Multicast & iptables
Tue, 6 Jul 2004 11:35:03 +0200 (CEST)
Hello guys & gals
I have a question w.r.t. multicast and iptables for a very 'unique'
application. It's a kind of 'box in the middle' application.
So that you're warned :-)
I have a userspace application opening a socket on the external interface
and subscribing itself to a multicast address.
When the box receives a packet addressed to itself on its internal
interface, it does a PREROUTING/DNAT to the multicast address and a
POSTROUNTING/SNAT to its external interface.
When the box receives a packet addressed to itself on its external
interface, it does a PREROUTING/DNAT to the internal default gateway for
multicast and a POSTROUNTING/SNAT to its internal interface.
I do have ip_forwarding on 1 in /proc :-)
However, this does not seem to work :-(
When I sniff traffic I do see that IGMP is ok, so my userspace app. is
doing ok, but I don't see the NATted traffic at all.
Are multicast addresses 'blocked' by iptables or am I making a mistake here?