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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 "ackvec.h"
  20 #include "ccid.h"
  21 #include "dccp.h"
  22
  23 static void dccp_fin(struct sock *sk, struct sk_buff *skb)
  24 {
  25         sk->sk_shutdown |= RCV_SHUTDOWN;
  26         sock_set_flag(sk, SOCK_DONE);
  27         __skb_pull(skb, dccp_hdr(skb)->dccph_doff * 4);
  28         __skb_queue_tail(&sk->sk_receive_queue, skb);
  29         skb_set_owner_r(skb, sk);
  30         sk->sk_data_ready(sk, 0);
  31 }
  32
  33 static void dccp_rcv_close(struct sock *sk, struct sk_buff *skb)
  34 {
  35         dccp_v4_send_reset(sk, DCCP_RESET_CODE_CLOSED);
  36         dccp_fin(sk, skb);
  37         dccp_set_state(sk, DCCP_CLOSED);
  38         sk_wake_async(sk, 1, POLL_HUP);
  39 }
  40
  41 static void dccp_rcv_closereq(struct sock *sk, struct sk_buff *skb)
  42 {
  43         /*
  44          *   Step 7: Check for unexpected packet types
  45          *      If (S.is_server and P.type == CloseReq)
  46          *        Send Sync packet acknowledging P.seqno
  47          *        Drop packet and return
  48          */
  49         if (dccp_sk(sk)->dccps_role != DCCP_ROLE_CLIENT) {
  50                 dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq, DCCP_PKT_SYNC);
  51                 return;
  52         }
  53
  54         if (sk->sk_state != DCCP_CLOSING)
  55                 dccp_set_state(sk, DCCP_CLOSING);
  56         dccp_send_close(sk, 0);
  57 }
  58
  59 static inline void dccp_event_ack_recv(struct sock *sk, struct sk_buff *skb)
  60 {
  61         struct dccp_sock *dp = dccp_sk(sk);
  62
  63         if (dp->dccps_options.dccpo_send_ack_vector)
  64                 dccp_ackvec_check_rcv_ackno(dp->dccps_hc_rx_ackvec, sk,
  65                                             DCCP_SKB_CB(skb)->dccpd_ack_seq);
  66 }
  67
  68 static int dccp_check_seqno(struct sock *sk, struct sk_buff *skb)
  69 {
  70         const struct dccp_hdr *dh = dccp_hdr(skb);
  71         struct dccp_sock *dp = dccp_sk(sk);
  72         u64 lswl, lawl;
  73
  74         /*
  75          *   Step 5: Prepare sequence numbers for Sync
  76          *     If P.type == Sync or P.type == SyncAck,
  77          *        If S.AWL <= P.ackno <= S.AWH and P.seqno >= S.SWL,
  78          *           / * P is valid, so update sequence number variables
  79          *               accordingly.  After this update, P will pass the tests
  80          *               in Step 6.  A SyncAck is generated if necessary in
  81          *               Step 15 * /
  82          *           Update S.GSR, S.SWL, S.SWH
  83          *        Otherwise,
  84          *           Drop packet and return
  85          */
  86         if (dh->dccph_type == DCCP_PKT_SYNC ||
  87             dh->dccph_type == DCCP_PKT_SYNCACK) {
  88                 if (between48(DCCP_SKB_CB(skb)->dccpd_ack_seq,
  89                               dp->dccps_awl, dp->dccps_awh) &&
  90                     !before48(DCCP_SKB_CB(skb)->dccpd_seq, dp->dccps_swl))
  91                         dccp_update_gsr(sk, DCCP_SKB_CB(skb)->dccpd_seq);
  92                 else
  93                         return -1;
  94         }
  95
  96         /*
  97          *   Step 6: Check sequence numbers
  98          *      Let LSWL = S.SWL and LAWL = S.AWL
  99          *      If P.type == CloseReq or P.type == Close or P.type == Reset,
 100          *        LSWL := S.GSR + 1, LAWL := S.GAR
 101          *      If LSWL <= P.seqno <= S.SWH
 102          *           and (P.ackno does not exist or LAWL <= P.ackno <= S.AWH),
 103          *        Update S.GSR, S.SWL, S.SWH
 104          *        If P.type != Sync,
 105          *           Update S.GAR
 106          *      Otherwise,
 107          *        Send Sync packet acknowledging P.seqno
 108          *        Drop packet and return
 109          */
 110         lswl = dp->dccps_swl;
 111         lawl = dp->dccps_awl;
 112
 113         if (dh->dccph_type == DCCP_PKT_CLOSEREQ ||
 114             dh->dccph_type == DCCP_PKT_CLOSE ||
 115             dh->dccph_type == DCCP_PKT_RESET) {
 116                 lswl = dp->dccps_gsr;
 117                 dccp_inc_seqno(&lswl);
 118                 lawl = dp->dccps_gar;
 119         }
 120
 121         if (between48(DCCP_SKB_CB(skb)->dccpd_seq, lswl, dp->dccps_swh) &&
 122             (DCCP_SKB_CB(skb)->dccpd_ack_seq == DCCP_PKT_WITHOUT_ACK_SEQ ||
 123              between48(DCCP_SKB_CB(skb)->dccpd_ack_seq,
 124                        lawl, dp->dccps_awh))) {
 125                 dccp_update_gsr(sk, DCCP_SKB_CB(skb)->dccpd_seq);
 126
 127                 if (dh->dccph_type != DCCP_PKT_SYNC &&
 128                     (DCCP_SKB_CB(skb)->dccpd_ack_seq !=
 129                      DCCP_PKT_WITHOUT_ACK_SEQ))
 130                         dp->dccps_gar = DCCP_SKB_CB(skb)->dccpd_ack_seq;
 131         } else {
 132                 LIMIT_NETDEBUG(KERN_WARNING "DCCP: Step 6 failed for %s packet, "
 133                                             "(LSWL(%llu) <= P.seqno(%llu) <= S.SWH(%llu)) and "
 134                                             "(P.ackno %s or LAWL(%llu) <= P.ackno(%llu) <= S.AWH(%llu), "
 135                                             "sending SYNC...\n",
 136                                dccp_packet_name(dh->dccph_type),
 137                                (unsigned long long) lswl,
 138                                (unsigned long long)
 139                                DCCP_SKB_CB(skb)->dccpd_seq,
 140                                (unsigned long long) dp->dccps_swh,
 141                                (DCCP_SKB_CB(skb)->dccpd_ack_seq ==
 142                                 DCCP_PKT_WITHOUT_ACK_SEQ) ? "doesn't exist" : "exists",
 143                                (unsigned long long) lawl,
 144                                (unsigned long long)
 145                                DCCP_SKB_CB(skb)->dccpd_ack_seq,
 146                                (unsigned long long) dp->dccps_awh);
 147                 dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq, DCCP_PKT_SYNC);
 148                 return -1;
 149         }
 150
 151         return 0;
 152 }
 153
 154 static inline int __dccp_rcv_established(struct sock *sk, struct sk_buff *skb,
 155                                          const struct dccp_hdr *dh,
 156                                          const unsigned len)
 157 {
 158         struct dccp_sock *dp = dccp_sk(sk);
 159
 160         switch (dccp_hdr(skb)->dccph_type) {
 161         case DCCP_PKT_DATAACK:
 162         case DCCP_PKT_DATA:
 163                 /*
 164                  * FIXME: check if sk_receive_queue is full, schedule DATA_DROPPED
 165                  * option if it is.
 166                  */
 167                 __skb_pull(skb, dh->dccph_doff * 4);
 168                 __skb_queue_tail(&sk->sk_receive_queue, skb);
 169                 skb_set_owner_r(skb, sk);
 170                 sk->sk_data_ready(sk, 0);
 171                 return 0;
 172         case DCCP_PKT_ACK:
 173                 goto discard;
 174         case DCCP_PKT_RESET:
 175                 /*
 176                  *  Step 9: Process Reset
 177                  *      If P.type == Reset,
 178                  *              Tear down connection
 179                  *              S.state := TIMEWAIT
 180                  *              Set TIMEWAIT timer
 181                  *              Drop packet and return
 182                 */
 183                 dccp_fin(sk, skb);
 184                 dccp_time_wait(sk, DCCP_TIME_WAIT, 0);
 185                 return 0;
 186         case DCCP_PKT_CLOSEREQ:
 187                 dccp_rcv_closereq(sk, skb);
 188                 goto discard;
 189         case DCCP_PKT_CLOSE:
 190                 dccp_rcv_close(sk, skb);
 191                 return 0;
 192         case DCCP_PKT_REQUEST:
 193                 /* Step 7
 194                  *   or (S.is_server and P.type == Response)
 195                  *   or (S.is_client and P.type == Request)
 196                  *   or (S.state >= OPEN and P.type == Request
 197                  *      and P.seqno >= S.OSR)
 198                  *    or (S.state >= OPEN and P.type == Response
 199                  *      and P.seqno >= S.OSR)
 200                  *    or (S.state == RESPOND and P.type == Data),
 201                  *  Send Sync packet acknowledging P.seqno
 202                  *  Drop packet and return
 203                  */
 204                 if (dp->dccps_role != DCCP_ROLE_LISTEN)
 205                         goto send_sync;
 206                 goto check_seq;
 207         case DCCP_PKT_RESPONSE:
 208                 if (dp->dccps_role != DCCP_ROLE_CLIENT)
 209                         goto send_sync;
 210 check_seq:
 211                 if (!before48(DCCP_SKB_CB(skb)->dccpd_seq, dp->dccps_osr)) {
 212 send_sync:
 213                         dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq,
 214                                        DCCP_PKT_SYNC);
 215                 }
 216                 break;
 217         case DCCP_PKT_SYNC:
 218                 dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq,
 219                                DCCP_PKT_SYNCACK);
 220                 /*
 221                  * From the draft:
 222                  *
 223                  * As with DCCP-Ack packets, DCCP-Sync and DCCP-SyncAck packets
 224                  * MAY have non-zero-length application data areas, whose
 225                  * contents * receivers MUST ignore.
 226                  */
 227                 goto discard;
 228         }
 229
 230         DCCP_INC_STATS_BH(DCCP_MIB_INERRS);
 231 discard:
 232         __kfree_skb(skb);
 233         return 0;
 234 }
 235
 236 int dccp_rcv_established(struct sock *sk, struct sk_buff *skb,
 237                          const struct dccp_hdr *dh, const unsigned len)
 238 {
 239         struct dccp_sock *dp = dccp_sk(sk);
 240
 241         if (dccp_check_seqno(sk, skb))
 242                 goto discard;
 243
 244         if (dccp_parse_options(sk, skb))
 245                 goto discard;
 246
 247         if (DCCP_SKB_CB(skb)->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
 248                 dccp_event_ack_recv(sk, skb);
 249
 250         if (dp->dccps_options.dccpo_send_ack_vector &&
 251             dccp_ackvec_add(dp->dccps_hc_rx_ackvec, sk,
 252                             DCCP_SKB_CB(skb)->dccpd_seq,
 253                             DCCP_ACKVEC_STATE_RECEIVED))
 254                 goto discard;
 255
 256         ccid_hc_rx_packet_recv(dp->dccps_hc_rx_ccid, sk, skb);
 257         ccid_hc_tx_packet_recv(dp->dccps_hc_tx_ccid, sk, skb);
 258
 259         return __dccp_rcv_established(sk, skb, dh, len);
 260 discard:
 261         __kfree_skb(skb);
 262         return 0;
 263 }
 264
 265 EXPORT_SYMBOL_GPL(dccp_rcv_established);
 266
 267 static int dccp_rcv_request_sent_state_process(struct sock *sk,
 268                                                struct sk_buff *skb,
 269                                                const struct dccp_hdr *dh,
 270                                                const unsigned len)
 271 {
 272         /*
 273          *  Step 4: Prepare sequence numbers in REQUEST
 274          *     If S.state == REQUEST,
 275          *        If (P.type == Response or P.type == Reset)
 276          *              and S.AWL <= P.ackno <= S.AWH,
 277          *           / * Set sequence number variables corresponding to the
 278          *              other endpoint, so P will pass the tests in Step 6 * /
 279          *           Set S.GSR, S.ISR, S.SWL, S.SWH
 280          *           / * Response processing continues in Step 10; Reset
 281          *              processing continues in Step 9 * /
 282         */
 283         if (dh->dccph_type == DCCP_PKT_RESPONSE) {
 284                 const struct inet_connection_sock *icsk = inet_csk(sk);
 285                 struct dccp_sock *dp = dccp_sk(sk);
 286
 287                 /* Stop the REQUEST timer */
 288                 inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS);
 289                 BUG_TRAP(sk->sk_send_head != NULL);
 290                 __kfree_skb(sk->sk_send_head);
 291                 sk->sk_send_head = NULL;
 292
 293                 if (!between48(DCCP_SKB_CB(skb)->dccpd_ack_seq,
 294                                dp->dccps_awl, dp->dccps_awh)) {
 295                         dccp_pr_debug("invalid ackno: S.AWL=%llu, "
 296                                       "P.ackno=%llu, S.AWH=%llu \n",
 297                                       (unsigned long long)dp->dccps_awl,
 298                            (unsigned long long)DCCP_SKB_CB(skb)->dccpd_ack_seq,
 299                                       (unsigned long long)dp->dccps_awh);
 300                         goto out_invalid_packet;
 301                 }
 302
 303                 if (dp->dccps_options.dccpo_send_ack_vector &&
 304                     dccp_ackvec_add(dp->dccps_hc_rx_ackvec, sk,
 305                                     DCCP_SKB_CB(skb)->dccpd_seq,
 306                                     DCCP_ACKVEC_STATE_RECEIVED))
 307                         goto out_invalid_packet; /* FIXME: change error code */
 308
 309                 dp->dccps_isr = DCCP_SKB_CB(skb)->dccpd_seq;
 310                 dccp_update_gsr(sk, dp->dccps_isr);
 311                 /*
 312                  * SWL and AWL are initially adjusted so that they are not less than
 313                  * the initial Sequence Numbers received and sent, respectively:
 314                  *      SWL := max(GSR + 1 - floor(W/4), ISR),
 315                  *      AWL := max(GSS - W' + 1, ISS).
 316                  * These adjustments MUST be applied only at the beginning of the
 317                  * connection.
 318                  *
 319                  * AWL was adjusted in dccp_v4_connect -acme
 320                  */
 321                 dccp_set_seqno(&dp->dccps_swl,
 322                                max48(dp->dccps_swl, dp->dccps_isr));
 323
 324                 if (ccid_hc_rx_init(dp->dccps_hc_rx_ccid, sk) != 0 ||
 325                     ccid_hc_tx_init(dp->dccps_hc_tx_ccid, sk) != 0) {
 326                         ccid_hc_rx_exit(dp->dccps_hc_rx_ccid, sk);
 327                         ccid_hc_tx_exit(dp->dccps_hc_tx_ccid, sk);
 328                         /* FIXME: send appropriate RESET code */
 329                         goto out_invalid_packet;
 330                 }
 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          *      (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 (inet_csk(sk)->icsk_af_ops->conn_request(sk,
 468                                                                     skb) < 0)
 469                                 return 1;
 470
 471                         /* FIXME: do congestion control initialization */
 472                         goto discard;
 473                 }
 474                 if (dh->dccph_type == DCCP_PKT_RESET)
 475                         goto discard;
 476
 477                 /* Caller (dccp_v4_do_rcv) will send Reset */
 478                 dcb->dccpd_reset_code = DCCP_RESET_CODE_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 (dcb->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
 493                         dccp_event_ack_recv(sk, skb);
 494
 495                 ccid_hc_rx_packet_recv(dp->dccps_hc_rx_ccid, sk, skb);
 496                 ccid_hc_tx_packet_recv(dp->dccps_hc_tx_ccid, sk, skb);
 497
 498                 if (dp->dccps_options.dccpo_send_ack_vector &&
 499                     dccp_ackvec_add(dp->dccps_hc_rx_ackvec, sk,
 500                                     DCCP_SKB_CB(skb)->dccpd_seq,
 501                                     DCCP_ACKVEC_STATE_RECEIVED))
 502                         goto discard;
 503         }
 504
 505         /*
 506          *  Step 9: Process Reset
 507          *      If P.type == Reset,
 508          *              Tear down connection
 509          *              S.state := TIMEWAIT
 510          *              Set TIMEWAIT timer
 511          *              Drop packet and return
 512         */
 513         if (dh->dccph_type == DCCP_PKT_RESET) {
 514                 /*
 515                  * Queue the equivalent of TCP fin so that dccp_recvmsg
 516                  * exits the loop
 517                  */
 518                 dccp_fin(sk, skb);
 519                 dccp_time_wait(sk, DCCP_TIME_WAIT, 0);
 520                 return 0;
 521                 /*
 522                  *   Step 7: Check for unexpected packet types
 523                  *      If (S.is_server and P.type == CloseReq)
 524                  *          or (S.is_server and P.type == Response)
 525                  *          or (S.is_client and P.type == Request)
 526                  *          or (S.state == RESPOND and P.type == Data),
 527                  *        Send Sync packet acknowledging P.seqno
 528                  *        Drop packet and return
 529                  */
 530         } else if ((dp->dccps_role != DCCP_ROLE_CLIENT &&
 531                     (dh->dccph_type == DCCP_PKT_RESPONSE ||
 532                      dh->dccph_type == DCCP_PKT_CLOSEREQ)) ||
 533                     (dp->dccps_role == DCCP_ROLE_CLIENT &&
 534                      dh->dccph_type == DCCP_PKT_REQUEST) ||
 535                     (sk->sk_state == DCCP_RESPOND &&
 536                      dh->dccph_type == DCCP_PKT_DATA)) {
 537                 dccp_send_sync(sk, dcb->dccpd_seq, DCCP_PKT_SYNC);
 538                 goto discard;
 539         } else if (dh->dccph_type == DCCP_PKT_CLOSEREQ) {
 540                 dccp_rcv_closereq(sk, skb);
 541                 goto discard;
 542         } else if (dh->dccph_type == DCCP_PKT_CLOSE) {
 543                 dccp_rcv_close(sk, skb);
 544                 return 0;
 545         }
 546
 547         if (unlikely(dh->dccph_type == DCCP_PKT_SYNC)) {
 548                 dccp_send_sync(sk, dcb->dccpd_seq, DCCP_PKT_SYNCACK);
 549                 goto discard;
 550         }
 551
 552         switch (sk->sk_state) {
 553         case DCCP_CLOSED:
 554                 dcb->dccpd_reset_code = DCCP_RESET_CODE_NO_CONNECTION;
 555                 return 1;
 556
 557         case DCCP_REQUESTING:
 558                 /* FIXME: do congestion control initialization */
 559
 560                 queued = dccp_rcv_request_sent_state_process(sk, skb, dh, len);
 561                 if (queued >= 0)
 562                         return queued;
 563
 564                 __kfree_skb(skb);
 565                 return 0;
 566
 567         case DCCP_RESPOND:
 568         case DCCP_PARTOPEN:
 569                 queued = dccp_rcv_respond_partopen_state_process(sk, skb,
 570                                                                  dh, len);
 571                 break;
 572         }
 573
 574         if (dh->dccph_type == DCCP_PKT_ACK ||
 575             dh->dccph_type == DCCP_PKT_DATAACK) {
 576                 switch (old_state) {
 577                 case DCCP_PARTOPEN:
 578                         sk->sk_state_change(sk);
 579                         sk_wake_async(sk, 0, POLL_OUT);
 580                         break;
 581                 }
 582         }
 583
 584         if (!queued) {
 585 discard:
 586                 __kfree_skb(skb);
 587         }
 588         return 0;
 589 }
 590
 591 EXPORT_SYMBOL_GPL(dccp_rcv_state_process);