[skissane]

Cool, did not know that. Indeed I see this in shared/afunix.h:

    #define SIO_AF_UNIX_GETPEERPID _WSAIOR(IOC_VENDOR, 256) // Returns ULONG PID of the connected peer process
    #define SIO_AF_UNIX_SETBINDPARENTPATH _WSAIOW(IOC_VENDOR, 257) // Set the parent path for bind calls
    #define SIO_AF_UNIX_SETCONNPARENTPATH _WSAIOW(IOC_VENDOR, 258) // Set the parent path for connect calls
    // NOTE: setting the parent path is not thread safe.

SIO_AF_UNIX_GETPEERPID is something I did not know about either, although apparently a bit buggy – https://github.com/microsoft/WSL/issues/4676

What does the "NOTE: setting the parent path is not thread safe" comment mean? Not thread safe if multiple threads are sharing the same socket? (Which seems like an acceptable limitation.) Or something worse than that?