Backporting Keepalive Windows Extended Socket Options (JDK-8308593) to 11u and 17u

[Severin Gehwolf]

Hi Terry,

On Thu, 2023-08-24 at 00:54 +0000, Terry Chow (Simba Technologies Inc) wrote:
> Hi maintainers of OpenJDK updates,
> 
> I'd like to backport JDK-8308593 (keepalive extended socket options for Windows) to 11u and 17u (maybe 8u later as well). And so, I just want to open discussion on this topic to hear your opinions before I start the backporting process. I did some initial investigation on the backport and I learned the following:
> 
> Backporting to 11u requires three additional changes to be made on top of the backport in order for it to work.
>    1. Lib-jdk.net.gmk will need to be updated to support building extnet for Windows.
>    2. jdk.net.ExtendedSocketOption will need to add a case to support returning a Windows instance of PlatformSocketOptions.
>    3. The Windows PlainSocketImpl class needs to have the same code on lines 61 - 96 in the Unix PlainSocketImpl class.
> Backporting to 17u requires two additional changes (similar to 11u).
>    1. jdk.net/Lib.gmkwill need to be updated to support building extnet for Windows.
>    2. jdk.net.ExtendedSocketOption will need to add a case to support returning a Windows instance of PlatformSocketOptions.
> Let me know if the additional changes are acceptable or if they're disruptive.

As the change went into JDK 22, I'd first suggest to get this into JDK
21u which would bring this feature to LTS users. JDK 17u seems OK as a
next step from a brief glance (once it's in 21u). Only then we should
evaluate JDK 11u and older releases.

Thanks,
Severin