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