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   1 /*
   2  *  net/dccp/input.c
   3  *
   4  *  An implementation of the DCCP protocol
   5  *  Arnaldo Carvalho de Melo <acme@conectiva.com.br>
   6  *
   7  *      This program is free software; you can redistribute it and/or
   8  *      modify it under the terms of the GNU General Public License
   9  *      as published by the Free Software Foundation; either version
  10  *      2 of the License, or (at your option) any later version.
  11  */
  12
  13 #include <linux/dccp.h>
  14 #include <linux/skbuff.h>
  15
  16 #include <net/sock.h>
  17
  18 #include "ackvec.h"
  19 #include "ccid.h"
  20 #include "dccp.h"
  21
  22 static void dccp_fin(struct sock *sk, struct sk_buff *skb)
  23 {
  24         sk->sk_shutdown |= RCV_SHUTDOWN;
  25         sock_set_flag(sk, SOCK_DONE);
  26         __skb_pull(skb, dccp_hdr(skb)->dccph_doff * 4);
  27         __skb_queue_tail(&sk->sk_receive_queue, skb);
  28         skb_set_owner_r(skb, sk);
  29         sk->sk_data_ready(sk, 0);
  30 }
  31
  32 static void dccp_rcv_close(struct sock *sk, struct sk_buff *skb)
  33 {
  34         dccp_send_reset(sk, DCCP_RESET_CODE_CLOSED);
  35         dccp_fin(sk, skb);
  36         dccp_set_state(sk, DCCP_CLOSED);
  37         sk_wake_async(sk, 1, POLL_HUP);
  38 }
  39
  40 static void dccp_rcv_closereq(struct sock *sk, struct sk_buff *skb)
  41 {
  42         /*
  43          *   Step 7: Check for unexpected packet types
  44          *      If (S.is_server and P.type == CloseReq)
  45          *        Send Sync packet acknowledging P.seqno
  46          *        Drop packet and return
  47          */
  48         if (dccp_sk(sk)->dccps_role != DCCP_ROLE_CLIENT) {
  49                 dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq, DCCP_PKT_SYNC);
  50                 return;
  51         }
  52
  53         if (sk->sk_state != DCCP_CLOSING)
  54                 dccp_set_state(sk, DCCP_CLOSING);
  55         dccp_send_close(sk, 0);
  56 }
  57
  58 static void dccp_event_ack_recv(struct sock *sk, struct sk_buff *skb)
  59 {
  60         struct dccp_sock *dp = dccp_sk(sk);
  61
  62         if (dccp_msk(sk)->dccpms_send_ack_vector)
  63                 dccp_ackvec_check_rcv_ackno(dp->dccps_hc_rx_ackvec, sk,
  64                                             DCCP_SKB_CB(skb)->dccpd_ack_seq);
  65 }
  66
  67 static int dccp_check_seqno(struct sock *sk, struct sk_buff *skb)
  68 {
  69         const struct dccp_hdr *dh = dccp_hdr(skb);
  70         struct dccp_sock *dp = dccp_sk(sk);
  71         u64 lswl, lawl;
  72
  73         /*
  74          *   Step 5: Prepare sequence numbers for Sync
  75          *     If P.type == Sync or P.type == SyncAck,
  76          *        If S.AWL <= P.ackno <= S.AWH and P.seqno >= S.SWL,
  77          *           / * P is valid, so update sequence number variables
  78          *               accordingly.  After this update, P will pass the tests
  79          *               in Step 6.  A SyncAck is generated if necessary in
  80          *               Step 15 * /
  81          *           Update S.GSR, S.SWL, S.SWH
  82          *        Otherwise,
  83          *           Drop packet and return
  84          */
  85         if (dh->dccph_type == DCCP_PKT_SYNC ||
  86             dh->dccph_type == DCCP_PKT_SYNCACK) {
  87                 if (between48(DCCP_SKB_CB(skb)->dccpd_ack_seq,
  88                               dp->dccps_awl, dp->dccps_awh) &&
  89                     dccp_delta_seqno(dp->dccps_swl,
  90                                      DCCP_SKB_CB(skb)->dccpd_seq) >= 0)
  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                 DCCP_WARN("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",  dccp_packet_name(dh->dccph_type),
 136                           (unsigned long long) lswl,
 137                           (unsigned long long) DCCP_SKB_CB(skb)->dccpd_seq,
 138                           (unsigned long long) dp->dccps_swh,
 139                           (DCCP_SKB_CB(skb)->dccpd_ack_seq ==
 140                                 DCCP_PKT_WITHOUT_ACK_SEQ) ? "doesn't exist" : "exists",
 141                           (unsigned long long) lawl,
 142                           (unsigned long long) DCCP_SKB_CB(skb)->dccpd_ack_seq,
 143                           (unsigned long long) dp->dccps_awh);
 144                 dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq, DCCP_PKT_SYNC);
 145                 return -1;
 146         }
 147
 148         return 0;
 149 }
 150
 151 static int __dccp_rcv_established(struct sock *sk, struct sk_buff *skb,
 152                                   const struct dccp_hdr *dh, const unsigned len)
 153 {
 154         struct dccp_sock *dp = dccp_sk(sk);
 155
 156         switch (dccp_hdr(skb)->dccph_type) {
 157         case DCCP_PKT_DATAACK:
 158         case DCCP_PKT_DATA:
 159                 /*
 160                  * FIXME: check if sk_receive_queue is full, schedule DATA_DROPPED
 161                  * option if it is.
 162                  */
 163                 __skb_pull(skb, dh->dccph_doff * 4);
 164                 __skb_queue_tail(&sk->sk_receive_queue, skb);
 165                 skb_set_owner_r(skb, sk);
 166                 sk->sk_data_ready(sk, 0);
 167                 return 0;
 168         case DCCP_PKT_ACK:
 169                 goto discard;
 170         case DCCP_PKT_RESET:
 171                 /*
 172                  *  Step 9: Process Reset
 173                  *      If P.type == Reset,
 174                  *              Tear down connection
 175                  *              S.state := TIMEWAIT
 176                  *              Set TIMEWAIT timer
 177                  *              Drop packet and return
 178                 */
 179                 dccp_fin(sk, skb);
 180                 dccp_time_wait(sk, DCCP_TIME_WAIT, 0);
 181                 return 0;
 182         case DCCP_PKT_CLOSEREQ:
 183                 dccp_rcv_closereq(sk, skb);
 184                 goto discard;
 185         case DCCP_PKT_CLOSE:
 186                 dccp_rcv_close(sk, skb);
 187                 return 0;
 188         case DCCP_PKT_REQUEST:
 189                 /* Step 7
 190                  *   or (S.is_server and P.type == Response)
 191                  *   or (S.is_client and P.type == Request)
 192                  *   or (S.state >= OPEN and P.type == Request
 193                  *      and P.seqno >= S.OSR)
 194                  *    or (S.state >= OPEN and P.type == Response
 195                  *      and P.seqno >= S.OSR)
 196                  *    or (S.state == RESPOND and P.type == Data),
 197                  *  Send Sync packet acknowledging P.seqno
 198                  *  Drop packet and return
 199                  */
 200                 if (dp->dccps_role != DCCP_ROLE_LISTEN)
 201                         goto send_sync;
 202                 goto check_seq;
 203         case DCCP_PKT_RESPONSE:
 204                 if (dp->dccps_role != DCCP_ROLE_CLIENT)
 205                         goto send_sync;
 206 check_seq:
 207                 if (dccp_delta_seqno(dp->dccps_osr,
 208                                      DCCP_SKB_CB(skb)->dccpd_seq) >= 0) {
 209 send_sync:
 210                         dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq,
 211                                        DCCP_PKT_SYNC);
 212                 }
 213                 break;
 214         case DCCP_PKT_SYNC:
 215                 dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq,
 216                                DCCP_PKT_SYNCACK);
 217                 /*
 218                  * From RFC 4340, sec. 5.7
 219                  *
 220                  * As with DCCP-Ack packets, DCCP-Sync and DCCP-SyncAck packets
 221                  * MAY have non-zero-length application data areas, whose
 222                  * contents receivers MUST ignore.
 223                  */
 224                 goto discard;
 225         }
 226
 227         DCCP_INC_STATS_BH(DCCP_MIB_INERRS);
 228 discard:
 229         __kfree_skb(skb);
 230         return 0;
 231 }
 232
 233 int dccp_rcv_established(struct sock *sk, struct sk_buff *skb,
 234                          const struct dccp_hdr *dh, const unsigned len)
 235 {
 236         struct dccp_sock *dp = dccp_sk(sk);
 237
 238         if (dccp_check_seqno(sk, skb))
 239                 goto discard;
 240
 241         if (dccp_parse_options(sk, skb))
 242                 goto discard;
 243
 244         if (DCCP_SKB_CB(skb)->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
 245                 dccp_event_ack_recv(sk, skb);
 246
 247         if (dccp_msk(sk)->dccpms_send_ack_vector &&
 248             dccp_ackvec_add(dp->dccps_hc_rx_ackvec, sk,
 249                             DCCP_SKB_CB(skb)->dccpd_seq,
 250                             DCCP_ACKVEC_STATE_RECEIVED))
 251                 goto discard;
 252
 253         ccid_hc_rx_packet_recv(dp->dccps_hc_rx_ccid, sk, skb);
 254         ccid_hc_tx_packet_recv(dp->dccps_hc_tx_ccid, sk, skb);
 255
 256         return __dccp_rcv_established(sk, skb, dh, len);
 257 discard:
 258         __kfree_skb(skb);
 259         return 0;
 260 }
 261
 262 EXPORT_SYMBOL_GPL(dccp_rcv_established);
 263
 264 static int dccp_rcv_request_sent_state_process(struct sock *sk,
 265                                                struct sk_buff *skb,
 266                                                const struct dccp_hdr *dh,
 267                                                const unsigned len)
 268 {
 269         /*
 270          *  Step 4: Prepare sequence numbers in REQUEST
 271          *     If S.state == REQUEST,
 272          *        If (P.type == Response or P.type == Reset)
 273          *              and S.AWL <= P.ackno <= S.AWH,
 274          *           / * Set sequence number variables corresponding to the
 275          *              other endpoint, so P will pass the tests in Step 6 * /
 276          *           Set S.GSR, S.ISR, S.SWL, S.SWH
 277          *           / * Response processing continues in Step 10; Reset
 278          *              processing continues in Step 9 * /
 279         */
 280         if (dh->dccph_type == DCCP_PKT_RESPONSE) {
 281                 const struct inet_connection_sock *icsk = inet_csk(sk);
 282                 struct dccp_sock *dp = dccp_sk(sk);
 283                 long tstamp = dccp_timestamp();
 284
 285                 /* Stop the REQUEST timer */
 286                 inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS);
 287                 BUG_TRAP(sk->sk_send_head != NULL);
 288                 __kfree_skb(sk->sk_send_head);
 289                 sk->sk_send_head = NULL;
 290
 291                 if (!between48(DCCP_SKB_CB(skb)->dccpd_ack_seq,
 292                                dp->dccps_awl, dp->dccps_awh)) {
 293                         dccp_pr_debug("invalid ackno: S.AWL=%llu, "
 294                                       "P.ackno=%llu, S.AWH=%llu \n",
 295                                       (unsigned long long)dp->dccps_awl,
 296                            (unsigned long long)DCCP_SKB_CB(skb)->dccpd_ack_seq,
 297                                       (unsigned long long)dp->dccps_awh);
 298                         goto out_invalid_packet;
 299                 }
 300
 301                 if (dccp_parse_options(sk, skb))
 302                         goto out_invalid_packet;
 303
 304                 /* Obtain usec RTT sample from SYN exchange (used by CCID 3) */
 305                 if (likely(dp->dccps_options_received.dccpor_timestamp_echo))
 306                         dp->dccps_syn_rtt = dccp_sample_rtt(sk, 10 * (tstamp -
 307                             dp->dccps_options_received.dccpor_timestamp_echo));
 308
 309                 if (dccp_msk(sk)->dccpms_send_ack_vector &&
 310                     dccp_ackvec_add(dp->dccps_hc_rx_ackvec, sk,
 311                                     DCCP_SKB_CB(skb)->dccpd_seq,
 312                                     DCCP_ACKVEC_STATE_RECEIVED))
 313                         goto out_invalid_packet; /* FIXME: change error code */
 314
 315                 dp->dccps_isr = DCCP_SKB_CB(skb)->dccpd_seq;
 316                 dccp_update_gsr(sk, dp->dccps_isr);
 317                 /*
 318                  * SWL and AWL are initially adjusted so that they are not less than
 319                  * the initial Sequence Numbers received and sent, respectively:
 320                  *      SWL := max(GSR + 1 - floor(W/4), ISR),
 321                  *      AWL := max(GSS - W' + 1, ISS).
 322                  * These adjustments MUST be applied only at the beginning of the
 323                  * connection.
 324                  *
 325                  * AWL was adjusted in dccp_v4_connect -acme
 326                  */
 327                 dccp_set_seqno(&dp->dccps_swl,
 328                                max48(dp->dccps_swl, dp->dccps_isr));
 329
 330                 dccp_sync_mss(sk, icsk->icsk_pmtu_cookie);
 331
 332                 /*
 333                  *    Step 10: Process REQUEST state (second part)
 334                  *       If S.state == REQUEST,
 335                  *        / * If we get here, P is a valid Response from the
 336                  *            server (see Step 4), and we should move to
 337                  *            PARTOPEN state. PARTOPEN means send an Ack,
 338                  *            don't send Data packets, retransmit Acks
 339                  *            periodically, and always include any Init Cookie
 340                  *            from the Response * /
 341                  *        S.state := PARTOPEN
 342                  *        Set PARTOPEN timer
 343                  *        Continue with S.state == PARTOPEN
 344                  *        / * Step 12 will send the Ack completing the
 345                  *            three-way handshake * /
 346                  */
 347                 dccp_set_state(sk, DCCP_PARTOPEN);
 348
 349                 /* Make sure socket is routed, for correct metrics. */
 350                 icsk->icsk_af_ops->rebuild_header(sk);
 351
 352                 if (!sock_flag(sk, SOCK_DEAD)) {
 353                         sk->sk_state_change(sk);
 354                         sk_wake_async(sk, 0, POLL_OUT);
 355                 }
 356
 357                 if (sk->sk_write_pending || icsk->icsk_ack.pingpong ||
 358                     icsk->icsk_accept_queue.rskq_defer_accept) {
 359                         /* Save one ACK. Data will be ready after
 360                          * several ticks, if write_pending is set.
 361                          *
 362                          * It may be deleted, but with this feature tcpdumps
 363                          * look so _wonderfully_ clever, that I was not able
 364                          * to stand against the temptation 8)     --ANK
 365                          */
 366                         /*
 367                          * OK, in DCCP we can as well do a similar trick, its
 368                          * even in the draft, but there is no need for us to
 369                          * schedule an ack here, as dccp_sendmsg does this for
 370                          * us, also stated in the draft. -acme
 371                          */
 372                         __kfree_skb(skb);
 373                         return 0;
 374                 }
 375                 dccp_send_ack(sk);
 376                 return -1;
 377         }
 378
 379 out_invalid_packet:
 380         /* dccp_v4_do_rcv will send a reset */
 381         DCCP_SKB_CB(skb)->dccpd_reset_code = DCCP_RESET_CODE_PACKET_ERROR;
 382         return 1;
 383 }
 384
 385 static int dccp_rcv_respond_partopen_state_process(struct sock *sk,
 386                                                    struct sk_buff *skb,
 387                                                    const struct dccp_hdr *dh,
 388                                                    const unsigned len)
 389 {
 390         int queued = 0;
 391
 392         switch (dh->dccph_type) {
 393         case DCCP_PKT_RESET:
 394                 inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
 395                 break;
 396         case DCCP_PKT_DATA:
 397                 if (sk->sk_state == DCCP_RESPOND)
 398                         break;
 399         case DCCP_PKT_DATAACK:
 400         case DCCP_PKT_ACK:
 401                 /*
 402                  * FIXME: we should be reseting the PARTOPEN (DELACK) timer
 403                  * here but only if we haven't used the DELACK timer for
 404                  * something else, like sending a delayed ack for a TIMESTAMP
 405                  * echo, etc, for now were not clearing it, sending an extra
 406                  * ACK when there is nothing else to do in DELACK is not a big
 407                  * deal after all.
 408                  */
 409
 410                 /* Stop the PARTOPEN timer */
 411                 if (sk->sk_state == DCCP_PARTOPEN)
 412                         inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
 413
 414                 dccp_sk(sk)->dccps_osr = DCCP_SKB_CB(skb)->dccpd_seq;
 415                 dccp_set_state(sk, DCCP_OPEN);
 416
 417                 if (dh->dccph_type == DCCP_PKT_DATAACK ||
 418                     dh->dccph_type == DCCP_PKT_DATA) {
 419                         __dccp_rcv_established(sk, skb, dh, len);
 420                         queued = 1; /* packet was queued
 421                                        (by __dccp_rcv_established) */
 422                 }
 423                 break;
 424         }
 425
 426         return queued;
 427 }
 428
 429 int dccp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
 430                            struct dccp_hdr *dh, unsigned len)
 431 {
 432         struct dccp_sock *dp = dccp_sk(sk);
 433         struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
 434         const int old_state = sk->sk_state;
 435         int queued = 0;
 436
 437         /*
 438          *  Step 3: Process LISTEN state
 439          *
 440          *     If S.state == LISTEN,
 441          *       If P.type == Request or P contains a valid Init Cookie option,
 442          *            (* Must scan the packet's options to check for Init
 443          *               Cookies.  Only Init Cookies are processed here,
 444          *               however; other options are processed in Step 8.  This
 445          *               scan need only be performed if the endpoint uses Init
 446          *               Cookies *)
 447          *            (* Generate a new socket and switch to that socket *)
 448          *            Set S := new socket for this port pair
 449          *            S.state = RESPOND
 450          *            Choose S.ISS (initial seqno) or set from Init Cookies
 451          *            Initialize S.GAR := S.ISS
 452          *            Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init
 453          *            Cookies Continue with S.state == RESPOND
 454          *            (* A Response packet will be generated in Step 11 *)
 455          *       Otherwise,
 456          *            Generate Reset(No Connection) unless P.type == Reset
 457          *            Drop packet and return
 458          */
 459         if (sk->sk_state == DCCP_LISTEN) {
 460                 if (dh->dccph_type == DCCP_PKT_REQUEST) {
 461                         if (inet_csk(sk)->icsk_af_ops->conn_request(sk,
 462                                                                     skb) < 0)
 463                                 return 1;
 464
 465                         /* FIXME: do congestion control initialization */
 466                         goto discard;
 467                 }
 468                 if (dh->dccph_type == DCCP_PKT_RESET)
 469                         goto discard;
 470
 471                 /* Caller (dccp_v4_do_rcv) will send Reset */
 472                 dcb->dccpd_reset_code = DCCP_RESET_CODE_NO_CONNECTION;
 473                 return 1;
 474         }
 475
 476         if (sk->sk_state != DCCP_REQUESTING) {
 477                 if (dccp_check_seqno(sk, skb))
 478                         goto discard;
 479
 480                 /*
 481                  * Step 8: Process options and mark acknowledgeable
 482                  */
 483                 if (dccp_parse_options(sk, skb))
 484                         goto discard;
 485
 486                 if (dcb->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
 487                         dccp_event_ack_recv(sk, skb);
 488
 489                 if (dccp_msk(sk)->dccpms_send_ack_vector &&
 490                     dccp_ackvec_add(dp->dccps_hc_rx_ackvec, sk,
 491                                     DCCP_SKB_CB(skb)->dccpd_seq,
 492                                     DCCP_ACKVEC_STATE_RECEIVED))
 493                         goto discard;
 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
 499         /*
 500          *  Step 9: Process Reset
 501          *      If P.type == Reset,
 502          *              Tear down connection
 503          *              S.state := TIMEWAIT
 504          *              Set TIMEWAIT timer
 505          *              Drop packet and return
 506         */
 507         if (dh->dccph_type == DCCP_PKT_RESET) {
 508                 /*
 509                  * Queue the equivalent of TCP fin so that dccp_recvmsg
 510                  * exits the loop
 511                  */
 512                 dccp_fin(sk, skb);
 513                 dccp_time_wait(sk, DCCP_TIME_WAIT, 0);
 514                 return 0;
 515                 /*
 516                  *   Step 7: Check for unexpected packet types
 517                  *      If (S.is_server and P.type == CloseReq)
 518                  *          or (S.is_server and P.type == Response)
 519                  *          or (S.is_client and P.type == Request)
 520                  *          or (S.state == RESPOND and P.type == Data),
 521                  *        Send Sync packet acknowledging P.seqno
 522                  *        Drop packet and return
 523                  */
 524         } else if ((dp->dccps_role != DCCP_ROLE_CLIENT &&
 525                     (dh->dccph_type == DCCP_PKT_RESPONSE ||
 526                      dh->dccph_type == DCCP_PKT_CLOSEREQ)) ||
 527                     (dp->dccps_role == DCCP_ROLE_CLIENT &&
 528                      dh->dccph_type == DCCP_PKT_REQUEST) ||
 529                     (sk->sk_state == DCCP_RESPOND &&
 530                      dh->dccph_type == DCCP_PKT_DATA)) {
 531                 dccp_send_sync(sk, dcb->dccpd_seq, DCCP_PKT_SYNC);
 532                 goto discard;
 533         } else if (dh->dccph_type == DCCP_PKT_CLOSEREQ) {
 534                 dccp_rcv_closereq(sk, skb);
 535                 goto discard;
 536         } else if (dh->dccph_type == DCCP_PKT_CLOSE) {
 537                 dccp_rcv_close(sk, skb);
 538                 return 0;
 539         }
 540
 541         if (unlikely(dh->dccph_type == DCCP_PKT_SYNC)) {
 542                 dccp_send_sync(sk, dcb->dccpd_seq, DCCP_PKT_SYNCACK);
 543                 goto discard;
 544         }
 545
 546         switch (sk->sk_state) {
 547         case DCCP_CLOSED:
 548                 dcb->dccpd_reset_code = DCCP_RESET_CODE_NO_CONNECTION;
 549                 return 1;
 550
 551         case DCCP_REQUESTING:
 552                 /* FIXME: do congestion control initialization */
 553
 554                 queued = dccp_rcv_request_sent_state_process(sk, skb, dh, len);
 555                 if (queued >= 0)
 556                         return queued;
 557
 558                 __kfree_skb(skb);
 559                 return 0;
 560
 561         case DCCP_RESPOND:
 562         case DCCP_PARTOPEN:
 563                 queued = dccp_rcv_respond_partopen_state_process(sk, skb,
 564                                                                  dh, len);
 565                 break;
 566         }
 567
 568         if (dh->dccph_type == DCCP_PKT_ACK ||
 569             dh->dccph_type == DCCP_PKT_DATAACK) {
 570                 switch (old_state) {
 571                 case DCCP_PARTOPEN:
 572                         sk->sk_state_change(sk);
 573                         sk_wake_async(sk, 0, POLL_OUT);
 574                         break;
 575                 }
 576         }
 577
 578         if (!queued) {
 579 discard:
 580                 __kfree_skb(skb);
 581         }
 582         return 0;
 583 }
 584
 585 EXPORT_SYMBOL_GPL(dccp_rcv_state_process);
 586
 587 /**
 588  *  dccp_sample_rtt  -  Validate and finalise computation of RTT sample
 589  *  @delta:     number of microseconds between packet and acknowledgment
 590  *  The routine is kept generic to work in different contexts. It should be
 591  *  called immediately when the ACK used for the RTT sample arrives.
 592  */
 593 u32 dccp_sample_rtt(struct sock *sk, long delta)
 594 {
 595         /* dccpor_elapsed_time is either zeroed out or set and > 0 */
 596         delta -= dccp_sk(sk)->dccps_options_received.dccpor_elapsed_time * 10;
 597
 598         if (unlikely(delta <= 0)) {
 599                 DCCP_WARN("unusable RTT sample %ld, using min\n", delta);
 600                 return DCCP_SANE_RTT_MIN;
 601         }
 602         if (unlikely(delta > DCCP_SANE_RTT_MAX)) {
 603                 DCCP_WARN("RTT sample %ld too large, using max\n", delta);
 604                 return DCCP_SANE_RTT_MAX;
 605         }
 606
 607         return delta;
 608 }
 609
 610 EXPORT_SYMBOL_GPL(dccp_sample_rtt);