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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  * 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         u32 daddr, nexthop;
  54         int tmp;
  55         int err;
  56
  57         dp->dccps_role = DCCP_ROLE_CLIENT;
  58
  59         if (dccp_service_not_initialized(sk))
  60                 return -EPROTO;
  61
  62         if (addr_len < sizeof(struct sockaddr_in))
  63                 return -EINVAL;
  64
  65         if (usin->sin_family != AF_INET)
  66                 return -EAFNOSUPPORT;
  67
  68         nexthop = daddr = usin->sin_addr.s_addr;
  69         if (inet->opt != NULL && inet->opt->srr) {
  70                 if (daddr == 0)
  71                         return -EINVAL;
  72                 nexthop = inet->opt->faddr;
  73         }
  74
  75         tmp = ip_route_connect(&rt, nexthop, inet->saddr,
  76                                RT_CONN_FLAGS(sk), sk->sk_bound_dev_if,
  77                                IPPROTO_DCCP,
  78                                inet->sport, usin->sin_port, sk);
  79         if (tmp < 0)
  80                 return tmp;
  81
  82         if (rt->rt_flags & (RTCF_MULTICAST | RTCF_BROADCAST)) {
  83                 ip_rt_put(rt);
  84                 return -ENETUNREACH;
  85         }
  86
  87         if (inet->opt == NULL || !inet->opt->srr)
  88                 daddr = rt->rt_dst;
  89
  90         if (inet->saddr == 0)
  91                 inet->saddr = rt->rt_src;
  92         inet->rcv_saddr = inet->saddr;
  93
  94         inet->dport = usin->sin_port;
  95         inet->daddr = daddr;
  96
  97         inet_csk(sk)->icsk_ext_hdr_len = 0;
  98         if (inet->opt != NULL)
  99                 inet_csk(sk)->icsk_ext_hdr_len = inet->opt->optlen;
 100         /*
 101          * Socket identity is still unknown (sport may be zero).
 102          * However we set state to DCCP_REQUESTING and not releasing socket
 103          * lock select source port, enter ourselves into the hash tables and
 104          * complete initialization after this.
 105          */
 106         dccp_set_state(sk, DCCP_REQUESTING);
 107         err = inet_hash_connect(&dccp_death_row, sk);
 108         if (err != 0)
 109                 goto failure;
 110
 111         err = ip_route_newports(&rt, IPPROTO_DCCP, inet->sport, inet->dport,
 112                                 sk);
 113         if (err != 0)
 114                 goto failure;
 115
 116         /* OK, now commit destination to socket.  */
 117         sk_setup_caps(sk, &rt->u.dst);
 118
 119         dp->dccps_gar =
 120                 dp->dccps_iss = secure_dccp_sequence_number(inet->saddr,
 121                                                             inet->daddr,
 122                                                             inet->sport,
 123                                                             usin->sin_port);
 124         dccp_update_gss(sk, dp->dccps_iss);
 125
 126         inet->id = dp->dccps_iss ^ jiffies;
 127
 128         err = dccp_connect(sk);
 129         rt = NULL;
 130         if (err != 0)
 131                 goto failure;
 132 out:
 133         return err;
 134 failure:
 135         /*
 136          * This unhashes the socket and releases the local port, if necessary.
 137          */
 138         dccp_set_state(sk, DCCP_CLOSED);
 139         ip_rt_put(rt);
 140         sk->sk_route_caps = 0;
 141         inet->dport = 0;
 142         goto out;
 143 }
 144
 145 EXPORT_SYMBOL_GPL(dccp_v4_connect);
 146
 147 /*
 148  * This routine does path mtu discovery as defined in RFC1191.
 149  */
 150 static inline void dccp_do_pmtu_discovery(struct sock *sk,
 151                                           const struct iphdr *iph,
 152                                           u32 mtu)
 153 {
 154         struct dst_entry *dst;
 155         const struct inet_sock *inet = inet_sk(sk);
 156         const struct dccp_sock *dp = dccp_sk(sk);
 157
 158         /* We are not interested in DCCP_LISTEN and request_socks (RESPONSEs
 159          * send out by Linux are always < 576bytes so they should go through
 160          * unfragmented).
 161          */
 162         if (sk->sk_state == DCCP_LISTEN)
 163                 return;
 164
 165         /* We don't check in the destentry if pmtu discovery is forbidden
 166          * on this route. We just assume that no packet_to_big packets
 167          * are send back when pmtu discovery is not active.
 168          * There is a small race when the user changes this flag in the
 169          * route, but I think that's acceptable.
 170          */
 171         if ((dst = __sk_dst_check(sk, 0)) == NULL)
 172                 return;
 173
 174         dst->ops->update_pmtu(dst, mtu);
 175
 176         /* Something is about to be wrong... Remember soft error
 177          * for the case, if this connection will not able to recover.
 178          */
 179         if (mtu < dst_mtu(dst) && ip_dont_fragment(sk, dst))
 180                 sk->sk_err_soft = EMSGSIZE;
 181
 182         mtu = dst_mtu(dst);
 183
 184         if (inet->pmtudisc != IP_PMTUDISC_DONT &&
 185             inet_csk(sk)->icsk_pmtu_cookie > mtu) {
 186                 dccp_sync_mss(sk, mtu);
 187
 188                 /*
 189                  * From: draft-ietf-dccp-spec-11.txt
 190                  *
 191                  *      DCCP-Sync packets are the best choice for upward
 192                  *      probing, since DCCP-Sync probes do not risk application
 193                  *      data loss.
 194                  */
 195                 dccp_send_sync(sk, dp->dccps_gsr, DCCP_PKT_SYNC);
 196         } /* else let the usual retransmit timer handle it */
 197 }
 198
 199 static void dccp_v4_reqsk_send_ack(struct sk_buff *rxskb,
 200                                    struct request_sock *req)
 201 {
 202         int err;
 203         struct dccp_hdr *rxdh = dccp_hdr(rxskb), *dh;
 204         const u32 dccp_hdr_ack_len = sizeof(struct dccp_hdr) +
 205                                      sizeof(struct dccp_hdr_ext) +
 206                                      sizeof(struct dccp_hdr_ack_bits);
 207         struct sk_buff *skb;
 208
 209         if (((struct rtable *)rxskb->dst)->rt_type != RTN_LOCAL)
 210                 return;
 211
 212         skb = alloc_skb(dccp_v4_ctl_socket->sk->sk_prot->max_header, GFP_ATOMIC);
 213         if (skb == NULL)
 214                 return;
 215
 216         /* Reserve space for headers. */
 217         skb_reserve(skb, dccp_v4_ctl_socket->sk->sk_prot->max_header);
 218
 219         skb->dst = dst_clone(rxskb->dst);
 220
 221         skb->h.raw = skb_push(skb, dccp_hdr_ack_len);
 222         dh = dccp_hdr(skb);
 223         memset(dh, 0, dccp_hdr_ack_len);
 224
 225         /* Build DCCP header and checksum it. */
 226         dh->dccph_type     = DCCP_PKT_ACK;
 227         dh->dccph_sport    = rxdh->dccph_dport;
 228         dh->dccph_dport    = rxdh->dccph_sport;
 229         dh->dccph_doff     = dccp_hdr_ack_len / 4;
 230         dh->dccph_x        = 1;
 231
 232         dccp_hdr_set_seq(dh, DCCP_SKB_CB(rxskb)->dccpd_ack_seq);
 233         dccp_hdr_set_ack(dccp_hdr_ack_bits(skb),
 234                          DCCP_SKB_CB(rxskb)->dccpd_seq);
 235
 236         bh_lock_sock(dccp_v4_ctl_socket->sk);
 237         err = ip_build_and_send_pkt(skb, dccp_v4_ctl_socket->sk,
 238                                     rxskb->nh.iph->daddr,
 239                                     rxskb->nh.iph->saddr, NULL);
 240         bh_unlock_sock(dccp_v4_ctl_socket->sk);
 241
 242         if (err == NET_XMIT_CN || err == 0) {
 243                 DCCP_INC_STATS_BH(DCCP_MIB_OUTSEGS);
 244                 DCCP_INC_STATS_BH(DCCP_MIB_OUTRSTS);
 245         }
 246 }
 247
 248 static int dccp_v4_send_response(struct sock *sk, struct request_sock *req,
 249                                  struct dst_entry *dst)
 250 {
 251         int err = -1;
 252         struct sk_buff *skb;
 253
 254         /* First, grab a route. */
 255
 256         if (dst == NULL && (dst = inet_csk_route_req(sk, req)) == NULL)
 257                 goto out;
 258
 259         skb = dccp_make_response(sk, dst, req);
 260         if (skb != NULL) {
 261                 const struct inet_request_sock *ireq = inet_rsk(req);
 262                 struct dccp_hdr *dh = dccp_hdr(skb);
 263
 264                 dh->dccph_checksum = dccp_v4_checksum(skb, ireq->loc_addr,
 265                                                       ireq->rmt_addr);
 266                 memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
 267                 err = ip_build_and_send_pkt(skb, sk, ireq->loc_addr,
 268                                             ireq->rmt_addr,
 269                                             ireq->opt);
 270                 if (err == NET_XMIT_CN)
 271                         err = 0;
 272         }
 273
 274 out:
 275         dst_release(dst);
 276         return err;
 277 }
 278
 279 /*
 280  * This routine is called by the ICMP module when it gets some sort of error
 281  * condition. If err < 0 then the socket should be closed and the error
 282  * returned to the user. If err > 0 it's just the icmp type << 8 | icmp code.
 283  * After adjustment header points to the first 8 bytes of the tcp header. We
 284  * need to find the appropriate port.
 285  *
 286  * The locking strategy used here is very "optimistic". When someone else
 287  * accesses the socket the ICMP is just dropped and for some paths there is no
 288  * check at all. A more general error queue to queue errors for later handling
 289  * is probably better.
 290  */
 291 static void dccp_v4_err(struct sk_buff *skb, u32 info)
 292 {
 293         const struct iphdr *iph = (struct iphdr *)skb->data;
 294         const struct dccp_hdr *dh = (struct dccp_hdr *)(skb->data +
 295                                                         (iph->ihl << 2));
 296         struct dccp_sock *dp;
 297         struct inet_sock *inet;
 298         const int type = skb->h.icmph->type;
 299         const int code = skb->h.icmph->code;
 300         struct sock *sk;
 301         __u64 seq;
 302         int err;
 303
 304         if (skb->len < (iph->ihl << 2) + 8) {
 305                 ICMP_INC_STATS_BH(ICMP_MIB_INERRORS);
 306                 return;
 307         }
 308
 309         sk = inet_lookup(&dccp_hashinfo, iph->daddr, dh->dccph_dport,
 310                          iph->saddr, dh->dccph_sport, inet_iif(skb));
 311         if (sk == NULL) {
 312                 ICMP_INC_STATS_BH(ICMP_MIB_INERRORS);
 313                 return;
 314         }
 315
 316         if (sk->sk_state == DCCP_TIME_WAIT) {
 317                 inet_twsk_put((struct inet_timewait_sock *)sk);
 318                 return;
 319         }
 320
 321         bh_lock_sock(sk);
 322         /* If too many ICMPs get dropped on busy
 323          * servers this needs to be solved differently.
 324          */
 325         if (sock_owned_by_user(sk))
 326                 NET_INC_STATS_BH(LINUX_MIB_LOCKDROPPEDICMPS);
 327
 328         if (sk->sk_state == DCCP_CLOSED)
 329                 goto out;
 330
 331         dp = dccp_sk(sk);
 332         seq = dccp_hdr_seq(skb);
 333         if (sk->sk_state != DCCP_LISTEN &&
 334             !between48(seq, dp->dccps_swl, dp->dccps_swh)) {
 335                 NET_INC_STATS(LINUX_MIB_OUTOFWINDOWICMPS);
 336                 goto out;
 337         }
 338
 339         switch (type) {
 340         case ICMP_SOURCE_QUENCH:
 341                 /* Just silently ignore these. */
 342                 goto out;
 343         case ICMP_PARAMETERPROB:
 344                 err = EPROTO;
 345                 break;
 346         case ICMP_DEST_UNREACH:
 347                 if (code > NR_ICMP_UNREACH)
 348                         goto out;
 349
 350                 if (code == ICMP_FRAG_NEEDED) { /* PMTU discovery (RFC1191) */
 351                         if (!sock_owned_by_user(sk))
 352                                 dccp_do_pmtu_discovery(sk, iph, info);
 353                         goto out;
 354                 }
 355
 356                 err = icmp_err_convert[code].errno;
 357                 break;
 358         case ICMP_TIME_EXCEEDED:
 359                 err = EHOSTUNREACH;
 360                 break;
 361         default:
 362                 goto out;
 363         }
 364
 365         switch (sk->sk_state) {
 366                 struct request_sock *req , **prev;
 367         case DCCP_LISTEN:
 368                 if (sock_owned_by_user(sk))
 369                         goto out;
 370                 req = inet_csk_search_req(sk, &prev, dh->dccph_dport,
 371                                           iph->daddr, iph->saddr);
 372                 if (!req)
 373                         goto out;
 374
 375                 /*
 376                  * ICMPs are not backlogged, hence we cannot get an established
 377                  * socket here.
 378                  */
 379                 BUG_TRAP(!req->sk);
 380
 381                 if (seq != dccp_rsk(req)->dreq_iss) {
 382                         NET_INC_STATS_BH(LINUX_MIB_OUTOFWINDOWICMPS);
 383                         goto out;
 384                 }
 385                 /*
 386                  * Still in RESPOND, just remove it silently.
 387                  * There is no good way to pass the error to the newly
 388                  * created socket, and POSIX does not want network
 389                  * errors returned from accept().
 390                  */
 391                 inet_csk_reqsk_queue_drop(sk, req, prev);
 392                 goto out;
 393
 394         case DCCP_REQUESTING:
 395         case DCCP_RESPOND:
 396                 if (!sock_owned_by_user(sk)) {
 397                         DCCP_INC_STATS_BH(DCCP_MIB_ATTEMPTFAILS);
 398                         sk->sk_err = err;
 399
 400                         sk->sk_error_report(sk);
 401
 402                         dccp_done(sk);
 403                 } else
 404                         sk->sk_err_soft = err;
 405                 goto out;
 406         }
 407
 408         /* If we've already connected we will keep trying
 409          * until we time out, or the user gives up.
 410          *
 411          * rfc1122 4.2.3.9 allows to consider as hard errors
 412          * only PROTO_UNREACH and PORT_UNREACH (well, FRAG_FAILED too,
 413          * but it is obsoleted by pmtu discovery).
 414          *
 415          * Note, that in modern internet, where routing is unreliable
 416          * and in each dark corner broken firewalls sit, sending random
 417          * errors ordered by their masters even this two messages finally lose
 418          * their original sense (even Linux sends invalid PORT_UNREACHs)
 419          *
 420          * Now we are in compliance with RFCs.
 421          *                                                      --ANK (980905)
 422          */
 423
 424         inet = inet_sk(sk);
 425         if (!sock_owned_by_user(sk) && inet->recverr) {
 426                 sk->sk_err = err;
 427                 sk->sk_error_report(sk);
 428         } else /* Only an error on timeout */
 429                 sk->sk_err_soft = err;
 430 out:
 431         bh_unlock_sock(sk);
 432         sock_put(sk);
 433 }
 434
 435 /* This routine computes an IPv4 DCCP checksum. */
 436 void dccp_v4_send_check(struct sock *sk, int len, struct sk_buff *skb)
 437 {
 438         const struct inet_sock *inet = inet_sk(sk);
 439         struct dccp_hdr *dh = dccp_hdr(skb);
 440
 441         dh->dccph_checksum = dccp_v4_checksum(skb, inet->saddr, inet->daddr);
 442 }
 443
 444 EXPORT_SYMBOL_GPL(dccp_v4_send_check);
 445
 446 static inline u64 dccp_v4_init_sequence(const struct sock *sk,
 447                                         const struct sk_buff *skb)
 448 {
 449         return secure_dccp_sequence_number(skb->nh.iph->daddr,
 450                                            skb->nh.iph->saddr,
 451                                            dccp_hdr(skb)->dccph_dport,
 452                                            dccp_hdr(skb)->dccph_sport);
 453 }
 454
 455 int dccp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
 456 {
 457         struct inet_request_sock *ireq;
 458         struct dccp_sock dp;
 459         struct request_sock *req;
 460         struct dccp_request_sock *dreq;
 461         const __be32 saddr = skb->nh.iph->saddr;
 462         const __be32 daddr = skb->nh.iph->daddr;
 463         const __be32 service = dccp_hdr_request(skb)->dccph_req_service;
 464         struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
 465         __u8 reset_code = DCCP_RESET_CODE_TOO_BUSY;
 466
 467         /* Never answer to DCCP_PKT_REQUESTs send to broadcast or multicast */
 468         if (((struct rtable *)skb->dst)->rt_flags &
 469             (RTCF_BROADCAST | RTCF_MULTICAST)) {
 470                 reset_code = DCCP_RESET_CODE_NO_CONNECTION;
 471                 goto drop;
 472         }
 473
 474         if (dccp_bad_service_code(sk, service)) {
 475                 reset_code = DCCP_RESET_CODE_BAD_SERVICE_CODE;
 476                 goto drop;
 477         }
 478         /*
 479          * TW buckets are converted to open requests without
 480          * limitations, they conserve resources and peer is
 481          * evidently real one.
 482          */
 483         if (inet_csk_reqsk_queue_is_full(sk))
 484                 goto drop;
 485
 486         /*
 487          * Accept backlog is full. If we have already queued enough
 488          * of warm entries in syn queue, drop request. It is better than
 489          * clogging syn queue with openreqs with exponentially increasing
 490          * timeout.
 491          */
 492         if (sk_acceptq_is_full(sk) && inet_csk_reqsk_queue_young(sk) > 1)
 493                 goto drop;
 494
 495         req = reqsk_alloc(sk->sk_prot->rsk_prot);
 496         if (req == NULL)
 497                 goto drop;
 498
 499         if (dccp_parse_options(sk, skb))
 500                 goto drop_and_free;
 501
 502         dccp_openreq_init(req, &dp, skb);
 503
 504         ireq = inet_rsk(req);
 505         ireq->loc_addr = daddr;
 506         ireq->rmt_addr = saddr;
 507         req->rcv_wnd    = 100; /* Fake, option parsing will get the
 508                                   right value */
 509         ireq->opt       = NULL;
 510
 511         /*
 512          * Step 3: Process LISTEN state
 513          *
 514          * Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init Cookie
 515          *
 516          * In fact we defer setting S.GSR, S.SWL, S.SWH to
 517          * dccp_create_openreq_child.
 518          */
 519         dreq = dccp_rsk(req);
 520         dreq->dreq_isr     = dcb->dccpd_seq;
 521         dreq->dreq_iss     = dccp_v4_init_sequence(sk, skb);
 522         dreq->dreq_service = service;
 523
 524         if (dccp_v4_send_response(sk, req, NULL))
 525                 goto drop_and_free;
 526
 527         inet_csk_reqsk_queue_hash_add(sk, req, DCCP_TIMEOUT_INIT);
 528         return 0;
 529
 530 drop_and_free:
 531         reqsk_free(req);
 532 drop:
 533         DCCP_INC_STATS_BH(DCCP_MIB_ATTEMPTFAILS);
 534         dcb->dccpd_reset_code = reset_code;
 535         return -1;
 536 }
 537
 538 EXPORT_SYMBOL_GPL(dccp_v4_conn_request);
 539
 540 /*
 541  * The three way handshake has completed - we got a valid ACK or DATAACK -
 542  * now create the new socket.
 543  *
 544  * This is the equivalent of TCP's tcp_v4_syn_recv_sock
 545  */
 546 struct sock *dccp_v4_request_recv_sock(struct sock *sk, struct sk_buff *skb,
 547                                        struct request_sock *req,
 548                                        struct dst_entry *dst)
 549 {
 550         struct inet_request_sock *ireq;
 551         struct inet_sock *newinet;
 552         struct dccp_sock *newdp;
 553         struct sock *newsk;
 554
 555         if (sk_acceptq_is_full(sk))
 556                 goto exit_overflow;
 557
 558         if (dst == NULL && (dst = inet_csk_route_req(sk, req)) == NULL)
 559                 goto exit;
 560
 561         newsk = dccp_create_openreq_child(sk, req, skb);
 562         if (newsk == NULL)
 563                 goto exit;
 564
 565         sk_setup_caps(newsk, dst);
 566
 567         newdp              = dccp_sk(newsk);
 568         newinet            = inet_sk(newsk);
 569         ireq               = inet_rsk(req);
 570         newinet->daddr     = ireq->rmt_addr;
 571         newinet->rcv_saddr = ireq->loc_addr;
 572         newinet->saddr     = ireq->loc_addr;
 573         newinet->opt       = ireq->opt;
 574         ireq->opt          = NULL;
 575         newinet->mc_index  = inet_iif(skb);
 576         newinet->mc_ttl    = skb->nh.iph->ttl;
 577         newinet->id        = jiffies;
 578
 579         dccp_sync_mss(newsk, dst_mtu(dst));
 580
 581         __inet_hash(&dccp_hashinfo, newsk, 0);
 582         __inet_inherit_port(&dccp_hashinfo, sk, newsk);
 583
 584         return newsk;
 585
 586 exit_overflow:
 587         NET_INC_STATS_BH(LINUX_MIB_LISTENOVERFLOWS);
 588 exit:
 589         NET_INC_STATS_BH(LINUX_MIB_LISTENDROPS);
 590         dst_release(dst);
 591         return NULL;
 592 }
 593
 594 EXPORT_SYMBOL_GPL(dccp_v4_request_recv_sock);
 595
 596 static struct sock *dccp_v4_hnd_req(struct sock *sk, struct sk_buff *skb)
 597 {
 598         const struct dccp_hdr *dh = dccp_hdr(skb);
 599         const struct iphdr *iph = skb->nh.iph;
 600         struct sock *nsk;
 601         struct request_sock **prev;
 602         /* Find possible connection requests. */
 603         struct request_sock *req = inet_csk_search_req(sk, &prev,
 604                                                        dh->dccph_sport,
 605                                                        iph->saddr, iph->daddr);
 606         if (req != NULL)
 607                 return dccp_check_req(sk, skb, req, prev);
 608
 609         nsk = __inet_lookup_established(&dccp_hashinfo,
 610                                         iph->saddr, dh->dccph_sport,
 611                                         iph->daddr, ntohs(dh->dccph_dport),
 612                                         inet_iif(skb));
 613         if (nsk != NULL) {
 614                 if (nsk->sk_state != DCCP_TIME_WAIT) {
 615                         bh_lock_sock(nsk);
 616                         return nsk;
 617                 }
 618                 inet_twsk_put((struct inet_timewait_sock *)nsk);
 619                 return NULL;
 620         }
 621
 622         return sk;
 623 }
 624
 625 int dccp_v4_checksum(const struct sk_buff *skb, const __be32 saddr,
 626                      const __be32 daddr)
 627 {
 628         const struct dccp_hdr* dh = dccp_hdr(skb);
 629         int checksum_len;
 630         u32 tmp;
 631
 632         if (dh->dccph_cscov == 0)
 633                 checksum_len = skb->len;
 634         else {
 635                 checksum_len = (dh->dccph_cscov + dh->dccph_x) * sizeof(u32);
 636                 checksum_len = checksum_len < skb->len ? checksum_len :
 637                                                          skb->len;
 638         }
 639
 640         tmp = csum_partial((unsigned char *)dh, checksum_len, 0);
 641         return csum_tcpudp_magic(saddr, daddr, checksum_len,
 642                                  IPPROTO_DCCP, tmp);
 643 }
 644
 645 EXPORT_SYMBOL_GPL(dccp_v4_checksum);
 646
 647 static int dccp_v4_verify_checksum(struct sk_buff *skb,
 648                                    const __be32 saddr, const __be32 daddr)
 649 {
 650         struct dccp_hdr *dh = dccp_hdr(skb);
 651         int checksum_len;
 652         u32 tmp;
 653
 654         if (dh->dccph_cscov == 0)
 655                 checksum_len = skb->len;
 656         else {
 657                 checksum_len = (dh->dccph_cscov + dh->dccph_x) * sizeof(u32);
 658                 checksum_len = checksum_len < skb->len ? checksum_len :
 659                                                          skb->len;
 660         }
 661         tmp = csum_partial((unsigned char *)dh, checksum_len, 0);
 662         return csum_tcpudp_magic(saddr, daddr, checksum_len,
 663                                  IPPROTO_DCCP, tmp) == 0 ? 0 : -1;
 664 }
 665
 666 static struct dst_entry* dccp_v4_route_skb(struct sock *sk,
 667                                            struct sk_buff *skb)
 668 {
 669         struct rtable *rt;
 670         struct flowi fl = { .oif = ((struct rtable *)skb->dst)->rt_iif,
 671                             .nl_u = { .ip4_u =
 672                                       { .daddr = skb->nh.iph->saddr,
 673                                         .saddr = skb->nh.iph->daddr,
 674                                         .tos = RT_CONN_FLAGS(sk) } },
 675                             .proto = sk->sk_protocol,
 676                             .uli_u = { .ports =
 677                                        { .sport = dccp_hdr(skb)->dccph_dport,
 678                                          .dport = dccp_hdr(skb)->dccph_sport }
 679                                      }
 680                           };
 681
 682         if (ip_route_output_flow(&rt, &fl, sk, 0)) {
 683                 IP_INC_STATS_BH(IPSTATS_MIB_OUTNOROUTES);
 684                 return NULL;
 685         }
 686
 687         return &rt->u.dst;
 688 }
 689
 690 static void dccp_v4_ctl_send_reset(struct sk_buff *rxskb)
 691 {
 692         int err;
 693         struct dccp_hdr *rxdh = dccp_hdr(rxskb), *dh;
 694         const int dccp_hdr_reset_len = sizeof(struct dccp_hdr) +
 695                                        sizeof(struct dccp_hdr_ext) +
 696                                        sizeof(struct dccp_hdr_reset);
 697         struct sk_buff *skb;
 698         struct dst_entry *dst;
 699         u64 seqno;
 700
 701         /* Never send a reset in response to a reset. */
 702         if (rxdh->dccph_type == DCCP_PKT_RESET)
 703                 return;
 704
 705         if (((struct rtable *)rxskb->dst)->rt_type != RTN_LOCAL)
 706                 return;
 707
 708         dst = dccp_v4_route_skb(dccp_v4_ctl_socket->sk, rxskb);
 709         if (dst == NULL)
 710                 return;
 711
 712         skb = alloc_skb(dccp_v4_ctl_socket->sk->sk_prot->max_header,
 713                         GFP_ATOMIC);
 714         if (skb == NULL)
 715                 goto out;
 716
 717         /* Reserve space for headers. */
 718         skb_reserve(skb, dccp_v4_ctl_socket->sk->sk_prot->max_header);
 719         skb->dst = dst_clone(dst);
 720
 721         skb->h.raw = skb_push(skb, dccp_hdr_reset_len);
 722         dh = dccp_hdr(skb);
 723         memset(dh, 0, dccp_hdr_reset_len);
 724
 725         /* Build DCCP header and checksum it. */
 726         dh->dccph_type     = DCCP_PKT_RESET;
 727         dh->dccph_sport    = rxdh->dccph_dport;
 728         dh->dccph_dport    = rxdh->dccph_sport;
 729         dh->dccph_doff     = dccp_hdr_reset_len / 4;
 730         dh->dccph_x        = 1;
 731         dccp_hdr_reset(skb)->dccph_reset_code =
 732                                 DCCP_SKB_CB(rxskb)->dccpd_reset_code;
 733
 734         /* See "8.3.1. Abnormal Termination" in draft-ietf-dccp-spec-11 */
 735         seqno = 0;
 736         if (DCCP_SKB_CB(rxskb)->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
 737                 dccp_set_seqno(&seqno, DCCP_SKB_CB(rxskb)->dccpd_ack_seq + 1);
 738
 739         dccp_hdr_set_seq(dh, seqno);
 740         dccp_hdr_set_ack(dccp_hdr_ack_bits(skb),
 741                          DCCP_SKB_CB(rxskb)->dccpd_seq);
 742
 743         dh->dccph_checksum = dccp_v4_checksum(skb, rxskb->nh.iph->saddr,
 744                                               rxskb->nh.iph->daddr);
 745
 746         bh_lock_sock(dccp_v4_ctl_socket->sk);
 747         err = ip_build_and_send_pkt(skb, dccp_v4_ctl_socket->sk,
 748                                     rxskb->nh.iph->daddr,
 749                                     rxskb->nh.iph->saddr, NULL);
 750         bh_unlock_sock(dccp_v4_ctl_socket->sk);
 751
 752         if (err == NET_XMIT_CN || err == 0) {
 753                 DCCP_INC_STATS_BH(DCCP_MIB_OUTSEGS);
 754                 DCCP_INC_STATS_BH(DCCP_MIB_OUTRSTS);
 755         }
 756 out:
 757          dst_release(dst);
 758 }
 759
 760 int dccp_v4_do_rcv(struct sock *sk, struct sk_buff *skb)
 761 {
 762         struct dccp_hdr *dh = dccp_hdr(skb);
 763
 764         if (sk->sk_state == DCCP_OPEN) { /* Fast path */
 765                 if (dccp_rcv_established(sk, skb, dh, skb->len))
 766                         goto reset;
 767                 return 0;
 768         }
 769
 770         /*
 771          *  Step 3: Process LISTEN state
 772          *     If S.state == LISTEN,
 773          *        If P.type == Request or P contains a valid Init Cookie
 774          *              option,
 775          *           * Must scan the packet's options to check for an Init
 776          *              Cookie.  Only the Init Cookie is processed here,
 777          *              however; other options are processed in Step 8.  This
 778          *              scan need only be performed if the endpoint uses Init
 779          *              Cookies *
 780          *           * Generate a new socket and switch to that socket *
 781          *           Set S := new socket for this port pair
 782          *           S.state = RESPOND
 783          *           Choose S.ISS (initial seqno) or set from Init Cookie
 784          *           Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init Cookie
 785          *           Continue with S.state == RESPOND
 786          *           * A Response packet will be generated in Step 11 *
 787          *        Otherwise,
 788          *           Generate Reset(No Connection) unless P.type == Reset
 789          *           Drop packet and return
 790          *
 791          * NOTE: the check for the packet types is done in
 792          *       dccp_rcv_state_process
 793          */
 794         if (sk->sk_state == DCCP_LISTEN) {
 795                 struct sock *nsk = dccp_v4_hnd_req(sk, skb);
 796
 797                 if (nsk == NULL)
 798                         goto discard;
 799
 800                 if (nsk != sk) {
 801                         if (dccp_child_process(sk, nsk, skb))
 802                                 goto reset;
 803                         return 0;
 804                 }
 805         }
 806
 807         if (dccp_rcv_state_process(sk, skb, dh, skb->len))
 808                 goto reset;
 809         return 0;
 810
 811 reset:
 812         dccp_v4_ctl_send_reset(skb);
 813 discard:
 814         kfree_skb(skb);
 815         return 0;
 816 }
 817
 818 EXPORT_SYMBOL_GPL(dccp_v4_do_rcv);
 819
 820 int dccp_invalid_packet(struct sk_buff *skb)
 821 {
 822         const struct dccp_hdr *dh;
 823
 824         if (skb->pkt_type != PACKET_HOST)
 825                 return 1;
 826
 827         if (!pskb_may_pull(skb, sizeof(struct dccp_hdr))) {
 828                 LIMIT_NETDEBUG(KERN_WARNING "DCCP: pskb_may_pull failed\n");
 829                 return 1;
 830         }
 831
 832         dh = dccp_hdr(skb);
 833
 834         /* If the packet type is not understood, drop packet and return */
 835         if (dh->dccph_type >= DCCP_PKT_INVALID) {
 836                 LIMIT_NETDEBUG(KERN_WARNING "DCCP: invalid packet type\n");
 837                 return 1;
 838         }
 839
 840         /*
 841          * If P.Data Offset is too small for packet type, or too large for
 842          * packet, drop packet and return
 843          */
 844         if (dh->dccph_doff < dccp_hdr_len(skb) / sizeof(u32)) {
 845                 LIMIT_NETDEBUG(KERN_WARNING "DCCP: P.Data Offset(%u) "
 846                                             "too small 1\n",
 847                                dh->dccph_doff);
 848                 return 1;
 849         }
 850
 851         if (!pskb_may_pull(skb, dh->dccph_doff * sizeof(u32))) {
 852                 LIMIT_NETDEBUG(KERN_WARNING "DCCP: P.Data Offset(%u) "
 853                                             "too small 2\n",
 854                                dh->dccph_doff);
 855                 return 1;
 856         }
 857
 858         dh = dccp_hdr(skb);
 859
 860         /*
 861          * If P.type is not Data, Ack, or DataAck and P.X == 0 (the packet
 862          * has short sequence numbers), drop packet and return
 863          */
 864         if (dh->dccph_x == 0 &&
 865             dh->dccph_type != DCCP_PKT_DATA &&
 866             dh->dccph_type != DCCP_PKT_ACK &&
 867             dh->dccph_type != DCCP_PKT_DATAACK) {
 868                 LIMIT_NETDEBUG(KERN_WARNING "DCCP: P.type (%s) not Data, Ack "
 869                                             "nor DataAck and P.X == 0\n",
 870                                dccp_packet_name(dh->dccph_type));
 871                 return 1;
 872         }
 873
 874         return 0;
 875 }
 876
 877 EXPORT_SYMBOL_GPL(dccp_invalid_packet);
 878
 879 /* this is called when real data arrives */
 880 static int dccp_v4_rcv(struct sk_buff *skb)
 881 {
 882         const struct dccp_hdr *dh;
 883         struct sock *sk;
 884
 885         /* Step 1: Check header basics: */
 886
 887         if (dccp_invalid_packet(skb))
 888                 goto discard_it;
 889
 890         /* If the header checksum is incorrect, drop packet and return */
 891         if (dccp_v4_verify_checksum(skb, skb->nh.iph->saddr,
 892                                     skb->nh.iph->daddr) < 0) {
 893                 LIMIT_NETDEBUG(KERN_WARNING "%s: incorrect header checksum\n",
 894                                __FUNCTION__);
 895                 goto discard_it;
 896         }
 897
 898         dh = dccp_hdr(skb);
 899
 900         DCCP_SKB_CB(skb)->dccpd_seq  = dccp_hdr_seq(skb);
 901         DCCP_SKB_CB(skb)->dccpd_type = dh->dccph_type;
 902
 903         dccp_pr_debug("%8.8s "
 904                       "src=%u.%u.%u.%u@%-5d "
 905                       "dst=%u.%u.%u.%u@%-5d seq=%llu",
 906                       dccp_packet_name(dh->dccph_type),
 907                       NIPQUAD(skb->nh.iph->saddr), ntohs(dh->dccph_sport),
 908                       NIPQUAD(skb->nh.iph->daddr), ntohs(dh->dccph_dport),
 909                       (unsigned long long) DCCP_SKB_CB(skb)->dccpd_seq);
 910
 911         if (dccp_packet_without_ack(skb)) {
 912                 DCCP_SKB_CB(skb)->dccpd_ack_seq = DCCP_PKT_WITHOUT_ACK_SEQ;
 913                 dccp_pr_debug_cat("\n");
 914         } else {
 915                 DCCP_SKB_CB(skb)->dccpd_ack_seq = dccp_hdr_ack_seq(skb);
 916                 dccp_pr_debug_cat(", ack=%llu\n",
 917                                   (unsigned long long)
 918                                   DCCP_SKB_CB(skb)->dccpd_ack_seq);
 919         }
 920
 921         /* Step 2:
 922          *      Look up flow ID in table and get corresponding socket */
 923         sk = __inet_lookup(&dccp_hashinfo,
 924                            skb->nh.iph->saddr, dh->dccph_sport,
 925                            skb->nh.iph->daddr, ntohs(dh->dccph_dport),
 926                            inet_iif(skb));
 927
 928         /*
 929          * Step 2:
 930          *      If no socket ...
 931          *              Generate Reset(No Connection) unless P.type == Reset
 932          *              Drop packet and return
 933          */
 934         if (sk == NULL) {
 935                 dccp_pr_debug("failed to look up flow ID in table and "
 936                               "get corresponding socket\n");
 937                 goto no_dccp_socket;
 938         }
 939
 940         /*
 941          * Step 2:
 942          *      ... or S.state == TIMEWAIT,
 943          *              Generate Reset(No Connection) unless P.type == Reset
 944          *              Drop packet and return
 945          */
 946
 947         if (sk->sk_state == DCCP_TIME_WAIT) {
 948                 dccp_pr_debug("sk->sk_state == DCCP_TIME_WAIT: "
 949                               "do_time_wait\n");
 950                 goto do_time_wait;
 951         }
 952
 953         if (!xfrm4_policy_check(sk, XFRM_POLICY_IN, skb))
 954                 goto discard_and_relse;
 955         nf_reset(skb);
 956
 957         return sk_receive_skb(sk, skb);
 958
 959 no_dccp_socket:
 960         if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb))
 961                 goto discard_it;
 962         /*
 963          * Step 2:
 964          *              Generate Reset(No Connection) unless P.type == Reset
 965          *              Drop packet and return
 966          */
 967         if (dh->dccph_type != DCCP_PKT_RESET) {
 968                 DCCP_SKB_CB(skb)->dccpd_reset_code =
 969                                         DCCP_RESET_CODE_NO_CONNECTION;
 970                 dccp_v4_ctl_send_reset(skb);
 971         }
 972
 973 discard_it:
 974         /* Discard frame. */
 975         kfree_skb(skb);
 976         return 0;
 977
 978 discard_and_relse:
 979         sock_put(sk);
 980         goto discard_it;
 981
 982 do_time_wait:
 983         inet_twsk_put((struct inet_timewait_sock *)sk);
 984         goto no_dccp_socket;
 985 }
 986
 987 static struct inet_connection_sock_af_ops dccp_ipv4_af_ops = {
 988         .queue_xmit        = ip_queue_xmit,
 989         .send_check        = dccp_v4_send_check,
 990         .rebuild_header    = inet_sk_rebuild_header,
 991         .conn_request      = dccp_v4_conn_request,
 992         .syn_recv_sock     = dccp_v4_request_recv_sock,
 993         .net_header_len    = sizeof(struct iphdr),
 994         .setsockopt        = ip_setsockopt,
 995         .getsockopt        = ip_getsockopt,
 996         .addr2sockaddr     = inet_csk_addr2sockaddr,
 997         .sockaddr_len      = sizeof(struct sockaddr_in),
 998 #ifdef CONFIG_COMPAT
 999         .compat_setsockopt = compat_ip_setsockopt,
1000         .compat_getsockopt = compat_ip_getsockopt,
1001 #endif
1002 };
1003
1004 static int dccp_v4_init_sock(struct sock *sk)
1005 {
1006         static __u8 dccp_v4_ctl_sock_initialized;
1007         int err = dccp_init_sock(sk, dccp_v4_ctl_sock_initialized);
1008
1009         if (err == 0) {
1010                 if (unlikely(!dccp_v4_ctl_sock_initialized))
1011                         dccp_v4_ctl_sock_initialized = 1;
1012                 inet_csk(sk)->icsk_af_ops = &dccp_ipv4_af_ops;
1013         }
1014
1015         return err;
1016 }
1017
1018 static void dccp_v4_reqsk_destructor(struct request_sock *req)
1019 {
1020         kfree(inet_rsk(req)->opt);
1021 }
1022
1023 static struct request_sock_ops dccp_request_sock_ops = {
1024         .family         = PF_INET,
1025         .obj_size       = sizeof(struct dccp_request_sock),
1026         .rtx_syn_ack    = dccp_v4_send_response,
1027         .send_ack       = dccp_v4_reqsk_send_ack,
1028         .destructor     = dccp_v4_reqsk_destructor,
1029         .send_reset     = dccp_v4_ctl_send_reset,
1030 };
1031
1032 static struct timewait_sock_ops dccp_timewait_sock_ops = {
1033         .twsk_obj_size  = sizeof(struct inet_timewait_sock),
1034 };
1035
1036 static struct proto dccp_v4_prot = {
1037         .name                   = "DCCP",
1038         .owner                  = THIS_MODULE,
1039         .close                  = dccp_close,
1040         .connect                = dccp_v4_connect,
1041         .disconnect             = dccp_disconnect,
1042         .ioctl                  = dccp_ioctl,
1043         .init                   = dccp_v4_init_sock,
1044         .setsockopt             = dccp_setsockopt,
1045         .getsockopt             = dccp_getsockopt,
1046         .sendmsg                = dccp_sendmsg,
1047         .recvmsg                = dccp_recvmsg,
1048         .backlog_rcv            = dccp_v4_do_rcv,
1049         .hash                   = dccp_hash,
1050         .unhash                 = dccp_unhash,
1051         .accept                 = inet_csk_accept,
1052         .get_port               = dccp_v4_get_port,
1053         .shutdown               = dccp_shutdown,
1054         .destroy                = dccp_destroy_sock,
1055         .orphan_count           = &dccp_orphan_count,
1056         .max_header             = MAX_DCCP_HEADER,
1057         .obj_size               = sizeof(struct dccp_sock),
1058         .rsk_prot               = &dccp_request_sock_ops,
1059         .twsk_prot              = &dccp_timewait_sock_ops,
1060 #ifdef CONFIG_COMPAT
1061         .compat_setsockopt      = compat_dccp_setsockopt,
1062         .compat_getsockopt      = compat_dccp_getsockopt,
1063 #endif
1064 };
1065
1066 static struct net_protocol dccp_v4_protocol = {
1067         .handler        = dccp_v4_rcv,
1068         .err_handler    = dccp_v4_err,
1069         .no_policy      = 1,
1070 };
1071
1072 static const struct proto_ops inet_dccp_ops = {
1073         .family            = PF_INET,
1074         .owner             = THIS_MODULE,
1075         .release           = inet_release,
1076         .bind              = inet_bind,
1077         .connect           = inet_stream_connect,
1078         .socketpair        = sock_no_socketpair,
1079         .accept            = inet_accept,
1080         .getname           = inet_getname,
1081         /* FIXME: work on tcp_poll to rename it to inet_csk_poll */
1082         .poll              = dccp_poll,
1083         .ioctl             = inet_ioctl,
1084         /* FIXME: work on inet_listen to rename it to sock_common_listen */
1085         .listen            = inet_dccp_listen,
1086         .shutdown          = inet_shutdown,
1087         .setsockopt        = sock_common_setsockopt,
1088         .getsockopt        = sock_common_getsockopt,
1089         .sendmsg           = inet_sendmsg,
1090         .recvmsg           = sock_common_recvmsg,
1091         .mmap              = sock_no_mmap,
1092         .sendpage          = sock_no_sendpage,
1093 #ifdef CONFIG_COMPAT
1094         .compat_setsockopt = compat_sock_common_setsockopt,
1095         .compat_getsockopt = compat_sock_common_getsockopt,
1096 #endif
1097 };
1098
1099 static struct inet_protosw dccp_v4_protosw = {
1100         .type           = SOCK_DCCP,
1101         .protocol       = IPPROTO_DCCP,
1102         .prot           = &dccp_v4_prot,
1103         .ops            = &inet_dccp_ops,
1104         .capability     = -1,
1105         .no_check       = 0,
1106         .flags          = INET_PROTOSW_ICSK,
1107 };
1108
1109 static int __init dccp_v4_init(void)
1110 {
1111         int err = proto_register(&dccp_v4_prot, 1);
1112
1113         if (err != 0)
1114                 goto out;
1115
1116         err = inet_add_protocol(&dccp_v4_protocol, IPPROTO_DCCP);
1117         if (err != 0)
1118                 goto out_proto_unregister;
1119
1120         inet_register_protosw(&dccp_v4_protosw);
1121
1122         err = inet_csk_ctl_sock_create(&dccp_v4_ctl_socket, PF_INET,
1123                                        SOCK_DCCP, IPPROTO_DCCP);
1124         if (err)
1125                 goto out_unregister_protosw;
1126 out:
1127         return err;
1128 out_unregister_protosw:
1129         inet_unregister_protosw(&dccp_v4_protosw);
1130         inet_del_protocol(&dccp_v4_protocol, IPPROTO_DCCP);
1131 out_proto_unregister:
1132         proto_unregister(&dccp_v4_prot);
1133         goto out;
1134 }
1135
1136 static void __exit dccp_v4_exit(void)
1137 {
1138         inet_unregister_protosw(&dccp_v4_protosw);
1139         inet_del_protocol(&dccp_v4_protocol, IPPROTO_DCCP);
1140         proto_unregister(&dccp_v4_prot);
1141 }
1142
1143 module_init(dccp_v4_init);
1144 module_exit(dccp_v4_exit);
1145
1146 /*
1147  * __stringify doesn't likes enums, so use SOCK_DCCP (6) and IPPROTO_DCCP (33)
1148  * values directly, Also cover the case where the protocol is not specified,
1149  * i.e. net-pf-PF_INET-proto-0-type-SOCK_DCCP
1150  */
1151 MODULE_ALIAS("net-pf-" __stringify(PF_INET) "-proto-33-type-6");
1152 MODULE_ALIAS("net-pf-" __stringify(PF_INET) "-proto-0-type-6");
1153 MODULE_LICENSE("GPL");
1154 MODULE_AUTHOR("Arnaldo Carvalho de Melo <acme@mandriva.com>");
1155 MODULE_DESCRIPTION("DCCP - Datagram Congestion Controlled Protocol");