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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/skbuff.h>
  17
  18 #include <net/sock.h>
  19
  20 int dccp_insert_option_ackvec(struct sock *sk, struct sk_buff *skb)
  21 {
  22         struct dccp_sock *dp = dccp_sk(sk);
  23 #ifdef CONFIG_IP_DCCP_DEBUG
  24         const char *debug_prefix = dp->dccps_role == DCCP_ROLE_CLIENT ?
  25                                 "CLIENT tx: " : "server tx: ";
  26 #endif
  27         struct dccp_ackvec *av = dp->dccps_hc_rx_ackvec;
  28         int len = av->dccpav_vec_len + 2;
  29         struct timeval now;
  30         u32 elapsed_time;
  31         unsigned char *to, *from;
  32
  33         dccp_timestamp(sk, &now);
  34         elapsed_time = timeval_delta(&now, &av->dccpav_time) / 10;
  35
  36         if (elapsed_time != 0)
  37                 dccp_insert_option_elapsed_time(sk, skb, elapsed_time);
  38
  39         if (DCCP_SKB_CB(skb)->dccpd_opt_len + len > DCCP_MAX_OPT_LEN)
  40                 return -1;
  41
  42         /*
  43          * XXX: now we have just one ack vector sent record, so
  44          * we have to wait for it to be cleared.
  45          *
  46          * Of course this is not acceptable, but this is just for
  47          * basic testing now.
  48          */
  49         if (av->dccpav_ack_seqno != DCCP_MAX_SEQNO + 1)
  50                 return -1;
  51
  52         DCCP_SKB_CB(skb)->dccpd_opt_len += len;
  53
  54         to    = skb_push(skb, len);
  55         *to++ = DCCPO_ACK_VECTOR_0;
  56         *to++ = len;
  57
  58         len  = av->dccpav_vec_len;
  59         from = av->dccpav_buf + av->dccpav_buf_head;
  60
  61         /* Check if buf_head wraps */
  62         if ((int)av->dccpav_buf_head + len > av->dccpav_vec_len) {
  63                 const u32 tailsize = av->dccpav_vec_len - av->dccpav_buf_head;
  64
  65                 memcpy(to, from, tailsize);
  66                 to   += tailsize;
  67                 len  -= tailsize;
  68                 from = av->dccpav_buf;
  69         }
  70
  71         memcpy(to, from, len);
  72         /*
  73          *      From draft-ietf-dccp-spec-11.txt:
  74          *
  75          *      For each acknowledgement it sends, the HC-Receiver will add an
  76          *      acknowledgement record.  ack_seqno will equal the HC-Receiver
  77          *      sequence number it used for the ack packet; ack_ptr will equal
  78          *      buf_head; ack_ackno will equal buf_ackno; and ack_nonce will
  79          *      equal buf_nonce.
  80          *
  81          * This implemention uses just one ack record for now.
  82          */
  83         av->dccpav_ack_seqno = DCCP_SKB_CB(skb)->dccpd_seq;
  84         av->dccpav_ack_ptr   = av->dccpav_buf_head;
  85         av->dccpav_ack_ackno = av->dccpav_buf_ackno;
  86         av->dccpav_ack_nonce = av->dccpav_buf_nonce;
  87         av->dccpav_sent_len  = av->dccpav_vec_len;
  88
  89         dccp_pr_debug("%sACK Vector 0, len=%d, ack_seqno=%llu, "
  90                       "ack_ackno=%llu\n",
  91                       debug_prefix, av->dccpav_sent_len,
  92                       (unsigned long long)av->dccpav_ack_seqno,
  93                       (unsigned long long)av->dccpav_ack_ackno);
  94         return -1;
  95 }
  96
  97 struct dccp_ackvec *dccp_ackvec_alloc(const gfp_t priority)
  98 {
  99         struct dccp_ackvec *av = kmalloc(sizeof(*av), priority);
 100
 101         if (av != NULL) {
 102                 av->dccpav_buf_head     =
 103                         av->dccpav_buf_tail = DCCP_MAX_ACKVEC_LEN - 1;
 104                 av->dccpav_buf_ackno    =
 105                         av->dccpav_ack_ackno = av->dccpav_ack_seqno = ~0LLU;
 106                 av->dccpav_buf_nonce = av->dccpav_buf_nonce = 0;
 107                 av->dccpav_ack_ptr      = 0;
 108                 av->dccpav_time.tv_sec  = 0;
 109                 av->dccpav_time.tv_usec = 0;
 110                 av->dccpav_sent_len     = av->dccpav_vec_len = 0;
 111         }
 112
 113         return av;
 114 }
 115
 116 void dccp_ackvec_free(struct dccp_ackvec *av)
 117 {
 118         kfree(av);
 119 }
 120
 121 static inline u8 dccp_ackvec_state(const struct dccp_ackvec *av,
 122                                    const u8 index)
 123 {
 124         return av->dccpav_buf[index] & DCCP_ACKVEC_STATE_MASK;
 125 }
 126
 127 static inline u8 dccp_ackvec_len(const struct dccp_ackvec *av,
 128                                  const u8 index)
 129 {
 130         return av->dccpav_buf[index] & DCCP_ACKVEC_LEN_MASK;
 131 }
 132
 133 /*
 134  * If several packets are missing, the HC-Receiver may prefer to enter multiple
 135  * bytes with run length 0, rather than a single byte with a larger run length;
 136  * this simplifies table updates if one of the missing packets arrives.
 137  */
 138 static inline int dccp_ackvec_set_buf_head_state(struct dccp_ackvec *av,
 139                                                  const unsigned int packets,
 140                                                  const unsigned char state)
 141 {
 142         unsigned int gap;
 143         long new_head;
 144
 145         if (av->dccpav_vec_len + packets > DCCP_MAX_ACKVEC_LEN)
 146                 return -ENOBUFS;
 147
 148         gap      = packets - 1;
 149         new_head = av->dccpav_buf_head - packets;
 150
 151         if (new_head < 0) {
 152                 if (gap > 0) {
 153                         memset(av->dccpav_buf, DCCP_ACKVEC_STATE_NOT_RECEIVED,
 154                                gap + new_head + 1);
 155                         gap = -new_head;
 156                 }
 157                 new_head += DCCP_MAX_ACKVEC_LEN;
 158         }
 159
 160         av->dccpav_buf_head = new_head;
 161
 162         if (gap > 0)
 163                 memset(av->dccpav_buf + av->dccpav_buf_head + 1,
 164                        DCCP_ACKVEC_STATE_NOT_RECEIVED, gap);
 165
 166         av->dccpav_buf[av->dccpav_buf_head] = state;
 167         av->dccpav_vec_len += packets;
 168         return 0;
 169 }
 170
 171 /*
 172  * Implements the draft-ietf-dccp-spec-11.txt Appendix A
 173  */
 174 int dccp_ackvec_add(struct dccp_ackvec *av, const struct sock *sk,
 175                     const u64 ackno, const u8 state)
 176 {
 177         /*
 178          * Check at the right places if the buffer is full, if it is, tell the
 179          * caller to start dropping packets till the HC-Sender acks our ACK
 180          * vectors, when we will free up space in dccpav_buf.
 181          *
 182          * We may well decide to do buffer compression, etc, but for now lets
 183          * just drop.
 184          *
 185          * From Appendix A:
 186          *
 187          *      Of course, the circular buffer may overflow, either when the
 188          *      HC-Sender is sending data at a very high rate, when the
 189          *      HC-Receiver's acknowledgements are not reaching the HC-Sender,
 190          *      or when the HC-Sender is forgetting to acknowledge those acks
 191          *      (so the HC-Receiver is unable to clean up old state). In this
 192          *      case, the HC-Receiver should either compress the buffer (by
 193          *      increasing run lengths when possible), transfer its state to
 194          *      a larger buffer, or, as a last resort, drop all received
 195          *      packets, without processing them whatsoever, until its buffer
 196          *      shrinks again.
 197          */
 198
 199         /* See if this is the first ackno being inserted */
 200         if (av->dccpav_vec_len == 0) {
 201                 av->dccpav_buf[av->dccpav_buf_head] = state;
 202                 av->dccpav_vec_len = 1;
 203         } else if (after48(ackno, av->dccpav_buf_ackno)) {
 204                 const u64 delta = dccp_delta_seqno(av->dccpav_buf_ackno,
 205                                                    ackno);
 206
 207                 /*
 208                  * Look if the state of this packet is the same as the
 209                  * previous ackno and if so if we can bump the head len.
 210                  */
 211                 if (delta == 1 &&
 212                     dccp_ackvec_state(av, av->dccpav_buf_head) == state &&
 213                     (dccp_ackvec_len(av, av->dccpav_buf_head) <
 214                      DCCP_ACKVEC_LEN_MASK))
 215                         av->dccpav_buf[av->dccpav_buf_head]++;
 216                 else if (dccp_ackvec_set_buf_head_state(av, delta, state))
 217                         return -ENOBUFS;
 218         } else {
 219                 /*
 220                  * A.1.2.  Old Packets
 221                  *
 222                  *      When a packet with Sequence Number S arrives, and
 223                  *      S <= buf_ackno, the HC-Receiver will scan the table
 224                  *      for the byte corresponding to S. (Indexing structures
 225                  *      could reduce the complexity of this scan.)
 226                  */
 227                 u64 delta = dccp_delta_seqno(ackno, av->dccpav_buf_ackno);
 228                 u8 index = av->dccpav_buf_head;
 229
 230                 while (1) {
 231                         const u8 len = dccp_ackvec_len(av, index);
 232                         const u8 state = dccp_ackvec_state(av, index);
 233                         /*
 234                          * valid packets not yet in dccpav_buf have a reserved
 235                          * entry, with a len equal to 0.
 236                          */
 237                         if (state == DCCP_ACKVEC_STATE_NOT_RECEIVED &&
 238                             len == 0 && delta == 0) { /* Found our
 239                                                          reserved seat! */
 240                                 dccp_pr_debug("Found %llu reserved seat!\n",
 241                                               (unsigned long long)ackno);
 242                                 av->dccpav_buf[index] = state;
 243                                 goto out;
 244                         }
 245                         /* len == 0 means one packet */
 246                         if (delta < len + 1)
 247                                 goto out_duplicate;
 248
 249                         delta -= len + 1;
 250                         if (++index == DCCP_MAX_ACKVEC_LEN)
 251                                 index = 0;
 252                 }
 253         }
 254
 255         av->dccpav_buf_ackno = ackno;
 256         dccp_timestamp(sk, &av->dccpav_time);
 257 out:
 258         dccp_pr_debug("");
 259         return 0;
 260
 261 out_duplicate:
 262         /* Duplicate packet */
 263         dccp_pr_debug("Received a dup or already considered lost "
 264                       "packet: %llu\n", (unsigned long long)ackno);
 265         return -EILSEQ;
 266 }
 267
 268 #ifdef CONFIG_IP_DCCP_DEBUG
 269 void dccp_ackvector_print(const u64 ackno, const unsigned char *vector, int len)
 270 {
 271         if (!dccp_debug)
 272                 return;
 273
 274         printk("ACK vector len=%d, ackno=%llu |", len,
 275                (unsigned long long)ackno);
 276
 277         while (len--) {
 278                 const u8 state = (*vector & DCCP_ACKVEC_STATE_MASK) >> 6;
 279                 const u8 rl = *vector & DCCP_ACKVEC_LEN_MASK;
 280
 281                 printk("%d,%d|", state, rl);
 282                 ++vector;
 283         }
 284
 285         printk("\n");
 286 }
 287
 288 void dccp_ackvec_print(const struct dccp_ackvec *av)
 289 {
 290         dccp_ackvector_print(av->dccpav_buf_ackno,
 291                              av->dccpav_buf + av->dccpav_buf_head,
 292                              av->dccpav_vec_len);
 293 }
 294 #endif
 295
 296 static void dccp_ackvec_throw_away_ack_record(struct dccp_ackvec *av)
 297 {
 298         /*
 299          * As we're keeping track of the ack vector size (dccpav_vec_len) and
 300          * the sent ack vector size (dccpav_sent_len) we don't need
 301          * dccpav_buf_tail at all, but keep this code here as in the future
 302          * we'll implement a vector of ack records, as suggested in
 303          * draft-ietf-dccp-spec-11.txt Appendix A. -acme
 304          */
 305 #if 0
 306         u32 new_buf_tail = av->dccpav_ack_ptr + 1;
 307         if (new_buf_tail >= av->dccpav_vec_len)
 308                 new_buf_tail -= av->dccpav_vec_len;
 309         av->dccpav_buf_tail = new_buf_tail;
 310 #endif
 311         av->dccpav_vec_len -= av->dccpav_sent_len;
 312 }
 313
 314 void dccp_ackvec_check_rcv_ackno(struct dccp_ackvec *av, struct sock *sk,
 315                                  const u64 ackno)
 316 {
 317         /* Check if we actually sent an ACK vector */
 318         if (av->dccpav_ack_seqno == DCCP_MAX_SEQNO + 1)
 319                 return;
 320
 321         if (ackno == av->dccpav_ack_seqno) {
 322 #ifdef CONFIG_IP_DCCP_DEBUG
 323                 struct dccp_sock *dp = dccp_sk(sk);
 324                 const char *debug_prefix = dp->dccps_role == DCCP_ROLE_CLIENT ?
 325                                         "CLIENT rx ack: " : "server rx ack: ";
 326 #endif
 327                 dccp_pr_debug("%sACK packet 0, len=%d, ack_seqno=%llu, "
 328                               "ack_ackno=%llu, ACKED!\n",
 329                               debug_prefix, 1,
 330                               (unsigned long long)av->dccpav_ack_seqno,
 331                               (unsigned long long)av->dccpav_ack_ackno);
 332                 dccp_ackvec_throw_away_ack_record(av);
 333                 av->dccpav_ack_seqno = DCCP_MAX_SEQNO + 1;
 334         }
 335 }
 336
 337 static void dccp_ackvec_check_rcv_ackvector(struct dccp_ackvec *av,
 338                                             struct sock *sk, u64 ackno,
 339                                             const unsigned char len,
 340                                             const unsigned char *vector)
 341 {
 342         unsigned char i;
 343
 344         /* Check if we actually sent an ACK vector */
 345         if (av->dccpav_ack_seqno == DCCP_MAX_SEQNO + 1)
 346                 return;
 347         /*
 348          * We're in the receiver half connection, so if the received an ACK
 349          * vector ackno (e.g. 50) before dccpav_ack_seqno (e.g. 52), we're
 350          * not interested.
 351          *
 352          * Extra explanation with example:
 353          *
 354          * if we received an ACK vector with ackno 50, it can only be acking
 355          * 50, 49, 48, etc, not 52 (the seqno for the ACK vector we sent).
 356          */
 357         /* dccp_pr_debug("is %llu < %llu? ", ackno, av->dccpav_ack_seqno); */
 358         if (before48(ackno, av->dccpav_ack_seqno)) {
 359                 /* dccp_pr_debug_cat("yes\n"); */
 360                 return;
 361         }
 362         /* dccp_pr_debug_cat("no\n"); */
 363
 364         i = len;
 365         while (i--) {
 366                 const u8 rl = *vector & DCCP_ACKVEC_LEN_MASK;
 367                 u64 ackno_end_rl;
 368
 369                 dccp_set_seqno(&ackno_end_rl, ackno - rl);
 370
 371                 /*
 372                  * dccp_pr_debug("is %llu <= %llu <= %llu? ", ackno_end_rl,
 373                  * av->dccpav_ack_seqno, ackno);
 374                  */
 375                 if (between48(av->dccpav_ack_seqno, ackno_end_rl, ackno)) {
 376                         const u8 state = (*vector &
 377                                           DCCP_ACKVEC_STATE_MASK) >> 6;
 378                         /* dccp_pr_debug_cat("yes\n"); */
 379
 380                         if (state != DCCP_ACKVEC_STATE_NOT_RECEIVED) {
 381 #ifdef CONFIG_IP_DCCP_DEBUG
 382                                 struct dccp_sock *dp = dccp_sk(sk);
 383                                 const char *debug_prefix =
 384                                         dp->dccps_role == DCCP_ROLE_CLIENT ?
 385                                         "CLIENT rx ack: " : "server rx ack: ";
 386 #endif
 387                                 dccp_pr_debug("%sACK vector 0, len=%d, "
 388                                               "ack_seqno=%llu, ack_ackno=%llu, "
 389                                               "ACKED!\n",
 390                                               debug_prefix, len,
 391                                               (unsigned long long)
 392                                               av->dccpav_ack_seqno,
 393                                               (unsigned long long)
 394                                               av->dccpav_ack_ackno);
 395                                 dccp_ackvec_throw_away_ack_record(av);
 396                         }
 397                         /*
 398                          * If dccpav_ack_seqno was not received, no problem
 399                          * we'll send another ACK vector.
 400                          */
 401                         av->dccpav_ack_seqno = DCCP_MAX_SEQNO + 1;
 402                         break;
 403                 }
 404                 /* dccp_pr_debug_cat("no\n"); */
 405
 406                 dccp_set_seqno(&ackno, ackno_end_rl - 1);
 407                 ++vector;
 408         }
 409 }
 410
 411 int dccp_ackvec_parse(struct sock *sk, const struct sk_buff *skb,
 412                       const u8 opt, const u8 *value, const u8 len)
 413 {
 414         if (len > DCCP_MAX_ACKVEC_LEN)
 415                 return -1;
 416
 417         /* dccp_ackvector_print(DCCP_SKB_CB(skb)->dccpd_ack_seq, value, len); */
 418         dccp_ackvec_check_rcv_ackvector(dccp_sk(sk)->dccps_hc_rx_ackvec, sk,
 419                                         DCCP_SKB_CB(skb)->dccpd_ack_seq,
 420                                         len, value);
 421         return 0;
 422 }