From owner-freebsd-net  Wed Feb 28  3:23:58 2001
Delivered-To: freebsd-net@freebsd.org
Received: from cobweb.example.org (par-ilm-dhcp1-vl132-24.cisco.com [144.254.57.219])
	by hub.freebsd.org (Postfix) with SMTP id 1EEA437B71A
	for <freebsd-net@freebsd.org>; Wed, 28 Feb 2001 03:23:54 -0800 (PST)
	(envelope-from molter@tin.it)
Received: (qmail 1757 invoked by uid 1000); 28 Feb 2001 11:23:44 -0000
Date: Wed, 28 Feb 2001 12:23:44 +0100
From: Marco Molteni <molter@tin.it>
To: freebsd-net@freebsd.org
Subject: How to implement a transport protocol with netgraph?
Message-ID: <20010228122343.A425@cobweb.example.org>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
User-Agent: Mutt/1.2.5i
Sender: owner-freebsd-net@FreeBSD.ORG
Precedence: bulk
X-Loop: FreeBSD.org

Hi all,

I have to implement a kernel version of the transport protocol SCTP
(Stream Control Transmission Protocol, RFC 2960), plus a socket
interface to it as in draft-ietf-stewart-sctpsocket-sigtran-01.txt
(the RFC has an ad hoc user interface).

It seems to me that the modularity of netgraph would help a lot in
this project, as opposed to go hacking half the kernel networking
stack to put SCTP in it (and yes, this is my first big project in
kernel land).

I read the netgraph blueprint article on Daemonnews and the various
netgraph manpages. The problem is that all the examples and
applications I could find are layer 2 and layer 3, there is no example
of a transport protocol done with netgraph.

Since SCTP is reliable, at the very minimum I will have to handle
timers, buffers, retransmissions and friends.

So my questions are: 

o Any example of a transport protocol done with netgraph, or any hints
  (the more detailed the better :-) on how to tackle this task? Is
  netgraph suited for this (I think yes) ?

o Let's say the socket interface will be something like
  sd = socket(PF_INET, SOCK_STREAM, IPPROTO_SCTP)
  How (or where) do I connect the socket system call to the netgraph
  framework?

Thanks for the help
Marco

To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-net" in the body of the message