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