netdev - Re: Problem with tcp (2.6.31) as first

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Message-ID: <4B138C73.8040401@gmail.com>
Date:	Mon, 30 Nov 2009 10:12:19 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Miller <davem@...emloft.net>
CC:	ilpo.jarvinen@...sinki.fi, ole@....pl, herbert@...dor.apana.org.au,
	Linux Netdev List <netdev@...r.kernel.org>
Subject: Re: Problem with tcp (2.6.31) as first

David Miller a écrit :
> From: Eric Dumazet <eric.dumazet@...il.com>
> Date: Thu, 26 Nov 2009 23:42:46 +0100
> 
>> Following patch solves this problem, but maybe we need a flag
>> (a la sk->sk_userlocks |= SOCK_WINCLAMP_LOCK;)
>> in case user set window_clamp.
>> Or just document the clearing after a tcp disconnect ?
>>
>> [PATCH] tcp: tcp_disconnect() should clear window_clamp
>>
>> Or reuse of socket possibly selects a small window, wscale = 0 for next connection.
> 
> Eric, can you post this with proper signoff to netdev?
> 
> Thanks.

Sure, here it is.

Thanks

[PATCH] tcp: tcp_disconnect() should clear window_clamp

NFS can reuse its TCP socket after calling tcp_disconnect().
We noticed window scaling was not negotiated in SYN packet of next connection request.

Fix is to clear tp->window_clamp in tcp_disconnect().

Reported-by: Krzysztof Oledzki <ole@....pl>
Tested-by: Krzysztof Oledzki <ole@....pl>
Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
---

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index f1813bc..d7a884c 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2059,6 +2059,7 @@ int tcp_disconnect(struct sock *sk, int flags)
 	tp->snd_ssthresh = TCP_INFINITE_SSTHRESH;
 	tp->snd_cwnd_cnt = 0;
 	tp->bytes_acked = 0;
+	tp->window_clamp = 0;
 	tcp_set_ca_state(sk, TCP_CA_Open);
 	tcp_clear_retrans(tp);
 	inet_csk_delack_init(sk)
--
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