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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 /* rate-limit for syncs in reply to sequence-invalid packets; RFC 4340, 7.5.4 */
  23 int sysctl_dccp_sync_ratelimit  __read_mostly = HZ / 8;
  24
  25 static void dccp_fin(struct sock *sk, struct sk_buff *skb)
  26 {
  27         sk->sk_shutdown |= RCV_SHUTDOWN;
  28         sock_set_flag(sk, SOCK_DONE);
  29         __skb_pull(skb, dccp_hdr(skb)->dccph_doff * 4);
  30         __skb_queue_tail(&sk->sk_receive_queue, skb);
  31         skb_set_owner_r(skb, sk);
  32         sk->sk_data_ready(sk, 0);
  33 }
  34
  35 static void dccp_rcv_close(struct sock *sk, struct sk_buff *skb)
  36 {
  37         dccp_send_reset(sk, DCCP_RESET_CODE_CLOSED);
  38         dccp_fin(sk, skb);
  39         dccp_set_state(sk, DCCP_CLOSED);
  40         sk_wake_async(sk, 1, POLL_HUP);
  41 }
  42
  43 static void dccp_rcv_closereq(struct sock *sk, struct sk_buff *skb)
  44 {
  45         /*
  46          *   Step 7: Check for unexpected packet types
  47          *      If (S.is_server and P.type == CloseReq)
  48          *        Send Sync packet acknowledging P.seqno
  49          *        Drop packet and return
  50          */
  51         if (dccp_sk(sk)->dccps_role != DCCP_ROLE_CLIENT) {
  52                 dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq, DCCP_PKT_SYNC);
  53                 return;
  54         }
  55
  56         if (sk->sk_state != DCCP_CLOSING)
  57                 dccp_set_state(sk, DCCP_CLOSING);
  58         dccp_send_close(sk, 0);
  59 }
  60
  61 static u8 dccp_reset_code_convert(const u8 code)
  62 {
  63         const u8 error_code[] = {
  64         [DCCP_RESET_CODE_CLOSED]             = 0,       /* normal termination */
  65         [DCCP_RESET_CODE_UNSPECIFIED]        = 0,       /* nothing known */
  66         [DCCP_RESET_CODE_ABORTED]            = ECONNRESET,
  67
  68         [DCCP_RESET_CODE_NO_CONNECTION]      = ECONNREFUSED,
  69         [DCCP_RESET_CODE_CONNECTION_REFUSED] = ECONNREFUSED,
  70         [DCCP_RESET_CODE_TOO_BUSY]           = EUSERS,
  71         [DCCP_RESET_CODE_AGGRESSION_PENALTY] = EDQUOT,
  72
  73         [DCCP_RESET_CODE_PACKET_ERROR]       = ENOMSG,
  74         [DCCP_RESET_CODE_BAD_INIT_COOKIE]    = EBADR,
  75         [DCCP_RESET_CODE_BAD_SERVICE_CODE]   = EBADRQC,
  76         [DCCP_RESET_CODE_OPTION_ERROR]       = EILSEQ,
  77         [DCCP_RESET_CODE_MANDATORY_ERROR]    = EOPNOTSUPP,
  78         };
  79
  80         return code >= DCCP_MAX_RESET_CODES ? 0 : error_code[code];
  81 }
  82
  83 static void dccp_rcv_reset(struct sock *sk, struct sk_buff *skb)
  84 {
  85         u8 err = dccp_reset_code_convert(dccp_hdr_reset(skb)->dccph_reset_code);
  86
  87         sk->sk_err = err;
  88
  89         /* Queue the equivalent of TCP fin so that dccp_recvmsg exits the loop */
  90         dccp_fin(sk, skb);
  91
  92         if (err && !sock_flag(sk, SOCK_DEAD))
  93                 sk_wake_async(sk, 0, POLL_ERR);
  94         dccp_time_wait(sk, DCCP_TIME_WAIT, 0);
  95 }
  96
  97 static void dccp_event_ack_recv(struct sock *sk, struct sk_buff *skb)
  98 {
  99         struct dccp_sock *dp = dccp_sk(sk);
 100
 101         if (dccp_msk(sk)->dccpms_send_ack_vector)
 102                 dccp_ackvec_check_rcv_ackno(dp->dccps_hc_rx_ackvec, sk,
 103                                             DCCP_SKB_CB(skb)->dccpd_ack_seq);
 104 }
 105
 106 static int dccp_check_seqno(struct sock *sk, struct sk_buff *skb)
 107 {
 108         const struct dccp_hdr *dh = dccp_hdr(skb);
 109         struct dccp_sock *dp = dccp_sk(sk);
 110         u64 lswl, lawl, seqno = DCCP_SKB_CB(skb)->dccpd_seq,
 111                         ackno = DCCP_SKB_CB(skb)->dccpd_ack_seq;
 112
 113         /*
 114          *   Step 5: Prepare sequence numbers for Sync
 115          *     If P.type == Sync or P.type == SyncAck,
 116          *        If S.AWL <= P.ackno <= S.AWH and P.seqno >= S.SWL,
 117          *           / * P is valid, so update sequence number variables
 118          *               accordingly.  After this update, P will pass the tests
 119          *               in Step 6.  A SyncAck is generated if necessary in
 120          *               Step 15 * /
 121          *           Update S.GSR, S.SWL, S.SWH
 122          *        Otherwise,
 123          *           Drop packet and return
 124          */
 125         if (dh->dccph_type == DCCP_PKT_SYNC ||
 126             dh->dccph_type == DCCP_PKT_SYNCACK) {
 127                 if (between48(ackno, dp->dccps_awl, dp->dccps_awh) &&
 128                     dccp_delta_seqno(dp->dccps_swl, seqno) >= 0)
 129                         dccp_update_gsr(sk, seqno);
 130                 else
 131                         return -1;
 132         }
 133
 134         /*
 135          *   Step 6: Check sequence numbers
 136          *      Let LSWL = S.SWL and LAWL = S.AWL
 137          *      If P.type == CloseReq or P.type == Close or P.type == Reset,
 138          *        LSWL := S.GSR + 1, LAWL := S.GAR
 139          *      If LSWL <= P.seqno <= S.SWH
 140          *           and (P.ackno does not exist or LAWL <= P.ackno <= S.AWH),
 141          *        Update S.GSR, S.SWL, S.SWH
 142          *        If P.type != Sync,
 143          *           Update S.GAR
 144          */
 145         lswl = dp->dccps_swl;
 146         lawl = dp->dccps_awl;
 147
 148         if (dh->dccph_type == DCCP_PKT_CLOSEREQ ||
 149             dh->dccph_type == DCCP_PKT_CLOSE ||
 150             dh->dccph_type == DCCP_PKT_RESET) {
 151                 lswl = ADD48(dp->dccps_gsr, 1);
 152                 lawl = dp->dccps_gar;
 153         }
 154
 155         if (between48(seqno, lswl, dp->dccps_swh) &&
 156             (ackno == DCCP_PKT_WITHOUT_ACK_SEQ ||
 157              between48(ackno, lawl, dp->dccps_awh))) {
 158                 dccp_update_gsr(sk, seqno);
 159
 160                 if (dh->dccph_type != DCCP_PKT_SYNC &&
 161                     (ackno != DCCP_PKT_WITHOUT_ACK_SEQ))
 162                         dp->dccps_gar = ackno;
 163         } else {
 164                 unsigned long now = jiffies;
 165                 /*
 166                  *   Step 6: Check sequence numbers
 167                  *      Otherwise,
 168                  *         If P.type == Reset,
 169                  *            Send Sync packet acknowledging S.GSR
 170                  *         Otherwise,
 171                  *            Send Sync packet acknowledging P.seqno
 172                  *      Drop packet and return
 173                  *
 174                  *   These Syncs are rate-limited as per RFC 4340, 7.5.4:
 175                  *   at most 1 / (dccp_sync_rate_limit * HZ) Syncs per second.
 176                  */
 177                 if (time_before(now, (dp->dccps_rate_last +
 178                                       sysctl_dccp_sync_ratelimit)))
 179                         return 0;
 180
 181                 DCCP_WARN("DCCP: Step 6 failed for %s packet, "
 182                           "(LSWL(%llu) <= P.seqno(%llu) <= S.SWH(%llu)) and "
 183                           "(P.ackno %s or LAWL(%llu) <= P.ackno(%llu) <= S.AWH(%llu), "
 184                           "sending SYNC...\n",  dccp_packet_name(dh->dccph_type),
 185                           (unsigned long long) lswl, (unsigned long long) seqno,
 186                           (unsigned long long) dp->dccps_swh,
 187                           (ackno == DCCP_PKT_WITHOUT_ACK_SEQ) ? "doesn't exist"
 188                                                               : "exists",
 189                           (unsigned long long) lawl, (unsigned long long) ackno,
 190                           (unsigned long long) dp->dccps_awh);
 191
 192                 dp->dccps_rate_last = now;
 193
 194                 if (dh->dccph_type == DCCP_PKT_RESET)
 195                         seqno = dp->dccps_gsr;
 196                 dccp_send_sync(sk, seqno, DCCP_PKT_SYNC);
 197                 return -1;
 198         }
 199
 200         return 0;
 201 }
 202
 203 static int __dccp_rcv_established(struct sock *sk, struct sk_buff *skb,
 204                                   const struct dccp_hdr *dh, const unsigned len)
 205 {
 206         struct dccp_sock *dp = dccp_sk(sk);
 207
 208         switch (dccp_hdr(skb)->dccph_type) {
 209         case DCCP_PKT_DATAACK:
 210         case DCCP_PKT_DATA:
 211                 /*
 212                  * FIXME: check if sk_receive_queue is full, schedule DATA_DROPPED
 213                  * option if it is.
 214                  */
 215                 __skb_pull(skb, dh->dccph_doff * 4);
 216                 __skb_queue_tail(&sk->sk_receive_queue, skb);
 217                 skb_set_owner_r(skb, sk);
 218                 sk->sk_data_ready(sk, 0);
 219                 return 0;
 220         case DCCP_PKT_ACK:
 221                 goto discard;
 222         case DCCP_PKT_RESET:
 223                 /*
 224                  *  Step 9: Process Reset
 225                  *      If P.type == Reset,
 226                  *              Tear down connection
 227                  *              S.state := TIMEWAIT
 228                  *              Set TIMEWAIT timer
 229                  *              Drop packet and return
 230                  */
 231                 dccp_rcv_reset(sk, skb);
 232                 return 0;
 233         case DCCP_PKT_CLOSEREQ:
 234                 dccp_rcv_closereq(sk, skb);
 235                 goto discard;
 236         case DCCP_PKT_CLOSE:
 237                 dccp_rcv_close(sk, skb);
 238                 return 0;
 239         case DCCP_PKT_REQUEST:
 240                 /* Step 7
 241                  *   or (S.is_server and P.type == Response)
 242                  *   or (S.is_client and P.type == Request)
 243                  *   or (S.state >= OPEN and P.type == Request
 244                  *      and P.seqno >= S.OSR)
 245                  *    or (S.state >= OPEN and P.type == Response
 246                  *      and P.seqno >= S.OSR)
 247                  *    or (S.state == RESPOND and P.type == Data),
 248                  *  Send Sync packet acknowledging P.seqno
 249                  *  Drop packet and return
 250                  */
 251                 if (dp->dccps_role != DCCP_ROLE_LISTEN)
 252                         goto send_sync;
 253                 goto check_seq;
 254         case DCCP_PKT_RESPONSE:
 255                 if (dp->dccps_role != DCCP_ROLE_CLIENT)
 256                         goto send_sync;
 257 check_seq:
 258                 if (dccp_delta_seqno(dp->dccps_osr,
 259                                      DCCP_SKB_CB(skb)->dccpd_seq) >= 0) {
 260 send_sync:
 261                         dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq,
 262                                        DCCP_PKT_SYNC);
 263                 }
 264                 break;
 265         case DCCP_PKT_SYNC:
 266                 dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq,
 267                                DCCP_PKT_SYNCACK);
 268                 /*
 269                  * From RFC 4340, sec. 5.7
 270                  *
 271                  * As with DCCP-Ack packets, DCCP-Sync and DCCP-SyncAck packets
 272                  * MAY have non-zero-length application data areas, whose
 273                  * contents receivers MUST ignore.
 274                  */
 275                 goto discard;
 276         }
 277
 278         DCCP_INC_STATS_BH(DCCP_MIB_INERRS);
 279 discard:
 280         __kfree_skb(skb);
 281         return 0;
 282 }
 283
 284 int dccp_rcv_established(struct sock *sk, struct sk_buff *skb,
 285                          const struct dccp_hdr *dh, const unsigned len)
 286 {
 287         struct dccp_sock *dp = dccp_sk(sk);
 288
 289         if (dccp_check_seqno(sk, skb))
 290                 goto discard;
 291
 292         if (dccp_parse_options(sk, skb))
 293                 goto discard;
 294
 295         if (DCCP_SKB_CB(skb)->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
 296                 dccp_event_ack_recv(sk, skb);
 297
 298         if (dccp_msk(sk)->dccpms_send_ack_vector &&
 299             dccp_ackvec_add(dp->dccps_hc_rx_ackvec, sk,
 300                             DCCP_SKB_CB(skb)->dccpd_seq,
 301                             DCCP_ACKVEC_STATE_RECEIVED))
 302                 goto discard;
 303
 304         ccid_hc_rx_packet_recv(dp->dccps_hc_rx_ccid, sk, skb);
 305         ccid_hc_tx_packet_recv(dp->dccps_hc_tx_ccid, sk, skb);
 306
 307         return __dccp_rcv_established(sk, skb, dh, len);
 308 discard:
 309         __kfree_skb(skb);
 310         return 0;
 311 }
 312
 313 EXPORT_SYMBOL_GPL(dccp_rcv_established);
 314
 315 static int dccp_rcv_request_sent_state_process(struct sock *sk,
 316                                                struct sk_buff *skb,
 317                                                const struct dccp_hdr *dh,
 318                                                const unsigned len)
 319 {
 320         /*
 321          *  Step 4: Prepare sequence numbers in REQUEST
 322          *     If S.state == REQUEST,
 323          *        If (P.type == Response or P.type == Reset)
 324          *              and S.AWL <= P.ackno <= S.AWH,
 325          *           / * Set sequence number variables corresponding to the
 326          *              other endpoint, so P will pass the tests in Step 6 * /
 327          *           Set S.GSR, S.ISR, S.SWL, S.SWH
 328          *           / * Response processing continues in Step 10; Reset
 329          *              processing continues in Step 9 * /
 330         */
 331         if (dh->dccph_type == DCCP_PKT_RESPONSE) {
 332                 const struct inet_connection_sock *icsk = inet_csk(sk);
 333                 struct dccp_sock *dp = dccp_sk(sk);
 334                 long tstamp = dccp_timestamp();
 335
 336                 /* Stop the REQUEST timer */
 337                 inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS);
 338                 BUG_TRAP(sk->sk_send_head != NULL);
 339                 __kfree_skb(sk->sk_send_head);
 340                 sk->sk_send_head = NULL;
 341
 342                 if (!between48(DCCP_SKB_CB(skb)->dccpd_ack_seq,
 343                                dp->dccps_awl, dp->dccps_awh)) {
 344                         dccp_pr_debug("invalid ackno: S.AWL=%llu, "
 345                                       "P.ackno=%llu, S.AWH=%llu \n",
 346                                       (unsigned long long)dp->dccps_awl,
 347                            (unsigned long long)DCCP_SKB_CB(skb)->dccpd_ack_seq,
 348                                       (unsigned long long)dp->dccps_awh);
 349                         goto out_invalid_packet;
 350                 }
 351
 352                 if (dccp_parse_options(sk, skb))
 353                         goto out_invalid_packet;
 354
 355                 /* Obtain usec RTT sample from SYN exchange (used by CCID 3) */
 356                 if (likely(dp->dccps_options_received.dccpor_timestamp_echo))
 357                         dp->dccps_syn_rtt = dccp_sample_rtt(sk, 10 * (tstamp -
 358                             dp->dccps_options_received.dccpor_timestamp_echo));
 359
 360                 if (dccp_msk(sk)->dccpms_send_ack_vector &&
 361                     dccp_ackvec_add(dp->dccps_hc_rx_ackvec, sk,
 362                                     DCCP_SKB_CB(skb)->dccpd_seq,
 363                                     DCCP_ACKVEC_STATE_RECEIVED))
 364                         goto out_invalid_packet; /* FIXME: change error code */
 365
 366                 dp->dccps_isr = DCCP_SKB_CB(skb)->dccpd_seq;
 367                 dccp_update_gsr(sk, dp->dccps_isr);
 368                 /*
 369                  * SWL and AWL are initially adjusted so that they are not less than
 370                  * the initial Sequence Numbers received and sent, respectively:
 371                  *      SWL := max(GSR + 1 - floor(W/4), ISR),
 372                  *      AWL := max(GSS - W' + 1, ISS).
 373                  * These adjustments MUST be applied only at the beginning of the
 374                  * connection.
 375                  *
 376                  * AWL was adjusted in dccp_v4_connect -acme
 377                  */
 378                 dccp_set_seqno(&dp->dccps_swl,
 379                                max48(dp->dccps_swl, dp->dccps_isr));
 380
 381                 dccp_sync_mss(sk, icsk->icsk_pmtu_cookie);
 382
 383                 /*
 384                  *    Step 10: Process REQUEST state (second part)
 385                  *       If S.state == REQUEST,
 386                  *        / * If we get here, P is a valid Response from the
 387                  *            server (see Step 4), and we should move to
 388                  *            PARTOPEN state. PARTOPEN means send an Ack,
 389                  *            don't send Data packets, retransmit Acks
 390                  *            periodically, and always include any Init Cookie
 391                  *            from the Response * /
 392                  *        S.state := PARTOPEN
 393                  *        Set PARTOPEN timer
 394                  *        Continue with S.state == PARTOPEN
 395                  *        / * Step 12 will send the Ack completing the
 396                  *            three-way handshake * /
 397                  */
 398                 dccp_set_state(sk, DCCP_PARTOPEN);
 399
 400                 /* Make sure socket is routed, for correct metrics. */
 401                 icsk->icsk_af_ops->rebuild_header(sk);
 402
 403                 if (!sock_flag(sk, SOCK_DEAD)) {
 404                         sk->sk_state_change(sk);
 405                         sk_wake_async(sk, 0, POLL_OUT);
 406                 }
 407
 408                 if (sk->sk_write_pending || icsk->icsk_ack.pingpong ||
 409                     icsk->icsk_accept_queue.rskq_defer_accept) {
 410                         /* Save one ACK. Data will be ready after
 411                          * several ticks, if write_pending is set.
 412                          *
 413                          * It may be deleted, but with this feature tcpdumps
 414                          * look so _wonderfully_ clever, that I was not able
 415                          * to stand against the temptation 8)     --ANK
 416                          */
 417                         /*
 418                          * OK, in DCCP we can as well do a similar trick, its
 419                          * even in the draft, but there is no need for us to
 420                          * schedule an ack here, as dccp_sendmsg does this for
 421                          * us, also stated in the draft. -acme
 422                          */
 423                         __kfree_skb(skb);
 424                         return 0;
 425                 }
 426                 dccp_send_ack(sk);
 427                 return -1;
 428         }
 429
 430 out_invalid_packet:
 431         /* dccp_v4_do_rcv will send a reset */
 432         DCCP_SKB_CB(skb)->dccpd_reset_code = DCCP_RESET_CODE_PACKET_ERROR;
 433         return 1;
 434 }
 435
 436 static int dccp_rcv_respond_partopen_state_process(struct sock *sk,
 437                                                    struct sk_buff *skb,
 438                                                    const struct dccp_hdr *dh,
 439                                                    const unsigned len)
 440 {
 441         int queued = 0;
 442
 443         switch (dh->dccph_type) {
 444         case DCCP_PKT_RESET:
 445                 inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
 446                 break;
 447         case DCCP_PKT_DATA:
 448                 if (sk->sk_state == DCCP_RESPOND)
 449                         break;
 450         case DCCP_PKT_DATAACK:
 451         case DCCP_PKT_ACK:
 452                 /*
 453                  * FIXME: we should be reseting the PARTOPEN (DELACK) timer
 454                  * here but only if we haven't used the DELACK timer for
 455                  * something else, like sending a delayed ack for a TIMESTAMP
 456                  * echo, etc, for now were not clearing it, sending an extra
 457                  * ACK when there is nothing else to do in DELACK is not a big
 458                  * deal after all.
 459                  */
 460
 461                 /* Stop the PARTOPEN timer */
 462                 if (sk->sk_state == DCCP_PARTOPEN)
 463                         inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
 464
 465                 dccp_sk(sk)->dccps_osr = DCCP_SKB_CB(skb)->dccpd_seq;
 466                 dccp_set_state(sk, DCCP_OPEN);
 467
 468                 if (dh->dccph_type == DCCP_PKT_DATAACK ||
 469                     dh->dccph_type == DCCP_PKT_DATA) {
 470                         __dccp_rcv_established(sk, skb, dh, len);
 471                         queued = 1; /* packet was queued
 472                                        (by __dccp_rcv_established) */
 473                 }
 474                 break;
 475         }
 476
 477         return queued;
 478 }
 479
 480 int dccp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
 481                            struct dccp_hdr *dh, unsigned len)
 482 {
 483         struct dccp_sock *dp = dccp_sk(sk);
 484         struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
 485         const int old_state = sk->sk_state;
 486         int queued = 0;
 487
 488         /*
 489          *  Step 3: Process LISTEN state
 490          *
 491          *     If S.state == LISTEN,
 492          *       If P.type == Request or P contains a valid Init Cookie option,
 493          *            (* Must scan the packet's options to check for Init
 494          *               Cookies.  Only Init Cookies are processed here,
 495          *               however; other options are processed in Step 8.  This
 496          *               scan need only be performed if the endpoint uses Init
 497          *               Cookies *)
 498          *            (* Generate a new socket and switch to that socket *)
 499          *            Set S := new socket for this port pair
 500          *            S.state = RESPOND
 501          *            Choose S.ISS (initial seqno) or set from Init Cookies
 502          *            Initialize S.GAR := S.ISS
 503          *            Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init
 504          *            Cookies Continue with S.state == RESPOND
 505          *            (* A Response packet will be generated in Step 11 *)
 506          *       Otherwise,
 507          *            Generate Reset(No Connection) unless P.type == Reset
 508          *            Drop packet and return
 509          */
 510         if (sk->sk_state == DCCP_LISTEN) {
 511                 if (dh->dccph_type == DCCP_PKT_REQUEST) {
 512                         if (inet_csk(sk)->icsk_af_ops->conn_request(sk,
 513                                                                     skb) < 0)
 514                                 return 1;
 515
 516                         /* FIXME: do congestion control initialization */
 517                         goto discard;
 518                 }
 519                 if (dh->dccph_type == DCCP_PKT_RESET)
 520                         goto discard;
 521
 522                 /* Caller (dccp_v4_do_rcv) will send Reset */
 523                 dcb->dccpd_reset_code = DCCP_RESET_CODE_NO_CONNECTION;
 524                 return 1;
 525         }
 526
 527         if (sk->sk_state != DCCP_REQUESTING) {
 528                 if (dccp_check_seqno(sk, skb))
 529                         goto discard;
 530
 531                 /*
 532                  * Step 8: Process options and mark acknowledgeable
 533                  */
 534                 if (dccp_parse_options(sk, skb))
 535                         goto discard;
 536
 537                 if (dcb->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
 538                         dccp_event_ack_recv(sk, skb);
 539
 540                 if (dccp_msk(sk)->dccpms_send_ack_vector &&
 541                     dccp_ackvec_add(dp->dccps_hc_rx_ackvec, sk,
 542                                     DCCP_SKB_CB(skb)->dccpd_seq,
 543                                     DCCP_ACKVEC_STATE_RECEIVED))
 544                         goto discard;
 545
 546                 ccid_hc_rx_packet_recv(dp->dccps_hc_rx_ccid, sk, skb);
 547                 ccid_hc_tx_packet_recv(dp->dccps_hc_tx_ccid, sk, skb);
 548         }
 549
 550         /*
 551          *  Step 9: Process Reset
 552          *      If P.type == Reset,
 553          *              Tear down connection
 554          *              S.state := TIMEWAIT
 555          *              Set TIMEWAIT timer
 556          *              Drop packet and return
 557         */
 558         if (dh->dccph_type == DCCP_PKT_RESET) {
 559                 dccp_rcv_reset(sk, skb);
 560                 return 0;
 561                 /*
 562                  *   Step 7: Check for unexpected packet types
 563                  *      If (S.is_server and P.type == CloseReq)
 564                  *          or (S.is_server and P.type == Response)
 565                  *          or (S.is_client and P.type == Request)
 566                  *          or (S.state == RESPOND and P.type == Data),
 567                  *        Send Sync packet acknowledging P.seqno
 568                  *        Drop packet and return
 569                  */
 570         } else if ((dp->dccps_role != DCCP_ROLE_CLIENT &&
 571                     (dh->dccph_type == DCCP_PKT_RESPONSE ||
 572                      dh->dccph_type == DCCP_PKT_CLOSEREQ)) ||
 573                     (dp->dccps_role == DCCP_ROLE_CLIENT &&
 574                      dh->dccph_type == DCCP_PKT_REQUEST) ||
 575                     (sk->sk_state == DCCP_RESPOND &&
 576                      dh->dccph_type == DCCP_PKT_DATA)) {
 577                 dccp_send_sync(sk, dcb->dccpd_seq, DCCP_PKT_SYNC);
 578                 goto discard;
 579         } else if (dh->dccph_type == DCCP_PKT_CLOSEREQ) {
 580                 dccp_rcv_closereq(sk, skb);
 581                 goto discard;
 582         } else if (dh->dccph_type == DCCP_PKT_CLOSE) {
 583                 dccp_rcv_close(sk, skb);
 584                 return 0;
 585         }
 586
 587         switch (sk->sk_state) {
 588         case DCCP_CLOSED:
 589                 dcb->dccpd_reset_code = DCCP_RESET_CODE_NO_CONNECTION;
 590                 return 1;
 591
 592         case DCCP_REQUESTING:
 593                 /* FIXME: do congestion control initialization */
 594
 595                 queued = dccp_rcv_request_sent_state_process(sk, skb, dh, len);
 596                 if (queued >= 0)
 597                         return queued;
 598
 599                 __kfree_skb(skb);
 600                 return 0;
 601
 602         case DCCP_RESPOND:
 603         case DCCP_PARTOPEN:
 604                 queued = dccp_rcv_respond_partopen_state_process(sk, skb,
 605                                                                  dh, len);
 606                 break;
 607         }
 608
 609         if (dh->dccph_type == DCCP_PKT_ACK ||
 610             dh->dccph_type == DCCP_PKT_DATAACK) {
 611                 switch (old_state) {
 612                 case DCCP_PARTOPEN:
 613                         sk->sk_state_change(sk);
 614                         sk_wake_async(sk, 0, POLL_OUT);
 615                         break;
 616                 }
 617         } else if (unlikely(dh->dccph_type == DCCP_PKT_SYNC)) {
 618                 dccp_send_sync(sk, dcb->dccpd_seq, DCCP_PKT_SYNCACK);
 619                 goto discard;
 620         }
 621
 622         if (!queued) {
 623 discard:
 624                 __kfree_skb(skb);
 625         }
 626         return 0;
 627 }
 628
 629 EXPORT_SYMBOL_GPL(dccp_rcv_state_process);
 630
 631 /**
 632  *  dccp_sample_rtt  -  Validate and finalise computation of RTT sample
 633  *  @delta:     number of microseconds between packet and acknowledgment
 634  *  The routine is kept generic to work in different contexts. It should be
 635  *  called immediately when the ACK used for the RTT sample arrives.
 636  */
 637 u32 dccp_sample_rtt(struct sock *sk, long delta)
 638 {
 639         /* dccpor_elapsed_time is either zeroed out or set and > 0 */
 640         delta -= dccp_sk(sk)->dccps_options_received.dccpor_elapsed_time * 10;
 641
 642         if (unlikely(delta <= 0)) {
 643                 DCCP_WARN("unusable RTT sample %ld, using min\n", delta);
 644                 return DCCP_SANE_RTT_MIN;
 645         }
 646         if (unlikely(delta > DCCP_SANE_RTT_MAX)) {
 647                 DCCP_WARN("RTT sample %ld too large, using max\n", delta);
 648                 return DCCP_SANE_RTT_MAX;
 649         }
 650
 651         return delta;
 652 }
 653
 654 EXPORT_SYMBOL_GPL(dccp_sample_rtt);