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/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,
  97                               dp->dccps_awl, dp->dccps_awh) &&
  98                     !before48(DCCP_SKB_CB(skb)->dccpd_seq, dp->dccps_swl))
  99                         dccp_update_gsr(sk, DCCP_SKB_CB(skb)->dccpd_seq);
 100                 else
 101                         return -1;
 102         /*
 103          *   Step 6: Check sequence numbers
 104          *      Let LSWL = S.SWL and LAWL = S.AWL
 105          *      If P.type == CloseReq or P.type == Close or P.type == Reset,
 106          *        LSWL := S.GSR + 1, LAWL := S.GAR
 107          *      If LSWL <= P.seqno <= S.SWH
 108          *           and (P.ackno does not exist or LAWL <= P.ackno <= S.AWH),
 109          *        Update S.GSR, S.SWL, S.SWH
 110          *        If P.type != Sync,
 111          *           Update S.GAR
 112          *      Otherwise,
 113          *        Send Sync packet acknowledging P.seqno
 114          *        Drop packet and return
 115          */
 116         } else if (dh->dccph_type == DCCP_PKT_CLOSEREQ ||
 117                    dh->dccph_type == DCCP_PKT_CLOSE ||
 118                    dh->dccph_type == DCCP_PKT_RESET) {
 119                 lswl = dp->dccps_gsr;
 120                 dccp_inc_seqno(&lswl);
 121                 lawl = dp->dccps_gar;
 122         }
 123
 124         if (between48(DCCP_SKB_CB(skb)->dccpd_seq, lswl, dp->dccps_swh) &&
 125             (DCCP_SKB_CB(skb)->dccpd_ack_seq == DCCP_PKT_WITHOUT_ACK_SEQ ||
 126              between48(DCCP_SKB_CB(skb)->dccpd_ack_seq,
 127                        lawl, dp->dccps_awh))) {
 128                 dccp_update_gsr(sk, DCCP_SKB_CB(skb)->dccpd_seq);
 129
 130                 if (dh->dccph_type != DCCP_PKT_SYNC &&
 131                     (DCCP_SKB_CB(skb)->dccpd_ack_seq !=
 132                      DCCP_PKT_WITHOUT_ACK_SEQ))
 133                         dp->dccps_gar = DCCP_SKB_CB(skb)->dccpd_ack_seq;
 134         } else {
 135                 dccp_pr_debug("Step 6 failed, sending SYNC...\n");
 136                 dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq);
 137                 return -1;
 138         }
 139
 140         return 0;
 141 }
 142
 143 int dccp_rcv_established(struct sock *sk, struct sk_buff *skb,
 144                          const struct dccp_hdr *dh, const unsigned len)
 145 {
 146         struct dccp_sock *dp = dccp_sk(sk);
 147
 148         if (dccp_check_seqno(sk, skb))
 149                 goto discard;
 150
 151         if (dccp_parse_options(sk, skb))
 152                 goto discard;
 153
 154         if (DCCP_SKB_CB(skb)->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
 155                 dccp_event_ack_recv(sk, skb);
 156
 157         /*
 158          * FIXME: check ECN to see if we should use
 159          * DCCP_ACKPKTS_STATE_ECN_MARKED
 160          */
 161         if (dp->dccps_options.dccpo_send_ack_vector) {
 162                 struct dccp_ackpkts *ap = dp->dccps_hc_rx_ackpkts;
 163
 164                 if (dccp_ackpkts_add(dp->dccps_hc_rx_ackpkts,
 165                                      DCCP_SKB_CB(skb)->dccpd_seq,
 166                                      DCCP_ACKPKTS_STATE_RECEIVED)) {
 167                         LIMIT_NETDEBUG(KERN_INFO "DCCP: acknowledgeable "
 168                                                  "packets buffer full!\n");
 169                         ap->dccpap_ack_seqno = DCCP_MAX_SEQNO + 1;
 170                         inet_csk_schedule_ack(sk);
 171                         inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
 172                                                   TCP_DELACK_MIN,
 173                                                   DCCP_RTO_MAX);
 174                         goto discard;
 175                 }
 176
 177                 /*
 178                  * FIXME: this activation is probably wrong, have to study more
 179                  * TCP delack machinery and how it fits into DCCP draft, but
 180                  * for now it kinda "works" 8)
 181                  */
 182                 if (!inet_csk_ack_scheduled(sk)) {
 183                         inet_csk_schedule_ack(sk);
 184                         inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK, 5 * HZ,
 185                                                   DCCP_RTO_MAX);
 186                 }
 187         }
 188
 189         ccid_hc_rx_packet_recv(dp->dccps_hc_rx_ccid, sk, skb);
 190         ccid_hc_tx_packet_recv(dp->dccps_hc_tx_ccid, sk, skb);
 191
 192         switch (dccp_hdr(skb)->dccph_type) {
 193         case DCCP_PKT_DATAACK:
 194         case DCCP_PKT_DATA:
 195                 /*
 196                  * FIXME: check if sk_receive_queue is full, schedule DATA_DROPPED
 197                  * option if it is.
 198                  */
 199                 __skb_pull(skb, dh->dccph_doff * 4);
 200                 __skb_queue_tail(&sk->sk_receive_queue, skb);
 201                 skb_set_owner_r(skb, sk);
 202                 sk->sk_data_ready(sk, 0);
 203                 return 0;
 204         case DCCP_PKT_ACK:
 205                 goto discard;
 206         case DCCP_PKT_RESET:
 207                 /*
 208                  *  Step 9: Process Reset
 209                  *      If P.type == Reset,
 210                  *              Tear down connection
 211                  *              S.state := TIMEWAIT
 212                  *              Set TIMEWAIT timer
 213                  *              Drop packet and return
 214                 */
 215                 dccp_fin(sk, skb);
 216                 dccp_time_wait(sk, DCCP_TIME_WAIT, 0);
 217                 return 0;
 218         case DCCP_PKT_CLOSEREQ:
 219                 dccp_rcv_closereq(sk, skb);
 220                 goto discard;
 221         case DCCP_PKT_CLOSE:
 222                 dccp_rcv_close(sk, skb);
 223                 return 0;
 224         case DCCP_PKT_REQUEST:
 225                 /* Step 7
 226                  *   or (S.is_server and P.type == Response)
 227                  *   or (S.is_client and P.type == Request)
 228                  *   or (S.state >= OPEN and P.type == Request
 229                  *      and P.seqno >= S.OSR)
 230                  *    or (S.state >= OPEN and P.type == Response
 231                  *      and P.seqno >= S.OSR)
 232                  *    or (S.state == RESPOND and P.type == Data),
 233                  *  Send Sync packet acknowledging P.seqno
 234                  *  Drop packet and return
 235                  */
 236                 if (dp->dccps_role != DCCP_ROLE_LISTEN)
 237                         goto send_sync;
 238                 goto check_seq;
 239         case DCCP_PKT_RESPONSE:
 240                 if (dp->dccps_role != DCCP_ROLE_CLIENT)
 241                         goto send_sync;
 242 check_seq:
 243                 if (!before48(DCCP_SKB_CB(skb)->dccpd_seq, dp->dccps_osr)) {
 244 send_sync:
 245                         dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq);
 246                 }
 247                 break;
 248         }
 249
 250         DCCP_INC_STATS_BH(DCCP_MIB_INERRS);
 251 discard:
 252         __kfree_skb(skb);
 253         return 0;
 254 }
 255
 256 static int dccp_rcv_request_sent_state_process(struct sock *sk,
 257                                                struct sk_buff *skb,
 258                                                const struct dccp_hdr *dh,
 259                                                const unsigned len)
 260 {
 261         /*
 262          *  Step 4: Prepare sequence numbers in REQUEST
 263          *     If S.state == REQUEST,
 264          *        If (P.type == Response or P.type == Reset)
 265          *              and S.AWL <= P.ackno <= S.AWH,
 266          *           / * Set sequence number variables corresponding to the
 267          *              other endpoint, so P will pass the tests in Step 6 * /
 268          *           Set S.GSR, S.ISR, S.SWL, S.SWH
 269          *           / * Response processing continues in Step 10; Reset
 270          *              processing continues in Step 9 * /
 271         */
 272         if (dh->dccph_type == DCCP_PKT_RESPONSE) {
 273                 const struct inet_connection_sock *icsk = inet_csk(sk);
 274                 struct dccp_sock *dp = dccp_sk(sk);
 275
 276                 /* Stop the REQUEST timer */
 277                 inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS);
 278                 BUG_TRAP(sk->sk_send_head != NULL);
 279                 __kfree_skb(sk->sk_send_head);
 280                 sk->sk_send_head = NULL;
 281
 282                 if (!between48(DCCP_SKB_CB(skb)->dccpd_ack_seq,
 283                                dp->dccps_awl, dp->dccps_awh)) {
 284                         dccp_pr_debug("invalid ackno: S.AWL=%llu, "
 285                                       "P.ackno=%llu, S.AWH=%llu \n",
 286                                       (unsigned long long)dp->dccps_awl,
 287                            (unsigned long long)DCCP_SKB_CB(skb)->dccpd_ack_seq,
 288                                       (unsigned long long)dp->dccps_awh);
 289                         goto out_invalid_packet;
 290                 }
 291
 292                 dp->dccps_isr = DCCP_SKB_CB(skb)->dccpd_seq;
 293                 dccp_update_gsr(sk, DCCP_SKB_CB(skb)->dccpd_seq);
 294
 295                 if (ccid_hc_rx_init(dp->dccps_hc_rx_ccid, sk) != 0 ||
 296                     ccid_hc_tx_init(dp->dccps_hc_tx_ccid, sk) != 0) {
 297                         ccid_hc_rx_exit(dp->dccps_hc_rx_ccid, sk);
 298                         ccid_hc_tx_exit(dp->dccps_hc_tx_ccid, sk);
 299                         /* FIXME: send appropriate RESET code */
 300                         goto out_invalid_packet;
 301                 }
 302
 303                 dccp_sync_mss(sk, dp->dccps_pmtu_cookie);
 304
 305                 /*
 306                  *    Step 10: Process REQUEST state (second part)
 307                  *       If S.state == REQUEST,
 308                  *        / * If we get here, P is a valid Response from the
 309                  *            server (see Step 4), and we should move to
 310                  *            PARTOPEN state. PARTOPEN means send an Ack,
 311                  *            don't send Data packets, retransmit Acks
 312                  *            periodically, and always include any Init Cookie
 313                  *            from the Response * /
 314                  *        S.state := PARTOPEN
 315                  *        Set PARTOPEN timer
 316                  *        Continue with S.state == PARTOPEN
 317                  *        / * Step 12 will send the Ack completing the
 318                  *            three-way handshake * /
 319                  */
 320                 dccp_set_state(sk, DCCP_PARTOPEN);
 321
 322                 /* Make sure socket is routed, for correct metrics. */
 323                 inet_sk_rebuild_header(sk);
 324
 325                 if (!sock_flag(sk, SOCK_DEAD)) {
 326                         sk->sk_state_change(sk);
 327                         sk_wake_async(sk, 0, POLL_OUT);
 328                 }
 329
 330                 if (sk->sk_write_pending || icsk->icsk_ack.pingpong ||
 331                     icsk->icsk_accept_queue.rskq_defer_accept) {
 332                         /* Save one ACK. Data will be ready after
 333                          * several ticks, if write_pending is set.
 334                          *
 335                          * It may be deleted, but with this feature tcpdumps
 336                          * look so _wonderfully_ clever, that I was not able
 337                          * to stand against the temptation 8)     --ANK
 338                          */
 339                         /*
 340                          * OK, in DCCP we can as well do a similar trick, its
 341                          * even in the draft, but there is no need for us to
 342                          * schedule an ack here, as dccp_sendmsg does this for
 343                          * us, also stated in the draft. -acme
 344                          */
 345                         __kfree_skb(skb);
 346                         return 0;
 347                 }
 348                 dccp_send_ack(sk);
 349                 return -1;
 350         }
 351
 352 out_invalid_packet:
 353         return 1; /* dccp_v4_do_rcv will send a reset, but...
 354                      FIXME: the reset code should be
 355                             DCCP_RESET_CODE_PACKET_ERROR */
 356 }
 357
 358 static int dccp_rcv_respond_partopen_state_process(struct sock *sk,
 359                                                    struct sk_buff *skb,
 360                                                    const struct dccp_hdr *dh,
 361                                                    const unsigned len)
 362 {
 363         int queued = 0;
 364
 365         switch (dh->dccph_type) {
 366         case DCCP_PKT_RESET:
 367                 inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
 368                 break;
 369         case DCCP_PKT_DATAACK:
 370         case DCCP_PKT_ACK:
 371                 /*
 372                  * FIXME: we should be reseting the PARTOPEN (DELACK) timer
 373                  * here but only if we haven't used the DELACK timer for
 374                  * something else, like sending a delayed ack for a TIMESTAMP
 375                  * echo, etc, for now were not clearing it, sending an extra
 376                  * ACK when there is nothing else to do in DELACK is not a big
 377                  * deal after all.
 378                  */
 379
 380                 /* Stop the PARTOPEN timer */
 381                 if (sk->sk_state == DCCP_PARTOPEN)
 382                         inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
 383
 384                 dccp_sk(sk)->dccps_osr = DCCP_SKB_CB(skb)->dccpd_seq;
 385                 dccp_set_state(sk, DCCP_OPEN);
 386
 387                 if (dh->dccph_type == DCCP_PKT_DATAACK) {
 388                         dccp_rcv_established(sk, skb, dh, len);
 389                         queued = 1; /* packet was queued
 390                                        (by dccp_rcv_established) */
 391                 }
 392                 break;
 393         }
 394
 395         return queued;
 396 }
 397
 398 int dccp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
 399                            struct dccp_hdr *dh, unsigned len)
 400 {
 401         struct dccp_sock *dp = dccp_sk(sk);
 402         const int old_state = sk->sk_state;
 403         int queued = 0;
 404
 405         if (sk->sk_state != DCCP_LISTEN && sk->sk_state != DCCP_REQUESTING) {
 406                 if (dccp_check_seqno(sk, skb))
 407                         goto discard;
 408
 409                 /*
 410                  * Step 8: Process options and mark acknowledgeable
 411                  */
 412                 if (dccp_parse_options(sk, skb))
 413                         goto discard;
 414
 415                 if (DCCP_SKB_CB(skb)->dccpd_ack_seq !=
 416                     DCCP_PKT_WITHOUT_ACK_SEQ)
 417                         dccp_event_ack_recv(sk, skb);
 418
 419                 ccid_hc_rx_packet_recv(dp->dccps_hc_rx_ccid, sk, skb);
 420                 ccid_hc_tx_packet_recv(dp->dccps_hc_tx_ccid, sk, skb);
 421
 422                 /*
 423                  * FIXME: check ECN to see if we should use
 424                  * DCCP_ACKPKTS_STATE_ECN_MARKED
 425                  */
 426                 if (dp->dccps_options.dccpo_send_ack_vector) {
 427                         if (dccp_ackpkts_add(dp->dccps_hc_rx_ackpkts,
 428                                              DCCP_SKB_CB(skb)->dccpd_seq,
 429                                              DCCP_ACKPKTS_STATE_RECEIVED))
 430                                 goto discard;
 431                         /*
 432                          * FIXME: this activation is probably wrong, have to
 433                          * study more TCP delack machinery and how it fits into
 434                          * DCCP draft, but for now it kinda "works" 8)
 435                          */
 436                         if ((dp->dccps_hc_rx_ackpkts->dccpap_ack_seqno ==
 437                              DCCP_MAX_SEQNO + 1) &&
 438                             !inet_csk_ack_scheduled(sk)) {
 439                                 inet_csk_schedule_ack(sk);
 440                                 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
 441                                                           TCP_DELACK_MIN,
 442                                                           DCCP_RTO_MAX);
 443                         }
 444                 }
 445         }
 446
 447         /*
 448          *  Step 9: Process Reset
 449          *      If P.type == Reset,
 450          *              Tear down connection
 451          *              S.state := TIMEWAIT
 452          *              Set TIMEWAIT timer
 453          *              Drop packet and return
 454         */
 455         if (dh->dccph_type == DCCP_PKT_RESET) {
 456                 /*
 457                  * Queue the equivalent of TCP fin so that dccp_recvmsg
 458                  * exits the loop
 459                  */
 460                 dccp_fin(sk, skb);
 461                 dccp_time_wait(sk, DCCP_TIME_WAIT, 0);
 462                 return 0;
 463                 /*
 464                  *   Step 7: Check for unexpected packet types
 465                  *      If (S.is_server and P.type == CloseReq)
 466                  *          or (S.is_server and P.type == Response)
 467                  *          or (S.is_client and P.type == Request)
 468                  *          or (S.state == RESPOND and P.type == Data),
 469                  *        Send Sync packet acknowledging P.seqno
 470                  *        Drop packet and return
 471                  */
 472         } else if ((dp->dccps_role != DCCP_ROLE_CLIENT &&
 473                     (dh->dccph_type == DCCP_PKT_RESPONSE ||
 474                      dh->dccph_type == DCCP_PKT_CLOSEREQ)) ||
 475                     (dp->dccps_role == DCCP_ROLE_CLIENT &&
 476                      dh->dccph_type == DCCP_PKT_REQUEST) ||
 477                     (sk->sk_state == DCCP_RESPOND &&
 478                      dh->dccph_type == DCCP_PKT_DATA)) {
 479                 dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq);
 480                 goto discard;
 481         }
 482
 483         switch (sk->sk_state) {
 484         case DCCP_CLOSED:
 485                 return 1;
 486
 487         case DCCP_LISTEN:
 488                 if (dh->dccph_type == DCCP_PKT_ACK ||
 489                     dh->dccph_type == DCCP_PKT_DATAACK)
 490                         return 1;
 491
 492                 if (dh->dccph_type == DCCP_PKT_RESET)
 493                         goto discard;
 494
 495                 if (dh->dccph_type == DCCP_PKT_REQUEST) {
 496                         if (dccp_v4_conn_request(sk, skb) < 0)
 497                                 return 1;
 498
 499                         /* FIXME: do congestion control initialization */
 500                         goto discard;
 501                 }
 502                 goto discard;
 503
 504         case DCCP_REQUESTING:
 505                 /* FIXME: do congestion control initialization */
 506
 507                 queued = dccp_rcv_request_sent_state_process(sk, skb, dh, len);
 508                 if (queued >= 0)
 509                         return queued;
 510
 511                 __kfree_skb(skb);
 512                 return 0;
 513
 514         case DCCP_RESPOND:
 515         case DCCP_PARTOPEN:
 516                 queued = dccp_rcv_respond_partopen_state_process(sk, skb,
 517                                                                  dh, len);
 518                 break;
 519         }
 520
 521         if (dh->dccph_type == DCCP_PKT_ACK ||
 522             dh->dccph_type == DCCP_PKT_DATAACK) {
 523                 switch (old_state) {
 524                 case DCCP_PARTOPEN:
 525                         sk->sk_state_change(sk);
 526                         sk_wake_async(sk, 0, POLL_OUT);
 527                         break;
 528                 }
 529         }
 530
 531         if (!queued) {
 532 discard:
 533                 __kfree_skb(skb);
 534         }
 535         return 0;
 536 }