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/*
* net/dccp/ccids/lib/loss_interval.c
*
* Copyright (c) 2007 The University of Aberdeen, Scotland, UK
* Copyright (c) 2005-7 The University of Waikato, Hamilton, New Zealand.
* Copyright (c) 2005-7 Ian McDonald <ian.mcdonald@jandi.co.nz>
* Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@conectiva.com.br>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*/
#include <net/sock.h>
#include "tfrc.h"
static struct kmem_cache *tfrc_lh_slab __read_mostly;
/* Loss Interval weights from [RFC 3448, 5.4], scaled by 10 */
static const int tfrc_lh_weights[NINTERVAL] = { 10, 10, 10, 10, 8, 6, 4, 2 };
/* implements LIFO semantics on the array */
static inline u8 LIH_INDEX(const u8 ctr)
{
return (LIH_SIZE - 1 - (ctr % LIH_SIZE));
}
/* the `counter' index always points at the next entry to be populated */
static inline struct tfrc_loss_interval *tfrc_lh_peek(struct tfrc_loss_hist *lh)
{
return lh->counter ? lh->ring[LIH_INDEX(lh->counter - 1)] : NULL;
}
/* given i with 0 <= i <= k, return I_i as per the rfc3448bis notation */
static inline u32 tfrc_lh_get_interval(struct tfrc_loss_hist *lh, const u8 i)
{
BUG_ON(i >= lh->counter);
return lh->ring[LIH_INDEX(lh->counter - i - 1)]->li_length;
}
/*
* On-demand allocation and de-allocation of entries
*/
static struct tfrc_loss_interval *tfrc_lh_demand_next(struct tfrc_loss_hist *lh)
{
if (lh->ring[LIH_INDEX(lh->counter)] == NULL)
lh->ring[LIH_INDEX(lh->counter)] = kmem_cache_alloc(tfrc_lh_slab,
GFP_ATOMIC);
return lh->ring[LIH_INDEX(lh->counter)];
}
void tfrc_lh_cleanup(struct tfrc_loss_hist *lh)
{
if (!tfrc_lh_is_initialised(lh))
return;
for (lh->counter = 0; lh->counter < LIH_SIZE; lh->counter++)
if (lh->ring[LIH_INDEX(lh->counter)] != NULL) {
kmem_cache_free(tfrc_lh_slab,
lh->ring[LIH_INDEX(lh->counter)]);
lh->ring[LIH_INDEX(lh->counter)] = NULL;
}
}
static void tfrc_lh_calc_i_mean(struct tfrc_loss_hist *lh)
{
u32 i_i, i_tot0 = 0, i_tot1 = 0, w_tot = 0;
int i, k = tfrc_lh_length(lh) - 1; /* k is as in rfc3448bis, 5.4 */
if (k <= 0)
return;
for (i = 0; i <= k; i++) {
i_i = tfrc_lh_get_interval(lh, i);
if (i < k) {
i_tot0 += i_i * tfrc_lh_weights[i];
w_tot += tfrc_lh_weights[i];
}
if (i > 0)
i_tot1 += i_i * tfrc_lh_weights[i-1];
}
lh->i_mean = max(i_tot0, i_tot1) / w_tot;
}
/**
* tfrc_lh_update_i_mean - Update the `open' loss interval I_0
* For recomputing p: returns `true' if p > p_prev <=> 1/p < 1/p_prev
*/
u8 tfrc_lh_update_i_mean(struct tfrc_loss_hist *lh, struct sk_buff *skb)
{
struct tfrc_loss_interval *cur = tfrc_lh_peek(lh);
u32 old_i_mean = lh->i_mean;
s64 len;
if (cur == NULL) /* not initialised */
return 0;
len = dccp_delta_seqno(cur->li_seqno, DCCP_SKB_CB(skb)->dccpd_seq) + 1;
if (len - (s64)cur->li_length <= 0) /* duplicate or reordered */
return 0;
if (SUB16(dccp_hdr(skb)->dccph_ccval, cur->li_ccval) > 4)
/*
* Implements RFC 4342, 10.2:
* If a packet S (skb) exists whose seqno comes `after' the one
* starting the current loss interval (cur) and if the modulo-16
* distance from C(cur) to C(S) is greater than 4, consider all
* subsequent packets as belonging to a new loss interval. This
* test is necessary since CCVal may wrap between intervals.
*/
cur->li_is_closed = 1;
if (tfrc_lh_length(lh) == 1) /* due to RFC 3448, 6.3.1 */
return 0;
cur->li_length = len;
tfrc_lh_calc_i_mean(lh);
return (lh->i_mean < old_i_mean);
}
/* Determine if `new_loss' does begin a new loss interval [RFC 4342, 10.2] */
static inline u8 tfrc_lh_is_new_loss(struct tfrc_loss_interval *cur,
struct tfrc_rx_hist_entry *new_loss)
{
return dccp_delta_seqno(cur->li_seqno, new_loss->tfrchrx_seqno) > 0 &&
(cur->li_is_closed || SUB16(new_loss->tfrchrx_ccval, cur->li_ccval) > 4);
}
/** tfrc_lh_interval_add - Insert new record into the Loss Interval database
* @lh: Loss Interval database
* @rh: Receive history containing a fresh loss event
* @calc_first_li: Caller-dependent routine to compute length of first interval
* @sk: Used by @calc_first_li in caller-specific way (subtyping)
* Updates I_mean and returns 1 if a new interval has in fact been added to @lh.
*/
int tfrc_lh_interval_add(struct tfrc_loss_hist *lh, struct tfrc_rx_hist *rh,
u32 (*calc_first_li)(struct sock *), struct sock *sk)
{
struct tfrc_loss_interval *cur = tfrc_lh_peek(lh), *new;
if (cur != NULL && !tfrc_lh_is_new_loss(cur, tfrc_rx_hist_loss_prev(rh)))
return 0;
new = tfrc_lh_demand_next(lh);
if (unlikely(new == NULL)) {
DCCP_CRIT("Cannot allocate/add loss record.");
return 0;
}
new->li_seqno = tfrc_rx_hist_loss_prev(rh)->tfrchrx_seqno;
new->li_ccval = tfrc_rx_hist_loss_prev(rh)->tfrchrx_ccval;
new->li_is_closed = 0;
if (++lh->counter == 1)
lh->i_mean = new->li_length = (*calc_first_li)(sk);
else {
cur->li_length = dccp_delta_seqno(cur->li_seqno, new->li_seqno);
new->li_length = dccp_delta_seqno(new->li_seqno,
tfrc_rx_hist_last_rcv(rh)->tfrchrx_seqno) + 1;
if (lh->counter > (2*LIH_SIZE))
lh->counter -= LIH_SIZE;
tfrc_lh_calc_i_mean(lh);
}
return 1;
}
int __init tfrc_li_init(void)
{
tfrc_lh_slab = kmem_cache_create("tfrc_li_hist",
sizeof(struct tfrc_loss_interval), 0,
SLAB_HWCACHE_ALIGN, NULL);
return tfrc_lh_slab == NULL ? -ENOBUFS : 0;
}
void tfrc_li_exit(void)
{
if (tfrc_lh_slab != NULL) {
kmem_cache_destroy(tfrc_lh_slab);
tfrc_lh_slab = NULL;
}
}
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