KEY: {
         __u8 key[TCP_FASTOPEN_KEY_BUF_LENGTH];
         __u8 *backup_key = NULL;
 
         /* Allow a backup key as well to facilitate key rotation
          * First key is the active one.
          */
         if (optlen != TCP_FASTOPEN_KEY_LENGTH &&
             optlen != TCP_FASTOPEN_KEY_BUF_LENGTH)
             return -EINVAL;
 
         if (copy_from_sockptr(key, optval, optlen))
             return -EFAULT;
 
         if (optlen == TCP_FASTOPEN_KEY_BUF_LENGTH)
             backup_key = key + TCP_FASTOPEN_KEY_LENGTH;
 
         return tcp_fastopen_reset_cipher(net, sk, key, backup_key);
     }
     default:
         /* fallthru */
         break;
     }
 
     if (optlen < sizeof(int))
         return -EINVAL;
 
     if (copy_from_sockptr(&val, optval, sizeof(val)))
         return -EFAULT;
 
     lock_sock(sk);
 
     switch (optname) {
     case TCP_MAXSEG:
         /* Values greater than interface MTU won't take effect. However
          * at the point when this call is done we typically don't yet
          * know which interface is going to be used
          */
         if (val && (val < TCP_MIN_MSS || val > MAX_TCP_WINDOW)) {
             err = -EINVAL;
             break;
         }
         tp->rx_opt.user_mss = val;
         break;
 
     case TCP_NODELAY:
         __tcp_sock_set_nodelay(sk, val);
         break;
 
     case TCP_THIN_LINEAR_TIMEOUTS:
         if (val < 0 || val > 1)
             err = -EINVAL;
         else
             tp->thin_lto = val;
         break;
 
     case TCP_THIN_DUPACK:
         if (val < 0 || val > 1)
             err = -EINVAL;
         break;
 
     case TCP_REPAIR:
         if (!tcp_can_repair_sock(sk))
             err = -EPERM;
         else if (val == TCP_REPAIR_ON) {
             tp->repair = 1;
             sk->sk_reuse = SK_FORCE_REUSE;
             tp->repair_queue = TCP_NO_QUEUE;
         } else if (val == TCP_REPAIR_OFF) {
             tp->repair = 0;
             sk->sk_reuse = SK_NO_REUSE;
             tcp_send_window_probe(sk);
         } else if (val == TCP_REPAIR_OFF_NO_WP) {
             tp->repair = 0;
             sk->sk_reuse = SK_NO_REUSE;
         } else
             err = -EINVAL;
 
         break;
 
     case TCP_REPAIR_QUEUE:
         if (!tp->repair)
             err = -EPERM;
         else if ((unsigned int)val < TCP_QUEUES_NR)
             tp->repair_queue = val;
         else
             err = -EINVAL;
         break;
 
     case TCP_QUEUE_SEQ:
         if (sk->sk_state != TCP_CLOSE) {
             err = -EPERM;
         } else if (tp->repair_queue == TCP_SEND_QUEUE) {
             if (!tcp_rtx_queue_empty(sk))
                 err = -EPERM;
             else
                 WRITE_ONCE(tp->write_seq, val);
         } else if (tp->repair_queue == TCP_RECV_QUEUE) {
             if (tp->rcv_nxt != tp->copied_seq) {
                 err = -EPERM;
             } else {
                 WRITE_ONCE(tp->rcv_nxt, val);
                 WRITE_ONCE(tp->copied_seq, val);
             }
         } else {
             err = -EINVAL;
         }
         break;
 
     case TCP_REPAIR_OPTIONS:
         if (!tp->repair)
             err = -EINVAL;
         else if (sk->sk_state == TCP_ESTABLISHED)
             err = tcp_repair_options_est(sk, optval, optlen);
         else
             err = -EPERM;
         break;
 
     case TCP_CORK:
         __tcp_sock_set_cork(sk, val);
         break;
 
     case TCP_KEEPIDLE:
         err = tcp_sock_set_keepidle_locked(sk, val);
         break;
     case TCP_KEEPINTVL:
         if (val < 1 || val > MAX_TCP_KEEPINTVL)
             err = -EINVAL;
         else
             tp->keepalive_intvl = val * HZ;
         break;
     case TCP_KEEPCNT:
         if (val < 1 || val > MAX_TCP_KEEPCNT)
             err = -EINVAL;
         else
             tp->keepalive_probes = val;
         break;
     case TCP_SYNCNT:
         if (val < 1 || val > MAX_TCP_SYNCNT)
             err = -EINVAL;
         else
             icsk->icsk_syn_retries = val;
         break;
 
     case TCP_SAVE_SYN:
         /* 0: disable, 1: enable, 2: start from ether_header */
         if (val < 0 || val > 2)
             err = -EINVAL;
         else
             tp->save_syn = val;
         break;
 
     case TCP_LINGER2:
         if (val < 0)
             tp->linger2 = -1;
         else if (val > TCP_FIN_TIMEOUT_MAX / HZ)
             tp->linger2 = TCP_FIN_TIMEOUT_MAX;
         else
             tp->linger2 = val * HZ;
         break;
 
     case TCP_DEFER_ACCEPT:
         /* Translate value in seconds to number of retransmits */
         icsk->icsk_accept_queue.rskq_defer_accept =
             secs_to_retrans(val, TCP_TIMEOUT_INIT / HZ,
                     TCP_RTO_MAX / HZ);
         break;
 
     case TCP_WINDOW_CLAMP:
         err = tcp_set_window_clamp(sk, val);
         break;
 
     case TCP_QUICKACK:
         __tcp_sock_set_quickack(sk, val);
         break;
 
 #ifdef CONFIG_TCP_MD5SIG
     case TCP_MD5SIG:
     case TCP_MD5SIG_EXT:
         err = tp->af_specific->md5_parse(sk, optname, optval, optlen);
         break;
 #endif
     case TCP_USER_TIMEOUT:
         /* Cap the max time in ms TCP will retry or probe the window
          * before giving up and aborting (ETIMEDOUT) a connection.
          */
         if (val < 0)
             err = -EINVAL;
         else
             icsk->icsk_user_timeout = val;
         break;
 
     case TCP_FASTOPEN:
         if (val >= 0 && ((1 << sk->sk_state) & (TCPF_CLOSE |
             TCPF_LISTEN))) {
             tcp_fastopen_init_key_once(net);
 
             fastopen_queue_tune(sk, val);
         } else {
             err = -EINVAL;
         }
         break;
     case TCP_FASTOPEN_CONNECT:
         if (val > 1 || val < 0) {
             err = -EINVAL;
         } else if (READ_ONCE(net->ipv4.sysctl_tcp_fastopen) &
                TFO_CLIENT_ENABLE) {
             if (sk->sk_state == TCP_CLOSE)
                 tp->fastopen_connect = val;
             else
                 err = -EINVAL;
         } else {
             err = -EOPNOTSUPP;
         }
         break;
     case TCP_FASTOPEN_NO_COOKIE:
         if (val > 1 || val < 0)
             err = -EINVAL;
         else if (!((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)))
             err = -EINVAL;
         else
             tp->fastopen_no_cookie = val;
         break;
     case TCP_TIMESTAMP:
         if (!tp->repair)
             err = -EPERM;
         else
             tp->tsoffset = val - tcp_time_stamp_raw();
         break;
     case TCP_REPAIR_WINDOW:
         err = tcp_repair_set_window(tp, optval, optlen);
         break;
     case TCP_NOTSENT_LOWAT:
         tp->notsent_lowat = val;
         sk->sk_write_space(sk);
         break;
     case TCP_INQ:
         if (val > 1 || val < 0)
             err = -EINVAL;
         else
             tp->recvmsg_inq = val;
         break;
     case TCP_TX_DELAY:
         if (val)
             tcp_enable_tx_delay();
         tp->tcp_tx_delay = val;
         break;
     default:
         err = -ENOPROTOOPT;
         break;
     }
 
     release_sock(sk);
     return err;
 }
 
 int tcp_setsockopt(struct sock *sk, int level, int optname, sockptr_t optval,
            unsigned int optlen)
 {
     const struct inet_connection_sock *icsk = inet_csk(sk);
 
     if (level != SOL_TCP)
         return icsk->icsk_af_ops->setsockopt(sk, level, optname,
                              optval, optlen);
     return do_tcp_setsockopt(sk, level, optname, optval, optlen);
 }
 EXPORT_SYMBOL(tcp_setsockopt);
 
 static void tcp_get_info_chrono_stats(const struct tcp_sock *tp,
                       struct tcp_info *info)
 {
     u64 stats[__TCP_CHRONO_MAX], total = 0;
     enum tcp_chrono i;
 
     for (i = TCP_CHRONO_BUSY; i < __TCP_CHRONO_MAX; ++i) {
         stats[i] = tp->chrono_stat[i - 1];
         if (i == tp->chrono_type)
             stats[i] += tcp_jiffies32 - tp->chrono_start;
         stats[i] *= USEC_PER_SEC / HZ;
         total += stats[i];
     }
 
     info->tcpi_busy_time = total;
     info->tcpi_rwnd_limited = stats[TCP_CHRONO_RWND_LIMITED];
     info->tcpi_sndbuf_limited = stats[TCP_CHRONO_SNDBUF_LIMITED];
 }
 
 /* Return information about state of tcp endpoint in API format. */
 void tcp_get_info(struct sock *sk, struct tcp_info *info)
 {
     const struct tcp_sock *tp = tcp_sk(sk); /* iff sk_type == SOCK_STREAM */
     const struct inet_connection_sock *icsk = inet_csk(sk);
     unsigned long rate;
     u32 now;
     u64 rate64;
     bool slow;
 
     memset(info, 0, sizeof(*info));
     if (sk->sk_type != SOCK_STREAM)
         return;
 
     info->tcpi_state = inet_sk_state_load(sk);
 
     /* Report meaningful fields for all TCP states, including listeners */
     rate = READ_ONCE(sk->sk_pacing_rate);
     rate64 = (rate != ~0UL) ? rate : ~0ULL;
     info->tcpi_pacing_rate = rate64;
 
     rate = READ_ONCE(sk->sk_max_pacing_rate);
     rate64 = (rate != ~0UL) ? rate : ~0ULL;
     info->tcpi_max_pacing_rate = rate64;
 
     info->tcpi_reordering = tp->reordering;
     info->tcpi_snd_cwnd = tcp_snd_cwnd(tp);
 
     if (info->tcpi_state == TCP_LISTEN) {
         /* listeners aliased fields :
          * tcpi_unacked -> Number of children ready for accept()
          * tcpi_sacked  -> max backlog
          */
         info->tcpi_unacked = READ_ONCE(sk->sk_ack_backlog);
         info->tcpi_sacked = READ_ONCE(sk->sk_max_ack_backlog);
         return;
     }
 
     slow = lock_sock_fast(sk);
 
     info->tcpi_ca_state = icsk->icsk_ca_state;
     info->tcpi_retransmits = icsk->icsk_retransmits;
     info->tcpi_probes = icsk->icsk_probes_out;
     info->tcpi_backoff = icsk->icsk_backoff;
 
     if (tp->rx_opt.tstamp_ok)
         info->tcpi_options |= TCPI_OPT_TIMESTAMPS;
     if (tcp_is_sack(tp))
         info->tcpi_options |= TCPI_OPT_SACK;
     if (tp->rx_opt.wscale_ok) {
         info->tcpi_options |= TCPI_OPT_WSCALE;
         info->tcpi_snd_wscale = tp->rx_opt.snd_wscale;
         info->tcpi_rcv_wscale = tp->rx_opt.rcv_wscale;
     }
 
     if (tp->ecn_flags & TCP_ECN_OK)
         info->tcpi_options |= TCPI_OPT_ECN;
     if (tp->ecn_flags & TCP_ECN_SEEN)
         info->tcpi_options |= TCPI_OPT_ECN_SEEN;
     if (tp->syn_data_acked)
         info->tcpi_options |= TCPI_OPT_SYN_DATA;
 
     info->tcpi_rto = jiffies_to_usecs(icsk->icsk_rto);
     info->tcpi_ato = jiffies_to_usecs(icsk->icsk_ack.ato);
     info->tcpi_snd_mss = tp->mss_cache;
     info->tcpi_rcv_mss = icsk->icsk_ack.rcv_mss;
 
     info->tcpi_unacked = tp->packets_out;
     info->tcpi_sacked = tp->sacked_out;
 
     info->tcpi_lost = tp->lost_out;
     info->tcpi_retrans = tp->retrans_out;
 
     now = tcp_jiffies32;
     info->tcpi_last_data_sent = jiffies_to_msecs(now - tp->lsndtime);
     info->tcpi_last_data_recv = jiffies_to_msecs(now - icsk->icsk_ack.lrcvtime);
     info->tcpi_last_ack_recv = jiffies_to_msecs(now - tp->rcv_tstamp);
 
     info->tcpi_pmtu = icsk->icsk_pmtu_cookie;
     info->tcpi_rcv_ssthresh = tp->rcv_ssthresh;
     info->tcpi_rtt = tp->srtt_us >> 3;
     info->tcpi_rttvar = tp->mdev_us >> 2;
     info->tcpi_snd_ssthresh = tp->snd_ssthresh;
     info->tcpi_advmss = tp->advmss;
 
     info->tcpi_rcv_rtt = tp->rcv_rtt_est.rtt_us >> 3;
     info->tcpi_rcv_space = tp->rcvq_space.space;
 
     info->tcpi_total_retrans = tp->total_retrans;
 
     info->tcpi_bytes_acked = tp->bytes_acked;
     info->tcpi_bytes_received = tp->bytes_received;
     info->tcpi_notsent_bytes = max_t(int, 0, tp->write_seq - tp->snd_nxt);
     tcp_get_info_chrono_stats(tp, info);
 
     info->tcpi_segs_out = tp->segs_out;
 
     /* segs_in and data_segs_in can be updated from tcp_segs_in() from BH */
     info->tcpi_segs_in = READ_ONCE(tp->segs_in);
     info->tcpi_data_segs_in = READ_ONCE(tp->data_segs_in);
 
     info->tcpi_min_rtt = tcp_min_rtt(tp);
     info->tcpi_data_segs_out = tp->data_segs_out;
 
     info->tcpi_delivery_rate_app_limited = tp->rate_app_limited ? 1 : 0;
     rate64 = tcp_compute_delivery_rate(tp);
     if (rate64)
         info->tcpi_delivery_rate = rate64;
     info->tcpi_delivered = tp->delivered;
     info->tcpi_delivered_ce = tp->delivered_ce;
     info->tcpi_bytes_sent = tp->bytes_sent;
     info->tcpi_bytes_retrans = tp->bytes_retrans;
     info->tcpi_dsack_dups = tp->dsack_dups;
     info->tcpi_reord_seen = tp->reord_seen;
     info->tcpi_rcv_ooopack = tp->rcv_ooopack;
     info->tcpi_snd_wnd = tp->snd_wnd;
     info->tcpi_fastopen_client_fail = tp->fastopen_client_fail;
     unlock_sock_fast(sk, slow);
 }
 EXPORT_SYMBOL_GPL(tcp_get_info);
 
 static size_t tcp_opt_stats_get_size(void)
 {
     return
         nla_total_size_64bit(sizeof(u64)) + /* TCP_NLA_BUSY */
         nla_total_size_64bit(sizeof(u64)) + /* TCP_NLA_RWND_LIMITED */
         nla_total_size_64bit(sizeof(u64)) + /* TCP_NLA_SNDBUF_LIMITED */
         nla_total_size_64bit(sizeof(u64)) + /* TCP_NLA_DATA_SEGS_OUT */
         nla_total_size_64bit(sizeof(u64)) + /* TCP_NLA_TOTAL_RETRANS */
         nla_total_size_64bit(sizeof(u64)) + /* TCP_NLA_PACING_RATE */
         nla_total_size_64bit(sizeof(u64)) + /* TCP_NLA_DELIVERY_RATE */
         nla_total_size(sizeof(u32)) + /* TCP_NLA_SND_CWND */
         nla_total_size(sizeof(u32)) + /* TCP_NLA_REORDERING */
         nla_total_size(sizeof(u32)) + /* TCP_NLA_MIN_RTT */
         nla_total_size(sizeof(u8)) + /* TCP_NLA_RECUR_RETRANS */
         nla_total_size(sizeof(u8)) + /* TCP_NLA_DELIVERY_RATE_APP_LMT */
         nla_total_size(sizeof(u32)) + /* TCP_NLA_SNDQ_SIZE */
         nla_total_size(sizeof(u8)) + /* TCP_NLA_CA_STATE */
         nla_total_size(sizeof(u32)) + /* TCP_NLA_SND_SSTHRESH */
         nla_total_size(sizeof(u32)) + /* TCP_NLA_DELIVERED */
         nla_total_size(sizeof(u32)) + /* TCP_NLA_DELIVERED_CE */
         nla_total_size_64bit(sizeof(u64)) + /* TCP_NLA_BYTES_SENT */
         nla_total_size_64bit(sizeof(u64)) + /* TCP_NLA_BYTES_RETRANS */
         nla_total_size(sizeof(u32)) + /* TCP_NLA_DSACK_DUPS */
         nla_total_size(sizeof(u32)) + /* TCP_NLA_REORD_SEEN */
         nla_total_size(sizeof(u32)) + /* TCP_NLA_SRTT */
         nla_total_size(sizeof(u16)) + /* TCP_NLA_TIMEOUT_REHASH */
         nla_total_size(sizeof(u32)) + /* TCP_NLA_BYTES_NOTSENT */
         nla_total_size_64bit(sizeof(u64)) + /* TCP_NLA_EDT */
         nla_total_size(sizeof(u8)) + /* TCP_NLA_TTL */
         0;
 }
 
 /* Returns TTL or hop limit of an incoming packet from skb. */
 static u8 tcp_skb_ttl_or_hop_limit(const struct sk_buff *skb)
 {
     if (skb->protocol == htons(ETH_P_IP))
         return ip_hdr(skb)->ttl;
     else if (skb->protocol == htons(ETH_P_IPV6))
         return ipv6_hdr(skb)->hop_limit;
     else
         return 0;
 }
 
 struct sk_buff *tcp_get_timestamping_opt_stats(const struct sock *sk,
                            const struct sk_buff *orig_skb,
                            const struct sk_buff *ack_skb)
 {
     const struct tcp_sock *tp = tcp_sk(sk);
     struct sk_buff *stats;
     struct tcp_info info;
     unsigned long rate;
     u64 rate64;
 
     stats = alloc_skb(tcp_opt_stats_get_size(), GFP_ATOMIC);
     if (!stats)
         return NULL;
 
     tcp_get_info_chrono_stats(tp, &info);
     nla_put_u64_64bit(stats, TCP_NLA_BUSY,
               info.tcpi_busy_time, TCP_NLA_PAD);
     nla_put_u64_64bit(stats, TCP_NLA_RWND_LIMITED,
               info.tcpi_rwnd_limited, TCP_NLA_PAD);
     nla_put_u64_64bit(stats, TCP_NLA_SNDBUF_LIMITED,
               info.tcpi_sndbuf_limited, TCP_NLA_PAD);
     nla_put_u64_64bit(stats, TCP_NLA_DATA_SEGS_OUT,
               tp->data_segs_out, TCP_NLA_PAD);
     nla_put_u64_64bit(stats, TCP_NLA_TOTAL_RETRANS,
               tp->total_retrans, TCP_NLA_PAD);
 
     rate = READ_ONCE(sk->sk_pacing_rate);
     rate64 = (rate != ~0UL) ? rate : ~0ULL;
     nla_put_u64_64bit(stats, TCP_NLA_PACING_RATE, rate64, TCP_NLA_PAD);
 
     rate64 = tcp_compute_delivery_rate(tp);
     nla_put_u64_64bit(stats, TCP_NLA_DELIVERY_RATE, rate64, TCP_NLA_PAD);
 
     nla_put_u32(stats, TCP_NLA_SND_CWND, tcp_snd_cwnd(tp));
     nla_put_u32(stats, TCP_NLA_REORDERING, tp->reordering);
     nla_put_u32(stats, TCP_NLA_MIN_RTT, tcp_min_rtt(tp));
 
     nla_put_u8(stats, TCP_NLA_RECUR_RETRANS, inet_csk(sk)->icsk_retransmits);
     nla_put_u8(stats, TCP_NLA_DELIVERY_RATE_APP_LMT, !!tp->rate_app_limited);
     nla_put_u32(stats, TCP_NLA_SND_SSTHRESH, tp->snd_ssthresh);
     nla_put_u32(stats, TCP_NLA_DELIVERED, tp->delivered);
     nla_put_u32(stats, TCP_NLA_DELIVERED_CE, tp->delivered_ce);
 
     nla_put_u32(stats, TCP_NLA_SNDQ_SIZE, tp->write_seq - tp->snd_una);
     nla_put_u8(stats, TCP_NLA_CA_STATE, inet_csk(sk)->icsk_ca_state);
 
     nla_put_u64_64bit(stats, TCP_NLA_BYTES_SENT, tp->bytes_sent,
               TCP_NLA_PAD);
     nla_put_u64_64bit(stats, TCP_NLA_BYTES_RETRANS, tp->bytes_retrans,
               TCP_NLA_PAD);
     nla_put_u32(stats, TCP_NLA_DSACK_DUPS, tp->dsack_dups);
     nla_put_u32(stats, TCP_NLA_REORD_SEEN, tp->reord_seen);
     nla_put_u32(stats, TCP_NLA_SRTT, tp->srtt_us >> 3);
     nla_put_u16(stats, TCP_NLA_TIMEOUT_REHASH, tp->timeout_rehash);
     nla_put_u32(stats, TCP_NLA_BYTES_NOTSENT,
             max_t(int, 0, tp->write_seq - tp->snd_nxt));
     nla_put_u64_64bit(stats, TCP_NLA_EDT, orig_skb->skb_mstamp_ns,
               TCP_NLA_PAD);
     if (ack_skb)
         nla_put_u8(stats, TCP_NLA_TTL,
                tcp_skb_ttl_or_hop_limit(ack_skb));
 
     return stats;
 }
 
 static int do_tcp_getsockopt(struct sock *sk, int level,
         int optname, char __user *optval, int __user *optlen)
 {
     struct inet_connection_sock *icsk = inet_csk(sk);
     struct tcp_sock *tp = tcp_sk(sk);
     struct net *net = sock_net(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 TCP_MAXSEG:
         val = tp->mss_cache;
         if (!val && ((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)))
             val = tp->rx_opt.user_mss;
         if (tp->repair)
             val = tp->rx_opt.mss_clamp;
         break;
     case TCP_NODELAY:
         val = !!(tp->nonagle&TCP_NAGLE_OFF);
         break;
     case TCP_CORK:
         val = !!(tp->nonagle&TCP_NAGLE_CORK);
         break;
     case TCP_KEEPIDLE:
         val = keepalive_time_when(tp) / HZ;
         break;
     case TCP_KEEPINTVL:
         val = keepalive_intvl_when(tp) / HZ;
         break;
     case TCP_KEEPCNT:
         val = keepalive_probes(tp);
         break;
     case TCP_SYNCNT:
         val = icsk->icsk_syn_retries ? :
             READ_ONCE(net->ipv4.sysctl_tcp_syn_retries);
         break;
     case TCP_LINGER2:
         val = tp->linger2;
         if (val >= 0)
             val = (val ? : READ_ONCE(net->ipv4.sysctl_tcp_fin_timeout)) / HZ;
         break;
     case TCP_DEFER_ACCEPT:
         val = retrans_to_secs(icsk->icsk_accept_queue.rskq_defer_accept,
                       TCP_TIMEOUT_INIT / HZ, TCP_RTO_MAX / HZ);
         break;
     case TCP_WINDOW_CLAMP:
         val = tp->window_clamp;
         break;
     case TCP_INFO: {
         struct tcp_info info;
 
         if (get_user(len, optlen))
             return -EFAULT;
 
         tcp_get_info(sk, &info);
 
         len = min_t(unsigned int, len, sizeof(info));
         if (put_user(len, optlen))
             return -EFAULT;
         if (copy_to_user(optval, &info, len))
             return -EFAULT;
         return 0;
     }
     case TCP_CC_INFO: {
         const struct tcp_congestion_ops *ca_ops;
         union tcp_cc_info info;
         size_t sz = 0;
         int attr;
 
         if (get_user(len, optlen))
             return -EFAULT;
 
         ca_ops = icsk->icsk_ca_ops;
         if (ca_ops && ca_ops->get_info)
             sz = ca_ops->get_info(sk, ~0U, &attr, &info);
 
         len = min_t(unsigned int, len, sz);
         if (put_user(len, optlen))
             return -EFAULT;
         if (copy_to_user(optval, &info, len))
             return -EFAULT;
         return 0;
     }
     case TCP_QUICKACK:
         val = !inet_csk_in_pingpong_mode(sk);
         break;
 
     case TCP_CONGESTION:
         if (get_user(len, optlen))
             return -EFAULT;
         len = min_t(unsigned int, len, TCP_CA_NAME_MAX);
         if (put_user(len, optlen))
             return -EFAULT;
         if (copy_to_user(optval, icsk->icsk_ca_ops->name, len))
             return -EFAULT;
         return 0;
 
     case TCP_ULP:
         if (get_user(len, optlen))
             return -EFAULT;
         len = min_t(unsigned int, len, TCP_ULP_NAME_MAX);
         if (!icsk->icsk_ulp_ops) {
             if (put_user(0, optlen))
                 return -EFAULT;
             return 0;
         }
         if (put_user(len, optlen))
             return -EFAULT;
         if (copy_to_user(optval, icsk->icsk_ulp_ops->name, len))
             return -EFAULT;
         return 0;
 
     case TCP_FASTOPEN_KEY: {
         u64 key[TCP_FASTOPEN_KEY_BUF_LENGTH / sizeof(u64)];
         unsigned int key_len;
 
         if (get_user(len, optlen))
             return -EFAULT;
 
         key_len = tcp_fastopen_get_cipher(net, icsk, key) *
                 TCP_FASTOPEN_KEY_LENGTH;
         len = min_t(unsigned int, len, key_len);
         if (put_user(len, optlen))
             return -EFAULT;
         if (copy_to_user(optval, key, len))
             return -EFAULT;
         return 0;
     }
     case TCP_THIN_LINEAR_TIMEOUTS:
         val = tp->thin_lto;
         break;
 
     case TCP_THIN_DUPACK:
         val = 0;
         break;
 
     case TCP_REPAIR:
         val = tp->repair;
         break;
 
     case TCP_REPAIR_QUEUE:
         if (tp->repair)
             val = tp->repair_queue;
         else
             return -EINVAL;
         break;
 
     case TCP_REPAIR_WINDOW: {
         struct tcp_repair_window opt;
 
         if (get_user(len, optlen))
             return -EFAULT;
 
         if (len != sizeof(opt))
             return -EINVAL;
 
         if (!tp->repair)
             return -EPERM;
 
         opt.snd_wl1 = tp->snd_wl1;
         opt.snd_wnd = tp->snd_wnd;
         opt.max_window  = tp->max_window;
         opt.rcv_wnd = tp->rcv_wnd;
         opt.rcv_wup = tp->rcv_wup;
 
         if (copy_to_user(optval, &opt, len))
             return -EFAULT;
         return 0;
     }
     case TCP_QUEUE_SEQ:
         if (tp->repair_queue == TCP_SEND_QUEUE)
             val = tp->write_seq;
         else if (tp->repair_queue == TCP_RECV_QUEUE)
             val = tp->rcv_nxt;
         else
             return -EINVAL;
         break;
 
     case TCP_USER_TIMEOUT:
         val = icsk->icsk_user_timeout;
         break;
 
     case TCP_FASTOPEN:
         val = icsk->icsk_accept_queue.fastopenq.max_qlen;
         break;
 
     case TCP_FASTOPEN_CONNECT:
         val = tp->fastopen_connect;
         break;
 
     case TCP_FASTOPEN_NO_COOKIE:
         val = tp->fastopen_no_cookie;
         break;
 
     case TCP_TX_DELAY:
         val = tp->tcp_tx_delay;
         break;
 
     case TCP_TIMESTAMP:
         val = tcp_time_stamp_raw() + tp->tsoffset;
         break;
     case TCP_NOTSENT_LOWAT:
         val = tp->notsent_lowat;
         break;
     case TCP_INQ:
         val = tp->recvmsg_inq;
         break;
     case TCP_SAVE_SYN:
         val = tp->save_syn;
         break;
     case TCP_SAVED_SYN: {
         if (get_user(len, optlen))
             return -EFAULT;
 
         lock_sock(sk);
         if (tp->saved_syn) {
             if (len < tcp_saved_syn_len(tp->saved_syn)) {
                 if (put_user(tcp_saved_syn_len(tp->saved_syn),
                          optlen)) {
                     release_sock(sk);
                     return -EFAULT;
                 }
                 release_sock(sk);
                 return -EINVAL;
             }
             len = tcp_saved_syn_len(tp->saved_syn);
             if (put_user(len, optlen)) {
                 release_sock(sk);
                 return -EFAULT;
             }
             if (copy_to_user(optval, tp->saved_syn->data, len)) {
                 release_sock(sk);
                 return -EFAULT;
             }
             tcp_saved_syn_free(tp);
             release_sock(sk);
         } else {
             release_sock(sk);
             len = 0;
             if (put_user(len, optlen))
                 return -EFAULT;
         }
         return 0;
     }
 #ifdef CONFIG_MMU
     case TCP_ZEROCOPY_RECEIVE: {
         struct scm_timestamping_internal tss;
         struct tcp_zerocopy_receive zc = {};
         int err;
 
         if (get_user(len, optlen))
             return -EFAULT;
         if (len < 0 ||
             len < offsetofend(struct tcp_zerocopy_receive, length))
             return -EINVAL;
         if (unlikely(len > sizeof(zc))) {
             err = check_zeroed_user(optval + sizeof(zc),
                         len - sizeof(zc));
             if (err < 1)
                 return err == 0 ? -EINVAL : err;
             len = sizeof(zc);
             if (put_user(len, optlen))
                 return -EFAULT;
         }
         if (copy_from_user(&zc, optval, len))
             return -EFAULT;
         if (zc.reserved)
             return -EINVAL;
         if (zc.msg_flags &  ~(TCP_VALID_ZC_MSG_FLAGS))
             return -EINVAL;
         lock_sock(sk);
         err = tcp_zerocopy_receive(sk, &zc, &tss);
         err = BPF_CGROUP_RUN_PROG_GETSOCKOPT_KERN(sk, level, optname,
                               &zc, &len, err);
         release_sock(sk);
         if (len >= offsetofend(struct tcp_zerocopy_receive, msg_flags))
             goto zerocopy_rcv_cmsg;
         switch (len) {
         case offsetofend(struct tcp_zerocopy_receive, msg_flags):
             goto zerocopy_rcv_cmsg;
         case offsetofend(struct tcp_zerocopy_receive, msg_controllen):
         case offsetofend(struct tcp_zerocopy_receive, msg_control):
         case offsetofend(struct tcp_zerocopy_receive, flags):
         case offsetofend(struct tcp_zerocopy_receive, copybuf_len):
         case offsetofend(struct tcp_zerocopy_receive, copybuf_address):
         case offsetofend(struct tcp_zerocopy_receive, err):
             goto zerocopy_rcv_sk_err;
         case offsetofend(struct tcp_zerocopy_receive, inq):
             goto zerocopy_rcv_inq;
         case offsetofend(struct tcp_zerocopy_receive, length):
         default:
             goto zerocopy_rcv_out;
         }
 zerocopy_rcv_cmsg:
         if (zc.msg_flags & TCP_CMSG_TS)
             tcp_zc_finalize_rx_tstamp(sk, &zc, &tss);
         else
             zc.msg_flags = 0;
 zerocopy_rcv_sk_err:
         if (!err)
             zc.err = sock_error(sk);
 zerocopy_rcv_inq:
         zc.inq = tcp_inq_hint(sk);
 zerocopy_rcv_out:
         if (!err && copy_to_user(optval, &zc, len))
             err = -EFAULT;
         return err;
     }
 #endif
     default:
         return -ENOPROTOOPT;
     }
 
     if (put_user(len, optlen))
         return -EFAULT;
     if (copy_to_user(optval, &val, len))
         return -EFAULT;
     return 0;
 }
 
 bool tcp_bpf_bypass_getsockopt(int level, int optname)
 {
     /* TCP do_tcp_getsockopt has optimized getsockopt implementation
      * to avoid extra socket lock for TCP_ZEROCOPY_RECEIVE.
      */
     if (level == SOL_TCP && optname == TCP_ZEROCOPY_RECEIVE)
         return true;
 
     return false;
 }
 EXPORT_SYMBOL(tcp_bpf_bypass_getsockopt);
 
 int tcp_getsockopt(struct sock *sk, int level, int optname, char __user *optval,
            int __user *optlen)
 {
     struct inet_connection_sock *icsk = inet_csk(sk);
 
     if (level != SOL_TCP)
         return icsk->icsk_af_ops->getsockopt(sk, level, optname,
                              optval, optlen);
     return do_tcp_getsockopt(sk, level, optname, optval, optlen);
 }
 EXPORT_SYMBOL(tcp_getsockopt);
 
 #ifdef CONFIG_TCP_MD5SIG
 static DEFINE_PER_CPU(struct tcp_md5sig_pool, tcp_md5sig_pool);
 static DEFINE_MUTEX(tcp_md5sig_mutex);
 static bool tcp_md5sig_pool_populated = false;
 
 static void __tcp_alloc_md5sig_pool(void)
 {
     struct crypto_ahash *hash;
     int cpu;
 
     hash = crypto_alloc_ahash("md5", 0, CRYPTO_ALG_ASYNC);
     if (IS_ERR(hash))
         return;
 
     for_each_possible_cpu(cpu) {
         void *scratch = per_cpu(tcp_md5sig_pool, cpu).scratch;
         struct ahash_request *req;
 
         if (!scratch) {
             scratch = kmalloc_node(sizeof(union tcp_md5sum_block) +
                            sizeof(struct tcphdr),
                            GFP_KERNEL,
                            cpu_to_node(cpu));
             if (!scratch)
                 return;
             per_cpu(tcp_md5sig_pool, cpu).scratch = scratch;
         }
         if (per_cpu(tcp_md5sig_pool, cpu).md5_req)
             continue;
 
         req = ahash_request_alloc(hash, GFP_KERNEL);
         if (!req)
             return;
 
         ahash_request_set_callback(req, 0, NULL, NULL);
 
         per_cpu(tcp_md5sig_pool, cpu).md5_req = req;
     }
     /* before setting tcp_md5sig_pool_populated, we must commit all writes
      * to memory. See smp_rmb() in tcp_get_md5sig_pool()
      */
     smp_wmb();
     tcp_md5sig_pool_populated = true;
 }
 
 bool tcp_alloc_md5sig_pool(void)
 {
     if (unlikely(!tcp_md5sig_pool_populated)) {
         mutex_lock(&tcp_md5sig_mutex);
 
         if (!tcp_md5sig_pool_populated) {
             __tcp_alloc_md5sig_pool();
             if (tcp_md5sig_pool_populated)
                 static_branch_inc(&tcp_md5_needed);
         }
 
         mutex_unlock(&tcp_md5sig_mutex);
     }
     return tcp_md5sig_pool_populated;
 }
 EXPORT_SYMBOL(tcp_alloc_md5sig_pool);
 
 
 /**
  *  tcp_get_md5sig_pool - get md5sig_pool for this user
  *
  *  We use percpu structure, so if we succeed, we exit with preemption
  *  and BH disabled, to make sure another thread or softirq handling
  *  wont try to get same context.
  */
 struct tcp_md5sig_pool *tcp_get_md5sig_pool(void)
 {
     local_bh_disable();
 
     if (tcp_md5sig_pool_populated) {
         /* coupled with smp_wmb() in __tcp_alloc_md5sig_pool() */
         smp_rmb();
         return this_cpu_ptr(&tcp_md5sig_pool);
     }
     local_bh_enable();
     return NULL;
 }
 EXPORT_SYMBOL(tcp_get_md5sig_pool);
 
 int tcp_md5_hash_skb_data(struct tcp_md5sig_pool *hp,
               const struct sk_buff *skb, unsigned int header_len)
 {
     struct scatterlist sg;
     const struct tcphdr *tp = tcp_hdr(skb);
     struct ahash_request *req = hp->md5_req;
     unsigned int i;
     const unsigned int head_data_len = skb_headlen(skb) > header_len ?
                        skb_headlen(skb) - header_len : 0;
     const struct skb_shared_info *shi = skb_shinfo(skb);
     struct sk_buff *frag_iter;
 
     sg_init_table(&sg, 1);
 
     sg_set_buf(&sg, ((u8 *) tp) + header_len, head_data_len);
     ahash_request_set_crypt(req, &sg, NULL, head_data_len);
     if (crypto_ahash_update(req))
         return 1;
 
     for (i = 0; i < shi->nr_frags; ++i) {
         const skb_frag_t *f = &shi->frags[i];
         unsigned int offset = skb_frag_off(f);
         struct page *page = skb_frag_page(f) + (offset >> PAGE_SHIFT);
 
         sg_set_page(&sg, page, skb_frag_size(f),
                 offset_in_page(offset));
         ahash_request_set_crypt(req, &sg, NULL, skb_frag_size(f));
         if (crypto_ahash_update(req))
             return 1;
     }
 
     skb_walk_frags(skb, frag_iter)
         if (tcp_md5_hash_skb_data(hp, frag_iter, 0))
             return 1;
 
     return 0;
 }
 EXPORT_SYMBOL(tcp_md5_hash_skb_data);
 
 int tcp_md5_hash_key(struct tcp_md5sig_pool *hp, const struct tcp_md5sig_key *key)
 {
     u8 keylen = READ_ONCE(key->keylen); /* paired with WRITE_ONCE() in tcp_md5_do_add */
     struct scatterlist sg;
 
     sg_init_one(&sg, key->key, keylen);
     ahash_request_set_crypt(hp->md5_req, &sg, NULL, keylen);
 
     /* We use data_race() because tcp_md5_do_add() might change key->key under us */
     return data_race(crypto_ahash_update(hp->md5_req));
 }
 EXPORT_SYMBOL(tcp_md5_hash_key);
 
 /* Called with rcu_read_lock() */
 enum skb_drop_reason
 tcp_inbound_md5_hash(const struct sock *sk, const struct sk_buff *skb,
              const void *saddr, const void *daddr,
              int family, int dif, int sdif)
 {
     /*
      * This gets called for each TCP segment that arrives
      * so we want to be efficient.
      * We have 3 drop cases:
      * o No MD5 hash and one expected.
      * o MD5 hash and we're not expecting one.
      * o MD5 hash and its wrong.
      */
     const __u8 *hash_location = NULL;
     struct tcp_md5sig_key *hash_expected;
     const struct tcphdr *th = tcp_hdr(skb);
     struct tcp_sock *tp = tcp_sk(sk);
     int genhash, l3index;
     u8 newhash[16];
 
     /* sdif set, means packet ingressed via a device
      * in an L3 domain and dif is set to the l3mdev
      */
     l3index = sdif ? dif : 0;
 
     hash_expected = tcp_md5_do_lookup(sk, l3index, saddr, family);
     hash_location = tcp_parse_md5sig_option(th);
 
     /* We've parsed the options - do we have a hash? */
     if (!hash_expected && !hash_location)
         return SKB_NOT_DROPPED_YET;
 
     if (hash_expected && !hash_location) {
         NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPMD5NOTFOUND);
         return SKB_DROP_REASON_TCP_MD5NOTFOUND;
     }
 
     if (!hash_expected && hash_location) {
         NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPMD5UNEXPECTED);
         return SKB_DROP_REASON_TCP_MD5UNEXPECTED;
     }
 
     /* Check the signature.
      * To support dual stack listeners, we need to handle
      * IPv4-mapped case.
      */
     if (family == AF_INET)
         genhash = tcp_v4_md5_hash_skb(newhash,
                           hash_expected,
                           NULL, skb);
     else
         genhash = tp->af_specific->calc_md5_hash(newhash,
                              hash_expected,
                              NULL, skb);
 
     if (genhash || memcmp(hash_location, newhash, 16) != 0) {
         NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPMD5FAILURE);
         if (family == AF_INET) {
             net_info_ratelimited("MD5 Hash failed for (%pI4, %d)->(%pI4, %d)%s L3 index %d\n",
                     saddr, ntohs(th->source),
                     daddr, ntohs(th->dest),
                     genhash ? " tcp_v4_calc_md5_hash failed"
                     : "", l3index);
         } else {
             net_info_ratelimited("MD5 Hash %s for [%pI6c]:%u->[%pI6c]:%u L3 index %d\n",
                     genhash ? "failed" : "mismatch",
                     saddr, ntohs(th->source),
                     daddr, ntohs(th->dest), l3index);
         }
         return SKB_DROP_REASON_TCP_MD5FAILURE;
     }
     return SKB_NOT_DROPPED_YET;
 }
 EXPORT_SYMBOL(tcp_inbound_md5_hash);
 
 #endif
 
 void tcp_done(struct sock *sk)
 {
     struct request_sock *req;
 
     /* We might be called with a new socket, after
      * inet_csk_prepare_forced_close() has been called
      * so we can not use lockdep_sock_is_held(sk)
      */
     req = rcu_dereference_protected(tcp_sk(sk)->fastopen_rsk, 1);
 
     if (sk->sk_state == TCP_SYN_SENT || sk->sk_state == TCP_SYN_RECV)
         TCP_INC_STATS(sock_net(sk), TCP_MIB_ATTEMPTFAILS);
 
     tcp_set_state(sk, TCP_CLOSE);
     tcp_clear_xmit_timers(sk);
     if (req)
         reqsk_fastopen_remove(sk, req, false);
 
     sk->sk_shutdown = SHUTDOWN_MASK;
 
     if (!sock_flag(sk, SOCK_DEAD))
         sk->sk_state_change(sk);
     else
         inet_csk_destroy_sock(sk);
 }
 EXPORT_SYMBOL_GPL(tcp_done);
 
 int tcp_abort(struct sock *sk, int err)
 {
     int state = inet_sk_state_load(sk);
 
     if (state == TCP_NEW_SYN_RECV) {
         struct request_sock *req = inet_reqsk(sk);
 
         local_bh_disable();
         inet_csk_reqsk_queue_drop(req->rsk_listener, req);
         local_bh_enable();
         return 0;
     }
     if (state == TCP_TIME_WAIT) {
         struct inet_timewait_sock *tw = inet_twsk(sk);
 
         refcount_inc(&tw->tw_refcnt);
         local_bh_disable();
         inet_twsk_deschedule_put(tw);
         local_bh_enable();
         return 0;
     }
 
     /* Don't race with userspace socket closes such as tcp_close. */
     lock_sock(sk);
 
     if (sk->sk_state == TCP_LISTEN) {
         tcp_set_state(sk, TCP_CLOSE);
         inet_csk_listen_stop(sk);
     }
 
     /* Don't race with BH socket closes such as inet_csk_listen_stop. */
     local_bh_disable();
     bh_lock_sock(sk);
 
     if (!sock_flag(sk, SOCK_DEAD)) {
         sk->sk_err = err;
         /* This barrier is coupled with smp_rmb() in tcp_poll() */
         smp_wmb();
         sk_error_report(sk);
         if (tcp_need_reset(sk->sk_state))
             tcp_send_active_reset(sk, GFP_ATOMIC);
         tcp_done(sk);
     }
 
     bh_unlock_sock(sk);
     local_bh_enable();
     tcp_write_queue_purge(sk);
     release_sock(sk);
     return 0;
 }
 EXPORT_SYMBOL_GPL(tcp_abort);
 
 extern struct tcp_congestion_ops tcp_reno;
 
 static __initdata unsigned long thash_entries;
 static int __init set_thash_entries(char *str)
 {
     ssize_t ret;
 
     if (!str)
         return 0;
 
     ret = kstrtoul(str, 0, &thash_entries);
     if (ret)
         return 0;
 
     return 1;
 }
 __setup("thash_entries=", set_thash_entries);
 
 static void __init tcp_init_mem(void)
 {
     unsigned long limit = nr_free_buffer_pages() / 16;
 
     limit = max(limit, 128UL);
     sysctl_tcp_mem[0] = limit / 4 * 3;      /* 4.68 % */
     sysctl_tcp_mem[1] = limit;          /* 6.25 % */
     sysctl_tcp_mem[2] = sysctl_tcp_mem[0] * 2;  /* 9.37 % */
 }
 
 void __init tcp_init(void)
 {
     int max_rshare, max_wshare, cnt;
     unsigned long limit;
     unsigned int i;
 
     BUILD_BUG_ON(TCP_MIN_SND_MSS <= MAX_TCP_OPTION_SPACE);
     BUILD_BUG_ON(sizeof(struct tcp_skb_cb) >
              sizeof_field(struct sk_buff, cb));
 
     percpu_counter_init(&tcp_sockets_allocated, 0, GFP_KERNEL);
 
     timer_setup(&tcp_orphan_timer, tcp_orphan_update, TIMER_DEFERRABLE);
     mod_timer(&tcp_orphan_timer, jiffies + TCP_ORPHAN_TIMER_PERIOD);
 
     inet_hashinfo2_init(&tcp_hashinfo, "tcp_listen_portaddr_hash",
                 thash_entries, 21,  /* one slot per 2 MB*/
                 0, 64 * 1024);
     tcp_hashinfo.bind_bucket_cachep =
         kmem_cache_create("tcp_bind_bucket",
                   sizeof(struct inet_bind_bucket), 0,
                   SLAB_HWCACHE_ALIGN | SLAB_PANIC |
                   SLAB_ACCOUNT,
                   NULL);
 
     /* Size and allocate the main established and bind bucket
      * hash tables.
      *
      * The methodology is similar to that of the buffer cache.
      */
     tcp_hashinfo.ehash =
         alloc_large_system_hash("TCP established",
                     sizeof(struct inet_ehash_bucket),
                     thash_entries,
                     17, /* one slot per 128 KB of memory */
                     0,
                     NULL,
                     &tcp_hashinfo.ehash_mask,
                     0,
                     thash_entries ? 0 : 512 * 1024);
     for (i = 0; i <= tcp_hashinfo.ehash_mask; i++)
         INIT_HLIST_NULLS_HEAD(&tcp_hashinfo.ehash[i].chain, i);
 
     if (inet_ehash_locks_alloc(&tcp_hashinfo))
         panic("TCP: failed to alloc ehash_locks");
     tcp_hashinfo.bhash =
         alloc_large_system_hash("TCP bind",
                     sizeof(struct inet_bind_hashbucket),
                     tcp_hashinfo.ehash_mask + 1,
                     17, /* one slot per 128 KB of memory */
                     0,
                     &tcp_hashinfo.bhash_size,
                     NULL,
                     0,
                     64 * 1024);
     tcp_hashinfo.bhash_size = 1U << tcp_hashinfo.bhash_size;
     for (i = 0; i < tcp_hashinfo.bhash_size; i++) {
         spin_lock_init(&tcp_hashinfo.bhash[i].lock);
         INIT_HLIST_HEAD(&tcp_hashinfo.bhash[i].chain);
     }
 
 
     cnt = tcp_hashinfo.ehash_mask + 1;
     sysctl_tcp_max_orphans = cnt / 2;
 
     tcp_init_mem();
     /* Set per-socket limits to no more than 1/128 the pressure threshold */
     limit = nr_free_buffer_pages() << (PAGE_SHIFT - 7);
     max_wshare = min(4UL*1024*1024, limit);
     max_rshare = min(6UL*1024*1024, limit);
 
     init_net.ipv4.sysctl_tcp_wmem[0] = PAGE_SIZE;
     init_net.ipv4.sysctl_tcp_wmem[1] = 16*1024;
     init_net.ipv4.sysctl_tcp_wmem[2] = max(64*1024, max_wshare);
 
     init_net.ipv4.sysctl_tcp_rmem[0] = PAGE_SIZE;
     init_net.ipv4.sysctl_tcp_rmem[1] = 131072;
     init_net.ipv4.sysctl_tcp_rmem[2] = max(131072, max_rshare);
 
     pr_info("Hash tables configured (established %u bind %u)\n",
         tcp_hashinfo.ehash_mask + 1, tcp_hashinfo.bhash_size);
 
     tcp_v4_init();
     tcp_metrics_init();
     BUG_ON(tcp_register_congestion_control(&tcp_reno) != 0);
     tcp_tasklet_init();
     mptcp_init();
 }