On Fri, 14 Jun 2002, David Ehlers wrote:
> 1. Summary: Can't receive multi-cast data correctly when using unique
> multi-cast
> addresses but a common port.
>
> 2. Description
> I'm converting an application that runs under SGI IRIX 6.2 to run under
> Linux.
> It works under IRIX. I can't receive multi-cast data correctly under
> Linux when
> using a unique multi-cast addresses but a common port. Any process that
> is
> listening to a particular port will receive all data for that port
> irregardless
> of the address.
>
> Everything works if each process uses unique multi-cast address and
> unique
> ports. No common ports at all. It was my understanding that a connection
> requires a unique 5-tuple. Source and destination address, source and
> destination port, and protocol.
>
1. UDP is passed to a process by associating a destination port number.
2a. UDP is connection-less.
2b. If you're stuck with only one physical interface (i.e. eth0 xor eth1),
then you could make IP aliases for the number of groups that you need to join.
Then for each mcast group (one socket for each right?) that you open, bind
to a unique IP alias address.
Sample Mapping:
Socket for 239.0.0.1 group gets bind'ed to aliased IP 192.168.69.1
239.0.0.2 192.168.69.2
239.0.0.3 192.168.69.3
In theory this should work, but I have not tested it.
The kernel guru's should be able to tell you if this would work, as I
don't know the kernel networking internals that may prevent such a thing.
Good luck!
Tuan
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