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 "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_v4_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 inline void dccp_event_ack_recv(struct sock *sk, struct sk_buff *skb)
  59 {
  60         struct dccp_sock *dp = dccp_sk(sk);
  61
  62         if (dp->dccps_options.dccpo_send_ack_vector)
  63                 dccp_ackpkts_check_rcv_ackno(dp->dccps_hc_rx_ackpkts, 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 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         if (dccp_check_seqno(sk, skb))
 159                 goto discard;
 160
 161         if (dccp_parse_options(sk, skb))
 162                 goto discard;
 163
 164         if (DCCP_SKB_CB(skb)->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
 165                 dccp_event_ack_recv(sk, skb);
 166
 167         /*
 168          * FIXME: check ECN to see if we should use
 169          * DCCP_ACKPKTS_STATE_ECN_MARKED
 170          */
 171         if (dp->dccps_options.dccpo_send_ack_vector) {
 172                 struct dccp_ackpkts *ap = dp->dccps_hc_rx_ackpkts;
 173
 174                 if (dccp_ackpkts_add(dp->dccps_hc_rx_ackpkts, sk,
 175                                      DCCP_SKB_CB(skb)->dccpd_seq,
 176                                      DCCP_ACKPKTS_STATE_RECEIVED)) {
 177                         LIMIT_NETDEBUG(KERN_WARNING "DCCP: acknowledgeable "
 178                                                     "packets buffer full!\n");
 179                         ap->dccpap_ack_seqno = DCCP_MAX_SEQNO + 1;
 180                         inet_csk_schedule_ack(sk);
 181                         inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
 182                                                   TCP_DELACK_MIN,
 183                                                   DCCP_RTO_MAX);
 184                         goto discard;
 185                 }
 186
 187                 /*
 188                  * FIXME: this activation is probably wrong, have to study more
 189                  * TCP delack machinery and how it fits into DCCP draft, but
 190                  * for now it kinda "works" 8)
 191                  */
 192                 if (!inet_csk_ack_scheduled(sk)) {
 193                         inet_csk_schedule_ack(sk);
 194                         inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK, 5 * HZ,
 195                                                   DCCP_RTO_MAX);
 196                 }
 197         }
 198
 199         ccid_hc_rx_packet_recv(dp->dccps_hc_rx_ccid, sk, skb);
 200         ccid_hc_tx_packet_recv(dp->dccps_hc_tx_ccid, sk, skb);
 201
 202         switch (dccp_hdr(skb)->dccph_type) {
 203         case DCCP_PKT_DATAACK:
 204         case DCCP_PKT_DATA:
 205                 /*
 206                  * FIXME: check if sk_receive_queue is full, schedule DATA_DROPPED
 207                  * option if it is.
 208                  */
 209                 __skb_pull(skb, dh->dccph_doff * 4);
 210                 __skb_queue_tail(&sk->sk_receive_queue, skb);
 211                 skb_set_owner_r(skb, sk);
 212                 sk->sk_data_ready(sk, 0);
 213                 return 0;
 214         case DCCP_PKT_ACK:
 215                 goto discard;
 216         case DCCP_PKT_RESET:
 217                 /*
 218                  *  Step 9: Process Reset
 219                  *      If P.type == Reset,
 220                  *              Tear down connection
 221                  *              S.state := TIMEWAIT
 222                  *              Set TIMEWAIT timer
 223                  *              Drop packet and return
 224                 */
 225                 dccp_fin(sk, skb);
 226                 dccp_time_wait(sk, DCCP_TIME_WAIT, 0);
 227                 return 0;
 228         case DCCP_PKT_CLOSEREQ:
 229                 dccp_rcv_closereq(sk, skb);
 230                 goto discard;
 231         case DCCP_PKT_CLOSE:
 232                 dccp_rcv_close(sk, skb);
 233                 return 0;
 234         case DCCP_PKT_REQUEST:
 235                 /* Step 7
 236                  *   or (S.is_server and P.type == Response)
 237                  *   or (S.is_client and P.type == Request)
 238                  *   or (S.state >= OPEN and P.type == Request
 239                  *      and P.seqno >= S.OSR)
 240                  *    or (S.state >= OPEN and P.type == Response
 241                  *      and P.seqno >= S.OSR)
 242                  *    or (S.state == RESPOND and P.type == Data),
 243                  *  Send Sync packet acknowledging P.seqno
 244                  *  Drop packet and return
 245                  */
 246                 if (dp->dccps_role != DCCP_ROLE_LISTEN)
 247                         goto send_sync;
 248                 goto check_seq;
 249         case DCCP_PKT_RESPONSE:
 250                 if (dp->dccps_role != DCCP_ROLE_CLIENT)
 251                         goto send_sync;
 252 check_seq:
 253                 if (!before48(DCCP_SKB_CB(skb)->dccpd_seq, dp->dccps_osr)) {
 254 send_sync:
 255                         dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq,
 256                                        DCCP_PKT_SYNC);
 257                 }
 258                 break;
 259         case DCCP_PKT_SYNC:
 260                 dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq,
 261                                DCCP_PKT_SYNCACK);
 262                 /*
 263                  * From the draft:
 264                  *
 265                  * As with DCCP-Ack packets, DCCP-Sync and DCCP-SyncAck packets
 266                  * MAY have non-zero-length application data areas, whose
 267                  * contents * receivers MUST ignore.
 268                  */
 269                 goto discard;
 270         }
 271
 272         DCCP_INC_STATS_BH(DCCP_MIB_INERRS);
 273 discard:
 274         __kfree_skb(skb);
 275         return 0;
 276 }
 277
 278 static int dccp_rcv_request_sent_state_process(struct sock *sk,
 279                                                struct sk_buff *skb,
 280                                                const struct dccp_hdr *dh,
 281                                                const unsigned len)
 282 {
 283         /*
 284          *  Step 4: Prepare sequence numbers in REQUEST
 285          *     If S.state == REQUEST,
 286          *        If (P.type == Response or P.type == Reset)
 287          *              and S.AWL <= P.ackno <= S.AWH,
 288          *           / * Set sequence number variables corresponding to the
 289          *              other endpoint, so P will pass the tests in Step 6 * /
 290          *           Set S.GSR, S.ISR, S.SWL, S.SWH
 291          *           / * Response processing continues in Step 10; Reset
 292          *              processing continues in Step 9 * /
 293         */
 294         if (dh->dccph_type == DCCP_PKT_RESPONSE) {
 295                 const struct inet_connection_sock *icsk = inet_csk(sk);
 296                 struct dccp_sock *dp = dccp_sk(sk);
 297
 298                 /* Stop the REQUEST timer */
 299                 inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS);
 300                 BUG_TRAP(sk->sk_send_head != NULL);
 301                 __kfree_skb(sk->sk_send_head);
 302                 sk->sk_send_head = NULL;
 303
 304                 if (!between48(DCCP_SKB_CB(skb)->dccpd_ack_seq,
 305                                dp->dccps_awl, dp->dccps_awh)) {
 306                         dccp_pr_debug("invalid ackno: S.AWL=%llu, "
 307                                       "P.ackno=%llu, S.AWH=%llu \n",
 308                                       (unsigned long long)dp->dccps_awl,
 309                            (unsigned long long)DCCP_SKB_CB(skb)->dccpd_ack_seq,
 310                                       (unsigned long long)dp->dccps_awh);
 311                         goto out_invalid_packet;
 312                 }
 313
 314                 dp->dccps_isr = DCCP_SKB_CB(skb)->dccpd_seq;
 315                 dccp_update_gsr(sk, dp->dccps_isr);
 316                 /*
 317                  * SWL and AWL are initially adjusted so that they are not less than
 318                  * the initial Sequence Numbers received and sent, respectively:
 319                  *      SWL := max(GSR + 1 - floor(W/4), ISR),
 320                  *      AWL := max(GSS - W' + 1, ISS).
 321                  * These adjustments MUST be applied only at the beginning of the
 322                  * connection.
 323                  *
 324                  * AWL was adjusted in dccp_v4_connect -acme
 325                  */
 326                 dccp_set_seqno(&dp->dccps_swl,
 327                                max48(dp->dccps_swl, dp->dccps_isr));
 328
 329                 if (ccid_hc_rx_init(dp->dccps_hc_rx_ccid, sk) != 0 ||
 330                     ccid_hc_tx_init(dp->dccps_hc_tx_ccid, sk) != 0) {
 331                         ccid_hc_rx_exit(dp->dccps_hc_rx_ccid, sk);
 332                         ccid_hc_tx_exit(dp->dccps_hc_tx_ccid, sk);
 333                         /* FIXME: send appropriate RESET code */
 334                         goto out_invalid_packet;
 335                 }
 336
 337                 dccp_sync_mss(sk, dp->dccps_pmtu_cookie);
 338
 339                 /*
 340                  *    Step 10: Process REQUEST state (second part)
 341                  *       If S.state == REQUEST,
 342                  *        / * If we get here, P is a valid Response from the
 343                  *            server (see Step 4), and we should move to
 344                  *            PARTOPEN state. PARTOPEN means send an Ack,
 345                  *            don't send Data packets, retransmit Acks
 346                  *            periodically, and always include any Init Cookie
 347                  *            from the Response * /
 348                  *        S.state := PARTOPEN
 349                  *        Set PARTOPEN timer
 350                  *        Continue with S.state == PARTOPEN
 351                  *        / * Step 12 will send the Ack completing the
 352                  *            three-way handshake * /
 353                  */
 354                 dccp_set_state(sk, DCCP_PARTOPEN);
 355
 356                 /* Make sure socket is routed, for correct metrics. */
 357                 inet_sk_rebuild_header(sk);
 358
 359                 if (!sock_flag(sk, SOCK_DEAD)) {
 360                         sk->sk_state_change(sk);
 361                         sk_wake_async(sk, 0, POLL_OUT);
 362                 }
 363
 364                 if (sk->sk_write_pending || icsk->icsk_ack.pingpong ||
 365                     icsk->icsk_accept_queue.rskq_defer_accept) {
 366                         /* Save one ACK. Data will be ready after
 367                          * several ticks, if write_pending is set.
 368                          *
 369                          * It may be deleted, but with this feature tcpdumps
 370                          * look so _wonderfully_ clever, that I was not able
 371                          * to stand against the temptation 8)     --ANK
 372                          */
 373                         /*
 374                          * OK, in DCCP we can as well do a similar trick, its
 375                          * even in the draft, but there is no need for us to
 376                          * schedule an ack here, as dccp_sendmsg does this for
 377                          * us, also stated in the draft. -acme
 378                          */
 379                         __kfree_skb(skb);
 380                         return 0;
 381                 }
 382                 dccp_send_ack(sk);
 383                 return -1;
 384         }
 385
 386 out_invalid_packet:
 387         return 1; /* dccp_v4_do_rcv will send a reset, but...
 388                      FIXME: the reset code should be
 389                             DCCP_RESET_CODE_PACKET_ERROR */
 390 }
 391
 392 static int dccp_rcv_respond_partopen_state_process(struct sock *sk,
 393                                                    struct sk_buff *skb,
 394                                                    const struct dccp_hdr *dh,
 395                                                    const unsigned len)
 396 {
 397         int queued = 0;
 398
 399         switch (dh->dccph_type) {
 400         case DCCP_PKT_RESET:
 401                 inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
 402                 break;
 403         case DCCP_PKT_DATAACK:
 404         case DCCP_PKT_ACK:
 405                 /*
 406                  * FIXME: we should be reseting the PARTOPEN (DELACK) timer
 407                  * here but only if we haven't used the DELACK timer for
 408                  * something else, like sending a delayed ack for a TIMESTAMP
 409                  * echo, etc, for now were not clearing it, sending an extra
 410                  * ACK when there is nothing else to do in DELACK is not a big
 411                  * deal after all.
 412                  */
 413
 414                 /* Stop the PARTOPEN timer */
 415                 if (sk->sk_state == DCCP_PARTOPEN)
 416                         inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
 417
 418                 dccp_sk(sk)->dccps_osr = DCCP_SKB_CB(skb)->dccpd_seq;
 419                 dccp_set_state(sk, DCCP_OPEN);
 420
 421                 if (dh->dccph_type == DCCP_PKT_DATAACK) {
 422                         dccp_rcv_established(sk, skb, dh, len);
 423                         queued = 1; /* packet was queued
 424                                        (by dccp_rcv_established) */
 425                 }
 426                 break;
 427         }
 428
 429         return queued;
 430 }
 431
 432 int dccp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
 433                            struct dccp_hdr *dh, unsigned len)
 434 {
 435         struct dccp_sock *dp = dccp_sk(sk);
 436         const int old_state = sk->sk_state;
 437         int queued = 0;
 438
 439         /*
 440          *  Step 3: Process LISTEN state
 441          *      (Continuing from dccp_v4_do_rcv and dccp_v6_do_rcv)
 442          *
 443          *     If S.state == LISTEN,
 444          *        If P.type == Request or P contains a valid Init Cookie
 445          *              option,
 446          *           * Must scan the packet's options to check for an Init
 447          *              Cookie.  Only the Init Cookie is processed here,
 448          *              however; other options are processed in Step 8.  This
 449          *              scan need only be performed if the endpoint uses Init
 450          *              Cookies *
 451          *           * Generate a new socket and switch to that socket *
 452          *           Set S := new socket for this port pair
 453          *           S.state = RESPOND
 454          *           Choose S.ISS (initial seqno) or set from Init Cookie
 455          *           Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init Cookie
 456          *           Continue with S.state == RESPOND
 457          *           * A Response packet will be generated in Step 11 *
 458          *        Otherwise,
 459          *           Generate Reset(No Connection) unless P.type == Reset
 460          *           Drop packet and return
 461          *
 462          * NOTE: the check for the packet types is done in
 463          *       dccp_rcv_state_process
 464          */
 465         if (sk->sk_state == DCCP_LISTEN) {
 466                 if (dh->dccph_type == DCCP_PKT_REQUEST) {
 467                         if (dccp_v4_conn_request(sk, skb) < 0)
 468                                 return 1;
 469
 470                         /* FIXME: do congestion control initialization */
 471                         goto discard;
 472                 }
 473                 if (dh->dccph_type == DCCP_PKT_RESET)
 474                         goto discard;
 475
 476                 /* Caller (dccp_v4_do_rcv) will send Reset(No Connection)*/
 477                 return 1;
 478         }
 479
 480         if (sk->sk_state != DCCP_REQUESTING) {
 481                 if (dccp_check_seqno(sk, skb))
 482                         goto discard;
 483
 484                 /*
 485                  * Step 8: Process options and mark acknowledgeable
 486                  */
 487                 if (dccp_parse_options(sk, skb))
 488                         goto discard;
 489
 490                 if (DCCP_SKB_CB(skb)->dccpd_ack_seq !=
 491                     DCCP_PKT_WITHOUT_ACK_SEQ)
 492                         dccp_event_ack_recv(sk, skb);
 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                  * FIXME: check ECN to see if we should use
 499                  * DCCP_ACKPKTS_STATE_ECN_MARKED
 500                  */
 501                 if (dp->dccps_options.dccpo_send_ack_vector) {
 502                         if (dccp_ackpkts_add(dp->dccps_hc_rx_ackpkts, sk,
 503                                              DCCP_SKB_CB(skb)->dccpd_seq,
 504                                              DCCP_ACKPKTS_STATE_RECEIVED))
 505                                 goto discard;
 506                         /*
 507                          * FIXME: this activation is probably wrong, have to
 508                          * study more TCP delack machinery and how it fits into
 509                          * DCCP draft, but for now it kinda "works" 8)
 510                          */
 511                         if ((dp->dccps_hc_rx_ackpkts->dccpap_ack_seqno ==
 512                              DCCP_MAX_SEQNO + 1) &&
 513                             !inet_csk_ack_scheduled(sk)) {
 514                                 inet_csk_schedule_ack(sk);
 515                                 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
 516                                                           TCP_DELACK_MIN,
 517                                                           DCCP_RTO_MAX);
 518                         }
 519                 }
 520         }
 521
 522         /*
 523          *  Step 9: Process Reset
 524          *      If P.type == Reset,
 525          *              Tear down connection
 526          *              S.state := TIMEWAIT
 527          *              Set TIMEWAIT timer
 528          *              Drop packet and return
 529         */
 530         if (dh->dccph_type == DCCP_PKT_RESET) {
 531                 /*
 532                  * Queue the equivalent of TCP fin so that dccp_recvmsg
 533                  * exits the loop
 534                  */
 535                 dccp_fin(sk, skb);
 536                 dccp_time_wait(sk, DCCP_TIME_WAIT, 0);
 537                 return 0;
 538                 /*
 539                  *   Step 7: Check for unexpected packet types
 540                  *      If (S.is_server and P.type == CloseReq)
 541                  *          or (S.is_server and P.type == Response)
 542                  *          or (S.is_client and P.type == Request)
 543                  *          or (S.state == RESPOND and P.type == Data),
 544                  *        Send Sync packet acknowledging P.seqno
 545                  *        Drop packet and return
 546                  */
 547         } else if ((dp->dccps_role != DCCP_ROLE_CLIENT &&
 548                     (dh->dccph_type == DCCP_PKT_RESPONSE ||
 549                      dh->dccph_type == DCCP_PKT_CLOSEREQ)) ||
 550                     (dp->dccps_role == DCCP_ROLE_CLIENT &&
 551                      dh->dccph_type == DCCP_PKT_REQUEST) ||
 552                     (sk->sk_state == DCCP_RESPOND &&
 553                      dh->dccph_type == DCCP_PKT_DATA)) {
 554                 dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq,
 555                                DCCP_PKT_SYNC);
 556                 goto discard;
 557         } else if (dh->dccph_type == DCCP_PKT_CLOSEREQ) {
 558                 dccp_rcv_closereq(sk, skb);
 559                 goto discard;
 560         } else if (dh->dccph_type == DCCP_PKT_CLOSE) {
 561                 dccp_rcv_close(sk, skb);
 562                 return 0;
 563         }
 564
 565         if (unlikely(dh->dccph_type == DCCP_PKT_SYNC)) {
 566                 dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq,
 567                                DCCP_PKT_SYNCACK);
 568                 goto discard;
 569         }
 570
 571         switch (sk->sk_state) {
 572         case DCCP_CLOSED:
 573                 return 1;
 574
 575         case DCCP_REQUESTING:
 576                 /* FIXME: do congestion control initialization */
 577
 578                 queued = dccp_rcv_request_sent_state_process(sk, skb, dh, len);
 579                 if (queued >= 0)
 580                         return queued;
 581
 582                 __kfree_skb(skb);
 583                 return 0;
 584
 585         case DCCP_RESPOND:
 586         case DCCP_PARTOPEN:
 587                 queued = dccp_rcv_respond_partopen_state_process(sk, skb,
 588                                                                  dh, len);
 589                 break;
 590         }
 591
 592         if (dh->dccph_type == DCCP_PKT_ACK ||
 593             dh->dccph_type == DCCP_PKT_DATAACK) {
 594                 switch (old_state) {
 595                 case DCCP_PARTOPEN:
 596                         sk->sk_state_change(sk);
 597                         sk_wake_async(sk, 0, POLL_OUT);
 598                         break;
 599                 }
 600         }
 601
 602         if (!queued) {
 603 discard:
 604                 __kfree_skb(skb);
 605         }
 606         return 0;
 607 }