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