net/ipv4/tcp_ipv4.c

   1 /*
   2  * INET         An implementation of the TCP/IP protocol suite for the LINUX
   3  *              operating system.  INET is implemented using the  BSD Socket
   4  *              interface as the means of communication with the user level.
   5  *
   6  *              Implementation of the Transmission Control Protocol(TCP).
   7  *
   8  * Version:     $Id: tcp_ipv4.c,v 1.240 2002/02/01 22:01:04 davem Exp $
   9  *
  10  *              IPv4 specific functions
  11  *
  12  *
  13  *              code split from:
  14  *              linux/ipv4/tcp.c
  15  *              linux/ipv4/tcp_input.c
  16  *              linux/ipv4/tcp_output.c
  17  *
  18  *              See tcp.c for author information
  19  *
  20  *      This program is free software; you can redistribute it and/or
  21  *      modify it under the terms of the GNU General Public License
  22  *      as published by the Free Software Foundation; either version
  23  *      2 of the License, or (at your option) any later version.
  24  */
  25
  26 /*
  27  * Changes:
  28  *              David S. Miller :       New socket lookup architecture.
  29  *                                      This code is dedicated to John Dyson.
  30  *              David S. Miller :       Change semantics of established hash,
  31  *                                      half is devoted to TIME_WAIT sockets
  32  *                                      and the rest go in the other half.
  33  *              Andi Kleen :            Add support for syncookies and fixed
  34  *                                      some bugs: ip options weren't passed to
  35  *                                      the TCP layer, missed a check for an
  36  *                                      ACK bit.
  37  *              Andi Kleen :            Implemented fast path mtu discovery.
  38  *                                      Fixed many serious bugs in the
  39  *                                      request_sock handling and moved
  40  *                                      most of it into the af independent code.
  41  *                                      Added tail drop and some other bugfixes.
  42  *                                      Added new listen semantics.
  43  *              Mike McLagan    :       Routing by source
  44  *      Juan Jose Ciarlante:            ip_dynaddr bits
  45  *              Andi Kleen:             various fixes.
  46  *      Vitaly E. Lavrov        :       Transparent proxy revived after year
  47  *                                      coma.
  48  *      Andi Kleen              :       Fix new listen.
  49  *      Andi Kleen              :       Fix accept error reporting.
  50  *      YOSHIFUJI Hideaki @USAGI and:   Support IPV6_V6ONLY socket option, which
  51  *      Alexey Kuznetsov                allow both IPv4 and IPv6 sockets to bind
  52  *                                      a single port at the same time.
  53  */
  54
  55 #include <linux/config.h>
  56
  57 #include <linux/types.h>
  58 #include <linux/fcntl.h>
  59 #include <linux/module.h>
  60 #include <linux/random.h>
  61 #include <linux/cache.h>
  62 #include <linux/jhash.h>
  63 #include <linux/init.h>
  64 #include <linux/times.h>
  65
  66 #include <net/icmp.h>
  67 #include <net/inet_hashtables.h>
  68 #include <net/tcp.h>
  69 #include <net/transp_v6.h>
  70 #include <net/ipv6.h>
  71 #include <net/inet_common.h>
  72 #include <net/timewait_sock.h>
  73 #include <net/xfrm.h>
  74
  75 #include <linux/inet.h>
  76 #include <linux/ipv6.h>
  77 #include <linux/stddef.h>
  78 #include <linux/proc_fs.h>
  79 #include <linux/seq_file.h>
  80
  81 int sysctl_tcp_tw_reuse;
  82 int sysctl_tcp_low_latency;
  83
  84 /* Check TCP sequence numbers in ICMP packets. */
  85 #define ICMP_MIN_LENGTH 8
  86
  87 /* Socket used for sending RSTs */
  88 static struct socket *tcp_socket;
  89
  90 void tcp_v4_send_check(struct sock *sk, int len, struct sk_buff *skb);
  91
  92 struct inet_hashinfo __cacheline_aligned tcp_hashinfo = {
  93         .lhash_lock     = RW_LOCK_UNLOCKED,
  94         .lhash_users    = ATOMIC_INIT(0),
  95         .lhash_wait     = __WAIT_QUEUE_HEAD_INITIALIZER(tcp_hashinfo.lhash_wait),
  96 };
  97
  98 static int tcp_v4_get_port(struct sock *sk, unsigned short snum)
  99 {
 100         return inet_csk_get_port(&tcp_hashinfo, sk, snum,
 101                                  inet_csk_bind_conflict);
 102 }
 103
 104 static void tcp_v4_hash(struct sock *sk)
 105 {
 106         inet_hash(&tcp_hashinfo, sk);
 107 }
 108
 109 void tcp_unhash(struct sock *sk)
 110 {
 111         inet_unhash(&tcp_hashinfo, sk);
 112 }
 113
 114 static inline __u32 tcp_v4_init_sequence(struct sock *sk, struct sk_buff *skb)
 115 {
 116         return secure_tcp_sequence_number(skb->nh.iph->daddr,
 117                                           skb->nh.iph->saddr,
 118                                           skb->h.th->dest,
 119                                           skb->h.th->source);
 120 }
 121
 122 int tcp_twsk_unique(struct sock *sk, struct sock *sktw, void *twp)
 123 {
 124         const struct tcp_timewait_sock *tcptw = tcp_twsk(sktw);
 125         struct tcp_sock *tp = tcp_sk(sk);
 126
 127         /* With PAWS, it is safe from the viewpoint
 128            of data integrity. Even without PAWS it is safe provided sequence
 129            spaces do not overlap i.e. at data rates <= 80Mbit/sec.
 130
 131            Actually, the idea is close to VJ's one, only timestamp cache is
 132            held not per host, but per port pair and TW bucket is used as state
 133            holder.
 134
 135            If TW bucket has been already destroyed we fall back to VJ's scheme
 136            and use initial timestamp retrieved from peer table.
 137          */
 138         if (tcptw->tw_ts_recent_stamp &&
 139             (twp == NULL || (sysctl_tcp_tw_reuse &&
 140                              xtime.tv_sec - tcptw->tw_ts_recent_stamp > 1))) {
 141                 tp->write_seq = tcptw->tw_snd_nxt + 65535 + 2;
 142                 if (tp->write_seq == 0)
 143                         tp->write_seq = 1;
 144                 tp->rx_opt.ts_recent       = tcptw->tw_ts_recent;
 145                 tp->rx_opt.ts_recent_stamp = tcptw->tw_ts_recent_stamp;
 146                 sock_hold(sktw);
 147                 return 1;
 148         }
 149
 150         return 0;
 151 }
 152
 153 EXPORT_SYMBOL_GPL(tcp_twsk_unique);
 154
 155 /* This will initiate an outgoing connection. */
 156 int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
 157 {
 158         struct inet_sock *inet = inet_sk(sk);
 159         struct tcp_sock *tp = tcp_sk(sk);
 160         struct sockaddr_in *usin = (struct sockaddr_in *)uaddr;
 161         struct rtable *rt;
 162         u32 daddr, nexthop;
 163         int tmp;
 164         int err;
 165
 166         if (addr_len < sizeof(struct sockaddr_in))
 167                 return -EINVAL;
 168
 169         if (usin->sin_family != AF_INET)
 170                 return -EAFNOSUPPORT;
 171
 172         nexthop = daddr = usin->sin_addr.s_addr;
 173         if (inet->opt && inet->opt->srr) {
 174                 if (!daddr)
 175                         return -EINVAL;
 176                 nexthop = inet->opt->faddr;
 177         }
 178
 179         tmp = ip_route_connect(&rt, nexthop, inet->saddr,
 180                                RT_CONN_FLAGS(sk), sk->sk_bound_dev_if,
 181                                IPPROTO_TCP,
 182                                inet->sport, usin->sin_port, sk);
 183         if (tmp < 0)
 184                 return tmp;
 185
 186         if (rt->rt_flags & (RTCF_MULTICAST | RTCF_BROADCAST)) {
 187                 ip_rt_put(rt);
 188                 return -ENETUNREACH;
 189         }
 190
 191         if (!inet->opt || !inet->opt->srr)
 192                 daddr = rt->rt_dst;
 193
 194         if (!inet->saddr)
 195                 inet->saddr = rt->rt_src;
 196         inet->rcv_saddr = inet->saddr;
 197
 198         if (tp->rx_opt.ts_recent_stamp && inet->daddr != daddr) {
 199                 /* Reset inherited state */
 200                 tp->rx_opt.ts_recent       = 0;
 201                 tp->rx_opt.ts_recent_stamp = 0;
 202                 tp->write_seq              = 0;
 203         }
 204
 205         if (tcp_death_row.sysctl_tw_recycle &&
 206             !tp->rx_opt.ts_recent_stamp && rt->rt_dst == daddr) {
 207                 struct inet_peer *peer = rt_get_peer(rt);
 208
 209                 /* VJ's idea. We save last timestamp seen from
 210                  * the destination in peer table, when entering state TIME-WAIT
 211                  * and initialize rx_opt.ts_recent from it, when trying new connection.
 212                  */
 213
 214                 if (peer && peer->tcp_ts_stamp + TCP_PAWS_MSL >= xtime.tv_sec) {
 215                         tp->rx_opt.ts_recent_stamp = peer->tcp_ts_stamp;
 216                         tp->rx_opt.ts_recent = peer->tcp_ts;
 217                 }
 218         }
 219
 220         inet->dport = usin->sin_port;
 221         inet->daddr = daddr;
 222
 223         inet_csk(sk)->icsk_ext_hdr_len = 0;
 224         if (inet->opt)
 225                 inet_csk(sk)->icsk_ext_hdr_len = inet->opt->optlen;
 226
 227         tp->rx_opt.mss_clamp = 536;
 228
 229         /* Socket identity is still unknown (sport may be zero).
 230          * However we set state to SYN-SENT and not releasing socket
 231          * lock select source port, enter ourselves into the hash tables and
 232          * complete initialization after this.
 233          */
 234         tcp_set_state(sk, TCP_SYN_SENT);
 235         err = inet_hash_connect(&tcp_death_row, sk);
 236         if (err)
 237                 goto failure;
 238
 239         err = ip_route_newports(&rt, IPPROTO_TCP, inet->sport, inet->dport, sk);
 240         if (err)
 241                 goto failure;
 242
 243         /* OK, now commit destination to socket.  */
 244         sk_setup_caps(sk, &rt->u.dst);
 245
 246         if (!tp->write_seq)
 247                 tp->write_seq = secure_tcp_sequence_number(inet->saddr,
 248                                                            inet->daddr,
 249                                                            inet->sport,
 250                                                            usin->sin_port);
 251
 252         inet->id = tp->write_seq ^ jiffies;
 253
 254         err = tcp_connect(sk);
 255         rt = NULL;
 256         if (err)
 257                 goto failure;
 258
 259         return 0;
 260
 261 failure:
 262         /* This unhashes the socket and releases the local port, if necessary. */
 263         tcp_set_state(sk, TCP_CLOSE);
 264         ip_rt_put(rt);
 265         sk->sk_route_caps = 0;
 266         inet->dport = 0;
 267         return err;
 268 }
 269
 270 /*
 271  * This routine does path mtu discovery as defined in RFC1191.
 272  */
 273 static void do_pmtu_discovery(struct sock *sk, struct iphdr *iph, u32 mtu)
 274 {
 275         struct dst_entry *dst;
 276         struct inet_sock *inet = inet_sk(sk);
 277
 278         /* We are not interested in TCP_LISTEN and open_requests (SYN-ACKs
 279          * send out by Linux are always <576bytes so they should go through
 280          * unfragmented).
 281          */
 282         if (sk->sk_state == TCP_LISTEN)
 283                 return;
 284
 285         /* We don't check in the destentry if pmtu discovery is forbidden
 286          * on this route. We just assume that no packet_to_big packets
 287          * are send back when pmtu discovery is not active.
 288          * There is a small race when the user changes this flag in the
 289          * route, but I think that's acceptable.
 290          */
 291         if ((dst = __sk_dst_check(sk, 0)) == NULL)
 292                 return;
 293
 294         dst->ops->update_pmtu(dst, mtu);
 295
 296         /* Something is about to be wrong... Remember soft error
 297          * for the case, if this connection will not able to recover.
 298          */
 299         if (mtu < dst_mtu(dst) && ip_dont_fragment(sk, dst))
 300                 sk->sk_err_soft = EMSGSIZE;
 301
 302         mtu = dst_mtu(dst);
 303
 304         if (inet->pmtudisc != IP_PMTUDISC_DONT &&
 305             inet_csk(sk)->icsk_pmtu_cookie > mtu) {
 306                 tcp_sync_mss(sk, mtu);
 307
 308                 /* Resend the TCP packet because it's
 309                  * clear that the old packet has been
 310                  * dropped. This is the new "fast" path mtu
 311                  * discovery.
 312                  */
 313                 tcp_simple_retransmit(sk);
 314         } /* else let the usual retransmit timer handle it */
 315 }
 316
 317 /*
 318  * This routine is called by the ICMP module when it gets some
 319  * sort of error condition.  If err < 0 then the socket should
 320  * be closed and the error returned to the user.  If err > 0
 321  * it's just the icmp type << 8 | icmp code.  After adjustment
 322  * header points to the first 8 bytes of the tcp header.  We need
 323  * to find the appropriate port.
 324  *
 325  * The locking strategy used here is very "optimistic". When
 326  * someone else accesses the socket the ICMP is just dropped
 327  * and for some paths there is no check at all.
 328  * A more general error queue to queue errors for later handling
 329  * is probably better.
 330  *
 331  */
 332
 333 void tcp_v4_err(struct sk_buff *skb, u32 info)
 334 {
 335         struct iphdr *iph = (struct iphdr *)skb->data;
 336         struct tcphdr *th = (struct tcphdr *)(skb->data + (iph->ihl << 2));
 337         struct tcp_sock *tp;
 338         struct inet_sock *inet;
 339         int type = skb->h.icmph->type;
 340         int code = skb->h.icmph->code;
 341         struct sock *sk;
 342         __u32 seq;
 343         int err;
 344
 345         if (skb->len < (iph->ihl << 2) + 8) {
 346                 ICMP_INC_STATS_BH(ICMP_MIB_INERRORS);
 347                 return;
 348         }
 349
 350         sk = inet_lookup(&tcp_hashinfo, iph->daddr, th->dest, iph->saddr,
 351                          th->source, inet_iif(skb));
 352         if (!sk) {
 353                 ICMP_INC_STATS_BH(ICMP_MIB_INERRORS);
 354                 return;
 355         }
 356         if (sk->sk_state == TCP_TIME_WAIT) {
 357                 inet_twsk_put((struct inet_timewait_sock *)sk);
 358                 return;
 359         }
 360
 361         bh_lock_sock(sk);
 362         /* If too many ICMPs get dropped on busy
 363          * servers this needs to be solved differently.
 364          */
 365         if (sock_owned_by_user(sk))
 366                 NET_INC_STATS_BH(LINUX_MIB_LOCKDROPPEDICMPS);
 367
 368         if (sk->sk_state == TCP_CLOSE)
 369                 goto out;
 370
 371         tp = tcp_sk(sk);
 372         seq = ntohl(th->seq);
 373         if (sk->sk_state != TCP_LISTEN &&
 374             !between(seq, tp->snd_una, tp->snd_nxt)) {
 375                 NET_INC_STATS(LINUX_MIB_OUTOFWINDOWICMPS);
 376                 goto out;
 377         }
 378
 379         switch (type) {
 380         case ICMP_SOURCE_QUENCH:
 381                 /* Just silently ignore these. */
 382                 goto out;
 383         case ICMP_PARAMETERPROB:
 384                 err = EPROTO;
 385                 break;
 386         case ICMP_DEST_UNREACH:
 387                 if (code > NR_ICMP_UNREACH)
 388                         goto out;
 389
 390                 if (code == ICMP_FRAG_NEEDED) { /* PMTU discovery (RFC1191) */
 391                         if (!sock_owned_by_user(sk))
 392                                 do_pmtu_discovery(sk, iph, info);
 393                         goto out;
 394                 }
 395
 396                 err = icmp_err_convert[code].errno;
 397                 break;
 398         case ICMP_TIME_EXCEEDED:
 399                 err = EHOSTUNREACH;
 400                 break;
 401         default:
 402                 goto out;
 403         }
 404
 405         switch (sk->sk_state) {
 406                 struct request_sock *req, **prev;
 407         case TCP_LISTEN:
 408                 if (sock_owned_by_user(sk))
 409                         goto out;
 410
 411                 req = inet_csk_search_req(sk, &prev, th->dest,
 412                                           iph->daddr, iph->saddr);
 413                 if (!req)
 414                         goto out;
 415
 416                 /* ICMPs are not backlogged, hence we cannot get
 417                    an established socket here.
 418                  */
 419                 BUG_TRAP(!req->sk);
 420
 421                 if (seq != tcp_rsk(req)->snt_isn) {
 422                         NET_INC_STATS_BH(LINUX_MIB_OUTOFWINDOWICMPS);
 423                         goto out;
 424                 }
 425
 426                 /*
 427                  * Still in SYN_RECV, just remove it silently.
 428                  * There is no good way to pass the error to the newly
 429                  * created socket, and POSIX does not want network
 430                  * errors returned from accept().
 431                  */
 432                 inet_csk_reqsk_queue_drop(sk, req, prev);
 433                 goto out;
 434
 435         case TCP_SYN_SENT:
 436         case TCP_SYN_RECV:  /* Cannot happen.
 437                                It can f.e. if SYNs crossed.
 438                              */
 439                 if (!sock_owned_by_user(sk)) {
 440                         TCP_INC_STATS_BH(TCP_MIB_ATTEMPTFAILS);
 441                         sk->sk_err = err;
 442
 443                         sk->sk_error_report(sk);
 444
 445                         tcp_done(sk);
 446                 } else {
 447                         sk->sk_err_soft = err;
 448                 }
 449                 goto out;
 450         }
 451
 452         /* If we've already connected we will keep trying
 453          * until we time out, or the user gives up.
 454          *
 455          * rfc1122 4.2.3.9 allows to consider as hard errors
 456          * only PROTO_UNREACH and PORT_UNREACH (well, FRAG_FAILED too,
 457          * but it is obsoleted by pmtu discovery).
 458          *
 459          * Note, that in modern internet, where routing is unreliable
 460          * and in each dark corner broken firewalls sit, sending random
 461          * errors ordered by their masters even this two messages finally lose
 462          * their original sense (even Linux sends invalid PORT_UNREACHs)
 463          *
 464          * Now we are in compliance with RFCs.
 465          *                                                      --ANK (980905)
 466          */
 467
 468         inet = inet_sk(sk);
 469         if (!sock_owned_by_user(sk) && inet->recverr) {
 470                 sk->sk_err = err;
 471                 sk->sk_error_report(sk);
 472         } else  { /* Only an error on timeout */
 473                 sk->sk_err_soft = err;
 474         }
 475
 476 out:
 477         bh_unlock_sock(sk);
 478         sock_put(sk);
 479 }
 480
 481 /* This routine computes an IPv4 TCP checksum. */
 482 void tcp_v4_send_check(struct sock *sk, int len, struct sk_buff *skb)
 483 {
 484         struct inet_sock *inet = inet_sk(sk);
 485         struct tcphdr *th = skb->h.th;
 486
 487         if (skb->ip_summed == CHECKSUM_HW) {
 488                 th->check = ~tcp_v4_check(th, len, inet->saddr, inet->daddr, 0);
 489                 skb->csum = offsetof(struct tcphdr, check);
 490         } else {
 491                 th->check = tcp_v4_check(th, len, inet->saddr, inet->daddr,
 492                                          csum_partial((char *)th,
 493                                                       th->doff << 2,
 494                                                       skb->csum));
 495         }
 496 }
 497
 498 /*
 499  *      This routine will send an RST to the other tcp.
 500  *
 501  *      Someone asks: why I NEVER use socket parameters (TOS, TTL etc.)
 502  *                    for reset.
 503  *      Answer: if a packet caused RST, it is not for a socket
 504  *              existing in our system, if it is matched to a socket,
 505  *              it is just duplicate segment or bug in other side's TCP.
 506  *              So that we build reply only basing on parameters
 507  *              arrived with segment.
 508  *      Exception: precedence violation. We do not implement it in any case.
 509  */
 510
 511 static void tcp_v4_send_reset(struct sk_buff *skb)
 512 {
 513         struct tcphdr *th = skb->h.th;
 514         struct tcphdr rth;
 515         struct ip_reply_arg arg;
 516
 517         /* Never send a reset in response to a reset. */
 518         if (th->rst)
 519                 return;
 520
 521         if (((struct rtable *)skb->dst)->rt_type != RTN_LOCAL)
 522                 return;
 523
 524         /* Swap the send and the receive. */
 525         memset(&rth, 0, sizeof(struct tcphdr));
 526         rth.dest   = th->source;
 527         rth.source = th->dest;
 528         rth.doff   = sizeof(struct tcphdr) / 4;
 529         rth.rst    = 1;
 530
 531         if (th->ack) {
 532                 rth.seq = th->ack_seq;
 533         } else {
 534                 rth.ack = 1;
 535                 rth.ack_seq = htonl(ntohl(th->seq) + th->syn + th->fin +
 536                                     skb->len - (th->doff << 2));
 537         }
 538
 539         memset(&arg, 0, sizeof arg);
 540         arg.iov[0].iov_base = (unsigned char *)&rth;
 541         arg.iov[0].iov_len  = sizeof rth;
 542         arg.csum = csum_tcpudp_nofold(skb->nh.iph->daddr,
 543                                       skb->nh.iph->saddr, /*XXX*/
 544                                       sizeof(struct tcphdr), IPPROTO_TCP, 0);
 545         arg.csumoffset = offsetof(struct tcphdr, check) / 2;
 546
 547         ip_send_reply(tcp_socket->sk, skb, &arg, sizeof rth);
 548
 549         TCP_INC_STATS_BH(TCP_MIB_OUTSEGS);
 550         TCP_INC_STATS_BH(TCP_MIB_OUTRSTS);
 551 }
 552
 553 /* The code following below sending ACKs in SYN-RECV and TIME-WAIT states
 554    outside socket context is ugly, certainly. What can I do?
 555  */
 556
 557 static void tcp_v4_send_ack(struct sk_buff *skb, u32 seq, u32 ack,
 558                             u32 win, u32 ts)
 559 {
 560         struct tcphdr *th = skb->h.th;
 561         struct {
 562                 struct tcphdr th;
 563                 u32 tsopt[3];
 564         } rep;
 565         struct ip_reply_arg arg;
 566
 567         memset(&rep.th, 0, sizeof(struct tcphdr));
 568         memset(&arg, 0, sizeof arg);
 569
 570         arg.iov[0].iov_base = (unsigned char *)&rep;
 571         arg.iov[0].iov_len  = sizeof(rep.th);
 572         if (ts) {
 573                 rep.tsopt[0] = htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) |
 574                                      (TCPOPT_TIMESTAMP << 8) |
 575                                      TCPOLEN_TIMESTAMP);
 576                 rep.tsopt[1] = htonl(tcp_time_stamp);
 577                 rep.tsopt[2] = htonl(ts);
 578                 arg.iov[0].iov_len = sizeof(rep);
 579         }
 580
 581         /* Swap the send and the receive. */
 582         rep.th.dest    = th->source;
 583         rep.th.source  = th->dest;
 584         rep.th.doff    = arg.iov[0].iov_len / 4;
 585         rep.th.seq     = htonl(seq);
 586         rep.th.ack_seq = htonl(ack);
 587         rep.th.ack     = 1;
 588         rep.th.window  = htons(win);
 589
 590         arg.csum = csum_tcpudp_nofold(skb->nh.iph->daddr,
 591                                       skb->nh.iph->saddr, /*XXX*/
 592                                       arg.iov[0].iov_len, IPPROTO_TCP, 0);
 593         arg.csumoffset = offsetof(struct tcphdr, check) / 2;
 594
 595         ip_send_reply(tcp_socket->sk, skb, &arg, arg.iov[0].iov_len);
 596
 597         TCP_INC_STATS_BH(TCP_MIB_OUTSEGS);
 598 }
 599
 600 static void tcp_v4_timewait_ack(struct sock *sk, struct sk_buff *skb)
 601 {
 602         struct inet_timewait_sock *tw = inet_twsk(sk);
 603         const struct tcp_timewait_sock *tcptw = tcp_twsk(sk);
 604
 605         tcp_v4_send_ack(skb, tcptw->tw_snd_nxt, tcptw->tw_rcv_nxt,
 606                         tcptw->tw_rcv_wnd >> tw->tw_rcv_wscale, tcptw->tw_ts_recent);
 607
 608         inet_twsk_put(tw);
 609 }
 610
 611 static void tcp_v4_reqsk_send_ack(struct sk_buff *skb, struct request_sock *req)
 612 {
 613         tcp_v4_send_ack(skb, tcp_rsk(req)->snt_isn + 1, tcp_rsk(req)->rcv_isn + 1, req->rcv_wnd,
 614                         req->ts_recent);
 615 }
 616
 617 /*
 618  *      Send a SYN-ACK after having received an ACK.
 619  *      This still operates on a request_sock only, not on a big
 620  *      socket.
 621  */
 622 static int tcp_v4_send_synack(struct sock *sk, struct request_sock *req,
 623                               struct dst_entry *dst)
 624 {
 625         const struct inet_request_sock *ireq = inet_rsk(req);
 626         int err = -1;
 627         struct sk_buff * skb;
 628
 629         /* First, grab a route. */
 630         if (!dst && (dst = inet_csk_route_req(sk, req)) == NULL)
 631                 goto out;
 632
 633         skb = tcp_make_synack(sk, dst, req);
 634
 635         if (skb) {
 636                 struct tcphdr *th = skb->h.th;
 637
 638                 th->check = tcp_v4_check(th, skb->len,
 639                                          ireq->loc_addr,
 640                                          ireq->rmt_addr,
 641                                          csum_partial((char *)th, skb->len,
 642                                                       skb->csum));
 643
 644                 err = ip_build_and_send_pkt(skb, sk, ireq->loc_addr,
 645                                             ireq->rmt_addr,
 646                                             ireq->opt);
 647                 if (err == NET_XMIT_CN)
 648                         err = 0;
 649         }
 650
 651 out:
 652         dst_release(dst);
 653         return err;
 654 }
 655
 656 /*
 657  *      IPv4 request_sock destructor.
 658  */
 659 static void tcp_v4_reqsk_destructor(struct request_sock *req)
 660 {
 661         kfree(inet_rsk(req)->opt);
 662 }
 663
 664 #ifdef CONFIG_SYN_COOKIES
 665 static void syn_flood_warning(struct sk_buff *skb)
 666 {
 667         static unsigned long warntime;
 668
 669         if (time_after(jiffies, (warntime + HZ * 60))) {
 670                 warntime = jiffies;
 671                 printk(KERN_INFO
 672                        "possible SYN flooding on port %d. Sending cookies.\n",
 673                        ntohs(skb->h.th->dest));
 674         }
 675 }
 676 #endif
 677
 678 /*
 679  * Save and compile IPv4 options into the request_sock if needed.
 680  */
 681 static struct ip_options *tcp_v4_save_options(struct sock *sk,
 682                                               struct sk_buff *skb)
 683 {
 684         struct ip_options *opt = &(IPCB(skb)->opt);
 685         struct ip_options *dopt = NULL;
 686
 687         if (opt && opt->optlen) {
 688                 int opt_size = optlength(opt);
 689                 dopt = kmalloc(opt_size, GFP_ATOMIC);
 690                 if (dopt) {
 691                         if (ip_options_echo(dopt, skb)) {
 692                                 kfree(dopt);
 693                                 dopt = NULL;
 694                         }
 695                 }
 696         }
 697         return dopt;
 698 }
 699
 700 struct request_sock_ops tcp_request_sock_ops = {
 701         .family         =       PF_INET,
 702         .obj_size       =       sizeof(struct tcp_request_sock),
 703         .rtx_syn_ack    =       tcp_v4_send_synack,
 704         .send_ack       =       tcp_v4_reqsk_send_ack,
 705         .destructor     =       tcp_v4_reqsk_destructor,
 706         .send_reset     =       tcp_v4_send_reset,
 707 };
 708
 709 static struct timewait_sock_ops tcp_timewait_sock_ops = {
 710         .twsk_obj_size  = sizeof(struct tcp_timewait_sock),
 711         .twsk_unique    = tcp_twsk_unique,
 712 };
 713
 714 int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
 715 {
 716         struct inet_request_sock *ireq;
 717         struct tcp_options_received tmp_opt;
 718         struct request_sock *req;
 719         __u32 saddr = skb->nh.iph->saddr;
 720         __u32 daddr = skb->nh.iph->daddr;
 721         __u32 isn = TCP_SKB_CB(skb)->when;
 722         struct dst_entry *dst = NULL;
 723 #ifdef CONFIG_SYN_COOKIES
 724         int want_cookie = 0;
 725 #else
 726 #define want_cookie 0 /* Argh, why doesn't gcc optimize this :( */
 727 #endif
 728
 729         /* Never answer to SYNs send to broadcast or multicast */
 730         if (((struct rtable *)skb->dst)->rt_flags &
 731             (RTCF_BROADCAST | RTCF_MULTICAST))
 732                 goto drop;
 733
 734         /* TW buckets are converted to open requests without
 735          * limitations, they conserve resources and peer is
 736          * evidently real one.
 737          */
 738         if (inet_csk_reqsk_queue_is_full(sk) && !isn) {
 739 #ifdef CONFIG_SYN_COOKIES
 740                 if (sysctl_tcp_syncookies) {
 741                         want_cookie = 1;
 742                 } else
 743 #endif
 744                 goto drop;
 745         }
 746
 747         /* Accept backlog is full. If we have already queued enough
 748          * of warm entries in syn queue, drop request. It is better than
 749          * clogging syn queue with openreqs with exponentially increasing
 750          * timeout.
 751          */
 752         if (sk_acceptq_is_full(sk) && inet_csk_reqsk_queue_young(sk) > 1)
 753                 goto drop;
 754
 755         req = reqsk_alloc(&tcp_request_sock_ops);
 756         if (!req)
 757                 goto drop;
 758
 759         tcp_clear_options(&tmp_opt);
 760         tmp_opt.mss_clamp = 536;
 761         tmp_opt.user_mss  = tcp_sk(sk)->rx_opt.user_mss;
 762
 763         tcp_parse_options(skb, &tmp_opt, 0);
 764
 765         if (want_cookie) {
 766                 tcp_clear_options(&tmp_opt);
 767                 tmp_opt.saw_tstamp = 0;
 768         }
 769
 770         if (tmp_opt.saw_tstamp && !tmp_opt.rcv_tsval) {
 771                 /* Some OSes (unknown ones, but I see them on web server, which
 772                  * contains information interesting only for windows'
 773                  * users) do not send their stamp in SYN. It is easy case.
 774                  * We simply do not advertise TS support.
 775                  */
 776                 tmp_opt.saw_tstamp = 0;
 777                 tmp_opt.tstamp_ok  = 0;
 778         }
 779         tmp_opt.tstamp_ok = tmp_opt.saw_tstamp;
 780
 781         tcp_openreq_init(req, &tmp_opt, skb);
 782
 783         ireq = inet_rsk(req);
 784         ireq->loc_addr = daddr;
 785         ireq->rmt_addr = saddr;
 786         ireq->opt = tcp_v4_save_options(sk, skb);
 787         if (!want_cookie)
 788                 TCP_ECN_create_request(req, skb->h.th);
 789
 790         if (want_cookie) {
 791 #ifdef CONFIG_SYN_COOKIES
 792                 syn_flood_warning(skb);
 793 #endif
 794                 isn = cookie_v4_init_sequence(sk, skb, &req->mss);
 795         } else if (!isn) {
 796                 struct inet_peer *peer = NULL;
 797
 798                 /* VJ's idea. We save last timestamp seen
 799                  * from the destination in peer table, when entering
 800                  * state TIME-WAIT, and check against it before
 801                  * accepting new connection request.
 802                  *
 803                  * If "isn" is not zero, this request hit alive
 804                  * timewait bucket, so that all the necessary checks
 805                  * are made in the function processing timewait state.
 806                  */
 807                 if (tmp_opt.saw_tstamp &&
 808                     tcp_death_row.sysctl_tw_recycle &&
 809                     (dst = inet_csk_route_req(sk, req)) != NULL &&
 810                     (peer = rt_get_peer((struct rtable *)dst)) != NULL &&
 811                     peer->v4daddr == saddr) {
 812                         if (xtime.tv_sec < peer->tcp_ts_stamp + TCP_PAWS_MSL &&
 813                             (s32)(peer->tcp_ts - req->ts_recent) >
 814                                                         TCP_PAWS_WINDOW) {
 815                                 NET_INC_STATS_BH(LINUX_MIB_PAWSPASSIVEREJECTED);
 816                                 dst_release(dst);
 817                                 goto drop_and_free;
 818                         }
 819                 }
 820                 /* Kill the following clause, if you dislike this way. */
 821                 else if (!sysctl_tcp_syncookies &&
 822                          (sysctl_max_syn_backlog - inet_csk_reqsk_queue_len(sk) <
 823                           (sysctl_max_syn_backlog >> 2)) &&
 824                          (!peer || !peer->tcp_ts_stamp) &&
 825                          (!dst || !dst_metric(dst, RTAX_RTT))) {
 826                         /* Without syncookies last quarter of
 827                          * backlog is filled with destinations,
 828                          * proven to be alive.
 829                          * It means that we continue to communicate
 830                          * to destinations, already remembered
 831                          * to the moment of synflood.
 832                          */
 833                         LIMIT_NETDEBUG(KERN_DEBUG "TCP: drop open "
 834                                        "request from %u.%u.%u.%u/%u\n",
 835                                        NIPQUAD(saddr),
 836                                        ntohs(skb->h.th->source));
 837                         dst_release(dst);
 838                         goto drop_and_free;
 839                 }
 840
 841                 isn = tcp_v4_init_sequence(sk, skb);
 842         }
 843         tcp_rsk(req)->snt_isn = isn;
 844
 845         if (tcp_v4_send_synack(sk, req, dst))
 846                 goto drop_and_free;
 847
 848         if (want_cookie) {
 849                 reqsk_free(req);
 850         } else {
 851                 inet_csk_reqsk_queue_hash_add(sk, req, TCP_TIMEOUT_INIT);
 852         }
 853         return 0;
 854
 855 drop_and_free:
 856         reqsk_free(req);
 857 drop:
 858         TCP_INC_STATS_BH(TCP_MIB_ATTEMPTFAILS);
 859         return 0;
 860 }
 861
 862
 863 /*
 864  * The three way handshake has completed - we got a valid synack -
 865  * now create the new socket.
 866  */
 867 struct sock *tcp_v4_syn_recv_sock(struct sock *sk, struct sk_buff *skb,
 868                                   struct request_sock *req,
 869                                   struct dst_entry *dst)
 870 {
 871         struct inet_request_sock *ireq;
 872         struct inet_sock *newinet;
 873         struct tcp_sock *newtp;
 874         struct sock *newsk;
 875
 876         if (sk_acceptq_is_full(sk))
 877                 goto exit_overflow;
 878
 879         if (!dst && (dst = inet_csk_route_req(sk, req)) == NULL)
 880                 goto exit;
 881
 882         newsk = tcp_create_openreq_child(sk, req, skb);
 883         if (!newsk)
 884                 goto exit;
 885
 886         sk_setup_caps(newsk, dst);
 887
 888         newtp                 = tcp_sk(newsk);
 889         newinet               = inet_sk(newsk);
 890         ireq                  = inet_rsk(req);
 891         newinet->daddr        = ireq->rmt_addr;
 892         newinet->rcv_saddr    = ireq->loc_addr;
 893         newinet->saddr        = ireq->loc_addr;
 894         newinet->opt          = ireq->opt;
 895         ireq->opt             = NULL;
 896         newinet->mc_index     = inet_iif(skb);
 897         newinet->mc_ttl       = skb->nh.iph->ttl;
 898         inet_csk(newsk)->icsk_ext_hdr_len = 0;
 899         if (newinet->opt)
 900                 inet_csk(newsk)->icsk_ext_hdr_len = newinet->opt->optlen;
 901         newinet->id = newtp->write_seq ^ jiffies;
 902
 903         tcp_mtup_init(newsk);
 904         tcp_sync_mss(newsk, dst_mtu(dst));
 905         newtp->advmss = dst_metric(dst, RTAX_ADVMSS);
 906         tcp_initialize_rcv_mss(newsk);
 907
 908         __inet_hash(&tcp_hashinfo, newsk, 0);
 909         __inet_inherit_port(&tcp_hashinfo, sk, newsk);
 910
 911         return newsk;
 912
 913 exit_overflow:
 914         NET_INC_STATS_BH(LINUX_MIB_LISTENOVERFLOWS);
 915 exit:
 916         NET_INC_STATS_BH(LINUX_MIB_LISTENDROPS);
 917         dst_release(dst);
 918         return NULL;
 919 }
 920
 921 static struct sock *tcp_v4_hnd_req(struct sock *sk, struct sk_buff *skb)
 922 {
 923         struct tcphdr *th = skb->h.th;
 924         struct iphdr *iph = skb->nh.iph;
 925         struct sock *nsk;
 926         struct request_sock **prev;
 927         /* Find possible connection requests. */
 928         struct request_sock *req = inet_csk_search_req(sk, &prev, th->source,
 929                                                        iph->saddr, iph->daddr);
 930         if (req)
 931                 return tcp_check_req(sk, skb, req, prev);
 932
 933         nsk = __inet_lookup_established(&tcp_hashinfo, skb->nh.iph->saddr,
 934                                         th->source, skb->nh.iph->daddr,
 935                                         ntohs(th->dest), inet_iif(skb));
 936
 937         if (nsk) {
 938                 if (nsk->sk_state != TCP_TIME_WAIT) {
 939                         bh_lock_sock(nsk);
 940                         return nsk;
 941                 }
 942                 inet_twsk_put((struct inet_timewait_sock *)nsk);
 943                 return NULL;
 944         }
 945
 946 #ifdef CONFIG_SYN_COOKIES
 947         if (!th->rst && !th->syn && th->ack)
 948                 sk = cookie_v4_check(sk, skb, &(IPCB(skb)->opt));
 949 #endif
 950         return sk;
 951 }
 952
 953 static int tcp_v4_checksum_init(struct sk_buff *skb)
 954 {
 955         if (skb->ip_summed == CHECKSUM_HW) {
 956                 if (!tcp_v4_check(skb->h.th, skb->len, skb->nh.iph->saddr,
 957                                   skb->nh.iph->daddr, skb->csum)) {
 958                         skb->ip_summed = CHECKSUM_UNNECESSARY;
 959                         return 0;
 960                 }
 961         }
 962
 963         skb->csum = csum_tcpudp_nofold(skb->nh.iph->saddr, skb->nh.iph->daddr,
 964                                        skb->len, IPPROTO_TCP, 0);
 965
 966         if (skb->len <= 76) {
 967                 return __skb_checksum_complete(skb);
 968         }
 969         return 0;
 970 }
 971
 972
 973 /* The socket must have it's spinlock held when we get
 974  * here.
 975  *
 976  * We have a potential double-lock case here, so even when
 977  * doing backlog processing we use the BH locking scheme.
 978  * This is because we cannot sleep with the original spinlock
 979  * held.
 980  */
 981 int tcp_v4_do_rcv(struct sock *sk, struct sk_buff *skb)
 982 {
 983         if (sk->sk_state == TCP_ESTABLISHED) { /* Fast path */
 984                 TCP_CHECK_TIMER(sk);
 985                 if (tcp_rcv_established(sk, skb, skb->h.th, skb->len))
 986                         goto reset;
 987                 TCP_CHECK_TIMER(sk);
 988                 return 0;
 989         }
 990
 991         if (skb->len < (skb->h.th->doff << 2) || tcp_checksum_complete(skb))
 992                 goto csum_err;
 993
 994         if (sk->sk_state == TCP_LISTEN) {
 995                 struct sock *nsk = tcp_v4_hnd_req(sk, skb);
 996                 if (!nsk)
 997                         goto discard;
 998
 999                 if (nsk != sk) {
1000                         if (tcp_child_process(sk, nsk, skb))
1001                                 goto reset;
1002                         return 0;
1003                 }
1004         }
1005
1006         TCP_CHECK_TIMER(sk);
1007         if (tcp_rcv_state_process(sk, skb, skb->h.th, skb->len))
1008                 goto reset;
1009         TCP_CHECK_TIMER(sk);
1010         return 0;
1011
1012 reset:
1013         tcp_v4_send_reset(skb);
1014 discard:
1015         kfree_skb(skb);
1016         /* Be careful here. If this function gets more complicated and
1017          * gcc suffers from register pressure on the x86, sk (in %ebx)
1018          * might be destroyed here. This current version compiles correctly,
1019          * but you have been warned.
1020          */
1021         return 0;
1022
1023 csum_err:
1024         TCP_INC_STATS_BH(TCP_MIB_INERRS);
1025         goto discard;
1026 }
1027
1028 /*
1029  *      From tcp_input.c
1030  */
1031
1032 int tcp_v4_rcv(struct sk_buff *skb)
1033 {
1034         struct tcphdr *th;
1035         struct sock *sk;
1036         int ret;
1037
1038         if (skb->pkt_type != PACKET_HOST)
1039                 goto discard_it;
1040
1041         /* Count it even if it's bad */
1042         TCP_INC_STATS_BH(TCP_MIB_INSEGS);
1043
1044         if (!pskb_may_pull(skb, sizeof(struct tcphdr)))
1045                 goto discard_it;
1046
1047         th = skb->h.th;
1048
1049         if (th->doff < sizeof(struct tcphdr) / 4)
1050                 goto bad_packet;
1051         if (!pskb_may_pull(skb, th->doff * 4))
1052                 goto discard_it;
1053
1054         /* An explanation is required here, I think.
1055          * Packet length and doff are validated by header prediction,
1056          * provided case of th->doff==0 is eliminated.
1057          * So, we defer the checks. */
1058         if ((skb->ip_summed != CHECKSUM_UNNECESSARY &&
1059              tcp_v4_checksum_init(skb)))
1060                 goto bad_packet;
1061
1062         th = skb->h.th;
1063         TCP_SKB_CB(skb)->seq = ntohl(th->seq);
1064         TCP_SKB_CB(skb)->end_seq = (TCP_SKB_CB(skb)->seq + th->syn + th->fin +
1065                                     skb->len - th->doff * 4);
1066         TCP_SKB_CB(skb)->ack_seq = ntohl(th->ack_seq);
1067         TCP_SKB_CB(skb)->when    = 0;
1068         TCP_SKB_CB(skb)->flags   = skb->nh.iph->tos;
1069         TCP_SKB_CB(skb)->sacked  = 0;
1070
1071         sk = __inet_lookup(&tcp_hashinfo, skb->nh.iph->saddr, th->source,
1072                            skb->nh.iph->daddr, ntohs(th->dest),
1073                            inet_iif(skb));
1074
1075         if (!sk)
1076                 goto no_tcp_socket;
1077
1078 process:
1079         if (sk->sk_state == TCP_TIME_WAIT)
1080                 goto do_time_wait;
1081
1082         if (!xfrm4_policy_check(sk, XFRM_POLICY_IN, skb))
1083                 goto discard_and_relse;
1084         nf_reset(skb);
1085
1086         if (sk_filter(sk, skb, 0))
1087                 goto discard_and_relse;
1088
1089         skb->dev = NULL;
1090
1091         bh_lock_sock(sk);
1092         ret = 0;
1093         if (!sock_owned_by_user(sk)) {
1094                 if (!tcp_prequeue(sk, skb))
1095                         ret = tcp_v4_do_rcv(sk, skb);
1096         } else
1097                 sk_add_backlog(sk, skb);
1098         bh_unlock_sock(sk);
1099
1100         sock_put(sk);
1101
1102         return ret;
1103
1104 no_tcp_socket:
1105         if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb))
1106                 goto discard_it;
1107
1108         if (skb->len < (th->doff << 2) || tcp_checksum_complete(skb)) {
1109 bad_packet:
1110                 TCP_INC_STATS_BH(TCP_MIB_INERRS);
1111         } else {
1112                 tcp_v4_send_reset(skb);
1113         }
1114
1115 discard_it:
1116         /* Discard frame. */
1117         kfree_skb(skb);
1118         return 0;
1119
1120 discard_and_relse:
1121         sock_put(sk);
1122         goto discard_it;
1123
1124 do_time_wait:
1125         if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) {
1126                 inet_twsk_put((struct inet_timewait_sock *) sk);
1127                 goto discard_it;
1128         }
1129
1130         if (skb->len < (th->doff << 2) || tcp_checksum_complete(skb)) {
1131                 TCP_INC_STATS_BH(TCP_MIB_INERRS);
1132                 inet_twsk_put((struct inet_timewait_sock *) sk);
1133                 goto discard_it;
1134         }
1135         switch (tcp_timewait_state_process((struct inet_timewait_sock *)sk,
1136                                            skb, th)) {
1137         case TCP_TW_SYN: {
1138                 struct sock *sk2 = inet_lookup_listener(&tcp_hashinfo,
1139                                                         skb->nh.iph->daddr,
1140                                                         ntohs(th->dest),
1141                                                         inet_iif(skb));
1142                 if (sk2) {
1143                         inet_twsk_deschedule((struct inet_timewait_sock *)sk,
1144                                              &tcp_death_row);
1145                         inet_twsk_put((struct inet_timewait_sock *)sk);
1146                         sk = sk2;
1147                         goto process;
1148                 }
1149                 /* Fall through to ACK */
1150         }
1151         case TCP_TW_ACK:
1152                 tcp_v4_timewait_ack(sk, skb);
1153                 break;
1154         case TCP_TW_RST:
1155                 goto no_tcp_socket;
1156         case TCP_TW_SUCCESS:;
1157         }
1158         goto discard_it;
1159 }
1160
1161 /* VJ's idea. Save last timestamp seen from this destination
1162  * and hold it at least for normal timewait interval to use for duplicate
1163  * segment detection in subsequent connections, before they enter synchronized
1164  * state.
1165  */
1166
1167 int tcp_v4_remember_stamp(struct sock *sk)
1168 {
1169         struct inet_sock *inet = inet_sk(sk);
1170         struct tcp_sock *tp = tcp_sk(sk);
1171         struct rtable *rt = (struct rtable *)__sk_dst_get(sk);
1172         struct inet_peer *peer = NULL;
1173         int release_it = 0;
1174
1175         if (!rt || rt->rt_dst != inet->daddr) {
1176                 peer = inet_getpeer(inet->daddr, 1);
1177                 release_it = 1;
1178         } else {
1179                 if (!rt->peer)
1180                         rt_bind_peer(rt, 1);
1181                 peer = rt->peer;
1182         }
1183
1184         if (peer) {
1185                 if ((s32)(peer->tcp_ts - tp->rx_opt.ts_recent) <= 0 ||
1186                     (peer->tcp_ts_stamp + TCP_PAWS_MSL < xtime.tv_sec &&
1187                      peer->tcp_ts_stamp <= tp->rx_opt.ts_recent_stamp)) {
1188                         peer->tcp_ts_stamp = tp->rx_opt.ts_recent_stamp;
1189                         peer->tcp_ts = tp->rx_opt.ts_recent;
1190                 }
1191                 if (release_it)
1192                         inet_putpeer(peer);
1193                 return 1;
1194         }
1195
1196         return 0;
1197 }
1198
1199 int tcp_v4_tw_remember_stamp(struct inet_timewait_sock *tw)
1200 {
1201         struct inet_peer *peer = inet_getpeer(tw->tw_daddr, 1);
1202
1203         if (peer) {
1204                 const struct tcp_timewait_sock *tcptw = tcp_twsk((struct sock *)tw);
1205
1206                 if ((s32)(peer->tcp_ts - tcptw->tw_ts_recent) <= 0 ||
1207                     (peer->tcp_ts_stamp + TCP_PAWS_MSL < xtime.tv_sec &&
1208                      peer->tcp_ts_stamp <= tcptw->tw_ts_recent_stamp)) {
1209                         peer->tcp_ts_stamp = tcptw->tw_ts_recent_stamp;
1210                         peer->tcp_ts       = tcptw->tw_ts_recent;
1211                 }
1212                 inet_putpeer(peer);
1213                 return 1;
1214         }
1215
1216         return 0;
1217 }
1218
1219 struct inet_connection_sock_af_ops ipv4_specific = {
1220         .queue_xmit     =       ip_queue_xmit,
1221         .send_check     =       tcp_v4_send_check,
1222         .rebuild_header =       inet_sk_rebuild_header,
1223         .conn_request   =       tcp_v4_conn_request,
1224         .syn_recv_sock  =       tcp_v4_syn_recv_sock,
1225         .remember_stamp =       tcp_v4_remember_stamp,
1226         .net_header_len =       sizeof(struct iphdr),
1227         .setsockopt     =       ip_setsockopt,
1228         .getsockopt     =       ip_getsockopt,
1229         .addr2sockaddr  =       inet_csk_addr2sockaddr,
1230         .sockaddr_len   =       sizeof(struct sockaddr_in),
1231 };
1232
1233 /* NOTE: A lot of things set to zero explicitly by call to
1234  *       sk_alloc() so need not be done here.
1235  */
1236 static int tcp_v4_init_sock(struct sock *sk)
1237 {
1238         struct inet_connection_sock *icsk = inet_csk(sk);
1239         struct tcp_sock *tp = tcp_sk(sk);
1240
1241         skb_queue_head_init(&tp->out_of_order_queue);
1242         tcp_init_xmit_timers(sk);
1243         tcp_prequeue_init(tp);
1244
1245         icsk->icsk_rto = TCP_TIMEOUT_INIT;
1246         tp->mdev = TCP_TIMEOUT_INIT;
1247
1248         /* So many TCP implementations out there (incorrectly) count the
1249          * initial SYN frame in their delayed-ACK and congestion control
1250          * algorithms that we must have the following bandaid to talk
1251          * efficiently to them.  -DaveM
1252          */
1253         tp->snd_cwnd = 2;
1254
1255         /* See draft-stevens-tcpca-spec-01 for discussion of the
1256          * initialization of these values.
1257          */
1258         tp->snd_ssthresh = 0x7fffffff;  /* Infinity */
1259         tp->snd_cwnd_clamp = ~0;
1260         tp->mss_cache = 536;
1261
1262         tp->reordering = sysctl_tcp_reordering;
1263         icsk->icsk_ca_ops = &tcp_init_congestion_ops;
1264
1265         sk->sk_state = TCP_CLOSE;
1266
1267         sk->sk_write_space = sk_stream_write_space;
1268         sock_set_flag(sk, SOCK_USE_WRITE_QUEUE);
1269
1270         icsk->icsk_af_ops = &ipv4_specific;
1271         icsk->icsk_sync_mss = tcp_sync_mss;
1272
1273         sk->sk_sndbuf = sysctl_tcp_wmem[1];
1274         sk->sk_rcvbuf = sysctl_tcp_rmem[1];
1275
1276         atomic_inc(&tcp_sockets_allocated);
1277
1278         return 0;
1279 }
1280
1281 int tcp_v4_destroy_sock(struct sock *sk)
1282 {
1283         struct tcp_sock *tp = tcp_sk(sk);
1284
1285         tcp_clear_xmit_timers(sk);
1286
1287         tcp_cleanup_congestion_control(sk);
1288
1289         /* Cleanup up the write buffer. */
1290         sk_stream_writequeue_purge(sk);
1291
1292         /* Cleans up our, hopefully empty, out_of_order_queue. */
1293         __skb_queue_purge(&tp->out_of_order_queue);
1294
1295         /* Clean prequeue, it must be empty really */
1296         __skb_queue_purge(&tp->ucopy.prequeue);
1297
1298         /* Clean up a referenced TCP bind bucket. */
1299         if (inet_csk(sk)->icsk_bind_hash)
1300                 inet_put_port(&tcp_hashinfo, sk);
1301
1302         /*
1303          * If sendmsg cached page exists, toss it.
1304          */
1305         if (sk->sk_sndmsg_page) {
1306                 __free_page(sk->sk_sndmsg_page);
1307                 sk->sk_sndmsg_page = NULL;
1308         }
1309
1310         atomic_dec(&tcp_sockets_allocated);
1311
1312         return 0;
1313 }
1314
1315 EXPORT_SYMBOL(tcp_v4_destroy_sock);
1316
1317 #ifdef CONFIG_PROC_FS
1318 /* Proc filesystem TCP sock list dumping. */
1319
1320 static inline struct inet_timewait_sock *tw_head(struct hlist_head *head)
1321 {
1322         return hlist_empty(head) ? NULL :
1323                 list_entry(head->first, struct inet_timewait_sock, tw_node);
1324 }
1325
1326 static inline struct inet_timewait_sock *tw_next(struct inet_timewait_sock *tw)
1327 {
1328         return tw->tw_node.next ?
1329                 hlist_entry(tw->tw_node.next, typeof(*tw), tw_node) : NULL;
1330 }
1331
1332 static void *listening_get_next(struct seq_file *seq, void *cur)
1333 {
1334         struct inet_connection_sock *icsk;
1335         struct hlist_node *node;
1336         struct sock *sk = cur;
1337         struct tcp_iter_state* st = seq->private;
1338
1339         if (!sk) {
1340                 st->bucket = 0;
1341                 sk = sk_head(&tcp_hashinfo.listening_hash[0]);
1342                 goto get_sk;
1343         }
1344
1345         ++st->num;
1346
1347         if (st->state == TCP_SEQ_STATE_OPENREQ) {
1348                 struct request_sock *req = cur;
1349
1350                 icsk = inet_csk(st->syn_wait_sk);
1351                 req = req->dl_next;
1352                 while (1) {
1353                         while (req) {
1354                                 if (req->rsk_ops->family == st->family) {
1355                                         cur = req;
1356                                         goto out;
1357                                 }
1358                                 req = req->dl_next;
1359                         }
1360                         if (++st->sbucket >= TCP_SYNQ_HSIZE)
1361                                 break;
1362 get_req:
1363                         req = icsk->icsk_accept_queue.listen_opt->syn_table[st->sbucket];
1364                 }
1365                 sk        = sk_next(st->syn_wait_sk);
1366                 st->state = TCP_SEQ_STATE_LISTENING;
1367                 read_unlock_bh(&icsk->icsk_accept_queue.syn_wait_lock);
1368         } else {
1369                 icsk = inet_csk(sk);
1370                 read_lock_bh(&icsk->icsk_accept_queue.syn_wait_lock);
1371                 if (reqsk_queue_len(&icsk->icsk_accept_queue))
1372                         goto start_req;
1373                 read_unlock_bh(&icsk->icsk_accept_queue.syn_wait_lock);
1374                 sk = sk_next(sk);
1375         }
1376 get_sk:
1377         sk_for_each_from(sk, node) {
1378                 if (sk->sk_family == st->family) {
1379                         cur = sk;
1380                         goto out;
1381                 }
1382                 icsk = inet_csk(sk);
1383                 read_lock_bh(&icsk->icsk_accept_queue.syn_wait_lock);
1384                 if (reqsk_queue_len(&icsk->icsk_accept_queue)) {
1385 start_req:
1386                         st->uid         = sock_i_uid(sk);
1387                         st->syn_wait_sk = sk;
1388                         st->state       = TCP_SEQ_STATE_OPENREQ;
1389                         st->sbucket     = 0;
1390                         goto get_req;
1391                 }
1392                 read_unlock_bh(&icsk->icsk_accept_queue.syn_wait_lock);
1393         }
1394         if (++st->bucket < INET_LHTABLE_SIZE) {
1395                 sk = sk_head(&tcp_hashinfo.listening_hash[st->bucket]);
1396                 goto get_sk;
1397         }
1398         cur = NULL;
1399 out:
1400         return cur;
1401 }
1402
1403 static void *listening_get_idx(struct seq_file *seq, loff_t *pos)
1404 {
1405         void *rc = listening_get_next(seq, NULL);
1406
1407         while (rc && *pos) {
1408                 rc = listening_get_next(seq, rc);
1409                 --*pos;
1410         }
1411         return rc;
1412 }
1413
1414 static void *established_get_first(struct seq_file *seq)
1415 {
1416         struct tcp_iter_state* st = seq->private;
1417         void *rc = NULL;
1418
1419         for (st->bucket = 0; st->bucket < tcp_hashinfo.ehash_size; ++st->bucket) {
1420                 struct sock *sk;
1421                 struct hlist_node *node;
1422                 struct inet_timewait_sock *tw;
1423
1424                 /* We can reschedule _before_ having picked the target: */
1425                 cond_resched_softirq();
1426
1427                 read_lock(&tcp_hashinfo.ehash[st->bucket].lock);
1428                 sk_for_each(sk, node, &tcp_hashinfo.ehash[st->bucket].chain) {
1429                         if (sk->sk_family != st->family) {
1430                                 continue;
1431                         }
1432                         rc = sk;
1433                         goto out;
1434                 }
1435                 st->state = TCP_SEQ_STATE_TIME_WAIT;
1436                 inet_twsk_for_each(tw, node,
1437                                    &tcp_hashinfo.ehash[st->bucket + tcp_hashinfo.ehash_size].chain) {
1438                         if (tw->tw_family != st->family) {
1439                                 continue;
1440                         }
1441                         rc = tw;
1442                         goto out;
1443                 }
1444                 read_unlock(&tcp_hashinfo.ehash[st->bucket].lock);
1445                 st->state = TCP_SEQ_STATE_ESTABLISHED;
1446         }
1447 out:
1448         return rc;
1449 }
1450
1451 static void *established_get_next(struct seq_file *seq, void *cur)
1452 {
1453         struct sock *sk = cur;
1454         struct inet_timewait_sock *tw;
1455         struct hlist_node *node;
1456         struct tcp_iter_state* st = seq->private;
1457
1458         ++st->num;
1459
1460         if (st->state == TCP_SEQ_STATE_TIME_WAIT) {
1461                 tw = cur;
1462                 tw = tw_next(tw);
1463 get_tw:
1464                 while (tw && tw->tw_family != st->family) {
1465                         tw = tw_next(tw);
1466                 }
1467                 if (tw) {
1468                         cur = tw;
1469                         goto out;
1470                 }
1471                 read_unlock(&tcp_hashinfo.ehash[st->bucket].lock);
1472                 st->state = TCP_SEQ_STATE_ESTABLISHED;
1473
1474                 /* We can reschedule between buckets: */
1475                 cond_resched_softirq();
1476
1477                 if (++st->bucket < tcp_hashinfo.ehash_size) {
1478                         read_lock(&tcp_hashinfo.ehash[st->bucket].lock);
1479                         sk = sk_head(&tcp_hashinfo.ehash[st->bucket].chain);
1480                 } else {
1481                         cur = NULL;
1482                         goto out;
1483                 }
1484         } else
1485                 sk = sk_next(sk);
1486
1487         sk_for_each_from(sk, node) {
1488                 if (sk->sk_family == st->family)
1489                         goto found;
1490         }
1491
1492         st->state = TCP_SEQ_STATE_TIME_WAIT;
1493         tw = tw_head(&tcp_hashinfo.ehash[st->bucket + tcp_hashinfo.ehash_size].chain);
1494         goto get_tw;
1495 found:
1496         cur = sk;
1497 out:
1498         return cur;
1499 }
1500
1501 static void *established_get_idx(struct seq_file *seq, loff_t pos)
1502 {
1503         void *rc = established_get_first(seq);
1504
1505         while (rc && pos) {
1506                 rc = established_get_next(seq, rc);
1507                 --pos;
1508         }
1509         return rc;
1510 }
1511
1512 static void *tcp_get_idx(struct seq_file *seq, loff_t pos)
1513 {
1514         void *rc;
1515         struct tcp_iter_state* st = seq->private;
1516
1517         inet_listen_lock(&tcp_hashinfo);
1518         st->state = TCP_SEQ_STATE_LISTENING;
1519         rc        = listening_get_idx(seq, &pos);
1520
1521         if (!rc) {
1522                 inet_listen_unlock(&tcp_hashinfo);
1523                 local_bh_disable();
1524                 st->state = TCP_SEQ_STATE_ESTABLISHED;
1525                 rc        = established_get_idx(seq, pos);
1526         }
1527
1528         return rc;
1529 }
1530
1531 static void *tcp_seq_start(struct seq_file *seq, loff_t *pos)
1532 {
1533         struct tcp_iter_state* st = seq->private;
1534         st->state = TCP_SEQ_STATE_LISTENING;
1535         st->num = 0;
1536         return *pos ? tcp_get_idx(seq, *pos - 1) : SEQ_START_TOKEN;
1537 }
1538
1539 static void *tcp_seq_next(struct seq_file *seq, void *v, loff_t *pos)
1540 {
1541         void *rc = NULL;
1542         struct tcp_iter_state* st;
1543
1544         if (v == SEQ_START_TOKEN) {
1545                 rc = tcp_get_idx(seq, 0);
1546                 goto out;
1547         }
1548         st = seq->private;
1549
1550         switch (st->state) {
1551         case TCP_SEQ_STATE_OPENREQ:
1552         case TCP_SEQ_STATE_LISTENING:
1553                 rc = listening_get_next(seq, v);
1554                 if (!rc) {
1555                         inet_listen_unlock(&tcp_hashinfo);
1556                         local_bh_disable();
1557                         st->state = TCP_SEQ_STATE_ESTABLISHED;
1558                         rc        = established_get_first(seq);
1559                 }
1560                 break;
1561         case TCP_SEQ_STATE_ESTABLISHED:
1562         case TCP_SEQ_STATE_TIME_WAIT:
1563                 rc = established_get_next(seq, v);
1564                 break;
1565         }
1566 out:
1567         ++*pos;
1568         return rc;
1569 }
1570
1571 static void tcp_seq_stop(struct seq_file *seq, void *v)
1572 {
1573         struct tcp_iter_state* st = seq->private;
1574
1575         switch (st->state) {
1576         case TCP_SEQ_STATE_OPENREQ:
1577                 if (v) {
1578                         struct inet_connection_sock *icsk = inet_csk(st->syn_wait_sk);
1579                         read_unlock_bh(&icsk->icsk_accept_queue.syn_wait_lock);
1580                 }
1581         case TCP_SEQ_STATE_LISTENING:
1582                 if (v != SEQ_START_TOKEN)
1583                         inet_listen_unlock(&tcp_hashinfo);
1584                 break;
1585         case TCP_SEQ_STATE_TIME_WAIT:
1586         case TCP_SEQ_STATE_ESTABLISHED:
1587                 if (v)
1588                         read_unlock(&tcp_hashinfo.ehash[st->bucket].lock);
1589                 local_bh_enable();
1590                 break;
1591         }
1592 }
1593
1594 static int tcp_seq_open(struct inode *inode, struct file *file)
1595 {
1596         struct tcp_seq_afinfo *afinfo = PDE(inode)->data;
1597         struct seq_file *seq;
1598         struct tcp_iter_state *s;
1599         int rc;
1600
1601         if (unlikely(afinfo == NULL))
1602                 return -EINVAL;
1603
1604         s = kmalloc(sizeof(*s), GFP_KERNEL);
1605         if (!s)
1606                 return -ENOMEM;
1607         memset(s, 0, sizeof(*s));
1608         s->family               = afinfo->family;
1609         s->seq_ops.start        = tcp_seq_start;
1610         s->seq_ops.next         = tcp_seq_next;
1611         s->seq_ops.show         = afinfo->seq_show;
1612         s->seq_ops.stop         = tcp_seq_stop;
1613
1614         rc = seq_open(file, &s->seq_ops);
1615         if (rc)
1616                 goto out_kfree;
1617         seq          = file->private_data;
1618         seq->private = s;
1619 out:
1620         return rc;
1621 out_kfree:
1622         kfree(s);
1623         goto out;
1624 }
1625
1626 int tcp_proc_register(struct tcp_seq_afinfo *afinfo)
1627 {
1628         int rc = 0;
1629         struct proc_dir_entry *p;
1630
1631         if (!afinfo)
1632                 return -EINVAL;
1633         afinfo->seq_fops->owner         = afinfo->owner;
1634         afinfo->seq_fops->open          = tcp_seq_open;
1635         afinfo->seq_fops->read          = seq_read;
1636         afinfo->seq_fops->llseek        = seq_lseek;
1637         afinfo->seq_fops->release       = seq_release_private;
1638
1639         p = proc_net_fops_create(afinfo->name, S_IRUGO, afinfo->seq_fops);
1640         if (p)
1641                 p->data = afinfo;
1642         else
1643                 rc = -ENOMEM;
1644         return rc;
1645 }
1646
1647 void tcp_proc_unregister(struct tcp_seq_afinfo *afinfo)
1648 {
1649         if (!afinfo)
1650                 return;
1651         proc_net_remove(afinfo->name);
1652         memset(afinfo->seq_fops, 0, sizeof(*afinfo->seq_fops));
1653 }
1654
1655 static void get_openreq4(struct sock *sk, struct request_sock *req,
1656                          char *tmpbuf, int i, int uid)
1657 {
1658         const struct inet_request_sock *ireq = inet_rsk(req);
1659         int ttd = req->expires - jiffies;
1660
1661         sprintf(tmpbuf, "%4d: %08X:%04X %08X:%04X"
1662                 " %02X %08X:%08X %02X:%08lX %08X %5d %8d %u %d %p",
1663                 i,
1664                 ireq->loc_addr,
1665                 ntohs(inet_sk(sk)->sport),
1666                 ireq->rmt_addr,
1667                 ntohs(ireq->rmt_port),
1668                 TCP_SYN_RECV,
1669                 0, 0, /* could print option size, but that is af dependent. */
1670                 1,    /* timers active (only the expire timer) */
1671                 jiffies_to_clock_t(ttd),
1672                 req->retrans,
1673                 uid,
1674                 0,  /* non standard timer */
1675                 0, /* open_requests have no inode */
1676                 atomic_read(&sk->sk_refcnt),
1677                 req);
1678 }
1679
1680 static void get_tcp4_sock(struct sock *sp, char *tmpbuf, int i)
1681 {
1682         int timer_active;
1683         unsigned long timer_expires;
1684         struct tcp_sock *tp = tcp_sk(sp);
1685         const struct inet_connection_sock *icsk = inet_csk(sp);
1686         struct inet_sock *inet = inet_sk(sp);
1687         unsigned int dest = inet->daddr;
1688         unsigned int src = inet->rcv_saddr;
1689         __u16 destp = ntohs(inet->dport);
1690         __u16 srcp = ntohs(inet->sport);
1691
1692         if (icsk->icsk_pending == ICSK_TIME_RETRANS) {
1693                 timer_active    = 1;
1694                 timer_expires   = icsk->icsk_timeout;
1695         } else if (icsk->icsk_pending == ICSK_TIME_PROBE0) {
1696                 timer_active    = 4;
1697                 timer_expires   = icsk->icsk_timeout;
1698         } else if (timer_pending(&sp->sk_timer)) {
1699                 timer_active    = 2;
1700                 timer_expires   = sp->sk_timer.expires;
1701         } else {
1702                 timer_active    = 0;
1703                 timer_expires = jiffies;
1704         }
1705
1706         sprintf(tmpbuf, "%4d: %08X:%04X %08X:%04X %02X %08X:%08X %02X:%08lX "
1707                         "%08X %5d %8d %lu %d %p %u %u %u %u %d",
1708                 i, src, srcp, dest, destp, sp->sk_state,
1709                 tp->write_seq - tp->snd_una, tp->rcv_nxt - tp->copied_seq,
1710                 timer_active,
1711                 jiffies_to_clock_t(timer_expires - jiffies),
1712                 icsk->icsk_retransmits,
1713                 sock_i_uid(sp),
1714                 icsk->icsk_probes_out,
1715                 sock_i_ino(sp),
1716                 atomic_read(&sp->sk_refcnt), sp,
1717                 icsk->icsk_rto,
1718                 icsk->icsk_ack.ato,
1719                 (icsk->icsk_ack.quick << 1) | icsk->icsk_ack.pingpong,
1720                 tp->snd_cwnd,
1721                 tp->snd_ssthresh >= 0xFFFF ? -1 : tp->snd_ssthresh);
1722 }
1723
1724 static void get_timewait4_sock(struct inet_timewait_sock *tw, char *tmpbuf, int i)
1725 {
1726         unsigned int dest, src;
1727         __u16 destp, srcp;
1728         int ttd = tw->tw_ttd - jiffies;
1729
1730         if (ttd < 0)
1731                 ttd = 0;
1732
1733         dest  = tw->tw_daddr;
1734         src   = tw->tw_rcv_saddr;
1735         destp = ntohs(tw->tw_dport);
1736         srcp  = ntohs(tw->tw_sport);
1737
1738         sprintf(tmpbuf, "%4d: %08X:%04X %08X:%04X"
1739                 " %02X %08X:%08X %02X:%08lX %08X %5d %8d %d %d %p",
1740                 i, src, srcp, dest, destp, tw->tw_substate, 0, 0,
1741                 3, jiffies_to_clock_t(ttd), 0, 0, 0, 0,
1742                 atomic_read(&tw->tw_refcnt), tw);
1743 }
1744
1745 #define TMPSZ 150
1746
1747 static int tcp4_seq_show(struct seq_file *seq, void *v)
1748 {
1749         struct tcp_iter_state* st;
1750         char tmpbuf[TMPSZ + 1];
1751
1752         if (v == SEQ_START_TOKEN) {
1753                 seq_printf(seq, "%-*s\n", TMPSZ - 1,
1754                            "  sl  local_address rem_address   st tx_queue "
1755                            "rx_queue tr tm->when retrnsmt   uid  timeout "
1756                            "inode");
1757                 goto out;
1758         }
1759         st = seq->private;
1760
1761         switch (st->state) {
1762         case TCP_SEQ_STATE_LISTENING:
1763         case TCP_SEQ_STATE_ESTABLISHED:
1764                 get_tcp4_sock(v, tmpbuf, st->num);
1765                 break;
1766         case TCP_SEQ_STATE_OPENREQ:
1767                 get_openreq4(st->syn_wait_sk, v, tmpbuf, st->num, st->uid);
1768                 break;
1769         case TCP_SEQ_STATE_TIME_WAIT:
1770                 get_timewait4_sock(v, tmpbuf, st->num);
1771                 break;
1772         }
1773         seq_printf(seq, "%-*s\n", TMPSZ - 1, tmpbuf);
1774 out:
1775         return 0;
1776 }
1777
1778 static struct file_operations tcp4_seq_fops;
1779 static struct tcp_seq_afinfo tcp4_seq_afinfo = {
1780         .owner          = THIS_MODULE,
1781         .name           = "tcp",
1782         .family         = AF_INET,
1783         .seq_show       = tcp4_seq_show,
1784         .seq_fops       = &tcp4_seq_fops,
1785 };
1786
1787 int __init tcp4_proc_init(void)
1788 {
1789         return tcp_proc_register(&tcp4_seq_afinfo);
1790 }
1791
1792 void tcp4_proc_exit(void)
1793 {
1794         tcp_proc_unregister(&tcp4_seq_afinfo);
1795 }
1796 #endif /* CONFIG_PROC_FS */
1797
1798 struct proto tcp_prot = {
1799         .name                   = "TCP",
1800         .owner                  = THIS_MODULE,
1801         .close                  = tcp_close,
1802         .connect                = tcp_v4_connect,
1803         .disconnect             = tcp_disconnect,
1804         .accept                 = inet_csk_accept,
1805         .ioctl                  = tcp_ioctl,
1806         .init                   = tcp_v4_init_sock,
1807         .destroy                = tcp_v4_destroy_sock,
1808         .shutdown               = tcp_shutdown,
1809         .setsockopt             = tcp_setsockopt,
1810         .getsockopt             = tcp_getsockopt,
1811         .sendmsg                = tcp_sendmsg,
1812         .recvmsg                = tcp_recvmsg,
1813         .backlog_rcv            = tcp_v4_do_rcv,
1814         .hash                   = tcp_v4_hash,
1815         .unhash                 = tcp_unhash,
1816         .get_port               = tcp_v4_get_port,
1817         .enter_memory_pressure  = tcp_enter_memory_pressure,
1818         .sockets_allocated      = &tcp_sockets_allocated,
1819         .orphan_count           = &tcp_orphan_count,
1820         .memory_allocated       = &tcp_memory_allocated,
1821         .memory_pressure        = &tcp_memory_pressure,
1822         .sysctl_mem             = sysctl_tcp_mem,
1823         .sysctl_wmem            = sysctl_tcp_wmem,
1824         .sysctl_rmem            = sysctl_tcp_rmem,
1825         .max_header             = MAX_TCP_HEADER,
1826         .obj_size               = sizeof(struct tcp_sock),
1827         .twsk_prot              = &tcp_timewait_sock_ops,
1828         .rsk_prot               = &tcp_request_sock_ops,
1829 };
1830
1831
1832
1833 void __init tcp_v4_init(struct net_proto_family *ops)
1834 {
1835         int err = sock_create_kern(PF_INET, SOCK_RAW, IPPROTO_TCP, &tcp_socket);
1836         if (err < 0)
1837                 panic("Failed to create the TCP control socket.\n");
1838         tcp_socket->sk->sk_allocation   = GFP_ATOMIC;
1839         inet_sk(tcp_socket->sk)->uc_ttl = -1;
1840
1841         /* Unhash it so that IP input processing does not even
1842          * see it, we do not wish this socket to see incoming
1843          * packets.
1844          */
1845         tcp_socket->sk->sk_prot->unhash(tcp_socket->sk);
1846 }
1847
1848 EXPORT_SYMBOL(ipv4_specific);
1849 EXPORT_SYMBOL(tcp_hashinfo);
1850 EXPORT_SYMBOL(tcp_prot);
1851 EXPORT_SYMBOL(tcp_unhash);
1852 EXPORT_SYMBOL(tcp_v4_conn_request);
1853 EXPORT_SYMBOL(tcp_v4_connect);
1854 EXPORT_SYMBOL(tcp_v4_do_rcv);
1855 EXPORT_SYMBOL(tcp_v4_remember_stamp);
1856 EXPORT_SYMBOL(tcp_v4_send_check);
1857 EXPORT_SYMBOL(tcp_v4_syn_recv_sock);
1858
1859 #ifdef CONFIG_PROC_FS
1860 EXPORT_SYMBOL(tcp_proc_register);
1861 EXPORT_SYMBOL(tcp_proc_unregister);
1862 #endif
1863 EXPORT_SYMBOL(sysctl_local_port_range);
1864 EXPORT_SYMBOL(sysctl_tcp_low_latency);
1865 EXPORT_SYMBOL(sysctl_tcp_tw_reuse);
1866