Hi
Will the RTnet module work with IP aliases? And "REUSE_PORT" option?
I need to have 2 different IPs bind to 1 NIC. I need to be able to receive IP dependend packages for every single IP, and I need to receive broadcast messages on their subnet.
So is it possible to use more than 1 IP on the same network device with this RTnet module.
Well, IP aliasing is not explicitly supported by RTnet. I'm currently having some troubles to imagine a real-time networking scenario where you may need such a feature (maybe you can help me :) ).
However, with some tricks and the latest CVS version, this is not impossible. As long as a RTnet node is not configured as router (see README.routing), the latest version performs no more destination IP check at the IP layer itself. The only check is now done at the UDP layer when the "acceptance mask" of the destination socket is applied. So, when you do not bind your socket to any specific interface IP (i.e. INADDR_ANY), you will be able to receive even "misdirected" packets.
An additional step is required on the sender's side. As the ARP layer of RTnet still only replies to requests about the interface's IP, you have to patch to routing of the sender. If it is a RTnet node, simply run "rtroute add <alias-ip> <remote-hw-addr> dev <local-interface>".
SO_REUSE_PORT, if it means that two sockets can be bound to the same local port and will receive the same data, is not supported by RTnet. Internally, this would mean to have an arbitrary number of users of any incoming data packet. This would be possible (and is implemented in most standard network stacks), but it would add overhead to all users - even those with unshared ports. We would likely need this feature as an option when we - someday :) - include multicast support. But, so far, no one has done this work. So, when you are interested in contributing... ;)
Jan
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