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[DCCP] ccid3: Fix bug in calculation of send rate

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The main object of this patch is the following bug:
 ==> In ccid3_hc_tx_packet_recv, the parameters p and X_recv were updated
     _after_ the send rate was calculated. This is clearly an error and is
     resolved by re-ordering statements.

In addition,
  * r_sample is converted from u32 to long to check whether the time difference
    was negative (it would otherwise be converted to a large u32 value)
  * protection against RTT=0 (this is possible) is provided in a further patch
  * t_elapsed is also converted to long, to match the type of r_sample
  * adds a a more debugging information regarding current send rates
  * various trivial comment/documentation updates

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Acked-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
This commit is contained in:
Gerrit Renker 2006-12-03 14:50:56 -02:00 committed by Arnaldo Carvalho de Melo
parent 76d127779e
commit 5c3fbb6acf
1 changed files with 52 additions and 37 deletions
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89
net/dccp/ccids/ccid3.c
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@ -121,12 +121,15 @@ static inline void ccid3_update_send_time(struct ccid3_hc_tx_sock *hctx)
/*
* Update X by
* If (p > 0)
* x_calc = calcX(s, R, p);
* X_calc = calcX(s, R, p);
* X = max(min(X_calc, 2 * X_recv), s / t_mbi);
* Else
* If (now - tld >= R)
* X = max(min(2 * X, 2 * X_recv), s / R);
* tld = now;
*
* If X has changed, we also update the scheduled send time t_now,
* the inter-packet interval t_ipi, and the delta value.
*/
static void ccid3_hc_tx_update_x(struct sock *sk, struct timeval *now)
@ -413,10 +416,8 @@ static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
struct dccp_tx_hist_entry *packet;
struct timeval now;
unsigned long t_nfb;
u32 t_elapsed;
u32 pinv;
u32 x_recv;
u32 r_sample;
long r_sample, t_elapsed;
BUG_ON(hctx == NULL);
@ -427,31 +428,51 @@ static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
opt_recv = &hctx->ccid3hctx_options_received;
t_elapsed = dp->dccps_options_received.dccpor_elapsed_time * 10;
x_recv = opt_recv->ccid3or_receive_rate;
pinv = opt_recv->ccid3or_loss_event_rate;
switch (hctx->ccid3hctx_state) {
case TFRC_SSTATE_NO_FBACK:
case TFRC_SSTATE_FBACK:
/* Calculate new round trip sample by
* R_sample = (now - t_recvdata) - t_delay */
/* get t_recvdata from history */
/* get packet from history to look up t_recvdata */
packet = dccp_tx_hist_find_entry(&hctx->ccid3hctx_hist,
DCCP_SKB_CB(skb)->dccpd_ack_seq);
if (unlikely(packet == NULL)) {
DCCP_WARN("%s, sk=%p, seqno %llu(%s) does't exist "
DCCP_WARN("%s(%p), seqno %llu(%s) doesn't exist "
"in history!\n", dccp_role(sk), sk,
(unsigned long long)DCCP_SKB_CB(skb)->dccpd_ack_seq,
dccp_packet_name(DCCP_SKB_CB(skb)->dccpd_type));
return;
}
/* Update RTT */
/* Update receive rate */
hctx->ccid3hctx_x_recv = opt_recv->ccid3or_receive_rate;
/* Update loss event rate */
pinv = opt_recv->ccid3or_loss_event_rate;
if (pinv == ~0U || pinv == 0)
hctx->ccid3hctx_p = 0;
else {
hctx->ccid3hctx_p = 1000000 / pinv;
if (hctx->ccid3hctx_p < TFRC_SMALLEST_P) {
hctx->ccid3hctx_p = TFRC_SMALLEST_P;
ccid3_pr_debug("%s, sk=%p, Smallest p used!\n",
dccp_role(sk), sk);
}
}
dccp_timestamp(sk, &now);
r_sample = timeval_delta(&now, &packet->dccphtx_tstamp);
if (unlikely(r_sample <= t_elapsed))
DCCP_WARN("r_sample=%uus,t_elapsed=%uus\n",
/*
* Calculate new round trip sample as per [RFC 3448, 4.3] by
* R_sample = (now - t_recvdata) - t_elapsed
*/
r_sample = timeval_delta(&now, &packet->dccphtx_tstamp);
t_elapsed = dp->dccps_options_received.dccpor_elapsed_time * 10;
if (unlikely(r_sample <= 0)) {
DCCP_WARN("WARNING: R_sample (%ld) <= 0!\n", r_sample);
r_sample = 0;
} else if (unlikely(r_sample <= t_elapsed))
DCCP_WARN("WARNING: r_sample=%ldus <= t_elapsed=%ldus\n",
r_sample, t_elapsed);
else
r_sample -= t_elapsed;
@ -474,31 +495,25 @@ static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
hctx->ccid3hctx_t_ld = now;
ccid3_update_send_time(hctx);
ccid3_pr_debug("%s(%p), s=%u, w_init=%u, "
"R_sample=%ldus, X=%u\n", dccp_role(sk),
sk, hctx->ccid3hctx_s, w_init, r_sample,
hctx->ccid3hctx_x);
ccid3_hc_tx_set_state(sk, TFRC_SSTATE_FBACK);
} else {
hctx->ccid3hctx_rtt = (hctx->ccid3hctx_rtt * 9) / 10 +
r_sample / 10;
hctx->ccid3hctx_rtt = (9 * hctx->ccid3hctx_rtt +
(u32)r_sample ) / 10;
ccid3_hc_tx_update_x(sk, &now);
}
ccid3_pr_debug("%s, sk=%p, New RTT estimate=%uus, "
"r_sample=%us\n", dccp_role(sk), sk,
hctx->ccid3hctx_rtt, r_sample);
/* Update receive rate */
hctx->ccid3hctx_x_recv = x_recv;/* X_recv in bytes per sec */
/* Update loss event rate */
if (pinv == ~0 || pinv == 0)
hctx->ccid3hctx_p = 0;
else {
hctx->ccid3hctx_p = 1000000 / pinv;
if (hctx->ccid3hctx_p < TFRC_SMALLEST_P) {
hctx->ccid3hctx_p = TFRC_SMALLEST_P;
ccid3_pr_debug("%s, sk=%p, Smallest p used!\n",
dccp_role(sk), sk);
}
ccid3_pr_debug("%s(%p), RTT=%uus (sample=%ldus), s=%u, "
"p=%u, X_calc=%u, X=%u\n", dccp_role(sk),
sk, hctx->ccid3hctx_rtt, r_sample,
hctx->ccid3hctx_s, hctx->ccid3hctx_p,
hctx->ccid3hctx_x_calc,
hctx->ccid3hctx_x);
}
/* unschedule no feedback timer */