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[3.11.y.z,extended,stable] Patch "tcp: fix cwnd undo on DSACK in F-RTO" has been added to staging queue

Message ID 1403779059-13571-1-git-send-email-luis.henriques@canonical.com
State New
Headers show

Commit Message

Luis Henriques June 26, 2014, 10:37 a.m. UTC 
This is a note to let you know that I have just added a patch titled

    tcp: fix cwnd undo on DSACK in F-RTO

to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.11.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

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From 71d6f6613f1a8b8b6e0b5f4a6412b4d8250e9afb Mon Sep 17 00:00:00 2001
From: Yuchung Cheng <ycheng@google.com>
Date: Fri, 30 May 2014 15:25:59 -0700
Subject: tcp: fix cwnd undo on DSACK in F-RTO

commit 0cfa5c07d6d1d7f8e710fc671c5ba1ce85e09fa4 upstream.

This bug is discovered by an recent F-RTO issue on tcpm list
https://www.ietf.org/mail-archive/web/tcpm/current/msg08794.html

The bug is that currently F-RTO does not use DSACK to undo cwnd in
certain cases: upon receiving an ACK after the RTO retransmission in
F-RTO, and the ACK has DSACK indicating the retransmission is spurious,
the sender only calls tcp_try_undo_loss() if some never retransmisted
data is sacked (FLAG_ORIG_DATA_SACKED).

The correct behavior is to unconditionally call tcp_try_undo_loss so
the DSACK information is used properly to undo the cwnd reduction.

Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-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 | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

--
1.9.1
diff mbox

Patch

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 723951aec07e..d8e4c81bc114 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -2622,13 +2622,12 @@  static void tcp_process_loss(struct sock *sk, int flag, bool is_dupack)
 	bool recovered = !before(tp->snd_una, tp->high_seq);

 	if (tp->frto) { /* F-RTO RFC5682 sec 3.1 (sack enhanced version). */
-		if (flag & FLAG_ORIG_SACK_ACKED) {
-			/* Step 3.b. A timeout is spurious if not all data are
-			 * lost, i.e., never-retransmitted data are (s)acked.
-			 */
-			tcp_try_undo_loss(sk, true);
+		/* Step 3.b. A timeout is spurious if not all data are
+		 * lost, i.e., never-retransmitted data are (s)acked.
+		 */
+		if (tcp_try_undo_loss(sk, flag & FLAG_ORIG_SACK_ACKED))
 			return;
-		}
+
 		if (after(tp->snd_nxt, tp->high_seq) &&
 		    (flag & FLAG_DATA_SACKED || is_dupack)) {
 			tp->frto = 0; /* Loss was real: 2nd part of step 3.a */