On 07/09/2018 12:33, Andre Naujoks wrote:
:
Hi Alan.
First of all, thank you for the quick reply. I was not aware, that there
was actually a bug opened for that issue.
The join is not the problem at this point. We need to bind the socket to
the address to avoid receiving traffic from all multicast groups, that
are joined on the system. Since a join joins the system (not the socket)
to the group, all sockets bound to a port, which receive multicast
traffic will receive all of that traffic, no matter the destination
address. The bind prevents that. IP_MULTICAST_ALL sadly only works for
IPv4 and the patch I tried to get IPV6_MULTICAST_ALL upstream into the
kernel was even more sadly (almost) ignored. see
https://marc.info/?l=linux-netdev&m=152344460530252&w=2
The JDK sets IP_MULTICAST_ALL to 0 on Linux to avoid this interference
and get the behavior consistent with other platforms. It's news to me
that it doesn't work on IPv6 as we always disable it, even if the socket
is IPv6. Does it work when the IPv6 socket joins an IPv4 multicast group?
-Alan.
