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   1 /*
   2  *  net/dccp/ackvec.c
   3  *
   4  *  An implementation of the DCCP protocol
   5  *  Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
   6  *
   7  *      This program is free software; you can redistribute it and/or modify it
   8  *      under the terms of the GNU General Public License as published by the
   9  *      Free Software Foundation; version 2 of the License;
  10  */
  11
  12 #include "ackvec.h"
  13 #include "dccp.h"
  14
  15 #include <linux/dccp.h>
  16 #include <linux/init.h>
  17 #include <linux/errno.h>
  18 #include <linux/kernel.h>
  19 #include <linux/skbuff.h>
  20 #include <linux/slab.h>
  21
  22 #include <net/sock.h>
  23
  24 static kmem_cache_t *dccp_ackvec_slab;
  25 static kmem_cache_t *dccp_ackvec_record_slab;
  26
  27 static struct dccp_ackvec_record *dccp_ackvec_record_new(void)
  28 {
  29         struct dccp_ackvec_record *avr =
  30                         kmem_cache_alloc(dccp_ackvec_record_slab, GFP_ATOMIC);
  31
  32         if (avr != NULL)
  33                 INIT_LIST_HEAD(&avr->dccpavr_node);
  34
  35         return avr;
  36 }
  37
  38 static void dccp_ackvec_record_delete(struct dccp_ackvec_record *avr)
  39 {
  40         if (unlikely(avr == NULL))
  41                 return;
  42         /* Check if deleting a linked record */
  43         WARN_ON(!list_empty(&avr->dccpavr_node));
  44         kmem_cache_free(dccp_ackvec_record_slab, avr);
  45 }
  46
  47 static void dccp_ackvec_insert_avr(struct dccp_ackvec *av,
  48                                    struct dccp_ackvec_record *avr)
  49 {
  50         /*
  51          * AVRs are sorted by seqno. Since we are sending them in order, we
  52          * just add the AVR at the head of the list.
  53          * -sorbo.
  54          */
  55         if (!list_empty(&av->dccpav_records)) {
  56                 const struct dccp_ackvec_record *head =
  57                                         list_entry(av->dccpav_records.next,
  58                                                    struct dccp_ackvec_record,
  59                                                    dccpavr_node);
  60                 BUG_ON(before48(avr->dccpavr_ack_seqno,
  61                                 head->dccpavr_ack_seqno));
  62         }
  63
  64         list_add(&avr->dccpavr_node, &av->dccpav_records);
  65 }
  66
  67 int dccp_insert_option_ackvec(struct sock *sk, struct sk_buff *skb)
  68 {
  69         struct dccp_sock *dp = dccp_sk(sk);
  70 #ifdef CONFIG_IP_DCCP_DEBUG
  71         const char *debug_prefix = dp->dccps_role == DCCP_ROLE_CLIENT ?
  72                                 "CLIENT tx: " : "server tx: ";
  73 #endif
  74         struct dccp_ackvec *av = dp->dccps_hc_rx_ackvec;
  75         int len = av->dccpav_vec_len + 2;
  76         struct timeval now;
  77         u32 elapsed_time;
  78         unsigned char *to, *from;
  79         struct dccp_ackvec_record *avr;
  80
  81         if (DCCP_SKB_CB(skb)->dccpd_opt_len + len > DCCP_MAX_OPT_LEN)
  82                 return -1;
  83
  84         dccp_timestamp(sk, &now);
  85         elapsed_time = timeval_delta(&now, &av->dccpav_time) / 10;
  86
  87         if (elapsed_time != 0 &&
  88             dccp_insert_option_elapsed_time(sk, skb, elapsed_time))
  89                 return -1;
  90
  91         avr = dccp_ackvec_record_new();
  92         if (avr == NULL)
  93                 return -1;
  94
  95         DCCP_SKB_CB(skb)->dccpd_opt_len += len;
  96
  97         to    = skb_push(skb, len);
  98         *to++ = DCCPO_ACK_VECTOR_0;
  99         *to++ = len;
 100
 101         len  = av->dccpav_vec_len;
 102         from = av->dccpav_buf + av->dccpav_buf_head;
 103
 104         /* Check if buf_head wraps */
 105         if ((int)av->dccpav_buf_head + len > DCCP_MAX_ACKVEC_LEN) {
 106                 const u32 tailsize = DCCP_MAX_ACKVEC_LEN - av->dccpav_buf_head;
 107
 108                 memcpy(to, from, tailsize);
 109                 to   += tailsize;
 110                 len  -= tailsize;
 111                 from = av->dccpav_buf;
 112         }
 113
 114         memcpy(to, from, len);
 115         /*
 116          *      From RFC 4340, A.2:
 117          *
 118          *      For each acknowledgement it sends, the HC-Receiver will add an
 119          *      acknowledgement record.  ack_seqno will equal the HC-Receiver
 120          *      sequence number it used for the ack packet; ack_ptr will equal
 121          *      buf_head; ack_ackno will equal buf_ackno; and ack_nonce will
 122          *      equal buf_nonce.
 123          */
 124         avr->dccpavr_ack_seqno = DCCP_SKB_CB(skb)->dccpd_seq;
 125         avr->dccpavr_ack_ptr   = av->dccpav_buf_head;
 126         avr->dccpavr_ack_ackno = av->dccpav_buf_ackno;
 127         avr->dccpavr_ack_nonce = av->dccpav_buf_nonce;
 128         avr->dccpavr_sent_len  = av->dccpav_vec_len;
 129
 130         dccp_ackvec_insert_avr(av, avr);
 131
 132         dccp_pr_debug("%sACK Vector 0, len=%d, ack_seqno=%llu, "
 133                       "ack_ackno=%llu\n",
 134                       debug_prefix, avr->dccpavr_sent_len,
 135                       (unsigned long long)avr->dccpavr_ack_seqno,
 136                       (unsigned long long)avr->dccpavr_ack_ackno);
 137         return 0;
 138 }
 139
 140 struct dccp_ackvec *dccp_ackvec_alloc(const gfp_t priority)
 141 {
 142         struct dccp_ackvec *av = kmem_cache_alloc(dccp_ackvec_slab, priority);
 143
 144         if (av != NULL) {
 145                 av->dccpav_buf_head     = DCCP_MAX_ACKVEC_LEN - 1;
 146                 av->dccpav_buf_ackno    = DCCP_MAX_SEQNO + 1;
 147                 av->dccpav_buf_nonce = av->dccpav_buf_nonce = 0;
 148                 av->dccpav_ack_ptr      = 0;
 149                 av->dccpav_time.tv_sec  = 0;
 150                 av->dccpav_time.tv_usec = 0;
 151                 av->dccpav_vec_len      = 0;
 152                 INIT_LIST_HEAD(&av->dccpav_records);
 153         }
 154
 155         return av;
 156 }
 157
 158 void dccp_ackvec_free(struct dccp_ackvec *av)
 159 {
 160         if (unlikely(av == NULL))
 161                 return;
 162
 163         if (!list_empty(&av->dccpav_records)) {
 164                 struct dccp_ackvec_record *avr, *next;
 165
 166                 list_for_each_entry_safe(avr, next, &av->dccpav_records,
 167                                          dccpavr_node) {
 168                         list_del_init(&avr->dccpavr_node);
 169                         dccp_ackvec_record_delete(avr);
 170                 }
 171         }
 172
 173         kmem_cache_free(dccp_ackvec_slab, av);
 174 }
 175
 176 static inline u8 dccp_ackvec_state(const struct dccp_ackvec *av,
 177                                    const u8 index)
 178 {
 179         return av->dccpav_buf[index] & DCCP_ACKVEC_STATE_MASK;
 180 }
 181
 182 static inline u8 dccp_ackvec_len(const struct dccp_ackvec *av,
 183                                  const u8 index)
 184 {
 185         return av->dccpav_buf[index] & DCCP_ACKVEC_LEN_MASK;
 186 }
 187
 188 /*
 189  * If several packets are missing, the HC-Receiver may prefer to enter multiple
 190  * bytes with run length 0, rather than a single byte with a larger run length;
 191  * this simplifies table updates if one of the missing packets arrives.
 192  */
 193 static inline int dccp_ackvec_set_buf_head_state(struct dccp_ackvec *av,
 194                                                  const unsigned int packets,
 195                                                  const unsigned char state)
 196 {
 197         unsigned int gap;
 198         long new_head;
 199
 200         if (av->dccpav_vec_len + packets > DCCP_MAX_ACKVEC_LEN)
 201                 return -ENOBUFS;
 202
 203         gap      = packets - 1;
 204         new_head = av->dccpav_buf_head - packets;
 205
 206         if (new_head < 0) {
 207                 if (gap > 0) {
 208                         memset(av->dccpav_buf, DCCP_ACKVEC_STATE_NOT_RECEIVED,
 209                                gap + new_head + 1);
 210                         gap = -new_head;
 211                 }
 212                 new_head += DCCP_MAX_ACKVEC_LEN;
 213         }
 214
 215         av->dccpav_buf_head = new_head;
 216
 217         if (gap > 0)
 218                 memset(av->dccpav_buf + av->dccpav_buf_head + 1,
 219                        DCCP_ACKVEC_STATE_NOT_RECEIVED, gap);
 220
 221         av->dccpav_buf[av->dccpav_buf_head] = state;
 222         av->dccpav_vec_len += packets;
 223         return 0;
 224 }
 225
 226 /*
 227  * Implements the RFC 4340, Appendix A
 228  */
 229 int dccp_ackvec_add(struct dccp_ackvec *av, const struct sock *sk,
 230                     const u64 ackno, const u8 state)
 231 {
 232         /*
 233          * Check at the right places if the buffer is full, if it is, tell the
 234          * caller to start dropping packets till the HC-Sender acks our ACK
 235          * vectors, when we will free up space in dccpav_buf.
 236          *
 237          * We may well decide to do buffer compression, etc, but for now lets
 238          * just drop.
 239          *
 240          * From Appendix A.1.1 (`New Packets'):
 241          *
 242          *      Of course, the circular buffer may overflow, either when the
 243          *      HC-Sender is sending data at a very high rate, when the
 244          *      HC-Receiver's acknowledgements are not reaching the HC-Sender,
 245          *      or when the HC-Sender is forgetting to acknowledge those acks
 246          *      (so the HC-Receiver is unable to clean up old state). In this
 247          *      case, the HC-Receiver should either compress the buffer (by
 248          *      increasing run lengths when possible), transfer its state to
 249          *      a larger buffer, or, as a last resort, drop all received
 250          *      packets, without processing them whatsoever, until its buffer
 251          *      shrinks again.
 252          */
 253
 254         /* See if this is the first ackno being inserted */
 255         if (av->dccpav_vec_len == 0) {
 256                 av->dccpav_buf[av->dccpav_buf_head] = state;
 257                 av->dccpav_vec_len = 1;
 258         } else if (after48(ackno, av->dccpav_buf_ackno)) {
 259                 const u64 delta = dccp_delta_seqno(av->dccpav_buf_ackno,
 260                                                    ackno);
 261
 262                 /*
 263                  * Look if the state of this packet is the same as the
 264                  * previous ackno and if so if we can bump the head len.
 265                  */
 266                 if (delta == 1 &&
 267                     dccp_ackvec_state(av, av->dccpav_buf_head) == state &&
 268                     (dccp_ackvec_len(av, av->dccpav_buf_head) <
 269                      DCCP_ACKVEC_LEN_MASK))
 270                         av->dccpav_buf[av->dccpav_buf_head]++;
 271                 else if (dccp_ackvec_set_buf_head_state(av, delta, state))
 272                         return -ENOBUFS;
 273         } else {
 274                 /*
 275                  * A.1.2.  Old Packets
 276                  *
 277                  *      When a packet with Sequence Number S <= buf_ackno
 278                  *      arrives, the HC-Receiver will scan the table for
 279                  *      the byte corresponding to S. (Indexing structures
 280                  *      could reduce the complexity of this scan.)
 281                  */
 282                 u64 delta = dccp_delta_seqno(ackno, av->dccpav_buf_ackno);
 283                 u8 index = av->dccpav_buf_head;
 284
 285                 while (1) {
 286                         const u8 len = dccp_ackvec_len(av, index);
 287                         const u8 state = dccp_ackvec_state(av, index);
 288                         /*
 289                          * valid packets not yet in dccpav_buf have a reserved
 290                          * entry, with a len equal to 0.
 291                          */
 292                         if (state == DCCP_ACKVEC_STATE_NOT_RECEIVED &&
 293                             len == 0 && delta == 0) { /* Found our
 294                                                          reserved seat! */
 295                                 dccp_pr_debug("Found %llu reserved seat!\n",
 296                                               (unsigned long long)ackno);
 297                                 av->dccpav_buf[index] = state;
 298                                 goto out;
 299                         }
 300                         /* len == 0 means one packet */
 301                         if (delta < len + 1)
 302                                 goto out_duplicate;
 303
 304                         delta -= len + 1;
 305                         if (++index == DCCP_MAX_ACKVEC_LEN)
 306                                 index = 0;
 307                 }
 308         }
 309
 310         av->dccpav_buf_ackno = ackno;
 311         dccp_timestamp(sk, &av->dccpav_time);
 312 out:
 313         return 0;
 314
 315 out_duplicate:
 316         /* Duplicate packet */
 317         dccp_pr_debug("Received a dup or already considered lost "
 318                       "packet: %llu\n", (unsigned long long)ackno);
 319         return -EILSEQ;
 320 }
 321
 322 #ifdef CONFIG_IP_DCCP_DEBUG
 323 void dccp_ackvector_print(const u64 ackno, const unsigned char *vector, int len)
 324 {
 325         if (!dccp_debug)
 326                 return;
 327
 328         printk("ACK vector len=%d, ackno=%llu |", len,
 329                (unsigned long long)ackno);
 330
 331         while (len--) {
 332                 const u8 state = (*vector & DCCP_ACKVEC_STATE_MASK) >> 6;
 333                 const u8 rl = *vector & DCCP_ACKVEC_LEN_MASK;
 334
 335                 printk("%d,%d|", state, rl);
 336                 ++vector;
 337         }
 338
 339         printk("\n");
 340 }
 341
 342 void dccp_ackvec_print(const struct dccp_ackvec *av)
 343 {
 344         dccp_ackvector_print(av->dccpav_buf_ackno,
 345                              av->dccpav_buf + av->dccpav_buf_head,
 346                              av->dccpav_vec_len);
 347 }
 348 #endif
 349
 350 static void dccp_ackvec_throw_record(struct dccp_ackvec *av,
 351                                      struct dccp_ackvec_record *avr)
 352 {
 353         struct dccp_ackvec_record *next;
 354
 355         /* sort out vector length */
 356         if (av->dccpav_buf_head <= avr->dccpavr_ack_ptr)
 357                 av->dccpav_vec_len = avr->dccpavr_ack_ptr - av->dccpav_buf_head;
 358         else
 359                 av->dccpav_vec_len = DCCP_MAX_ACKVEC_LEN - 1
 360                                      - av->dccpav_buf_head
 361                                      + avr->dccpavr_ack_ptr;
 362
 363         /* free records */
 364         list_for_each_entry_safe_from(avr, next, &av->dccpav_records,
 365                                       dccpavr_node) {
 366                 list_del_init(&avr->dccpavr_node);
 367                 dccp_ackvec_record_delete(avr);
 368         }
 369 }
 370
 371 void dccp_ackvec_check_rcv_ackno(struct dccp_ackvec *av, struct sock *sk,
 372                                  const u64 ackno)
 373 {
 374         struct dccp_ackvec_record *avr;
 375
 376         /*
 377          * If we traverse backwards, it should be faster when we have large
 378          * windows. We will be receiving ACKs for stuff we sent a while back
 379          * -sorbo.
 380          */
 381         list_for_each_entry_reverse(avr, &av->dccpav_records, dccpavr_node) {
 382                 if (ackno == avr->dccpavr_ack_seqno) {
 383 #ifdef CONFIG_IP_DCCP_DEBUG
 384                         struct dccp_sock *dp = dccp_sk(sk);
 385                         const char *debug_prefix = dp->dccps_role == DCCP_ROLE_CLIENT ?
 386                                                 "CLIENT rx ack: " : "server rx ack: ";
 387 #endif
 388                         dccp_pr_debug("%sACK packet 0, len=%d, ack_seqno=%llu, "
 389                                       "ack_ackno=%llu, ACKED!\n",
 390                                       debug_prefix, 1,
 391                                       (unsigned long long)avr->dccpavr_ack_seqno,
 392                                       (unsigned long long)avr->dccpavr_ack_ackno);
 393                         dccp_ackvec_throw_record(av, avr);
 394                         break;
 395                 }
 396         }
 397 }
 398
 399 static void dccp_ackvec_check_rcv_ackvector(struct dccp_ackvec *av,
 400                                             struct sock *sk, u64 ackno,
 401                                             const unsigned char len,
 402                                             const unsigned char *vector)
 403 {
 404         unsigned char i;
 405         struct dccp_ackvec_record *avr;
 406
 407         /* Check if we actually sent an ACK vector */
 408         if (list_empty(&av->dccpav_records))
 409                 return;
 410
 411         i = len;
 412         /*
 413          * XXX
 414          * I think it might be more efficient to work backwards. See comment on
 415          * rcv_ackno. -sorbo.
 416          */
 417         avr = list_entry(av->dccpav_records.next, struct dccp_ackvec_record,
 418                          dccpavr_node);
 419         while (i--) {
 420                 const u8 rl = *vector & DCCP_ACKVEC_LEN_MASK;
 421                 u64 ackno_end_rl;
 422
 423                 dccp_set_seqno(&ackno_end_rl, ackno - rl);
 424
 425                 /*
 426                  * If our AVR sequence number is greater than the ack, go
 427                  * forward in the AVR list until it is not so.
 428                  */
 429                 list_for_each_entry_from(avr, &av->dccpav_records,
 430                                          dccpavr_node) {
 431                         if (!after48(avr->dccpavr_ack_seqno, ackno))
 432                                 goto found;
 433                 }
 434                 /* End of the dccpav_records list, not found, exit */
 435                 break;
 436 found:
 437                 if (between48(avr->dccpavr_ack_seqno, ackno_end_rl, ackno)) {
 438                         const u8 state = *vector & DCCP_ACKVEC_STATE_MASK;
 439                         if (state != DCCP_ACKVEC_STATE_NOT_RECEIVED) {
 440 #ifdef CONFIG_IP_DCCP_DEBUG
 441                                 struct dccp_sock *dp = dccp_sk(sk);
 442                                 const char *debug_prefix =
 443                                         dp->dccps_role == DCCP_ROLE_CLIENT ?
 444                                         "CLIENT rx ack: " : "server rx ack: ";
 445 #endif
 446                                 dccp_pr_debug("%sACK vector 0, len=%d, "
 447                                               "ack_seqno=%llu, ack_ackno=%llu, "
 448                                               "ACKED!\n",
 449                                               debug_prefix, len,
 450                                               (unsigned long long)
 451                                               avr->dccpavr_ack_seqno,
 452                                               (unsigned long long)
 453                                               avr->dccpavr_ack_ackno);
 454                                 dccp_ackvec_throw_record(av, avr);
 455                                 break;
 456                         }
 457                         /*
 458                          * If it wasn't received, continue scanning... we might
 459                          * find another one.
 460                          */
 461                 }
 462
 463                 dccp_set_seqno(&ackno, ackno_end_rl - 1);
 464                 ++vector;
 465         }
 466 }
 467
 468 int dccp_ackvec_parse(struct sock *sk, const struct sk_buff *skb,
 469                       const u8 opt, const u8 *value, const u8 len)
 470 {
 471         if (len > DCCP_MAX_ACKVEC_LEN)
 472                 return -1;
 473
 474         /* dccp_ackvector_print(DCCP_SKB_CB(skb)->dccpd_ack_seq, value, len); */
 475         dccp_ackvec_check_rcv_ackvector(dccp_sk(sk)->dccps_hc_rx_ackvec, sk,
 476                                         DCCP_SKB_CB(skb)->dccpd_ack_seq,
 477                                         len, value);
 478         return 0;
 479 }
 480
 481 static char dccp_ackvec_slab_msg[] __initdata =
 482         KERN_CRIT "DCCP: Unable to create ack vectors slab caches\n";
 483
 484 int __init dccp_ackvec_init(void)
 485 {
 486         dccp_ackvec_slab = kmem_cache_create("dccp_ackvec",
 487                                              sizeof(struct dccp_ackvec), 0,
 488                                              SLAB_HWCACHE_ALIGN, NULL, NULL);
 489         if (dccp_ackvec_slab == NULL)
 490                 goto out_err;
 491
 492         dccp_ackvec_record_slab =
 493                         kmem_cache_create("dccp_ackvec_record",
 494                                           sizeof(struct dccp_ackvec_record),
 495                                           0, SLAB_HWCACHE_ALIGN, NULL, NULL);
 496         if (dccp_ackvec_record_slab == NULL)
 497                 goto out_destroy_slab;
 498
 499         return 0;
 500
 501 out_destroy_slab:
 502         kmem_cache_destroy(dccp_ackvec_slab);
 503         dccp_ackvec_slab = NULL;
 504 out_err:
 505         printk(dccp_ackvec_slab_msg);
 506         return -ENOBUFS;
 507 }
 508
 509 void dccp_ackvec_exit(void)
 510 {
 511         if (dccp_ackvec_slab != NULL) {
 512                 kmem_cache_destroy(dccp_ackvec_slab);
 513                 dccp_ackvec_slab = NULL;
 514         }
 515         if (dccp_ackvec_record_slab != NULL) {
 516                 kmem_cache_destroy(dccp_ackvec_record_slab);
 517                 dccp_ackvec_record_slab = NULL;
 518         }
 519 }