netListenUnixPosix

fn netListenUnixPosix(
    userdata: ?*anyopaque,
    address: *const net.UnixAddress,
    options: net.UnixAddress.ListenOptions,
) net.UnixAddress.ListenError!net.Socket.Handle {
    if (!net.has_unix_sockets) return error.AddressFamilyUnsupported;
    const t: *Threaded = @ptrCast(@alignCast(userdata));
    _ = t;
    const socket_fd = openSocketPosix(posix.AF.UNIX, .{ .mode = .stream }) catch |err| switch (err) {
        error.ProtocolUnsupportedBySystem => return error.AddressFamilyUnsupported,
        error.ProtocolUnsupportedByAddressFamily => return error.AddressFamilyUnsupported,
        error.SocketModeUnsupported => return error.AddressFamilyUnsupported,
        error.OptionUnsupported => return error.Unexpected,
        else => |e| return e,
    };
    errdefer closeFd(socket_fd);

    var storage: UnixAddress = undefined;
    const addr_len = addressUnixToPosix(address, &storage);
    try posixBindUnix(socket_fd, &storage.any, addr_len);

    const syscall: Syscall = try .start();
    while (true) {
        switch (posix.errno(posix.system.listen(socket_fd, options.kernel_backlog))) {
            .SUCCESS => {
                syscall.finish();
                break;
            },
            .INTR => {
                try syscall.checkCancel();
                continue;
            },
            .ADDRINUSE => return syscall.fail(error.AddressInUse),
            .BADF => |err| return syscall.errnoBug(err), // File descriptor used after closed.
            else => |err| return syscall.unexpectedErrno(err),
        }
    }

    return socket_fd;
}