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Date:	Mon, 30 Nov 2009 10:12:19 +0100
From:	Eric Dumazet <>
To:	David Miller <>
	Linux Netdev List <>
Subject: Re: Problem with tcp (2.6.31) as first

David Miller a écrit :
> From: Eric Dumazet <>
> 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.


[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 <>
Tested-by: Krzysztof Oledzki <>
Signed-off-by: Eric Dumazet <>

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);
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