p2p/discover: new endpoint format

This commit changes the discovery protocol to use the new "v4" endpoint
format, which allows for separate UDP and TCP ports and makes it
possible to discover the UDP address after NAT.

7 files changed, 150 insertions, 119 deletions

diff --git a/p2p/discover/database_test.go b/p2p/discover/database_test.go
index f327cf73b..0cc0dec32 100644
--- a/p2p/discover/database_test.go
+++ b/p2p/discover/database_test.go
@@ -6,6 +6,7 @@ import (
 	"net"
 	"os"
 	"path/filepath"
+	"reflect"
 	"testing"
 	"time"
 )
@@ -86,9 +87,10 @@ func TestNodeDBInt64(t *testing.T) {
 
 func TestNodeDBFetchStore(t *testing.T) {
 	node := &Node{
-		ID:      MustHexID("0x1dd9d65c4552b5eb43d5ad55a2ee3f56c6cbc1c64a5c8d659f51fcd51bace24351232b8d7821617d2b29b54b81cdefb9b3e9c37d7fd5f63270bcc9e1a6f6a439"),
-		IP:      net.IP([]byte{192, 168, 0, 1}),
-		TCPPort: 30303,
+		ID:  MustHexID("0x1dd9d65c4552b5eb43d5ad55a2ee3f56c6cbc1c64a5c8d659f51fcd51bace24351232b8d7821617d2b29b54b81cdefb9b3e9c37d7fd5f63270bcc9e1a6f6a439"),
+		IP:  net.IP([]byte{192, 168, 0, 1}),
+		UDP: 30303,
+		TCP: 30303,
 	}
 	inst := time.Now()
 
@@ -124,7 +126,7 @@ func TestNodeDBFetchStore(t *testing.T) {
 	}
 	if stored := db.node(node.ID); stored == nil {
 		t.Errorf("node: not found")
-	} else if !bytes.Equal(stored.ID[:], node.ID[:]) || !stored.IP.Equal(node.IP) || stored.TCPPort != node.TCPPort {
+	} else if !reflect.DeepEqual(stored, node) {
 		t.Errorf("node: data mismatch: have %v, want %v", stored, node)
 	}
 }
diff --git a/p2p/discover/node.go b/p2p/discover/node.go
index e66ca37a4..cfb6ff552 100644
--- a/p2p/discover/node.go
+++ b/p2p/discover/node.go
@@ -6,7 +6,6 @@ import (
 	"encoding/hex"
 	"errors"
 	"fmt"
-	"io"
 	"math/big"
 	"math/rand"
 	"net"
@@ -16,49 +15,45 @@ import (
 
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/crypto/secp256k1"
-	"github.com/ethereum/go-ethereum/rlp"
 )
 
 const nodeIDBits = 512
 
 // Node represents a host on the network.
 type Node struct {
-	ID NodeID
-	IP net.IP
-
-	DiscPort int // UDP listening port for discovery protocol
-	TCPPort  int // TCP listening port for RLPx
+	IP       net.IP // len 4 for IPv4 or 16 for IPv6
+	UDP, TCP uint16 // port numbers
+	ID       NodeID
 }
 
 func newNode(id NodeID, addr *net.UDPAddr) *Node {
+	ip := addr.IP.To4()
+	if ip == nil {
+		ip = addr.IP.To16()
+	}
 	return &Node{
-		ID:       id,
-		IP:       addr.IP,
-		DiscPort: addr.Port,
-		TCPPort:  addr.Port,
+		IP:  ip,
+		UDP: uint16(addr.Port),
+		TCP: uint16(addr.Port),
+		ID:  id,
 	}
 }
 
-func (n *Node) isValid() bool {
-	// TODO: don't accept localhost, LAN addresses from internet hosts
-	return !n.IP.IsMulticast() && !n.IP.IsUnspecified() && n.TCPPort != 0 && n.DiscPort != 0
-}
-
 func (n *Node) addr() *net.UDPAddr {
-	return &net.UDPAddr{IP: n.IP, Port: n.DiscPort}
+	return &net.UDPAddr{IP: n.IP, Port: int(n.UDP)}
 }
 
 // The string representation of a Node is a URL.
 // Please see ParseNode for a description of the format.
 func (n *Node) String() string {
-	addr := net.TCPAddr{IP: n.IP, Port: n.TCPPort}
+	addr := net.TCPAddr{IP: n.IP, Port: int(n.TCP)}
 	u := url.URL{
 		Scheme: "enode",
 		User:   url.User(fmt.Sprintf("%x", n.ID[:])),
 		Host:   addr.String(),
 	}
-	if n.DiscPort != n.TCPPort {
-		u.RawQuery = "discport=" + strconv.Itoa(n.DiscPort)
+	if n.UDP != n.TCP {
+		u.RawQuery = "discport=" + strconv.Itoa(int(n.UDP))
 	}
 	return u.String()
 }
@@ -98,16 +93,20 @@ func ParseNode(rawurl string) (*Node, error) {
 	if n.IP = net.ParseIP(ip); n.IP == nil {
 		return nil, errors.New("invalid IP address")
 	}
-	if n.TCPPort, err = strconv.Atoi(port); err != nil {
+	tcp, err := strconv.ParseUint(port, 10, 16)
+	if err != nil {
 		return nil, errors.New("invalid port")
 	}
+	n.TCP = uint16(tcp)
 	qv := u.Query()
 	if qv.Get("discport") == "" {
-		n.DiscPort = n.TCPPort
+		n.UDP = n.TCP
 	} else {
-		if n.DiscPort, err = strconv.Atoi(qv.Get("discport")); err != nil {
+		udp, err := strconv.ParseUint(qv.Get("discport"), 10, 16)
+		if err != nil {
 			return nil, errors.New("invalid discport in query")
 		}
+		n.UDP = uint16(udp)
 	}
 	return &n, nil
 }
@@ -121,22 +120,6 @@ func MustParseNode(rawurl string) *Node {
 	return n
 }
 
-func (n Node) EncodeRLP(w io.Writer) error {
-	return rlp.Encode(w, rpcNode{IP: n.IP.String(), Port: uint16(n.TCPPort), ID: n.ID})
-}
-func (n *Node) DecodeRLP(s *rlp.Stream) (err error) {
-	var ext rpcNode
-	if err = s.Decode(&ext); err == nil {
-		n.TCPPort = int(ext.Port)
-		n.DiscPort = int(ext.Port)
-		n.ID = ext.ID
-		if n.IP = net.ParseIP(ext.IP); n.IP == nil {
-			return errors.New("invalid IP string")
-		}
-	}
-	return err
-}
-
 // NodeID is a unique identifier for each node.
 // The node identifier is a marshaled elliptic curve public key.
 type NodeID [nodeIDBits / 8]byte
diff --git a/p2p/discover/node_test.go b/p2p/discover/node_test.go
index 60b01b6ca..8ea9018c5 100644
--- a/p2p/discover/node_test.go
+++ b/p2p/discover/node_test.go
@@ -49,28 +49,28 @@ var parseNodeTests = []struct {
 	{
 		rawurl: "enode://1dd9d65c4552b5eb43d5ad55a2ee3f56c6cbc1c64a5c8d659f51fcd51bace24351232b8d7821617d2b29b54b81cdefb9b3e9c37d7fd5f63270bcc9e1a6f6a439@127.0.0.1:52150",
 		wantResult: &Node{
-			ID:       MustHexID("0x1dd9d65c4552b5eb43d5ad55a2ee3f56c6cbc1c64a5c8d659f51fcd51bace24351232b8d7821617d2b29b54b81cdefb9b3e9c37d7fd5f63270bcc9e1a6f6a439"),
-			IP:       net.ParseIP("127.0.0.1"),
-			DiscPort: 52150,
-			TCPPort:  52150,
+			ID:  MustHexID("0x1dd9d65c4552b5eb43d5ad55a2ee3f56c6cbc1c64a5c8d659f51fcd51bace24351232b8d7821617d2b29b54b81cdefb9b3e9c37d7fd5f63270bcc9e1a6f6a439"),
+			IP:  net.ParseIP("127.0.0.1"),
+			UDP: 52150,
+			TCP: 52150,
 		},
 	},
 	{
 		rawurl: "enode://1dd9d65c4552b5eb43d5ad55a2ee3f56c6cbc1c64a5c8d659f51fcd51bace24351232b8d7821617d2b29b54b81cdefb9b3e9c37d7fd5f63270bcc9e1a6f6a439@[::]:52150",
 		wantResult: &Node{
-			ID:       MustHexID("0x1dd9d65c4552b5eb43d5ad55a2ee3f56c6cbc1c64a5c8d659f51fcd51bace24351232b8d7821617d2b29b54b81cdefb9b3e9c37d7fd5f63270bcc9e1a6f6a439"),
-			IP:       net.ParseIP("::"),
-			DiscPort: 52150,
-			TCPPort:  52150,
+			ID:  MustHexID("0x1dd9d65c4552b5eb43d5ad55a2ee3f56c6cbc1c64a5c8d659f51fcd51bace24351232b8d7821617d2b29b54b81cdefb9b3e9c37d7fd5f63270bcc9e1a6f6a439"),
+			IP:  net.ParseIP("::"),
+			UDP: 52150,
+			TCP: 52150,
 		},
 	},
 	{
-		rawurl: "enode://1dd9d65c4552b5eb43d5ad55a2ee3f56c6cbc1c64a5c8d659f51fcd51bace24351232b8d7821617d2b29b54b81cdefb9b3e9c37d7fd5f63270bcc9e1a6f6a439@127.0.0.1:52150?discport=223344",
+		rawurl: "enode://1dd9d65c4552b5eb43d5ad55a2ee3f56c6cbc1c64a5c8d659f51fcd51bace24351232b8d7821617d2b29b54b81cdefb9b3e9c37d7fd5f63270bcc9e1a6f6a439@127.0.0.1:52150?discport=22334",
 		wantResult: &Node{
-			ID:       MustHexID("0x1dd9d65c4552b5eb43d5ad55a2ee3f56c6cbc1c64a5c8d659f51fcd51bace24351232b8d7821617d2b29b54b81cdefb9b3e9c37d7fd5f63270bcc9e1a6f6a439"),
-			IP:       net.ParseIP("127.0.0.1"),
-			DiscPort: 223344,
-			TCPPort:  52150,
+			ID:  MustHexID("0x1dd9d65c4552b5eb43d5ad55a2ee3f56c6cbc1c64a5c8d659f51fcd51bace24351232b8d7821617d2b29b54b81cdefb9b3e9c37d7fd5f63270bcc9e1a6f6a439"),
+			IP:  net.ParseIP("127.0.0.1"),
+			UDP: 22334,
+			TCP: 52150,
 		},
 	},
 }
diff --git a/p2p/discover/table.go b/p2p/discover/table.go
index d3fe373f4..bbd40fde9 100644
--- a/p2p/discover/table.go
+++ b/p2p/discover/table.go
@@ -220,7 +220,7 @@ func (tab *Table) bondall(nodes []*Node) (result []*Node) {
 	rc := make(chan *Node, len(nodes))
 	for i := range nodes {
 		go func(n *Node) {
-			nn, _ := tab.bond(false, n.ID, n.addr(), uint16(n.TCPPort))
+			nn, _ := tab.bond(false, n.ID, n.addr(), uint16(n.TCP))
 			rc <- nn
 		}(nodes[i])
 	}
@@ -299,12 +299,7 @@ func (tab *Table) pingpong(w *bondproc, pinged bool, id NodeID, addr *net.UDPAdd
 		tab.net.waitping(id)
 	}
 	// Bonding succeeded, update the node database
-	w.n = &Node{
-		ID:       id,
-		IP:       addr.IP,
-		DiscPort: addr.Port,
-		TCPPort:  int(tcpPort),
-	}
+	w.n = &Node{ID: id, IP: addr.IP, UDP: uint16(addr.Port), TCP: tcpPort}
 	tab.db.updateNode(w.n)
 	close(w.done)
 }
diff --git a/p2p/discover/table_test.go b/p2p/discover/table_test.go
index e2bd3c8ad..e7394756d 100644
--- a/p2p/discover/table_test.go
+++ b/p2p/discover/table_test.go
@@ -261,9 +261,9 @@ func (t findnodeOracle) findnode(toid NodeID, toaddr *net.UDPAddr, target NodeID
 		panic("query to node at distance 0")
 	default:
 		// TODO: add more randomness to distances
-		next := toaddr.Port - 1
+		next := uint16(toaddr.Port) - 1
 		for i := 0; i < bucketSize; i++ {
-			result = append(result, &Node{ID: randomID(t.target, next), DiscPort: next})
+			result = append(result, &Node{ID: randomID(t.target, int(next)), UDP: next})
 		}
 	}
 	return result, nil
diff --git a/p2p/discover/udp.go b/p2p/discover/udp.go
index 65741b5f5..baff75a63 100644
--- a/p2p/discover/udp.go
+++ b/p2p/discover/udp.go
@@ -49,16 +49,20 @@ const (
 // RPC request structures
 type (
 	ping struct {
-		Version    uint   // must match Version
-		IP         string // our IP
-		Port       uint16 // our port
+		Version    uint
+		From, To   rpcEndpoint
 		Expiration uint64
 	}
 
-	// reply to Ping
+	// pong is the reply to ping.
 	pong struct {
-		ReplyTok   []byte
-		Expiration uint64
+		// 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.
 	}
 
 	findnode struct {
@@ -73,12 +77,25 @@ type (
 		Nodes      []*Node
 		Expiration uint64
 	}
+
+	rpcEndpoint struct {
+		IP  net.IP // len 4 for IPv4 or 16 for IPv6
+		UDP uint16 // for discovery protocol
+		TCP uint16 // for RLPx protocol
+	}
 )
 
-type rpcNode struct {
-	IP   string
-	Port uint16
-	ID   NodeID
+func makeEndpoint(addr *net.UDPAddr, tcpPort uint16) rpcEndpoint {
+	ip := addr.IP.To4()
+	if ip == nil {
+		ip = addr.IP.To16()
+	}
+	return rpcEndpoint{IP: ip, UDP: uint16(addr.Port), TCP: tcpPort}
+}
+
+func validNode(n *Node) bool {
+	// TODO: don't accept localhost, LAN addresses from internet hosts
+	return !n.IP.IsMulticast() && !n.IP.IsUnspecified() && n.UDP != 0
 }
 
 type packet interface {
@@ -94,8 +111,9 @@ type conn interface {
 
 // udp implements the RPC protocol.
 type udp struct {
-	conn conn
-	priv *ecdsa.PrivateKey
+	conn        conn
+	priv        *ecdsa.PrivateKey
+	ourEndpoint rpcEndpoint
 
 	addpending chan *pending
 	gotreply   chan reply
@@ -176,6 +194,8 @@ func newUDP(priv *ecdsa.PrivateKey, c conn, natm nat.Interface, nodeDBPath strin
 			realaddr = &net.UDPAddr{IP: ext, Port: realaddr.Port}
 		}
 	}
+	// TODO: separate TCP port
+	udp.ourEndpoint = makeEndpoint(realaddr, uint16(realaddr.Port))
 	udp.Table = newTable(udp, PubkeyID(&priv.PublicKey), realaddr, nodeDBPath)
 	go udp.loop()
 	go udp.readLoop()
@@ -194,8 +214,8 @@ func (t *udp) ping(toid NodeID, toaddr *net.UDPAddr) error {
 	errc := t.pending(toid, pongPacket, func(interface{}) bool { return true })
 	t.send(toaddr, pingPacket, ping{
 		Version:    Version,
-		IP:         t.self.IP.String(),
-		Port:       uint16(t.self.TCPPort),
+		From:       t.ourEndpoint,
+		To:         makeEndpoint(toaddr, 0), // TODO: maybe use known TCP port from DB
 		Expiration: uint64(time.Now().Add(expiration).Unix()),
 	})
 	return <-errc
@@ -214,7 +234,7 @@ func (t *udp) findnode(toid NodeID, toaddr *net.UDPAddr, target NodeID) ([]*Node
 		reply := r.(*neighbors)
 		for _, n := range reply.Nodes {
 			nreceived++
-			if n.isValid() {
+			if validNode(n) {
 				nodes = append(nodes, n)
 			}
 		}
@@ -374,17 +394,22 @@ func (t *udp) readLoop() {
 		if err != nil {
 			return
 		}
-		packet, fromID, hash, err := decodePacket(buf[:nbytes])
-		if err != nil {
-			glog.V(logger.Debug).Infof("Bad packet from %v: %v\n", from, err)
-			continue
-		}
-		status := "ok"
-		if err := packet.handle(t, from, fromID, hash); err != nil {
-			status = err.Error()
-		}
-		glog.V(logger.Detail).Infof("<<< %v %T: %s\n", from, packet, status)
+		t.handlePacket(from, buf[:nbytes])
+	}
+}
+
+func (t *udp) handlePacket(from *net.UDPAddr, buf []byte) error {
+	packet, fromID, hash, err := decodePacket(buf)
+	if err != nil {
+		glog.V(logger.Debug).Infof("Bad packet from %v: %v\n", from, err)
+		return err
 	}
+	status := "ok"
+	if err = packet.handle(t, from, fromID, hash); err != nil {
+		status = err.Error()
+	}
+	glog.V(logger.Detail).Infof("<<< %v %T: %s\n", from, packet, status)
+	return err
 }
 
 func decodePacket(buf []byte) (packet, NodeID, []byte, error) {
@@ -425,12 +450,13 @@ func (req *ping) handle(t *udp, from *net.UDPAddr, fromID NodeID, mac []byte) er
 		return errBadVersion
 	}
 	t.send(from, pongPacket, pong{
+		To:         makeEndpoint(from, req.From.TCP),
 		ReplyTok:   mac,
 		Expiration: uint64(time.Now().Add(expiration).Unix()),
 	})
 	if !t.handleReply(fromID, pingPacket, req) {
 		// Note: we're ignoring the provided IP address right now
-		go t.bond(true, fromID, from, req.Port)
+		go t.bond(true, fromID, from, req.From.TCP)
 	}
 	return nil
 }
diff --git a/p2p/discover/udp_test.go b/p2p/discover/udp_test.go
index 47e04b85a..378edaaa7 100644
--- a/p2p/discover/udp_test.go
+++ b/p2p/discover/udp_test.go
@@ -23,6 +23,15 @@ func init() {
 	logger.AddLogSystem(logger.NewStdLogSystem(os.Stdout, logpkg.LstdFlags, logger.ErrorLevel))
 }
 
+// shared test variables
+var (
+	futureExp          = uint64(time.Now().Add(10 * time.Hour).Unix())
+	testTarget         = MustHexID("01010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101")
+	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}
+)
+
 type udpTest struct {
 	t                   *testing.T
 	pipe                *dgramPipe
@@ -52,8 +61,7 @@ func (test *udpTest) packetIn(wantError error, ptype byte, data packet) error {
 		return test.errorf("packet (%d) encode error: %v", err)
 	}
 	test.sent = append(test.sent, enc)
-	err = data.handle(test.udp, test.remoteaddr, PubkeyID(&test.remotekey.PublicKey), enc[:macSize])
-	if err != wantError {
+	if err = test.udp.handlePacket(test.remoteaddr, enc); err != wantError {
 		return test.errorf("error mismatch: got %q, want %q", err, wantError)
 	}
 	return nil
@@ -90,18 +98,12 @@ func (test *udpTest) errorf(format string, args ...interface{}) error {
 	return err
 }
 
-// shared test variables
-var (
-	futureExp  = uint64(time.Now().Add(10 * time.Hour).Unix())
-	testTarget = MustHexID("01010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101")
-)
-
 func TestUDP_packetErrors(t *testing.T) {
 	test := newUDPTest(t)
 	defer test.table.Close()
 
-	test.packetIn(errExpired, pingPacket, &ping{IP: "foo", Port: 99, Version: Version})
-	test.packetIn(errBadVersion, pingPacket, &ping{IP: "foo", Port: 99, Version: 99, Expiration: futureExp})
+	test.packetIn(errExpired, pingPacket, &ping{From: testRemote, To: testLocalAnnounced, Version: Version})
+	test.packetIn(errBadVersion, pingPacket, &ping{From: testRemote, To: testLocalAnnounced, Version: 99, Expiration: futureExp})
 	test.packetIn(errUnsolicitedReply, pongPacket, &pong{ReplyTok: []byte{}, Expiration: futureExp})
 	test.packetIn(errUnknownNode, findnodePacket, &findnode{Expiration: futureExp})
 	test.packetIn(errUnsolicitedReply, neighborsPacket, &neighbors{Expiration: futureExp})
@@ -147,10 +149,10 @@ func TestUDP_findnode(t *testing.T) {
 	nodes := &nodesByDistance{target: target}
 	for i := 0; i < bucketSize; i++ {
 		nodes.push(&Node{
-			IP:       net.IP{1, 2, 3, byte(i)},
-			DiscPort: i + 2,
-			TCPPort:  i + 2,
-			ID:       randomID(test.table.self.ID, i+2),
+			IP:  net.IP{1, 2, 3, byte(i)},
+			UDP: uint16(i + 2),
+			TCP: uint16(i + 3),
+			ID:  randomID(test.table.self.ID, i+2),
 		}, bucketSize)
 	}
 	test.table.add(nodes.entries)
@@ -158,10 +160,10 @@ func TestUDP_findnode(t *testing.T) {
 	// ensure there's a bond with the test node,
 	// findnode won't be accepted otherwise.
 	test.table.db.updateNode(&Node{
-		ID:       PubkeyID(&test.remotekey.PublicKey),
-		IP:       test.remoteaddr.IP,
-		DiscPort: test.remoteaddr.Port,
-		TCPPort:  99,
+		ID:  PubkeyID(&test.remotekey.PublicKey),
+		IP:  test.remoteaddr.IP,
+		UDP: uint16(test.remoteaddr.Port),
+		TCP: 99,
 	})
 	// check that closest neighbors are returned.
 	test.packetIn(nil, findnodePacket, &findnode{Target: testTarget, Expiration: futureExp})
@@ -204,9 +206,9 @@ func TestUDP_findnodeMultiReply(t *testing.T) {
 
 	// send the reply as two packets.
 	list := []*Node{
-		MustParseNode("enode://ba85011c70bcc5c04d8607d3a0ed29aa6179c092cbdda10d5d32684fb33ed01bd94f588ca8f91ac48318087dcb02eaf36773a7a453f0eedd6742af668097b29c@10.0.1.16:30303"),
+		MustParseNode("enode://ba85011c70bcc5c04d8607d3a0ed29aa6179c092cbdda10d5d32684fb33ed01bd94f588ca8f91ac48318087dcb02eaf36773a7a453f0eedd6742af668097b29c@10.0.1.16:30303?discport=30304"),
 		MustParseNode("enode://81fa361d25f157cd421c60dcc28d8dac5ef6a89476633339c5df30287474520caca09627da18543d9079b5b288698b542d56167aa5c09111e55acdbbdf2ef799@10.0.1.16:30303"),
-		MustParseNode("enode://9bffefd833d53fac8e652415f4973bee289e8b1a5c6c4cbe70abf817ce8a64cee11b823b66a987f51aaa9fba0d6a91b3e6bf0d5a5d1042de8e9eeea057b217f8@10.0.1.36:30301"),
+		MustParseNode("enode://9bffefd833d53fac8e652415f4973bee289e8b1a5c6c4cbe70abf817ce8a64cee11b823b66a987f51aaa9fba0d6a91b3e6bf0d5a5d1042de8e9eeea057b217f8@10.0.1.36:30301?discport=17"),
 		MustParseNode("enode://1b5b4aa662d7cb44a7221bfba67302590b643028197a7d5214790f3bac7aaa4a3241be9e83c09cf1f6c69d007c634faae3dc1b1221793e8446c0b3a09de65960@10.0.1.16:30303"),
 	}
 	test.packetIn(nil, neighborsPacket, &neighbors{Expiration: futureExp, Nodes: list[:2]})
@@ -231,7 +233,8 @@ func TestUDP_successfulPing(t *testing.T) {
 
 	done := make(chan struct{})
 	go func() {
-		test.packetIn(nil, pingPacket, &ping{IP: "foo", Port: 99, Version: Version, Expiration: futureExp})
+		// The remote side sends a ping packet to initiate the exchange.
+		test.packetIn(nil, pingPacket, &ping{From: testRemote, To: testLocalAnnounced, Version: Version, Expiration: futureExp})
 		close(done)
 	}()
 
@@ -239,12 +242,34 @@ func TestUDP_successfulPing(t *testing.T) {
 	test.waitPacketOut(func(p *pong) {
 		pinghash := test.sent[0][:macSize]
 		if !bytes.Equal(p.ReplyTok, pinghash) {
-			t.Errorf("got ReplyTok %x, want %x", p.ReplyTok, pinghash)
+			t.Errorf("got pong.ReplyTok %x, want %x", p.ReplyTok, pinghash)
+		}
+		wantTo := rpcEndpoint{
+			// 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
+			TCP: testRemote.TCP,
+		}
+		if !reflect.DeepEqual(p.To, wantTo) {
+			t.Errorf("got pong.To %v, want %v", p.To, wantTo)
 		}
 	})
 
 	// remote is unknown, the table pings back.
-	test.waitPacketOut(func(p *ping) error { return nil })
+	test.waitPacketOut(func(p *ping) error {
+		if !reflect.DeepEqual(p.From, test.udp.ourEndpoint) {
+			t.Errorf("got ping.From %v, want %v", p.From, test.udp.ourEndpoint)
+		}
+		wantTo := rpcEndpoint{
+			// The mirrored UDP address is the UDP packet sender.
+			IP: test.remoteaddr.IP, UDP: uint16(test.remoteaddr.Port),
+			TCP: 0,
+		}
+		if !reflect.DeepEqual(p.To, wantTo) {
+			t.Errorf("got ping.To %v, want %v", p.To, wantTo)
+		}
+		return nil
+	})
 	test.packetIn(nil, pongPacket, &pong{Expiration: futureExp})
 
 	// ping should return shortly after getting the pong packet.
@@ -259,11 +284,11 @@ func TestUDP_successfulPing(t *testing.T) {
 	if !bytes.Equal(rnode.IP, test.remoteaddr.IP) {
 		t.Errorf("node has wrong IP: got %v, want: %v", rnode.IP, test.remoteaddr.IP)
 	}
-	if rnode.DiscPort != test.remoteaddr.Port {
-		t.Errorf("node has wrong Port: got %v, want: %v", rnode.DiscPort, test.remoteaddr.Port)
+	if int(rnode.UDP) != test.remoteaddr.Port {
+		t.Errorf("node has wrong UDP port: got %v, want: %v", rnode.UDP, test.remoteaddr.Port)
 	}
-	if rnode.TCPPort != 99 {
-		t.Errorf("node has wrong Port: got %v, want: %v", rnode.TCPPort, 99)
+	if rnode.TCP != testRemote.TCP {
+		t.Errorf("node has wrong TCP port: got %v, want: %v", rnode.TCP, testRemote.TCP)
 	}
 }
 
@@ -327,7 +352,7 @@ func (c *dgramPipe) Close() error {
 }
 
 func (c *dgramPipe) LocalAddr() net.Addr {
-	return &net.UDPAddr{}
+	return &net.UDPAddr{IP: testLocal.IP, Port: int(testLocal.UDP)}
 }
 
 func (c *dgramPipe) waitPacketOut() []byte {