netdev - Re: SCTP connect() both ways

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Date:	Mon, 09 Jun 2014 14:40:55 -0400
From:	Vlad Yasevich <vyasevich@...il.com>
To:	David Laight <David.Laight@...LAB.COM>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: SCTP connect() both ways

On 06/09/2014 05:41 AM, David Laight wrote:
> When SCTP is used for protocols like M3UA it seems common
> to configure both port numbers for a connection (typically
> to the same value).
> 
> Rather than having one system call connect() and the other
> listen(), both systems really want to try to establish the
> connection by sending out INIT chunks.

The correct way to do this is to not used connect() call.
Both systems should do a listen() and then use an implicit
connect by using an sctp_sendmsg() or similar calls to
send the data.

> 
> The connection then gets established as soon as the second of the
> two systems attempts to establish it.
> 
> However if the remote system responds with an ABORT (or maybe
> an ICMP error is received) the Linux SCTP stack immediately
> reports 'connect failed'.
> For these sorts of connections it would be much better if the
> received ABORT just increased the retry timer to large value.
> 
> Thoughts?

We don't know why the remote ABORTED.  There could be a lot of
reasons.  It is up to the application to retry.  This is no
different then receiving an RST in response to a SYN.

-vlad

> 
> 	David
> 
> 
> 
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