linux/net/dccp/ccids/lib/packet_history.c

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/*
* net/dccp/packet_history.c
*
* Copyright (c) 2007 The University of Aberdeen, Scotland, UK
* Copyright (c) 2005-7 The University of Waikato, Hamilton, New Zealand.
*
* An implementation of the DCCP protocol
*
* This code has been developed by the University of Waikato WAND
* research group. For further information please see http://www.wand.net.nz/
* or e-mail Ian McDonald - ian.mcdonald@jandi.co.nz
*
* This code also uses code from Lulea University, rereleased as GPL by its
* authors:
* Copyright (c) 2003 Nils-Erik Mattsson, Joacim Haggmark, Magnus Erixzon
*
* Changes to meet Linux coding standards, to make it meet latest ccid3 draft
* and to make it work as a loadable module in the DCCP stack written by
* Arnaldo Carvalho de Melo <acme@conectiva.com.br>.
*
* 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.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#include <linux/string.h>
#include <linux/slab.h>
#include "packet_history.h"
#include "../../dccp.h"
/**
* tfrc_tx_hist_entry - Simple singly-linked TX history list
* @next: next oldest entry (LIFO order)
* @seqno: sequence number of this entry
* @stamp: send time of packet with sequence number @seqno
*/
struct tfrc_tx_hist_entry {
struct tfrc_tx_hist_entry *next;
u64 seqno;
ktime_t stamp;
};
/*
* Transmitter History Routines
*/
static struct kmem_cache *tfrc_tx_hist_slab;
int __init tfrc_tx_packet_history_init(void)
{
tfrc_tx_hist_slab = kmem_cache_create("tfrc_tx_hist",
sizeof(struct tfrc_tx_hist_entry),
0, SLAB_HWCACHE_ALIGN, NULL);
return tfrc_tx_hist_slab == NULL ? -ENOBUFS : 0;
}
void tfrc_tx_packet_history_exit(void)
{
if (tfrc_tx_hist_slab != NULL) {
kmem_cache_destroy(tfrc_tx_hist_slab);
tfrc_tx_hist_slab = NULL;
}
}
static struct tfrc_tx_hist_entry *
tfrc_tx_hist_find_entry(struct tfrc_tx_hist_entry *head, u64 seqno)
{
while (head != NULL && head->seqno != seqno)
head = head->next;
return head;
}
int tfrc_tx_hist_add(struct tfrc_tx_hist_entry **headp, u64 seqno)
{
struct tfrc_tx_hist_entry *entry = kmem_cache_alloc(tfrc_tx_hist_slab, gfp_any());
if (entry == NULL)
return -ENOBUFS;
entry->seqno = seqno;
entry->stamp = ktime_get_real();
entry->next = *headp;
*headp = entry;
return 0;
}
EXPORT_SYMBOL_GPL(tfrc_tx_hist_add);
void tfrc_tx_hist_purge(struct tfrc_tx_hist_entry **headp)
{
struct tfrc_tx_hist_entry *head = *headp;
while (head != NULL) {
struct tfrc_tx_hist_entry *next = head->next;
kmem_cache_free(tfrc_tx_hist_slab, head);
head = next;
}
*headp = NULL;
}
EXPORT_SYMBOL_GPL(tfrc_tx_hist_purge);
u32 tfrc_tx_hist_rtt(struct tfrc_tx_hist_entry *head, const u64 seqno,
const ktime_t now)
{
u32 rtt = 0;
struct tfrc_tx_hist_entry *packet = tfrc_tx_hist_find_entry(head, seqno);
if (packet != NULL) {
rtt = ktime_us_delta(now, packet->stamp);
/*
* Garbage-collect older (irrelevant) entries:
*/
tfrc_tx_hist_purge(&packet->next);
}
return rtt;
}
EXPORT_SYMBOL_GPL(tfrc_tx_hist_rtt);
/*
* Receiver History Routines
*/
static struct kmem_cache *tfrc_rx_hist_slab;
int __init tfrc_rx_packet_history_init(void)
{
tfrc_rx_hist_slab = kmem_cache_create("tfrc_rxh_cache",
sizeof(struct tfrc_rx_hist_entry),
0, SLAB_HWCACHE_ALIGN, NULL);
return tfrc_rx_hist_slab == NULL ? -ENOBUFS : 0;
}
void tfrc_rx_packet_history_exit(void)
{
if (tfrc_rx_hist_slab != NULL) {
kmem_cache_destroy(tfrc_rx_hist_slab);
tfrc_rx_hist_slab = NULL;
}
}
static inline void tfrc_rx_hist_entry_from_skb(struct tfrc_rx_hist_entry *entry,
const struct sk_buff *skb,
const u32 ndp)
{
const struct dccp_hdr *dh = dccp_hdr(skb);
entry->tfrchrx_seqno = DCCP_SKB_CB(skb)->dccpd_seq;
entry->tfrchrx_ccval = dh->dccph_ccval;
entry->tfrchrx_type = dh->dccph_type;
entry->tfrchrx_ndp = ndp;
entry->tfrchrx_tstamp = ktime_get_real();
}
void tfrc_rx_hist_add_packet(struct tfrc_rx_hist *h,
const struct sk_buff *skb,
const u32 ndp)
{
struct tfrc_rx_hist_entry *entry = tfrc_rx_hist_last_rcv(h);
tfrc_rx_hist_entry_from_skb(entry, skb, ndp);
}
EXPORT_SYMBOL_GPL(tfrc_rx_hist_add_packet);
/* has the packet contained in skb been seen before? */
int tfrc_rx_hist_duplicate(struct tfrc_rx_hist *h, struct sk_buff *skb)
{
const u64 seq = DCCP_SKB_CB(skb)->dccpd_seq;
int i;
if (dccp_delta_seqno(tfrc_rx_hist_loss_prev(h)->tfrchrx_seqno, seq) <= 0)
return 1;
for (i = 1; i <= h->loss_count; i++)
if (tfrc_rx_hist_entry(h, i)->tfrchrx_seqno == seq)
return 1;
return 0;
}
EXPORT_SYMBOL_GPL(tfrc_rx_hist_duplicate);
static void tfrc_rx_hist_swap(struct tfrc_rx_hist *h, const u8 a, const u8 b)
{
const u8 idx_a = tfrc_rx_hist_index(h, a),
idx_b = tfrc_rx_hist_index(h, b);
struct tfrc_rx_hist_entry *tmp = h->ring[idx_a];
h->ring[idx_a] = h->ring[idx_b];
h->ring[idx_b] = tmp;
}
/*
* Private helper functions for loss detection.
*
* In the descriptions, `Si' refers to the sequence number of entry number i,
* whose NDP count is `Ni' (lower case is used for variables).
* Note: All __after_loss functions expect that a test against duplicates has
* been performed already: the seqno of the skb must not be less than the
* seqno of loss_prev; and it must not equal that of any valid hist_entry.
*/
static void __one_after_loss(struct tfrc_rx_hist *h, struct sk_buff *skb, u32 n2)
{
u64 s0 = tfrc_rx_hist_loss_prev(h)->tfrchrx_seqno,
s1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_seqno,
s2 = DCCP_SKB_CB(skb)->dccpd_seq;
int n1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_ndp,
d12 = dccp_delta_seqno(s1, s2), d2;
if (d12 > 0) { /* S1 < S2 */
h->loss_count = 2;
tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 2), skb, n2);
return;
}
/* S0 < S2 < S1 */
d2 = dccp_delta_seqno(s0, s2);
if (d2 == 1 || n2 >= d2) { /* S2 is direct successor of S0 */
int d21 = -d12;
if (d21 == 1 || n1 >= d21) {
/* hole is filled: S0, S2, and S1 are consecutive */
h->loss_count = 0;
h->loss_start = tfrc_rx_hist_index(h, 1);
} else
/* gap between S2 and S1: just update loss_prev */
tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_loss_prev(h), skb, n2);
} else { /* hole between S0 and S2 */
/*
* Reorder history to insert S2 between S0 and s1
*/
tfrc_rx_hist_swap(h, 0, 3);
h->loss_start = tfrc_rx_hist_index(h, 3);
tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 1), skb, n2);
h->loss_count = 2;
}
}
/* return 1 if a new loss event has been identified */
static int __two_after_loss(struct tfrc_rx_hist *h, struct sk_buff *skb, u32 n3)
{
u64 s0 = tfrc_rx_hist_loss_prev(h)->tfrchrx_seqno,
s1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_seqno,
s2 = tfrc_rx_hist_entry(h, 2)->tfrchrx_seqno,
s3 = DCCP_SKB_CB(skb)->dccpd_seq;
int n1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_ndp,
d23 = dccp_delta_seqno(s2, s3), d13, d3, d31;
if (d23 > 0) { /* S2 < S3 */
h->loss_count = 3;
tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 3), skb, n3);
return 1;
}
/* S3 < S2 */
d13 = dccp_delta_seqno(s1, s3);
if (d13 > 0) {
/*
* The sequence number order is S1, S3, S2
* Reorder history to insert entry between S1 and S2
*/
tfrc_rx_hist_swap(h, 2, 3);
tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 2), skb, n3);
h->loss_count = 3;
return 1;
}
/* S0 < S3 < S1 */
d31 = -d13;
d3 = dccp_delta_seqno(s0, s3);
if (d3 == 1 || n3 >= d3) { /* S3 is a successor of S0 */
if (d31 == 1 || n1 >= d31) {
/* hole between S0 and S1 filled by S3 */
int d2 = dccp_delta_seqno(s1, s2),
n2 = tfrc_rx_hist_entry(h, 2)->tfrchrx_ndp;
if (d2 == 1 || n2 >= d2) {
/* entire hole filled by S0, S3, S1, S2 */
h->loss_start = tfrc_rx_hist_index(h, 2);
h->loss_count = 0;
} else {
/* gap remains between S1 and S2 */
h->loss_start = tfrc_rx_hist_index(h, 1);
h->loss_count = 1;
}
} else /* gap exists between S3 and S1, loss_count stays at 2 */
tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_loss_prev(h), skb, n3);
return 0;
}
/*
* The remaining case: S3 is not a successor of S0.
* Sequence order is S0, S3, S1, S2; reorder to insert between S0 and S1
*/
tfrc_rx_hist_swap(h, 0, 3);
h->loss_start = tfrc_rx_hist_index(h, 3);
tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 1), skb, n3);
h->loss_count = 3;
return 1;
}
/* return the signed modulo-2^48 sequence number distance from entry e1 to e2 */
static s64 tfrc_rx_hist_delta_seqno(struct tfrc_rx_hist *h, u8 e1, u8 e2)
{
DCCP_BUG_ON(e1 > h->loss_count || e2 > h->loss_count);
return dccp_delta_seqno(tfrc_rx_hist_entry(h, e1)->tfrchrx_seqno,
tfrc_rx_hist_entry(h, e2)->tfrchrx_seqno);
}
/* recycle RX history records to continue loss detection if necessary */
static void __three_after_loss(struct tfrc_rx_hist *h)
{
/*
* The distance between S0 and S1 is always greater than 1 and the NDP
* count of S1 is smaller than this distance. Otherwise there would
* have been no loss. Hence it is only necessary to see whether there
* are further missing data packets between S1/S2 and S2/S3.
*/
int d2 = tfrc_rx_hist_delta_seqno(h, 1, 2),
d3 = tfrc_rx_hist_delta_seqno(h, 2, 3),
n2 = tfrc_rx_hist_entry(h, 2)->tfrchrx_ndp,
n3 = tfrc_rx_hist_entry(h, 3)->tfrchrx_ndp;
if (d2 == 1 || n2 >= d2) { /* S2 is successor to S1 */
if (d3 == 1 || n3 >= d3) {
/* S3 is successor of S2: entire hole is filled */
h->loss_start = tfrc_rx_hist_index(h, 3);
h->loss_count = 0;
} else {
/* gap between S2 and S3 */
h->loss_start = tfrc_rx_hist_index(h, 2);
h->loss_count = 1;
}
} else { /* gap between S1 and S2 */
h->loss_start = tfrc_rx_hist_index(h, 1);
h->loss_count = 2;
}
}
/**
* tfrc_rx_handle_loss - Loss detection and further processing
* @h: The non-empty RX history object
* @lh: Loss Intervals database to update
* @skb: Currently received packet
* @ndp: The NDP count belonging to @skb
* @calc_first_li: Caller-dependent computation of first loss interval in @lh
* @sk: Used by @calc_first_li (see tfrc_lh_interval_add)
* Chooses action according to pending loss, updates LI database when a new
* loss was detected, and does required post-processing. Returns 1 when caller
* should send feedback, 0 otherwise.
*/
int tfrc_rx_handle_loss(struct tfrc_rx_hist *h,
struct tfrc_loss_hist *lh,
struct sk_buff *skb, u32 ndp,
u32 (*calc_first_li)(struct sock *), struct sock *sk)
{
int is_new_loss = 0;
if (h->loss_count == 1) {
__one_after_loss(h, skb, ndp);
} else if (h->loss_count != 2) {
DCCP_BUG("invalid loss_count %d", h->loss_count);
} else if (__two_after_loss(h, skb, ndp)) {
/*
* Update Loss Interval database and recycle RX records
*/
is_new_loss = tfrc_lh_interval_add(lh, h, calc_first_li, sk);
__three_after_loss(h);
}
return is_new_loss;
}
EXPORT_SYMBOL_GPL(tfrc_rx_handle_loss);
int tfrc_rx_hist_alloc(struct tfrc_rx_hist *h)
{
int i;
for (i = 0; i <= TFRC_NDUPACK; i++) {
h->ring[i] = kmem_cache_alloc(tfrc_rx_hist_slab, GFP_ATOMIC);
if (h->ring[i] == NULL)
goto out_free;
}
h->loss_count = h->loss_start = 0;
return 0;
out_free:
while (i-- != 0) {
kmem_cache_free(tfrc_rx_hist_slab, h->ring[i]);
h->ring[i] = NULL;
}
return -ENOBUFS;
}
EXPORT_SYMBOL_GPL(tfrc_rx_hist_alloc);
void tfrc_rx_hist_purge(struct tfrc_rx_hist *h)
{
int i;
for (i = 0; i <= TFRC_NDUPACK; ++i)
if (h->ring[i] != NULL) {
kmem_cache_free(tfrc_rx_hist_slab, h->ring[i]);
h->ring[i] = NULL;
}
}
EXPORT_SYMBOL_GPL(tfrc_rx_hist_purge);
/**
* tfrc_rx_hist_rtt_last_s - reference entry to compute RTT samples against
*/
static inline struct tfrc_rx_hist_entry *
tfrc_rx_hist_rtt_last_s(const struct tfrc_rx_hist *h)
{
return h->ring[0];
}
/**
* tfrc_rx_hist_rtt_prev_s: previously suitable (wrt rtt_last_s) RTT-sampling entry
*/
static inline struct tfrc_rx_hist_entry *
tfrc_rx_hist_rtt_prev_s(const struct tfrc_rx_hist *h)
{
return h->ring[h->rtt_sample_prev];
}
/**
* tfrc_rx_hist_sample_rtt - Sample RTT from timestamp / CCVal
* Based on ideas presented in RFC 4342, 8.1. Returns 0 if it was not able
* to compute a sample with given data - calling function should check this.
*/
u32 tfrc_rx_hist_sample_rtt(struct tfrc_rx_hist *h, const struct sk_buff *skb)
{
u32 sample = 0,
delta_v = SUB16(dccp_hdr(skb)->dccph_ccval,
tfrc_rx_hist_rtt_last_s(h)->tfrchrx_ccval);
if (delta_v < 1 || delta_v > 4) { /* unsuitable CCVal delta */
if (h->rtt_sample_prev == 2) { /* previous candidate stored */
sample = SUB16(tfrc_rx_hist_rtt_prev_s(h)->tfrchrx_ccval,
tfrc_rx_hist_rtt_last_s(h)->tfrchrx_ccval);
if (sample)
sample = 4 / sample *
ktime_us_delta(tfrc_rx_hist_rtt_prev_s(h)->tfrchrx_tstamp,
tfrc_rx_hist_rtt_last_s(h)->tfrchrx_tstamp);
else /*
* FIXME: This condition is in principle not
* possible but occurs when CCID is used for
* two-way data traffic. I have tried to trace
* it, but the cause does not seem to be here.
*/
DCCP_BUG("please report to dccp@vger.kernel.org"
" => prev = %u, last = %u",
tfrc_rx_hist_rtt_prev_s(h)->tfrchrx_ccval,
tfrc_rx_hist_rtt_last_s(h)->tfrchrx_ccval);
} else if (delta_v < 1) {
h->rtt_sample_prev = 1;
goto keep_ref_for_next_time;
}
} else if (delta_v == 4) /* optimal match */
sample = ktime_to_us(net_timedelta(tfrc_rx_hist_rtt_last_s(h)->tfrchrx_tstamp));
else { /* suboptimal match */
h->rtt_sample_prev = 2;
goto keep_ref_for_next_time;
}
if (unlikely(sample > DCCP_SANE_RTT_MAX)) {
DCCP_WARN("RTT sample %u too large, using max\n", sample);
sample = DCCP_SANE_RTT_MAX;
}
h->rtt_sample_prev = 0; /* use current entry as next reference */
keep_ref_for_next_time:
return sample;
}
EXPORT_SYMBOL_GPL(tfrc_rx_hist_sample_rtt);