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 #include <net/netdma.h>
  75
  76 #include <linux/inet.h>
  77 #include <linux/ipv6.h>
  78 #include <linux/stddef.h>
  79 #include <linux/proc_fs.h>
  80 #include <linux/seq_file.h>
  81
  82 int sysctl_tcp_tw_reuse;
  83 int sysctl_tcp_low_latency;
  84
  85 /* Check TCP sequence numbers in ICMP packets. */
  86 #define ICMP_MIN_LENGTH 8
  87
  88 /* Socket used for sending RSTs */
  89 static struct socket *tcp_socket;
  90
  91 void tcp_v4_send_check(struct sock *sk, int len, struct sk_buff *skb);
  92
  93 struct inet_hashinfo __cacheline_aligned tcp_hashinfo = {
  94         .lhash_lock     = RW_LOCK_UNLOCKED,
  95         .lhash_users    = ATOMIC_INIT(0),
  96         .lhash_wait     = __WAIT_QUEUE_HEAD_INITIALIZER(tcp_hashinfo.lhash_wait),
  97 };
  98
  99 static int tcp_v4_get_port(struct sock *sk, unsigned short snum)
 100 {
 101         return inet_csk_get_port(&tcp_hashinfo, sk, snum,
 102                                  inet_csk_bind_conflict);
 103 }
 104
 105 static void tcp_v4_hash(struct sock *sk)
 106 {
 107         inet_hash(&tcp_hashinfo, sk);
 108 }
 109
 110 void tcp_unhash(struct sock *sk)
 111 {
 112         inet_unhash(&tcp_hashinfo, sk);
 113 }
 114
 115 static inline __u32 tcp_v4_init_sequence(struct sock *sk, struct sk_buff *skb)
 116 {
 117         return secure_tcp_sequence_number(skb->nh.iph->daddr,
 118                                           skb->nh.iph->saddr,
 119                                           skb->h.th->dest,
 120                                           skb->h.th->source);
 121 }
 122
 123 int tcp_twsk_unique(struct sock *sk, struct sock *sktw, void *twp)
 124 {
 125         const struct tcp_timewait_sock *tcptw = tcp_twsk(sktw);
 126         struct tcp_sock *tp = tcp_sk(sk);
 127
 128         /* With PAWS, it is safe from the viewpoint
 129            of data integrity. Even without PAWS it is safe provided sequence
 130            spaces do not overlap i.e. at data rates <= 80Mbit/sec.
 131
 132            Actually, the idea is close to VJ's one, only timestamp cache is
 133            held not per host, but per port pair and TW bucket is used as state
 134            holder.
 135
 136            If TW bucket has been already destroyed we fall back to VJ's scheme
 137            and use initial timestamp retrieved from peer table.
 138          */
 139         if (tcptw->tw_ts_recent_stamp &&
 140             (twp == NULL || (sysctl_tcp_tw_reuse &&
 141                              xtime.tv_sec - tcptw->tw_ts_recent_stamp > 1))) {
 142                 tp->write_seq = tcptw->tw_snd_nxt + 65535 + 2;
 143                 if (tp->write_seq == 0)
 144                         tp->write_seq = 1;
 145                 tp->rx_opt.ts_recent       = tcptw->tw_ts_recent;
 146                 tp->rx_opt.ts_recent_stamp = tcptw->tw_ts_recent_stamp;
 147                 sock_hold(sktw);
 148                 return 1;
 149         }
 150
 151         return 0;
 152 }
 153
 154 EXPORT_SYMBOL_GPL(tcp_twsk_unique);
 155
 156 /* This will initiate an outgoing connection. */
 157 int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
 158 {
 159         struct inet_sock *inet = inet_sk(sk);
 160         struct tcp_sock *tp = tcp_sk(sk);
 161         struct sockaddr_in *usin = (struct sockaddr_in *)uaddr;
 162         struct rtable *rt;
 163         u32 daddr, nexthop;
 164         int tmp;
 165         int err;
 166
 167         if (addr_len < sizeof(struct sockaddr_in))
 168                 return -EINVAL;
 169
 170         if (usin->sin_family != AF_INET)
 171                 return -EAFNOSUPPORT;
 172
 173         nexthop = daddr = usin->sin_addr.s_addr;
 174         if (inet->opt && inet->opt->srr) {
 175                 if (!daddr)
 176                         return -EINVAL;
 177                 nexthop = inet->opt->faddr;
 178         }
 179
 180         tmp = ip_route_connect(&rt, nexthop, inet->saddr,
 181                                RT_CONN_FLAGS(sk), sk->sk_bound_dev_if,
 182                                IPPROTO_TCP,
 183                                inet->sport, usin->sin_port, sk);
 184         if (tmp < 0)
 185                 return tmp;
 186
 187         if (rt->rt_flags & (RTCF_MULTICAST | RTCF_BROADCAST)) {
 188                 ip_rt_put(rt);
 189                 return -ENETUNREACH;
 190         }
 191
 192         if (!inet->opt || !inet->opt->srr)
 193                 daddr = rt->rt_dst;
 194
 195         if (!inet->saddr)
 196                 inet->saddr = rt->rt_src;
 197         inet->rcv_saddr = inet->saddr;
 198
 199         if (tp->rx_opt.ts_recent_stamp && inet->daddr != daddr) {
 200                 /* Reset inherited state */
 201                 tp->rx_opt.ts_recent       = 0;
 202                 tp->rx_opt.ts_recent_stamp = 0;
 203                 tp->write_seq              = 0;
 204         }
 205
 206         if (tcp_death_row.sysctl_tw_recycle &&
 207             !tp->rx_opt.ts_recent_stamp && rt->rt_dst == daddr) {
 208                 struct inet_peer *peer = rt_get_peer(rt);
 209
 210                 /* VJ's idea. We save last timestamp seen from
 211                  * the destination in peer table, when entering state TIME-WAIT
 212                  * and initialize rx_opt.ts_recent from it, when trying new connection.
 213                  */
 214
 215                 if (peer && peer->tcp_ts_stamp + TCP_PAWS_MSL >= xtime.tv_sec) {
 216                         tp->rx_opt.ts_recent_stamp = peer->tcp_ts_stamp;
 217                         tp->rx_opt.ts_recent = peer->tcp_ts;
 218                 }
 219         }
 220
 221         inet->dport = usin->sin_port;
 222         inet->daddr = daddr;
 223
 224         inet_csk(sk)->icsk_ext_hdr_len = 0;
 225         if (inet->opt)
 226                 inet_csk(sk)->icsk_ext_hdr_len = inet->opt->optlen;
 227
 228         tp->rx_opt.mss_clamp = 536;
 229
 230         /* Socket identity is still unknown (sport may be zero).
 231          * However we set state to SYN-SENT and not releasing socket
 232          * lock select source port, enter ourselves into the hash tables and
 233          * complete initialization after this.
 234          */
 235         tcp_set_state(sk, TCP_SYN_SENT);
 236         err = inet_hash_connect(&tcp_death_row, sk);
 237         if (err)
 238                 goto failure;
 239
 240         err = ip_route_newports(&rt, IPPROTO_TCP, inet->sport, inet->dport, sk);
 241         if (err)
 242                 goto failure;
 243
 244         /* OK, now commit destination to socket.  */
 245         sk_setup_caps(sk, &rt->u.dst);
 246
 247         if (!tp->write_seq)
 248                 tp->write_seq = secure_tcp_sequence_number(inet->saddr,
 249                                                            inet->daddr,
 250                                                            inet->sport,
 251                                                            usin->sin_port);
 252
 253         inet->id = tp->write_seq ^ jiffies;
 254
 255         err = tcp_connect(sk);
 256         rt = NULL;
 257         if (err)
 258                 goto failure;
 259
 260         return 0;
 261
 262 failure:
 263         /* This unhashes the socket and releases the local port, if necessary. */
 264         tcp_set_state(sk, TCP_CLOSE);
 265         ip_rt_put(rt);
 266         sk->sk_route_caps = 0;
 267         inet->dport = 0;
 268         return err;
 269 }
 270
 271 /*
 272  * This routine does path mtu discovery as defined in RFC1191.
 273  */
 274 static void do_pmtu_discovery(struct sock *sk, struct iphdr *iph, u32 mtu)
 275 {
 276         struct dst_entry *dst;
 277         struct inet_sock *inet = inet_sk(sk);
 278
 279         /* We are not interested in TCP_LISTEN and open_requests (SYN-ACKs
 280          * send out by Linux are always <576bytes so they should go through
 281          * unfragmented).
 282          */
 283         if (sk->sk_state == TCP_LISTEN)
 284                 return;
 285
 286         /* We don't check in the destentry if pmtu discovery is forbidden
 287          * on this route. We just assume that no packet_to_big packets
 288          * are send back when pmtu discovery is not active.
 289          * There is a small race when the user changes this flag in the
 290          * route, but I think that's acceptable.
 291          */
 292         if ((dst = __sk_dst_check(sk, 0)) == NULL)
 293                 return;
 294
 295         dst->ops->update_pmtu(dst, mtu);
 296
 297         /* Something is about to be wrong... Remember soft error
 298          * for the case, if this connection will not able to recover.
 299          */
 300         if (mtu < dst_mtu(dst) && ip_dont_fragment(sk, dst))
 301                 sk->sk_err_soft = EMSGSIZE;
 302
 303         mtu = dst_mtu(dst);
 304
 305         if (inet->pmtudisc != IP_PMTUDISC_DONT &&
 306             inet_csk(sk)->icsk_pmtu_cookie > mtu) {
 307                 tcp_sync_mss(sk, mtu);
 308
 309                 /* Resend the TCP packet because it's
 310                  * clear that the old packet has been
 311                  * dropped. This is the new "fast" path mtu
 312                  * discovery.
 313                  */
 314                 tcp_simple_retransmit(sk);
 315         } /* else let the usual retransmit timer handle it */
 316 }
 317
 318 /*
 319  * This routine is called by the ICMP module when it gets some
 320  * sort of error condition.  If err < 0 then the socket should
 321  * be closed and the error returned to the user.  If err > 0
 322  * it's just the icmp type << 8 | icmp code.  After adjustment
 323  * header points to the first 8 bytes of the tcp header.  We need
 324  * to find the appropriate port.
 325  *
 326  * The locking strategy used here is very "optimistic". When
 327  * someone else accesses the socket the ICMP is just dropped
 328  * and for some paths there is no check at all.
 329  * A more general error queue to queue errors for later handling
 330  * is probably better.
 331  *
 332  */
 333
 334 void tcp_v4_err(struct sk_buff *skb, u32 info)
 335 {
 336         struct iphdr *iph = (struct iphdr *)skb->data;
 337         struct tcphdr *th = (struct tcphdr *)(skb->data + (iph->ihl << 2));
 338         struct tcp_sock *tp;
 339         struct inet_sock *inet;
 340         int type = skb->h.icmph->type;
 341         int code = skb->h.icmph->code;
 342         struct sock *sk;
 343         __u32 seq;
 344         int err;
 345
 346         if (skb->len < (iph->ihl << 2) + 8) {
 347                 ICMP_INC_STATS_BH(ICMP_MIB_INERRORS);
 348                 return;
 349         }
 350
 351         sk = inet_lookup(&tcp_hashinfo, iph->daddr, th->dest, iph->saddr,
 352                          th->source, inet_iif(skb));
 353         if (!sk) {
 354                 ICMP_INC_STATS_BH(ICMP_MIB_INERRORS);
 355                 return;
 356         }
 357         if (sk->sk_state == TCP_TIME_WAIT) {
 358                 inet_twsk_put((struct inet_timewait_sock *)sk);
 359                 return;
 360         }
 361
 362         bh_lock_sock(sk);
 363         /* If too many ICMPs get dropped on busy
 364          * servers this needs to be solved differently.
 365          */
 366         if (sock_owned_by_user(sk))
 367                 NET_INC_STATS_BH(LINUX_MIB_LOCKDROPPEDICMPS);
 368
 369         if (sk->sk_state == TCP_CLOSE)
 370                 goto out;
 371
 372         tp = tcp_sk(sk);
 373         seq = ntohl(th->seq);
 374         if (sk->sk_state != TCP_LISTEN &&
 375             !between(seq, tp->snd_una, tp->snd_nxt)) {
 376                 NET_INC_STATS(LINUX_MIB_OUTOFWINDOWICMPS);
 377                 goto out;
 378         }
 379
 380         switch (type) {
 381         case ICMP_SOURCE_QUENCH:
 382                 /* Just silently ignore these. */
 383                 goto out;
 384         case ICMP_PARAMETERPROB:
 385                 err = EPROTO;
 386                 break;
 387         case ICMP_DEST_UNREACH:
 388                 if (code > NR_ICMP_UNREACH)
 389                         goto out;
 390
 391                 if (code == ICMP_FRAG_NEEDED) { /* PMTU discovery (RFC1191) */
 392                         if (!sock_owned_by_user(sk))
 393                                 do_pmtu_discovery(sk, iph, info);
 394                         goto out;
 395                 }
 396
 397                 err = icmp_err_convert[code].errno;
 398                 break;
 399         case ICMP_TIME_EXCEEDED:
 400                 err = EHOSTUNREACH;
 401                 break;
 402         default:
 403                 goto out;
 404         }
 405
 406         switch (sk->sk_state) {
 407                 struct request_sock *req, **prev;
 408         case TCP_LISTEN:
 409                 if (sock_owned_by_user(sk))
 410                         goto out;
 411
 412                 req = inet_csk_search_req(sk, &prev, th->dest,
 413                                           iph->daddr, iph->saddr);
 414                 if (!req)
 415                         goto out;
 416
 417                 /* ICMPs are not backlogged, hence we cannot get
 418                    an established socket here.
 419                  */
 420                 BUG_TRAP(!req->sk);
 421
 422                 if (seq != tcp_rsk(req)->snt_isn) {
 423                         NET_INC_STATS_BH(LINUX_MIB_OUTOFWINDOWICMPS);
 424                         goto out;
 425                 }
 426
 427                 /*
 428                  * Still in SYN_RECV, just remove it silently.
 429                  * There is no good way to pass the error to the newly
 430                  * created socket, and POSIX does not want network
 431                  * errors returned from accept().
 432                  */
 433                 inet_csk_reqsk_queue_drop(sk, req, prev);
 434                 goto out;
 435
 436         case TCP_SYN_SENT:
 437         case TCP_SYN_RECV:  /* Cannot happen.
 438                                It can f.e. if SYNs crossed.
 439                              */
 440                 if (!sock_owned_by_user(sk)) {
 441                         TCP_INC_STATS_BH(TCP_MIB_ATTEMPTFAILS);
 442                         sk->sk_err = err;
 443
 444                         sk->sk_error_report(sk);
 445
 446                         tcp_done(sk);
 447                 } else {
 448                         sk->sk_err_soft = err;
 449                 }
 450                 goto out;
 451         }
 452
 453         /* If we've already connected we will keep trying
 454          * until we time out, or the user gives up.
 455          *
 456          * rfc1122 4.2.3.9 allows to consider as hard errors
 457          * only PROTO_UNREACH and PORT_UNREACH (well, FRAG_FAILED too,
 458          * but it is obsoleted by pmtu discovery).
 459          *
 460          * Note, that in modern internet, where routing is unreliable
 461          * and in each dark corner broken firewalls sit, sending random
 462          * errors ordered by their masters even this two messages finally lose
 463          * their original sense (even Linux sends invalid PORT_UNREACHs)
 464          *
 465          * Now we are in compliance with RFCs.
 466          *                                                      --ANK (980905)
 467          */
 468
 469         inet = inet_sk(sk);
 470         if (!sock_owned_by_user(sk) && inet->recverr) {
 471                 sk->sk_err = err;
 472                 sk->sk_error_report(sk);
 473         } else  { /* Only an error on timeout */
 474                 sk->sk_err_soft = err;
 475         }
 476
 477 out:
 478         bh_unlock_sock(sk);
 479         sock_put(sk);
 480 }
 481
 482 /* This routine computes an IPv4 TCP checksum. */
 483 void tcp_v4_send_check(struct sock *sk, int len, struct sk_buff *skb)
 484 {
 485         struct inet_sock *inet = inet_sk(sk);
 486         struct tcphdr *th = skb->h.th;
 487
 488         if (skb->ip_summed == CHECKSUM_HW) {
 489                 th->check = ~tcp_v4_check(th, len, inet->saddr, inet->daddr, 0);
 490                 skb->csum = offsetof(struct tcphdr, check);
 491         } else {
 492                 th->check = tcp_v4_check(th, len, inet->saddr, inet->daddr,
 493                                          csum_partial((char *)th,
 494                                                       th->doff << 2,
 495                                                       skb->csum));
 496         }
 497 }
 498
 499 /*
 500  *      This routine will send an RST to the other tcp.
 501  *
 502  *      Someone asks: why I NEVER use socket parameters (TOS, TTL etc.)
 503  *                    for reset.
 504  *      Answer: if a packet caused RST, it is not for a socket
 505  *              existing in our system, if it is matched to a socket,
 506  *              it is just duplicate segment or bug in other side's TCP.
 507  *              So that we build reply only basing on parameters
 508  *              arrived with segment.
 509  *      Exception: precedence violation. We do not implement it in any case.
 510  */
 511
 512 static void tcp_v4_send_reset(struct sk_buff *skb)
 513 {
 514         struct tcphdr *th = skb->h.th;
 515         struct tcphdr rth;
 516         struct ip_reply_arg arg;
 517
 518         /* Never send a reset in response to a reset. */
 519         if (th->rst)
 520                 return;
 521
 522         if (((struct rtable *)skb->dst)->rt_type != RTN_LOCAL)
 523                 return;
 524
 525         /* Swap the send and the receive. */
 526         memset(&rth, 0, sizeof(struct tcphdr));
 527         rth.dest   = th->source;
 528         rth.source = th->dest;
 529         rth.doff   = sizeof(struct tcphdr) / 4;
 530         rth.rst    = 1;
 531
 532         if (th->ack) {
 533                 rth.seq = th->ack_seq;
 534         } else {
 535                 rth.ack = 1;
 536                 rth.ack_seq = htonl(ntohl(th->seq) + th->syn + th->fin +
 537                                     skb->len - (th->doff << 2));
 538         }
 539
 540         memset(&arg, 0, sizeof arg);
 541         arg.iov[0].iov_base = (unsigned char *)&rth;
 542         arg.iov[0].iov_len  = sizeof rth;
 543         arg.csum = csum_tcpudp_nofold(skb->nh.iph->daddr,
 544                                       skb->nh.iph->saddr, /*XXX*/
 545                                       sizeof(struct tcphdr), IPPROTO_TCP, 0);
 546         arg.csumoffset = offsetof(struct tcphdr, check) / 2;
 547
 548         ip_send_reply(tcp_socket->sk, skb, &arg, sizeof rth);
 549
 550         TCP_INC_STATS_BH(TCP_MIB_OUTSEGS);
 551         TCP_INC_STATS_BH(TCP_MIB_OUTRSTS);
 552 }
 553
 554 /* The code following below sending ACKs in SYN-RECV and TIME-WAIT states
 555    outside socket context is ugly, certainly. What can I do?
 556  */
 557
 558 static void tcp_v4_send_ack(struct sk_buff *skb, u32 seq, u32 ack,
 559                             u32 win, u32 ts)
 560 {
 561         struct tcphdr *th = skb->h.th;
 562         struct {
 563                 struct tcphdr th;
 564                 u32 tsopt[3];
 565         } rep;
 566         struct ip_reply_arg arg;
 567
 568         memset(&rep.th, 0, sizeof(struct tcphdr));
 569         memset(&arg, 0, sizeof arg);
 570
 571         arg.iov[0].iov_base = (unsigned char *)&rep;
 572         arg.iov[0].iov_len  = sizeof(rep.th);
 573         if (ts) {
 574                 rep.tsopt[0] = htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) |
 575                                      (TCPOPT_TIMESTAMP << 8) |
 576                                      TCPOLEN_TIMESTAMP);
 577                 rep.tsopt[1] = htonl(tcp_time_stamp);
 578                 rep.tsopt[2] = htonl(ts);
 579                 arg.iov[0].iov_len = sizeof(rep);
 580         }
 581
 582         /* Swap the send and the receive. */
 583         rep.th.dest    = th->source;
 584         rep.th.source  = th->dest;
 585         rep.th.doff    = arg.iov[0].iov_len / 4;
 586         rep.th.seq     = htonl(seq);
 587         rep.th.ack_seq = htonl(ack);
 588         rep.th.ack     = 1;
 589         rep.th.window  = htons(win);
 590
 591         arg.csum = csum_tcpudp_nofold(skb->nh.iph->daddr,
 592                                       skb->nh.iph->saddr, /*XXX*/
 593                                       arg.iov[0].iov_len, IPPROTO_TCP, 0);
 594         arg.csumoffset = offsetof(struct tcphdr, check) / 2;
 595
 596         ip_send_reply(tcp_socket->sk, skb, &arg, arg.iov[0].iov_len);
 597
 598         TCP_INC_STATS_BH(TCP_MIB_OUTSEGS);
 599 }
 600
 601 static void tcp_v4_timewait_ack(struct sock *sk, struct sk_buff *skb)
 602 {
 603         struct inet_timewait_sock *tw = inet_twsk(sk);
 604         const struct tcp_timewait_sock *tcptw = tcp_twsk(sk);
 605
 606         tcp_v4_send_ack(skb, tcptw->tw_snd_nxt, tcptw->tw_rcv_nxt,
 607                         tcptw->tw_rcv_wnd >> tw->tw_rcv_wscale, tcptw->tw_ts_recent);
 608
 609         inet_twsk_put(tw);
 610 }
 611
 612 static void tcp_v4_reqsk_send_ack(struct sk_buff *skb, struct request_sock *req)
 613 {
 614         tcp_v4_send_ack(skb, tcp_rsk(req)->snt_isn + 1, tcp_rsk(req)->rcv_isn + 1, req->rcv_wnd,
 615                         req->ts_recent);
 616 }
 617
 618 /*
 619  *      Send a SYN-ACK after having received an ACK.
 620  *      This still operates on a request_sock only, not on a big
 621  *      socket.
 622  */
 623 static int tcp_v4_send_synack(struct sock *sk, struct request_sock *req,
 624                               struct dst_entry *dst)
 625 {
 626         const struct inet_request_sock *ireq = inet_rsk(req);
 627         int err = -1;
 628         struct sk_buff * skb;
 629
 630         /* First, grab a route. */
 631         if (!dst && (dst = inet_csk_route_req(sk, req)) == NULL)
 632                 goto out;
 633
 634         skb = tcp_make_synack(sk, dst, req);
 635
 636         if (skb) {
 637                 struct tcphdr *th = skb->h.th;
 638
 639                 th->check = tcp_v4_check(th, skb->len,
 640                                          ireq->loc_addr,
 641                                          ireq->rmt_addr,
 642                                          csum_partial((char *)th, skb->len,
 643                                                       skb->csum));
 644
 645                 err = ip_build_and_send_pkt(skb, sk, ireq->loc_addr,
 646                                             ireq->rmt_addr,
 647                                             ireq->opt);
 648                 if (err == NET_XMIT_CN)
 649                         err = 0;
 650         }
 651
 652 out:
 653         dst_release(dst);
 654         return err;
 655 }
 656
 657 /*
 658  *      IPv4 request_sock destructor.
 659  */
 660 static void tcp_v4_reqsk_destructor(struct request_sock *req)
 661 {
 662         kfree(inet_rsk(req)->opt);
 663 }
 664
 665 #ifdef CONFIG_SYN_COOKIES
 666 static void syn_flood_warning(struct sk_buff *skb)
 667 {
 668         static unsigned long warntime;
 669
 670         if (time_after(jiffies, (warntime + HZ * 60))) {
 671                 warntime = jiffies;
 672                 printk(KERN_INFO
 673                        "possible SYN flooding on port %d. Sending cookies.\n",
 674                        ntohs(skb->h.th->dest));
 675         }
 676 }
 677 #endif
 678
 679 /*
 680  * Save and compile IPv4 options into the request_sock if needed.
 681  */
 682 static struct ip_options *tcp_v4_save_options(struct sock *sk,
 683                                               struct sk_buff *skb)
 684 {
 685         struct ip_options *opt = &(IPCB(skb)->opt);
 686         struct ip_options *dopt = NULL;
 687
 688         if (opt && opt->optlen) {
 689                 int opt_size = optlength(opt);
 690                 dopt = kmalloc(opt_size, GFP_ATOMIC);
 691                 if (dopt) {
 692                         if (ip_options_echo(dopt, skb)) {
 693                                 kfree(dopt);
 694                                 dopt = NULL;
 695                         }
 696                 }
 697         }
 698         return dopt;
 699 }
 700
 701 struct request_sock_ops tcp_request_sock_ops = {
 702         .family         =       PF_INET,
 703         .obj_size       =       sizeof(struct tcp_request_sock),
 704         .rtx_syn_ack    =       tcp_v4_send_synack,
 705         .send_ack       =       tcp_v4_reqsk_send_ack,
 706         .destructor     =       tcp_v4_reqsk_destructor,
 707         .send_reset     =       tcp_v4_send_reset,
 708 };
 709
 710 static struct timewait_sock_ops tcp_timewait_sock_ops = {
 711         .twsk_obj_size  = sizeof(struct tcp_timewait_sock),
 712         .twsk_unique    = tcp_twsk_unique,
 713 };
 714
 715 int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
 716 {
 717         struct inet_request_sock *ireq;
 718         struct tcp_options_received tmp_opt;
 719         struct request_sock *req;
 720         __u32 saddr = skb->nh.iph->saddr;
 721         __u32 daddr = skb->nh.iph->daddr;
 722         __u32 isn = TCP_SKB_CB(skb)->when;
 723         struct dst_entry *dst = NULL;
 724 #ifdef CONFIG_SYN_COOKIES
 725         int want_cookie = 0;
 726 #else
 727 #define want_cookie 0 /* Argh, why doesn't gcc optimize this :( */
 728 #endif
 729
 730         /* Never answer to SYNs send to broadcast or multicast */
 731         if (((struct rtable *)skb->dst)->rt_flags &
 732             (RTCF_BROADCAST | RTCF_MULTICAST))
 733                 goto drop;
 734
 735         /* TW buckets are converted to open requests without
 736          * limitations, they conserve resources and peer is
 737          * evidently real one.
 738          */
 739         if (inet_csk_reqsk_queue_is_full(sk) && !isn) {
 740 #ifdef CONFIG_SYN_COOKIES
 741                 if (sysctl_tcp_syncookies) {
 742                         want_cookie = 1;
 743                 } else
 744 #endif
 745                 goto drop;
 746         }
 747
 748         /* Accept backlog is full. If we have already queued enough
 749          * of warm entries in syn queue, drop request. It is better than
 750          * clogging syn queue with openreqs with exponentially increasing
 751          * timeout.
 752          */
 753         if (sk_acceptq_is_full(sk) && inet_csk_reqsk_queue_young(sk) > 1)
 754                 goto drop;
 755
 756         req = reqsk_alloc(&tcp_request_sock_ops);
 757         if (!req)
 758                 goto drop;
 759
 760         tcp_clear_options(&tmp_opt);
 761         tmp_opt.mss_clamp = 536;
 762         tmp_opt.user_mss  = tcp_sk(sk)->rx_opt.user_mss;
 763
 764         tcp_parse_options(skb, &tmp_opt, 0);
 765
 766         if (want_cookie) {
 767                 tcp_clear_options(&tmp_opt);
 768                 tmp_opt.saw_tstamp = 0;
 769         }
 770
 771         if (tmp_opt.saw_tstamp && !tmp_opt.rcv_tsval) {
 772                 /* Some OSes (unknown ones, but I see them on web server, which
 773                  * contains information interesting only for windows'
 774                  * users) do not send their stamp in SYN. It is easy case.
 775                  * We simply do not advertise TS support.
 776                  */
 777                 tmp_opt.saw_tstamp = 0;
 778                 tmp_opt.tstamp_ok  = 0;
 779         }
 780         tmp_opt.tstamp_ok = tmp_opt.saw_tstamp;
 781
 782         tcp_openreq_init(req, &tmp_opt, skb);
 783
 784         ireq = inet_rsk(req);
 785         ireq->loc_addr = daddr;
 786         ireq->rmt_addr = saddr;
 787         ireq->opt = tcp_v4_save_options(sk, skb);
 788         if (!want_cookie)
 789                 TCP_ECN_create_request(req, skb->h.th);
 790
 791         if (want_cookie) {
 792 #ifdef CONFIG_SYN_COOKIES
 793                 syn_flood_warning(skb);
 794 #endif
 795                 isn = cookie_v4_init_sequence(sk, skb, &req->mss);
 796         } else if (!isn) {
 797                 struct inet_peer *peer = NULL;
 798
 799                 /* VJ's idea. We save last timestamp seen
 800                  * from the destination in peer table, when entering
 801                  * state TIME-WAIT, and check against it before
 802                  * accepting new connection request.
 803                  *
 804                  * If "isn" is not zero, this request hit alive
 805                  * timewait bucket, so that all the necessary checks
 806                  * are made in the function processing timewait state.
 807                  */
 808                 if (tmp_opt.saw_tstamp &&
 809                     tcp_death_row.sysctl_tw_recycle &&
 810                     (dst = inet_csk_route_req(sk, req)) != NULL &&
 811                     (peer = rt_get_peer((struct rtable *)dst)) != NULL &&
 812                     peer->v4daddr == saddr) {
 813                         if (xtime.tv_sec < peer->tcp_ts_stamp + TCP_PAWS_MSL &&
 814                             (s32)(peer->tcp_ts - req->ts_recent) >
 815                                                         TCP_PAWS_WINDOW) {
 816                                 NET_INC_STATS_BH(LINUX_MIB_PAWSPASSIVEREJECTED);
 817                                 dst_release(dst);
 818                                 goto drop_and_free;
 819                         }
 820                 }
 821                 /* Kill the following clause, if you dislike this way. */
 822                 else if (!sysctl_tcp_syncookies &&
 823                          (sysctl_max_syn_backlog - inet_csk_reqsk_queue_len(sk) <
 824                           (sysctl_max_syn_backlog >> 2)) &&
 825                          (!peer || !peer->tcp_ts_stamp) &&
 826                          (!dst || !dst_metric(dst, RTAX_RTT))) {
 827                         /* Without syncookies last quarter of
 828                          * backlog is filled with destinations,
 829                          * proven to be alive.
 830                          * It means that we continue to communicate
 831                          * to destinations, already remembered
 832                          * to the moment of synflood.
 833                          */
 834                         LIMIT_NETDEBUG(KERN_DEBUG "TCP: drop open "
 835                                        "request from %u.%u.%u.%u/%u\n",
 836                                        NIPQUAD(saddr),
 837                                        ntohs(skb->h.th->source));
 838                         dst_release(dst);
 839                         goto drop_and_free;
 840                 }
 841
 842                 isn = tcp_v4_init_sequence(sk, skb);
 843         }
 844         tcp_rsk(req)->snt_isn = isn;
 845
 846         if (tcp_v4_send_synack(sk, req, dst))
 847                 goto drop_and_free;
 848
 849         if (want_cookie) {
 850                 reqsk_free(req);
 851         } else {
 852                 inet_csk_reqsk_queue_hash_add(sk, req, TCP_TIMEOUT_INIT);
 853         }
 854         return 0;
 855
 856 drop_and_free:
 857         reqsk_free(req);
 858 drop:
 859         TCP_INC_STATS_BH(TCP_MIB_ATTEMPTFAILS);
 860         return 0;
 861 }
 862
 863
 864 /*
 865  * The three way handshake has completed - we got a valid synack -
 866  * now create the new socket.
 867  */
 868 struct sock *tcp_v4_syn_recv_sock(struct sock *sk, struct sk_buff *skb,
 869                                   struct request_sock *req,
 870                                   struct dst_entry *dst)
 871 {
 872         struct inet_request_sock *ireq;
 873         struct inet_sock *newinet;
 874         struct tcp_sock *newtp;
 875         struct sock *newsk;
 876
 877         if (sk_acceptq_is_full(sk))
 878                 goto exit_overflow;
 879
 880         if (!dst && (dst = inet_csk_route_req(sk, req)) == NULL)
 881                 goto exit;
 882
 883         newsk = tcp_create_openreq_child(sk, req, skb);
 884         if (!newsk)
 885                 goto exit;
 886
 887         sk_setup_caps(newsk, dst);
 888
 889         newtp                 = tcp_sk(newsk);
 890         newinet               = inet_sk(newsk);
 891         ireq                  = inet_rsk(req);
 892         newinet->daddr        = ireq->rmt_addr;
 893         newinet->rcv_saddr    = ireq->loc_addr;
 894         newinet->saddr        = ireq->loc_addr;
 895         newinet->opt          = ireq->opt;
 896         ireq->opt             = NULL;
 897         newinet->mc_index     = inet_iif(skb);
 898         newinet->mc_ttl       = skb->nh.iph->ttl;
 899         inet_csk(newsk)->icsk_ext_hdr_len = 0;
 900         if (newinet->opt)
 901                 inet_csk(newsk)->icsk_ext_hdr_len = newinet->opt->optlen;
 902         newinet->id = newtp->write_seq ^ jiffies;
 903
 904         tcp_mtup_init(newsk);
 905         tcp_sync_mss(newsk, dst_mtu(dst));
 906         newtp->advmss = dst_metric(dst, RTAX_ADVMSS);
 907         tcp_initialize_rcv_mss(newsk);
 908
 909         __inet_hash(&tcp_hashinfo, newsk, 0);
 910         __inet_inherit_port(&tcp_hashinfo, sk, newsk);
 911
 912         return newsk;
 913
 914 exit_overflow:
 915         NET_INC_STATS_BH(LINUX_MIB_LISTENOVERFLOWS);
 916 exit:
 917         NET_INC_STATS_BH(LINUX_MIB_LISTENDROPS);
 918         dst_release(dst);
 919         return NULL;
 920 }
 921
 922 static struct sock *tcp_v4_hnd_req(struct sock *sk, struct sk_buff *skb)
 923 {
 924         struct tcphdr *th = skb->h.th;
 925         struct iphdr *iph = skb->nh.iph;
 926         struct sock *nsk;
 927         struct request_sock **prev;
 928         /* Find possible connection requests. */
 929         struct request_sock *req = inet_csk_search_req(sk, &prev, th->source,
 930                                                        iph->saddr, iph->daddr);
 931         if (req)
 932                 return tcp_check_req(sk, skb, req, prev);
 933
 934         nsk = __inet_lookup_established(&tcp_hashinfo, skb->nh.iph->saddr,
 935                                         th->source, skb->nh.iph->daddr,
 936                                         ntohs(th->dest), inet_iif(skb));
 937
 938         if (nsk) {
 939                 if (nsk->sk_state != TCP_TIME_WAIT) {
 940                         bh_lock_sock(nsk);
 941                         return nsk;
 942                 }
 943                 inet_twsk_put((struct inet_timewait_sock *)nsk);
 944                 return NULL;
 945         }
 946
 947 #ifdef CONFIG_SYN_COOKIES
 948         if (!th->rst && !th->syn && th->ack)
 949                 sk = cookie_v4_check(sk, skb, &(IPCB(skb)->opt));
 950 #endif
 951         return sk;
 952 }
 953
 954 static int tcp_v4_checksum_init(struct sk_buff *skb)
 955 {
 956         if (skb->ip_summed == CHECKSUM_HW) {
 957                 if (!tcp_v4_check(skb->h.th, skb->len, skb->nh.iph->saddr,
 958                                   skb->nh.iph->daddr, skb->csum)) {
 959                         skb->ip_summed = CHECKSUM_UNNECESSARY;
 960                         return 0;
 961                 }
 962         }
 963
 964         skb->csum = csum_tcpudp_nofold(skb->nh.iph->saddr, skb->nh.iph->daddr,
 965                                        skb->len, IPPROTO_TCP, 0);
 966
 967         if (skb->len <= 76) {
 968                 return __skb_checksum_complete(skb);
 969         }
 970         return 0;
 971 }
 972
 973
 974 /* The socket must have it's spinlock held when we get
 975  * here.
 976  *
 977  * We have a potential double-lock case here, so even when
 978  * doing backlog processing we use the BH locking scheme.
 979  * This is because we cannot sleep with the original spinlock
 980  * held.
 981  */
 982 int tcp_v4_do_rcv(struct sock *sk, struct sk_buff *skb)
 983 {
 984         if (sk->sk_state == TCP_ESTABLISHED) { /* Fast path */
 985                 TCP_CHECK_TIMER(sk);
 986                 if (tcp_rcv_established(sk, skb, skb->h.th, skb->len))
 987                         goto reset;
 988                 TCP_CHECK_TIMER(sk);
 989                 return 0;
 990         }
 991
 992         if (skb->len < (skb->h.th->doff << 2) || tcp_checksum_complete(skb))
 993                 goto csum_err;
 994
 995         if (sk->sk_state == TCP_LISTEN) {
 996                 struct sock *nsk = tcp_v4_hnd_req(sk, skb);
 997                 if (!nsk)
 998                         goto discard;
 999
1000                 if (nsk != sk) {
1001                         if (tcp_child_process(sk, nsk, skb))
1002                                 goto reset;
1003                         return 0;
1004                 }
1005         }
1006
1007         TCP_CHECK_TIMER(sk);
1008         if (tcp_rcv_state_process(sk, skb, skb->h.th, skb->len))
1009                 goto reset;
1010         TCP_CHECK_TIMER(sk);
1011         return 0;
1012
1013 reset:
1014         tcp_v4_send_reset(skb);
1015 discard:
1016         kfree_skb(skb);
1017         /* Be careful here. If this function gets more complicated and
1018          * gcc suffers from register pressure on the x86, sk (in %ebx)
1019          * might be destroyed here. This current version compiles correctly,
1020          * but you have been warned.
1021          */
1022         return 0;
1023
1024 csum_err:
1025         TCP_INC_STATS_BH(TCP_MIB_INERRS);
1026         goto discard;
1027 }
1028
1029 /*
1030  *      From tcp_input.c
1031  */
1032
1033 int tcp_v4_rcv(struct sk_buff *skb)
1034 {
1035         struct tcphdr *th;
1036         struct sock *sk;
1037         int ret;
1038
1039         if (skb->pkt_type != PACKET_HOST)
1040                 goto discard_it;
1041
1042         /* Count it even if it's bad */
1043         TCP_INC_STATS_BH(TCP_MIB_INSEGS);
1044
1045         if (!pskb_may_pull(skb, sizeof(struct tcphdr)))
1046                 goto discard_it;
1047
1048         th = skb->h.th;
1049
1050         if (th->doff < sizeof(struct tcphdr) / 4)
1051                 goto bad_packet;
1052         if (!pskb_may_pull(skb, th->doff * 4))
1053                 goto discard_it;
1054
1055         /* An explanation is required here, I think.
1056          * Packet length and doff are validated by header prediction,
1057          * provided case of th->doff==0 is eliminated.
1058          * So, we defer the checks. */
1059         if ((skb->ip_summed != CHECKSUM_UNNECESSARY &&
1060              tcp_v4_checksum_init(skb)))
1061                 goto bad_packet;
1062
1063         th = skb->h.th;
1064         TCP_SKB_CB(skb)->seq = ntohl(th->seq);
1065         TCP_SKB_CB(skb)->end_seq = (TCP_SKB_CB(skb)->seq + th->syn + th->fin +
1066                                     skb->len - th->doff * 4);
1067         TCP_SKB_CB(skb)->ack_seq = ntohl(th->ack_seq);
1068         TCP_SKB_CB(skb)->when    = 0;
1069         TCP_SKB_CB(skb)->flags   = skb->nh.iph->tos;
1070         TCP_SKB_CB(skb)->sacked  = 0;
1071
1072         sk = __inet_lookup(&tcp_hashinfo, skb->nh.iph->saddr, th->source,
1073                            skb->nh.iph->daddr, ntohs(th->dest),
1074                            inet_iif(skb));
1075
1076         if (!sk)
1077                 goto no_tcp_socket;
1078
1079 process:
1080         if (sk->sk_state == TCP_TIME_WAIT)
1081                 goto do_time_wait;
1082
1083         if (!xfrm4_policy_check(sk, XFRM_POLICY_IN, skb))
1084                 goto discard_and_relse;
1085         nf_reset(skb);
1086
1087         if (sk_filter(sk, skb, 0))
1088                 goto discard_and_relse;
1089
1090         skb->dev = NULL;
1091
1092         bh_lock_sock(sk);
1093         ret = 0;
1094         if (!sock_owned_by_user(sk)) {
1095 #ifdef CONFIG_NET_DMA
1096                 struct tcp_sock *tp = tcp_sk(sk);
1097                 if (!tp->ucopy.dma_chan && tp->ucopy.pinned_list)
1098                         tp->ucopy.dma_chan = get_softnet_dma();
1099                 if (tp->ucopy.dma_chan)
1100                         ret = tcp_v4_do_rcv(sk, skb);
1101                 else
1102 #endif
1103                 {
1104                         if (!tcp_prequeue(sk, skb))
1105                         ret = tcp_v4_do_rcv(sk, skb);
1106                 }
1107         } else
1108                 sk_add_backlog(sk, skb);
1109         bh_unlock_sock(sk);
1110
1111         sock_put(sk);
1112
1113         return ret;
1114
1115 no_tcp_socket:
1116         if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb))
1117                 goto discard_it;
1118
1119         if (skb->len < (th->doff << 2) || tcp_checksum_complete(skb)) {
1120 bad_packet:
1121                 TCP_INC_STATS_BH(TCP_MIB_INERRS);
1122         } else {
1123                 tcp_v4_send_reset(skb);
1124         }
1125
1126 discard_it:
1127         /* Discard frame. */
1128         kfree_skb(skb);
1129         return 0;
1130
1131 discard_and_relse:
1132         sock_put(sk);
1133         goto discard_it;
1134
1135 do_time_wait:
1136         if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) {
1137                 inet_twsk_put((struct inet_timewait_sock *) sk);
1138                 goto discard_it;
1139         }
1140
1141         if (skb->len < (th->doff << 2) || tcp_checksum_complete(skb)) {
1142                 TCP_INC_STATS_BH(TCP_MIB_INERRS);
1143                 inet_twsk_put((struct inet_timewait_sock *) sk);
1144                 goto discard_it;
1145         }
1146         switch (tcp_timewait_state_process((struct inet_timewait_sock *)sk,
1147                                            skb, th)) {
1148         case TCP_TW_SYN: {
1149                 struct sock *sk2 = inet_lookup_listener(&tcp_hashinfo,
1150                                                         skb->nh.iph->daddr,
1151                                                         ntohs(th->dest),
1152                                                         inet_iif(skb));
1153                 if (sk2) {
1154                         inet_twsk_deschedule((struct inet_timewait_sock *)sk,
1155                                              &tcp_death_row);
1156                         inet_twsk_put((struct inet_timewait_sock *)sk);
1157                         sk = sk2;
1158                         goto process;
1159                 }
1160                 /* Fall through to ACK */
1161         }
1162         case TCP_TW_ACK:
1163                 tcp_v4_timewait_ack(sk, skb);
1164                 break;
1165         case TCP_TW_RST:
1166                 goto no_tcp_socket;
1167         case TCP_TW_SUCCESS:;
1168         }
1169         goto discard_it;
1170 }
1171
1172 /* VJ's idea. Save last timestamp seen from this destination
1173  * and hold it at least for normal timewait interval to use for duplicate
1174  * segment detection in subsequent connections, before they enter synchronized
1175  * state.
1176  */
1177
1178 int tcp_v4_remember_stamp(struct sock *sk)
1179 {
1180         struct inet_sock *inet = inet_sk(sk);
1181         struct tcp_sock *tp = tcp_sk(sk);
1182         struct rtable *rt = (struct rtable *)__sk_dst_get(sk);
1183         struct inet_peer *peer = NULL;
1184         int release_it = 0;
1185
1186         if (!rt || rt->rt_dst != inet->daddr) {
1187                 peer = inet_getpeer(inet->daddr, 1);
1188                 release_it = 1;
1189         } else {
1190                 if (!rt->peer)
1191                         rt_bind_peer(rt, 1);
1192                 peer = rt->peer;
1193         }
1194
1195         if (peer) {
1196                 if ((s32)(peer->tcp_ts - tp->rx_opt.ts_recent) <= 0 ||
1197                     (peer->tcp_ts_stamp + TCP_PAWS_MSL < xtime.tv_sec &&
1198                      peer->tcp_ts_stamp <= tp->rx_opt.ts_recent_stamp)) {
1199                         peer->tcp_ts_stamp = tp->rx_opt.ts_recent_stamp;
1200                         peer->tcp_ts = tp->rx_opt.ts_recent;
1201                 }
1202                 if (release_it)
1203                         inet_putpeer(peer);
1204                 return 1;
1205         }
1206
1207         return 0;
1208 }
1209
1210 int tcp_v4_tw_remember_stamp(struct inet_timewait_sock *tw)
1211 {
1212         struct inet_peer *peer = inet_getpeer(tw->tw_daddr, 1);
1213
1214         if (peer) {
1215                 const struct tcp_timewait_sock *tcptw = tcp_twsk((struct sock *)tw);
1216
1217                 if ((s32)(peer->tcp_ts - tcptw->tw_ts_recent) <= 0 ||
1218                     (peer->tcp_ts_stamp + TCP_PAWS_MSL < xtime.tv_sec &&
1219                      peer->tcp_ts_stamp <= tcptw->tw_ts_recent_stamp)) {
1220                         peer->tcp_ts_stamp = tcptw->tw_ts_recent_stamp;
1221                         peer->tcp_ts       = tcptw->tw_ts_recent;
1222                 }
1223                 inet_putpeer(peer);
1224                 return 1;
1225         }
1226
1227         return 0;
1228 }
1229
1230 struct inet_connection_sock_af_ops ipv4_specific = {
1231         .queue_xmit        = ip_queue_xmit,
1232         .send_check        = tcp_v4_send_check,
1233         .rebuild_header    = inet_sk_rebuild_header,
1234         .conn_request      = tcp_v4_conn_request,
1235         .syn_recv_sock     = tcp_v4_syn_recv_sock,
1236         .remember_stamp    = tcp_v4_remember_stamp,
1237         .net_header_len    = sizeof(struct iphdr),
1238         .setsockopt        = ip_setsockopt,
1239         .getsockopt        = ip_getsockopt,
1240         .addr2sockaddr     = inet_csk_addr2sockaddr,
1241         .sockaddr_len      = sizeof(struct sockaddr_in),
1242 #ifdef CONFIG_COMPAT
1243         .compat_setsockopt = compat_ip_setsockopt,
1244         .compat_getsockopt = compat_ip_getsockopt,
1245 #endif
1246 };
1247
1248 /* NOTE: A lot of things set to zero explicitly by call to
1249  *       sk_alloc() so need not be done here.
1250  */
1251 static int tcp_v4_init_sock(struct sock *sk)
1252 {
1253         struct inet_connection_sock *icsk = inet_csk(sk);
1254         struct tcp_sock *tp = tcp_sk(sk);
1255
1256         skb_queue_head_init(&tp->out_of_order_queue);
1257         tcp_init_xmit_timers(sk);
1258         tcp_prequeue_init(tp);
1259
1260         icsk->icsk_rto = TCP_TIMEOUT_INIT;
1261         tp->mdev = TCP_TIMEOUT_INIT;
1262
1263         /* So many TCP implementations out there (incorrectly) count the
1264          * initial SYN frame in their delayed-ACK and congestion control
1265          * algorithms that we must have the following bandaid to talk
1266          * efficiently to them.  -DaveM
1267          */
1268         tp->snd_cwnd = 2;
1269
1270         /* See draft-stevens-tcpca-spec-01 for discussion of the
1271          * initialization of these values.
1272          */
1273         tp->snd_ssthresh = 0x7fffffff;  /* Infinity */
1274         tp->snd_cwnd_clamp = ~0;
1275         tp->mss_cache = 536;
1276
1277         tp->reordering = sysctl_tcp_reordering;
1278         icsk->icsk_ca_ops = &tcp_init_congestion_ops;
1279
1280         sk->sk_state = TCP_CLOSE;
1281
1282         sk->sk_write_space = sk_stream_write_space;
1283         sock_set_flag(sk, SOCK_USE_WRITE_QUEUE);
1284
1285         icsk->icsk_af_ops = &ipv4_specific;
1286         icsk->icsk_sync_mss = tcp_sync_mss;
1287
1288         sk->sk_sndbuf = sysctl_tcp_wmem[1];
1289         sk->sk_rcvbuf = sysctl_tcp_rmem[1];
1290
1291         atomic_inc(&tcp_sockets_allocated);
1292
1293         return 0;
1294 }
1295
1296 int tcp_v4_destroy_sock(struct sock *sk)
1297 {
1298         struct tcp_sock *tp = tcp_sk(sk);
1299
1300         tcp_clear_xmit_timers(sk);
1301
1302         tcp_cleanup_congestion_control(sk);
1303
1304         /* Cleanup up the write buffer. */
1305         sk_stream_writequeue_purge(sk);
1306
1307         /* Cleans up our, hopefully empty, out_of_order_queue. */
1308         __skb_queue_purge(&tp->out_of_order_queue);
1309
1310 #ifdef CONFIG_NET_DMA
1311         /* Cleans up our sk_async_wait_queue */
1312         __skb_queue_purge(&sk->sk_async_wait_queue);
1313 #endif
1314
1315         /* Clean prequeue, it must be empty really */
1316         __skb_queue_purge(&tp->ucopy.prequeue);
1317
1318         /* Clean up a referenced TCP bind bucket. */
1319         if (inet_csk(sk)->icsk_bind_hash)
1320                 inet_put_port(&tcp_hashinfo, sk);
1321
1322         /*
1323          * If sendmsg cached page exists, toss it.
1324          */
1325         if (sk->sk_sndmsg_page) {
1326                 __free_page(sk->sk_sndmsg_page);
1327                 sk->sk_sndmsg_page = NULL;
1328         }
1329
1330         atomic_dec(&tcp_sockets_allocated);
1331
1332         return 0;
1333 }
1334
1335 EXPORT_SYMBOL(tcp_v4_destroy_sock);
1336
1337 #ifdef CONFIG_PROC_FS
1338 /* Proc filesystem TCP sock list dumping. */
1339
1340 static inline struct inet_timewait_sock *tw_head(struct hlist_head *head)
1341 {
1342         return hlist_empty(head) ? NULL :
1343                 list_entry(head->first, struct inet_timewait_sock, tw_node);
1344 }
1345
1346 static inline struct inet_timewait_sock *tw_next(struct inet_timewait_sock *tw)
1347 {
1348         return tw->tw_node.next ?
1349                 hlist_entry(tw->tw_node.next, typeof(*tw), tw_node) : NULL;
1350 }
1351
1352 static void *listening_get_next(struct seq_file *seq, void *cur)
1353 {
1354         struct inet_connection_sock *icsk;
1355         struct hlist_node *node;
1356         struct sock *sk = cur;
1357         struct tcp_iter_state* st = seq->private;
1358
1359         if (!sk) {
1360                 st->bucket = 0;
1361                 sk = sk_head(&tcp_hashinfo.listening_hash[0]);
1362                 goto get_sk;
1363         }
1364
1365         ++st->num;
1366
1367         if (st->state == TCP_SEQ_STATE_OPENREQ) {
1368                 struct request_sock *req = cur;
1369
1370                 icsk = inet_csk(st->syn_wait_sk);
1371                 req = req->dl_next;
1372                 while (1) {
1373                         while (req) {
1374                                 if (req->rsk_ops->family == st->family) {
1375                                         cur = req;
1376                                         goto out;
1377                                 }
1378                                 req = req->dl_next;
1379                         }
1380                         if (++st->sbucket >= TCP_SYNQ_HSIZE)
1381                                 break;
1382 get_req:
1383                         req = icsk->icsk_accept_queue.listen_opt->syn_table[st->sbucket];
1384                 }
1385                 sk        = sk_next(st->syn_wait_sk);
1386                 st->state = TCP_SEQ_STATE_LISTENING;
1387                 read_unlock_bh(&icsk->icsk_accept_queue.syn_wait_lock);
1388         } else {
1389                 icsk = inet_csk(sk);
1390                 read_lock_bh(&icsk->icsk_accept_queue.syn_wait_lock);
1391                 if (reqsk_queue_len(&icsk->icsk_accept_queue))
1392                         goto start_req;
1393                 read_unlock_bh(&icsk->icsk_accept_queue.syn_wait_lock);
1394                 sk = sk_next(sk);
1395         }
1396 get_sk:
1397         sk_for_each_from(sk, node) {
1398                 if (sk->sk_family == st->family) {
1399                         cur = sk;
1400                         goto out;
1401                 }
1402                 icsk = inet_csk(sk);
1403                 read_lock_bh(&icsk->icsk_accept_queue.syn_wait_lock);
1404                 if (reqsk_queue_len(&icsk->icsk_accept_queue)) {
1405 start_req:
1406                         st->uid         = sock_i_uid(sk);
1407                         st->syn_wait_sk = sk;
1408                         st->state       = TCP_SEQ_STATE_OPENREQ;
1409                         st->sbucket     = 0;
1410                         goto get_req;
1411                 }
1412                 read_unlock_bh(&icsk->icsk_accept_queue.syn_wait_lock);
1413         }
1414         if (++st->bucket < INET_LHTABLE_SIZE) {
1415                 sk = sk_head(&tcp_hashinfo.listening_hash[st->bucket]);
1416                 goto get_sk;
1417         }
1418         cur = NULL;
1419 out:
1420         return cur;
1421 }
1422
1423 static void *listening_get_idx(struct seq_file *seq, loff_t *pos)
1424 {
1425         void *rc = listening_get_next(seq, NULL);
1426
1427         while (rc && *pos) {
1428                 rc = listening_get_next(seq, rc);
1429                 --*pos;
1430         }
1431         return rc;
1432 }
1433
1434 static void *established_get_first(struct seq_file *seq)
1435 {
1436         struct tcp_iter_state* st = seq->private;
1437         void *rc = NULL;
1438
1439         for (st->bucket = 0; st->bucket < tcp_hashinfo.ehash_size; ++st->bucket) {
1440                 struct sock *sk;
1441                 struct hlist_node *node;
1442                 struct inet_timewait_sock *tw;
1443
1444                 /* We can reschedule _before_ having picked the target: */
1445                 cond_resched_softirq();
1446
1447                 read_lock(&tcp_hashinfo.ehash[st->bucket].lock);
1448                 sk_for_each(sk, node, &tcp_hashinfo.ehash[st->bucket].chain) {
1449                         if (sk->sk_family != st->family) {
1450                                 continue;
1451                         }
1452                         rc = sk;
1453                         goto out;
1454                 }
1455                 st->state = TCP_SEQ_STATE_TIME_WAIT;
1456                 inet_twsk_for_each(tw, node,
1457                                    &tcp_hashinfo.ehash[st->bucket + tcp_hashinfo.ehash_size].chain) {
1458                         if (tw->tw_family != st->family) {
1459                                 continue;
1460                         }
1461                         rc = tw;
1462                         goto out;
1463                 }
1464                 read_unlock(&tcp_hashinfo.ehash[st->bucket].lock);
1465                 st->state = TCP_SEQ_STATE_ESTABLISHED;
1466         }
1467 out:
1468         return rc;
1469 }
1470
1471 static void *established_get_next(struct seq_file *seq, void *cur)
1472 {
1473         struct sock *sk = cur;
1474         struct inet_timewait_sock *tw;
1475         struct hlist_node *node;
1476         struct tcp_iter_state* st = seq->private;
1477
1478         ++st->num;
1479
1480         if (st->state == TCP_SEQ_STATE_TIME_WAIT) {
1481                 tw = cur;
1482                 tw = tw_next(tw);
1483 get_tw:
1484                 while (tw && tw->tw_family != st->family) {
1485                         tw = tw_next(tw);
1486                 }
1487                 if (tw) {
1488                         cur = tw;
1489                         goto out;
1490                 }
1491                 read_unlock(&tcp_hashinfo.ehash[st->bucket].lock);
1492                 st->state = TCP_SEQ_STATE_ESTABLISHED;
1493
1494                 /* We can reschedule between buckets: */
1495                 cond_resched_softirq();
1496
1497                 if (++st->bucket < tcp_hashinfo.ehash_size) {
1498                         read_lock(&tcp_hashinfo.ehash[st->bucket].lock);
1499                         sk = sk_head(&tcp_hashinfo.ehash[st->bucket].chain);
1500                 } else {
1501                         cur = NULL;
1502                         goto out;
1503                 }
1504         } else
1505                 sk = sk_next(sk);
1506
1507         sk_for_each_from(sk, node) {
1508                 if (sk->sk_family == st->family)
1509                         goto found;
1510         }
1511
1512         st->state = TCP_SEQ_STATE_TIME_WAIT;
1513         tw = tw_head(&tcp_hashinfo.ehash[st->bucket + tcp_hashinfo.ehash_size].chain);
1514         goto get_tw;
1515 found:
1516         cur = sk;
1517 out:
1518         return cur;
1519 }
1520
1521 static void *established_get_idx(struct seq_file *seq, loff_t pos)
1522 {
1523         void *rc = established_get_first(seq);
1524
1525         while (rc && pos) {
1526                 rc = established_get_next(seq, rc);
1527                 --pos;
1528         }
1529         return rc;
1530 }
1531
1532 static void *tcp_get_idx(struct seq_file *seq, loff_t pos)
1533 {
1534         void *rc;
1535         struct tcp_iter_state* st = seq->private;
1536
1537         inet_listen_lock(&tcp_hashinfo);
1538         st->state = TCP_SEQ_STATE_LISTENING;
1539         rc        = listening_get_idx(seq, &pos);
1540
1541         if (!rc) {
1542                 inet_listen_unlock(&tcp_hashinfo);
1543                 local_bh_disable();
1544                 st->state = TCP_SEQ_STATE_ESTABLISHED;
1545                 rc        = established_get_idx(seq, pos);
1546         }
1547
1548         return rc;
1549 }
1550
1551 static void *tcp_seq_start(struct seq_file *seq, loff_t *pos)
1552 {
1553         struct tcp_iter_state* st = seq->private;
1554         st->state = TCP_SEQ_STATE_LISTENING;
1555         st->num = 0;
1556         return *pos ? tcp_get_idx(seq, *pos - 1) : SEQ_START_TOKEN;
1557 }
1558
1559 static void *tcp_seq_next(struct seq_file *seq, void *v, loff_t *pos)
1560 {
1561         void *rc = NULL;
1562         struct tcp_iter_state* st;
1563
1564         if (v == SEQ_START_TOKEN) {
1565                 rc = tcp_get_idx(seq, 0);
1566                 goto out;
1567         }
1568         st = seq->private;
1569
1570         switch (st->state) {
1571         case TCP_SEQ_STATE_OPENREQ:
1572         case TCP_SEQ_STATE_LISTENING:
1573                 rc = listening_get_next(seq, v);
1574                 if (!rc) {
1575                         inet_listen_unlock(&tcp_hashinfo);
1576                         local_bh_disable();
1577                         st->state = TCP_SEQ_STATE_ESTABLISHED;
1578                         rc        = established_get_first(seq);
1579                 }
1580                 break;
1581         case TCP_SEQ_STATE_ESTABLISHED:
1582         case TCP_SEQ_STATE_TIME_WAIT:
1583                 rc = established_get_next(seq, v);
1584                 break;
1585         }
1586 out:
1587         ++*pos;
1588         return rc;
1589 }
1590
1591 static void tcp_seq_stop(struct seq_file *seq, void *v)
1592 {
1593         struct tcp_iter_state* st = seq->private;
1594
1595         switch (st->state) {
1596         case TCP_SEQ_STATE_OPENREQ:
1597                 if (v) {
1598                         struct inet_connection_sock *icsk = inet_csk(st->syn_wait_sk);
1599                         read_unlock_bh(&icsk->icsk_accept_queue.syn_wait_lock);
1600                 }
1601         case TCP_SEQ_STATE_LISTENING:
1602                 if (v != SEQ_START_TOKEN)
1603                         inet_listen_unlock(&tcp_hashinfo);
1604                 break;
1605         case TCP_SEQ_STATE_TIME_WAIT:
1606         case TCP_SEQ_STATE_ESTABLISHED:
1607                 if (v)
1608                         read_unlock(&tcp_hashinfo.ehash[st->bucket].lock);
1609                 local_bh_enable();
1610                 break;
1611         }
1612 }
1613
1614 static int tcp_seq_open(struct inode *inode, struct file *file)
1615 {
1616         struct tcp_seq_afinfo *afinfo = PDE(inode)->data;
1617         struct seq_file *seq;
1618         struct tcp_iter_state *s;
1619         int rc;
1620
1621         if (unlikely(afinfo == NULL))
1622                 return -EINVAL;
1623
1624         s = kmalloc(sizeof(*s), GFP_KERNEL);
1625         if (!s)
1626                 return -ENOMEM;
1627         memset(s, 0, sizeof(*s));
1628         s->family               = afinfo->family;
1629         s->seq_ops.start        = tcp_seq_start;
1630         s->seq_ops.next         = tcp_seq_next;
1631         s->seq_ops.show         = afinfo->seq_show;
1632         s->seq_ops.stop         = tcp_seq_stop;
1633
1634         rc = seq_open(file, &s->seq_ops);
1635         if (rc)
1636                 goto out_kfree;
1637         seq          = file->private_data;
1638         seq->private = s;
1639 out:
1640         return rc;
1641 out_kfree:
1642         kfree(s);
1643         goto out;
1644 }
1645
1646 int tcp_proc_register(struct tcp_seq_afinfo *afinfo)
1647 {
1648         int rc = 0;
1649         struct proc_dir_entry *p;
1650
1651         if (!afinfo)
1652                 return -EINVAL;
1653         afinfo->seq_fops->owner         = afinfo->owner;
1654         afinfo->seq_fops->open          = tcp_seq_open;
1655         afinfo->seq_fops->read          = seq_read;
1656         afinfo->seq_fops->llseek        = seq_lseek;
1657         afinfo->seq_fops->release       = seq_release_private;
1658
1659         p = proc_net_fops_create(afinfo->name, S_IRUGO, afinfo->seq_fops);
1660         if (p)
1661                 p->data = afinfo;
1662         else
1663                 rc = -ENOMEM;
1664         return rc;
1665 }
1666
1667 void tcp_proc_unregister(struct tcp_seq_afinfo *afinfo)
1668 {
1669         if (!afinfo)
1670                 return;
1671         proc_net_remove(afinfo->name);
1672         memset(afinfo->seq_fops, 0, sizeof(*afinfo->seq_fops));
1673 }
1674
1675 static void get_openreq4(struct sock *sk, struct request_sock *req,
1676                          char *tmpbuf, int i, int uid)
1677 {
1678         const struct inet_request_sock *ireq = inet_rsk(req);
1679         int ttd = req->expires - jiffies;
1680
1681         sprintf(tmpbuf, "%4d: %08X:%04X %08X:%04X"
1682                 " %02X %08X:%08X %02X:%08lX %08X %5d %8d %u %d %p",
1683                 i,
1684                 ireq->loc_addr,
1685                 ntohs(inet_sk(sk)->sport),
1686                 ireq->rmt_addr,
1687                 ntohs(ireq->rmt_port),
1688                 TCP_SYN_RECV,
1689                 0, 0, /* could print option size, but that is af dependent. */
1690                 1,    /* timers active (only the expire timer) */
1691                 jiffies_to_clock_t(ttd),
1692                 req->retrans,
1693                 uid,
1694                 0,  /* non standard timer */
1695                 0, /* open_requests have no inode */
1696                 atomic_read(&sk->sk_refcnt),
1697                 req);
1698 }
1699
1700 static void get_tcp4_sock(struct sock *sp, char *tmpbuf, int i)
1701 {
1702         int timer_active;
1703         unsigned long timer_expires;
1704         struct tcp_sock *tp = tcp_sk(sp);
1705         const struct inet_connection_sock *icsk = inet_csk(sp);
1706         struct inet_sock *inet = inet_sk(sp);
1707         unsigned int dest = inet->daddr;
1708         unsigned int src = inet->rcv_saddr;
1709         __u16 destp = ntohs(inet->dport);
1710         __u16 srcp = ntohs(inet->sport);
1711
1712         if (icsk->icsk_pending == ICSK_TIME_RETRANS) {
1713                 timer_active    = 1;
1714                 timer_expires   = icsk->icsk_timeout;
1715         } else if (icsk->icsk_pending == ICSK_TIME_PROBE0) {
1716                 timer_active    = 4;
1717                 timer_expires   = icsk->icsk_timeout;
1718         } else if (timer_pending(&sp->sk_timer)) {
1719                 timer_active    = 2;
1720                 timer_expires   = sp->sk_timer.expires;
1721         } else {
1722                 timer_active    = 0;
1723                 timer_expires = jiffies;
1724         }
1725
1726         sprintf(tmpbuf, "%4d: %08X:%04X %08X:%04X %02X %08X:%08X %02X:%08lX "
1727                         "%08X %5d %8d %lu %d %p %u %u %u %u %d",
1728                 i, src, srcp, dest, destp, sp->sk_state,
1729                 tp->write_seq - tp->snd_una, tp->rcv_nxt - tp->copied_seq,
1730                 timer_active,
1731                 jiffies_to_clock_t(timer_expires - jiffies),
1732                 icsk->icsk_retransmits,
1733                 sock_i_uid(sp),
1734                 icsk->icsk_probes_out,
1735                 sock_i_ino(sp),
1736                 atomic_read(&sp->sk_refcnt), sp,
1737                 icsk->icsk_rto,
1738                 icsk->icsk_ack.ato,
1739                 (icsk->icsk_ack.quick << 1) | icsk->icsk_ack.pingpong,
1740                 tp->snd_cwnd,
1741                 tp->snd_ssthresh >= 0xFFFF ? -1 : tp->snd_ssthresh);
1742 }
1743
1744 static void get_timewait4_sock(struct inet_timewait_sock *tw, char *tmpbuf, int i)
1745 {
1746         unsigned int dest, src;
1747         __u16 destp, srcp;
1748         int ttd = tw->tw_ttd - jiffies;
1749
1750         if (ttd < 0)
1751                 ttd = 0;
1752
1753         dest  = tw->tw_daddr;
1754         src   = tw->tw_rcv_saddr;
1755         destp = ntohs(tw->tw_dport);
1756         srcp  = ntohs(tw->tw_sport);
1757
1758         sprintf(tmpbuf, "%4d: %08X:%04X %08X:%04X"
1759                 " %02X %08X:%08X %02X:%08lX %08X %5d %8d %d %d %p",
1760                 i, src, srcp, dest, destp, tw->tw_substate, 0, 0,
1761                 3, jiffies_to_clock_t(ttd), 0, 0, 0, 0,
1762                 atomic_read(&tw->tw_refcnt), tw);
1763 }
1764
1765 #define TMPSZ 150
1766
1767 static int tcp4_seq_show(struct seq_file *seq, void *v)
1768 {
1769         struct tcp_iter_state* st;
1770         char tmpbuf[TMPSZ + 1];
1771
1772         if (v == SEQ_START_TOKEN) {
1773                 seq_printf(seq, "%-*s\n", TMPSZ - 1,
1774                            "  sl  local_address rem_address   st tx_queue "
1775                            "rx_queue tr tm->when retrnsmt   uid  timeout "
1776                            "inode");
1777                 goto out;
1778         }
1779         st = seq->private;
1780
1781         switch (st->state) {
1782         case TCP_SEQ_STATE_LISTENING:
1783         case TCP_SEQ_STATE_ESTABLISHED:
1784                 get_tcp4_sock(v, tmpbuf, st->num);
1785                 break;
1786         case TCP_SEQ_STATE_OPENREQ:
1787                 get_openreq4(st->syn_wait_sk, v, tmpbuf, st->num, st->uid);
1788                 break;
1789         case TCP_SEQ_STATE_TIME_WAIT:
1790                 get_timewait4_sock(v, tmpbuf, st->num);
1791                 break;
1792         }
1793         seq_printf(seq, "%-*s\n", TMPSZ - 1, tmpbuf);
1794 out:
1795         return 0;
1796 }
1797
1798 static struct file_operations tcp4_seq_fops;
1799 static struct tcp_seq_afinfo tcp4_seq_afinfo = {
1800         .owner          = THIS_MODULE,
1801         .name           = "tcp",
1802         .family         = AF_INET,
1803         .seq_show       = tcp4_seq_show,
1804         .seq_fops       = &tcp4_seq_fops,
1805 };
1806
1807 int __init tcp4_proc_init(void)
1808 {
1809         return tcp_proc_register(&tcp4_seq_afinfo);
1810 }
1811
1812 void tcp4_proc_exit(void)
1813 {
1814         tcp_proc_unregister(&tcp4_seq_afinfo);
1815 }
1816 #endif /* CONFIG_PROC_FS */
1817
1818 struct proto tcp_prot = {
1819         .name                   = "TCP",
1820         .owner                  = THIS_MODULE,
1821         .close                  = tcp_close,
1822         .connect                = tcp_v4_connect,
1823         .disconnect             = tcp_disconnect,
1824         .accept                 = inet_csk_accept,
1825         .ioctl                  = tcp_ioctl,
1826         .init                   = tcp_v4_init_sock,
1827         .destroy                = tcp_v4_destroy_sock,
1828         .shutdown               = tcp_shutdown,
1829         .setsockopt             = tcp_setsockopt,
1830         .getsockopt             = tcp_getsockopt,
1831         .sendmsg                = tcp_sendmsg,
1832         .recvmsg                = tcp_recvmsg,
1833         .backlog_rcv            = tcp_v4_do_rcv,
1834         .hash                   = tcp_v4_hash,
1835         .unhash                 = tcp_unhash,
1836         .get_port               = tcp_v4_get_port,
1837         .enter_memory_pressure  = tcp_enter_memory_pressure,
1838         .sockets_allocated      = &tcp_sockets_allocated,
1839         .orphan_count           = &tcp_orphan_count,
1840         .memory_allocated       = &tcp_memory_allocated,
1841         .memory_pressure        = &tcp_memory_pressure,
1842         .sysctl_mem             = sysctl_tcp_mem,
1843         .sysctl_wmem            = sysctl_tcp_wmem,
1844         .sysctl_rmem            = sysctl_tcp_rmem,
1845         .max_header             = MAX_TCP_HEADER,
1846         .obj_size               = sizeof(struct tcp_sock),
1847         .twsk_prot              = &tcp_timewait_sock_ops,
1848         .rsk_prot               = &tcp_request_sock_ops,
1849 #ifdef CONFIG_COMPAT
1850         .compat_setsockopt      = compat_tcp_setsockopt,
1851         .compat_getsockopt      = compat_tcp_getsockopt,
1852 #endif
1853 };
1854
1855 void __init tcp_v4_init(struct net_proto_family *ops)
1856 {
1857         if (inet_csk_ctl_sock_create(&tcp_socket, PF_INET, SOCK_RAW, IPPROTO_TCP) < 0)
1858                 panic("Failed to create the TCP control socket.\n");
1859 }
1860
1861 EXPORT_SYMBOL(ipv4_specific);
1862 EXPORT_SYMBOL(tcp_hashinfo);
1863 EXPORT_SYMBOL(tcp_prot);
1864 EXPORT_SYMBOL(tcp_unhash);
1865 EXPORT_SYMBOL(tcp_v4_conn_request);
1866 EXPORT_SYMBOL(tcp_v4_connect);
1867 EXPORT_SYMBOL(tcp_v4_do_rcv);
1868 EXPORT_SYMBOL(tcp_v4_remember_stamp);
1869 EXPORT_SYMBOL(tcp_v4_send_check);
1870 EXPORT_SYMBOL(tcp_v4_syn_recv_sock);
1871
1872 #ifdef CONFIG_PROC_FS
1873 EXPORT_SYMBOL(tcp_proc_register);
1874 EXPORT_SYMBOL(tcp_proc_unregister);
1875 #endif
1876 EXPORT_SYMBOL(sysctl_local_port_range);
1877 EXPORT_SYMBOL(sysctl_tcp_low_latency);
1878