Date: Sat, 3 Mar 2001 10:54:05 GMT
Message-Id: <200103031054.KAA29868@localhost.localdomain>
From: Jon Masters <jonathan@jonmasters.org>
To: LKML <linux-kernel@vger.kernel.org>
Subject: Forwarding broadcast traffic
Cc: jonathan@jonmasters.org
Mailer: Jon Masters. Copyleft 1981. All rights and Freedoms reserved.
Sender: linux-kernel-owner@vger.kernel.org

Hello,
	I have a brain-dead application here which relies on broadcast
traffic for client/server discovery and I have a question with regard
to forwarding broadcast traffic.

A small part of my local LAN looks like this:

                 REST OF LAN
                      |
                      | (router eth1)
                      |
                 masquerading
                router (kernel 2.2.14)
                      |
                      | (router eth0)
                      |
                   desktop (private IP)
                    boxen  (kernel 2.4.2)

* upgrading the router is not a problem[0].

I wish to have the router forward certain broadcast traffic coming
from either side out to the other (as well as itself).

e.g. on desktop a broadcast udp packet (with a specified port) needs to
go not only to itself and the router but also the "REST OF LAN" part
too - and vice versa. Removing the router is not an option.

I know this isn't a *nice* idea and ordinarily I wouldn't be jumping up
and down suggesting one throws broadcast traffic around however I need
to do this for various reasons and the solution appears to be
non-obvious at least to me[1].

I have considered the idea of creating a transparent bridge however I
would really rather not do that here for various reasons.

I have posted this message to groups elsewhere however I have not yet
had any useful responses beyond basic instruction of IP forwarding,
etc. which is not what I need here :P

Any ideas? I think this one has come up before but I could not find a
helpful answer in my archives.

Appreciate your time,
			--jcm

P.S. My lkml feed at home is great but here it is not so could you
     please CC me on replies thanks.

[0] Yeah, yeah, I know 2.2.14 is old but it's an old router and when I
    move that box over to Debian I'll upgrade the kernel at the same
    time :P
[1] either due to general stupidity or tiredness, or both.
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