I've encountered this problem with multicast and alias interfaces
(tryed to run ospf/gated over an alias interface).
While group membership for the alias interface is set properly (as
/proc/net/igmr indicates), multicast packets which should be received
by an alias interface are discarded.
The reason for this is that the ip_rcv routine only checks the list of
groups assigned to the interface which received the packet. Since this
obviously can't be the alias interface, the packet will be dropped if
the multicast group is only assigned to the alias, but not the
real (physical) interface.
This seems a bit inconsistent to me (if an alias cannot receive the
packets destined to one of the multicast groups it is a member of,
then why bother keeping the group membership list for it).
Could this be changed so that ip_rcv also checks the groups assigned
to alias interfaces ? Is there a reason for not doing it ?
Matei
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