Re: native AF_UNIX support inquiry

On 8/17/2026 7:10 PM, Eric Cai via Cygwin wrote:
> Respectable Cygwin developers:
>    I would have to bother you for the specification of the AF_UNIX support in Cygwin. Despite the claim in the documentation that AF_UNIX in Cygwin is implemented by AF_INET( newlib-cygwin - newlib and cygwin  ), I have also noticed that the part of the documentation was added in 2013 and have remained unchanged since then, while it was not until 2017 that Windows started to support AF_UNIX natively( AF_UNIX comes to Windows - Windows Command Line  ). Therefore, may I inquiry that whether Cygwin's socket API( Chapter 1. Compatibility  ) is able to use the native AF_UNIX in Windows currently despite it was not informed by the document?

AFAIK current Cygwin still implements AF_UNIX support via AF_INET over 
the loopback interface.  There was significant work done several years 
ago on a replacement AF_UNIX implementation but it eventually stalled on 
one or more unsolvable problems with certain socket options.

Along the way Microsoft added what they called AF_UNIX support to 
Windows.  It is not a complete implementation, in that it lacks at least 
socketpair(), SOCK_DGRAM, and the same socket options that our upgrade 
attempt was unable to provide.  It seems there has been no further 
evolution of the Windows AF_UNIX support by Microsoft over the years 
since its introduction.

AF_UNIX support is one more area of Cygwin where we could really use the 
input of another developer with time and patience to finish our 
replacement AF_UNIX implementation.  System-level coding and debugging 
experience (both Windows and Unix/Linux) practically required for this 
kind of thing.

..mark

-- 
Problem reports:      https://cygwin.com/problems.html
FAQ:                  https://cygwin.com/faq/
Documentation:        https://cygwin.com/docs.html
Unsubscribe info:     https://cygwin.com/ml/#unsubscribe-simple