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

[Michael McMahon]

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.

-------------

Commit messages:
 - added test comment
 - Merge branch 'master' into ipv6opt
 - test fix
 - fix whitespace
 - added test
 - initial impl

Changes: https://git.openjdk.org/jdk/pull/14491/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14491&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8241800
  Stats: 184 lines in 2 files changed: 184 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/14491.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14491/head:pull/14491

PR: https://git.openjdk.org/jdk/pull/14491