cleanup

[linux-2.4.21-pre4.git] / net / ipv4 / tcp.c

/*
 * 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).
 *
 * Version:     $Id: tcp.c,v 1.1.1.1 2005/04/11 02:51:13 jack Exp $
 *
 * Authors:     Ross Biro, <bir7@leland.Stanford.Edu>
 *              Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
 *              Mark Evans, <evansmp@uhura.aston.ac.uk>
 *              Corey Minyard <wf-rch!minyard@relay.EU.net>
 *              Florian La Roche, <flla@stud.uni-sb.de>
 *              Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
 *              Linus Torvalds, <torvalds@cs.helsinki.fi>
 *              Alan Cox, <gw4pts@gw4pts.ampr.org>
 *              Matthew Dillon, <dillon@apollo.west.oic.com>
 *              Arnt Gulbrandsen, <agulbra@nvg.unit.no>
 *              Jorge Cwik, <jorge@laser.satlink.net>
 *
 * Fixes:
 *              Alan Cox        :       Numerous verify_area() calls
 *              Alan Cox        :       Set the ACK bit on a reset
 *              Alan Cox        :       Stopped it crashing if it closed while
 *                                      sk->inuse=1 and was trying to connect
 *                                      (tcp_err()).
 *              Alan Cox        :       All icmp error handling was broken
 *                                      pointers passed where wrong and the
 *                                      socket was looked up backwards. Nobody
 *                                      tested any icmp error code obviously.
 *              Alan Cox        :       tcp_err() now handled properly. It
 *                                      wakes people on errors. poll
 *                                      behaves and the icmp error race
 *                                      has gone by moving it into sock.c
 *              Alan Cox        :       tcp_send_reset() fixed to work for
 *                                      everything not just packets for
 *                                      unknown sockets.
 *              Alan Cox        :       tcp option processing.
 *              Alan Cox        :       Reset tweaked (still not 100%) [Had
 *                                      syn rule wrong]
 *              Herp Rosmanith  :       More reset fixes
 *              Alan Cox        :       No longer acks invalid rst frames.
 *                                      Acking any kind of RST is right out.
 *              Alan Cox        :       Sets an ignore me flag on an rst
 *                                      receive otherwise odd bits of prattle
 *                                      escape still
 *              Alan Cox        :       Fixed another acking RST frame bug.
 *                                      Should stop LAN workplace lockups.
 *              Alan Cox        :       Some tidyups using the new skb list
 *                                      facilities
 *              Alan Cox        :       sk->keepopen now seems to work
 *              Alan Cox        :       Pulls options out correctly on accepts
 *              Alan Cox        :       Fixed assorted sk->rqueue->next errors
 *              Alan Cox        :       PSH doesn't end a TCP read. Switched a
 *                                      bit to skb ops.
 *              Alan Cox        :       Tidied tcp_data to avoid a potential
 *                                      nasty.
 *              Alan Cox        :       Added some better commenting, as the
 *                                      tcp is hard to follow
 *              Alan Cox        :       Removed incorrect check for 20 * psh
 *      Michael O'Reilly        :       ack < copied bug fix.
 *      Johannes Stille         :       Misc tcp fixes (not all in yet).
 *              Alan Cox        :       FIN with no memory -> CRASH
 *              Alan Cox        :       Added socket option proto entries.
 *                                      Also added awareness of them to accept.
 *              Alan Cox        :       Added TCP options (SOL_TCP)
 *              Alan Cox        :       Switched wakeup calls to callbacks,
 *                                      so the kernel can layer network
 *                                      sockets.
 *              Alan Cox        :       Use ip_tos/ip_ttl settings.
 *              Alan Cox        :       Handle FIN (more) properly (we hope).
 *              Alan Cox        :       RST frames sent on unsynchronised
 *                                      state ack error.
 *              Alan Cox        :       Put in missing check for SYN bit.
 *              Alan Cox        :       Added tcp_select_window() aka NET2E
 *                                      window non shrink trick.
 *              Alan Cox        :       Added a couple of small NET2E timer
 *                                      fixes
 *              Charles Hedrick :       TCP fixes
 *              Toomas Tamm     :       TCP window fixes
 *              Alan Cox        :       Small URG fix to rlogin ^C ack fight
 *              Charles Hedrick :       Rewrote most of it to actually work
 *              Linus           :       Rewrote tcp_read() and URG handling
 *                                      completely
 *              Gerhard Koerting:       Fixed some missing timer handling
 *              Matthew Dillon  :       Reworked TCP machine states as per RFC
 *              Gerhard Koerting:       PC/TCP workarounds
 *              Adam Caldwell   :       Assorted timer/timing errors
 *              Matthew Dillon  :       Fixed another RST bug
 *              Alan Cox        :       Move to kernel side addressing changes.
 *              Alan Cox        :       Beginning work on TCP fastpathing
 *                                      (not yet usable)
 *              Arnt Gulbrandsen:       Turbocharged tcp_check() routine.
 *              Alan Cox        :       TCP fast path debugging
 *              Alan Cox        :       Window clamping
 *              Michael Riepe   :       Bug in tcp_check()
 *              Matt Dillon     :       More TCP improvements and RST bug fixes
 *              Matt Dillon     :       Yet more small nasties remove from the
 *                                      TCP code (Be very nice to this man if
 *                                      tcp finally works 100%) 8)
 *              Alan Cox        :       BSD accept semantics.
 *              Alan Cox        :       Reset on closedown bug.
 *      Peter De Schrijver      :       ENOTCONN check missing in tcp_sendto().
 *              Michael Pall    :       Handle poll() after URG properly in
 *                                      all cases.
 *              Michael Pall    :       Undo the last fix in tcp_read_urg()
 *                                      (multi URG PUSH broke rlogin).
 *              Michael Pall    :       Fix the multi URG PUSH problem in
 *                                      tcp_readable(), poll() after URG
 *                                      works now.
 *              Michael Pall    :       recv(...,MSG_OOB) never blocks in the
 *                                      BSD api.
 *              Alan Cox        :       Changed the semantics of sk->socket to
 *                                      fix a race and a signal problem with
 *                                      accept() and async I/O.
 *              Alan Cox        :       Relaxed the rules on tcp_sendto().
 *              Yury Shevchuk   :       Really fixed accept() blocking problem.
 *              Craig I. Hagan  :       Allow for BSD compatible TIME_WAIT for
 *                                      clients/servers which listen in on
 *                                      fixed ports.
 *              Alan Cox        :       Cleaned the above up and shrank it to
 *                                      a sensible code size.
 *              Alan Cox        :       Self connect lockup fix.
 *              Alan Cox        :       No connect to multicast.
 *              Ross Biro       :       Close unaccepted children on master
 *                                      socket close.
 *              Alan Cox        :       Reset tracing code.
 *              Alan Cox        :       Spurious resets on shutdown.
 *              Alan Cox        :       Giant 15 minute/60 second timer error
 *              Alan Cox        :       Small whoops in polling before an
 *                                      accept.
 *              Alan Cox        :       Kept the state trace facility since
 *                                      it's handy for debugging.
 *              Alan Cox        :       More reset handler fixes.
 *              Alan Cox        :       Started rewriting the code based on
 *                                      the RFC's for other useful protocol
 *                                      references see: Comer, KA9Q NOS, and
 *                                      for a reference on the difference
 *                                      between specifications and how BSD
 *                                      works see the 4.4lite source.
 *              A.N.Kuznetsov   :       Don't time wait on completion of tidy
 *                                      close.
 *              Linus Torvalds  :       Fin/Shutdown & copied_seq changes.
 *              Linus Torvalds  :       Fixed BSD port reuse to work first syn
 *              Alan Cox        :       Reimplemented timers as per the RFC
 *                                      and using multiple timers for sanity.
 *              Alan Cox        :       Small bug fixes, and a lot of new
 *                                      comments.
 *              Alan Cox        :       Fixed dual reader crash by locking
 *                                      the buffers (much like datagram.c)
 *              Alan Cox        :       Fixed stuck sockets in probe. A probe
 *                                      now gets fed up of retrying without
 *                                      (even a no space) answer.
 *              Alan Cox        :       Extracted closing code better
 *              Alan Cox        :       Fixed the closing state machine to
 *                                      resemble the RFC.
 *              Alan Cox        :       More 'per spec' fixes.
 *              Jorge Cwik      :       Even faster checksumming.
 *              Alan Cox        :       tcp_data() doesn't ack illegal PSH
 *                                      only frames. At least one pc tcp stack
 *                                      generates them.
 *              Alan Cox        :       Cache last socket.
 *              Alan Cox        :       Per route irtt.
 *              Matt Day        :       poll()->select() match BSD precisely on error
 *              Alan Cox        :       New buffers
 *              Marc Tamsky     :       Various sk->prot->retransmits and
 *                                      sk->retransmits misupdating fixed.
 *                                      Fixed tcp_write_timeout: stuck close,
 *                                      and TCP syn retries gets used now.
 *              Mark Yarvis     :       In tcp_read_wakeup(), don't send an
 *                                      ack if state is TCP_CLOSED.
 *              Alan Cox        :       Look up device on a retransmit - routes may
 *                                      change. Doesn't yet cope with MSS shrink right
 *                                      but its 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)
 *                                      
 *              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
 */

#include <linux/config.h>
#include <linux/types.h>
#include <linux/fcntl.h>
#include <linux/poll.h>
#include <linux/init.h>
#include <linux/smp_lock.h>
#include <linux/fs.h>

#include <net/icmp.h>
#include <net/tcp.h>

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

int sysctl_tcp_fin_timeout = TCP_FIN_TIMEOUT;

struct tcp_mib  tcp_statistics[NR_CPUS*2];

kmem_cache_t *tcp_openreq_cachep;
kmem_cache_t *tcp_bucket_cachep;
kmem_cache_t *tcp_timewait_cachep;

atomic_t tcp_orphan_count = ATOMIC_INIT(0);

int sysctl_tcp_mem[3];
int sysctl_tcp_wmem[3] = { 4*1024, 16*1024, 128*1024 };
int sysctl_tcp_rmem[3] = { 4*1024, 87380, 87380*2 };

atomic_t tcp_memory_allocated;  /* Current allocated memory. */
atomic_t tcp_sockets_allocated; /* Current number of TCP sockets. */

/* Pressure flag: try to collapse.
 * Technical note: it is used by multiple contexts non atomically.
 * All the tcp_mem_schedule() is of this nature: accounting
 * is strict, actions are advisory and have some latency. */
int tcp_memory_pressure;

#define TCP_PAGES(amt) (((amt)+TCP_MEM_QUANTUM-1)/TCP_MEM_QUANTUM)

int tcp_mem_schedule(struct sock *sk, int size, int kind)
{
        int amt = TCP_PAGES(size);

        sk->forward_alloc += amt*TCP_MEM_QUANTUM;
        atomic_add(amt, &tcp_memory_allocated);

        /* Under limit. */
        if (atomic_read(&tcp_memory_allocated) < sysctl_tcp_mem[0]) {
                if (tcp_memory_pressure)
                        tcp_memory_pressure = 0;
                return 1;
        }

        /* Over hard limit. */
        if (atomic_read(&tcp_memory_allocated) > sysctl_tcp_mem[2]) {
                tcp_enter_memory_pressure();
                goto suppress_allocation;
        }

        /* Under pressure. */
        if (atomic_read(&tcp_memory_allocated) > sysctl_tcp_mem[1])
                tcp_enter_memory_pressure();

        if (kind) {
                if (atomic_read(&sk->rmem_alloc) < sysctl_tcp_rmem[0])
                        return 1;
        } else {
                if (sk->wmem_queued < sysctl_tcp_wmem[0])
                        return 1;
        }

        if (!tcp_memory_pressure ||
            sysctl_tcp_mem[2] > atomic_read(&tcp_sockets_allocated)
            * TCP_PAGES(sk->wmem_queued+atomic_read(&sk->rmem_alloc)+
                        sk->forward_alloc))
                return 1;

suppress_allocation:

        if (kind == 0) {
                tcp_moderate_sndbuf(sk);

                /* Fail only if socket is _under_ its sndbuf.
                 * In this case we cannot block, so that we have to fail.
                 */
                if (sk->wmem_queued+size >= sk->sndbuf)
                        return 1;
        }

        /* Alas. Undo changes. */
        sk->forward_alloc -= amt*TCP_MEM_QUANTUM;
        atomic_sub(amt, &tcp_memory_allocated);
        return 0;
}

void __tcp_mem_reclaim(struct sock *sk)
{
        if (sk->forward_alloc >= TCP_MEM_QUANTUM) {
                atomic_sub(sk->forward_alloc/TCP_MEM_QUANTUM, &tcp_memory_allocated);
                sk->forward_alloc &= (TCP_MEM_QUANTUM-1);
                if (tcp_memory_pressure &&
                    atomic_read(&tcp_memory_allocated) < sysctl_tcp_mem[0])
                        tcp_memory_pressure = 0;
        }
}

void tcp_rfree(struct sk_buff *skb)
{
        struct sock *sk = skb->sk;

        atomic_sub(skb->truesize, &sk->rmem_alloc);
        sk->forward_alloc += skb->truesize;
}

/*
 * LISTEN is a special case for poll..
 */
static __inline__ unsigned int tcp_listen_poll(struct sock *sk, poll_table *wait)
{
        return sk->tp_pinfo.af_tcp.accept_queue ? (POLLIN | POLLRDNORM) : 0;
}

/*
 *      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;
        struct tcp_opt *tp = &(sk->tp_pinfo.af_tcp);

        poll_wait(file, sk->sleep, wait);
        if (sk->state == TCP_LISTEN)
                return tcp_listen_poll(sk, wait);

        /* Socket is not locked. We are protected from async events
           by poll logic and correct handling of state changes
           made by another threads is impossible in any case.
         */

        mask = 0;
        if (sk->err)
                mask = POLLERR;

        /*
         * 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 PULLHUP were maskable,
         * then we could set it on SND_SHUTDOWN. BTW examples given
         * in Stevens' books assume exactly this behaviour, it explains
         * why PULLHUP 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->shutdown == SHUTDOWN_MASK || sk->state == TCP_CLOSE)
                mask |= POLLHUP;
        if (sk->shutdown & RCV_SHUTDOWN)
                mask |= POLLIN | POLLRDNORM;

        /* Connected? */
        if ((1 << sk->state) & ~(TCPF_SYN_SENT|TCPF_SYN_RECV)) {
                /* Potential race condition. If read of tp below will
                 * escape above sk->state, we can be illegally awaken
                 * in SYN_* states. */
                if ((tp->rcv_nxt != tp->copied_seq) &&
                    (tp->urg_seq != tp->copied_seq ||
                     tp->rcv_nxt != tp->copied_seq+1 ||
                     sk->urginline || !tp->urg_data))
                        mask |= POLLIN | POLLRDNORM;

                if (!(sk->shutdown & SEND_SHUTDOWN)) {
                        if (tcp_wspace(sk) >= tcp_min_write_space(sk)) {
                                mask |= POLLOUT | POLLWRNORM;
                        } else {  /* send SIGIO later */
                                set_bit(SOCK_ASYNC_NOSPACE, &sk->socket->flags);
                                set_bit(SOCK_NOSPACE, &sk->socket->flags);

                                /* Race breaker. If space is freed after
                                 * wspace test but before the flags are set,
                                 * IO signal will be lost.
                                 */
                                if (tcp_wspace(sk) >= tcp_min_write_space(sk))
                                        mask |= POLLOUT | POLLWRNORM;
                        }
                }

                if (tp->urg_data & TCP_URG_VALID)
                        mask |= POLLPRI;
        }
        return mask;
}

/*
 *      TCP socket write_space callback.
 */
void tcp_write_space(struct sock *sk)
{
        struct socket *sock = sk->socket;

        if (tcp_wspace(sk) >= tcp_min_write_space(sk) && sock) {
                clear_bit(SOCK_NOSPACE, &sock->flags);

                if (sk->sleep && waitqueue_active(sk->sleep))
                        wake_up_interruptible(sk->sleep);

                if (sock->fasync_list && !(sk->shutdown&SEND_SHUTDOWN))
                        sock_wake_async(sock, 2, POLL_OUT);
        }
}

int tcp_ioctl(struct sock *sk, int cmd, unsigned long arg)
{
        struct tcp_opt *tp = &(sk->tp_pinfo.af_tcp);
        int answ;

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

                lock_sock(sk);
                if ((1<<sk->state) & (TCPF_SYN_SENT|TCPF_SYN_RECV))
                        answ = 0;
                else if (sk->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 is in queue. */
                        if (answ && !skb_queue_empty(&sk->receive_queue))
                                answ -= ((struct sk_buff*)sk->receive_queue.prev)->h.th->fin;
                } 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->state == TCP_LISTEN)
                        return(-EINVAL);

                if ((1<<sk->state) & (TCPF_SYN_SENT|TCPF_SYN_RECV))
                        answ = 0;
                else
                        answ = tp->write_seq - tp->snd_una;
                break;
        default:
                return(-ENOIOCTLCMD);
        };

        return put_user(answ, (int *)arg);
}


int tcp_listen_start(struct sock *sk)
{
        struct tcp_opt *tp = &(sk->tp_pinfo.af_tcp);
        struct tcp_listen_opt *lopt;

        sk->max_ack_backlog = 0;
        sk->ack_backlog = 0;
        tp->accept_queue = tp->accept_queue_tail = NULL;
        tp->syn_wait_lock = RW_LOCK_UNLOCKED;
        tcp_delack_init(tp);

        lopt = kmalloc(sizeof(struct tcp_listen_opt), GFP_KERNEL);
        if (!lopt)
                return -ENOMEM;

        memset(lopt, 0, sizeof(struct tcp_listen_opt));
        for (lopt->max_qlen_log = 6; ; lopt->max_qlen_log++)
                if ((1<<lopt->max_qlen_log) >= sysctl_max_syn_backlog)
                        break;

        write_lock_bh(&tp->syn_wait_lock);
        tp->listen_opt = lopt;
        write_unlock_bh(&tp->syn_wait_lock);

        /* There is race window here: we announce ourselves listening,
         * but this transition is still not validated by get_port().
         * It is OK, because this socket enters to hash table only
         * after validation is complete.
         */
        sk->state = TCP_LISTEN;
        if (sk->prot->get_port(sk, sk->num) == 0) {
                sk->sport = htons(sk->num);

                sk_dst_reset(sk);
                sk->prot->hash(sk);

                return 0;
        }

        sk->state = TCP_CLOSE;
        write_lock_bh(&tp->syn_wait_lock);
        tp->listen_opt = NULL;
        write_unlock_bh(&tp->syn_wait_lock);
        kfree(lopt);
        return -EADDRINUSE;
}

/*
 *      This routine closes sockets which have been at least partially
 *      opened, but not yet accepted.
 */

static void tcp_listen_stop (struct sock *sk)
{
        struct tcp_opt *tp = &(sk->tp_pinfo.af_tcp);
        struct tcp_listen_opt *lopt = tp->listen_opt;
        struct open_request *acc_req = tp->accept_queue;
        struct open_request *req;
        int i;

        tcp_delete_keepalive_timer(sk);

        /* make all the listen_opt local to us */
        write_lock_bh(&tp->syn_wait_lock);
        tp->listen_opt =NULL;
        write_unlock_bh(&tp->syn_wait_lock);
        tp->accept_queue = tp->accept_queue_tail = NULL;

        if (lopt->qlen) {
                for (i=0; i<TCP_SYNQ_HSIZE; i++) {
                        while ((req = lopt->syn_table[i]) != NULL) {
                                lopt->syn_table[i] = req->dl_next;
                                lopt->qlen--;
                                tcp_openreq_free(req);

                /* Following specs, it would be better either to send FIN
                 * (and enter FIN-WAIT-1, it is normal close)
                 * or to send active reset (abort). 
                 * Certainly, it is pretty dangerous while synflood, but it is
                 * bad justification for our negligence 8)
                 * To be honest, we are not able to make either
                 * of the variants now.                 --ANK
                 */
                        }
                }
        }
        BUG_TRAP(lopt->qlen == 0);

        kfree(lopt);

        while ((req=acc_req) != NULL) {
                struct sock *child = req->sk;

                acc_req = req->dl_next;

                local_bh_disable();
                bh_lock_sock(child);
                BUG_TRAP(child->lock.users==0);
                sock_hold(child);

                tcp_disconnect(child, O_NONBLOCK);

                sock_orphan(child);

                atomic_inc(&tcp_orphan_count);

                tcp_destroy_sock(child);

                bh_unlock_sock(child);
                local_bh_enable();
                sock_put(child);

                tcp_acceptq_removed(sk);
                tcp_openreq_fastfree(req);
        }
        BUG_TRAP(sk->ack_backlog == 0);
}

/*
 *      Wait for a socket to get into the connected state
 *
 *      Note: Must be called with the socket locked.
 */
static int wait_for_tcp_connect(struct sock * sk, int flags, long *timeo_p)
{
        struct task_struct *tsk = current;
        DECLARE_WAITQUEUE(wait, tsk);

        while((1 << sk->state) & ~(TCPF_ESTABLISHED | TCPF_CLOSE_WAIT)) {
                if(sk->err)
                        return sock_error(sk);
                if((1 << sk->state) &
                   ~(TCPF_SYN_SENT | TCPF_SYN_RECV))
                        return -EPIPE;
                if(!*timeo_p)
                        return -EAGAIN;
                if(signal_pending(tsk))
                        return sock_intr_errno(*timeo_p);

                __set_task_state(tsk, TASK_INTERRUPTIBLE);
                add_wait_queue(sk->sleep, &wait);
                sk->tp_pinfo.af_tcp.write_pending++;

                release_sock(sk);
                *timeo_p = schedule_timeout(*timeo_p);
                lock_sock(sk);

                __set_task_state(tsk, TASK_RUNNING);
                remove_wait_queue(sk->sleep, &wait);
                sk->tp_pinfo.af_tcp.write_pending--;
        }
        return 0;
}

static inline int tcp_memory_free(struct sock *sk)
{
        return sk->wmem_queued < sk->sndbuf;
}

/*
 *      Wait for more memory for a socket
 */
static int wait_for_tcp_memory(struct sock * sk, long *timeo)
{
        int err = 0;
        long vm_wait = 0;
        long current_timeo = *timeo;
        DECLARE_WAITQUEUE(wait, current);

        if (tcp_memory_free(sk))
                current_timeo = vm_wait = (net_random()%(HZ/5))+2;

        add_wait_queue(sk->sleep, &wait);
        for (;;) {
                set_bit(SOCK_ASYNC_NOSPACE, &sk->socket->flags);

                set_current_state(TASK_INTERRUPTIBLE);

                if (sk->err || (sk->shutdown & SEND_SHUTDOWN))
                        goto do_error;
                if (!*timeo)
                        goto do_nonblock;
                if (signal_pending(current))
                        goto do_interrupted;
                clear_bit(SOCK_ASYNC_NOSPACE, &sk->socket->flags);
                if (tcp_memory_free(sk) && !vm_wait)
                        break;

                set_bit(SOCK_NOSPACE, &sk->socket->flags);
                sk->tp_pinfo.af_tcp.write_pending++;
                release_sock(sk);
                if (!tcp_memory_free(sk) || vm_wait)
                        current_timeo = schedule_timeout(current_timeo);
                lock_sock(sk);
                sk->tp_pinfo.af_tcp.write_pending--;

                if (vm_wait) {
                        vm_wait -= current_timeo;
                        current_timeo = *timeo;
                        if (current_timeo != MAX_SCHEDULE_TIMEOUT &&
                            (current_timeo -= vm_wait) < 0)
                                current_timeo = 0;
                        vm_wait = 0;
                }
                *timeo = current_timeo;
        }
out:
        current->state = TASK_RUNNING;
        remove_wait_queue(sk->sleep, &wait);
        return err;

do_error:
        err = -EPIPE;
        goto out;
do_nonblock:
        err = -EAGAIN;
        goto out;
do_interrupted:
        err = sock_intr_errno(*timeo);
        goto out;
}

ssize_t do_tcp_sendpages(struct sock *sk, struct page **pages, int poffset, size_t psize, int flags);

static inline int
can_coalesce(struct sk_buff *skb, int i, struct page *page, int off)
{
        if (i) {
                skb_frag_t *frag = &skb_shinfo(skb)->frags[i-1];
                return page == frag->page &&
                        off == frag->page_offset+frag->size;
        }
        return 0;
}

static inline void
fill_page_desc(struct sk_buff *skb, int i, struct page *page, int off, int size)
{
        skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
        frag->page = page;
        frag->page_offset = off;
        frag->size = size;
        skb_shinfo(skb)->nr_frags = i+1;
}

static inline void tcp_mark_push(struct tcp_opt *tp, struct sk_buff *skb)
{
        TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_PSH;
        tp->pushed_seq = tp->write_seq;
}

static inline int forced_push(struct tcp_opt *tp)
{
        return after(tp->write_seq, tp->pushed_seq + (tp->max_window>>1));
}

static inline void
skb_entail(struct sock *sk, struct tcp_opt *tp, struct sk_buff *skb)
{
        skb->csum = 0;
        TCP_SKB_CB(skb)->seq = tp->write_seq;
        TCP_SKB_CB(skb)->end_seq = tp->write_seq;
        TCP_SKB_CB(skb)->flags = TCPCB_FLAG_ACK;
        TCP_SKB_CB(skb)->sacked = 0;
        __skb_queue_tail(&sk->write_queue, skb);
        tcp_charge_skb(sk, skb);
        if (tp->send_head == NULL)
                tp->send_head = skb;
}

static inline void
tcp_mark_urg(struct tcp_opt *tp, int flags, struct sk_buff *skb)
{
        if (flags & MSG_OOB) {
                tp->urg_mode = 1;
                tp->snd_up = tp->write_seq;
                TCP_SKB_CB(skb)->sacked |= TCPCB_URG;
        }
}

static inline void
tcp_push(struct sock *sk, struct tcp_opt *tp, int flags, int mss_now, int nonagle)
{
        if (tp->send_head) {
                struct sk_buff *skb = sk->write_queue.prev;
                if (!(flags&MSG_MORE) || forced_push(tp))
                        tcp_mark_push(tp, skb);
                tcp_mark_urg(tp, flags, skb);
                __tcp_push_pending_frames(sk, tp, mss_now, (flags&MSG_MORE) ? 2 : nonagle);
        }
}

static int tcp_error(struct sock *sk, int flags, int err)
{
        if (err == -EPIPE)
                err = sock_error(sk) ? : -EPIPE;
        if (err == -EPIPE && !(flags&MSG_NOSIGNAL))
                send_sig(SIGPIPE, current, 0);
        return err;
}

ssize_t do_tcp_sendpages(struct sock *sk, struct page **pages, int poffset, size_t psize, int flags)
{
        struct tcp_opt *tp = &(sk->tp_pinfo.af_tcp);
        int mss_now;
        int err;
        ssize_t copied;
        long timeo = sock_sndtimeo(sk, flags&MSG_DONTWAIT);

        /* Wait for a connection to finish. */
        if ((1 << sk->state) & ~(TCPF_ESTABLISHED | TCPF_CLOSE_WAIT))
                if((err = wait_for_tcp_connect(sk, 0, &timeo)) != 0)
                        goto out_err;

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

        mss_now = tcp_current_mss(sk);
        copied = 0;

        err = -EPIPE;
        if (sk->err || (sk->shutdown & SEND_SHUTDOWN))
                goto do_error;

        while (psize > 0) {
                struct sk_buff *skb = sk->write_queue.prev;
                int offset, size, copy, i;
                struct page *page;

                page = pages[poffset/PAGE_SIZE];
                offset = poffset % PAGE_SIZE;
                size = min_t(size_t, psize, PAGE_SIZE-offset);

                if (tp->send_head==NULL || (copy = mss_now - skb->len) <= 0) {
new_segment:
                        if (!tcp_memory_free(sk))
                                goto wait_for_sndbuf;

                        skb = tcp_alloc_pskb(sk, 0, tp->mss_cache, sk->allocation);
                        if (skb == NULL)
                                goto wait_for_memory;

                        skb_entail(sk, tp, skb);
                        copy = mss_now;
                }

                if (copy > size)
                        copy = size;

                i = skb_shinfo(skb)->nr_frags;
                if (can_coalesce(skb, i, page, offset)) {
                        skb_shinfo(skb)->frags[i-1].size += copy;
                } else if (i < MAX_SKB_FRAGS) {
                        get_page(page);
                        fill_page_desc(skb, i, page, offset, copy);
                } else {
                        tcp_mark_push(tp, skb);
                        goto new_segment;
                }

                skb->len += copy;
                skb->data_len += copy;
                skb->ip_summed = CHECKSUM_HW;
                tp->write_seq += copy;
                TCP_SKB_CB(skb)->end_seq += copy;

                if (!copied)
                        TCP_SKB_CB(skb)->flags &= ~TCPCB_FLAG_PSH;

                copied += copy;
                poffset += copy;
                if (!(psize -= copy))
                        goto out;

                if (skb->len != mss_now || (flags&MSG_OOB))
                        continue;

                if (forced_push(tp)) {
                        tcp_mark_push(tp, skb);
                        __tcp_push_pending_frames(sk, tp, mss_now, 1);
                } else if (skb == tp->send_head)
                        tcp_push_one(sk, mss_now);
                continue;

wait_for_sndbuf:
                set_bit(SOCK_NOSPACE, &sk->socket->flags);
wait_for_memory:
                if (copied)
                        tcp_push(sk, tp, flags&~MSG_MORE, mss_now, 1);

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

                mss_now = tcp_current_mss(sk);
        }

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

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

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

#define TCP_ZC_CSUM_FLAGS (NETIF_F_IP_CSUM|NETIF_F_NO_CSUM|NETIF_F_HW_CSUM)

        if (!(sk->route_caps & NETIF_F_SG) || 
            !(sk->route_caps & TCP_ZC_CSUM_FLAGS))
                return sock_no_sendpage(sock, page, offset, size, flags);

#undef TCP_ZC_CSUM_FLAGS

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

#define TCP_PAGE(sk)    (sk->tp_pinfo.af_tcp.sndmsg_page)
#define TCP_OFF(sk)     (sk->tp_pinfo.af_tcp.sndmsg_off)

static inline int
tcp_copy_to_page(struct sock *sk, char *from, struct sk_buff *skb,
                 struct page *page, int off, int copy)
{
        int err = 0;
        unsigned int csum;

        csum = csum_and_copy_from_user(from, page_address(page)+off,
                                       copy, 0, &err);
        if (!err) {
                if (skb->ip_summed == CHECKSUM_NONE)
                        skb->csum = csum_block_add(skb->csum, csum, skb->len);
                skb->len += copy;
                skb->data_len += copy;
                skb->truesize += copy;
                sk->wmem_queued += copy;
                sk->forward_alloc -= copy;
        }
        return err;
}

static inline int
skb_add_data(struct sk_buff *skb, char *from, int copy)
{
        int err = 0;
        unsigned int csum;
        int off = skb->len;

        csum = csum_and_copy_from_user(from, skb_put(skb, copy),
                                       copy, 0, &err);
        if (!err) {
                skb->csum = csum_block_add(skb->csum, csum, off);
                return 0;
        }

        __skb_trim(skb, off);
        return -EFAULT;
}

static inline int select_size(struct sock *sk, struct tcp_opt *tp)
{
        int tmp = tp->mss_cache;

        if (sk->route_caps&NETIF_F_SG) {
                int pgbreak = SKB_MAX_HEAD(MAX_TCP_HEADER);

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

int tcp_sendmsg(struct sock *sk, struct msghdr *msg, int size)
{
        struct iovec *iov;
        struct tcp_opt *tp;
        struct sk_buff *skb;
        int iovlen, flags;
        int mss_now;
        int err, copied;
        long timeo;

        tp = &(sk->tp_pinfo.af_tcp);

        lock_sock(sk);
        TCP_CHECK_TIMER(sk);

        flags = msg->msg_flags;
        timeo = sock_sndtimeo(sk, flags&MSG_DONTWAIT);

        /* Wait for a connection to finish. */
        if ((1 << sk->state) & ~(TCPF_ESTABLISHED | TCPF_CLOSE_WAIT))
                if((err = wait_for_tcp_connect(sk, flags, &timeo)) != 0)
                        goto out_err;

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

        mss_now = tcp_current_mss(sk);

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

        err = -EPIPE;
        if (sk->err || (sk->shutdown&SEND_SHUTDOWN))
                goto do_error;

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

                iov++;

                while (seglen > 0) {
                        int copy;
                        
                        skb = sk->write_queue.prev;

                        if (tp->send_head == NULL ||
                            (copy = mss_now - skb->len) <= 0) {

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

                                skb = tcp_alloc_pskb(sk, select_size(sk, tp), 0, sk->allocation);
                                if (skb == NULL)
                                        goto wait_for_memory;

                                skb_entail(sk, tp, skb);
                                copy = mss_now;
                        }

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

                        /* Where to copy to? */
                        if (skb_tailroom(skb) > 0) {
                                /* We have some space in skb head. Superb! */
                                if (copy > skb_tailroom(skb))
                                        copy = skb_tailroom(skb);
                                if ((err = skb_add_data(skb, from, copy)) != 0)
                                        goto do_fault;
                        } else {
                                int merge = 0;
                                int i = skb_shinfo(skb)->nr_frags;
                                struct page *page = TCP_PAGE(sk);
                                int off = TCP_OFF(sk);

                                if (can_coalesce(skb, i, page, off) && off != PAGE_SIZE) {
                                        /* We can extend the last page fragment. */
                                        merge = 1;
                                } else if (i == MAX_SKB_FRAGS ||
                                           (i == 0 && !(sk->route_caps&NETIF_F_SG))) {
                                        /* Need to add new fragment and cannot
                                         * do this because interface is non-SG,
                                         * or because all the page slots are busy.
                                         */
                                        tcp_mark_push(tp, skb);
                                        goto new_segment;
                                } else if (page) {
                                        /* If page is cached, align
                                         * offset to L1 cache boundary
                                         */
                                        off = (off+L1_CACHE_BYTES-1)&~(L1_CACHE_BYTES-1);
                                        if (off == PAGE_SIZE) {
                                                put_page(page);
                                                TCP_PAGE(sk) = page = NULL;
                                        }
                                }

                                if (!page) {
                                        /* Allocate new cache page. */
                                        if (!(page=tcp_alloc_page(sk)))
                                                goto wait_for_memory;
                                        off = 0;
                                }

                                if (copy > PAGE_SIZE-off)
                                        copy = PAGE_SIZE-off;

                                /* Time to copy data. We are close to the end! */
                                err = tcp_copy_to_page(sk, from, skb, page, off, copy);
                                if (err) {
                                        /* If this page was new, give it to the
                                         * socket so it does not get leaked.
                                         */
                                        if (TCP_PAGE(sk) == NULL) {
                                                TCP_PAGE(sk) = page;
                                                TCP_OFF(sk) = 0;
                                        }
                                        goto do_error;
                                }

                                /* Update the skb. */
                                if (merge) {
                                        skb_shinfo(skb)->frags[i-1].size += copy;
                                } else {
                                        fill_page_desc(skb, i, page, off, copy);
                                        if (TCP_PAGE(sk)) {
                                                get_page(page);
                                        } else if (off + copy < PAGE_SIZE) {
                                                get_page(page);
                                                TCP_PAGE(sk) = page;
                                        }
                                }

                                TCP_OFF(sk) = off+copy;
                        }

                        if (!copied)
                                TCP_SKB_CB(skb)->flags &= ~TCPCB_FLAG_PSH;

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

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

                        if (skb->len != mss_now || (flags&MSG_OOB))
                                continue;

                        if (forced_push(tp)) {
                                tcp_mark_push(tp, skb);
                                __tcp_push_pending_frames(sk, tp, mss_now, 1);
                        } else if (skb == tp->send_head)
                                tcp_push_one(sk, mss_now);
                        continue;

wait_for_sndbuf:
                        set_bit(SOCK_NOSPACE, &sk->socket->flags);
wait_for_memory:
                        if (copied)
                                tcp_push(sk, tp, flags&~MSG_MORE, mss_now, 1);

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

                        mss_now = tcp_current_mss(sk);
                }
        }

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

do_fault:
        if (skb->len == 0) {
                if (tp->send_head == skb)
                        tp->send_head = NULL;
                __skb_unlink(skb, skb->list);
                tcp_free_skb(sk, skb);
        }

do_error:
        if (copied)
                goto out;
out_err:
        err = tcp_error(sk, flags, err);
        TCP_CHECK_TIMER(sk);
        release_sock(sk);
        return err;
}

/*
 *      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, long timeo,
                        struct msghdr *msg, int len, int flags, 
                        int *addr_len)
{
        struct tcp_opt *tp = &(sk->tp_pinfo.af_tcp);

        /* No URG data to read. */
        if (sk->urginline || !tp->urg_data || tp->urg_data == TCP_URG_READ)
                return -EINVAL; /* Yes this is right ! */

        if (sk->state==TCP_CLOSE && !sk->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->state == TCP_CLOSE || (sk->shutdown & RCV_SHUTDOWN))
                return 0;

        /* Fixed the recv(..., MSG_OOB) behaviour.  BSD docs and
         * the available implementations agree in this case:
         * this call should never block, independent of the
         * blocking state of the socket.
         * Mike <pall@rz.uni-karlsruhe.de>
         */
        return -EAGAIN;
}

/*
 *      Release a skb if it is no longer needed. This routine
 *      must be called with interrupts disabled or with the
 *      socket locked so that the sk_buff queue operation is ok.
 */

static inline void tcp_eat_skb(struct sock *sk, struct sk_buff * skb)
{
        __skb_unlink(skb, &sk->receive_queue);
        __kfree_skb(skb);
}

/* Clean up the receive buffer for full frames taken by the user,
 * then send an ACK if necessary.  COPIED is the number of bytes
 * tcp_recvmsg has given to the user so far, it speeds up the
 * calculation of whether or not we must ACK for the sake of
 * a window update.
 */
static void cleanup_rbuf(struct sock *sk, int copied)
{
        struct tcp_opt *tp = &(sk->tp_pinfo.af_tcp);
        int time_to_ack = 0;

#if TCP_DEBUG
        struct sk_buff *skb = skb_peek(&sk->receive_queue);

        BUG_TRAP(skb==NULL || before(tp->copied_seq, TCP_SKB_CB(skb)->end_seq));
#endif

        if (tcp_ack_scheduled(tp)) {
                   /* Delayed ACKs frequently hit locked sockets during bulk receive. */
                if (tp->ack.blocked
                    /* Once-per-two-segments ACK was not sent by tcp_input.c */
                    || tp->rcv_nxt - tp->rcv_wup > tp->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 &&
                        (tp->ack.pending&TCP_ACK_PUSHED) &&
                        !tp->ack.pingpong &&
                        atomic_read(&sk->rmem_alloc) == 0)) {
                        time_to_ack = 1;
                }
        }

        /* 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->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 = 1;
                }
        }
        if (time_to_ack)
                tcp_send_ack(sk);
}

/* Now socket state including sk->err is changed only under lock,
 * hence we may omit checks after joining wait queue.
 * We check receive queue before schedule() only as optimization;
 * it is very likely that release_sock() added new data.
 */

static long tcp_data_wait(struct sock *sk, long timeo)
{
        DECLARE_WAITQUEUE(wait, current);

        add_wait_queue(sk->sleep, &wait);

        __set_current_state(TASK_INTERRUPTIBLE);

        set_bit(SOCK_ASYNC_WAITDATA, &sk->socket->flags);
        release_sock(sk);

        if (skb_queue_empty(&sk->receive_queue))
                timeo = schedule_timeout(timeo);

        lock_sock(sk);
        clear_bit(SOCK_ASYNC_WAITDATA, &sk->socket->flags);

        remove_wait_queue(sk->sleep, &wait);
        __set_current_state(TASK_RUNNING);
        return timeo;
}

static void tcp_prequeue_process(struct sock *sk)
{
        struct sk_buff *skb;
        struct tcp_opt *tp = &(sk->tp_pinfo.af_tcp);

        net_statistics[smp_processor_id()*2+1].TCPPrequeued += skb_queue_len(&tp->ucopy.prequeue);

        /* 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;
}

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->receive_queue, skb) {
                offset = seq - TCP_SKB_CB(skb)->seq;
                if (skb->h.th->syn)
                        offset--;
                if (offset < skb->len || skb->h.th->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_opt *tp = &(sk->tp_pinfo.af_tcp);
        u32 seq = tp->copied_seq;
        u32 offset;
        int copied = 0;

        if (sk->state == TCP_LISTEN)
                return -ENOTCONN;
        while ((skb = tcp_recv_skb(sk, seq, &offset)) != NULL) {
                if (offset < skb->len) {
                        size_t used, 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 <= len) {
                                seq += used;
                                copied += used;
                                offset += used;
                        }
                        if (offset != skb->len)
                                break;
                }
                if (skb->h.th->fin) {
                        tcp_eat_skb(sk, skb);
                        ++seq;
                        break;
                }
                tcp_eat_skb(sk, skb);
                if (!desc->count)
                        break;
        }
        tp->copied_seq = seq;
        /* Clean up data we have read: This will do ACK frames. */
        if (copied)
                cleanup_rbuf(sk, copied);
        return copied;
}

/*
 *      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 sock *sk, struct msghdr *msg,
                int len, int nonblock, int flags, int *addr_len)
{
        struct tcp_opt *tp = &(sk->tp_pinfo.af_tcp);
        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;

        lock_sock(sk);

        TCP_CHECK_TIMER(sk);

        err = -ENOTCONN;
        if (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;

        seq = &tp->copied_seq;
        if (flags & MSG_PEEK) {
                peek_seq = tp->copied_seq;
                seq = &peek_seq;
        }

        target = sock_rcvlowat(sk, flags & MSG_WAITALL, len);

        do {
                struct sk_buff * skb;
                u32 offset;

                /* Are we at urgent data? Stop if we have read anything. */
                if (copied && tp->urg_data && tp->urg_seq == *seq)
                        break;

                /* We need to check signals first, to get correct SIGURG
                 * handling. FIXME: Need to check this doesn't impact 1003.1g
                 * and move it down to the bottom of the loop
                 */
                if (signal_pending(current)) {
                        if (copied)
                                break;
                        copied = timeo ? sock_intr_errno(timeo) : -EAGAIN;
                        break;
                }

                /* Next get a buffer. */

                skb = skb_peek(&sk->receive_queue);
                do {
                        if (!skb)
                                break;

                        /* Now that we have two receive queues this 
                         * shouldn't happen.
                         */
                        if (before(*seq, TCP_SKB_CB(skb)->seq)) {
                                printk(KERN_INFO "recvmsg bug: copied %X seq %X\n",
                                       *seq, TCP_SKB_CB(skb)->seq);
                                break;
                        }
                        offset = *seq - TCP_SKB_CB(skb)->seq;
                        if (skb->h.th->syn)
                                offset--;
                        if (offset < skb->len)
                                goto found_ok_skb;
                        if (skb->h.th->fin)
                                goto found_fin_ok;
                        BUG_TRAP(flags&MSG_PEEK);
                        skb = skb->next;
                } while (skb != (struct sk_buff *)&sk->receive_queue);

                /* Well, if we have backlog, try to process it now yet. */

                if (copied >= target && sk->backlog.tail == NULL)
                        break;

                if (copied) {
                        if (sk->err ||
                            sk->state == TCP_CLOSE ||
                            (sk->shutdown & RCV_SHUTDOWN) ||
                            !timeo ||
                            (flags & MSG_PEEK))
                                break;
                } else {
                        if (sk->done)
                                break;

                        if (sk->err) {
                                copied = sock_error(sk);
                                break;
                        }

                        if (sk->shutdown & RCV_SHUTDOWN)
                                break;

                        if (sk->state == TCP_CLOSE) {
                                if (!sk->done) {
                                        /* This occurs when user tries to read
                                         * from never connected socket.
                                         */
                                        copied = -ENOTCONN;
                                        break;
                                }
                                break;
                        }

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

                cleanup_rbuf(sk, copied);

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

                        tp->ucopy.len = len;

                        BUG_TRAP(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 second 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_len(&tp->ucopy.prequeue))
                                goto do_prequeue;

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

                if (copied >= target) {
                        /* Do not sleep, just process backlog. */
                        release_sock(sk);
                        lock_sock(sk);
                } else {
                        timeo = tcp_data_wait(sk, timeo);
                }

                if (user_recv) {
                        int chunk;

                        /* __ Restore normal policy in scheduler __ */

                        if ((chunk = len - tp->ucopy.len) != 0) {
                                net_statistics[smp_processor_id()*2+1].TCPDirectCopyFromBacklog += chunk;
                                len -= chunk;
                                copied += chunk;
                        }

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

                                if ((chunk = len - tp->ucopy.len) != 0) {
                                        net_statistics[smp_processor_id()*2+1].TCPDirectCopyFromPrequeue += chunk;
                                        len -= chunk;
                                        copied += chunk;
                                }
                        }
                }
                if ((flags & MSG_PEEK) && peek_seq != tp->copied_seq) {
                        if (net_ratelimit())
                                printk(KERN_DEBUG "TCP(%s:%d): Application bug, race in MSG_PEEK.\n",
                                       current->comm, current->pid);
                        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 (!sk->urginline) {
                                                ++*seq;
                                                offset++;
                                                used--;
                                                if (!used)
                                                        goto skip_copy;
                                        }
                                } else
                                        used = urg_offset;
                        }
                }

                if (!(flags&MSG_TRUNC)) {
                        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;

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

                if (skb->h.th->fin)
                        goto found_fin_ok;
                if (!(flags & MSG_PEEK))
                        tcp_eat_skb(sk, skb);
                continue;

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

        if (user_recv) {
                if (skb_queue_len(&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_statistics[smp_processor_id()*2+1].TCPDirectCopyFromPrequeue += chunk;
                                len -= chunk;
                                copied += chunk;
                        }
                }

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

        /* According to UNIX98, msg_name/msg_namelen are ignored
         * on connected socket. I was just happy when found this 8) --ANK
         */

        /* Clean up data we have read: This will do ACK frames. */
        cleanup_rbuf(sk, copied);

        TCP_CHECK_TIMER(sk);
        release_sock(sk);
        return copied;

out:
        TCP_CHECK_TIMER(sk);
        release_sock(sk);
        return err;

recv_urg:
        err = tcp_recv_urg(sk, timeo, msg, len, flags, addr_len);
        goto out;
}

/*
 *      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 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->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 set sk->dead.
 */

void tcp_shutdown(struct sock *sk, int how)
{
        /*      We need to grab some memory, and put together a FIN,
         *      and then put it into the queue to be sent.
         *              Tim MacKenzie(tym@dibbler.cs.monash.edu.au) 4 Dec '92.
         */
        if (!(how & SEND_SHUTDOWN))
                return;

        /* If we've already sent a FIN, or it's a closed state, skip this. */
        if ((1 << sk->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);
        }
}


/*
 *      Return 1 if we still have things to send in our buffers.
 */

static inline int closing(struct sock * sk)
{
        return ((1 << sk->state) & (TCPF_FIN_WAIT1|TCPF_CLOSING|TCPF_LAST_ACK));
}

static __inline__ void tcp_kill_sk_queues(struct sock *sk)
{
        /* First the read buffer. */
        __skb_queue_purge(&sk->receive_queue);

        /* Next, the error queue. */
        __skb_queue_purge(&sk->error_queue);

        /* Next, the write queue. */
        BUG_TRAP(skb_queue_empty(&sk->write_queue));

        /* Account for returned memory. */
        tcp_mem_reclaim(sk);

        BUG_TRAP(sk->wmem_queued == 0);
        BUG_TRAP(sk->forward_alloc == 0);

        /* It is _impossible_ for the backlog to contain anything
         * when we get here.  All user references to this socket
         * have gone away, only the net layer knows can touch it.
         */
}

/*
 * At this point, there should be no process reference to this
 * socket, and thus no user references at all.  Therefore we
 * can assume the socket waitqueue is inactive and nobody will
 * try to jump onto it.
 */
void tcp_destroy_sock(struct sock *sk)
{
        BUG_TRAP(sk->state==TCP_CLOSE);
        BUG_TRAP(sk->dead);

        /* It cannot be in hash table! */
        BUG_TRAP(sk->pprev==NULL);

        /* If it has not 0 sk->num, it must be bound */
        BUG_TRAP(!sk->num || sk->prev!=NULL);

#ifdef TCP_DEBUG
        if (sk->zapped) {
                printk(KERN_DEBUG "TCP: double destroy sk=%p\n", sk);
                sock_hold(sk);
        }
        sk->zapped = 1;
#endif

        sk->prot->destroy(sk);

        tcp_kill_sk_queues(sk);

#ifdef INET_REFCNT_DEBUG
        if (atomic_read(&sk->refcnt) != 1) {
                printk(KERN_DEBUG "Destruction TCP %p delayed, c=%d\n", sk, atomic_read(&sk->refcnt));
        }
#endif

        atomic_dec(&tcp_orphan_count);
        sock_put(sk);
}

void tcp_close(struct sock *sk, long timeout)
{
        struct sk_buff *skb;
        int data_was_unread = 0;

        lock_sock(sk);
        sk->shutdown = SHUTDOWN_MASK;

        if(sk->state == TCP_LISTEN) {
                tcp_set_state(sk, TCP_CLOSE);

                /* Special case. */
                tcp_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->receive_queue))!=NULL) {
                u32 len = TCP_SKB_CB(skb)->end_seq - TCP_SKB_CB(skb)->seq - skb->h.th->fin;
                data_was_unread += len;
                __kfree_skb(skb);
        }

        tcp_mem_reclaim(sk);

        /* As outlined in draft-ietf-tcpimpl-prob-03.txt, section
         * 3.10, 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(data_was_unread != 0) {
                /* Unread data was tossed, zap the connection. */
                NET_INC_STATS_USER(TCPAbortOnClose);
                tcp_set_state(sk, TCP_CLOSE);
                tcp_send_active_reset(sk, GFP_KERNEL);
        } else if (sk->linger && sk->lingertime==0) {
                /* Check zero linger _after_ checking for unread data. */
                sk->prot->disconnect(sk, 0);
                NET_INC_STATS_USER(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
                 */
                tcp_send_fin(sk);
        }

        if (timeout) {
                struct task_struct *tsk = current;
                DECLARE_WAITQUEUE(wait, current);

                add_wait_queue(sk->sleep, &wait);

                do {
                        set_current_state(TASK_INTERRUPTIBLE);
                        if (!closing(sk))
                                break;
                        release_sock(sk);
                        timeout = schedule_timeout(timeout);
                        lock_sock(sk);
                } while (!signal_pending(tsk) && timeout);

                tsk->state = TASK_RUNNING;
                remove_wait_queue(sk->sleep, &wait);
        }

adjudge_to_death:
        /* 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);
        BUG_TRAP(sk->lock.users==0);

        sock_hold(sk);
        sock_orphan(sk);

        /*      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->state == TCP_FIN_WAIT2) {
                struct tcp_opt *tp = &(sk->tp_pinfo.af_tcp);
                if (tp->linger2 < 0) {
                        tcp_set_state(sk, TCP_CLOSE);
                        tcp_send_active_reset(sk, GFP_ATOMIC);
                        NET_INC_STATS_BH(TCPAbortOnLinger);
                } else {
                        int tmo = tcp_fin_time(tp);

                        if (tmo > TCP_TIMEWAIT_LEN) {
                                tcp_reset_keepalive_timer(sk, tcp_fin_time(tp));
                        } else {
                                atomic_inc(&tcp_orphan_count);
                                tcp_time_wait(sk, TCP_FIN_WAIT2, tmo);
                                goto out;
                        }
                }
        }
        if (sk->state != TCP_CLOSE) {
                tcp_mem_reclaim(sk);
                if (atomic_read(&tcp_orphan_count) > sysctl_tcp_max_orphans ||
                    (sk->wmem_queued > SOCK_MIN_SNDBUF &&
                     atomic_read(&tcp_memory_allocated) > sysctl_tcp_mem[2])) {
                        if (net_ratelimit())
                                printk(KERN_INFO "TCP: too many of orphaned sockets\n");
                        tcp_set_state(sk, TCP_CLOSE);
                        tcp_send_active_reset(sk, GFP_ATOMIC);
                        NET_INC_STATS_BH(TCPAbortOnMemory);
                }
        }
        atomic_inc(&tcp_orphan_count);

        if (sk->state == TCP_CLOSE)
                tcp_destroy_sock(sk);
        /* Otherwise, socket is reprieved until protocol close. */

out:
        bh_unlock_sock(sk);
        local_bh_enable();
        sock_put(sk);
}

/* These states need RST on ABORT according to RFC793 */

extern __inline__ int 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 tcp_opt *tp = &sk->tp_pinfo.af_tcp;
        int old_state;
        int err = 0;

        old_state = sk->state;
        if (old_state != TCP_CLOSE)
                tcp_set_state(sk, TCP_CLOSE);

        /* ABORT function of RFC793 */
        if (old_state == TCP_LISTEN) {
                tcp_listen_stop(sk);
        } 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 discrepance of Linux wrt. RFC
                 * states
                 */
                tcp_send_active_reset(sk, gfp_any());
                sk->err = ECONNRESET;
        } else if (old_state == TCP_SYN_SENT)
                sk->err = ECONNRESET;

        tcp_clear_xmit_timers(sk);
        __skb_queue_purge(&sk->receive_queue);
        tcp_writequeue_purge(sk);
        __skb_queue_purge(&tp->out_of_order_queue);

        sk->dport = 0;

        if (!(sk->userlocks&SOCK_BINDADDR_LOCK)) {
                sk->rcv_saddr = 0;
                sk->saddr = 0;
#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
                memset(&sk->net_pinfo.af_inet6.saddr, 0, 16);
                memset(&sk->net_pinfo.af_inet6.rcv_saddr, 0, 16);
#endif
        }

        sk->shutdown = 0;
        sk->done = 0;
        tp->srtt = 0;
        if ((tp->write_seq += tp->max_window+2) == 0)
                tp->write_seq = 1;
        tp->backoff = 0;
        tp->snd_cwnd = 2;
        tp->probes_out = 0;
        tp->packets_out = 0;
        tp->snd_ssthresh = 0x7fffffff;
        tp->snd_cwnd_cnt = 0;
        tp->ca_state = TCP_CA_Open;
        tcp_clear_retrans(tp);
        tcp_delack_init(tp);
        tp->send_head = NULL;
        tp->saw_tstamp = 0;
        tcp_sack_reset(tp);
        __sk_dst_reset(sk);

        BUG_TRAP(!sk->num || sk->prev);

        sk->error_report(sk);
        return err;
}

/*
 *      Wait for an incoming connection, avoid race
 *      conditions. This must be called with the socket locked.
 */
static int wait_for_connect(struct sock * sk, long timeo)
{
        DECLARE_WAITQUEUE(wait, current);
        int err;

        /*
         * True wake-one mechanism for incoming connections: only
         * one process gets woken up, not the 'whole herd'.
         * Since we do not 'race & poll' for established sockets
         * anymore, the common case will execute the loop only once.
         *
         * Subtle issue: "add_wait_queue_exclusive()" will be added
         * after any current non-exclusive waiters, and we know that
         * it will always _stay_ after any new non-exclusive waiters
         * because all non-exclusive waiters are added at the
         * beginning of the wait-queue. As such, it's ok to "drop"
         * our exclusiveness temporarily when we get woken up without
         * having to remove and re-insert us on the wait queue.
         */
        add_wait_queue_exclusive(sk->sleep, &wait);
        for (;;) {
                current->state = TASK_INTERRUPTIBLE;
                release_sock(sk);
                if (sk->tp_pinfo.af_tcp.accept_queue == NULL)
                        timeo = schedule_timeout(timeo);
                lock_sock(sk);
                err = 0;
                if (sk->tp_pinfo.af_tcp.accept_queue)
                        break;
                err = -EINVAL;
                if (sk->state != TCP_LISTEN)
                        break;
                err = sock_intr_errno(timeo);
                if (signal_pending(current))
                        break;
                err = -EAGAIN;
                if (!timeo)
                        break;
        }
        current->state = TASK_RUNNING;
        remove_wait_queue(sk->sleep, &wait);
        return err;
}

/*
 *      This will accept the next outstanding connection.
 */

struct sock *tcp_accept(struct sock *sk, int flags, int *err)
{
        struct tcp_opt *tp = &sk->tp_pinfo.af_tcp;
        struct open_request *req;
        struct sock *newsk;
        int error;

        lock_sock(sk); 

        /* We need to make sure that this socket is listening,
         * and that it has something pending.
         */
        error = -EINVAL;
        if (sk->state != TCP_LISTEN)
                goto out;

        /* Find already established connection */
        if (!tp->accept_queue) {
                long timeo = sock_rcvtimeo(sk, flags & O_NONBLOCK);

                /* If this is a non blocking socket don't sleep */
                error = -EAGAIN;
                if (!timeo)
                        goto out;

                error = wait_for_connect(sk, timeo);
                if (error)
                        goto out;
        }

        req = tp->accept_queue;
        if ((tp->accept_queue = req->dl_next) == NULL)
                tp->accept_queue_tail = NULL;

        newsk = req->sk;
        tcp_acceptq_removed(sk);
        tcp_openreq_fastfree(req);
        BUG_TRAP(newsk->state != TCP_SYN_RECV);
        release_sock(sk);
        return newsk;

out:
        release_sock(sk);
        *err = error; 
        return NULL;
}

/*
 *      Socket option code for TCP. 
 */
  
int tcp_setsockopt(struct sock *sk, int level, int optname, char *optval, 
                   int optlen)
{
        struct tcp_opt *tp = &(sk->tp_pinfo.af_tcp);
        int val;
        int err = 0;

        if (level != SOL_TCP)
                return tp->af_specific->setsockopt(sk, level, optname, 
                                                   optval, optlen);

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

        if (get_user(val, (int *)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 < 8 || val > MAX_TCP_WINDOW) {
                        err = -EINVAL;
                        break;
                }
                tp->user_mss = val;
                break;

        case TCP_NODELAY:
                /* You cannot try to use this and TCP_CORK in
                 * tandem, so let the user know.
                 */
                if (tp->nonagle == 2) {
                        err = -EINVAL;
                        break;
                }
                tp->nonagle = (val == 0) ? 0 : 1;
                if (val)
                        tcp_push_pending_frames(sk, tp);
                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.
                 *
                 * You cannot try to use TCP_NODELAY and this mechanism
                 * at the same time, so let the user know.
                 */
                if (tp->nonagle == 1) {
                        err = -EINVAL;
                        break;
                }
                if (val != 0) {
                        tp->nonagle = 2;
                } else {
                        tp->nonagle = 0;

                        tcp_push_pending_frames(sk, tp);
                }
                break;
                
        case TCP_KEEPIDLE:
                if (val < 1 || val > MAX_TCP_KEEPIDLE)
                        err = -EINVAL;
                else {
                        tp->keepalive_time = val * HZ;
                        if (sk->keepopen && !((1<<sk->state)&(TCPF_CLOSE|TCPF_LISTEN))) {
                                __u32 elapsed = tcp_time_stamp - tp->rcv_tstamp;
                                if (tp->keepalive_time > elapsed)
                                        elapsed = tp->keepalive_time - elapsed;
                                else
                                        elapsed = 0;
                                tcp_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
                        tp->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:
                tp->defer_accept = 0;
                if (val > 0) {
                        /* Translate value in seconds to number of retransmits */
                        while (tp->defer_accept < 32 && val > ((TCP_TIMEOUT_INIT/HZ)<<tp->defer_accept))
                                tp->defer_accept++;
                        tp->defer_accept++;
                }
                break;

        case TCP_WINDOW_CLAMP:
                if (val==0) {
                        if (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) {
                        tp->ack.pingpong = 1;
                } else {
                        tp->ack.pingpong = 0;
                        if ((1<<sk->state)&(TCPF_ESTABLISHED|TCPF_CLOSE_WAIT) &&
                            tcp_ack_scheduled(tp)) {
                                tp->ack.pending |= TCP_ACK_PUSHED;
                                cleanup_rbuf(sk, 1);
                                if (!(val & 1))
                                        tp->ack.pingpong = 1;
                        }
                }
                break;

        default:
                err = -ENOPROTOOPT;
                break;
        };
        release_sock(sk);
        return err;
}

int tcp_getsockopt(struct sock *sk, int level, int optname, char *optval,
                   int *optlen)
{
        struct tcp_opt *tp = &(sk->tp_pinfo.af_tcp);
        int val, len;

        if(level != SOL_TCP)
                return tp->af_specific->getsockopt(sk, level, optname,
                                                   optval, optlen);

        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 == 0 && ((1<<sk->state)&(TCPF_CLOSE|TCPF_LISTEN)))
                        val = tp->user_mss;
                break;
        case TCP_NODELAY:
                val = (tp->nonagle == 1);
                break;
        case TCP_CORK:
                val = (tp->nonagle == 2);
                break;
        case TCP_KEEPIDLE:
                val = (tp->keepalive_time ? : sysctl_tcp_keepalive_time)/HZ;
                break;
        case TCP_KEEPINTVL:
                val = (tp->keepalive_intvl ? : sysctl_tcp_keepalive_intvl)/HZ;
                break;
        case TCP_KEEPCNT:
                val = tp->keepalive_probes ? : sysctl_tcp_keepalive_probes;
                break;
        case TCP_SYNCNT:
                val = tp->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 = tp->defer_accept == 0 ? 0 : ((TCP_TIMEOUT_INIT/HZ)<<(tp->defer_accept-1));
                break;
        case TCP_WINDOW_CLAMP:
                val = tp->window_clamp;
                break;
        case TCP_INFO:
        {
                struct tcp_info info;
                u32 now = tcp_time_stamp;

                if(get_user(len,optlen))
                        return -EFAULT;
                info.tcpi_state = sk->state;
                info.tcpi_ca_state = tp->ca_state;
                info.tcpi_retransmits = tp->retransmits;
                info.tcpi_probes = tp->probes_out;
                info.tcpi_backoff = tp->backoff;
                info.tcpi_options = 0;
                if (tp->tstamp_ok)
                        info.tcpi_options |= TCPI_OPT_TIMESTAMPS;
                if (tp->sack_ok)
                        info.tcpi_options |= TCPI_OPT_SACK;
                if (tp->wscale_ok) {
                        info.tcpi_options |= TCPI_OPT_WSCALE;
                        info.tcpi_snd_wscale = tp->snd_wscale;
                        info.tcpi_rcv_wscale = tp->rcv_wscale;
                } else {
                        info.tcpi_snd_wscale = 0;
                        info.tcpi_rcv_wscale = 0;
                }
                if (tp->ecn_flags&TCP_ECN_OK)
                        info.tcpi_options |= TCPI_OPT_ECN;

                info.tcpi_rto = (1000000*tp->rto)/HZ;
                info.tcpi_ato = (1000000*tp->ack.ato)/HZ;
                info.tcpi_snd_mss = tp->mss_cache;
                info.tcpi_rcv_mss = tp->ack.rcv_mss;

                info.tcpi_unacked = tp->packets_out;
                info.tcpi_sacked = tp->sacked_out;
                info.tcpi_lost = tp->lost_out;
                info.tcpi_retrans = tp->retrans_out;
                info.tcpi_fackets = tp->fackets_out;

                info.tcpi_last_data_sent = ((now - tp->lsndtime)*1000)/HZ;
                info.tcpi_last_ack_sent = 0;
                info.tcpi_last_data_recv = ((now - tp->ack.lrcvtime)*1000)/HZ;
                info.tcpi_last_ack_recv = ((now - tp->rcv_tstamp)*1000)/HZ;

                info.tcpi_pmtu = tp->pmtu_cookie;
                info.tcpi_rcv_ssthresh = tp->rcv_ssthresh;
                info.tcpi_rtt = ((1000000*tp->srtt)/HZ)>>3;
                info.tcpi_rttvar = ((1000000*tp->mdev)/HZ)>>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;

                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 = !tp->ack.pingpong;
                break;
        default:
                return -ENOPROTOOPT;
        };

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


extern void __skb_cb_too_small_for_tcp(int, int);
extern void tcpdiag_init(void);

void __init tcp_init(void)
{
        struct sk_buff *skb = NULL;
        unsigned long goal;
        int order, i;

        if(sizeof(struct tcp_skb_cb) > sizeof(skb->cb))
                __skb_cb_too_small_for_tcp(sizeof(struct tcp_skb_cb),
                                           sizeof(skb->cb));

        tcp_openreq_cachep = kmem_cache_create("tcp_open_request",
                                                   sizeof(struct open_request),
                                               0, SLAB_HWCACHE_ALIGN,
                                               NULL, NULL);
        if(!tcp_openreq_cachep)
                panic("tcp_init: Cannot alloc open_request cache.");

        tcp_bucket_cachep = kmem_cache_create("tcp_bind_bucket",
                                              sizeof(struct tcp_bind_bucket),
                                              0, SLAB_HWCACHE_ALIGN,
                                              NULL, NULL);
        if(!tcp_bucket_cachep)
                panic("tcp_init: Cannot alloc tcp_bind_bucket cache.");

        tcp_timewait_cachep = kmem_cache_create("tcp_tw_bucket",
                                                sizeof(struct tcp_tw_bucket),
                                                0, SLAB_HWCACHE_ALIGN,
                                                NULL, NULL);
        if(!tcp_timewait_cachep)
                panic("tcp_init: Cannot alloc tcp_tw_bucket cache.");

        /* Size and allocate the main established and bind bucket
         * hash tables.
         *
         * The methodology is similar to that of the buffer cache.
         */
        if (num_physpages >= (128 * 1024))
                goal = num_physpages >> (21 - PAGE_SHIFT);
        else
                goal = num_physpages >> (23 - PAGE_SHIFT);

        for(order = 0; (1UL << order) < goal; order++)
                ;
        do {
                tcp_ehash_size = (1UL << order) * PAGE_SIZE /
                        sizeof(struct tcp_ehash_bucket);
                tcp_ehash_size >>= 1;
                while (tcp_ehash_size & (tcp_ehash_size-1))
                        tcp_ehash_size--;
                tcp_ehash = (struct tcp_ehash_bucket *)
                        __get_free_pages(GFP_ATOMIC, order);
        } while (tcp_ehash == NULL && --order > 0);

        if (!tcp_ehash)
                panic("Failed to allocate TCP established hash table\n");
        for (i = 0; i < (tcp_ehash_size<<1); i++) {
                tcp_ehash[i].lock = RW_LOCK_UNLOCKED;
                tcp_ehash[i].chain = NULL;
        }

        do {
                tcp_bhash_size = (1UL << order) * PAGE_SIZE /
                        sizeof(struct tcp_bind_hashbucket);
                if ((tcp_bhash_size > (64 * 1024)) && order > 0)
                        continue;
                tcp_bhash = (struct tcp_bind_hashbucket *)
                        __get_free_pages(GFP_ATOMIC, order);
        } while (tcp_bhash == NULL && --order >= 0);

        if (!tcp_bhash)
                panic("Failed to allocate TCP bind hash table\n");
        for (i = 0; i < tcp_bhash_size; i++) {
                tcp_bhash[i].lock = SPIN_LOCK_UNLOCKED;
                tcp_bhash[i].chain = NULL;
        }

        /* Try to be a bit smarter and adjust defaults depending
         * on available memory.
         */
        if (order > 4) {
                sysctl_local_port_range[0] = 32768;
                sysctl_local_port_range[1] = 61000;
                sysctl_tcp_max_tw_buckets = 180000;
                sysctl_tcp_max_orphans = 4096<<(order-4);
                sysctl_max_syn_backlog = 1024;
        } else if (order < 3) {
                sysctl_local_port_range[0] = 1024*(3-order);
                sysctl_tcp_max_tw_buckets >>= (3-order);
                sysctl_tcp_max_orphans >>= (3-order);
                sysctl_max_syn_backlog = 128;
        }
        tcp_port_rover = sysctl_local_port_range[0] - 1;

        sysctl_tcp_mem[0] = 768<<order;
        sysctl_tcp_mem[1] = 1024<<order;
        sysctl_tcp_mem[2] = 1536<<order;
        if (sysctl_tcp_mem[2] - sysctl_tcp_mem[1] > 512)
                sysctl_tcp_mem[1] = sysctl_tcp_mem[2] - 512;
        if (sysctl_tcp_mem[1] - sysctl_tcp_mem[0] > 512)
                sysctl_tcp_mem[0] = sysctl_tcp_mem[1] - 512;

        if (order < 3) {
                sysctl_tcp_wmem[2] = 64*1024;
                sysctl_tcp_rmem[0] = PAGE_SIZE;
                sysctl_tcp_rmem[1] = 43689;
                sysctl_tcp_rmem[2] = 2*43689;
        }

        printk(KERN_INFO "TCP: Hash tables configured (established %d bind %d)\n",
               tcp_ehash_size<<1, tcp_bhash_size);

        tcpdiag_init();
}