tcp.c

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/*
 * 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, <[email protected]>
 *      Mark Evans, <[email protected]>
 *      Corey Minyard <[email protected]>
 *      Florian La Roche, <[email protected]>
 *      Charles Hedrick, <[email protected]>
 *      Linus Torvalds, <[email protected]>
 *      Alan Cox, <[email protected]>
 *      Matthew Dillon, <[email protected]>
 *      Arnt Gulbrandsen, <[email protected]>
 *      Jorge Cwik, <[email protected]>
 *
 * 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.
 *
 *      This program is free software; you can redistribute it and/or
 *      modify it under the terms of the GNU General Public License
 *      as published by the Free Software Foundation; either version
 *      2 of the License, or(at your option) any later version.
 *
 * 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 <linux/kernel.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/fcntl.h>
#include <linux/poll.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/bootmem.h>
#include <linux/highmem.h>
#include <linux/swap.h>
#include <linux/cache.h>
#include <linux/err.h>
#include <linux/crypto.h>
#include <linux/time.h>
#include <linux/slab.h>

#include <net/icmp.h>
#include <net/inet_common.h>
#include <net/tcp.h>
#include <net/xfrm.h>
#include <net/ip.h>
#include <net/netdma.h>
#include <net/sock.h>

#include <asm/uaccess.h>
#include <asm/ioctls.h>

int sysctl_tcp_fin_timeout __read_mostly = TCP_FIN_TIMEOUT;

struct percpu_counter tcp_orphan_count;
EXPORT_SYMBOL_GPL(tcp_orphan_count);

int sysctl_tcp_wmem[3] __read_mostly;
int sysctl_tcp_rmem[3] __read_mostly;

EXPORT_SYMBOL(sysctl_tcp_rmem);
EXPORT_SYMBOL(sysctl_tcp_wmem);

atomic_long_t tcp_memory_allocated; /* Current allocated memory. */
EXPORT_SYMBOL(tcp_memory_allocated);

/*
 * Current number of TCP sockets.
 */
struct percpu_counter tcp_sockets_allocated;
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.
 */
int tcp_memory_pressure __read_mostly;
EXPORT_SYMBOL(tcp_memory_pressure);

void tcp_enter_memory_pressure(struct sock *sk)
{
    if (!tcp_memory_pressure) {
        NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPMEMORYPRESSURES);
        tcp_memory_pressure = 1;
    }
}
EXPORT_SYMBOL(tcp_enter_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;
}

/* 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);

    skb_queue_head_init(&tp->out_of_order_queue);
    tcp_init_xmit_timers(sk);
    tcp_prequeue_init(tp);
    INIT_LIST_HEAD(&tp->tsq_node);

    icsk->icsk_rto = TCP_TIMEOUT_INIT;
    tp->mdev = TCP_TIMEOUT_INIT;

    /* 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
     */
    tp->snd_cwnd = TCP_INIT_CWND;

    /* 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 = sysctl_tcp_reordering;
    tcp_enable_early_retrans(tp);
    icsk->icsk_ca_ops = &tcp_init_congestion_ops;

    sk->sk_state = TCP_CLOSE;

    sk->sk_write_space = sk_stream_write_space;
    sock_set_flag(sk, SOCK_USE_WRITE_QUEUE);

    icsk->icsk_sync_mss = tcp_sync_mss;

    /* TCP Cookie Transactions */
    if (sysctl_tcp_cookie_size > 0) {
        /* Default, cookies without s_data_payload. */
        tp->cookie_values =
            kzalloc(sizeof(*tp->cookie_values),
                sk->sk_allocation);
        if (tp->cookie_values != NULL)
            kref_init(&tp->cookie_values->kref);
    }
    /* Presumed zeroed, in order of appearance:
     *  cookie_in_always, cookie_out_never,
     *  s_data_constant, s_data_in, s_data_out
     */
    sk->sk_sndbuf = sysctl_tcp_wmem[1];
    sk->sk_rcvbuf = sysctl_tcp_rmem[1];

    local_bh_disable();
    sock_update_memcg(sk);
    sk_sockets_allocated_inc(sk);
    local_bh_enable();
}
EXPORT_SYMBOL(tcp_init_sock);

/*
 *  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.
 */
unsigned int tcp_poll(struct file *file, struct socket *sock, poll_table *wait)
{
    unsigned int mask;
    struct sock *sk = sock->sk;
    const struct tcp_sock *tp = tcp_sk(sk);

    sock_poll_wait(file, sk_sleep(sk), wait);
    if (sk->sk_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;

    /*
     * POLLHUP 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 POLLHUP is incompatible
     * with the POLLOUT/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. POLLHUP 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 POLLHUP
     * 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 POLLHUP were maskable,
     * then we could set it on SND_SHUTDOWN. BTW examples given
     * in Stevens' books assume exactly this behaviour, it explains
     * why POLLHUP is incompatible with POLLOUT.    --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 || sk->sk_state == TCP_CLOSE)
        mask |= POLLHUP;
    if (sk->sk_shutdown & RCV_SHUTDOWN)
        mask |= POLLIN | POLLRDNORM | POLLRDHUP;

    /* Connected or passive Fast Open socket? */
    if (sk->sk_state != TCP_SYN_SENT &&
        (sk->sk_state != TCP_SYN_RECV || tp->fastopen_rsk != NULL)) {
        int target = sock_rcvlowat(sk, 0, INT_MAX);

        if (tp->urg_seq == tp->copied_seq &&
            !sock_flag(sk, SOCK_URGINLINE) &&
            tp->urg_data)
            target++;

        /* Potential race condition. If read of tp below will
         * escape above sk->sk_state, we can be illegally awaken
         * in SYN_* states. */
        if (tp->rcv_nxt - tp->copied_seq >= target)
            mask |= POLLIN | POLLRDNORM;

        if (!(sk->sk_shutdown & SEND_SHUTDOWN)) {
            if (sk_stream_wspace(sk) >= sk_stream_min_wspace(sk)) {
                mask |= POLLOUT | POLLWRNORM;
            } else {  /* send SIGIO later */
                set_bit(SOCK_ASYNC_NOSPACE,
                    &sk->sk_socket->flags);
                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.
                 */
                if (sk_stream_wspace(sk) >= sk_stream_min_wspace(sk))
                    mask |= POLLOUT | POLLWRNORM;
            }
        } else
            mask |= POLLOUT | POLLWRNORM;

        if (tp->urg_data & TCP_URG_VALID)
            mask |= POLLPRI;
    }
    /* This barrier is coupled with smp_wmb() in tcp_reset() */
    smp_rmb();
    if (sk->sk_err)
        mask |= POLLERR;

    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;

    switch (cmd) {
    case SIOCINQ:
        if (sk->sk_state == TCP_LISTEN)
            return -EINVAL;

        lock_sock(sk);
        if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV))
            answ = 0;
        else if (sock_flag(sk, SOCK_URGINLINE) ||
             !tp->urg_data ||
             before(tp->urg_seq, tp->copied_seq) ||
             !before(tp->urg_seq, tp->rcv_nxt)) {

            answ = tp->rcv_nxt - tp->copied_seq;

            /* Subtract 1, if FIN was received */
            if (answ && sock_flag(sk, SOCK_DONE))
                answ--;
        } else
            answ = tp->urg_seq - tp->copied_seq;
        release_sock(sk);
        break;
    case SIOCATMARK:
        answ = tp->urg_data && tp->urg_seq == 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 = 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 = tp->write_seq - tp->snd_nxt;
        break;
    default:
        return -ENOIOCTLCMD;
    }

    return put_user(answ, (int __user *)arg);
}
EXPORT_SYMBOL(tcp_ioctl);

static inline 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));
}

static inline void 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);

    skb->csum    = 0;
    tcb->seq     = tcb->end_seq = tp->write_seq;
    tcb->tcp_flags = TCPHDR_ACK;
    tcb->sacked  = 0;
    skb_header_release(skb);
    tcp_add_write_queue_tail(sk, skb);
    sk->sk_wmem_queued += skb->truesize;
    sk_mem_charge(sk, skb->truesize);
    if (tp->nonagle & TCP_NAGLE_PUSH)
        tp->nonagle &= ~TCP_NAGLE_PUSH;
}

static inline void tcp_mark_urg(struct tcp_sock *tp, int flags)
{
    if (flags & MSG_OOB)
        tp->snd_up = tp->write_seq;
}

static inline void tcp_push(struct sock *sk, int flags, int mss_now,
                int nonagle)
{
    if (tcp_send_head(sk)) {
        struct tcp_sock *tp = tcp_sk(sk);

        if (!(flags & MSG_MORE) || forced_push(tp))
            tcp_mark_push(tp, tcp_write_queue_tail(sk));

        tcp_mark_urg(tp, flags);
        __tcp_push_pending_frames(sk, mss_now,
                      (flags & MSG_MORE) ? TCP_NAGLE_CORK : 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, 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);
}

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.
                 */
                if (!sock_flag(sk, SOCK_DONE))
                    ret = -ENOTCONN;
                break;
            }
            if (!timeo) {
                ret = -EAGAIN;
                break;
            }
            sk_wait_data(sk, &timeo);
            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 *sk_stream_alloc_skb(struct sock *sk, int size, gfp_t gfp)
{
    struct sk_buff *skb;

    /* The TCP header must be at least 32-bit aligned.  */
    size = ALIGN(size, 4);

    skb = alloc_skb_fclone(size + sk->sk_prot->max_header, gfp);
    if (skb) {
        if (sk_wmem_schedule(sk, skb->truesize)) {
            skb_reserve(skb, sk->sk_prot->max_header);
            /*
             * Make sure that we have exactly size bytes
             * available to the caller, no more, no less.
             */
            skb->avail_size = size;
            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 xmit_size_goal, old_size_goal;

    xmit_size_goal = mss_now;

    if (large_allowed && sk_can_gso(sk)) {
        xmit_size_goal = ((sk->sk_gso_max_size - 1) -
                  inet_csk(sk)->icsk_af_ops->net_header_len -
                  inet_csk(sk)->icsk_ext_hdr_len -
                  tp->tcp_header_len);

        /* TSQ : try to have two TSO segments in flight */
        xmit_size_goal = min_t(u32, xmit_size_goal,
                       sysctl_tcp_limit_output_bytes >> 1);

        xmit_size_goal = tcp_bound_to_half_wnd(tp, xmit_size_goal);

        /* We try hard to avoid divides here */
        old_size_goal = tp->xmit_size_goal_segs * mss_now;

        if (likely(old_size_goal <= xmit_size_goal &&
               old_size_goal + mss_now > xmit_size_goal)) {
            xmit_size_goal = old_size_goal;
        } else {
            tp->xmit_size_goal_segs =
                min_t(u16, xmit_size_goal / mss_now,
                      sk->sk_gso_max_segs);
            xmit_size_goal = tp->xmit_size_goal_segs * mss_now;
        }
    }

    return max(xmit_size_goal, mss_now);
}

static 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;
}

static 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);

    /* 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)) {
        if ((err = sk_stream_wait_connect(sk, &timeo)) != 0)
            goto out_err;
    }

    clear_bit(SOCK_ASYNC_NOSPACE, &sk->sk_socket->flags);

    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 = tcp_write_queue_tail(sk);
        int copy, i;
        bool can_coalesce;

        if (!tcp_send_head(sk) || (copy = size_goal - skb->len) <= 0) {
new_segment:
            if (!sk_stream_memory_free(sk))
                goto wait_for_sndbuf;

            skb = sk_stream_alloc_skb(sk, 0, sk->sk_allocation);
            if (!skb)
                goto wait_for_memory;

            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 >= MAX_SKB_FRAGS) {
            tcp_mark_push(tp, skb);
            goto new_segment;
        }
        if (!sk_wmem_schedule(sk, copy))
            goto wait_for_memory;

        if (can_coalesce) {
            skb_frag_size_add(&skb_shinfo(skb)->frags[i - 1], copy);
        } else {
            get_page(page);
            skb_fill_page_desc(skb, i, page, offset, copy);
        }

        skb->len += copy;
        skb->data_len += copy;
        skb->truesize += copy;
        sk->sk_wmem_queued += copy;
        sk_mem_charge(sk, copy);
        skb->ip_summed = CHECKSUM_PARTIAL;
        tp->write_seq += copy;
        TCP_SKB_CB(skb)->end_seq += copy;
        skb_shinfo(skb)->gso_segs = 0;

        if (!copied)
            TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_PSH;

        copied += copy;
        offset += copy;
        if (!(size -= copy))
            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_sndbuf:
        set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
wait_for_memory:
        tcp_push(sk, flags & ~MSG_MORE, mss_now, TCP_NAGLE_PUSH);

        if ((err = sk_stream_wait_memory(sk, &timeo)) != 0)
            goto do_error;

        mss_now = tcp_send_mss(sk, &size_goal, flags);
    }

out:
    if (copied && !(flags & MSG_SENDPAGE_NOTLAST))
        tcp_push(sk, flags, mss_now, tp->nonagle);
    return copied;

do_error:
    if (copied)
        goto out;
out_err:
    return sk_stream_error(sk, flags, err);
}

int tcp_sendpage(struct sock *sk, struct page *page, int offset,
         size_t size, int flags)
{
    ssize_t res;

    if (!(sk->sk_route_caps & NETIF_F_SG) ||
        !(sk->sk_route_caps & NETIF_F_ALL_CSUM))
        return sock_no_sendpage(sk->sk_socket, page, offset, size,
                    flags);

    lock_sock(sk);
    res = do_tcp_sendpages(sk, page, offset, size, flags);
    release_sock(sk);
    return res;
}
EXPORT_SYMBOL(tcp_sendpage);

static inline int select_size(const struct sock *sk, bool sg)
{
    const struct tcp_sock *tp = tcp_sk(sk);
    int tmp = tp->mss_cache;

    if (sg) {
        if (sk_can_gso(sk)) {
            /* Small frames wont use a full page:
             * Payload will immediately follow tcp header.
             */
            tmp = SKB_WITH_OVERHEAD(2048 - MAX_TCP_HEADER);
        } else {
            int pgbreak = SKB_MAX_HEAD(MAX_TCP_HEADER);

            if (tmp >= pgbreak &&
                tmp <= pgbreak + (MAX_SKB_FRAGS - 1) * PAGE_SIZE)
                tmp = pgbreak;
        }
    }

    return tmp;
}

void tcp_free_fastopen_req(struct tcp_sock *tp)
{
    if (tp->fastopen_req != NULL) {
        kfree(tp->fastopen_req);
        tp->fastopen_req = NULL;
    }
}

static int tcp_sendmsg_fastopen(struct sock *sk, struct msghdr *msg, int *size)
{
    struct tcp_sock *tp = tcp_sk(sk);
    int err, flags;

    if (!(sysctl_tcp_fastopen & TFO_CLIENT_ENABLE))
        return -EOPNOTSUPP;
    if (tp->fastopen_req != NULL)
        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 == NULL))
        return -ENOBUFS;
    tp->fastopen_req->data = msg;

    flags = (msg->msg_flags & MSG_DONTWAIT) ? O_NONBLOCK : 0;
    err = __inet_stream_connect(sk->sk_socket, msg->msg_name,
                    msg->msg_namelen, flags);
    *size = tp->fastopen_req->copied;
    tcp_free_fastopen_req(tp);
    return err;
}

int tcp_sendmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
        size_t size)
{
    struct iovec *iov;
    struct tcp_sock *tp = tcp_sk(sk);
    struct sk_buff *skb;
    int iovlen, flags, err, copied = 0;
    int mss_now = 0, size_goal, copied_syn = 0, offset = 0;
    bool sg;
    long timeo;

    lock_sock(sk);

    flags = msg->msg_flags;
    if (flags & MSG_FASTOPEN) {
        err = tcp_sendmsg_fastopen(sk, msg, &copied_syn);
        if (err == -EINPROGRESS && copied_syn > 0)
            goto out;
        else if (err)
            goto out_err;
        offset = copied_syn;
    }

    timeo = sock_sndtimeo(sk, flags & MSG_DONTWAIT);

    /* 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)) {
        if ((err = sk_stream_wait_connect(sk, &timeo)) != 0)
            goto do_error;
    }

    if (unlikely(tp->repair)) {
        if (tp->repair_queue == TCP_RECV_QUEUE) {
            copied = tcp_send_rcvq(sk, msg, size);
            goto out;
        }

        err = -EINVAL;
        if (tp->repair_queue == TCP_NO_QUEUE)
            goto out_err;

        /* 'common' sending to sendq */
    }

    /* This should be in poll */
    clear_bit(SOCK_ASYNC_NOSPACE, &sk->sk_socket->flags);

    mss_now = tcp_send_mss(sk, &size_goal, flags);

    /* Ok commence sending. */
    iovlen = msg->msg_iovlen;
    iov = msg->msg_iov;
    copied = 0;

    err = -EPIPE;
    if (sk->sk_err || (sk->sk_shutdown & SEND_SHUTDOWN))
        goto out_err;

    sg = !!(sk->sk_route_caps & NETIF_F_SG);

    while (--iovlen >= 0) {
        size_t seglen = iov->iov_len;
        unsigned char __user *from = iov->iov_base;

        iov++;
        if (unlikely(offset > 0)) {  /* Skip bytes copied in SYN */
            if (offset >= seglen) {
                offset -= seglen;
                continue;
            }
            seglen -= offset;
            from += offset;
            offset = 0;
        }

        while (seglen > 0) {
            int copy = 0;
            int max = size_goal;

            skb = tcp_write_queue_tail(sk);
            if (tcp_send_head(sk)) {
                if (skb->ip_summed == CHECKSUM_NONE)
                    max = mss_now;
                copy = max - skb->len;
            }

            if (copy <= 0) {
new_segment:
                /* Allocate new segment. If the interface is SG,
                 * allocate skb fitting to single page.
                 */
                if (!sk_stream_memory_free(sk))
                    goto wait_for_sndbuf;

                skb = sk_stream_alloc_skb(sk,
                              select_size(sk, sg),
                              sk->sk_allocation);
                if (!skb)
                    goto wait_for_memory;

                /*
                 * Check whether we can use HW checksum.
                 */
                if (sk->sk_route_caps & NETIF_F_ALL_CSUM)
                    skb->ip_summed = CHECKSUM_PARTIAL;

                skb_entail(sk, skb);
                copy = size_goal;
                max = size_goal;
            }

            /* Try to append data to the end of skb. */
            if (copy > seglen)
                copy = seglen;

            /* Where to copy to? */
            if (skb_availroom(skb) > 0) {
                /* We have some space in skb head. Superb! */
                copy = min_t(int, copy, skb_availroom(skb));
                err = skb_add_data_nocache(sk, skb, from, copy);
                if (err)
                    goto do_fault;
            } else {
                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_memory;

                if (!skb_can_coalesce(skb, i, pfrag->page,
                              pfrag->offset)) {
                    if (i == MAX_SKB_FRAGS || !sg) {
                        tcp_mark_push(tp, skb);
                        goto new_segment;
                    }
                    merge = false;
                }

                copy = min_t(int, copy, pfrag->size - pfrag->offset);

                if (!sk_wmem_schedule(sk, copy))
                    goto wait_for_memory;

                err = skb_copy_to_page_nocache(sk, from, 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);
                    get_page(pfrag->page);
                }
                pfrag->offset += copy;
            }

            if (!copied)
                TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_PSH;

            tp->write_seq += copy;
            TCP_SKB_CB(skb)->end_seq += copy;
            skb_shinfo(skb)->gso_segs = 0;

            from += copy;
            copied += copy;
            if ((seglen -= copy) == 0 && iovlen == 0)
                goto out;

            if (skb->len < max || (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_sndbuf:
            set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
wait_for_memory:
            if (copied)
                tcp_push(sk, flags & ~MSG_MORE, mss_now, TCP_NAGLE_PUSH);

            if ((err = sk_stream_wait_memory(sk, &timeo)) != 0)
                goto do_error;

            mss_now = tcp_send_mss(sk, &size_goal, flags);
        }
    }

out:
    if (copied)
        tcp_push(sk, flags, mss_now, tp->nonagle);
    release_sock(sk);
    return copied + copied_syn;

do_fault:
    if (!skb->len) {
        tcp_unlink_write_queue(skb, sk);
        /* It is the one place in all of TCP, except connection
         * reset, where we can be unlinking the send_head.
         */
        tcp_check_send_head(sk, skb);
        sk_wmem_free_skb(sk, skb);
    }

do_error:
    if (copied + copied_syn)
        goto out;
out_err:
    err = sk_stream_error(sk, flags, err);
    release_sock(sk);
    return err;
}
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))
            tp->urg_data = TCP_URG_READ;

        /* Read urgent data. */
        msg->msg_flags |= MSG_OOB;

        if (len > 0) {
            if (!(flags & MSG_TRUNC))
                err = memcpy_toiovec(msg->msg_iov, &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 <[email protected]>
     */
    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_queue_walk(&sk->sk_write_queue, skb) {
        err = skb_copy_datagram_iovec(skb, 0, msg->msg_iov, 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.
 */
void tcp_cleanup_rbuf(struct sock *sk, int copied)
{
    struct tcp_sock *tp = tcp_sk(sk);
    bool time_to_ack = false;

    struct sk_buff *skb = skb_peek(&sk->sk_receive_queue);

    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);

    if (inet_csk_ack_scheduled(sk)) {
        const struct inet_connection_sock *icsk = inet_csk(sk);
           /* Delayed ACKs frequently hit locked sockets during bulk
            * receive. */
        if (icsk->icsk_ack.blocked ||
            /* 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) &&
               !icsk->icsk_ack.pingpong)) &&
              !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);
}

static void tcp_prequeue_process(struct sock *sk)
{
    struct sk_buff *skb;
    struct tcp_sock *tp = tcp_sk(sk);

    NET_INC_STATS_USER(sock_net(sk), LINUX_MIB_TCPPREQUEUED);

    /* RX process wants to run with disabled BHs, though it is not
     * necessary */
    local_bh_disable();
    while ((skb = __skb_dequeue(&tp->ucopy.prequeue)) != NULL)
        sk_backlog_rcv(sk, skb);
    local_bh_enable();

    /* Clear memory counter. */
    tp->ucopy.memory = 0;
}

#ifdef CONFIG_NET_DMA
static void tcp_service_net_dma(struct sock *sk, bool wait)
{
    dma_cookie_t done, used;
    dma_cookie_t last_issued;
    struct tcp_sock *tp = tcp_sk(sk);

    if (!tp->ucopy.dma_chan)
        return;

    last_issued = tp->ucopy.dma_cookie;
    dma_async_memcpy_issue_pending(tp->ucopy.dma_chan);

    do {
        if (dma_async_memcpy_complete(tp->ucopy.dma_chan,
                          last_issued, &done,
                          &used) == DMA_SUCCESS) {
            /* Safe to free early-copied skbs now */
            __skb_queue_purge(&sk->sk_async_wait_queue);
            break;
        } else {
            struct sk_buff *skb;
            while ((skb = skb_peek(&sk->sk_async_wait_queue)) &&
                   (dma_async_is_complete(skb->dma_cookie, done,
                              used) == DMA_SUCCESS)) {
                __skb_dequeue(&sk->sk_async_wait_queue);
                kfree_skb(skb);
            }
        }
    } while (wait);
}
#endif

static inline struct sk_buff *tcp_recv_skb(struct sock *sk, u32 seq, u32 *off)
{
    struct sk_buff *skb;
    u32 offset;

    skb_queue_walk(&sk->sk_receive_queue, skb) {
        offset = seq - TCP_SKB_CB(skb)->seq;
        if (tcp_hdr(skb)->syn)
            offset--;
        if (offset < skb->len || tcp_hdr(skb)->fin) {
            *off = offset;
            return skb;
        }
    }
    return NULL;
}

/*
 * 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 (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;
            } else if (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 || (offset+1 != skb->len))
                break;
        }
        if (tcp_hdr(skb)->fin) {
            sk_eat_skb(sk, skb, false);
            ++seq;
            break;
        }
        sk_eat_skb(sk, skb, false);
        if (!desc->count)
            break;
        tp->copied_seq = seq;
    }
    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_sock);

/*
 *  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.
 */

int tcp_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
        size_t len, int nonblock, int flags, int *addr_len)
{
    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 task_struct *user_recv = NULL;
    bool copied_early = false;
    struct sk_buff *skb;
    u32 urg_hole = 0;

    lock_sock(sk);

    err = -ENOTCONN;
    if (sk->sk_state == TCP_LISTEN)
        goto out;

    timeo = sock_rcvtimeo(sk, nonblock);

    /* 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);

#ifdef CONFIG_NET_DMA
    tp->ucopy.dma_chan = NULL;
    preempt_disable();
    skb = skb_peek_tail(&sk->sk_receive_queue);
    {
        int available = 0;

        if (skb)
            available = TCP_SKB_CB(skb)->seq + skb->len - (*seq);
        if ((available < target) &&
            (len > sysctl_tcp_dma_copybreak) && !(flags & MSG_PEEK) &&
            !sysctl_tcp_low_latency &&
            net_dma_find_channel()) {
            preempt_enable_no_resched();
            tp->ucopy.pinned_list =
                    dma_pin_iovec_pages(msg->msg_iov, len);
        } else {
            preempt_enable_no_resched();
        }
    }
#endif

    do {
        u32 offset;

        /* Are we at urgent data? Stop if we have read anything or have SIGURG pending. */
        if (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. */

        skb_queue_walk(&sk->sk_receive_queue, skb) {
            /* Now that we have two receive queues this
             * shouldn't happen.
             */
            if (WARN(before(*seq, TCP_SKB_CB(skb)->seq),
                 "recvmsg 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 (tcp_hdr(skb)->syn)
                offset--;
            if (offset < skb->len)
                goto found_ok_skb;
            if (tcp_hdr(skb)->fin)
                goto found_fin_ok;
            WARN(!(flags & MSG_PEEK),
                 "recvmsg 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 && !sk->sk_backlog.tail)
            break;

        if (copied) {
            if (sk->sk_err ||
                sk->sk_state == TCP_CLOSE ||
                (sk->sk_shutdown & RCV_SHUTDOWN) ||
                !timeo ||
                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) {
                if (!sock_flag(sk, SOCK_DONE)) {
                    /* This occurs when user tries to read
                     * from never connected socket.
                     */
                    copied = -ENOTCONN;
                    break;
                }
                break;
            }

            if (!timeo) {
                copied = -EAGAIN;
                break;
            }

            if (signal_pending(current)) {
                copied = sock_intr_errno(timeo);
                break;
            }
        }

        tcp_cleanup_rbuf(sk, copied);

        if (!sysctl_tcp_low_latency && tp->ucopy.task == user_recv) {
            /* Install new reader */
            if (!user_recv && !(flags & (MSG_TRUNC | MSG_PEEK))) {
                user_recv = current;
                tp->ucopy.task = user_recv;
                tp->ucopy.iov = msg->msg_iov;
            }

            tp->ucopy.len = len;

            WARN_ON(tp->copied_seq != tp->rcv_nxt &&
                !(flags & (MSG_PEEK | MSG_TRUNC)));

            /* Ugly... If prequeue is not empty, we have to
             * process it before releasing socket, otherwise
             * order will be broken at second iteration.
             * More elegant solution is required!!!
             *
             * Look: we have the following (pseudo)queues:
             *
             * 1. packets in flight
             * 2. backlog
             * 3. prequeue
             * 4. receive_queue
             *
             * Each queue can be processed only if the next ones
             * are empty. At this point we have empty receive_queue.
             * But prequeue _can_ be not empty after 2nd iteration,
             * when we jumped to start of loop because backlog
             * processing added something to receive_queue.
             * We cannot release_sock(), because backlog contains
             * packets arrived _after_ prequeued ones.
             *
             * Shortly, algorithm is clear --- to process all
             * the queues in order. We could make it more directly,
             * requeueing packets from backlog to prequeue, if
             * is not empty. It is more elegant, but eats cycles,
             * unfortunately.
             */
            if (!skb_queue_empty(&tp->ucopy.prequeue))
                goto do_prequeue;

            /* __ Set realtime policy in scheduler __ */
        }

#ifdef CONFIG_NET_DMA
        if (tp->ucopy.dma_chan) {
            if (tp->rcv_wnd == 0 &&
                !skb_queue_empty(&sk->sk_async_wait_queue)) {
                tcp_service_net_dma(sk, true);
                tcp_cleanup_rbuf(sk, copied);
            } else
                dma_async_memcpy_issue_pending(tp->ucopy.dma_chan);
        }
#endif
        if (copied >= target) {
            /* Do not sleep, just process backlog. */
            release_sock(sk);
            lock_sock(sk);
        } else
            sk_wait_data(sk, &timeo);

#ifdef CONFIG_NET_DMA
        tcp_service_net_dma(sk, false);  /* Don't block */
        tp->ucopy.wakeup = 0;
#endif

        if (user_recv) {
            int chunk;

            /* __ Restore normal policy in scheduler __ */

            if ((chunk = len - tp->ucopy.len) != 0) {
                NET_ADD_STATS_USER(sock_net(sk), LINUX_MIB_TCPDIRECTCOPYFROMBACKLOG, chunk);
                len -= chunk;
                copied += chunk;
            }

            if (tp->rcv_nxt == tp->copied_seq &&
                !skb_queue_empty(&tp->ucopy.prequeue)) {
do_prequeue:
                tcp_prequeue_process(sk);

                if ((chunk = len - tp->ucopy.len) != 0) {
                    NET_ADD_STATS_USER(sock_net(sk), LINUX_MIB_TCPDIRECTCOPYFROMPREQUEUE, chunk);
                    len -= chunk;
                    copied += chunk;
                }
            }
        }
        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 (tp->urg_data) {
            u32 urg_offset = tp->urg_seq - *seq;
            if (urg_offset < used) {
                if (!urg_offset) {
                    if (!sock_flag(sk, SOCK_URGINLINE)) {
                        ++*seq;
                        urg_hole++;
                        offset++;
                        used--;
                        if (!used)
                            goto skip_copy;
                    }
                } else
                    used = urg_offset;
            }
        }

        if (!(flags & MSG_TRUNC)) {
#ifdef CONFIG_NET_DMA
            if (!tp->ucopy.dma_chan && tp->ucopy.pinned_list)
                tp->ucopy.dma_chan = net_dma_find_channel();

            if (tp->ucopy.dma_chan) {
                tp->ucopy.dma_cookie = dma_skb_copy_datagram_iovec(
                    tp->ucopy.dma_chan, skb, offset,
                    msg->msg_iov, used,
                    tp->ucopy.pinned_list);

                if (tp->ucopy.dma_cookie < 0) {

                    pr_alert("%s: dma_cookie < 0\n",
                         __func__);

                    /* Exception. Bailout! */
                    if (!copied)
                        copied = -EFAULT;
                    break;
                }

                dma_async_memcpy_issue_pending(tp->ucopy.dma_chan);

                if ((offset + used) == skb->len)
                    copied_early = true;

            } else
#endif
            {
                err = skb_copy_datagram_iovec(skb, offset,
                        msg->msg_iov, used);
                if (err) {
                    /* Exception. Bailout! */
                    if (!copied)
                        copied = -EFAULT;
                    break;
                }
            }
        }

        *seq += used;
        copied += used;
        len -= used;

        tcp_rcv_space_adjust(sk);

skip_copy:
        if (tp->urg_data && after(tp->copied_seq, tp->urg_seq)) {
            tp->urg_data = 0;
            tcp_fast_path_check(sk);
        }
        if (used + offset < skb->len)
            continue;

        if (tcp_hdr(skb)->fin)
            goto found_fin_ok;
        if (!(flags & MSG_PEEK)) {
            sk_eat_skb(sk, skb, copied_early);
            copied_early = false;
        }
        continue;

    found_fin_ok:
        /* Process the FIN. */
        ++*seq;
        if (!(flags & MSG_PEEK)) {
            sk_eat_skb(sk, skb, copied_early);
            copied_early = false;
        }
        break;
    } while (len > 0);

    if (user_recv) {
        if (!skb_queue_empty(&tp->ucopy.prequeue)) {
            int chunk;

            tp->ucopy.len = copied > 0 ? len : 0;

            tcp_prequeue_process(sk);

            if (copied > 0 && (chunk = len - tp->ucopy.len) != 0) {
                NET_ADD_STATS_USER(sock_net(sk), LINUX_MIB_TCPDIRECTCOPYFROMPREQUEUE, chunk);
                len -= chunk;
                copied += chunk;
            }
        }

        tp->ucopy.task = NULL;
        tp->ucopy.len = 0;
    }

#ifdef CONFIG_NET_DMA
    tcp_service_net_dma(sk, true);  /* Wait for queue to drain */
    tp->ucopy.dma_chan = NULL;

    if (tp->ucopy.pinned_list) {
        dma_unpin_iovec_pages(tp->ucopy.pinned_list);
        tp->ucopy.pinned_list = NULL;
    }
#endif

    /* 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);

    release_sock(sk);
    return copied;

out:
    release_sock(sk);
    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;
}
EXPORT_SYMBOL(tcp_recvmsg);

void tcp_set_state(struct sock *sk, int state)
{
    int oldstate = sk->sk_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);
        /* fall through */
    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.
     */
    sk->sk_state = state;

#ifdef STATE_TRACE
    SOCK_DEBUG(sk, "TCP sk=%p, State %s -> %s\n", sk, statename[oldstate], statename[state]);
#endif
}
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:  */
  /* (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,
};

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([email protected]) 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);

bool tcp_check_oom(struct sock *sk, int shift)
{
    bool too_many_orphans, out_of_socket_memory;

    too_many_orphans = tcp_too_many_orphans(sk, 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;

    lock_sock(sk);
    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 -
              tcp_hdr(skb)->fin;
        data_was_unread += len;
        __kfree_skb(skb);
    }

    sk_mem_reclaim(sk);

    /* 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_USER(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_USER(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);

    /* It is the last release_sock in its life. It will remove backlog. */
    release_sock(sk);


    /* Now socket is owned by kernel and we acquire BH lock
       to finish close. No need to check for user refs.
     */
    local_bh_disable();
    bh_lock_sock(sk);
    WARN_ON(sock_owned_by_user(sk));

    percpu_counter_inc(sk->sk_prot->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 3 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_BH(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) {
        sk_mem_reclaim(sk);
        if (tcp_check_oom(sk, 0)) {
            tcp_set_state(sk, TCP_CLOSE);
            tcp_send_active_reset(sk, GFP_ATOMIC);
            NET_INC_STATS_BH(sock_net(sk),
                    LINUX_MIB_TCPABORTONMEMORY);
        }
    }

    if (sk->sk_state == TCP_CLOSE) {
        struct request_sock *req = tcp_sk(sk)->fastopen_rsk;
        /* 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 != NULL)
            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();
    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);
}

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 err = 0;
    int old_state = sk->sk_state;

    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);
    tcp_write_queue_purge(sk);
    __skb_queue_purge(&tp->out_of_order_queue);
#ifdef CONFIG_NET_DMA
    __skb_queue_purge(&sk->sk_async_wait_queue);
#endif

    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 = 0;
    if ((tp->write_seq += tp->max_window + 2) == 0)
        tp->write_seq = 1;
    icsk->icsk_backoff = 0;
    tp->snd_cwnd = 2;
    icsk->icsk_probes_out = 0;
    tp->packets_out = 0;
    tp->snd_ssthresh = TCP_INFINITE_SSTHRESH;
    tp->snd_cwnd_cnt = 0;
    tp->bytes_acked = 0;
    tp->window_clamp = 0;
    tcp_set_ca_state(sk, TCP_CA_Open);
    tcp_clear_retrans(tp);
    inet_csk_delack_init(sk);
    tcp_init_send_head(sk);
    memset(&tp->rx_opt, 0, sizeof(tp->rx_opt));
    __sk_dst_reset(sk);

    WARN_ON(inet->inet_num && !icsk->icsk_bind_hash);

    sk->sk_error_report(sk);
    return err;
}
EXPORT_SYMBOL(tcp_disconnect);

void tcp_sock_destruct(struct sock *sk)
{
    inet_sock_destruct(sk);

    kfree(inet_csk(sk)->icsk_accept_queue.fastopenq);
}

static inline bool tcp_can_repair_sock(const struct sock *sk)
{
    return capable(CAP_NET_ADMIN) &&
        ((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_ESTABLISHED));
}

static int tcp_repair_options_est(struct tcp_sock *tp,
        struct tcp_repair_opt __user *optbuf, unsigned int len)
{
    struct tcp_repair_opt opt;

    while (len >= sizeof(opt)) {
        if (copy_from_user(&opt, optbuf, sizeof(opt)))
            return -EFAULT;

        optbuf++;
        len -= sizeof(opt);

        switch (opt.opt_code) {
        case TCPOPT_MSS:
            tp->rx_opt.mss_clamp = opt.opt_val;
            break;
        case TCPOPT_WINDOW:
            {
                u16 snd_wscale = opt.opt_val & 0xFFFF;
                u16 rcv_wscale = opt.opt_val >> 16;

                if (snd_wscale > 14 || rcv_wscale > 14)
                    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;
            if (sysctl_tcp_fack)
                tcp_enable_fack(tp);
            break;
        case TCPOPT_TIMESTAMP:
            if (opt.opt_val != 0)
                return -EINVAL;

            tp->rx_opt.tstamp_ok = 1;
            break;
        }
    }

    return 0;
}

/*
 *  Socket option code for TCP.
 */
static int do_tcp_setsockopt(struct sock *sk, int level,
        int optname, char __user *optval, unsigned int optlen)
{
    struct tcp_sock *tp = tcp_sk(sk);
    struct inet_connection_sock *icsk = inet_csk(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_user(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);
        release_sock(sk);
        return err;
    }
    case TCP_COOKIE_TRANSACTIONS: {
        struct tcp_cookie_transactions ctd;
        struct tcp_cookie_values *cvp = NULL;

        if (sizeof(ctd) > optlen)
            return -EINVAL;
        if (copy_from_user(&ctd, optval, sizeof(ctd)))
            return -EFAULT;

        if (ctd.tcpct_used > sizeof(ctd.tcpct_value) ||
            ctd.tcpct_s_data_desired > TCP_MSS_DESIRED)
            return -EINVAL;

        if (ctd.tcpct_cookie_desired == 0) {
            /* default to global value */
        } else if ((0x1 & ctd.tcpct_cookie_desired) ||
               ctd.tcpct_cookie_desired > TCP_COOKIE_MAX ||
               ctd.tcpct_cookie_desired < TCP_COOKIE_MIN) {
            return -EINVAL;
        }

        if (TCP_COOKIE_OUT_NEVER & ctd.tcpct_flags) {
            /* Supercedes all other values */
            lock_sock(sk);
            if (tp->cookie_values != NULL) {
                kref_put(&tp->cookie_values->kref,
                     tcp_cookie_values_release);
                tp->cookie_values = NULL;
            }
            tp->rx_opt.cookie_in_always = 0; /* false */
            tp->rx_opt.cookie_out_never = 1; /* true */
            release_sock(sk);
            return err;
        }

        /* Allocate ancillary memory before locking.
         */
        if (ctd.tcpct_used > 0 ||
            (tp->cookie_values == NULL &&
             (sysctl_tcp_cookie_size > 0 ||
              ctd.tcpct_cookie_desired > 0 ||
              ctd.tcpct_s_data_desired > 0))) {
            cvp = kzalloc(sizeof(*cvp) + ctd.tcpct_used,
                      GFP_KERNEL);
            if (cvp == NULL)
                return -ENOMEM;

            kref_init(&cvp->kref);
        }
        lock_sock(sk);
        tp->rx_opt.cookie_in_always =
            (TCP_COOKIE_IN_ALWAYS & ctd.tcpct_flags);
        tp->rx_opt.cookie_out_never = 0; /* false */

        if (tp->cookie_values != NULL) {
            if (cvp != NULL) {
                /* Changed values are recorded by a changed
                 * pointer, ensuring the cookie will differ,
                 * without separately hashing each value later.
                 */
                kref_put(&tp->cookie_values->kref,
                     tcp_cookie_values_release);
            } else {
                cvp = tp->cookie_values;
            }
        }

        if (cvp != NULL) {
            cvp->cookie_desired = ctd.tcpct_cookie_desired;

            if (ctd.tcpct_used > 0) {
                memcpy(cvp->s_data_payload, ctd.tcpct_value,
                       ctd.tcpct_used);
                cvp->s_data_desired = ctd.tcpct_used;
                cvp->s_data_constant = 1; /* true */
            } else {
                /* No constant payload data. */
                cvp->s_data_desired = ctd.tcpct_s_data_desired;
                cvp->s_data_constant = 0; /* false */
            }

            tp->cookie_values = cvp;
        }
        release_sock(sk);
        return err;
    }
    default:
        /* fallthru */
        break;
    }

    if (optlen < sizeof(int))
        return -EINVAL;

    if (get_user(val, (int __user *)optval))
        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 < TCP_MIN_MSS || val > MAX_TCP_WINDOW) {
            err = -EINVAL;
            break;
        }
        tp->rx_opt.user_mss = val;
        break;

    case TCP_NODELAY:
        if (val) {
            /* 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.
             */
            tp->nonagle |= TCP_NAGLE_OFF|TCP_NAGLE_PUSH;
            tcp_push_pending_frames(sk);
        } else {
            tp->nonagle &= ~TCP_NAGLE_OFF;
        }
        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;
        else
            tp->thin_dupack = val;
            if (tp->thin_dupack)
                tcp_disable_early_retrans(tp);
        break;

    case TCP_REPAIR:
        if (!tcp_can_repair_sock(sk))
            err = -EPERM;
        else if (val == 1) {
            tp->repair = 1;
            sk->sk_reuse = SK_FORCE_REUSE;
            tp->repair_queue = TCP_NO_QUEUE;
        } else if (val == 0) {
            tp->repair = 0;
            sk->sk_reuse = SK_NO_REUSE;
            tcp_send_window_probe(sk);
        } else
            err = -EINVAL;

        break;

    case TCP_REPAIR_QUEUE:
        if (!tp->repair)
            err = -EPERM;
        else if (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)
            tp->write_seq = val;
        else if (tp->repair_queue == TCP_RECV_QUEUE)
            tp->rcv_nxt = 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(tp,
                    (struct tcp_repair_opt __user *)optval,
                    optlen);
        else
            err = -EPERM;
        break;

    case TCP_CORK:
        /* 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.
         */
        if (val) {
            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);
        }
        break;

    case TCP_KEEPIDLE:
        if (val < 1 || val > MAX_TCP_KEEPIDLE)
            err = -EINVAL;
        else {
            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);
            }
        }
        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_LINGER2:
        if (val < 0)
            tp->linger2 = -1;
        else if (val > sysctl_tcp_fin_timeout / HZ)
            tp->linger2 = 0;
        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:
        if (!val) {
            if (sk->sk_state != TCP_CLOSE) {
                err = -EINVAL;
                break;
            }
            tp->window_clamp = 0;
        } else
            tp->window_clamp = val < SOCK_MIN_RCVBUF / 2 ?
                        SOCK_MIN_RCVBUF / 2 : val;
        break;

    case TCP_QUICKACK:
        if (!val) {
            icsk->icsk_ack.pingpong = 1;
        } else {
            icsk->icsk_ack.pingpong = 0;
            if ((1 << sk->sk_state) &
                (TCPF_ESTABLISHED | TCPF_CLOSE_WAIT) &&
                inet_csk_ack_scheduled(sk)) {
                icsk->icsk_ack.pending |= ICSK_ACK_PUSHED;
                tcp_cleanup_rbuf(sk, 1);
                if (!(val & 1))
                    icsk->icsk_ack.pingpong = 1;
            }
        }
        break;

#ifdef CONFIG_TCP_MD5SIG
    case TCP_MD5SIG:
        /* Read the IP->Key mappings from userspace */
        err = tp->af_specific->md5_parse(sk, optval, optlen);
        break;
#endif
    case TCP_USER_TIMEOUT:
        /* Cap the max timeout in ms TCP will retry/retrans
         * before giving up and aborting (ETIMEDOUT) a connection.
         */
        if (val < 0)
            err = -EINVAL;
        else
            icsk->icsk_user_timeout = msecs_to_jiffies(val);
        break;

    case TCP_FASTOPEN:
        if (val >= 0 && ((1 << sk->sk_state) & (TCPF_CLOSE |
            TCPF_LISTEN)))
            err = fastopen_init_queue(sk, val);
        else
            err = -EINVAL;
        break;
    default:
        err = -ENOPROTOOPT;
        break;
    }

    release_sock(sk);
    return err;
}

int tcp_setsockopt(struct sock *sk, int level, int optname, char __user *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);

#ifdef CONFIG_COMPAT
int compat_tcp_setsockopt(struct sock *sk, int level, int optname,
              char __user *optval, unsigned int optlen)
{
    if (level != SOL_TCP)
        return inet_csk_compat_setsockopt(sk, level, optname,
                          optval, optlen);
    return do_tcp_setsockopt(sk, level, optname, optval, optlen);
}
EXPORT_SYMBOL(compat_tcp_setsockopt);
#endif

/* Return information about state of tcp endpoint in API format. */
void tcp_get_info(const struct sock *sk, struct tcp_info *info)
{
    const struct tcp_sock *tp = tcp_sk(sk);
    const struct inet_connection_sock *icsk = inet_csk(sk);
    u32 now = tcp_time_stamp;

    memset(info, 0, sizeof(*info));

    info->tcpi_state = sk->sk_state;
    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;

    if (sk->sk_state == TCP_LISTEN) {
        info->tcpi_unacked = sk->sk_ack_backlog;
        info->tcpi_sacked = sk->sk_max_ack_backlog;
    } else {
        info->tcpi_unacked = tp->packets_out;
        info->tcpi_sacked = tp->sacked_out;
    }
    info->tcpi_lost = tp->lost_out;
    info->tcpi_retrans = tp->retrans_out;
    info->tcpi_fackets = tp->fackets_out;

    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 = jiffies_to_usecs(tp->srtt)>>3;
    info->tcpi_rttvar = jiffies_to_usecs(tp->mdev)>>2;
    info->tcpi_snd_ssthresh = tp->snd_ssthresh;
    info->tcpi_snd_cwnd = tp->snd_cwnd;
    info->tcpi_advmss = tp->advmss;
    info->tcpi_reordering = tp->reordering;

    info->tcpi_rcv_rtt = jiffies_to_usecs(tp->rcv_rtt_est.rtt)>>3;
    info->tcpi_rcv_space = tp->rcvq_space.space;

    info->tcpi_total_retrans = tp->total_retrans;
}
EXPORT_SYMBOL_GPL(tcp_get_info);

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);
    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 ? : sysctl_tcp_syn_retries;
        break;
    case TCP_LINGER2:
        val = tp->linger2;
        if (val >= 0)
            val = (val ? : 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_QUICKACK:
        val = !icsk->icsk_ack.pingpong;
        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_COOKIE_TRANSACTIONS: {
        struct tcp_cookie_transactions ctd;
        struct tcp_cookie_values *cvp = tp->cookie_values;

        if (get_user(len, optlen))
            return -EFAULT;
        if (len < sizeof(ctd))
            return -EINVAL;

        memset(&ctd, 0, sizeof(ctd));
        ctd.tcpct_flags = (tp->rx_opt.cookie_in_always ?
                   TCP_COOKIE_IN_ALWAYS : 0)
                | (tp->rx_opt.cookie_out_never ?
                   TCP_COOKIE_OUT_NEVER : 0);

        if (cvp != NULL) {
            ctd.tcpct_flags |= (cvp->s_data_in ?
                        TCP_S_DATA_IN : 0)
                     | (cvp->s_data_out ?
                        TCP_S_DATA_OUT : 0);

            ctd.tcpct_cookie_desired = cvp->cookie_desired;
            ctd.tcpct_s_data_desired = cvp->s_data_desired;

            memcpy(&ctd.tcpct_value[0], &cvp->cookie_pair[0],
                   cvp->cookie_pair_size);
            ctd.tcpct_used = cvp->cookie_pair_size;
        }

        if (put_user(sizeof(ctd), optlen))
            return -EFAULT;
        if (copy_to_user(optval, &ctd, sizeof(ctd)))
            return -EFAULT;
        return 0;
    }
    case TCP_THIN_LINEAR_TIMEOUTS:
        val = tp->thin_lto;
        break;
    case TCP_THIN_DUPACK:
        val = tp->thin_dupack;
        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_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 = jiffies_to_msecs(icsk->icsk_user_timeout);
        break;
    default:
        return -ENOPROTOOPT;
    }

    if (put_user(len, optlen))
        return -EFAULT;
    if (copy_to_user(optval, &val, len))
        return -EFAULT;
    return 0;
}

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_COMPAT
int compat_tcp_getsockopt(struct sock *sk, int level, int optname,
              char __user *optval, int __user *optlen)
{
    if (level != SOL_TCP)
        return inet_csk_compat_getsockopt(sk, level, optname,
                          optval, optlen);
    return do_tcp_getsockopt(sk, level, optname, optval, optlen);
}
EXPORT_SYMBOL(compat_tcp_getsockopt);
#endif

struct sk_buff *tcp_tso_segment(struct sk_buff *skb,
    netdev_features_t features)
{
    struct sk_buff *segs = ERR_PTR(-EINVAL);
    struct tcphdr *th;
    unsigned int thlen;
    unsigned int seq;
    __be32 delta;
    unsigned int oldlen;
    unsigned int mss;

    if (!pskb_may_pull(skb, sizeof(*th)))
        goto out;

    th = tcp_hdr(skb);
    thlen = th->doff * 4;
    if (thlen < sizeof(*th))
        goto out;

    if (!pskb_may_pull(skb, thlen))
        goto out;

    oldlen = (u16)~skb->len;
    __skb_pull(skb, thlen);

    mss = skb_shinfo(skb)->gso_size;
    if (unlikely(skb->len <= mss))
        goto out;

    if (skb_gso_ok(skb, features | NETIF_F_GSO_ROBUST)) {
        /* Packet is from an untrusted source, reset gso_segs. */
        int type = skb_shinfo(skb)->gso_type;

        if (unlikely(type &
                 ~(SKB_GSO_TCPV4 |
                   SKB_GSO_DODGY |
                   SKB_GSO_TCP_ECN |
                   SKB_GSO_TCPV6 |
                   0) ||
                 !(type & (SKB_GSO_TCPV4 | SKB_GSO_TCPV6))))
            goto out;

        skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(skb->len, mss);

        segs = NULL;
        goto out;
    }

    segs = skb_segment(skb, features);
    if (IS_ERR(segs))
        goto out;

    delta = htonl(oldlen + (thlen + mss));

    skb = segs;
    th = tcp_hdr(skb);
    seq = ntohl(th->seq);

    do {
        th->fin = th->psh = 0;

        th->check = ~csum_fold((__force __wsum)((__force u32)th->check +
                       (__force u32)delta));
        if (skb->ip_summed != CHECKSUM_PARTIAL)
            th->check =
                 csum_fold(csum_partial(skb_transport_header(skb),
                            thlen, skb->csum));

        seq += mss;
        skb = skb->next;
        th = tcp_hdr(skb);

        th->seq = htonl(seq);
        th->cwr = 0;
    } while (skb->next);

    delta = htonl(oldlen + (skb->tail - skb->transport_header) +
              skb->data_len);
    th->check = ~csum_fold((__force __wsum)((__force u32)th->check +
                (__force u32)delta));
    if (skb->ip_summed != CHECKSUM_PARTIAL)
        th->check = csum_fold(csum_partial(skb_transport_header(skb),
                           thlen, skb->csum));

out:
    return segs;
}
EXPORT_SYMBOL(tcp_tso_segment);

struct sk_buff **tcp_gro_receive(struct sk_buff **head, struct sk_buff *skb)
{
    struct sk_buff **pp = NULL;
    struct sk_buff *p;
    struct tcphdr *th;
    struct tcphdr *th2;
    unsigned int len;
    unsigned int thlen;
    __be32 flags;
    unsigned int mss = 1;
    unsigned int hlen;
    unsigned int off;
    int flush = 1;
    int i;

    off = skb_gro_offset(skb);
    hlen = off + sizeof(*th);
    th = skb_gro_header_fast(skb, off);
    if (skb_gro_header_hard(skb, hlen)) {
        th = skb_gro_header_slow(skb, hlen, off);
        if (unlikely(!th))
            goto out;
    }

    thlen = th->doff * 4;
    if (thlen < sizeof(*th))
        goto out;

    hlen = off + thlen;
    if (skb_gro_header_hard(skb, hlen)) {
        th = skb_gro_header_slow(skb, hlen, off);
        if (unlikely(!th))
            goto out;
    }

    skb_gro_pull(skb, thlen);

    len = skb_gro_len(skb);
    flags = tcp_flag_word(th);

    for (; (p = *head); head = &p->next) {
        if (!NAPI_GRO_CB(p)->same_flow)
            continue;

        th2 = tcp_hdr(p);

        if (*(u32 *)&th->source ^ *(u32 *)&th2->source) {
            NAPI_GRO_CB(p)->same_flow = 0;
            continue;
        }

        goto found;
    }

    goto out_check_final;

found:
    flush = NAPI_GRO_CB(p)->flush;
    flush |= (__force int)(flags & TCP_FLAG_CWR);
    flush |= (__force int)((flags ^ tcp_flag_word(th2)) &
          ~(TCP_FLAG_CWR | TCP_FLAG_FIN | TCP_FLAG_PSH));
    flush |= (__force int)(th->ack_seq ^ th2->ack_seq);
    for (i = sizeof(*th); i < thlen; i += 4)
        flush |= *(u32 *)((u8 *)th + i) ^
             *(u32 *)((u8 *)th2 + i);

    mss = skb_shinfo(p)->gso_size;

    flush |= (len - 1) >= mss;
    flush |= (ntohl(th2->seq) + skb_gro_len(p)) ^ ntohl(th->seq);

    if (flush || skb_gro_receive(head, skb)) {
        mss = 1;
        goto out_check_final;
    }

    p = *head;
    th2 = tcp_hdr(p);
    tcp_flag_word(th2) |= flags & (TCP_FLAG_FIN | TCP_FLAG_PSH);

out_check_final:
    flush = len < mss;
    flush |= (__force int)(flags & (TCP_FLAG_URG | TCP_FLAG_PSH |
                    TCP_FLAG_RST | TCP_FLAG_SYN |
                    TCP_FLAG_FIN));

    if (p && (!NAPI_GRO_CB(skb)->same_flow || flush))
        pp = head;

out:
    NAPI_GRO_CB(skb)->flush |= flush;

    return pp;
}
EXPORT_SYMBOL(tcp_gro_receive);

int tcp_gro_complete(struct sk_buff *skb)
{
    struct tcphdr *th = tcp_hdr(skb);

    skb->csum_start = skb_transport_header(skb) - skb->head;
    skb->csum_offset = offsetof(struct tcphdr, check);
    skb->ip_summed = CHECKSUM_PARTIAL;

    skb_shinfo(skb)->gso_segs = NAPI_GRO_CB(skb)->count;

    if (th->cwr)
        skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN;

    return 0;
}
EXPORT_SYMBOL(tcp_gro_complete);

#ifdef CONFIG_TCP_MD5SIG
static unsigned long tcp_md5sig_users;
static struct tcp_md5sig_pool __percpu *tcp_md5sig_pool;
static DEFINE_SPINLOCK(tcp_md5sig_pool_lock);

static void __tcp_free_md5sig_pool(struct tcp_md5sig_pool __percpu *pool)
{
    int cpu;

    for_each_possible_cpu(cpu) {
        struct tcp_md5sig_pool *p = per_cpu_ptr(pool, cpu);

        if (p->md5_desc.tfm)
            crypto_free_hash(p->md5_desc.tfm);
    }
    free_percpu(pool);
}

void tcp_free_md5sig_pool(void)
{
    struct tcp_md5sig_pool __percpu *pool = NULL;

    spin_lock_bh(&tcp_md5sig_pool_lock);
    if (--tcp_md5sig_users == 0) {
        pool = tcp_md5sig_pool;
        tcp_md5sig_pool = NULL;
    }
    spin_unlock_bh(&tcp_md5sig_pool_lock);
    if (pool)
        __tcp_free_md5sig_pool(pool);
}
EXPORT_SYMBOL(tcp_free_md5sig_pool);

static struct tcp_md5sig_pool __percpu *
__tcp_alloc_md5sig_pool(struct sock *sk)
{
    int cpu;
    struct tcp_md5sig_pool __percpu *pool;

    pool = alloc_percpu(struct tcp_md5sig_pool);
    if (!pool)
        return NULL;

    for_each_possible_cpu(cpu) {
        struct crypto_hash *hash;

        hash = crypto_alloc_hash("md5", 0, CRYPTO_ALG_ASYNC);
        if (!hash || IS_ERR(hash))
            goto out_free;

        per_cpu_ptr(pool, cpu)->md5_desc.tfm = hash;
    }
    return pool;
out_free:
    __tcp_free_md5sig_pool(pool);
    return NULL;
}

struct tcp_md5sig_pool __percpu *tcp_alloc_md5sig_pool(struct sock *sk)
{
    struct tcp_md5sig_pool __percpu *pool;
    bool alloc = false;

retry:
    spin_lock_bh(&tcp_md5sig_pool_lock);
    pool = tcp_md5sig_pool;
    if (tcp_md5sig_users++ == 0) {
        alloc = true;
        spin_unlock_bh(&tcp_md5sig_pool_lock);
    } else if (!pool) {
        tcp_md5sig_users--;
        spin_unlock_bh(&tcp_md5sig_pool_lock);
        cpu_relax();
        goto retry;
    } else
        spin_unlock_bh(&tcp_md5sig_pool_lock);

    if (alloc) {
        /* we cannot hold spinlock here because this may sleep. */
        struct tcp_md5sig_pool __percpu *p;

        p = __tcp_alloc_md5sig_pool(sk);
        spin_lock_bh(&tcp_md5sig_pool_lock);
        if (!p) {
            tcp_md5sig_users--;
            spin_unlock_bh(&tcp_md5sig_pool_lock);
            return NULL;
        }
        pool = tcp_md5sig_pool;
        if (pool) {
            /* oops, it has already been assigned. */
            spin_unlock_bh(&tcp_md5sig_pool_lock);
            __tcp_free_md5sig_pool(p);
        } else {
            tcp_md5sig_pool = pool = p;
            spin_unlock_bh(&tcp_md5sig_pool_lock);
        }
    }
    return pool;
}
EXPORT_SYMBOL(tcp_alloc_md5sig_pool);


struct tcp_md5sig_pool *tcp_get_md5sig_pool(void)
{
    struct tcp_md5sig_pool __percpu *p;

    local_bh_disable();

    spin_lock(&tcp_md5sig_pool_lock);
    p = tcp_md5sig_pool;
    if (p)
        tcp_md5sig_users++;
    spin_unlock(&tcp_md5sig_pool_lock);

    if (p)
        return this_cpu_ptr(p);

    local_bh_enable();
    return NULL;
}
EXPORT_SYMBOL(tcp_get_md5sig_pool);

void tcp_put_md5sig_pool(void)
{
    local_bh_enable();
    tcp_free_md5sig_pool();
}
EXPORT_SYMBOL(tcp_put_md5sig_pool);

int tcp_md5_hash_header(struct tcp_md5sig_pool *hp,
            const struct tcphdr *th)
{
    struct scatterlist sg;
    struct tcphdr hdr;
    int err;

    /* We are not allowed to change tcphdr, make a local copy */
    memcpy(&hdr, th, sizeof(hdr));
    hdr.check = 0;

    /* options aren't included in the hash */
    sg_init_one(&sg, &hdr, sizeof(hdr));
    err = crypto_hash_update(&hp->md5_desc, &sg, sizeof(hdr));
    return err;
}
EXPORT_SYMBOL(tcp_md5_hash_header);

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 hash_desc *desc = &hp->md5_desc;
    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);
    if (crypto_hash_update(desc, &sg, head_data_len))
        return 1;

    for (i = 0; i < shi->nr_frags; ++i) {
        const struct skb_frag_struct *f = &shi->frags[i];
        struct page *page = skb_frag_page(f);
        sg_set_page(&sg, page, skb_frag_size(f), f->page_offset);
        if (crypto_hash_update(desc, &sg, skb_frag_size(f)))
            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)
{
    struct scatterlist sg;

    sg_init_one(&sg, key->key, key->keylen);
    return crypto_hash_update(&hp->md5_desc, &sg, key->keylen);
}
EXPORT_SYMBOL(tcp_md5_hash_key);

#endif

/* Each Responder maintains up to two secret values concurrently for
 * efficient secret rollover.  Each secret value has 4 states:
 *
 * Generating.  (tcp_secret_generating != tcp_secret_primary)
 *    Generates new Responder-Cookies, but not yet used for primary
 *    verification.  This is a short-term state, typically lasting only
 *    one round trip time (RTT).
 *
 * Primary.  (tcp_secret_generating == tcp_secret_primary)
 *    Used both for generation and primary verification.
 *
 * Retiring.  (tcp_secret_retiring != tcp_secret_secondary)
 *    Used for verification, until the first failure that can be
 *    verified by the newer Generating secret.  At that time, this
 *    cookie's state is changed to Secondary, and the Generating
 *    cookie's state is changed to Primary.  This is a short-term state,
 *    typically lasting only one round trip time (RTT).
 *
 * Secondary.  (tcp_secret_retiring == tcp_secret_secondary)
 *    Used for secondary verification, after primary verification
 *    failures.  This state lasts no more than twice the Maximum Segment
 *    Lifetime (2MSL).  Then, the secret is discarded.
 */
struct tcp_cookie_secret {
    /* The secret is divided into two parts.  The digest part is the
     * equivalent of previously hashing a secret and saving the state,
     * and serves as an initialization vector (IV).  The message part
     * serves as the trailing secret.
     */
    u32             secrets[COOKIE_WORKSPACE_WORDS];
    unsigned long           expires;
};

#define TCP_SECRET_1MSL (HZ * TCP_PAWS_MSL)
#define TCP_SECRET_2MSL (HZ * TCP_PAWS_MSL * 2)
#define TCP_SECRET_LIFE (HZ * 600)

static struct tcp_cookie_secret tcp_secret_one;
static struct tcp_cookie_secret tcp_secret_two;

/* Essentially a circular list, without dynamic allocation. */
static struct tcp_cookie_secret *tcp_secret_generating;
static struct tcp_cookie_secret *tcp_secret_primary;
static struct tcp_cookie_secret *tcp_secret_retiring;
static struct tcp_cookie_secret *tcp_secret_secondary;

static DEFINE_SPINLOCK(tcp_secret_locker);

/* Select a pseudo-random word in the cookie workspace.
 */
static inline u32 tcp_cookie_work(const u32 *ws, const int n)
{
    return ws[COOKIE_DIGEST_WORDS + ((COOKIE_MESSAGE_WORDS-1) & ws[n])];
}

/* Fill bakery[COOKIE_WORKSPACE_WORDS] with generator, updating as needed.
 * Called in softirq context.
 * Returns: 0 for success.
 */
int tcp_cookie_generator(u32 *bakery)
{
    unsigned long jiffy = jiffies;

    if (unlikely(time_after_eq(jiffy, tcp_secret_generating->expires))) {
        spin_lock_bh(&tcp_secret_locker);
        if (!time_after_eq(jiffy, tcp_secret_generating->expires)) {
            /* refreshed by another */
            memcpy(bakery,
                   &tcp_secret_generating->secrets[0],
                   COOKIE_WORKSPACE_WORDS);
        } else {
            /* still needs refreshing */
            get_random_bytes(bakery, COOKIE_WORKSPACE_WORDS);

            /* The first time, paranoia assumes that the
             * randomization function isn't as strong.  But,
             * this secret initialization is delayed until
             * the last possible moment (packet arrival).
             * Although that time is observable, it is
             * unpredictably variable.  Mash in the most
             * volatile clock bits available, and expire the
             * secret extra quickly.
             */
            if (unlikely(tcp_secret_primary->expires ==
                     tcp_secret_secondary->expires)) {
                struct timespec tv;

                getnstimeofday(&tv);
                bakery[COOKIE_DIGEST_WORDS+0] ^=
                    (u32)tv.tv_nsec;

                tcp_secret_secondary->expires = jiffy
                    + TCP_SECRET_1MSL
                    + (0x0f & tcp_cookie_work(bakery, 0));
            } else {
                tcp_secret_secondary->expires = jiffy
                    + TCP_SECRET_LIFE
                    + (0xff & tcp_cookie_work(bakery, 1));
                tcp_secret_primary->expires = jiffy
                    + TCP_SECRET_2MSL
                    + (0x1f & tcp_cookie_work(bakery, 2));
            }
            memcpy(&tcp_secret_secondary->secrets[0],
                   bakery, COOKIE_WORKSPACE_WORDS);

            rcu_assign_pointer(tcp_secret_generating,
                       tcp_secret_secondary);
            rcu_assign_pointer(tcp_secret_retiring,
                       tcp_secret_primary);
            /*
             * Neither call_rcu() nor synchronize_rcu() needed.
             * Retiring data is not freed.  It is replaced after
             * further (locked) pointer updates, and a quiet time
             * (minimum 1MSL, maximum LIFE - 2MSL).
             */
        }
        spin_unlock_bh(&tcp_secret_locker);
    } else {
        rcu_read_lock_bh();
        memcpy(bakery,
               &rcu_dereference(tcp_secret_generating)->secrets[0],
               COOKIE_WORKSPACE_WORDS);
        rcu_read_unlock_bh();
    }
    return 0;
}
EXPORT_SYMBOL(tcp_cookie_generator);

void tcp_done(struct sock *sk)
{
    struct request_sock *req = tcp_sk(sk)->fastopen_rsk;

    if (sk->sk_state == TCP_SYN_SENT || sk->sk_state == TCP_SYN_RECV)
        TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_ATTEMPTFAILS);

    tcp_set_state(sk, TCP_CLOSE);
    tcp_clear_xmit_timers(sk);
    if (req != NULL)
        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);

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);

void tcp_init_mem(struct net *net)
{
    unsigned long limit = nr_free_buffer_pages() / 8;
    limit = max(limit, 128UL);
    net->ipv4.sysctl_tcp_mem[0] = limit / 4 * 3;
    net->ipv4.sysctl_tcp_mem[1] = limit;
    net->ipv4.sysctl_tcp_mem[2] = net->ipv4.sysctl_tcp_mem[0] * 2;
}

void __init tcp_init(void)
{
    struct sk_buff *skb = NULL;
    unsigned long limit;
    int max_rshare, max_wshare, cnt;
    unsigned int i;
    unsigned long jiffy = jiffies;

    BUILD_BUG_ON(sizeof(struct tcp_skb_cb) > sizeof(skb->cb));

    percpu_counter_init(&tcp_sockets_allocated, 0);
    percpu_counter_init(&tcp_orphan_count, 0);
    tcp_hashinfo.bind_bucket_cachep =
        kmem_cache_create("tcp_bind_bucket",
                  sizeof(struct inet_bind_bucket), 0,
                  SLAB_HWCACHE_ALIGN|SLAB_PANIC, 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,
                    (totalram_pages >= 128 * 1024) ?
                    13 : 15,
                    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);
        INIT_HLIST_NULLS_HEAD(&tcp_hashinfo.ehash[i].twchain, 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,
                    (totalram_pages >= 128 * 1024) ?
                    13 : 15,
                    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;

    tcp_death_row.sysctl_max_tw_buckets = cnt / 2;
    sysctl_tcp_max_orphans = cnt / 2;
    sysctl_max_syn_backlog = max(128, cnt / 256);

    tcp_init_mem(&init_net);
    /* 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);

    sysctl_tcp_wmem[0] = SK_MEM_QUANTUM;
    sysctl_tcp_wmem[1] = 16*1024;
    sysctl_tcp_wmem[2] = max(64*1024, max_wshare);

    sysctl_tcp_rmem[0] = SK_MEM_QUANTUM;
    sysctl_tcp_rmem[1] = 87380;
    sysctl_tcp_rmem[2] = max(87380, max_rshare);

    pr_info("Hash tables configured (established %u bind %u)\n",
        tcp_hashinfo.ehash_mask + 1, tcp_hashinfo.bhash_size);

    tcp_metrics_init();

    tcp_register_congestion_control(&tcp_reno);

    memset(&tcp_secret_one.secrets[0], 0, sizeof(tcp_secret_one.secrets));
    memset(&tcp_secret_two.secrets[0], 0, sizeof(tcp_secret_two.secrets));
    tcp_secret_one.expires = jiffy; /* past due */
    tcp_secret_two.expires = jiffy; /* past due */
    tcp_secret_generating = &tcp_secret_one;
    tcp_secret_primary = &tcp_secret_one;
    tcp_secret_retiring = &tcp_secret_two;
    tcp_secret_secondary = &tcp_secret_two;
    tcp_tasklet_init();
}