buf := make([]byte, udpHeaderSize+len(b))
	i := copy(buf, h.Bytes())
	copy(buf[i:], b)
	if _, err := c.fd.Write(buf); err != nil {
		return 0, err
	}
	return len(b), nil
}

func (c *UDPConn) writeToAddrPort(b []byte, addr netip.AddrPort) (int, error) {
	return c.writeTo(b, UDPAddrFromAddrPort(addr)) // TODO: optimize instead of allocating
}

func (c *UDPConn) writeMsg(b, oob []byte, addr *UDPAddr) (n, oobn int, err error) {

		if err != nil {
			return 0, err
		}
		return c.fd.writeToInet6(b, &sa)
	default:
		return 0, &AddrError{Err: "invalid address family", Addr: addr.IP.String()}
	}
}

func (c *UDPConn) writeToAddrPort(b []byte, addr netip.AddrPort) (int, error) {
	if c.fd.isConnected {
		return 0, ErrWriteToConnected
	}
	if !addr.IsValid() {
		return 0, errMissingAddress
	}

	switch c.fd.family {

// WriteToUDPAddrPort acts like WriteTo but takes a netip.AddrPort.
func (c *UDPConn) WriteToUDPAddrPort(b []byte, addr netip.AddrPort) (int, error) {
	if !c.ok() {
		return 0, syscall.EINVAL
	}
	n, err := c.writeToAddrPort(b, addr)
	if err != nil {
		err = &OpError{Op: "write", Net: c.fd.net, Source: c.fd.laddr, Addr: addrPortUDPAddr{addr}, Err: err}
	}
	return n, err
}

// WriteTo implements the PacketConn WriteTo method.