linux/net/dccp/input.c
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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#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 */
  24int sysctl_dccp_sync_ratelimit  __read_mostly = HZ / 8;
  25
  26static 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, 0);
  32}
  33
  34static 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
  47static 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
  93static 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
 127static 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
 149static 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
 163static 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
 174static 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
 189static 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
 287static 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;
 341check_seq:
 342                if (dccp_delta_seqno(dp->dccps_osr,
 343                                     DCCP_SKB_CB(skb)->dccpd_seq) >= 0) {
 344send_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);
 363discard:
 364        __kfree_skb(skb);
 365        return 0;
 366}
 367
 368int 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);
 381discard:
 382        __kfree_skb(skb);
 383        return 0;
 384}
 385
 386EXPORT_SYMBOL_GPL(dccp_rcv_established);
 387
 388static 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
 505out_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
 510unable_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
 521static 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
 574int 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) {
 702discard:
 703                __kfree_skb(skb);
 704        }
 705        return 0;
 706}
 707
 708EXPORT_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 */
 717u32 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}
 733
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