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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 #ifdef CONFIG_IP_DCCP_DEBUG
  71         const char *debug_prefix = dp->dccps_role == DCCP_ROLE_CLIENT ?
  72                                 "CLIENT tx: " : "server tx: ";
  73 #endif
  74         struct dccp_ackvec *av = dp->dccps_hc_rx_ackvec;
  75         int len = av->dccpav_vec_len + 2;
  76         struct timeval now;
  77         u32 elapsed_time;
  78         unsigned char *to, *from;
  79         struct dccp_ackvec_record *avr;
  80
  81         if (DCCP_SKB_CB(skb)->dccpd_opt_len + len > DCCP_MAX_OPT_LEN)
  82                 return -1;
  83
  84         avr = dccp_ackvec_record_new();
  85         if (avr == NULL)
  86                 return -1;
  87
  88         dccp_timestamp(sk, &now);
  89         elapsed_time = timeval_delta(&now, &av->dccpav_time) / 10;
  90
  91         if (elapsed_time != 0)
  92                 dccp_insert_option_elapsed_time(sk, skb, elapsed_time);
  93
  94         DCCP_SKB_CB(skb)->dccpd_opt_len += len;
  95
  96         to    = skb_push(skb, len);
  97         *to++ = DCCPO_ACK_VECTOR_0;
  98         *to++ = len;
  99
 100         len  = av->dccpav_vec_len;
 101         from = av->dccpav_buf + av->dccpav_buf_head;
 102
 103         /* Check if buf_head wraps */
 104         if ((int)av->dccpav_buf_head + len > DCCP_MAX_ACKVEC_LEN) {
 105                 const u32 tailsize = DCCP_MAX_ACKVEC_LEN - av->dccpav_buf_head;
 106
 107                 memcpy(to, from, tailsize);
 108                 to   += tailsize;
 109                 len  -= tailsize;
 110                 from = av->dccpav_buf;
 111         }
 112
 113         memcpy(to, from, len);
 114         /*
 115          *      From draft-ietf-dccp-spec-11.txt:
 116          *
 117          *      For each acknowledgement it sends, the HC-Receiver will add an
 118          *      acknowledgement record.  ack_seqno will equal the HC-Receiver
 119          *      sequence number it used for the ack packet; ack_ptr will equal
 120          *      buf_head; ack_ackno will equal buf_ackno; and ack_nonce will
 121          *      equal buf_nonce.
 122          */
 123         avr->dccpavr_ack_seqno = DCCP_SKB_CB(skb)->dccpd_seq;
 124         avr->dccpavr_ack_ptr   = av->dccpav_buf_head;
 125         avr->dccpavr_ack_ackno = av->dccpav_buf_ackno;
 126         avr->dccpavr_ack_nonce = av->dccpav_buf_nonce;
 127         avr->dccpavr_sent_len  = av->dccpav_vec_len;
 128
 129         dccp_ackvec_insert_avr(av, avr);
 130
 131         dccp_pr_debug("%sACK Vector 0, len=%d, ack_seqno=%llu, "
 132                       "ack_ackno=%llu\n",
 133                       debug_prefix, avr->dccpavr_sent_len,
 134                       (unsigned long long)avr->dccpavr_ack_seqno,
 135                       (unsigned long long)avr->dccpavr_ack_ackno);
 136         return 0;
 137 }
 138
 139 struct dccp_ackvec *dccp_ackvec_alloc(const gfp_t priority)
 140 {
 141         struct dccp_ackvec *av = kmem_cache_alloc(dccp_ackvec_slab, priority);
 142
 143         if (av != NULL) {
 144                 av->dccpav_buf_head     =
 145                         av->dccpav_buf_tail = DCCP_MAX_ACKVEC_LEN - 1;
 146                 av->dccpav_buf_ackno    = DCCP_MAX_SEQNO + 1;
 147                 av->dccpav_buf_nonce = av->dccpav_buf_nonce = 0;
 148                 av->dccpav_ack_ptr      = 0;
 149                 av->dccpav_time.tv_sec  = 0;
 150                 av->dccpav_time.tv_usec = 0;
 151                 av->dccpav_sent_len     = av->dccpav_vec_len = 0;
 152                 INIT_LIST_HEAD(&av->dccpav_records);
 153         }
 154
 155         return av;
 156 }
 157
 158 void dccp_ackvec_free(struct dccp_ackvec *av)
 159 {
 160         if (unlikely(av == NULL))
 161                 return;
 162         WARN_ON(!list_empty(&av->dccpav_records));
 163         kmem_cache_free(dccp_ackvec_slab, av);
 164 }
 165
 166 static inline u8 dccp_ackvec_state(const struct dccp_ackvec *av,
 167                                    const u8 index)
 168 {
 169         return av->dccpav_buf[index] & DCCP_ACKVEC_STATE_MASK;
 170 }
 171
 172 static inline u8 dccp_ackvec_len(const struct dccp_ackvec *av,
 173                                  const u8 index)
 174 {
 175         return av->dccpav_buf[index] & DCCP_ACKVEC_LEN_MASK;
 176 }
 177
 178 /*
 179  * If several packets are missing, the HC-Receiver may prefer to enter multiple
 180  * bytes with run length 0, rather than a single byte with a larger run length;
 181  * this simplifies table updates if one of the missing packets arrives.
 182  */
 183 static inline int dccp_ackvec_set_buf_head_state(struct dccp_ackvec *av,
 184                                                  const unsigned int packets,
 185                                                  const unsigned char state)
 186 {
 187         unsigned int gap;
 188         long new_head;
 189
 190         if (av->dccpav_vec_len + packets > DCCP_MAX_ACKVEC_LEN)
 191                 return -ENOBUFS;
 192
 193         gap      = packets - 1;
 194         new_head = av->dccpav_buf_head - packets;
 195
 196         if (new_head < 0) {
 197                 if (gap > 0) {
 198                         memset(av->dccpav_buf, DCCP_ACKVEC_STATE_NOT_RECEIVED,
 199                                gap + new_head + 1);
 200                         gap = -new_head;
 201                 }
 202                 new_head += DCCP_MAX_ACKVEC_LEN;
 203         }
 204
 205         av->dccpav_buf_head = new_head;
 206
 207         if (gap > 0)
 208                 memset(av->dccpav_buf + av->dccpav_buf_head + 1,
 209                        DCCP_ACKVEC_STATE_NOT_RECEIVED, gap);
 210
 211         av->dccpav_buf[av->dccpav_buf_head] = state;
 212         av->dccpav_vec_len += packets;
 213         return 0;
 214 }
 215
 216 /*
 217  * Implements the draft-ietf-dccp-spec-11.txt Appendix A
 218  */
 219 int dccp_ackvec_add(struct dccp_ackvec *av, const struct sock *sk,
 220                     const u64 ackno, const u8 state)
 221 {
 222         /*
 223          * Check at the right places if the buffer is full, if it is, tell the
 224          * caller to start dropping packets till the HC-Sender acks our ACK
 225          * vectors, when we will free up space in dccpav_buf.
 226          *
 227          * We may well decide to do buffer compression, etc, but for now lets
 228          * just drop.
 229          *
 230          * From Appendix A:
 231          *
 232          *      Of course, the circular buffer may overflow, either when the
 233          *      HC-Sender is sending data at a very high rate, when the
 234          *      HC-Receiver's acknowledgements are not reaching the HC-Sender,
 235          *      or when the HC-Sender is forgetting to acknowledge those acks
 236          *      (so the HC-Receiver is unable to clean up old state). In this
 237          *      case, the HC-Receiver should either compress the buffer (by
 238          *      increasing run lengths when possible), transfer its state to
 239          *      a larger buffer, or, as a last resort, drop all received
 240          *      packets, without processing them whatsoever, until its buffer
 241          *      shrinks again.
 242          */
 243
 244         /* See if this is the first ackno being inserted */
 245         if (av->dccpav_vec_len == 0) {
 246                 av->dccpav_buf[av->dccpav_buf_head] = state;
 247                 av->dccpav_vec_len = 1;
 248         } else if (after48(ackno, av->dccpav_buf_ackno)) {
 249                 const u64 delta = dccp_delta_seqno(av->dccpav_buf_ackno,
 250                                                    ackno);
 251
 252                 /*
 253                  * Look if the state of this packet is the same as the
 254                  * previous ackno and if so if we can bump the head len.
 255                  */
 256                 if (delta == 1 &&
 257                     dccp_ackvec_state(av, av->dccpav_buf_head) == state &&
 258                     (dccp_ackvec_len(av, av->dccpav_buf_head) <
 259                      DCCP_ACKVEC_LEN_MASK))
 260                         av->dccpav_buf[av->dccpav_buf_head]++;
 261                 else if (dccp_ackvec_set_buf_head_state(av, delta, state))
 262                         return -ENOBUFS;
 263         } else {
 264                 /*
 265                  * A.1.2.  Old Packets
 266                  *
 267                  *      When a packet with Sequence Number S arrives, and
 268                  *      S <= buf_ackno, the HC-Receiver will scan the table
 269                  *      for the byte corresponding to S. (Indexing structures
 270                  *      could reduce the complexity of this scan.)
 271                  */
 272                 u64 delta = dccp_delta_seqno(ackno, av->dccpav_buf_ackno);
 273                 u8 index = av->dccpav_buf_head;
 274
 275                 while (1) {
 276                         const u8 len = dccp_ackvec_len(av, index);
 277                         const u8 state = dccp_ackvec_state(av, index);
 278                         /*
 279                          * valid packets not yet in dccpav_buf have a reserved
 280                          * entry, with a len equal to 0.
 281                          */
 282                         if (state == DCCP_ACKVEC_STATE_NOT_RECEIVED &&
 283                             len == 0 && delta == 0) { /* Found our
 284                                                          reserved seat! */
 285                                 dccp_pr_debug("Found %llu reserved seat!\n",
 286                                               (unsigned long long)ackno);
 287                                 av->dccpav_buf[index] = state;
 288                                 goto out;
 289                         }
 290                         /* len == 0 means one packet */
 291                         if (delta < len + 1)
 292                                 goto out_duplicate;
 293
 294                         delta -= len + 1;
 295                         if (++index == DCCP_MAX_ACKVEC_LEN)
 296                                 index = 0;
 297                 }
 298         }
 299
 300         av->dccpav_buf_ackno = ackno;
 301         dccp_timestamp(sk, &av->dccpav_time);
 302 out:
 303         dccp_pr_debug("");
 304         return 0;
 305
 306 out_duplicate:
 307         /* Duplicate packet */
 308         dccp_pr_debug("Received a dup or already considered lost "
 309                       "packet: %llu\n", (unsigned long long)ackno);
 310         return -EILSEQ;
 311 }
 312
 313 #ifdef CONFIG_IP_DCCP_DEBUG
 314 void dccp_ackvector_print(const u64 ackno, const unsigned char *vector, int len)
 315 {
 316         if (!dccp_debug)
 317                 return;
 318
 319         printk("ACK vector len=%d, ackno=%llu |", len,
 320                (unsigned long long)ackno);
 321
 322         while (len--) {
 323                 const u8 state = (*vector & DCCP_ACKVEC_STATE_MASK) >> 6;
 324                 const u8 rl = *vector & DCCP_ACKVEC_LEN_MASK;
 325
 326                 printk("%d,%d|", state, rl);
 327                 ++vector;
 328         }
 329
 330         printk("\n");
 331 }
 332
 333 void dccp_ackvec_print(const struct dccp_ackvec *av)
 334 {
 335         dccp_ackvector_print(av->dccpav_buf_ackno,
 336                              av->dccpav_buf + av->dccpav_buf_head,
 337                              av->dccpav_vec_len);
 338 }
 339 #endif
 340
 341 static void dccp_ackvec_throw_record(struct dccp_ackvec *av,
 342                                      struct dccp_ackvec_record *avr)
 343 {
 344         struct dccp_ackvec_record *next;
 345
 346         av->dccpav_buf_tail = avr->dccpavr_ack_ptr - 1;
 347         if (av->dccpav_buf_tail == 0)
 348                 av->dccpav_buf_tail = DCCP_MAX_ACKVEC_LEN - 1;
 349
 350         av->dccpav_vec_len -= avr->dccpavr_sent_len;
 351
 352         /* free records */
 353         list_for_each_entry_safe_from(avr, next, &av->dccpav_records,
 354                                       dccpavr_node) {
 355                 list_del_init(&avr->dccpavr_node);
 356                 dccp_ackvec_record_delete(avr);
 357         }
 358 }
 359
 360 void dccp_ackvec_check_rcv_ackno(struct dccp_ackvec *av, struct sock *sk,
 361                                  const u64 ackno)
 362 {
 363         struct dccp_ackvec_record *avr;
 364
 365         /*
 366          * If we traverse backwards, it should be faster when we have large
 367          * windows. We will be receiving ACKs for stuff we sent a while back
 368          * -sorbo.
 369          */
 370         list_for_each_entry_reverse(avr, &av->dccpav_records, dccpavr_node) {
 371                 if (ackno == avr->dccpavr_ack_seqno) {
 372 #ifdef CONFIG_IP_DCCP_DEBUG
 373                         struct dccp_sock *dp = dccp_sk(sk);
 374                         const char *debug_prefix = dp->dccps_role == DCCP_ROLE_CLIENT ?
 375                                                 "CLIENT rx ack: " : "server rx ack: ";
 376 #endif
 377                         dccp_pr_debug("%sACK packet 0, len=%d, ack_seqno=%llu, "
 378                                       "ack_ackno=%llu, ACKED!\n",
 379                                       debug_prefix, 1,
 380                                       (unsigned long long)avr->dccpavr_ack_seqno,
 381                                       (unsigned long long)avr->dccpavr_ack_ackno);
 382                         dccp_ackvec_throw_record(av, avr);
 383                         break;
 384                 }
 385         }
 386 }
 387
 388 static void dccp_ackvec_check_rcv_ackvector(struct dccp_ackvec *av,
 389                                             struct sock *sk, u64 ackno,
 390                                             const unsigned char len,
 391                                             const unsigned char *vector)
 392 {
 393         unsigned char i;
 394         struct dccp_ackvec_record *avr;
 395
 396         /* Check if we actually sent an ACK vector */
 397         if (list_empty(&av->dccpav_records))
 398                 return;
 399
 400         i = len;
 401         /*
 402          * XXX
 403          * I think it might be more efficient to work backwards. See comment on
 404          * rcv_ackno. -sorbo.
 405          */
 406         avr = list_entry(av->dccpav_records.next, struct dccp_ackvec_record,
 407                          dccpavr_node);
 408         while (i--) {
 409                 const u8 rl = *vector & DCCP_ACKVEC_LEN_MASK;
 410                 u64 ackno_end_rl;
 411
 412                 dccp_set_seqno(&ackno_end_rl, ackno - rl);
 413
 414                 /*
 415                  * If our AVR sequence number is greater than the ack, go
 416                  * forward in the AVR list until it is not so.
 417                  */
 418                 list_for_each_entry_from(avr, &av->dccpav_records,
 419                                          dccpavr_node) {
 420                         if (!after48(avr->dccpavr_ack_seqno, ackno))
 421                                 goto found;
 422                 }
 423                 /* End of the dccpav_records list, not found, exit */
 424                 break;
 425 found:
 426                 if (between48(avr->dccpavr_ack_seqno, ackno_end_rl, ackno)) {
 427                         const u8 state = (*vector &
 428                                           DCCP_ACKVEC_STATE_MASK) >> 6;
 429                         if (state != DCCP_ACKVEC_STATE_NOT_RECEIVED) {
 430 #ifdef CONFIG_IP_DCCP_DEBUG
 431                                 struct dccp_sock *dp = dccp_sk(sk);
 432                                 const char *debug_prefix =
 433                                         dp->dccps_role == DCCP_ROLE_CLIENT ?
 434                                         "CLIENT rx ack: " : "server rx ack: ";
 435 #endif
 436                                 dccp_pr_debug("%sACK vector 0, len=%d, "
 437                                               "ack_seqno=%llu, ack_ackno=%llu, "
 438                                               "ACKED!\n",
 439                                               debug_prefix, len,
 440                                               (unsigned long long)
 441                                               avr->dccpavr_ack_seqno,
 442                                               (unsigned long long)
 443                                               avr->dccpavr_ack_ackno);
 444                                 dccp_ackvec_throw_record(av, avr);
 445                         }
 446                         /*
 447                          * If it wasn't received, continue scanning... we might
 448                          * find another one.
 449                          */
 450                 }
 451
 452                 dccp_set_seqno(&ackno, ackno_end_rl - 1);
 453                 ++vector;
 454         }
 455 }
 456
 457 int dccp_ackvec_parse(struct sock *sk, const struct sk_buff *skb,
 458                       const u8 opt, const u8 *value, const u8 len)
 459 {
 460         if (len > DCCP_MAX_ACKVEC_LEN)
 461                 return -1;
 462
 463         /* dccp_ackvector_print(DCCP_SKB_CB(skb)->dccpd_ack_seq, value, len); */
 464         dccp_ackvec_check_rcv_ackvector(dccp_sk(sk)->dccps_hc_rx_ackvec, sk,
 465                                         DCCP_SKB_CB(skb)->dccpd_ack_seq,
 466                                         len, value);
 467         return 0;
 468 }
 469
 470 static char dccp_ackvec_slab_msg[] __initdata =
 471         KERN_CRIT "DCCP: Unable to create ack vectors slab caches\n";
 472
 473 int __init dccp_ackvec_init(void)
 474 {
 475         dccp_ackvec_slab = kmem_cache_create("dccp_ackvec",
 476                                              sizeof(struct dccp_ackvec), 0,
 477                                              SLAB_HWCACHE_ALIGN, NULL, NULL);
 478         if (dccp_ackvec_slab == NULL)
 479                 goto out_err;
 480
 481         dccp_ackvec_record_slab =
 482                         kmem_cache_create("dccp_ackvec_record",
 483                                           sizeof(struct dccp_ackvec_record),
 484                                           0, SLAB_HWCACHE_ALIGN, NULL, NULL);
 485         if (dccp_ackvec_record_slab == NULL)
 486                 goto out_destroy_slab;
 487
 488         return 0;
 489
 490 out_destroy_slab:
 491         kmem_cache_destroy(dccp_ackvec_slab);
 492         dccp_ackvec_slab = NULL;
 493 out_err:
 494         printk(dccp_ackvec_slab_msg);
 495         return -ENOBUFS;
 496 }
 497
 498 void dccp_ackvec_exit(void)
 499 {
 500         if (dccp_ackvec_slab != NULL) {
 501                 kmem_cache_destroy(dccp_ackvec_slab);
 502                 dccp_ackvec_slab = NULL;
 503         }
 504         if (dccp_ackvec_record_slab != NULL) {
 505                 kmem_cache_destroy(dccp_ackvec_record_slab);
 506                 dccp_ackvec_record_slab = NULL;
 507         }
 508 }