Date: Fri, 13 Jul 2001 14:05:23 -0300 From: "Daniel C. Sobral" <dcs@newsguy.com> To: mark tinguely <tinguely@web.cs.ndsu.NoDak.edu> Cc: net@FreeBSD.ORG Subject: Re: Multicasting and routes Message-ID: <3B4F2A53.1A4353EE@newsguy.com> References: <200107121424.f6CEO1040030@web.cs.ndsu.NoDak.edu>
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mark tinguely wrote:
>
> > It seems there is a problem in our IP stack with regards to
> > multicasting. The symptoms is the inability to send multicast packets on
> > correctly configured sockets in the absence of a default (or,
> > erroneously, multicast address being used) route.
>
> I don't know if I am reading your question correctly, but have you
> tried adding a multicast route? In /etc/rc.conf:
>
> static_routes="multicast loopback"
> route_multicast="224.0.0.0 -netmask 0xf0000000 -interface ${hostname}"
>
> this allows only one interface to send the multicast packets, and requires
> a multicast router to place the packets on the other interfaces.
A multicast application specifies what interface it wants to send the
multicast packet through. The "one interface" limit mentioned on rfc1112
refers to the behavior when no interface is specified: a default is
choosen and used.
The route above is essentially incorrect. Fortunately, our IP stack
behaves correctly when a default route (or a route to the multicast
address) exists: it ignores it. Unfortunately, it only does so after
checking if it knows a route to that address and returning host
unreachable otherwise.
I have a patch at http://people.freebsd.org/~dcs/ip_output.patch which I
intend to commit unless someone objects. What it does is skip the route
checking code if a interface was specified for the multicast packet.
--
Daniel C. Sobral (8-DCS)
dcs@newsguy.com
dcs@freebsd.org
capo@the.secret.bsdconspiracy.net
wow regex humor... I'm a geek
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