linux/net/dccp/ipv4.c
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   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
  27#include "ackvec.h"
  28#include "ccid.h"
  29#include "dccp.h"
  30#include "feat.h"
  31
  32/*
  33 * The per-net dccp.v4_ctl_sk socket is used for responding to
  34 * the Out-of-the-blue (OOTB) packets. A control sock will be created
  35 * for this socket at the initialization time.
  36 */
  37
  38int dccp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
  39{
  40        const struct sockaddr_in *usin = (struct sockaddr_in *)uaddr;
  41        struct inet_sock *inet = inet_sk(sk);
  42        struct dccp_sock *dp = dccp_sk(sk);
  43        __be16 orig_sport, orig_dport;
  44        __be32 daddr, nexthop;
  45        struct flowi4 *fl4;
  46        struct rtable *rt;
  47        int err;
  48        struct ip_options_rcu *inet_opt;
  49
  50        dp->dccps_role = DCCP_ROLE_CLIENT;
  51
  52        if (addr_len < sizeof(struct sockaddr_in))
  53                return -EINVAL;
  54
  55        if (usin->sin_family != AF_INET)
  56                return -EAFNOSUPPORT;
  57
  58        nexthop = daddr = usin->sin_addr.s_addr;
  59
  60        inet_opt = rcu_dereference_protected(inet->inet_opt,
  61                                             lockdep_sock_is_held(sk));
  62        if (inet_opt != NULL && inet_opt->opt.srr) {
  63                if (daddr == 0)
  64                        return -EINVAL;
  65                nexthop = inet_opt->opt.faddr;
  66        }
  67
  68        orig_sport = inet->inet_sport;
  69        orig_dport = usin->sin_port;
  70        fl4 = &inet->cork.fl.u.ip4;
  71        rt = ip_route_connect(fl4, nexthop, inet->inet_saddr,
  72                              RT_CONN_FLAGS(sk), sk->sk_bound_dev_if,
  73                              IPPROTO_DCCP,
  74                              orig_sport, orig_dport, sk);
  75        if (IS_ERR(rt))
  76                return PTR_ERR(rt);
  77
  78        if (rt->rt_flags & (RTCF_MULTICAST | RTCF_BROADCAST)) {
  79                ip_rt_put(rt);
  80                return -ENETUNREACH;
  81        }
  82
  83        if (inet_opt == NULL || !inet_opt->opt.srr)
  84                daddr = fl4->daddr;
  85
  86        if (inet->inet_saddr == 0)
  87                inet->inet_saddr = fl4->saddr;
  88        sk_rcv_saddr_set(sk, inet->inet_saddr);
  89        inet->inet_dport = usin->sin_port;
  90        sk_daddr_set(sk, daddr);
  91
  92        inet_csk(sk)->icsk_ext_hdr_len = 0;
  93        if (inet_opt)
  94                inet_csk(sk)->icsk_ext_hdr_len = inet_opt->opt.optlen;
  95        /*
  96         * Socket identity is still unknown (sport may be zero).
  97         * However we set state to DCCP_REQUESTING and not releasing socket
  98         * lock select source port, enter ourselves into the hash tables and
  99         * complete initialization after this.
 100         */
 101        dccp_set_state(sk, DCCP_REQUESTING);
 102        err = inet_hash_connect(&dccp_death_row, sk);
 103        if (err != 0)
 104                goto failure;
 105
 106        rt = ip_route_newports(fl4, rt, orig_sport, orig_dport,
 107                               inet->inet_sport, inet->inet_dport, sk);
 108        if (IS_ERR(rt)) {
 109                err = PTR_ERR(rt);
 110                rt = NULL;
 111                goto failure;
 112        }
 113        /* OK, now commit destination to socket.  */
 114        sk_setup_caps(sk, &rt->dst);
 115
 116        dp->dccps_iss = secure_dccp_sequence_number(inet->inet_saddr,
 117                                                    inet->inet_daddr,
 118                                                    inet->inet_sport,
 119                                                    inet->inet_dport);
 120        inet->inet_id = prandom_u32();
 121
 122        err = dccp_connect(sk);
 123        rt = NULL;
 124        if (err != 0)
 125                goto failure;
 126out:
 127        return err;
 128failure:
 129        /*
 130         * This unhashes the socket and releases the local port, if necessary.
 131         */
 132        dccp_set_state(sk, DCCP_CLOSED);
 133        ip_rt_put(rt);
 134        sk->sk_route_caps = 0;
 135        inet->inet_dport = 0;
 136        goto out;
 137}
 138EXPORT_SYMBOL_GPL(dccp_v4_connect);
 139
 140/*
 141 * This routine does path mtu discovery as defined in RFC1191.
 142 */
 143static inline void dccp_do_pmtu_discovery(struct sock *sk,
 144                                          const struct iphdr *iph,
 145                                          u32 mtu)
 146{
 147        struct dst_entry *dst;
 148        const struct inet_sock *inet = inet_sk(sk);
 149        const struct dccp_sock *dp = dccp_sk(sk);
 150
 151        /* We are not interested in DCCP_LISTEN and request_socks (RESPONSEs
 152         * send out by Linux are always < 576bytes so they should go through
 153         * unfragmented).
 154         */
 155        if (sk->sk_state == DCCP_LISTEN)
 156                return;
 157
 158        dst = inet_csk_update_pmtu(sk, mtu);
 159        if (!dst)
 160                return;
 161
 162        /* Something is about to be wrong... Remember soft error
 163         * for the case, if this connection will not able to recover.
 164         */
 165        if (mtu < dst_mtu(dst) && ip_dont_fragment(sk, dst))
 166                sk->sk_err_soft = EMSGSIZE;
 167
 168        mtu = dst_mtu(dst);
 169
 170        if (inet->pmtudisc != IP_PMTUDISC_DONT &&
 171            ip_sk_accept_pmtu(sk) &&
 172            inet_csk(sk)->icsk_pmtu_cookie > mtu) {
 173                dccp_sync_mss(sk, mtu);
 174
 175                /*
 176                 * From RFC 4340, sec. 14.1:
 177                 *
 178                 *      DCCP-Sync packets are the best choice for upward
 179                 *      probing, since DCCP-Sync probes do not risk application
 180                 *      data loss.
 181                 */
 182                dccp_send_sync(sk, dp->dccps_gsr, DCCP_PKT_SYNC);
 183        } /* else let the usual retransmit timer handle it */
 184}
 185
 186static void dccp_do_redirect(struct sk_buff *skb, struct sock *sk)
 187{
 188        struct dst_entry *dst = __sk_dst_check(sk, 0);
 189
 190        if (dst)
 191                dst->ops->redirect(dst, sk, skb);
 192}
 193
 194void dccp_req_err(struct sock *sk, u64 seq)
 195        {
 196        struct request_sock *req = inet_reqsk(sk);
 197        struct net *net = sock_net(sk);
 198
 199        /*
 200         * ICMPs are not backlogged, hence we cannot get an established
 201         * socket here.
 202         */
 203        if (!between48(seq, dccp_rsk(req)->dreq_iss, dccp_rsk(req)->dreq_gss)) {
 204                __NET_INC_STATS(net, LINUX_MIB_OUTOFWINDOWICMPS);
 205        } else {
 206                /*
 207                 * Still in RESPOND, just remove it silently.
 208                 * There is no good way to pass the error to the newly
 209                 * created socket, and POSIX does not want network
 210                 * errors returned from accept().
 211                 */
 212                inet_csk_reqsk_queue_drop(req->rsk_listener, req);
 213        }
 214        reqsk_put(req);
 215}
 216EXPORT_SYMBOL(dccp_req_err);
 217
 218/*
 219 * This routine is called by the ICMP module when it gets some sort of error
 220 * condition. If err < 0 then the socket should be closed and the error
 221 * returned to the user. If err > 0 it's just the icmp type << 8 | icmp code.
 222 * After adjustment header points to the first 8 bytes of the tcp header. We
 223 * need to find the appropriate port.
 224 *
 225 * The locking strategy used here is very "optimistic". When someone else
 226 * accesses the socket the ICMP is just dropped and for some paths there is no
 227 * check at all. A more general error queue to queue errors for later handling
 228 * is probably better.
 229 */
 230static int dccp_v4_err(struct sk_buff *skb, u32 info)
 231{
 232        const struct iphdr *iph = (struct iphdr *)skb->data;
 233        const u8 offset = iph->ihl << 2;
 234        const struct dccp_hdr *dh;
 235        struct dccp_sock *dp;
 236        struct inet_sock *inet;
 237        const int type = icmp_hdr(skb)->type;
 238        const int code = icmp_hdr(skb)->code;
 239        struct sock *sk;
 240        __u64 seq;
 241        int err;
 242        struct net *net = dev_net(skb->dev);
 243
 244        /* Only need dccph_dport & dccph_sport which are the first
 245         * 4 bytes in dccp header.
 246         * Our caller (icmp_socket_deliver()) already pulled 8 bytes for us.
 247         */
 248        BUILD_BUG_ON(offsetofend(struct dccp_hdr, dccph_sport) > 8);
 249        BUILD_BUG_ON(offsetofend(struct dccp_hdr, dccph_dport) > 8);
 250        dh = (struct dccp_hdr *)(skb->data + offset);
 251
 252        sk = __inet_lookup_established(net, &dccp_hashinfo,
 253                                       iph->daddr, dh->dccph_dport,
 254                                       iph->saddr, ntohs(dh->dccph_sport),
 255                                       inet_iif(skb), 0);
 256        if (!sk) {
 257                __ICMP_INC_STATS(net, ICMP_MIB_INERRORS);
 258                return -ENOENT;
 259        }
 260
 261        if (sk->sk_state == DCCP_TIME_WAIT) {
 262                inet_twsk_put(inet_twsk(sk));
 263                return 0;
 264        }
 265        seq = dccp_hdr_seq(dh);
 266        if (sk->sk_state == DCCP_NEW_SYN_RECV) {
 267                dccp_req_err(sk, seq);
 268                return 0;
 269        }
 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                if (!sock_owned_by_user(sk))
 291                        dccp_do_redirect(skb, sk);
 292                goto out;
 293        case ICMP_SOURCE_QUENCH:
 294                /* Just silently ignore these. */
 295                goto out;
 296        case ICMP_PARAMETERPROB:
 297                err = EPROTO;
 298                break;
 299        case ICMP_DEST_UNREACH:
 300                if (code > NR_ICMP_UNREACH)
 301                        goto out;
 302
 303                if (code == ICMP_FRAG_NEEDED) { /* PMTU discovery (RFC1191) */
 304                        if (!sock_owned_by_user(sk))
 305                                dccp_do_pmtu_discovery(sk, iph, info);
 306                        goto out;
 307                }
 308
 309                err = icmp_err_convert[code].errno;
 310                break;
 311        case ICMP_TIME_EXCEEDED:
 312                err = EHOSTUNREACH;
 313                break;
 314        default:
 315                goto out;
 316        }
 317
 318        switch (sk->sk_state) {
 319        case DCCP_REQUESTING:
 320        case DCCP_RESPOND:
 321                if (!sock_owned_by_user(sk)) {
 322                        __DCCP_INC_STATS(DCCP_MIB_ATTEMPTFAILS);
 323                        sk->sk_err = err;
 324
 325                        sk->sk_error_report(sk);
 326
 327                        dccp_done(sk);
 328                } else
 329                        sk->sk_err_soft = err;
 330                goto out;
 331        }
 332
 333        /* If we've already connected we will keep trying
 334         * until we time out, or the user gives up.
 335         *
 336         * rfc1122 4.2.3.9 allows to consider as hard errors
 337         * only PROTO_UNREACH and PORT_UNREACH (well, FRAG_FAILED too,
 338         * but it is obsoleted by pmtu discovery).
 339         *
 340         * Note, that in modern internet, where routing is unreliable
 341         * and in each dark corner broken firewalls sit, sending random
 342         * errors ordered by their masters even this two messages finally lose
 343         * their original sense (even Linux sends invalid PORT_UNREACHs)
 344         *
 345         * Now we are in compliance with RFCs.
 346         *                                                      --ANK (980905)
 347         */
 348
 349        inet = inet_sk(sk);
 350        if (!sock_owned_by_user(sk) && inet->recverr) {
 351                sk->sk_err = err;
 352                sk->sk_error_report(sk);
 353        } else /* Only an error on timeout */
 354                sk->sk_err_soft = err;
 355out:
 356        bh_unlock_sock(sk);
 357        sock_put(sk);
 358        return 0;
 359}
 360
 361static inline __sum16 dccp_v4_csum_finish(struct sk_buff *skb,
 362                                      __be32 src, __be32 dst)
 363{
 364        return csum_tcpudp_magic(src, dst, skb->len, IPPROTO_DCCP, skb->csum);
 365}
 366
 367void dccp_v4_send_check(struct sock *sk, struct sk_buff *skb)
 368{
 369        const struct inet_sock *inet = inet_sk(sk);
 370        struct dccp_hdr *dh = dccp_hdr(skb);
 371
 372        dccp_csum_outgoing(skb);
 373        dh->dccph_checksum = dccp_v4_csum_finish(skb,
 374                                                 inet->inet_saddr,
 375                                                 inet->inet_daddr);
 376}
 377EXPORT_SYMBOL_GPL(dccp_v4_send_check);
 378
 379static inline u64 dccp_v4_init_sequence(const struct sk_buff *skb)
 380{
 381        return secure_dccp_sequence_number(ip_hdr(skb)->daddr,
 382                                           ip_hdr(skb)->saddr,
 383                                           dccp_hdr(skb)->dccph_dport,
 384                                           dccp_hdr(skb)->dccph_sport);
 385}
 386
 387/*
 388 * The three way handshake has completed - we got a valid ACK or DATAACK -
 389 * now create the new socket.
 390 *
 391 * This is the equivalent of TCP's tcp_v4_syn_recv_sock
 392 */
 393struct sock *dccp_v4_request_recv_sock(const struct sock *sk,
 394                                       struct sk_buff *skb,
 395                                       struct request_sock *req,
 396                                       struct dst_entry *dst,
 397                                       struct request_sock *req_unhash,
 398                                       bool *own_req)
 399{
 400        struct inet_request_sock *ireq;
 401        struct inet_sock *newinet;
 402        struct sock *newsk;
 403
 404        if (sk_acceptq_is_full(sk))
 405                goto exit_overflow;
 406
 407        newsk = dccp_create_openreq_child(sk, req, skb);
 408        if (newsk == NULL)
 409                goto exit_nonewsk;
 410
 411        newinet            = inet_sk(newsk);
 412        ireq               = inet_rsk(req);
 413        sk_daddr_set(newsk, ireq->ir_rmt_addr);
 414        sk_rcv_saddr_set(newsk, ireq->ir_loc_addr);
 415        newinet->inet_saddr     = ireq->ir_loc_addr;
 416        RCU_INIT_POINTER(newinet->inet_opt, rcu_dereference(ireq->ireq_opt));
 417        newinet->mc_index  = inet_iif(skb);
 418        newinet->mc_ttl    = ip_hdr(skb)->ttl;
 419        newinet->inet_id   = prandom_u32();
 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        *own_req = inet_ehash_nolisten(newsk, req_to_sk(req_unhash), NULL);
 431        if (*own_req)
 432                ireq->ireq_opt = NULL;
 433        else
 434                newinet->inet_opt = NULL;
 435        return newsk;
 436
 437exit_overflow:
 438        __NET_INC_STATS(sock_net(sk), LINUX_MIB_LISTENOVERFLOWS);
 439exit_nonewsk:
 440        dst_release(dst);
 441exit:
 442        __NET_INC_STATS(sock_net(sk), LINUX_MIB_LISTENDROPS);
 443        return NULL;
 444put_and_exit:
 445        newinet->inet_opt = NULL;
 446        inet_csk_prepare_forced_close(newsk);
 447        dccp_done(newsk);
 448        goto exit;
 449}
 450EXPORT_SYMBOL_GPL(dccp_v4_request_recv_sock);
 451
 452static struct dst_entry* dccp_v4_route_skb(struct net *net, struct sock *sk,
 453                                           struct sk_buff *skb)
 454{
 455        struct rtable *rt;
 456        const struct iphdr *iph = ip_hdr(skb);
 457        struct flowi4 fl4 = {
 458                .flowi4_oif = inet_iif(skb),
 459                .daddr = iph->saddr,
 460                .saddr = iph->daddr,
 461                .flowi4_tos = RT_CONN_FLAGS(sk),
 462                .flowi4_proto = sk->sk_protocol,
 463                .fl4_sport = dccp_hdr(skb)->dccph_dport,
 464                .fl4_dport = dccp_hdr(skb)->dccph_sport,
 465        };
 466
 467        security_skb_classify_flow(skb, flowi4_to_flowi(&fl4));
 468        rt = ip_route_output_flow(net, &fl4, sk);
 469        if (IS_ERR(rt)) {
 470                IP_INC_STATS(net, IPSTATS_MIB_OUTNOROUTES);
 471                return NULL;
 472        }
 473
 474        return &rt->dst;
 475}
 476
 477static int dccp_v4_send_response(const struct sock *sk, struct request_sock *req)
 478{
 479        int err = -1;
 480        struct sk_buff *skb;
 481        struct dst_entry *dst;
 482        struct flowi4 fl4;
 483
 484        dst = inet_csk_route_req(sk, &fl4, req);
 485        if (dst == NULL)
 486                goto out;
 487
 488        skb = dccp_make_response(sk, dst, req);
 489        if (skb != NULL) {
 490                const struct inet_request_sock *ireq = inet_rsk(req);
 491                struct dccp_hdr *dh = dccp_hdr(skb);
 492
 493                dh->dccph_checksum = dccp_v4_csum_finish(skb, ireq->ir_loc_addr,
 494                                                              ireq->ir_rmt_addr);
 495                rcu_read_lock();
 496                err = ip_build_and_send_pkt(skb, sk, ireq->ir_loc_addr,
 497                                            ireq->ir_rmt_addr,
 498                                            rcu_dereference(ireq->ireq_opt),
 499                                            inet_sk(sk)->tos);
 500                rcu_read_unlock();
 501                err = net_xmit_eval(err);
 502        }
 503
 504out:
 505        dst_release(dst);
 506        return err;
 507}
 508
 509static void dccp_v4_ctl_send_reset(const struct sock *sk, struct sk_buff *rxskb)
 510{
 511        int err;
 512        const struct iphdr *rxiph;
 513        struct sk_buff *skb;
 514        struct dst_entry *dst;
 515        struct net *net = dev_net(skb_dst(rxskb)->dev);
 516        struct sock *ctl_sk = net->dccp.v4_ctl_sk;
 517
 518        /* Never send a reset in response to a reset. */
 519        if (dccp_hdr(rxskb)->dccph_type == DCCP_PKT_RESET)
 520                return;
 521
 522        if (skb_rtable(rxskb)->rt_type != RTN_LOCAL)
 523                return;
 524
 525        dst = dccp_v4_route_skb(net, ctl_sk, rxskb);
 526        if (dst == NULL)
 527                return;
 528
 529        skb = dccp_ctl_make_reset(ctl_sk, rxskb);
 530        if (skb == NULL)
 531                goto out;
 532
 533        rxiph = ip_hdr(rxskb);
 534        dccp_hdr(skb)->dccph_checksum = dccp_v4_csum_finish(skb, rxiph->saddr,
 535                                                                 rxiph->daddr);
 536        skb_dst_set(skb, dst_clone(dst));
 537
 538        local_bh_disable();
 539        bh_lock_sock(ctl_sk);
 540        err = ip_build_and_send_pkt(skb, ctl_sk,
 541                                    rxiph->daddr, rxiph->saddr, NULL,
 542                                    inet_sk(ctl_sk)->tos);
 543        bh_unlock_sock(ctl_sk);
 544
 545        if (net_xmit_eval(err) == 0) {
 546                __DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
 547                __DCCP_INC_STATS(DCCP_MIB_OUTRSTS);
 548        }
 549        local_bh_enable();
 550out:
 551        dst_release(dst);
 552}
 553
 554static void dccp_v4_reqsk_destructor(struct request_sock *req)
 555{
 556        dccp_feat_list_purge(&dccp_rsk(req)->dreq_featneg);
 557        kfree(rcu_dereference_protected(inet_rsk(req)->ireq_opt, 1));
 558}
 559
 560void dccp_syn_ack_timeout(const struct request_sock *req)
 561{
 562}
 563EXPORT_SYMBOL(dccp_syn_ack_timeout);
 564
 565static struct request_sock_ops dccp_request_sock_ops __read_mostly = {
 566        .family         = PF_INET,
 567        .obj_size       = sizeof(struct dccp_request_sock),
 568        .rtx_syn_ack    = dccp_v4_send_response,
 569        .send_ack       = dccp_reqsk_send_ack,
 570        .destructor     = dccp_v4_reqsk_destructor,
 571        .send_reset     = dccp_v4_ctl_send_reset,
 572        .syn_ack_timeout = dccp_syn_ack_timeout,
 573};
 574
 575int dccp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
 576{
 577        struct inet_request_sock *ireq;
 578        struct request_sock *req;
 579        struct dccp_request_sock *dreq;
 580        const __be32 service = dccp_hdr_request(skb)->dccph_req_service;
 581        struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
 582
 583        /* Never answer to DCCP_PKT_REQUESTs send to broadcast or multicast */
 584        if (skb_rtable(skb)->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
 585                return 0;       /* discard, don't send a reset here */
 586
 587        if (dccp_bad_service_code(sk, service)) {
 588                dcb->dccpd_reset_code = DCCP_RESET_CODE_BAD_SERVICE_CODE;
 589                goto drop;
 590        }
 591        /*
 592         * TW buckets are converted to open requests without
 593         * limitations, they conserve resources and peer is
 594         * evidently real one.
 595         */
 596        dcb->dccpd_reset_code = DCCP_RESET_CODE_TOO_BUSY;
 597        if (inet_csk_reqsk_queue_is_full(sk))
 598                goto drop;
 599
 600        if (sk_acceptq_is_full(sk))
 601                goto drop;
 602
 603        req = inet_reqsk_alloc(&dccp_request_sock_ops, sk, true);
 604        if (req == NULL)
 605                goto drop;
 606
 607        if (dccp_reqsk_init(req, dccp_sk(sk), skb))
 608                goto drop_and_free;
 609
 610        dreq = dccp_rsk(req);
 611        if (dccp_parse_options(sk, dreq, skb))
 612                goto drop_and_free;
 613
 614        if (security_inet_conn_request(sk, skb, req))
 615                goto drop_and_free;
 616
 617        ireq = inet_rsk(req);
 618        sk_rcv_saddr_set(req_to_sk(req), ip_hdr(skb)->daddr);
 619        sk_daddr_set(req_to_sk(req), ip_hdr(skb)->saddr);
 620        ireq->ir_mark = inet_request_mark(sk, skb);
 621        ireq->ireq_family = AF_INET;
 622        ireq->ir_iif = sk->sk_bound_dev_if;
 623
 624        /*
 625         * Step 3: Process LISTEN state
 626         *
 627         * Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init Cookie
 628         *
 629         * Setting S.SWL/S.SWH to is deferred to dccp_create_openreq_child().
 630         */
 631        dreq->dreq_isr     = dcb->dccpd_seq;
 632        dreq->dreq_gsr     = dreq->dreq_isr;
 633        dreq->dreq_iss     = dccp_v4_init_sequence(skb);
 634        dreq->dreq_gss     = dreq->dreq_iss;
 635        dreq->dreq_service = service;
 636
 637        if (dccp_v4_send_response(sk, req))
 638                goto drop_and_free;
 639
 640        inet_csk_reqsk_queue_hash_add(sk, req, DCCP_TIMEOUT_INIT);
 641        reqsk_put(req);
 642        return 0;
 643
 644drop_and_free:
 645        reqsk_free(req);
 646drop:
 647        __DCCP_INC_STATS(DCCP_MIB_ATTEMPTFAILS);
 648        return -1;
 649}
 650EXPORT_SYMBOL_GPL(dccp_v4_conn_request);
 651
 652int dccp_v4_do_rcv(struct sock *sk, struct sk_buff *skb)
 653{
 654        struct dccp_hdr *dh = dccp_hdr(skb);
 655
 656        if (sk->sk_state == DCCP_OPEN) { /* Fast path */
 657                if (dccp_rcv_established(sk, skb, dh, skb->len))
 658                        goto reset;
 659                return 0;
 660        }
 661
 662        /*
 663         *  Step 3: Process LISTEN state
 664         *       If P.type == Request or P contains a valid Init Cookie option,
 665         *            (* Must scan the packet's options to check for Init
 666         *               Cookies.  Only Init Cookies are processed here,
 667         *               however; other options are processed in Step 8.  This
 668         *               scan need only be performed if the endpoint uses Init
 669         *               Cookies *)
 670         *            (* Generate a new socket and switch to that socket *)
 671         *            Set S := new socket for this port pair
 672         *            S.state = RESPOND
 673         *            Choose S.ISS (initial seqno) or set from Init Cookies
 674         *            Initialize S.GAR := S.ISS
 675         *            Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init Cookies
 676         *            Continue with S.state == RESPOND
 677         *            (* A Response packet will be generated in Step 11 *)
 678         *       Otherwise,
 679         *            Generate Reset(No Connection) unless P.type == Reset
 680         *            Drop packet and return
 681         *
 682         * NOTE: the check for the packet types is done in
 683         *       dccp_rcv_state_process
 684         */
 685
 686        if (dccp_rcv_state_process(sk, skb, dh, skb->len))
 687                goto reset;
 688        return 0;
 689
 690reset:
 691        dccp_v4_ctl_send_reset(sk, skb);
 692        kfree_skb(skb);
 693        return 0;
 694}
 695EXPORT_SYMBOL_GPL(dccp_v4_do_rcv);
 696
 697/**
 698 *      dccp_invalid_packet  -  check for malformed packets
 699 *      @skb: Packet to validate
 700 *
 701 *      Implements RFC 4340, 8.5:  Step 1: Check header basics
 702 *      Packets that fail these checks are ignored and do not receive Resets.
 703 */
 704int dccp_invalid_packet(struct sk_buff *skb)
 705{
 706        const struct dccp_hdr *dh;
 707        unsigned int cscov;
 708        u8 dccph_doff;
 709
 710        if (skb->pkt_type != PACKET_HOST)
 711                return 1;
 712
 713        /* If the packet is shorter than 12 bytes, drop packet and return */
 714        if (!pskb_may_pull(skb, sizeof(struct dccp_hdr))) {
 715                DCCP_WARN("pskb_may_pull failed\n");
 716                return 1;
 717        }
 718
 719        dh = dccp_hdr(skb);
 720
 721        /* If P.type is not understood, drop packet and return */
 722        if (dh->dccph_type >= DCCP_PKT_INVALID) {
 723                DCCP_WARN("invalid packet type\n");
 724                return 1;
 725        }
 726
 727        /*
 728         * If P.Data Offset is too small for packet type, drop packet and return
 729         */
 730        dccph_doff = dh->dccph_doff;
 731        if (dccph_doff < dccp_hdr_len(skb) / sizeof(u32)) {
 732                DCCP_WARN("P.Data Offset(%u) too small\n", dccph_doff);
 733                return 1;
 734        }
 735        /*
 736         * If P.Data Offset is too large for packet, drop packet and return
 737         */
 738        if (!pskb_may_pull(skb, dccph_doff * sizeof(u32))) {
 739                DCCP_WARN("P.Data Offset(%u) too large\n", dccph_doff);
 740                return 1;
 741        }
 742        dh = dccp_hdr(skb);
 743        /*
 744         * If P.type is not Data, Ack, or DataAck and P.X == 0 (the packet
 745         * has short sequence numbers), drop packet and return
 746         */
 747        if ((dh->dccph_type < DCCP_PKT_DATA    ||
 748            dh->dccph_type > DCCP_PKT_DATAACK) && dh->dccph_x == 0)  {
 749                DCCP_WARN("P.type (%s) not Data || [Data]Ack, while P.X == 0\n",
 750                          dccp_packet_name(dh->dccph_type));
 751                return 1;
 752        }
 753
 754        /*
 755         * If P.CsCov is too large for the packet size, drop packet and return.
 756         * This must come _before_ checksumming (not as RFC 4340 suggests).
 757         */
 758        cscov = dccp_csum_coverage(skb);
 759        if (cscov > skb->len) {
 760                DCCP_WARN("P.CsCov %u exceeds packet length %d\n",
 761                          dh->dccph_cscov, skb->len);
 762                return 1;
 763        }
 764
 765        /* If header checksum is incorrect, drop packet and return.
 766         * (This step is completed in the AF-dependent functions.) */
 767        skb->csum = skb_checksum(skb, 0, cscov, 0);
 768
 769        return 0;
 770}
 771EXPORT_SYMBOL_GPL(dccp_invalid_packet);
 772
 773/* this is called when real data arrives */
 774static int dccp_v4_rcv(struct sk_buff *skb)
 775{
 776        const struct dccp_hdr *dh;
 777        const struct iphdr *iph;
 778        bool refcounted;
 779        struct sock *sk;
 780        int min_cov;
 781
 782        /* Step 1: Check header basics */
 783
 784        if (dccp_invalid_packet(skb))
 785                goto discard_it;
 786
 787        iph = ip_hdr(skb);
 788        /* Step 1: If header checksum is incorrect, drop packet and return */
 789        if (dccp_v4_csum_finish(skb, iph->saddr, iph->daddr)) {
 790                DCCP_WARN("dropped packet with invalid checksum\n");
 791                goto discard_it;
 792        }
 793
 794        dh = dccp_hdr(skb);
 795
 796        DCCP_SKB_CB(skb)->dccpd_seq  = dccp_hdr_seq(dh);
 797        DCCP_SKB_CB(skb)->dccpd_type = dh->dccph_type;
 798
 799        dccp_pr_debug("%8.8s src=%pI4@%-5d dst=%pI4@%-5d seq=%llu",
 800                      dccp_packet_name(dh->dccph_type),
 801                      &iph->saddr, ntohs(dh->dccph_sport),
 802                      &iph->daddr, ntohs(dh->dccph_dport),
 803                      (unsigned long long) DCCP_SKB_CB(skb)->dccpd_seq);
 804
 805        if (dccp_packet_without_ack(skb)) {
 806                DCCP_SKB_CB(skb)->dccpd_ack_seq = DCCP_PKT_WITHOUT_ACK_SEQ;
 807                dccp_pr_debug_cat("\n");
 808        } else {
 809                DCCP_SKB_CB(skb)->dccpd_ack_seq = dccp_hdr_ack_seq(skb);
 810                dccp_pr_debug_cat(", ack=%llu\n", (unsigned long long)
 811                                  DCCP_SKB_CB(skb)->dccpd_ack_seq);
 812        }
 813
 814lookup:
 815        sk = __inet_lookup_skb(&dccp_hashinfo, skb, __dccp_hdr_len(dh),
 816                               dh->dccph_sport, dh->dccph_dport, 0, &refcounted);
 817        if (!sk) {
 818                dccp_pr_debug("failed to look up flow ID in table and "
 819                              "get corresponding socket\n");
 820                goto no_dccp_socket;
 821        }
 822
 823        /*
 824         * Step 2:
 825         *      ... or S.state == TIMEWAIT,
 826         *              Generate Reset(No Connection) unless P.type == Reset
 827         *              Drop packet and return
 828         */
 829        if (sk->sk_state == DCCP_TIME_WAIT) {
 830                dccp_pr_debug("sk->sk_state == DCCP_TIME_WAIT: do_time_wait\n");
 831                inet_twsk_put(inet_twsk(sk));
 832                goto no_dccp_socket;
 833        }
 834
 835        if (sk->sk_state == DCCP_NEW_SYN_RECV) {
 836                struct request_sock *req = inet_reqsk(sk);
 837                struct sock *nsk;
 838
 839                sk = req->rsk_listener;
 840                if (unlikely(sk->sk_state != DCCP_LISTEN)) {
 841                        inet_csk_reqsk_queue_drop_and_put(sk, req);
 842                        goto lookup;
 843                }
 844                sock_hold(sk);
 845                refcounted = true;
 846                nsk = dccp_check_req(sk, skb, req);
 847                if (!nsk) {
 848                        reqsk_put(req);
 849                        goto discard_and_relse;
 850                }
 851                if (nsk == sk) {
 852                        reqsk_put(req);
 853                } else if (dccp_child_process(sk, nsk, skb)) {
 854                        dccp_v4_ctl_send_reset(sk, skb);
 855                        goto discard_and_relse;
 856                } else {
 857                        sock_put(sk);
 858                        return 0;
 859                }
 860        }
 861        /*
 862         * RFC 4340, sec. 9.2.1: Minimum Checksum Coverage
 863         *      o if MinCsCov = 0, only packets with CsCov = 0 are accepted
 864         *      o if MinCsCov > 0, also accept packets with CsCov >= MinCsCov
 865         */
 866        min_cov = dccp_sk(sk)->dccps_pcrlen;
 867        if (dh->dccph_cscov && (min_cov == 0 || dh->dccph_cscov < min_cov))  {
 868                dccp_pr_debug("Packet CsCov %d does not satisfy MinCsCov %d\n",
 869                              dh->dccph_cscov, min_cov);
 870                /* FIXME: "Such packets SHOULD be reported using Data Dropped
 871                 *         options (Section 11.7) with Drop Code 0, Protocol
 872                 *         Constraints."                                     */
 873                goto discard_and_relse;
 874        }
 875
 876        if (!xfrm4_policy_check(sk, XFRM_POLICY_IN, skb))
 877                goto discard_and_relse;
 878        nf_reset_ct(skb);
 879
 880        return __sk_receive_skb(sk, skb, 1, dh->dccph_doff * 4, refcounted);
 881
 882no_dccp_socket:
 883        if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb))
 884                goto discard_it;
 885        /*
 886         * Step 2:
 887         *      If no socket ...
 888         *              Generate Reset(No Connection) unless P.type == Reset
 889         *              Drop packet and return
 890         */
 891        if (dh->dccph_type != DCCP_PKT_RESET) {
 892                DCCP_SKB_CB(skb)->dccpd_reset_code =
 893                                        DCCP_RESET_CODE_NO_CONNECTION;
 894                dccp_v4_ctl_send_reset(sk, skb);
 895        }
 896
 897discard_it:
 898        kfree_skb(skb);
 899        return 0;
 900
 901discard_and_relse:
 902        if (refcounted)
 903                sock_put(sk);
 904        goto discard_it;
 905}
 906
 907static const struct inet_connection_sock_af_ops dccp_ipv4_af_ops = {
 908        .queue_xmit        = ip_queue_xmit,
 909        .send_check        = dccp_v4_send_check,
 910        .rebuild_header    = inet_sk_rebuild_header,
 911        .conn_request      = dccp_v4_conn_request,
 912        .syn_recv_sock     = dccp_v4_request_recv_sock,
 913        .net_header_len    = sizeof(struct iphdr),
 914        .setsockopt        = ip_setsockopt,
 915        .getsockopt        = ip_getsockopt,
 916        .addr2sockaddr     = inet_csk_addr2sockaddr,
 917        .sockaddr_len      = sizeof(struct sockaddr_in),
 918};
 919
 920static int dccp_v4_init_sock(struct sock *sk)
 921{
 922        static __u8 dccp_v4_ctl_sock_initialized;
 923        int err = dccp_init_sock(sk, dccp_v4_ctl_sock_initialized);
 924
 925        if (err == 0) {
 926                if (unlikely(!dccp_v4_ctl_sock_initialized))
 927                        dccp_v4_ctl_sock_initialized = 1;
 928                inet_csk(sk)->icsk_af_ops = &dccp_ipv4_af_ops;
 929        }
 930
 931        return err;
 932}
 933
 934static struct timewait_sock_ops dccp_timewait_sock_ops = {
 935        .twsk_obj_size  = sizeof(struct inet_timewait_sock),
 936};
 937
 938static struct proto dccp_v4_prot = {
 939        .name                   = "DCCP",
 940        .owner                  = THIS_MODULE,
 941        .close                  = dccp_close,
 942        .connect                = dccp_v4_connect,
 943        .disconnect             = dccp_disconnect,
 944        .ioctl                  = dccp_ioctl,
 945        .init                   = dccp_v4_init_sock,
 946        .setsockopt             = dccp_setsockopt,
 947        .getsockopt             = dccp_getsockopt,
 948        .sendmsg                = dccp_sendmsg,
 949        .recvmsg                = dccp_recvmsg,
 950        .backlog_rcv            = dccp_v4_do_rcv,
 951        .hash                   = inet_hash,
 952        .unhash                 = inet_unhash,
 953        .accept                 = inet_csk_accept,
 954        .get_port               = inet_csk_get_port,
 955        .shutdown               = dccp_shutdown,
 956        .destroy                = dccp_destroy_sock,
 957        .orphan_count           = &dccp_orphan_count,
 958        .max_header             = MAX_DCCP_HEADER,
 959        .obj_size               = sizeof(struct dccp_sock),
 960        .slab_flags             = SLAB_TYPESAFE_BY_RCU,
 961        .rsk_prot               = &dccp_request_sock_ops,
 962        .twsk_prot              = &dccp_timewait_sock_ops,
 963        .h.hashinfo             = &dccp_hashinfo,
 964};
 965
 966static const struct net_protocol dccp_v4_protocol = {
 967        .handler        = dccp_v4_rcv,
 968        .err_handler    = dccp_v4_err,
 969        .no_policy      = 1,
 970        .netns_ok       = 1,
 971        .icmp_strict_tag_validation = 1,
 972};
 973
 974static const struct proto_ops inet_dccp_ops = {
 975        .family            = PF_INET,
 976        .owner             = THIS_MODULE,
 977        .release           = inet_release,
 978        .bind              = inet_bind,
 979        .connect           = inet_stream_connect,
 980        .socketpair        = sock_no_socketpair,
 981        .accept            = inet_accept,
 982        .getname           = inet_getname,
 983        /* FIXME: work on tcp_poll to rename it to inet_csk_poll */
 984        .poll              = dccp_poll,
 985        .ioctl             = inet_ioctl,
 986        .gettstamp         = sock_gettstamp,
 987        /* FIXME: work on inet_listen to rename it to sock_common_listen */
 988        .listen            = inet_dccp_listen,
 989        .shutdown          = inet_shutdown,
 990        .setsockopt        = sock_common_setsockopt,
 991        .getsockopt        = sock_common_getsockopt,
 992        .sendmsg           = inet_sendmsg,
 993        .recvmsg           = sock_common_recvmsg,
 994        .mmap              = sock_no_mmap,
 995        .sendpage          = sock_no_sendpage,
 996};
 997
 998static struct inet_protosw dccp_v4_protosw = {
 999        .type           = SOCK_DCCP,
1000        .protocol       = IPPROTO_DCCP,
1001        .prot           = &dccp_v4_prot,
1002        .ops            = &inet_dccp_ops,
1003        .flags          = INET_PROTOSW_ICSK,
1004};
1005
1006static int __net_init dccp_v4_init_net(struct net *net)
1007{
1008        if (dccp_hashinfo.bhash == NULL)
1009                return -ESOCKTNOSUPPORT;
1010
1011        return inet_ctl_sock_create(&net->dccp.v4_ctl_sk, PF_INET,
1012                                    SOCK_DCCP, IPPROTO_DCCP, net);
1013}
1014
1015static void __net_exit dccp_v4_exit_net(struct net *net)
1016{
1017        inet_ctl_sock_destroy(net->dccp.v4_ctl_sk);
1018}
1019
1020static void __net_exit dccp_v4_exit_batch(struct list_head *net_exit_list)
1021{
1022        inet_twsk_purge(&dccp_hashinfo, AF_INET);
1023}
1024
1025static struct pernet_operations dccp_v4_ops = {
1026        .init   = dccp_v4_init_net,
1027        .exit   = dccp_v4_exit_net,
1028        .exit_batch = dccp_v4_exit_batch,
1029};
1030
1031static int __init dccp_v4_init(void)
1032{
1033        int err = proto_register(&dccp_v4_prot, 1);
1034
1035        if (err)
1036                goto out;
1037
1038        inet_register_protosw(&dccp_v4_protosw);
1039
1040        err = register_pernet_subsys(&dccp_v4_ops);
1041        if (err)
1042                goto out_destroy_ctl_sock;
1043
1044        err = inet_add_protocol(&dccp_v4_protocol, IPPROTO_DCCP);
1045        if (err)
1046                goto out_proto_unregister;
1047
1048out:
1049        return err;
1050out_proto_unregister:
1051        unregister_pernet_subsys(&dccp_v4_ops);
1052out_destroy_ctl_sock:
1053        inet_unregister_protosw(&dccp_v4_protosw);
1054        proto_unregister(&dccp_v4_prot);
1055        goto out;
1056}
1057
1058static void __exit dccp_v4_exit(void)
1059{
1060        inet_del_protocol(&dccp_v4_protocol, IPPROTO_DCCP);
1061        unregister_pernet_subsys(&dccp_v4_ops);
1062        inet_unregister_protosw(&dccp_v4_protosw);
1063        proto_unregister(&dccp_v4_prot);
1064}
1065
1066module_init(dccp_v4_init);
1067module_exit(dccp_v4_exit);
1068
1069/*
1070 * __stringify doesn't likes enums, so use SOCK_DCCP (6) and IPPROTO_DCCP (33)
1071 * values directly, Also cover the case where the protocol is not specified,
1072 * i.e. net-pf-PF_INET-proto-0-type-SOCK_DCCP
1073 */
1074MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_INET, 33, 6);
1075MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_INET, 0, 6);
1076MODULE_LICENSE("GPL");
1077MODULE_AUTHOR("Arnaldo Carvalho de Melo <acme@mandriva.com>");
1078MODULE_DESCRIPTION("DCCP - Datagram Congestion Controlled Protocol");
1079