netdev - Re: [PATCH] sctp: allow authenticating DATA chunks that are bundled with COOKIE

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Date:	Fri, 12 Jun 2015 07:26:40 -0400
From:	Neil Horman <nhorman@...driver.com>
To:	David Miller <davem@...emloft.net>
Cc:	mleitner@...hat.com, netdev@...r.kernel.org,
	linux-sctp@...r.kernel.org, vyasevich@...il.com
Subject: Re: [PATCH] sctp: allow authenticating DATA chunks that are bundled
 with COOKIE_ECHO

On Thu, Jun 11, 2015 at 05:27:45PM -0700, David Miller wrote:
> From: mleitner@...hat.com
> Date: Thu, 11 Jun 2015 14:49:46 -0300
> 
> > From: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
> > 
> > Currently, we can ask to authenticate DATA chunks and we can send DATA
> > chunks on the same packet as COOKIE_ECHO, but if you try to combine
> > both, the DATA chunk will be sent unauthenticated and peer won't accept
> > it, leading to a communication failure.
> > 
> > This happens because even though the data was queued after it was
> > requested to authenticate DATA chunks, it was also queued before we
> > could know that remote peer can handle authenticating, so
> > sctp_auth_send_cid() returns false.
> > 
> > The fix is whenever we set up an active key, re-check send queue for
> > chunks that now should be authenticated. As a result, such packet will
> > now contain COOKIE_ECHO + AUTH + DATA chunks, in that order.
> > 
> > Reported-by: Liu Wei <weliu@...hat.com>
> > Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
> 
> Vlad/Neil, please review.
> 

sorry Dave, though I had sent email on that already.

I had an initial concern that there could be a race in which a previous
iteration of sctp_outq_flush would move some chunks to a packet, but not flush
it to the network layer yet (due to not being full), and that would result in
the same condition.  But since this only happens with a COOKIE_ECHO chunk (which
is a control chunk), we should be ok, as those are sent immediately.

Acked-by: Neil Horman <nhorman@...driver.com>

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