net/dccp/input.c

   1 /*
   2  *  net/dccp/input.c
   3  *
   4  *  An implementation of the DCCP protocol
   5  *  Arnaldo Carvalho de Melo <acme@conectiva.com.br>
   6  *
   7  *      This program is free software; you can redistribute it and/or
   8  *      modify it under the terms of the GNU General Public License
   9  *      as published by the Free Software Foundation; either version
  10  *      2 of the License, or (at your option) any later version.
  11  */
  12
  13 #include <linux/dccp.h>
  14 #include <linux/skbuff.h>
  15 #include <linux/slab.h>
  16
  17 #include <net/sock.h>
  18
  19 #include "ackvec.h"
  20 #include "ccid.h"
  21 #include "dccp.h"
  22
  23 /* rate-limit for syncs in reply to sequence-invalid packets; RFC 4340, 7.5.4 */
  24 int sysctl_dccp_sync_ratelimit  __read_mostly = HZ / 8;
  25
  26 static void dccp_enqueue_skb(struct sock *sk, struct sk_buff *skb)
  27 {
  28         __skb_pull(skb, dccp_hdr(skb)->dccph_doff * 4);
  29         __skb_queue_tail(&sk->sk_receive_queue, skb);
  30         skb_set_owner_r(skb, sk);
  31         sk->sk_data_ready(sk);
  32 }
  33
  34 static void dccp_fin(struct sock *sk, struct sk_buff *skb)
  35 {
  36         /*
  37          * On receiving Close/CloseReq, both RD/WR shutdown are performed.
  38          * RFC 4340, 8.3 says that we MAY send further Data/DataAcks after
  39          * receiving the closing segment, but there is no guarantee that such
  40          * data will be processed at all.
  41          */
  42         sk->sk_shutdown = SHUTDOWN_MASK;
  43         sock_set_flag(sk, SOCK_DONE);
  44         dccp_enqueue_skb(sk, skb);
  45 }
  46
  47 static int dccp_rcv_close(struct sock *sk, struct sk_buff *skb)
  48 {
  49         int queued = 0;
  50
  51         switch (sk->sk_state) {
  52         /*
  53          * We ignore Close when received in one of the following states:
  54          *  - CLOSED            (may be a late or duplicate packet)
  55          *  - PASSIVE_CLOSEREQ  (the peer has sent a CloseReq earlier)
  56          *  - RESPOND           (already handled by dccp_check_req)
  57          */
  58         case DCCP_CLOSING:
  59                 /*
  60                  * Simultaneous-close: receiving a Close after sending one. This
  61                  * can happen if both client and server perform active-close and
  62                  * will result in an endless ping-pong of crossing and retrans-
  63                  * mitted Close packets, which only terminates when one of the
  64                  * nodes times out (min. 64 seconds). Quicker convergence can be
  65                  * achieved when one of the nodes acts as tie-breaker.
  66                  * This is ok as both ends are done with data transfer and each
  67                  * end is just waiting for the other to acknowledge termination.
  68                  */
  69                 if (dccp_sk(sk)->dccps_role != DCCP_ROLE_CLIENT)
  70                         break;
  71                 /* fall through */
  72         case DCCP_REQUESTING:
  73         case DCCP_ACTIVE_CLOSEREQ:
  74                 dccp_send_reset(sk, DCCP_RESET_CODE_CLOSED);
  75                 dccp_done(sk);
  76                 break;
  77         case DCCP_OPEN:
  78         case DCCP_PARTOPEN:
  79                 /* Give waiting application a chance to read pending data */
  80                 queued = 1;
  81                 dccp_fin(sk, skb);
  82                 dccp_set_state(sk, DCCP_PASSIVE_CLOSE);
  83                 /* fall through */
  84         case DCCP_PASSIVE_CLOSE:
  85                 /*
  86                  * Retransmitted Close: we have already enqueued the first one.
  87                  */
  88                 sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_HUP);
  89         }
  90         return queued;
  91 }
  92
  93 static int dccp_rcv_closereq(struct sock *sk, struct sk_buff *skb)
  94 {
  95         int queued = 0;
  96
  97         /*
  98          *   Step 7: Check for unexpected packet types
  99          *      If (S.is_server and P.type == CloseReq)
 100          *        Send Sync packet acknowledging P.seqno
 101          *        Drop packet and return
 102          */
 103         if (dccp_sk(sk)->dccps_role != DCCP_ROLE_CLIENT) {
 104                 dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq, DCCP_PKT_SYNC);
 105                 return queued;
 106         }
 107
 108         /* Step 13: process relevant Client states < CLOSEREQ */
 109         switch (sk->sk_state) {
 110         case DCCP_REQUESTING:
 111                 dccp_send_close(sk, 0);
 112                 dccp_set_state(sk, DCCP_CLOSING);
 113                 break;
 114         case DCCP_OPEN:
 115         case DCCP_PARTOPEN:
 116                 /* Give waiting application a chance to read pending data */
 117                 queued = 1;
 118                 dccp_fin(sk, skb);
 119                 dccp_set_state(sk, DCCP_PASSIVE_CLOSEREQ);
 120                 /* fall through */
 121         case DCCP_PASSIVE_CLOSEREQ:
 122                 sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_HUP);
 123         }
 124         return queued;
 125 }
 126
 127 static u16 dccp_reset_code_convert(const u8 code)
 128 {
 129         const u16 error_code[] = {
 130         [DCCP_RESET_CODE_CLOSED]             = 0,       /* normal termination */
 131         [DCCP_RESET_CODE_UNSPECIFIED]        = 0,       /* nothing known */
 132         [DCCP_RESET_CODE_ABORTED]            = ECONNRESET,
 133
 134         [DCCP_RESET_CODE_NO_CONNECTION]      = ECONNREFUSED,
 135         [DCCP_RESET_CODE_CONNECTION_REFUSED] = ECONNREFUSED,
 136         [DCCP_RESET_CODE_TOO_BUSY]           = EUSERS,
 137         [DCCP_RESET_CODE_AGGRESSION_PENALTY] = EDQUOT,
 138
 139         [DCCP_RESET_CODE_PACKET_ERROR]       = ENOMSG,
 140         [DCCP_RESET_CODE_BAD_INIT_COOKIE]    = EBADR,
 141         [DCCP_RESET_CODE_BAD_SERVICE_CODE]   = EBADRQC,
 142         [DCCP_RESET_CODE_OPTION_ERROR]       = EILSEQ,
 143         [DCCP_RESET_CODE_MANDATORY_ERROR]    = EOPNOTSUPP,
 144         };
 145
 146         return code >= DCCP_MAX_RESET_CODES ? 0 : error_code[code];
 147 }
 148
 149 static void dccp_rcv_reset(struct sock *sk, struct sk_buff *skb)
 150 {
 151         u16 err = dccp_reset_code_convert(dccp_hdr_reset(skb)->dccph_reset_code);
 152
 153         sk->sk_err = err;
 154
 155         /* Queue the equivalent of TCP fin so that dccp_recvmsg exits the loop */
 156         dccp_fin(sk, skb);
 157
 158         if (err && !sock_flag(sk, SOCK_DEAD))
 159                 sk_wake_async(sk, SOCK_WAKE_IO, POLL_ERR);
 160         dccp_time_wait(sk, DCCP_TIME_WAIT, 0);
 161 }
 162
 163 static void dccp_handle_ackvec_processing(struct sock *sk, struct sk_buff *skb)
 164 {
 165         struct dccp_ackvec *av = dccp_sk(sk)->dccps_hc_rx_ackvec;
 166
 167         if (av == NULL)
 168                 return;
 169         if (DCCP_SKB_CB(skb)->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
 170                 dccp_ackvec_clear_state(av, DCCP_SKB_CB(skb)->dccpd_ack_seq);
 171         dccp_ackvec_input(av, skb);
 172 }
 173
 174 static void dccp_deliver_input_to_ccids(struct sock *sk, struct sk_buff *skb)
 175 {
 176         const struct dccp_sock *dp = dccp_sk(sk);
 177
 178         /* Don't deliver to RX CCID when node has shut down read end. */
 179         if (!(sk->sk_shutdown & RCV_SHUTDOWN))
 180                 ccid_hc_rx_packet_recv(dp->dccps_hc_rx_ccid, sk, skb);
 181         /*
 182          * Until the TX queue has been drained, we can not honour SHUT_WR, since
 183          * we need received feedback as input to adjust congestion control.
 184          */
 185         if (sk->sk_write_queue.qlen > 0 || !(sk->sk_shutdown & SEND_SHUTDOWN))
 186                 ccid_hc_tx_packet_recv(dp->dccps_hc_tx_ccid, sk, skb);
 187 }
 188
 189 static int dccp_check_seqno(struct sock *sk, struct sk_buff *skb)
 190 {
 191         const struct dccp_hdr *dh = dccp_hdr(skb);
 192         struct dccp_sock *dp = dccp_sk(sk);
 193         u64 lswl, lawl, seqno = DCCP_SKB_CB(skb)->dccpd_seq,
 194                         ackno = DCCP_SKB_CB(skb)->dccpd_ack_seq;
 195
 196         /*
 197          *   Step 5: Prepare sequence numbers for Sync
 198          *     If P.type == Sync or P.type == SyncAck,
 199          *        If S.AWL <= P.ackno <= S.AWH and P.seqno >= S.SWL,
 200          *           / * P is valid, so update sequence number variables
 201          *               accordingly.  After this update, P will pass the tests
 202          *               in Step 6.  A SyncAck is generated if necessary in
 203          *               Step 15 * /
 204          *           Update S.GSR, S.SWL, S.SWH
 205          *        Otherwise,
 206          *           Drop packet and return
 207          */
 208         if (dh->dccph_type == DCCP_PKT_SYNC ||
 209             dh->dccph_type == DCCP_PKT_SYNCACK) {
 210                 if (between48(ackno, dp->dccps_awl, dp->dccps_awh) &&
 211                     dccp_delta_seqno(dp->dccps_swl, seqno) >= 0)
 212                         dccp_update_gsr(sk, seqno);
 213                 else
 214                         return -1;
 215         }
 216
 217         /*
 218          *   Step 6: Check sequence numbers
 219          *      Let LSWL = S.SWL and LAWL = S.AWL
 220          *      If P.type == CloseReq or P.type == Close or P.type == Reset,
 221          *        LSWL := S.GSR + 1, LAWL := S.GAR
 222          *      If LSWL <= P.seqno <= S.SWH
 223          *           and (P.ackno does not exist or LAWL <= P.ackno <= S.AWH),
 224          *        Update S.GSR, S.SWL, S.SWH
 225          *        If P.type != Sync,
 226          *           Update S.GAR
 227          */
 228         lswl = dp->dccps_swl;
 229         lawl = dp->dccps_awl;
 230
 231         if (dh->dccph_type == DCCP_PKT_CLOSEREQ ||
 232             dh->dccph_type == DCCP_PKT_CLOSE ||
 233             dh->dccph_type == DCCP_PKT_RESET) {
 234                 lswl = ADD48(dp->dccps_gsr, 1);
 235                 lawl = dp->dccps_gar;
 236         }
 237
 238         if (between48(seqno, lswl, dp->dccps_swh) &&
 239             (ackno == DCCP_PKT_WITHOUT_ACK_SEQ ||
 240              between48(ackno, lawl, dp->dccps_awh))) {
 241                 dccp_update_gsr(sk, seqno);
 242
 243                 if (dh->dccph_type != DCCP_PKT_SYNC &&
 244                     ackno != DCCP_PKT_WITHOUT_ACK_SEQ &&
 245                     after48(ackno, dp->dccps_gar))
 246                         dp->dccps_gar = ackno;
 247         } else {
 248                 unsigned long now = jiffies;
 249                 /*
 250                  *   Step 6: Check sequence numbers
 251                  *      Otherwise,
 252                  *         If P.type == Reset,
 253                  *            Send Sync packet acknowledging S.GSR
 254                  *         Otherwise,
 255                  *            Send Sync packet acknowledging P.seqno
 256                  *      Drop packet and return
 257                  *
 258                  *   These Syncs are rate-limited as per RFC 4340, 7.5.4:
 259                  *   at most 1 / (dccp_sync_rate_limit * HZ) Syncs per second.
 260                  */
 261                 if (time_before(now, (dp->dccps_rate_last +
 262                                       sysctl_dccp_sync_ratelimit)))
 263                         return -1;
 264
 265                 DCCP_WARN("Step 6 failed for %s packet, "
 266                           "(LSWL(%llu) <= P.seqno(%llu) <= S.SWH(%llu)) and "
 267                           "(P.ackno %s or LAWL(%llu) <= P.ackno(%llu) <= S.AWH(%llu), "
 268                           "sending SYNC...\n",  dccp_packet_name(dh->dccph_type),
 269                           (unsigned long long) lswl, (unsigned long long) seqno,
 270                           (unsigned long long) dp->dccps_swh,
 271                           (ackno == DCCP_PKT_WITHOUT_ACK_SEQ) ? "doesn't exist"
 272                                                               : "exists",
 273                           (unsigned long long) lawl, (unsigned long long) ackno,
 274                           (unsigned long long) dp->dccps_awh);
 275
 276                 dp->dccps_rate_last = now;
 277
 278                 if (dh->dccph_type == DCCP_PKT_RESET)
 279                         seqno = dp->dccps_gsr;
 280                 dccp_send_sync(sk, seqno, DCCP_PKT_SYNC);
 281                 return -1;
 282         }
 283
 284         return 0;
 285 }
 286
 287 static int __dccp_rcv_established(struct sock *sk, struct sk_buff *skb,
 288                                   const struct dccp_hdr *dh, const unsigned int len)
 289 {
 290         struct dccp_sock *dp = dccp_sk(sk);
 291
 292         switch (dccp_hdr(skb)->dccph_type) {
 293         case DCCP_PKT_DATAACK:
 294         case DCCP_PKT_DATA:
 295                 /*
 296                  * FIXME: schedule DATA_DROPPED (RFC 4340, 11.7.2) if and when
 297                  * - sk_shutdown == RCV_SHUTDOWN, use Code 1, "Not Listening"
 298                  * - sk_receive_queue is full, use Code 2, "Receive Buffer"
 299                  */
 300                 dccp_enqueue_skb(sk, skb);
 301                 return 0;
 302         case DCCP_PKT_ACK:
 303                 goto discard;
 304         case DCCP_PKT_RESET:
 305                 /*
 306                  *  Step 9: Process Reset
 307                  *      If P.type == Reset,
 308                  *              Tear down connection
 309                  *              S.state := TIMEWAIT
 310                  *              Set TIMEWAIT timer
 311                  *              Drop packet and return
 312                  */
 313                 dccp_rcv_reset(sk, skb);
 314                 return 0;
 315         case DCCP_PKT_CLOSEREQ:
 316                 if (dccp_rcv_closereq(sk, skb))
 317                         return 0;
 318                 goto discard;
 319         case DCCP_PKT_CLOSE:
 320                 if (dccp_rcv_close(sk, skb))
 321                         return 0;
 322                 goto discard;
 323         case DCCP_PKT_REQUEST:
 324                 /* Step 7
 325                  *   or (S.is_server and P.type == Response)
 326                  *   or (S.is_client and P.type == Request)
 327                  *   or (S.state >= OPEN and P.type == Request
 328                  *      and P.seqno >= S.OSR)
 329                  *    or (S.state >= OPEN and P.type == Response
 330                  *      and P.seqno >= S.OSR)
 331                  *    or (S.state == RESPOND and P.type == Data),
 332                  *  Send Sync packet acknowledging P.seqno
 333                  *  Drop packet and return
 334                  */
 335                 if (dp->dccps_role != DCCP_ROLE_LISTEN)
 336                         goto send_sync;
 337                 goto check_seq;
 338         case DCCP_PKT_RESPONSE:
 339                 if (dp->dccps_role != DCCP_ROLE_CLIENT)
 340                         goto send_sync;
 341 check_seq:
 342                 if (dccp_delta_seqno(dp->dccps_osr,
 343                                      DCCP_SKB_CB(skb)->dccpd_seq) >= 0) {
 344 send_sync:
 345                         dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq,
 346                                        DCCP_PKT_SYNC);
 347                 }
 348                 break;
 349         case DCCP_PKT_SYNC:
 350                 dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq,
 351                                DCCP_PKT_SYNCACK);
 352                 /*
 353                  * From RFC 4340, sec. 5.7
 354                  *
 355                  * As with DCCP-Ack packets, DCCP-Sync and DCCP-SyncAck packets
 356                  * MAY have non-zero-length application data areas, whose
 357                  * contents receivers MUST ignore.
 358                  */
 359                 goto discard;
 360         }
 361
 362         DCCP_INC_STATS_BH(DCCP_MIB_INERRS);
 363 discard:
 364         __kfree_skb(skb);
 365         return 0;
 366 }
 367
 368 int dccp_rcv_established(struct sock *sk, struct sk_buff *skb,
 369                          const struct dccp_hdr *dh, const unsigned int len)
 370 {
 371         if (dccp_check_seqno(sk, skb))
 372                 goto discard;
 373
 374         if (dccp_parse_options(sk, NULL, skb))
 375                 return 1;
 376
 377         dccp_handle_ackvec_processing(sk, skb);
 378         dccp_deliver_input_to_ccids(sk, skb);
 379
 380         return __dccp_rcv_established(sk, skb, dh, len);
 381 discard:
 382         __kfree_skb(skb);
 383         return 0;
 384 }
 385
 386 EXPORT_SYMBOL_GPL(dccp_rcv_established);
 387
 388 static int dccp_rcv_request_sent_state_process(struct sock *sk,
 389                                                struct sk_buff *skb,
 390                                                const struct dccp_hdr *dh,
 391                                                const unsigned int len)
 392 {
 393         /*
 394          *  Step 4: Prepare sequence numbers in REQUEST
 395          *     If S.state == REQUEST,
 396          *        If (P.type == Response or P.type == Reset)
 397          *              and S.AWL <= P.ackno <= S.AWH,
 398          *           / * Set sequence number variables corresponding to the
 399          *              other endpoint, so P will pass the tests in Step 6 * /
 400          *           Set S.GSR, S.ISR, S.SWL, S.SWH
 401          *           / * Response processing continues in Step 10; Reset
 402          *              processing continues in Step 9 * /
 403         */
 404         if (dh->dccph_type == DCCP_PKT_RESPONSE) {
 405                 const struct inet_connection_sock *icsk = inet_csk(sk);
 406                 struct dccp_sock *dp = dccp_sk(sk);
 407                 long tstamp = dccp_timestamp();
 408
 409                 if (!between48(DCCP_SKB_CB(skb)->dccpd_ack_seq,
 410                                dp->dccps_awl, dp->dccps_awh)) {
 411                         dccp_pr_debug("invalid ackno: S.AWL=%llu, "
 412                                       "P.ackno=%llu, S.AWH=%llu\n",
 413                                       (unsigned long long)dp->dccps_awl,
 414                            (unsigned long long)DCCP_SKB_CB(skb)->dccpd_ack_seq,
 415                                       (unsigned long long)dp->dccps_awh);
 416                         goto out_invalid_packet;
 417                 }
 418
 419                 /*
 420                  * If option processing (Step 8) failed, return 1 here so that
 421                  * dccp_v4_do_rcv() sends a Reset. The Reset code depends on
 422                  * the option type and is set in dccp_parse_options().
 423                  */
 424                 if (dccp_parse_options(sk, NULL, skb))
 425                         return 1;
 426
 427                 /* Obtain usec RTT sample from SYN exchange (used by TFRC). */
 428                 if (likely(dp->dccps_options_received.dccpor_timestamp_echo))
 429                         dp->dccps_syn_rtt = dccp_sample_rtt(sk, 10 * (tstamp -
 430                             dp->dccps_options_received.dccpor_timestamp_echo));
 431
 432                 /* Stop the REQUEST timer */
 433                 inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS);
 434                 WARN_ON(sk->sk_send_head == NULL);
 435                 kfree_skb(sk->sk_send_head);
 436                 sk->sk_send_head = NULL;
 437
 438                 /*
 439                  * Set ISR, GSR from packet. ISS was set in dccp_v{4,6}_connect
 440                  * and GSS in dccp_transmit_skb(). Setting AWL/AWH and SWL/SWH
 441                  * is done as part of activating the feature values below, since
 442                  * these settings depend on the local/remote Sequence Window
 443                  * features, which were undefined or not confirmed until now.
 444                  */
 445                 dp->dccps_gsr = dp->dccps_isr = DCCP_SKB_CB(skb)->dccpd_seq;
 446
 447                 dccp_sync_mss(sk, icsk->icsk_pmtu_cookie);
 448
 449                 /*
 450                  *    Step 10: Process REQUEST state (second part)
 451                  *       If S.state == REQUEST,
 452                  *        / * If we get here, P is a valid Response from the
 453                  *            server (see Step 4), and we should move to
 454                  *            PARTOPEN state. PARTOPEN means send an Ack,
 455                  *            don't send Data packets, retransmit Acks
 456                  *            periodically, and always include any Init Cookie
 457                  *            from the Response * /
 458                  *        S.state := PARTOPEN
 459                  *        Set PARTOPEN timer
 460                  *        Continue with S.state == PARTOPEN
 461                  *        / * Step 12 will send the Ack completing the
 462                  *            three-way handshake * /
 463                  */
 464                 dccp_set_state(sk, DCCP_PARTOPEN);
 465
 466                 /*
 467                  * If feature negotiation was successful, activate features now;
 468                  * an activation failure means that this host could not activate
 469                  * one ore more features (e.g. insufficient memory), which would
 470                  * leave at least one feature in an undefined state.
 471                  */
 472                 if (dccp_feat_activate_values(sk, &dp->dccps_featneg))
 473                         goto unable_to_proceed;
 474
 475                 /* Make sure socket is routed, for correct metrics. */
 476                 icsk->icsk_af_ops->rebuild_header(sk);
 477
 478                 if (!sock_flag(sk, SOCK_DEAD)) {
 479                         sk->sk_state_change(sk);
 480                         sk_wake_async(sk, SOCK_WAKE_IO, POLL_OUT);
 481                 }
 482
 483                 if (sk->sk_write_pending || icsk->icsk_ack.pingpong ||
 484                     icsk->icsk_accept_queue.rskq_defer_accept) {
 485                         /* Save one ACK. Data will be ready after
 486                          * several ticks, if write_pending is set.
 487                          *
 488                          * It may be deleted, but with this feature tcpdumps
 489                          * look so _wonderfully_ clever, that I was not able
 490                          * to stand against the temptation 8)     --ANK
 491                          */
 492                         /*
 493                          * OK, in DCCP we can as well do a similar trick, its
 494                          * even in the draft, but there is no need for us to
 495                          * schedule an ack here, as dccp_sendmsg does this for
 496                          * us, also stated in the draft. -acme
 497                          */
 498                         __kfree_skb(skb);
 499                         return 0;
 500                 }
 501                 dccp_send_ack(sk);
 502                 return -1;
 503         }
 504
 505 out_invalid_packet:
 506         /* dccp_v4_do_rcv will send a reset */
 507         DCCP_SKB_CB(skb)->dccpd_reset_code = DCCP_RESET_CODE_PACKET_ERROR;
 508         return 1;
 509
 510 unable_to_proceed:
 511         DCCP_SKB_CB(skb)->dccpd_reset_code = DCCP_RESET_CODE_ABORTED;
 512         /*
 513          * We mark this socket as no longer usable, so that the loop in
 514          * dccp_sendmsg() terminates and the application gets notified.
 515          */
 516         dccp_set_state(sk, DCCP_CLOSED);
 517         sk->sk_err = ECOMM;
 518         return 1;
 519 }
 520
 521 static int dccp_rcv_respond_partopen_state_process(struct sock *sk,
 522                                                    struct sk_buff *skb,
 523                                                    const struct dccp_hdr *dh,
 524                                                    const unsigned int len)
 525 {
 526         struct dccp_sock *dp = dccp_sk(sk);
 527         u32 sample = dp->dccps_options_received.dccpor_timestamp_echo;
 528         int queued = 0;
 529
 530         switch (dh->dccph_type) {
 531         case DCCP_PKT_RESET:
 532                 inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
 533                 break;
 534         case DCCP_PKT_DATA:
 535                 if (sk->sk_state == DCCP_RESPOND)
 536                         break;
 537         case DCCP_PKT_DATAACK:
 538         case DCCP_PKT_ACK:
 539                 /*
 540                  * FIXME: we should be reseting the PARTOPEN (DELACK) timer
 541                  * here but only if we haven't used the DELACK timer for
 542                  * something else, like sending a delayed ack for a TIMESTAMP
 543                  * echo, etc, for now were not clearing it, sending an extra
 544                  * ACK when there is nothing else to do in DELACK is not a big
 545                  * deal after all.
 546                  */
 547
 548                 /* Stop the PARTOPEN timer */
 549                 if (sk->sk_state == DCCP_PARTOPEN)
 550                         inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
 551
 552                 /* Obtain usec RTT sample from SYN exchange (used by TFRC). */
 553                 if (likely(sample)) {
 554                         long delta = dccp_timestamp() - sample;
 555
 556                         dp->dccps_syn_rtt = dccp_sample_rtt(sk, 10 * delta);
 557                 }
 558
 559                 dp->dccps_osr = DCCP_SKB_CB(skb)->dccpd_seq;
 560                 dccp_set_state(sk, DCCP_OPEN);
 561
 562                 if (dh->dccph_type == DCCP_PKT_DATAACK ||
 563                     dh->dccph_type == DCCP_PKT_DATA) {
 564                         __dccp_rcv_established(sk, skb, dh, len);
 565                         queued = 1; /* packet was queued
 566                                        (by __dccp_rcv_established) */
 567                 }
 568                 break;
 569         }
 570
 571         return queued;
 572 }
 573
 574 int dccp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
 575                            struct dccp_hdr *dh, unsigned int len)
 576 {
 577         struct dccp_sock *dp = dccp_sk(sk);
 578         struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
 579         const int old_state = sk->sk_state;
 580         int queued = 0;
 581
 582         /*
 583          *  Step 3: Process LISTEN state
 584          *
 585          *     If S.state == LISTEN,
 586          *       If P.type == Request or P contains a valid Init Cookie option,
 587          *            (* Must scan the packet's options to check for Init
 588          *               Cookies.  Only Init Cookies are processed here,
 589          *               however; other options are processed in Step 8.  This
 590          *               scan need only be performed if the endpoint uses Init
 591          *               Cookies *)
 592          *            (* Generate a new socket and switch to that socket *)
 593          *            Set S := new socket for this port pair
 594          *            S.state = RESPOND
 595          *            Choose S.ISS (initial seqno) or set from Init Cookies
 596          *            Initialize S.GAR := S.ISS
 597          *            Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init
 598          *            Cookies Continue with S.state == RESPOND
 599          *            (* A Response packet will be generated in Step 11 *)
 600          *       Otherwise,
 601          *            Generate Reset(No Connection) unless P.type == Reset
 602          *            Drop packet and return
 603          */
 604         if (sk->sk_state == DCCP_LISTEN) {
 605                 if (dh->dccph_type == DCCP_PKT_REQUEST) {
 606                         if (inet_csk(sk)->icsk_af_ops->conn_request(sk,
 607                                                                     skb) < 0)
 608                                 return 1;
 609                         goto discard;
 610                 }
 611                 if (dh->dccph_type == DCCP_PKT_RESET)
 612                         goto discard;
 613
 614                 /* Caller (dccp_v4_do_rcv) will send Reset */
 615                 dcb->dccpd_reset_code = DCCP_RESET_CODE_NO_CONNECTION;
 616                 return 1;
 617         } else if (sk->sk_state == DCCP_CLOSED) {
 618                 dcb->dccpd_reset_code = DCCP_RESET_CODE_NO_CONNECTION;
 619                 return 1;
 620         }
 621
 622         /* Step 6: Check sequence numbers (omitted in LISTEN/REQUEST state) */
 623         if (sk->sk_state != DCCP_REQUESTING && dccp_check_seqno(sk, skb))
 624                 goto discard;
 625
 626         /*
 627          *   Step 7: Check for unexpected packet types
 628          *      If (S.is_server and P.type == Response)
 629          *          or (S.is_client and P.type == Request)
 630          *          or (S.state == RESPOND and P.type == Data),
 631          *        Send Sync packet acknowledging P.seqno
 632          *        Drop packet and return
 633          */
 634         if ((dp->dccps_role != DCCP_ROLE_CLIENT &&
 635              dh->dccph_type == DCCP_PKT_RESPONSE) ||
 636             (dp->dccps_role == DCCP_ROLE_CLIENT &&
 637              dh->dccph_type == DCCP_PKT_REQUEST) ||
 638             (sk->sk_state == DCCP_RESPOND && dh->dccph_type == DCCP_PKT_DATA)) {
 639                 dccp_send_sync(sk, dcb->dccpd_seq, DCCP_PKT_SYNC);
 640                 goto discard;
 641         }
 642
 643         /*  Step 8: Process options */
 644         if (dccp_parse_options(sk, NULL, skb))
 645                 return 1;
 646
 647         /*
 648          *  Step 9: Process Reset
 649          *      If P.type == Reset,
 650          *              Tear down connection
 651          *              S.state := TIMEWAIT
 652          *              Set TIMEWAIT timer
 653          *              Drop packet and return
 654          */
 655         if (dh->dccph_type == DCCP_PKT_RESET) {
 656                 dccp_rcv_reset(sk, skb);
 657                 return 0;
 658         } else if (dh->dccph_type == DCCP_PKT_CLOSEREQ) {       /* Step 13 */
 659                 if (dccp_rcv_closereq(sk, skb))
 660                         return 0;
 661                 goto discard;
 662         } else if (dh->dccph_type == DCCP_PKT_CLOSE) {          /* Step 14 */
 663                 if (dccp_rcv_close(sk, skb))
 664                         return 0;
 665                 goto discard;
 666         }
 667
 668         switch (sk->sk_state) {
 669         case DCCP_REQUESTING:
 670                 queued = dccp_rcv_request_sent_state_process(sk, skb, dh, len);
 671                 if (queued >= 0)
 672                         return queued;
 673
 674                 __kfree_skb(skb);
 675                 return 0;
 676
 677         case DCCP_PARTOPEN:
 678                 /* Step 8: if using Ack Vectors, mark packet acknowledgeable */
 679                 dccp_handle_ackvec_processing(sk, skb);
 680                 dccp_deliver_input_to_ccids(sk, skb);
 681                 /* fall through */
 682         case DCCP_RESPOND:
 683                 queued = dccp_rcv_respond_partopen_state_process(sk, skb,
 684                                                                  dh, len);
 685                 break;
 686         }
 687
 688         if (dh->dccph_type == DCCP_PKT_ACK ||
 689             dh->dccph_type == DCCP_PKT_DATAACK) {
 690                 switch (old_state) {
 691                 case DCCP_PARTOPEN:
 692                         sk->sk_state_change(sk);
 693                         sk_wake_async(sk, SOCK_WAKE_IO, POLL_OUT);
 694                         break;
 695                 }
 696         } else if (unlikely(dh->dccph_type == DCCP_PKT_SYNC)) {
 697                 dccp_send_sync(sk, dcb->dccpd_seq, DCCP_PKT_SYNCACK);
 698                 goto discard;
 699         }
 700
 701         if (!queued) {
 702 discard:
 703                 __kfree_skb(skb);
 704         }
 705         return 0;
 706 }
 707
 708 EXPORT_SYMBOL_GPL(dccp_rcv_state_process);
 709
 710 /**
 711  *  dccp_sample_rtt  -  Validate and finalise computation of RTT sample
 712  *  @delta:     number of microseconds between packet and acknowledgment
 713  *
 714  *  The routine is kept generic to work in different contexts. It should be
 715  *  called immediately when the ACK used for the RTT sample arrives.
 716  */
 717 u32 dccp_sample_rtt(struct sock *sk, long delta)
 718 {
 719         /* dccpor_elapsed_time is either zeroed out or set and > 0 */
 720         delta -= dccp_sk(sk)->dccps_options_received.dccpor_elapsed_time * 10;
 721
 722         if (unlikely(delta <= 0)) {
 723                 DCCP_WARN("unusable RTT sample %ld, using min\n", delta);
 724                 return DCCP_SANE_RTT_MIN;
 725         }
 726         if (unlikely(delta > DCCP_SANE_RTT_MAX)) {
 727                 DCCP_WARN("RTT sample %ld too large, using max\n", delta);
 728                 return DCCP_SANE_RTT_MAX;
 729         }
 730
 731         return delta;
 732 }