netdev - RE: [PATCH] sctp: handle association restarts when the socket is closed.

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Date:	Mon, 6 Oct 2014 11:09:52 +0000
From:	David Laight <David.Laight@...LAB.COM>
To:	'David Miller' <davem@...emloft.net>,
	"vyasevich@...il.com" <vyasevich@...il.com>
CC:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: [PATCH] sctp: handle association restarts when the socket is
 closed.

From: David Miller
> From: Vladislav Yasevich <vyasevich@...il.com>
> Date: Fri,  3 Oct 2014 18:16:20 -0400
> 
> > From: Vlad Yasevich <vyasevich@...il.com>
> >
> > Currently association restarts do not take into consideration the
> > state of the socket.  When a restart happens, the current assocation
> > simply transitions into established state.  This creates a condition
> > where a remote system, through a the restart procedure, may create a
> > local association that is no way reachable by user.  The conditions
> > to trigger this are as follows:
> >   1) Remote does not acknoledge some data causing data to remain
> >      outstanding.
> >   2) Local application calls close() on the socket.  Since data
> >      is still outstanding, the association is placed in SHUTDOWN_PENDING
> >      state.  However, the socket is closed.
> >   3) The remote tries to create a new association, triggering a restart
> >      on the local system.  The association moves from SHUTDOWN_PENDING
> >      to ESTABLISHED.  At this point, it is no longer reachable by
> >      any socket on the local system.
> >
> > This patch addresses the above situation by moving the newly ESTABLISHED
> > association into SHUTDOWN-SENT state and bundling a SHUTDOWN after
> > the COOKIE-ACK chunk.  This way, the restarted associate immidiately
> > enters the shutdown procedure and forces the termination of the
> > unreachable association.
> >
> > Reported-by: David Laight <David.Laight@...lab.com>
> > Signed-off-by: Vlad Yasevich <vyasevich@...il.com>
> 
> Applied, thanks.
> 
> Candidate for -stable?

Maybe, but while I raised the problem and tested the fix, I added
a workaround to our M3UA code to ABORT sctp connections.
I'll predicate it on a kernel version when I know which one it is in,
but I'm not going to check backports to old distributions.
(I'm tempted to disable sctp on 2.6.18 kernels...)

So I'm not worried -stable.

Other sctp users may be more worried.

	David



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