net/dccp/input.c

   1 /*
   2  *  net/dccp/input.c
   3  *
   4  *  An implementation of the DCCP protocol
   5  *  Arnaldo Carvalho de Melo <acme@conectiva.com.br>
   6  *
   7  *      This program is free software; you can redistribute it and/or
   8  *      modify it under the terms of the GNU General Public License
   9  *      as published by the Free Software Foundation; either version
  10  *      2 of the License, or (at your option) any later version.
  11  */
  12
  13 #include <linux/dccp.h>
  14 #include <linux/skbuff.h>
  15 #include <linux/slab.h>
  16
  17 #include <net/sock.h>
  18
  19 #include "ackvec.h"
  20 #include "ccid.h"
  21 #include "dccp.h"
  22
  23 /* rate-limit for syncs in reply to sequence-invalid packets; RFC 4340, 7.5.4 */
  24 int sysctl_dccp_sync_ratelimit  __read_mostly = HZ / 8;
  25
  26 static void dccp_enqueue_skb(struct sock *sk, struct sk_buff *skb)
  27 {
  28         __skb_pull(skb, dccp_hdr(skb)->dccph_doff * 4);
  29         __skb_queue_tail(&sk->sk_receive_queue, skb);
  30         skb_set_owner_r(skb, sk);
  31         sk->sk_data_ready(sk, 0);
  32 }
  33
  34 static void dccp_fin(struct sock *sk, struct sk_buff *skb)
  35 {
  36         /*
  37          * On receiving Close/CloseReq, both RD/WR shutdown are performed.
  38          * RFC 4340, 8.3 says that we MAY send further Data/DataAcks after
  39          * receiving the closing segment, but there is no guarantee that such
  40          * data will be processed at all.
  41          */
  42         sk->sk_shutdown = SHUTDOWN_MASK;
  43         sock_set_flag(sk, SOCK_DONE);
  44         dccp_enqueue_skb(sk, skb);
  45 }
  46
  47 static int dccp_rcv_close(struct sock *sk, struct sk_buff *skb)
  48 {
  49         int queued = 0;
  50
  51         switch (sk->sk_state) {
  52         /*
  53          * We ignore Close when received in one of the following states:
  54          *  - CLOSED            (may be a late or duplicate packet)
  55          *  - PASSIVE_CLOSEREQ  (the peer has sent a CloseReq earlier)
  56          *  - RESPOND           (already handled by dccp_check_req)
  57          */
  58         case DCCP_CLOSING:
  59                 /*
  60                  * Simultaneous-close: receiving a Close after sending one. This
  61                  * can happen if both client and server perform active-close and
  62                  * will result in an endless ping-pong of crossing and retrans-
  63                  * mitted Close packets, which only terminates when one of the
  64                  * nodes times out (min. 64 seconds). Quicker convergence can be
  65                  * achieved when one of the nodes acts as tie-breaker.
  66                  * This is ok as both ends are done with data transfer and each
  67                  * end is just waiting for the other to acknowledge termination.
  68                  */
  69                 if (dccp_sk(sk)->dccps_role != DCCP_ROLE_CLIENT)
  70                         break;
  71                 /* fall through */
  72         case DCCP_REQUESTING:
  73         case DCCP_ACTIVE_CLOSEREQ:
  74                 dccp_send_reset(sk, DCCP_RESET_CODE_CLOSED);
  75                 dccp_done(sk);
  76                 break;
  77         case DCCP_OPEN:
  78         case DCCP_PARTOPEN:
  79                 /* Give waiting application a chance to read pending data */
  80                 queued = 1;
  81                 dccp_fin(sk, skb);
  82                 dccp_set_state(sk, DCCP_PASSIVE_CLOSE);
  83                 /* fall through */
  84         case DCCP_PASSIVE_CLOSE:
  85                 /*
  86                  * Retransmitted Close: we have already enqueued the first one.
  87                  */
  88                 sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_HUP);
  89         }
  90         return queued;
  91 }
  92
  93 static int dccp_rcv_closereq(struct sock *sk, struct sk_buff *skb)
  94 {
  95         int queued = 0;
  96
  97         /*
  98          *   Step 7: Check for unexpected packet types
  99          *      If (S.is_server and P.type == CloseReq)
 100          *        Send Sync packet acknowledging P.seqno
 101          *        Drop packet and return
 102          */
 103         if (dccp_sk(sk)->dccps_role != DCCP_ROLE_CLIENT) {
 104                 dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq, DCCP_PKT_SYNC);
 105                 return queued;
 106         }
 107
 108         /* Step 13: process relevant Client states < CLOSEREQ */
 109         switch (sk->sk_state) {
 110         case DCCP_REQUESTING:
 111                 dccp_send_close(sk, 0);
 112                 dccp_set_state(sk, DCCP_CLOSING);
 113                 break;
 114         case DCCP_OPEN:
 115         case DCCP_PARTOPEN:
 116                 /* Give waiting application a chance to read pending data */
 117                 queued = 1;
 118                 dccp_fin(sk, skb);
 119                 dccp_set_state(sk, DCCP_PASSIVE_CLOSEREQ);
 120                 /* fall through */
 121         case DCCP_PASSIVE_CLOSEREQ:
 122                 sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_HUP);
 123         }
 124         return queued;
 125 }
 126
 127 static u16 dccp_reset_code_convert(const u8 code)
 128 {
 129         const u16 error_code[] = {
 130         [DCCP_RESET_CODE_CLOSED]             = 0,       /* normal termination */
 131         [DCCP_RESET_CODE_UNSPECIFIED]        = 0,       /* nothing known */
 132         [DCCP_RESET_CODE_ABORTED]            = ECONNRESET,
 133
 134         [DCCP_RESET_CODE_NO_CONNECTION]      = ECONNREFUSED,
 135         [DCCP_RESET_CODE_CONNECTION_REFUSED] = ECONNREFUSED,
 136         [DCCP_RESET_CODE_TOO_BUSY]           = EUSERS,
 137         [DCCP_RESET_CODE_AGGRESSION_PENALTY] = EDQUOT,
 138
 139         [DCCP_RESET_CODE_PACKET_ERROR]       = ENOMSG,
 140         [DCCP_RESET_CODE_BAD_INIT_COOKIE]    = EBADR,
 141         [DCCP_RESET_CODE_BAD_SERVICE_CODE]   = EBADRQC,
 142         [DCCP_RESET_CODE_OPTION_ERROR]       = EILSEQ,
 143         [DCCP_RESET_CODE_MANDATORY_ERROR]    = EOPNOTSUPP,
 144         };
 145
 146         return code >= DCCP_MAX_RESET_CODES ? 0 : error_code[code];
 147 }
 148
 149 static void dccp_rcv_reset(struct sock *sk, struct sk_buff *skb)
 150 {
 151         u16 err = dccp_reset_code_convert(dccp_hdr_reset(skb)->dccph_reset_code);
 152
 153         sk->sk_err = err;
 154
 155         /* Queue the equivalent of TCP fin so that dccp_recvmsg exits the loop */
 156         dccp_fin(sk, skb);
 157
 158         if (err && !sock_flag(sk, SOCK_DEAD))
 159                 sk_wake_async(sk, SOCK_WAKE_IO, POLL_ERR);
 160         dccp_time_wait(sk, DCCP_TIME_WAIT, 0);
 161 }
 162
 163 static void dccp_event_ack_recv(struct sock *sk, struct sk_buff *skb)
 164 {
 165         struct dccp_sock *dp = dccp_sk(sk);
 166
 167         if (dp->dccps_hc_rx_ackvec != NULL)
 168                 dccp_ackvec_check_rcv_ackno(dp->dccps_hc_rx_ackvec, sk,
 169                                             DCCP_SKB_CB(skb)->dccpd_ack_seq);
 170 }
 171
 172 static void dccp_deliver_input_to_ccids(struct sock *sk, struct sk_buff *skb)
 173 {
 174         const struct dccp_sock *dp = dccp_sk(sk);
 175
 176         /* Don't deliver to RX CCID when node has shut down read end. */
 177         if (!(sk->sk_shutdown & RCV_SHUTDOWN))
 178                 ccid_hc_rx_packet_recv(dp->dccps_hc_rx_ccid, sk, skb);
 179         /*
 180          * Until the TX queue has been drained, we can not honour SHUT_WR, since
 181          * we need received feedback as input to adjust congestion control.
 182          */
 183         if (sk->sk_write_queue.qlen > 0 || !(sk->sk_shutdown & SEND_SHUTDOWN))
 184                 ccid_hc_tx_packet_recv(dp->dccps_hc_tx_ccid, sk, skb);
 185 }
 186
 187 static int dccp_check_seqno(struct sock *sk, struct sk_buff *skb)
 188 {
 189         const struct dccp_hdr *dh = dccp_hdr(skb);
 190         struct dccp_sock *dp = dccp_sk(sk);
 191         u64 lswl, lawl, seqno = DCCP_SKB_CB(skb)->dccpd_seq,
 192                         ackno = DCCP_SKB_CB(skb)->dccpd_ack_seq;
 193
 194         /*
 195          *   Step 5: Prepare sequence numbers for Sync
 196          *     If P.type == Sync or P.type == SyncAck,
 197          *        If S.AWL <= P.ackno <= S.AWH and P.seqno >= S.SWL,
 198          *           / * P is valid, so update sequence number variables
 199          *               accordingly.  After this update, P will pass the tests
 200          *               in Step 6.  A SyncAck is generated if necessary in
 201          *               Step 15 * /
 202          *           Update S.GSR, S.SWL, S.SWH
 203          *        Otherwise,
 204          *           Drop packet and return
 205          */
 206         if (dh->dccph_type == DCCP_PKT_SYNC ||
 207             dh->dccph_type == DCCP_PKT_SYNCACK) {
 208                 if (between48(ackno, dp->dccps_awl, dp->dccps_awh) &&
 209                     dccp_delta_seqno(dp->dccps_swl, seqno) >= 0)
 210                         dccp_update_gsr(sk, seqno);
 211                 else
 212                         return -1;
 213         }
 214
 215         /*
 216          *   Step 6: Check sequence numbers
 217          *      Let LSWL = S.SWL and LAWL = S.AWL
 218          *      If P.type == CloseReq or P.type == Close or P.type == Reset,
 219          *        LSWL := S.GSR + 1, LAWL := S.GAR
 220          *      If LSWL <= P.seqno <= S.SWH
 221          *           and (P.ackno does not exist or LAWL <= P.ackno <= S.AWH),
 222          *        Update S.GSR, S.SWL, S.SWH
 223          *        If P.type != Sync,
 224          *           Update S.GAR
 225          */
 226         lswl = dp->dccps_swl;
 227         lawl = dp->dccps_awl;
 228
 229         if (dh->dccph_type == DCCP_PKT_CLOSEREQ ||
 230             dh->dccph_type == DCCP_PKT_CLOSE ||
 231             dh->dccph_type == DCCP_PKT_RESET) {
 232                 lswl = ADD48(dp->dccps_gsr, 1);
 233                 lawl = dp->dccps_gar;
 234         }
 235
 236         if (between48(seqno, lswl, dp->dccps_swh) &&
 237             (ackno == DCCP_PKT_WITHOUT_ACK_SEQ ||
 238              between48(ackno, lawl, dp->dccps_awh))) {
 239                 dccp_update_gsr(sk, seqno);
 240
 241                 if (dh->dccph_type != DCCP_PKT_SYNC &&
 242                     (ackno != DCCP_PKT_WITHOUT_ACK_SEQ))
 243                         dp->dccps_gar = ackno;
 244         } else {
 245                 unsigned long now = jiffies;
 246                 /*
 247                  *   Step 6: Check sequence numbers
 248                  *      Otherwise,
 249                  *         If P.type == Reset,
 250                  *            Send Sync packet acknowledging S.GSR
 251                  *         Otherwise,
 252                  *            Send Sync packet acknowledging P.seqno
 253                  *      Drop packet and return
 254                  *
 255                  *   These Syncs are rate-limited as per RFC 4340, 7.5.4:
 256                  *   at most 1 / (dccp_sync_rate_limit * HZ) Syncs per second.
 257                  */
 258                 if (time_before(now, (dp->dccps_rate_last +
 259                                       sysctl_dccp_sync_ratelimit)))
 260                         return 0;
 261
 262                 DCCP_WARN("Step 6 failed for %s packet, "
 263                           "(LSWL(%llu) <= P.seqno(%llu) <= S.SWH(%llu)) and "
 264                           "(P.ackno %s or LAWL(%llu) <= P.ackno(%llu) <= S.AWH(%llu), "
 265                           "sending SYNC...\n",  dccp_packet_name(dh->dccph_type),
 266                           (unsigned long long) lswl, (unsigned long long) seqno,
 267                           (unsigned long long) dp->dccps_swh,
 268                           (ackno == DCCP_PKT_WITHOUT_ACK_SEQ) ? "doesn't exist"
 269                                                               : "exists",
 270                           (unsigned long long) lawl, (unsigned long long) ackno,
 271                           (unsigned long long) dp->dccps_awh);
 272
 273                 dp->dccps_rate_last = now;
 274
 275                 if (dh->dccph_type == DCCP_PKT_RESET)
 276                         seqno = dp->dccps_gsr;
 277                 dccp_send_sync(sk, seqno, DCCP_PKT_SYNC);
 278                 return -1;
 279         }
 280
 281         return 0;
 282 }
 283
 284 static int __dccp_rcv_established(struct sock *sk, struct sk_buff *skb,
 285                                   const struct dccp_hdr *dh, const unsigned len)
 286 {
 287         struct dccp_sock *dp = dccp_sk(sk);
 288
 289         switch (dccp_hdr(skb)->dccph_type) {
 290         case DCCP_PKT_DATAACK:
 291         case DCCP_PKT_DATA:
 292                 /*
 293                  * FIXME: schedule DATA_DROPPED (RFC 4340, 11.7.2) if and when
 294                  * - sk_shutdown == RCV_SHUTDOWN, use Code 1, "Not Listening"
 295                  * - sk_receive_queue is full, use Code 2, "Receive Buffer"
 296                  */
 297                 dccp_enqueue_skb(sk, skb);
 298                 return 0;
 299         case DCCP_PKT_ACK:
 300                 goto discard;
 301         case DCCP_PKT_RESET:
 302                 /*
 303                  *  Step 9: Process Reset
 304                  *      If P.type == Reset,
 305                  *              Tear down connection
 306                  *              S.state := TIMEWAIT
 307                  *              Set TIMEWAIT timer
 308                  *              Drop packet and return
 309                  */
 310                 dccp_rcv_reset(sk, skb);
 311                 return 0;
 312         case DCCP_PKT_CLOSEREQ:
 313                 if (dccp_rcv_closereq(sk, skb))
 314                         return 0;
 315                 goto discard;
 316         case DCCP_PKT_CLOSE:
 317                 if (dccp_rcv_close(sk, skb))
 318                         return 0;
 319                 goto discard;
 320         case DCCP_PKT_REQUEST:
 321                 /* Step 7
 322                  *   or (S.is_server and P.type == Response)
 323                  *   or (S.is_client and P.type == Request)
 324                  *   or (S.state >= OPEN and P.type == Request
 325                  *      and P.seqno >= S.OSR)
 326                  *    or (S.state >= OPEN and P.type == Response
 327                  *      and P.seqno >= S.OSR)
 328                  *    or (S.state == RESPOND and P.type == Data),
 329                  *  Send Sync packet acknowledging P.seqno
 330                  *  Drop packet and return
 331                  */
 332                 if (dp->dccps_role != DCCP_ROLE_LISTEN)
 333                         goto send_sync;
 334                 goto check_seq;
 335         case DCCP_PKT_RESPONSE:
 336                 if (dp->dccps_role != DCCP_ROLE_CLIENT)
 337                         goto send_sync;
 338 check_seq:
 339                 if (dccp_delta_seqno(dp->dccps_osr,
 340                                      DCCP_SKB_CB(skb)->dccpd_seq) >= 0) {
 341 send_sync:
 342                         dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq,
 343                                        DCCP_PKT_SYNC);
 344                 }
 345                 break;
 346         case DCCP_PKT_SYNC:
 347                 dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq,
 348                                DCCP_PKT_SYNCACK);
 349                 /*
 350                  * From RFC 4340, sec. 5.7
 351                  *
 352                  * As with DCCP-Ack packets, DCCP-Sync and DCCP-SyncAck packets
 353                  * MAY have non-zero-length application data areas, whose
 354                  * contents receivers MUST ignore.
 355                  */
 356                 goto discard;
 357         }
 358
 359         DCCP_INC_STATS_BH(DCCP_MIB_INERRS);
 360 discard:
 361         __kfree_skb(skb);
 362         return 0;
 363 }
 364
 365 int dccp_rcv_established(struct sock *sk, struct sk_buff *skb,
 366                          const struct dccp_hdr *dh, const unsigned len)
 367 {
 368         struct dccp_sock *dp = dccp_sk(sk);
 369
 370         if (dccp_check_seqno(sk, skb))
 371                 goto discard;
 372
 373         if (dccp_parse_options(sk, NULL, skb))
 374                 return 1;
 375
 376         if (DCCP_SKB_CB(skb)->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
 377                 dccp_event_ack_recv(sk, skb);
 378
 379         if (dp->dccps_hc_rx_ackvec != NULL &&
 380             dccp_ackvec_add(dp->dccps_hc_rx_ackvec, sk,
 381                             DCCP_SKB_CB(skb)->dccpd_seq, DCCPAV_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                 if (!between48(DCCP_SKB_CB(skb)->dccpd_ack_seq,
 415                                dp->dccps_awl, dp->dccps_awh)) {
 416                         dccp_pr_debug("invalid ackno: S.AWL=%llu, "
 417                                       "P.ackno=%llu, S.AWH=%llu\n",
 418                                       (unsigned long long)dp->dccps_awl,
 419                            (unsigned long long)DCCP_SKB_CB(skb)->dccpd_ack_seq,
 420                                       (unsigned long long)dp->dccps_awh);
 421                         goto out_invalid_packet;
 422                 }
 423
 424                 /*
 425                  * If option processing (Step 8) failed, return 1 here so that
 426                  * dccp_v4_do_rcv() sends a Reset. The Reset code depends on
 427                  * the option type and is set in dccp_parse_options().
 428                  */
 429                 if (dccp_parse_options(sk, NULL, skb))
 430                         return 1;
 431
 432                 /* Obtain usec RTT sample from SYN exchange (used by TFRC). */
 433                 if (likely(dp->dccps_options_received.dccpor_timestamp_echo))
 434                         dp->dccps_syn_rtt = dccp_sample_rtt(sk, 10 * (tstamp -
 435                             dp->dccps_options_received.dccpor_timestamp_echo));
 436
 437                 /* Stop the REQUEST timer */
 438                 inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS);
 439                 WARN_ON(sk->sk_send_head == NULL);
 440                 kfree_skb(sk->sk_send_head);
 441                 sk->sk_send_head = NULL;
 442
 443                 /*
 444                  * Set ISR, GSR from packet. ISS was set in dccp_v{4,6}_connect
 445                  * and GSS in dccp_transmit_skb(). Setting AWL/AWH and SWL/SWH
 446                  * is done as part of activating the feature values below, since
 447                  * these settings depend on the local/remote Sequence Window
 448                  * features, which were undefined or not confirmed until now.
 449                  */
 450                 dp->dccps_gsr = dp->dccps_isr = DCCP_SKB_CB(skb)->dccpd_seq;
 451
 452                 dccp_sync_mss(sk, icsk->icsk_pmtu_cookie);
 453
 454                 /*
 455                  *    Step 10: Process REQUEST state (second part)
 456                  *       If S.state == REQUEST,
 457                  *        / * If we get here, P is a valid Response from the
 458                  *            server (see Step 4), and we should move to
 459                  *            PARTOPEN state. PARTOPEN means send an Ack,
 460                  *            don't send Data packets, retransmit Acks
 461                  *            periodically, and always include any Init Cookie
 462                  *            from the Response * /
 463                  *        S.state := PARTOPEN
 464                  *        Set PARTOPEN timer
 465                  *        Continue with S.state == PARTOPEN
 466                  *        / * Step 12 will send the Ack completing the
 467                  *            three-way handshake * /
 468                  */
 469                 dccp_set_state(sk, DCCP_PARTOPEN);
 470
 471                 /*
 472                  * If feature negotiation was successful, activate features now;
 473                  * an activation failure means that this host could not activate
 474                  * one ore more features (e.g. insufficient memory), which would
 475                  * leave at least one feature in an undefined state.
 476                  */
 477                 if (dccp_feat_activate_values(sk, &dp->dccps_featneg))
 478                         goto unable_to_proceed;
 479
 480                 /* Make sure socket is routed, for correct metrics. */
 481                 icsk->icsk_af_ops->rebuild_header(sk);
 482
 483                 if (!sock_flag(sk, SOCK_DEAD)) {
 484                         sk->sk_state_change(sk);
 485                         sk_wake_async(sk, SOCK_WAKE_IO, POLL_OUT);
 486                 }
 487
 488                 if (sk->sk_write_pending || icsk->icsk_ack.pingpong ||
 489                     icsk->icsk_accept_queue.rskq_defer_accept) {
 490                         /* Save one ACK. Data will be ready after
 491                          * several ticks, if write_pending is set.
 492                          *
 493                          * It may be deleted, but with this feature tcpdumps
 494                          * look so _wonderfully_ clever, that I was not able
 495                          * to stand against the temptation 8)     --ANK
 496                          */
 497                         /*
 498                          * OK, in DCCP we can as well do a similar trick, its
 499                          * even in the draft, but there is no need for us to
 500                          * schedule an ack here, as dccp_sendmsg does this for
 501                          * us, also stated in the draft. -acme
 502                          */
 503                         __kfree_skb(skb);
 504                         return 0;
 505                 }
 506                 dccp_send_ack(sk);
 507                 return -1;
 508         }
 509
 510 out_invalid_packet:
 511         /* dccp_v4_do_rcv will send a reset */
 512         DCCP_SKB_CB(skb)->dccpd_reset_code = DCCP_RESET_CODE_PACKET_ERROR;
 513         return 1;
 514
 515 unable_to_proceed:
 516         DCCP_SKB_CB(skb)->dccpd_reset_code = DCCP_RESET_CODE_ABORTED;
 517         /*
 518          * We mark this socket as no longer usable, so that the loop in
 519          * dccp_sendmsg() terminates and the application gets notified.
 520          */
 521         dccp_set_state(sk, DCCP_CLOSED);
 522         sk->sk_err = ECOMM;
 523         return 1;
 524 }
 525
 526 static int dccp_rcv_respond_partopen_state_process(struct sock *sk,
 527                                                    struct sk_buff *skb,
 528                                                    const struct dccp_hdr *dh,
 529                                                    const unsigned len)
 530 {
 531         struct dccp_sock *dp = dccp_sk(sk);
 532         u32 sample = dp->dccps_options_received.dccpor_timestamp_echo;
 533         int queued = 0;
 534
 535         switch (dh->dccph_type) {
 536         case DCCP_PKT_RESET:
 537                 inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
 538                 break;
 539         case DCCP_PKT_DATA:
 540                 if (sk->sk_state == DCCP_RESPOND)
 541                         break;
 542         case DCCP_PKT_DATAACK:
 543         case DCCP_PKT_ACK:
 544                 /*
 545                  * FIXME: we should be reseting the PARTOPEN (DELACK) timer
 546                  * here but only if we haven't used the DELACK timer for
 547                  * something else, like sending a delayed ack for a TIMESTAMP
 548                  * echo, etc, for now were not clearing it, sending an extra
 549                  * ACK when there is nothing else to do in DELACK is not a big
 550                  * deal after all.
 551                  */
 552
 553                 /* Stop the PARTOPEN timer */
 554                 if (sk->sk_state == DCCP_PARTOPEN)
 555                         inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
 556
 557                 /* Obtain usec RTT sample from SYN exchange (used by TFRC). */
 558                 if (likely(sample)) {
 559                         long delta = dccp_timestamp() - sample;
 560
 561                         dp->dccps_syn_rtt = dccp_sample_rtt(sk, 10 * delta);
 562                 }
 563
 564                 dp->dccps_osr = DCCP_SKB_CB(skb)->dccpd_seq;
 565                 dccp_set_state(sk, DCCP_OPEN);
 566
 567                 if (dh->dccph_type == DCCP_PKT_DATAACK ||
 568                     dh->dccph_type == DCCP_PKT_DATA) {
 569                         __dccp_rcv_established(sk, skb, dh, len);
 570                         queued = 1; /* packet was queued
 571                                        (by __dccp_rcv_established) */
 572                 }
 573                 break;
 574         }
 575
 576         return queued;
 577 }
 578
 579 int dccp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
 580                            struct dccp_hdr *dh, unsigned len)
 581 {
 582         struct dccp_sock *dp = dccp_sk(sk);
 583         struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
 584         const int old_state = sk->sk_state;
 585         int queued = 0;
 586
 587         /*
 588          *  Step 3: Process LISTEN state
 589          *
 590          *     If S.state == LISTEN,
 591          *       If P.type == Request or P contains a valid Init Cookie option,
 592          *            (* Must scan the packet's options to check for Init
 593          *               Cookies.  Only Init Cookies are processed here,
 594          *               however; other options are processed in Step 8.  This
 595          *               scan need only be performed if the endpoint uses Init
 596          *               Cookies *)
 597          *            (* Generate a new socket and switch to that socket *)
 598          *            Set S := new socket for this port pair
 599          *            S.state = RESPOND
 600          *            Choose S.ISS (initial seqno) or set from Init Cookies
 601          *            Initialize S.GAR := S.ISS
 602          *            Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init
 603          *            Cookies Continue with S.state == RESPOND
 604          *            (* A Response packet will be generated in Step 11 *)
 605          *       Otherwise,
 606          *            Generate Reset(No Connection) unless P.type == Reset
 607          *            Drop packet and return
 608          */
 609         if (sk->sk_state == DCCP_LISTEN) {
 610                 if (dh->dccph_type == DCCP_PKT_REQUEST) {
 611                         if (inet_csk(sk)->icsk_af_ops->conn_request(sk,
 612                                                                     skb) < 0)
 613                                 return 1;
 614                         goto discard;
 615                 }
 616                 if (dh->dccph_type == DCCP_PKT_RESET)
 617                         goto discard;
 618
 619                 /* Caller (dccp_v4_do_rcv) will send Reset */
 620                 dcb->dccpd_reset_code = DCCP_RESET_CODE_NO_CONNECTION;
 621                 return 1;
 622         }
 623
 624         if (sk->sk_state != DCCP_REQUESTING && sk->sk_state != DCCP_RESPOND) {
 625                 if (dccp_check_seqno(sk, skb))
 626                         goto discard;
 627
 628                 /*
 629                  * Step 8: Process options and mark acknowledgeable
 630                  */
 631                 if (dccp_parse_options(sk, NULL, skb))
 632                         return 1;
 633
 634                 if (dcb->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
 635                         dccp_event_ack_recv(sk, skb);
 636
 637                 if (dp->dccps_hc_rx_ackvec != NULL &&
 638                     dccp_ackvec_add(dp->dccps_hc_rx_ackvec, sk,
 639                                     DCCP_SKB_CB(skb)->dccpd_seq, DCCPAV_RECEIVED))
 640                         goto discard;
 641
 642                 dccp_deliver_input_to_ccids(sk, skb);
 643         }
 644
 645         /*
 646          *  Step 9: Process Reset
 647          *      If P.type == Reset,
 648          *              Tear down connection
 649          *              S.state := TIMEWAIT
 650          *              Set TIMEWAIT timer
 651          *              Drop packet and return
 652         */
 653         if (dh->dccph_type == DCCP_PKT_RESET) {
 654                 dccp_rcv_reset(sk, skb);
 655                 return 0;
 656                 /*
 657                  *   Step 7: Check for unexpected packet types
 658                  *      If (S.is_server and P.type == Response)
 659                  *          or (S.is_client and P.type == Request)
 660                  *          or (S.state == RESPOND and P.type == Data),
 661                  *        Send Sync packet acknowledging P.seqno
 662                  *        Drop packet and return
 663                  */
 664         } else if ((dp->dccps_role != DCCP_ROLE_CLIENT &&
 665                     dh->dccph_type == DCCP_PKT_RESPONSE) ||
 666                     (dp->dccps_role == DCCP_ROLE_CLIENT &&
 667                      dh->dccph_type == DCCP_PKT_REQUEST) ||
 668                     (sk->sk_state == DCCP_RESPOND &&
 669                      dh->dccph_type == DCCP_PKT_DATA)) {
 670                 dccp_send_sync(sk, dcb->dccpd_seq, DCCP_PKT_SYNC);
 671                 goto discard;
 672         } else if (dh->dccph_type == DCCP_PKT_CLOSEREQ) {
 673                 if (dccp_rcv_closereq(sk, skb))
 674                         return 0;
 675                 goto discard;
 676         } else if (dh->dccph_type == DCCP_PKT_CLOSE) {
 677                 if (dccp_rcv_close(sk, skb))
 678                         return 0;
 679                 goto discard;
 680         }
 681
 682         switch (sk->sk_state) {
 683         case DCCP_CLOSED:
 684                 dcb->dccpd_reset_code = DCCP_RESET_CODE_NO_CONNECTION;
 685                 return 1;
 686
 687         case DCCP_REQUESTING:
 688                 queued = dccp_rcv_request_sent_state_process(sk, skb, dh, len);
 689                 if (queued >= 0)
 690                         return queued;
 691
 692                 __kfree_skb(skb);
 693                 return 0;
 694
 695         case DCCP_RESPOND:
 696         case DCCP_PARTOPEN:
 697                 queued = dccp_rcv_respond_partopen_state_process(sk, skb,
 698                                                                  dh, len);
 699                 break;
 700         }
 701
 702         if (dh->dccph_type == DCCP_PKT_ACK ||
 703             dh->dccph_type == DCCP_PKT_DATAACK) {
 704                 switch (old_state) {
 705                 case DCCP_PARTOPEN:
 706                         sk->sk_state_change(sk);
 707                         sk_wake_async(sk, SOCK_WAKE_IO, POLL_OUT);
 708                         break;
 709                 }
 710         } else if (unlikely(dh->dccph_type == DCCP_PKT_SYNC)) {
 711                 dccp_send_sync(sk, dcb->dccpd_seq, DCCP_PKT_SYNCACK);
 712                 goto discard;
 713         }
 714
 715         if (!queued) {
 716 discard:
 717                 __kfree_skb(skb);
 718         }
 719         return 0;
 720 }
 721
 722 EXPORT_SYMBOL_GPL(dccp_rcv_state_process);
 723
 724 /**
 725  *  dccp_sample_rtt  -  Validate and finalise computation of RTT sample
 726  *  @delta:     number of microseconds between packet and acknowledgment
 727  *  The routine is kept generic to work in different contexts. It should be
 728  *  called immediately when the ACK used for the RTT sample arrives.
 729  */
 730 u32 dccp_sample_rtt(struct sock *sk, long delta)
 731 {
 732         /* dccpor_elapsed_time is either zeroed out or set and > 0 */
 733         delta -= dccp_sk(sk)->dccps_options_received.dccpor_elapsed_time * 10;
 734
 735         if (unlikely(delta <= 0)) {
 736                 DCCP_WARN("unusable RTT sample %ld, using min\n", delta);
 737                 return DCCP_SANE_RTT_MIN;
 738         }
 739         if (unlikely(delta > DCCP_SANE_RTT_MAX)) {
 740                 DCCP_WARN("RTT sample %ld too large, using max\n", delta);
 741                 return DCCP_SANE_RTT_MAX;
 742         }
 743
 744         return delta;
 745 }