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/slab.h>
  16 #include <linux/module.h>
  17 #include <linux/skbuff.h>
  18 #include <linux/random.h>
  19
  20 #include <net/icmp.h>
  21 #include <net/inet_common.h>
  22 #include <net/inet_hashtables.h>
  23 #include <net/inet_sock.h>
  24 #include <net/protocol.h>
  25 #include <net/sock.h>
  26 #include <net/timewait_sock.h>
  27 #include <net/tcp_states.h>
  28 #include <net/xfrm.h>
  29 #include <net/secure_seq.h>
  30
  31 #include "ackvec.h"
  32 #include "ccid.h"
  33 #include "dccp.h"
  34 #include "feat.h"
  35
  36 /*
  37  * The per-net dccp.v4_ctl_sk socket is used for responding to
  38  * the Out-of-the-blue (OOTB) packets. A control sock will be created
  39  * for this socket at the initialization time.
  40  */
  41
  42 int dccp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
  43 {
  44         const struct sockaddr_in *usin = (struct sockaddr_in *)uaddr;
  45         struct inet_sock *inet = inet_sk(sk);
  46         struct dccp_sock *dp = dccp_sk(sk);
  47         __be16 orig_sport, orig_dport;
  48         __be32 daddr, nexthop;
  49         struct flowi4 *fl4;
  50         struct rtable *rt;
  51         int err;
  52         struct ip_options_rcu *inet_opt;
  53
  54         dp->dccps_role = DCCP_ROLE_CLIENT;
  55
  56         if (addr_len < sizeof(struct sockaddr_in))
  57                 return -EINVAL;
  58
  59         if (usin->sin_family != AF_INET)
  60                 return -EAFNOSUPPORT;
  61
  62         nexthop = daddr = usin->sin_addr.s_addr;
  63
  64         inet_opt = rcu_dereference_protected(inet->inet_opt,
  65                                              lockdep_sock_is_held(sk));
  66         if (inet_opt != NULL && inet_opt->opt.srr) {
  67                 if (daddr == 0)
  68                         return -EINVAL;
  69                 nexthop = inet_opt->opt.faddr;
  70         }
  71
  72         orig_sport = inet->inet_sport;
  73         orig_dport = usin->sin_port;
  74         fl4 = &inet->cork.fl.u.ip4;
  75         rt = ip_route_connect(fl4, nexthop, inet->inet_saddr,
  76                               RT_CONN_FLAGS(sk), sk->sk_bound_dev_if,
  77                               IPPROTO_DCCP,
  78                               orig_sport, orig_dport, sk);
  79         if (IS_ERR(rt))
  80                 return PTR_ERR(rt);
  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->opt.srr)
  88                 daddr = fl4->daddr;
  89
  90         if (inet->inet_saddr == 0)
  91                 inet->inet_saddr = fl4->saddr;
  92         sk_rcv_saddr_set(sk, inet->inet_saddr);
  93         inet->inet_dport = usin->sin_port;
  94         sk_daddr_set(sk, daddr);
  95
  96         inet_csk(sk)->icsk_ext_hdr_len = 0;
  97         if (inet_opt)
  98                 inet_csk(sk)->icsk_ext_hdr_len = inet_opt->opt.optlen;
  99         /*
 100          * Socket identity is still unknown (sport may be zero).
 101          * However we set state to DCCP_REQUESTING and not releasing socket
 102          * lock select source port, enter ourselves into the hash tables and
 103          * complete initialization after this.
 104          */
 105         dccp_set_state(sk, DCCP_REQUESTING);
 106         err = inet_hash_connect(&dccp_death_row, sk);
 107         if (err != 0)
 108                 goto failure;
 109
 110         rt = ip_route_newports(fl4, rt, orig_sport, orig_dport,
 111                                inet->inet_sport, inet->inet_dport, sk);
 112         if (IS_ERR(rt)) {
 113                 err = PTR_ERR(rt);
 114                 rt = NULL;
 115                 goto failure;
 116         }
 117         /* OK, now commit destination to socket.  */
 118         sk_setup_caps(sk, &rt->dst);
 119
 120         dp->dccps_iss = secure_dccp_sequence_number(inet->inet_saddr,
 121                                                     inet->inet_daddr,
 122                                                     inet->inet_sport,
 123                                                     inet->inet_dport);
 124         inet->inet_id = dp->dccps_iss ^ jiffies;
 125
 126         err = dccp_connect(sk);
 127         rt = NULL;
 128         if (err != 0)
 129                 goto failure;
 130 out:
 131         return err;
 132 failure:
 133         /*
 134          * This unhashes the socket and releases the local port, if necessary.
 135          */
 136         dccp_set_state(sk, DCCP_CLOSED);
 137         ip_rt_put(rt);
 138         sk->sk_route_caps = 0;
 139         inet->inet_dport = 0;
 140         goto out;
 141 }
 142 EXPORT_SYMBOL_GPL(dccp_v4_connect);
 143
 144 /*
 145  * This routine does path mtu discovery as defined in RFC1191.
 146  */
 147 static inline void dccp_do_pmtu_discovery(struct sock *sk,
 148                                           const struct iphdr *iph,
 149                                           u32 mtu)
 150 {
 151         struct dst_entry *dst;
 152         const struct inet_sock *inet = inet_sk(sk);
 153         const struct dccp_sock *dp = dccp_sk(sk);
 154
 155         /* We are not interested in DCCP_LISTEN and request_socks (RESPONSEs
 156          * send out by Linux are always < 576bytes so they should go through
 157          * unfragmented).
 158          */
 159         if (sk->sk_state == DCCP_LISTEN)
 160                 return;
 161
 162         dst = inet_csk_update_pmtu(sk, mtu);
 163         if (!dst)
 164                 return;
 165
 166         /* Something is about to be wrong... Remember soft error
 167          * for the case, if this connection will not able to recover.
 168          */
 169         if (mtu < dst_mtu(dst) && ip_dont_fragment(sk, dst))
 170                 sk->sk_err_soft = EMSGSIZE;
 171
 172         mtu = dst_mtu(dst);
 173
 174         if (inet->pmtudisc != IP_PMTUDISC_DONT &&
 175             ip_sk_accept_pmtu(sk) &&
 176             inet_csk(sk)->icsk_pmtu_cookie > mtu) {
 177                 dccp_sync_mss(sk, mtu);
 178
 179                 /*
 180                  * From RFC 4340, sec. 14.1:
 181                  *
 182                  *      DCCP-Sync packets are the best choice for upward
 183                  *      probing, since DCCP-Sync probes do not risk application
 184                  *      data loss.
 185                  */
 186                 dccp_send_sync(sk, dp->dccps_gsr, DCCP_PKT_SYNC);
 187         } /* else let the usual retransmit timer handle it */
 188 }
 189
 190 static void dccp_do_redirect(struct sk_buff *skb, struct sock *sk)
 191 {
 192         struct dst_entry *dst = __sk_dst_check(sk, 0);
 193
 194         if (dst)
 195                 dst->ops->redirect(dst, sk, skb);
 196 }
 197
 198 void dccp_req_err(struct sock *sk, u64 seq)
 199         {
 200         struct request_sock *req = inet_reqsk(sk);
 201         struct net *net = sock_net(sk);
 202
 203         /*
 204          * ICMPs are not backlogged, hence we cannot get an established
 205          * socket here.
 206          */
 207         if (!between48(seq, dccp_rsk(req)->dreq_iss, dccp_rsk(req)->dreq_gss)) {
 208                 __NET_INC_STATS(net, LINUX_MIB_OUTOFWINDOWICMPS);
 209         } else {
 210                 /*
 211                  * Still in RESPOND, just remove it silently.
 212                  * There is no good way to pass the error to the newly
 213                  * created socket, and POSIX does not want network
 214                  * errors returned from accept().
 215                  */
 216                 inet_csk_reqsk_queue_drop(req->rsk_listener, req);
 217         }
 218         reqsk_put(req);
 219 }
 220 EXPORT_SYMBOL(dccp_req_err);
 221
 222 /*
 223  * This routine is called by the ICMP module when it gets some sort of error
 224  * condition. If err < 0 then the socket should be closed and the error
 225  * returned to the user. If err > 0 it's just the icmp type << 8 | icmp code.
 226  * After adjustment header points to the first 8 bytes of the tcp header. We
 227  * need to find the appropriate port.
 228  *
 229  * The locking strategy used here is very "optimistic". When someone else
 230  * accesses the socket the ICMP is just dropped and for some paths there is no
 231  * check at all. A more general error queue to queue errors for later handling
 232  * is probably better.
 233  */
 234 static void dccp_v4_err(struct sk_buff *skb, u32 info)
 235 {
 236         const struct iphdr *iph = (struct iphdr *)skb->data;
 237         const u8 offset = iph->ihl << 2;
 238         const struct dccp_hdr *dh = (struct dccp_hdr *)(skb->data + offset);
 239         struct dccp_sock *dp;
 240         struct inet_sock *inet;
 241         const int type = icmp_hdr(skb)->type;
 242         const int code = icmp_hdr(skb)->code;
 243         struct sock *sk;
 244         __u64 seq;
 245         int err;
 246         struct net *net = dev_net(skb->dev);
 247
 248         if (skb->len < offset + sizeof(*dh) ||
 249             skb->len < offset + __dccp_basic_hdr_len(dh)) {
 250                 __ICMP_INC_STATS(net, ICMP_MIB_INERRORS);
 251                 return;
 252         }
 253
 254         sk = __inet_lookup_established(net, &dccp_hashinfo,
 255                                        iph->daddr, dh->dccph_dport,
 256                                        iph->saddr, ntohs(dh->dccph_sport),
 257                                        inet_iif(skb));
 258         if (!sk) {
 259                 __ICMP_INC_STATS(net, ICMP_MIB_INERRORS);
 260                 return;
 261         }
 262
 263         if (sk->sk_state == DCCP_TIME_WAIT) {
 264                 inet_twsk_put(inet_twsk(sk));
 265                 return;
 266         }
 267         seq = dccp_hdr_seq(dh);
 268         if (sk->sk_state == DCCP_NEW_SYN_RECV)
 269                 return dccp_req_err(sk, seq);
 270
 271         bh_lock_sock(sk);
 272         /* If too many ICMPs get dropped on busy
 273          * servers this needs to be solved differently.
 274          */
 275         if (sock_owned_by_user(sk))
 276                 __NET_INC_STATS(net, LINUX_MIB_LOCKDROPPEDICMPS);
 277
 278         if (sk->sk_state == DCCP_CLOSED)
 279                 goto out;
 280
 281         dp = dccp_sk(sk);
 282         if ((1 << sk->sk_state) & ~(DCCPF_REQUESTING | DCCPF_LISTEN) &&
 283             !between48(seq, dp->dccps_awl, dp->dccps_awh)) {
 284                 __NET_INC_STATS(net, LINUX_MIB_OUTOFWINDOWICMPS);
 285                 goto out;
 286         }
 287
 288         switch (type) {
 289         case ICMP_REDIRECT:
 290                 dccp_do_redirect(skb, sk);
 291                 goto out;
 292         case ICMP_SOURCE_QUENCH:
 293                 /* Just silently ignore these. */
 294                 goto out;
 295         case ICMP_PARAMETERPROB:
 296                 err = EPROTO;
 297                 break;
 298         case ICMP_DEST_UNREACH:
 299                 if (code > NR_ICMP_UNREACH)
 300                         goto out;
 301
 302                 if (code == ICMP_FRAG_NEEDED) { /* PMTU discovery (RFC1191) */
 303                         if (!sock_owned_by_user(sk))
 304                                 dccp_do_pmtu_discovery(sk, iph, info);
 305                         goto out;
 306                 }
 307
 308                 err = icmp_err_convert[code].errno;
 309                 break;
 310         case ICMP_TIME_EXCEEDED:
 311                 err = EHOSTUNREACH;
 312                 break;
 313         default:
 314                 goto out;
 315         }
 316
 317         switch (sk->sk_state) {
 318         case DCCP_REQUESTING:
 319         case DCCP_RESPOND:
 320                 if (!sock_owned_by_user(sk)) {
 321                         __DCCP_INC_STATS(DCCP_MIB_ATTEMPTFAILS);
 322                         sk->sk_err = err;
 323
 324                         sk->sk_error_report(sk);
 325
 326                         dccp_done(sk);
 327                 } else
 328                         sk->sk_err_soft = err;
 329                 goto out;
 330         }
 331
 332         /* If we've already connected we will keep trying
 333          * until we time out, or the user gives up.
 334          *
 335          * rfc1122 4.2.3.9 allows to consider as hard errors
 336          * only PROTO_UNREACH and PORT_UNREACH (well, FRAG_FAILED too,
 337          * but it is obsoleted by pmtu discovery).
 338          *
 339          * Note, that in modern internet, where routing is unreliable
 340          * and in each dark corner broken firewalls sit, sending random
 341          * errors ordered by their masters even this two messages finally lose
 342          * their original sense (even Linux sends invalid PORT_UNREACHs)
 343          *
 344          * Now we are in compliance with RFCs.
 345          *                                                      --ANK (980905)
 346          */
 347
 348         inet = inet_sk(sk);
 349         if (!sock_owned_by_user(sk) && inet->recverr) {
 350                 sk->sk_err = err;
 351                 sk->sk_error_report(sk);
 352         } else /* Only an error on timeout */
 353                 sk->sk_err_soft = err;
 354 out:
 355         bh_unlock_sock(sk);
 356         sock_put(sk);
 357 }
 358
 359 static inline __sum16 dccp_v4_csum_finish(struct sk_buff *skb,
 360                                       __be32 src, __be32 dst)
 361 {
 362         return csum_tcpudp_magic(src, dst, skb->len, IPPROTO_DCCP, skb->csum);
 363 }
 364
 365 void dccp_v4_send_check(struct sock *sk, struct sk_buff *skb)
 366 {
 367         const struct inet_sock *inet = inet_sk(sk);
 368         struct dccp_hdr *dh = dccp_hdr(skb);
 369
 370         dccp_csum_outgoing(skb);
 371         dh->dccph_checksum = dccp_v4_csum_finish(skb,
 372                                                  inet->inet_saddr,
 373                                                  inet->inet_daddr);
 374 }
 375 EXPORT_SYMBOL_GPL(dccp_v4_send_check);
 376
 377 static inline u64 dccp_v4_init_sequence(const struct sk_buff *skb)
 378 {
 379         return secure_dccp_sequence_number(ip_hdr(skb)->daddr,
 380                                            ip_hdr(skb)->saddr,
 381                                            dccp_hdr(skb)->dccph_dport,
 382                                            dccp_hdr(skb)->dccph_sport);
 383 }
 384
 385 /*
 386  * The three way handshake has completed - we got a valid ACK or DATAACK -
 387  * now create the new socket.
 388  *
 389  * This is the equivalent of TCP's tcp_v4_syn_recv_sock
 390  */
 391 struct sock *dccp_v4_request_recv_sock(const struct sock *sk,
 392                                        struct sk_buff *skb,
 393                                        struct request_sock *req,
 394                                        struct dst_entry *dst,
 395                                        struct request_sock *req_unhash,
 396                                        bool *own_req)
 397 {
 398         struct inet_request_sock *ireq;
 399         struct inet_sock *newinet;
 400         struct sock *newsk;
 401
 402         if (sk_acceptq_is_full(sk))
 403                 goto exit_overflow;
 404
 405         newsk = dccp_create_openreq_child(sk, req, skb);
 406         if (newsk == NULL)
 407                 goto exit_nonewsk;
 408
 409         newinet            = inet_sk(newsk);
 410         ireq               = inet_rsk(req);
 411         sk_daddr_set(newsk, ireq->ir_rmt_addr);
 412         sk_rcv_saddr_set(newsk, ireq->ir_loc_addr);
 413         newinet->inet_saddr     = ireq->ir_loc_addr;
 414         newinet->inet_opt       = ireq->opt;
 415         ireq->opt          = NULL;
 416         newinet->mc_index  = inet_iif(skb);
 417         newinet->mc_ttl    = ip_hdr(skb)->ttl;
 418         newinet->inet_id   = jiffies;
 419
 420         if (dst == NULL && (dst = inet_csk_route_child_sock(sk, newsk, req)) == NULL)
 421                 goto put_and_exit;
 422
 423         sk_setup_caps(newsk, dst);
 424
 425         dccp_sync_mss(newsk, dst_mtu(dst));
 426
 427         if (__inet_inherit_port(sk, newsk) < 0)
 428                 goto put_and_exit;
 429         *own_req = inet_ehash_nolisten(newsk, req_to_sk(req_unhash));
 430
 431         return newsk;
 432
 433 exit_overflow:
 434         __NET_INC_STATS(sock_net(sk), LINUX_MIB_LISTENOVERFLOWS);
 435 exit_nonewsk:
 436         dst_release(dst);
 437 exit:
 438         __NET_INC_STATS(sock_net(sk), LINUX_MIB_LISTENDROPS);
 439         return NULL;
 440 put_and_exit:
 441         inet_csk_prepare_forced_close(newsk);
 442         dccp_done(newsk);
 443         goto exit;
 444 }
 445 EXPORT_SYMBOL_GPL(dccp_v4_request_recv_sock);
 446
 447 static struct dst_entry* dccp_v4_route_skb(struct net *net, struct sock *sk,
 448                                            struct sk_buff *skb)
 449 {
 450         struct rtable *rt;
 451         const struct iphdr *iph = ip_hdr(skb);
 452         struct flowi4 fl4 = {
 453                 .flowi4_oif = inet_iif(skb),
 454                 .daddr = iph->saddr,
 455                 .saddr = iph->daddr,
 456                 .flowi4_tos = RT_CONN_FLAGS(sk),
 457                 .flowi4_proto = sk->sk_protocol,
 458                 .fl4_sport = dccp_hdr(skb)->dccph_dport,
 459                 .fl4_dport = dccp_hdr(skb)->dccph_sport,
 460         };
 461
 462         security_skb_classify_flow(skb, flowi4_to_flowi(&fl4));
 463         rt = ip_route_output_flow(net, &fl4, sk);
 464         if (IS_ERR(rt)) {
 465                 __IP_INC_STATS(net, IPSTATS_MIB_OUTNOROUTES);
 466                 return NULL;
 467         }
 468
 469         return &rt->dst;
 470 }
 471
 472 static int dccp_v4_send_response(const struct sock *sk, struct request_sock *req)
 473 {
 474         int err = -1;
 475         struct sk_buff *skb;
 476         struct dst_entry *dst;
 477         struct flowi4 fl4;
 478
 479         dst = inet_csk_route_req(sk, &fl4, req);
 480         if (dst == NULL)
 481                 goto out;
 482
 483         skb = dccp_make_response(sk, dst, req);
 484         if (skb != NULL) {
 485                 const struct inet_request_sock *ireq = inet_rsk(req);
 486                 struct dccp_hdr *dh = dccp_hdr(skb);
 487
 488                 dh->dccph_checksum = dccp_v4_csum_finish(skb, ireq->ir_loc_addr,
 489                                                               ireq->ir_rmt_addr);
 490                 err = ip_build_and_send_pkt(skb, sk, ireq->ir_loc_addr,
 491                                             ireq->ir_rmt_addr,
 492                                             ireq->opt);
 493                 err = net_xmit_eval(err);
 494         }
 495
 496 out:
 497         dst_release(dst);
 498         return err;
 499 }
 500
 501 static void dccp_v4_ctl_send_reset(const struct sock *sk, struct sk_buff *rxskb)
 502 {
 503         int err;
 504         const struct iphdr *rxiph;
 505         struct sk_buff *skb;
 506         struct dst_entry *dst;
 507         struct net *net = dev_net(skb_dst(rxskb)->dev);
 508         struct sock *ctl_sk = net->dccp.v4_ctl_sk;
 509
 510         /* Never send a reset in response to a reset. */
 511         if (dccp_hdr(rxskb)->dccph_type == DCCP_PKT_RESET)
 512                 return;
 513
 514         if (skb_rtable(rxskb)->rt_type != RTN_LOCAL)
 515                 return;
 516
 517         dst = dccp_v4_route_skb(net, ctl_sk, rxskb);
 518         if (dst == NULL)
 519                 return;
 520
 521         skb = dccp_ctl_make_reset(ctl_sk, rxskb);
 522         if (skb == NULL)
 523                 goto out;
 524
 525         rxiph = ip_hdr(rxskb);
 526         dccp_hdr(skb)->dccph_checksum = dccp_v4_csum_finish(skb, rxiph->saddr,
 527                                                                  rxiph->daddr);
 528         skb_dst_set(skb, dst_clone(dst));
 529
 530         bh_lock_sock(ctl_sk);
 531         err = ip_build_and_send_pkt(skb, ctl_sk,
 532                                     rxiph->daddr, rxiph->saddr, NULL);
 533         bh_unlock_sock(ctl_sk);
 534
 535         if (net_xmit_eval(err) == 0) {
 536                 DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
 537                 DCCP_INC_STATS(DCCP_MIB_OUTRSTS);
 538         }
 539 out:
 540          dst_release(dst);
 541 }
 542
 543 static void dccp_v4_reqsk_destructor(struct request_sock *req)
 544 {
 545         dccp_feat_list_purge(&dccp_rsk(req)->dreq_featneg);
 546         kfree(inet_rsk(req)->opt);
 547 }
 548
 549 void dccp_syn_ack_timeout(const struct request_sock *req)
 550 {
 551 }
 552 EXPORT_SYMBOL(dccp_syn_ack_timeout);
 553
 554 static struct request_sock_ops dccp_request_sock_ops __read_mostly = {
 555         .family         = PF_INET,
 556         .obj_size       = sizeof(struct dccp_request_sock),
 557         .rtx_syn_ack    = dccp_v4_send_response,
 558         .send_ack       = dccp_reqsk_send_ack,
 559         .destructor     = dccp_v4_reqsk_destructor,
 560         .send_reset     = dccp_v4_ctl_send_reset,
 561         .syn_ack_timeout = dccp_syn_ack_timeout,
 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 (skb_rtable(skb)->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
 574                 return 0;       /* discard, don't send a reset here */
 575
 576         if (dccp_bad_service_code(sk, service)) {
 577                 dcb->dccpd_reset_code = DCCP_RESET_CODE_BAD_SERVICE_CODE;
 578                 goto drop;
 579         }
 580         /*
 581          * TW buckets are converted to open requests without
 582          * limitations, they conserve resources and peer is
 583          * evidently real one.
 584          */
 585         dcb->dccpd_reset_code = DCCP_RESET_CODE_TOO_BUSY;
 586         if (inet_csk_reqsk_queue_is_full(sk))
 587                 goto drop;
 588
 589         /*
 590          * Accept backlog is full. If we have already queued enough
 591          * of warm entries in syn queue, drop request. It is better than
 592          * clogging syn queue with openreqs with exponentially increasing
 593          * timeout.
 594          */
 595         if (sk_acceptq_is_full(sk) && inet_csk_reqsk_queue_young(sk) > 1)
 596                 goto drop;
 597
 598         req = inet_reqsk_alloc(&dccp_request_sock_ops, sk, true);
 599         if (req == NULL)
 600                 goto drop;
 601
 602         if (dccp_reqsk_init(req, dccp_sk(sk), skb))
 603                 goto drop_and_free;
 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         sk_rcv_saddr_set(req_to_sk(req), ip_hdr(skb)->daddr);
 614         sk_daddr_set(req_to_sk(req), ip_hdr(skb)->saddr);
 615         ireq->ireq_family = AF_INET;
 616         ireq->ir_iif = sk->sk_bound_dev_if;
 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          * Setting S.SWL/S.SWH to is deferred to dccp_create_openreq_child().
 624          */
 625         dreq->dreq_isr     = dcb->dccpd_seq;
 626         dreq->dreq_gsr     = dreq->dreq_isr;
 627         dreq->dreq_iss     = dccp_v4_init_sequence(skb);
 628         dreq->dreq_gss     = dreq->dreq_iss;
 629         dreq->dreq_service = service;
 630
 631         if (dccp_v4_send_response(sk, req))
 632                 goto drop_and_free;
 633
 634         inet_csk_reqsk_queue_hash_add(sk, req, DCCP_TIMEOUT_INIT);
 635         return 0;
 636
 637 drop_and_free:
 638         reqsk_free(req);
 639 drop:
 640         __DCCP_INC_STATS(DCCP_MIB_ATTEMPTFAILS);
 641         return -1;
 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
 679         if (dccp_rcv_state_process(sk, skb, dh, skb->len))
 680                 goto reset;
 681         return 0;
 682
 683 reset:
 684         dccp_v4_ctl_send_reset(sk, skb);
 685         kfree_skb(skb);
 686         return 0;
 687 }
 688 EXPORT_SYMBOL_GPL(dccp_v4_do_rcv);
 689
 690 /**
 691  *      dccp_invalid_packet  -  check for malformed packets
 692  *      Implements RFC 4340, 8.5:  Step 1: Check header basics
 693  *      Packets that fail these checks are ignored and do not receive Resets.
 694  */
 695 int dccp_invalid_packet(struct sk_buff *skb)
 696 {
 697         const struct dccp_hdr *dh;
 698         unsigned int cscov;
 699
 700         if (skb->pkt_type != PACKET_HOST)
 701                 return 1;
 702
 703         /* If the packet is shorter than 12 bytes, drop packet and return */
 704         if (!pskb_may_pull(skb, sizeof(struct dccp_hdr))) {
 705                 DCCP_WARN("pskb_may_pull failed\n");
 706                 return 1;
 707         }
 708
 709         dh = dccp_hdr(skb);
 710
 711         /* If P.type is not understood, drop packet and return */
 712         if (dh->dccph_type >= DCCP_PKT_INVALID) {
 713                 DCCP_WARN("invalid packet type\n");
 714                 return 1;
 715         }
 716
 717         /*
 718          * If P.Data Offset is too small for packet type, drop packet and return
 719          */
 720         if (dh->dccph_doff < dccp_hdr_len(skb) / sizeof(u32)) {
 721                 DCCP_WARN("P.Data Offset(%u) too small\n", dh->dccph_doff);
 722                 return 1;
 723         }
 724         /*
 725          * If P.Data Offset is too too large for packet, drop packet and return
 726          */
 727         if (!pskb_may_pull(skb, dh->dccph_doff * sizeof(u32))) {
 728                 DCCP_WARN("P.Data Offset(%u) too large\n", dh->dccph_doff);
 729                 return 1;
 730         }
 731
 732         /*
 733          * If P.type is not Data, Ack, or DataAck and P.X == 0 (the packet
 734          * has short sequence numbers), drop packet and return
 735          */
 736         if ((dh->dccph_type < DCCP_PKT_DATA    ||
 737             dh->dccph_type > DCCP_PKT_DATAACK) && dh->dccph_x == 0)  {
 738                 DCCP_WARN("P.type (%s) not Data || [Data]Ack, while P.X == 0\n",
 739                           dccp_packet_name(dh->dccph_type));
 740                 return 1;
 741         }
 742
 743         /*
 744          * If P.CsCov is too large for the packet size, drop packet and return.
 745          * This must come _before_ checksumming (not as RFC 4340 suggests).
 746          */
 747         cscov = dccp_csum_coverage(skb);
 748         if (cscov > skb->len) {
 749                 DCCP_WARN("P.CsCov %u exceeds packet length %d\n",
 750                           dh->dccph_cscov, skb->len);
 751                 return 1;
 752         }
 753
 754         /* If header checksum is incorrect, drop packet and return.
 755          * (This step is completed in the AF-dependent functions.) */
 756         skb->csum = skb_checksum(skb, 0, cscov, 0);
 757
 758         return 0;
 759 }
 760 EXPORT_SYMBOL_GPL(dccp_invalid_packet);
 761
 762 /* this is called when real data arrives */
 763 static int dccp_v4_rcv(struct sk_buff *skb)
 764 {
 765         const struct dccp_hdr *dh;
 766         const struct iphdr *iph;
 767         bool refcounted;
 768         struct sock *sk;
 769         int min_cov;
 770
 771         /* Step 1: Check header basics */
 772
 773         if (dccp_invalid_packet(skb))
 774                 goto discard_it;
 775
 776         iph = ip_hdr(skb);
 777         /* Step 1: If header checksum is incorrect, drop packet and return */
 778         if (dccp_v4_csum_finish(skb, iph->saddr, iph->daddr)) {
 779                 DCCP_WARN("dropped packet with invalid checksum\n");
 780                 goto discard_it;
 781         }
 782
 783         dh = dccp_hdr(skb);
 784
 785         DCCP_SKB_CB(skb)->dccpd_seq  = dccp_hdr_seq(dh);
 786         DCCP_SKB_CB(skb)->dccpd_type = dh->dccph_type;
 787
 788         dccp_pr_debug("%8.8s src=%pI4@%-5d dst=%pI4@%-5d seq=%llu",
 789                       dccp_packet_name(dh->dccph_type),
 790                       &iph->saddr, ntohs(dh->dccph_sport),
 791                       &iph->daddr, ntohs(dh->dccph_dport),
 792                       (unsigned long long) DCCP_SKB_CB(skb)->dccpd_seq);
 793
 794         if (dccp_packet_without_ack(skb)) {
 795                 DCCP_SKB_CB(skb)->dccpd_ack_seq = DCCP_PKT_WITHOUT_ACK_SEQ;
 796                 dccp_pr_debug_cat("\n");
 797         } else {
 798                 DCCP_SKB_CB(skb)->dccpd_ack_seq = dccp_hdr_ack_seq(skb);
 799                 dccp_pr_debug_cat(", ack=%llu\n", (unsigned long long)
 800                                   DCCP_SKB_CB(skb)->dccpd_ack_seq);
 801         }
 802
 803 lookup:
 804         sk = __inet_lookup_skb(&dccp_hashinfo, skb, __dccp_hdr_len(dh),
 805                                dh->dccph_sport, dh->dccph_dport, &refcounted);
 806         if (!sk) {
 807                 dccp_pr_debug("failed to look up flow ID in table and "
 808                               "get corresponding socket\n");
 809                 goto no_dccp_socket;
 810         }
 811
 812         /*
 813          * Step 2:
 814          *      ... or S.state == TIMEWAIT,
 815          *              Generate Reset(No Connection) unless P.type == Reset
 816          *              Drop packet and return
 817          */
 818         if (sk->sk_state == DCCP_TIME_WAIT) {
 819                 dccp_pr_debug("sk->sk_state == DCCP_TIME_WAIT: do_time_wait\n");
 820                 inet_twsk_put(inet_twsk(sk));
 821                 goto no_dccp_socket;
 822         }
 823
 824         if (sk->sk_state == DCCP_NEW_SYN_RECV) {
 825                 struct request_sock *req = inet_reqsk(sk);
 826                 struct sock *nsk;
 827
 828                 sk = req->rsk_listener;
 829                 if (unlikely(sk->sk_state != DCCP_LISTEN)) {
 830                         inet_csk_reqsk_queue_drop_and_put(sk, req);
 831                         goto lookup;
 832                 }
 833                 sock_hold(sk);
 834                 refcounted = true;
 835                 nsk = dccp_check_req(sk, skb, req);
 836                 if (!nsk) {
 837                         reqsk_put(req);
 838                         goto discard_and_relse;
 839                 }
 840                 if (nsk == sk) {
 841                         reqsk_put(req);
 842                 } else if (dccp_child_process(sk, nsk, skb)) {
 843                         dccp_v4_ctl_send_reset(sk, skb);
 844                         goto discard_and_relse;
 845                 } else {
 846                         sock_put(sk);
 847                         return 0;
 848                 }
 849         }
 850         /*
 851          * RFC 4340, sec. 9.2.1: Minimum Checksum Coverage
 852          *      o if MinCsCov = 0, only packets with CsCov = 0 are accepted
 853          *      o if MinCsCov > 0, also accept packets with CsCov >= MinCsCov
 854          */
 855         min_cov = dccp_sk(sk)->dccps_pcrlen;
 856         if (dh->dccph_cscov && (min_cov == 0 || dh->dccph_cscov < min_cov))  {
 857                 dccp_pr_debug("Packet CsCov %d does not satisfy MinCsCov %d\n",
 858                               dh->dccph_cscov, min_cov);
 859                 /* FIXME: "Such packets SHOULD be reported using Data Dropped
 860                  *         options (Section 11.7) with Drop Code 0, Protocol
 861                  *         Constraints."                                     */
 862                 goto discard_and_relse;
 863         }
 864
 865         if (!xfrm4_policy_check(sk, XFRM_POLICY_IN, skb))
 866                 goto discard_and_relse;
 867         nf_reset(skb);
 868
 869         return sk_receive_skb(sk, skb, 1);
 870
 871 no_dccp_socket:
 872         if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb))
 873                 goto discard_it;
 874         /*
 875          * Step 2:
 876          *      If no socket ...
 877          *              Generate Reset(No Connection) unless P.type == Reset
 878          *              Drop packet and return
 879          */
 880         if (dh->dccph_type != DCCP_PKT_RESET) {
 881                 DCCP_SKB_CB(skb)->dccpd_reset_code =
 882                                         DCCP_RESET_CODE_NO_CONNECTION;
 883                 dccp_v4_ctl_send_reset(sk, skb);
 884         }
 885
 886 discard_it:
 887         kfree_skb(skb);
 888         return 0;
 889
 890 discard_and_relse:
 891         if (refcounted)
 892                 sock_put(sk);
 893         goto discard_it;
 894 }
 895
 896 static const struct inet_connection_sock_af_ops dccp_ipv4_af_ops = {
 897         .queue_xmit        = ip_queue_xmit,
 898         .send_check        = dccp_v4_send_check,
 899         .rebuild_header    = inet_sk_rebuild_header,
 900         .conn_request      = dccp_v4_conn_request,
 901         .syn_recv_sock     = dccp_v4_request_recv_sock,
 902         .net_header_len    = sizeof(struct iphdr),
 903         .setsockopt        = ip_setsockopt,
 904         .getsockopt        = ip_getsockopt,
 905         .addr2sockaddr     = inet_csk_addr2sockaddr,
 906         .sockaddr_len      = sizeof(struct sockaddr_in),
 907         .bind_conflict     = inet_csk_bind_conflict,
 908 #ifdef CONFIG_COMPAT
 909         .compat_setsockopt = compat_ip_setsockopt,
 910         .compat_getsockopt = compat_ip_getsockopt,
 911 #endif
 912 };
 913
 914 static int dccp_v4_init_sock(struct sock *sk)
 915 {
 916         static __u8 dccp_v4_ctl_sock_initialized;
 917         int err = dccp_init_sock(sk, dccp_v4_ctl_sock_initialized);
 918
 919         if (err == 0) {
 920                 if (unlikely(!dccp_v4_ctl_sock_initialized))
 921                         dccp_v4_ctl_sock_initialized = 1;
 922                 inet_csk(sk)->icsk_af_ops = &dccp_ipv4_af_ops;
 923         }
 924
 925         return err;
 926 }
 927
 928 static struct timewait_sock_ops dccp_timewait_sock_ops = {
 929         .twsk_obj_size  = sizeof(struct inet_timewait_sock),
 930 };
 931
 932 static struct proto dccp_v4_prot = {
 933         .name                   = "DCCP",
 934         .owner                  = THIS_MODULE,
 935         .close                  = dccp_close,
 936         .connect                = dccp_v4_connect,
 937         .disconnect             = dccp_disconnect,
 938         .ioctl                  = dccp_ioctl,
 939         .init                   = dccp_v4_init_sock,
 940         .setsockopt             = dccp_setsockopt,
 941         .getsockopt             = dccp_getsockopt,
 942         .sendmsg                = dccp_sendmsg,
 943         .recvmsg                = dccp_recvmsg,
 944         .backlog_rcv            = dccp_v4_do_rcv,
 945         .hash                   = inet_hash,
 946         .unhash                 = inet_unhash,
 947         .accept                 = inet_csk_accept,
 948         .get_port               = inet_csk_get_port,
 949         .shutdown               = dccp_shutdown,
 950         .destroy                = dccp_destroy_sock,
 951         .orphan_count           = &dccp_orphan_count,
 952         .max_header             = MAX_DCCP_HEADER,
 953         .obj_size               = sizeof(struct dccp_sock),
 954         .slab_flags             = SLAB_DESTROY_BY_RCU,
 955         .rsk_prot               = &dccp_request_sock_ops,
 956         .twsk_prot              = &dccp_timewait_sock_ops,
 957         .h.hashinfo             = &dccp_hashinfo,
 958 #ifdef CONFIG_COMPAT
 959         .compat_setsockopt      = compat_dccp_setsockopt,
 960         .compat_getsockopt      = compat_dccp_getsockopt,
 961 #endif
 962 };
 963
 964 static const struct net_protocol dccp_v4_protocol = {
 965         .handler        = dccp_v4_rcv,
 966         .err_handler    = dccp_v4_err,
 967         .no_policy      = 1,
 968         .netns_ok       = 1,
 969         .icmp_strict_tag_validation = 1,
 970 };
 971
 972 static const struct proto_ops inet_dccp_ops = {
 973         .family            = PF_INET,
 974         .owner             = THIS_MODULE,
 975         .release           = inet_release,
 976         .bind              = inet_bind,
 977         .connect           = inet_stream_connect,
 978         .socketpair        = sock_no_socketpair,
 979         .accept            = inet_accept,
 980         .getname           = inet_getname,
 981         /* FIXME: work on tcp_poll to rename it to inet_csk_poll */
 982         .poll              = dccp_poll,
 983         .ioctl             = inet_ioctl,
 984         /* FIXME: work on inet_listen to rename it to sock_common_listen */
 985         .listen            = inet_dccp_listen,
 986         .shutdown          = inet_shutdown,
 987         .setsockopt        = sock_common_setsockopt,
 988         .getsockopt        = sock_common_getsockopt,
 989         .sendmsg           = inet_sendmsg,
 990         .recvmsg           = sock_common_recvmsg,
 991         .mmap              = sock_no_mmap,
 992         .sendpage          = sock_no_sendpage,
 993 #ifdef CONFIG_COMPAT
 994         .compat_setsockopt = compat_sock_common_setsockopt,
 995         .compat_getsockopt = compat_sock_common_getsockopt,
 996 #endif
 997 };
 998
 999 static struct inet_protosw dccp_v4_protosw = {
1000         .type           = SOCK_DCCP,
1001         .protocol       = IPPROTO_DCCP,
1002         .prot           = &dccp_v4_prot,
1003         .ops            = &inet_dccp_ops,
1004         .flags          = INET_PROTOSW_ICSK,
1005 };
1006
1007 static int __net_init dccp_v4_init_net(struct net *net)
1008 {
1009         if (dccp_hashinfo.bhash == NULL)
1010                 return -ESOCKTNOSUPPORT;
1011
1012         return inet_ctl_sock_create(&net->dccp.v4_ctl_sk, PF_INET,
1013                                     SOCK_DCCP, IPPROTO_DCCP, net);
1014 }
1015
1016 static void __net_exit dccp_v4_exit_net(struct net *net)
1017 {
1018         inet_ctl_sock_destroy(net->dccp.v4_ctl_sk);
1019 }
1020
1021 static struct pernet_operations dccp_v4_ops = {
1022         .init   = dccp_v4_init_net,
1023         .exit   = dccp_v4_exit_net,
1024 };
1025
1026 static int __init dccp_v4_init(void)
1027 {
1028         int err = proto_register(&dccp_v4_prot, 1);
1029
1030         if (err != 0)
1031                 goto out;
1032
1033         err = inet_add_protocol(&dccp_v4_protocol, IPPROTO_DCCP);
1034         if (err != 0)
1035                 goto out_proto_unregister;
1036
1037         inet_register_protosw(&dccp_v4_protosw);
1038
1039         err = register_pernet_subsys(&dccp_v4_ops);
1040         if (err)
1041                 goto out_destroy_ctl_sock;
1042 out:
1043         return err;
1044 out_destroy_ctl_sock:
1045         inet_unregister_protosw(&dccp_v4_protosw);
1046         inet_del_protocol(&dccp_v4_protocol, IPPROTO_DCCP);
1047 out_proto_unregister:
1048         proto_unregister(&dccp_v4_prot);
1049         goto out;
1050 }
1051
1052 static void __exit dccp_v4_exit(void)
1053 {
1054         unregister_pernet_subsys(&dccp_v4_ops);
1055         inet_unregister_protosw(&dccp_v4_protosw);
1056         inet_del_protocol(&dccp_v4_protocol, IPPROTO_DCCP);
1057         proto_unregister(&dccp_v4_prot);
1058 }
1059
1060 module_init(dccp_v4_init);
1061 module_exit(dccp_v4_exit);
1062
1063 /*
1064  * __stringify doesn't likes enums, so use SOCK_DCCP (6) and IPPROTO_DCCP (33)
1065  * values directly, Also cover the case where the protocol is not specified,
1066  * i.e. net-pf-PF_INET-proto-0-type-SOCK_DCCP
1067  */
1068 MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_INET, 33, 6);
1069 MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_INET, 0, 6);
1070 MODULE_LICENSE("GPL");
1071 MODULE_AUTHOR("Arnaldo Carvalho de Melo <acme@mandriva.com>");
1072 MODULE_DESCRIPTION("DCCP - Datagram Congestion Controlled Protocol");