net/dccp/ipv4.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  *  net/dccp/ipv4.c
   4  *
   5  *  An implementation of the DCCP protocol
   6  *  Arnaldo Carvalho de Melo <acme@conectiva.com.br>
   7  */
   8
   9 #include <linux/dccp.h>
  10 #include <linux/icmp.h>
  11 #include <linux/slab.h>
  12 #include <linux/module.h>
  13 #include <linux/skbuff.h>
  14 #include <linux/random.h>
  15
  16 #include <net/icmp.h>
  17 #include <net/inet_common.h>
  18 #include <net/inet_hashtables.h>
  19 #include <net/inet_sock.h>
  20 #include <net/protocol.h>
  21 #include <net/sock.h>
  22 #include <net/timewait_sock.h>
  23 #include <net/tcp_states.h>
  24 #include <net/xfrm.h>
  25 #include <net/secure_seq.h>
  26 #include <net/netns/generic.h>
  27
  28 #include "ackvec.h"
  29 #include "ccid.h"
  30 #include "dccp.h"
  31 #include "feat.h"
  32
  33 struct dccp_v4_pernet {
  34         struct sock *v4_ctl_sk;
  35 };
  36
  37 static unsigned int dccp_v4_pernet_id __read_mostly;
  38
  39 /*
  40  * The per-net v4_ctl_sk socket is used for responding to
  41  * the Out-of-the-blue (OOTB) packets. A control sock will be created
  42  * for this socket at the initialization time.
  43  */
  44
  45 int dccp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
  46 {
  47         const struct sockaddr_in *usin = (struct sockaddr_in *)uaddr;
  48         struct inet_bind_hashbucket *prev_addr_hashbucket = NULL;
  49         __be32 daddr, nexthop, prev_sk_rcv_saddr;
  50         struct inet_sock *inet = inet_sk(sk);
  51         struct dccp_sock *dp = dccp_sk(sk);
  52         __be16 orig_sport, orig_dport;
  53         struct flowi4 *fl4;
  54         struct rtable *rt;
  55         int err;
  56         struct ip_options_rcu *inet_opt;
  57
  58         dp->dccps_role = DCCP_ROLE_CLIENT;
  59
  60         if (addr_len < sizeof(struct sockaddr_in))
  61                 return -EINVAL;
  62
  63         if (usin->sin_family != AF_INET)
  64                 return -EAFNOSUPPORT;
  65
  66         nexthop = daddr = usin->sin_addr.s_addr;
  67
  68         inet_opt = rcu_dereference_protected(inet->inet_opt,
  69                                              lockdep_sock_is_held(sk));
  70         if (inet_opt != NULL && inet_opt->opt.srr) {
  71                 if (daddr == 0)
  72                         return -EINVAL;
  73                 nexthop = inet_opt->opt.faddr;
  74         }
  75
  76         orig_sport = inet->inet_sport;
  77         orig_dport = usin->sin_port;
  78         fl4 = &inet->cork.fl.u.ip4;
  79         rt = ip_route_connect(fl4, nexthop, inet->inet_saddr,
  80                               sk->sk_bound_dev_if, IPPROTO_DCCP, orig_sport,
  81                               orig_dport, sk);
  82         if (IS_ERR(rt))
  83                 return PTR_ERR(rt);
  84
  85         if (rt->rt_flags & (RTCF_MULTICAST | RTCF_BROADCAST)) {
  86                 ip_rt_put(rt);
  87                 return -ENETUNREACH;
  88         }
  89
  90         if (inet_opt == NULL || !inet_opt->opt.srr)
  91                 daddr = fl4->daddr;
  92
  93         if (inet->inet_saddr == 0) {
  94                 if (inet_csk(sk)->icsk_bind2_hash) {
  95                         prev_addr_hashbucket =
  96                                 inet_bhashfn_portaddr(&dccp_hashinfo, sk,
  97                                                       sock_net(sk),
  98                                                       inet->inet_num);
  99                         prev_sk_rcv_saddr = sk->sk_rcv_saddr;
 100                 }
 101                 inet->inet_saddr = fl4->saddr;
 102         }
 103
 104         sk_rcv_saddr_set(sk, inet->inet_saddr);
 105
 106         if (prev_addr_hashbucket) {
 107                 err = inet_bhash2_update_saddr(prev_addr_hashbucket, sk);
 108                 if (err) {
 109                         inet->inet_saddr = 0;
 110                         sk_rcv_saddr_set(sk, prev_sk_rcv_saddr);
 111                         ip_rt_put(rt);
 112                         return err;
 113                 }
 114         }
 115
 116         inet->inet_dport = usin->sin_port;
 117         sk_daddr_set(sk, daddr);
 118
 119         inet_csk(sk)->icsk_ext_hdr_len = 0;
 120         if (inet_opt)
 121                 inet_csk(sk)->icsk_ext_hdr_len = inet_opt->opt.optlen;
 122         /*
 123          * Socket identity is still unknown (sport may be zero).
 124          * However we set state to DCCP_REQUESTING and not releasing socket
 125          * lock select source port, enter ourselves into the hash tables and
 126          * complete initialization after this.
 127          */
 128         dccp_set_state(sk, DCCP_REQUESTING);
 129         err = inet_hash_connect(&dccp_death_row, sk);
 130         if (err != 0)
 131                 goto failure;
 132
 133         rt = ip_route_newports(fl4, rt, orig_sport, orig_dport,
 134                                inet->inet_sport, inet->inet_dport, sk);
 135         if (IS_ERR(rt)) {
 136                 err = PTR_ERR(rt);
 137                 rt = NULL;
 138                 goto failure;
 139         }
 140         /* OK, now commit destination to socket.  */
 141         sk_setup_caps(sk, &rt->dst);
 142
 143         dp->dccps_iss = secure_dccp_sequence_number(inet->inet_saddr,
 144                                                     inet->inet_daddr,
 145                                                     inet->inet_sport,
 146                                                     inet->inet_dport);
 147         inet->inet_id = get_random_u16();
 148
 149         err = dccp_connect(sk);
 150         rt = NULL;
 151         if (err != 0)
 152                 goto failure;
 153 out:
 154         return err;
 155 failure:
 156         /*
 157          * This unhashes the socket and releases the local port, if necessary.
 158          */
 159         dccp_set_state(sk, DCCP_CLOSED);
 160         ip_rt_put(rt);
 161         sk->sk_route_caps = 0;
 162         inet->inet_dport = 0;
 163         goto out;
 164 }
 165 EXPORT_SYMBOL_GPL(dccp_v4_connect);
 166
 167 /*
 168  * This routine does path mtu discovery as defined in RFC1191.
 169  */
 170 static inline void dccp_do_pmtu_discovery(struct sock *sk,
 171                                           const struct iphdr *iph,
 172                                           u32 mtu)
 173 {
 174         struct dst_entry *dst;
 175         const struct inet_sock *inet = inet_sk(sk);
 176         const struct dccp_sock *dp = dccp_sk(sk);
 177
 178         /* We are not interested in DCCP_LISTEN and request_socks (RESPONSEs
 179          * send out by Linux are always < 576bytes so they should go through
 180          * unfragmented).
 181          */
 182         if (sk->sk_state == DCCP_LISTEN)
 183                 return;
 184
 185         dst = inet_csk_update_pmtu(sk, mtu);
 186         if (!dst)
 187                 return;
 188
 189         /* Something is about to be wrong... Remember soft error
 190          * for the case, if this connection will not able to recover.
 191          */
 192         if (mtu < dst_mtu(dst) && ip_dont_fragment(sk, dst))
 193                 sk->sk_err_soft = EMSGSIZE;
 194
 195         mtu = dst_mtu(dst);
 196
 197         if (inet->pmtudisc != IP_PMTUDISC_DONT &&
 198             ip_sk_accept_pmtu(sk) &&
 199             inet_csk(sk)->icsk_pmtu_cookie > mtu) {
 200                 dccp_sync_mss(sk, mtu);
 201
 202                 /*
 203                  * From RFC 4340, sec. 14.1:
 204                  *
 205                  *      DCCP-Sync packets are the best choice for upward
 206                  *      probing, since DCCP-Sync probes do not risk application
 207                  *      data loss.
 208                  */
 209                 dccp_send_sync(sk, dp->dccps_gsr, DCCP_PKT_SYNC);
 210         } /* else let the usual retransmit timer handle it */
 211 }
 212
 213 static void dccp_do_redirect(struct sk_buff *skb, struct sock *sk)
 214 {
 215         struct dst_entry *dst = __sk_dst_check(sk, 0);
 216
 217         if (dst)
 218                 dst->ops->redirect(dst, sk, skb);
 219 }
 220
 221 void dccp_req_err(struct sock *sk, u64 seq)
 222         {
 223         struct request_sock *req = inet_reqsk(sk);
 224         struct net *net = sock_net(sk);
 225
 226         /*
 227          * ICMPs are not backlogged, hence we cannot get an established
 228          * socket here.
 229          */
 230         if (!between48(seq, dccp_rsk(req)->dreq_iss, dccp_rsk(req)->dreq_gss)) {
 231                 __NET_INC_STATS(net, LINUX_MIB_OUTOFWINDOWICMPS);
 232         } else {
 233                 /*
 234                  * Still in RESPOND, just remove it silently.
 235                  * There is no good way to pass the error to the newly
 236                  * created socket, and POSIX does not want network
 237                  * errors returned from accept().
 238                  */
 239                 inet_csk_reqsk_queue_drop(req->rsk_listener, req);
 240         }
 241         reqsk_put(req);
 242 }
 243 EXPORT_SYMBOL(dccp_req_err);
 244
 245 /*
 246  * This routine is called by the ICMP module when it gets some sort of error
 247  * condition. If err < 0 then the socket should be closed and the error
 248  * returned to the user. If err > 0 it's just the icmp type << 8 | icmp code.
 249  * After adjustment header points to the first 8 bytes of the tcp header. We
 250  * need to find the appropriate port.
 251  *
 252  * The locking strategy used here is very "optimistic". When someone else
 253  * accesses the socket the ICMP is just dropped and for some paths there is no
 254  * check at all. A more general error queue to queue errors for later handling
 255  * is probably better.
 256  */
 257 static int dccp_v4_err(struct sk_buff *skb, u32 info)
 258 {
 259         const struct iphdr *iph = (struct iphdr *)skb->data;
 260         const u8 offset = iph->ihl << 2;
 261         const struct dccp_hdr *dh;
 262         struct dccp_sock *dp;
 263         struct inet_sock *inet;
 264         const int type = icmp_hdr(skb)->type;
 265         const int code = icmp_hdr(skb)->code;
 266         struct sock *sk;
 267         __u64 seq;
 268         int err;
 269         struct net *net = dev_net(skb->dev);
 270
 271         /* Only need dccph_dport & dccph_sport which are the first
 272          * 4 bytes in dccp header.
 273          * Our caller (icmp_socket_deliver()) already pulled 8 bytes for us.
 274          */
 275         BUILD_BUG_ON(offsetofend(struct dccp_hdr, dccph_sport) > 8);
 276         BUILD_BUG_ON(offsetofend(struct dccp_hdr, dccph_dport) > 8);
 277         dh = (struct dccp_hdr *)(skb->data + offset);
 278
 279         sk = __inet_lookup_established(net, &dccp_hashinfo,
 280                                        iph->daddr, dh->dccph_dport,
 281                                        iph->saddr, ntohs(dh->dccph_sport),
 282                                        inet_iif(skb), 0);
 283         if (!sk) {
 284                 __ICMP_INC_STATS(net, ICMP_MIB_INERRORS);
 285                 return -ENOENT;
 286         }
 287
 288         if (sk->sk_state == DCCP_TIME_WAIT) {
 289                 inet_twsk_put(inet_twsk(sk));
 290                 return 0;
 291         }
 292         seq = dccp_hdr_seq(dh);
 293         if (sk->sk_state == DCCP_NEW_SYN_RECV) {
 294                 dccp_req_err(sk, seq);
 295                 return 0;
 296         }
 297
 298         bh_lock_sock(sk);
 299         /* If too many ICMPs get dropped on busy
 300          * servers this needs to be solved differently.
 301          */
 302         if (sock_owned_by_user(sk))
 303                 __NET_INC_STATS(net, LINUX_MIB_LOCKDROPPEDICMPS);
 304
 305         if (sk->sk_state == DCCP_CLOSED)
 306                 goto out;
 307
 308         dp = dccp_sk(sk);
 309         if ((1 << sk->sk_state) & ~(DCCPF_REQUESTING | DCCPF_LISTEN) &&
 310             !between48(seq, dp->dccps_awl, dp->dccps_awh)) {
 311                 __NET_INC_STATS(net, LINUX_MIB_OUTOFWINDOWICMPS);
 312                 goto out;
 313         }
 314
 315         switch (type) {
 316         case ICMP_REDIRECT:
 317                 if (!sock_owned_by_user(sk))
 318                         dccp_do_redirect(skb, sk);
 319                 goto out;
 320         case ICMP_SOURCE_QUENCH:
 321                 /* Just silently ignore these. */
 322                 goto out;
 323         case ICMP_PARAMETERPROB:
 324                 err = EPROTO;
 325                 break;
 326         case ICMP_DEST_UNREACH:
 327                 if (code > NR_ICMP_UNREACH)
 328                         goto out;
 329
 330                 if (code == ICMP_FRAG_NEEDED) { /* PMTU discovery (RFC1191) */
 331                         if (!sock_owned_by_user(sk))
 332                                 dccp_do_pmtu_discovery(sk, iph, info);
 333                         goto out;
 334                 }
 335
 336                 err = icmp_err_convert[code].errno;
 337                 break;
 338         case ICMP_TIME_EXCEEDED:
 339                 err = EHOSTUNREACH;
 340                 break;
 341         default:
 342                 goto out;
 343         }
 344
 345         switch (sk->sk_state) {
 346         case DCCP_REQUESTING:
 347         case DCCP_RESPOND:
 348                 if (!sock_owned_by_user(sk)) {
 349                         __DCCP_INC_STATS(DCCP_MIB_ATTEMPTFAILS);
 350                         sk->sk_err = err;
 351
 352                         sk_error_report(sk);
 353
 354                         dccp_done(sk);
 355                 } else
 356                         sk->sk_err_soft = err;
 357                 goto out;
 358         }
 359
 360         /* If we've already connected we will keep trying
 361          * until we time out, or the user gives up.
 362          *
 363          * rfc1122 4.2.3.9 allows to consider as hard errors
 364          * only PROTO_UNREACH and PORT_UNREACH (well, FRAG_FAILED too,
 365          * but it is obsoleted by pmtu discovery).
 366          *
 367          * Note, that in modern internet, where routing is unreliable
 368          * and in each dark corner broken firewalls sit, sending random
 369          * errors ordered by their masters even this two messages finally lose
 370          * their original sense (even Linux sends invalid PORT_UNREACHs)
 371          *
 372          * Now we are in compliance with RFCs.
 373          *                                                      --ANK (980905)
 374          */
 375
 376         inet = inet_sk(sk);
 377         if (!sock_owned_by_user(sk) && inet->recverr) {
 378                 sk->sk_err = err;
 379                 sk_error_report(sk);
 380         } else /* Only an error on timeout */
 381                 sk->sk_err_soft = err;
 382 out:
 383         bh_unlock_sock(sk);
 384         sock_put(sk);
 385         return 0;
 386 }
 387
 388 static inline __sum16 dccp_v4_csum_finish(struct sk_buff *skb,
 389                                       __be32 src, __be32 dst)
 390 {
 391         return csum_tcpudp_magic(src, dst, skb->len, IPPROTO_DCCP, skb->csum);
 392 }
 393
 394 void dccp_v4_send_check(struct sock *sk, struct sk_buff *skb)
 395 {
 396         const struct inet_sock *inet = inet_sk(sk);
 397         struct dccp_hdr *dh = dccp_hdr(skb);
 398
 399         dccp_csum_outgoing(skb);
 400         dh->dccph_checksum = dccp_v4_csum_finish(skb,
 401                                                  inet->inet_saddr,
 402                                                  inet->inet_daddr);
 403 }
 404 EXPORT_SYMBOL_GPL(dccp_v4_send_check);
 405
 406 static inline u64 dccp_v4_init_sequence(const struct sk_buff *skb)
 407 {
 408         return secure_dccp_sequence_number(ip_hdr(skb)->daddr,
 409                                            ip_hdr(skb)->saddr,
 410                                            dccp_hdr(skb)->dccph_dport,
 411                                            dccp_hdr(skb)->dccph_sport);
 412 }
 413
 414 /*
 415  * The three way handshake has completed - we got a valid ACK or DATAACK -
 416  * now create the new socket.
 417  *
 418  * This is the equivalent of TCP's tcp_v4_syn_recv_sock
 419  */
 420 struct sock *dccp_v4_request_recv_sock(const struct sock *sk,
 421                                        struct sk_buff *skb,
 422                                        struct request_sock *req,
 423                                        struct dst_entry *dst,
 424                                        struct request_sock *req_unhash,
 425                                        bool *own_req)
 426 {
 427         struct inet_request_sock *ireq;
 428         struct inet_sock *newinet;
 429         struct sock *newsk;
 430
 431         if (sk_acceptq_is_full(sk))
 432                 goto exit_overflow;
 433
 434         newsk = dccp_create_openreq_child(sk, req, skb);
 435         if (newsk == NULL)
 436                 goto exit_nonewsk;
 437
 438         newinet            = inet_sk(newsk);
 439         ireq               = inet_rsk(req);
 440         sk_daddr_set(newsk, ireq->ir_rmt_addr);
 441         sk_rcv_saddr_set(newsk, ireq->ir_loc_addr);
 442         newinet->inet_saddr     = ireq->ir_loc_addr;
 443         RCU_INIT_POINTER(newinet->inet_opt, rcu_dereference(ireq->ireq_opt));
 444         newinet->mc_index  = inet_iif(skb);
 445         newinet->mc_ttl    = ip_hdr(skb)->ttl;
 446         newinet->inet_id   = get_random_u16();
 447
 448         if (dst == NULL && (dst = inet_csk_route_child_sock(sk, newsk, req)) == NULL)
 449                 goto put_and_exit;
 450
 451         sk_setup_caps(newsk, dst);
 452
 453         dccp_sync_mss(newsk, dst_mtu(dst));
 454
 455         if (__inet_inherit_port(sk, newsk) < 0)
 456                 goto put_and_exit;
 457         *own_req = inet_ehash_nolisten(newsk, req_to_sk(req_unhash), NULL);
 458         if (*own_req)
 459                 ireq->ireq_opt = NULL;
 460         else
 461                 newinet->inet_opt = NULL;
 462         return newsk;
 463
 464 exit_overflow:
 465         __NET_INC_STATS(sock_net(sk), LINUX_MIB_LISTENOVERFLOWS);
 466 exit_nonewsk:
 467         dst_release(dst);
 468 exit:
 469         __NET_INC_STATS(sock_net(sk), LINUX_MIB_LISTENDROPS);
 470         return NULL;
 471 put_and_exit:
 472         newinet->inet_opt = NULL;
 473         inet_csk_prepare_forced_close(newsk);
 474         dccp_done(newsk);
 475         goto exit;
 476 }
 477 EXPORT_SYMBOL_GPL(dccp_v4_request_recv_sock);
 478
 479 static struct dst_entry* dccp_v4_route_skb(struct net *net, struct sock *sk,
 480                                            struct sk_buff *skb)
 481 {
 482         struct rtable *rt;
 483         const struct iphdr *iph = ip_hdr(skb);
 484         struct flowi4 fl4 = {
 485                 .flowi4_oif = inet_iif(skb),
 486                 .daddr = iph->saddr,
 487                 .saddr = iph->daddr,
 488                 .flowi4_tos = RT_CONN_FLAGS(sk),
 489                 .flowi4_proto = sk->sk_protocol,
 490                 .fl4_sport = dccp_hdr(skb)->dccph_dport,
 491                 .fl4_dport = dccp_hdr(skb)->dccph_sport,
 492         };
 493
 494         security_skb_classify_flow(skb, flowi4_to_flowi_common(&fl4));
 495         rt = ip_route_output_flow(net, &fl4, sk);
 496         if (IS_ERR(rt)) {
 497                 IP_INC_STATS(net, IPSTATS_MIB_OUTNOROUTES);
 498                 return NULL;
 499         }
 500
 501         return &rt->dst;
 502 }
 503
 504 static int dccp_v4_send_response(const struct sock *sk, struct request_sock *req)
 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->ir_loc_addr,
 521                                                               ireq->ir_rmt_addr);
 522                 rcu_read_lock();
 523                 err = ip_build_and_send_pkt(skb, sk, ireq->ir_loc_addr,
 524                                             ireq->ir_rmt_addr,
 525                                             rcu_dereference(ireq->ireq_opt),
 526                                             inet_sk(sk)->tos);
 527                 rcu_read_unlock();
 528                 err = net_xmit_eval(err);
 529         }
 530
 531 out:
 532         dst_release(dst);
 533         return err;
 534 }
 535
 536 static void dccp_v4_ctl_send_reset(const struct sock *sk, struct sk_buff *rxskb)
 537 {
 538         int err;
 539         const struct iphdr *rxiph;
 540         struct sk_buff *skb;
 541         struct dst_entry *dst;
 542         struct net *net = dev_net(skb_dst(rxskb)->dev);
 543         struct dccp_v4_pernet *pn;
 544         struct sock *ctl_sk;
 545
 546         /* Never send a reset in response to a reset. */
 547         if (dccp_hdr(rxskb)->dccph_type == DCCP_PKT_RESET)
 548                 return;
 549
 550         if (skb_rtable(rxskb)->rt_type != RTN_LOCAL)
 551                 return;
 552
 553         pn = net_generic(net, dccp_v4_pernet_id);
 554         ctl_sk = pn->v4_ctl_sk;
 555         dst = dccp_v4_route_skb(net, ctl_sk, rxskb);
 556         if (dst == NULL)
 557                 return;
 558
 559         skb = dccp_ctl_make_reset(ctl_sk, rxskb);
 560         if (skb == NULL)
 561                 goto out;
 562
 563         rxiph = ip_hdr(rxskb);
 564         dccp_hdr(skb)->dccph_checksum = dccp_v4_csum_finish(skb, rxiph->saddr,
 565                                                                  rxiph->daddr);
 566         skb_dst_set(skb, dst_clone(dst));
 567
 568         local_bh_disable();
 569         bh_lock_sock(ctl_sk);
 570         err = ip_build_and_send_pkt(skb, ctl_sk,
 571                                     rxiph->daddr, rxiph->saddr, NULL,
 572                                     inet_sk(ctl_sk)->tos);
 573         bh_unlock_sock(ctl_sk);
 574
 575         if (net_xmit_eval(err) == 0) {
 576                 __DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
 577                 __DCCP_INC_STATS(DCCP_MIB_OUTRSTS);
 578         }
 579         local_bh_enable();
 580 out:
 581         dst_release(dst);
 582 }
 583
 584 static void dccp_v4_reqsk_destructor(struct request_sock *req)
 585 {
 586         dccp_feat_list_purge(&dccp_rsk(req)->dreq_featneg);
 587         kfree(rcu_dereference_protected(inet_rsk(req)->ireq_opt, 1));
 588 }
 589
 590 void dccp_syn_ack_timeout(const struct request_sock *req)
 591 {
 592 }
 593 EXPORT_SYMBOL(dccp_syn_ack_timeout);
 594
 595 static struct request_sock_ops dccp_request_sock_ops __read_mostly = {
 596         .family         = PF_INET,
 597         .obj_size       = sizeof(struct dccp_request_sock),
 598         .rtx_syn_ack    = dccp_v4_send_response,
 599         .send_ack       = dccp_reqsk_send_ack,
 600         .destructor     = dccp_v4_reqsk_destructor,
 601         .send_reset     = dccp_v4_ctl_send_reset,
 602         .syn_ack_timeout = dccp_syn_ack_timeout,
 603 };
 604
 605 int dccp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
 606 {
 607         struct inet_request_sock *ireq;
 608         struct request_sock *req;
 609         struct dccp_request_sock *dreq;
 610         const __be32 service = dccp_hdr_request(skb)->dccph_req_service;
 611         struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
 612
 613         /* Never answer to DCCP_PKT_REQUESTs send to broadcast or multicast */
 614         if (skb_rtable(skb)->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
 615                 return 0;       /* discard, don't send a reset here */
 616
 617         if (dccp_bad_service_code(sk, service)) {
 618                 dcb->dccpd_reset_code = DCCP_RESET_CODE_BAD_SERVICE_CODE;
 619                 goto drop;
 620         }
 621         /*
 622          * TW buckets are converted to open requests without
 623          * limitations, they conserve resources and peer is
 624          * evidently real one.
 625          */
 626         dcb->dccpd_reset_code = DCCP_RESET_CODE_TOO_BUSY;
 627         if (inet_csk_reqsk_queue_is_full(sk))
 628                 goto drop;
 629
 630         if (sk_acceptq_is_full(sk))
 631                 goto drop;
 632
 633         req = inet_reqsk_alloc(&dccp_request_sock_ops, sk, true);
 634         if (req == NULL)
 635                 goto drop;
 636
 637         if (dccp_reqsk_init(req, dccp_sk(sk), skb))
 638                 goto drop_and_free;
 639
 640         dreq = dccp_rsk(req);
 641         if (dccp_parse_options(sk, dreq, skb))
 642                 goto drop_and_free;
 643
 644         if (security_inet_conn_request(sk, skb, req))
 645                 goto drop_and_free;
 646
 647         ireq = inet_rsk(req);
 648         sk_rcv_saddr_set(req_to_sk(req), ip_hdr(skb)->daddr);
 649         sk_daddr_set(req_to_sk(req), ip_hdr(skb)->saddr);
 650         ireq->ir_mark = inet_request_mark(sk, skb);
 651         ireq->ireq_family = AF_INET;
 652         ireq->ir_iif = READ_ONCE(sk->sk_bound_dev_if);
 653
 654         /*
 655          * Step 3: Process LISTEN state
 656          *
 657          * Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init Cookie
 658          *
 659          * Setting S.SWL/S.SWH to is deferred to dccp_create_openreq_child().
 660          */
 661         dreq->dreq_isr     = dcb->dccpd_seq;
 662         dreq->dreq_gsr     = dreq->dreq_isr;
 663         dreq->dreq_iss     = dccp_v4_init_sequence(skb);
 664         dreq->dreq_gss     = dreq->dreq_iss;
 665         dreq->dreq_service = service;
 666
 667         if (dccp_v4_send_response(sk, req))
 668                 goto drop_and_free;
 669
 670         inet_csk_reqsk_queue_hash_add(sk, req, DCCP_TIMEOUT_INIT);
 671         reqsk_put(req);
 672         return 0;
 673
 674 drop_and_free:
 675         reqsk_free(req);
 676 drop:
 677         __DCCP_INC_STATS(DCCP_MIB_ATTEMPTFAILS);
 678         return -1;
 679 }
 680 EXPORT_SYMBOL_GPL(dccp_v4_conn_request);
 681
 682 int dccp_v4_do_rcv(struct sock *sk, struct sk_buff *skb)
 683 {
 684         struct dccp_hdr *dh = dccp_hdr(skb);
 685
 686         if (sk->sk_state == DCCP_OPEN) { /* Fast path */
 687                 if (dccp_rcv_established(sk, skb, dh, skb->len))
 688                         goto reset;
 689                 return 0;
 690         }
 691
 692         /*
 693          *  Step 3: Process LISTEN state
 694          *       If P.type == Request or P contains a valid Init Cookie option,
 695          *            (* Must scan the packet's options to check for Init
 696          *               Cookies.  Only Init Cookies are processed here,
 697          *               however; other options are processed in Step 8.  This
 698          *               scan need only be performed if the endpoint uses Init
 699          *               Cookies *)
 700          *            (* Generate a new socket and switch to that socket *)
 701          *            Set S := new socket for this port pair
 702          *            S.state = RESPOND
 703          *            Choose S.ISS (initial seqno) or set from Init Cookies
 704          *            Initialize S.GAR := S.ISS
 705          *            Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init Cookies
 706          *            Continue with S.state == RESPOND
 707          *            (* A Response packet will be generated in Step 11 *)
 708          *       Otherwise,
 709          *            Generate Reset(No Connection) unless P.type == Reset
 710          *            Drop packet and return
 711          *
 712          * NOTE: the check for the packet types is done in
 713          *       dccp_rcv_state_process
 714          */
 715
 716         if (dccp_rcv_state_process(sk, skb, dh, skb->len))
 717                 goto reset;
 718         return 0;
 719
 720 reset:
 721         dccp_v4_ctl_send_reset(sk, skb);
 722         kfree_skb(skb);
 723         return 0;
 724 }
 725 EXPORT_SYMBOL_GPL(dccp_v4_do_rcv);
 726
 727 /**
 728  *      dccp_invalid_packet  -  check for malformed packets
 729  *      @skb: Packet to validate
 730  *
 731  *      Implements RFC 4340, 8.5:  Step 1: Check header basics
 732  *      Packets that fail these checks are ignored and do not receive Resets.
 733  */
 734 int dccp_invalid_packet(struct sk_buff *skb)
 735 {
 736         const struct dccp_hdr *dh;
 737         unsigned int cscov;
 738         u8 dccph_doff;
 739
 740         if (skb->pkt_type != PACKET_HOST)
 741                 return 1;
 742
 743         /* If the packet is shorter than 12 bytes, drop packet and return */
 744         if (!pskb_may_pull(skb, sizeof(struct dccp_hdr))) {
 745                 DCCP_WARN("pskb_may_pull failed\n");
 746                 return 1;
 747         }
 748
 749         dh = dccp_hdr(skb);
 750
 751         /* If P.type is not understood, drop packet and return */
 752         if (dh->dccph_type >= DCCP_PKT_INVALID) {
 753                 DCCP_WARN("invalid packet type\n");
 754                 return 1;
 755         }
 756
 757         /*
 758          * If P.Data Offset is too small for packet type, drop packet and return
 759          */
 760         dccph_doff = dh->dccph_doff;
 761         if (dccph_doff < dccp_hdr_len(skb) / sizeof(u32)) {
 762                 DCCP_WARN("P.Data Offset(%u) too small\n", dccph_doff);
 763                 return 1;
 764         }
 765         /*
 766          * If P.Data Offset is too large for packet, drop packet and return
 767          */
 768         if (!pskb_may_pull(skb, dccph_doff * sizeof(u32))) {
 769                 DCCP_WARN("P.Data Offset(%u) too large\n", dccph_doff);
 770                 return 1;
 771         }
 772         dh = dccp_hdr(skb);
 773         /*
 774          * If P.type is not Data, Ack, or DataAck and P.X == 0 (the packet
 775          * has short sequence numbers), drop packet and return
 776          */
 777         if ((dh->dccph_type < DCCP_PKT_DATA    ||
 778             dh->dccph_type > DCCP_PKT_DATAACK) && dh->dccph_x == 0)  {
 779                 DCCP_WARN("P.type (%s) not Data || [Data]Ack, while P.X == 0\n",
 780                           dccp_packet_name(dh->dccph_type));
 781                 return 1;
 782         }
 783
 784         /*
 785          * If P.CsCov is too large for the packet size, drop packet and return.
 786          * This must come _before_ checksumming (not as RFC 4340 suggests).
 787          */
 788         cscov = dccp_csum_coverage(skb);
 789         if (cscov > skb->len) {
 790                 DCCP_WARN("P.CsCov %u exceeds packet length %d\n",
 791                           dh->dccph_cscov, skb->len);
 792                 return 1;
 793         }
 794
 795         /* If header checksum is incorrect, drop packet and return.
 796          * (This step is completed in the AF-dependent functions.) */
 797         skb->csum = skb_checksum(skb, 0, cscov, 0);
 798
 799         return 0;
 800 }
 801 EXPORT_SYMBOL_GPL(dccp_invalid_packet);
 802
 803 /* this is called when real data arrives */
 804 static int dccp_v4_rcv(struct sk_buff *skb)
 805 {
 806         const struct dccp_hdr *dh;
 807         const struct iphdr *iph;
 808         bool refcounted;
 809         struct sock *sk;
 810         int min_cov;
 811
 812         /* Step 1: Check header basics */
 813
 814         if (dccp_invalid_packet(skb))
 815                 goto discard_it;
 816
 817         iph = ip_hdr(skb);
 818         /* Step 1: If header checksum is incorrect, drop packet and return */
 819         if (dccp_v4_csum_finish(skb, iph->saddr, iph->daddr)) {
 820                 DCCP_WARN("dropped packet with invalid checksum\n");
 821                 goto discard_it;
 822         }
 823
 824         dh = dccp_hdr(skb);
 825
 826         DCCP_SKB_CB(skb)->dccpd_seq  = dccp_hdr_seq(dh);
 827         DCCP_SKB_CB(skb)->dccpd_type = dh->dccph_type;
 828
 829         dccp_pr_debug("%8.8s src=%pI4@%-5d dst=%pI4@%-5d seq=%llu",
 830                       dccp_packet_name(dh->dccph_type),
 831                       &iph->saddr, ntohs(dh->dccph_sport),
 832                       &iph->daddr, ntohs(dh->dccph_dport),
 833                       (unsigned long long) DCCP_SKB_CB(skb)->dccpd_seq);
 834
 835         if (dccp_packet_without_ack(skb)) {
 836                 DCCP_SKB_CB(skb)->dccpd_ack_seq = DCCP_PKT_WITHOUT_ACK_SEQ;
 837                 dccp_pr_debug_cat("\n");
 838         } else {
 839                 DCCP_SKB_CB(skb)->dccpd_ack_seq = dccp_hdr_ack_seq(skb);
 840                 dccp_pr_debug_cat(", ack=%llu\n", (unsigned long long)
 841                                   DCCP_SKB_CB(skb)->dccpd_ack_seq);
 842         }
 843
 844 lookup:
 845         sk = __inet_lookup_skb(&dccp_hashinfo, skb, __dccp_hdr_len(dh),
 846                                dh->dccph_sport, dh->dccph_dport, 0, &refcounted);
 847         if (!sk) {
 848                 dccp_pr_debug("failed to look up flow ID in table and "
 849                               "get corresponding socket\n");
 850                 goto no_dccp_socket;
 851         }
 852
 853         /*
 854          * Step 2:
 855          *      ... or S.state == TIMEWAIT,
 856          *              Generate Reset(No Connection) unless P.type == Reset
 857          *              Drop packet and return
 858          */
 859         if (sk->sk_state == DCCP_TIME_WAIT) {
 860                 dccp_pr_debug("sk->sk_state == DCCP_TIME_WAIT: do_time_wait\n");
 861                 inet_twsk_put(inet_twsk(sk));
 862                 goto no_dccp_socket;
 863         }
 864
 865         if (sk->sk_state == DCCP_NEW_SYN_RECV) {
 866                 struct request_sock *req = inet_reqsk(sk);
 867                 struct sock *nsk;
 868
 869                 sk = req->rsk_listener;
 870                 if (unlikely(sk->sk_state != DCCP_LISTEN)) {
 871                         inet_csk_reqsk_queue_drop_and_put(sk, req);
 872                         goto lookup;
 873                 }
 874                 sock_hold(sk);
 875                 refcounted = true;
 876                 nsk = dccp_check_req(sk, skb, req);
 877                 if (!nsk) {
 878                         reqsk_put(req);
 879                         goto discard_and_relse;
 880                 }
 881                 if (nsk == sk) {
 882                         reqsk_put(req);
 883                 } else if (dccp_child_process(sk, nsk, skb)) {
 884                         dccp_v4_ctl_send_reset(sk, skb);
 885                         goto discard_and_relse;
 886                 } else {
 887                         sock_put(sk);
 888                         return 0;
 889                 }
 890         }
 891         /*
 892          * RFC 4340, sec. 9.2.1: Minimum Checksum Coverage
 893          *      o if MinCsCov = 0, only packets with CsCov = 0 are accepted
 894          *      o if MinCsCov > 0, also accept packets with CsCov >= MinCsCov
 895          */
 896         min_cov = dccp_sk(sk)->dccps_pcrlen;
 897         if (dh->dccph_cscov && (min_cov == 0 || dh->dccph_cscov < min_cov))  {
 898                 dccp_pr_debug("Packet CsCov %d does not satisfy MinCsCov %d\n",
 899                               dh->dccph_cscov, min_cov);
 900                 /* FIXME: "Such packets SHOULD be reported using Data Dropped
 901                  *         options (Section 11.7) with Drop Code 0, Protocol
 902                  *         Constraints."                                     */
 903                 goto discard_and_relse;
 904         }
 905
 906         if (!xfrm4_policy_check(sk, XFRM_POLICY_IN, skb))
 907                 goto discard_and_relse;
 908         nf_reset_ct(skb);
 909
 910         return __sk_receive_skb(sk, skb, 1, dh->dccph_doff * 4, refcounted);
 911
 912 no_dccp_socket:
 913         if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb))
 914                 goto discard_it;
 915         /*
 916          * Step 2:
 917          *      If no socket ...
 918          *              Generate Reset(No Connection) unless P.type == Reset
 919          *              Drop packet and return
 920          */
 921         if (dh->dccph_type != DCCP_PKT_RESET) {
 922                 DCCP_SKB_CB(skb)->dccpd_reset_code =
 923                                         DCCP_RESET_CODE_NO_CONNECTION;
 924                 dccp_v4_ctl_send_reset(sk, skb);
 925         }
 926
 927 discard_it:
 928         kfree_skb(skb);
 929         return 0;
 930
 931 discard_and_relse:
 932         if (refcounted)
 933                 sock_put(sk);
 934         goto discard_it;
 935 }
 936
 937 static const struct inet_connection_sock_af_ops dccp_ipv4_af_ops = {
 938         .queue_xmit        = ip_queue_xmit,
 939         .send_check        = dccp_v4_send_check,
 940         .rebuild_header    = inet_sk_rebuild_header,
 941         .conn_request      = dccp_v4_conn_request,
 942         .syn_recv_sock     = dccp_v4_request_recv_sock,
 943         .net_header_len    = sizeof(struct iphdr),
 944         .setsockopt        = ip_setsockopt,
 945         .getsockopt        = ip_getsockopt,
 946         .addr2sockaddr     = inet_csk_addr2sockaddr,
 947         .sockaddr_len      = sizeof(struct sockaddr_in),
 948 };
 949
 950 static int dccp_v4_init_sock(struct sock *sk)
 951 {
 952         static __u8 dccp_v4_ctl_sock_initialized;
 953         int err = dccp_init_sock(sk, dccp_v4_ctl_sock_initialized);
 954
 955         if (err == 0) {
 956                 if (unlikely(!dccp_v4_ctl_sock_initialized))
 957                         dccp_v4_ctl_sock_initialized = 1;
 958                 inet_csk(sk)->icsk_af_ops = &dccp_ipv4_af_ops;
 959         }
 960
 961         return err;
 962 }
 963
 964 static struct timewait_sock_ops dccp_timewait_sock_ops = {
 965         .twsk_obj_size  = sizeof(struct inet_timewait_sock),
 966 };
 967
 968 static struct proto dccp_v4_prot = {
 969         .name                   = "DCCP",
 970         .owner                  = THIS_MODULE,
 971         .close                  = dccp_close,
 972         .connect                = dccp_v4_connect,
 973         .disconnect             = dccp_disconnect,
 974         .ioctl                  = dccp_ioctl,
 975         .init                   = dccp_v4_init_sock,
 976         .setsockopt             = dccp_setsockopt,
 977         .getsockopt             = dccp_getsockopt,
 978         .sendmsg                = dccp_sendmsg,
 979         .recvmsg                = dccp_recvmsg,
 980         .backlog_rcv            = dccp_v4_do_rcv,
 981         .hash                   = inet_hash,
 982         .unhash                 = inet_unhash,
 983         .accept                 = inet_csk_accept,
 984         .get_port               = inet_csk_get_port,
 985         .shutdown               = dccp_shutdown,
 986         .destroy                = dccp_destroy_sock,
 987         .orphan_count           = &dccp_orphan_count,
 988         .max_header             = MAX_DCCP_HEADER,
 989         .obj_size               = sizeof(struct dccp_sock),
 990         .slab_flags             = SLAB_TYPESAFE_BY_RCU,
 991         .rsk_prot               = &dccp_request_sock_ops,
 992         .twsk_prot              = &dccp_timewait_sock_ops,
 993         .h.hashinfo             = &dccp_hashinfo,
 994 };
 995
 996 static const struct net_protocol dccp_v4_protocol = {
 997         .handler        = dccp_v4_rcv,
 998         .err_handler    = dccp_v4_err,
 999         .no_policy      = 1,
1000         .icmp_strict_tag_validation = 1,
1001 };
1002
1003 static const struct proto_ops inet_dccp_ops = {
1004         .family            = PF_INET,
1005         .owner             = THIS_MODULE,
1006         .release           = inet_release,
1007         .bind              = inet_bind,
1008         .connect           = inet_stream_connect,
1009         .socketpair        = sock_no_socketpair,
1010         .accept            = inet_accept,
1011         .getname           = inet_getname,
1012         /* FIXME: work on tcp_poll to rename it to inet_csk_poll */
1013         .poll              = dccp_poll,
1014         .ioctl             = inet_ioctl,
1015         .gettstamp         = sock_gettstamp,
1016         /* FIXME: work on inet_listen to rename it to sock_common_listen */
1017         .listen            = inet_dccp_listen,
1018         .shutdown          = inet_shutdown,
1019         .setsockopt        = sock_common_setsockopt,
1020         .getsockopt        = sock_common_getsockopt,
1021         .sendmsg           = inet_sendmsg,
1022         .recvmsg           = sock_common_recvmsg,
1023         .mmap              = sock_no_mmap,
1024         .sendpage          = sock_no_sendpage,
1025 };
1026
1027 static struct inet_protosw dccp_v4_protosw = {
1028         .type           = SOCK_DCCP,
1029         .protocol       = IPPROTO_DCCP,
1030         .prot           = &dccp_v4_prot,
1031         .ops            = &inet_dccp_ops,
1032         .flags          = INET_PROTOSW_ICSK,
1033 };
1034
1035 static int __net_init dccp_v4_init_net(struct net *net)
1036 {
1037         struct dccp_v4_pernet *pn = net_generic(net, dccp_v4_pernet_id);
1038
1039         if (dccp_hashinfo.bhash == NULL)
1040                 return -ESOCKTNOSUPPORT;
1041
1042         return inet_ctl_sock_create(&pn->v4_ctl_sk, PF_INET,
1043                                     SOCK_DCCP, IPPROTO_DCCP, net);
1044 }
1045
1046 static void __net_exit dccp_v4_exit_net(struct net *net)
1047 {
1048         struct dccp_v4_pernet *pn = net_generic(net, dccp_v4_pernet_id);
1049
1050         inet_ctl_sock_destroy(pn->v4_ctl_sk);
1051 }
1052
1053 static void __net_exit dccp_v4_exit_batch(struct list_head *net_exit_list)
1054 {
1055         inet_twsk_purge(&dccp_hashinfo, AF_INET);
1056 }
1057
1058 static struct pernet_operations dccp_v4_ops = {
1059         .init   = dccp_v4_init_net,
1060         .exit   = dccp_v4_exit_net,
1061         .exit_batch = dccp_v4_exit_batch,
1062         .id     = &dccp_v4_pernet_id,
1063         .size   = sizeof(struct dccp_v4_pernet),
1064 };
1065
1066 static int __init dccp_v4_init(void)
1067 {
1068         int err = proto_register(&dccp_v4_prot, 1);
1069
1070         if (err)
1071                 goto out;
1072
1073         inet_register_protosw(&dccp_v4_protosw);
1074
1075         err = register_pernet_subsys(&dccp_v4_ops);
1076         if (err)
1077                 goto out_destroy_ctl_sock;
1078
1079         err = inet_add_protocol(&dccp_v4_protocol, IPPROTO_DCCP);
1080         if (err)
1081                 goto out_proto_unregister;
1082
1083 out:
1084         return err;
1085 out_proto_unregister:
1086         unregister_pernet_subsys(&dccp_v4_ops);
1087 out_destroy_ctl_sock:
1088         inet_unregister_protosw(&dccp_v4_protosw);
1089         proto_unregister(&dccp_v4_prot);
1090         goto out;
1091 }
1092
1093 static void __exit dccp_v4_exit(void)
1094 {
1095         inet_del_protocol(&dccp_v4_protocol, IPPROTO_DCCP);
1096         unregister_pernet_subsys(&dccp_v4_ops);
1097         inet_unregister_protosw(&dccp_v4_protosw);
1098         proto_unregister(&dccp_v4_prot);
1099 }
1100
1101 module_init(dccp_v4_init);
1102 module_exit(dccp_v4_exit);
1103
1104 /*
1105  * __stringify doesn't likes enums, so use SOCK_DCCP (6) and IPPROTO_DCCP (33)
1106  * values directly, Also cover the case where the protocol is not specified,
1107  * i.e. net-pf-PF_INET-proto-0-type-SOCK_DCCP
1108  */
1109 MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_INET, 33, 6);
1110 MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_INET, 0, 6);
1111 MODULE_LICENSE("GPL");
1112 MODULE_AUTHOR("Arnaldo Carvalho de Melo <acme@mandriva.com>");
1113 MODULE_DESCRIPTION("DCCP - Datagram Congestion Controlled Protocol");