net/dccp/ccids/lib/loss_interval.c

   1 /*
   2  *  net/dccp/ccids/lib/loss_interval.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  *  Copyright (c) 2005-7 Ian McDonald <ian.mcdonald@jandi.co.nz>
   7  *  Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@conectiva.com.br>
   8  *
   9  *  This program is free software; you can redistribute it and/or modify
  10  *  it under the terms of the GNU General Public License as published by
  11  *  the Free Software Foundation; either version 2 of the License, or
  12  *  (at your option) any later version.
  13  */
  14 #include <net/sock.h>
  15 #include "tfrc.h"
  16
  17 static struct kmem_cache  *tfrc_lh_slab  __read_mostly;
  18 /* Loss Interval weights from [RFC 3448, 5.4], scaled by 10 */
  19 static const int tfrc_lh_weights[NINTERVAL] = { 10, 10, 10, 10, 8, 6, 4, 2 };
  20
  21 /* implements LIFO semantics on the array */
  22 static inline u8 LIH_INDEX(const u8 ctr)
  23 {
  24         return (LIH_SIZE - 1 - (ctr % LIH_SIZE));
  25 }
  26
  27 /* the `counter' index always points at the next entry to be populated */
  28 static inline struct tfrc_loss_interval *tfrc_lh_peek(struct tfrc_loss_hist *lh)
  29 {
  30         return lh->counter ? lh->ring[LIH_INDEX(lh->counter - 1)] : NULL;
  31 }
  32
  33 /* given i with 0 <= i <= k, return I_i as per the rfc3448bis notation */
  34 static inline u32 tfrc_lh_get_interval(struct tfrc_loss_hist *lh, const u8 i)
  35 {
  36         BUG_ON(i >= lh->counter);
  37         return lh->ring[LIH_INDEX(lh->counter - i - 1)]->li_length;
  38 }
  39
  40 /*
  41  *      On-demand allocation and de-allocation of entries
  42  */
  43 static struct tfrc_loss_interval *tfrc_lh_demand_next(struct tfrc_loss_hist *lh)
  44 {
  45         if (lh->ring[LIH_INDEX(lh->counter)] == NULL)
  46                 lh->ring[LIH_INDEX(lh->counter)] = kmem_cache_alloc(tfrc_lh_slab,
  47                                                                     GFP_ATOMIC);
  48         return lh->ring[LIH_INDEX(lh->counter)];
  49 }
  50
  51 void tfrc_lh_cleanup(struct tfrc_loss_hist *lh)
  52 {
  53         if (!tfrc_lh_is_initialised(lh))
  54                 return;
  55
  56         for (lh->counter = 0; lh->counter < LIH_SIZE; lh->counter++)
  57                 if (lh->ring[LIH_INDEX(lh->counter)] != NULL) {
  58                         kmem_cache_free(tfrc_lh_slab,
  59                                         lh->ring[LIH_INDEX(lh->counter)]);
  60                         lh->ring[LIH_INDEX(lh->counter)] = NULL;
  61                 }
  62 }
  63 EXPORT_SYMBOL_GPL(tfrc_lh_cleanup);
  64
  65 static void tfrc_lh_calc_i_mean(struct tfrc_loss_hist *lh)
  66 {
  67         u32 i_i, i_tot0 = 0, i_tot1 = 0, w_tot = 0;
  68         int i, k = tfrc_lh_length(lh) - 1; /* k is as in rfc3448bis, 5.4 */
  69
  70         if (k <= 0)
  71                 return;
  72
  73         for (i = 0; i <= k; i++) {
  74                 i_i = tfrc_lh_get_interval(lh, i);
  75
  76                 if (i < k) {
  77                         i_tot0 += i_i * tfrc_lh_weights[i];
  78                         w_tot  += tfrc_lh_weights[i];
  79                 }
  80                 if (i > 0)
  81                         i_tot1 += i_i * tfrc_lh_weights[i-1];
  82         }
  83
  84         lh->i_mean = max(i_tot0, i_tot1) / w_tot;
  85 }
  86
  87 /**
  88  * tfrc_lh_update_i_mean  -  Update the `open' loss interval I_0
  89  * This updates I_mean as the sequence numbers increase. As a consequence, the
  90  * open loss interval I_0 increases, hence p = W_tot/max(I_tot0, I_tot1)
  91  * decreases, and thus there is no need to send renewed feedback.
  92  */
  93 void tfrc_lh_update_i_mean(struct tfrc_loss_hist *lh, struct sk_buff *skb)
  94 {
  95         struct tfrc_loss_interval *cur = tfrc_lh_peek(lh);
  96         s64 len;
  97
  98         if (cur == NULL)                        /* not initialised */
  99                 return;
 100
 101         /* FIXME: should probably also count non-data packets (RFC 4342, 6.1) */
 102         if (!dccp_data_packet(skb))
 103                 return;
 104
 105         len = dccp_delta_seqno(cur->li_seqno, DCCP_SKB_CB(skb)->dccpd_seq) + 1;
 106
 107         if (len - (s64)cur->li_length <= 0)     /* duplicate or reordered */
 108                 return;
 109
 110         if (SUB16(dccp_hdr(skb)->dccph_ccval, cur->li_ccval) > 4)
 111                 /*
 112                  * Implements RFC 4342, 10.2:
 113                  * If a packet S (skb) exists whose seqno comes `after' the one
 114                  * starting the current loss interval (cur) and if the modulo-16
 115                  * distance from C(cur) to C(S) is greater than 4, consider all
 116                  * subsequent packets as belonging to a new loss interval. This
 117                  * test is necessary since CCVal may wrap between intervals.
 118                  */
 119                 cur->li_is_closed = 1;
 120
 121         if (tfrc_lh_length(lh) == 1)            /* due to RFC 3448, 6.3.1 */
 122                 return;
 123
 124         cur->li_length = len;
 125         tfrc_lh_calc_i_mean(lh);
 126 }
 127
 128 /* Determine if `new_loss' does begin a new loss interval [RFC 4342, 10.2] */
 129 static inline u8 tfrc_lh_is_new_loss(struct tfrc_loss_interval *cur,
 130                                      struct tfrc_rx_hist_entry *new_loss)
 131 {
 132         return  dccp_delta_seqno(cur->li_seqno, new_loss->tfrchrx_seqno) > 0 &&
 133                 (cur->li_is_closed || SUB16(new_loss->tfrchrx_ccval, cur->li_ccval) > 4);
 134 }
 135
 136 /** tfrc_lh_interval_add  -  Insert new record into the Loss Interval database
 137  * @lh:            Loss Interval database
 138  * @rh:            Receive history containing a fresh loss event
 139  * @calc_first_li: Caller-dependent routine to compute length of first interval
 140  * @sk:            Used by @calc_first_li in caller-specific way (subtyping)
 141  * Updates I_mean and returns 1 if a new interval has in fact been added to @lh.
 142  */
 143 bool tfrc_lh_interval_add(struct tfrc_loss_hist *lh, struct tfrc_rx_hist *rh,
 144                           u32 (*calc_first_li)(struct sock *), struct sock *sk)
 145 {
 146         struct tfrc_loss_interval *cur = tfrc_lh_peek(lh), *new;
 147
 148         if (cur != NULL && !tfrc_lh_is_new_loss(cur, tfrc_rx_hist_loss_prev(rh)))
 149                 return false;
 150
 151         new = tfrc_lh_demand_next(lh);
 152         if (unlikely(new == NULL)) {
 153                 DCCP_CRIT("Cannot allocate/add loss record.");
 154                 return false;
 155         }
 156
 157         new->li_seqno     = tfrc_rx_hist_loss_prev(rh)->tfrchrx_seqno;
 158         new->li_ccval     = tfrc_rx_hist_loss_prev(rh)->tfrchrx_ccval;
 159         new->li_is_closed = 0;
 160
 161         if (++lh->counter == 1)
 162                 lh->i_mean = new->li_length = (*calc_first_li)(sk);
 163         else {
 164                 cur->li_length = dccp_delta_seqno(cur->li_seqno, new->li_seqno);
 165                 new->li_length = dccp_delta_seqno(new->li_seqno,
 166                                   tfrc_rx_hist_last_rcv(rh)->tfrchrx_seqno) + 1;
 167                 if (lh->counter > (2*LIH_SIZE))
 168                         lh->counter -= LIH_SIZE;
 169
 170                 tfrc_lh_calc_i_mean(lh);
 171         }
 172         return true;
 173 }
 174 EXPORT_SYMBOL_GPL(tfrc_lh_interval_add);
 175
 176 int __init tfrc_li_init(void)
 177 {
 178         tfrc_lh_slab = kmem_cache_create("tfrc_li_hist",
 179                                          sizeof(struct tfrc_loss_interval), 0,
 180                                          SLAB_HWCACHE_ALIGN, NULL);
 181         return tfrc_lh_slab == NULL ? -ENOBUFS : 0;
 182 }
 183
 184 void tfrc_li_exit(void)
 185 {
 186         if (tfrc_lh_slab != NULL) {
 187                 kmem_cache_destroy(tfrc_lh_slab);
 188                 tfrc_lh_slab = NULL;
 189         }
 190 }