Re: Multicast and Masquerade clash

Gregory P. Smith (greg@nas.nasa.gov)
Fri, 11 Dec 1998 13:25:43 -0800

> In muc.lists.linux-kernel, you wrote:
> >A shortish term fix, which I don't like much since it puts some policy
> >into the kernel, would be to make the demasquerade conditional on the
> >stuff not being multicast. Multicast has a well defined address range set
> >so detecting if the source/dest are multicast sets should be easy enough
> >to do.
>
> What happens if someone wants to masquerade multicast connections ?
> I could imagine that masquerading multicast protocols is useful in
> some circumstances.

Yes, it would be. I've been meaning to masquerade multicast at home
and look into what needs to be done for the masq. code to support it
correctly. The problem I'm guessing that masq. multicast needs to fix
[I haven't tested it yet] is that the source address of anything my
masqueraded hosts send would still show up as my 192.168/16 addresses.
For many protocols this would not really matter as all traffic is being
-sent- on the class D multicast address but it is still impolite if not
rude or forbidden to send packets with a bogus source address as
receivers would not have any idea where the packet came from if it
even made it to them at all (ie: wasn't blocked by a typical router
filter).

-G

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