Commit 52c63f1e authored Feb 21, 2007 by Ilpo Järvinen Committed by David S. Miller Apr 25, 2007

[TCP]: Don't enter to fast recovery while using FRTO



Because TCP is not in Loss state during FRTO recovery, fast
recovery could be triggered by accident. Non-SACK FRTO is more
robust than not yet included SACK-enhanced version (that can
receiver high number of duplicate ACKs with SACK blocks during
FRTO), at least with unidirectional transfers, but under
extraordinary patterns fast recovery can be incorrectly
triggered, e.g., Data loss+ACK losses => cumulative ACK with
enough SACK blocks to meet sacked_out >= dupthresh condition).

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent aa8b6a7a

net/ipv4/tcp_input.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -1547,6 +1547,10 @@ static int tcp_time_to_recover(struct sock sk, struct tcp_sock tp)
		{
		__u32 packets_out;

		/* Do not perform any recovery during FRTO algorithm */
		if (tp->frto_counter)
		return 0;

		/* Trick#1: The loss is proven. */
		if (tp->lost_out)
		return 1;

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