root/net/dccp/ccids/lib/loss_interval.c

DEFINITIONS

1. LIH_INDEX
2. tfrc_lh_peek
3. tfrc_lh_get_interval
4. tfrc_lh_demand_next
5. tfrc_lh_cleanup
6. tfrc_lh_calc_i_mean
7. tfrc_lh_update_i_mean
8. tfrc_lh_is_new_loss
9. tfrc_lh_interval_add
10. tfrc_li_init
11. tfrc_li_exit

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  *  Copyright (c) 2007   The University of Aberdeen, Scotland, UK
   4  *  Copyright (c) 2005-7 The University of Waikato, Hamilton, New Zealand.
   5  *  Copyright (c) 2005-7 Ian McDonald <ian.mcdonald@jandi.co.nz>
   6  *  Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@conectiva.com.br>
   7  */
   8 #include <net/sock.h>
   9 #include "tfrc.h"
  10 
  11 static struct kmem_cache  *tfrc_lh_slab  __read_mostly;
  12 /* Loss Interval weights from [RFC 3448, 5.4], scaled by 10 */
  13 static const int tfrc_lh_weights[NINTERVAL] = { 10, 10, 10, 10, 8, 6, 4, 2 };
  14 
  15 /* implements LIFO semantics on the array */
  16 static inline u8 LIH_INDEX(const u8 ctr)
  17 {
  18         return LIH_SIZE - 1 - (ctr % LIH_SIZE);
  19 }
  20 
  21 /* the `counter' index always points at the next entry to be populated */
  22 static inline struct tfrc_loss_interval *tfrc_lh_peek(struct tfrc_loss_hist *lh)
  23 {
  24         return lh->counter ? lh->ring[LIH_INDEX(lh->counter - 1)] : NULL;
  25 }
  26 
  27 /* given i with 0 <= i <= k, return I_i as per the rfc3448bis notation */
  28 static inline u32 tfrc_lh_get_interval(struct tfrc_loss_hist *lh, const u8 i)
  29 {
  30         BUG_ON(i >= lh->counter);
  31         return lh->ring[LIH_INDEX(lh->counter - i - 1)]->li_length;
  32 }
  33 
  34 /*
  35  *      On-demand allocation and de-allocation of entries
  36  */
  37 static struct tfrc_loss_interval *tfrc_lh_demand_next(struct tfrc_loss_hist *lh)
  38 {
  39         if (lh->ring[LIH_INDEX(lh->counter)] == NULL)
  40                 lh->ring[LIH_INDEX(lh->counter)] = kmem_cache_alloc(tfrc_lh_slab,
  41                                                                     GFP_ATOMIC);
  42         return lh->ring[LIH_INDEX(lh->counter)];
  43 }
  44 
  45 void tfrc_lh_cleanup(struct tfrc_loss_hist *lh)
  46 {
  47         if (!tfrc_lh_is_initialised(lh))
  48                 return;
  49 
  50         for (lh->counter = 0; lh->counter < LIH_SIZE; lh->counter++)
  51                 if (lh->ring[LIH_INDEX(lh->counter)] != NULL) {
  52                         kmem_cache_free(tfrc_lh_slab,
  53                                         lh->ring[LIH_INDEX(lh->counter)]);
  54                         lh->ring[LIH_INDEX(lh->counter)] = NULL;
  55                 }
  56 }
  57 
  58 static void tfrc_lh_calc_i_mean(struct tfrc_loss_hist *lh)
  59 {
  60         u32 i_i, i_tot0 = 0, i_tot1 = 0, w_tot = 0;
  61         int i, k = tfrc_lh_length(lh) - 1; /* k is as in rfc3448bis, 5.4 */
  62 
  63         if (k <= 0)
  64                 return;
  65 
  66         for (i = 0; i <= k; i++) {
  67                 i_i = tfrc_lh_get_interval(lh, i);
  68 
  69                 if (i < k) {
  70                         i_tot0 += i_i * tfrc_lh_weights[i];
  71                         w_tot  += tfrc_lh_weights[i];
  72                 }
  73                 if (i > 0)
  74                         i_tot1 += i_i * tfrc_lh_weights[i-1];
  75         }
  76 
  77         lh->i_mean = max(i_tot0, i_tot1) / w_tot;
  78 }
  79 
  80 /**
  81  * tfrc_lh_update_i_mean  -  Update the `open' loss interval I_0
  82  * For recomputing p: returns `true' if p > p_prev  <=>  1/p < 1/p_prev
  83  */
  84 u8 tfrc_lh_update_i_mean(struct tfrc_loss_hist *lh, struct sk_buff *skb)
  85 {
  86         struct tfrc_loss_interval *cur = tfrc_lh_peek(lh);
  87         u32 old_i_mean = lh->i_mean;
  88         s64 len;
  89 
  90         if (cur == NULL)                        /* not initialised */
  91                 return 0;
  92 
  93         len = dccp_delta_seqno(cur->li_seqno, DCCP_SKB_CB(skb)->dccpd_seq) + 1;
  94 
  95         if (len - (s64)cur->li_length <= 0)     /* duplicate or reordered */
  96                 return 0;
  97 
  98         if (SUB16(dccp_hdr(skb)->dccph_ccval, cur->li_ccval) > 4)
  99                 /*
 100                  * Implements RFC 4342, 10.2:
 101                  * If a packet S (skb) exists whose seqno comes `after' the one
 102                  * starting the current loss interval (cur) and if the modulo-16
 103                  * distance from C(cur) to C(S) is greater than 4, consider all
 104                  * subsequent packets as belonging to a new loss interval. This
 105                  * test is necessary since CCVal may wrap between intervals.
 106                  */
 107                 cur->li_is_closed = 1;
 108 
 109         if (tfrc_lh_length(lh) == 1)            /* due to RFC 3448, 6.3.1 */
 110                 return 0;
 111 
 112         cur->li_length = len;
 113         tfrc_lh_calc_i_mean(lh);
 114 
 115         return lh->i_mean < old_i_mean;
 116 }
 117 
 118 /* Determine if `new_loss' does begin a new loss interval [RFC 4342, 10.2] */
 119 static inline u8 tfrc_lh_is_new_loss(struct tfrc_loss_interval *cur,
 120                                      struct tfrc_rx_hist_entry *new_loss)
 121 {
 122         return  dccp_delta_seqno(cur->li_seqno, new_loss->tfrchrx_seqno) > 0 &&
 123                 (cur->li_is_closed || SUB16(new_loss->tfrchrx_ccval, cur->li_ccval) > 4);
 124 }
 125 
 126 /**
 127  * tfrc_lh_interval_add  -  Insert new record into the Loss Interval database
 128  * @lh:            Loss Interval database
 129  * @rh:            Receive history containing a fresh loss event
 130  * @calc_first_li: Caller-dependent routine to compute length of first interval
 131  * @sk:            Used by @calc_first_li in caller-specific way (subtyping)
 132  *
 133  * Updates I_mean and returns 1 if a new interval has in fact been added to @lh.
 134  */
 135 int tfrc_lh_interval_add(struct tfrc_loss_hist *lh, struct tfrc_rx_hist *rh,
 136                          u32 (*calc_first_li)(struct sock *), struct sock *sk)
 137 {
 138         struct tfrc_loss_interval *cur = tfrc_lh_peek(lh), *new;
 139 
 140         if (cur != NULL && !tfrc_lh_is_new_loss(cur, tfrc_rx_hist_loss_prev(rh)))
 141                 return 0;
 142 
 143         new = tfrc_lh_demand_next(lh);
 144         if (unlikely(new == NULL)) {
 145                 DCCP_CRIT("Cannot allocate/add loss record.");
 146                 return 0;
 147         }
 148 
 149         new->li_seqno     = tfrc_rx_hist_loss_prev(rh)->tfrchrx_seqno;
 150         new->li_ccval     = tfrc_rx_hist_loss_prev(rh)->tfrchrx_ccval;
 151         new->li_is_closed = 0;
 152 
 153         if (++lh->counter == 1)
 154                 lh->i_mean = new->li_length = (*calc_first_li)(sk);
 155         else {
 156                 cur->li_length = dccp_delta_seqno(cur->li_seqno, new->li_seqno);
 157                 new->li_length = dccp_delta_seqno(new->li_seqno,
 158                                   tfrc_rx_hist_last_rcv(rh)->tfrchrx_seqno) + 1;
 159                 if (lh->counter > (2*LIH_SIZE))
 160                         lh->counter -= LIH_SIZE;
 161 
 162                 tfrc_lh_calc_i_mean(lh);
 163         }
 164         return 1;
 165 }
 166 
 167 int __init tfrc_li_init(void)
 168 {
 169         tfrc_lh_slab = kmem_cache_create("tfrc_li_hist",
 170                                          sizeof(struct tfrc_loss_interval), 0,
 171                                          SLAB_HWCACHE_ALIGN, NULL);
 172         return tfrc_lh_slab == NULL ? -ENOBUFS : 0;
 173 }
 174 
 175 void tfrc_li_exit(void)
 176 {
 177         if (tfrc_lh_slab != NULL) {
 178                 kmem_cache_destroy(tfrc_lh_slab);
 179                 tfrc_lh_slab = NULL;
 180         }
 181 }