p2p, p2p/discover, p2p/discv5: implement UDP port sharing (#15200)

This commit affects p2p/discv5 "topic discovery" by running it on
the same UDP port where the old discovery works. This is realized
by giving an "unhandled" packet channel to the old v4 discovery
packet handler where all invalid packets are sent. These packets
are then processed by v5. v5 packets are always invalid when
interpreted by v4 and vice versa. This is ensured by adding one
to the first byte of the packet hash in v5 packets.

DiscoveryV5Bootnodes is also changed to point to new bootnodes
that are implementing the changed packet format with modified
hash. Existing and new v5 bootnodes are both running on different
ports ATM.

5 files changed, 22 insertions, 33 deletions

diff --git a/p2p/discv5/net.go b/p2p/discv5/net.go
index cd9981584..f9baf126f 100644
--- a/p2p/discv5/net.go
+++ b/p2p/discv5/net.go
@@ -29,7 +29,6 @@ import (
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/crypto/sha3"
 	"github.com/ethereum/go-ethereum/log"
-	"github.com/ethereum/go-ethereum/p2p/nat"
 	"github.com/ethereum/go-ethereum/p2p/netutil"
 	"github.com/ethereum/go-ethereum/rlp"
 )
@@ -134,7 +133,7 @@ type timeoutEvent struct {
 	node *Node
 }
 
-func newNetwork(conn transport, ourPubkey ecdsa.PublicKey, natm nat.Interface, dbPath string, netrestrict *netutil.Netlist) (*Network, error) {
+func newNetwork(conn transport, ourPubkey ecdsa.PublicKey, dbPath string, netrestrict *netutil.Netlist) (*Network, error) {
 	ourID := PubkeyID(&ourPubkey)
 
 	var db *nodeDB
diff --git a/p2p/discv5/net_test.go b/p2p/discv5/net_test.go
index bd234f5ba..369282ca9 100644
--- a/p2p/discv5/net_test.go
+++ b/p2p/discv5/net_test.go
@@ -28,7 +28,7 @@ import (
 
 func TestNetwork_Lookup(t *testing.T) {
 	key, _ := crypto.GenerateKey()
-	network, err := newNetwork(lookupTestnet, key.PublicKey, nil, "", nil)
+	network, err := newNetwork(lookupTestnet, key.PublicKey, "", nil)
 	if err != nil {
 		t.Fatal(err)
 	}
diff --git a/p2p/discv5/sim_test.go b/p2p/discv5/sim_test.go
index bf57872e2..543faecd4 100644
--- a/p2p/discv5/sim_test.go
+++ b/p2p/discv5/sim_test.go
@@ -282,7 +282,7 @@ func (s *simulation) launchNode(log bool) *Network {
 	addr := &net.UDPAddr{IP: ip, Port: 30303}
 
 	transport := &simTransport{joinTime: time.Now(), sender: id, senderAddr: addr, sim: s, priv: key}
-	net, err := newNetwork(transport, key.PublicKey, nil, "<no database>", nil)
+	net, err := newNetwork(transport, key.PublicKey, "<no database>", nil)
 	if err != nil {
 		panic("cannot launch new node: " + err.Error())
 	}
diff --git a/p2p/discv5/ticket.go b/p2p/discv5/ticket.go
index b45ec4d2b..023c5000d 100644
--- a/p2p/discv5/ticket.go
+++ b/p2p/discv5/ticket.go
@@ -642,7 +642,7 @@ func (s *ticketStore) gotTopicNodes(from *Node, hash common.Hash, nodes []rpcNod
 		if ip.IsUnspecified() || ip.IsLoopback() {
 			ip = from.IP
 		}
-		n := NewNode(node.ID, ip, node.UDP-1, node.TCP-1) // subtract one from port while discv5 is running in test mode on UDPport+1
+		n := NewNode(node.ID, ip, node.UDP, node.TCP)
 		select {
 		case chn <- n:
 		default:
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: