Hello VServer experts!
I'm working on a project that uses VServer to provide application isolation functionality. As part of the development we came across a problem supporting multicast binding from inside vserver unless NET_ADMIN capability is turned on. It appears that VServer treats multicast addresses as any other network address. So in order to allow multicast addresses in vserver they need to be a part of NX_INFO list. This list can become quite large if all multicast address space is included.
I've looked at af_inet.c code and it appears that it's easy to provide multicast support if multicast addresses are differentiated from the rest of the address space. I believe this is safe to do because multicast addresses are handled differently by the kernel than normal IP addresses. I've attached a patch against a stable VServer release and 2.6.22 kernel that provides multicast support to vservers without NET_ADMIN capability.
Would it be possible to review this patch for any criticism and possibly inclusion into upcoming stable VServer release if it is useful?
multicast-plain.diff : Kernel patch
demo_mc_bind.c : C program that demonstrates lack of multicast support inside VServer
Thank you in advance!
Sincerely,
Artem Dmytrenko
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