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   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  * The per-net dccp.v4_ctl_sk socket is 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
  40 int dccp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
  41 {
  42         struct inet_sock *inet = inet_sk(sk);
  43         struct dccp_sock *dp = dccp_sk(sk);
  44         const struct sockaddr_in *usin = (struct sockaddr_in *)uaddr;
  45         struct rtable *rt;
  46         __be32 daddr, nexthop;
  47         int tmp;
  48         int err;
  49
  50         dp->dccps_role = DCCP_ROLE_CLIENT;
  51
  52         if (addr_len < sizeof(struct sockaddr_in))
  53                 return -EINVAL;
  54
  55         if (usin->sin_family != AF_INET)
  56                 return -EAFNOSUPPORT;
  57
  58         nexthop = daddr = usin->sin_addr.s_addr;
  59         if (inet->opt != NULL && inet->opt->srr) {
  60                 if (daddr == 0)
  61                         return -EINVAL;
  62                 nexthop = inet->opt->faddr;
  63         }
  64
  65         tmp = ip_route_connect(&rt, nexthop, inet->inet_saddr,
  66                                RT_CONN_FLAGS(sk), sk->sk_bound_dev_if,
  67                                IPPROTO_DCCP,
  68                                inet->inet_sport, usin->sin_port, sk, 1);
  69         if (tmp < 0)
  70                 return tmp;
  71
  72         if (rt->rt_flags & (RTCF_MULTICAST | RTCF_BROADCAST)) {
  73                 ip_rt_put(rt);
  74                 return -ENETUNREACH;
  75         }
  76
  77         if (inet->opt == NULL || !inet->opt->srr)
  78                 daddr = rt->rt_dst;
  79
  80         if (inet->inet_saddr == 0)
  81                 inet->inet_saddr = rt->rt_src;
  82         inet->inet_rcv_saddr = inet->inet_saddr;
  83
  84         inet->inet_dport = usin->sin_port;
  85         inet->inet_daddr = daddr;
  86
  87         inet_csk(sk)->icsk_ext_hdr_len = 0;
  88         if (inet->opt != NULL)
  89                 inet_csk(sk)->icsk_ext_hdr_len = inet->opt->optlen;
  90         /*
  91          * Socket identity is still unknown (sport may be zero).
  92          * However we set state to DCCP_REQUESTING and not releasing socket
  93          * lock select source port, enter ourselves into the hash tables and
  94          * complete initialization after this.
  95          */
  96         dccp_set_state(sk, DCCP_REQUESTING);
  97         err = inet_hash_connect(&dccp_death_row, sk);
  98         if (err != 0)
  99                 goto failure;
 100
 101         err = ip_route_newports(&rt, IPPROTO_DCCP, inet->inet_sport,
 102                                 inet->inet_dport, sk);
 103         if (err != 0)
 104                 goto failure;
 105
 106         /* OK, now commit destination to socket.  */
 107         sk_setup_caps(sk, &rt->u.dst);
 108
 109         dp->dccps_iss = secure_dccp_sequence_number(inet->inet_saddr,
 110                                                     inet->inet_daddr,
 111                                                     inet->inet_sport,
 112                                                     inet->inet_dport);
 113         inet->inet_id = dp->dccps_iss ^ jiffies;
 114
 115         err = dccp_connect(sk);
 116         rt = NULL;
 117         if (err != 0)
 118                 goto failure;
 119 out:
 120         return err;
 121 failure:
 122         /*
 123          * This unhashes the socket and releases the local port, if necessary.
 124          */
 125         dccp_set_state(sk, DCCP_CLOSED);
 126         ip_rt_put(rt);
 127         sk->sk_route_caps = 0;
 128         inet->inet_dport = 0;
 129         goto out;
 130 }
 131
 132 EXPORT_SYMBOL_GPL(dccp_v4_connect);
 133
 134 /*
 135  * This routine does path mtu discovery as defined in RFC1191.
 136  */
 137 static inline void dccp_do_pmtu_discovery(struct sock *sk,
 138                                           const struct iphdr *iph,
 139                                           u32 mtu)
 140 {
 141         struct dst_entry *dst;
 142         const struct inet_sock *inet = inet_sk(sk);
 143         const struct dccp_sock *dp = dccp_sk(sk);
 144
 145         /* We are not interested in DCCP_LISTEN and request_socks (RESPONSEs
 146          * send out by Linux are always < 576bytes so they should go through
 147          * unfragmented).
 148          */
 149         if (sk->sk_state == DCCP_LISTEN)
 150                 return;
 151
 152         /* We don't check in the destentry if pmtu discovery is forbidden
 153          * on this route. We just assume that no packet_to_big packets
 154          * are send back when pmtu discovery is not active.
 155          * There is a small race when the user changes this flag in the
 156          * route, but I think that's acceptable.
 157          */
 158         if ((dst = __sk_dst_check(sk, 0)) == NULL)
 159                 return;
 160
 161         dst->ops->update_pmtu(dst, mtu);
 162
 163         /* Something is about to be wrong... Remember soft error
 164          * for the case, if this connection will not able to recover.
 165          */
 166         if (mtu < dst_mtu(dst) && ip_dont_fragment(sk, dst))
 167                 sk->sk_err_soft = EMSGSIZE;
 168
 169         mtu = dst_mtu(dst);
 170
 171         if (inet->pmtudisc != IP_PMTUDISC_DONT &&
 172             inet_csk(sk)->icsk_pmtu_cookie > mtu) {
 173                 dccp_sync_mss(sk, mtu);
 174
 175                 /*
 176                  * From RFC 4340, sec. 14.1:
 177                  *
 178                  *      DCCP-Sync packets are the best choice for upward
 179                  *      probing, since DCCP-Sync probes do not risk application
 180                  *      data loss.
 181                  */
 182                 dccp_send_sync(sk, dp->dccps_gsr, DCCP_PKT_SYNC);
 183         } /* else let the usual retransmit timer handle it */
 184 }
 185
 186 /*
 187  * This routine is called by the ICMP module when it gets some sort of error
 188  * condition. If err < 0 then the socket should be closed and the error
 189  * returned to the user. If err > 0 it's just the icmp type << 8 | icmp code.
 190  * After adjustment header points to the first 8 bytes of the tcp header. We
 191  * need to find the appropriate port.
 192  *
 193  * The locking strategy used here is very "optimistic". When someone else
 194  * accesses the socket the ICMP is just dropped and for some paths there is no
 195  * check at all. A more general error queue to queue errors for later handling
 196  * is probably better.
 197  */
 198 static void dccp_v4_err(struct sk_buff *skb, u32 info)
 199 {
 200         const struct iphdr *iph = (struct iphdr *)skb->data;
 201         const u8 offset = iph->ihl << 2;
 202         const struct dccp_hdr *dh = (struct dccp_hdr *)(skb->data + offset);
 203         struct dccp_sock *dp;
 204         struct inet_sock *inet;
 205         const int type = icmp_hdr(skb)->type;
 206         const int code = icmp_hdr(skb)->code;
 207         struct sock *sk;
 208         __u64 seq;
 209         int err;
 210         struct net *net = dev_net(skb->dev);
 211
 212         if (skb->len < offset + sizeof(*dh) ||
 213             skb->len < offset + __dccp_basic_hdr_len(dh)) {
 214                 ICMP_INC_STATS_BH(net, ICMP_MIB_INERRORS);
 215                 return;
 216         }
 217
 218         sk = inet_lookup(net, &dccp_hashinfo,
 219                         iph->daddr, dh->dccph_dport,
 220                         iph->saddr, dh->dccph_sport, inet_iif(skb));
 221         if (sk == NULL) {
 222                 ICMP_INC_STATS_BH(net, ICMP_MIB_INERRORS);
 223                 return;
 224         }
 225
 226         if (sk->sk_state == DCCP_TIME_WAIT) {
 227                 inet_twsk_put(inet_twsk(sk));
 228                 return;
 229         }
 230
 231         bh_lock_sock(sk);
 232         /* If too many ICMPs get dropped on busy
 233          * servers this needs to be solved differently.
 234          */
 235         if (sock_owned_by_user(sk))
 236                 NET_INC_STATS_BH(net, LINUX_MIB_LOCKDROPPEDICMPS);
 237
 238         if (sk->sk_state == DCCP_CLOSED)
 239                 goto out;
 240
 241         dp = dccp_sk(sk);
 242         seq = dccp_hdr_seq(dh);
 243         if ((1 << sk->sk_state) & ~(DCCPF_REQUESTING | DCCPF_LISTEN) &&
 244             !between48(seq, dp->dccps_awl, dp->dccps_awh)) {
 245                 NET_INC_STATS_BH(net, LINUX_MIB_OUTOFWINDOWICMPS);
 246                 goto out;
 247         }
 248
 249         switch (type) {
 250         case ICMP_SOURCE_QUENCH:
 251                 /* Just silently ignore these. */
 252                 goto out;
 253         case ICMP_PARAMETERPROB:
 254                 err = EPROTO;
 255                 break;
 256         case ICMP_DEST_UNREACH:
 257                 if (code > NR_ICMP_UNREACH)
 258                         goto out;
 259
 260                 if (code == ICMP_FRAG_NEEDED) { /* PMTU discovery (RFC1191) */
 261                         if (!sock_owned_by_user(sk))
 262                                 dccp_do_pmtu_discovery(sk, iph, info);
 263                         goto out;
 264                 }
 265
 266                 err = icmp_err_convert[code].errno;
 267                 break;
 268         case ICMP_TIME_EXCEEDED:
 269                 err = EHOSTUNREACH;
 270                 break;
 271         default:
 272                 goto out;
 273         }
 274
 275         switch (sk->sk_state) {
 276                 struct request_sock *req , **prev;
 277         case DCCP_LISTEN:
 278                 if (sock_owned_by_user(sk))
 279                         goto out;
 280                 req = inet_csk_search_req(sk, &prev, dh->dccph_dport,
 281                                           iph->daddr, iph->saddr);
 282                 if (!req)
 283                         goto out;
 284
 285                 /*
 286                  * ICMPs are not backlogged, hence we cannot get an established
 287                  * socket here.
 288                  */
 289                 WARN_ON(req->sk);
 290
 291                 if (seq != dccp_rsk(req)->dreq_iss) {
 292                         NET_INC_STATS_BH(net, LINUX_MIB_OUTOFWINDOWICMPS);
 293                         goto out;
 294                 }
 295                 /*
 296                  * Still in RESPOND, just remove it silently.
 297                  * There is no good way to pass the error to the newly
 298                  * created socket, and POSIX does not want network
 299                  * errors returned from accept().
 300                  */
 301                 inet_csk_reqsk_queue_drop(sk, req, prev);
 302                 goto out;
 303
 304         case DCCP_REQUESTING:
 305         case DCCP_RESPOND:
 306                 if (!sock_owned_by_user(sk)) {
 307                         DCCP_INC_STATS_BH(DCCP_MIB_ATTEMPTFAILS);
 308                         sk->sk_err = err;
 309
 310                         sk->sk_error_report(sk);
 311
 312                         dccp_done(sk);
 313                 } else
 314                         sk->sk_err_soft = err;
 315                 goto out;
 316         }
 317
 318         /* If we've already connected we will keep trying
 319          * until we time out, or the user gives up.
 320          *
 321          * rfc1122 4.2.3.9 allows to consider as hard errors
 322          * only PROTO_UNREACH and PORT_UNREACH (well, FRAG_FAILED too,
 323          * but it is obsoleted by pmtu discovery).
 324          *
 325          * Note, that in modern internet, where routing is unreliable
 326          * and in each dark corner broken firewalls sit, sending random
 327          * errors ordered by their masters even this two messages finally lose
 328          * their original sense (even Linux sends invalid PORT_UNREACHs)
 329          *
 330          * Now we are in compliance with RFCs.
 331          *                                                      --ANK (980905)
 332          */
 333
 334         inet = inet_sk(sk);
 335         if (!sock_owned_by_user(sk) && inet->recverr) {
 336                 sk->sk_err = err;
 337                 sk->sk_error_report(sk);
 338         } else /* Only an error on timeout */
 339                 sk->sk_err_soft = err;
 340 out:
 341         bh_unlock_sock(sk);
 342         sock_put(sk);
 343 }
 344
 345 static inline __sum16 dccp_v4_csum_finish(struct sk_buff *skb,
 346                                       __be32 src, __be32 dst)
 347 {
 348         return csum_tcpudp_magic(src, dst, skb->len, IPPROTO_DCCP, skb->csum);
 349 }
 350
 351 void dccp_v4_send_check(struct sock *sk, int unused, struct sk_buff *skb)
 352 {
 353         const struct inet_sock *inet = inet_sk(sk);
 354         struct dccp_hdr *dh = dccp_hdr(skb);
 355
 356         dccp_csum_outgoing(skb);
 357         dh->dccph_checksum = dccp_v4_csum_finish(skb,
 358                                                  inet->inet_saddr,
 359                                                  inet->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->inet_daddr     = ireq->rmt_addr;
 401         newinet->inet_rcv_saddr = ireq->loc_addr;
 402         newinet->inet_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->inet_id   = jiffies;
 408
 409         dccp_sync_mss(newsk, dst_mtu(dst));
 410
 411         __inet_hash_nolisten(newsk, NULL);
 412         __inet_inherit_port(sk, newsk);
 413
 414         return newsk;
 415
 416 exit_overflow:
 417         NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_LISTENOVERFLOWS);
 418 exit:
 419         NET_INC_STATS_BH(sock_net(sk), 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(sock_net(sk), &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 net *net, struct sock *sk,
 456                                            struct sk_buff *skb)
 457 {
 458         struct rtable *rt;
 459         struct flowi fl = { .oif = skb_rtable(skb)->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(net, &rt, &fl, sk, 0)) {
 473                 IP_INC_STATS_BH(net, 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 request_values *rv_unused)
 482 {
 483         int err = -1;
 484         struct sk_buff *skb;
 485         struct dst_entry *dst;
 486
 487         dst = inet_csk_route_req(sk, req);
 488         if (dst == 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                 err = ip_build_and_send_pkt(skb, sk, ireq->loc_addr,
 499                                             ireq->rmt_addr,
 500                                             ireq->opt);
 501                 err = net_xmit_eval(err);
 502         }
 503
 504 out:
 505         dst_release(dst);
 506         return err;
 507 }
 508
 509 static void dccp_v4_ctl_send_reset(struct sock *sk, struct sk_buff *rxskb)
 510 {
 511         int err;
 512         const struct iphdr *rxiph;
 513         struct sk_buff *skb;
 514         struct dst_entry *dst;
 515         struct net *net = dev_net(skb_dst(rxskb)->dev);
 516         struct sock *ctl_sk = net->dccp.v4_ctl_sk;
 517
 518         /* Never send a reset in response to a reset. */
 519         if (dccp_hdr(rxskb)->dccph_type == DCCP_PKT_RESET)
 520                 return;
 521
 522         if (skb_rtable(rxskb)->rt_type != RTN_LOCAL)
 523                 return;
 524
 525         dst = dccp_v4_route_skb(net, ctl_sk, rxskb);
 526         if (dst == NULL)
 527                 return;
 528
 529         skb = dccp_ctl_make_reset(ctl_sk, rxskb);
 530         if (skb == NULL)
 531                 goto out;
 532
 533         rxiph = ip_hdr(rxskb);
 534         dccp_hdr(skb)->dccph_checksum = dccp_v4_csum_finish(skb, rxiph->saddr,
 535                                                                  rxiph->daddr);
 536         skb_dst_set(skb, dst_clone(dst));
 537
 538         bh_lock_sock(ctl_sk);
 539         err = ip_build_and_send_pkt(skb, ctl_sk,
 540                                     rxiph->daddr, rxiph->saddr, NULL);
 541         bh_unlock_sock(ctl_sk);
 542
 543         if (net_xmit_eval(err) == 0) {
 544                 DCCP_INC_STATS_BH(DCCP_MIB_OUTSEGS);
 545                 DCCP_INC_STATS_BH(DCCP_MIB_OUTRSTS);
 546         }
 547 out:
 548          dst_release(dst);
 549 }
 550
 551 static void dccp_v4_reqsk_destructor(struct request_sock *req)
 552 {
 553         dccp_feat_list_purge(&dccp_rsk(req)->dreq_featneg);
 554         kfree(inet_rsk(req)->opt);
 555 }
 556
 557 static struct request_sock_ops dccp_request_sock_ops __read_mostly = {
 558         .family         = PF_INET,
 559         .obj_size       = sizeof(struct dccp_request_sock),
 560         .rtx_syn_ack    = dccp_v4_send_response,
 561         .send_ack       = dccp_reqsk_send_ack,
 562         .destructor     = dccp_v4_reqsk_destructor,
 563         .send_reset     = dccp_v4_ctl_send_reset,
 564 };
 565
 566 int dccp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
 567 {
 568         struct inet_request_sock *ireq;
 569         struct request_sock *req;
 570         struct dccp_request_sock *dreq;
 571         const __be32 service = dccp_hdr_request(skb)->dccph_req_service;
 572         struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
 573
 574         /* Never answer to DCCP_PKT_REQUESTs send to broadcast or multicast */
 575         if (skb_rtable(skb)->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
 576                 return 0;       /* discard, don't send a reset here */
 577
 578         if (dccp_bad_service_code(sk, service)) {
 579                 dcb->dccpd_reset_code = DCCP_RESET_CODE_BAD_SERVICE_CODE;
 580                 goto drop;
 581         }
 582         /*
 583          * TW buckets are converted to open requests without
 584          * limitations, they conserve resources and peer is
 585          * evidently real one.
 586          */
 587         dcb->dccpd_reset_code = DCCP_RESET_CODE_TOO_BUSY;
 588         if (inet_csk_reqsk_queue_is_full(sk))
 589                 goto drop;
 590
 591         /*
 592          * Accept backlog is full. If we have already queued enough
 593          * of warm entries in syn queue, drop request. It is better than
 594          * clogging syn queue with openreqs with exponentially increasing
 595          * timeout.
 596          */
 597         if (sk_acceptq_is_full(sk) && inet_csk_reqsk_queue_young(sk) > 1)
 598                 goto drop;
 599
 600         req = inet_reqsk_alloc(&dccp_request_sock_ops);
 601         if (req == NULL)
 602                 goto drop;
 603
 604         if (dccp_reqsk_init(req, dccp_sk(sk), skb))
 605                 goto drop_and_free;
 606
 607         dreq = dccp_rsk(req);
 608         if (dccp_parse_options(sk, dreq, skb))
 609                 goto drop_and_free;
 610
 611         if (security_inet_conn_request(sk, skb, req))
 612                 goto drop_and_free;
 613
 614         ireq = inet_rsk(req);
 615         ireq->loc_addr = ip_hdr(skb)->daddr;
 616         ireq->rmt_addr = ip_hdr(skb)->saddr;
 617
 618         /*
 619          * Step 3: Process LISTEN state
 620          *
 621          * Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init Cookie
 622          *
 623          * In fact we defer setting S.GSR, S.SWL, S.SWH to
 624          * dccp_create_openreq_child.
 625          */
 626         dreq->dreq_isr     = dcb->dccpd_seq;
 627         dreq->dreq_iss     = dccp_v4_init_sequence(skb);
 628         dreq->dreq_service = service;
 629
 630         if (dccp_v4_send_response(sk, req, NULL))
 631                 goto drop_and_free;
 632
 633         inet_csk_reqsk_queue_hash_add(sk, req, DCCP_TIMEOUT_INIT);
 634         return 0;
 635
 636 drop_and_free:
 637         reqsk_free(req);
 638 drop:
 639         DCCP_INC_STATS_BH(DCCP_MIB_ATTEMPTFAILS);
 640         return -1;
 641 }
 642
 643 EXPORT_SYMBOL_GPL(dccp_v4_conn_request);
 644
 645 int dccp_v4_do_rcv(struct sock *sk, struct sk_buff *skb)
 646 {
 647         struct dccp_hdr *dh = dccp_hdr(skb);
 648
 649         if (sk->sk_state == DCCP_OPEN) { /* Fast path */
 650                 if (dccp_rcv_established(sk, skb, dh, skb->len))
 651                         goto reset;
 652                 return 0;
 653         }
 654
 655         /*
 656          *  Step 3: Process LISTEN state
 657          *       If P.type == Request or P contains a valid Init Cookie option,
 658          *            (* Must scan the packet's options to check for Init
 659          *               Cookies.  Only Init Cookies are processed here,
 660          *               however; other options are processed in Step 8.  This
 661          *               scan need only be performed if the endpoint uses Init
 662          *               Cookies *)
 663          *            (* Generate a new socket and switch to that socket *)
 664          *            Set S := new socket for this port pair
 665          *            S.state = RESPOND
 666          *            Choose S.ISS (initial seqno) or set from Init Cookies
 667          *            Initialize S.GAR := S.ISS
 668          *            Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init Cookies
 669          *            Continue with S.state == RESPOND
 670          *            (* A Response packet will be generated in Step 11 *)
 671          *       Otherwise,
 672          *            Generate Reset(No Connection) unless P.type == Reset
 673          *            Drop packet and return
 674          *
 675          * NOTE: the check for the packet types is done in
 676          *       dccp_rcv_state_process
 677          */
 678         if (sk->sk_state == DCCP_LISTEN) {
 679                 struct sock *nsk = dccp_v4_hnd_req(sk, skb);
 680
 681                 if (nsk == NULL)
 682                         goto discard;
 683
 684                 if (nsk != sk) {
 685                         if (dccp_child_process(sk, nsk, skb))
 686                                 goto reset;
 687                         return 0;
 688                 }
 689         }
 690
 691         if (dccp_rcv_state_process(sk, skb, dh, skb->len))
 692                 goto reset;
 693         return 0;
 694
 695 reset:
 696         dccp_v4_ctl_send_reset(sk, skb);
 697 discard:
 698         kfree_skb(skb);
 699         return 0;
 700 }
 701
 702 EXPORT_SYMBOL_GPL(dccp_v4_do_rcv);
 703
 704 /**
 705  *      dccp_invalid_packet  -  check for malformed packets
 706  *      Implements RFC 4340, 8.5:  Step 1: Check header basics
 707  *      Packets that fail these checks are ignored and do not receive Resets.
 708  */
 709 int dccp_invalid_packet(struct sk_buff *skb)
 710 {
 711         const struct dccp_hdr *dh;
 712         unsigned int cscov;
 713
 714         if (skb->pkt_type != PACKET_HOST)
 715                 return 1;
 716
 717         /* If the packet is shorter than 12 bytes, drop packet and return */
 718         if (!pskb_may_pull(skb, sizeof(struct dccp_hdr))) {
 719                 DCCP_WARN("pskb_may_pull failed\n");
 720                 return 1;
 721         }
 722
 723         dh = dccp_hdr(skb);
 724
 725         /* If P.type is not understood, drop packet and return */
 726         if (dh->dccph_type >= DCCP_PKT_INVALID) {
 727                 DCCP_WARN("invalid packet type\n");
 728                 return 1;
 729         }
 730
 731         /*
 732          * If P.Data Offset is too small for packet type, drop packet and return
 733          */
 734         if (dh->dccph_doff < dccp_hdr_len(skb) / sizeof(u32)) {
 735                 DCCP_WARN("P.Data Offset(%u) too small\n", dh->dccph_doff);
 736                 return 1;
 737         }
 738         /*
 739          * If P.Data Offset is too too large for packet, drop packet and return
 740          */
 741         if (!pskb_may_pull(skb, dh->dccph_doff * sizeof(u32))) {
 742                 DCCP_WARN("P.Data Offset(%u) too large\n", dh->dccph_doff);
 743                 return 1;
 744         }
 745
 746         /*
 747          * If P.type is not Data, Ack, or DataAck and P.X == 0 (the packet
 748          * has short sequence numbers), drop packet and return
 749          */
 750         if ((dh->dccph_type < DCCP_PKT_DATA    ||
 751             dh->dccph_type > DCCP_PKT_DATAACK) && dh->dccph_x == 0)  {
 752                 DCCP_WARN("P.type (%s) not Data || [Data]Ack, while P.X == 0\n",
 753                           dccp_packet_name(dh->dccph_type));
 754                 return 1;
 755         }
 756
 757         /*
 758          * If P.CsCov is too large for the packet size, drop packet and return.
 759          * This must come _before_ checksumming (not as RFC 4340 suggests).
 760          */
 761         cscov = dccp_csum_coverage(skb);
 762         if (cscov > skb->len) {
 763                 DCCP_WARN("P.CsCov %u exceeds packet length %d\n",
 764                           dh->dccph_cscov, skb->len);
 765                 return 1;
 766         }
 767
 768         /* If header checksum is incorrect, drop packet and return.
 769          * (This step is completed in the AF-dependent functions.) */
 770         skb->csum = skb_checksum(skb, 0, cscov, 0);
 771
 772         return 0;
 773 }
 774
 775 EXPORT_SYMBOL_GPL(dccp_invalid_packet);
 776
 777 /* this is called when real data arrives */
 778 static int dccp_v4_rcv(struct sk_buff *skb)
 779 {
 780         const struct dccp_hdr *dh;
 781         const struct iphdr *iph;
 782         struct sock *sk;
 783         int min_cov;
 784
 785         /* Step 1: Check header basics */
 786
 787         if (dccp_invalid_packet(skb))
 788                 goto discard_it;
 789
 790         iph = ip_hdr(skb);
 791         /* Step 1: If header checksum is incorrect, drop packet and return */
 792         if (dccp_v4_csum_finish(skb, iph->saddr, iph->daddr)) {
 793                 DCCP_WARN("dropped packet with invalid checksum\n");
 794                 goto discard_it;
 795         }
 796
 797         dh = dccp_hdr(skb);
 798
 799         DCCP_SKB_CB(skb)->dccpd_seq  = dccp_hdr_seq(dh);
 800         DCCP_SKB_CB(skb)->dccpd_type = dh->dccph_type;
 801
 802         dccp_pr_debug("%8.8s src=%pI4@%-5d dst=%pI4@%-5d seq=%llu",
 803                       dccp_packet_name(dh->dccph_type),
 804                       &iph->saddr, ntohs(dh->dccph_sport),
 805                       &iph->daddr, ntohs(dh->dccph_dport),
 806                       (unsigned long long) DCCP_SKB_CB(skb)->dccpd_seq);
 807
 808         if (dccp_packet_without_ack(skb)) {
 809                 DCCP_SKB_CB(skb)->dccpd_ack_seq = DCCP_PKT_WITHOUT_ACK_SEQ;
 810                 dccp_pr_debug_cat("\n");
 811         } else {
 812                 DCCP_SKB_CB(skb)->dccpd_ack_seq = dccp_hdr_ack_seq(skb);
 813                 dccp_pr_debug_cat(", ack=%llu\n", (unsigned long long)
 814                                   DCCP_SKB_CB(skb)->dccpd_ack_seq);
 815         }
 816
 817         /* Step 2:
 818          *      Look up flow ID in table and get corresponding socket */
 819         sk = __inet_lookup_skb(&dccp_hashinfo, skb,
 820                                dh->dccph_sport, dh->dccph_dport);
 821         /*
 822          * Step 2:
 823          *      If no socket ...
 824          */
 825         if (sk == NULL) {
 826                 dccp_pr_debug("failed to look up flow ID in table and "
 827                               "get corresponding socket\n");
 828                 goto no_dccp_socket;
 829         }
 830
 831         /*
 832          * Step 2:
 833          *      ... or S.state == TIMEWAIT,
 834          *              Generate Reset(No Connection) unless P.type == Reset
 835          *              Drop packet and return
 836          */
 837         if (sk->sk_state == DCCP_TIME_WAIT) {
 838                 dccp_pr_debug("sk->sk_state == DCCP_TIME_WAIT: do_time_wait\n");
 839                 inet_twsk_put(inet_twsk(sk));
 840                 goto no_dccp_socket;
 841         }
 842
 843         /*
 844          * RFC 4340, sec. 9.2.1: Minimum Checksum Coverage
 845          *      o if MinCsCov = 0, only packets with CsCov = 0 are accepted
 846          *      o if MinCsCov > 0, also accept packets with CsCov >= MinCsCov
 847          */
 848         min_cov = dccp_sk(sk)->dccps_pcrlen;
 849         if (dh->dccph_cscov && (min_cov == 0 || dh->dccph_cscov < min_cov))  {
 850                 dccp_pr_debug("Packet CsCov %d does not satisfy MinCsCov %d\n",
 851                               dh->dccph_cscov, min_cov);
 852                 /* FIXME: "Such packets SHOULD be reported using Data Dropped
 853                  *         options (Section 11.7) with Drop Code 0, Protocol
 854                  *         Constraints."                                     */
 855                 goto discard_and_relse;
 856         }
 857
 858         if (!xfrm4_policy_check(sk, XFRM_POLICY_IN, skb))
 859                 goto discard_and_relse;
 860         nf_reset(skb);
 861
 862         return sk_receive_skb(sk, skb, 1);
 863
 864 no_dccp_socket:
 865         if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb))
 866                 goto discard_it;
 867         /*
 868          * Step 2:
 869          *      If no socket ...
 870          *              Generate Reset(No Connection) unless P.type == Reset
 871          *              Drop packet and return
 872          */
 873         if (dh->dccph_type != DCCP_PKT_RESET) {
 874                 DCCP_SKB_CB(skb)->dccpd_reset_code =
 875                                         DCCP_RESET_CODE_NO_CONNECTION;
 876                 dccp_v4_ctl_send_reset(sk, skb);
 877         }
 878
 879 discard_it:
 880         kfree_skb(skb);
 881         return 0;
 882
 883 discard_and_relse:
 884         sock_put(sk);
 885         goto discard_it;
 886 }
 887
 888 static const struct inet_connection_sock_af_ops dccp_ipv4_af_ops = {
 889         .queue_xmit        = ip_queue_xmit,
 890         .send_check        = dccp_v4_send_check,
 891         .rebuild_header    = inet_sk_rebuild_header,
 892         .conn_request      = dccp_v4_conn_request,
 893         .syn_recv_sock     = dccp_v4_request_recv_sock,
 894         .net_header_len    = sizeof(struct iphdr),
 895         .setsockopt        = ip_setsockopt,
 896         .getsockopt        = ip_getsockopt,
 897         .addr2sockaddr     = inet_csk_addr2sockaddr,
 898         .sockaddr_len      = sizeof(struct sockaddr_in),
 899         .bind_conflict     = inet_csk_bind_conflict,
 900 #ifdef CONFIG_COMPAT
 901         .compat_setsockopt = compat_ip_setsockopt,
 902         .compat_getsockopt = compat_ip_getsockopt,
 903 #endif
 904 };
 905
 906 static int dccp_v4_init_sock(struct sock *sk)
 907 {
 908         static __u8 dccp_v4_ctl_sock_initialized;
 909         int err = dccp_init_sock(sk, dccp_v4_ctl_sock_initialized);
 910
 911         if (err == 0) {
 912                 if (unlikely(!dccp_v4_ctl_sock_initialized))
 913                         dccp_v4_ctl_sock_initialized = 1;
 914                 inet_csk(sk)->icsk_af_ops = &dccp_ipv4_af_ops;
 915         }
 916
 917         return err;
 918 }
 919
 920 static struct timewait_sock_ops dccp_timewait_sock_ops = {
 921         .twsk_obj_size  = sizeof(struct inet_timewait_sock),
 922 };
 923
 924 static struct proto dccp_v4_prot = {
 925         .name                   = "DCCP",
 926         .owner                  = THIS_MODULE,
 927         .close                  = dccp_close,
 928         .connect                = dccp_v4_connect,
 929         .disconnect             = dccp_disconnect,
 930         .ioctl                  = dccp_ioctl,
 931         .init                   = dccp_v4_init_sock,
 932         .setsockopt             = dccp_setsockopt,
 933         .getsockopt             = dccp_getsockopt,
 934         .sendmsg                = dccp_sendmsg,
 935         .recvmsg                = dccp_recvmsg,
 936         .backlog_rcv            = dccp_v4_do_rcv,
 937         .hash                   = inet_hash,
 938         .unhash                 = inet_unhash,
 939         .accept                 = inet_csk_accept,
 940         .get_port               = inet_csk_get_port,
 941         .shutdown               = dccp_shutdown,
 942         .destroy                = dccp_destroy_sock,
 943         .orphan_count           = &dccp_orphan_count,
 944         .max_header             = MAX_DCCP_HEADER,
 945         .obj_size               = sizeof(struct dccp_sock),
 946         .slab_flags             = SLAB_DESTROY_BY_RCU,
 947         .rsk_prot               = &dccp_request_sock_ops,
 948         .twsk_prot              = &dccp_timewait_sock_ops,
 949         .h.hashinfo             = &dccp_hashinfo,
 950 #ifdef CONFIG_COMPAT
 951         .compat_setsockopt      = compat_dccp_setsockopt,
 952         .compat_getsockopt      = compat_dccp_getsockopt,
 953 #endif
 954 };
 955
 956 static const struct net_protocol dccp_v4_protocol = {
 957         .handler        = dccp_v4_rcv,
 958         .err_handler    = dccp_v4_err,
 959         .no_policy      = 1,
 960         .netns_ok       = 1,
 961 };
 962
 963 static const struct proto_ops inet_dccp_ops = {
 964         .family            = PF_INET,
 965         .owner             = THIS_MODULE,
 966         .release           = inet_release,
 967         .bind              = inet_bind,
 968         .connect           = inet_stream_connect,
 969         .socketpair        = sock_no_socketpair,
 970         .accept            = inet_accept,
 971         .getname           = inet_getname,
 972         /* FIXME: work on tcp_poll to rename it to inet_csk_poll */
 973         .poll              = dccp_poll,
 974         .ioctl             = inet_ioctl,
 975         /* FIXME: work on inet_listen to rename it to sock_common_listen */
 976         .listen            = inet_dccp_listen,
 977         .shutdown          = inet_shutdown,
 978         .setsockopt        = sock_common_setsockopt,
 979         .getsockopt        = sock_common_getsockopt,
 980         .sendmsg           = inet_sendmsg,
 981         .recvmsg           = sock_common_recvmsg,
 982         .mmap              = sock_no_mmap,
 983         .sendpage          = sock_no_sendpage,
 984 #ifdef CONFIG_COMPAT
 985         .compat_setsockopt = compat_sock_common_setsockopt,
 986         .compat_getsockopt = compat_sock_common_getsockopt,
 987 #endif
 988 };
 989
 990 static struct inet_protosw dccp_v4_protosw = {
 991         .type           = SOCK_DCCP,
 992         .protocol       = IPPROTO_DCCP,
 993         .prot           = &dccp_v4_prot,
 994         .ops            = &inet_dccp_ops,
 995         .no_check       = 0,
 996         .flags          = INET_PROTOSW_ICSK,
 997 };
 998
 999 static int __net_init dccp_v4_init_net(struct net *net)
1000 {
1001         int err;
1002
1003         err = inet_ctl_sock_create(&net->dccp.v4_ctl_sk, PF_INET,
1004                                    SOCK_DCCP, IPPROTO_DCCP, net);
1005         return err;
1006 }
1007
1008 static void __net_exit dccp_v4_exit_net(struct net *net)
1009 {
1010         inet_ctl_sock_destroy(net->dccp.v4_ctl_sk);
1011 }
1012
1013 static struct pernet_operations dccp_v4_ops = {
1014         .init   = dccp_v4_init_net,
1015         .exit   = dccp_v4_exit_net,
1016 };
1017
1018 static int __init dccp_v4_init(void)
1019 {
1020         int err = proto_register(&dccp_v4_prot, 1);
1021
1022         if (err != 0)
1023                 goto out;
1024
1025         err = inet_add_protocol(&dccp_v4_protocol, IPPROTO_DCCP);
1026         if (err != 0)
1027                 goto out_proto_unregister;
1028
1029         inet_register_protosw(&dccp_v4_protosw);
1030
1031         err = register_pernet_subsys(&dccp_v4_ops);
1032         if (err)
1033                 goto out_destroy_ctl_sock;
1034 out:
1035         return err;
1036 out_destroy_ctl_sock:
1037         inet_unregister_protosw(&dccp_v4_protosw);
1038         inet_del_protocol(&dccp_v4_protocol, IPPROTO_DCCP);
1039 out_proto_unregister:
1040         proto_unregister(&dccp_v4_prot);
1041         goto out;
1042 }
1043
1044 static void __exit dccp_v4_exit(void)
1045 {
1046         unregister_pernet_subsys(&dccp_v4_ops);
1047         inet_unregister_protosw(&dccp_v4_protosw);
1048         inet_del_protocol(&dccp_v4_protocol, IPPROTO_DCCP);
1049         proto_unregister(&dccp_v4_prot);
1050 }
1051
1052 module_init(dccp_v4_init);
1053 module_exit(dccp_v4_exit);
1054
1055 /*
1056  * __stringify doesn't likes enums, so use SOCK_DCCP (6) and IPPROTO_DCCP (33)
1057  * values directly, Also cover the case where the protocol is not specified,
1058  * i.e. net-pf-PF_INET-proto-0-type-SOCK_DCCP
1059  */
1060 MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_INET, 33, 6);
1061 MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_INET, 0, 6);
1062 MODULE_LICENSE("GPL");
1063 MODULE_AUTHOR("Arnaldo Carvalho de Melo <acme@mandriva.com>");
1064 MODULE_DESCRIPTION("DCCP - Datagram Congestion Controlled Protocol");