netdev - Re: tcp: disallow bind() to reuse addr/port regression in 2.6.38

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Message-ID: <1301779083.2837.30.camel@edumazet-laptop>
Date:	Sat, 02 Apr 2011 23:18:03 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Cyril Bonté <cyril.bonte@...e.fr>
Cc:	Willy Tarreau <w@....eu>, netdev@...r.kernel.org,
	Daniel Baluta <daniel.baluta@...il.com>,
	Gaspar Chilingarov <gasparch@...il.com>,
	Charles Duffy <charles@...is.net>
Subject: Re: tcp: disallow bind() to reuse addr/port regression in 2.6.38

Le samedi 02 avril 2011 à 23:00 +0200, Cyril Bonté a écrit :
> Le samedi 2 avril 2011 22:37:27, Willy Tarreau a écrit :
> > On Sat, Apr 02, 2011 at 09:44:55PM +0200, Eric Dumazet wrote:
> > > Is Cyril program running OK on FreeBsd ?
> > 
> > I don't think so, as from memories, both FreeBSD and OpenBSD fail
> > on isten() after a shutdown(SHUT_RD), hence the strange looking
> > shut+listen+shut sequence you noticed (in order to detect whether
> > listen will work again or not).
> 
> Well, I've just tested it on FreeBSD 8.1.
> As Willy said, the listen() fails but what I observe is that as soon as 
> shutdown(SHUT_RW) is called, it is possible to bind a new socket on the same 
> port. A modified version of the program to sleep after the shutdown shows that 
> launching 3 processes in parallel (delayed to let them bind then shutdown) 
> will give 3 connections in CLOSE state.
> 

Yes, but as soon as shutdown(SHUT_RDWR) is called on socket fd1, is this
same socket reusable ?

Maybe the only possible action is a close(fd1), and socket not any more
bound.

Man page on shutdown() is a bit silent, and makes sense for non
listening sockets.



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