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   1 /*
   2  *  net/dccp/ackvec.c
   3  *
   4  *  An implementation of Ack Vectors for the DCCP protocol
   5  *  Copyright (c) 2007 University of Aberdeen, Scotland, UK
   6  *  Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
   7  *
   8  *      This program is free software; you can redistribute it and/or modify it
   9  *      under the terms of the GNU General Public License as published by the
  10  *      Free Software Foundation; version 2 of the License;
  11  */
  12
  13 #include "ackvec.h"
  14 #include "dccp.h"
  15
  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 struct dccp_ackvec *dccp_ackvec_alloc(const gfp_t priority)
  28 {
  29         struct dccp_ackvec *av = kmem_cache_zalloc(dccp_ackvec_slab, priority);
  30
  31         if (av != NULL) {
  32                 av->av_buf_head = DCCPAV_MAX_ACKVEC_LEN - 1;
  33                 INIT_LIST_HEAD(&av->av_records);
  34         }
  35         return av;
  36 }
  37
  38 static void dccp_ackvec_purge_records(struct dccp_ackvec *av)
  39 {
  40         struct dccp_ackvec_record *cur, *next;
  41
  42         list_for_each_entry_safe(cur, next, &av->av_records, avr_node)
  43                 kmem_cache_free(dccp_ackvec_record_slab, cur);
  44         INIT_LIST_HEAD(&av->av_records);
  45 }
  46
  47 void dccp_ackvec_free(struct dccp_ackvec *av)
  48 {
  49         if (likely(av != NULL)) {
  50                 dccp_ackvec_purge_records(av);
  51                 kmem_cache_free(dccp_ackvec_slab, av);
  52         }
  53 }
  54
  55 /**
  56  * dccp_ackvec_update_records  -  Record information about sent Ack Vectors
  57  * @av:         Ack Vector records to update
  58  * @seqno:      Sequence number of the packet carrying the Ack Vector just sent
  59  * @nonce_sum:  The sum of all buffer nonces contained in the Ack Vector
  60  */
  61 int dccp_ackvec_update_records(struct dccp_ackvec *av, u64 seqno, u8 nonce_sum)
  62 {
  63         struct dccp_ackvec_record *avr;
  64
  65         avr = kmem_cache_alloc(dccp_ackvec_record_slab, GFP_ATOMIC);
  66         if (avr == NULL)
  67                 return -ENOBUFS;
  68
  69         avr->avr_ack_seqno  = seqno;
  70         avr->avr_ack_ptr    = av->av_buf_head;
  71         avr->avr_ack_ackno  = av->av_buf_ackno;
  72         avr->avr_ack_nonce  = nonce_sum;
  73         avr->avr_ack_runlen = dccp_ackvec_runlen(av->av_buf + av->av_buf_head);
  74         /*
  75          * Since GSS is incremented for each packet, the list is automatically
  76          * arranged in descending order of @ack_seqno.
  77          */
  78         list_add(&avr->avr_node, &av->av_records);
  79
  80         dccp_pr_debug("Added Vector, ack_seqno=%llu, ack_ackno=%llu (rl=%u)\n",
  81                       (unsigned long long)avr->avr_ack_seqno,
  82                       (unsigned long long)avr->avr_ack_ackno,
  83                       avr->avr_ack_runlen);
  84         return 0;
  85 }
  86
  87 /*
  88  * If several packets are missing, the HC-Receiver may prefer to enter multiple
  89  * bytes with run length 0, rather than a single byte with a larger run length;
  90  * this simplifies table updates if one of the missing packets arrives.
  91  */
  92 static inline int dccp_ackvec_set_buf_head_state(struct dccp_ackvec *av,
  93                                                  const unsigned int packets,
  94                                                  const unsigned char state)
  95 {
  96         unsigned int gap;
  97         long new_head;
  98
  99         if (av->av_vec_len + packets > DCCPAV_MAX_ACKVEC_LEN)
 100                 return -ENOBUFS;
 101
 102         gap      = packets - 1;
 103         new_head = av->av_buf_head - packets;
 104
 105         if (new_head < 0) {
 106                 if (gap > 0) {
 107                         memset(av->av_buf, DCCPAV_NOT_RECEIVED,
 108                                gap + new_head + 1);
 109                         gap = -new_head;
 110                 }
 111                 new_head += DCCPAV_MAX_ACKVEC_LEN;
 112         }
 113
 114         av->av_buf_head = new_head;
 115
 116         if (gap > 0)
 117                 memset(av->av_buf + av->av_buf_head + 1,
 118                        DCCPAV_NOT_RECEIVED, gap);
 119
 120         av->av_buf[av->av_buf_head] = state;
 121         av->av_vec_len += packets;
 122         return 0;
 123 }
 124
 125 /*
 126  * Implements the RFC 4340, Appendix A
 127  */
 128 int dccp_ackvec_add(struct dccp_ackvec *av, const struct sock *sk,
 129                     const u64 ackno, const u8 state)
 130 {
 131         u8 *cur_head = av->av_buf + av->av_buf_head,
 132            *buf_end  = av->av_buf + DCCPAV_MAX_ACKVEC_LEN;
 133         /*
 134          * Check at the right places if the buffer is full, if it is, tell the
 135          * caller to start dropping packets till the HC-Sender acks our ACK
 136          * vectors, when we will free up space in av_buf.
 137          *
 138          * We may well decide to do buffer compression, etc, but for now lets
 139          * just drop.
 140          *
 141          * From Appendix A.1.1 (`New Packets'):
 142          *
 143          *      Of course, the circular buffer may overflow, either when the
 144          *      HC-Sender is sending data at a very high rate, when the
 145          *      HC-Receiver's acknowledgements are not reaching the HC-Sender,
 146          *      or when the HC-Sender is forgetting to acknowledge those acks
 147          *      (so the HC-Receiver is unable to clean up old state). In this
 148          *      case, the HC-Receiver should either compress the buffer (by
 149          *      increasing run lengths when possible), transfer its state to
 150          *      a larger buffer, or, as a last resort, drop all received
 151          *      packets, without processing them whatsoever, until its buffer
 152          *      shrinks again.
 153          */
 154
 155         /* See if this is the first ackno being inserted */
 156         if (av->av_vec_len == 0) {
 157                 *cur_head = state;
 158                 av->av_vec_len = 1;
 159         } else if (after48(ackno, av->av_buf_ackno)) {
 160                 const u64 delta = dccp_delta_seqno(av->av_buf_ackno, ackno);
 161
 162                 /*
 163                  * Look if the state of this packet is the same as the
 164                  * previous ackno and if so if we can bump the head len.
 165                  */
 166                 if (delta == 1 && dccp_ackvec_state(cur_head) == state &&
 167                     dccp_ackvec_runlen(cur_head) < DCCPAV_MAX_RUNLEN)
 168                         *cur_head += 1;
 169                 else if (dccp_ackvec_set_buf_head_state(av, delta, state))
 170                         return -ENOBUFS;
 171         } else {
 172                 /*
 173                  * A.1.2.  Old Packets
 174                  *
 175                  *      When a packet with Sequence Number S <= buf_ackno
 176                  *      arrives, the HC-Receiver will scan the table for
 177                  *      the byte corresponding to S. (Indexing structures
 178                  *      could reduce the complexity of this scan.)
 179                  */
 180                 u64 delta = dccp_delta_seqno(ackno, av->av_buf_ackno);
 181
 182                 while (1) {
 183                         const u8 len = dccp_ackvec_runlen(cur_head);
 184                         /*
 185                          * valid packets not yet in av_buf have a reserved
 186                          * entry, with a len equal to 0.
 187                          */
 188                         if (*cur_head == DCCPAV_NOT_RECEIVED && delta == 0) {
 189                                 dccp_pr_debug("Found %llu reserved seat!\n",
 190                                               (unsigned long long)ackno);
 191                                 *cur_head = state;
 192                                 goto out;
 193                         }
 194                         /* len == 0 means one packet */
 195                         if (delta < len + 1)
 196                                 goto out_duplicate;
 197
 198                         delta -= len + 1;
 199                         if (++cur_head == buf_end)
 200                                 cur_head = av->av_buf;
 201                 }
 202         }
 203
 204         av->av_buf_ackno = ackno;
 205 out:
 206         return 0;
 207
 208 out_duplicate:
 209         /* Duplicate packet */
 210         dccp_pr_debug("Received a dup or already considered lost "
 211                       "packet: %llu\n", (unsigned long long)ackno);
 212         return -EILSEQ;
 213 }
 214
 215 static void dccp_ackvec_throw_record(struct dccp_ackvec *av,
 216                                      struct dccp_ackvec_record *avr)
 217 {
 218         struct dccp_ackvec_record *next;
 219
 220         /* sort out vector length */
 221         if (av->av_buf_head <= avr->avr_ack_ptr)
 222                 av->av_vec_len = avr->avr_ack_ptr - av->av_buf_head;
 223         else
 224                 av->av_vec_len = DCCPAV_MAX_ACKVEC_LEN - 1 -
 225                                  av->av_buf_head + avr->avr_ack_ptr;
 226
 227         /* free records */
 228         list_for_each_entry_safe_from(avr, next, &av->av_records, avr_node) {
 229                 list_del(&avr->avr_node);
 230                 kmem_cache_free(dccp_ackvec_record_slab, avr);
 231         }
 232 }
 233
 234 void dccp_ackvec_check_rcv_ackno(struct dccp_ackvec *av, struct sock *sk,
 235                                  const u64 ackno)
 236 {
 237         struct dccp_ackvec_record *avr;
 238
 239         /*
 240          * If we traverse backwards, it should be faster when we have large
 241          * windows. We will be receiving ACKs for stuff we sent a while back
 242          * -sorbo.
 243          */
 244         list_for_each_entry_reverse(avr, &av->av_records, avr_node) {
 245                 if (ackno == avr->avr_ack_seqno) {
 246                         dccp_pr_debug("%s ACK packet 0, len=%d, ack_seqno=%llu, "
 247                                       "ack_ackno=%llu, ACKED!\n",
 248                                       dccp_role(sk), avr->avr_ack_runlen,
 249                                       (unsigned long long)avr->avr_ack_seqno,
 250                                       (unsigned long long)avr->avr_ack_ackno);
 251                         dccp_ackvec_throw_record(av, avr);
 252                         break;
 253                 } else if (avr->avr_ack_seqno > ackno)
 254                         break; /* old news */
 255         }
 256 }
 257
 258 static void dccp_ackvec_check_rcv_ackvector(struct dccp_ackvec *av,
 259                                             struct sock *sk, u64 *ackno,
 260                                             const unsigned char len,
 261                                             const unsigned char *vector)
 262 {
 263         unsigned char i;
 264         struct dccp_ackvec_record *avr;
 265
 266         /* Check if we actually sent an ACK vector */
 267         if (list_empty(&av->av_records))
 268                 return;
 269
 270         i = len;
 271         /*
 272          * XXX
 273          * I think it might be more efficient to work backwards. See comment on
 274          * rcv_ackno. -sorbo.
 275          */
 276         avr = list_entry(av->av_records.next, struct dccp_ackvec_record, avr_node);
 277         while (i--) {
 278                 const u8 rl = dccp_ackvec_runlen(vector);
 279                 u64 ackno_end_rl;
 280
 281                 dccp_set_seqno(&ackno_end_rl, *ackno - rl);
 282
 283                 /*
 284                  * If our AVR sequence number is greater than the ack, go
 285                  * forward in the AVR list until it is not so.
 286                  */
 287                 list_for_each_entry_from(avr, &av->av_records, avr_node) {
 288                         if (!after48(avr->avr_ack_seqno, *ackno))
 289                                 goto found;
 290                 }
 291                 /* End of the av_records list, not found, exit */
 292                 break;
 293 found:
 294                 if (between48(avr->avr_ack_seqno, ackno_end_rl, *ackno)) {
 295                         if (dccp_ackvec_state(vector) != DCCPAV_NOT_RECEIVED) {
 296                                 dccp_pr_debug("%s ACK vector 0, len=%d, "
 297                                               "ack_seqno=%llu, ack_ackno=%llu, "
 298                                               "ACKED!\n",
 299                                               dccp_role(sk), len,
 300                                               (unsigned long long)
 301                                               avr->avr_ack_seqno,
 302                                               (unsigned long long)
 303                                               avr->avr_ack_ackno);
 304                                 dccp_ackvec_throw_record(av, avr);
 305                                 break;
 306                         }
 307                         /*
 308                          * If it wasn't received, continue scanning... we might
 309                          * find another one.
 310                          */
 311                 }
 312
 313                 dccp_set_seqno(ackno, ackno_end_rl - 1);
 314                 ++vector;
 315         }
 316 }
 317
 318 int dccp_ackvec_parse(struct sock *sk, const struct sk_buff *skb,
 319                       u64 *ackno, const u8 opt, const u8 *value, const u8 len)
 320 {
 321         if (len > DCCP_SINGLE_OPT_MAXLEN)
 322                 return -1;
 323
 324         /* dccp_ackvector_print(DCCP_SKB_CB(skb)->dccpd_ack_seq, value, len); */
 325         dccp_ackvec_check_rcv_ackvector(dccp_sk(sk)->dccps_hc_rx_ackvec, sk,
 326                                         ackno, len, value);
 327         return 0;
 328 }
 329
 330 int __init dccp_ackvec_init(void)
 331 {
 332         dccp_ackvec_slab = kmem_cache_create("dccp_ackvec",
 333                                              sizeof(struct dccp_ackvec), 0,
 334                                              SLAB_HWCACHE_ALIGN, NULL);
 335         if (dccp_ackvec_slab == NULL)
 336                 goto out_err;
 337
 338         dccp_ackvec_record_slab = kmem_cache_create("dccp_ackvec_record",
 339                                              sizeof(struct dccp_ackvec_record),
 340                                              0, SLAB_HWCACHE_ALIGN, NULL);
 341         if (dccp_ackvec_record_slab == NULL)
 342                 goto out_destroy_slab;
 343
 344         return 0;
 345
 346 out_destroy_slab:
 347         kmem_cache_destroy(dccp_ackvec_slab);
 348         dccp_ackvec_slab = NULL;
 349 out_err:
 350         DCCP_CRIT("Unable to create Ack Vector slab cache");
 351         return -ENOBUFS;
 352 }
 353
 354 void dccp_ackvec_exit(void)
 355 {
 356         if (dccp_ackvec_slab != NULL) {
 357                 kmem_cache_destroy(dccp_ackvec_slab);
 358                 dccp_ackvec_slab = NULL;
 359         }
 360         if (dccp_ackvec_record_slab != NULL) {
 361                 kmem_cache_destroy(dccp_ackvec_record_slab);
 362                 dccp_ackvec_record_slab = NULL;
 363         }
 364 }