if err == nil {
			ip := from.Addr // copy from.Addr; ip escapes, so this line allocates 16 bytes
			*addr = UDPAddr{IP: ip[:], Port: from.Port, Zone: zoneCache.name(int(from.ZoneId))}
		}
	}
	if err != nil {
		// No sockaddr, so don't return UDPAddr.
		addr = nil
	}
	return n, addr, err
}

func (c *UDPConn) readFromAddrPort(b []byte) (n int, addr netip.AddrPort, err error) {
	var ip netip.Addr

}

func (sd *sysDialer) dialTCP(ctx context.Context, laddr, raddr *TCPAddr) (*TCPConn, error) {
	if h := sd.testHookDialTCP; h != nil {
		return h(ctx, sd.network, laddr, raddr)
	}
	if h := testHookDialTCP; h != nil {
		return h(ctx, sd.network, laddr, raddr)
	}
	return sd.doDialTCP(ctx, laddr, raddr)
}

func (sd *sysDialer) doDialTCP(ctx context.Context, laddr, raddr *TCPAddr) (*TCPConn, error) {
	switch sd.network {

}

func (sd *sysDialer) dialTCP(ctx context.Context, laddr, raddr *TCPAddr) (*TCPConn, error) {
	if h := sd.testHookDialTCP; h != nil {
		return h(ctx, sd.network, laddr, raddr)
	}
	if h := testHookDialTCP; h != nil {
		return h(ctx, sd.network, laddr, raddr)
	}
	return sd.doDialTCP(ctx, laddr, raddr)
}

func (sd *sysDialer) doDialTCP(ctx context.Context, laddr, raddr *TCPAddr) (*TCPConn, error) {

		return &OpError{Op: "set", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
	}
	if err := setKeepAliveIdle(c.fd, config.Idle); err != nil {
		return &OpError{Op: "set", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
	}
	if err := setKeepAliveInterval(c.fd, config.Interval); err != nil {
		return &OpError{Op: "set", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
	}

		}
	} else if err := setKeepAliveIdleAndInterval(c.fd, config.Idle, config.Interval); err != nil {
		return &OpError{Op: "set", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
	}
	if err := setKeepAliveCount(c.fd, config.Count); err != nil {
		return &OpError{Op: "set", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
	}

	return nil

		sotype = syscall.SOCK_SEQPACKET
	default:
		return nil, UnknownNetworkError(net)
	}

	switch mode {
	case "dial":
		if laddr != nil && laddr.isWildcard() {
			laddr = nil
		}
		if raddr != nil && raddr.isWildcard() {
			raddr = nil
		}
		if raddr == nil && (sotype != syscall.SOCK_DGRAM || laddr == nil) {
			return nil, errMissingAddress
		}
	case "listen":
	default:
		return nil, errors.New("unknown mode: " + mode)

	if !windows.SupportUnixSocket() {
		t.Skip("unix test")
	}
	handler := func(ls *localServer, ln Listener) {}
	for _, laddr := range []string{"", testUnixAddr(t)} {
		laddr := laddr
		taddr := testUnixAddr(t)
		ta, err := ResolveUnixAddr("unix", taddr)
		if err != nil {
			t.Fatal(err)
		}
		ln, err := ListenUnix("unix", ta)
		if err != nil {
			t.Fatal(err)
		}

		poll.CloseFunc(s)
		return nil, err
	}
	laddr := fd.addrFunc()(lsa)
	raddr := fd.addrFunc()(rsa)
	fd.net = laddr.Network()
	if err := fd.init(); err != nil {
		fd.Close()
		return nil, err
	}
	fd.setAddr(laddr, raddr)
	return fd, nil
}

func fileConn(f *os.File) (Conn, error) {
	fd, err := newFileFD(f)
	if err != nil {
		return nil, err
	}
	switch fd.laddr.(type) {
	case *TCPAddr:

			addr = s.Value
		} else if s.Name == end {
			eaddr = s.Value
		}
		if addr != 0 && eaddr != 0 {
			break
		}
	}
	if addr == 0 || eaddr < addr {
		return nil
	}
	size := eaddr - addr
	data := make([]byte, size)
	for _, prog := range f.elf.Progs {
		if prog.Vaddr <= addr && addr+size-1 <= prog.Vaddr+prog.Filesz-1 {
			if _, err := prog.ReadAt(data, int64(addr-prog.Vaddr)); err != nil {
				return nil

		return nil, mapErr(ctx.Err())
	}
}

func dialPlan9Blocking(ctx context.Context, net string, laddr, raddr Addr) (fd *netFD, err error) {
	if isWildcard(raddr) {
		raddr = toLocal(raddr, net)
	}
	f, dest, proto, name, err := startPlan9(ctx, net, raddr)
	if err != nil {
		return nil, err
	}
	if la := plan9LocalAddr(laddr); la == "" {
		err = hangupCtlWrite(ctx, proto, f, "connect "+dest)
	} else {