From owner-freebsd-arch  Mon Mar  4  7:12:33 2002
Delivered-To: freebsd-arch@freebsd.org
Received: from nimbus.nj.caldera.com (nimbus.nj.caldera.com [132.147.103.56])
	by hub.freebsd.org (Postfix) with ESMTP id 33EC937B434
	for <arch@freebsd.org>; Mon,  4 Mar 2002 07:11:54 -0800 (PST)
Received: from caldera.com (bird [132.147.135.198]) by nimbus.nj.caldera.com (8.10.1/UW7.1.1-NSCd) with ESMTP id g24FBlI26694; Mon, 4 Mar 2002 10:11:48 -0500 (EST)
Message-ID: <3C838EB3.C38E23D2@caldera.com>
Date: Mon, 04 Mar 2002 10:11:47 -0500
From: Sergey Babkin <sergey@caldera.com>
Organization: Caldera International, Inc.
X-Mailer: Mozilla 4.7 [en] (X11; U; FreeBSD 4.0-19990626-CURRENT i386)
X-Accept-Language: ru, en
MIME-Version: 1.0
To: Ian Dowse <iedowse@maths.tcd.ie>
Cc: arch@freebsd.org, chawla@caldera.com,
	Christoph Hellwig <hch@caldera.de>, davem@redhat.com
Subject: Re: proposition for new socket syscalls {send,recv}fromto
References: <200203020245.aa34899@salmon.maths.tcd.ie>
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Sender: owner-freebsd-arch@FreeBSD.ORG
Precedence: bulk
List-ID: <freebsd-arch.FreeBSD.ORG>
List-Archive: <http://docs.freebsd.org/mail/> (Web Archive)
List-Help: <mailto:majordomo@FreeBSD.ORG?subject=help> (List Instructions)
List-Subscribe: <mailto:majordomo@FreeBSD.ORG?subject=subscribe%20freebsd-arch>
List-Unsubscribe: <mailto:majordomo@FreeBSD.ORG?subject=unsubscribe%20freebsd-arch>
X-Loop: FreeBSD.ORG

Ian Dowse wrote:
> 
> In message <3C800A80.96CEA9D2@caldera.com>, Sergey Babkin writes:
> >
> >The fix in short: the server should do a bind() to the right address
> >before doing the reply. However in practice this code gets much more
> >compilcated and ugly, as will be discussed further.
> 
> Linux has an IP_PKTINFO socket option and IP_PKTINFO control message
> that (I think) allows you record the destination IP on incoming
> datagrams and set the source address on outgoing ones. A quick,
> minimally tested sample program which uses it is at:
> 
>         http://www.maths.tcd.ie/~iedowse/FreeBSD/pktinfo.c

It's doing essentially the same thing as I described with
IP_RECVDSTADDR, I guess IP_RECVDSTADDR returns a subset of information
returned by IP_PKTINFO.

> In FreeBSD, we only seem to have this capability for IPv6, using
> the IPV6_PKTINFO option and control messages. Implementations of
> either an IP_PKTINFO or an IP_SENDSRCADDR control message have been
> discussed on freebsd-net a few times, but nothing has been committed
> yet.

Yes, IP_SENDSRCADDR would make the sending side of things a lot
easier.

> For systems that have such a mechanism, the proposed syscalls could
> just be implemented as library functions instead.

Agreed.

-SB

-- 
Sergey Babkin                             sergey@caldera.com
Escalations Research Group, Caldera - NJ  (908)790-2385

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