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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         /* Figure out how many options do we need to represent the ackvec */
  72         const u16 nr_opts = (av->dccpav_vec_len +
  73                              DCCP_MAX_ACKVEC_OPT_LEN - 1) /
  74                             DCCP_MAX_ACKVEC_OPT_LEN;
  75         u16 len = av->dccpav_vec_len + 2 * nr_opts, i;
  76         struct timeval now;
  77         u32 elapsed_time;
  78         const unsigned char *tail, *from;
  79         unsigned char *to;
  80         struct dccp_ackvec_record *avr;
  81
  82         if (DCCP_SKB_CB(skb)->dccpd_opt_len + len > DCCP_MAX_OPT_LEN)
  83                 return -1;
  84
  85         dccp_timestamp(sk, &now);
  86         elapsed_time = timeval_delta(&now, &av->dccpav_time) / 10;
  87
  88         if (elapsed_time != 0 &&
  89             dccp_insert_option_elapsed_time(sk, skb, elapsed_time))
  90                 return -1;
  91
  92         avr = dccp_ackvec_record_new();
  93         if (avr == NULL)
  94                 return -1;
  95
  96         DCCP_SKB_CB(skb)->dccpd_opt_len += len;
  97
  98         to   = skb_push(skb, len);
  99         len  = av->dccpav_vec_len;
 100         from = av->dccpav_buf + av->dccpav_buf_head;
 101         tail = av->dccpav_buf + DCCP_MAX_ACKVEC_LEN;
 102
 103         for (i = 0; i < nr_opts; ++i) {
 104                 int copylen = len;
 105
 106                 if (len > DCCP_MAX_ACKVEC_OPT_LEN)
 107                         copylen = DCCP_MAX_ACKVEC_OPT_LEN;
 108
 109                 *to++ = DCCPO_ACK_VECTOR_0;
 110                 *to++ = copylen + 2;
 111
 112                 /* Check if buf_head wraps */
 113                 if (from + copylen > tail) {
 114                         const u16 tailsize = tail - from;
 115
 116                         memcpy(to, from, tailsize);
 117                         to      += tailsize;
 118                         len     -= tailsize;
 119                         copylen -= tailsize;
 120                         from    = av->dccpav_buf;
 121                 }
 122
 123                 memcpy(to, from, copylen);
 124                 from += copylen;
 125                 to   += copylen;
 126                 len  -= copylen;
 127         }
 128
 129         /*
 130          *      From RFC 4340, A.2:
 131          *
 132          *      For each acknowledgement it sends, the HC-Receiver will add an
 133          *      acknowledgement record.  ack_seqno will equal the HC-Receiver
 134          *      sequence number it used for the ack packet; ack_ptr will equal
 135          *      buf_head; ack_ackno will equal buf_ackno; and ack_nonce will
 136          *      equal buf_nonce.
 137          */
 138         avr->dccpavr_ack_seqno = DCCP_SKB_CB(skb)->dccpd_seq;
 139         avr->dccpavr_ack_ptr   = av->dccpav_buf_head;
 140         avr->dccpavr_ack_ackno = av->dccpav_buf_ackno;
 141         avr->dccpavr_ack_nonce = av->dccpav_buf_nonce;
 142         avr->dccpavr_sent_len  = av->dccpav_vec_len;
 143
 144         dccp_ackvec_insert_avr(av, avr);
 145
 146         dccp_pr_debug("%s ACK Vector 0, len=%d, ack_seqno=%llu, "
 147                       "ack_ackno=%llu\n",
 148                       dccp_role(sk), avr->dccpavr_sent_len,
 149                       (unsigned long long)avr->dccpavr_ack_seqno,
 150                       (unsigned long long)avr->dccpavr_ack_ackno);
 151         return 0;
 152 }
 153
 154 struct dccp_ackvec *dccp_ackvec_alloc(const gfp_t priority)
 155 {
 156         struct dccp_ackvec *av = kmem_cache_alloc(dccp_ackvec_slab, priority);
 157
 158         if (av != NULL) {
 159                 av->dccpav_buf_head     = DCCP_MAX_ACKVEC_LEN - 1;
 160                 av->dccpav_buf_ackno    = DCCP_MAX_SEQNO + 1;
 161                 av->dccpav_buf_nonce = av->dccpav_buf_nonce = 0;
 162                 av->dccpav_time.tv_sec  = 0;
 163                 av->dccpav_time.tv_usec = 0;
 164                 av->dccpav_vec_len      = 0;
 165                 INIT_LIST_HEAD(&av->dccpav_records);
 166         }
 167
 168         return av;
 169 }
 170
 171 void dccp_ackvec_free(struct dccp_ackvec *av)
 172 {
 173         if (unlikely(av == NULL))
 174                 return;
 175
 176         if (!list_empty(&av->dccpav_records)) {
 177                 struct dccp_ackvec_record *avr, *next;
 178
 179                 list_for_each_entry_safe(avr, next, &av->dccpav_records,
 180                                          dccpavr_node) {
 181                         list_del_init(&avr->dccpavr_node);
 182                         dccp_ackvec_record_delete(avr);
 183                 }
 184         }
 185
 186         kmem_cache_free(dccp_ackvec_slab, av);
 187 }
 188
 189 static inline u8 dccp_ackvec_state(const struct dccp_ackvec *av,
 190                                    const u32 index)
 191 {
 192         return av->dccpav_buf[index] & DCCP_ACKVEC_STATE_MASK;
 193 }
 194
 195 static inline u8 dccp_ackvec_len(const struct dccp_ackvec *av,
 196                                  const u32 index)
 197 {
 198         return av->dccpav_buf[index] & DCCP_ACKVEC_LEN_MASK;
 199 }
 200
 201 /*
 202  * If several packets are missing, the HC-Receiver may prefer to enter multiple
 203  * bytes with run length 0, rather than a single byte with a larger run length;
 204  * this simplifies table updates if one of the missing packets arrives.
 205  */
 206 static inline int dccp_ackvec_set_buf_head_state(struct dccp_ackvec *av,
 207                                                  const unsigned int packets,
 208                                                  const unsigned char state)
 209 {
 210         unsigned int gap;
 211         long new_head;
 212
 213         if (av->dccpav_vec_len + packets > DCCP_MAX_ACKVEC_LEN)
 214                 return -ENOBUFS;
 215
 216         gap      = packets - 1;
 217         new_head = av->dccpav_buf_head - packets;
 218
 219         if (new_head < 0) {
 220                 if (gap > 0) {
 221                         memset(av->dccpav_buf, DCCP_ACKVEC_STATE_NOT_RECEIVED,
 222                                gap + new_head + 1);
 223                         gap = -new_head;
 224                 }
 225                 new_head += DCCP_MAX_ACKVEC_LEN;
 226         }
 227
 228         av->dccpav_buf_head = new_head;
 229
 230         if (gap > 0)
 231                 memset(av->dccpav_buf + av->dccpav_buf_head + 1,
 232                        DCCP_ACKVEC_STATE_NOT_RECEIVED, gap);
 233
 234         av->dccpav_buf[av->dccpav_buf_head] = state;
 235         av->dccpav_vec_len += packets;
 236         return 0;
 237 }
 238
 239 /*
 240  * Implements the RFC 4340, Appendix A
 241  */
 242 int dccp_ackvec_add(struct dccp_ackvec *av, const struct sock *sk,
 243                     const u64 ackno, const u8 state)
 244 {
 245         /*
 246          * Check at the right places if the buffer is full, if it is, tell the
 247          * caller to start dropping packets till the HC-Sender acks our ACK
 248          * vectors, when we will free up space in dccpav_buf.
 249          *
 250          * We may well decide to do buffer compression, etc, but for now lets
 251          * just drop.
 252          *
 253          * From Appendix A.1.1 (`New Packets'):
 254          *
 255          *      Of course, the circular buffer may overflow, either when the
 256          *      HC-Sender is sending data at a very high rate, when the
 257          *      HC-Receiver's acknowledgements are not reaching the HC-Sender,
 258          *      or when the HC-Sender is forgetting to acknowledge those acks
 259          *      (so the HC-Receiver is unable to clean up old state). In this
 260          *      case, the HC-Receiver should either compress the buffer (by
 261          *      increasing run lengths when possible), transfer its state to
 262          *      a larger buffer, or, as a last resort, drop all received
 263          *      packets, without processing them whatsoever, until its buffer
 264          *      shrinks again.
 265          */
 266
 267         /* See if this is the first ackno being inserted */
 268         if (av->dccpav_vec_len == 0) {
 269                 av->dccpav_buf[av->dccpav_buf_head] = state;
 270                 av->dccpav_vec_len = 1;
 271         } else if (after48(ackno, av->dccpav_buf_ackno)) {
 272                 const u64 delta = dccp_delta_seqno(av->dccpav_buf_ackno,
 273                                                    ackno);
 274
 275                 /*
 276                  * Look if the state of this packet is the same as the
 277                  * previous ackno and if so if we can bump the head len.
 278                  */
 279                 if (delta == 1 &&
 280                     dccp_ackvec_state(av, av->dccpav_buf_head) == state &&
 281                     (dccp_ackvec_len(av, av->dccpav_buf_head) <
 282                      DCCP_ACKVEC_LEN_MASK))
 283                         av->dccpav_buf[av->dccpav_buf_head]++;
 284                 else if (dccp_ackvec_set_buf_head_state(av, delta, state))
 285                         return -ENOBUFS;
 286         } else {
 287                 /*
 288                  * A.1.2.  Old Packets
 289                  *
 290                  *      When a packet with Sequence Number S <= buf_ackno
 291                  *      arrives, the HC-Receiver will scan the table for
 292                  *      the byte corresponding to S. (Indexing structures
 293                  *      could reduce the complexity of this scan.)
 294                  */
 295                 u64 delta = dccp_delta_seqno(ackno, av->dccpav_buf_ackno);
 296                 u32 index = av->dccpav_buf_head;
 297
 298                 while (1) {
 299                         const u8 len = dccp_ackvec_len(av, index);
 300                         const u8 state = dccp_ackvec_state(av, index);
 301                         /*
 302                          * valid packets not yet in dccpav_buf have a reserved
 303                          * entry, with a len equal to 0.
 304                          */
 305                         if (state == DCCP_ACKVEC_STATE_NOT_RECEIVED &&
 306                             len == 0 && delta == 0) { /* Found our
 307                                                          reserved seat! */
 308                                 dccp_pr_debug("Found %llu reserved seat!\n",
 309                                               (unsigned long long)ackno);
 310                                 av->dccpav_buf[index] = state;
 311                                 goto out;
 312                         }
 313                         /* len == 0 means one packet */
 314                         if (delta < len + 1)
 315                                 goto out_duplicate;
 316
 317                         delta -= len + 1;
 318                         if (++index == DCCP_MAX_ACKVEC_LEN)
 319                                 index = 0;
 320                 }
 321         }
 322
 323         av->dccpav_buf_ackno = ackno;
 324         dccp_timestamp(sk, &av->dccpav_time);
 325 out:
 326         return 0;
 327
 328 out_duplicate:
 329         /* Duplicate packet */
 330         dccp_pr_debug("Received a dup or already considered lost "
 331                       "packet: %llu\n", (unsigned long long)ackno);
 332         return -EILSEQ;
 333 }
 334
 335 #ifdef CONFIG_IP_DCCP_DEBUG
 336 void dccp_ackvector_print(const u64 ackno, const unsigned char *vector, int len)
 337 {
 338         dccp_pr_debug_cat("ACK vector len=%d, ackno=%llu |", len,
 339                                         (unsigned long long)ackno);
 340
 341         while (len--) {
 342                 const u8 state = (*vector & DCCP_ACKVEC_STATE_MASK) >> 6;
 343                 const u8 rl = *vector & DCCP_ACKVEC_LEN_MASK;
 344
 345                 dccp_pr_debug_cat("%d,%d|", state, rl);
 346                 ++vector;
 347         }
 348
 349         dccp_pr_debug_cat("\n");
 350 }
 351
 352 void dccp_ackvec_print(const struct dccp_ackvec *av)
 353 {
 354         dccp_ackvector_print(av->dccpav_buf_ackno,
 355                              av->dccpav_buf + av->dccpav_buf_head,
 356                              av->dccpav_vec_len);
 357 }
 358 #endif
 359
 360 static void dccp_ackvec_throw_record(struct dccp_ackvec *av,
 361                                      struct dccp_ackvec_record *avr)
 362 {
 363         struct dccp_ackvec_record *next;
 364
 365         /* sort out vector length */
 366         if (av->dccpav_buf_head <= avr->dccpavr_ack_ptr)
 367                 av->dccpav_vec_len = avr->dccpavr_ack_ptr - av->dccpav_buf_head;
 368         else
 369                 av->dccpav_vec_len = DCCP_MAX_ACKVEC_LEN - 1
 370                                      - av->dccpav_buf_head
 371                                      + avr->dccpavr_ack_ptr;
 372
 373         /* free records */
 374         list_for_each_entry_safe_from(avr, next, &av->dccpav_records,
 375                                       dccpavr_node) {
 376                 list_del_init(&avr->dccpavr_node);
 377                 dccp_ackvec_record_delete(avr);
 378         }
 379 }
 380
 381 void dccp_ackvec_check_rcv_ackno(struct dccp_ackvec *av, struct sock *sk,
 382                                  const u64 ackno)
 383 {
 384         struct dccp_ackvec_record *avr;
 385
 386         /*
 387          * If we traverse backwards, it should be faster when we have large
 388          * windows. We will be receiving ACKs for stuff we sent a while back
 389          * -sorbo.
 390          */
 391         list_for_each_entry_reverse(avr, &av->dccpav_records, dccpavr_node) {
 392                 if (ackno == avr->dccpavr_ack_seqno) {
 393                         dccp_pr_debug("%s ACK packet 0, len=%d, ack_seqno=%llu, "
 394                                       "ack_ackno=%llu, ACKED!\n",
 395                                       dccp_role(sk), 1,
 396                                       (unsigned long long)avr->dccpavr_ack_seqno,
 397                                       (unsigned long long)avr->dccpavr_ack_ackno);
 398                         dccp_ackvec_throw_record(av, avr);
 399                         break;
 400                 } else if (avr->dccpavr_ack_seqno > ackno)
 401                         break; /* old news */
 402         }
 403 }
 404
 405 static void dccp_ackvec_check_rcv_ackvector(struct dccp_ackvec *av,
 406                                             struct sock *sk, u64 *ackno,
 407                                             const unsigned char len,
 408                                             const unsigned char *vector)
 409 {
 410         unsigned char i;
 411         struct dccp_ackvec_record *avr;
 412
 413         /* Check if we actually sent an ACK vector */
 414         if (list_empty(&av->dccpav_records))
 415                 return;
 416
 417         i = len;
 418         /*
 419          * XXX
 420          * I think it might be more efficient to work backwards. See comment on
 421          * rcv_ackno. -sorbo.
 422          */
 423         avr = list_entry(av->dccpav_records.next, struct dccp_ackvec_record,
 424                          dccpavr_node);
 425         while (i--) {
 426                 const u8 rl = *vector & DCCP_ACKVEC_LEN_MASK;
 427                 u64 ackno_end_rl;
 428
 429                 dccp_set_seqno(&ackno_end_rl, *ackno - rl);
 430
 431                 /*
 432                  * If our AVR sequence number is greater than the ack, go
 433                  * forward in the AVR list until it is not so.
 434                  */
 435                 list_for_each_entry_from(avr, &av->dccpav_records,
 436                                          dccpavr_node) {
 437                         if (!after48(avr->dccpavr_ack_seqno, *ackno))
 438                                 goto found;
 439                 }
 440                 /* End of the dccpav_records list, not found, exit */
 441                 break;
 442 found:
 443                 if (between48(avr->dccpavr_ack_seqno, ackno_end_rl, *ackno)) {
 444                         const u8 state = *vector & DCCP_ACKVEC_STATE_MASK;
 445                         if (state != DCCP_ACKVEC_STATE_NOT_RECEIVED) {
 446                                 dccp_pr_debug("%s ACK vector 0, len=%d, "
 447                                               "ack_seqno=%llu, ack_ackno=%llu, "
 448                                               "ACKED!\n",
 449                                               dccp_role(sk), 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                       u64 *ackno, const u8 opt, const u8 *value, const u8 len)
 470 {
 471         if (len > DCCP_MAX_ACKVEC_OPT_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                                         ackno, len, value);
 477         return 0;
 478 }
 479
 480 int __init dccp_ackvec_init(void)
 481 {
 482         dccp_ackvec_slab = kmem_cache_create("dccp_ackvec",
 483                                              sizeof(struct dccp_ackvec), 0,
 484                                              SLAB_HWCACHE_ALIGN, NULL, NULL);
 485         if (dccp_ackvec_slab == NULL)
 486                 goto out_err;
 487
 488         dccp_ackvec_record_slab =
 489                         kmem_cache_create("dccp_ackvec_record",
 490                                           sizeof(struct dccp_ackvec_record),
 491                                           0, SLAB_HWCACHE_ALIGN, NULL, NULL);
 492         if (dccp_ackvec_record_slab == NULL)
 493                 goto out_destroy_slab;
 494
 495         return 0;
 496
 497 out_destroy_slab:
 498         kmem_cache_destroy(dccp_ackvec_slab);
 499         dccp_ackvec_slab = NULL;
 500 out_err:
 501         DCCP_CRIT("Unable to create Ack Vector slab cache");
 502         return -ENOBUFS;
 503 }
 504
 505 void dccp_ackvec_exit(void)
 506 {
 507         if (dccp_ackvec_slab != NULL) {
 508                 kmem_cache_destroy(dccp_ackvec_slab);
 509                 dccp_ackvec_slab = NULL;
 510         }
 511         if (dccp_ackvec_record_slab != NULL) {
 512                 kmem_cache_destroy(dccp_ackvec_record_slab);
 513                 dccp_ackvec_record_slab = NULL;
 514         }
 515 }