git.oblomov.eu Git - linux-2.6/blob - net/dccp/ipv4.c

   1 /*
   2  *  net/dccp/ipv4.c
   3  *
   4  *  An implementation of the DCCP protocol
   5  *  Arnaldo Carvalho de Melo <acme@conectiva.com.br>
   6  *
   7  *      This program is free software; you can redistribute it and/or
   8  *      modify it under the terms of the GNU General Public License
   9  *      as published by the Free Software Foundation; either version
  10  *      2 of the License, or (at your option) any later version.
  11  */
  12
  13 #include <linux/dccp.h>
  14 #include <linux/icmp.h>
  15 #include <linux/module.h>
  16 #include <linux/skbuff.h>
  17 #include <linux/random.h>
  18
  19 #include <net/icmp.h>
  20 #include <net/inet_common.h>
  21 #include <net/inet_hashtables.h>
  22 #include <net/inet_sock.h>
  23 #include <net/protocol.h>
  24 #include <net/sock.h>
  25 #include <net/timewait_sock.h>
  26 #include <net/tcp_states.h>
  27 #include <net/xfrm.h>
  28
  29 #include "ackvec.h"
  30 #include "ccid.h"
  31 #include "dccp.h"
  32 #include "feat.h"
  33
  34 /*
  35  * This is the global socket data structure used for responding to
  36  * the Out-of-the-blue (OOTB) packets. A control sock will be created
  37  * for this socket at the initialization time.
  38  */
  39 static struct socket *dccp_v4_ctl_socket;
  40
  41 static int dccp_v4_get_port(struct sock *sk, const unsigned short snum)
  42 {
  43         return inet_csk_get_port(&dccp_hashinfo, sk, snum,
  44                                  inet_csk_bind_conflict);
  45 }
  46
  47 int dccp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
  48 {
  49         struct inet_sock *inet = inet_sk(sk);
  50         struct dccp_sock *dp = dccp_sk(sk);
  51         const struct sockaddr_in *usin = (struct sockaddr_in *)uaddr;
  52         struct rtable *rt;
  53         __be32 daddr, nexthop;
  54         int tmp;
  55         int err;
  56
  57         dp->dccps_role = DCCP_ROLE_CLIENT;
  58
  59         if (addr_len < sizeof(struct sockaddr_in))
  60                 return -EINVAL;
  61
  62         if (usin->sin_family != AF_INET)
  63                 return -EAFNOSUPPORT;
  64
  65         nexthop = daddr = usin->sin_addr.s_addr;
  66         if (inet->opt != NULL && inet->opt->srr) {
  67                 if (daddr == 0)
  68                         return -EINVAL;
  69                 nexthop = inet->opt->faddr;
  70         }
  71
  72         tmp = ip_route_connect(&rt, nexthop, inet->saddr,
  73                                RT_CONN_FLAGS(sk), sk->sk_bound_dev_if,
  74                                IPPROTO_DCCP,
  75                                inet->sport, usin->sin_port, sk, 1);
  76         if (tmp < 0)
  77                 return tmp;
  78
  79         if (rt->rt_flags & (RTCF_MULTICAST | RTCF_BROADCAST)) {
  80                 ip_rt_put(rt);
  81                 return -ENETUNREACH;
  82         }
  83
  84         if (inet->opt == NULL || !inet->opt->srr)
  85                 daddr = rt->rt_dst;
  86
  87         if (inet->saddr == 0)
  88                 inet->saddr = rt->rt_src;
  89         inet->rcv_saddr = inet->saddr;
  90
  91         inet->dport = usin->sin_port;
  92         inet->daddr = daddr;
  93
  94         inet_csk(sk)->icsk_ext_hdr_len = 0;
  95         if (inet->opt != NULL)
  96                 inet_csk(sk)->icsk_ext_hdr_len = inet->opt->optlen;
  97         /*
  98          * Socket identity is still unknown (sport may be zero).
  99          * However we set state to DCCP_REQUESTING and not releasing socket
 100          * lock select source port, enter ourselves into the hash tables and
 101          * complete initialization after this.
 102          */
 103         dccp_set_state(sk, DCCP_REQUESTING);
 104         err = inet_hash_connect(&dccp_death_row, sk);
 105         if (err != 0)
 106                 goto failure;
 107
 108         err = ip_route_newports(&rt, IPPROTO_DCCP, inet->sport, inet->dport,
 109                                 sk);
 110         if (err != 0)
 111                 goto failure;
 112
 113         /* OK, now commit destination to socket.  */
 114         sk_setup_caps(sk, &rt->u.dst);
 115
 116         dp->dccps_iss = secure_dccp_sequence_number(inet->saddr, inet->daddr,
 117                                                     inet->sport, inet->dport);
 118         inet->id = dp->dccps_iss ^ jiffies;
 119
 120         err = dccp_connect(sk);
 121         rt = NULL;
 122         if (err != 0)
 123                 goto failure;
 124 out:
 125         return err;
 126 failure:
 127         /*
 128          * This unhashes the socket and releases the local port, if necessary.
 129          */
 130         dccp_set_state(sk, DCCP_CLOSED);
 131         ip_rt_put(rt);
 132         sk->sk_route_caps = 0;
 133         inet->dport = 0;
 134         goto out;
 135 }
 136
 137 EXPORT_SYMBOL_GPL(dccp_v4_connect);
 138
 139 /*
 140  * This routine does path mtu discovery as defined in RFC1191.
 141  */
 142 static inline void dccp_do_pmtu_discovery(struct sock *sk,
 143                                           const struct iphdr *iph,
 144                                           u32 mtu)
 145 {
 146         struct dst_entry *dst;
 147         const struct inet_sock *inet = inet_sk(sk);
 148         const struct dccp_sock *dp = dccp_sk(sk);
 149
 150         /* We are not interested in DCCP_LISTEN and request_socks (RESPONSEs
 151          * send out by Linux are always < 576bytes so they should go through
 152          * unfragmented).
 153          */
 154         if (sk->sk_state == DCCP_LISTEN)
 155                 return;
 156
 157         /* We don't check in the destentry if pmtu discovery is forbidden
 158          * on this route. We just assume that no packet_to_big packets
 159          * are send back when pmtu discovery is not active.
 160          * There is a small race when the user changes this flag in the
 161          * route, but I think that's acceptable.
 162          */
 163         if ((dst = __sk_dst_check(sk, 0)) == NULL)
 164                 return;
 165
 166         dst->ops->update_pmtu(dst, mtu);
 167
 168         /* Something is about to be wrong... Remember soft error
 169          * for the case, if this connection will not able to recover.
 170          */
 171         if (mtu < dst_mtu(dst) && ip_dont_fragment(sk, dst))
 172                 sk->sk_err_soft = EMSGSIZE;
 173
 174         mtu = dst_mtu(dst);
 175
 176         if (inet->pmtudisc != IP_PMTUDISC_DONT &&
 177             inet_csk(sk)->icsk_pmtu_cookie > mtu) {
 178                 dccp_sync_mss(sk, mtu);
 179
 180                 /*
 181                  * From RFC 4340, sec. 14.1:
 182                  *
 183                  *      DCCP-Sync packets are the best choice for upward
 184                  *      probing, since DCCP-Sync probes do not risk application
 185                  *      data loss.
 186                  */
 187                 dccp_send_sync(sk, dp->dccps_gsr, DCCP_PKT_SYNC);
 188         } /* else let the usual retransmit timer handle it */
 189 }
 190
 191 /*
 192  * This routine is called by the ICMP module when it gets some sort of error
 193  * condition. If err < 0 then the socket should be closed and the error
 194  * returned to the user. If err > 0 it's just the icmp type << 8 | icmp code.
 195  * After adjustment header points to the first 8 bytes of the tcp header. We
 196  * need to find the appropriate port.
 197  *
 198  * The locking strategy used here is very "optimistic". When someone else
 199  * accesses the socket the ICMP is just dropped and for some paths there is no
 200  * check at all. A more general error queue to queue errors for later handling
 201  * is probably better.
 202  */
 203 static void dccp_v4_err(struct sk_buff *skb, u32 info)
 204 {
 205         const struct iphdr *iph = (struct iphdr *)skb->data;
 206         const struct dccp_hdr *dh = (struct dccp_hdr *)(skb->data +
 207                                                         (iph->ihl << 2));
 208         struct dccp_sock *dp;
 209         struct inet_sock *inet;
 210         const int type = icmp_hdr(skb)->type;
 211         const int code = icmp_hdr(skb)->code;
 212         struct sock *sk;
 213         __u64 seq;
 214         int err;
 215
 216         if (skb->len < (iph->ihl << 2) + 8) {
 217                 ICMP_INC_STATS_BH(ICMP_MIB_INERRORS);
 218                 return;
 219         }
 220
 221         sk = inet_lookup(&dccp_hashinfo, iph->daddr, dh->dccph_dport,
 222                          iph->saddr, dh->dccph_sport, inet_iif(skb));
 223         if (sk == NULL) {
 224                 ICMP_INC_STATS_BH(ICMP_MIB_INERRORS);
 225                 return;
 226         }
 227
 228         if (sk->sk_state == DCCP_TIME_WAIT) {
 229                 inet_twsk_put(inet_twsk(sk));
 230                 return;
 231         }
 232
 233         bh_lock_sock(sk);
 234         /* If too many ICMPs get dropped on busy
 235          * servers this needs to be solved differently.
 236          */
 237         if (sock_owned_by_user(sk))
 238                 NET_INC_STATS_BH(LINUX_MIB_LOCKDROPPEDICMPS);
 239
 240         if (sk->sk_state == DCCP_CLOSED)
 241                 goto out;
 242
 243         dp = dccp_sk(sk);
 244         seq = dccp_hdr_seq(dh);
 245         if ((1 << sk->sk_state) & ~(DCCPF_REQUESTING | DCCPF_LISTEN) &&
 246             !between48(seq, dp->dccps_swl, dp->dccps_swh)) {
 247                 NET_INC_STATS_BH(LINUX_MIB_OUTOFWINDOWICMPS);
 248                 goto out;
 249         }
 250
 251         switch (type) {
 252         case ICMP_SOURCE_QUENCH:
 253                 /* Just silently ignore these. */
 254                 goto out;
 255         case ICMP_PARAMETERPROB:
 256                 err = EPROTO;
 257                 break;
 258         case ICMP_DEST_UNREACH:
 259                 if (code > NR_ICMP_UNREACH)
 260                         goto out;
 261
 262                 if (code == ICMP_FRAG_NEEDED) { /* PMTU discovery (RFC1191) */
 263                         if (!sock_owned_by_user(sk))
 264                                 dccp_do_pmtu_discovery(sk, iph, info);
 265                         goto out;
 266                 }
 267
 268                 err = icmp_err_convert[code].errno;
 269                 break;
 270         case ICMP_TIME_EXCEEDED:
 271                 err = EHOSTUNREACH;
 272                 break;
 273         default:
 274                 goto out;
 275         }
 276
 277         switch (sk->sk_state) {
 278                 struct request_sock *req , **prev;
 279         case DCCP_LISTEN:
 280                 if (sock_owned_by_user(sk))
 281                         goto out;
 282                 req = inet_csk_search_req(sk, &prev, dh->dccph_dport,
 283                                           iph->daddr, iph->saddr);
 284                 if (!req)
 285                         goto out;
 286
 287                 /*
 288                  * ICMPs are not backlogged, hence we cannot get an established
 289                  * socket here.
 290                  */
 291                 BUG_TRAP(!req->sk);
 292
 293                 if (seq != dccp_rsk(req)->dreq_iss) {
 294                         NET_INC_STATS_BH(LINUX_MIB_OUTOFWINDOWICMPS);
 295                         goto out;
 296                 }
 297                 /*
 298                  * Still in RESPOND, just remove it silently.
 299                  * There is no good way to pass the error to the newly
 300                  * created socket, and POSIX does not want network
 301                  * errors returned from accept().
 302                  */
 303                 inet_csk_reqsk_queue_drop(sk, req, prev);
 304                 goto out;
 305
 306         case DCCP_REQUESTING:
 307         case DCCP_RESPOND:
 308                 if (!sock_owned_by_user(sk)) {
 309                         DCCP_INC_STATS_BH(DCCP_MIB_ATTEMPTFAILS);
 310                         sk->sk_err = err;
 311
 312                         sk->sk_error_report(sk);
 313
 314                         dccp_done(sk);
 315                 } else
 316                         sk->sk_err_soft = err;
 317                 goto out;
 318         }
 319
 320         /* If we've already connected we will keep trying
 321          * until we time out, or the user gives up.
 322          *
 323          * rfc1122 4.2.3.9 allows to consider as hard errors
 324          * only PROTO_UNREACH and PORT_UNREACH (well, FRAG_FAILED too,
 325          * but it is obsoleted by pmtu discovery).
 326          *
 327          * Note, that in modern internet, where routing is unreliable
 328          * and in each dark corner broken firewalls sit, sending random
 329          * errors ordered by their masters even this two messages finally lose
 330          * their original sense (even Linux sends invalid PORT_UNREACHs)
 331          *
 332          * Now we are in compliance with RFCs.
 333          *                                                      --ANK (980905)
 334          */
 335
 336         inet = inet_sk(sk);
 337         if (!sock_owned_by_user(sk) && inet->recverr) {
 338                 sk->sk_err = err;
 339                 sk->sk_error_report(sk);
 340         } else /* Only an error on timeout */
 341                 sk->sk_err_soft = err;
 342 out:
 343         bh_unlock_sock(sk);
 344         sock_put(sk);
 345 }
 346
 347 static inline __sum16 dccp_v4_csum_finish(struct sk_buff *skb,
 348                                       __be32 src, __be32 dst)
 349 {
 350         return csum_tcpudp_magic(src, dst, skb->len, IPPROTO_DCCP, skb->csum);
 351 }
 352
 353 void dccp_v4_send_check(struct sock *sk, int unused, struct sk_buff *skb)
 354 {
 355         const struct inet_sock *inet = inet_sk(sk);
 356         struct dccp_hdr *dh = dccp_hdr(skb);
 357
 358         dccp_csum_outgoing(skb);
 359         dh->dccph_checksum = dccp_v4_csum_finish(skb, inet->saddr, inet->daddr);
 360 }
 361
 362 EXPORT_SYMBOL_GPL(dccp_v4_send_check);
 363
 364 static inline u64 dccp_v4_init_sequence(const struct sk_buff *skb)
 365 {
 366         return secure_dccp_sequence_number(ip_hdr(skb)->daddr,
 367                                            ip_hdr(skb)->saddr,
 368                                            dccp_hdr(skb)->dccph_dport,
 369                                            dccp_hdr(skb)->dccph_sport);
 370 }
 371
 372 /*
 373  * The three way handshake has completed - we got a valid ACK or DATAACK -
 374  * now create the new socket.
 375  *
 376  * This is the equivalent of TCP's tcp_v4_syn_recv_sock
 377  */
 378 struct sock *dccp_v4_request_recv_sock(struct sock *sk, struct sk_buff *skb,
 379                                        struct request_sock *req,
 380                                        struct dst_entry *dst)
 381 {
 382         struct inet_request_sock *ireq;
 383         struct inet_sock *newinet;
 384         struct sock *newsk;
 385
 386         if (sk_acceptq_is_full(sk))
 387                 goto exit_overflow;
 388
 389         if (dst == NULL && (dst = inet_csk_route_req(sk, req)) == NULL)
 390                 goto exit;
 391
 392         newsk = dccp_create_openreq_child(sk, req, skb);
 393         if (newsk == NULL)
 394                 goto exit;
 395
 396         sk_setup_caps(newsk, dst);
 397
 398         newinet            = inet_sk(newsk);
 399         ireq               = inet_rsk(req);
 400         newinet->daddr     = ireq->rmt_addr;
 401         newinet->rcv_saddr = ireq->loc_addr;
 402         newinet->saddr     = ireq->loc_addr;
 403         newinet->opt       = ireq->opt;
 404         ireq->opt          = NULL;
 405         newinet->mc_index  = inet_iif(skb);
 406         newinet->mc_ttl    = ip_hdr(skb)->ttl;
 407         newinet->id        = jiffies;
 408
 409         dccp_sync_mss(newsk, dst_mtu(dst));
 410
 411         __inet_hash_nolisten(&dccp_hashinfo, newsk);
 412         __inet_inherit_port(&dccp_hashinfo, sk, newsk);
 413
 414         return newsk;
 415
 416 exit_overflow:
 417         NET_INC_STATS_BH(LINUX_MIB_LISTENOVERFLOWS);
 418 exit:
 419         NET_INC_STATS_BH(LINUX_MIB_LISTENDROPS);
 420         dst_release(dst);
 421         return NULL;
 422 }
 423
 424 EXPORT_SYMBOL_GPL(dccp_v4_request_recv_sock);
 425
 426 static struct sock *dccp_v4_hnd_req(struct sock *sk, struct sk_buff *skb)
 427 {
 428         const struct dccp_hdr *dh = dccp_hdr(skb);
 429         const struct iphdr *iph = ip_hdr(skb);
 430         struct sock *nsk;
 431         struct request_sock **prev;
 432         /* Find possible connection requests. */
 433         struct request_sock *req = inet_csk_search_req(sk, &prev,
 434                                                        dh->dccph_sport,
 435                                                        iph->saddr, iph->daddr);
 436         if (req != NULL)
 437                 return dccp_check_req(sk, skb, req, prev);
 438
 439         nsk = inet_lookup_established(&dccp_hashinfo,
 440                                       iph->saddr, dh->dccph_sport,
 441                                       iph->daddr, dh->dccph_dport,
 442                                       inet_iif(skb));
 443         if (nsk != NULL) {
 444                 if (nsk->sk_state != DCCP_TIME_WAIT) {
 445                         bh_lock_sock(nsk);
 446                         return nsk;
 447                 }
 448                 inet_twsk_put(inet_twsk(nsk));
 449                 return NULL;
 450         }
 451
 452         return sk;
 453 }
 454
 455 static struct dst_entry* dccp_v4_route_skb(struct sock *sk,
 456                                            struct sk_buff *skb)
 457 {
 458         struct rtable *rt;
 459         struct flowi fl = { .oif = ((struct rtable *)skb->dst)->rt_iif,
 460                             .nl_u = { .ip4_u =
 461                                       { .daddr = ip_hdr(skb)->saddr,
 462                                         .saddr = ip_hdr(skb)->daddr,
 463                                         .tos = RT_CONN_FLAGS(sk) } },
 464                             .proto = sk->sk_protocol,
 465                             .uli_u = { .ports =
 466                                        { .sport = dccp_hdr(skb)->dccph_dport,
 467                                          .dport = dccp_hdr(skb)->dccph_sport }
 468                                      }
 469                           };
 470
 471         security_skb_classify_flow(skb, &fl);
 472         if (ip_route_output_flow(&init_net, &rt, &fl, sk, 0)) {
 473                 IP_INC_STATS_BH(IPSTATS_MIB_OUTNOROUTES);
 474                 return NULL;
 475         }
 476
 477         return &rt->u.dst;
 478 }
 479
 480 static int dccp_v4_send_response(struct sock *sk, struct request_sock *req,
 481                                  struct dst_entry *dst)
 482 {
 483         int err = -1;
 484         struct sk_buff *skb;
 485
 486         /* First, grab a route. */
 487
 488         if (dst == NULL && (dst = inet_csk_route_req(sk, req)) == NULL)
 489                 goto out;
 490
 491         skb = dccp_make_response(sk, dst, req);
 492         if (skb != NULL) {
 493                 const struct inet_request_sock *ireq = inet_rsk(req);
 494                 struct dccp_hdr *dh = dccp_hdr(skb);
 495
 496                 dh->dccph_checksum = dccp_v4_csum_finish(skb, ireq->loc_addr,
 497                                                               ireq->rmt_addr);
 498                 memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
 499                 err = ip_build_and_send_pkt(skb, sk, ireq->loc_addr,
 500                                             ireq->rmt_addr,
 501                                             ireq->opt);
 502                 err = net_xmit_eval(err);
 503         }
 504
 505 out:
 506         dst_release(dst);
 507         return err;
 508 }
 509
 510 static void dccp_v4_ctl_send_reset(struct sock *sk, struct sk_buff *rxskb)
 511 {
 512         int err;
 513         const struct iphdr *rxiph;
 514         struct sk_buff *skb;
 515         struct dst_entry *dst;
 516
 517         /* Never send a reset in response to a reset. */
 518         if (dccp_hdr(rxskb)->dccph_type == DCCP_PKT_RESET)
 519                 return;
 520
 521         if (((struct rtable *)rxskb->dst)->rt_type != RTN_LOCAL)
 522                 return;
 523
 524         dst = dccp_v4_route_skb(dccp_v4_ctl_socket->sk, rxskb);
 525         if (dst == NULL)
 526                 return;
 527
 528         skb = dccp_ctl_make_reset(dccp_v4_ctl_socket, rxskb);
 529         if (skb == NULL)
 530                 goto out;
 531
 532         rxiph = ip_hdr(rxskb);
 533         dccp_hdr(skb)->dccph_checksum = dccp_v4_csum_finish(skb, rxiph->saddr,
 534                                                                  rxiph->daddr);
 535         skb->dst = dst_clone(dst);
 536
 537         bh_lock_sock(dccp_v4_ctl_socket->sk);
 538         err = ip_build_and_send_pkt(skb, dccp_v4_ctl_socket->sk,
 539                                     rxiph->daddr, rxiph->saddr, NULL);
 540         bh_unlock_sock(dccp_v4_ctl_socket->sk);
 541
 542         if (net_xmit_eval(err) == 0) {
 543                 DCCP_INC_STATS_BH(DCCP_MIB_OUTSEGS);
 544                 DCCP_INC_STATS_BH(DCCP_MIB_OUTRSTS);
 545         }
 546 out:
 547          dst_release(dst);
 548 }
 549
 550 static void dccp_v4_reqsk_destructor(struct request_sock *req)
 551 {
 552         kfree(inet_rsk(req)->opt);
 553 }
 554
 555 static struct request_sock_ops dccp_request_sock_ops __read_mostly = {
 556         .family         = PF_INET,
 557         .obj_size       = sizeof(struct dccp_request_sock),
 558         .rtx_syn_ack    = dccp_v4_send_response,
 559         .send_ack       = dccp_reqsk_send_ack,
 560         .destructor     = dccp_v4_reqsk_destructor,
 561         .send_reset     = dccp_v4_ctl_send_reset,
 562 };
 563
 564 int dccp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
 565 {
 566         struct inet_request_sock *ireq;
 567         struct request_sock *req;
 568         struct dccp_request_sock *dreq;
 569         const __be32 service = dccp_hdr_request(skb)->dccph_req_service;
 570         struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
 571
 572         /* Never answer to DCCP_PKT_REQUESTs send to broadcast or multicast */
 573         if (((struct rtable *)skb->dst)->rt_flags &
 574             (RTCF_BROADCAST | RTCF_MULTICAST))
 575                 return 0;       /* discard, don't send a reset here */
 576
 577         if (dccp_bad_service_code(sk, service)) {
 578                 dcb->dccpd_reset_code = DCCP_RESET_CODE_BAD_SERVICE_CODE;
 579                 goto drop;
 580         }
 581         /*
 582          * TW buckets are converted to open requests without
 583          * limitations, they conserve resources and peer is
 584          * evidently real one.
 585          */
 586         dcb->dccpd_reset_code = DCCP_RESET_CODE_TOO_BUSY;
 587         if (inet_csk_reqsk_queue_is_full(sk))
 588                 goto drop;
 589
 590         /*
 591          * Accept backlog is full. If we have already queued enough
 592          * of warm entries in syn queue, drop request. It is better than
 593          * clogging syn queue with openreqs with exponentially increasing
 594          * timeout.
 595          */
 596         if (sk_acceptq_is_full(sk) && inet_csk_reqsk_queue_young(sk) > 1)
 597                 goto drop;
 598
 599         req = reqsk_alloc(&dccp_request_sock_ops);
 600         if (req == NULL)
 601                 goto drop;
 602
 603         dccp_reqsk_init(req, skb);
 604
 605         dreq = dccp_rsk(req);
 606         if (dccp_parse_options(sk, dreq, skb))
 607                 goto drop_and_free;
 608
 609         if (security_inet_conn_request(sk, skb, req))
 610                 goto drop_and_free;
 611
 612         ireq = inet_rsk(req);
 613         ireq->loc_addr = ip_hdr(skb)->daddr;
 614         ireq->rmt_addr = ip_hdr(skb)->saddr;
 615         ireq->opt       = NULL;
 616
 617         /*
 618          * Step 3: Process LISTEN state
 619          *
 620          * Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init Cookie
 621          *
 622          * In fact we defer setting S.GSR, S.SWL, S.SWH to
 623          * dccp_create_openreq_child.
 624          */
 625         dreq->dreq_isr     = dcb->dccpd_seq;
 626         dreq->dreq_iss     = dccp_v4_init_sequence(skb);
 627         dreq->dreq_service = service;
 628
 629         if (dccp_v4_send_response(sk, req, NULL))
 630                 goto drop_and_free;
 631
 632         inet_csk_reqsk_queue_hash_add(sk, req, DCCP_TIMEOUT_INIT);
 633         return 0;
 634
 635 drop_and_free:
 636         reqsk_free(req);
 637 drop:
 638         DCCP_INC_STATS_BH(DCCP_MIB_ATTEMPTFAILS);
 639         return -1;
 640 }
 641
 642 EXPORT_SYMBOL_GPL(dccp_v4_conn_request);
 643
 644 int dccp_v4_do_rcv(struct sock *sk, struct sk_buff *skb)
 645 {
 646         struct dccp_hdr *dh = dccp_hdr(skb);
 647
 648         if (sk->sk_state == DCCP_OPEN) { /* Fast path */
 649                 if (dccp_rcv_established(sk, skb, dh, skb->len))
 650                         goto reset;
 651                 return 0;
 652         }
 653
 654         /*
 655          *  Step 3: Process LISTEN state
 656          *       If P.type == Request or P contains a valid Init Cookie option,
 657          *            (* Must scan the packet's options to check for Init
 658          *               Cookies.  Only Init Cookies are processed here,
 659          *               however; other options are processed in Step 8.  This
 660          *               scan need only be performed if the endpoint uses Init
 661          *               Cookies *)
 662          *            (* Generate a new socket and switch to that socket *)
 663          *            Set S := new socket for this port pair
 664          *            S.state = RESPOND
 665          *            Choose S.ISS (initial seqno) or set from Init Cookies
 666          *            Initialize S.GAR := S.ISS
 667          *            Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init Cookies
 668          *            Continue with S.state == RESPOND
 669          *            (* A Response packet will be generated in Step 11 *)
 670          *       Otherwise,
 671          *            Generate Reset(No Connection) unless P.type == Reset
 672          *            Drop packet and return
 673          *
 674          * NOTE: the check for the packet types is done in
 675          *       dccp_rcv_state_process
 676          */
 677         if (sk->sk_state == DCCP_LISTEN) {
 678                 struct sock *nsk = dccp_v4_hnd_req(sk, skb);
 679
 680                 if (nsk == NULL)
 681                         goto discard;
 682
 683                 if (nsk != sk) {
 684                         if (dccp_child_process(sk, nsk, skb))
 685                                 goto reset;
 686                         return 0;
 687                 }
 688         }
 689
 690         if (dccp_rcv_state_process(sk, skb, dh, skb->len))
 691                 goto reset;
 692         return 0;
 693
 694 reset:
 695         dccp_v4_ctl_send_reset(sk, skb);
 696 discard:
 697         kfree_skb(skb);
 698         return 0;
 699 }
 700
 701 EXPORT_SYMBOL_GPL(dccp_v4_do_rcv);
 702
 703 /**
 704  *      dccp_invalid_packet  -  check for malformed packets
 705  *      Implements RFC 4340, 8.5:  Step 1: Check header basics
 706  *      Packets that fail these checks are ignored and do not receive Resets.
 707  */
 708 int dccp_invalid_packet(struct sk_buff *skb)
 709 {
 710         const struct dccp_hdr *dh;
 711         unsigned int cscov;
 712
 713         if (skb->pkt_type != PACKET_HOST)
 714                 return 1;
 715
 716         /* If the packet is shorter than 12 bytes, drop packet and return */
 717         if (!pskb_may_pull(skb, sizeof(struct dccp_hdr))) {
 718                 DCCP_WARN("pskb_may_pull failed\n");
 719                 return 1;
 720         }
 721
 722         dh = dccp_hdr(skb);
 723
 724         /* If P.type is not understood, drop packet and return */
 725         if (dh->dccph_type >= DCCP_PKT_INVALID) {
 726                 DCCP_WARN("invalid packet type\n");
 727                 return 1;
 728         }
 729
 730         /*
 731          * If P.Data Offset is too small for packet type, drop packet and return
 732          */
 733         if (dh->dccph_doff < dccp_hdr_len(skb) / sizeof(u32)) {
 734                 DCCP_WARN("P.Data Offset(%u) too small\n", dh->dccph_doff);
 735                 return 1;
 736         }
 737         /*
 738          * If P.Data Offset is too too large for packet, drop packet and return
 739          */
 740         if (!pskb_may_pull(skb, dh->dccph_doff * sizeof(u32))) {
 741                 DCCP_WARN("P.Data Offset(%u) too large\n", dh->dccph_doff);
 742                 return 1;
 743         }
 744
 745         /*
 746          * If P.type is not Data, Ack, or DataAck and P.X == 0 (the packet
 747          * has short sequence numbers), drop packet and return
 748          */
 749         if (dh->dccph_type >= DCCP_PKT_DATA    &&
 750             dh->dccph_type <= DCCP_PKT_DATAACK && dh->dccph_x == 0)  {
 751                 DCCP_WARN("P.type (%s) not Data || [Data]Ack, while P.X == 0\n",
 752                           dccp_packet_name(dh->dccph_type));
 753                 return 1;
 754         }
 755
 756         /*
 757          * If P.CsCov is too large for the packet size, drop packet and return.
 758          * This must come _before_ checksumming (not as RFC 4340 suggests).
 759          */
 760         cscov = dccp_csum_coverage(skb);
 761         if (cscov > skb->len) {
 762                 DCCP_WARN("P.CsCov %u exceeds packet length %d\n",
 763                           dh->dccph_cscov, skb->len);
 764                 return 1;
 765         }
 766
 767         /* If header checksum is incorrect, drop packet and return.
 768          * (This step is completed in the AF-dependent functions.) */
 769         skb->csum = skb_checksum(skb, 0, cscov, 0);
 770
 771         return 0;
 772 }
 773
 774 EXPORT_SYMBOL_GPL(dccp_invalid_packet);
 775
 776 /* this is called when real data arrives */
 777 static int dccp_v4_rcv(struct sk_buff *skb)
 778 {
 779         const struct dccp_hdr *dh;
 780         const struct iphdr *iph;
 781         struct sock *sk;
 782         int min_cov;
 783
 784         /* Step 1: Check header basics */
 785
 786         if (dccp_invalid_packet(skb))
 787                 goto discard_it;
 788
 789         iph = ip_hdr(skb);
 790         /* Step 1: If header checksum is incorrect, drop packet and return */
 791         if (dccp_v4_csum_finish(skb, iph->saddr, iph->daddr)) {
 792                 DCCP_WARN("dropped packet with invalid checksum\n");
 793                 goto discard_it;
 794         }
 795
 796         dh = dccp_hdr(skb);
 797
 798         DCCP_SKB_CB(skb)->dccpd_seq  = dccp_hdr_seq(dh);
 799         DCCP_SKB_CB(skb)->dccpd_type = dh->dccph_type;
 800
 801         dccp_pr_debug("%8.8s "
 802                       "src=%u.%u.%u.%u@%-5d "
 803                       "dst=%u.%u.%u.%u@%-5d seq=%llu",
 804                       dccp_packet_name(dh->dccph_type),
 805                       NIPQUAD(iph->saddr), ntohs(dh->dccph_sport),
 806                       NIPQUAD(iph->daddr), ntohs(dh->dccph_dport),
 807                       (unsigned long long) DCCP_SKB_CB(skb)->dccpd_seq);
 808
 809         if (dccp_packet_without_ack(skb)) {
 810                 DCCP_SKB_CB(skb)->dccpd_ack_seq = DCCP_PKT_WITHOUT_ACK_SEQ;
 811                 dccp_pr_debug_cat("\n");
 812         } else {
 813                 DCCP_SKB_CB(skb)->dccpd_ack_seq = dccp_hdr_ack_seq(skb);
 814                 dccp_pr_debug_cat(", ack=%llu\n", (unsigned long long)
 815                                   DCCP_SKB_CB(skb)->dccpd_ack_seq);
 816         }
 817
 818         /* Step 2:
 819          *      Look up flow ID in table and get corresponding socket */
 820         sk = __inet_lookup(&dccp_hashinfo,
 821                            iph->saddr, dh->dccph_sport,
 822                            iph->daddr, dh->dccph_dport, inet_iif(skb));
 823         /*
 824          * Step 2:
 825          *      If no socket ...
 826          */
 827         if (sk == NULL) {
 828                 dccp_pr_debug("failed to look up flow ID in table and "
 829                               "get corresponding socket\n");
 830                 goto no_dccp_socket;
 831         }
 832
 833         /*
 834          * Step 2:
 835          *      ... or S.state == TIMEWAIT,
 836          *              Generate Reset(No Connection) unless P.type == Reset
 837          *              Drop packet and return
 838          */
 839         if (sk->sk_state == DCCP_TIME_WAIT) {
 840                 dccp_pr_debug("sk->sk_state == DCCP_TIME_WAIT: do_time_wait\n");
 841                 inet_twsk_put(inet_twsk(sk));
 842                 goto no_dccp_socket;
 843         }
 844
 845         /*
 846          * RFC 4340, sec. 9.2.1: Minimum Checksum Coverage
 847          *      o if MinCsCov = 0, only packets with CsCov = 0 are accepted
 848          *      o if MinCsCov > 0, also accept packets with CsCov >= MinCsCov
 849          */
 850         min_cov = dccp_sk(sk)->dccps_pcrlen;
 851         if (dh->dccph_cscov && (min_cov == 0 || dh->dccph_cscov < min_cov))  {
 852                 dccp_pr_debug("Packet CsCov %d does not satisfy MinCsCov %d\n",
 853                               dh->dccph_cscov, min_cov);
 854                 /* FIXME: "Such packets SHOULD be reported using Data Dropped
 855                  *         options (Section 11.7) with Drop Code 0, Protocol
 856                  *         Constraints."                                     */
 857                 goto discard_and_relse;
 858         }
 859
 860         if (!xfrm4_policy_check(sk, XFRM_POLICY_IN, skb))
 861                 goto discard_and_relse;
 862         nf_reset(skb);
 863
 864         return sk_receive_skb(sk, skb, 1);
 865
 866 no_dccp_socket:
 867         if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb))
 868                 goto discard_it;
 869         /*
 870          * Step 2:
 871          *      If no socket ...
 872          *              Generate Reset(No Connection) unless P.type == Reset
 873          *              Drop packet and return
 874          */
 875         if (dh->dccph_type != DCCP_PKT_RESET) {
 876                 DCCP_SKB_CB(skb)->dccpd_reset_code =
 877                                         DCCP_RESET_CODE_NO_CONNECTION;
 878                 dccp_v4_ctl_send_reset(sk, skb);
 879         }
 880
 881 discard_it:
 882         kfree_skb(skb);
 883         return 0;
 884
 885 discard_and_relse:
 886         sock_put(sk);
 887         goto discard_it;
 888 }
 889
 890 static struct inet_connection_sock_af_ops dccp_ipv4_af_ops = {
 891         .queue_xmit        = ip_queue_xmit,
 892         .send_check        = dccp_v4_send_check,
 893         .rebuild_header    = inet_sk_rebuild_header,
 894         .conn_request      = dccp_v4_conn_request,
 895         .syn_recv_sock     = dccp_v4_request_recv_sock,
 896         .net_header_len    = sizeof(struct iphdr),
 897         .setsockopt        = ip_setsockopt,
 898         .getsockopt        = ip_getsockopt,
 899         .addr2sockaddr     = inet_csk_addr2sockaddr,
 900         .sockaddr_len      = sizeof(struct sockaddr_in),
 901 #ifdef CONFIG_COMPAT
 902         .compat_setsockopt = compat_ip_setsockopt,
 903         .compat_getsockopt = compat_ip_getsockopt,
 904 #endif
 905 };
 906
 907 static int dccp_v4_init_sock(struct sock *sk)
 908 {
 909         static __u8 dccp_v4_ctl_sock_initialized;
 910         int err = dccp_init_sock(sk, dccp_v4_ctl_sock_initialized);
 911
 912         if (err == 0) {
 913                 if (unlikely(!dccp_v4_ctl_sock_initialized))
 914                         dccp_v4_ctl_sock_initialized = 1;
 915                 inet_csk(sk)->icsk_af_ops = &dccp_ipv4_af_ops;
 916         }
 917
 918         return err;
 919 }
 920
 921 static struct timewait_sock_ops dccp_timewait_sock_ops = {
 922         .twsk_obj_size  = sizeof(struct inet_timewait_sock),
 923 };
 924
 925 DEFINE_PROTO_INUSE(dccp_v4)
 926
 927 static struct proto dccp_v4_prot = {
 928         .name                   = "DCCP",
 929         .owner                  = THIS_MODULE,
 930         .close                  = dccp_close,
 931         .connect                = dccp_v4_connect,
 932         .disconnect             = dccp_disconnect,
 933         .ioctl                  = dccp_ioctl,
 934         .init                   = dccp_v4_init_sock,
 935         .setsockopt             = dccp_setsockopt,
 936         .getsockopt             = dccp_getsockopt,
 937         .sendmsg                = dccp_sendmsg,
 938         .recvmsg                = dccp_recvmsg,
 939         .backlog_rcv            = dccp_v4_do_rcv,
 940         .hash                   = dccp_hash,
 941         .unhash                 = dccp_unhash,
 942         .accept                 = inet_csk_accept,
 943         .get_port               = dccp_v4_get_port,
 944         .shutdown               = dccp_shutdown,
 945         .destroy                = dccp_destroy_sock,
 946         .orphan_count           = &dccp_orphan_count,
 947         .max_header             = MAX_DCCP_HEADER,
 948         .obj_size               = sizeof(struct dccp_sock),
 949         .rsk_prot               = &dccp_request_sock_ops,
 950         .twsk_prot              = &dccp_timewait_sock_ops,
 951 #ifdef CONFIG_COMPAT
 952         .compat_setsockopt      = compat_dccp_setsockopt,
 953         .compat_getsockopt      = compat_dccp_getsockopt,
 954 #endif
 955         REF_PROTO_INUSE(dccp_v4)
 956 };
 957
 958 static struct net_protocol dccp_v4_protocol = {
 959         .handler        = dccp_v4_rcv,
 960         .err_handler    = dccp_v4_err,
 961         .no_policy      = 1,
 962 };
 963
 964 static const struct proto_ops inet_dccp_ops = {
 965         .family            = PF_INET,
 966         .owner             = THIS_MODULE,
 967         .release           = inet_release,
 968         .bind              = inet_bind,
 969         .connect           = inet_stream_connect,
 970         .socketpair        = sock_no_socketpair,
 971         .accept            = inet_accept,
 972         .getname           = inet_getname,
 973         /* FIXME: work on tcp_poll to rename it to inet_csk_poll */
 974         .poll              = dccp_poll,
 975         .ioctl             = inet_ioctl,
 976         /* FIXME: work on inet_listen to rename it to sock_common_listen */
 977         .listen            = inet_dccp_listen,
 978         .shutdown          = inet_shutdown,
 979         .setsockopt        = sock_common_setsockopt,
 980         .getsockopt        = sock_common_getsockopt,
 981         .sendmsg           = inet_sendmsg,
 982         .recvmsg           = sock_common_recvmsg,
 983         .mmap              = sock_no_mmap,
 984         .sendpage          = sock_no_sendpage,
 985 #ifdef CONFIG_COMPAT
 986         .compat_setsockopt = compat_sock_common_setsockopt,
 987         .compat_getsockopt = compat_sock_common_getsockopt,
 988 #endif
 989 };
 990
 991 static struct inet_protosw dccp_v4_protosw = {
 992         .type           = SOCK_DCCP,
 993         .protocol       = IPPROTO_DCCP,
 994         .prot           = &dccp_v4_prot,
 995         .ops            = &inet_dccp_ops,
 996         .capability     = -1,
 997         .no_check       = 0,
 998         .flags          = INET_PROTOSW_ICSK,
 999 };
1000
1001 static int __init dccp_v4_init(void)
1002 {
1003         int err = proto_register(&dccp_v4_prot, 1);
1004
1005         if (err != 0)
1006                 goto out;
1007
1008         err = inet_add_protocol(&dccp_v4_protocol, IPPROTO_DCCP);
1009         if (err != 0)
1010                 goto out_proto_unregister;
1011
1012         inet_register_protosw(&dccp_v4_protosw);
1013
1014         err = inet_csk_ctl_sock_create(&dccp_v4_ctl_socket, PF_INET,
1015                                        SOCK_DCCP, IPPROTO_DCCP);
1016         if (err)
1017                 goto out_unregister_protosw;
1018 out:
1019         return err;
1020 out_unregister_protosw:
1021         inet_unregister_protosw(&dccp_v4_protosw);
1022         inet_del_protocol(&dccp_v4_protocol, IPPROTO_DCCP);
1023 out_proto_unregister:
1024         proto_unregister(&dccp_v4_prot);
1025         goto out;
1026 }
1027
1028 static void __exit dccp_v4_exit(void)
1029 {
1030         inet_unregister_protosw(&dccp_v4_protosw);
1031         inet_del_protocol(&dccp_v4_protocol, IPPROTO_DCCP);
1032         proto_unregister(&dccp_v4_prot);
1033 }
1034
1035 module_init(dccp_v4_init);
1036 module_exit(dccp_v4_exit);
1037
1038 /*
1039  * __stringify doesn't likes enums, so use SOCK_DCCP (6) and IPPROTO_DCCP (33)
1040  * values directly, Also cover the case where the protocol is not specified,
1041  * i.e. net-pf-PF_INET-proto-0-type-SOCK_DCCP
1042  */
1043 MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_INET, 33, 6);
1044 MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_INET, 0, 6);
1045 MODULE_LICENSE("GPL");
1046 MODULE_AUTHOR("Arnaldo Carvalho de Melo <acme@mandriva.com>");
1047 MODULE_DESCRIPTION("DCCP - Datagram Congestion Controlled Protocol");