[ 3.5.y.z extended stable ] Patch "tcp: fix retransmission in repair mode" has been added to staging queue

[Herton Ronaldo Krzesinski]

This is a note to let you know that I have just added a patch titled

    tcp: fix retransmission in repair mode

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

------

>From 6206b054fd5815f220b607af985a21f1af2ed409 Mon Sep 17 00:00:00 2001
From: Andrew Vagin <avagin at openvz.org>
Date: Thu, 15 Nov 2012 04:03:17 +0000
Subject: [PATCH] tcp: fix retransmission in repair mode

commit ec34232575083fd0f43d3a101e8ebb041b203761 upstream.

Currently if a socket was repaired with a few packet in a write queue,
a kernel bug may be triggered:

kernel BUG at net/ipv4/tcp_output.c:2330!
RIP: 0010:[<ffffffff8155784f>] tcp_retransmit_skb+0x5ff/0x610

According to the initial realization v3.4-rc2-963-gc0e88ff,
all skb-s should look like already posted. This patch fixes code
according with this sentence.

Here are three points, which were not done in the initial patch:
1. A tcp send head should not be changed
2. Initialize TSO state of a skb
3. Reset the retransmission time

This patch moves logic from tcp_sendmsg to tcp_write_xmit. A packet
passes the ussual way, but isn't sent to network. This patch solves
all described problems and handles tcp_sendpages.

Cc: Pavel Emelyanov <xemul at parallels.com>
Cc: "David S. Miller" <davem at davemloft.net>
Cc: Alexey Kuznetsov <kuznet at ms2.inr.ac.ru>
Cc: James Morris <jmorris at namei.org>
Cc: Hideaki YOSHIFUJI <yoshfuji at linux-ipv6.org>
Cc: Patrick McHardy <kaber at trash.net>
Signed-off-by: Andrey Vagin <avagin at openvz.org>
Acked-by: Pavel Emelyanov <xemul at parallels.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
[ herton: adjust context ]
Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski at canonical.com>
---
 net/ipv4/tcp.c        |    4 ++--
 net/ipv4/tcp_output.c |    4 ++++
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index d758741..34b23da 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -1180,7 +1180,7 @@ new_segment:
 wait_for_sndbuf:
 			set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
 wait_for_memory:
-			if (copied && likely(!tp->repair))
+			if (copied)
 				tcp_push(sk, flags & ~MSG_MORE, mss_now, TCP_NAGLE_PUSH);

 			if ((err = sk_stream_wait_memory(sk, &timeo)) != 0)
@@ -1191,7 +1191,7 @@ wait_for_memory:
 	}

 out:
-	if (copied && likely(!tp->repair))
+	if (copied)
 		tcp_push(sk, flags, mss_now, tp->nonagle);
 	release_sock(sk);
 	return copied;
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 90b10d0..305aafe 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -1784,6 +1784,9 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
 		tso_segs = tcp_init_tso_segs(sk, skb, mss_now);
 		BUG_ON(!tso_segs);

+		if (unlikely(tp->repair) && tp->repair_queue == TCP_SEND_QUEUE)
+			goto repair; /* Skip network transmission */
+
 		cwnd_quota = tcp_cwnd_test(tp, skb);
 		if (!cwnd_quota)
 			break;
@@ -1817,6 +1820,7 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
 		if (unlikely(tcp_transmit_skb(sk, skb, 1, gfp)))
 			break;

+repair:
 		/* Advance the send_head.  This one is sent out.
 		 * This call will increment packets_out.
 		 */
--
1.7.9.5