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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                 DCCP_WARN("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",  dccp_packet_name(dh->dccph_type),
 135                           (unsigned long long) lswl,
 136                           (unsigned long long) DCCP_SKB_CB(skb)->dccpd_seq,
 137                           (unsigned long long) dp->dccps_swh,
 138                           (DCCP_SKB_CB(skb)->dccpd_ack_seq ==
 139                                 DCCP_PKT_WITHOUT_ACK_SEQ) ? "doesn't exist" : "exists",
 140                           (unsigned long long) lawl,
 141                           (unsigned long long) DCCP_SKB_CB(skb)->dccpd_ack_seq,
 142                           (unsigned long long) dp->dccps_awh);
 143                 dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq, DCCP_PKT_SYNC);
 144                 return -1;
 145         }
 146
 147         return 0;
 148 }
 149
 150 static int __dccp_rcv_established(struct sock *sk, struct sk_buff *skb,
 151                                   const struct dccp_hdr *dh, const unsigned len)
 152 {
 153         struct dccp_sock *dp = dccp_sk(sk);
 154
 155         switch (dccp_hdr(skb)->dccph_type) {
 156         case DCCP_PKT_DATAACK:
 157         case DCCP_PKT_DATA:
 158                 /*
 159                  * FIXME: check if sk_receive_queue is full, schedule DATA_DROPPED
 160                  * option if it is.
 161                  */
 162                 __skb_pull(skb, dh->dccph_doff * 4);
 163                 __skb_queue_tail(&sk->sk_receive_queue, skb);
 164                 skb_set_owner_r(skb, sk);
 165                 sk->sk_data_ready(sk, 0);
 166                 return 0;
 167         case DCCP_PKT_ACK:
 168                 goto discard;
 169         case DCCP_PKT_RESET:
 170                 /*
 171                  *  Step 9: Process Reset
 172                  *      If P.type == Reset,
 173                  *              Tear down connection
 174                  *              S.state := TIMEWAIT
 175                  *              Set TIMEWAIT timer
 176                  *              Drop packet and return
 177                 */
 178                 dccp_fin(sk, skb);
 179                 dccp_time_wait(sk, DCCP_TIME_WAIT, 0);
 180                 return 0;
 181         case DCCP_PKT_CLOSEREQ:
 182                 dccp_rcv_closereq(sk, skb);
 183                 goto discard;
 184         case DCCP_PKT_CLOSE:
 185                 dccp_rcv_close(sk, skb);
 186                 return 0;
 187         case DCCP_PKT_REQUEST:
 188                 /* Step 7
 189                  *   or (S.is_server and P.type == Response)
 190                  *   or (S.is_client and P.type == Request)
 191                  *   or (S.state >= OPEN and P.type == Request
 192                  *      and P.seqno >= S.OSR)
 193                  *    or (S.state >= OPEN and P.type == Response
 194                  *      and P.seqno >= S.OSR)
 195                  *    or (S.state == RESPOND and P.type == Data),
 196                  *  Send Sync packet acknowledging P.seqno
 197                  *  Drop packet and return
 198                  */
 199                 if (dp->dccps_role != DCCP_ROLE_LISTEN)
 200                         goto send_sync;
 201                 goto check_seq;
 202         case DCCP_PKT_RESPONSE:
 203                 if (dp->dccps_role != DCCP_ROLE_CLIENT)
 204                         goto send_sync;
 205 check_seq:
 206                 if (!before48(DCCP_SKB_CB(skb)->dccpd_seq, dp->dccps_osr)) {
 207 send_sync:
 208                         dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq,
 209                                        DCCP_PKT_SYNC);
 210                 }
 211                 break;
 212         case DCCP_PKT_SYNC:
 213                 dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq,
 214                                DCCP_PKT_SYNCACK);
 215                 /*
 216                  * From RFC 4340, sec. 5.7
 217                  *
 218                  * As with DCCP-Ack packets, DCCP-Sync and DCCP-SyncAck packets
 219                  * MAY have non-zero-length application data areas, whose
 220                  * contents receivers MUST ignore.
 221                  */
 222                 goto discard;
 223         }
 224
 225         DCCP_INC_STATS_BH(DCCP_MIB_INERRS);
 226 discard:
 227         __kfree_skb(skb);
 228         return 0;
 229 }
 230
 231 int dccp_rcv_established(struct sock *sk, struct sk_buff *skb,
 232                          const struct dccp_hdr *dh, const unsigned len)
 233 {
 234         struct dccp_sock *dp = dccp_sk(sk);
 235
 236         if (dccp_check_seqno(sk, skb))
 237                 goto discard;
 238
 239         if (dccp_parse_options(sk, skb))
 240                 goto discard;
 241
 242         if (DCCP_SKB_CB(skb)->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
 243                 dccp_event_ack_recv(sk, skb);
 244
 245         if (dccp_msk(sk)->dccpms_send_ack_vector &&
 246             dccp_ackvec_add(dp->dccps_hc_rx_ackvec, sk,
 247                             DCCP_SKB_CB(skb)->dccpd_seq,
 248                             DCCP_ACKVEC_STATE_RECEIVED))
 249                 goto discard;
 250
 251         /*
 252          * Deliver to the CCID module in charge.
 253          * FIXME: Currently DCCP operates one-directional only, i.e. a listening
 254          *        server is not at the same time a connecting client. There is
 255          *        not much sense in delivering to both rx/tx sides at the moment
 256          *        (only one is active at a time); when moving to bidirectional
 257          *        service, this needs to be revised.
 258          */
 259         if (dccp_sk(sk)->dccps_role == DCCP_ROLE_SERVER)
 260                 ccid_hc_rx_packet_recv(dp->dccps_hc_rx_ccid, sk, skb);
 261         else
 262                 ccid_hc_tx_packet_recv(dp->dccps_hc_tx_ccid, sk, skb);
 263
 264         return __dccp_rcv_established(sk, skb, dh, len);
 265 discard:
 266         __kfree_skb(skb);
 267         return 0;
 268 }
 269
 270 EXPORT_SYMBOL_GPL(dccp_rcv_established);
 271
 272 static int dccp_rcv_request_sent_state_process(struct sock *sk,
 273                                                struct sk_buff *skb,
 274                                                const struct dccp_hdr *dh,
 275                                                const unsigned len)
 276 {
 277         /*
 278          *  Step 4: Prepare sequence numbers in REQUEST
 279          *     If S.state == REQUEST,
 280          *        If (P.type == Response or P.type == Reset)
 281          *              and S.AWL <= P.ackno <= S.AWH,
 282          *           / * Set sequence number variables corresponding to the
 283          *              other endpoint, so P will pass the tests in Step 6 * /
 284          *           Set S.GSR, S.ISR, S.SWL, S.SWH
 285          *           / * Response processing continues in Step 10; Reset
 286          *              processing continues in Step 9 * /
 287         */
 288         if (dh->dccph_type == DCCP_PKT_RESPONSE) {
 289                 const struct inet_connection_sock *icsk = inet_csk(sk);
 290                 struct dccp_sock *dp = dccp_sk(sk);
 291
 292                 /* Stop the REQUEST timer */
 293                 inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS);
 294                 BUG_TRAP(sk->sk_send_head != NULL);
 295                 __kfree_skb(sk->sk_send_head);
 296                 sk->sk_send_head = NULL;
 297
 298                 if (!between48(DCCP_SKB_CB(skb)->dccpd_ack_seq,
 299                                dp->dccps_awl, dp->dccps_awh)) {
 300                         dccp_pr_debug("invalid ackno: S.AWL=%llu, "
 301                                       "P.ackno=%llu, S.AWH=%llu \n",
 302                                       (unsigned long long)dp->dccps_awl,
 303                            (unsigned long long)DCCP_SKB_CB(skb)->dccpd_ack_seq,
 304                                       (unsigned long long)dp->dccps_awh);
 305                         goto out_invalid_packet;
 306                 }
 307
 308                 if (dccp_parse_options(sk, skb))
 309                         goto out_invalid_packet;
 310
 311                 if (dccp_msk(sk)->dccpms_send_ack_vector &&
 312                     dccp_ackvec_add(dp->dccps_hc_rx_ackvec, sk,
 313                                     DCCP_SKB_CB(skb)->dccpd_seq,
 314                                     DCCP_ACKVEC_STATE_RECEIVED))
 315                         goto out_invalid_packet; /* FIXME: change error code */
 316
 317                 dp->dccps_isr = DCCP_SKB_CB(skb)->dccpd_seq;
 318                 dccp_update_gsr(sk, dp->dccps_isr);
 319                 /*
 320                  * SWL and AWL are initially adjusted so that they are not less than
 321                  * the initial Sequence Numbers received and sent, respectively:
 322                  *      SWL := max(GSR + 1 - floor(W/4), ISR),
 323                  *      AWL := max(GSS - W' + 1, ISS).
 324                  * These adjustments MUST be applied only at the beginning of the
 325                  * connection.
 326                  *
 327                  * AWL was adjusted in dccp_v4_connect -acme
 328                  */
 329                 dccp_set_seqno(&dp->dccps_swl,
 330                                max48(dp->dccps_swl, dp->dccps_isr));
 331
 332                 dccp_sync_mss(sk, icsk->icsk_pmtu_cookie);
 333
 334                 /*
 335                  *    Step 10: Process REQUEST state (second part)
 336                  *       If S.state == REQUEST,
 337                  *        / * If we get here, P is a valid Response from the
 338                  *            server (see Step 4), and we should move to
 339                  *            PARTOPEN state. PARTOPEN means send an Ack,
 340                  *            don't send Data packets, retransmit Acks
 341                  *            periodically, and always include any Init Cookie
 342                  *            from the Response * /
 343                  *        S.state := PARTOPEN
 344                  *        Set PARTOPEN timer
 345                  *        Continue with S.state == PARTOPEN
 346                  *        / * Step 12 will send the Ack completing the
 347                  *            three-way handshake * /
 348                  */
 349                 dccp_set_state(sk, DCCP_PARTOPEN);
 350
 351                 /* Make sure socket is routed, for correct metrics. */
 352                 icsk->icsk_af_ops->rebuild_header(sk);
 353
 354                 if (!sock_flag(sk, SOCK_DEAD)) {
 355                         sk->sk_state_change(sk);
 356                         sk_wake_async(sk, 0, POLL_OUT);
 357                 }
 358
 359                 if (sk->sk_write_pending || icsk->icsk_ack.pingpong ||
 360                     icsk->icsk_accept_queue.rskq_defer_accept) {
 361                         /* Save one ACK. Data will be ready after
 362                          * several ticks, if write_pending is set.
 363                          *
 364                          * It may be deleted, but with this feature tcpdumps
 365                          * look so _wonderfully_ clever, that I was not able
 366                          * to stand against the temptation 8)     --ANK
 367                          */
 368                         /*
 369                          * OK, in DCCP we can as well do a similar trick, its
 370                          * even in the draft, but there is no need for us to
 371                          * schedule an ack here, as dccp_sendmsg does this for
 372                          * us, also stated in the draft. -acme
 373                          */
 374                         __kfree_skb(skb);
 375                         return 0;
 376                 }
 377                 dccp_send_ack(sk);
 378                 return -1;
 379         }
 380
 381 out_invalid_packet:
 382         /* dccp_v4_do_rcv will send a reset */
 383         DCCP_SKB_CB(skb)->dccpd_reset_code = DCCP_RESET_CODE_PACKET_ERROR;
 384         return 1;
 385 }
 386
 387 static int dccp_rcv_respond_partopen_state_process(struct sock *sk,
 388                                                    struct sk_buff *skb,
 389                                                    const struct dccp_hdr *dh,
 390                                                    const unsigned len)
 391 {
 392         int queued = 0;
 393
 394         switch (dh->dccph_type) {
 395         case DCCP_PKT_RESET:
 396                 inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
 397                 break;
 398         case DCCP_PKT_DATA:
 399                 if (sk->sk_state == DCCP_RESPOND)
 400                         break;
 401         case DCCP_PKT_DATAACK:
 402         case DCCP_PKT_ACK:
 403                 /*
 404                  * FIXME: we should be reseting the PARTOPEN (DELACK) timer
 405                  * here but only if we haven't used the DELACK timer for
 406                  * something else, like sending a delayed ack for a TIMESTAMP
 407                  * echo, etc, for now were not clearing it, sending an extra
 408                  * ACK when there is nothing else to do in DELACK is not a big
 409                  * deal after all.
 410                  */
 411
 412                 /* Stop the PARTOPEN timer */
 413                 if (sk->sk_state == DCCP_PARTOPEN)
 414                         inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
 415
 416                 dccp_sk(sk)->dccps_osr = DCCP_SKB_CB(skb)->dccpd_seq;
 417                 dccp_set_state(sk, DCCP_OPEN);
 418
 419                 if (dh->dccph_type == DCCP_PKT_DATAACK ||
 420                     dh->dccph_type == DCCP_PKT_DATA) {
 421                         __dccp_rcv_established(sk, skb, dh, len);
 422                         queued = 1; /* packet was queued
 423                                        (by __dccp_rcv_established) */
 424                 }
 425                 break;
 426         }
 427
 428         return queued;
 429 }
 430
 431 int dccp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
 432                            struct dccp_hdr *dh, unsigned len)
 433 {
 434         struct dccp_sock *dp = dccp_sk(sk);
 435         struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
 436         const int old_state = sk->sk_state;
 437         int queued = 0;
 438
 439         /*
 440          *  Step 3: Process LISTEN state
 441          *
 442          *     If S.state == LISTEN,
 443          *       If P.type == Request or P contains a valid Init Cookie option,
 444          *            (* Must scan the packet's options to check for Init
 445          *               Cookies.  Only Init Cookies are processed here,
 446          *               however; other options are processed in Step 8.  This
 447          *               scan need only be performed if the endpoint uses Init
 448          *               Cookies *)
 449          *            (* Generate a new socket and switch to that socket *)
 450          *            Set S := new socket for this port pair
 451          *            S.state = RESPOND
 452          *            Choose S.ISS (initial seqno) or set from Init Cookies
 453          *            Initialize S.GAR := S.ISS
 454          *            Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init
 455          *            Cookies Continue with S.state == RESPOND
 456          *            (* A Response packet will be generated in Step 11 *)
 457          *       Otherwise,
 458          *            Generate Reset(No Connection) unless P.type == Reset
 459          *            Drop packet and return
 460          */
 461         if (sk->sk_state == DCCP_LISTEN) {
 462                 if (dh->dccph_type == DCCP_PKT_REQUEST) {
 463                         if (inet_csk(sk)->icsk_af_ops->conn_request(sk,
 464                                                                     skb) < 0)
 465                                 return 1;
 466
 467                         /* FIXME: do congestion control initialization */
 468                         goto discard;
 469                 }
 470                 if (dh->dccph_type == DCCP_PKT_RESET)
 471                         goto discard;
 472
 473                 /* Caller (dccp_v4_do_rcv) will send Reset */
 474                 dcb->dccpd_reset_code = DCCP_RESET_CODE_NO_CONNECTION;
 475                 return 1;
 476         }
 477
 478         if (sk->sk_state != DCCP_REQUESTING) {
 479                 if (dccp_check_seqno(sk, skb))
 480                         goto discard;
 481
 482                 /*
 483                  * Step 8: Process options and mark acknowledgeable
 484                  */
 485                 if (dccp_parse_options(sk, skb))
 486                         goto discard;
 487
 488                 if (dcb->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
 489                         dccp_event_ack_recv(sk, skb);
 490
 491                 if (dccp_msk(sk)->dccpms_send_ack_vector &&
 492                     dccp_ackvec_add(dp->dccps_hc_rx_ackvec, sk,
 493                                     DCCP_SKB_CB(skb)->dccpd_seq,
 494                                     DCCP_ACKVEC_STATE_RECEIVED))
 495                         goto discard;
 496
 497                 /* XXX see the comments in dccp_rcv_established about this */
 498                 if (dccp_sk(sk)->dccps_role == DCCP_ROLE_SERVER)
 499                         ccid_hc_rx_packet_recv(dp->dccps_hc_rx_ccid, sk, skb);
 500                 else
 501                         ccid_hc_tx_packet_recv(dp->dccps_hc_tx_ccid, sk, skb);
 502         }
 503
 504         /*
 505          *  Step 9: Process Reset
 506          *      If P.type == Reset,
 507          *              Tear down connection
 508          *              S.state := TIMEWAIT
 509          *              Set TIMEWAIT timer
 510          *              Drop packet and return
 511         */
 512         if (dh->dccph_type == DCCP_PKT_RESET) {
 513                 /*
 514                  * Queue the equivalent of TCP fin so that dccp_recvmsg
 515                  * exits the loop
 516                  */
 517                 dccp_fin(sk, skb);
 518                 dccp_time_wait(sk, DCCP_TIME_WAIT, 0);
 519                 return 0;
 520                 /*
 521                  *   Step 7: Check for unexpected packet types
 522                  *      If (S.is_server and P.type == CloseReq)
 523                  *          or (S.is_server and P.type == Response)
 524                  *          or (S.is_client and P.type == Request)
 525                  *          or (S.state == RESPOND and P.type == Data),
 526                  *        Send Sync packet acknowledging P.seqno
 527                  *        Drop packet and return
 528                  */
 529         } else if ((dp->dccps_role != DCCP_ROLE_CLIENT &&
 530                     (dh->dccph_type == DCCP_PKT_RESPONSE ||
 531                      dh->dccph_type == DCCP_PKT_CLOSEREQ)) ||
 532                     (dp->dccps_role == DCCP_ROLE_CLIENT &&
 533                      dh->dccph_type == DCCP_PKT_REQUEST) ||
 534                     (sk->sk_state == DCCP_RESPOND &&
 535                      dh->dccph_type == DCCP_PKT_DATA)) {
 536                 dccp_send_sync(sk, dcb->dccpd_seq, DCCP_PKT_SYNC);
 537                 goto discard;
 538         } else if (dh->dccph_type == DCCP_PKT_CLOSEREQ) {
 539                 dccp_rcv_closereq(sk, skb);
 540                 goto discard;
 541         } else if (dh->dccph_type == DCCP_PKT_CLOSE) {
 542                 dccp_rcv_close(sk, skb);
 543                 return 0;
 544         }
 545
 546         if (unlikely(dh->dccph_type == DCCP_PKT_SYNC)) {
 547                 dccp_send_sync(sk, dcb->dccpd_seq, DCCP_PKT_SYNCACK);
 548                 goto discard;
 549         }
 550
 551         switch (sk->sk_state) {
 552         case DCCP_CLOSED:
 553                 dcb->dccpd_reset_code = DCCP_RESET_CODE_NO_CONNECTION;
 554                 return 1;
 555
 556         case DCCP_REQUESTING:
 557                 /* FIXME: do congestion control initialization */
 558
 559                 queued = dccp_rcv_request_sent_state_process(sk, skb, dh, len);
 560                 if (queued >= 0)
 561                         return queued;
 562
 563                 __kfree_skb(skb);
 564                 return 0;
 565
 566         case DCCP_RESPOND:
 567         case DCCP_PARTOPEN:
 568                 queued = dccp_rcv_respond_partopen_state_process(sk, skb,
 569                                                                  dh, len);
 570                 break;
 571         }
 572
 573         if (dh->dccph_type == DCCP_PKT_ACK ||
 574             dh->dccph_type == DCCP_PKT_DATAACK) {
 575                 switch (old_state) {
 576                 case DCCP_PARTOPEN:
 577                         sk->sk_state_change(sk);
 578                         sk_wake_async(sk, 0, POLL_OUT);
 579                         break;
 580                 }
 581         }
 582
 583         if (!queued) {
 584 discard:
 585                 __kfree_skb(skb);
 586         }
 587         return 0;
 588 }
 589
 590 EXPORT_SYMBOL_GPL(dccp_rcv_state_process);