net/dccp/ccids/lib/packet_history.c

   1 /*
   2  *  net/dccp/packet_history.c
   3  *
   4  *  Copyright (c) 2007   The University of Aberdeen, Scotland, UK
   5  *  Copyright (c) 2005-7 The University of Waikato, Hamilton, New Zealand.
   6  *
   7  *  An implementation of the DCCP protocol
   8  *
   9  *  This code has been developed by the University of Waikato WAND
  10  *  research group. For further information please see http://www.wand.net.nz/
  11  *  or e-mail Ian McDonald - ian.mcdonald@jandi.co.nz
  12  *
  13  *  This code also uses code from Lulea University, rereleased as GPL by its
  14  *  authors:
  15  *  Copyright (c) 2003 Nils-Erik Mattsson, Joacim Haggmark, Magnus Erixzon
  16  *
  17  *  Changes to meet Linux coding standards, to make it meet latest ccid3 draft
  18  *  and to make it work as a loadable module in the DCCP stack written by
  19  *  Arnaldo Carvalho de Melo <acme@conectiva.com.br>.
  20  *
  21  *  Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@conectiva.com.br>
  22  *
  23  *  This program is free software; you can redistribute it and/or modify
  24  *  it under the terms of the GNU General Public License as published by
  25  *  the Free Software Foundation; either version 2 of the License, or
  26  *  (at your option) any later version.
  27  *
  28  *  This program is distributed in the hope that it will be useful,
  29  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  30  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  31  *  GNU General Public License for more details.
  32  *
  33  *  You should have received a copy of the GNU General Public License
  34  *  along with this program; if not, write to the Free Software
  35  *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  36  */
  37
  38 #include <linux/string.h>
  39 #include <linux/slab.h>
  40 #include "packet_history.h"
  41 #include "../../dccp.h"
  42
  43 /**
  44  *  tfrc_tx_hist_entry  -  Simple singly-linked TX history list
  45  *  @next:  next oldest entry (LIFO order)
  46  *  @seqno: sequence number of this entry
  47  *  @stamp: send time of packet with sequence number @seqno
  48  */
  49 struct tfrc_tx_hist_entry {
  50         struct tfrc_tx_hist_entry *next;
  51         u64                       seqno;
  52         ktime_t                   stamp;
  53 };
  54
  55 /*
  56  * Transmitter History Routines
  57  */
  58 static struct kmem_cache *tfrc_tx_hist_slab;
  59
  60 static struct tfrc_tx_hist_entry *
  61         tfrc_tx_hist_find_entry(struct tfrc_tx_hist_entry *head, u64 seqno)
  62 {
  63         while (head != NULL && head->seqno != seqno)
  64                 head = head->next;
  65
  66         return head;
  67 }
  68
  69 int tfrc_tx_hist_add(struct tfrc_tx_hist_entry **headp, u64 seqno)
  70 {
  71         struct tfrc_tx_hist_entry *entry = kmem_cache_alloc(tfrc_tx_hist_slab, gfp_any());
  72
  73         if (entry == NULL)
  74                 return -ENOBUFS;
  75         entry->seqno = seqno;
  76         entry->stamp = ktime_get_real();
  77         entry->next  = *headp;
  78         *headp       = entry;
  79         return 0;
  80 }
  81 EXPORT_SYMBOL_GPL(tfrc_tx_hist_add);
  82
  83 void tfrc_tx_hist_purge(struct tfrc_tx_hist_entry **headp)
  84 {
  85         struct tfrc_tx_hist_entry *head = *headp;
  86
  87         while (head != NULL) {
  88                 struct tfrc_tx_hist_entry *next = head->next;
  89
  90                 kmem_cache_free(tfrc_tx_hist_slab, head);
  91                 head = next;
  92         }
  93
  94         *headp = NULL;
  95 }
  96 EXPORT_SYMBOL_GPL(tfrc_tx_hist_purge);
  97
  98 u32 tfrc_tx_hist_rtt(struct tfrc_tx_hist_entry *head, const u64 seqno,
  99                      const ktime_t now)
 100 {
 101         u32 rtt = 0;
 102         struct tfrc_tx_hist_entry *packet = tfrc_tx_hist_find_entry(head, seqno);
 103
 104         if (packet != NULL) {
 105                 rtt = ktime_us_delta(now, packet->stamp);
 106                 /*
 107                  * Garbage-collect older (irrelevant) entries:
 108                  */
 109                 tfrc_tx_hist_purge(&packet->next);
 110         }
 111
 112         return rtt;
 113 }
 114 EXPORT_SYMBOL_GPL(tfrc_tx_hist_rtt);
 115
 116
 117 /**
 118  * tfrc_rx_hist_index - index to reach n-th entry after loss_start
 119  */
 120 static inline u8 tfrc_rx_hist_index(const struct tfrc_rx_hist *h, const u8 n)
 121 {
 122         return (h->loss_start + n) & TFRC_NDUPACK;
 123 }
 124
 125 /**
 126  * tfrc_rx_hist_last_rcv - entry with highest-received-seqno so far
 127  */
 128 static inline struct tfrc_rx_hist_entry *
 129                         tfrc_rx_hist_last_rcv(const struct tfrc_rx_hist *h)
 130 {
 131         return h->ring[tfrc_rx_hist_index(h, h->loss_count)];
 132 }
 133
 134 /*
 135  *      Receiver History Routines
 136  */
 137 static struct kmem_cache *tfrc_rx_hist_slab;
 138
 139 void tfrc_rx_hist_add_packet(struct tfrc_rx_hist *h,
 140                              const struct sk_buff *skb,
 141                              const u32 ndp)
 142 {
 143         struct tfrc_rx_hist_entry *entry = tfrc_rx_hist_last_rcv(h);
 144         const struct dccp_hdr *dh = dccp_hdr(skb);
 145
 146         entry->tfrchrx_seqno = DCCP_SKB_CB(skb)->dccpd_seq;
 147         entry->tfrchrx_ccval = dh->dccph_ccval;
 148         entry->tfrchrx_type  = dh->dccph_type;
 149         entry->tfrchrx_ndp   = ndp;
 150         entry->tfrchrx_tstamp = ktime_get_real();
 151 }
 152 EXPORT_SYMBOL_GPL(tfrc_rx_hist_add_packet);
 153
 154 static inline void tfrc_rx_hist_entry_delete(struct tfrc_rx_hist_entry *entry)
 155 {
 156         kmem_cache_free(tfrc_rx_hist_slab, entry);
 157 }
 158
 159 /**
 160  * tfrc_rx_hist_entry - return the n-th history entry after loss_start
 161  */
 162 static inline struct tfrc_rx_hist_entry *
 163                 tfrc_rx_hist_entry(const struct tfrc_rx_hist *h, const u8 n)
 164 {
 165         return h->ring[tfrc_rx_hist_index(h, n)];
 166 }
 167
 168 /**
 169  * tfrc_rx_hist_loss_prev - entry with highest-received-seqno before loss was detected
 170  */
 171 static inline struct tfrc_rx_hist_entry *
 172                         tfrc_rx_hist_loss_prev(const struct tfrc_rx_hist *h)
 173 {
 174         return h->ring[h->loss_start];
 175 }
 176
 177 /* has the packet contained in skb been seen before? */
 178 int tfrc_rx_hist_duplicate(struct tfrc_rx_hist *h, struct sk_buff *skb)
 179 {
 180         const u64 seq = DCCP_SKB_CB(skb)->dccpd_seq;
 181         int i;
 182
 183         if (dccp_delta_seqno(tfrc_rx_hist_loss_prev(h)->tfrchrx_seqno, seq) <= 0)
 184                 return 1;
 185
 186         for (i = 1; i <= h->loss_count; i++)
 187                 if (tfrc_rx_hist_entry(h, i)->tfrchrx_seqno == seq)
 188                         return 1;
 189
 190         return 0;
 191 }
 192 EXPORT_SYMBOL_GPL(tfrc_rx_hist_duplicate);
 193
 194 /* initialise loss detection and disable RTT sampling */
 195 static inline void tfrc_rx_hist_loss_indicated(struct tfrc_rx_hist *h)
 196 {
 197         h->loss_count = 1;
 198 }
 199
 200 /* indicate whether previously a packet was detected missing */
 201 static inline int tfrc_rx_hist_loss_pending(const struct tfrc_rx_hist *h)
 202 {
 203         return h->loss_count;
 204 }
 205
 206 /* any data packets missing between last reception and skb ? */
 207 int tfrc_rx_hist_new_loss_indicated(struct tfrc_rx_hist *h,
 208                                     const struct sk_buff *skb, u32 ndp)
 209 {
 210         int delta = dccp_delta_seqno(tfrc_rx_hist_last_rcv(h)->tfrchrx_seqno,
 211                                      DCCP_SKB_CB(skb)->dccpd_seq);
 212
 213         if (delta > 1 && ndp < delta)
 214                 tfrc_rx_hist_loss_indicated(h);
 215
 216         return tfrc_rx_hist_loss_pending(h);
 217 }
 218 EXPORT_SYMBOL_GPL(tfrc_rx_hist_new_loss_indicated);
 219
 220 int tfrc_rx_hist_alloc(struct tfrc_rx_hist *h)
 221 {
 222         int i;
 223
 224         for (i = 0; i <= TFRC_NDUPACK; i++) {
 225                 h->ring[i] = kmem_cache_alloc(tfrc_rx_hist_slab, GFP_ATOMIC);
 226                 if (h->ring[i] == NULL)
 227                         goto out_free;
 228         }
 229
 230         h->loss_count = h->loss_start = 0;
 231         return 0;
 232
 233 out_free:
 234         while (i-- != 0) {
 235                 kmem_cache_free(tfrc_rx_hist_slab, h->ring[i]);
 236                 h->ring[i] = NULL;
 237         }
 238         return -ENOBUFS;
 239 }
 240 EXPORT_SYMBOL_GPL(tfrc_rx_hist_alloc);
 241
 242 void tfrc_rx_hist_purge(struct tfrc_rx_hist *h)
 243 {
 244         int i;
 245
 246         for (i = 0; i <= TFRC_NDUPACK; ++i)
 247                 if (h->ring[i] != NULL) {
 248                         kmem_cache_free(tfrc_rx_hist_slab, h->ring[i]);
 249                         h->ring[i] = NULL;
 250                 }
 251 }
 252 EXPORT_SYMBOL_GPL(tfrc_rx_hist_purge);
 253
 254 /**
 255  * tfrc_rx_hist_rtt_last_s - reference entry to compute RTT samples against
 256  */
 257 static inline struct tfrc_rx_hist_entry *
 258                         tfrc_rx_hist_rtt_last_s(const struct tfrc_rx_hist *h)
 259 {
 260         return h->ring[0];
 261 }
 262
 263 /**
 264  * tfrc_rx_hist_rtt_prev_s: previously suitable (wrt rtt_last_s) RTT-sampling entry
 265  */
 266 static inline struct tfrc_rx_hist_entry *
 267                         tfrc_rx_hist_rtt_prev_s(const struct tfrc_rx_hist *h)
 268 {
 269         return h->ring[h->rtt_sample_prev];
 270 }
 271
 272 /**
 273  * tfrc_rx_hist_sample_rtt  -  Sample RTT from timestamp / CCVal
 274  * Based on ideas presented in RFC 4342, 8.1. Returns 0 if it was not able
 275  * to compute a sample with given data - calling function should check this.
 276  */
 277 u32 tfrc_rx_hist_sample_rtt(struct tfrc_rx_hist *h, const struct sk_buff *skb)
 278 {
 279         u32 sample = 0,
 280             delta_v = SUB16(dccp_hdr(skb)->dccph_ccval,
 281                             tfrc_rx_hist_rtt_last_s(h)->tfrchrx_ccval);
 282
 283         if (delta_v < 1 || delta_v > 4) {       /* unsuitable CCVal delta */
 284                 if (h->rtt_sample_prev == 2) {  /* previous candidate stored */
 285                         sample = SUB16(tfrc_rx_hist_rtt_prev_s(h)->tfrchrx_ccval,
 286                                        tfrc_rx_hist_rtt_last_s(h)->tfrchrx_ccval);
 287                         if (sample)
 288                                 sample = 4 / sample *
 289                                          ktime_us_delta(tfrc_rx_hist_rtt_prev_s(h)->tfrchrx_tstamp,
 290                                                         tfrc_rx_hist_rtt_last_s(h)->tfrchrx_tstamp);
 291                         else    /*
 292                                  * FIXME: This condition is in principle not
 293                                  * possible but occurs when CCID is used for
 294                                  * two-way data traffic. I have tried to trace
 295                                  * it, but the cause does not seem to be here.
 296                                  */
 297                                 DCCP_BUG("please report to dccp@vger.kernel.org"
 298                                          " => prev = %u, last = %u",
 299                                          tfrc_rx_hist_rtt_prev_s(h)->tfrchrx_ccval,
 300                                          tfrc_rx_hist_rtt_last_s(h)->tfrchrx_ccval);
 301                 } else if (delta_v < 1) {
 302                         h->rtt_sample_prev = 1;
 303                         goto keep_ref_for_next_time;
 304                 }
 305
 306         } else if (delta_v == 4) /* optimal match */
 307                 sample = ktime_to_us(net_timedelta(tfrc_rx_hist_rtt_last_s(h)->tfrchrx_tstamp));
 308         else {                   /* suboptimal match */
 309                 h->rtt_sample_prev = 2;
 310                 goto keep_ref_for_next_time;
 311         }
 312
 313         if (unlikely(sample > DCCP_SANE_RTT_MAX)) {
 314                 DCCP_WARN("RTT sample %u too large, using max\n", sample);
 315                 sample = DCCP_SANE_RTT_MAX;
 316         }
 317
 318         h->rtt_sample_prev = 0;        /* use current entry as next reference */
 319 keep_ref_for_next_time:
 320
 321         return sample;
 322 }
 323 EXPORT_SYMBOL_GPL(tfrc_rx_hist_sample_rtt);
 324
 325 __init int packet_history_init(void)
 326 {
 327         tfrc_tx_hist_slab = kmem_cache_create("tfrc_tx_hist",
 328                                               sizeof(struct tfrc_tx_hist_entry), 0,
 329                                               SLAB_HWCACHE_ALIGN, NULL);
 330         if (tfrc_tx_hist_slab == NULL)
 331                 goto out_err;
 332
 333         tfrc_rx_hist_slab = kmem_cache_create("tfrc_rx_hist",
 334                                               sizeof(struct tfrc_rx_hist_entry), 0,
 335                                               SLAB_HWCACHE_ALIGN, NULL);
 336         if (tfrc_rx_hist_slab == NULL)
 337                 goto out_free_tx;
 338
 339         return 0;
 340
 341 out_free_tx:
 342         kmem_cache_destroy(tfrc_tx_hist_slab);
 343         tfrc_tx_hist_slab = NULL;
 344 out_err:
 345         return -ENOBUFS;
 346 }
 347
 348 void packet_history_exit(void)
 349 {
 350         if (tfrc_tx_hist_slab != NULL) {
 351                 kmem_cache_destroy(tfrc_tx_hist_slab);
 352                 tfrc_tx_hist_slab = NULL;
 353         }
 354
 355         if (tfrc_rx_hist_slab != NULL) {
 356                 kmem_cache_destroy(tfrc_rx_hist_slab);
 357                 tfrc_rx_hist_slab = NULL;
 358         }
 359 }