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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_fin(struct sock *sk, struct sk_buff *skb)
  26 {
  27         sk->sk_shutdown |= RCV_SHUTDOWN;
  28         sock_set_flag(sk, SOCK_DONE);
  29         __skb_pull(skb, dccp_hdr(skb)->dccph_doff * 4);
  30         __skb_queue_tail(&sk->sk_receive_queue, skb);
  31         skb_set_owner_r(skb, sk);
  32         sk->sk_data_ready(sk, 0);
  33 }
  34
  35 static int dccp_rcv_close(struct sock *sk, struct sk_buff *skb)
  36 {
  37         int queued = 0;
  38
  39         switch (sk->sk_state) {
  40         /*
  41          * We ignore Close when received in one of the following states:
  42          *  - CLOSED            (may be a late or duplicate packet)
  43          *  - PASSIVE_CLOSEREQ  (the peer has sent a CloseReq earlier)
  44          *  - RESPOND           (already handled by dccp_check_req)
  45          */
  46         case DCCP_CLOSING:
  47                 /*
  48                  * Simultaneous-close: receiving a Close after sending one. This
  49                  * can happen if both client and server perform active-close and
  50                  * will result in an endless ping-pong of crossing and retrans-
  51                  * mitted Close packets, which only terminates when one of the
  52                  * nodes times out (min. 64 seconds). Quicker convergence can be
  53                  * achieved when one of the nodes acts as tie-breaker.
  54                  * This is ok as both ends are done with data transfer and each
  55                  * end is just waiting for the other to acknowledge termination.
  56                  */
  57                 if (dccp_sk(sk)->dccps_role != DCCP_ROLE_CLIENT)
  58                         break;
  59                 /* fall through */
  60         case DCCP_REQUESTING:
  61         case DCCP_ACTIVE_CLOSEREQ:
  62                 dccp_send_reset(sk, DCCP_RESET_CODE_CLOSED);
  63                 dccp_done(sk);
  64                 break;
  65         case DCCP_OPEN:
  66         case DCCP_PARTOPEN:
  67                 /* Give waiting application a chance to read pending data */
  68                 queued = 1;
  69                 dccp_fin(sk, skb);
  70                 dccp_set_state(sk, DCCP_PASSIVE_CLOSE);
  71                 /* fall through */
  72         case DCCP_PASSIVE_CLOSE:
  73                 /*
  74                  * Retransmitted Close: we have already enqueued the first one.
  75                  */
  76                 sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_HUP);
  77         }
  78         return queued;
  79 }
  80
  81 static int dccp_rcv_closereq(struct sock *sk, struct sk_buff *skb)
  82 {
  83         int queued = 0;
  84
  85         /*
  86          *   Step 7: Check for unexpected packet types
  87          *      If (S.is_server and P.type == CloseReq)
  88          *        Send Sync packet acknowledging P.seqno
  89          *        Drop packet and return
  90          */
  91         if (dccp_sk(sk)->dccps_role != DCCP_ROLE_CLIENT) {
  92                 dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq, DCCP_PKT_SYNC);
  93                 return queued;
  94         }
  95
  96         /* Step 13: process relevant Client states < CLOSEREQ */
  97         switch (sk->sk_state) {
  98         case DCCP_REQUESTING:
  99                 dccp_send_close(sk, 0);
 100                 dccp_set_state(sk, DCCP_CLOSING);
 101                 break;
 102         case DCCP_OPEN:
 103         case DCCP_PARTOPEN:
 104                 /* Give waiting application a chance to read pending data */
 105                 queued = 1;
 106                 dccp_fin(sk, skb);
 107                 dccp_set_state(sk, DCCP_PASSIVE_CLOSEREQ);
 108                 /* fall through */
 109         case DCCP_PASSIVE_CLOSEREQ:
 110                 sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_HUP);
 111         }
 112         return queued;
 113 }
 114
 115 static u8 dccp_reset_code_convert(const u8 code)
 116 {
 117         const u8 error_code[] = {
 118         [DCCP_RESET_CODE_CLOSED]             = 0,       /* normal termination */
 119         [DCCP_RESET_CODE_UNSPECIFIED]        = 0,       /* nothing known */
 120         [DCCP_RESET_CODE_ABORTED]            = ECONNRESET,
 121
 122         [DCCP_RESET_CODE_NO_CONNECTION]      = ECONNREFUSED,
 123         [DCCP_RESET_CODE_CONNECTION_REFUSED] = ECONNREFUSED,
 124         [DCCP_RESET_CODE_TOO_BUSY]           = EUSERS,
 125         [DCCP_RESET_CODE_AGGRESSION_PENALTY] = EDQUOT,
 126
 127         [DCCP_RESET_CODE_PACKET_ERROR]       = ENOMSG,
 128         [DCCP_RESET_CODE_BAD_INIT_COOKIE]    = EBADR,
 129         [DCCP_RESET_CODE_BAD_SERVICE_CODE]   = EBADRQC,
 130         [DCCP_RESET_CODE_OPTION_ERROR]       = EILSEQ,
 131         [DCCP_RESET_CODE_MANDATORY_ERROR]    = EOPNOTSUPP,
 132         };
 133
 134         return code >= DCCP_MAX_RESET_CODES ? 0 : error_code[code];
 135 }
 136
 137 static void dccp_rcv_reset(struct sock *sk, struct sk_buff *skb)
 138 {
 139         u8 err = dccp_reset_code_convert(dccp_hdr_reset(skb)->dccph_reset_code);
 140
 141         sk->sk_err = err;
 142
 143         /* Queue the equivalent of TCP fin so that dccp_recvmsg exits the loop */
 144         dccp_fin(sk, skb);
 145
 146         if (err && !sock_flag(sk, SOCK_DEAD))
 147                 sk_wake_async(sk, SOCK_WAKE_IO, POLL_ERR);
 148         dccp_time_wait(sk, DCCP_TIME_WAIT, 0);
 149 }
 150
 151 static void dccp_event_ack_recv(struct sock *sk, struct sk_buff *skb)
 152 {
 153         struct dccp_sock *dp = dccp_sk(sk);
 154
 155         if (dccp_msk(sk)->dccpms_send_ack_vector)
 156                 dccp_ackvec_check_rcv_ackno(dp->dccps_hc_rx_ackvec, sk,
 157                                             DCCP_SKB_CB(skb)->dccpd_ack_seq);
 158 }
 159
 160 static void dccp_deliver_input_to_ccids(struct sock *sk, struct sk_buff *skb)
 161 {
 162         const struct dccp_sock *dp = dccp_sk(sk);
 163
 164         /* Don't deliver to RX CCID when node has shut down read end. */
 165         if (!(sk->sk_shutdown & RCV_SHUTDOWN))
 166                 ccid_hc_rx_packet_recv(dp->dccps_hc_rx_ccid, sk, skb);
 167         /*
 168          * Until the TX queue has been drained, we can not honour SHUT_WR, since
 169          * we need received feedback as input to adjust congestion control.
 170          */
 171         if (sk->sk_write_queue.qlen > 0 || !(sk->sk_shutdown & SEND_SHUTDOWN))
 172                 ccid_hc_tx_packet_recv(dp->dccps_hc_tx_ccid, sk, skb);
 173 }
 174
 175 static int dccp_check_seqno(struct sock *sk, struct sk_buff *skb)
 176 {
 177         const struct dccp_hdr *dh = dccp_hdr(skb);
 178         struct dccp_sock *dp = dccp_sk(sk);
 179         u64 lswl, lawl, seqno = DCCP_SKB_CB(skb)->dccpd_seq,
 180                         ackno = DCCP_SKB_CB(skb)->dccpd_ack_seq;
 181
 182         /*
 183          *   Step 5: Prepare sequence numbers for Sync
 184          *     If P.type == Sync or P.type == SyncAck,
 185          *        If S.AWL <= P.ackno <= S.AWH and P.seqno >= S.SWL,
 186          *           / * P is valid, so update sequence number variables
 187          *               accordingly.  After this update, P will pass the tests
 188          *               in Step 6.  A SyncAck is generated if necessary in
 189          *               Step 15 * /
 190          *           Update S.GSR, S.SWL, S.SWH
 191          *        Otherwise,
 192          *           Drop packet and return
 193          */
 194         if (dh->dccph_type == DCCP_PKT_SYNC ||
 195             dh->dccph_type == DCCP_PKT_SYNCACK) {
 196                 if (between48(ackno, dp->dccps_awl, dp->dccps_awh) &&
 197                     dccp_delta_seqno(dp->dccps_swl, seqno) >= 0)
 198                         dccp_update_gsr(sk, seqno);
 199                 else
 200                         return -1;
 201         }
 202
 203         /*
 204          *   Step 6: Check sequence numbers
 205          *      Let LSWL = S.SWL and LAWL = S.AWL
 206          *      If P.type == CloseReq or P.type == Close or P.type == Reset,
 207          *        LSWL := S.GSR + 1, LAWL := S.GAR
 208          *      If LSWL <= P.seqno <= S.SWH
 209          *           and (P.ackno does not exist or LAWL <= P.ackno <= S.AWH),
 210          *        Update S.GSR, S.SWL, S.SWH
 211          *        If P.type != Sync,
 212          *           Update S.GAR
 213          */
 214         lswl = dp->dccps_swl;
 215         lawl = dp->dccps_awl;
 216
 217         if (dh->dccph_type == DCCP_PKT_CLOSEREQ ||
 218             dh->dccph_type == DCCP_PKT_CLOSE ||
 219             dh->dccph_type == DCCP_PKT_RESET) {
 220                 lswl = ADD48(dp->dccps_gsr, 1);
 221                 lawl = dp->dccps_gar;
 222         }
 223
 224         if (between48(seqno, lswl, dp->dccps_swh) &&
 225             (ackno == DCCP_PKT_WITHOUT_ACK_SEQ ||
 226              between48(ackno, lawl, dp->dccps_awh))) {
 227                 dccp_update_gsr(sk, seqno);
 228
 229                 if (dh->dccph_type != DCCP_PKT_SYNC &&
 230                     (ackno != DCCP_PKT_WITHOUT_ACK_SEQ))
 231                         dp->dccps_gar = ackno;
 232         } else {
 233                 unsigned long now = jiffies;
 234                 /*
 235                  *   Step 6: Check sequence numbers
 236                  *      Otherwise,
 237                  *         If P.type == Reset,
 238                  *            Send Sync packet acknowledging S.GSR
 239                  *         Otherwise,
 240                  *            Send Sync packet acknowledging P.seqno
 241                  *      Drop packet and return
 242                  *
 243                  *   These Syncs are rate-limited as per RFC 4340, 7.5.4:
 244                  *   at most 1 / (dccp_sync_rate_limit * HZ) Syncs per second.
 245                  */
 246                 if (time_before(now, (dp->dccps_rate_last +
 247                                       sysctl_dccp_sync_ratelimit)))
 248                         return 0;
 249
 250                 DCCP_WARN("DCCP: Step 6 failed for %s packet, "
 251                           "(LSWL(%llu) <= P.seqno(%llu) <= S.SWH(%llu)) and "
 252                           "(P.ackno %s or LAWL(%llu) <= P.ackno(%llu) <= S.AWH(%llu), "
 253                           "sending SYNC...\n",  dccp_packet_name(dh->dccph_type),
 254                           (unsigned long long) lswl, (unsigned long long) seqno,
 255                           (unsigned long long) dp->dccps_swh,
 256                           (ackno == DCCP_PKT_WITHOUT_ACK_SEQ) ? "doesn't exist"
 257                                                               : "exists",
 258                           (unsigned long long) lawl, (unsigned long long) ackno,
 259                           (unsigned long long) dp->dccps_awh);
 260
 261                 dp->dccps_rate_last = now;
 262
 263                 if (dh->dccph_type == DCCP_PKT_RESET)
 264                         seqno = dp->dccps_gsr;
 265                 dccp_send_sync(sk, seqno, DCCP_PKT_SYNC);
 266                 return -1;
 267         }
 268
 269         return 0;
 270 }
 271
 272 static int __dccp_rcv_established(struct sock *sk, struct sk_buff *skb,
 273                                   const struct dccp_hdr *dh, const unsigned len)
 274 {
 275         struct dccp_sock *dp = dccp_sk(sk);
 276
 277         switch (dccp_hdr(skb)->dccph_type) {
 278         case DCCP_PKT_DATAACK:
 279         case DCCP_PKT_DATA:
 280                 /*
 281                  * FIXME: schedule DATA_DROPPED (RFC 4340, 11.7.2) if and when
 282                  * - sk_shutdown == RCV_SHUTDOWN, use Code 1, "Not Listening"
 283                  * - sk_receive_queue is full, use Code 2, "Receive Buffer"
 284                  */
 285                 __skb_pull(skb, dh->dccph_doff * 4);
 286                 __skb_queue_tail(&sk->sk_receive_queue, skb);
 287                 skb_set_owner_r(skb, sk);
 288                 sk->sk_data_ready(sk, 0);
 289                 return 0;
 290         case DCCP_PKT_ACK:
 291                 goto discard;
 292         case DCCP_PKT_RESET:
 293                 /*
 294                  *  Step 9: Process Reset
 295                  *      If P.type == Reset,
 296                  *              Tear down connection
 297                  *              S.state := TIMEWAIT
 298                  *              Set TIMEWAIT timer
 299                  *              Drop packet and return
 300                  */
 301                 dccp_rcv_reset(sk, skb);
 302                 return 0;
 303         case DCCP_PKT_CLOSEREQ:
 304                 if (dccp_rcv_closereq(sk, skb))
 305                         return 0;
 306                 goto discard;
 307         case DCCP_PKT_CLOSE:
 308                 if (dccp_rcv_close(sk, skb))
 309                         return 0;
 310                 goto discard;
 311         case DCCP_PKT_REQUEST:
 312                 /* Step 7
 313                  *   or (S.is_server and P.type == Response)
 314                  *   or (S.is_client and P.type == Request)
 315                  *   or (S.state >= OPEN and P.type == Request
 316                  *      and P.seqno >= S.OSR)
 317                  *    or (S.state >= OPEN and P.type == Response
 318                  *      and P.seqno >= S.OSR)
 319                  *    or (S.state == RESPOND and P.type == Data),
 320                  *  Send Sync packet acknowledging P.seqno
 321                  *  Drop packet and return
 322                  */
 323                 if (dp->dccps_role != DCCP_ROLE_LISTEN)
 324                         goto send_sync;
 325                 goto check_seq;
 326         case DCCP_PKT_RESPONSE:
 327                 if (dp->dccps_role != DCCP_ROLE_CLIENT)
 328                         goto send_sync;
 329 check_seq:
 330                 if (dccp_delta_seqno(dp->dccps_osr,
 331                                      DCCP_SKB_CB(skb)->dccpd_seq) >= 0) {
 332 send_sync:
 333                         dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq,
 334                                        DCCP_PKT_SYNC);
 335                 }
 336                 break;
 337         case DCCP_PKT_SYNC:
 338                 dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq,
 339                                DCCP_PKT_SYNCACK);
 340                 /*
 341                  * From RFC 4340, sec. 5.7
 342                  *
 343                  * As with DCCP-Ack packets, DCCP-Sync and DCCP-SyncAck packets
 344                  * MAY have non-zero-length application data areas, whose
 345                  * contents receivers MUST ignore.
 346                  */
 347                 goto discard;
 348         }
 349
 350         DCCP_INC_STATS_BH(DCCP_MIB_INERRS);
 351 discard:
 352         __kfree_skb(skb);
 353         return 0;
 354 }
 355
 356 int dccp_rcv_established(struct sock *sk, struct sk_buff *skb,
 357                          const struct dccp_hdr *dh, const unsigned len)
 358 {
 359         struct dccp_sock *dp = dccp_sk(sk);
 360
 361         if (dccp_check_seqno(sk, skb))
 362                 goto discard;
 363
 364         if (dccp_parse_options(sk, skb))
 365                 goto discard;
 366
 367         if (DCCP_SKB_CB(skb)->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
 368                 dccp_event_ack_recv(sk, skb);
 369
 370         if (dccp_msk(sk)->dccpms_send_ack_vector &&
 371             dccp_ackvec_add(dp->dccps_hc_rx_ackvec, sk,
 372                             DCCP_SKB_CB(skb)->dccpd_seq,
 373                             DCCP_ACKVEC_STATE_RECEIVED))
 374                 goto discard;
 375         dccp_deliver_input_to_ccids(sk, skb);
 376
 377         return __dccp_rcv_established(sk, skb, dh, len);
 378 discard:
 379         __kfree_skb(skb);
 380         return 0;
 381 }
 382
 383 EXPORT_SYMBOL_GPL(dccp_rcv_established);
 384
 385 static int dccp_rcv_request_sent_state_process(struct sock *sk,
 386                                                struct sk_buff *skb,
 387                                                const struct dccp_hdr *dh,
 388                                                const unsigned len)
 389 {
 390         /*
 391          *  Step 4: Prepare sequence numbers in REQUEST
 392          *     If S.state == REQUEST,
 393          *        If (P.type == Response or P.type == Reset)
 394          *              and S.AWL <= P.ackno <= S.AWH,
 395          *           / * Set sequence number variables corresponding to the
 396          *              other endpoint, so P will pass the tests in Step 6 * /
 397          *           Set S.GSR, S.ISR, S.SWL, S.SWH
 398          *           / * Response processing continues in Step 10; Reset
 399          *              processing continues in Step 9 * /
 400         */
 401         if (dh->dccph_type == DCCP_PKT_RESPONSE) {
 402                 const struct inet_connection_sock *icsk = inet_csk(sk);
 403                 struct dccp_sock *dp = dccp_sk(sk);
 404                 long tstamp = dccp_timestamp();
 405
 406                 /* Stop the REQUEST timer */
 407                 inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS);
 408                 BUG_TRAP(sk->sk_send_head != NULL);
 409                 __kfree_skb(sk->sk_send_head);
 410                 sk->sk_send_head = NULL;
 411
 412                 if (!between48(DCCP_SKB_CB(skb)->dccpd_ack_seq,
 413                                dp->dccps_awl, dp->dccps_awh)) {
 414                         dccp_pr_debug("invalid ackno: S.AWL=%llu, "
 415                                       "P.ackno=%llu, S.AWH=%llu \n",
 416                                       (unsigned long long)dp->dccps_awl,
 417                            (unsigned long long)DCCP_SKB_CB(skb)->dccpd_ack_seq,
 418                                       (unsigned long long)dp->dccps_awh);
 419                         goto out_invalid_packet;
 420                 }
 421
 422                 if (dccp_parse_options(sk, skb))
 423                         goto out_invalid_packet;
 424
 425                 /* Obtain usec RTT sample from SYN exchange (used by CCID 3) */
 426                 if (likely(dp->dccps_options_received.dccpor_timestamp_echo))
 427                         dp->dccps_syn_rtt = dccp_sample_rtt(sk, 10 * (tstamp -
 428                             dp->dccps_options_received.dccpor_timestamp_echo));
 429
 430                 if (dccp_msk(sk)->dccpms_send_ack_vector &&
 431                     dccp_ackvec_add(dp->dccps_hc_rx_ackvec, sk,
 432                                     DCCP_SKB_CB(skb)->dccpd_seq,
 433                                     DCCP_ACKVEC_STATE_RECEIVED))
 434                         goto out_invalid_packet; /* FIXME: change error code */
 435
 436                 dp->dccps_isr = DCCP_SKB_CB(skb)->dccpd_seq;
 437                 dccp_update_gsr(sk, dp->dccps_isr);
 438                 /*
 439                  * SWL and AWL are initially adjusted so that they are not less than
 440                  * the initial Sequence Numbers received and sent, respectively:
 441                  *      SWL := max(GSR + 1 - floor(W/4), ISR),
 442                  *      AWL := max(GSS - W' + 1, ISS).
 443                  * These adjustments MUST be applied only at the beginning of the
 444                  * connection.
 445                  *
 446                  * AWL was adjusted in dccp_v4_connect -acme
 447                  */
 448                 dccp_set_seqno(&dp->dccps_swl,
 449                                max48(dp->dccps_swl, dp->dccps_isr));
 450
 451                 dccp_sync_mss(sk, icsk->icsk_pmtu_cookie);
 452
 453                 /*
 454                  *    Step 10: Process REQUEST state (second part)
 455                  *       If S.state == REQUEST,
 456                  *        / * If we get here, P is a valid Response from the
 457                  *            server (see Step 4), and we should move to
 458                  *            PARTOPEN state. PARTOPEN means send an Ack,
 459                  *            don't send Data packets, retransmit Acks
 460                  *            periodically, and always include any Init Cookie
 461                  *            from the Response * /
 462                  *        S.state := PARTOPEN
 463                  *        Set PARTOPEN timer
 464                  *        Continue with S.state == PARTOPEN
 465                  *        / * Step 12 will send the Ack completing the
 466                  *            three-way handshake * /
 467                  */
 468                 dccp_set_state(sk, DCCP_PARTOPEN);
 469
 470                 /* Make sure socket is routed, for correct metrics. */
 471                 icsk->icsk_af_ops->rebuild_header(sk);
 472
 473                 if (!sock_flag(sk, SOCK_DEAD)) {
 474                         sk->sk_state_change(sk);
 475                         sk_wake_async(sk, SOCK_WAKE_IO, POLL_OUT);
 476                 }
 477
 478                 if (sk->sk_write_pending || icsk->icsk_ack.pingpong ||
 479                     icsk->icsk_accept_queue.rskq_defer_accept) {
 480                         /* Save one ACK. Data will be ready after
 481                          * several ticks, if write_pending is set.
 482                          *
 483                          * It may be deleted, but with this feature tcpdumps
 484                          * look so _wonderfully_ clever, that I was not able
 485                          * to stand against the temptation 8)     --ANK
 486                          */
 487                         /*
 488                          * OK, in DCCP we can as well do a similar trick, its
 489                          * even in the draft, but there is no need for us to
 490                          * schedule an ack here, as dccp_sendmsg does this for
 491                          * us, also stated in the draft. -acme
 492                          */
 493                         __kfree_skb(skb);
 494                         return 0;
 495                 }
 496                 dccp_send_ack(sk);
 497                 return -1;
 498         }
 499
 500 out_invalid_packet:
 501         /* dccp_v4_do_rcv will send a reset */
 502         DCCP_SKB_CB(skb)->dccpd_reset_code = DCCP_RESET_CODE_PACKET_ERROR;
 503         return 1;
 504 }
 505
 506 static int dccp_rcv_respond_partopen_state_process(struct sock *sk,
 507                                                    struct sk_buff *skb,
 508                                                    const struct dccp_hdr *dh,
 509                                                    const unsigned len)
 510 {
 511         int queued = 0;
 512
 513         switch (dh->dccph_type) {
 514         case DCCP_PKT_RESET:
 515                 inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
 516                 break;
 517         case DCCP_PKT_DATA:
 518                 if (sk->sk_state == DCCP_RESPOND)
 519                         break;
 520         case DCCP_PKT_DATAACK:
 521         case DCCP_PKT_ACK:
 522                 /*
 523                  * FIXME: we should be reseting the PARTOPEN (DELACK) timer
 524                  * here but only if we haven't used the DELACK timer for
 525                  * something else, like sending a delayed ack for a TIMESTAMP
 526                  * echo, etc, for now were not clearing it, sending an extra
 527                  * ACK when there is nothing else to do in DELACK is not a big
 528                  * deal after all.
 529                  */
 530
 531                 /* Stop the PARTOPEN timer */
 532                 if (sk->sk_state == DCCP_PARTOPEN)
 533                         inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
 534
 535                 dccp_sk(sk)->dccps_osr = DCCP_SKB_CB(skb)->dccpd_seq;
 536                 dccp_set_state(sk, DCCP_OPEN);
 537
 538                 if (dh->dccph_type == DCCP_PKT_DATAACK ||
 539                     dh->dccph_type == DCCP_PKT_DATA) {
 540                         __dccp_rcv_established(sk, skb, dh, len);
 541                         queued = 1; /* packet was queued
 542                                        (by __dccp_rcv_established) */
 543                 }
 544                 break;
 545         }
 546
 547         return queued;
 548 }
 549
 550 int dccp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
 551                            struct dccp_hdr *dh, unsigned len)
 552 {
 553         struct dccp_sock *dp = dccp_sk(sk);
 554         struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
 555         const int old_state = sk->sk_state;
 556         int queued = 0;
 557
 558         /*
 559          *  Step 3: Process LISTEN state
 560          *
 561          *     If S.state == LISTEN,
 562          *       If P.type == Request or P contains a valid Init Cookie option,
 563          *            (* Must scan the packet's options to check for Init
 564          *               Cookies.  Only Init Cookies are processed here,
 565          *               however; other options are processed in Step 8.  This
 566          *               scan need only be performed if the endpoint uses Init
 567          *               Cookies *)
 568          *            (* Generate a new socket and switch to that socket *)
 569          *            Set S := new socket for this port pair
 570          *            S.state = RESPOND
 571          *            Choose S.ISS (initial seqno) or set from Init Cookies
 572          *            Initialize S.GAR := S.ISS
 573          *            Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init
 574          *            Cookies Continue with S.state == RESPOND
 575          *            (* A Response packet will be generated in Step 11 *)
 576          *       Otherwise,
 577          *            Generate Reset(No Connection) unless P.type == Reset
 578          *            Drop packet and return
 579          */
 580         if (sk->sk_state == DCCP_LISTEN) {
 581                 if (dh->dccph_type == DCCP_PKT_REQUEST) {
 582                         if (inet_csk(sk)->icsk_af_ops->conn_request(sk,
 583                                                                     skb) < 0)
 584                                 return 1;
 585
 586                         /* FIXME: do congestion control initialization */
 587                         goto discard;
 588                 }
 589                 if (dh->dccph_type == DCCP_PKT_RESET)
 590                         goto discard;
 591
 592                 /* Caller (dccp_v4_do_rcv) will send Reset */
 593                 dcb->dccpd_reset_code = DCCP_RESET_CODE_NO_CONNECTION;
 594                 return 1;
 595         }
 596
 597         if (sk->sk_state != DCCP_REQUESTING) {
 598                 if (dccp_check_seqno(sk, skb))
 599                         goto discard;
 600
 601                 /*
 602                  * Step 8: Process options and mark acknowledgeable
 603                  */
 604                 if (dccp_parse_options(sk, skb))
 605                         goto discard;
 606
 607                 if (dcb->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
 608                         dccp_event_ack_recv(sk, skb);
 609
 610                 if (dccp_msk(sk)->dccpms_send_ack_vector &&
 611                     dccp_ackvec_add(dp->dccps_hc_rx_ackvec, sk,
 612                                     DCCP_SKB_CB(skb)->dccpd_seq,
 613                                     DCCP_ACKVEC_STATE_RECEIVED))
 614                         goto discard;
 615
 616                 dccp_deliver_input_to_ccids(sk, skb);
 617         }
 618
 619         /*
 620          *  Step 9: Process Reset
 621          *      If P.type == Reset,
 622          *              Tear down connection
 623          *              S.state := TIMEWAIT
 624          *              Set TIMEWAIT timer
 625          *              Drop packet and return
 626         */
 627         if (dh->dccph_type == DCCP_PKT_RESET) {
 628                 dccp_rcv_reset(sk, skb);
 629                 return 0;
 630                 /*
 631                  *   Step 7: Check for unexpected packet types
 632                  *      If (S.is_server and P.type == Response)
 633                  *          or (S.is_client and P.type == Request)
 634                  *          or (S.state == RESPOND and P.type == Data),
 635                  *        Send Sync packet acknowledging P.seqno
 636                  *        Drop packet and return
 637                  */
 638         } else if ((dp->dccps_role != DCCP_ROLE_CLIENT &&
 639                     dh->dccph_type == DCCP_PKT_RESPONSE) ||
 640                     (dp->dccps_role == DCCP_ROLE_CLIENT &&
 641                      dh->dccph_type == DCCP_PKT_REQUEST) ||
 642                     (sk->sk_state == DCCP_RESPOND &&
 643                      dh->dccph_type == DCCP_PKT_DATA)) {
 644                 dccp_send_sync(sk, dcb->dccpd_seq, DCCP_PKT_SYNC);
 645                 goto discard;
 646         } else if (dh->dccph_type == DCCP_PKT_CLOSEREQ) {
 647                 if (dccp_rcv_closereq(sk, skb))
 648                         return 0;
 649                 goto discard;
 650         } else if (dh->dccph_type == DCCP_PKT_CLOSE) {
 651                 if (dccp_rcv_close(sk, skb))
 652                         return 0;
 653                 goto discard;
 654         }
 655
 656         switch (sk->sk_state) {
 657         case DCCP_CLOSED:
 658                 dcb->dccpd_reset_code = DCCP_RESET_CODE_NO_CONNECTION;
 659                 return 1;
 660
 661         case DCCP_REQUESTING:
 662                 /* FIXME: do congestion control initialization */
 663
 664                 queued = dccp_rcv_request_sent_state_process(sk, skb, dh, len);
 665                 if (queued >= 0)
 666                         return queued;
 667
 668                 __kfree_skb(skb);
 669                 return 0;
 670
 671         case DCCP_RESPOND:
 672         case DCCP_PARTOPEN:
 673                 queued = dccp_rcv_respond_partopen_state_process(sk, skb,
 674                                                                  dh, len);
 675                 break;
 676         }
 677
 678         if (dh->dccph_type == DCCP_PKT_ACK ||
 679             dh->dccph_type == DCCP_PKT_DATAACK) {
 680                 switch (old_state) {
 681                 case DCCP_PARTOPEN:
 682                         sk->sk_state_change(sk);
 683                         sk_wake_async(sk, SOCK_WAKE_IO, POLL_OUT);
 684                         break;
 685                 }
 686         } else if (unlikely(dh->dccph_type == DCCP_PKT_SYNC)) {
 687                 dccp_send_sync(sk, dcb->dccpd_seq, DCCP_PKT_SYNCACK);
 688                 goto discard;
 689         }
 690
 691         if (!queued) {
 692 discard:
 693                 __kfree_skb(skb);
 694         }
 695         return 0;
 696 }
 697
 698 EXPORT_SYMBOL_GPL(dccp_rcv_state_process);
 699
 700 /**
 701  *  dccp_sample_rtt  -  Validate and finalise computation of RTT sample
 702  *  @delta:     number of microseconds between packet and acknowledgment
 703  *  The routine is kept generic to work in different contexts. It should be
 704  *  called immediately when the ACK used for the RTT sample arrives.
 705  */
 706 u32 dccp_sample_rtt(struct sock *sk, long delta)
 707 {
 708         /* dccpor_elapsed_time is either zeroed out or set and > 0 */
 709         delta -= dccp_sk(sk)->dccps_options_received.dccpor_elapsed_time * 10;
 710
 711         if (unlikely(delta <= 0)) {
 712                 DCCP_WARN("unusable RTT sample %ld, using min\n", delta);
 713                 return DCCP_SANE_RTT_MIN;
 714         }
 715         if (unlikely(delta > DCCP_SANE_RTT_MAX)) {
 716                 DCCP_WARN("RTT sample %ld too large, using max\n", delta);
 717                 return DCCP_SANE_RTT_MAX;
 718         }
 719
 720         return delta;
 721 }
 722
 723 EXPORT_SYMBOL_GPL(dccp_sample_rtt);