Re: forward udp broadcast packets on same subnet /interface with diff source

[George Alexandru Dragoi <waruiinu@gmail.com>]

Because i am not used with this mailing list, the message that follows
was sent before the ip_forward thingy, but arrived to tom only. And
one thing, you can always change routes for all sort of packets, like
DNAT of packets hich aparently rached theyr destination


---------- Forwarded message ----------
From: George Alexandru Dragoi <waruiinu@gmail.com>
Date: Wed, 14 Jul 2004 07:31:47 +0200
Subject: Re: forward udp broadcast packets on same subnet /interface
with diff source
To: Tom Thumb <tomthumb888@yahoo.com>

Take a loot here:
http://www.netfilter.org/patch-o-matic/pom-extra.html#pom-extra-ROUTE

My ideea (not tested) si to do an
iptables -t mangle -A PREROUTING -p udp -d 192.168.1.255 -s
192.168.1.6 -j ROUTE --gw 192.168.1.5 --continue
iptables -t mangle -A PREROUTING -p udp -d 192.168.1.255 -s
192.168.1.6 -j MARK --set-mark 0x1
then:
iptables -t nat -A POSTROUTING -m mark --mark 0x1 -j SNAT --to 192.168.1.7



On Tue, 13 Jul 2004 22:02:47 -0700 (PDT), Tom Thumb
<tomthumb888@yahoo.com> wrote:
> Hi,
>
> Can I use iptables to forward UDP broadcast packets on
> the same subnet and interface but just change the
> source IP?
>
> That is, the forwarding machine is 192.168.1.5, with
> mask 255.255.255.0 and has a single NIC.
>
> A machine with IP 192.168.1.6 with the same mask sends
> a UDP broadcast to 192.168.1.255.
>
> The forwarding machine receives this packet. Can it be
> configured to resend it out on the same interface that
> it received it on (its only interface) and just change
> the source IP to be a 3rd address, like 192.168.1.7,
> but also as a UDP broadcast to 192.168.1.255?
>
> Is there any way to do this without adding a physical
> NIC?  Do I need to add a "virtual" NIC to do it? How?
>
> Thanks
>
>
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