netdev - Connect hangs for a while before returns -1 with ECONNREFUSED on 3.2 for loopback

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Message-ID: <4F2B7DF1.5050303@oktetlabs.ru>
Date:	Fri, 03 Feb 2012 10:25:53 +0400
From:	"Yurij M. Plotnikov" <Yurij.Plotnikov@...etlabs.ru>
To:	netdev@...r.kernel.org
Subject: Connect hangs for a while before returns -1 with ECONNREFUSED on
 3.2 for loopback

On kernel 3.2.0-0.bpo.1-amd64 I see some strange behaviour of connect() 
in case of connection via loopback. Lets see the following steps (there 
are two processes on the host, and the first one with two threads)

Thread1:
1. socket(PF_INET, SOCK_STREAM, 0) ->  3
2. bind(10.27.10.1:26820) ->  0 /* The address is bound to some interface, eth1 */
3. listen(3, 1) ->  0

sleep for a while

Thread2:
4. shutdown(3, SHUT_RD) ->  0

sleep for a while

Another process:
5. socket(PF_INET, SOCK_STREAM, 0) ->  4
6. connect(4, 10.27.10.1:26820)

connect() returns -1 with ECONNREFUSED but after some time. In case of 
two peer hosts connect() returns -1 with ECONNREFUSED almost 
immediately, so does for the other kernel versions.

In attachment c program to reproduce this problem.

View attachment "connect_loopback.c" of type "text/x-csrc" (1043 bytes)