Bug in ExtendedSocketOptions: TCP_QUICKACK can't be set in linux due to incorrect syscall level

[Alan Bateman]

On 07/06/2023 07:17, Bruno Da Silva wrote:
> Hi all,
>
> Random SWE here. I've found a bug in the LinuxSocketOptions.c native 
> implementation of getting/setting quickack on a socket. When running 
> strace, the socket option that is set is actually changing the 
> SO_PRIORITY.
>
> This is because the syscall is incorrectly called with level=SO_SOCKET 
> rather than level=SOL_TCP. You can see this in the openjdk 
> implementation on line 92 and 105:
> https://github.com/openjdk/jdk/blob/a08c5cb3f1be7a20c8f955951d1605bb8b1c1aa4/src/jdk.net/linux/native/libextnet/LinuxSocketOptions.c#L92. 
> It has existed since the original implementation in JDK-8145635.
>
> I believe the fix is to change both get/set syscalls like this:
> setsockopt(fd, SOL_SOCKET, TCP_QUICKACK, &optval, sizeof (optval));
> to
> setsockopt(fd, SOL_TCP, TCP_QUICKACK, &optval, sizeof (optval));
>
> The bug has existed since JDK 10 and I see it still exists in the most 
> recent versions of Java. It was found and tested in JDK 11.
>
>
> As a non-contributor, I don't know of a way of submitting a patch or 
> directly reporting this bug. Can someone provide guidance on where to 
> take it from here?
>
Good find, I've created JDK-8309591 [1] to track it. Create a PR if you 
want to run with this, otherwise someone else will need to pick this up.

-Alan

[1] https://bugs.openjdk.org/browse/JDK-8309591