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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/init.h>
  16 #include <linux/errno.h>
  17 #include <linux/kernel.h>
  18 #include <linux/skbuff.h>
  19 #include <linux/slab.h>
  20
  21 #include <net/sock.h>
  22
  23 static struct kmem_cache *dccp_ackvec_slab;
  24 static struct kmem_cache *dccp_ackvec_record_slab;
  25
  26 static struct dccp_ackvec_record *dccp_ackvec_record_new(void)
  27 {
  28         struct dccp_ackvec_record *avr =
  29                         kmem_cache_alloc(dccp_ackvec_record_slab, GFP_ATOMIC);
  30
  31         if (avr != NULL)
  32                 INIT_LIST_HEAD(&avr->avr_node);
  33
  34         return avr;
  35 }
  36
  37 static void dccp_ackvec_record_delete(struct dccp_ackvec_record *avr)
  38 {
  39         if (unlikely(avr == NULL))
  40                 return;
  41         /* Check if deleting a linked record */
  42         WARN_ON(!list_empty(&avr->avr_node));
  43         kmem_cache_free(dccp_ackvec_record_slab, avr);
  44 }
  45
  46 static void dccp_ackvec_insert_avr(struct dccp_ackvec *av,
  47                                    struct dccp_ackvec_record *avr)
  48 {
  49         /*
  50          * AVRs are sorted by seqno. Since we are sending them in order, we
  51          * just add the AVR at the head of the list.
  52          * -sorbo.
  53          */
  54         if (!list_empty(&av->av_records)) {
  55                 const struct dccp_ackvec_record *head =
  56                                         list_entry(av->av_records.next,
  57                                                    struct dccp_ackvec_record,
  58                                                    avr_node);
  59                 BUG_ON(before48(avr->avr_ack_seqno, head->avr_ack_seqno));
  60         }
  61
  62         list_add(&avr->avr_node, &av->av_records);
  63 }
  64
  65 int dccp_insert_option_ackvec(struct sock *sk, struct sk_buff *skb)
  66 {
  67         struct dccp_sock *dp = dccp_sk(sk);
  68         struct dccp_ackvec *av = dp->dccps_hc_rx_ackvec;
  69         /* Figure out how many options do we need to represent the ackvec */
  70         const u8 nr_opts = DIV_ROUND_UP(av->av_vec_len, DCCP_SINGLE_OPT_MAXLEN);
  71         u16 len = av->av_vec_len + 2 * nr_opts, i;
  72         u32 elapsed_time;
  73         const unsigned char *tail, *from;
  74         unsigned char *to;
  75         struct dccp_ackvec_record *avr;
  76         suseconds_t delta;
  77
  78         if (DCCP_SKB_CB(skb)->dccpd_opt_len + len > DCCP_MAX_OPT_LEN)
  79                 return -1;
  80
  81         delta = ktime_us_delta(ktime_get_real(), av->av_time);
  82         elapsed_time = delta / 10;
  83
  84         if (elapsed_time != 0 &&
  85             dccp_insert_option_elapsed_time(sk, skb, elapsed_time))
  86                 return -1;
  87
  88         avr = dccp_ackvec_record_new();
  89         if (avr == NULL)
  90                 return -1;
  91
  92         DCCP_SKB_CB(skb)->dccpd_opt_len += len;
  93
  94         to   = skb_push(skb, len);
  95         len  = av->av_vec_len;
  96         from = av->av_buf + av->av_buf_head;
  97         tail = av->av_buf + DCCP_MAX_ACKVEC_LEN;
  98
  99         for (i = 0; i < nr_opts; ++i) {
 100                 int copylen = len;
 101
 102                 if (len > DCCP_SINGLE_OPT_MAXLEN)
 103                         copylen = DCCP_SINGLE_OPT_MAXLEN;
 104
 105                 *to++ = DCCPO_ACK_VECTOR_0;
 106                 *to++ = copylen + 2;
 107
 108                 /* Check if buf_head wraps */
 109                 if (from + copylen > tail) {
 110                         const u16 tailsize = tail - from;
 111
 112                         memcpy(to, from, tailsize);
 113                         to      += tailsize;
 114                         len     -= tailsize;
 115                         copylen -= tailsize;
 116                         from    = av->av_buf;
 117                 }
 118
 119                 memcpy(to, from, copylen);
 120                 from += copylen;
 121                 to   += copylen;
 122                 len  -= copylen;
 123         }
 124
 125         /*
 126          *      From RFC 4340, A.2:
 127          *
 128          *      For each acknowledgement it sends, the HC-Receiver will add an
 129          *      acknowledgement record.  ack_seqno will equal the HC-Receiver
 130          *      sequence number it used for the ack packet; ack_ptr will equal
 131          *      buf_head; ack_ackno will equal buf_ackno; and ack_nonce will
 132          *      equal buf_nonce.
 133          */
 134         avr->avr_ack_seqno = DCCP_SKB_CB(skb)->dccpd_seq;
 135         avr->avr_ack_ptr   = av->av_buf_head;
 136         avr->avr_ack_ackno = av->av_buf_ackno;
 137         avr->avr_ack_nonce = av->av_buf_nonce;
 138         avr->avr_sent_len  = av->av_vec_len;
 139
 140         dccp_ackvec_insert_avr(av, avr);
 141
 142         dccp_pr_debug("%s ACK Vector 0, len=%d, ack_seqno=%llu, "
 143                       "ack_ackno=%llu\n",
 144                       dccp_role(sk), avr->avr_sent_len,
 145                       (unsigned long long)avr->avr_ack_seqno,
 146                       (unsigned long long)avr->avr_ack_ackno);
 147         return 0;
 148 }
 149
 150 struct dccp_ackvec *dccp_ackvec_alloc(const gfp_t priority)
 151 {
 152         struct dccp_ackvec *av = kmem_cache_alloc(dccp_ackvec_slab, priority);
 153
 154         if (av != NULL) {
 155                 av->av_buf_head  = DCCP_MAX_ACKVEC_LEN - 1;
 156                 av->av_buf_ackno = UINT48_MAX + 1;
 157                 av->av_buf_nonce = 0;
 158                 av->av_time      = ktime_set(0, 0);
 159                 av->av_vec_len   = 0;
 160                 INIT_LIST_HEAD(&av->av_records);
 161         }
 162
 163         return av;
 164 }
 165
 166 void dccp_ackvec_free(struct dccp_ackvec *av)
 167 {
 168         if (unlikely(av == NULL))
 169                 return;
 170
 171         if (!list_empty(&av->av_records)) {
 172                 struct dccp_ackvec_record *avr, *next;
 173
 174                 list_for_each_entry_safe(avr, next, &av->av_records, avr_node) {
 175                         list_del_init(&avr->avr_node);
 176                         dccp_ackvec_record_delete(avr);
 177                 }
 178         }
 179
 180         kmem_cache_free(dccp_ackvec_slab, av);
 181 }
 182
 183 static inline u8 dccp_ackvec_state(const struct dccp_ackvec *av,
 184                                    const u32 index)
 185 {
 186         return av->av_buf[index] & DCCP_ACKVEC_STATE_MASK;
 187 }
 188
 189 static inline u8 dccp_ackvec_len(const struct dccp_ackvec *av,
 190                                  const u32 index)
 191 {
 192         return av->av_buf[index] & DCCP_ACKVEC_LEN_MASK;
 193 }
 194
 195 /*
 196  * If several packets are missing, the HC-Receiver may prefer to enter multiple
 197  * bytes with run length 0, rather than a single byte with a larger run length;
 198  * this simplifies table updates if one of the missing packets arrives.
 199  */
 200 static inline int dccp_ackvec_set_buf_head_state(struct dccp_ackvec *av,
 201                                                  const unsigned int packets,
 202                                                  const unsigned char state)
 203 {
 204         unsigned int gap;
 205         long new_head;
 206
 207         if (av->av_vec_len + packets > DCCP_MAX_ACKVEC_LEN)
 208                 return -ENOBUFS;
 209
 210         gap      = packets - 1;
 211         new_head = av->av_buf_head - packets;
 212
 213         if (new_head < 0) {
 214                 if (gap > 0) {
 215                         memset(av->av_buf, DCCP_ACKVEC_STATE_NOT_RECEIVED,
 216                                gap + new_head + 1);
 217                         gap = -new_head;
 218                 }
 219                 new_head += DCCP_MAX_ACKVEC_LEN;
 220         }
 221
 222         av->av_buf_head = new_head;
 223
 224         if (gap > 0)
 225                 memset(av->av_buf + av->av_buf_head + 1,
 226                        DCCP_ACKVEC_STATE_NOT_RECEIVED, gap);
 227
 228         av->av_buf[av->av_buf_head] = state;
 229         av->av_vec_len += packets;
 230         return 0;
 231 }
 232
 233 /*
 234  * Implements the RFC 4340, Appendix A
 235  */
 236 int dccp_ackvec_add(struct dccp_ackvec *av, const struct sock *sk,
 237                     const u64 ackno, const u8 state)
 238 {
 239         /*
 240          * Check at the right places if the buffer is full, if it is, tell the
 241          * caller to start dropping packets till the HC-Sender acks our ACK
 242          * vectors, when we will free up space in av_buf.
 243          *
 244          * We may well decide to do buffer compression, etc, but for now lets
 245          * just drop.
 246          *
 247          * From Appendix A.1.1 (`New Packets'):
 248          *
 249          *      Of course, the circular buffer may overflow, either when the
 250          *      HC-Sender is sending data at a very high rate, when the
 251          *      HC-Receiver's acknowledgements are not reaching the HC-Sender,
 252          *      or when the HC-Sender is forgetting to acknowledge those acks
 253          *      (so the HC-Receiver is unable to clean up old state). In this
 254          *      case, the HC-Receiver should either compress the buffer (by
 255          *      increasing run lengths when possible), transfer its state to
 256          *      a larger buffer, or, as a last resort, drop all received
 257          *      packets, without processing them whatsoever, until its buffer
 258          *      shrinks again.
 259          */
 260
 261         /* See if this is the first ackno being inserted */
 262         if (av->av_vec_len == 0) {
 263                 av->av_buf[av->av_buf_head] = state;
 264                 av->av_vec_len = 1;
 265         } else if (after48(ackno, av->av_buf_ackno)) {
 266                 const u64 delta = dccp_delta_seqno(av->av_buf_ackno, ackno);
 267
 268                 /*
 269                  * Look if the state of this packet is the same as the
 270                  * previous ackno and if so if we can bump the head len.
 271                  */
 272                 if (delta == 1 &&
 273                     dccp_ackvec_state(av, av->av_buf_head) == state &&
 274                     dccp_ackvec_len(av, av->av_buf_head) < DCCP_ACKVEC_LEN_MASK)
 275                         av->av_buf[av->av_buf_head]++;
 276                 else if (dccp_ackvec_set_buf_head_state(av, delta, state))
 277                         return -ENOBUFS;
 278         } else {
 279                 /*
 280                  * A.1.2.  Old Packets
 281                  *
 282                  *      When a packet with Sequence Number S <= buf_ackno
 283                  *      arrives, the HC-Receiver will scan the table for
 284                  *      the byte corresponding to S. (Indexing structures
 285                  *      could reduce the complexity of this scan.)
 286                  */
 287                 u64 delta = dccp_delta_seqno(ackno, av->av_buf_ackno);
 288                 u32 index = av->av_buf_head;
 289
 290                 while (1) {
 291                         const u8 len = dccp_ackvec_len(av, index);
 292                         const u8 av_state = dccp_ackvec_state(av, index);
 293                         /*
 294                          * valid packets not yet in av_buf have a reserved
 295                          * entry, with a len equal to 0.
 296                          */
 297                         if (av_state == DCCP_ACKVEC_STATE_NOT_RECEIVED &&
 298                             len == 0 && delta == 0) { /* Found our
 299                                                          reserved seat! */
 300                                 dccp_pr_debug("Found %llu reserved seat!\n",
 301                                               (unsigned long long)ackno);
 302                                 av->av_buf[index] = state;
 303                                 goto out;
 304                         }
 305                         /* len == 0 means one packet */
 306                         if (delta < len + 1)
 307                                 goto out_duplicate;
 308
 309                         delta -= len + 1;
 310                         if (++index == DCCP_MAX_ACKVEC_LEN)
 311                                 index = 0;
 312                 }
 313         }
 314
 315         av->av_buf_ackno = ackno;
 316         av->av_time = ktime_get_real();
 317 out:
 318         return 0;
 319
 320 out_duplicate:
 321         /* Duplicate packet */
 322         dccp_pr_debug("Received a dup or already considered lost "
 323                       "packet: %llu\n", (unsigned long long)ackno);
 324         return -EILSEQ;
 325 }
 326
 327 static void dccp_ackvec_throw_record(struct dccp_ackvec *av,
 328                                      struct dccp_ackvec_record *avr)
 329 {
 330         struct dccp_ackvec_record *next;
 331
 332         /* sort out vector length */
 333         if (av->av_buf_head <= avr->avr_ack_ptr)
 334                 av->av_vec_len = avr->avr_ack_ptr - av->av_buf_head;
 335         else
 336                 av->av_vec_len = DCCP_MAX_ACKVEC_LEN - 1 -
 337                                  av->av_buf_head + avr->avr_ack_ptr;
 338
 339         /* free records */
 340         list_for_each_entry_safe_from(avr, next, &av->av_records, avr_node) {
 341                 list_del_init(&avr->avr_node);
 342                 dccp_ackvec_record_delete(avr);
 343         }
 344 }
 345
 346 void dccp_ackvec_check_rcv_ackno(struct dccp_ackvec *av, struct sock *sk,
 347                                  const u64 ackno)
 348 {
 349         struct dccp_ackvec_record *avr;
 350
 351         /*
 352          * If we traverse backwards, it should be faster when we have large
 353          * windows. We will be receiving ACKs for stuff we sent a while back
 354          * -sorbo.
 355          */
 356         list_for_each_entry_reverse(avr, &av->av_records, avr_node) {
 357                 if (ackno == avr->avr_ack_seqno) {
 358                         dccp_pr_debug("%s ACK packet 0, len=%d, ack_seqno=%llu, "
 359                                       "ack_ackno=%llu, ACKED!\n",
 360                                       dccp_role(sk), 1,
 361                                       (unsigned long long)avr->avr_ack_seqno,
 362                                       (unsigned long long)avr->avr_ack_ackno);
 363                         dccp_ackvec_throw_record(av, avr);
 364                         break;
 365                 } else if (avr->avr_ack_seqno > ackno)
 366                         break; /* old news */
 367         }
 368 }
 369
 370 static void dccp_ackvec_check_rcv_ackvector(struct dccp_ackvec *av,
 371                                             struct sock *sk, u64 *ackno,
 372                                             const unsigned char len,
 373                                             const unsigned char *vector)
 374 {
 375         unsigned char i;
 376         struct dccp_ackvec_record *avr;
 377
 378         /* Check if we actually sent an ACK vector */
 379         if (list_empty(&av->av_records))
 380                 return;
 381
 382         i = len;
 383         /*
 384          * XXX
 385          * I think it might be more efficient to work backwards. See comment on
 386          * rcv_ackno. -sorbo.
 387          */
 388         avr = list_entry(av->av_records.next, struct dccp_ackvec_record, avr_node);
 389         while (i--) {
 390                 const u8 rl = *vector & DCCP_ACKVEC_LEN_MASK;
 391                 u64 ackno_end_rl;
 392
 393                 dccp_set_seqno(&ackno_end_rl, *ackno - rl);
 394
 395                 /*
 396                  * If our AVR sequence number is greater than the ack, go
 397                  * forward in the AVR list until it is not so.
 398                  */
 399                 list_for_each_entry_from(avr, &av->av_records, avr_node) {
 400                         if (!after48(avr->avr_ack_seqno, *ackno))
 401                                 goto found;
 402                 }
 403                 /* End of the av_records list, not found, exit */
 404                 break;
 405 found:
 406                 if (between48(avr->avr_ack_seqno, ackno_end_rl, *ackno)) {
 407                         const u8 state = *vector & DCCP_ACKVEC_STATE_MASK;
 408                         if (state != DCCP_ACKVEC_STATE_NOT_RECEIVED) {
 409                                 dccp_pr_debug("%s ACK vector 0, len=%d, "
 410                                               "ack_seqno=%llu, ack_ackno=%llu, "
 411                                               "ACKED!\n",
 412                                               dccp_role(sk), len,
 413                                               (unsigned long long)
 414                                               avr->avr_ack_seqno,
 415                                               (unsigned long long)
 416                                               avr->avr_ack_ackno);
 417                                 dccp_ackvec_throw_record(av, avr);
 418                                 break;
 419                         }
 420                         /*
 421                          * If it wasn't received, continue scanning... we might
 422                          * find another one.
 423                          */
 424                 }
 425
 426                 dccp_set_seqno(ackno, ackno_end_rl - 1);
 427                 ++vector;
 428         }
 429 }
 430
 431 int dccp_ackvec_parse(struct sock *sk, const struct sk_buff *skb,
 432                       u64 *ackno, const u8 opt, const u8 *value, const u8 len)
 433 {
 434         if (len > DCCP_SINGLE_OPT_MAXLEN)
 435                 return -1;
 436
 437         /* dccp_ackvector_print(DCCP_SKB_CB(skb)->dccpd_ack_seq, value, len); */
 438         dccp_ackvec_check_rcv_ackvector(dccp_sk(sk)->dccps_hc_rx_ackvec, sk,
 439                                         ackno, len, value);
 440         return 0;
 441 }
 442
 443 int __init dccp_ackvec_init(void)
 444 {
 445         dccp_ackvec_slab = kmem_cache_create("dccp_ackvec",
 446                                              sizeof(struct dccp_ackvec), 0,
 447                                              SLAB_HWCACHE_ALIGN, NULL);
 448         if (dccp_ackvec_slab == NULL)
 449                 goto out_err;
 450
 451         dccp_ackvec_record_slab =
 452                         kmem_cache_create("dccp_ackvec_record",
 453                                           sizeof(struct dccp_ackvec_record),
 454                                           0, SLAB_HWCACHE_ALIGN, NULL);
 455         if (dccp_ackvec_record_slab == NULL)
 456                 goto out_destroy_slab;
 457
 458         return 0;
 459
 460 out_destroy_slab:
 461         kmem_cache_destroy(dccp_ackvec_slab);
 462         dccp_ackvec_slab = NULL;
 463 out_err:
 464         DCCP_CRIT("Unable to create Ack Vector slab cache");
 465         return -ENOBUFS;
 466 }
 467
 468 void dccp_ackvec_exit(void)
 469 {
 470         if (dccp_ackvec_slab != NULL) {
 471                 kmem_cache_destroy(dccp_ackvec_slab);
 472                 dccp_ackvec_slab = NULL;
 473         }
 474         if (dccp_ackvec_record_slab != NULL) {
 475                 kmem_cache_destroy(dccp_ackvec_record_slab);
 476                 dccp_ackvec_record_slab = NULL;
 477         }
 478 }