[3.8.y.z,extended,stable] Patch "tcp: reset timer after any SYNACK retransmit" has been added to staging queue

Message ID 1369417079-8771-1-git-send-email-kamal@canonical.com
State New
Headers show

Commit Message

Kamal Mostafa May 24, 2013, 5:37 p.m.
This is a note to let you know that I have just added a patch titled

    tcp: reset timer after any SYNACK retransmit

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:


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

For more information about the 3.8.y.z tree, see



From c6bb76b5e686b95ea8c9559dc612e0a1c2836582 Mon Sep 17 00:00:00 2001
From: Yuchung Cheng <ycheng@google.com>
Date: Mon, 29 Apr 2013 08:44:51 +0000
Subject: tcp: reset timer after any SYNACK retransmit

[ Upstream commit cd75eff64dae8856afbf6ef0f0ca3c145465d8e0 ]

Linux immediately returns SYNACK on (spurious) SYN retransmits, but
keeps the SYNACK timer running independently. Thus the timer may
fire right after the SYNACK retransmit and causes a SYN-SYNACK
cross-fire burst.

Adopt the fast retransmit/recovery idea in established state by
re-arming the SYNACK timer after the fast (SYNACK) retransmit. The
timer may fire late up to 500ms due to the current SYNACK timer wheel,
but it's OK to be conservative when network is congested. Eric's new
listener design should address this issue.

Signed-off-by: Yuchung Cheng <ycheng@google.com>
Acked-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: Kamal Mostafa <kamal@canonical.com>
 net/ipv4/tcp_minisocks.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)



diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index f35f2df..18e230d 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -581,8 +581,13 @@  struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
 		 * Note that even if there is new data in the SYN packet
 		 * they will be thrown away too.
+		 *
+		 * Reset timer after retransmitting SYNACK, similar to
+		 * the idea of fast retransmit in recovery.
-		inet_rtx_syn_ack(sk, req);
+		if (!inet_rtx_syn_ack(sk, req))
+			req->expires = min(TCP_TIMEOUT_INIT << req->num_timeout,
+					   TCP_RTO_MAX) + jiffies;
 		return NULL;