Patchwork [3.5.y.z,extended,stable] Patch "tcp: fix for zero packets_in_flight was too broad" has been added to staging queue

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Submitter Herton Ronaldo Krzesinski
Date Feb. 15, 2013, 3:11 a.m.
Message ID <1360897913-16485-1-git-send-email-herton.krzesinski@canonical.com>
Download mbox | patch
Permalink /patch/220613/
State New
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Comments

Herton Ronaldo Krzesinski - Feb. 15, 2013, 3:11 a.m.
This is a note to let you know that I have just added a patch titled

    tcp: fix for zero packets_in_flight was too broad

to the linux-3.5.y-queue branch of the 3.5.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-3.5.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 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Herton

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From 6d1fff9a36315a41cc728cc362b0112f5fb2fdbe Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ilpo=20J=C3=A4rvinen?= <ilpo.jarvinen@helsinki.fi>
Date: Mon, 4 Feb 2013 02:14:25 +0000
Subject: [PATCH] tcp: fix for zero packets_in_flight was too broad
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

commit 6731d2095bd4aef18027c72ef845ab1087c3ba63 upstream.

There are transients during normal FRTO procedure during which
the packets_in_flight can go to zero between write_queue state
updates and firing the resulting segments out. As FRTO processing
occurs during that window the check must be more precise to
not match "spuriously" :-). More specificly, e.g., when
packets_in_flight is zero but FLAG_DATA_ACKED is true the problematic
branch that set cwnd into zero would not be taken and new segments
might be sent out later.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Tested-by: Eric Dumazet <edumazet@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski@canonical.com>
---
 net/ipv4/tcp_input.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

--
1.7.9.5

Patch

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 6affa92..3b14d81 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3695,8 +3695,7 @@  static bool tcp_process_frto(struct sock *sk, int flag)
 	    ((tp->frto_counter >= 2) && (flag & FLAG_RETRANS_DATA_ACKED)))
 		tp->undo_marker = 0;

-	if (!before(tp->snd_una, tp->frto_highmark) ||
-	    !tcp_packets_in_flight(tp)) {
+	if (!before(tp->snd_una, tp->frto_highmark)) {
 		tcp_enter_frto_loss(sk, (tp->frto_counter == 1 ? 2 : 3), flag);
 		return true;
 	}
@@ -3716,6 +3715,11 @@  static bool tcp_process_frto(struct sock *sk, int flag)
 		}
 	} else {
 		if (!(flag & FLAG_DATA_ACKED) && (tp->frto_counter == 1)) {
+			if (!tcp_packets_in_flight(tp)) {
+				tcp_enter_frto_loss(sk, 2, flag);
+				return true;
+			}
+
 			/* Prevent sending of new data. */
 			tp->snd_cwnd = min(tp->snd_cwnd,
 					   tcp_packets_in_flight(tp));