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->avr_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->avr_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->av_records)) {
  56                 const struct dccp_ackvec_record *head =
  57                                         list_entry(av->av_records.next,
  58                                                    struct dccp_ackvec_record,
  59                                                    avr_node);
  60                 BUG_ON(before48(avr->avr_ack_seqno, head->avr_ack_seqno));
  61         }
  62
  63         list_add(&avr->avr_node, &av->av_records);
  64 }
  65
  66 int dccp_insert_option_ackvec(struct sock *sk, struct sk_buff *skb)
  67 {
  68         struct dccp_sock *dp = dccp_sk(sk);
  69         struct dccp_ackvec *av = dp->dccps_hc_rx_ackvec;
  70         /* Figure out how many options do we need to represent the ackvec */
  71         const u16 nr_opts = DIV_ROUND_UP(av->av_vec_len, DCCP_MAX_ACKVEC_OPT_LEN);
  72         u16 len = av->av_vec_len + 2 * nr_opts, i;
  73         u32 elapsed_time;
  74         const unsigned char *tail, *from;
  75         unsigned char *to;
  76         struct dccp_ackvec_record *avr;
  77         suseconds_t delta;
  78
  79         if (DCCP_SKB_CB(skb)->dccpd_opt_len + len > DCCP_MAX_OPT_LEN)
  80                 return -1;
  81
  82         delta = ktime_us_delta(ktime_get_real(), av->av_time);
  83         elapsed_time = delta / 10;
  84
  85         if (elapsed_time != 0 &&
  86             dccp_insert_option_elapsed_time(sk, skb, elapsed_time))
  87                 return -1;
  88
  89         avr = dccp_ackvec_record_new();
  90         if (avr == NULL)
  91                 return -1;
  92
  93         DCCP_SKB_CB(skb)->dccpd_opt_len += len;
  94
  95         to   = skb_push(skb, len);
  96         len  = av->av_vec_len;
  97         from = av->av_buf + av->av_buf_head;
  98         tail = av->av_buf + DCCP_MAX_ACKVEC_LEN;
  99
 100         for (i = 0; i < nr_opts; ++i) {
 101                 int copylen = len;
 102
 103                 if (len > DCCP_MAX_ACKVEC_OPT_LEN)
 104                         copylen = DCCP_MAX_ACKVEC_OPT_LEN;
 105
 106                 *to++ = DCCPO_ACK_VECTOR_0;
 107                 *to++ = copylen + 2;
 108
 109                 /* Check if buf_head wraps */
 110                 if (from + copylen > tail) {
 111                         const u16 tailsize = tail - from;
 112
 113                         memcpy(to, from, tailsize);
 114                         to      += tailsize;
 115                         len     -= tailsize;
 116                         copylen -= tailsize;
 117                         from    = av->av_buf;
 118                 }
 119
 120                 memcpy(to, from, copylen);
 121                 from += copylen;
 122                 to   += copylen;
 123                 len  -= copylen;
 124         }
 125
 126         /*
 127          *      From RFC 4340, A.2:
 128          *
 129          *      For each acknowledgement it sends, the HC-Receiver will add an
 130          *      acknowledgement record.  ack_seqno will equal the HC-Receiver
 131          *      sequence number it used for the ack packet; ack_ptr will equal
 132          *      buf_head; ack_ackno will equal buf_ackno; and ack_nonce will
 133          *      equal buf_nonce.
 134          */
 135         avr->avr_ack_seqno = DCCP_SKB_CB(skb)->dccpd_seq;
 136         avr->avr_ack_ptr   = av->av_buf_head;
 137         avr->avr_ack_ackno = av->av_buf_ackno;
 138         avr->avr_ack_nonce = av->av_buf_nonce;
 139         avr->avr_sent_len  = av->av_vec_len;
 140
 141         dccp_ackvec_insert_avr(av, avr);
 142
 143         dccp_pr_debug("%s ACK Vector 0, len=%d, ack_seqno=%llu, "
 144                       "ack_ackno=%llu\n",
 145                       dccp_role(sk), avr->avr_sent_len,
 146                       (unsigned long long)avr->avr_ack_seqno,
 147                       (unsigned long long)avr->avr_ack_ackno);
 148         return 0;
 149 }
 150
 151 struct dccp_ackvec *dccp_ackvec_alloc(const gfp_t priority)
 152 {
 153         struct dccp_ackvec *av = kmem_cache_alloc(dccp_ackvec_slab, priority);
 154
 155         if (av != NULL) {
 156                 av->av_buf_head  = DCCP_MAX_ACKVEC_LEN - 1;
 157                 av->av_buf_ackno = UINT48_MAX + 1;
 158                 av->av_buf_nonce = 0;
 159                 av->av_time      = ktime_set(0, 0);
 160                 av->av_vec_len   = 0;
 161                 INIT_LIST_HEAD(&av->av_records);
 162         }
 163
 164         return av;
 165 }
 166
 167 void dccp_ackvec_free(struct dccp_ackvec *av)
 168 {
 169         if (unlikely(av == NULL))
 170                 return;
 171
 172         if (!list_empty(&av->av_records)) {
 173                 struct dccp_ackvec_record *avr, *next;
 174
 175                 list_for_each_entry_safe(avr, next, &av->av_records, avr_node) {
 176                         list_del_init(&avr->avr_node);
 177                         dccp_ackvec_record_delete(avr);
 178                 }
 179         }
 180
 181         kmem_cache_free(dccp_ackvec_slab, av);
 182 }
 183
 184 static inline u8 dccp_ackvec_state(const struct dccp_ackvec *av,
 185                                    const u32 index)
 186 {
 187         return av->av_buf[index] & DCCP_ACKVEC_STATE_MASK;
 188 }
 189
 190 static inline u8 dccp_ackvec_len(const struct dccp_ackvec *av,
 191                                  const u32 index)
 192 {
 193         return av->av_buf[index] & DCCP_ACKVEC_LEN_MASK;
 194 }
 195
 196 /*
 197  * If several packets are missing, the HC-Receiver may prefer to enter multiple
 198  * bytes with run length 0, rather than a single byte with a larger run length;
 199  * this simplifies table updates if one of the missing packets arrives.
 200  */
 201 static inline int dccp_ackvec_set_buf_head_state(struct dccp_ackvec *av,
 202                                                  const unsigned int packets,
 203                                                  const unsigned char state)
 204 {
 205         unsigned int gap;
 206         long new_head;
 207
 208         if (av->av_vec_len + packets > DCCP_MAX_ACKVEC_LEN)
 209                 return -ENOBUFS;
 210
 211         gap      = packets - 1;
 212         new_head = av->av_buf_head - packets;
 213
 214         if (new_head < 0) {
 215                 if (gap > 0) {
 216                         memset(av->av_buf, DCCP_ACKVEC_STATE_NOT_RECEIVED,
 217                                gap + new_head + 1);
 218                         gap = -new_head;
 219                 }
 220                 new_head += DCCP_MAX_ACKVEC_LEN;
 221         }
 222
 223         av->av_buf_head = new_head;
 224
 225         if (gap > 0)
 226                 memset(av->av_buf + av->av_buf_head + 1,
 227                        DCCP_ACKVEC_STATE_NOT_RECEIVED, gap);
 228
 229         av->av_buf[av->av_buf_head] = state;
 230         av->av_vec_len += packets;
 231         return 0;
 232 }
 233
 234 /*
 235  * Implements the RFC 4340, Appendix A
 236  */
 237 int dccp_ackvec_add(struct dccp_ackvec *av, const struct sock *sk,
 238                     const u64 ackno, const u8 state)
 239 {
 240         /*
 241          * Check at the right places if the buffer is full, if it is, tell the
 242          * caller to start dropping packets till the HC-Sender acks our ACK
 243          * vectors, when we will free up space in av_buf.
 244          *
 245          * We may well decide to do buffer compression, etc, but for now lets
 246          * just drop.
 247          *
 248          * From Appendix A.1.1 (`New Packets'):
 249          *
 250          *      Of course, the circular buffer may overflow, either when the
 251          *      HC-Sender is sending data at a very high rate, when the
 252          *      HC-Receiver's acknowledgements are not reaching the HC-Sender,
 253          *      or when the HC-Sender is forgetting to acknowledge those acks
 254          *      (so the HC-Receiver is unable to clean up old state). In this
 255          *      case, the HC-Receiver should either compress the buffer (by
 256          *      increasing run lengths when possible), transfer its state to
 257          *      a larger buffer, or, as a last resort, drop all received
 258          *      packets, without processing them whatsoever, until its buffer
 259          *      shrinks again.
 260          */
 261
 262         /* See if this is the first ackno being inserted */
 263         if (av->av_vec_len == 0) {
 264                 av->av_buf[av->av_buf_head] = state;
 265                 av->av_vec_len = 1;
 266         } else if (after48(ackno, av->av_buf_ackno)) {
 267                 const u64 delta = dccp_delta_seqno(av->av_buf_ackno, ackno);
 268
 269                 /*
 270                  * Look if the state of this packet is the same as the
 271                  * previous ackno and if so if we can bump the head len.
 272                  */
 273                 if (delta == 1 &&
 274                     dccp_ackvec_state(av, av->av_buf_head) == state &&
 275                     dccp_ackvec_len(av, av->av_buf_head) < DCCP_ACKVEC_LEN_MASK)
 276                         av->av_buf[av->av_buf_head]++;
 277                 else if (dccp_ackvec_set_buf_head_state(av, delta, state))
 278                         return -ENOBUFS;
 279         } else {
 280                 /*
 281                  * A.1.2.  Old Packets
 282                  *
 283                  *      When a packet with Sequence Number S <= buf_ackno
 284                  *      arrives, the HC-Receiver will scan the table for
 285                  *      the byte corresponding to S. (Indexing structures
 286                  *      could reduce the complexity of this scan.)
 287                  */
 288                 u64 delta = dccp_delta_seqno(ackno, av->av_buf_ackno);
 289                 u32 index = av->av_buf_head;
 290
 291                 while (1) {
 292                         const u8 len = dccp_ackvec_len(av, index);
 293                         const u8 av_state = dccp_ackvec_state(av, index);
 294                         /*
 295                          * valid packets not yet in av_buf have a reserved
 296                          * entry, with a len equal to 0.
 297                          */
 298                         if (av_state == DCCP_ACKVEC_STATE_NOT_RECEIVED &&
 299                             len == 0 && delta == 0) { /* Found our
 300                                                          reserved seat! */
 301                                 dccp_pr_debug("Found %llu reserved seat!\n",
 302                                               (unsigned long long)ackno);
 303                                 av->av_buf[index] = state;
 304                                 goto out;
 305                         }
 306                         /* len == 0 means one packet */
 307                         if (delta < len + 1)
 308                                 goto out_duplicate;
 309
 310                         delta -= len + 1;
 311                         if (++index == DCCP_MAX_ACKVEC_LEN)
 312                                 index = 0;
 313                 }
 314         }
 315
 316         av->av_buf_ackno = ackno;
 317         av->av_time = ktime_get_real();
 318 out:
 319         return 0;
 320
 321 out_duplicate:
 322         /* Duplicate packet */
 323         dccp_pr_debug("Received a dup or already considered lost "
 324                       "packet: %llu\n", (unsigned long long)ackno);
 325         return -EILSEQ;
 326 }
 327
 328 static void dccp_ackvec_throw_record(struct dccp_ackvec *av,
 329                                      struct dccp_ackvec_record *avr)
 330 {
 331         struct dccp_ackvec_record *next;
 332
 333         /* sort out vector length */
 334         if (av->av_buf_head <= avr->avr_ack_ptr)
 335                 av->av_vec_len = avr->avr_ack_ptr - av->av_buf_head;
 336         else
 337                 av->av_vec_len = DCCP_MAX_ACKVEC_LEN - 1 -
 338                                  av->av_buf_head + avr->avr_ack_ptr;
 339
 340         /* free records */
 341         list_for_each_entry_safe_from(avr, next, &av->av_records, avr_node) {
 342                 list_del_init(&avr->avr_node);
 343                 dccp_ackvec_record_delete(avr);
 344         }
 345 }
 346
 347 void dccp_ackvec_check_rcv_ackno(struct dccp_ackvec *av, struct sock *sk,
 348                                  const u64 ackno)
 349 {
 350         struct dccp_ackvec_record *avr;
 351
 352         /*
 353          * If we traverse backwards, it should be faster when we have large
 354          * windows. We will be receiving ACKs for stuff we sent a while back
 355          * -sorbo.
 356          */
 357         list_for_each_entry_reverse(avr, &av->av_records, avr_node) {
 358                 if (ackno == avr->avr_ack_seqno) {
 359                         dccp_pr_debug("%s ACK packet 0, len=%d, ack_seqno=%llu, "
 360                                       "ack_ackno=%llu, ACKED!\n",
 361                                       dccp_role(sk), 1,
 362                                       (unsigned long long)avr->avr_ack_seqno,
 363                                       (unsigned long long)avr->avr_ack_ackno);
 364                         dccp_ackvec_throw_record(av, avr);
 365                         break;
 366                 } else if (avr->avr_ack_seqno > ackno)
 367                         break; /* old news */
 368         }
 369 }
 370
 371 static void dccp_ackvec_check_rcv_ackvector(struct dccp_ackvec *av,
 372                                             struct sock *sk, u64 *ackno,
 373                                             const unsigned char len,
 374                                             const unsigned char *vector)
 375 {
 376         unsigned char i;
 377         struct dccp_ackvec_record *avr;
 378
 379         /* Check if we actually sent an ACK vector */
 380         if (list_empty(&av->av_records))
 381                 return;
 382
 383         i = len;
 384         /*
 385          * XXX
 386          * I think it might be more efficient to work backwards. See comment on
 387          * rcv_ackno. -sorbo.
 388          */
 389         avr = list_entry(av->av_records.next, struct dccp_ackvec_record, avr_node);
 390         while (i--) {
 391                 const u8 rl = *vector & DCCP_ACKVEC_LEN_MASK;
 392                 u64 ackno_end_rl;
 393
 394                 dccp_set_seqno(&ackno_end_rl, *ackno - rl);
 395
 396                 /*
 397                  * If our AVR sequence number is greater than the ack, go
 398                  * forward in the AVR list until it is not so.
 399                  */
 400                 list_for_each_entry_from(avr, &av->av_records, avr_node) {
 401                         if (!after48(avr->avr_ack_seqno, *ackno))
 402                                 goto found;
 403                 }
 404                 /* End of the av_records list, not found, exit */
 405                 break;
 406 found:
 407                 if (between48(avr->avr_ack_seqno, ackno_end_rl, *ackno)) {
 408                         const u8 state = *vector & DCCP_ACKVEC_STATE_MASK;
 409                         if (state != DCCP_ACKVEC_STATE_NOT_RECEIVED) {
 410                                 dccp_pr_debug("%s ACK vector 0, len=%d, "
 411                                               "ack_seqno=%llu, ack_ackno=%llu, "
 412                                               "ACKED!\n",
 413                                               dccp_role(sk), len,
 414                                               (unsigned long long)
 415                                               avr->avr_ack_seqno,
 416                                               (unsigned long long)
 417                                               avr->avr_ack_ackno);
 418                                 dccp_ackvec_throw_record(av, avr);
 419                                 break;
 420                         }
 421                         /*
 422                          * If it wasn't received, continue scanning... we might
 423                          * find another one.
 424                          */
 425                 }
 426
 427                 dccp_set_seqno(ackno, ackno_end_rl - 1);
 428                 ++vector;
 429         }
 430 }
 431
 432 int dccp_ackvec_parse(struct sock *sk, const struct sk_buff *skb,
 433                       u64 *ackno, const u8 opt, const u8 *value, const u8 len)
 434 {
 435         if (len > DCCP_MAX_ACKVEC_OPT_LEN)
 436                 return -1;
 437
 438         /* dccp_ackvector_print(DCCP_SKB_CB(skb)->dccpd_ack_seq, value, len); */
 439         dccp_ackvec_check_rcv_ackvector(dccp_sk(sk)->dccps_hc_rx_ackvec, sk,
 440                                         ackno, len, value);
 441         return 0;
 442 }
 443
 444 int __init dccp_ackvec_init(void)
 445 {
 446         dccp_ackvec_slab = kmem_cache_create("dccp_ackvec",
 447                                              sizeof(struct dccp_ackvec), 0,
 448                                              SLAB_HWCACHE_ALIGN, NULL);
 449         if (dccp_ackvec_slab == NULL)
 450                 goto out_err;
 451
 452         dccp_ackvec_record_slab =
 453                         kmem_cache_create("dccp_ackvec_record",
 454                                           sizeof(struct dccp_ackvec_record),
 455                                           0, SLAB_HWCACHE_ALIGN, NULL);
 456         if (dccp_ackvec_record_slab == NULL)
 457                 goto out_destroy_slab;
 458
 459         return 0;
 460
 461 out_destroy_slab:
 462         kmem_cache_destroy(dccp_ackvec_slab);
 463         dccp_ackvec_slab = NULL;
 464 out_err:
 465         DCCP_CRIT("Unable to create Ack Vector slab cache");
 466         return -ENOBUFS;
 467 }
 468
 469 void dccp_ackvec_exit(void)
 470 {
 471         if (dccp_ackvec_slab != NULL) {
 472                 kmem_cache_destroy(dccp_ackvec_slab);
 473                 dccp_ackvec_slab = NULL;
 474         }
 475         if (dccp_ackvec_record_slab != NULL) {
 476                 kmem_cache_destroy(dccp_ackvec_record_slab);
 477                 dccp_ackvec_record_slab = NULL;
 478         }
 479 }