[RFR]: 8222562: IPv6 only systems fail on setsockopt(IPV6_V6ONLY, 0)

[Daniel Fuchs]

Hi Arthur,

On 17/04/2019 07:54, Alan Bateman wrote:
> On 16/04/2019 22:34, Arthur Eubanks wrote:
>> Hi,
>>
>> Copied from the bug https://bugs.openjdk.java.net/browse/JDK-8222562:
>> Some of the networking code tries to support dual socket support. 
>> However, it doesn't work with IPv6 only systems.
>>
>> setsockopt(fd, IPPROTO_IPV6, IPV6_V6ONLY, 0) returns a failure with 
>> errno EAFNOSUPPORT, and then the networking code bails. It should not 
>> bail when it sees that trying to set IPV6_V6ONLY fails.
>>
>> webrev: 
>> http://cr.openjdk.java.net/~aeubanks/ipv6setsockopt/webrev.00/index.html
>>
>> One thing to note is that similar code exists in the Windows part of 
>> the networking code (e.g. 
>> java.base/windows/native/libnet/PlainSocketImpl.c), but I don't know 
>> how to test Windows code so I'm only touching the Unix-specific part.
>>
> This code is compiled on other Unix-like ports too so I think we should 
> at least try to see if they also return EAFNOSUPPORT when configured for 
> IPv6-only.

Also should we have an ipv4_available() utility similar
to ipv6_available() and check that before making the decision not
to bail on EAFNOSUPPORT? Or would that be a chicken and egg problem?

best regards,

-- daniel

> 
> -Alan