p2p/discover: move discv4 encoding to new 'v4wire' package (#21147)

This moves all v4 protocol definitions to a new package, p2p/discover/v4wire.
The new package will be used for low-level protocol tests.

p2p/discover/node.go

@@ -61,17 +61,6 @@ func (e encPubkey) id() enode.ID {
 	return enode.ID(crypto.Keccak256Hash(e[:]))
 }
 
-// recoverNodeKey computes the public key used to sign the
-// given hash from the signature.
-func recoverNodeKey(hash, sig []byte) (key encPubkey, err error) {
-	pubkey, err := crypto.Ecrecover(hash, sig)
-	if err != nil {
-		return key, err
-	}
-	copy(key[:], pubkey[1:])
-	return key, nil
-}
-
 func wrapNode(n *enode.Node) *node {
 	return &node{Node: *n}
 }

p2p/discover/v4_lookup_test.go

@@ -24,6 +24,7 @@ import (
 	"testing"
 
 	"github.com/ethereum/go-ethereum/crypto"
+	"github.com/ethereum/go-ethereum/p2p/discover/v4wire"
 	"github.com/ethereum/go-ethereum/p2p/enode"
 	"github.com/ethereum/go-ethereum/p2p/enr"
 )
@@ -135,15 +136,15 @@ func TestUDPv4_LookupIteratorClose(t *testing.T) {
 
 func serveTestnet(test *udpTest, testnet *preminedTestnet) {
 	for done := false; !done; {
-		done = test.waitPacketOut(func(p packetV4, to *net.UDPAddr, hash []byte) {
+		done = test.waitPacketOut(func(p v4wire.Packet, to *net.UDPAddr, hash []byte) {
 			n, key := testnet.nodeByAddr(to)
 			switch p.(type) {
-			case *pingV4:
-				test.packetInFrom(nil, key, to, &pongV4{Expiration: futureExp, ReplyTok: hash})
-			case *findnodeV4:
+			case *v4wire.Ping:
+				test.packetInFrom(nil, key, to, &v4wire.Pong{Expiration: futureExp, ReplyTok: hash})
+			case *v4wire.Findnode:
 				dist := enode.LogDist(n.ID(), testnet.target.id())
 				nodes := testnet.nodesAtDistance(dist - 1)
-				test.packetInFrom(nil, key, to, &neighborsV4{Expiration: futureExp, Nodes: nodes})
+				test.packetInFrom(nil, key, to, &v4wire.Neighbors{Expiration: futureExp, Nodes: nodes})
 			}
 		})
 	}
@@ -270,8 +271,8 @@ func (tn *preminedTestnet) nodeByAddr(addr *net.UDPAddr) (*enode.Node, *ecdsa.Pr
 	return tn.node(dist, index), key
 }
 
-func (tn *preminedTestnet) nodesAtDistance(dist int) []rpcNode {
-	result := make([]rpcNode, len(tn.dists[dist]))
+func (tn *preminedTestnet) nodesAtDistance(dist int) []v4wire.Node {
+	result := make([]v4wire.Node, len(tn.dists[dist]))
 	for i := range result {
 		result[i] = nodeToRPC(wrapNode(tn.node(dist, i)))
 	}

p2p/discover/v4_udp.go

@@ -31,16 +31,14 @@ import (
 
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/log"
+	"github.com/ethereum/go-ethereum/p2p/discover/v4wire"
 	"github.com/ethereum/go-ethereum/p2p/enode"
-	"github.com/ethereum/go-ethereum/p2p/enr"
 	"github.com/ethereum/go-ethereum/p2p/netutil"
 	"github.com/ethereum/go-ethereum/rlp"
 )
 
 // Errors
 var (
-	errPacketTooSmall   = errors.New("too small")
-	errBadHash          = errors.New("bad hash")
 	errExpired          = errors.New("expired")
 	errUnsolicitedReply = errors.New("unsolicited reply")
 	errUnknownNode      = errors.New("unknown node")
@@ -66,135 +64,6 @@ const (
 	maxPacketSize = 1280
 )
 
-// RPC packet types
-const (
-	p_pingV4 = iota + 1 // zero is 'reserved'
-	p_pongV4
-	p_findnodeV4
-	p_neighborsV4
-	p_enrRequestV4
-	p_enrResponseV4
-)
-
-// RPC request structures
-type (
-	pingV4 struct {
-		senderKey *ecdsa.PublicKey // filled in by preverify
-
-		Version    uint
-		From, To   rpcEndpoint
-		Expiration uint64
-		// Ignore additional fields (for forward compatibility).
-		Rest []rlp.RawValue `rlp:"tail"`
-	}
-
-	// pongV4 is the reply to pingV4.
-	pongV4 struct {
-		// This field should mirror the UDP envelope address
-		// of the ping packet, which provides a way to discover the
-		// the external address (after NAT).
-		To rpcEndpoint
-
-		ReplyTok   []byte // This contains the hash of the ping packet.
-		Expiration uint64 // Absolute timestamp at which the packet becomes invalid.
-		// Ignore additional fields (for forward compatibility).
-		Rest []rlp.RawValue `rlp:"tail"`
-	}
-
-	// findnodeV4 is a query for nodes close to the given target.
-	findnodeV4 struct {
-		Target     encPubkey
-		Expiration uint64
-		// Ignore additional fields (for forward compatibility).
-		Rest []rlp.RawValue `rlp:"tail"`
-	}
-
-	// neighborsV4 is the reply to findnodeV4.
-	neighborsV4 struct {
-		Nodes      []rpcNode
-		Expiration uint64
-		// Ignore additional fields (for forward compatibility).
-		Rest []rlp.RawValue `rlp:"tail"`
-	}
-
-	// enrRequestV4 queries for the remote node's record.
-	enrRequestV4 struct {
-		Expiration uint64
-		// Ignore additional fields (for forward compatibility).
-		Rest []rlp.RawValue `rlp:"tail"`
-	}
-
-	// enrResponseV4 is the reply to enrRequestV4.
-	enrResponseV4 struct {
-		ReplyTok []byte // Hash of the enrRequest packet.
-		Record   enr.Record
-		// Ignore additional fields (for forward compatibility).
-		Rest []rlp.RawValue `rlp:"tail"`
-	}
-
-	rpcNode struct {
-		IP  net.IP // len 4 for IPv4 or 16 for IPv6
-		UDP uint16 // for discovery protocol
-		TCP uint16 // for RLPx protocol
-		ID  encPubkey
-	}
-
-	rpcEndpoint struct {
-		IP  net.IP // len 4 for IPv4 or 16 for IPv6
-		UDP uint16 // for discovery protocol
-		TCP uint16 // for RLPx protocol
-	}
-)
-
-// packetV4 is implemented by all v4 protocol messages.
-type packetV4 interface {
-	// preverify checks whether the packet is valid and should be handled at all.
-	preverify(t *UDPv4, from *net.UDPAddr, fromID enode.ID, fromKey encPubkey) error
-	// handle handles the packet.
-	handle(t *UDPv4, from *net.UDPAddr, fromID enode.ID, mac []byte)
-	// packet name and type for logging purposes.
-	name() string
-	kind() byte
-}
-
-func makeEndpoint(addr *net.UDPAddr, tcpPort uint16) rpcEndpoint {
-	ip := net.IP{}
-	if ip4 := addr.IP.To4(); ip4 != nil {
-		ip = ip4
-	} else if ip6 := addr.IP.To16(); ip6 != nil {
-		ip = ip6
-	}
-	return rpcEndpoint{IP: ip, UDP: uint16(addr.Port), TCP: tcpPort}
-}
-
-func (t *UDPv4) nodeFromRPC(sender *net.UDPAddr, rn rpcNode) (*node, error) {
-	if rn.UDP <= 1024 {
-		return nil, errLowPort
-	}
-	if err := netutil.CheckRelayIP(sender.IP, rn.IP); err != nil {
-		return nil, err
-	}
-	if t.netrestrict != nil && !t.netrestrict.Contains(rn.IP) {
-		return nil, errors.New("not contained in netrestrict whitelist")
-	}
-	key, err := decodePubkey(crypto.S256(), rn.ID)
-	if err != nil {
-		return nil, err
-	}
-	n := wrapNode(enode.NewV4(key, rn.IP, int(rn.TCP), int(rn.UDP)))
-	err = n.ValidateComplete()
-	return n, err
-}
-
-func nodeToRPC(n *node) rpcNode {
-	var key ecdsa.PublicKey
-	var ekey encPubkey
-	if err := n.Load((*enode.Secp256k1)(&key)); err == nil {
-		ekey = encodePubkey(&key)
-	}
-	return rpcNode{ID: ekey, IP: n.IP(), UDP: uint16(n.UDP()), TCP: uint16(n.TCP())}
-}
-
 // UDPv4 implements the v4 wire protocol.
 type UDPv4 struct {
 	conn        UDPConn
@@ -243,16 +112,16 @@ type replyMatcher struct {
 
 	// reply contains the most recent reply. This field is safe for reading after errc has
 	// received a value.
-	reply packetV4
+	reply v4wire.Packet
 }
 
-type replyMatchFunc func(interface{}) (matched bool, requestDone bool)
+type replyMatchFunc func(v4wire.Packet) (matched bool, requestDone bool)
 
 // reply is a reply packet from a certain node.
 type reply struct {
 	from enode.ID
 	ip   net.IP
-	data packetV4
+	data v4wire.Packet
 	// loop indicates whether there was
 	// a matching request by sending on this channel.
 	matched chan<- bool
@@ -332,10 +201,10 @@ func (t *UDPv4) Resolve(n *enode.Node) *enode.Node {
 	return n
 }
 
-func (t *UDPv4) ourEndpoint() rpcEndpoint {
+func (t *UDPv4) ourEndpoint() v4wire.Endpoint {
 	n := t.Self()
 	a := &net.UDPAddr{IP: n.IP(), Port: n.UDP()}
-	return makeEndpoint(a, uint16(n.TCP()))
+	return v4wire.NewEndpoint(a, uint16(n.TCP()))
 }
 
 // Ping sends a ping message to the given node.
@@ -348,7 +217,7 @@ func (t *UDPv4) Ping(n *enode.Node) error {
 func (t *UDPv4) ping(n *enode.Node) (seq uint64, err error) {
 	rm := t.sendPing(n.ID(), &net.UDPAddr{IP: n.IP(), Port: n.UDP()}, nil)
 	if err = <-rm.errc; err == nil {
-		seq = seqFromTail(rm.reply.(*pongV4).Rest)
+		seq = rm.reply.(*v4wire.Pong).ENRSeq()
 	}
 	return seq, err
 }
@@ -357,7 +226,7 @@ func (t *UDPv4) ping(n *enode.Node) (seq uint64, err error) {
 // when the reply arrives.
 func (t *UDPv4) sendPing(toid enode.ID, toaddr *net.UDPAddr, callback func()) *replyMatcher {
 	req := t.makePing(toaddr)
-	packet, hash, err := t.encode(t.priv, req)
+	packet, hash, err := v4wire.Encode(t.priv, req)
 	if err != nil {
 		errc := make(chan error, 1)
 		errc <- err
@@ -365,8 +234,8 @@ func (t *UDPv4) sendPing(toid enode.ID, toaddr *net.UDPAddr, callback func()) *r
 	}
 	// Add a matcher for the reply to the pending reply queue. Pongs are matched if they
 	// reference the ping we're about to send.
-	rm := t.pending(toid, toaddr.IP, p_pongV4, func(p interface{}) (matched bool, requestDone bool) {
-		matched = bytes.Equal(p.(*pongV4).ReplyTok, hash)
+	rm := t.pending(toid, toaddr.IP, v4wire.PongPacket, func(p v4wire.Packet) (matched bool, requestDone bool) {
+		matched = bytes.Equal(p.(*v4wire.Pong).ReplyTok, hash)
 		if matched && callback != nil {
 			callback()
 		}
@@ -374,16 +243,16 @@ func (t *UDPv4) sendPing(toid enode.ID, toaddr *net.UDPAddr, callback func()) *r
 	})
 	// Send the packet.
 	t.localNode.UDPContact(toaddr)
-	t.write(toaddr, toid, req.name(), packet)
+	t.write(toaddr, toid, req.Name(), packet)
 	return rm
 }
 
-func (t *UDPv4) makePing(toaddr *net.UDPAddr) *pingV4 {
+func (t *UDPv4) makePing(toaddr *net.UDPAddr) *v4wire.Ping {
 	seq, _ := rlp.EncodeToBytes(t.localNode.Node().Seq())
-	return &pingV4{
+	return &v4wire.Ping{
 		Version:    4,
 		From:       t.ourEndpoint(),
-		To:         makeEndpoint(toaddr, 0),
+		To:         v4wire.NewEndpoint(toaddr, 0),
 		Expiration: uint64(time.Now().Add(expiration).Unix()),
 		Rest:       []rlp.RawValue{seq},
 	}
@@ -422,23 +291,24 @@ func (t *UDPv4) newRandomLookup(ctx context.Context) *lookup {
 
 func (t *UDPv4) newLookup(ctx context.Context, targetKey encPubkey) *lookup {
 	target := enode.ID(crypto.Keccak256Hash(targetKey[:]))
+	ekey := v4wire.Pubkey(targetKey)
 	it := newLookup(ctx, t.tab, target, func(n *node) ([]*node, error) {
-		return t.findnode(n.ID(), n.addr(), targetKey)
+		return t.findnode(n.ID(), n.addr(), ekey)
 	})
 	return it
 }
 
 // findnode sends a findnode request to the given node and waits until
 // the node has sent up to k neighbors.
-func (t *UDPv4) findnode(toid enode.ID, toaddr *net.UDPAddr, target encPubkey) ([]*node, error) {
+func (t *UDPv4) findnode(toid enode.ID, toaddr *net.UDPAddr, target v4wire.Pubkey) ([]*node, error) {
 	t.ensureBond(toid, toaddr)
 
 	// Add a matcher for 'neighbours' replies to the pending reply queue. The matcher is
 	// active until enough nodes have been received.
 	nodes := make([]*node, 0, bucketSize)
 	nreceived := 0
-	rm := t.pending(toid, toaddr.IP, p_neighborsV4, func(r interface{}) (matched bool, requestDone bool) {
-		reply := r.(*neighborsV4)
+	rm := t.pending(toid, toaddr.IP, v4wire.NeighborsPacket, func(r v4wire.Packet) (matched bool, requestDone bool) {
+		reply := r.(*v4wire.Neighbors)
 		for _, rn := range reply.Nodes {
 			nreceived++
 			n, err := t.nodeFromRPC(toaddr, rn)
@@ -450,7 +320,7 @@ func (t *UDPv4) findnode(toid enode.ID, toaddr *net.UDPAddr, target encPubkey) (
 		}
 		return true, nreceived >= bucketSize
 	})
-	t.send(toaddr, toid, &findnodeV4{
+	t.send(toaddr, toid, &v4wire.Findnode{
 		Target:     target,
 		Expiration: uint64(time.Now().Add(expiration).Unix()),
 	})
@@ -462,26 +332,27 @@ func (t *UDPv4) RequestENR(n *enode.Node) (*enode.Node, error) {
 	addr := &net.UDPAddr{IP: n.IP(), Port: n.UDP()}
 	t.ensureBond(n.ID(), addr)
 
-	req := &enrRequestV4{
+	req := &v4wire.ENRRequest{
 		Expiration: uint64(time.Now().Add(expiration).Unix()),
 	}
-	packet, hash, err := t.encode(t.priv, req)
+	packet, hash, err := v4wire.Encode(t.priv, req)
 	if err != nil {
 		return nil, err
 	}
+
 	// Add a matcher for the reply to the pending reply queue. Responses are matched if
 	// they reference the request we're about to send.
-	rm := t.pending(n.ID(), addr.IP, p_enrResponseV4, func(r interface{}) (matched bool, requestDone bool) {
-		matched = bytes.Equal(r.(*enrResponseV4).ReplyTok, hash)
+	rm := t.pending(n.ID(), addr.IP, v4wire.ENRResponsePacket, func(r v4wire.Packet) (matched bool, requestDone bool) {
+		matched = bytes.Equal(r.(*v4wire.ENRResponse).ReplyTok, hash)
 		return matched, matched
 	})
 	// Send the packet and wait for the reply.
-	t.write(addr, n.ID(), req.name(), packet)
+	t.write(addr, n.ID(), req.Name(), packet)
 	if err := <-rm.errc; err != nil {
 		return nil, err
 	}
 	// Verify the response record.
-	respN, err := enode.New(enode.ValidSchemes, &rm.reply.(*enrResponseV4).Record)
+	respN, err := enode.New(enode.ValidSchemes, &rm.reply.(*v4wire.ENRResponse).Record)
 	if err != nil {
 		return nil, err
 	}
@@ -513,7 +384,7 @@ func (t *UDPv4) pending(id enode.ID, ip net.IP, ptype byte, callback replyMatchF
 
 // handleReply dispatches a reply packet, invoking reply matchers. It returns
 // whether any matcher considered the packet acceptable.
-func (t *UDPv4) handleReply(from enode.ID, fromIP net.IP, req packetV4) bool {
+func (t *UDPv4) handleReply(from enode.ID, fromIP net.IP, req v4wire.Packet) bool {
 	matched := make(chan bool, 1)
 	select {
 	case t.gotreply <- reply{from, fromIP, req, matched}:
@@ -579,7 +450,7 @@ func (t *UDPv4) loop() {
 			var matched bool // whether any replyMatcher considered the reply acceptable.
 			for el := plist.Front(); el != nil; el = el.Next() {
 				p := el.Value.(*replyMatcher)
-				if p.from == r.from && p.ptype == r.data.kind() && p.ip.Equal(r.ip) {
+				if p.from == r.from && p.ptype == r.data.Kind() && p.ip.Equal(r.ip) {
 					ok, requestDone := p.callback(r.data)
 					matched = matched || ok
 					// Remove the matcher if callback indicates that all replies have been received.
@@ -618,44 +489,12 @@ func (t *UDPv4) loop() {
 	}
 }
 
-const (
-	macSize  = 256 / 8
-	sigSize  = 520 / 8
-	headSize = macSize + sigSize // space of packet frame data
-)
-
-var (
-	headSpace = make([]byte, headSize)
-
-	// Neighbors replies are sent across multiple packets to
-	// stay below the packet size limit. We compute the maximum number
-	// of entries by stuffing a packet until it grows too large.
-	maxNeighbors int
-)
-
-func init() {
-	p := neighborsV4{Expiration: ^uint64(0)}
-	maxSizeNode := rpcNode{IP: make(net.IP, 16), UDP: ^uint16(0), TCP: ^uint16(0)}
-	for n := 0; ; n++ {
-		p.Nodes = append(p.Nodes, maxSizeNode)
-		size, _, err := rlp.EncodeToReader(p)
-		if err != nil {
-			// If this ever happens, it will be caught by the unit tests.
-			panic("cannot encode: " + err.Error())
-		}
-		if headSize+size+1 >= maxPacketSize {
-			maxNeighbors = n
-			break
-		}
-	}
-}
-
-func (t *UDPv4) send(toaddr *net.UDPAddr, toid enode.ID, req packetV4) ([]byte, error) {
-	packet, hash, err := t.encode(t.priv, req)
+func (t *UDPv4) send(toaddr *net.UDPAddr, toid enode.ID, req v4wire.Packet) ([]byte, error) {
+	packet, hash, err := v4wire.Encode(t.priv, req)
 	if err != nil {
 		return hash, err
 	}
-	return hash, t.write(toaddr, toid, req.name(), packet)
+	return hash, t.write(toaddr, toid, req.Name(), packet)
 }
 
 func (t *UDPv4) write(toaddr *net.UDPAddr, toid enode.ID, what string, packet []byte) error {
@@ -664,30 +503,6 @@ func (t *UDPv4) write(toaddr *net.UDPAddr, toid enode.ID, what string, packet []
 	return err
 }
 
-func (t *UDPv4) encode(priv *ecdsa.PrivateKey, req packetV4) (packet, hash []byte, err error) {
-	name := req.name()
-	b := new(bytes.Buffer)
-	b.Write(headSpace)
-	b.WriteByte(req.kind())
-	if err := rlp.Encode(b, req); err != nil {
-		t.log.Error(fmt.Sprintf("Can't encode %s packet", name), "err", err)
-		return nil, nil, err
-	}
-	packet = b.Bytes()
-	sig, err := crypto.Sign(crypto.Keccak256(packet[headSize:]), priv)
-	if err != nil {
-		t.log.Error(fmt.Sprintf("Can't sign %s packet", name), "err", 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. Our public key will be part of this hash in
-	// The future.
-	hash = crypto.Keccak256(packet[macSize:])
-	copy(packet, hash)
-	return packet, hash, nil
-}
-
 // readLoop runs in its own goroutine. it handles incoming UDP packets.
 func (t *UDPv4) readLoop(unhandled chan<- ReadPacket) {
 	defer t.wg.Done()
@@ -719,58 +534,23 @@ func (t *UDPv4) readLoop(unhandled chan<- ReadPacket) {
 }
 
 func (t *UDPv4) handlePacket(from *net.UDPAddr, buf []byte) error {
-	packet, fromKey, hash, err := decodeV4(buf)
+	rawpacket, fromKey, hash, err := v4wire.Decode(buf)
 	if err != nil {
 		t.log.Debug("Bad discv4 packet", "addr", from, "err", err)
 		return err
 	}
-	fromID := fromKey.id()
-	if err == nil {
-		err = packet.preverify(t, from, fromID, fromKey)
+	packet := t.wrapPacket(rawpacket)
+	fromID := fromKey.ID()
+	if err == nil && packet.preverify != nil {
+		err = packet.preverify(packet, from, fromID, fromKey)
 	}
-	t.log.Trace("<< "+packet.name(), "id", fromID, "addr", from, "err", err)
-	if err == nil {
-		packet.handle(t, from, fromID, hash)
+	t.log.Trace("<< "+packet.Name(), "id", fromID, "addr", from, "err", err)
+	if err == nil && packet.handle != nil {
+		packet.handle(packet, from, fromID, hash)
 	}
 	return err
 }
 
-func decodeV4(buf []byte) (packetV4, encPubkey, []byte, error) {
-	if len(buf) < headSize+1 {
-		return nil, encPubkey{}, nil, errPacketTooSmall
-	}
-	hash, sig, sigdata := buf[:macSize], buf[macSize:headSize], buf[headSize:]
-	shouldhash := crypto.Keccak256(buf[macSize:])
-	if !bytes.Equal(hash, shouldhash) {
-		return nil, encPubkey{}, nil, errBadHash
-	}
-	fromKey, err := recoverNodeKey(crypto.Keccak256(buf[headSize:]), sig)
-	if err != nil {
-		return nil, fromKey, hash, err
-	}
-
-	var req packetV4
-	switch ptype := sigdata[0]; ptype {
-	case p_pingV4:
-		req = new(pingV4)
-	case p_pongV4:
-		req = new(pongV4)
-	case p_findnodeV4:
-		req = new(findnodeV4)
-	case p_neighborsV4:
-		req = new(neighborsV4)
-	case p_enrRequestV4:
-		req = new(enrRequestV4)
-	case p_enrResponseV4:
-		req = new(enrResponseV4)
-	default:
-		return nil, fromKey, hash, fmt.Errorf("unknown type: %d", ptype)
-	}
-	s := rlp.NewStream(bytes.NewReader(sigdata[1:]), 0)
-	err = s.Decode(req)
-	return req, fromKey, hash, err
-}
-
 // checkBond checks if the given node has a recent enough endpoint proof.
 func (t *UDPv4) checkBond(id enode.ID, ip net.IP) bool {
 	return time.Since(t.db.LastPongReceived(id, ip)) < bondExpiration
@@ -788,49 +568,99 @@ func (t *UDPv4) ensureBond(toid enode.ID, toaddr *net.UDPAddr) {
 	}
 }
 
-// expired checks whether the given UNIX time stamp is in the past.
-func expired(ts uint64) bool {
-	return time.Unix(int64(ts), 0).Before(time.Now())
+func (t *UDPv4) nodeFromRPC(sender *net.UDPAddr, rn v4wire.Node) (*node, error) {
+	if rn.UDP <= 1024 {
+		return nil, errLowPort
+	}
+	if err := netutil.CheckRelayIP(sender.IP, rn.IP); err != nil {
+		return nil, err
+	}
+	if t.netrestrict != nil && !t.netrestrict.Contains(rn.IP) {
+		return nil, errors.New("not contained in netrestrict whitelist")
+	}
+	key, err := v4wire.DecodePubkey(crypto.S256(), rn.ID)
+	if err != nil {
+		return nil, err
+	}
+	n := wrapNode(enode.NewV4(key, rn.IP, int(rn.TCP), int(rn.UDP)))
+	err = n.ValidateComplete()
+	return n, err
 }
 
-func seqFromTail(tail []rlp.RawValue) uint64 {
-	if len(tail) == 0 {
-		return 0
-	}
-	var seq uint64
-	rlp.DecodeBytes(tail[0], &seq)
-	return seq
+func nodeToRPC(n *node) v4wire.Node {
+	var key ecdsa.PublicKey
+	var ekey v4wire.Pubkey
+	if err := n.Load((*enode.Secp256k1)(&key)); err == nil {
+		ekey = v4wire.EncodePubkey(&key)
+	}
+	return v4wire.Node{ID: ekey, IP: n.IP(), UDP: uint16(n.UDP()), TCP: uint16(n.TCP())}
+}
+
+// wrapPacket returns the handler functions applicable to a packet.
+func (t *UDPv4) wrapPacket(p v4wire.Packet) *packetHandlerV4 {
+	var h packetHandlerV4
+	h.Packet = p
+	switch p.(type) {
+	case *v4wire.Ping:
+		h.preverify = t.verifyPing
+		h.handle = t.handlePing
+	case *v4wire.Pong:
+		h.preverify = t.verifyPong
+	case *v4wire.Findnode:
+		h.preverify = t.verifyFindnode
+		h.handle = t.handleFindnode
+	case *v4wire.Neighbors:
+		h.preverify = t.verifyNeighbors
+	case *v4wire.ENRRequest:
+		h.preverify = t.verifyENRRequest
+		h.handle = t.handleENRRequest
+	case *v4wire.ENRResponse:
+		h.preverify = t.verifyENRResponse
+	}
+	return &h
+}
+
+// packetHandlerV4 wraps a packet with handler functions.
+type packetHandlerV4 struct {
+	v4wire.Packet
+	senderKey *ecdsa.PublicKey // used for ping
+
+	// preverify checks whether the packet is valid and should be handled at all.
+	preverify func(p *packetHandlerV4, from *net.UDPAddr, fromID enode.ID, fromKey v4wire.Pubkey) error
+	// handle handles the packet.
+	handle func(req *packetHandlerV4, from *net.UDPAddr, fromID enode.ID, mac []byte)
 }
 
 // PING/v4
 
-func (req *pingV4) name() string { return "PING/v4" }
-func (req *pingV4) kind() byte   { return p_pingV4 }
+func (t *UDPv4) verifyPing(h *packetHandlerV4, from *net.UDPAddr, fromID enode.ID, fromKey v4wire.Pubkey) error {
+	req := h.Packet.(*v4wire.Ping)
 
-func (req *pingV4) preverify(t *UDPv4, from *net.UDPAddr, fromID enode.ID, fromKey encPubkey) error {
-	if expired(req.Expiration) {
-		return errExpired
-	}
-	key, err := decodePubkey(crypto.S256(), fromKey)
+	senderKey, err := v4wire.DecodePubkey(crypto.S256(), fromKey)
 	if err != nil {
-		return errors.New("invalid public key")
+		return err
+	}
+	if v4wire.Expired(req.Expiration) {
+		return errExpired
 	}
-	req.senderKey = key
+	h.senderKey = senderKey
 	return nil
 }
 
-func (req *pingV4) handle(t *UDPv4, from *net.UDPAddr, fromID enode.ID, mac []byte) {
+func (t *UDPv4) handlePing(h *packetHandlerV4, from *net.UDPAddr, fromID enode.ID, mac []byte) {
+	req := h.Packet.(*v4wire.Ping)
+
 	// Reply.
 	seq, _ := rlp.EncodeToBytes(t.localNode.Node().Seq())
-	t.send(from, fromID, &pongV4{
-		To:         makeEndpoint(from, req.From.TCP),
+	t.send(from, fromID, &v4wire.Pong{
+		To:         v4wire.NewEndpoint(from, req.From.TCP),
 		ReplyTok:   mac,
 		Expiration: uint64(time.Now().Add(expiration).Unix()),
 		Rest:       []rlp.RawValue{seq},
 	})
 
 	// Ping back if our last pong on file is too far in the past.
-	n := wrapNode(enode.NewV4(req.senderKey, from.IP, int(req.From.TCP), from.Port))
+	n := wrapNode(enode.NewV4(h.senderKey, from.IP, int(req.From.TCP), from.Port))
 	if time.Since(t.db.LastPongReceived(n.ID(), from.IP)) > bondExpiration {
 		t.sendPing(fromID, from, func() {
 			t.tab.addVerifiedNode(n)
@@ -846,31 +676,26 @@ func (req *pingV4) handle(t *UDPv4, from *net.UDPAddr, fromID enode.ID, mac []by
 
 // PONG/v4
 
-func (req *pongV4) name() string { return "PONG/v4" }
-func (req *pongV4) kind() byte   { return p_pongV4 }
+func (t *UDPv4) verifyPong(h *packetHandlerV4, from *net.UDPAddr, fromID enode.ID, fromKey v4wire.Pubkey) error {
+	req := h.Packet.(*v4wire.Pong)
 
-func (req *pongV4) preverify(t *UDPv4, from *net.UDPAddr, fromID enode.ID, fromKey encPubkey) error {
-	if expired(req.Expiration) {
+	if v4wire.Expired(req.Expiration) {
 		return errExpired
 	}
 	if !t.handleReply(fromID, from.IP, req) {
 		return errUnsolicitedReply
 	}
-	return nil
-}
-
-func (req *pongV4) handle(t *UDPv4, from *net.UDPAddr, fromID enode.ID, mac []byte) {
 	t.localNode.UDPEndpointStatement(from, &net.UDPAddr{IP: req.To.IP, Port: int(req.To.UDP)})
 	t.db.UpdateLastPongReceived(fromID, from.IP, time.Now())
+	return nil
 }
 
 // FINDNODE/v4
 
-func (req *findnodeV4) name() string { return "FINDNODE/v4" }
-func (req *findnodeV4) kind() byte   { return p_findnodeV4 }
+func (t *UDPv4) verifyFindnode(h *packetHandlerV4, from *net.UDPAddr, fromID enode.ID, fromKey v4wire.Pubkey) error {
+	req := h.Packet.(*v4wire.Findnode)
 
-func (req *findnodeV4) preverify(t *UDPv4, from *net.UDPAddr, fromID enode.ID, fromKey encPubkey) error {
-	if expired(req.Expiration) {
+	if v4wire.Expired(req.Expiration) {
 		return errExpired
 	}
 	if !t.checkBond(fromID, from.IP) {
@@ -885,7 +710,9 @@ func (req *findnodeV4) preverify(t *UDPv4, from *net.UDPAddr, fromID enode.ID, f
 	return nil
 }
 
-func (req *findnodeV4) handle(t *UDPv4, from *net.UDPAddr, fromID enode.ID, mac []byte) {
+func (t *UDPv4) handleFindnode(h *packetHandlerV4, from *net.UDPAddr, fromID enode.ID, mac []byte) {
+	req := h.Packet.(*v4wire.Findnode)
+
 	// Determine closest nodes.
 	target := enode.ID(crypto.Keccak256Hash(req.Target[:]))
 	t.tab.mutex.Lock()
@@ -894,13 +721,13 @@ func (req *findnodeV4) handle(t *UDPv4, from *net.UDPAddr, fromID enode.ID, mac
 
 	// Send neighbors in chunks with at most maxNeighbors per packet
 	// to stay below the packet size limit.
-	p := neighborsV4{Expiration: uint64(time.Now().Add(expiration).Unix())}
+	p := v4wire.Neighbors{Expiration: uint64(time.Now().Add(expiration).Unix())}
 	var sent bool
 	for _, n := range closest {
 		if netutil.CheckRelayIP(from.IP, n.IP()) == nil {
 			p.Nodes = append(p.Nodes, nodeToRPC(n))
 		}
-		if len(p.Nodes) == maxNeighbors {
+		if len(p.Nodes) == v4wire.MaxNeighbors {
 			t.send(from, fromID, &p)
 			p.Nodes = p.Nodes[:0]
 			sent = true
@@ -913,29 +740,24 @@ func (req *findnodeV4) handle(t *UDPv4, from *net.UDPAddr, fromID enode.ID, mac
 
 // NEIGHBORS/v4
 
-func (req *neighborsV4) name() string { return "NEIGHBORS/v4" }
-func (req *neighborsV4) kind() byte   { return p_neighborsV4 }
+func (t *UDPv4) verifyNeighbors(h *packetHandlerV4, from *net.UDPAddr, fromID enode.ID, fromKey v4wire.Pubkey) error {
+	req := h.Packet.(*v4wire.Neighbors)
 
-func (req *neighborsV4) preverify(t *UDPv4, from *net.UDPAddr, fromID enode.ID, fromKey encPubkey) error {
-	if expired(req.Expiration) {
+	if v4wire.Expired(req.Expiration) {
 		return errExpired
 	}
-	if !t.handleReply(fromID, from.IP, req) {
+	if !t.handleReply(fromID, from.IP, h.Packet) {
 		return errUnsolicitedReply
 	}
 	return nil
 }
 
-func (req *neighborsV4) handle(t *UDPv4, from *net.UDPAddr, fromID enode.ID, mac []byte) {
-}
-
 // ENRREQUEST/v4
 
-func (req *enrRequestV4) name() string { return "ENRREQUEST/v4" }
-func (req *enrRequestV4) kind() byte   { return p_enrRequestV4 }
+func (t *UDPv4) verifyENRRequest(h *packetHandlerV4, from *net.UDPAddr, fromID enode.ID, fromKey v4wire.Pubkey) error {
+	req := h.Packet.(*v4wire.ENRRequest)
 
-func (req *enrRequestV4) preverify(t *UDPv4, from *net.UDPAddr, fromID enode.ID, fromKey encPubkey) error {
-	if expired(req.Expiration) {
+	if v4wire.Expired(req.Expiration) {
 		return errExpired
 	}
 	if !t.checkBond(fromID, from.IP) {
@@ -944,8 +766,8 @@ func (req *enrRequestV4) preverify(t *UDPv4, from *net.UDPAddr, fromID enode.ID,
 	return nil
 }
 
-func (req *enrRequestV4) handle(t *UDPv4, from *net.UDPAddr, fromID enode.ID, mac []byte) {
-	t.send(from, fromID, &enrResponseV4{
+func (t *UDPv4) handleENRRequest(h *packetHandlerV4, from *net.UDPAddr, fromID enode.ID, mac []byte) {
+	t.send(from, fromID, &v4wire.ENRResponse{
 		ReplyTok: mac,
 		Record:   *t.localNode.Node().Record(),
 	})
@@ -953,15 +775,9 @@ func (req *enrRequestV4) handle(t *UDPv4, from *net.UDPAddr, fromID enode.ID, ma
 
 // ENRRESPONSE/v4
 
-func (req *enrResponseV4) name() string { return "ENRRESPONSE/v4" }
-func (req *enrResponseV4) kind() byte   { return p_enrResponseV4 }
-
-func (req *enrResponseV4) preverify(t *UDPv4, from *net.UDPAddr, fromID enode.ID, fromKey encPubkey) error {
-	if !t.handleReply(fromID, from.IP, req) {
+func (t *UDPv4) verifyENRResponse(h *packetHandlerV4, from *net.UDPAddr, fromID enode.ID, fromKey v4wire.Pubkey) error {
+	if !t.handleReply(fromID, from.IP, h.Packet) {
 		return errUnsolicitedReply
 	}
 	return nil
 }
-
-func (req *enrResponseV4) handle(t *UDPv4, from *net.UDPAddr, fromID enode.ID, mac []byte) {
-}

p2p/discover/v4_udp_test.go

@@ -21,7 +21,6 @@ import (
 	"crypto/ecdsa"
 	crand "crypto/rand"
 	"encoding/binary"
-	"encoding/hex"
 	"errors"
 	"io"
 	"math/rand"
@@ -31,23 +30,20 @@ import (
 	"testing"
 	"time"
 
-	"github.com/davecgh/go-spew/spew"
-	"github.com/ethereum/go-ethereum/common"
-	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/internal/testlog"
 	"github.com/ethereum/go-ethereum/log"
+	"github.com/ethereum/go-ethereum/p2p/discover/v4wire"
 	"github.com/ethereum/go-ethereum/p2p/enode"
 	"github.com/ethereum/go-ethereum/p2p/enr"
-	"github.com/ethereum/go-ethereum/rlp"
 )
 
 // shared test variables
 var (
 	futureExp          = uint64(time.Now().Add(10 * time.Hour).Unix())
-	testTarget         = encPubkey{0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1}
-	testRemote         = rpcEndpoint{IP: net.ParseIP("1.1.1.1").To4(), UDP: 1, TCP: 2}
-	testLocalAnnounced = rpcEndpoint{IP: net.ParseIP("2.2.2.2").To4(), UDP: 3, TCP: 4}
-	testLocal          = rpcEndpoint{IP: net.ParseIP("3.3.3.3").To4(), UDP: 5, TCP: 6}
+	testTarget         = v4wire.Pubkey{0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1}
+	testRemote         = v4wire.Endpoint{IP: net.ParseIP("1.1.1.1").To4(), UDP: 1, TCP: 2}
+	testLocalAnnounced = v4wire.Endpoint{IP: net.ParseIP("2.2.2.2").To4(), UDP: 3, TCP: 4}
+	testLocal          = v4wire.Endpoint{IP: net.ParseIP("3.3.3.3").To4(), UDP: 5, TCP: 6}
 )
 
 type udpTest struct {
@@ -88,19 +84,19 @@ func (test *udpTest) close() {
 }
 
 // handles a packet as if it had been sent to the transport.
-func (test *udpTest) packetIn(wantError error, data packetV4) {
+func (test *udpTest) packetIn(wantError error, data v4wire.Packet) {
 	test.t.Helper()
 
 	test.packetInFrom(wantError, test.remotekey, test.remoteaddr, data)
 }
 
 // handles a packet as if it had been sent to the transport by the key/endpoint.
-func (test *udpTest) packetInFrom(wantError error, key *ecdsa.PrivateKey, addr *net.UDPAddr, data packetV4) {
+func (test *udpTest) packetInFrom(wantError error, key *ecdsa.PrivateKey, addr *net.UDPAddr, data v4wire.Packet) {
 	test.t.Helper()
 
-	enc, _, err := test.udp.encode(key, data)
+	enc, _, err := v4wire.Encode(key, data)
 	if err != nil {
-		test.t.Errorf("%s encode error: %v", data.name(), err)
+		test.t.Errorf("%s encode error: %v", data.Name(), err)
 	}
 	test.sent = append(test.sent, enc)
 	if err = test.udp.handlePacket(addr, enc); err != wantError {
@@ -120,7 +116,7 @@ func (test *udpTest) waitPacketOut(validate interface{}) (closed bool) {
 		test.t.Error("packet receive error:", err)
 		return false
 	}
-	p, _, hash, err := decodeV4(dgram.data)
+	p, _, hash, err := v4wire.Decode(dgram.data)
 	if err != nil {
 		test.t.Errorf("sent packet decode error: %v", err)
 		return false
@@ -139,10 +135,10 @@ func TestUDPv4_packetErrors(t *testing.T) {
 	test := newUDPTest(t)
 	defer test.close()
 
-	test.packetIn(errExpired, &pingV4{From: testRemote, To: testLocalAnnounced, Version: 4})
-	test.packetIn(errUnsolicitedReply, &pongV4{ReplyTok: []byte{}, Expiration: futureExp})
-	test.packetIn(errUnknownNode, &findnodeV4{Expiration: futureExp})
-	test.packetIn(errUnsolicitedReply, &neighborsV4{Expiration: futureExp})
+	test.packetIn(errExpired, &v4wire.Ping{From: testRemote, To: testLocalAnnounced, Version: 4})
+	test.packetIn(errUnsolicitedReply, &v4wire.Pong{ReplyTok: []byte{}, Expiration: futureExp})
+	test.packetIn(errUnknownNode, &v4wire.Findnode{Expiration: futureExp})
+	test.packetIn(errUnsolicitedReply, &v4wire.Neighbors{Expiration: futureExp})
 }
 
 func TestUDPv4_pingTimeout(t *testing.T) {
@@ -160,13 +156,8 @@ func TestUDPv4_pingTimeout(t *testing.T) {
 
 type testPacket byte
 
-func (req testPacket) kind() byte   { return byte(req) }
-func (req testPacket) name() string { return "" }
-func (req testPacket) preverify(*UDPv4, *net.UDPAddr, enode.ID, encPubkey) error {
-	return nil
-}
-func (req testPacket) handle(*UDPv4, *net.UDPAddr, enode.ID, []byte) {
-}
+func (req testPacket) Kind() byte   { return byte(req) }
+func (req testPacket) Name() string { return "" }
 
 func TestUDPv4_responseTimeouts(t *testing.T) {
 	t.Parallel()
@@ -191,7 +182,7 @@ func TestUDPv4_responseTimeouts(t *testing.T) {
 		// within the timeout window.
 		p := &replyMatcher{
 			ptype:    byte(rand.Intn(255)),
-			callback: func(interface{}) (bool, bool) { return true, true },
+			callback: func(v4wire.Packet) (bool, bool) { return true, true },
 		}
 		binary.BigEndian.PutUint64(p.from[:], uint64(i))
 		if p.ptype <= 128 {
@@ -247,7 +238,7 @@ func TestUDPv4_findnodeTimeout(t *testing.T) {
 
 	toaddr := &net.UDPAddr{IP: net.ParseIP("1.2.3.4"), Port: 2222}
 	toid := enode.ID{1, 2, 3, 4}
-	target := encPubkey{4, 5, 6, 7}
+	target := v4wire.Pubkey{4, 5, 6, 7}
 	result, err := test.udp.findnode(toid, toaddr, target)
 	if err != errTimeout {
 		t.Error("expected timeout error, got", err)
@@ -264,7 +255,7 @@ func TestUDPv4_findnode(t *testing.T) {
 	// put a few nodes into the table. their exact
 	// distribution shouldn't matter much, although we need to
 	// take care not to overflow any bucket.
-	nodes := &nodesByDistance{target: testTarget.id()}
+	nodes := &nodesByDistance{target: testTarget.ID()}
 	live := make(map[enode.ID]bool)
 	numCandidates := 2 * bucketSize
 	for i := 0; i < numCandidates; i++ {
@@ -282,32 +273,32 @@ func TestUDPv4_findnode(t *testing.T) {
 
 	// ensure there's a bond with the test node,
 	// findnode won't be accepted otherwise.
-	remoteID := encodePubkey(&test.remotekey.PublicKey).id()
+	remoteID := v4wire.EncodePubkey(&test.remotekey.PublicKey).ID()
 	test.table.db.UpdateLastPongReceived(remoteID, test.remoteaddr.IP, time.Now())
 
 	// check that closest neighbors are returned.
-	expected := test.table.closest(testTarget.id(), bucketSize, true)
-	test.packetIn(nil, &findnodeV4{Target: testTarget, Expiration: futureExp})
+	expected := test.table.closest(testTarget.ID(), bucketSize, true)
+	test.packetIn(nil, &v4wire.Findnode{Target: testTarget, Expiration: futureExp})
 	waitNeighbors := func(want []*node) {
-		test.waitPacketOut(func(p *neighborsV4, to *net.UDPAddr, hash []byte) {
+		test.waitPacketOut(func(p *v4wire.Neighbors, to *net.UDPAddr, hash []byte) {
 			if len(p.Nodes) != len(want) {
 				t.Errorf("wrong number of results: got %d, want %d", len(p.Nodes), bucketSize)
 			}
 			for i, n := range p.Nodes {
-				if n.ID.id() != want[i].ID() {
+				if n.ID.ID() != want[i].ID() {
 					t.Errorf("result mismatch at %d:\n  got:  %v\n  want: %v", i, n, expected.entries[i])
 				}
-				if !live[n.ID.id()] {
-					t.Errorf("result includes dead node %v", n.ID.id())
+				if !live[n.ID.ID()] {
+					t.Errorf("result includes dead node %v", n.ID.ID())
 				}
 			}
 		})
 	}
 	// Receive replies.
 	want := expected.entries
-	if len(want) > maxNeighbors {
-		waitNeighbors(want[:maxNeighbors])
-		want = want[maxNeighbors:]
+	if len(want) > v4wire.MaxNeighbors {
+		waitNeighbors(want[:v4wire.MaxNeighbors])
+		want = want[v4wire.MaxNeighbors:]
 	}
 	waitNeighbors(want)
 }
@@ -333,7 +324,7 @@ func TestUDPv4_findnodeMultiReply(t *testing.T) {
 
 	// wait for the findnode to be sent.
 	// after it is sent, the transport is waiting for a reply
-	test.waitPacketOut(func(p *findnodeV4, to *net.UDPAddr, hash []byte) {
+	test.waitPacketOut(func(p *v4wire.Findnode, to *net.UDPAddr, hash []byte) {
 		if p.Target != testTarget {
 			t.Errorf("wrong target: got %v, want %v", p.Target, testTarget)
 		}
@@ -346,12 +337,12 @@ func TestUDPv4_findnodeMultiReply(t *testing.T) {
 		wrapNode(enode.MustParse("enode://9bffefd833d53fac8e652415f4973bee289e8b1a5c6c4cbe70abf817ce8a64cee11b823b66a987f51aaa9fba0d6a91b3e6bf0d5a5d1042de8e9eeea057b217f8@10.0.1.36:30301?discport=17")),
 		wrapNode(enode.MustParse("enode://1b5b4aa662d7cb44a7221bfba67302590b643028197a7d5214790f3bac7aaa4a3241be9e83c09cf1f6c69d007c634faae3dc1b1221793e8446c0b3a09de65960@10.0.1.16:30303")),
 	}
-	rpclist := make([]rpcNode, len(list))
+	rpclist := make([]v4wire.Node, len(list))
 	for i := range list {
 		rpclist[i] = nodeToRPC(list[i])
 	}
-	test.packetIn(nil, &neighborsV4{Expiration: futureExp, Nodes: rpclist[:2]})
-	test.packetIn(nil, &neighborsV4{Expiration: futureExp, Nodes: rpclist[2:]})
+	test.packetIn(nil, &v4wire.Neighbors{Expiration: futureExp, Nodes: rpclist[:2]})
+	test.packetIn(nil, &v4wire.Neighbors{Expiration: futureExp, Nodes: rpclist[2:]})
 
 	// check that the sent neighbors are all returned by findnode
 	select {
@@ -375,10 +366,10 @@ func TestUDPv4_pingMatch(t *testing.T) {
 	randToken := make([]byte, 32)
 	crand.Read(randToken)
 
-	test.packetIn(nil, &pingV4{From: testRemote, To: testLocalAnnounced, Version: 4, Expiration: futureExp})
-	test.waitPacketOut(func(*pongV4, *net.UDPAddr, []byte) {})
-	test.waitPacketOut(func(*pingV4, *net.UDPAddr, []byte) {})
-	test.packetIn(errUnsolicitedReply, &pongV4{ReplyTok: randToken, To: testLocalAnnounced, Expiration: futureExp})
+	test.packetIn(nil, &v4wire.Ping{From: testRemote, To: testLocalAnnounced, Version: 4, Expiration: futureExp})
+	test.waitPacketOut(func(*v4wire.Pong, *net.UDPAddr, []byte) {})
+	test.waitPacketOut(func(*v4wire.Ping, *net.UDPAddr, []byte) {})
+	test.packetIn(errUnsolicitedReply, &v4wire.Pong{ReplyTok: randToken, To: testLocalAnnounced, Expiration: futureExp})
 }
 
 // This test checks that reply matching of pong verifies the sender IP address.
@@ -386,12 +377,12 @@ func TestUDPv4_pingMatchIP(t *testing.T) {
 	test := newUDPTest(t)
 	defer test.close()
 
-	test.packetIn(nil, &pingV4{From: testRemote, To: testLocalAnnounced, Version: 4, Expiration: futureExp})
-	test.waitPacketOut(func(*pongV4, *net.UDPAddr, []byte) {})
+	test.packetIn(nil, &v4wire.Ping{From: testRemote, To: testLocalAnnounced, Version: 4, Expiration: futureExp})
+	test.waitPacketOut(func(*v4wire.Pong, *net.UDPAddr, []byte) {})
 
-	test.waitPacketOut(func(p *pingV4, to *net.UDPAddr, hash []byte) {
+	test.waitPacketOut(func(p *v4wire.Ping, to *net.UDPAddr, hash []byte) {
 		wrongAddr := &net.UDPAddr{IP: net.IP{33, 44, 1, 2}, Port: 30000}
-		test.packetInFrom(errUnsolicitedReply, test.remotekey, wrongAddr, &pongV4{
+		test.packetInFrom(errUnsolicitedReply, test.remotekey, wrongAddr, &v4wire.Pong{
 			ReplyTok:   hash,
 			To:         testLocalAnnounced,
 			Expiration: futureExp,
@@ -406,15 +397,15 @@ func TestUDPv4_successfulPing(t *testing.T) {
 	defer test.close()
 
 	// The remote side sends a ping packet to initiate the exchange.
-	go test.packetIn(nil, &pingV4{From: testRemote, To: testLocalAnnounced, Version: 4, Expiration: futureExp})
+	go test.packetIn(nil, &v4wire.Ping{From: testRemote, To: testLocalAnnounced, Version: 4, Expiration: futureExp})
 
 	// The ping is replied to.
-	test.waitPacketOut(func(p *pongV4, to *net.UDPAddr, hash []byte) {
-		pinghash := test.sent[0][:macSize]
+	test.waitPacketOut(func(p *v4wire.Pong, to *net.UDPAddr, hash []byte) {
+		pinghash := test.sent[0][:32]
 		if !bytes.Equal(p.ReplyTok, pinghash) {
 			t.Errorf("got pong.ReplyTok %x, want %x", p.ReplyTok, pinghash)
 		}
-		wantTo := rpcEndpoint{
+		wantTo := v4wire.Endpoint{
 			// The mirrored UDP address is the UDP packet sender
 			IP: test.remoteaddr.IP, UDP: uint16(test.remoteaddr.Port),
 			// The mirrored TCP port is the one from the ping packet
@@ -426,11 +417,11 @@ func TestUDPv4_successfulPing(t *testing.T) {
 	})
 
 	// Remote is unknown, the table pings back.
-	test.waitPacketOut(func(p *pingV4, to *net.UDPAddr, hash []byte) {
+	test.waitPacketOut(func(p *v4wire.Ping, to *net.UDPAddr, hash []byte) {
 		if !reflect.DeepEqual(p.From, test.udp.ourEndpoint()) {
 			t.Errorf("got ping.From %#v, want %#v", p.From, test.udp.ourEndpoint())
 		}
-		wantTo := rpcEndpoint{
+		wantTo := v4wire.Endpoint{
 			// The mirrored UDP address is the UDP packet sender.
 			IP:  test.remoteaddr.IP,
 			UDP: uint16(test.remoteaddr.Port),
@@ -439,7 +430,7 @@ func TestUDPv4_successfulPing(t *testing.T) {
 		if !reflect.DeepEqual(p.To, wantTo) {
 			t.Errorf("got ping.To %v, want %v", p.To, wantTo)
 		}
-		test.packetIn(nil, &pongV4{ReplyTok: hash, Expiration: futureExp})
+		test.packetIn(nil, &v4wire.Pong{ReplyTok: hash, Expiration: futureExp})
 	})
 
 	// The node should be added to the table shortly after getting the
@@ -473,25 +464,25 @@ func TestUDPv4_EIP868(t *testing.T) {
 	wantNode := test.udp.localNode.Node()
 
 	// ENR requests aren't allowed before endpoint proof.
-	test.packetIn(errUnknownNode, &enrRequestV4{Expiration: futureExp})
+	test.packetIn(errUnknownNode, &v4wire.ENRRequest{Expiration: futureExp})
 
 	// Perform endpoint proof and check for sequence number in packet tail.
-	test.packetIn(nil, &pingV4{Expiration: futureExp})
-	test.waitPacketOut(func(p *pongV4, addr *net.UDPAddr, hash []byte) {
-		if seq := seqFromTail(p.Rest); seq != wantNode.Seq() {
-			t.Errorf("wrong sequence number in pong: %d, want %d", seq, wantNode.Seq())
+	test.packetIn(nil, &v4wire.Ping{Expiration: futureExp})
+	test.waitPacketOut(func(p *v4wire.Pong, addr *net.UDPAddr, hash []byte) {
+		if p.ENRSeq() != wantNode.Seq() {
+			t.Errorf("wrong sequence number in pong: %d, want %d", p.ENRSeq(), wantNode.Seq())
 		}
 	})
-	test.waitPacketOut(func(p *pingV4, addr *net.UDPAddr, hash []byte) {
-		if seq := seqFromTail(p.Rest); seq != wantNode.Seq() {
-			t.Errorf("wrong sequence number in ping: %d, want %d", seq, wantNode.Seq())
+	test.waitPacketOut(func(p *v4wire.Ping, addr *net.UDPAddr, hash []byte) {
+		if p.ENRSeq() != wantNode.Seq() {
+			t.Errorf("wrong sequence number in ping: %d, want %d", p.ENRSeq(), wantNode.Seq())
 		}
-		test.packetIn(nil, &pongV4{Expiration: futureExp, ReplyTok: hash})
+		test.packetIn(nil, &v4wire.Pong{Expiration: futureExp, ReplyTok: hash})
 	})
 
 	// Request should work now.
-	test.packetIn(nil, &enrRequestV4{Expiration: futureExp})
-	test.waitPacketOut(func(p *enrResponseV4, addr *net.UDPAddr, hash []byte) {
+	test.packetIn(nil, &v4wire.ENRRequest{Expiration: futureExp})
+	test.waitPacketOut(func(p *v4wire.ENRResponse, addr *net.UDPAddr, hash []byte) {
 		n, err := enode.New(enode.ValidSchemes, &p.Record)
 		if err != nil {
 			t.Fatalf("invalid record: %v", err)
@@ -502,116 +493,6 @@ func TestUDPv4_EIP868(t *testing.T) {
 	})
 }
 
-// EIP-8 test vectors.
-var testPackets = []struct {
-	input      string
-	wantPacket interface{}
-}{
-	{
-		input: "71dbda3a79554728d4f94411e42ee1f8b0d561c10e1e5f5893367948c6a7d70bb87b235fa28a77070271b6c164a2dce8c7e13a5739b53b5e96f2e5acb0e458a02902f5965d55ecbeb2ebb6cabb8b2b232896a36b737666c55265ad0a68412f250001ea04cb847f000001820cfa8215a8d790000000000000000000000000000000018208ae820d058443b9a355",
-		wantPacket: &pingV4{
-			Version:    4,
-			From:       rpcEndpoint{net.ParseIP("127.0.0.1").To4(), 3322, 5544},
-			To:         rpcEndpoint{net.ParseIP("::1"), 2222, 3333},
-			Expiration: 1136239445,
-			Rest:       []rlp.RawValue{},
-		},
-	},
-	{
-		input: "e9614ccfd9fc3e74360018522d30e1419a143407ffcce748de3e22116b7e8dc92ff74788c0b6663aaa3d67d641936511c8f8d6ad8698b820a7cf9e1be7155e9a241f556658c55428ec0563514365799a4be2be5a685a80971ddcfa80cb422cdd0101ec04cb847f000001820cfa8215a8d790000000000000000000000000000000018208ae820d058443b9a3550102",
-		wantPacket: &pingV4{
-			Version:    4,
-			From:       rpcEndpoint{net.ParseIP("127.0.0.1").To4(), 3322, 5544},
-			To:         rpcEndpoint{net.ParseIP("::1"), 2222, 3333},
-			Expiration: 1136239445,
-			Rest:       []rlp.RawValue{{0x01}, {0x02}},
-		},
-	},
-	{
-		input: "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",
-		wantPacket: &pingV4{
-			Version:    555,
-			From:       rpcEndpoint{net.ParseIP("2001:db8:3c4d:15::abcd:ef12"), 3322, 5544},
-			To:         rpcEndpoint{net.ParseIP("2001:db8:85a3:8d3:1319:8a2e:370:7348"), 2222, 33338},
-			Expiration: 1136239445,
-			Rest:       []rlp.RawValue{{0xC5, 0x01, 0x02, 0x03, 0x04, 0x05}},
-		},
-	},
-	{
-		input: "09b2428d83348d27cdf7064ad9024f526cebc19e4958f0fdad87c15eb598dd61d08423e0bf66b2069869e1724125f820d851c136684082774f870e614d95a2855d000f05d1648b2d5945470bc187c2d2216fbe870f43ed0909009882e176a46b0102f846d79020010db885a308d313198a2e037073488208ae82823aa0fbc914b16819237dcd8801d7e53f69e9719adecb3cc0e790c57e91ca4461c9548443b9a355c6010203c2040506a0c969a58f6f9095004c0177a6b47f451530cab38966a25cca5cb58f055542124e",
-		wantPacket: &pongV4{
-			To:         rpcEndpoint{net.ParseIP("2001:db8:85a3:8d3:1319:8a2e:370:7348"), 2222, 33338},
-			ReplyTok:   common.Hex2Bytes("fbc914b16819237dcd8801d7e53f69e9719adecb3cc0e790c57e91ca4461c954"),
-			Expiration: 1136239445,
-			Rest:       []rlp.RawValue{{0xC6, 0x01, 0x02, 0x03, 0xC2, 0x04, 0x05}, {0x06}},
-		},
-	},
-	{
-		input: "c7c44041b9f7c7e41934417ebac9a8e1a4c6298f74553f2fcfdcae6ed6fe53163eb3d2b52e39fe91831b8a927bf4fc222c3902202027e5e9eb812195f95d20061ef5cd31d502e47ecb61183f74a504fe04c51e73df81f25c4d506b26db4517490103f84eb840ca634cae0d49acb401d8a4c6b6fe8c55b70d115bf400769cc1400f3258cd31387574077f301b421bc84df7266c44e9e6d569fc56be00812904767bf5ccd1fc7f8443b9a35582999983999999280dc62cc8255c73471e0a61da0c89acdc0e035e260add7fc0c04ad9ebf3919644c91cb247affc82b69bd2ca235c71eab8e49737c937a2c396",
-		wantPacket: &findnodeV4{
-			Target:     hexEncPubkey("ca634cae0d49acb401d8a4c6b6fe8c55b70d115bf400769cc1400f3258cd31387574077f301b421bc84df7266c44e9e6d569fc56be00812904767bf5ccd1fc7f"),
-			Expiration: 1136239445,
-			Rest:       []rlp.RawValue{{0x82, 0x99, 0x99}, {0x83, 0x99, 0x99, 0x99}},
-		},
-	},
-	{
-		input: "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",
-		wantPacket: &neighborsV4{
-			Nodes: []rpcNode{
-				{
-					ID:  hexEncPubkey("3155e1427f85f10a5c9a7755877748041af1bcd8d474ec065eb33df57a97babf54bfd2103575fa829115d224c523596b401065a97f74010610fce76382c0bf32"),
-					IP:  net.ParseIP("99.33.22.55").To4(),
-					UDP: 4444,
-					TCP: 4445,
-				},
-				{
-					ID:  hexEncPubkey("312c55512422cf9b8a4097e9a6ad79402e87a15ae909a4bfefa22398f03d20951933beea1e4dfa6f968212385e829f04c2d314fc2d4e255e0d3bc08792b069db"),
-					IP:  net.ParseIP("1.2.3.4").To4(),
-					UDP: 1,
-					TCP: 1,
-				},
-				{
-					ID:  hexEncPubkey("38643200b172dcfef857492156971f0e6aa2c538d8b74010f8e140811d53b98c765dd2d96126051913f44582e8c199ad7c6d6819e9a56483f637feaac9448aac"),
-					IP:  net.ParseIP("2001:db8:3c4d:15::abcd:ef12"),
-					UDP: 3333,
-					TCP: 3333,
-				},
-				{
-					ID:  hexEncPubkey("8dcab8618c3253b558d459da53bd8fa68935a719aff8b811197101a4b2b47dd2d47295286fc00cc081bb542d760717d1bdd6bec2c37cd72eca367d6dd3b9df73"),
-					IP:  net.ParseIP("2001:db8:85a3:8d3:1319:8a2e:370:7348"),
-					UDP: 999,
-					TCP: 1000,
-				},
-			},
-			Expiration: 1136239445,
-			Rest:       []rlp.RawValue{{0x01}, {0x02}, {0x03}},
-		},
-	},
-}
-
-func TestUDPv4_forwardCompatibility(t *testing.T) {
-	testkey, _ := crypto.HexToECDSA("b71c71a67e1177ad4e901695e1b4b9ee17ae16c6668d313eac2f96dbcda3f291")
-	wantNodeKey := encodePubkey(&testkey.PublicKey)
-
-	for _, test := range testPackets {
-		input, err := hex.DecodeString(test.input)
-		if err != nil {
-			t.Fatalf("invalid hex: %s", test.input)
-		}
-		packet, nodekey, _, err := decodeV4(input)
-		if err != nil {
-			t.Errorf("did not accept packet %s\n%v", test.input, err)
-			continue
-		}
-		if !reflect.DeepEqual(packet, test.wantPacket) {
-			t.Errorf("got %s\nwant %s", spew.Sdump(packet), spew.Sdump(test.wantPacket))
-		}
-		if nodekey != wantNodeKey {
-			t.Errorf("got id %v\nwant id %v", nodekey, wantNodeKey)
-		}
-	}
-}
-
 // dgramPipe is a fake UDP socket. It queues all sent datagrams.
 type dgramPipe struct {
 	mu      *sync.Mutex

p2p/discover/v4wire/v4wire.go

@@ -0,0 +1,300 @@
+// Copyright 2019 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+// Package v4wire implements the Discovery v4 Wire Protocol.
+package v4wire
+
+import (
+	"bytes"
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"errors"
+	"fmt"
+	"math/big"
+	"net"
+	"time"
+
+	"github.com/ethereum/go-ethereum/common/math"
+	"github.com/ethereum/go-ethereum/crypto"
+	"github.com/ethereum/go-ethereum/p2p/enode"
+	"github.com/ethereum/go-ethereum/p2p/enr"
+	"github.com/ethereum/go-ethereum/rlp"
+)
+
+// RPC packet types
+const (
+	PingPacket = iota + 1 // zero is 'reserved'
+	PongPacket
+	FindnodePacket
+	NeighborsPacket
+	ENRRequestPacket
+	ENRResponsePacket
+)
+
+// RPC request structures
+type (
+	Ping struct {
+		Version    uint
+		From, To   Endpoint
+		Expiration uint64
+		// Ignore additional fields (for forward compatibility).
+		Rest []rlp.RawValue `rlp:"tail"`
+	}
+
+	// Pong is the reply to ping.
+	Pong struct {
+		// This field should mirror the UDP envelope address
+		// of the ping packet, which provides a way to discover the
+		// the external address (after NAT).
+		To         Endpoint
+		ReplyTok   []byte // This contains the hash of the ping packet.
+		Expiration uint64 // Absolute timestamp at which the packet becomes invalid.
+		// Ignore additional fields (for forward compatibility).
+		Rest []rlp.RawValue `rlp:"tail"`
+	}
+
+	// Findnode is a query for nodes close to the given target.
+	Findnode struct {
+		Target     Pubkey
+		Expiration uint64
+		// Ignore additional fields (for forward compatibility).
+		Rest []rlp.RawValue `rlp:"tail"`
+	}
+
+	// Neighbors is the reply to findnode.
+	Neighbors struct {
+		Nodes      []Node
+		Expiration uint64
+		// Ignore additional fields (for forward compatibility).
+		Rest []rlp.RawValue `rlp:"tail"`
+	}
+
+	// enrRequest queries for the remote node's record.
+	ENRRequest struct {
+		Expiration uint64
+		// Ignore additional fields (for forward compatibility).
+		Rest []rlp.RawValue `rlp:"tail"`
+	}
+
+	// enrResponse is the reply to enrRequest.
+	ENRResponse struct {
+		ReplyTok []byte // Hash of the enrRequest packet.
+		Record   enr.Record
+		// Ignore additional fields (for forward compatibility).
+		Rest []rlp.RawValue `rlp:"tail"`
+	}
+)
+
+// This number is the maximum number of neighbor nodes in a Neigbors packet.
+const MaxNeighbors = 12
+
+// This code computes the MaxNeighbors constant value.
+
+// func init() {
+// 	var maxNeighbors int
+// 	p := Neighbors{Expiration: ^uint64(0)}
+// 	maxSizeNode := Node{IP: make(net.IP, 16), UDP: ^uint16(0), TCP: ^uint16(0)}
+// 	for n := 0; ; n++ {
+// 		p.Nodes = append(p.Nodes, maxSizeNode)
+// 		size, _, err := rlp.EncodeToReader(p)
+// 		if err != nil {
+// 			// If this ever happens, it will be caught by the unit tests.
+// 			panic("cannot encode: " + err.Error())
+// 		}
+// 		if headSize+size+1 >= 1280 {
+// 			maxNeighbors = n
+// 			break
+// 		}
+// 	}
+// 	fmt.Println("maxNeighbors", maxNeighbors)
+// }
+
+// Pubkey represents an encoded 64-byte secp256k1 public key.
+type Pubkey [64]byte
+
+// ID returns the node ID corresponding to the public key.
+func (e Pubkey) ID() enode.ID {
+	return enode.ID(crypto.Keccak256Hash(e[:]))
+}
+
+// Node represents information about a node.
+type Node struct {
+	IP  net.IP // len 4 for IPv4 or 16 for IPv6
+	UDP uint16 // for discovery protocol
+	TCP uint16 // for RLPx protocol
+	ID  Pubkey
+}
+
+// Endpoint represents a network endpoint.
+type Endpoint struct {
+	IP  net.IP // len 4 for IPv4 or 16 for IPv6
+	UDP uint16 // for discovery protocol
+	TCP uint16 // for RLPx protocol
+}
+
+// NewEndpoint creates an endpoint.
+func NewEndpoint(addr *net.UDPAddr, tcpPort uint16) Endpoint {
+	ip := net.IP{}
+	if ip4 := addr.IP.To4(); ip4 != nil {
+		ip = ip4
+	} else if ip6 := addr.IP.To16(); ip6 != nil {
+		ip = ip6
+	}
+	return Endpoint{IP: ip, UDP: uint16(addr.Port), TCP: tcpPort}
+}
+
+type Packet interface {
+	// packet name and type for logging purposes.
+	Name() string
+	Kind() byte
+}
+
+func (req *Ping) Name() string   { return "PING/v4" }
+func (req *Ping) Kind() byte     { return PingPacket }
+func (req *Ping) ENRSeq() uint64 { return seqFromTail(req.Rest) }
+
+func (req *Pong) Name() string   { return "PONG/v4" }
+func (req *Pong) Kind() byte     { return PongPacket }
+func (req *Pong) ENRSeq() uint64 { return seqFromTail(req.Rest) }
+
+func (req *Findnode) Name() string { return "FINDNODE/v4" }
+func (req *Findnode) Kind() byte   { return FindnodePacket }
+
+func (req *Neighbors) Name() string { return "NEIGHBORS/v4" }
+func (req *Neighbors) Kind() byte   { return NeighborsPacket }
+
+func (req *ENRRequest) Name() string { return "ENRREQUEST/v4" }
+func (req *ENRRequest) Kind() byte   { return ENRRequestPacket }
+
+func (req *ENRResponse) Name() string { return "ENRRESPONSE/v4" }
+func (req *ENRResponse) Kind() byte   { return ENRResponsePacket }
+
+// Expired checks whether the given UNIX time stamp is in the past.
+func Expired(ts uint64) bool {
+	return time.Unix(int64(ts), 0).Before(time.Now())
+}
+
+func seqFromTail(tail []rlp.RawValue) uint64 {
+	if len(tail) == 0 {
+		return 0
+	}
+	var seq uint64
+	rlp.DecodeBytes(tail[0], &seq)
+	return seq
+}
+
+// Encoder/decoder.
+
+const (
+	macSize  = 32
+	sigSize  = crypto.SignatureLength
+	headSize = macSize + sigSize // space of packet frame data
+)
+
+var (
+	ErrPacketTooSmall = errors.New("too small")
+	ErrBadHash        = errors.New("bad hash")
+	ErrBadPoint       = errors.New("invalid curve point")
+)
+
+var headSpace = make([]byte, headSize)
+
+// Decode reads a discovery v4 packet.
+func Decode(input []byte) (Packet, Pubkey, []byte, error) {
+	if len(input) < headSize+1 {
+		return nil, Pubkey{}, nil, ErrPacketTooSmall
+	}
+	hash, sig, sigdata := input[:macSize], input[macSize:headSize], input[headSize:]
+	shouldhash := crypto.Keccak256(input[macSize:])
+	if !bytes.Equal(hash, shouldhash) {
+		return nil, Pubkey{}, nil, ErrBadHash
+	}
+	fromKey, err := recoverNodeKey(crypto.Keccak256(input[headSize:]), sig)
+	if err != nil {
+		return nil, fromKey, hash, err
+	}
+
+	var req Packet
+	switch ptype := sigdata[0]; ptype {
+	case PingPacket:
+		req = new(Ping)
+	case PongPacket:
+		req = new(Pong)
+	case FindnodePacket:
+		req = new(Findnode)
+	case NeighborsPacket:
+		req = new(Neighbors)
+	case ENRRequestPacket:
+		req = new(ENRRequest)
+	case ENRResponsePacket:
+		req = new(ENRResponse)
+	default:
+		return nil, fromKey, hash, fmt.Errorf("unknown type: %d", ptype)
+	}
+	s := rlp.NewStream(bytes.NewReader(sigdata[1:]), 0)
+	err = s.Decode(req)
+	return req, fromKey, hash, err
+}
+
+// Encode encodes a discovery packet.
+func Encode(priv *ecdsa.PrivateKey, req Packet) (packet, hash []byte, err error) {
+	b := new(bytes.Buffer)
+	b.Write(headSpace)
+	b.WriteByte(req.Kind())
+	if err := rlp.Encode(b, req); err != nil {
+		return nil, nil, err
+	}
+	packet = b.Bytes()
+	sig, err := crypto.Sign(crypto.Keccak256(packet[headSize:]), priv)
+	if err != nil {
+		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)
+	return packet, hash, nil
+}
+
+// recoverNodeKey computes the public key used to sign the given hash from the signature.
+func recoverNodeKey(hash, sig []byte) (key Pubkey, err error) {
+	pubkey, err := crypto.Ecrecover(hash, sig)
+	if err != nil {
+		return key, err
+	}
+	copy(key[:], pubkey[1:])
+	return key, nil
+}
+
+// EncodePubkey encodes a secp256k1 public key.
+func EncodePubkey(key *ecdsa.PublicKey) Pubkey {
+	var e Pubkey
+	math.ReadBits(key.X, e[:len(e)/2])
+	math.ReadBits(key.Y, e[len(e)/2:])
+	return e
+}
+
+// DecodePubkey reads an encoded secp256k1 public key.
+func DecodePubkey(curve elliptic.Curve, e Pubkey) (*ecdsa.PublicKey, error) {
+	p := &ecdsa.PublicKey{Curve: curve, X: new(big.Int), Y: new(big.Int)}
+	half := len(e) / 2
+	p.X.SetBytes(e[:half])
+	p.Y.SetBytes(e[half:])
+	if !p.Curve.IsOnCurve(p.X, p.Y) {
+		return nil, ErrBadPoint
+	}
+	return p, nil
+}

p2p/discover/v4wire/v4wire_test.go

@@ -0,0 +1,152 @@
+// Copyright 2019 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package v4wire
+
+import (
+	"encoding/hex"
+	"net"
+	"reflect"
+	"testing"
+
+	"github.com/davecgh/go-spew/spew"
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/crypto"
+	"github.com/ethereum/go-ethereum/rlp"
+)
+
+// EIP-8 test vectors.
+var testPackets = []struct {
+	input      string
+	wantPacket interface{}
+}{
+	{
+		input: "71dbda3a79554728d4f94411e42ee1f8b0d561c10e1e5f5893367948c6a7d70bb87b235fa28a77070271b6c164a2dce8c7e13a5739b53b5e96f2e5acb0e458a02902f5965d55ecbeb2ebb6cabb8b2b232896a36b737666c55265ad0a68412f250001ea04cb847f000001820cfa8215a8d790000000000000000000000000000000018208ae820d058443b9a355",
+		wantPacket: &Ping{
+			Version:    4,
+			From:       Endpoint{net.ParseIP("127.0.0.1").To4(), 3322, 5544},
+			To:         Endpoint{net.ParseIP("::1"), 2222, 3333},
+			Expiration: 1136239445,
+			Rest:       []rlp.RawValue{},
+		},
+	},
+	{
+		input: "e9614ccfd9fc3e74360018522d30e1419a143407ffcce748de3e22116b7e8dc92ff74788c0b6663aaa3d67d641936511c8f8d6ad8698b820a7cf9e1be7155e9a241f556658c55428ec0563514365799a4be2be5a685a80971ddcfa80cb422cdd0101ec04cb847f000001820cfa8215a8d790000000000000000000000000000000018208ae820d058443b9a3550102",
+		wantPacket: &Ping{
+			Version:    4,
+			From:       Endpoint{net.ParseIP("127.0.0.1").To4(), 3322, 5544},
+			To:         Endpoint{net.ParseIP("::1"), 2222, 3333},
+			Expiration: 1136239445,
+			Rest:       []rlp.RawValue{{0x01}, {0x02}},
+		},
+	},
+	{
+		input: "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",
+		wantPacket: &Ping{
+			Version:    555,
+			From:       Endpoint{net.ParseIP("2001:db8:3c4d:15::abcd:ef12"), 3322, 5544},
+			To:         Endpoint{net.ParseIP("2001:db8:85a3:8d3:1319:8a2e:370:7348"), 2222, 33338},
+			Expiration: 1136239445,
+			Rest:       []rlp.RawValue{{0xC5, 0x01, 0x02, 0x03, 0x04, 0x05}},
+		},
+	},
+	{
+		input: "09b2428d83348d27cdf7064ad9024f526cebc19e4958f0fdad87c15eb598dd61d08423e0bf66b2069869e1724125f820d851c136684082774f870e614d95a2855d000f05d1648b2d5945470bc187c2d2216fbe870f43ed0909009882e176a46b0102f846d79020010db885a308d313198a2e037073488208ae82823aa0fbc914b16819237dcd8801d7e53f69e9719adecb3cc0e790c57e91ca4461c9548443b9a355c6010203c2040506a0c969a58f6f9095004c0177a6b47f451530cab38966a25cca5cb58f055542124e",
+		wantPacket: &Pong{
+			To:         Endpoint{net.ParseIP("2001:db8:85a3:8d3:1319:8a2e:370:7348"), 2222, 33338},
+			ReplyTok:   common.Hex2Bytes("fbc914b16819237dcd8801d7e53f69e9719adecb3cc0e790c57e91ca4461c954"),
+			Expiration: 1136239445,
+			Rest:       []rlp.RawValue{{0xC6, 0x01, 0x02, 0x03, 0xC2, 0x04, 0x05}, {0x06}},
+		},
+	},
+	{
+		input: "c7c44041b9f7c7e41934417ebac9a8e1a4c6298f74553f2fcfdcae6ed6fe53163eb3d2b52e39fe91831b8a927bf4fc222c3902202027e5e9eb812195f95d20061ef5cd31d502e47ecb61183f74a504fe04c51e73df81f25c4d506b26db4517490103f84eb840ca634cae0d49acb401d8a4c6b6fe8c55b70d115bf400769cc1400f3258cd31387574077f301b421bc84df7266c44e9e6d569fc56be00812904767bf5ccd1fc7f8443b9a35582999983999999280dc62cc8255c73471e0a61da0c89acdc0e035e260add7fc0c04ad9ebf3919644c91cb247affc82b69bd2ca235c71eab8e49737c937a2c396",
+		wantPacket: &Findnode{
+			Target:     hexPubkey("ca634cae0d49acb401d8a4c6b6fe8c55b70d115bf400769cc1400f3258cd31387574077f301b421bc84df7266c44e9e6d569fc56be00812904767bf5ccd1fc7f"),
+			Expiration: 1136239445,
+			Rest:       []rlp.RawValue{{0x82, 0x99, 0x99}, {0x83, 0x99, 0x99, 0x99}},
+		},
+	},
+	{
+		input: "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",
+		wantPacket: &Neighbors{
+			Nodes: []Node{
+				{
+					ID:  hexPubkey("3155e1427f85f10a5c9a7755877748041af1bcd8d474ec065eb33df57a97babf54bfd2103575fa829115d224c523596b401065a97f74010610fce76382c0bf32"),
+					IP:  net.ParseIP("99.33.22.55").To4(),
+					UDP: 4444,
+					TCP: 4445,
+				},
+				{
+					ID:  hexPubkey("312c55512422cf9b8a4097e9a6ad79402e87a15ae909a4bfefa22398f03d20951933beea1e4dfa6f968212385e829f04c2d314fc2d4e255e0d3bc08792b069db"),
+					IP:  net.ParseIP("1.2.3.4").To4(),
+					UDP: 1,
+					TCP: 1,
+				},
+				{
+					ID:  hexPubkey("38643200b172dcfef857492156971f0e6aa2c538d8b74010f8e140811d53b98c765dd2d96126051913f44582e8c199ad7c6d6819e9a56483f637feaac9448aac"),
+					IP:  net.ParseIP("2001:db8:3c4d:15::abcd:ef12"),
+					UDP: 3333,
+					TCP: 3333,
+				},
+				{
+					ID:  hexPubkey("8dcab8618c3253b558d459da53bd8fa68935a719aff8b811197101a4b2b47dd2d47295286fc00cc081bb542d760717d1bdd6bec2c37cd72eca367d6dd3b9df73"),
+					IP:  net.ParseIP("2001:db8:85a3:8d3:1319:8a2e:370:7348"),
+					UDP: 999,
+					TCP: 1000,
+				},
+			},
+			Expiration: 1136239445,
+			Rest:       []rlp.RawValue{{0x01}, {0x02}, {0x03}},
+		},
+	},
+}
+
+// This test checks that the decoder accepts packets according to EIP-8.
+func TestForwardCompatibility(t *testing.T) {
+	testkey, _ := crypto.HexToECDSA("b71c71a67e1177ad4e901695e1b4b9ee17ae16c6668d313eac2f96dbcda3f291")
+	wantNodeKey := EncodePubkey(&testkey.PublicKey)
+
+	for _, test := range testPackets {
+		input, err := hex.DecodeString(test.input)
+		if err != nil {
+			t.Fatalf("invalid hex: %s", test.input)
+		}
+		packet, nodekey, _, err := Decode(input)
+		if err != nil {
+			t.Errorf("did not accept packet %s\n%v", test.input, err)
+			continue
+		}
+		if !reflect.DeepEqual(packet, test.wantPacket) {
+			t.Errorf("got %s\nwant %s", spew.Sdump(packet), spew.Sdump(test.wantPacket))
+		}
+		if nodekey != wantNodeKey {
+			t.Errorf("got id %v\nwant id %v", nodekey, wantNodeKey)
+		}
+	}
+}
+
+func hexPubkey(h string) (ret Pubkey) {
+	b, err := hex.DecodeString(h)
+	if err != nil {
+		panic(err)
+	}
+	if len(b) != len(ret) {
+		panic("invalid length")
+	}
+	copy(ret[:], b)
+	return ret
+}