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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_event_ack_recv(struct sock *sk, struct sk_buff *skb)
 163 {
 164         struct dccp_sock *dp = dccp_sk(sk);
 165
 166         if (dccp_msk(sk)->dccpms_send_ack_vector)
 167                 dccp_ackvec_check_rcv_ackno(dp->dccps_hc_rx_ackvec, sk,
 168                                             DCCP_SKB_CB(skb)->dccpd_ack_seq);
 169 }
 170
 171 static void dccp_deliver_input_to_ccids(struct sock *sk, struct sk_buff *skb)
 172 {
 173         const struct dccp_sock *dp = dccp_sk(sk);
 174
 175         /* Don't deliver to RX CCID when node has shut down read end. */
 176         if (!(sk->sk_shutdown & RCV_SHUTDOWN))
 177                 ccid_hc_rx_packet_recv(dp->dccps_hc_rx_ccid, sk, skb);
 178         /*
 179          * Until the TX queue has been drained, we can not honour SHUT_WR, since
 180          * we need received feedback as input to adjust congestion control.
 181          */
 182         if (sk->sk_write_queue.qlen > 0 || !(sk->sk_shutdown & SEND_SHUTDOWN))
 183                 ccid_hc_tx_packet_recv(dp->dccps_hc_tx_ccid, sk, skb);
 184 }
 185
 186 static int dccp_check_seqno(struct sock *sk, struct sk_buff *skb)
 187 {
 188         const struct dccp_hdr *dh = dccp_hdr(skb);
 189         struct dccp_sock *dp = dccp_sk(sk);
 190         u64 lswl, lawl, seqno = DCCP_SKB_CB(skb)->dccpd_seq,
 191                         ackno = DCCP_SKB_CB(skb)->dccpd_ack_seq;
 192
 193         /*
 194          *   Step 5: Prepare sequence numbers for Sync
 195          *     If P.type == Sync or P.type == SyncAck,
 196          *        If S.AWL <= P.ackno <= S.AWH and P.seqno >= S.SWL,
 197          *           / * P is valid, so update sequence number variables
 198          *               accordingly.  After this update, P will pass the tests
 199          *               in Step 6.  A SyncAck is generated if necessary in
 200          *               Step 15 * /
 201          *           Update S.GSR, S.SWL, S.SWH
 202          *        Otherwise,
 203          *           Drop packet and return
 204          */
 205         if (dh->dccph_type == DCCP_PKT_SYNC ||
 206             dh->dccph_type == DCCP_PKT_SYNCACK) {
 207                 if (between48(ackno, dp->dccps_awl, dp->dccps_awh) &&
 208                     dccp_delta_seqno(dp->dccps_swl, seqno) >= 0)
 209                         dccp_update_gsr(sk, seqno);
 210                 else
 211                         return -1;
 212         }
 213
 214         /*
 215          *   Step 6: Check sequence numbers
 216          *      Let LSWL = S.SWL and LAWL = S.AWL
 217          *      If P.type == CloseReq or P.type == Close or P.type == Reset,
 218          *        LSWL := S.GSR + 1, LAWL := S.GAR
 219          *      If LSWL <= P.seqno <= S.SWH
 220          *           and (P.ackno does not exist or LAWL <= P.ackno <= S.AWH),
 221          *        Update S.GSR, S.SWL, S.SWH
 222          *        If P.type != Sync,
 223          *           Update S.GAR
 224          */
 225         lswl = dp->dccps_swl;
 226         lawl = dp->dccps_awl;
 227
 228         if (dh->dccph_type == DCCP_PKT_CLOSEREQ ||
 229             dh->dccph_type == DCCP_PKT_CLOSE ||
 230             dh->dccph_type == DCCP_PKT_RESET) {
 231                 lswl = ADD48(dp->dccps_gsr, 1);
 232                 lawl = dp->dccps_gar;
 233         }
 234
 235         if (between48(seqno, lswl, dp->dccps_swh) &&
 236             (ackno == DCCP_PKT_WITHOUT_ACK_SEQ ||
 237              between48(ackno, lawl, dp->dccps_awh))) {
 238                 dccp_update_gsr(sk, seqno);
 239
 240                 if (dh->dccph_type != DCCP_PKT_SYNC &&
 241                     (ackno != DCCP_PKT_WITHOUT_ACK_SEQ))
 242                         dp->dccps_gar = ackno;
 243         } else {
 244                 unsigned long now = jiffies;
 245                 /*
 246                  *   Step 6: Check sequence numbers
 247                  *      Otherwise,
 248                  *         If P.type == Reset,
 249                  *            Send Sync packet acknowledging S.GSR
 250                  *         Otherwise,
 251                  *            Send Sync packet acknowledging P.seqno
 252                  *      Drop packet and return
 253                  *
 254                  *   These Syncs are rate-limited as per RFC 4340, 7.5.4:
 255                  *   at most 1 / (dccp_sync_rate_limit * HZ) Syncs per second.
 256                  */
 257                 if (time_before(now, (dp->dccps_rate_last +
 258                                       sysctl_dccp_sync_ratelimit)))
 259                         return 0;
 260
 261                 DCCP_WARN("DCCP: Step 6 failed for %s packet, "
 262                           "(LSWL(%llu) <= P.seqno(%llu) <= S.SWH(%llu)) and "
 263                           "(P.ackno %s or LAWL(%llu) <= P.ackno(%llu) <= S.AWH(%llu), "
 264                           "sending SYNC...\n",  dccp_packet_name(dh->dccph_type),
 265                           (unsigned long long) lswl, (unsigned long long) seqno,
 266                           (unsigned long long) dp->dccps_swh,
 267                           (ackno == DCCP_PKT_WITHOUT_ACK_SEQ) ? "doesn't exist"
 268                                                               : "exists",
 269                           (unsigned long long) lawl, (unsigned long long) ackno,
 270                           (unsigned long long) dp->dccps_awh);
 271
 272                 dp->dccps_rate_last = now;
 273
 274                 if (dh->dccph_type == DCCP_PKT_RESET)
 275                         seqno = dp->dccps_gsr;
 276                 dccp_send_sync(sk, seqno, DCCP_PKT_SYNC);
 277                 return -1;
 278         }
 279
 280         return 0;
 281 }
 282
 283 static int __dccp_rcv_established(struct sock *sk, struct sk_buff *skb,
 284                                   const struct dccp_hdr *dh, const unsigned len)
 285 {
 286         struct dccp_sock *dp = dccp_sk(sk);
 287
 288         switch (dccp_hdr(skb)->dccph_type) {
 289         case DCCP_PKT_DATAACK:
 290         case DCCP_PKT_DATA:
 291                 /*
 292                  * FIXME: schedule DATA_DROPPED (RFC 4340, 11.7.2) if and when
 293                  * - sk_shutdown == RCV_SHUTDOWN, use Code 1, "Not Listening"
 294                  * - sk_receive_queue is full, use Code 2, "Receive Buffer"
 295                  */
 296                 dccp_enqueue_skb(sk, skb);
 297                 return 0;
 298         case DCCP_PKT_ACK:
 299                 goto discard;
 300         case DCCP_PKT_RESET:
 301                 /*
 302                  *  Step 9: Process Reset
 303                  *      If P.type == Reset,
 304                  *              Tear down connection
 305                  *              S.state := TIMEWAIT
 306                  *              Set TIMEWAIT timer
 307                  *              Drop packet and return
 308                  */
 309                 dccp_rcv_reset(sk, skb);
 310                 return 0;
 311         case DCCP_PKT_CLOSEREQ:
 312                 if (dccp_rcv_closereq(sk, skb))
 313                         return 0;
 314                 goto discard;
 315         case DCCP_PKT_CLOSE:
 316                 if (dccp_rcv_close(sk, skb))
 317                         return 0;
 318                 goto discard;
 319         case DCCP_PKT_REQUEST:
 320                 /* Step 7
 321                  *   or (S.is_server and P.type == Response)
 322                  *   or (S.is_client and P.type == Request)
 323                  *   or (S.state >= OPEN and P.type == Request
 324                  *      and P.seqno >= S.OSR)
 325                  *    or (S.state >= OPEN and P.type == Response
 326                  *      and P.seqno >= S.OSR)
 327                  *    or (S.state == RESPOND and P.type == Data),
 328                  *  Send Sync packet acknowledging P.seqno
 329                  *  Drop packet and return
 330                  */
 331                 if (dp->dccps_role != DCCP_ROLE_LISTEN)
 332                         goto send_sync;
 333                 goto check_seq;
 334         case DCCP_PKT_RESPONSE:
 335                 if (dp->dccps_role != DCCP_ROLE_CLIENT)
 336                         goto send_sync;
 337 check_seq:
 338                 if (dccp_delta_seqno(dp->dccps_osr,
 339                                      DCCP_SKB_CB(skb)->dccpd_seq) >= 0) {
 340 send_sync:
 341                         dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq,
 342                                        DCCP_PKT_SYNC);
 343                 }
 344                 break;
 345         case DCCP_PKT_SYNC:
 346                 dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq,
 347                                DCCP_PKT_SYNCACK);
 348                 /*
 349                  * From RFC 4340, sec. 5.7
 350                  *
 351                  * As with DCCP-Ack packets, DCCP-Sync and DCCP-SyncAck packets
 352                  * MAY have non-zero-length application data areas, whose
 353                  * contents receivers MUST ignore.
 354                  */
 355                 goto discard;
 356         }
 357
 358         DCCP_INC_STATS_BH(DCCP_MIB_INERRS);
 359 discard:
 360         __kfree_skb(skb);
 361         return 0;
 362 }
 363
 364 int dccp_rcv_established(struct sock *sk, struct sk_buff *skb,
 365                          const struct dccp_hdr *dh, const unsigned len)
 366 {
 367         struct dccp_sock *dp = dccp_sk(sk);
 368
 369         if (dccp_check_seqno(sk, skb))
 370                 goto discard;
 371
 372         if (dccp_parse_options(sk, NULL, skb))
 373                 goto discard;
 374
 375         if (DCCP_SKB_CB(skb)->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
 376                 dccp_event_ack_recv(sk, skb);
 377
 378         if (dccp_msk(sk)->dccpms_send_ack_vector &&
 379             dccp_ackvec_add(dp->dccps_hc_rx_ackvec, sk,
 380                             DCCP_SKB_CB(skb)->dccpd_seq,
 381                             DCCP_ACKVEC_STATE_RECEIVED))
 382                 goto discard;
 383         dccp_deliver_input_to_ccids(sk, skb);
 384
 385         return __dccp_rcv_established(sk, skb, dh, len);
 386 discard:
 387         __kfree_skb(skb);
 388         return 0;
 389 }
 390
 391 EXPORT_SYMBOL_GPL(dccp_rcv_established);
 392
 393 static int dccp_rcv_request_sent_state_process(struct sock *sk,
 394                                                struct sk_buff *skb,
 395                                                const struct dccp_hdr *dh,
 396                                                const unsigned len)
 397 {
 398         /*
 399          *  Step 4: Prepare sequence numbers in REQUEST
 400          *     If S.state == REQUEST,
 401          *        If (P.type == Response or P.type == Reset)
 402          *              and S.AWL <= P.ackno <= S.AWH,
 403          *           / * Set sequence number variables corresponding to the
 404          *              other endpoint, so P will pass the tests in Step 6 * /
 405          *           Set S.GSR, S.ISR, S.SWL, S.SWH
 406          *           / * Response processing continues in Step 10; Reset
 407          *              processing continues in Step 9 * /
 408         */
 409         if (dh->dccph_type == DCCP_PKT_RESPONSE) {
 410                 const struct inet_connection_sock *icsk = inet_csk(sk);
 411                 struct dccp_sock *dp = dccp_sk(sk);
 412                 long tstamp = dccp_timestamp();
 413
 414                 /* Stop the REQUEST timer */
 415                 inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS);
 416                 BUG_TRAP(sk->sk_send_head != NULL);
 417                 __kfree_skb(sk->sk_send_head);
 418                 sk->sk_send_head = NULL;
 419
 420                 if (!between48(DCCP_SKB_CB(skb)->dccpd_ack_seq,
 421                                dp->dccps_awl, dp->dccps_awh)) {
 422                         dccp_pr_debug("invalid ackno: S.AWL=%llu, "
 423                                       "P.ackno=%llu, S.AWH=%llu \n",
 424                                       (unsigned long long)dp->dccps_awl,
 425                            (unsigned long long)DCCP_SKB_CB(skb)->dccpd_ack_seq,
 426                                       (unsigned long long)dp->dccps_awh);
 427                         goto out_invalid_packet;
 428                 }
 429
 430                 if (dccp_parse_options(sk, NULL, skb))
 431                         goto out_invalid_packet;
 432
 433                 /* Obtain usec RTT sample from SYN exchange (used by CCID 3) */
 434                 if (likely(dp->dccps_options_received.dccpor_timestamp_echo))
 435                         dp->dccps_syn_rtt = dccp_sample_rtt(sk, 10 * (tstamp -
 436                             dp->dccps_options_received.dccpor_timestamp_echo));
 437
 438                 if (dccp_msk(sk)->dccpms_send_ack_vector &&
 439                     dccp_ackvec_add(dp->dccps_hc_rx_ackvec, sk,
 440                                     DCCP_SKB_CB(skb)->dccpd_seq,
 441                                     DCCP_ACKVEC_STATE_RECEIVED))
 442                         goto out_invalid_packet; /* FIXME: change error code */
 443
 444                 dp->dccps_isr = DCCP_SKB_CB(skb)->dccpd_seq;
 445                 dccp_update_gsr(sk, dp->dccps_isr);
 446                 /*
 447                  * SWL and AWL are initially adjusted so that they are not less than
 448                  * the initial Sequence Numbers received and sent, respectively:
 449                  *      SWL := max(GSR + 1 - floor(W/4), ISR),
 450                  *      AWL := max(GSS - W' + 1, ISS).
 451                  * These adjustments MUST be applied only at the beginning of the
 452                  * connection.
 453                  *
 454                  * AWL was adjusted in dccp_v4_connect -acme
 455                  */
 456                 dccp_set_seqno(&dp->dccps_swl,
 457                                max48(dp->dccps_swl, dp->dccps_isr));
 458
 459                 dccp_sync_mss(sk, icsk->icsk_pmtu_cookie);
 460
 461                 /*
 462                  *    Step 10: Process REQUEST state (second part)
 463                  *       If S.state == REQUEST,
 464                  *        / * If we get here, P is a valid Response from the
 465                  *            server (see Step 4), and we should move to
 466                  *            PARTOPEN state. PARTOPEN means send an Ack,
 467                  *            don't send Data packets, retransmit Acks
 468                  *            periodically, and always include any Init Cookie
 469                  *            from the Response * /
 470                  *        S.state := PARTOPEN
 471                  *        Set PARTOPEN timer
 472                  *        Continue with S.state == PARTOPEN
 473                  *        / * Step 12 will send the Ack completing the
 474                  *            three-way handshake * /
 475                  */
 476                 dccp_set_state(sk, DCCP_PARTOPEN);
 477
 478                 /* Make sure socket is routed, for correct metrics. */
 479                 icsk->icsk_af_ops->rebuild_header(sk);
 480
 481                 if (!sock_flag(sk, SOCK_DEAD)) {
 482                         sk->sk_state_change(sk);
 483                         sk_wake_async(sk, SOCK_WAKE_IO, POLL_OUT);
 484                 }
 485
 486                 if (sk->sk_write_pending || icsk->icsk_ack.pingpong ||
 487                     icsk->icsk_accept_queue.rskq_defer_accept) {
 488                         /* Save one ACK. Data will be ready after
 489                          * several ticks, if write_pending is set.
 490                          *
 491                          * It may be deleted, but with this feature tcpdumps
 492                          * look so _wonderfully_ clever, that I was not able
 493                          * to stand against the temptation 8)     --ANK
 494                          */
 495                         /*
 496                          * OK, in DCCP we can as well do a similar trick, its
 497                          * even in the draft, but there is no need for us to
 498                          * schedule an ack here, as dccp_sendmsg does this for
 499                          * us, also stated in the draft. -acme
 500                          */
 501                         __kfree_skb(skb);
 502                         return 0;
 503                 }
 504                 dccp_send_ack(sk);
 505                 return -1;
 506         }
 507
 508 out_invalid_packet:
 509         /* dccp_v4_do_rcv will send a reset */
 510         DCCP_SKB_CB(skb)->dccpd_reset_code = DCCP_RESET_CODE_PACKET_ERROR;
 511         return 1;
 512 }
 513
 514 static int dccp_rcv_respond_partopen_state_process(struct sock *sk,
 515                                                    struct sk_buff *skb,
 516                                                    const struct dccp_hdr *dh,
 517                                                    const unsigned len)
 518 {
 519         int queued = 0;
 520
 521         switch (dh->dccph_type) {
 522         case DCCP_PKT_RESET:
 523                 inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
 524                 break;
 525         case DCCP_PKT_DATA:
 526                 if (sk->sk_state == DCCP_RESPOND)
 527                         break;
 528         case DCCP_PKT_DATAACK:
 529         case DCCP_PKT_ACK:
 530                 /*
 531                  * FIXME: we should be reseting the PARTOPEN (DELACK) timer
 532                  * here but only if we haven't used the DELACK timer for
 533                  * something else, like sending a delayed ack for a TIMESTAMP
 534                  * echo, etc, for now were not clearing it, sending an extra
 535                  * ACK when there is nothing else to do in DELACK is not a big
 536                  * deal after all.
 537                  */
 538
 539                 /* Stop the PARTOPEN timer */
 540                 if (sk->sk_state == DCCP_PARTOPEN)
 541                         inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
 542
 543                 dccp_sk(sk)->dccps_osr = DCCP_SKB_CB(skb)->dccpd_seq;
 544                 dccp_set_state(sk, DCCP_OPEN);
 545
 546                 if (dh->dccph_type == DCCP_PKT_DATAACK ||
 547                     dh->dccph_type == DCCP_PKT_DATA) {
 548                         __dccp_rcv_established(sk, skb, dh, len);
 549                         queued = 1; /* packet was queued
 550                                        (by __dccp_rcv_established) */
 551                 }
 552                 break;
 553         }
 554
 555         return queued;
 556 }
 557
 558 int dccp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
 559                            struct dccp_hdr *dh, unsigned len)
 560 {
 561         struct dccp_sock *dp = dccp_sk(sk);
 562         struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
 563         const int old_state = sk->sk_state;
 564         int queued = 0;
 565
 566         /*
 567          *  Step 3: Process LISTEN state
 568          *
 569          *     If S.state == LISTEN,
 570          *       If P.type == Request or P contains a valid Init Cookie option,
 571          *            (* Must scan the packet's options to check for Init
 572          *               Cookies.  Only Init Cookies are processed here,
 573          *               however; other options are processed in Step 8.  This
 574          *               scan need only be performed if the endpoint uses Init
 575          *               Cookies *)
 576          *            (* Generate a new socket and switch to that socket *)
 577          *            Set S := new socket for this port pair
 578          *            S.state = RESPOND
 579          *            Choose S.ISS (initial seqno) or set from Init Cookies
 580          *            Initialize S.GAR := S.ISS
 581          *            Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init
 582          *            Cookies Continue with S.state == RESPOND
 583          *            (* A Response packet will be generated in Step 11 *)
 584          *       Otherwise,
 585          *            Generate Reset(No Connection) unless P.type == Reset
 586          *            Drop packet and return
 587          */
 588         if (sk->sk_state == DCCP_LISTEN) {
 589                 if (dh->dccph_type == DCCP_PKT_REQUEST) {
 590                         if (inet_csk(sk)->icsk_af_ops->conn_request(sk,
 591                                                                     skb) < 0)
 592                                 return 1;
 593
 594                         /* FIXME: do congestion control initialization */
 595                         goto discard;
 596                 }
 597                 if (dh->dccph_type == DCCP_PKT_RESET)
 598                         goto discard;
 599
 600                 /* Caller (dccp_v4_do_rcv) will send Reset */
 601                 dcb->dccpd_reset_code = DCCP_RESET_CODE_NO_CONNECTION;
 602                 return 1;
 603         }
 604
 605         if (sk->sk_state != DCCP_REQUESTING) {
 606                 if (dccp_check_seqno(sk, skb))
 607                         goto discard;
 608
 609                 /*
 610                  * Step 8: Process options and mark acknowledgeable
 611                  */
 612                 if (dccp_parse_options(sk, NULL, skb))
 613                         goto discard;
 614
 615                 if (dcb->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
 616                         dccp_event_ack_recv(sk, skb);
 617
 618                 if (dccp_msk(sk)->dccpms_send_ack_vector &&
 619                     dccp_ackvec_add(dp->dccps_hc_rx_ackvec, sk,
 620                                     DCCP_SKB_CB(skb)->dccpd_seq,
 621                                     DCCP_ACKVEC_STATE_RECEIVED))
 622                         goto discard;
 623
 624                 dccp_deliver_input_to_ccids(sk, skb);
 625         }
 626
 627         /*
 628          *  Step 9: Process Reset
 629          *      If P.type == Reset,
 630          *              Tear down connection
 631          *              S.state := TIMEWAIT
 632          *              Set TIMEWAIT timer
 633          *              Drop packet and return
 634         */
 635         if (dh->dccph_type == DCCP_PKT_RESET) {
 636                 dccp_rcv_reset(sk, skb);
 637                 return 0;
 638                 /*
 639                  *   Step 7: Check for unexpected packet types
 640                  *      If (S.is_server and P.type == Response)
 641                  *          or (S.is_client and P.type == Request)
 642                  *          or (S.state == RESPOND and P.type == Data),
 643                  *        Send Sync packet acknowledging P.seqno
 644                  *        Drop packet and return
 645                  */
 646         } else if ((dp->dccps_role != DCCP_ROLE_CLIENT &&
 647                     dh->dccph_type == DCCP_PKT_RESPONSE) ||
 648                     (dp->dccps_role == DCCP_ROLE_CLIENT &&
 649                      dh->dccph_type == DCCP_PKT_REQUEST) ||
 650                     (sk->sk_state == DCCP_RESPOND &&
 651                      dh->dccph_type == DCCP_PKT_DATA)) {
 652                 dccp_send_sync(sk, dcb->dccpd_seq, DCCP_PKT_SYNC);
 653                 goto discard;
 654         } else if (dh->dccph_type == DCCP_PKT_CLOSEREQ) {
 655                 if (dccp_rcv_closereq(sk, skb))
 656                         return 0;
 657                 goto discard;
 658         } else if (dh->dccph_type == DCCP_PKT_CLOSE) {
 659                 if (dccp_rcv_close(sk, skb))
 660                         return 0;
 661                 goto discard;
 662         }
 663
 664         switch (sk->sk_state) {
 665         case DCCP_CLOSED:
 666                 dcb->dccpd_reset_code = DCCP_RESET_CODE_NO_CONNECTION;
 667                 return 1;
 668
 669         case DCCP_REQUESTING:
 670                 /* FIXME: do congestion control initialization */
 671
 672                 queued = dccp_rcv_request_sent_state_process(sk, skb, dh, len);
 673                 if (queued >= 0)
 674                         return queued;
 675
 676                 __kfree_skb(skb);
 677                 return 0;
 678
 679         case DCCP_RESPOND:
 680         case DCCP_PARTOPEN:
 681                 queued = dccp_rcv_respond_partopen_state_process(sk, skb,
 682                                                                  dh, len);
 683                 break;
 684         }
 685
 686         if (dh->dccph_type == DCCP_PKT_ACK ||
 687             dh->dccph_type == DCCP_PKT_DATAACK) {
 688                 switch (old_state) {
 689                 case DCCP_PARTOPEN:
 690                         sk->sk_state_change(sk);
 691                         sk_wake_async(sk, SOCK_WAKE_IO, POLL_OUT);
 692                         break;
 693                 }
 694         } else if (unlikely(dh->dccph_type == DCCP_PKT_SYNC)) {
 695                 dccp_send_sync(sk, dcb->dccpd_seq, DCCP_PKT_SYNCACK);
 696                 goto discard;
 697         }
 698
 699         if (!queued) {
 700 discard:
 701                 __kfree_skb(skb);
 702         }
 703         return 0;
 704 }
 705
 706 EXPORT_SYMBOL_GPL(dccp_rcv_state_process);
 707
 708 /**
 709  *  dccp_sample_rtt  -  Validate and finalise computation of RTT sample
 710  *  @delta:     number of microseconds between packet and acknowledgment
 711  *  The routine is kept generic to work in different contexts. It should be
 712  *  called immediately when the ACK used for the RTT sample arrives.
 713  */
 714 u32 dccp_sample_rtt(struct sock *sk, long delta)
 715 {
 716         /* dccpor_elapsed_time is either zeroed out or set and > 0 */
 717         delta -= dccp_sk(sk)->dccps_options_received.dccpor_elapsed_time * 10;
 718
 719         if (unlikely(delta <= 0)) {
 720                 DCCP_WARN("unusable RTT sample %ld, using min\n", delta);
 721                 return DCCP_SANE_RTT_MIN;
 722         }
 723         if (unlikely(delta > DCCP_SANE_RTT_MAX)) {
 724                 DCCP_WARN("RTT sample %ld too large, using max\n", delta);
 725                 return DCCP_SANE_RTT_MAX;
 726         }
 727
 728         return delta;
 729 }
 730
 731 EXPORT_SYMBOL_GPL(dccp_sample_rtt);