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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/config.h>
  14 #include <linux/dccp.h>
  15 #include <linux/skbuff.h>
  16
  17 #include <net/sock.h>
  18
  19 #include "ccid.h"
  20 #include "dccp.h"
  21
  22 static void dccp_fin(struct sock *sk, struct sk_buff *skb)
  23 {
  24         sk->sk_shutdown |= RCV_SHUTDOWN;
  25         sock_set_flag(sk, SOCK_DONE);
  26         __skb_pull(skb, dccp_hdr(skb)->dccph_doff * 4);
  27         __skb_queue_tail(&sk->sk_receive_queue, skb);
  28         skb_set_owner_r(skb, sk);
  29         sk->sk_data_ready(sk, 0);
  30 }
  31
  32 static void dccp_rcv_close(struct sock *sk, struct sk_buff *skb)
  33 {
  34         switch (sk->sk_state) {
  35         case DCCP_PARTOPEN:
  36         case DCCP_OPEN:
  37                 dccp_v4_send_reset(sk, DCCP_RESET_CODE_CLOSED);
  38                 dccp_fin(sk, skb);
  39                 dccp_set_state(sk, DCCP_CLOSED);
  40                 break;
  41         }
  42 }
  43
  44 static void dccp_rcv_closereq(struct sock *sk, struct sk_buff *skb)
  45 {
  46         /*
  47          *   Step 7: Check for unexpected packet types
  48          *      If (S.is_server and P.type == CloseReq)
  49          *        Send Sync packet acknowledging P.seqno
  50          *        Drop packet and return
  51          */
  52         if (dccp_sk(sk)->dccps_role != DCCP_ROLE_CLIENT) {
  53                 dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq);
  54                 return;
  55         }
  56
  57         switch (sk->sk_state) {
  58         case DCCP_PARTOPEN:
  59         case DCCP_OPEN:
  60                 dccp_set_state(sk, DCCP_CLOSING);
  61                 dccp_send_close(sk);
  62                 break;
  63         }
  64 }
  65
  66 static inline void dccp_event_ack_recv(struct sock *sk, struct sk_buff *skb)
  67 {
  68         struct dccp_sock *dp = dccp_sk(sk);
  69
  70         if (dp->dccps_options.dccpo_send_ack_vector)
  71                 dccp_ackpkts_check_rcv_ackno(dp->dccps_hc_rx_ackpkts, sk,
  72                                              DCCP_SKB_CB(skb)->dccpd_ack_seq);
  73 }
  74
  75 static int dccp_check_seqno(struct sock *sk, struct sk_buff *skb)
  76 {
  77         const struct dccp_hdr *dh = dccp_hdr(skb);
  78         struct dccp_sock *dp = dccp_sk(sk);
  79         u64 lswl = dp->dccps_swl;
  80         u64 lawl = dp->dccps_awl;
  81
  82         /*
  83          *   Step 5: Prepare sequence numbers for Sync
  84          *     If P.type == Sync or P.type == SyncAck,
  85          *        If S.AWL <= P.ackno <= S.AWH and P.seqno >= S.SWL,
  86          *           / * P is valid, so update sequence number variables
  87          *               accordingly.  After this update, P will pass the tests
  88          *               in Step 6.  A SyncAck is generated if necessary in
  89          *               Step 15 * /
  90          *           Update S.GSR, S.SWL, S.SWH
  91          *        Otherwise,
  92          *           Drop packet and return
  93          */
  94         if (dh->dccph_type == DCCP_PKT_SYNC ||
  95             dh->dccph_type == DCCP_PKT_SYNCACK) {
  96                 if (between48(DCCP_SKB_CB(skb)->dccpd_ack_seq, dp->dccps_awl, dp->dccps_awh) &&
  97                     !before48(DCCP_SKB_CB(skb)->dccpd_seq, dp->dccps_swl))
  98                         dccp_update_gsr(sk, DCCP_SKB_CB(skb)->dccpd_seq);
  99                 else
 100                         return -1;
 101         /*
 102          *   Step 6: Check sequence numbers
 103          *      Let LSWL = S.SWL and LAWL = S.AWL
 104          *      If P.type == CloseReq or P.type == Close or P.type == Reset,
 105          *        LSWL := S.GSR + 1, LAWL := S.GAR
 106          *      If LSWL <= P.seqno <= S.SWH
 107          *           and (P.ackno does not exist or LAWL <= P.ackno <= S.AWH),
 108          *        Update S.GSR, S.SWL, S.SWH
 109          *        If P.type != Sync,
 110          *           Update S.GAR
 111          *      Otherwise,
 112          *        Send Sync packet acknowledging P.seqno
 113          *        Drop packet and return
 114          */
 115         } else if (dh->dccph_type == DCCP_PKT_CLOSEREQ ||
 116                    dh->dccph_type == DCCP_PKT_CLOSE ||
 117                    dh->dccph_type == DCCP_PKT_RESET) {
 118                 lswl = dp->dccps_gsr;
 119                 dccp_inc_seqno(&lswl);
 120                 lawl = dp->dccps_gar;
 121         }
 122
 123         if (between48(DCCP_SKB_CB(skb)->dccpd_seq, lswl, dp->dccps_swh) &&
 124             (DCCP_SKB_CB(skb)->dccpd_ack_seq == DCCP_PKT_WITHOUT_ACK_SEQ ||
 125              between48(DCCP_SKB_CB(skb)->dccpd_ack_seq, lawl, dp->dccps_awh))) {
 126                 dccp_update_gsr(sk, DCCP_SKB_CB(skb)->dccpd_seq);
 127
 128                 if (dh->dccph_type != DCCP_PKT_SYNC &&
 129                     DCCP_SKB_CB(skb)->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
 130                         dp->dccps_gar = DCCP_SKB_CB(skb)->dccpd_ack_seq;
 131         } else {
 132                 dccp_pr_debug("Step 6 failed, sending SYNC...\n");
 133                 dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq);
 134                 return -1;
 135         }
 136
 137         return 0;
 138 }
 139
 140 int dccp_rcv_established(struct sock *sk, struct sk_buff *skb,
 141                          const struct dccp_hdr *dh, const unsigned len)
 142 {
 143         struct dccp_sock *dp = dccp_sk(sk);
 144
 145         if (dccp_check_seqno(sk, skb))
 146                 goto discard;
 147
 148         if (dccp_parse_options(sk, skb))
 149                 goto discard;
 150
 151         if (DCCP_SKB_CB(skb)->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
 152                 dccp_event_ack_recv(sk, skb);
 153
 154         /*
 155          * FIXME: check ECN to see if we should use
 156          * DCCP_ACKPKTS_STATE_ECN_MARKED
 157          */
 158         if (dp->dccps_options.dccpo_send_ack_vector) {
 159                 struct dccp_ackpkts *ap = dp->dccps_hc_rx_ackpkts;
 160
 161                 if (dccp_ackpkts_add(dp->dccps_hc_rx_ackpkts,
 162                                      DCCP_SKB_CB(skb)->dccpd_seq,
 163                                      DCCP_ACKPKTS_STATE_RECEIVED)) {
 164                         LIMIT_NETDEBUG(KERN_INFO "DCCP: acknowledgeable packets buffer full!\n");
 165                         ap->dccpap_ack_seqno = DCCP_MAX_SEQNO + 1;
 166                         inet_csk_schedule_ack(sk);
 167                         inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK, TCP_DELACK_MIN, TCP_RTO_MAX);
 168                         goto discard;
 169                 }
 170
 171                 /*
 172                  * FIXME: this activation is probably wrong, have to study more
 173                  * TCP delack machinery and how it fits into DCCP draft, but
 174                  * for now it kinda "works" 8)
 175                  */
 176                 if (!inet_csk_ack_scheduled(sk)) {
 177                         inet_csk_schedule_ack(sk);
 178                         inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK, 5 * HZ, TCP_RTO_MAX);
 179                 }
 180         }
 181
 182         ccid_hc_rx_packet_recv(dp->dccps_hc_rx_ccid, sk, skb);
 183         ccid_hc_tx_packet_recv(dp->dccps_hc_tx_ccid, sk, skb);
 184
 185         switch (dccp_hdr(skb)->dccph_type) {
 186         case DCCP_PKT_DATAACK:
 187         case DCCP_PKT_DATA:
 188                 /*
 189                  * FIXME: check if sk_receive_queue is full, schedule DATA_DROPPED option
 190                  * if it is.
 191                  */
 192                 __skb_pull(skb, dh->dccph_doff * 4);
 193                 __skb_queue_tail(&sk->sk_receive_queue, skb);
 194                 skb_set_owner_r(skb, sk);
 195                 sk->sk_data_ready(sk, 0);
 196                 return 0;
 197         case DCCP_PKT_ACK:
 198                 goto discard;
 199         case DCCP_PKT_RESET:
 200                 /*
 201                  *  Step 9: Process Reset
 202                  *      If P.type == Reset,
 203                  *              Tear down connection
 204                  *              S.state := TIMEWAIT
 205                  *              Set TIMEWAIT timer
 206                  *              Drop packet and return
 207                 */
 208                 dccp_fin(sk, skb);
 209                 dccp_time_wait(sk, DCCP_TIME_WAIT, 0);
 210                 return 0;
 211         case DCCP_PKT_CLOSEREQ:
 212                 dccp_rcv_closereq(sk, skb);
 213                 goto discard;
 214         case DCCP_PKT_CLOSE:
 215                 dccp_rcv_close(sk, skb);
 216                 return 0;
 217         case DCCP_PKT_REQUEST:
 218                 /* Step 7
 219                  *   or (S.is_server and P.type == Response)
 220                  *   or (S.is_client and P.type == Request)
 221                  *   or (S.state >= OPEN and P.type == Request
 222                  *      and P.seqno >= S.OSR)
 223                  *    or (S.state >= OPEN and P.type == Response
 224                  *      and P.seqno >= S.OSR)
 225                  *    or (S.state == RESPOND and P.type == Data),
 226                  *  Send Sync packet acknowledging P.seqno
 227                  *  Drop packet and return
 228                  */
 229                 if (dp->dccps_role != DCCP_ROLE_LISTEN)
 230                         goto send_sync;
 231                 goto check_seq;
 232         case DCCP_PKT_RESPONSE:
 233                 if (dp->dccps_role != DCCP_ROLE_CLIENT)
 234                         goto send_sync;
 235 check_seq:
 236                 if (!before48(DCCP_SKB_CB(skb)->dccpd_seq, dp->dccps_osr)) {
 237 send_sync:
 238                         dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq);
 239                 }
 240                 break;
 241         }
 242
 243         DCCP_INC_STATS_BH(DCCP_MIB_INERRS);
 244 discard:
 245         __kfree_skb(skb);
 246         return 0;
 247 }
 248
 249 static int dccp_rcv_request_sent_state_process(struct sock *sk,
 250                                                struct sk_buff *skb,
 251                                                const struct dccp_hdr *dh,
 252                                                const unsigned len)
 253 {
 254         /*
 255          *  Step 4: Prepare sequence numbers in REQUEST
 256          *     If S.state == REQUEST,
 257          *        If (P.type == Response or P.type == Reset)
 258          *              and S.AWL <= P.ackno <= S.AWH,
 259          *           / * Set sequence number variables corresponding to the
 260          *              other endpoint, so P will pass the tests in Step 6 * /
 261          *           Set S.GSR, S.ISR, S.SWL, S.SWH
 262          *           / * Response processing continues in Step 10; Reset
 263          *              processing continues in Step 9 * /
 264         */
 265         if (dh->dccph_type == DCCP_PKT_RESPONSE) {
 266                 const struct inet_connection_sock *icsk = inet_csk(sk);
 267                 struct dccp_sock *dp = dccp_sk(sk);
 268
 269                 /* Stop the REQUEST timer */
 270                 inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS);
 271                 BUG_TRAP(sk->sk_send_head != NULL);
 272                 __kfree_skb(sk->sk_send_head);
 273                 sk->sk_send_head = NULL;
 274
 275                 if (!between48(DCCP_SKB_CB(skb)->dccpd_ack_seq, dp->dccps_awl, dp->dccps_awh)) {
 276                         dccp_pr_debug("invalid ackno: S.AWL=%llu, P.ackno=%llu, S.AWH=%llu \n",
 277                                       (unsigned long long) dp->dccps_awl,
 278                                       (unsigned long long) DCCP_SKB_CB(skb)->dccpd_ack_seq,
 279                                       (unsigned long long) dp->dccps_awh);
 280                         goto out_invalid_packet;
 281                 }
 282
 283                 dp->dccps_isr = DCCP_SKB_CB(skb)->dccpd_seq;
 284                 dccp_update_gsr(sk, DCCP_SKB_CB(skb)->dccpd_seq);
 285
 286                 if (ccid_hc_rx_init(dp->dccps_hc_rx_ccid, sk) != 0 ||
 287                     ccid_hc_tx_init(dp->dccps_hc_tx_ccid, sk) != 0) {
 288                         ccid_hc_rx_exit(dp->dccps_hc_rx_ccid, sk);
 289                         ccid_hc_tx_exit(dp->dccps_hc_tx_ccid, sk);
 290                         /* FIXME: send appropriate RESET code */
 291                         goto out_invalid_packet;
 292                 }
 293
 294                 dccp_sync_mss(sk, dp->dccps_pmtu_cookie);
 295
 296                 /*
 297                  *    Step 10: Process REQUEST state (second part)
 298                  *       If S.state == REQUEST,
 299                  *        / * If we get here, P is a valid Response from the server (see
 300                  *           Step 4), and we should move to PARTOPEN state.  PARTOPEN
 301                  *           means send an Ack, don't send Data packets, retransmit
 302                  *           Acks periodically, and always include any Init Cookie from
 303                  *           the Response * /
 304                  *        S.state := PARTOPEN
 305                  *        Set PARTOPEN timer
 306                  *        Continue with S.state == PARTOPEN
 307                  *        / * Step 12 will send the Ack completing the three-way
 308                  *           handshake * /
 309                  */
 310                 dccp_set_state(sk, DCCP_PARTOPEN);
 311
 312                 /* Make sure socket is routed, for correct metrics. */
 313                 inet_sk_rebuild_header(sk);
 314
 315                 if (!sock_flag(sk, SOCK_DEAD)) {
 316                         sk->sk_state_change(sk);
 317                         sk_wake_async(sk, 0, POLL_OUT);
 318                 }
 319
 320                 if (sk->sk_write_pending || icsk->icsk_ack.pingpong ||
 321                     icsk->icsk_accept_queue.rskq_defer_accept) {
 322                         /* Save one ACK. Data will be ready after
 323                          * several ticks, if write_pending is set.
 324                          *
 325                          * It may be deleted, but with this feature tcpdumps
 326                          * look so _wonderfully_ clever, that I was not able
 327                          * to stand against the temptation 8)     --ANK
 328                          */
 329                         /*
 330                          * OK, in DCCP we can as well do a similar trick, its
 331                          * even in the draft, but there is no need for us to
 332                          * schedule an ack here, as dccp_sendmsg does this for
 333                          * us, also stated in the draft. -acme
 334                          */
 335                         __kfree_skb(skb);
 336                         return 0;
 337                 }
 338                 dccp_send_ack(sk);
 339                 return -1;
 340         }
 341
 342 out_invalid_packet:
 343         return 1; /* dccp_v4_do_rcv will send a reset, but...
 344                      FIXME: the reset code should be DCCP_RESET_CODE_PACKET_ERROR  */
 345 }
 346
 347 static int dccp_rcv_respond_partopen_state_process(struct sock *sk,
 348                                                    struct sk_buff *skb,
 349                                                    const struct dccp_hdr *dh,
 350                                                    const unsigned len)
 351 {
 352         int queued = 0;
 353
 354         switch (dh->dccph_type) {
 355         case DCCP_PKT_RESET:
 356                 inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
 357                 break;
 358         case DCCP_PKT_DATAACK:
 359         case DCCP_PKT_ACK:
 360                 /*
 361                  * FIXME: we should be reseting the PARTOPEN (DELACK) timer here,
 362                  * but only if we haven't used the DELACK timer for something else,
 363                  * like sending a delayed ack for a TIMESTAMP echo, etc, for now
 364                  * were not clearing it, sending an extra ACK when there is nothing
 365                  * else to do in DELACK is not a big deal after all.
 366                  */
 367
 368                 /* Stop the PARTOPEN timer */
 369                 if (sk->sk_state == DCCP_PARTOPEN)
 370                         inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
 371
 372                 dccp_sk(sk)->dccps_osr = DCCP_SKB_CB(skb)->dccpd_seq;
 373                 dccp_set_state(sk, DCCP_OPEN);
 374
 375                 if (dh->dccph_type == DCCP_PKT_DATAACK) {
 376                         dccp_rcv_established(sk, skb, dh, len);
 377                         queued = 1; /* packet was queued (by dccp_rcv_established) */
 378                 }
 379                 break;
 380         }
 381
 382         return queued;
 383 }
 384
 385 int dccp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
 386                            struct dccp_hdr *dh, unsigned len)
 387 {
 388         struct dccp_sock *dp = dccp_sk(sk);
 389         const int old_state = sk->sk_state;
 390         int queued = 0;
 391
 392         if (sk->sk_state != DCCP_LISTEN && sk->sk_state != DCCP_REQUESTING) {
 393                 if (dccp_check_seqno(sk, skb))
 394                         goto discard;
 395
 396                 /*
 397                  * Step 8: Process options and mark acknowledgeable
 398                  */
 399                 if (dccp_parse_options(sk, skb))
 400                         goto discard;
 401
 402                 if (DCCP_SKB_CB(skb)->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
 403                         dccp_event_ack_recv(sk, skb);
 404
 405                 ccid_hc_rx_packet_recv(dp->dccps_hc_rx_ccid, sk, skb);
 406                 ccid_hc_tx_packet_recv(dp->dccps_hc_tx_ccid, sk, skb);
 407
 408                 /*
 409                  * FIXME: check ECN to see if we should use
 410                  * DCCP_ACKPKTS_STATE_ECN_MARKED
 411                  */
 412                 if (dp->dccps_options.dccpo_send_ack_vector) {
 413                         if (dccp_ackpkts_add(dp->dccps_hc_rx_ackpkts,
 414                                              DCCP_SKB_CB(skb)->dccpd_seq,
 415                                              DCCP_ACKPKTS_STATE_RECEIVED))
 416                                 goto discard;
 417                         /*
 418                          * FIXME: this activation is probably wrong, have to study more
 419                          * TCP delack machinery and how it fits into DCCP draft, but
 420                          * for now it kinda "works" 8)
 421                          */
 422                         if (dp->dccps_hc_rx_ackpkts->dccpap_ack_seqno == DCCP_MAX_SEQNO + 1 &&
 423                             !inet_csk_ack_scheduled(sk)) {
 424                                 inet_csk_schedule_ack(sk);
 425                                 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK, TCP_DELACK_MIN, TCP_RTO_MAX);
 426                         }
 427                 }
 428         }
 429
 430         /*
 431          *  Step 9: Process Reset
 432          *      If P.type == Reset,
 433          *              Tear down connection
 434          *              S.state := TIMEWAIT
 435          *              Set TIMEWAIT timer
 436          *              Drop packet and return
 437         */
 438         if (dh->dccph_type == DCCP_PKT_RESET) {
 439                 /* Queue the equivalent of TCP fin so that dccp_recvmsg exits the loop */
 440                 dccp_fin(sk, skb);
 441                 dccp_time_wait(sk, DCCP_TIME_WAIT, 0);
 442                 return 0;
 443                 /*
 444                  *   Step 7: Check for unexpected packet types
 445                  *      If (S.is_server and P.type == CloseReq)
 446                  *          or (S.is_server and P.type == Response)
 447                  *          or (S.is_client and P.type == Request)
 448                  *          or (S.state == RESPOND and P.type == Data),
 449                  *        Send Sync packet acknowledging P.seqno
 450                  *        Drop packet and return
 451                  */
 452         } else if ((dp->dccps_role != DCCP_ROLE_CLIENT &&
 453                     (dh->dccph_type == DCCP_PKT_RESPONSE || dh->dccph_type == DCCP_PKT_CLOSEREQ)) ||
 454                     (dp->dccps_role == DCCP_ROLE_CLIENT &&
 455                      dh->dccph_type == DCCP_PKT_REQUEST) ||
 456                     (sk->sk_state == DCCP_RESPOND && dh->dccph_type == DCCP_PKT_DATA)) {
 457                 dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq);
 458                 goto discard;
 459         }
 460
 461         switch (sk->sk_state) {
 462         case DCCP_CLOSED:
 463                 return 1;
 464
 465         case DCCP_LISTEN:
 466                 if (dh->dccph_type == DCCP_PKT_ACK ||
 467                     dh->dccph_type == DCCP_PKT_DATAACK)
 468                         return 1;
 469
 470                 if (dh->dccph_type == DCCP_PKT_RESET)
 471                         goto discard;
 472
 473                 if (dh->dccph_type == DCCP_PKT_REQUEST) {
 474                         if (dccp_v4_conn_request(sk, skb) < 0)
 475                                 return 1;
 476
 477                         /* FIXME: do congestion control initialization */
 478                         goto discard;
 479                 }
 480                 goto discard;
 481
 482         case DCCP_REQUESTING:
 483                 /* FIXME: do congestion control initialization */
 484
 485                 queued = dccp_rcv_request_sent_state_process(sk, skb, dh, len);
 486                 if (queued >= 0)
 487                         return queued;
 488
 489                 __kfree_skb(skb);
 490                 return 0;
 491
 492         case DCCP_RESPOND:
 493         case DCCP_PARTOPEN:
 494                 queued = dccp_rcv_respond_partopen_state_process(sk, skb, dh, len);
 495                 break;
 496         }
 497
 498         if (dh->dccph_type == DCCP_PKT_ACK || dh->dccph_type == DCCP_PKT_DATAACK) {
 499                 switch (old_state) {
 500                 case DCCP_PARTOPEN:
 501                         sk->sk_state_change(sk);
 502                         sk_wake_async(sk, 0, POLL_OUT);
 503                         break;
 504                 }
 505         }
 506
 507         if (!queued) {
 508 discard:
 509                 __kfree_skb(skb);
 510         }
 511         return 0;
 512 }