net/dccp/ackvec.c

   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 struct kmem_cache *dccp_ackvec_slab;
  25 static struct kmem_cache *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 = DIV_ROUND_UP(av->dccpav_vec_len,
  73                                          DCCP_MAX_ACKVEC_OPT_LEN);
  74         u16 len = av->dccpav_vec_len + 2 * nr_opts, i;
  75         u32 elapsed_time;
  76         const unsigned char *tail, *from;
  77         unsigned char *to;
  78         struct dccp_ackvec_record *avr;
  79         suseconds_t delta;
  80
  81         if (DCCP_SKB_CB(skb)->dccpd_opt_len + len > DCCP_MAX_OPT_LEN)
  82                 return -1;
  83
  84         delta = ktime_us_delta(ktime_get_real(), av->dccpav_time);
  85         elapsed_time = delta / 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         len  = av->dccpav_vec_len;
  99         from = av->dccpav_buf + av->dccpav_buf_head;
 100         tail = av->dccpav_buf + DCCP_MAX_ACKVEC_LEN;
 101
 102         for (i = 0; i < nr_opts; ++i) {
 103                 int copylen = len;
 104
 105                 if (len > DCCP_MAX_ACKVEC_OPT_LEN)
 106                         copylen = DCCP_MAX_ACKVEC_OPT_LEN;
 107
 108                 *to++ = DCCPO_ACK_VECTOR_0;
 109                 *to++ = copylen + 2;
 110
 111                 /* Check if buf_head wraps */
 112                 if (from + copylen > tail) {
 113                         const u16 tailsize = tail - from;
 114
 115                         memcpy(to, from, tailsize);
 116                         to      += tailsize;
 117                         len     -= tailsize;
 118                         copylen -= tailsize;
 119                         from    = av->dccpav_buf;
 120                 }
 121
 122                 memcpy(to, from, copylen);
 123                 from += copylen;
 124                 to   += copylen;
 125                 len  -= copylen;
 126         }
 127
 128         /*
 129          *      From RFC 4340, A.2:
 130          *
 131          *      For each acknowledgement it sends, the HC-Receiver will add an
 132          *      acknowledgement record.  ack_seqno will equal the HC-Receiver
 133          *      sequence number it used for the ack packet; ack_ptr will equal
 134          *      buf_head; ack_ackno will equal buf_ackno; and ack_nonce will
 135          *      equal buf_nonce.
 136          */
 137         avr->dccpavr_ack_seqno = DCCP_SKB_CB(skb)->dccpd_seq;
 138         avr->dccpavr_ack_ptr   = av->dccpav_buf_head;
 139         avr->dccpavr_ack_ackno = av->dccpav_buf_ackno;
 140         avr->dccpavr_ack_nonce = av->dccpav_buf_nonce;
 141         avr->dccpavr_sent_len  = av->dccpav_vec_len;
 142
 143         dccp_ackvec_insert_avr(av, avr);
 144
 145         dccp_pr_debug("%s ACK Vector 0, len=%d, ack_seqno=%llu, "
 146                       "ack_ackno=%llu\n",
 147                       dccp_role(sk), avr->dccpavr_sent_len,
 148                       (unsigned long long)avr->dccpavr_ack_seqno,
 149                       (unsigned long long)avr->dccpavr_ack_ackno);
 150         return 0;
 151 }
 152
 153 struct dccp_ackvec *dccp_ackvec_alloc(const gfp_t priority)
 154 {
 155         struct dccp_ackvec *av = kmem_cache_alloc(dccp_ackvec_slab, priority);
 156
 157         if (av != NULL) {
 158                 av->dccpav_buf_head     = DCCP_MAX_ACKVEC_LEN - 1;
 159                 av->dccpav_buf_ackno    = UINT48_MAX + 1;
 160                 av->dccpav_buf_nonce = av->dccpav_buf_nonce = 0;
 161                 av->dccpav_time      = ktime_set(0, 0);
 162                 av->dccpav_vec_len      = 0;
 163                 INIT_LIST_HEAD(&av->dccpav_records);
 164         }
 165
 166         return av;
 167 }
 168
 169 void dccp_ackvec_free(struct dccp_ackvec *av)
 170 {
 171         if (unlikely(av == NULL))
 172                 return;
 173
 174         if (!list_empty(&av->dccpav_records)) {
 175                 struct dccp_ackvec_record *avr, *next;
 176
 177                 list_for_each_entry_safe(avr, next, &av->dccpav_records,
 178                                          dccpavr_node) {
 179                         list_del_init(&avr->dccpavr_node);
 180                         dccp_ackvec_record_delete(avr);
 181                 }
 182         }
 183
 184         kmem_cache_free(dccp_ackvec_slab, av);
 185 }
 186
 187 static inline u8 dccp_ackvec_state(const struct dccp_ackvec *av,
 188                                    const u32 index)
 189 {
 190         return av->dccpav_buf[index] & DCCP_ACKVEC_STATE_MASK;
 191 }
 192
 193 static inline u8 dccp_ackvec_len(const struct dccp_ackvec *av,
 194                                  const u32 index)
 195 {
 196         return av->dccpav_buf[index] & DCCP_ACKVEC_LEN_MASK;
 197 }
 198
 199 /*
 200  * If several packets are missing, the HC-Receiver may prefer to enter multiple
 201  * bytes with run length 0, rather than a single byte with a larger run length;
 202  * this simplifies table updates if one of the missing packets arrives.
 203  */
 204 static inline int dccp_ackvec_set_buf_head_state(struct dccp_ackvec *av,
 205                                                  const unsigned int packets,
 206                                                  const unsigned char state)
 207 {
 208         unsigned int gap;
 209         long new_head;
 210
 211         if (av->dccpav_vec_len + packets > DCCP_MAX_ACKVEC_LEN)
 212                 return -ENOBUFS;
 213
 214         gap      = packets - 1;
 215         new_head = av->dccpav_buf_head - packets;
 216
 217         if (new_head < 0) {
 218                 if (gap > 0) {
 219                         memset(av->dccpav_buf, DCCP_ACKVEC_STATE_NOT_RECEIVED,
 220                                gap + new_head + 1);
 221                         gap = -new_head;
 222                 }
 223                 new_head += DCCP_MAX_ACKVEC_LEN;
 224         }
 225
 226         av->dccpav_buf_head = new_head;
 227
 228         if (gap > 0)
 229                 memset(av->dccpav_buf + av->dccpav_buf_head + 1,
 230                        DCCP_ACKVEC_STATE_NOT_RECEIVED, gap);
 231
 232         av->dccpav_buf[av->dccpav_buf_head] = state;
 233         av->dccpav_vec_len += packets;
 234         return 0;
 235 }
 236
 237 /*
 238  * Implements the RFC 4340, Appendix A
 239  */
 240 int dccp_ackvec_add(struct dccp_ackvec *av, const struct sock *sk,
 241                     const u64 ackno, const u8 state)
 242 {
 243         /*
 244          * Check at the right places if the buffer is full, if it is, tell the
 245          * caller to start dropping packets till the HC-Sender acks our ACK
 246          * vectors, when we will free up space in dccpav_buf.
 247          *
 248          * We may well decide to do buffer compression, etc, but for now lets
 249          * just drop.
 250          *
 251          * From Appendix A.1.1 (`New Packets'):
 252          *
 253          *      Of course, the circular buffer may overflow, either when the
 254          *      HC-Sender is sending data at a very high rate, when the
 255          *      HC-Receiver's acknowledgements are not reaching the HC-Sender,
 256          *      or when the HC-Sender is forgetting to acknowledge those acks
 257          *      (so the HC-Receiver is unable to clean up old state). In this
 258          *      case, the HC-Receiver should either compress the buffer (by
 259          *      increasing run lengths when possible), transfer its state to
 260          *      a larger buffer, or, as a last resort, drop all received
 261          *      packets, without processing them whatsoever, until its buffer
 262          *      shrinks again.
 263          */
 264
 265         /* See if this is the first ackno being inserted */
 266         if (av->dccpav_vec_len == 0) {
 267                 av->dccpav_buf[av->dccpav_buf_head] = state;
 268                 av->dccpav_vec_len = 1;
 269         } else if (after48(ackno, av->dccpav_buf_ackno)) {
 270                 const u64 delta = dccp_delta_seqno(av->dccpav_buf_ackno,
 271                                                    ackno);
 272
 273                 /*
 274                  * Look if the state of this packet is the same as the
 275                  * previous ackno and if so if we can bump the head len.
 276                  */
 277                 if (delta == 1 &&
 278                     dccp_ackvec_state(av, av->dccpav_buf_head) == state &&
 279                     (dccp_ackvec_len(av, av->dccpav_buf_head) <
 280                      DCCP_ACKVEC_LEN_MASK))
 281                         av->dccpav_buf[av->dccpav_buf_head]++;
 282                 else if (dccp_ackvec_set_buf_head_state(av, delta, state))
 283                         return -ENOBUFS;
 284         } else {
 285                 /*
 286                  * A.1.2.  Old Packets
 287                  *
 288                  *      When a packet with Sequence Number S <= buf_ackno
 289                  *      arrives, the HC-Receiver will scan the table for
 290                  *      the byte corresponding to S. (Indexing structures
 291                  *      could reduce the complexity of this scan.)
 292                  */
 293                 u64 delta = dccp_delta_seqno(ackno, av->dccpav_buf_ackno);
 294                 u32 index = av->dccpav_buf_head;
 295
 296                 while (1) {
 297                         const u8 len = dccp_ackvec_len(av, index);
 298                         const u8 state = dccp_ackvec_state(av, index);
 299                         /*
 300                          * valid packets not yet in dccpav_buf have a reserved
 301                          * entry, with a len equal to 0.
 302                          */
 303                         if (state == DCCP_ACKVEC_STATE_NOT_RECEIVED &&
 304                             len == 0 && delta == 0) { /* Found our
 305                                                          reserved seat! */
 306                                 dccp_pr_debug("Found %llu reserved seat!\n",
 307                                               (unsigned long long)ackno);
 308                                 av->dccpav_buf[index] = state;
 309                                 goto out;
 310                         }
 311                         /* len == 0 means one packet */
 312                         if (delta < len + 1)
 313                                 goto out_duplicate;
 314
 315                         delta -= len + 1;
 316                         if (++index == DCCP_MAX_ACKVEC_LEN)
 317                                 index = 0;
 318                 }
 319         }
 320
 321         av->dccpav_buf_ackno = ackno;
 322         av->dccpav_time = ktime_get_real();
 323 out:
 324         return 0;
 325
 326 out_duplicate:
 327         /* Duplicate packet */
 328         dccp_pr_debug("Received a dup or already considered lost "
 329                       "packet: %llu\n", (unsigned long long)ackno);
 330         return -EILSEQ;
 331 }
 332
 333 #ifdef CONFIG_IP_DCCP_DEBUG
 334 void dccp_ackvector_print(const u64 ackno, const unsigned char *vector, int len)
 335 {
 336         dccp_pr_debug_cat("ACK vector len=%d, ackno=%llu |", len,
 337                          (unsigned long long)ackno);
 338
 339         while (len--) {
 340                 const u8 state = (*vector & DCCP_ACKVEC_STATE_MASK) >> 6;
 341                 const u8 rl = *vector & DCCP_ACKVEC_LEN_MASK;
 342
 343                 dccp_pr_debug_cat("%d,%d|", state, rl);
 344                 ++vector;
 345         }
 346
 347         dccp_pr_debug_cat("\n");
 348 }
 349
 350 void dccp_ackvec_print(const struct dccp_ackvec *av)
 351 {
 352         dccp_ackvector_print(av->dccpav_buf_ackno,
 353                              av->dccpav_buf + av->dccpav_buf_head,
 354                              av->dccpav_vec_len);
 355 }
 356 #endif
 357
 358 static void dccp_ackvec_throw_record(struct dccp_ackvec *av,
 359                                      struct dccp_ackvec_record *avr)
 360 {
 361         struct dccp_ackvec_record *next;
 362
 363         /* sort out vector length */
 364         if (av->dccpav_buf_head <= avr->dccpavr_ack_ptr)
 365                 av->dccpav_vec_len = avr->dccpavr_ack_ptr - av->dccpav_buf_head;
 366         else
 367                 av->dccpav_vec_len = DCCP_MAX_ACKVEC_LEN - 1
 368                                      - av->dccpav_buf_head
 369                                      + avr->dccpavr_ack_ptr;
 370
 371         /* free records */
 372         list_for_each_entry_safe_from(avr, next, &av->dccpav_records,
 373                                       dccpavr_node) {
 374                 list_del_init(&avr->dccpavr_node);
 375                 dccp_ackvec_record_delete(avr);
 376         }
 377 }
 378
 379 void dccp_ackvec_check_rcv_ackno(struct dccp_ackvec *av, struct sock *sk,
 380                                  const u64 ackno)
 381 {
 382         struct dccp_ackvec_record *avr;
 383
 384         /*
 385          * If we traverse backwards, it should be faster when we have large
 386          * windows. We will be receiving ACKs for stuff we sent a while back
 387          * -sorbo.
 388          */
 389         list_for_each_entry_reverse(avr, &av->dccpav_records, dccpavr_node) {
 390                 if (ackno == avr->dccpavr_ack_seqno) {
 391                         dccp_pr_debug("%s ACK packet 0, len=%d, ack_seqno=%llu, "
 392                                       "ack_ackno=%llu, ACKED!\n",
 393                                       dccp_role(sk), 1,
 394                                       (unsigned long long)avr->dccpavr_ack_seqno,
 395                                       (unsigned long long)avr->dccpavr_ack_ackno);
 396                         dccp_ackvec_throw_record(av, avr);
 397                         break;
 398                 } else if (avr->dccpavr_ack_seqno > ackno)
 399                         break; /* old news */
 400         }
 401 }
 402
 403 static void dccp_ackvec_check_rcv_ackvector(struct dccp_ackvec *av,
 404                                             struct sock *sk, u64 *ackno,
 405                                             const unsigned char len,
 406                                             const unsigned char *vector)
 407 {
 408         unsigned char i;
 409         struct dccp_ackvec_record *avr;
 410
 411         /* Check if we actually sent an ACK vector */
 412         if (list_empty(&av->dccpav_records))
 413                 return;
 414
 415         i = len;
 416         /*
 417          * XXX
 418          * I think it might be more efficient to work backwards. See comment on
 419          * rcv_ackno. -sorbo.
 420          */
 421         avr = list_entry(av->dccpav_records.next, struct dccp_ackvec_record,
 422                          dccpavr_node);
 423         while (i--) {
 424                 const u8 rl = *vector & DCCP_ACKVEC_LEN_MASK;
 425                 u64 ackno_end_rl;
 426
 427                 dccp_set_seqno(&ackno_end_rl, *ackno - rl);
 428
 429                 /*
 430                  * If our AVR sequence number is greater than the ack, go
 431                  * forward in the AVR list until it is not so.
 432                  */
 433                 list_for_each_entry_from(avr, &av->dccpav_records,
 434                                          dccpavr_node) {
 435                         if (!after48(avr->dccpavr_ack_seqno, *ackno))
 436                                 goto found;
 437                 }
 438                 /* End of the dccpav_records list, not found, exit */
 439                 break;
 440 found:
 441                 if (between48(avr->dccpavr_ack_seqno, ackno_end_rl, *ackno)) {
 442                         const u8 state = *vector & DCCP_ACKVEC_STATE_MASK;
 443                         if (state != DCCP_ACKVEC_STATE_NOT_RECEIVED) {
 444                                 dccp_pr_debug("%s ACK vector 0, len=%d, "
 445                                               "ack_seqno=%llu, ack_ackno=%llu, "
 446                                               "ACKED!\n",
 447                                               dccp_role(sk), len,
 448                                               (unsigned long long)
 449                                               avr->dccpavr_ack_seqno,
 450                                               (unsigned long long)
 451                                               avr->dccpavr_ack_ackno);
 452                                 dccp_ackvec_throw_record(av, avr);
 453                                 break;
 454                         }
 455                         /*
 456                          * If it wasn't received, continue scanning... we might
 457                          * find another one.
 458                          */
 459                 }
 460
 461                 dccp_set_seqno(ackno, ackno_end_rl - 1);
 462                 ++vector;
 463         }
 464 }
 465
 466 int dccp_ackvec_parse(struct sock *sk, const struct sk_buff *skb,
 467                       u64 *ackno, const u8 opt, const u8 *value, const u8 len)
 468 {
 469         if (len > DCCP_MAX_ACKVEC_OPT_LEN)
 470                 return -1;
 471
 472         /* dccp_ackvector_print(DCCP_SKB_CB(skb)->dccpd_ack_seq, value, len); */
 473         dccp_ackvec_check_rcv_ackvector(dccp_sk(sk)->dccps_hc_rx_ackvec, sk,
 474                                         ackno, len, value);
 475         return 0;
 476 }
 477
 478 int __init dccp_ackvec_init(void)
 479 {
 480         dccp_ackvec_slab = kmem_cache_create("dccp_ackvec",
 481                                              sizeof(struct dccp_ackvec), 0,
 482                                              SLAB_HWCACHE_ALIGN, NULL);
 483         if (dccp_ackvec_slab == NULL)
 484                 goto out_err;
 485
 486         dccp_ackvec_record_slab =
 487                         kmem_cache_create("dccp_ackvec_record",
 488                                           sizeof(struct dccp_ackvec_record),
 489                                           0, SLAB_HWCACHE_ALIGN, NULL);
 490         if (dccp_ackvec_record_slab == NULL)
 491                 goto out_destroy_slab;
 492
 493         return 0;
 494
 495 out_destroy_slab:
 496         kmem_cache_destroy(dccp_ackvec_slab);
 497         dccp_ackvec_slab = NULL;
 498 out_err:
 499         DCCP_CRIT("Unable to create Ack Vector slab cache");
 500         return -ENOBUFS;
 501 }
 502
 503 void dccp_ackvec_exit(void)
 504 {
 505         if (dccp_ackvec_slab != NULL) {
 506                 kmem_cache_destroy(dccp_ackvec_slab);
 507                 dccp_ackvec_slab = NULL;
 508         }
 509         if (dccp_ackvec_record_slab != NULL) {
 510                 kmem_cache_destroy(dccp_ackvec_record_slab);
 511                 dccp_ackvec_record_slab = NULL;
 512         }
 513 }