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   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/dccp.h>
  14 #include <linux/skbuff.h>
  15
  16 #include <net/sock.h>
  17
  18 #include "ackvec.h"
  19 #include "ccid.h"
  20 #include "dccp.h"
  21
  22 static void dccp_fin(struct sock *sk, struct sk_buff *skb)
  23 {
  24         sk->sk_shutdown |= RCV_SHUTDOWN;
  25         sock_set_flag(sk, SOCK_DONE);
  26         __skb_pull(skb, dccp_hdr(skb)->dccph_doff * 4);
  27         __skb_queue_tail(&sk->sk_receive_queue, skb);
  28         skb_set_owner_r(skb, sk);
  29         sk->sk_data_ready(sk, 0);
  30 }
  31
  32 static void dccp_rcv_close(struct sock *sk, struct sk_buff *skb)
  33 {
  34         dccp_send_reset(sk, DCCP_RESET_CODE_CLOSED);
  35         dccp_fin(sk, skb);
  36         dccp_set_state(sk, DCCP_CLOSED);
  37         sk_wake_async(sk, 1, POLL_HUP);
  38 }
  39
  40 static void dccp_rcv_closereq(struct sock *sk, struct sk_buff *skb)
  41 {
  42         /*
  43          *   Step 7: Check for unexpected packet types
  44          *      If (S.is_server and P.type == CloseReq)
  45          *        Send Sync packet acknowledging P.seqno
  46          *        Drop packet and return
  47          */
  48         if (dccp_sk(sk)->dccps_role != DCCP_ROLE_CLIENT) {
  49                 dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq, DCCP_PKT_SYNC);
  50                 return;
  51         }
  52
  53         if (sk->sk_state != DCCP_CLOSING)
  54                 dccp_set_state(sk, DCCP_CLOSING);
  55         dccp_send_close(sk, 0);
  56 }
  57
  58 static void dccp_event_ack_recv(struct sock *sk, struct sk_buff *skb)
  59 {
  60         struct dccp_sock *dp = dccp_sk(sk);
  61
  62         if (dccp_msk(sk)->dccpms_send_ack_vector)
  63                 dccp_ackvec_check_rcv_ackno(dp->dccps_hc_rx_ackvec, sk,
  64                                             DCCP_SKB_CB(skb)->dccpd_ack_seq);
  65 }
  66
  67 static int dccp_check_seqno(struct sock *sk, struct sk_buff *skb)
  68 {
  69         const struct dccp_hdr *dh = dccp_hdr(skb);
  70         struct dccp_sock *dp = dccp_sk(sk);
  71         u64 lswl, lawl;
  72
  73         /*
  74          *   Step 5: Prepare sequence numbers for Sync
  75          *     If P.type == Sync or P.type == SyncAck,
  76          *        If S.AWL <= P.ackno <= S.AWH and P.seqno >= S.SWL,
  77          *           / * P is valid, so update sequence number variables
  78          *               accordingly.  After this update, P will pass the tests
  79          *               in Step 6.  A SyncAck is generated if necessary in
  80          *               Step 15 * /
  81          *           Update S.GSR, S.SWL, S.SWH
  82          *        Otherwise,
  83          *           Drop packet and return
  84          */
  85         if (dh->dccph_type == DCCP_PKT_SYNC ||
  86             dh->dccph_type == DCCP_PKT_SYNCACK) {
  87                 if (between48(DCCP_SKB_CB(skb)->dccpd_ack_seq,
  88                               dp->dccps_awl, dp->dccps_awh) &&
  89                     !before48(DCCP_SKB_CB(skb)->dccpd_seq, dp->dccps_swl))
  90                         dccp_update_gsr(sk, DCCP_SKB_CB(skb)->dccpd_seq);
  91                 else
  92                         return -1;
  93         }
  94
  95         /*
  96          *   Step 6: Check sequence numbers
  97          *      Let LSWL = S.SWL and LAWL = S.AWL
  98          *      If P.type == CloseReq or P.type == Close or P.type == Reset,
  99          *        LSWL := S.GSR + 1, LAWL := S.GAR
 100          *      If LSWL <= P.seqno <= S.SWH
 101          *           and (P.ackno does not exist or LAWL <= P.ackno <= S.AWH),
 102          *        Update S.GSR, S.SWL, S.SWH
 103          *        If P.type != Sync,
 104          *           Update S.GAR
 105          *      Otherwise,
 106          *        Send Sync packet acknowledging P.seqno
 107          *        Drop packet and return
 108          */
 109         lswl = dp->dccps_swl;
 110         lawl = dp->dccps_awl;
 111
 112         if (dh->dccph_type == DCCP_PKT_CLOSEREQ ||
 113             dh->dccph_type == DCCP_PKT_CLOSE ||
 114             dh->dccph_type == DCCP_PKT_RESET) {
 115                 lswl = dp->dccps_gsr;
 116                 dccp_inc_seqno(&lswl);
 117                 lawl = dp->dccps_gar;
 118         }
 119
 120         if (between48(DCCP_SKB_CB(skb)->dccpd_seq, lswl, dp->dccps_swh) &&
 121             (DCCP_SKB_CB(skb)->dccpd_ack_seq == DCCP_PKT_WITHOUT_ACK_SEQ ||
 122              between48(DCCP_SKB_CB(skb)->dccpd_ack_seq,
 123                        lawl, dp->dccps_awh))) {
 124                 dccp_update_gsr(sk, DCCP_SKB_CB(skb)->dccpd_seq);
 125
 126                 if (dh->dccph_type != DCCP_PKT_SYNC &&
 127                     (DCCP_SKB_CB(skb)->dccpd_ack_seq !=
 128                      DCCP_PKT_WITHOUT_ACK_SEQ))
 129                         dp->dccps_gar = DCCP_SKB_CB(skb)->dccpd_ack_seq;
 130         } else {
 131                 LIMIT_NETDEBUG(KERN_WARNING "DCCP: Step 6 failed for %s packet, "
 132                                             "(LSWL(%llu) <= P.seqno(%llu) <= S.SWH(%llu)) and "
 133                                             "(P.ackno %s or LAWL(%llu) <= P.ackno(%llu) <= S.AWH(%llu), "
 134                                             "sending SYNC...\n",
 135                                dccp_packet_name(dh->dccph_type),
 136                                (unsigned long long) lswl,
 137                                (unsigned long long)
 138                                DCCP_SKB_CB(skb)->dccpd_seq,
 139                                (unsigned long long) dp->dccps_swh,
 140                                (DCCP_SKB_CB(skb)->dccpd_ack_seq ==
 141                                 DCCP_PKT_WITHOUT_ACK_SEQ) ? "doesn't exist" : "exists",
 142                                (unsigned long long) lawl,
 143                                (unsigned long long)
 144                                DCCP_SKB_CB(skb)->dccpd_ack_seq,
 145                                (unsigned long long) dp->dccps_awh);
 146                 dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq, DCCP_PKT_SYNC);
 147                 return -1;
 148         }
 149
 150         return 0;
 151 }
 152
 153 static int __dccp_rcv_established(struct sock *sk, struct sk_buff *skb,
 154                                   const struct dccp_hdr *dh, const unsigned len)
 155 {
 156         struct dccp_sock *dp = dccp_sk(sk);
 157
 158         switch (dccp_hdr(skb)->dccph_type) {
 159         case DCCP_PKT_DATAACK:
 160         case DCCP_PKT_DATA:
 161                 /*
 162                  * FIXME: check if sk_receive_queue is full, schedule DATA_DROPPED
 163                  * option if it is.
 164                  */
 165                 __skb_pull(skb, dh->dccph_doff * 4);
 166                 __skb_queue_tail(&sk->sk_receive_queue, skb);
 167                 skb_set_owner_r(skb, sk);
 168                 sk->sk_data_ready(sk, 0);
 169                 return 0;
 170         case DCCP_PKT_ACK:
 171                 goto discard;
 172         case DCCP_PKT_RESET:
 173                 /*
 174                  *  Step 9: Process Reset
 175                  *      If P.type == Reset,
 176                  *              Tear down connection
 177                  *              S.state := TIMEWAIT
 178                  *              Set TIMEWAIT timer
 179                  *              Drop packet and return
 180                 */
 181                 dccp_fin(sk, skb);
 182                 dccp_time_wait(sk, DCCP_TIME_WAIT, 0);
 183                 return 0;
 184         case DCCP_PKT_CLOSEREQ:
 185                 dccp_rcv_closereq(sk, skb);
 186                 goto discard;
 187         case DCCP_PKT_CLOSE:
 188                 dccp_rcv_close(sk, skb);
 189                 return 0;
 190         case DCCP_PKT_REQUEST:
 191                 /* Step 7
 192                  *   or (S.is_server and P.type == Response)
 193                  *   or (S.is_client and P.type == Request)
 194                  *   or (S.state >= OPEN and P.type == Request
 195                  *      and P.seqno >= S.OSR)
 196                  *    or (S.state >= OPEN and P.type == Response
 197                  *      and P.seqno >= S.OSR)
 198                  *    or (S.state == RESPOND and P.type == Data),
 199                  *  Send Sync packet acknowledging P.seqno
 200                  *  Drop packet and return
 201                  */
 202                 if (dp->dccps_role != DCCP_ROLE_LISTEN)
 203                         goto send_sync;
 204                 goto check_seq;
 205         case DCCP_PKT_RESPONSE:
 206                 if (dp->dccps_role != DCCP_ROLE_CLIENT)
 207                         goto send_sync;
 208 check_seq:
 209                 if (!before48(DCCP_SKB_CB(skb)->dccpd_seq, dp->dccps_osr)) {
 210 send_sync:
 211                         dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq,
 212                                        DCCP_PKT_SYNC);
 213                 }
 214                 break;
 215         case DCCP_PKT_SYNC:
 216                 dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq,
 217                                DCCP_PKT_SYNCACK);
 218                 /*
 219                  * From RFC 4340, sec. 5.7
 220                  *
 221                  * As with DCCP-Ack packets, DCCP-Sync and DCCP-SyncAck packets
 222                  * MAY have non-zero-length application data areas, whose
 223                  * contents receivers MUST ignore.
 224                  */
 225                 goto discard;
 226         }
 227
 228         DCCP_INC_STATS_BH(DCCP_MIB_INERRS);
 229 discard:
 230         __kfree_skb(skb);
 231         return 0;
 232 }
 233
 234 int dccp_rcv_established(struct sock *sk, struct sk_buff *skb,
 235                          const struct dccp_hdr *dh, const unsigned len)
 236 {
 237         struct dccp_sock *dp = dccp_sk(sk);
 238
 239         if (dccp_check_seqno(sk, skb))
 240                 goto discard;
 241
 242         if (dccp_parse_options(sk, skb))
 243                 goto discard;
 244
 245         if (DCCP_SKB_CB(skb)->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
 246                 dccp_event_ack_recv(sk, skb);
 247
 248         if (dccp_msk(sk)->dccpms_send_ack_vector &&
 249             dccp_ackvec_add(dp->dccps_hc_rx_ackvec, sk,
 250                             DCCP_SKB_CB(skb)->dccpd_seq,
 251                             DCCP_ACKVEC_STATE_RECEIVED))
 252                 goto discard;
 253
 254         ccid_hc_rx_packet_recv(dp->dccps_hc_rx_ccid, sk, skb);
 255         ccid_hc_tx_packet_recv(dp->dccps_hc_tx_ccid, sk, skb);
 256
 257         return __dccp_rcv_established(sk, skb, dh, len);
 258 discard:
 259         __kfree_skb(skb);
 260         return 0;
 261 }
 262
 263 EXPORT_SYMBOL_GPL(dccp_rcv_established);
 264
 265 static int dccp_rcv_request_sent_state_process(struct sock *sk,
 266                                                struct sk_buff *skb,
 267                                                const struct dccp_hdr *dh,
 268                                                const unsigned len)
 269 {
 270         /*
 271          *  Step 4: Prepare sequence numbers in REQUEST
 272          *     If S.state == REQUEST,
 273          *        If (P.type == Response or P.type == Reset)
 274          *              and S.AWL <= P.ackno <= S.AWH,
 275          *           / * Set sequence number variables corresponding to the
 276          *              other endpoint, so P will pass the tests in Step 6 * /
 277          *           Set S.GSR, S.ISR, S.SWL, S.SWH
 278          *           / * Response processing continues in Step 10; Reset
 279          *              processing continues in Step 9 * /
 280         */
 281         if (dh->dccph_type == DCCP_PKT_RESPONSE) {
 282                 const struct inet_connection_sock *icsk = inet_csk(sk);
 283                 struct dccp_sock *dp = dccp_sk(sk);
 284
 285                 /* Stop the REQUEST timer */
 286                 inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS);
 287                 BUG_TRAP(sk->sk_send_head != NULL);
 288                 __kfree_skb(sk->sk_send_head);
 289                 sk->sk_send_head = NULL;
 290
 291                 if (!between48(DCCP_SKB_CB(skb)->dccpd_ack_seq,
 292                                dp->dccps_awl, dp->dccps_awh)) {
 293                         dccp_pr_debug("invalid ackno: S.AWL=%llu, "
 294                                       "P.ackno=%llu, S.AWH=%llu \n",
 295                                       (unsigned long long)dp->dccps_awl,
 296                            (unsigned long long)DCCP_SKB_CB(skb)->dccpd_ack_seq,
 297                                       (unsigned long long)dp->dccps_awh);
 298                         goto out_invalid_packet;
 299                 }
 300
 301                 if (dccp_parse_options(sk, skb))
 302                         goto out_invalid_packet;
 303
 304                 if (dccp_msk(sk)->dccpms_send_ack_vector &&
 305                     dccp_ackvec_add(dp->dccps_hc_rx_ackvec, sk,
 306                                     DCCP_SKB_CB(skb)->dccpd_seq,
 307                                     DCCP_ACKVEC_STATE_RECEIVED))
 308                         goto out_invalid_packet; /* FIXME: change error code */
 309
 310                 dp->dccps_isr = DCCP_SKB_CB(skb)->dccpd_seq;
 311                 dccp_update_gsr(sk, dp->dccps_isr);
 312                 /*
 313                  * SWL and AWL are initially adjusted so that they are not less than
 314                  * the initial Sequence Numbers received and sent, respectively:
 315                  *      SWL := max(GSR + 1 - floor(W/4), ISR),
 316                  *      AWL := max(GSS - W' + 1, ISS).
 317                  * These adjustments MUST be applied only at the beginning of the
 318                  * connection.
 319                  *
 320                  * AWL was adjusted in dccp_v4_connect -acme
 321                  */
 322                 dccp_set_seqno(&dp->dccps_swl,
 323                                max48(dp->dccps_swl, dp->dccps_isr));
 324
 325                 dccp_sync_mss(sk, icsk->icsk_pmtu_cookie);
 326
 327                 /*
 328                  *    Step 10: Process REQUEST state (second part)
 329                  *       If S.state == REQUEST,
 330                  *        / * If we get here, P is a valid Response from the
 331                  *            server (see Step 4), and we should move to
 332                  *            PARTOPEN state. PARTOPEN means send an Ack,
 333                  *            don't send Data packets, retransmit Acks
 334                  *            periodically, and always include any Init Cookie
 335                  *            from the Response * /
 336                  *        S.state := PARTOPEN
 337                  *        Set PARTOPEN timer
 338                  *        Continue with S.state == PARTOPEN
 339                  *        / * Step 12 will send the Ack completing the
 340                  *            three-way handshake * /
 341                  */
 342                 dccp_set_state(sk, DCCP_PARTOPEN);
 343
 344                 /* Make sure socket is routed, for correct metrics. */
 345                 icsk->icsk_af_ops->rebuild_header(sk);
 346
 347                 if (!sock_flag(sk, SOCK_DEAD)) {
 348                         sk->sk_state_change(sk);
 349                         sk_wake_async(sk, 0, POLL_OUT);
 350                 }
 351
 352                 if (sk->sk_write_pending || icsk->icsk_ack.pingpong ||
 353                     icsk->icsk_accept_queue.rskq_defer_accept) {
 354                         /* Save one ACK. Data will be ready after
 355                          * several ticks, if write_pending is set.
 356                          *
 357                          * It may be deleted, but with this feature tcpdumps
 358                          * look so _wonderfully_ clever, that I was not able
 359                          * to stand against the temptation 8)     --ANK
 360                          */
 361                         /*
 362                          * OK, in DCCP we can as well do a similar trick, its
 363                          * even in the draft, but there is no need for us to
 364                          * schedule an ack here, as dccp_sendmsg does this for
 365                          * us, also stated in the draft. -acme
 366                          */
 367                         __kfree_skb(skb);
 368                         return 0;
 369                 }
 370                 dccp_send_ack(sk);
 371                 return -1;
 372         }
 373
 374 out_invalid_packet:
 375         /* dccp_v4_do_rcv will send a reset */
 376         DCCP_SKB_CB(skb)->dccpd_reset_code = DCCP_RESET_CODE_PACKET_ERROR;
 377         return 1;
 378 }
 379
 380 static int dccp_rcv_respond_partopen_state_process(struct sock *sk,
 381                                                    struct sk_buff *skb,
 382                                                    const struct dccp_hdr *dh,
 383                                                    const unsigned len)
 384 {
 385         int queued = 0;
 386
 387         switch (dh->dccph_type) {
 388         case DCCP_PKT_RESET:
 389                 inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
 390                 break;
 391         case DCCP_PKT_DATA:
 392                 if (sk->sk_state == DCCP_RESPOND)
 393                         break;
 394         case DCCP_PKT_DATAACK:
 395         case DCCP_PKT_ACK:
 396                 /*
 397                  * FIXME: we should be reseting the PARTOPEN (DELACK) timer
 398                  * here but only if we haven't used the DELACK timer for
 399                  * something else, like sending a delayed ack for a TIMESTAMP
 400                  * echo, etc, for now were not clearing it, sending an extra
 401                  * ACK when there is nothing else to do in DELACK is not a big
 402                  * deal after all.
 403                  */
 404
 405                 /* Stop the PARTOPEN timer */
 406                 if (sk->sk_state == DCCP_PARTOPEN)
 407                         inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
 408
 409                 dccp_sk(sk)->dccps_osr = DCCP_SKB_CB(skb)->dccpd_seq;
 410                 dccp_set_state(sk, DCCP_OPEN);
 411
 412                 if (dh->dccph_type == DCCP_PKT_DATAACK ||
 413                     dh->dccph_type == DCCP_PKT_DATA) {
 414                         __dccp_rcv_established(sk, skb, dh, len);
 415                         queued = 1; /* packet was queued
 416                                        (by __dccp_rcv_established) */
 417                 }
 418                 break;
 419         }
 420
 421         return queued;
 422 }
 423
 424 int dccp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
 425                            struct dccp_hdr *dh, unsigned len)
 426 {
 427         struct dccp_sock *dp = dccp_sk(sk);
 428         struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
 429         const int old_state = sk->sk_state;
 430         int queued = 0;
 431
 432         /*
 433          *  Step 3: Process LISTEN state
 434          *      (Continuing from dccp_v4_do_rcv and dccp_v6_do_rcv)
 435          *
 436          *     If S.state == LISTEN,
 437          *        If P.type == Request or P contains a valid Init Cookie
 438          *              option,
 439          *           * Must scan the packet's options to check for an Init
 440          *              Cookie.  Only the Init Cookie is processed here,
 441          *              however; other options are processed in Step 8.  This
 442          *              scan need only be performed if the endpoint uses Init
 443          *              Cookies *
 444          *           * Generate a new socket and switch to that socket *
 445          *           Set S := new socket for this port pair
 446          *           S.state = RESPOND
 447          *           Choose S.ISS (initial seqno) or set from Init Cookie
 448          *           Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init Cookie
 449          *           Continue with S.state == RESPOND
 450          *           * A Response packet will be generated in Step 11 *
 451          *        Otherwise,
 452          *           Generate Reset(No Connection) unless P.type == Reset
 453          *           Drop packet and return
 454          *
 455          * NOTE: the check for the packet types is done in
 456          *       dccp_rcv_state_process
 457          */
 458         if (sk->sk_state == DCCP_LISTEN) {
 459                 if (dh->dccph_type == DCCP_PKT_REQUEST) {
 460                         if (inet_csk(sk)->icsk_af_ops->conn_request(sk,
 461                                                                     skb) < 0)
 462                                 return 1;
 463
 464                         /* FIXME: do congestion control initialization */
 465                         goto discard;
 466                 }
 467                 if (dh->dccph_type == DCCP_PKT_RESET)
 468                         goto discard;
 469
 470                 /* Caller (dccp_v4_do_rcv) will send Reset */
 471                 dcb->dccpd_reset_code = DCCP_RESET_CODE_NO_CONNECTION;
 472                 return 1;
 473         }
 474
 475         if (sk->sk_state != DCCP_REQUESTING) {
 476                 if (dccp_check_seqno(sk, skb))
 477                         goto discard;
 478
 479                 /*
 480                  * Step 8: Process options and mark acknowledgeable
 481                  */
 482                 if (dccp_parse_options(sk, skb))
 483                         goto discard;
 484
 485                 if (dcb->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
 486                         dccp_event_ack_recv(sk, skb);
 487
 488                 if (dccp_msk(sk)->dccpms_send_ack_vector &&
 489                     dccp_ackvec_add(dp->dccps_hc_rx_ackvec, sk,
 490                                     DCCP_SKB_CB(skb)->dccpd_seq,
 491                                     DCCP_ACKVEC_STATE_RECEIVED))
 492                         goto discard;
 493
 494                 ccid_hc_rx_packet_recv(dp->dccps_hc_rx_ccid, sk, skb);
 495                 ccid_hc_tx_packet_recv(dp->dccps_hc_tx_ccid, sk, skb);
 496         }
 497
 498         /*
 499          *  Step 9: Process Reset
 500          *      If P.type == Reset,
 501          *              Tear down connection
 502          *              S.state := TIMEWAIT
 503          *              Set TIMEWAIT timer
 504          *              Drop packet and return
 505         */
 506         if (dh->dccph_type == DCCP_PKT_RESET) {
 507                 /*
 508                  * Queue the equivalent of TCP fin so that dccp_recvmsg
 509                  * exits the loop
 510                  */
 511                 dccp_fin(sk, skb);
 512                 dccp_time_wait(sk, DCCP_TIME_WAIT, 0);
 513                 return 0;
 514                 /*
 515                  *   Step 7: Check for unexpected packet types
 516                  *      If (S.is_server and P.type == CloseReq)
 517                  *          or (S.is_server and P.type == Response)
 518                  *          or (S.is_client and P.type == Request)
 519                  *          or (S.state == RESPOND and P.type == Data),
 520                  *        Send Sync packet acknowledging P.seqno
 521                  *        Drop packet and return
 522                  */
 523         } else if ((dp->dccps_role != DCCP_ROLE_CLIENT &&
 524                     (dh->dccph_type == DCCP_PKT_RESPONSE ||
 525                      dh->dccph_type == DCCP_PKT_CLOSEREQ)) ||
 526                     (dp->dccps_role == DCCP_ROLE_CLIENT &&
 527                      dh->dccph_type == DCCP_PKT_REQUEST) ||
 528                     (sk->sk_state == DCCP_RESPOND &&
 529                      dh->dccph_type == DCCP_PKT_DATA)) {
 530                 dccp_send_sync(sk, dcb->dccpd_seq, DCCP_PKT_SYNC);
 531                 goto discard;
 532         } else if (dh->dccph_type == DCCP_PKT_CLOSEREQ) {
 533                 dccp_rcv_closereq(sk, skb);
 534                 goto discard;
 535         } else if (dh->dccph_type == DCCP_PKT_CLOSE) {
 536                 dccp_rcv_close(sk, skb);
 537                 return 0;
 538         }
 539
 540         if (unlikely(dh->dccph_type == DCCP_PKT_SYNC)) {
 541                 dccp_send_sync(sk, dcb->dccpd_seq, DCCP_PKT_SYNCACK);
 542                 goto discard;
 543         }
 544
 545         switch (sk->sk_state) {
 546         case DCCP_CLOSED:
 547                 dcb->dccpd_reset_code = DCCP_RESET_CODE_NO_CONNECTION;
 548                 return 1;
 549
 550         case DCCP_REQUESTING:
 551                 /* FIXME: do congestion control initialization */
 552
 553                 queued = dccp_rcv_request_sent_state_process(sk, skb, dh, len);
 554                 if (queued >= 0)
 555                         return queued;
 556
 557                 __kfree_skb(skb);
 558                 return 0;
 559
 560         case DCCP_RESPOND:
 561         case DCCP_PARTOPEN:
 562                 queued = dccp_rcv_respond_partopen_state_process(sk, skb,
 563                                                                  dh, len);
 564                 break;
 565         }
 566
 567         if (dh->dccph_type == DCCP_PKT_ACK ||
 568             dh->dccph_type == DCCP_PKT_DATAACK) {
 569                 switch (old_state) {
 570                 case DCCP_PARTOPEN:
 571                         sk->sk_state_change(sk);
 572                         sk_wake_async(sk, 0, POLL_OUT);
 573                         break;
 574                 }
 575         }
 576
 577         if (!queued) {
 578 discard:
 579                 __kfree_skb(skb);
 580         }
 581         return 0;
 582 }
 583
 584 EXPORT_SYMBOL_GPL(dccp_rcv_state_process);