On 9/7/18 1:57 PM, Alan Bateman wrote: > 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?
I have not tried joining IPv4 groups on an IPv6 socket through java, since we do not use IPv4 at all in this particular environment. I have tried setting IP_MULTICAST_ALL to 0 in the IPv6 scenario (in a C++ project), hoping it would help, but it did not. Hence the patch for the linux kernel. Would it actually help, if I tried the IPv4 multicast group bind on an IPv6 socket? The bind to an address would be a workaround for the missing IPV6_MULTICAST_ALL handling. Andre > > -Alan. >
