1 files changed, 18 insertions, 28 deletions
diff --git a/p2p/discv5/udp.go b/p2p/discv5/udp.go
index 26087cd8e..e92152076 100644
--- a/p2p/discv5/udp.go
+++ b/p2p/discv5/udp.go
@@ -37,7 +37,7 @@ const Version = 4
 // Errors
 var (
 	errPacketTooSmall   = errors.New("too small")
-	errBadHash          = errors.New("bad hash")
+	errBadPrefix        = errors.New("bad prefix")
 	errExpired          = errors.New("expired")
 	errUnsolicitedReply = errors.New("unsolicited reply")
 	errUnknownNode      = errors.New("unknown node")
@@ -145,10 +145,11 @@ type (
 	}
 )
 
-const (
-	macSize  = 256 / 8
-	sigSize  = 520 / 8
-	headSize = macSize + sigSize // space of packet frame data
+var (
+	versionPrefix     = []byte("temporary discovery v5")
+	versionPrefixSize = len(versionPrefix)
+	sigSize           = 520 / 8
+	headSize          = versionPrefixSize + sigSize // space of packet frame data
 )
 
 // Neighbors replies are sent across multiple packets to
@@ -237,12 +238,12 @@ type udp struct {
 }
 
 // ListenUDP returns a new table that listens for UDP packets on laddr.
-func ListenUDP(priv *ecdsa.PrivateKey, laddr string, natm nat.Interface, nodeDBPath string, netrestrict *netutil.Netlist) (*Network, error) {
-	transport, err := listenUDP(priv, laddr)
+func ListenUDP(priv *ecdsa.PrivateKey, conn conn, realaddr *net.UDPAddr, nodeDBPath string, netrestrict *netutil.Netlist) (*Network, error) {
+	transport, err := listenUDP(priv, conn, realaddr)
 	if err != nil {
 		return nil, err
 	}
-	net, err := newNetwork(transport, priv.PublicKey, natm, nodeDBPath, netrestrict)
+	net, err := newNetwork(transport, priv.PublicKey, nodeDBPath, netrestrict)
 	if err != nil {
 		return nil, err
 	}
@@ -251,16 +252,8 @@ func ListenUDP(priv *ecdsa.PrivateKey, laddr string, natm nat.Interface, nodeDBP
 	return net, nil
 }
 
-func listenUDP(priv *ecdsa.PrivateKey, laddr string) (*udp, error) {
-	addr, err := net.ResolveUDPAddr("udp", laddr)
-	if err != nil {
-		return nil, err
-	}
-	conn, err := net.ListenUDP("udp", addr)
-	if err != nil {
-		return nil, err
-	}
-	return &udp{conn: conn, priv: priv, ourEndpoint: makeEndpoint(addr, uint16(addr.Port))}, nil
+func listenUDP(priv *ecdsa.PrivateKey, conn conn, realaddr *net.UDPAddr) (*udp, error) {
+	return &udp{conn: conn, priv: priv, ourEndpoint: makeEndpoint(realaddr, uint16(realaddr.Port))}, nil
 }
 
 func (t *udp) localAddr() *net.UDPAddr {
@@ -372,11 +365,9 @@ func encodePacket(priv *ecdsa.PrivateKey, ptype byte, req interface{}) (p, hash
 		log.Error(fmt.Sprint("could not sign packet:", err))
 		return nil, nil, err
 	}
-	copy(packet[macSize:], sig)
-	// add the hash to the front. Note: this doesn't protect the
-	// packet in any way.
-	hash = crypto.Keccak256(packet[macSize:])
-	copy(packet, hash)
+	copy(packet, versionPrefix)
+	copy(packet[versionPrefixSize:], sig)
+	hash = crypto.Keccak256(packet[versionPrefixSize:])
 	return packet, hash, nil
 }
 
@@ -420,17 +411,16 @@ func decodePacket(buffer []byte, pkt *ingressPacket) error {
 	}
 	buf := make([]byte, len(buffer))
 	copy(buf, buffer)
-	hash, sig, sigdata := buf[:macSize], buf[macSize:headSize], buf[headSize:]
-	shouldhash := crypto.Keccak256(buf[macSize:])
-	if !bytes.Equal(hash, shouldhash) {
-		return errBadHash
+	prefix, sig, sigdata := buf[:versionPrefixSize], buf[versionPrefixSize:headSize], buf[headSize:]
+	if !bytes.Equal(prefix, versionPrefix) {
+		return errBadPrefix
 	}
 	fromID, err := recoverNodeID(crypto.Keccak256(buf[headSize:]), sig)
 	if err != nil {
 		return err
 	}
 	pkt.rawData = buf
-	pkt.hash = hash
+	pkt.hash = crypto.Keccak256(buf[versionPrefixSize:])
 	pkt.remoteID = fromID
 	switch pkt.ev = nodeEvent(sigdata[0]); pkt.ev {
 	case pingPacket: