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[DCCP]: Fix CCID3
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This fixes CCID3 to give much closer performance to RFC4342.

CCID3 is meant to alter sending rate based on RTT and loss.

The performance was verified against:
http://wand.net.nz/~perry/max_download.php

For example I tested with netem and had the following parameters:
Delayed Acks 1, MSS 256 bytes, RTT 105 ms, packet loss 5%.

This gives a theoretical speed of 71.9 Kbits/s. I measured across three
runs with this patch set and got 70.1 Kbits/s. Without this patchset the
average was 232 Kbits/s which means Linux can't be used for CCID3 research
properly.

I also tested with netem turned off so box just acting as router with 1.2
msec RTT. The performance with this is the same with or without the patch
at around 30 Mbit/s.

Signed off by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Ian McDonald authored and David S. Miller committed Aug 27, 2006
1 parent 3a13813 commit 66a377c
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Showing 6 changed files with 154 additions and 193 deletions.
149 changes: 119 additions & 30 deletions net/dccp/ccids/ccid3.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -342,6 +342,8 @@ static int ccid3_hc_tx_send_packet(struct sock *sk,
new_packet->dccphtx_ccval =
DCCP_SKB_CB(skb)->dccpd_ccval =
hctx->ccid3hctx_last_win_count;
timeval_add_usecs(&hctx->ccid3hctx_t_nom,
hctx->ccid3hctx_t_ipi);
}
out:
return rc;
Expand Down Expand Up @@ -413,7 +415,8 @@ static void ccid3_hc_tx_packet_sent(struct sock *sk, int more, int len)
case TFRC_SSTATE_NO_FBACK:
case TFRC_SSTATE_FBACK:
if (len > 0) {
hctx->ccid3hctx_t_nom = now;
timeval_sub_usecs(&hctx->ccid3hctx_t_nom,
hctx->ccid3hctx_t_ipi);
ccid3_calc_new_t_ipi(hctx);
ccid3_calc_new_delta(hctx);
timeval_add_usecs(&hctx->ccid3hctx_t_nom,
Expand Down Expand Up @@ -757,8 +760,7 @@ static void ccid3_hc_rx_send_feedback(struct sock *sk)
}

hcrx->ccid3hcrx_tstamp_last_feedback = now;
hcrx->ccid3hcrx_last_counter = packet->dccphrx_ccval;
hcrx->ccid3hcrx_seqno_last_counter = packet->dccphrx_seqno;
hcrx->ccid3hcrx_ccval_last_counter = packet->dccphrx_ccval;
hcrx->ccid3hcrx_bytes_recv = 0;

/* Convert to multiples of 10us */
Expand All @@ -782,7 +784,7 @@ static int ccid3_hc_rx_insert_options(struct sock *sk, struct sk_buff *skb)
if (!(sk->sk_state == DCCP_OPEN || sk->sk_state == DCCP_PARTOPEN))
return 0;

DCCP_SKB_CB(skb)->dccpd_ccval = hcrx->ccid3hcrx_last_counter;
DCCP_SKB_CB(skb)->dccpd_ccval = hcrx->ccid3hcrx_ccval_last_counter;

if (dccp_packet_without_ack(skb))
return 0;
Expand Down Expand Up @@ -854,6 +856,11 @@ static u32 ccid3_hc_rx_calc_first_li(struct sock *sk)
interval = 1;
}
found:
if (!tail) {
LIMIT_NETDEBUG(KERN_WARNING "%s: tail is null\n",
__FUNCTION__);
return ~0;
}
rtt = timeval_delta(&tstamp, &tail->dccphrx_tstamp) * 4 / interval;
ccid3_pr_debug("%s, sk=%p, approximated RTT to %uus\n",
dccp_role(sk), sk, rtt);
Expand All @@ -864,9 +871,20 @@ static u32 ccid3_hc_rx_calc_first_li(struct sock *sk)
delta = timeval_delta(&tstamp, &hcrx->ccid3hcrx_tstamp_last_feedback);
x_recv = usecs_div(hcrx->ccid3hcrx_bytes_recv, delta);

if (x_recv == 0)
x_recv = hcrx->ccid3hcrx_x_recv;

tmp1 = (u64)x_recv * (u64)rtt;
do_div(tmp1,10000000);
tmp2 = (u32)tmp1;

if (!tmp2) {
LIMIT_NETDEBUG(KERN_WARNING "tmp2 = 0 "
"%s: x_recv = %u, rtt =%u\n",
__FUNCTION__, x_recv, rtt);
return ~0;
}

fval = (hcrx->ccid3hcrx_s * 100000) / tmp2;
/* do not alter order above or you will get overflow on 32 bit */
p = tfrc_calc_x_reverse_lookup(fval);
Expand All @@ -882,31 +900,101 @@ static u32 ccid3_hc_rx_calc_first_li(struct sock *sk)
static void ccid3_hc_rx_update_li(struct sock *sk, u64 seq_loss, u8 win_loss)
{
struct ccid3_hc_rx_sock *hcrx = ccid3_hc_rx_sk(sk);
struct dccp_li_hist_entry *next, *head;
u64 seq_temp;

if (seq_loss != DCCP_MAX_SEQNO + 1 &&
list_empty(&hcrx->ccid3hcrx_li_hist)) {
struct dccp_li_hist_entry *li_tail;
if (list_empty(&hcrx->ccid3hcrx_li_hist)) {
if (!dccp_li_hist_interval_new(ccid3_li_hist,
&hcrx->ccid3hcrx_li_hist, seq_loss, win_loss))
return;

li_tail = dccp_li_hist_interval_new(ccid3_li_hist,
&hcrx->ccid3hcrx_li_hist,
seq_loss, win_loss);
if (li_tail == NULL)
next = (struct dccp_li_hist_entry *)
hcrx->ccid3hcrx_li_hist.next;
next->dccplih_interval = ccid3_hc_rx_calc_first_li(sk);
} else {
struct dccp_li_hist_entry *entry;
struct list_head *tail;

head = (struct dccp_li_hist_entry *)
hcrx->ccid3hcrx_li_hist.next;
/* FIXME win count check removed as was wrong */
/* should make this check with receive history */
/* and compare there as per section 10.2 of RFC4342 */

/* new loss event detected */
/* calculate last interval length */
seq_temp = dccp_delta_seqno(head->dccplih_seqno, seq_loss);
entry = dccp_li_hist_entry_new(ccid3_li_hist, SLAB_ATOMIC);

if (entry == NULL) {
printk(KERN_CRIT "%s: out of memory\n",__FUNCTION__);
dump_stack();
return;
li_tail->dccplih_interval = ccid3_hc_rx_calc_first_li(sk);
} else
LIMIT_NETDEBUG(KERN_WARNING "%s: FIXME: find end of "
"interval\n", __FUNCTION__);
}

list_add(&entry->dccplih_node, &hcrx->ccid3hcrx_li_hist);

tail = hcrx->ccid3hcrx_li_hist.prev;
list_del(tail);
kmem_cache_free(ccid3_li_hist->dccplih_slab, tail);

/* Create the newest interval */
entry->dccplih_seqno = seq_loss;
entry->dccplih_interval = seq_temp;
entry->dccplih_win_count = win_loss;
}
}

static void ccid3_hc_rx_detect_loss(struct sock *sk)
static int ccid3_hc_rx_detect_loss(struct sock *sk,
struct dccp_rx_hist_entry *packet)
{
struct ccid3_hc_rx_sock *hcrx = ccid3_hc_rx_sk(sk);
u8 win_loss;
const u64 seq_loss = dccp_rx_hist_detect_loss(&hcrx->ccid3hcrx_hist,
&hcrx->ccid3hcrx_li_hist,
&win_loss);
struct dccp_rx_hist_entry *rx_hist = dccp_rx_hist_head(&hcrx->ccid3hcrx_hist);
u64 seqno = packet->dccphrx_seqno;
u64 tmp_seqno;
int loss = 0;
u8 ccval;


tmp_seqno = hcrx->ccid3hcrx_seqno_nonloss;

if (!rx_hist ||
follows48(packet->dccphrx_seqno, hcrx->ccid3hcrx_seqno_nonloss)) {
hcrx->ccid3hcrx_seqno_nonloss = seqno;
hcrx->ccid3hcrx_ccval_nonloss = packet->dccphrx_ccval;
goto detect_out;
}


ccid3_hc_rx_update_li(sk, seq_loss, win_loss);
while (dccp_delta_seqno(hcrx->ccid3hcrx_seqno_nonloss, seqno)
> TFRC_RECV_NUM_LATE_LOSS) {
loss = 1;
ccid3_hc_rx_update_li(sk, hcrx->ccid3hcrx_seqno_nonloss,
hcrx->ccid3hcrx_ccval_nonloss);
tmp_seqno = hcrx->ccid3hcrx_seqno_nonloss;
dccp_inc_seqno(&tmp_seqno);
hcrx->ccid3hcrx_seqno_nonloss = tmp_seqno;
dccp_inc_seqno(&tmp_seqno);
while (dccp_rx_hist_find_entry(&hcrx->ccid3hcrx_hist,
tmp_seqno, &ccval)) {
hcrx->ccid3hcrx_seqno_nonloss = tmp_seqno;
hcrx->ccid3hcrx_ccval_nonloss = ccval;
dccp_inc_seqno(&tmp_seqno);
}
}

/* FIXME - this code could be simplified with above while */
/* but works at moment */
if (follows48(packet->dccphrx_seqno, hcrx->ccid3hcrx_seqno_nonloss)) {
hcrx->ccid3hcrx_seqno_nonloss = seqno;
hcrx->ccid3hcrx_ccval_nonloss = packet->dccphrx_ccval;
}

detect_out:
dccp_rx_hist_add_packet(ccid3_rx_hist, &hcrx->ccid3hcrx_hist,
&hcrx->ccid3hcrx_li_hist, packet,
hcrx->ccid3hcrx_seqno_nonloss);
return loss;
}

static void ccid3_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
Expand All @@ -916,8 +1004,8 @@ static void ccid3_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
struct dccp_rx_hist_entry *packet;
struct timeval now;
u8 win_count;
u32 p_prev, r_sample, t_elapsed;
int ins;
u32 p_prev, rtt_prev, r_sample, t_elapsed;
int loss;

BUG_ON(hcrx == NULL ||
!(hcrx->ccid3hcrx_state == TFRC_RSTATE_NO_DATA ||
Expand All @@ -932,7 +1020,7 @@ static void ccid3_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
case DCCP_PKT_DATAACK:
if (opt_recv->dccpor_timestamp_echo == 0)
break;
p_prev = hcrx->ccid3hcrx_rtt;
rtt_prev = hcrx->ccid3hcrx_rtt;
dccp_timestamp(sk, &now);
timeval_sub_usecs(&now, opt_recv->dccpor_timestamp_echo * 10);
r_sample = timeval_usecs(&now);
Expand All @@ -951,8 +1039,8 @@ static void ccid3_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
hcrx->ccid3hcrx_rtt = (hcrx->ccid3hcrx_rtt * 9) / 10 +
r_sample / 10;

if (p_prev != hcrx->ccid3hcrx_rtt)
ccid3_pr_debug("%s, New RTT=%luus, elapsed time=%u\n",
if (rtt_prev != hcrx->ccid3hcrx_rtt)
ccid3_pr_debug("%s, New RTT=%uus, elapsed time=%u\n",
dccp_role(sk), hcrx->ccid3hcrx_rtt,
opt_recv->dccpor_elapsed_time);
break;
Expand All @@ -973,8 +1061,7 @@ static void ccid3_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)

win_count = packet->dccphrx_ccval;

ins = dccp_rx_hist_add_packet(ccid3_rx_hist, &hcrx->ccid3hcrx_hist,
&hcrx->ccid3hcrx_li_hist, packet);
loss = ccid3_hc_rx_detect_loss(sk, packet);

if (DCCP_SKB_CB(skb)->dccpd_type == DCCP_PKT_ACK)
return;
Expand All @@ -991,7 +1078,7 @@ static void ccid3_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
case TFRC_RSTATE_DATA:
hcrx->ccid3hcrx_bytes_recv += skb->len -
dccp_hdr(skb)->dccph_doff * 4;
if (ins != 0)
if (loss)
break;

dccp_timestamp(sk, &now);
Expand All @@ -1012,7 +1099,6 @@ static void ccid3_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
ccid3_pr_debug("%s, sk=%p(%s), data loss! Reacting...\n",
dccp_role(sk), sk, dccp_state_name(sk->sk_state));

ccid3_hc_rx_detect_loss(sk);
p_prev = hcrx->ccid3hcrx_p;

/* Calculate loss event rate */
Expand All @@ -1022,6 +1108,9 @@ static void ccid3_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
/* Scaling up by 1000000 as fixed decimal */
if (i_mean != 0)
hcrx->ccid3hcrx_p = 1000000 / i_mean;
} else {
printk(KERN_CRIT "%s: empty loss hist\n",__FUNCTION__);
dump_stack();
}

if (hcrx->ccid3hcrx_p > p_prev) {
Expand Down
5 changes: 3 additions & 2 deletions net/dccp/ccids/ccid3.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -120,9 +120,10 @@ struct ccid3_hc_rx_sock {
#define ccid3hcrx_x_recv ccid3hcrx_tfrc.tfrcrx_x_recv
#define ccid3hcrx_rtt ccid3hcrx_tfrc.tfrcrx_rtt
#define ccid3hcrx_p ccid3hcrx_tfrc.tfrcrx_p
u64 ccid3hcrx_seqno_last_counter:48,
u64 ccid3hcrx_seqno_nonloss:48,
ccid3hcrx_ccval_nonloss:4,
ccid3hcrx_state:8,
ccid3hcrx_last_counter:4;
ccid3hcrx_ccval_last_counter:4;
u32 ccid3hcrx_bytes_recv;
struct timeval ccid3hcrx_tstamp_last_feedback;
struct timeval ccid3hcrx_tstamp_last_ack;
Expand Down
34 changes: 17 additions & 17 deletions net/dccp/ccids/lib/loss_interval.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -12,6 +12,7 @@
*/

#include <linux/module.h>
#include <net/sock.h>

#include "loss_interval.h"

Expand Down Expand Up @@ -90,13 +91,13 @@ u32 dccp_li_hist_calc_i_mean(struct list_head *list)
u32 w_tot = 0;

list_for_each_entry_safe(li_entry, li_next, list, dccplih_node) {
if (i < DCCP_LI_HIST_IVAL_F_LENGTH) {
if (li_entry->dccplih_interval != ~0) {
i_tot0 += li_entry->dccplih_interval * dccp_li_hist_w[i];
w_tot += dccp_li_hist_w[i];
if (i != 0)
i_tot1 += li_entry->dccplih_interval * dccp_li_hist_w[i - 1];
}

if (i != 0)
i_tot1 += li_entry->dccplih_interval * dccp_li_hist_w[i - 1];

if (++i > DCCP_LI_HIST_IVAL_F_LENGTH)
break;
Expand All @@ -107,37 +108,36 @@ u32 dccp_li_hist_calc_i_mean(struct list_head *list)

i_tot = max(i_tot0, i_tot1);

/* FIXME: Why do we do this? -Ian McDonald */
if (i_tot * 4 < w_tot)
i_tot = w_tot * 4;
if (!w_tot) {
LIMIT_NETDEBUG(KERN_WARNING "%s: w_tot = 0\n", __FUNCTION__);
return 1;
}

return i_tot * 4 / w_tot;
return i_tot / w_tot;
}

EXPORT_SYMBOL_GPL(dccp_li_hist_calc_i_mean);

struct dccp_li_hist_entry *dccp_li_hist_interval_new(struct dccp_li_hist *hist,
struct list_head *list,
const u64 seq_loss,
const u8 win_loss)
int dccp_li_hist_interval_new(struct dccp_li_hist *hist,
struct list_head *list, const u64 seq_loss, const u8 win_loss)
{
struct dccp_li_hist_entry *tail = NULL, *entry;
struct dccp_li_hist_entry *entry;
int i;

for (i = 0; i <= DCCP_LI_HIST_IVAL_F_LENGTH; ++i) {
for (i = 0; i < DCCP_LI_HIST_IVAL_F_LENGTH; i++) {
entry = dccp_li_hist_entry_new(hist, SLAB_ATOMIC);
if (entry == NULL) {
dccp_li_hist_purge(hist, list);
return NULL;
dump_stack();
return 0;
}
if (tail == NULL)
tail = entry;
entry->dccplih_interval = ~0;
list_add(&entry->dccplih_node, list);
}

entry->dccplih_seqno = seq_loss;
entry->dccplih_win_count = win_loss;
return tail;
return 1;
}

EXPORT_SYMBOL_GPL(dccp_li_hist_interval_new);
7 changes: 2 additions & 5 deletions net/dccp/ccids/lib/loss_interval.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -52,9 +52,6 @@ extern void dccp_li_hist_purge(struct dccp_li_hist *hist,

extern u32 dccp_li_hist_calc_i_mean(struct list_head *list);

extern struct dccp_li_hist_entry *
dccp_li_hist_interval_new(struct dccp_li_hist *hist,
struct list_head *list,
const u64 seq_loss,
const u8 win_loss);
extern int dccp_li_hist_interval_new(struct dccp_li_hist *hist,
struct list_head *list, const u64 seq_loss, const u8 win_loss);
#endif /* _DCCP_LI_HIST_ */
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