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@xxxxxxxxxxxxxx>
Acked-by: Ian McDonald <ian.mcdonald@xxxxxxxxxxx>
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxxxx>
---
net/dccp/ccids/ccid3.c | 89 ++++++++++++++++++++++++++++--------------------
1 files changed, 52 insertions(+), 37 deletions(-)
diff --git a/net/dccp/ccids/ccid3.c b/net/dccp/ccids/ccid3.c
index 22a0724..bd35304 100644
--- a/net/dccp/ccids/ccid3.c
+++ b/net/dccp/ccids/ccid3.c
@@ -121,12 +121,15 @@ static inline void ccid3_update_send_tim
/*
* 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(stru
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(stru
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(stru
hctx->ccid3hctx_t_ld = now;
ccid3_update_send_time(hctx);
- ccid3_hc_tx_set_state(sk, TFRC_SSTATE_FBACK);
- } else {
- hctx->ccid3hctx_rtt = (hctx->ccid3hctx_rtt * 9) / 10 +
- 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);
+ 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);
- /* Update receive rate */
- hctx->ccid3hctx_x_recv = x_recv;/* X_recv in bytes per sec */
+ ccid3_hc_tx_set_state(sk, TFRC_SSTATE_FBACK);
+ } else {
+ hctx->ccid3hctx_rtt = (9 * hctx->ccid3hctx_rtt +
+ (u32)r_sample ) / 10;
- /* Update loss event rate */
- if (pinv == ~0 || pinv == 0)
- hctx->ccid3hctx_p = 0;
- else {
- hctx->ccid3hctx_p = 1000000 / pinv;
+ ccid3_hc_tx_update_x(sk, &now);
- 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 */
--
1.4.2.1.g3d5c
-
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