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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/config.h>
  14 #include <linux/dccp.h>
  15 #include <linux/skbuff.h>
  16
  17 #include <net/sock.h>
  18
  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         switch (sk->sk_state) {
  35         case DCCP_PARTOPEN:
  36         case DCCP_OPEN:
  37                 dccp_v4_send_reset(sk, DCCP_RESET_CODE_CLOSED);
  38                 dccp_fin(sk, skb);
  39                 dccp_set_state(sk, DCCP_CLOSED);
  40                 break;
  41         }
  42 }
  43
  44 static void dccp_rcv_closereq(struct sock *sk, struct sk_buff *skb)
  45 {
  46         /*
  47          *   Step 7: Check for unexpected packet types
  48          *      If (S.is_server and P.type == CloseReq)
  49          *        Send Sync packet acknowledging P.seqno
  50          *        Drop packet and return
  51          */
  52         if (dccp_sk(sk)->dccps_role != DCCP_ROLE_CLIENT) {
  53                 dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq, DCCP_PKT_SYNC);
  54                 return;
  55         }
  56
  57         switch (sk->sk_state) {
  58         case DCCP_PARTOPEN:
  59         case DCCP_OPEN:
  60                 dccp_set_state(sk, DCCP_CLOSING);
  61                 dccp_send_close(sk);
  62                 break;
  63         }
  64 }
  65
  66 static inline void dccp_event_ack_recv(struct sock *sk, struct sk_buff *skb)
  67 {
  68         struct dccp_sock *dp = dccp_sk(sk);
  69
  70         if (dp->dccps_options.dccpo_send_ack_vector)
  71                 dccp_ackpkts_check_rcv_ackno(dp->dccps_hc_rx_ackpkts, sk,
  72                                              DCCP_SKB_CB(skb)->dccpd_ack_seq);
  73 }
  74
  75 static int dccp_check_seqno(struct sock *sk, struct sk_buff *skb)
  76 {
  77         const struct dccp_hdr *dh = dccp_hdr(skb);
  78         struct dccp_sock *dp = dccp_sk(sk);
  79         u64 lswl, lawl;
  80
  81         /*
  82          *   Step 5: Prepare sequence numbers for Sync
  83          *     If P.type == Sync or P.type == SyncAck,
  84          *        If S.AWL <= P.ackno <= S.AWH and P.seqno >= S.SWL,
  85          *           / * P is valid, so update sequence number variables
  86          *               accordingly.  After this update, P will pass the tests
  87          *               in Step 6.  A SyncAck is generated if necessary in
  88          *               Step 15 * /
  89          *           Update S.GSR, S.SWL, S.SWH
  90          *        Otherwise,
  91          *           Drop packet and return
  92          */
  93         if (dh->dccph_type == DCCP_PKT_SYNC ||
  94             dh->dccph_type == DCCP_PKT_SYNCACK) {
  95                 if (between48(DCCP_SKB_CB(skb)->dccpd_ack_seq,
  96                               dp->dccps_awl, dp->dccps_awh) &&
  97                     !before48(DCCP_SKB_CB(skb)->dccpd_seq, dp->dccps_swl))
  98                         dccp_update_gsr(sk, DCCP_SKB_CB(skb)->dccpd_seq);
  99                 else
 100                         return -1;
 101         }
 102
 103         /*
 104          *   Step 6: Check sequence numbers
 105          *      Let LSWL = S.SWL and LAWL = S.AWL
 106          *      If P.type == CloseReq or P.type == Close or P.type == Reset,
 107          *        LSWL := S.GSR + 1, LAWL := S.GAR
 108          *      If LSWL <= P.seqno <= S.SWH
 109          *           and (P.ackno does not exist or LAWL <= P.ackno <= S.AWH),
 110          *        Update S.GSR, S.SWL, S.SWH
 111          *        If P.type != Sync,
 112          *           Update S.GAR
 113          *      Otherwise,
 114          *        Send Sync packet acknowledging P.seqno
 115          *        Drop packet and return
 116          */
 117         lswl = dp->dccps_swl;
 118         lawl = dp->dccps_awl;
 119
 120         if (dh->dccph_type == DCCP_PKT_CLOSEREQ ||
 121             dh->dccph_type == DCCP_PKT_CLOSE ||
 122             dh->dccph_type == DCCP_PKT_RESET) {
 123                 lswl = dp->dccps_gsr;
 124                 dccp_inc_seqno(&lswl);
 125                 lawl = dp->dccps_gar;
 126         }
 127
 128         if (between48(DCCP_SKB_CB(skb)->dccpd_seq, lswl, dp->dccps_swh) &&
 129             (DCCP_SKB_CB(skb)->dccpd_ack_seq == DCCP_PKT_WITHOUT_ACK_SEQ ||
 130              between48(DCCP_SKB_CB(skb)->dccpd_ack_seq,
 131                        lawl, dp->dccps_awh))) {
 132                 dccp_update_gsr(sk, DCCP_SKB_CB(skb)->dccpd_seq);
 133
 134                 if (dh->dccph_type != DCCP_PKT_SYNC &&
 135                     (DCCP_SKB_CB(skb)->dccpd_ack_seq !=
 136                      DCCP_PKT_WITHOUT_ACK_SEQ))
 137                         dp->dccps_gar = DCCP_SKB_CB(skb)->dccpd_ack_seq;
 138         } else {
 139                 LIMIT_NETDEBUG(KERN_WARNING "DCCP: Step 6 failed for %s packet, "
 140                                             "(LSWL(%llu) <= P.seqno(%llu) <= S.SWH(%llu)) and "
 141                                             "(P.ackno %s or LAWL(%llu) <= P.ackno(%llu) <= S.AWH(%llu), "
 142                                             "sending SYNC...\n",
 143                                dccp_packet_name(dh->dccph_type),
 144                                (unsigned long long) lswl,
 145                                (unsigned long long)
 146                                DCCP_SKB_CB(skb)->dccpd_seq,
 147                                (unsigned long long) dp->dccps_swh,
 148                                (DCCP_SKB_CB(skb)->dccpd_ack_seq ==
 149                                 DCCP_PKT_WITHOUT_ACK_SEQ) ? "doesn't exist" : "exists",
 150                                (unsigned long long) lawl,
 151                                (unsigned long long)
 152                                DCCP_SKB_CB(skb)->dccpd_ack_seq,
 153                                (unsigned long long) dp->dccps_awh);
 154                 dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq, DCCP_PKT_SYNC);
 155                 return -1;
 156         }
 157
 158         return 0;
 159 }
 160
 161 int dccp_rcv_established(struct sock *sk, struct sk_buff *skb,
 162                          const struct dccp_hdr *dh, const unsigned len)
 163 {
 164         struct dccp_sock *dp = dccp_sk(sk);
 165
 166         if (dccp_check_seqno(sk, skb))
 167                 goto discard;
 168
 169         if (dccp_parse_options(sk, skb))
 170                 goto discard;
 171
 172         if (DCCP_SKB_CB(skb)->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
 173                 dccp_event_ack_recv(sk, skb);
 174
 175         /*
 176          * FIXME: check ECN to see if we should use
 177          * DCCP_ACKPKTS_STATE_ECN_MARKED
 178          */
 179         if (dp->dccps_options.dccpo_send_ack_vector) {
 180                 struct dccp_ackpkts *ap = dp->dccps_hc_rx_ackpkts;
 181
 182                 if (dccp_ackpkts_add(dp->dccps_hc_rx_ackpkts,
 183                                      DCCP_SKB_CB(skb)->dccpd_seq,
 184                                      DCCP_ACKPKTS_STATE_RECEIVED)) {
 185                         LIMIT_NETDEBUG(KERN_WARNING "DCCP: acknowledgeable "
 186                                                     "packets buffer full!\n");
 187                         ap->dccpap_ack_seqno = DCCP_MAX_SEQNO + 1;
 188                         inet_csk_schedule_ack(sk);
 189                         inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
 190                                                   TCP_DELACK_MIN,
 191                                                   DCCP_RTO_MAX);
 192                         goto discard;
 193                 }
 194
 195                 /*
 196                  * FIXME: this activation is probably wrong, have to study more
 197                  * TCP delack machinery and how it fits into DCCP draft, but
 198                  * for now it kinda "works" 8)
 199                  */
 200                 if (!inet_csk_ack_scheduled(sk)) {
 201                         inet_csk_schedule_ack(sk);
 202                         inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK, 5 * HZ,
 203                                                   DCCP_RTO_MAX);
 204                 }
 205         }
 206
 207         ccid_hc_rx_packet_recv(dp->dccps_hc_rx_ccid, sk, skb);
 208         ccid_hc_tx_packet_recv(dp->dccps_hc_tx_ccid, sk, skb);
 209
 210         switch (dccp_hdr(skb)->dccph_type) {
 211         case DCCP_PKT_DATAACK:
 212         case DCCP_PKT_DATA:
 213                 /*
 214                  * FIXME: check if sk_receive_queue is full, schedule DATA_DROPPED
 215                  * option if it is.
 216                  */
 217                 __skb_pull(skb, dh->dccph_doff * 4);
 218                 __skb_queue_tail(&sk->sk_receive_queue, skb);
 219                 skb_set_owner_r(skb, sk);
 220                 sk->sk_data_ready(sk, 0);
 221                 return 0;
 222         case DCCP_PKT_ACK:
 223                 goto discard;
 224         case DCCP_PKT_RESET:
 225                 /*
 226                  *  Step 9: Process Reset
 227                  *      If P.type == Reset,
 228                  *              Tear down connection
 229                  *              S.state := TIMEWAIT
 230                  *              Set TIMEWAIT timer
 231                  *              Drop packet and return
 232                 */
 233                 dccp_fin(sk, skb);
 234                 dccp_time_wait(sk, DCCP_TIME_WAIT, 0);
 235                 return 0;
 236         case DCCP_PKT_CLOSEREQ:
 237                 dccp_rcv_closereq(sk, skb);
 238                 goto discard;
 239         case DCCP_PKT_CLOSE:
 240                 dccp_rcv_close(sk, skb);
 241                 return 0;
 242         case DCCP_PKT_REQUEST:
 243                 /* Step 7
 244                  *   or (S.is_server and P.type == Response)
 245                  *   or (S.is_client and P.type == Request)
 246                  *   or (S.state >= OPEN and P.type == Request
 247                  *      and P.seqno >= S.OSR)
 248                  *    or (S.state >= OPEN and P.type == Response
 249                  *      and P.seqno >= S.OSR)
 250                  *    or (S.state == RESPOND and P.type == Data),
 251                  *  Send Sync packet acknowledging P.seqno
 252                  *  Drop packet and return
 253                  */
 254                 if (dp->dccps_role != DCCP_ROLE_LISTEN)
 255                         goto send_sync;
 256                 goto check_seq;
 257         case DCCP_PKT_RESPONSE:
 258                 if (dp->dccps_role != DCCP_ROLE_CLIENT)
 259                         goto send_sync;
 260 check_seq:
 261                 if (!before48(DCCP_SKB_CB(skb)->dccpd_seq, dp->dccps_osr)) {
 262 send_sync:
 263                         dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq,
 264                                        DCCP_PKT_SYNC);
 265                 }
 266                 break;
 267         case DCCP_PKT_SYNC:
 268                 dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq,
 269                                DCCP_PKT_SYNCACK);
 270                 /*
 271                  * From the draft:
 272                  *
 273                  * As with DCCP-Ack packets, DCCP-Sync and DCCP-SyncAck packets
 274                  * MAY have non-zero-length application data areas, whose
 275                  * contents * receivers MUST ignore.
 276                  */
 277                 goto discard;
 278         }
 279
 280         DCCP_INC_STATS_BH(DCCP_MIB_INERRS);
 281 discard:
 282         __kfree_skb(skb);
 283         return 0;
 284 }
 285
 286 static int dccp_rcv_request_sent_state_process(struct sock *sk,
 287                                                struct sk_buff *skb,
 288                                                const struct dccp_hdr *dh,
 289                                                const unsigned len)
 290 {
 291         /*
 292          *  Step 4: Prepare sequence numbers in REQUEST
 293          *     If S.state == REQUEST,
 294          *        If (P.type == Response or P.type == Reset)
 295          *              and S.AWL <= P.ackno <= S.AWH,
 296          *           / * Set sequence number variables corresponding to the
 297          *              other endpoint, so P will pass the tests in Step 6 * /
 298          *           Set S.GSR, S.ISR, S.SWL, S.SWH
 299          *           / * Response processing continues in Step 10; Reset
 300          *              processing continues in Step 9 * /
 301         */
 302         if (dh->dccph_type == DCCP_PKT_RESPONSE) {
 303                 const struct inet_connection_sock *icsk = inet_csk(sk);
 304                 struct dccp_sock *dp = dccp_sk(sk);
 305
 306                 /* Stop the REQUEST timer */
 307                 inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS);
 308                 BUG_TRAP(sk->sk_send_head != NULL);
 309                 __kfree_skb(sk->sk_send_head);
 310                 sk->sk_send_head = NULL;
 311
 312                 if (!between48(DCCP_SKB_CB(skb)->dccpd_ack_seq,
 313                                dp->dccps_awl, dp->dccps_awh)) {
 314                         dccp_pr_debug("invalid ackno: S.AWL=%llu, "
 315                                       "P.ackno=%llu, S.AWH=%llu \n",
 316                                       (unsigned long long)dp->dccps_awl,
 317                            (unsigned long long)DCCP_SKB_CB(skb)->dccpd_ack_seq,
 318                                       (unsigned long long)dp->dccps_awh);
 319                         goto out_invalid_packet;
 320                 }
 321
 322                 dp->dccps_isr = DCCP_SKB_CB(skb)->dccpd_seq;
 323                 dccp_update_gsr(sk, dp->dccps_isr);
 324                 /*
 325                  * SWL and AWL are initially adjusted so that they are not less than
 326                  * the initial Sequence Numbers received and sent, respectively:
 327                  *      SWL := max(GSR + 1 - floor(W/4), ISR),
 328                  *      AWL := max(GSS - W' + 1, ISS).
 329                  * These adjustments MUST be applied only at the beginning of the
 330                  * connection.
 331                  *
 332                  * AWL was adjusted in dccp_v4_connect -acme
 333                  */
 334                 dccp_set_seqno(&dp->dccps_swl,
 335                                max48(dp->dccps_swl, dp->dccps_isr));
 336
 337                 if (ccid_hc_rx_init(dp->dccps_hc_rx_ccid, sk) != 0 ||
 338                     ccid_hc_tx_init(dp->dccps_hc_tx_ccid, sk) != 0) {
 339                         ccid_hc_rx_exit(dp->dccps_hc_rx_ccid, sk);
 340                         ccid_hc_tx_exit(dp->dccps_hc_tx_ccid, sk);
 341                         /* FIXME: send appropriate RESET code */
 342                         goto out_invalid_packet;
 343                 }
 344
 345                 dccp_sync_mss(sk, dp->dccps_pmtu_cookie);
 346
 347                 /*
 348                  *    Step 10: Process REQUEST state (second part)
 349                  *       If S.state == REQUEST,
 350                  *        / * If we get here, P is a valid Response from the
 351                  *            server (see Step 4), and we should move to
 352                  *            PARTOPEN state. PARTOPEN means send an Ack,
 353                  *            don't send Data packets, retransmit Acks
 354                  *            periodically, and always include any Init Cookie
 355                  *            from the Response * /
 356                  *        S.state := PARTOPEN
 357                  *        Set PARTOPEN timer
 358                  *        Continue with S.state == PARTOPEN
 359                  *        / * Step 12 will send the Ack completing the
 360                  *            three-way handshake * /
 361                  */
 362                 dccp_set_state(sk, DCCP_PARTOPEN);
 363
 364                 /* Make sure socket is routed, for correct metrics. */
 365                 inet_sk_rebuild_header(sk);
 366
 367                 if (!sock_flag(sk, SOCK_DEAD)) {
 368                         sk->sk_state_change(sk);
 369                         sk_wake_async(sk, 0, POLL_OUT);
 370                 }
 371
 372                 if (sk->sk_write_pending || icsk->icsk_ack.pingpong ||
 373                     icsk->icsk_accept_queue.rskq_defer_accept) {
 374                         /* Save one ACK. Data will be ready after
 375                          * several ticks, if write_pending is set.
 376                          *
 377                          * It may be deleted, but with this feature tcpdumps
 378                          * look so _wonderfully_ clever, that I was not able
 379                          * to stand against the temptation 8)     --ANK
 380                          */
 381                         /*
 382                          * OK, in DCCP we can as well do a similar trick, its
 383                          * even in the draft, but there is no need for us to
 384                          * schedule an ack here, as dccp_sendmsg does this for
 385                          * us, also stated in the draft. -acme
 386                          */
 387                         __kfree_skb(skb);
 388                         return 0;
 389                 }
 390                 dccp_send_ack(sk);
 391                 return -1;
 392         }
 393
 394 out_invalid_packet:
 395         return 1; /* dccp_v4_do_rcv will send a reset, but...
 396                      FIXME: the reset code should be
 397                             DCCP_RESET_CODE_PACKET_ERROR */
 398 }
 399
 400 static int dccp_rcv_respond_partopen_state_process(struct sock *sk,
 401                                                    struct sk_buff *skb,
 402                                                    const struct dccp_hdr *dh,
 403                                                    const unsigned len)
 404 {
 405         int queued = 0;
 406
 407         switch (dh->dccph_type) {
 408         case DCCP_PKT_RESET:
 409                 inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
 410                 break;
 411         case DCCP_PKT_DATAACK:
 412         case DCCP_PKT_ACK:
 413                 /*
 414                  * FIXME: we should be reseting the PARTOPEN (DELACK) timer
 415                  * here but only if we haven't used the DELACK timer for
 416                  * something else, like sending a delayed ack for a TIMESTAMP
 417                  * echo, etc, for now were not clearing it, sending an extra
 418                  * ACK when there is nothing else to do in DELACK is not a big
 419                  * deal after all.
 420                  */
 421
 422                 /* Stop the PARTOPEN timer */
 423                 if (sk->sk_state == DCCP_PARTOPEN)
 424                         inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
 425
 426                 dccp_sk(sk)->dccps_osr = DCCP_SKB_CB(skb)->dccpd_seq;
 427                 dccp_set_state(sk, DCCP_OPEN);
 428
 429                 if (dh->dccph_type == DCCP_PKT_DATAACK) {
 430                         dccp_rcv_established(sk, skb, dh, len);
 431                         queued = 1; /* packet was queued
 432                                        (by dccp_rcv_established) */
 433                 }
 434                 break;
 435         }
 436
 437         return queued;
 438 }
 439
 440 int dccp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
 441                            struct dccp_hdr *dh, unsigned len)
 442 {
 443         struct dccp_sock *dp = dccp_sk(sk);
 444         const int old_state = sk->sk_state;
 445         int queued = 0;
 446
 447         /*
 448          *  Step 3: Process LISTEN state
 449          *      (Continuing from dccp_v4_do_rcv and dccp_v6_do_rcv)
 450          *
 451          *     If S.state == LISTEN,
 452          *        If P.type == Request or P contains a valid Init Cookie
 453          *              option,
 454          *           * Must scan the packet's options to check for an Init
 455          *              Cookie.  Only the Init Cookie is processed here,
 456          *              however; other options are processed in Step 8.  This
 457          *              scan need only be performed if the endpoint uses Init
 458          *              Cookies *
 459          *           * Generate a new socket and switch to that socket *
 460          *           Set S := new socket for this port pair
 461          *           S.state = RESPOND
 462          *           Choose S.ISS (initial seqno) or set from Init Cookie
 463          *           Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init Cookie
 464          *           Continue with S.state == RESPOND
 465          *           * A Response packet will be generated in Step 11 *
 466          *        Otherwise,
 467          *           Generate Reset(No Connection) unless P.type == Reset
 468          *           Drop packet and return
 469          *
 470          * NOTE: the check for the packet types is done in
 471          *       dccp_rcv_state_process
 472          */
 473         if (sk->sk_state == DCCP_LISTEN) {
 474                 if (dh->dccph_type == DCCP_PKT_REQUEST) {
 475                         if (dccp_v4_conn_request(sk, skb) < 0)
 476                                 return 1;
 477
 478                         /* FIXME: do congestion control initialization */
 479                         goto discard;
 480                 }
 481                 if (dh->dccph_type == DCCP_PKT_RESET)
 482                         goto discard;
 483
 484                 /* Caller (dccp_v4_do_rcv) will send Reset(No Connection)*/
 485                 return 1;
 486         }
 487
 488         if (sk->sk_state != DCCP_REQUESTING) {
 489                 if (dccp_check_seqno(sk, skb))
 490                         goto discard;
 491
 492                 /*
 493                  * Step 8: Process options and mark acknowledgeable
 494                  */
 495                 if (dccp_parse_options(sk, skb))
 496                         goto discard;
 497
 498                 if (DCCP_SKB_CB(skb)->dccpd_ack_seq !=
 499                     DCCP_PKT_WITHOUT_ACK_SEQ)
 500                         dccp_event_ack_recv(sk, skb);
 501
 502                 ccid_hc_rx_packet_recv(dp->dccps_hc_rx_ccid, sk, skb);
 503                 ccid_hc_tx_packet_recv(dp->dccps_hc_tx_ccid, sk, skb);
 504
 505                 /*
 506                  * FIXME: check ECN to see if we should use
 507                  * DCCP_ACKPKTS_STATE_ECN_MARKED
 508                  */
 509                 if (dp->dccps_options.dccpo_send_ack_vector) {
 510                         if (dccp_ackpkts_add(dp->dccps_hc_rx_ackpkts,
 511                                              DCCP_SKB_CB(skb)->dccpd_seq,
 512                                              DCCP_ACKPKTS_STATE_RECEIVED))
 513                                 goto discard;
 514                         /*
 515                          * FIXME: this activation is probably wrong, have to
 516                          * study more TCP delack machinery and how it fits into
 517                          * DCCP draft, but for now it kinda "works" 8)
 518                          */
 519                         if ((dp->dccps_hc_rx_ackpkts->dccpap_ack_seqno ==
 520                              DCCP_MAX_SEQNO + 1) &&
 521                             !inet_csk_ack_scheduled(sk)) {
 522                                 inet_csk_schedule_ack(sk);
 523                                 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
 524                                                           TCP_DELACK_MIN,
 525                                                           DCCP_RTO_MAX);
 526                         }
 527                 }
 528         }
 529
 530         /*
 531          *  Step 9: Process Reset
 532          *      If P.type == Reset,
 533          *              Tear down connection
 534          *              S.state := TIMEWAIT
 535          *              Set TIMEWAIT timer
 536          *              Drop packet and return
 537         */
 538         if (dh->dccph_type == DCCP_PKT_RESET) {
 539                 /*
 540                  * Queue the equivalent of TCP fin so that dccp_recvmsg
 541                  * exits the loop
 542                  */
 543                 dccp_fin(sk, skb);
 544                 dccp_time_wait(sk, DCCP_TIME_WAIT, 0);
 545                 return 0;
 546                 /*
 547                  *   Step 7: Check for unexpected packet types
 548                  *      If (S.is_server and P.type == CloseReq)
 549                  *          or (S.is_server and P.type == Response)
 550                  *          or (S.is_client and P.type == Request)
 551                  *          or (S.state == RESPOND and P.type == Data),
 552                  *        Send Sync packet acknowledging P.seqno
 553                  *        Drop packet and return
 554                  */
 555         } else if ((dp->dccps_role != DCCP_ROLE_CLIENT &&
 556                     (dh->dccph_type == DCCP_PKT_RESPONSE ||
 557                      dh->dccph_type == DCCP_PKT_CLOSEREQ)) ||
 558                     (dp->dccps_role == DCCP_ROLE_CLIENT &&
 559                      dh->dccph_type == DCCP_PKT_REQUEST) ||
 560                     (sk->sk_state == DCCP_RESPOND &&
 561                      dh->dccph_type == DCCP_PKT_DATA)) {
 562                 dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq,
 563                                DCCP_PKT_SYNC);
 564                 goto discard;
 565         }
 566
 567         switch (sk->sk_state) {
 568         case DCCP_CLOSED:
 569                 return 1;
 570
 571         case DCCP_REQUESTING:
 572                 /* FIXME: do congestion control initialization */
 573
 574                 queued = dccp_rcv_request_sent_state_process(sk, skb, dh, len);
 575                 if (queued >= 0)
 576                         return queued;
 577
 578                 __kfree_skb(skb);
 579                 return 0;
 580
 581         case DCCP_RESPOND:
 582         case DCCP_PARTOPEN:
 583                 queued = dccp_rcv_respond_partopen_state_process(sk, skb,
 584                                                                  dh, len);
 585                 break;
 586         }
 587
 588         if (dh->dccph_type == DCCP_PKT_ACK ||
 589             dh->dccph_type == DCCP_PKT_DATAACK) {
 590                 switch (old_state) {
 591                 case DCCP_PARTOPEN:
 592                         sk->sk_state_change(sk);
 593                         sk_wake_async(sk, 0, POLL_OUT);
 594                         break;
 595                 }
 596         }
 597
 598         if (!queued) {
 599 discard:
 600                 __kfree_skb(skb);
 601         }
 602         return 0;
 603 }