On 04/16/10 09:23, Alexander Leidinger wrote:

IP multicast group membership is always scoped to physical links [1]. The 4.4BSD API originally used the "primary IP address" to identify each link. Unfortunately this is not a persistent identifier, especially so in the use-case which had problems.


Is/was this the reason why multicast does not work in jails?

The above point is totally unrelated to jail.

I think the problem with jail is the fact that to receive multicast, sockets normally need to be bound to INADDR_ANY. Obviously, jail changes socket behaviour in interesting ways.

This may require refactoring udp_input() considerably. We use the 4.4BSD legacy LIST_FOREACH() loop to deliver, rather than using a fan-in map (which is the Windows/Solaris approach).

Linux also has 4.4BSD semantics, but can work around this by examining the SO_BINDTODEVICE option in the same path.
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