net/dccp/input.c

   1 /*
   2  *  net/dccp/input.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/config.h>
  14 #include <linux/dccp.h>
  15 #include <linux/skbuff.h>
  16
  17 #include <net/sock.h>
  18
  19 #include "ackvec.h"
  20 #include "ccid.h"
  21 #include "dccp.h"
  22
  23 static void dccp_fin(struct sock *sk, struct sk_buff *skb)
  24 {
  25         sk->sk_shutdown |= RCV_SHUTDOWN;
  26         sock_set_flag(sk, SOCK_DONE);
  27         __skb_pull(skb, dccp_hdr(skb)->dccph_doff * 4);
  28         __skb_queue_tail(&sk->sk_receive_queue, skb);
  29         skb_set_owner_r(skb, sk);
  30         sk->sk_data_ready(sk, 0);
  31 }
  32
  33 static void dccp_rcv_close(struct sock *sk, struct sk_buff *skb)
  34 {
  35         dccp_send_reset(sk, DCCP_RESET_CODE_CLOSED);
  36         dccp_fin(sk, skb);
  37         dccp_set_state(sk, DCCP_CLOSED);
  38         sk_wake_async(sk, 1, POLL_HUP);
  39 }
  40
  41 static void dccp_rcv_closereq(struct sock *sk, struct sk_buff *skb)
  42 {
  43         /*
  44          *   Step 7: Check for unexpected packet types
  45          *      If (S.is_server and P.type == CloseReq)
  46          *        Send Sync packet acknowledging P.seqno
  47          *        Drop packet and return
  48          */
  49         if (dccp_sk(sk)->dccps_role != DCCP_ROLE_CLIENT) {
  50                 dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq, DCCP_PKT_SYNC);
  51                 return;
  52         }
  53
  54         if (sk->sk_state != DCCP_CLOSING)
  55                 dccp_set_state(sk, DCCP_CLOSING);
  56         dccp_send_close(sk, 0);
  57 }
  58
  59 static void dccp_event_ack_recv(struct sock *sk, struct sk_buff *skb)
  60 {
  61         struct dccp_sock *dp = dccp_sk(sk);
  62
  63         if (dccp_msk(sk)->dccpms_send_ack_vector)
  64                 dccp_ackvec_check_rcv_ackno(dp->dccps_hc_rx_ackvec, sk,
  65                                             DCCP_SKB_CB(skb)->dccpd_ack_seq);
  66 }
  67
  68 static int dccp_check_seqno(struct sock *sk, struct sk_buff *skb)
  69 {
  70         const struct dccp_hdr *dh = dccp_hdr(skb);
  71         struct dccp_sock *dp = dccp_sk(sk);
  72         u64 lswl, lawl;
  73
  74         /*
  75          *   Step 5: Prepare sequence numbers for Sync
  76          *     If P.type == Sync or P.type == SyncAck,
  77          *        If S.AWL <= P.ackno <= S.AWH and P.seqno >= S.SWL,
  78          *           / * P is valid, so update sequence number variables
  79          *               accordingly.  After this update, P will pass the tests
  80          *               in Step 6.  A SyncAck is generated if necessary in
  81          *               Step 15 * /
  82          *           Update S.GSR, S.SWL, S.SWH
  83          *        Otherwise,
  84          *           Drop packet and return
  85          */
  86         if (dh->dccph_type == DCCP_PKT_SYNC ||
  87             dh->dccph_type == DCCP_PKT_SYNCACK) {
  88                 if (between48(DCCP_SKB_CB(skb)->dccpd_ack_seq,
  89                               dp->dccps_awl, dp->dccps_awh) &&
  90                     !before48(DCCP_SKB_CB(skb)->dccpd_seq, dp->dccps_swl))
  91                         dccp_update_gsr(sk, DCCP_SKB_CB(skb)->dccpd_seq);
  92                 else
  93                         return -1;
  94         }
  95
  96         /*
  97          *   Step 6: Check sequence numbers
  98          *      Let LSWL = S.SWL and LAWL = S.AWL
  99          *      If P.type == CloseReq or P.type == Close or P.type == Reset,
 100          *        LSWL := S.GSR + 1, LAWL := S.GAR
 101          *      If LSWL <= P.seqno <= S.SWH
 102          *           and (P.ackno does not exist or LAWL <= P.ackno <= S.AWH),
 103          *        Update S.GSR, S.SWL, S.SWH
 104          *        If P.type != Sync,
 105          *           Update S.GAR
 106          *      Otherwise,
 107          *        Send Sync packet acknowledging P.seqno
 108          *        Drop packet and return
 109          */
 110         lswl = dp->dccps_swl;
 111         lawl = dp->dccps_awl;
 112
 113         if (dh->dccph_type == DCCP_PKT_CLOSEREQ ||
 114             dh->dccph_type == DCCP_PKT_CLOSE ||
 115             dh->dccph_type == DCCP_PKT_RESET) {
 116                 lswl = dp->dccps_gsr;
 117                 dccp_inc_seqno(&lswl);
 118                 lawl = dp->dccps_gar;
 119         }
 120
 121         if (between48(DCCP_SKB_CB(skb)->dccpd_seq, lswl, dp->dccps_swh) &&
 122             (DCCP_SKB_CB(skb)->dccpd_ack_seq == DCCP_PKT_WITHOUT_ACK_SEQ ||
 123              between48(DCCP_SKB_CB(skb)->dccpd_ack_seq,
 124                        lawl, dp->dccps_awh))) {
 125                 dccp_update_gsr(sk, DCCP_SKB_CB(skb)->dccpd_seq);
 126
 127                 if (dh->dccph_type != DCCP_PKT_SYNC &&
 128                     (DCCP_SKB_CB(skb)->dccpd_ack_seq !=
 129                      DCCP_PKT_WITHOUT_ACK_SEQ))
 130                         dp->dccps_gar = DCCP_SKB_CB(skb)->dccpd_ack_seq;
 131         } else {
 132                 LIMIT_NETDEBUG(KERN_WARNING "DCCP: Step 6 failed for %s packet, "
 133                                             "(LSWL(%llu) <= P.seqno(%llu) <= S.SWH(%llu)) and "
 134                                             "(P.ackno %s or LAWL(%llu) <= P.ackno(%llu) <= S.AWH(%llu), "
 135                                             "sending SYNC...\n",
 136                                dccp_packet_name(dh->dccph_type),
 137                                (unsigned long long) lswl,
 138                                (unsigned long long)
 139                                DCCP_SKB_CB(skb)->dccpd_seq,
 140                                (unsigned long long) dp->dccps_swh,
 141                                (DCCP_SKB_CB(skb)->dccpd_ack_seq ==
 142                                 DCCP_PKT_WITHOUT_ACK_SEQ) ? "doesn't exist" : "exists",
 143                                (unsigned long long) lawl,
 144                                (unsigned long long)
 145                                DCCP_SKB_CB(skb)->dccpd_ack_seq,
 146                                (unsigned long long) dp->dccps_awh);
 147                 dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq, DCCP_PKT_SYNC);
 148                 return -1;
 149         }
 150
 151         return 0;
 152 }
 153
 154 static int __dccp_rcv_established(struct sock *sk, struct sk_buff *skb,
 155                                   const struct dccp_hdr *dh, const unsigned len)
 156 {
 157         struct dccp_sock *dp = dccp_sk(sk);
 158
 159         switch (dccp_hdr(skb)->dccph_type) {
 160         case DCCP_PKT_DATAACK:
 161         case DCCP_PKT_DATA:
 162                 /*
 163                  * FIXME: check if sk_receive_queue is full, schedule DATA_DROPPED
 164                  * option if it is.
 165                  */
 166                 __skb_pull(skb, dh->dccph_doff * 4);
 167                 __skb_queue_tail(&sk->sk_receive_queue, skb);
 168                 skb_set_owner_r(skb, sk);
 169                 sk->sk_data_ready(sk, 0);
 170                 return 0;
 171         case DCCP_PKT_ACK:
 172                 goto discard;
 173         case DCCP_PKT_RESET:
 174                 /*
 175                  *  Step 9: Process Reset
 176                  *      If P.type == Reset,
 177                  *              Tear down connection
 178                  *              S.state := TIMEWAIT
 179                  *              Set TIMEWAIT timer
 180                  *              Drop packet and return
 181                 */
 182                 dccp_fin(sk, skb);
 183                 dccp_time_wait(sk, DCCP_TIME_WAIT, 0);
 184                 return 0;
 185         case DCCP_PKT_CLOSEREQ:
 186                 dccp_rcv_closereq(sk, skb);
 187                 goto discard;
 188         case DCCP_PKT_CLOSE:
 189                 dccp_rcv_close(sk, skb);
 190                 return 0;
 191         case DCCP_PKT_REQUEST:
 192                 /* Step 7
 193                  *   or (S.is_server and P.type == Response)
 194                  *   or (S.is_client and P.type == Request)
 195                  *   or (S.state >= OPEN and P.type == Request
 196                  *      and P.seqno >= S.OSR)
 197                  *    or (S.state >= OPEN and P.type == Response
 198                  *      and P.seqno >= S.OSR)
 199                  *    or (S.state == RESPOND and P.type == Data),
 200                  *  Send Sync packet acknowledging P.seqno
 201                  *  Drop packet and return
 202                  */
 203                 if (dp->dccps_role != DCCP_ROLE_LISTEN)
 204                         goto send_sync;
 205                 goto check_seq;
 206         case DCCP_PKT_RESPONSE:
 207                 if (dp->dccps_role != DCCP_ROLE_CLIENT)
 208                         goto send_sync;
 209 check_seq:
 210                 if (!before48(DCCP_SKB_CB(skb)->dccpd_seq, dp->dccps_osr)) {
 211 send_sync:
 212                         dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq,
 213                                        DCCP_PKT_SYNC);
 214                 }
 215                 break;
 216         case DCCP_PKT_SYNC:
 217                 dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq,
 218                                DCCP_PKT_SYNCACK);
 219                 /*
 220                  * From the draft:
 221                  *
 222                  * As with DCCP-Ack packets, DCCP-Sync and DCCP-SyncAck packets
 223                  * MAY have non-zero-length application data areas, whose
 224                  * contents * receivers MUST ignore.
 225                  */
 226                 goto discard;
 227         }
 228
 229         DCCP_INC_STATS_BH(DCCP_MIB_INERRS);
 230 discard:
 231         __kfree_skb(skb);
 232         return 0;
 233 }
 234
 235 int dccp_rcv_established(struct sock *sk, struct sk_buff *skb,
 236                          const struct dccp_hdr *dh, const unsigned len)
 237 {
 238         struct dccp_sock *dp = dccp_sk(sk);
 239
 240         if (dccp_check_seqno(sk, skb))
 241                 goto discard;
 242
 243         if (dccp_parse_options(sk, skb))
 244                 goto discard;
 245
 246         if (DCCP_SKB_CB(skb)->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
 247                 dccp_event_ack_recv(sk, skb);
 248
 249         if (dccp_msk(sk)->dccpms_send_ack_vector &&
 250             dccp_ackvec_add(dp->dccps_hc_rx_ackvec, sk,
 251                             DCCP_SKB_CB(skb)->dccpd_seq,
 252                             DCCP_ACKVEC_STATE_RECEIVED))
 253                 goto discard;
 254
 255         ccid_hc_rx_packet_recv(dp->dccps_hc_rx_ccid, sk, skb);
 256         ccid_hc_tx_packet_recv(dp->dccps_hc_tx_ccid, sk, skb);
 257
 258         return __dccp_rcv_established(sk, skb, dh, len);
 259 discard:
 260         __kfree_skb(skb);
 261         return 0;
 262 }
 263
 264 EXPORT_SYMBOL_GPL(dccp_rcv_established);
 265
 266 static int dccp_rcv_request_sent_state_process(struct sock *sk,
 267                                                struct sk_buff *skb,
 268                                                const struct dccp_hdr *dh,
 269                                                const unsigned len)
 270 {
 271         /*
 272          *  Step 4: Prepare sequence numbers in REQUEST
 273          *     If S.state == REQUEST,
 274          *        If (P.type == Response or P.type == Reset)
 275          *              and S.AWL <= P.ackno <= S.AWH,
 276          *           / * Set sequence number variables corresponding to the
 277          *              other endpoint, so P will pass the tests in Step 6 * /
 278          *           Set S.GSR, S.ISR, S.SWL, S.SWH
 279          *           / * Response processing continues in Step 10; Reset
 280          *              processing continues in Step 9 * /
 281         */
 282         if (dh->dccph_type == DCCP_PKT_RESPONSE) {
 283                 const struct inet_connection_sock *icsk = inet_csk(sk);
 284                 struct dccp_sock *dp = dccp_sk(sk);
 285
 286                 /* Stop the REQUEST timer */
 287                 inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS);
 288                 BUG_TRAP(sk->sk_send_head != NULL);
 289                 __kfree_skb(sk->sk_send_head);
 290                 sk->sk_send_head = NULL;
 291
 292                 if (!between48(DCCP_SKB_CB(skb)->dccpd_ack_seq,
 293                                dp->dccps_awl, dp->dccps_awh)) {
 294                         dccp_pr_debug("invalid ackno: S.AWL=%llu, "
 295                                       "P.ackno=%llu, S.AWH=%llu \n",
 296                                       (unsigned long long)dp->dccps_awl,
 297                            (unsigned long long)DCCP_SKB_CB(skb)->dccpd_ack_seq,
 298                                       (unsigned long long)dp->dccps_awh);
 299                         goto out_invalid_packet;
 300                 }
 301
 302                 if (dccp_parse_options(sk, skb))
 303                         goto out_invalid_packet;
 304
 305                 if (dccp_msk(sk)->dccpms_send_ack_vector &&
 306                     dccp_ackvec_add(dp->dccps_hc_rx_ackvec, sk,
 307                                     DCCP_SKB_CB(skb)->dccpd_seq,
 308                                     DCCP_ACKVEC_STATE_RECEIVED))
 309                         goto out_invalid_packet; /* FIXME: change error code */
 310
 311                 dp->dccps_isr = DCCP_SKB_CB(skb)->dccpd_seq;
 312                 dccp_update_gsr(sk, dp->dccps_isr);
 313                 /*
 314                  * SWL and AWL are initially adjusted so that they are not less than
 315                  * the initial Sequence Numbers received and sent, respectively:
 316                  *      SWL := max(GSR + 1 - floor(W/4), ISR),
 317                  *      AWL := max(GSS - W' + 1, ISS).
 318                  * These adjustments MUST be applied only at the beginning of the
 319                  * connection.
 320                  *
 321                  * AWL was adjusted in dccp_v4_connect -acme
 322                  */
 323                 dccp_set_seqno(&dp->dccps_swl,
 324                                max48(dp->dccps_swl, dp->dccps_isr));
 325
 326                 dccp_sync_mss(sk, icsk->icsk_pmtu_cookie);
 327
 328                 /*
 329                  *    Step 10: Process REQUEST state (second part)
 330                  *       If S.state == REQUEST,
 331                  *        / * If we get here, P is a valid Response from the
 332                  *            server (see Step 4), and we should move to
 333                  *            PARTOPEN state. PARTOPEN means send an Ack,
 334                  *            don't send Data packets, retransmit Acks
 335                  *            periodically, and always include any Init Cookie
 336                  *            from the Response * /
 337                  *        S.state := PARTOPEN
 338                  *        Set PARTOPEN timer
 339                  *        Continue with S.state == PARTOPEN
 340                  *        / * Step 12 will send the Ack completing the
 341                  *            three-way handshake * /
 342                  */
 343                 dccp_set_state(sk, DCCP_PARTOPEN);
 344
 345                 /* Make sure socket is routed, for correct metrics. */
 346                 icsk->icsk_af_ops->rebuild_header(sk);
 347
 348                 if (!sock_flag(sk, SOCK_DEAD)) {
 349                         sk->sk_state_change(sk);
 350                         sk_wake_async(sk, 0, POLL_OUT);
 351                 }
 352
 353                 if (sk->sk_write_pending || icsk->icsk_ack.pingpong ||
 354                     icsk->icsk_accept_queue.rskq_defer_accept) {
 355                         /* Save one ACK. Data will be ready after
 356                          * several ticks, if write_pending is set.
 357                          *
 358                          * It may be deleted, but with this feature tcpdumps
 359                          * look so _wonderfully_ clever, that I was not able
 360                          * to stand against the temptation 8)     --ANK
 361                          */
 362                         /*
 363                          * OK, in DCCP we can as well do a similar trick, its
 364                          * even in the draft, but there is no need for us to
 365                          * schedule an ack here, as dccp_sendmsg does this for
 366                          * us, also stated in the draft. -acme
 367                          */
 368                         __kfree_skb(skb);
 369                         return 0;
 370                 }
 371                 dccp_send_ack(sk);
 372                 return -1;
 373         }
 374
 375 out_invalid_packet:
 376         /* dccp_v4_do_rcv will send a reset */
 377         DCCP_SKB_CB(skb)->dccpd_reset_code = DCCP_RESET_CODE_PACKET_ERROR;
 378         return 1;
 379 }
 380
 381 static int dccp_rcv_respond_partopen_state_process(struct sock *sk,
 382                                                    struct sk_buff *skb,
 383                                                    const struct dccp_hdr *dh,
 384                                                    const unsigned len)
 385 {
 386         int queued = 0;
 387
 388         switch (dh->dccph_type) {
 389         case DCCP_PKT_RESET:
 390                 inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
 391                 break;
 392         case DCCP_PKT_DATA:
 393                 if (sk->sk_state == DCCP_RESPOND)
 394                         break;
 395         case DCCP_PKT_DATAACK:
 396         case DCCP_PKT_ACK:
 397                 /*
 398                  * FIXME: we should be reseting the PARTOPEN (DELACK) timer
 399                  * here but only if we haven't used the DELACK timer for
 400                  * something else, like sending a delayed ack for a TIMESTAMP
 401                  * echo, etc, for now were not clearing it, sending an extra
 402                  * ACK when there is nothing else to do in DELACK is not a big
 403                  * deal after all.
 404                  */
 405
 406                 /* Stop the PARTOPEN timer */
 407                 if (sk->sk_state == DCCP_PARTOPEN)
 408                         inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
 409
 410                 dccp_sk(sk)->dccps_osr = DCCP_SKB_CB(skb)->dccpd_seq;
 411                 dccp_set_state(sk, DCCP_OPEN);
 412
 413                 if (dh->dccph_type == DCCP_PKT_DATAACK ||
 414                     dh->dccph_type == DCCP_PKT_DATA) {
 415                         __dccp_rcv_established(sk, skb, dh, len);
 416                         queued = 1; /* packet was queued
 417                                        (by __dccp_rcv_established) */
 418                 }
 419                 break;
 420         }
 421
 422         return queued;
 423 }
 424
 425 int dccp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
 426                            struct dccp_hdr *dh, unsigned len)
 427 {
 428         struct dccp_sock *dp = dccp_sk(sk);
 429         struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
 430         const int old_state = sk->sk_state;
 431         int queued = 0;
 432
 433         /*
 434          *  Step 3: Process LISTEN state
 435          *      (Continuing from dccp_v4_do_rcv and dccp_v6_do_rcv)
 436          *
 437          *     If S.state == LISTEN,
 438          *        If P.type == Request or P contains a valid Init Cookie
 439          *              option,
 440          *           * Must scan the packet's options to check for an Init
 441          *              Cookie.  Only the Init Cookie is processed here,
 442          *              however; other options are processed in Step 8.  This
 443          *              scan need only be performed if the endpoint uses Init
 444          *              Cookies *
 445          *           * Generate a new socket and switch to that socket *
 446          *           Set S := new socket for this port pair
 447          *           S.state = RESPOND
 448          *           Choose S.ISS (initial seqno) or set from Init Cookie
 449          *           Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init Cookie
 450          *           Continue with S.state == RESPOND
 451          *           * A Response packet will be generated in Step 11 *
 452          *        Otherwise,
 453          *           Generate Reset(No Connection) unless P.type == Reset
 454          *           Drop packet and return
 455          *
 456          * NOTE: the check for the packet types is done in
 457          *       dccp_rcv_state_process
 458          */
 459         if (sk->sk_state == DCCP_LISTEN) {
 460                 if (dh->dccph_type == DCCP_PKT_REQUEST) {
 461                         if (inet_csk(sk)->icsk_af_ops->conn_request(sk,
 462                                                                     skb) < 0)
 463                                 return 1;
 464
 465                         /* FIXME: do congestion control initialization */
 466                         goto discard;
 467                 }
 468                 if (dh->dccph_type == DCCP_PKT_RESET)
 469                         goto discard;
 470
 471                 /* Caller (dccp_v4_do_rcv) will send Reset */
 472                 dcb->dccpd_reset_code = DCCP_RESET_CODE_NO_CONNECTION;
 473                 return 1;
 474         }
 475
 476         if (sk->sk_state != DCCP_REQUESTING) {
 477                 if (dccp_check_seqno(sk, skb))
 478                         goto discard;
 479
 480                 /*
 481                  * Step 8: Process options and mark acknowledgeable
 482                  */
 483                 if (dccp_parse_options(sk, skb))
 484                         goto discard;
 485
 486                 if (dcb->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
 487                         dccp_event_ack_recv(sk, skb);
 488
 489                 if (dccp_msk(sk)->dccpms_send_ack_vector &&
 490                     dccp_ackvec_add(dp->dccps_hc_rx_ackvec, sk,
 491                                     DCCP_SKB_CB(skb)->dccpd_seq,
 492                                     DCCP_ACKVEC_STATE_RECEIVED))
 493                         goto discard;
 494
 495                 ccid_hc_rx_packet_recv(dp->dccps_hc_rx_ccid, sk, skb);
 496                 ccid_hc_tx_packet_recv(dp->dccps_hc_tx_ccid, sk, skb);
 497         }
 498
 499         /*
 500          *  Step 9: Process Reset
 501          *      If P.type == Reset,
 502          *              Tear down connection
 503          *              S.state := TIMEWAIT
 504          *              Set TIMEWAIT timer
 505          *              Drop packet and return
 506         */
 507         if (dh->dccph_type == DCCP_PKT_RESET) {
 508                 /*
 509                  * Queue the equivalent of TCP fin so that dccp_recvmsg
 510                  * exits the loop
 511                  */
 512                 dccp_fin(sk, skb);
 513                 dccp_time_wait(sk, DCCP_TIME_WAIT, 0);
 514                 return 0;
 515                 /*
 516                  *   Step 7: Check for unexpected packet types
 517                  *      If (S.is_server and P.type == CloseReq)
 518                  *          or (S.is_server and P.type == Response)
 519                  *          or (S.is_client and P.type == Request)
 520                  *          or (S.state == RESPOND and P.type == Data),
 521                  *        Send Sync packet acknowledging P.seqno
 522                  *        Drop packet and return
 523                  */
 524         } else if ((dp->dccps_role != DCCP_ROLE_CLIENT &&
 525                     (dh->dccph_type == DCCP_PKT_RESPONSE ||
 526                      dh->dccph_type == DCCP_PKT_CLOSEREQ)) ||
 527                     (dp->dccps_role == DCCP_ROLE_CLIENT &&
 528                      dh->dccph_type == DCCP_PKT_REQUEST) ||
 529                     (sk->sk_state == DCCP_RESPOND &&
 530                      dh->dccph_type == DCCP_PKT_DATA)) {
 531                 dccp_send_sync(sk, dcb->dccpd_seq, DCCP_PKT_SYNC);
 532                 goto discard;
 533         } else if (dh->dccph_type == DCCP_PKT_CLOSEREQ) {
 534                 dccp_rcv_closereq(sk, skb);
 535                 goto discard;
 536         } else if (dh->dccph_type == DCCP_PKT_CLOSE) {
 537                 dccp_rcv_close(sk, skb);
 538                 return 0;
 539         }
 540
 541         if (unlikely(dh->dccph_type == DCCP_PKT_SYNC)) {
 542                 dccp_send_sync(sk, dcb->dccpd_seq, DCCP_PKT_SYNCACK);
 543                 goto discard;
 544         }
 545
 546         switch (sk->sk_state) {
 547         case DCCP_CLOSED:
 548                 dcb->dccpd_reset_code = DCCP_RESET_CODE_NO_CONNECTION;
 549                 return 1;
 550
 551         case DCCP_REQUESTING:
 552                 /* FIXME: do congestion control initialization */
 553
 554                 queued = dccp_rcv_request_sent_state_process(sk, skb, dh, len);
 555                 if (queued >= 0)
 556                         return queued;
 557
 558                 __kfree_skb(skb);
 559                 return 0;
 560
 561         case DCCP_RESPOND:
 562         case DCCP_PARTOPEN:
 563                 queued = dccp_rcv_respond_partopen_state_process(sk, skb,
 564                                                                  dh, len);
 565                 break;
 566         }
 567
 568         if (dh->dccph_type == DCCP_PKT_ACK ||
 569             dh->dccph_type == DCCP_PKT_DATAACK) {
 570                 switch (old_state) {
 571                 case DCCP_PARTOPEN:
 572                         sk->sk_state_change(sk);
 573                         sk_wake_async(sk, 0, POLL_OUT);
 574                         break;
 575                 }
 576         }
 577
 578         if (!queued) {
 579 discard:
 580                 __kfree_skb(skb);
 581         }
 582         return 0;
 583 }
 584
 585 EXPORT_SYMBOL_GPL(dccp_rcv_state_process);