RFR: JDK-8313804: JDWP support for -Djava.net.preferIPv6Addresses=system [v2]

[Liam Miller-Cushon]

On Mon, 18 Sep 2023 23:44:22 GMT, Chris Plummer <cjplummer at openjdk.org> wrote:

> Is the code starting at lines 748 and 970 still correct after your changes?

I think so, but scrutiny there is very welcome. I expected additional changes to be necessary.

* For 748, it's handling a situation where IPv4 isn't specifically preferred. The implementation comment notes 'if preferredAddressFamily is AF_INET6 or not set'.
* For 970 the first loop won't match, and on the second loop it will try in the order provided by `getaddrinfo`, which is what we want.

If that sounds right, suggestions for making it clearer / more explicit are welcome.

> src/jdk.jdwp.agent/share/native/libdt_socket/socketTransport.c line 1312:
> 
>> 1310:  *  - AF_INET6 if the property is "true";
>> 1311:  *  - AF_INET if the property is "false".
>> 1312:  *  - 0 if the property is "false".
> 
> I think you meant "system", not "false".

Thanks, updated to `AF_UNSPEC if the property is "system"`

> src/jdk.jdwp.agent/share/native/libdt_socket/socketTransport.c line 1338:
> 
>> 1336:             preferredAddressFamily = AF_INET;
>> 1337:         } else if (strcmp(theValue, "system") == 0) {
>> 1338:             preferredAddressFamily = 0;
> 
> Would `AF_UNSPEC` (which is 0) be a better choice than a literal 0 here?

SGTM, thanks!

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

PR Comment: https://git.openjdk.org/jdk/pull/15796#issuecomment-1724637144
PR Review Comment: https://git.openjdk.org/jdk/pull/15796#discussion_r1329401761
PR Review Comment: https://git.openjdk.org/jdk/pull/15796#discussion_r1329401756