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