RFR: 8241800: Disable IPV6_MULTICAST_ALL to prevent interference from all multicast groups

[Michael McMahon]

On Thu, 15 Jun 2023 10:47:58 GMT, Michael McMahon <michaelm at openjdk.org> wrote:

> Hi,
> 
> Can I get the following change reviewed please? It disables the IPV6_MULTICAST_ALL socket option on UDP sockets on Linux systems which support the option (kernel version 4.20+). This has the effect of disabling the surprising default behavior of multicast sockets on Linux where sockets can receive packets sent to groups the receiver has not joined, if some other socket has joined that group on the same system.
> 
> The equivalent behavior has already been implemented for IPv4 sockets.
> 
> Thanks,
> Michael.

> 

It's certainly the case that the IPv4 option can be called on AF_INET6 sockets but only affects the IPv4 stack. Which suggests the IPv6 option only affects the IPv6 stack. I'll see if I can confirm that is true.

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PR Comment: https://git.openjdk.org/jdk/pull/14491#issuecomment-1592872562