RFR: 8241800: Disable IPV6_MULTICAST_ALL to prevent interference from all multicast groups [v8]

[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.

Michael McMahon has updated the pull request incrementally with one additional commit since the last revision:

  missing parentheses

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Changes:
  - all: https://git.openjdk.org/jdk/pull/14491/files
  - new: https://git.openjdk.org/jdk/pull/14491/files/ed0243ba..b54baa04

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=14491&range=07
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=14491&range=06-07

  Stats: 3 lines in 2 files changed: 0 ins; 2 del; 1 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