Patchwork [061/102] tcp: undo spurious timeout after SACK reneging

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Submitter Luis Henriques
Date April 8, 2013, 9:50 a.m.
Message ID <1365414657-29191-62-git-send-email-luis.henriques@canonical.com>
Download mbox | patch
Permalink /patch/234678/
State New
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Comments

Luis Henriques - April 8, 2013, 9:50 a.m.
3.5.7.10 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Yuchung Cheng <ycheng@google.com>

commit 7ebe183c6d444ef5587d803b64a1f4734b18c564 upstream.

On SACK reneging the sender immediately retransmits and forces a
timeout but disables Eifel (undo). If the (buggy) receiver does not
drop any packet this can trigger a false slow-start retransmit storm
driven by the ACKs of the original packets. This can be detected with
undo and TCP timestamps.

Signed-off-by: Yuchung Cheng <ycheng@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
---
 net/ipv4/tcp_input.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

Patch

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 410b7c4..e75e4fb 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -2267,11 +2267,8 @@  void tcp_enter_loss(struct sock *sk, int how)
 	if (tcp_is_reno(tp))
 		tcp_reset_reno_sack(tp);
 
-	if (!how) {
-		/* Push undo marker, if it was plain RTO and nothing
-		 * was retransmitted. */
-		tp->undo_marker = tp->snd_una;
-	} else {
+	tp->undo_marker = tp->snd_una;
+	if (how) {
 		tp->sacked_out = 0;
 		tp->fackets_out = 0;
 	}