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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 draft-ietf-dccp-spec-11.txt:
 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     =
 146                         av->dccpav_buf_tail = DCCP_MAX_ACKVEC_LEN - 1;
 147                 av->dccpav_buf_ackno    = DCCP_MAX_SEQNO + 1;
 148                 av->dccpav_buf_nonce = av->dccpav_buf_nonce = 0;
 149                 av->dccpav_ack_ptr      = 0;
 150                 av->dccpav_time.tv_sec  = 0;
 151                 av->dccpav_time.tv_usec = 0;
 152                 av->dccpav_sent_len     = av->dccpav_vec_len = 0;
 153                 INIT_LIST_HEAD(&av->dccpav_records);
 154         }
 155
 156         return av;
 157 }
 158
 159 void dccp_ackvec_free(struct dccp_ackvec *av)
 160 {
 161         if (unlikely(av == NULL))
 162                 return;
 163
 164         if (!list_empty(&av->dccpav_records)) {
 165                 struct dccp_ackvec_record *avr, *next;
 166
 167                 list_for_each_entry_safe(avr, next, &av->dccpav_records,
 168                                          dccpavr_node) {
 169                         list_del_init(&avr->dccpavr_node);
 170                         dccp_ackvec_record_delete(avr);
 171                 }
 172         }
 173
 174         kmem_cache_free(dccp_ackvec_slab, av);
 175 }
 176
 177 static inline u8 dccp_ackvec_state(const struct dccp_ackvec *av,
 178                                    const u8 index)
 179 {
 180         return av->dccpav_buf[index] & DCCP_ACKVEC_STATE_MASK;
 181 }
 182
 183 static inline u8 dccp_ackvec_len(const struct dccp_ackvec *av,
 184                                  const u8 index)
 185 {
 186         return av->dccpav_buf[index] & DCCP_ACKVEC_LEN_MASK;
 187 }
 188
 189 /*
 190  * If several packets are missing, the HC-Receiver may prefer to enter multiple
 191  * bytes with run length 0, rather than a single byte with a larger run length;
 192  * this simplifies table updates if one of the missing packets arrives.
 193  */
 194 static inline int dccp_ackvec_set_buf_head_state(struct dccp_ackvec *av,
 195                                                  const unsigned int packets,
 196                                                  const unsigned char state)
 197 {
 198         unsigned int gap;
 199         long new_head;
 200
 201         if (av->dccpav_vec_len + packets > DCCP_MAX_ACKVEC_LEN)
 202                 return -ENOBUFS;
 203
 204         gap      = packets - 1;
 205         new_head = av->dccpav_buf_head - packets;
 206
 207         if (new_head < 0) {
 208                 if (gap > 0) {
 209                         memset(av->dccpav_buf, DCCP_ACKVEC_STATE_NOT_RECEIVED,
 210                                gap + new_head + 1);
 211                         gap = -new_head;
 212                 }
 213                 new_head += DCCP_MAX_ACKVEC_LEN;
 214         }
 215
 216         av->dccpav_buf_head = new_head;
 217
 218         if (gap > 0)
 219                 memset(av->dccpav_buf + av->dccpav_buf_head + 1,
 220                        DCCP_ACKVEC_STATE_NOT_RECEIVED, gap);
 221
 222         av->dccpav_buf[av->dccpav_buf_head] = state;
 223         av->dccpav_vec_len += packets;
 224         return 0;
 225 }
 226
 227 /*
 228  * Implements the draft-ietf-dccp-spec-11.txt Appendix A
 229  */
 230 int dccp_ackvec_add(struct dccp_ackvec *av, const struct sock *sk,
 231                     const u64 ackno, const u8 state)
 232 {
 233         /*
 234          * Check at the right places if the buffer is full, if it is, tell the
 235          * caller to start dropping packets till the HC-Sender acks our ACK
 236          * vectors, when we will free up space in dccpav_buf.
 237          *
 238          * We may well decide to do buffer compression, etc, but for now lets
 239          * just drop.
 240          *
 241          * From Appendix A:
 242          *
 243          *      Of course, the circular buffer may overflow, either when the
 244          *      HC-Sender is sending data at a very high rate, when the
 245          *      HC-Receiver's acknowledgements are not reaching the HC-Sender,
 246          *      or when the HC-Sender is forgetting to acknowledge those acks
 247          *      (so the HC-Receiver is unable to clean up old state). In this
 248          *      case, the HC-Receiver should either compress the buffer (by
 249          *      increasing run lengths when possible), transfer its state to
 250          *      a larger buffer, or, as a last resort, drop all received
 251          *      packets, without processing them whatsoever, until its buffer
 252          *      shrinks again.
 253          */
 254
 255         /* See if this is the first ackno being inserted */
 256         if (av->dccpav_vec_len == 0) {
 257                 av->dccpav_buf[av->dccpav_buf_head] = state;
 258                 av->dccpav_vec_len = 1;
 259         } else if (after48(ackno, av->dccpav_buf_ackno)) {
 260                 const u64 delta = dccp_delta_seqno(av->dccpav_buf_ackno,
 261                                                    ackno);
 262
 263                 /*
 264                  * Look if the state of this packet is the same as the
 265                  * previous ackno and if so if we can bump the head len.
 266                  */
 267                 if (delta == 1 &&
 268                     dccp_ackvec_state(av, av->dccpav_buf_head) == state &&
 269                     (dccp_ackvec_len(av, av->dccpav_buf_head) <
 270                      DCCP_ACKVEC_LEN_MASK))
 271                         av->dccpav_buf[av->dccpav_buf_head]++;
 272                 else if (dccp_ackvec_set_buf_head_state(av, delta, state))
 273                         return -ENOBUFS;
 274         } else {
 275                 /*
 276                  * A.1.2.  Old Packets
 277                  *
 278                  *      When a packet with Sequence Number S arrives, and
 279                  *      S <= buf_ackno, the HC-Receiver will scan the table
 280                  *      for the byte corresponding to S. (Indexing structures
 281                  *      could reduce the complexity of this scan.)
 282                  */
 283                 u64 delta = dccp_delta_seqno(ackno, av->dccpav_buf_ackno);
 284                 u8 index = av->dccpav_buf_head;
 285
 286                 while (1) {
 287                         const u8 len = dccp_ackvec_len(av, index);
 288                         const u8 state = dccp_ackvec_state(av, index);
 289                         /*
 290                          * valid packets not yet in dccpav_buf have a reserved
 291                          * entry, with a len equal to 0.
 292                          */
 293                         if (state == DCCP_ACKVEC_STATE_NOT_RECEIVED &&
 294                             len == 0 && delta == 0) { /* Found our
 295                                                          reserved seat! */
 296                                 dccp_pr_debug("Found %llu reserved seat!\n",
 297                                               (unsigned long long)ackno);
 298                                 av->dccpav_buf[index] = state;
 299                                 goto out;
 300                         }
 301                         /* len == 0 means one packet */
 302                         if (delta < len + 1)
 303                                 goto out_duplicate;
 304
 305                         delta -= len + 1;
 306                         if (++index == DCCP_MAX_ACKVEC_LEN)
 307                                 index = 0;
 308                 }
 309         }
 310
 311         av->dccpav_buf_ackno = ackno;
 312         dccp_timestamp(sk, &av->dccpav_time);
 313 out:
 314         return 0;
 315
 316 out_duplicate:
 317         /* Duplicate packet */
 318         dccp_pr_debug("Received a dup or already considered lost "
 319                       "packet: %llu\n", (unsigned long long)ackno);
 320         return -EILSEQ;
 321 }
 322
 323 #ifdef CONFIG_IP_DCCP_DEBUG
 324 void dccp_ackvector_print(const u64 ackno, const unsigned char *vector, int len)
 325 {
 326         if (!dccp_debug)
 327                 return;
 328
 329         printk("ACK vector len=%d, ackno=%llu |", len,
 330                (unsigned long long)ackno);
 331
 332         while (len--) {
 333                 const u8 state = (*vector & DCCP_ACKVEC_STATE_MASK) >> 6;
 334                 const u8 rl = *vector & DCCP_ACKVEC_LEN_MASK;
 335
 336                 printk("%d,%d|", state, rl);
 337                 ++vector;
 338         }
 339
 340         printk("\n");
 341 }
 342
 343 void dccp_ackvec_print(const struct dccp_ackvec *av)
 344 {
 345         dccp_ackvector_print(av->dccpav_buf_ackno,
 346                              av->dccpav_buf + av->dccpav_buf_head,
 347                              av->dccpav_vec_len);
 348 }
 349 #endif
 350
 351 static void dccp_ackvec_throw_record(struct dccp_ackvec *av,
 352                                      struct dccp_ackvec_record *avr)
 353 {
 354         struct dccp_ackvec_record *next;
 355
 356         av->dccpav_buf_tail = avr->dccpavr_ack_ptr - 1;
 357         if (av->dccpav_buf_tail == 0)
 358                 av->dccpav_buf_tail = DCCP_MAX_ACKVEC_LEN - 1;
 359
 360         av->dccpav_vec_len -= avr->dccpavr_sent_len;
 361
 362         /* free records */
 363         list_for_each_entry_safe_from(avr, next, &av->dccpav_records,
 364                                       dccpavr_node) {
 365                 list_del_init(&avr->dccpavr_node);
 366                 dccp_ackvec_record_delete(avr);
 367         }
 368 }
 369
 370 void dccp_ackvec_check_rcv_ackno(struct dccp_ackvec *av, struct sock *sk,
 371                                  const u64 ackno)
 372 {
 373         struct dccp_ackvec_record *avr;
 374
 375         /*
 376          * If we traverse backwards, it should be faster when we have large
 377          * windows. We will be receiving ACKs for stuff we sent a while back
 378          * -sorbo.
 379          */
 380         list_for_each_entry_reverse(avr, &av->dccpav_records, dccpavr_node) {
 381                 if (ackno == avr->dccpavr_ack_seqno) {
 382 #ifdef CONFIG_IP_DCCP_DEBUG
 383                         struct dccp_sock *dp = dccp_sk(sk);
 384                         const char *debug_prefix = dp->dccps_role == DCCP_ROLE_CLIENT ?
 385                                                 "CLIENT rx ack: " : "server rx ack: ";
 386 #endif
 387                         dccp_pr_debug("%sACK packet 0, len=%d, ack_seqno=%llu, "
 388                                       "ack_ackno=%llu, ACKED!\n",
 389                                       debug_prefix, 1,
 390                                       (unsigned long long)avr->dccpavr_ack_seqno,
 391                                       (unsigned long long)avr->dccpavr_ack_ackno);
 392                         dccp_ackvec_throw_record(av, avr);
 393                         break;
 394                 }
 395         }
 396 }
 397
 398 static void dccp_ackvec_check_rcv_ackvector(struct dccp_ackvec *av,
 399                                             struct sock *sk, u64 ackno,
 400                                             const unsigned char len,
 401                                             const unsigned char *vector)
 402 {
 403         unsigned char i;
 404         struct dccp_ackvec_record *avr;
 405
 406         /* Check if we actually sent an ACK vector */
 407         if (list_empty(&av->dccpav_records))
 408                 return;
 409
 410         i = len;
 411         /*
 412          * XXX
 413          * I think it might be more efficient to work backwards. See comment on
 414          * rcv_ackno. -sorbo.
 415          */
 416         avr = list_entry(av->dccpav_records.next, struct dccp_ackvec_record,
 417                          dccpavr_node);
 418         while (i--) {
 419                 const u8 rl = *vector & DCCP_ACKVEC_LEN_MASK;
 420                 u64 ackno_end_rl;
 421
 422                 dccp_set_seqno(&ackno_end_rl, ackno - rl);
 423
 424                 /*
 425                  * If our AVR sequence number is greater than the ack, go
 426                  * forward in the AVR list until it is not so.
 427                  */
 428                 list_for_each_entry_from(avr, &av->dccpav_records,
 429                                          dccpavr_node) {
 430                         if (!after48(avr->dccpavr_ack_seqno, ackno))
 431                                 goto found;
 432                 }
 433                 /* End of the dccpav_records list, not found, exit */
 434                 break;
 435 found:
 436                 if (between48(avr->dccpavr_ack_seqno, ackno_end_rl, ackno)) {
 437                         const u8 state = (*vector &
 438                                           DCCP_ACKVEC_STATE_MASK) >> 6;
 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                         }
 456                         /*
 457                          * If it wasn't received, continue scanning... we might
 458                          * find another one.
 459                          */
 460                 }
 461
 462                 dccp_set_seqno(&ackno, ackno_end_rl - 1);
 463                 ++vector;
 464         }
 465 }
 466
 467 int dccp_ackvec_parse(struct sock *sk, const struct sk_buff *skb,
 468                       const u8 opt, const u8 *value, const u8 len)
 469 {
 470         if (len > DCCP_MAX_ACKVEC_LEN)
 471                 return -1;
 472
 473         /* dccp_ackvector_print(DCCP_SKB_CB(skb)->dccpd_ack_seq, value, len); */
 474         dccp_ackvec_check_rcv_ackvector(dccp_sk(sk)->dccps_hc_rx_ackvec, sk,
 475                                         DCCP_SKB_CB(skb)->dccpd_ack_seq,
 476                                         len, value);
 477         return 0;
 478 }
 479
 480 static char dccp_ackvec_slab_msg[] __initdata =
 481         KERN_CRIT "DCCP: Unable to create ack vectors slab caches\n";
 482
 483 int __init dccp_ackvec_init(void)
 484 {
 485         dccp_ackvec_slab = kmem_cache_create("dccp_ackvec",
 486                                              sizeof(struct dccp_ackvec), 0,
 487                                              SLAB_HWCACHE_ALIGN, NULL, NULL);
 488         if (dccp_ackvec_slab == NULL)
 489                 goto out_err;
 490
 491         dccp_ackvec_record_slab =
 492                         kmem_cache_create("dccp_ackvec_record",
 493                                           sizeof(struct dccp_ackvec_record),
 494                                           0, SLAB_HWCACHE_ALIGN, NULL, NULL);
 495         if (dccp_ackvec_record_slab == NULL)
 496                 goto out_destroy_slab;
 497
 498         return 0;
 499
 500 out_destroy_slab:
 501         kmem_cache_destroy(dccp_ackvec_slab);
 502         dccp_ackvec_slab = NULL;
 503 out_err:
 504         printk(dccp_ackvec_slab_msg);
 505         return -ENOBUFS;
 506 }
 507
 508 void dccp_ackvec_exit(void)
 509 {
 510         if (dccp_ackvec_slab != NULL) {
 511                 kmem_cache_destroy(dccp_ackvec_slab);
 512                 dccp_ackvec_slab = NULL;
 513         }
 514         if (dccp_ackvec_record_slab != NULL) {
 515                 kmem_cache_destroy(dccp_ackvec_record_slab);
 516                 dccp_ackvec_record_slab = NULL;
 517         }
 518 }