Commit a6af2d6b authored Dec 04, 2008 by Doug Leith Committed by David S. Miller Dec 04, 2008

tcp: tcp_vegas ssthresh bug fix

This patch fixes a bug in tcp_vegas.c. At the moment this code leaves
ssthresh untouched. However, this means that the vegas congestion
control algorithm is effectively unable to reduce cwnd below the
ssthresh value (if the vegas update lowers the cwnd below ssthresh,
then slow start is activated to raise it back up). One example where
this matters is when during slow start cwnd overshoots the link
capacity and a flow then exits slow start with ssthresh set to a value
above where congestion avoidance would like to adjust it.

Signed-off-by: Doug Leith <doug.leith@nuim.ie>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent f706644d

net/ipv4/tcp_vegas.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -326,6 +326,8 @@ static void tcp_vegas_cong_avoid(struct sock *sk, u32 ack, u32 in_flight)
		tp->snd_cwnd = 2;
		else if (tp->snd_cwnd > tp->snd_cwnd_clamp)
		tp->snd_cwnd = tp->snd_cwnd_clamp;

		tp->snd_ssthresh = tcp_current_ssthresh(sk);
		}

		/* Wipe the slate clean for the next RTT. */

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