EHOSTUNREACH    Errno = 23
	EIDRM           Errno = 24
	EILSEQ          Errno = 25
	EINPROGRESS     Errno = 26
	EINTR           Errno = 27
	EINVAL          Errno = 28
	EIO             Errno = 29
	EISCONN         Errno = 30
	EISDIR          Errno = 31
	ELOOP           Errno = 32
	EMFILE          Errno = 33
	EMLINK          Errno = 34
	EMSGSIZE        Errno = 35
	EMULTIHOP       Errno = 36
	ENAMETOOLONG    Errno = 37

	// because fd is not yet accessible to user,
	// so no concurrent operations are possible.
	switch err := connectFunc(fd.pfd.Sysfd, ra); err {
	case syscall.EINPROGRESS, syscall.EALREADY, syscall.EINTR:
	case nil, syscall.EISCONN:
		select {
		case <-ctx.Done():
			return nil, mapErr(ctx.Err())
		default:
		}
		if err := fd.pfd.Init(fd.net, true); err != nil {
			return nil, err
		}
		runtime.KeepAlive(fd)
		return nil, nil

	if err = af.apply(so); err != nil {
		return -1, err
	}

	if so.Err != nil {
		return -1, so.Err
	}
	if opt == syscall.SO_ERROR && (so.SocketErr == syscall.Errno(0) || so.SocketErr == syscall.EISCONN) {
		sw.smu.Lock()
		sw.stats.getLocked(so.Cookie).Connected++
		sw.smu.Unlock()
	}
	return soerr, nil