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 #include <linux/vserver/debug.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_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                                 vxdprintk(VXD_CBIT(net, 6),
1355                                         "sk,req: %p [#%d] (from %d)", req->sk,
1356                                         (req->sk)?req->sk->sk_xid:0, vx_current_xid());
1357                                 if (req->sk &&
1358                                         !vx_check(req->sk->sk_xid, VX_IDENT|VX_WATCH))
1359                                         continue;
1360                                 if (req->rsk_ops->family == st->family) {
1361                                         cur = req;
1362                                         goto out;
1363                                 }
1364                                 req = req->dl_next;
1365                         }
1366                         if (++st->sbucket >= TCP_SYNQ_HSIZE)
1367                                 break;
1368 get_req:
1369                         req = icsk->icsk_accept_queue.listen_opt->syn_table[st->sbucket];
1370                 }
1371                 sk        = sk_next(st->syn_wait_sk);
1372                 st->state = TCP_SEQ_STATE_LISTENING;
1373                 read_unlock_bh(&icsk->icsk_accept_queue.syn_wait_lock);
1374         } else {
1375                 icsk = inet_csk(sk);
1376                 read_lock_bh(&icsk->icsk_accept_queue.syn_wait_lock);
1377                 if (reqsk_queue_len(&icsk->icsk_accept_queue))
1378                         goto start_req;
1379                 read_unlock_bh(&icsk->icsk_accept_queue.syn_wait_lock);
1380                 sk = sk_next(sk);
1381         }
1382 get_sk:
1383         sk_for_each_from(sk, node) {
1384                 vxdprintk(VXD_CBIT(net, 6), "sk: %p [#%d] (from %d)",
1385                         sk, sk->sk_xid, vx_current_xid());
1386                 if (!vx_check(sk->sk_xid, VX_IDENT|VX_WATCH))
1387                         continue;
1388                 if (sk->sk_family == st->family) {
1389                         cur = sk;
1390                         goto out;
1391                 }
1392                 icsk = inet_csk(sk);
1393                 read_lock_bh(&icsk->icsk_accept_queue.syn_wait_lock);
1394                 if (reqsk_queue_len(&icsk->icsk_accept_queue)) {
1395 start_req:
1396                         st->uid         = sock_i_uid(sk);
1397                         st->syn_wait_sk = sk;
1398                         st->state       = TCP_SEQ_STATE_OPENREQ;
1399                         st->sbucket     = 0;
1400                         goto get_req;
1401                 }
1402                 read_unlock_bh(&icsk->icsk_accept_queue.syn_wait_lock);
1403         }
1404         if (++st->bucket < INET_LHTABLE_SIZE) {
1405                 sk = sk_head(&tcp_hashinfo.listening_hash[st->bucket]);
1406                 goto get_sk;
1407         }
1408         cur = NULL;
1409 out:
1410         return cur;
1411 }
1412
1413 static void *listening_get_idx(struct seq_file *seq, loff_t *pos)
1414 {
1415         void *rc = listening_get_next(seq, NULL);
1416
1417         while (rc && *pos) {
1418                 rc = listening_get_next(seq, rc);
1419                 --*pos;
1420         }
1421         return rc;
1422 }
1423
1424 static void *established_get_first(struct seq_file *seq)
1425 {
1426         struct tcp_iter_state* st = seq->private;
1427         void *rc = NULL;
1428
1429         for (st->bucket = 0; st->bucket < tcp_hashinfo.ehash_size; ++st->bucket) {
1430                 struct sock *sk;
1431                 struct hlist_node *node;
1432                 struct inet_timewait_sock *tw;
1433
1434                 /* We can reschedule _before_ having picked the target: */
1435                 cond_resched_softirq();
1436
1437                 read_lock(&tcp_hashinfo.ehash[st->bucket].lock);
1438                 sk_for_each(sk, node, &tcp_hashinfo.ehash[st->bucket].chain) {
1439                         vxdprintk(VXD_CBIT(net, 6),
1440                                 "sk,egf: %p [#%d] (from %d)",
1441                                 sk, sk->sk_xid, vx_current_xid());
1442                         if (!vx_check(sk->sk_xid, VX_IDENT|VX_WATCH))
1443                                 continue;
1444                         if (sk->sk_family != st->family)
1445                                 continue;
1446                         rc = sk;
1447                         goto out;
1448                 }
1449                 st->state = TCP_SEQ_STATE_TIME_WAIT;
1450                 inet_twsk_for_each(tw, node,
1451                                    &tcp_hashinfo.ehash[st->bucket + tcp_hashinfo.ehash_size].chain) {
1452                         vxdprintk(VXD_CBIT(net, 6),
1453                                 "tw: %p [#%d] (from %d)",
1454                                 tw, tw->tw_xid, vx_current_xid());
1455                         if (!vx_check(tw->tw_xid, VX_IDENT|VX_WATCH))
1456                                 continue;
1457                         if (tw->tw_family != st->family)
1458                                 continue;
1459                         rc = tw;
1460                         goto out;
1461                 }
1462                 read_unlock(&tcp_hashinfo.ehash[st->bucket].lock);
1463                 st->state = TCP_SEQ_STATE_ESTABLISHED;
1464         }
1465 out:
1466         return rc;
1467 }
1468
1469 static void *established_get_next(struct seq_file *seq, void *cur)
1470 {
1471         struct sock *sk = cur;
1472         struct inet_timewait_sock *tw;
1473         struct hlist_node *node;
1474         struct tcp_iter_state* st = seq->private;
1475
1476         ++st->num;
1477
1478         if (st->state == TCP_SEQ_STATE_TIME_WAIT) {
1479                 tw = cur;
1480                 tw = tw_next(tw);
1481 get_tw:
1482                 while (tw && (tw->tw_family != st->family ||
1483                         !vx_check(tw->tw_xid, VX_IDENT|VX_WATCH))) {
1484                         tw = tw_next(tw);
1485                 }
1486                 if (tw) {
1487                         cur = tw;
1488                         goto out;
1489                 }
1490                 read_unlock(&tcp_hashinfo.ehash[st->bucket].lock);
1491                 st->state = TCP_SEQ_STATE_ESTABLISHED;
1492
1493                 /* We can reschedule between buckets: */
1494                 cond_resched_softirq();
1495
1496                 if (++st->bucket < tcp_hashinfo.ehash_size) {
1497                         read_lock(&tcp_hashinfo.ehash[st->bucket].lock);
1498                         sk = sk_head(&tcp_hashinfo.ehash[st->bucket].chain);
1499                 } else {
1500                         cur = NULL;
1501                         goto out;
1502                 }
1503         } else
1504                 sk = sk_next(sk);
1505
1506         sk_for_each_from(sk, node) {
1507                 vxdprintk(VXD_CBIT(net, 6),
1508                         "sk,egn: %p [#%d] (from %d)",
1509                         sk, sk->sk_xid, vx_current_xid());
1510                 if (!vx_check(sk->sk_xid, VX_IDENT|VX_WATCH))
1511                         continue;
1512                 if (sk->sk_family == st->family)
1513                         goto found;
1514         }
1515
1516         st->state = TCP_SEQ_STATE_TIME_WAIT;
1517         tw = tw_head(&tcp_hashinfo.ehash[st->bucket + tcp_hashinfo.ehash_size].chain);
1518         goto get_tw;
1519 found:
1520         cur = sk;
1521 out:
1522         return cur;
1523 }
1524
1525 static void *established_get_idx(struct seq_file *seq, loff_t pos)
1526 {
1527         void *rc = established_get_first(seq);
1528
1529         while (rc && pos) {
1530                 rc = established_get_next(seq, rc);
1531                 --pos;
1532         }
1533         return rc;
1534 }
1535
1536 static void *tcp_get_idx(struct seq_file *seq, loff_t pos)
1537 {
1538         void *rc;
1539         struct tcp_iter_state* st = seq->private;
1540
1541         inet_listen_lock(&tcp_hashinfo);
1542         st->state = TCP_SEQ_STATE_LISTENING;
1543         rc        = listening_get_idx(seq, &pos);
1544
1545         if (!rc) {
1546                 inet_listen_unlock(&tcp_hashinfo);
1547                 local_bh_disable();
1548                 st->state = TCP_SEQ_STATE_ESTABLISHED;
1549                 rc        = established_get_idx(seq, pos);
1550         }
1551
1552         return rc;
1553 }
1554
1555 static void *tcp_seq_start(struct seq_file *seq, loff_t *pos)
1556 {
1557         struct tcp_iter_state* st = seq->private;
1558         st->state = TCP_SEQ_STATE_LISTENING;
1559         st->num = 0;
1560         return *pos ? tcp_get_idx(seq, *pos - 1) : SEQ_START_TOKEN;
1561 }
1562
1563 static void *tcp_seq_next(struct seq_file *seq, void *v, loff_t *pos)
1564 {
1565         void *rc = NULL;
1566         struct tcp_iter_state* st;
1567
1568         if (v == SEQ_START_TOKEN) {
1569                 rc = tcp_get_idx(seq, 0);
1570                 goto out;
1571         }
1572         st = seq->private;
1573
1574         switch (st->state) {
1575         case TCP_SEQ_STATE_OPENREQ:
1576         case TCP_SEQ_STATE_LISTENING:
1577                 rc = listening_get_next(seq, v);
1578                 if (!rc) {
1579                         inet_listen_unlock(&tcp_hashinfo);
1580                         local_bh_disable();
1581                         st->state = TCP_SEQ_STATE_ESTABLISHED;
1582                         rc        = established_get_first(seq);
1583                 }
1584                 break;
1585         case TCP_SEQ_STATE_ESTABLISHED:
1586         case TCP_SEQ_STATE_TIME_WAIT:
1587                 rc = established_get_next(seq, v);
1588                 break;
1589         }
1590 out:
1591         ++*pos;
1592         return rc;
1593 }
1594
1595 static void tcp_seq_stop(struct seq_file *seq, void *v)
1596 {
1597         struct tcp_iter_state* st = seq->private;
1598
1599         switch (st->state) {
1600         case TCP_SEQ_STATE_OPENREQ:
1601                 if (v) {
1602                         struct inet_connection_sock *icsk = inet_csk(st->syn_wait_sk);
1603                         read_unlock_bh(&icsk->icsk_accept_queue.syn_wait_lock);
1604                 }
1605         case TCP_SEQ_STATE_LISTENING:
1606                 if (v != SEQ_START_TOKEN)
1607                         inet_listen_unlock(&tcp_hashinfo);
1608                 break;
1609         case TCP_SEQ_STATE_TIME_WAIT:
1610         case TCP_SEQ_STATE_ESTABLISHED:
1611                 if (v)
1612                         read_unlock(&tcp_hashinfo.ehash[st->bucket].lock);
1613                 local_bh_enable();
1614                 break;
1615         }
1616 }
1617
1618 static int tcp_seq_open(struct inode *inode, struct file *file)
1619 {
1620         struct tcp_seq_afinfo *afinfo = PDE(inode)->data;
1621         struct seq_file *seq;
1622         struct tcp_iter_state *s;
1623         int rc;
1624
1625         if (unlikely(afinfo == NULL))
1626                 return -EINVAL;
1627
1628         s = kmalloc(sizeof(*s), GFP_KERNEL);
1629         if (!s)
1630                 return -ENOMEM;
1631         memset(s, 0, sizeof(*s));
1632         s->family               = afinfo->family;
1633         s->seq_ops.start        = tcp_seq_start;
1634         s->seq_ops.next         = tcp_seq_next;
1635         s->seq_ops.show         = afinfo->seq_show;
1636         s->seq_ops.stop         = tcp_seq_stop;
1637
1638         rc = seq_open(file, &s->seq_ops);
1639         if (rc)
1640                 goto out_kfree;
1641         seq          = file->private_data;
1642         seq->private = s;
1643 out:
1644         return rc;
1645 out_kfree:
1646         kfree(s);
1647         goto out;
1648 }
1649
1650 int tcp_proc_register(struct tcp_seq_afinfo *afinfo)
1651 {
1652         int rc = 0;
1653         struct proc_dir_entry *p;
1654
1655         if (!afinfo)
1656                 return -EINVAL;
1657         afinfo->seq_fops->owner         = afinfo->owner;
1658         afinfo->seq_fops->open          = tcp_seq_open;
1659         afinfo->seq_fops->read          = seq_read;
1660         afinfo->seq_fops->llseek        = seq_lseek;
1661         afinfo->seq_fops->release       = seq_release_private;
1662
1663         p = proc_net_fops_create(afinfo->name, S_IRUGO, afinfo->seq_fops);
1664         if (p)
1665                 p->data = afinfo;
1666         else
1667                 rc = -ENOMEM;
1668         return rc;
1669 }
1670
1671 void tcp_proc_unregister(struct tcp_seq_afinfo *afinfo)
1672 {
1673         if (!afinfo)
1674                 return;
1675         proc_net_remove(afinfo->name);
1676         memset(afinfo->seq_fops, 0, sizeof(*afinfo->seq_fops));
1677 }
1678
1679 static void get_openreq4(struct sock *sk, struct request_sock *req,
1680                          char *tmpbuf, int i, int uid)
1681 {
1682         const struct inet_request_sock *ireq = inet_rsk(req);
1683         int ttd = req->expires - jiffies;
1684
1685         sprintf(tmpbuf, "%4d: %08X:%04X %08X:%04X"
1686                 " %02X %08X:%08X %02X:%08lX %08X %5d %8d %u %d %p",
1687                 i,
1688                 ireq->loc_addr,
1689                 ntohs(inet_sk(sk)->sport),
1690                 ireq->rmt_addr,
1691                 ntohs(ireq->rmt_port),
1692                 TCP_SYN_RECV,
1693                 0, 0, /* could print option size, but that is af dependent. */
1694                 1,    /* timers active (only the expire timer) */
1695                 jiffies_to_clock_t(ttd),
1696                 req->retrans,
1697                 uid,
1698                 0,  /* non standard timer */
1699                 0, /* open_requests have no inode */
1700                 atomic_read(&sk->sk_refcnt),
1701                 req);
1702 }
1703
1704 static void get_tcp4_sock(struct sock *sp, char *tmpbuf, int i)
1705 {
1706         int timer_active;
1707         unsigned long timer_expires;
1708         struct tcp_sock *tp = tcp_sk(sp);
1709         const struct inet_connection_sock *icsk = inet_csk(sp);
1710         struct inet_sock *inet = inet_sk(sp);
1711         unsigned int dest = inet->daddr;
1712         unsigned int src = inet->rcv_saddr;
1713         __u16 destp = ntohs(inet->dport);
1714         __u16 srcp = ntohs(inet->sport);
1715
1716         if (icsk->icsk_pending == ICSK_TIME_RETRANS) {
1717                 timer_active    = 1;
1718                 timer_expires   = icsk->icsk_timeout;
1719         } else if (icsk->icsk_pending == ICSK_TIME_PROBE0) {
1720                 timer_active    = 4;
1721                 timer_expires   = icsk->icsk_timeout;
1722         } else if (timer_pending(&sp->sk_timer)) {
1723                 timer_active    = 2;
1724                 timer_expires   = sp->sk_timer.expires;
1725         } else {
1726                 timer_active    = 0;
1727                 timer_expires = jiffies;
1728         }
1729
1730         sprintf(tmpbuf, "%4d: %08X:%04X %08X:%04X %02X %08X:%08X %02X:%08lX "
1731                         "%08X %5d %8d %lu %d %p %u %u %u %u %d",
1732                 i, src, srcp, dest, destp, sp->sk_state,
1733                 tp->write_seq - tp->snd_una, tp->rcv_nxt - tp->copied_seq,
1734                 timer_active,
1735                 jiffies_to_clock_t(timer_expires - jiffies),
1736                 icsk->icsk_retransmits,
1737                 sock_i_uid(sp),
1738                 icsk->icsk_probes_out,
1739                 sock_i_ino(sp),
1740                 atomic_read(&sp->sk_refcnt), sp,
1741                 icsk->icsk_rto,
1742                 icsk->icsk_ack.ato,
1743                 (icsk->icsk_ack.quick << 1) | icsk->icsk_ack.pingpong,
1744                 tp->snd_cwnd,
1745                 tp->snd_ssthresh >= 0xFFFF ? -1 : tp->snd_ssthresh);
1746 }
1747
1748 static void get_timewait4_sock(struct inet_timewait_sock *tw, char *tmpbuf, int i)
1749 {
1750         unsigned int dest, src;
1751         __u16 destp, srcp;
1752         int ttd = tw->tw_ttd - jiffies;
1753
1754         if (ttd < 0)
1755                 ttd = 0;
1756
1757         dest  = tw->tw_daddr;
1758         src   = tw->tw_rcv_saddr;
1759         destp = ntohs(tw->tw_dport);
1760         srcp  = ntohs(tw->tw_sport);
1761
1762         sprintf(tmpbuf, "%4d: %08X:%04X %08X:%04X"
1763                 " %02X %08X:%08X %02X:%08lX %08X %5d %8d %d %d %p",
1764                 i, src, srcp, dest, destp, tw->tw_substate, 0, 0,
1765                 3, jiffies_to_clock_t(ttd), 0, 0, 0, 0,
1766                 atomic_read(&tw->tw_refcnt), tw);
1767 }
1768
1769 #define TMPSZ 150
1770
1771 static int tcp4_seq_show(struct seq_file *seq, void *v)
1772 {
1773         struct tcp_iter_state* st;
1774         char tmpbuf[TMPSZ + 1];
1775
1776         if (v == SEQ_START_TOKEN) {
1777                 seq_printf(seq, "%-*s\n", TMPSZ - 1,
1778                            "  sl  local_address rem_address   st tx_queue "
1779                            "rx_queue tr tm->when retrnsmt   uid  timeout "
1780                            "inode");
1781                 goto out;
1782         }
1783         st = seq->private;
1784
1785         switch (st->state) {
1786         case TCP_SEQ_STATE_LISTENING:
1787         case TCP_SEQ_STATE_ESTABLISHED:
1788                 get_tcp4_sock(v, tmpbuf, st->num);
1789                 break;
1790         case TCP_SEQ_STATE_OPENREQ:
1791                 get_openreq4(st->syn_wait_sk, v, tmpbuf, st->num, st->uid);
1792                 break;
1793         case TCP_SEQ_STATE_TIME_WAIT:
1794                 get_timewait4_sock(v, tmpbuf, st->num);
1795                 break;
1796         }
1797         seq_printf(seq, "%-*s\n", TMPSZ - 1, tmpbuf);
1798 out:
1799         return 0;
1800 }
1801
1802 static struct file_operations tcp4_seq_fops;
1803 static struct tcp_seq_afinfo tcp4_seq_afinfo = {
1804         .owner          = THIS_MODULE,
1805         .name           = "tcp",
1806         .family         = AF_INET,
1807         .seq_show       = tcp4_seq_show,
1808         .seq_fops       = &tcp4_seq_fops,
1809 };
1810
1811 int __init tcp4_proc_init(void)
1812 {
1813         return tcp_proc_register(&tcp4_seq_afinfo);
1814 }
1815
1816 void tcp4_proc_exit(void)
1817 {
1818         tcp_proc_unregister(&tcp4_seq_afinfo);
1819 }
1820 #endif /* CONFIG_PROC_FS */
1821
1822 struct proto tcp_prot = {
1823         .name                   = "TCP",
1824         .owner                  = THIS_MODULE,
1825         .close                  = tcp_close,
1826         .connect                = tcp_v4_connect,
1827         .disconnect             = tcp_disconnect,
1828         .accept                 = inet_csk_accept,
1829         .ioctl                  = tcp_ioctl,
1830         .init                   = tcp_v4_init_sock,
1831         .destroy                = tcp_v4_destroy_sock,
1832         .shutdown               = tcp_shutdown,
1833         .setsockopt             = tcp_setsockopt,
1834         .getsockopt             = tcp_getsockopt,
1835         .sendmsg                = tcp_sendmsg,
1836         .recvmsg                = tcp_recvmsg,
1837         .backlog_rcv            = tcp_v4_do_rcv,
1838         .hash                   = tcp_v4_hash,
1839         .unhash                 = tcp_unhash,
1840         .get_port               = tcp_v4_get_port,
1841         .enter_memory_pressure  = tcp_enter_memory_pressure,
1842         .sockets_allocated      = &tcp_sockets_allocated,
1843         .orphan_count           = &tcp_orphan_count,
1844         .memory_allocated       = &tcp_memory_allocated,
1845         .memory_pressure        = &tcp_memory_pressure,
1846         .sysctl_mem             = sysctl_tcp_mem,
1847         .sysctl_wmem            = sysctl_tcp_wmem,
1848         .sysctl_rmem            = sysctl_tcp_rmem,
1849         .max_header             = MAX_TCP_HEADER,
1850         .obj_size               = sizeof(struct tcp_sock),
1851         .twsk_prot              = &tcp_timewait_sock_ops,
1852         .rsk_prot               = &tcp_request_sock_ops,
1853 };
1854
1855
1856
1857 void __init tcp_v4_init(struct net_proto_family *ops)
1858 {
1859         int err = sock_create_kern(PF_INET, SOCK_RAW, IPPROTO_TCP, &tcp_socket);
1860         if (err < 0)
1861                 panic("Failed to create the TCP control socket.\n");
1862         tcp_socket->sk->sk_allocation   = GFP_ATOMIC;
1863         inet_sk(tcp_socket->sk)->uc_ttl = -1;
1864
1865         /* Unhash it so that IP input processing does not even
1866          * see it, we do not wish this socket to see incoming
1867          * packets.
1868          */
1869         tcp_socket->sk->sk_prot->unhash(tcp_socket->sk);
1870 }
1871
1872 EXPORT_SYMBOL(ipv4_specific);
1873 EXPORT_SYMBOL(tcp_hashinfo);
1874 EXPORT_SYMBOL(tcp_prot);
1875 EXPORT_SYMBOL(tcp_unhash);
1876 EXPORT_SYMBOL(tcp_v4_conn_request);
1877 EXPORT_SYMBOL(tcp_v4_connect);
1878 EXPORT_SYMBOL(tcp_v4_do_rcv);
1879 EXPORT_SYMBOL(tcp_v4_remember_stamp);
1880 EXPORT_SYMBOL(tcp_v4_send_check);
1881 EXPORT_SYMBOL(tcp_v4_syn_recv_sock);
1882
1883 #ifdef CONFIG_PROC_FS
1884 EXPORT_SYMBOL(tcp_proc_register);
1885 EXPORT_SYMBOL(tcp_proc_unregister);
1886 #endif
1887 EXPORT_SYMBOL(sysctl_local_port_range);
1888 EXPORT_SYMBOL(sysctl_tcp_low_latency);
1889 EXPORT_SYMBOL(sysctl_tcp_tw_reuse);
1890