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.

1 files changed, 52 insertions, 26 deletions

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
 }