Integrated: 8330940: Impossible to create a socket backlog greater than 200 on Windows 8+

[Jaikiran Pai]

On Mon, 16 Jun 2025 06:54:56 GMT, Jaikiran Pai <jpai at openjdk.org> wrote:

> Can I please get a review of this change which proposes to enhance the implementation of `ServerSocket` and `ServerSocketChannel` to allow for `backlog` values to be greater than 200 on Windows? This addresses https://bugs.openjdk.org/browse/JDK-8330940.
> 
> As noted in that enhancement request, right now on Windows, if the backlog is specified to be more than 200, then Windows caps it to a platform internal `SOMAXCONN`. As noted in the documentation here https://learn.microsoft.com/en-us/windows/win32/api/winsock2/nf-winsock2-listen applications can increase that limit by using the `SOMAXCONN_HINT` macro. That macro then adjusts the value to be between 200 and 65535, thus allowing for a higher backlog of connections.
> 
> The commit in this PR uses this macro when the specified backlog is 200 or more. A new jtreg test has been introduced to verify this change. This test and other existing tests in tier1, tier2 and tier3 continue to pass.
> 
> A similar restriction on the backlog value applies in Linux too https://github.com/torvalds/linux/blob/master/Documentation/networking/ip-sysctl.rst#tcp-variables. But from what I can see, unlike Windows, it cannot be adjusted when calling `listen()`.

This pull request has now been integrated.

Changeset: 4dd1b3a6
Author:    Jaikiran Pai <jpai at openjdk.org>
URL:       https://git.openjdk.org/jdk/commit/4dd1b3a6100f9e379c7cee3c699d63d0d01144a7
Stats:     117 lines in 2 files changed: 117 ins; 0 del; 0 mod

8330940: Impossible to create a socket backlog greater than 200 on Windows 8+

Reviewed-by: michaelm, dfuchs, alanb

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

PR: https://git.openjdk.org/jdk/pull/25819