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                                              sock_owned_by_user(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, true);
  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         inet->inet_rcv_saddr = inet->inet_saddr;
  93
  94         inet->inet_dport = usin->sin_port;
  95         inet->inet_daddr = daddr;
  96
  97         inet_csk(sk)->icsk_ext_hdr_len = 0;
  98         if (inet_opt)
  99                 inet_csk(sk)->icsk_ext_hdr_len = inet_opt->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         rt = ip_route_newports(fl4, rt, orig_sport, orig_dport,
 112                                inet->inet_sport, inet->inet_dport, sk);
 113         if (IS_ERR(rt)) {
 114                 err = PTR_ERR(rt);
 115                 rt = NULL;
 116                 goto failure;
 117         }
 118         /* OK, now commit destination to socket.  */
 119         sk_setup_caps(sk, &rt->dst);
 120
 121         dp->dccps_iss = secure_dccp_sequence_number(inet->inet_saddr,
 122                                                     inet->inet_daddr,
 123                                                     inet->inet_sport,
 124                                                     inet->inet_dport);
 125         inet->inet_id = dp->dccps_iss ^ jiffies;
 126
 127         err = dccp_connect(sk);
 128         rt = NULL;
 129         if (err != 0)
 130                 goto failure;
 131 out:
 132         return err;
 133 failure:
 134         /*
 135          * This unhashes the socket and releases the local port, if necessary.
 136          */
 137         dccp_set_state(sk, DCCP_CLOSED);
 138         ip_rt_put(rt);
 139         sk->sk_route_caps = 0;
 140         inet->inet_dport = 0;
 141         goto out;
 142 }
 143
 144 EXPORT_SYMBOL_GPL(dccp_v4_connect);
 145
 146 /*
 147  * This routine does path mtu discovery as defined in RFC1191.
 148  */
 149 static inline void dccp_do_pmtu_discovery(struct sock *sk,
 150                                           const struct iphdr *iph,
 151                                           u32 mtu)
 152 {
 153         struct dst_entry *dst;
 154         const struct inet_sock *inet = inet_sk(sk);
 155         const struct dccp_sock *dp = dccp_sk(sk);
 156
 157         /* We are not interested in DCCP_LISTEN and request_socks (RESPONSEs
 158          * send out by Linux are always < 576bytes so they should go through
 159          * unfragmented).
 160          */
 161         if (sk->sk_state == DCCP_LISTEN)
 162                 return;
 163
 164         dst = inet_csk_update_pmtu(sk, mtu);
 165         if (!dst)
 166                 return;
 167
 168         /* Something is about to be wrong... Remember soft error
 169          * for the case, if this connection will not able to recover.
 170          */
 171         if (mtu < dst_mtu(dst) && ip_dont_fragment(sk, dst))
 172                 sk->sk_err_soft = EMSGSIZE;
 173
 174         mtu = dst_mtu(dst);
 175
 176         if (inet->pmtudisc != IP_PMTUDISC_DONT &&
 177             inet_csk(sk)->icsk_pmtu_cookie > mtu) {
 178                 dccp_sync_mss(sk, mtu);
 179
 180                 /*
 181                  * From RFC 4340, sec. 14.1:
 182                  *
 183                  *      DCCP-Sync packets are the best choice for upward
 184                  *      probing, since DCCP-Sync probes do not risk application
 185                  *      data loss.
 186                  */
 187                 dccp_send_sync(sk, dp->dccps_gsr, DCCP_PKT_SYNC);
 188         } /* else let the usual retransmit timer handle it */
 189 }
 190
 191 static void dccp_do_redirect(struct sk_buff *skb, struct sock *sk)
 192 {
 193         struct dst_entry *dst = __sk_dst_check(sk, 0);
 194
 195         if (dst)
 196                 dst->ops->redirect(dst, sk, skb);
 197 }
 198
 199 /*
 200  * This routine is called by the ICMP module when it gets some sort of error
 201  * condition. If err < 0 then the socket should be closed and the error
 202  * returned to the user. If err > 0 it's just the icmp type << 8 | icmp code.
 203  * After adjustment header points to the first 8 bytes of the tcp header. We
 204  * need to find the appropriate port.
 205  *
 206  * The locking strategy used here is very "optimistic". When someone else
 207  * accesses the socket the ICMP is just dropped and for some paths there is no
 208  * check at all. A more general error queue to queue errors for later handling
 209  * is probably better.
 210  */
 211 static void dccp_v4_err(struct sk_buff *skb, u32 info)
 212 {
 213         const struct iphdr *iph = (struct iphdr *)skb->data;
 214         const u8 offset = iph->ihl << 2;
 215         const struct dccp_hdr *dh = (struct dccp_hdr *)(skb->data + offset);
 216         struct dccp_sock *dp;
 217         struct inet_sock *inet;
 218         const int type = icmp_hdr(skb)->type;
 219         const int code = icmp_hdr(skb)->code;
 220         struct sock *sk;
 221         __u64 seq;
 222         int err;
 223         struct net *net = dev_net(skb->dev);
 224
 225         if (skb->len < offset + sizeof(*dh) ||
 226             skb->len < offset + __dccp_basic_hdr_len(dh)) {
 227                 ICMP_INC_STATS_BH(net, ICMP_MIB_INERRORS);
 228                 return;
 229         }
 230
 231         sk = inet_lookup(net, &dccp_hashinfo,
 232                         iph->daddr, dh->dccph_dport,
 233                         iph->saddr, dh->dccph_sport, inet_iif(skb));
 234         if (sk == NULL) {
 235                 ICMP_INC_STATS_BH(net, ICMP_MIB_INERRORS);
 236                 return;
 237         }
 238
 239         if (sk->sk_state == DCCP_TIME_WAIT) {
 240                 inet_twsk_put(inet_twsk(sk));
 241                 return;
 242         }
 243
 244         bh_lock_sock(sk);
 245         /* If too many ICMPs get dropped on busy
 246          * servers this needs to be solved differently.
 247          */
 248         if (sock_owned_by_user(sk))
 249                 NET_INC_STATS_BH(net, LINUX_MIB_LOCKDROPPEDICMPS);
 250
 251         if (sk->sk_state == DCCP_CLOSED)
 252                 goto out;
 253
 254         dp = dccp_sk(sk);
 255         seq = dccp_hdr_seq(dh);
 256         if ((1 << sk->sk_state) & ~(DCCPF_REQUESTING | DCCPF_LISTEN) &&
 257             !between48(seq, dp->dccps_awl, dp->dccps_awh)) {
 258                 NET_INC_STATS_BH(net, LINUX_MIB_OUTOFWINDOWICMPS);
 259                 goto out;
 260         }
 261
 262         switch (type) {
 263         case ICMP_REDIRECT:
 264                 dccp_do_redirect(skb, sk);
 265                 goto out;
 266         case ICMP_SOURCE_QUENCH:
 267                 /* Just silently ignore these. */
 268                 goto out;
 269         case ICMP_PARAMETERPROB:
 270                 err = EPROTO;
 271                 break;
 272         case ICMP_DEST_UNREACH:
 273                 if (code > NR_ICMP_UNREACH)
 274                         goto out;
 275
 276                 if (code == ICMP_FRAG_NEEDED) { /* PMTU discovery (RFC1191) */
 277                         if (!sock_owned_by_user(sk))
 278                                 dccp_do_pmtu_discovery(sk, iph, info);
 279                         goto out;
 280                 }
 281
 282                 err = icmp_err_convert[code].errno;
 283                 break;
 284         case ICMP_TIME_EXCEEDED:
 285                 err = EHOSTUNREACH;
 286                 break;
 287         default:
 288                 goto out;
 289         }
 290
 291         switch (sk->sk_state) {
 292                 struct request_sock *req , **prev;
 293         case DCCP_LISTEN:
 294                 if (sock_owned_by_user(sk))
 295                         goto out;
 296                 req = inet_csk_search_req(sk, &prev, dh->dccph_dport,
 297                                           iph->daddr, iph->saddr);
 298                 if (!req)
 299                         goto out;
 300
 301                 /*
 302                  * ICMPs are not backlogged, hence we cannot get an established
 303                  * socket here.
 304                  */
 305                 WARN_ON(req->sk);
 306
 307                 if (!between48(seq, dccp_rsk(req)->dreq_iss,
 308                                     dccp_rsk(req)->dreq_gss)) {
 309                         NET_INC_STATS_BH(net, LINUX_MIB_OUTOFWINDOWICMPS);
 310                         goto out;
 311                 }
 312                 /*
 313                  * Still in RESPOND, just remove it silently.
 314                  * There is no good way to pass the error to the newly
 315                  * created socket, and POSIX does not want network
 316                  * errors returned from accept().
 317                  */
 318                 inet_csk_reqsk_queue_drop(sk, req, prev);
 319                 goto out;
 320
 321         case DCCP_REQUESTING:
 322         case DCCP_RESPOND:
 323                 if (!sock_owned_by_user(sk)) {
 324                         DCCP_INC_STATS_BH(DCCP_MIB_ATTEMPTFAILS);
 325                         sk->sk_err = err;
 326
 327                         sk->sk_error_report(sk);
 328
 329                         dccp_done(sk);
 330                 } else
 331                         sk->sk_err_soft = err;
 332                 goto out;
 333         }
 334
 335         /* If we've already connected we will keep trying
 336          * until we time out, or the user gives up.
 337          *
 338          * rfc1122 4.2.3.9 allows to consider as hard errors
 339          * only PROTO_UNREACH and PORT_UNREACH (well, FRAG_FAILED too,
 340          * but it is obsoleted by pmtu discovery).
 341          *
 342          * Note, that in modern internet, where routing is unreliable
 343          * and in each dark corner broken firewalls sit, sending random
 344          * errors ordered by their masters even this two messages finally lose
 345          * their original sense (even Linux sends invalid PORT_UNREACHs)
 346          *
 347          * Now we are in compliance with RFCs.
 348          *                                                      --ANK (980905)
 349          */
 350
 351         inet = inet_sk(sk);
 352         if (!sock_owned_by_user(sk) && inet->recverr) {
 353                 sk->sk_err = err;
 354                 sk->sk_error_report(sk);
 355         } else /* Only an error on timeout */
 356                 sk->sk_err_soft = err;
 357 out:
 358         bh_unlock_sock(sk);
 359         sock_put(sk);
 360 }
 361
 362 static inline __sum16 dccp_v4_csum_finish(struct sk_buff *skb,
 363                                       __be32 src, __be32 dst)
 364 {
 365         return csum_tcpudp_magic(src, dst, skb->len, IPPROTO_DCCP, skb->csum);
 366 }
 367
 368 void dccp_v4_send_check(struct sock *sk, struct sk_buff *skb)
 369 {
 370         const struct inet_sock *inet = inet_sk(sk);
 371         struct dccp_hdr *dh = dccp_hdr(skb);
 372
 373         dccp_csum_outgoing(skb);
 374         dh->dccph_checksum = dccp_v4_csum_finish(skb,
 375                                                  inet->inet_saddr,
 376                                                  inet->inet_daddr);
 377 }
 378
 379 EXPORT_SYMBOL_GPL(dccp_v4_send_check);
 380
 381 static inline u64 dccp_v4_init_sequence(const struct sk_buff *skb)
 382 {
 383         return secure_dccp_sequence_number(ip_hdr(skb)->daddr,
 384                                            ip_hdr(skb)->saddr,
 385                                            dccp_hdr(skb)->dccph_dport,
 386                                            dccp_hdr(skb)->dccph_sport);
 387 }
 388
 389 /*
 390  * The three way handshake has completed - we got a valid ACK or DATAACK -
 391  * now create the new socket.
 392  *
 393  * This is the equivalent of TCP's tcp_v4_syn_recv_sock
 394  */
 395 struct sock *dccp_v4_request_recv_sock(struct sock *sk, struct sk_buff *skb,
 396                                        struct request_sock *req,
 397                                        struct dst_entry *dst)
 398 {
 399         struct inet_request_sock *ireq;
 400         struct inet_sock *newinet;
 401         struct sock *newsk;
 402
 403         if (sk_acceptq_is_full(sk))
 404                 goto exit_overflow;
 405
 406         newsk = dccp_create_openreq_child(sk, req, skb);
 407         if (newsk == NULL)
 408                 goto exit_nonewsk;
 409
 410         newinet            = inet_sk(newsk);
 411         ireq               = inet_rsk(req);
 412         newinet->inet_daddr     = ireq->rmt_addr;
 413         newinet->inet_rcv_saddr = ireq->loc_addr;
 414         newinet->inet_saddr     = ireq->loc_addr;
 415         newinet->inet_opt       = ireq->opt;
 416         ireq->opt          = NULL;
 417         newinet->mc_index  = inet_iif(skb);
 418         newinet->mc_ttl    = ip_hdr(skb)->ttl;
 419         newinet->inet_id   = jiffies;
 420
 421         if (dst == NULL && (dst = inet_csk_route_child_sock(sk, newsk, req)) == NULL)
 422                 goto put_and_exit;
 423
 424         sk_setup_caps(newsk, dst);
 425
 426         dccp_sync_mss(newsk, dst_mtu(dst));
 427
 428         if (__inet_inherit_port(sk, newsk) < 0)
 429                 goto put_and_exit;
 430         __inet_hash_nolisten(newsk, NULL);
 431
 432         return newsk;
 433
 434 exit_overflow:
 435         NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_LISTENOVERFLOWS);
 436 exit_nonewsk:
 437         dst_release(dst);
 438 exit:
 439         NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_LISTENDROPS);
 440         return NULL;
 441 put_and_exit:
 442         bh_unlock_sock(newsk);
 443         sock_put(newsk);
 444         goto exit;
 445 }
 446
 447 EXPORT_SYMBOL_GPL(dccp_v4_request_recv_sock);
 448
 449 static struct sock *dccp_v4_hnd_req(struct sock *sk, struct sk_buff *skb)
 450 {
 451         const struct dccp_hdr *dh = dccp_hdr(skb);
 452         const struct iphdr *iph = ip_hdr(skb);
 453         struct sock *nsk;
 454         struct request_sock **prev;
 455         /* Find possible connection requests. */
 456         struct request_sock *req = inet_csk_search_req(sk, &prev,
 457                                                        dh->dccph_sport,
 458                                                        iph->saddr, iph->daddr);
 459         if (req != NULL)
 460                 return dccp_check_req(sk, skb, req, prev);
 461
 462         nsk = inet_lookup_established(sock_net(sk), &dccp_hashinfo,
 463                                       iph->saddr, dh->dccph_sport,
 464                                       iph->daddr, dh->dccph_dport,
 465                                       inet_iif(skb));
 466         if (nsk != NULL) {
 467                 if (nsk->sk_state != DCCP_TIME_WAIT) {
 468                         bh_lock_sock(nsk);
 469                         return nsk;
 470                 }
 471                 inet_twsk_put(inet_twsk(nsk));
 472                 return NULL;
 473         }
 474
 475         return sk;
 476 }
 477
 478 static struct dst_entry* dccp_v4_route_skb(struct net *net, struct sock *sk,
 479                                            struct sk_buff *skb)
 480 {
 481         struct rtable *rt;
 482         const struct iphdr *iph = ip_hdr(skb);
 483         struct flowi4 fl4 = {
 484                 .flowi4_oif = inet_iif(skb),
 485                 .daddr = iph->saddr,
 486                 .saddr = iph->daddr,
 487                 .flowi4_tos = RT_CONN_FLAGS(sk),
 488                 .flowi4_proto = sk->sk_protocol,
 489                 .fl4_sport = dccp_hdr(skb)->dccph_dport,
 490                 .fl4_dport = dccp_hdr(skb)->dccph_sport,
 491         };
 492
 493         security_skb_classify_flow(skb, flowi4_to_flowi(&fl4));
 494         rt = ip_route_output_flow(net, &fl4, sk);
 495         if (IS_ERR(rt)) {
 496                 IP_INC_STATS_BH(net, IPSTATS_MIB_OUTNOROUTES);
 497                 return NULL;
 498         }
 499
 500         return &rt->dst;
 501 }
 502
 503 static int dccp_v4_send_response(struct sock *sk, struct request_sock *req,
 504                                  struct request_values *rv_unused)
 505 {
 506         int err = -1;
 507         struct sk_buff *skb;
 508         struct dst_entry *dst;
 509         struct flowi4 fl4;
 510
 511         dst = inet_csk_route_req(sk, &fl4, req);
 512         if (dst == NULL)
 513                 goto out;
 514
 515         skb = dccp_make_response(sk, dst, req);
 516         if (skb != NULL) {
 517                 const struct inet_request_sock *ireq = inet_rsk(req);
 518                 struct dccp_hdr *dh = dccp_hdr(skb);
 519
 520                 dh->dccph_checksum = dccp_v4_csum_finish(skb, ireq->loc_addr,
 521                                                               ireq->rmt_addr);
 522                 err = ip_build_and_send_pkt(skb, sk, ireq->loc_addr,
 523                                             ireq->rmt_addr,
 524                                             ireq->opt);
 525                 err = net_xmit_eval(err);
 526         }
 527
 528 out:
 529         dst_release(dst);
 530         return err;
 531 }
 532
 533 static void dccp_v4_ctl_send_reset(struct sock *sk, struct sk_buff *rxskb)
 534 {
 535         int err;
 536         const struct iphdr *rxiph;
 537         struct sk_buff *skb;
 538         struct dst_entry *dst;
 539         struct net *net = dev_net(skb_dst(rxskb)->dev);
 540         struct sock *ctl_sk = net->dccp.v4_ctl_sk;
 541
 542         /* Never send a reset in response to a reset. */
 543         if (dccp_hdr(rxskb)->dccph_type == DCCP_PKT_RESET)
 544                 return;
 545
 546         if (skb_rtable(rxskb)->rt_type != RTN_LOCAL)
 547                 return;
 548
 549         dst = dccp_v4_route_skb(net, ctl_sk, rxskb);
 550         if (dst == NULL)
 551                 return;
 552
 553         skb = dccp_ctl_make_reset(ctl_sk, rxskb);
 554         if (skb == NULL)
 555                 goto out;
 556
 557         rxiph = ip_hdr(rxskb);
 558         dccp_hdr(skb)->dccph_checksum = dccp_v4_csum_finish(skb, rxiph->saddr,
 559                                                                  rxiph->daddr);
 560         skb_dst_set(skb, dst_clone(dst));
 561
 562         bh_lock_sock(ctl_sk);
 563         err = ip_build_and_send_pkt(skb, ctl_sk,
 564                                     rxiph->daddr, rxiph->saddr, NULL);
 565         bh_unlock_sock(ctl_sk);
 566
 567         if (net_xmit_eval(err) == 0) {
 568                 DCCP_INC_STATS_BH(DCCP_MIB_OUTSEGS);
 569                 DCCP_INC_STATS_BH(DCCP_MIB_OUTRSTS);
 570         }
 571 out:
 572          dst_release(dst);
 573 }
 574
 575 static void dccp_v4_reqsk_destructor(struct request_sock *req)
 576 {
 577         dccp_feat_list_purge(&dccp_rsk(req)->dreq_featneg);
 578         kfree(inet_rsk(req)->opt);
 579 }
 580
 581 void dccp_syn_ack_timeout(struct sock *sk, struct request_sock *req)
 582 {
 583 }
 584 EXPORT_SYMBOL(dccp_syn_ack_timeout);
 585
 586 static struct request_sock_ops dccp_request_sock_ops __read_mostly = {
 587         .family         = PF_INET,
 588         .obj_size       = sizeof(struct dccp_request_sock),
 589         .rtx_syn_ack    = dccp_v4_send_response,
 590         .send_ack       = dccp_reqsk_send_ack,
 591         .destructor     = dccp_v4_reqsk_destructor,
 592         .send_reset     = dccp_v4_ctl_send_reset,
 593         .syn_ack_timeout = dccp_syn_ack_timeout,
 594 };
 595
 596 int dccp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
 597 {
 598         struct inet_request_sock *ireq;
 599         struct request_sock *req;
 600         struct dccp_request_sock *dreq;
 601         const __be32 service = dccp_hdr_request(skb)->dccph_req_service;
 602         struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
 603
 604         /* Never answer to DCCP_PKT_REQUESTs send to broadcast or multicast */
 605         if (skb_rtable(skb)->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
 606                 return 0;       /* discard, don't send a reset here */
 607
 608         if (dccp_bad_service_code(sk, service)) {
 609                 dcb->dccpd_reset_code = DCCP_RESET_CODE_BAD_SERVICE_CODE;
 610                 goto drop;
 611         }
 612         /*
 613          * TW buckets are converted to open requests without
 614          * limitations, they conserve resources and peer is
 615          * evidently real one.
 616          */
 617         dcb->dccpd_reset_code = DCCP_RESET_CODE_TOO_BUSY;
 618         if (inet_csk_reqsk_queue_is_full(sk))
 619                 goto drop;
 620
 621         /*
 622          * Accept backlog is full. If we have already queued enough
 623          * of warm entries in syn queue, drop request. It is better than
 624          * clogging syn queue with openreqs with exponentially increasing
 625          * timeout.
 626          */
 627         if (sk_acceptq_is_full(sk) && inet_csk_reqsk_queue_young(sk) > 1)
 628                 goto drop;
 629
 630         req = inet_reqsk_alloc(&dccp_request_sock_ops);
 631         if (req == NULL)
 632                 goto drop;
 633
 634         if (dccp_reqsk_init(req, dccp_sk(sk), skb))
 635                 goto drop_and_free;
 636
 637         dreq = dccp_rsk(req);
 638         if (dccp_parse_options(sk, dreq, skb))
 639                 goto drop_and_free;
 640
 641         if (security_inet_conn_request(sk, skb, req))
 642                 goto drop_and_free;
 643
 644         ireq = inet_rsk(req);
 645         ireq->loc_addr = ip_hdr(skb)->daddr;
 646         ireq->rmt_addr = ip_hdr(skb)->saddr;
 647
 648         /*
 649          * Step 3: Process LISTEN state
 650          *
 651          * Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init Cookie
 652          *
 653          * Setting S.SWL/S.SWH to is deferred to dccp_create_openreq_child().
 654          */
 655         dreq->dreq_isr     = dcb->dccpd_seq;
 656         dreq->dreq_gsr     = dreq->dreq_isr;
 657         dreq->dreq_iss     = dccp_v4_init_sequence(skb);
 658         dreq->dreq_gss     = dreq->dreq_iss;
 659         dreq->dreq_service = service;
 660
 661         if (dccp_v4_send_response(sk, req, NULL))
 662                 goto drop_and_free;
 663
 664         inet_csk_reqsk_queue_hash_add(sk, req, DCCP_TIMEOUT_INIT);
 665         return 0;
 666
 667 drop_and_free:
 668         reqsk_free(req);
 669 drop:
 670         DCCP_INC_STATS_BH(DCCP_MIB_ATTEMPTFAILS);
 671         return -1;
 672 }
 673
 674 EXPORT_SYMBOL_GPL(dccp_v4_conn_request);
 675
 676 int dccp_v4_do_rcv(struct sock *sk, struct sk_buff *skb)
 677 {
 678         struct dccp_hdr *dh = dccp_hdr(skb);
 679
 680         if (sk->sk_state == DCCP_OPEN) { /* Fast path */
 681                 if (dccp_rcv_established(sk, skb, dh, skb->len))
 682                         goto reset;
 683                 return 0;
 684         }
 685
 686         /*
 687          *  Step 3: Process LISTEN state
 688          *       If P.type == Request or P contains a valid Init Cookie option,
 689          *            (* Must scan the packet's options to check for Init
 690          *               Cookies.  Only Init Cookies are processed here,
 691          *               however; other options are processed in Step 8.  This
 692          *               scan need only be performed if the endpoint uses Init
 693          *               Cookies *)
 694          *            (* Generate a new socket and switch to that socket *)
 695          *            Set S := new socket for this port pair
 696          *            S.state = RESPOND
 697          *            Choose S.ISS (initial seqno) or set from Init Cookies
 698          *            Initialize S.GAR := S.ISS
 699          *            Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init Cookies
 700          *            Continue with S.state == RESPOND
 701          *            (* A Response packet will be generated in Step 11 *)
 702          *       Otherwise,
 703          *            Generate Reset(No Connection) unless P.type == Reset
 704          *            Drop packet and return
 705          *
 706          * NOTE: the check for the packet types is done in
 707          *       dccp_rcv_state_process
 708          */
 709         if (sk->sk_state == DCCP_LISTEN) {
 710                 struct sock *nsk = dccp_v4_hnd_req(sk, skb);
 711
 712                 if (nsk == NULL)
 713                         goto discard;
 714
 715                 if (nsk != sk) {
 716                         if (dccp_child_process(sk, nsk, skb))
 717                                 goto reset;
 718                         return 0;
 719                 }
 720         }
 721
 722         if (dccp_rcv_state_process(sk, skb, dh, skb->len))
 723                 goto reset;
 724         return 0;
 725
 726 reset:
 727         dccp_v4_ctl_send_reset(sk, skb);
 728 discard:
 729         kfree_skb(skb);
 730         return 0;
 731 }
 732
 733 EXPORT_SYMBOL_GPL(dccp_v4_do_rcv);
 734
 735 /**
 736  *      dccp_invalid_packet  -  check for malformed packets
 737  *      Implements RFC 4340, 8.5:  Step 1: Check header basics
 738  *      Packets that fail these checks are ignored and do not receive Resets.
 739  */
 740 int dccp_invalid_packet(struct sk_buff *skb)
 741 {
 742         const struct dccp_hdr *dh;
 743         unsigned int cscov;
 744
 745         if (skb->pkt_type != PACKET_HOST)
 746                 return 1;
 747
 748         /* If the packet is shorter than 12 bytes, drop packet and return */
 749         if (!pskb_may_pull(skb, sizeof(struct dccp_hdr))) {
 750                 DCCP_WARN("pskb_may_pull failed\n");
 751                 return 1;
 752         }
 753
 754         dh = dccp_hdr(skb);
 755
 756         /* If P.type is not understood, drop packet and return */
 757         if (dh->dccph_type >= DCCP_PKT_INVALID) {
 758                 DCCP_WARN("invalid packet type\n");
 759                 return 1;
 760         }
 761
 762         /*
 763          * If P.Data Offset is too small for packet type, drop packet and return
 764          */
 765         if (dh->dccph_doff < dccp_hdr_len(skb) / sizeof(u32)) {
 766                 DCCP_WARN("P.Data Offset(%u) too small\n", dh->dccph_doff);
 767                 return 1;
 768         }
 769         /*
 770          * If P.Data Offset is too too large for packet, drop packet and return
 771          */
 772         if (!pskb_may_pull(skb, dh->dccph_doff * sizeof(u32))) {
 773                 DCCP_WARN("P.Data Offset(%u) too large\n", dh->dccph_doff);
 774                 return 1;
 775         }
 776
 777         /*
 778          * If P.type is not Data, Ack, or DataAck and P.X == 0 (the packet
 779          * has short sequence numbers), drop packet and return
 780          */
 781         if ((dh->dccph_type < DCCP_PKT_DATA    ||
 782             dh->dccph_type > DCCP_PKT_DATAACK) && dh->dccph_x == 0)  {
 783                 DCCP_WARN("P.type (%s) not Data || [Data]Ack, while P.X == 0\n",
 784                           dccp_packet_name(dh->dccph_type));
 785                 return 1;
 786         }
 787
 788         /*
 789          * If P.CsCov is too large for the packet size, drop packet and return.
 790          * This must come _before_ checksumming (not as RFC 4340 suggests).
 791          */
 792         cscov = dccp_csum_coverage(skb);
 793         if (cscov > skb->len) {
 794                 DCCP_WARN("P.CsCov %u exceeds packet length %d\n",
 795                           dh->dccph_cscov, skb->len);
 796                 return 1;
 797         }
 798
 799         /* If header checksum is incorrect, drop packet and return.
 800          * (This step is completed in the AF-dependent functions.) */
 801         skb->csum = skb_checksum(skb, 0, cscov, 0);
 802
 803         return 0;
 804 }
 805
 806 EXPORT_SYMBOL_GPL(dccp_invalid_packet);
 807
 808 /* this is called when real data arrives */
 809 static int dccp_v4_rcv(struct sk_buff *skb)
 810 {
 811         const struct dccp_hdr *dh;
 812         const struct iphdr *iph;
 813         struct sock *sk;
 814         int min_cov;
 815
 816         /* Step 1: Check header basics */
 817
 818         if (dccp_invalid_packet(skb))
 819                 goto discard_it;
 820
 821         iph = ip_hdr(skb);
 822         /* Step 1: If header checksum is incorrect, drop packet and return */
 823         if (dccp_v4_csum_finish(skb, iph->saddr, iph->daddr)) {
 824                 DCCP_WARN("dropped packet with invalid checksum\n");
 825                 goto discard_it;
 826         }
 827
 828         dh = dccp_hdr(skb);
 829
 830         DCCP_SKB_CB(skb)->dccpd_seq  = dccp_hdr_seq(dh);
 831         DCCP_SKB_CB(skb)->dccpd_type = dh->dccph_type;
 832
 833         dccp_pr_debug("%8.8s src=%pI4@%-5d dst=%pI4@%-5d seq=%llu",
 834                       dccp_packet_name(dh->dccph_type),
 835                       &iph->saddr, ntohs(dh->dccph_sport),
 836                       &iph->daddr, ntohs(dh->dccph_dport),
 837                       (unsigned long long) DCCP_SKB_CB(skb)->dccpd_seq);
 838
 839         if (dccp_packet_without_ack(skb)) {
 840                 DCCP_SKB_CB(skb)->dccpd_ack_seq = DCCP_PKT_WITHOUT_ACK_SEQ;
 841                 dccp_pr_debug_cat("\n");
 842         } else {
 843                 DCCP_SKB_CB(skb)->dccpd_ack_seq = dccp_hdr_ack_seq(skb);
 844                 dccp_pr_debug_cat(", ack=%llu\n", (unsigned long long)
 845                                   DCCP_SKB_CB(skb)->dccpd_ack_seq);
 846         }
 847
 848         /* Step 2:
 849          *      Look up flow ID in table and get corresponding socket */
 850         sk = __inet_lookup_skb(&dccp_hashinfo, skb,
 851                                dh->dccph_sport, dh->dccph_dport);
 852         /*
 853          * Step 2:
 854          *      If no socket ...
 855          */
 856         if (sk == NULL) {
 857                 dccp_pr_debug("failed to look up flow ID in table and "
 858                               "get corresponding socket\n");
 859                 goto no_dccp_socket;
 860         }
 861
 862         /*
 863          * Step 2:
 864          *      ... or S.state == TIMEWAIT,
 865          *              Generate Reset(No Connection) unless P.type == Reset
 866          *              Drop packet and return
 867          */
 868         if (sk->sk_state == DCCP_TIME_WAIT) {
 869                 dccp_pr_debug("sk->sk_state == DCCP_TIME_WAIT: do_time_wait\n");
 870                 inet_twsk_put(inet_twsk(sk));
 871                 goto no_dccp_socket;
 872         }
 873
 874         /*
 875          * RFC 4340, sec. 9.2.1: Minimum Checksum Coverage
 876          *      o if MinCsCov = 0, only packets with CsCov = 0 are accepted
 877          *      o if MinCsCov > 0, also accept packets with CsCov >= MinCsCov
 878          */
 879         min_cov = dccp_sk(sk)->dccps_pcrlen;
 880         if (dh->dccph_cscov && (min_cov == 0 || dh->dccph_cscov < min_cov))  {
 881                 dccp_pr_debug("Packet CsCov %d does not satisfy MinCsCov %d\n",
 882                               dh->dccph_cscov, min_cov);
 883                 /* FIXME: "Such packets SHOULD be reported using Data Dropped
 884                  *         options (Section 11.7) with Drop Code 0, Protocol
 885                  *         Constraints."                                     */
 886                 goto discard_and_relse;
 887         }
 888
 889         if (!xfrm4_policy_check(sk, XFRM_POLICY_IN, skb))
 890                 goto discard_and_relse;
 891         nf_reset(skb);
 892
 893         return sk_receive_skb(sk, skb, 1);
 894
 895 no_dccp_socket:
 896         if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb))
 897                 goto discard_it;
 898         /*
 899          * Step 2:
 900          *      If no socket ...
 901          *              Generate Reset(No Connection) unless P.type == Reset
 902          *              Drop packet and return
 903          */
 904         if (dh->dccph_type != DCCP_PKT_RESET) {
 905                 DCCP_SKB_CB(skb)->dccpd_reset_code =
 906                                         DCCP_RESET_CODE_NO_CONNECTION;
 907                 dccp_v4_ctl_send_reset(sk, skb);
 908         }
 909
 910 discard_it:
 911         kfree_skb(skb);
 912         return 0;
 913
 914 discard_and_relse:
 915         sock_put(sk);
 916         goto discard_it;
 917 }
 918
 919 static const struct inet_connection_sock_af_ops dccp_ipv4_af_ops = {
 920         .queue_xmit        = ip_queue_xmit,
 921         .send_check        = dccp_v4_send_check,
 922         .rebuild_header    = inet_sk_rebuild_header,
 923         .conn_request      = dccp_v4_conn_request,
 924         .syn_recv_sock     = dccp_v4_request_recv_sock,
 925         .net_header_len    = sizeof(struct iphdr),
 926         .setsockopt        = ip_setsockopt,
 927         .getsockopt        = ip_getsockopt,
 928         .addr2sockaddr     = inet_csk_addr2sockaddr,
 929         .sockaddr_len      = sizeof(struct sockaddr_in),
 930         .bind_conflict     = inet_csk_bind_conflict,
 931 #ifdef CONFIG_COMPAT
 932         .compat_setsockopt = compat_ip_setsockopt,
 933         .compat_getsockopt = compat_ip_getsockopt,
 934 #endif
 935 };
 936
 937 static int dccp_v4_init_sock(struct sock *sk)
 938 {
 939         static __u8 dccp_v4_ctl_sock_initialized;
 940         int err = dccp_init_sock(sk, dccp_v4_ctl_sock_initialized);
 941
 942         if (err == 0) {
 943                 if (unlikely(!dccp_v4_ctl_sock_initialized))
 944                         dccp_v4_ctl_sock_initialized = 1;
 945                 inet_csk(sk)->icsk_af_ops = &dccp_ipv4_af_ops;
 946         }
 947
 948         return err;
 949 }
 950
 951 static struct timewait_sock_ops dccp_timewait_sock_ops = {
 952         .twsk_obj_size  = sizeof(struct inet_timewait_sock),
 953 };
 954
 955 static struct proto dccp_v4_prot = {
 956         .name                   = "DCCP",
 957         .owner                  = THIS_MODULE,
 958         .close                  = dccp_close,
 959         .connect                = dccp_v4_connect,
 960         .disconnect             = dccp_disconnect,
 961         .ioctl                  = dccp_ioctl,
 962         .init                   = dccp_v4_init_sock,
 963         .setsockopt             = dccp_setsockopt,
 964         .getsockopt             = dccp_getsockopt,
 965         .sendmsg                = dccp_sendmsg,
 966         .recvmsg                = dccp_recvmsg,
 967         .backlog_rcv            = dccp_v4_do_rcv,
 968         .hash                   = inet_hash,
 969         .unhash                 = inet_unhash,
 970         .accept                 = inet_csk_accept,
 971         .get_port               = inet_csk_get_port,
 972         .shutdown               = dccp_shutdown,
 973         .destroy                = dccp_destroy_sock,
 974         .orphan_count           = &dccp_orphan_count,
 975         .max_header             = MAX_DCCP_HEADER,
 976         .obj_size               = sizeof(struct dccp_sock),
 977         .slab_flags             = SLAB_DESTROY_BY_RCU,
 978         .rsk_prot               = &dccp_request_sock_ops,
 979         .twsk_prot              = &dccp_timewait_sock_ops,
 980         .h.hashinfo             = &dccp_hashinfo,
 981 #ifdef CONFIG_COMPAT
 982         .compat_setsockopt      = compat_dccp_setsockopt,
 983         .compat_getsockopt      = compat_dccp_getsockopt,
 984 #endif
 985 };
 986
 987 static const struct net_protocol dccp_v4_protocol = {
 988         .handler        = dccp_v4_rcv,
 989         .err_handler    = dccp_v4_err,
 990         .no_policy      = 1,
 991         .netns_ok       = 1,
 992 };
 993
 994 static const struct proto_ops inet_dccp_ops = {
 995         .family            = PF_INET,
 996         .owner             = THIS_MODULE,
 997         .release           = inet_release,
 998         .bind              = inet_bind,
 999         .connect           = inet_stream_connect,
1000         .socketpair        = sock_no_socketpair,
1001         .accept            = inet_accept,
1002         .getname           = inet_getname,
1003         /* FIXME: work on tcp_poll to rename it to inet_csk_poll */
1004         .poll              = dccp_poll,
1005         .ioctl             = inet_ioctl,
1006         /* FIXME: work on inet_listen to rename it to sock_common_listen */
1007         .listen            = inet_dccp_listen,
1008         .shutdown          = inet_shutdown,
1009         .setsockopt        = sock_common_setsockopt,
1010         .getsockopt        = sock_common_getsockopt,
1011         .sendmsg           = inet_sendmsg,
1012         .recvmsg           = sock_common_recvmsg,
1013         .mmap              = sock_no_mmap,
1014         .sendpage          = sock_no_sendpage,
1015 #ifdef CONFIG_COMPAT
1016         .compat_setsockopt = compat_sock_common_setsockopt,
1017         .compat_getsockopt = compat_sock_common_getsockopt,
1018 #endif
1019 };
1020
1021 static struct inet_protosw dccp_v4_protosw = {
1022         .type           = SOCK_DCCP,
1023         .protocol       = IPPROTO_DCCP,
1024         .prot           = &dccp_v4_prot,
1025         .ops            = &inet_dccp_ops,
1026         .no_check       = 0,
1027         .flags          = INET_PROTOSW_ICSK,
1028 };
1029
1030 static int __net_init dccp_v4_init_net(struct net *net)
1031 {
1032         if (dccp_hashinfo.bhash == NULL)
1033                 return -ESOCKTNOSUPPORT;
1034
1035         return inet_ctl_sock_create(&net->dccp.v4_ctl_sk, PF_INET,
1036                                     SOCK_DCCP, IPPROTO_DCCP, net);
1037 }
1038
1039 static void __net_exit dccp_v4_exit_net(struct net *net)
1040 {
1041         inet_ctl_sock_destroy(net->dccp.v4_ctl_sk);
1042 }
1043
1044 static struct pernet_operations dccp_v4_ops = {
1045         .init   = dccp_v4_init_net,
1046         .exit   = dccp_v4_exit_net,
1047 };
1048
1049 static int __init dccp_v4_init(void)
1050 {
1051         int err = proto_register(&dccp_v4_prot, 1);
1052
1053         if (err != 0)
1054                 goto out;
1055
1056         err = inet_add_protocol(&dccp_v4_protocol, IPPROTO_DCCP);
1057         if (err != 0)
1058                 goto out_proto_unregister;
1059
1060         inet_register_protosw(&dccp_v4_protosw);
1061
1062         err = register_pernet_subsys(&dccp_v4_ops);
1063         if (err)
1064                 goto out_destroy_ctl_sock;
1065 out:
1066         return err;
1067 out_destroy_ctl_sock:
1068         inet_unregister_protosw(&dccp_v4_protosw);
1069         inet_del_protocol(&dccp_v4_protocol, IPPROTO_DCCP);
1070 out_proto_unregister:
1071         proto_unregister(&dccp_v4_prot);
1072         goto out;
1073 }
1074
1075 static void __exit dccp_v4_exit(void)
1076 {
1077         unregister_pernet_subsys(&dccp_v4_ops);
1078         inet_unregister_protosw(&dccp_v4_protosw);
1079         inet_del_protocol(&dccp_v4_protocol, IPPROTO_DCCP);
1080         proto_unregister(&dccp_v4_prot);
1081 }
1082
1083 module_init(dccp_v4_init);
1084 module_exit(dccp_v4_exit);
1085
1086 /*
1087  * __stringify doesn't likes enums, so use SOCK_DCCP (6) and IPPROTO_DCCP (33)
1088  * values directly, Also cover the case where the protocol is not specified,
1089  * i.e. net-pf-PF_INET-proto-0-type-SOCK_DCCP
1090  */
1091 MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_INET, 33, 6);
1092 MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_INET, 0, 6);
1093 MODULE_LICENSE("GPL");
1094 MODULE_AUTHOR("Arnaldo Carvalho de Melo <acme@mandriva.com>");
1095 MODULE_DESCRIPTION("DCCP - Datagram Congestion Controlled Protocol");