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