diff --git a/main.go b/main.go
index 4344720..e94fd68 100644
--- a/main.go
+++ b/main.go
@@ -31,27 +31,36 @@ func (vx *vx46) transform46(msgs4 []ipv4.Message, msgs6 []ipv6.Message) error {
 	// embed the "client" ipv4 into the src address for the packet to the upstream vxlan ipv6 endpoint
 	// the destination is the upstream vxlan endpoint
 	for i := range msgs4 {
-		cm4 := ipv4.ControlMessage{}
-		if err := cm4.Parse(msgs4[i].OOB[:msgs4[i].NN]); err != nil {
-			return err
+		if len(msgs6[i].OOB) < OOB_SIZE {
+			msgs6[i].OOB = make([]byte, OOB_SIZE)
+			msgs6[i].NN = OOB_SIZE
 		}
 
+		var hdr syscall.Cmsghdr
+		hdr.SetLen(syscall.CmsgLen(syscall.SizeofInet6Pktinfo))
+		hdr.Level = syscall.IPPROTO_IPV6
+		hdr.Type = syscall.IPV6_PKTINFO
+
+		oobdata := msgs6[i].OOB[:0]
+
+		// set cmsg header
+		oobdata = binary.NativeEndian.AppendUint64(oobdata, hdr.Len)
+		oobdata = binary.NativeEndian.AppendUint32(oobdata, uint32(hdr.Level))
+		oobdata = binary.NativeEndian.AppendUint32(oobdata, uint32(hdr.Type))
+
+		// set the address
+		// prefix + embeded v4 + port
+		oobdata = append(oobdata, vx.natprefix[:10]...)
 		inUDPAddr4 := msgs4[i].Addr.(*net.UDPAddr)
-		egressSrcAddr := vx.natprefix.As16()
-		copy(egressSrcAddr[10:14], inUDPAddr4.IP.To4()[:4]) // panics if To4 returns nil
-		binary.BigEndian.PutUint16(egressSrcAddr[14:16], uint16(inUDPAddr4.Port))
+		oobdata = append(oobdata, inUDPAddr4.IP.To4()[:4]...)
+		oobdata = binary.BigEndian.AppendUint16(oobdata, uint16(inUDPAddr4.Port))
 
-		if vx.oobkey != egressSrcAddr {
-			vx.oobkey = egressSrcAddr
-			cm6 := ipv6.ControlMessage{Src: net.IP(egressSrcAddr[:])}
-			vx.oobcache = cm6.Marshal()
-		}
+		// let the kernel decide which interface to use
+		oobdata = binary.NativeEndian.AppendUint32(oobdata, 0) // iface
 
 		msgs6[i].Buffers[0] = msgs4[i].Buffers[0][:msgs4[i].N]
-		msgs6[i].OOB = vx.oobcache
 		msgs6[i].Addr = vx.upstream
 		msgs6[i].N = msgs4[i].N
-		msgs6[i].NN = len(msgs6[i].OOB)
 	}
 
 	return nil
@@ -93,21 +102,30 @@ func (vx *vx46) transform64(msgs6 []ipv6.Message, msgs4 []ipv4.Message) error {
 	// embed the "client" ipv4 into the src address for the packet to the upstream vxlan ipv6 endpoint
 	// the destination is the upstream vxlan endpoint
 	for i := range msgs6 {
-		cm6 := ipv6.ControlMessage{}
-		if err := cm6.Parse(msgs6[i].OOB[:msgs6[i].NN]); err != nil {
-			return err
+		var hdr syscall.Cmsghdr
+		hdr.Len = binary.NativeEndian.Uint64(msgs6[i].OOB[0:])
+		hdr.Level = int32(binary.NativeEndian.Uint32(msgs6[i].OOB[8:]))
+		hdr.Type = int32(binary.NativeEndian.Uint32(msgs6[i].OOB[12:]))
+
+		if hdr.Len != uint64(syscall.CmsgLen(syscall.SizeofInet6Pktinfo)) {
+			log.Fatal("OOB: unexpected Len: ", hdr.Len, syscall.CmsgLen(syscall.SizeofInet6Pktinfo))
 		}
-		if cm6.Dst.To16() == nil {
-			return fmt.Errorf("Destination information not available")
+		if hdr.Level != syscall.IPPROTO_IPV6 {
+			log.Fatal("OOB: unexpected Level", hdr.Level)
 		}
+		if hdr.Type != syscall.IPV6_PKTINFO {
+			log.Fatal("OOB: unexpected Type", hdr.Type)
+		}
+
+		dstaddr6 := msgs6[i].OOB[16:32]
 
 		msgs4[i].Buffers[0] = msgs6[i].Buffers[0][:msgs6[i].N]
 		if msgs4[i].Addr == nil {
 			msgs4[i].Addr = &net.UDPAddr{}
 		}
 		addr := msgs4[i].Addr.(*net.UDPAddr)
-		addr.IP = cm6.Dst[10:14]
-		addr.Port = int(binary.BigEndian.Uint16(cm6.Dst[14:16]))
+		addr.IP = dstaddr6[10:14]
+		addr.Port = int(binary.BigEndian.Uint16(dstaddr6[14:16]))
 		msgs4[i].N = msgs6[i].N
 		msgs4[i].OOB = nil
 		msgs4[i].NN = 0
@@ -190,15 +208,12 @@ func (vx *vx46) forward() error {
 type vx46 struct {
 	pc4          *ipv4.PacketConn
 	pc6          *ipv6.PacketConn
-	natprefix    netip.Addr
+	natprefix    [16]byte
 	upstreamAddr netip.Addr
 	upstream     *net.UDPAddr
 	port         uint16
 	mtu          uint16
 	buffers      int
-
-	oobkey   [16]byte
-	oobcache []byte
 }
 
 func vx46forward(natprefix netip.Addr, upstreamAddr netip.Addr, port uint16, mtu uint16) error {
@@ -309,7 +324,7 @@ func main() {
 		log.Println(vx46forward(natprefix, upstreamAddr, port, mtu))
 	} else {
 		vx := vx46{
-			natprefix: natprefix,
+			natprefix: natprefix.As16(),
 			upstream: &net.UDPAddr{
 				IP:   net.IP(upstreamAddr.AsSlice()),
 				Port: *portInt,