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Commit c80a5cdf authored by Doug Leith's avatar Doug Leith Committed by David S. Miller
Browse files

tcp: tcp_vegas ssthresh bugfix 



This patch fixes ssthresh accounting issues in tcp_vegas when cwnd decreases

Signed-off-by: default avatarDoug Leith <doug.leith@nuim.ie>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 217cbfa8

net/ipv4/tcp_vegas.c

+9 −2
Original line number Diff line number Diff line
@@ -158,6 +158,11 @@ void tcp_vegas_cwnd_event(struct sock *sk, enum tcp_ca_event event) 
}

EXPORT_SYMBOL_GPL(tcp_vegas_cwnd_event);



static inline u32 tcp_vegas_ssthresh(struct tcp_sock *tp)

{

	return  min(tp->snd_ssthresh, tp->snd_cwnd-1);

}



static void tcp_vegas_cong_avoid(struct sock *sk, u32 ack, u32 in_flight)

{

	struct tcp_sock *tp = tcp_sk(sk);
@@ -221,11 +226,10 @@ static void tcp_vegas_cong_avoid(struct sock *sk, u32 ack, u32 in_flight) 
			 */

			diff = tp->snd_cwnd * (rtt-vegas->baseRTT) / vegas->baseRTT;



			if (diff > gamma && tp->snd_ssthresh > 2 ) {

			if (diff > gamma && tp->snd_cwnd <= tp->snd_ssthresh) {

				/* Going too fast. Time to slow down

				 * and switch to congestion avoidance.

				 */

				tp->snd_ssthresh = 2;



				/* Set cwnd to match the actual rate

				 * exactly:
@@ -235,6 +239,7 @@ static void tcp_vegas_cong_avoid(struct sock *sk, u32 ack, u32 in_flight) 
				 * utilization.

				 */

				tp->snd_cwnd = min(tp->snd_cwnd, (u32)target_cwnd+1);

				tp->snd_ssthresh = tcp_vegas_ssthresh(tp);



			} else if (tp->snd_cwnd <= tp->snd_ssthresh) {

				/* Slow start.  */
@@ -250,6 +255,8 @@ static void tcp_vegas_cong_avoid(struct sock *sk, u32 ack, u32 in_flight) 
					 * we slow down.

					 */

					tp->snd_cwnd--;

					tp->snd_ssthresh

						= tcp_vegas_ssthresh(tp);

				} else if (diff < alpha) {

					/* We don't have enough extra packets

					 * in the network, so speed up.