[PATCH] tcp_v4_send_reset: binding oif to iif in no sock case

Binding RST packet outgoing interface to incoming interface
for tcp v4 when there is no socket associate with it.
This has few benefits:
1. tcp_v6_send_reset already did that.
2. This helps tcp connect with SO_BINDTODEVICE set. When
connection is lost, we still able to sending out RST using
same interface.
3. we are sending reply, it is most likely to be succeed
if iif is used

Signed-off-by: Shawn Lu <redacted>
---
V3: reformat comments as suggested
 net/ipv4/tcp_ipv4.c |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 90e4793..4d6f81c 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c

@@ -676,6 +676,11 @@ static void tcp_v4_send_reset(struct sock *sk, struct sk_buff *skb)
 				      arg.iov[0].iov_len, IPPROTO_TCP, 0);
 	arg.csumoffset = offsetof(struct tcphdr, check) / 2;
 	arg.flags = (sk && inet_sk(sk)->transparent) ? IP_REPLY_ARG_NOSRCCHECK : 0;
+	/* When socket is gone, all binding information is lost.
+	 * routing might fail in this case. using iif for oif to
+	 * make sure we can deliver it
+	 */
+	arg.bound_dev_if = sk ? sk->sk_bound_dev_if : inet_iif(skb);
 
 	net = dev_net(skb_dst(skb)->dev);
 	arg.tos = ip_hdr(skb)->tos;

-- 
1.7.0.4

From: Shawn Lu <redacted>
Date: Sat, 4 Feb 2012 13:44:57 -0800

Binding RST packet outgoing interface to incoming interface
for tcp v4 when there is no socket associate with it.
This has few benefits:
1. tcp_v6_send_reset already did that.
2. This helps tcp connect with SO_BINDTODEVICE set. When
connection is lost, we still able to sending out RST using
same interface.
3. we are sending reply, it is most likely to be succeed
if iif is used

Signed-off-by: Shawn Lu <redacted>

Sigh...

Thanks for giving Eric not credit whatsoever for his contributions
and feedback for this fix. :-/

Le samedi 04 février 2012 à 13:44 -0800, Shawn Lu a écrit :

Acked-by: Eric Dumazet <redacted>

Hi,David:

I do appreciate Eric's helpand contribution in this fix. 
I am a newer here. I just don't know how I can give credit to him. I thought
That you will put "Acked-by: Eric Dumazet [off-list ref]" to 
Credit his contribution.

Thanks!
Shawn Lu  

-----Original Message-----
From: David Miller [mailto:davem@davemloft.net] 
Sent: Saturday, February 04, 2012 1:47 PM
To: Shawn Lu
Cc: eric.dumazet@gmail.com; netdev@vger.kernel.org; xiaoclu@gmail.com
Subject: Re: [PATCH] tcp_v4_send_reset: binding oif to iif in 
no sock case

From: Shawn Lu <redacted>
Date: Sat, 4 Feb 2012 13:44:57 -0800

quoted

Binding RST packet outgoing interface to incoming interface 

for tcp v4 

quoted

when there is no socket associate with it.
This has few benefits:
1. tcp_v6_send_reset already did that.
2. This helps tcp connect with SO_BINDTODEVICE set. When 

connection is 

quoted

lost, we still able to sending out RST using same interface.
3. we are sending reply, it is most likely to be succeed if iif is 
used

Signed-off-by: Shawn Lu <redacted>

Sigh...

Thanks for giving Eric not credit whatsoever for his 
contributions and feedback for this fix. :-/