p2p/discover: add initial discovery v5 implementation (#20750)

This adds an implementation of the current discovery v5 spec.

There is full integration with cmd/devp2p and enode.Iterator in this
version. In theory we could enable the new protocol as a replacement of
discovery v4 at any time. In practice, there will likely be a few more
changes to the spec and implementation before this can happen.

cmd/devp2p/crawl.go

@@ -20,14 +20,13 @@ import (
 	"time"
 
 	"github.com/ethereum/go-ethereum/log"
-	"github.com/ethereum/go-ethereum/p2p/discover"
 	"github.com/ethereum/go-ethereum/p2p/enode"
 )
 
 type crawler struct {
 	input     nodeSet
 	output    nodeSet
-	disc      *discover.UDPv4
+	disc      resolver
 	iters     []enode.Iterator
 	inputIter enode.Iterator
 	ch        chan *enode.Node
@@ -37,7 +36,11 @@ type crawler struct {
 	revalidateInterval time.Duration
 }
 
-func newCrawler(input nodeSet, disc *discover.UDPv4, iters ...enode.Iterator) *crawler {
+type resolver interface {
+	RequestENR(*enode.Node) (*enode.Node, error)
+}
+
+func newCrawler(input nodeSet, disc resolver, iters ...enode.Iterator) *crawler {
 	c := &crawler{
 		input:     input,
 		output:    make(nodeSet, len(input)),

cmd/devp2p/discv4cmd.go

@@ -81,6 +81,18 @@ var (
 		Name:  "bootnodes",
 		Usage: "Comma separated nodes used for bootstrapping",
 	}
+	nodekeyFlag = cli.StringFlag{
+		Name:  "nodekey",
+		Usage: "Hex-encoded node key",
+	}
+	nodedbFlag = cli.StringFlag{
+		Name:  "nodedb",
+		Usage: "Nodes database location",
+	}
+	listenAddrFlag = cli.StringFlag{
+		Name:  "addr",
+		Usage: "Listening address",
+	}
 	crawlTimeoutFlag = cli.DurationFlag{
 		Name:  "timeout",
 		Usage: "Time limit for the crawl.",
@@ -172,6 +184,62 @@ func discv4Crawl(ctx *cli.Context) error {
 	return nil
 }
 
+// startV4 starts an ephemeral discovery V4 node.
+func startV4(ctx *cli.Context) *discover.UDPv4 {
+	ln, config := makeDiscoveryConfig(ctx)
+	socket := listen(ln, ctx.String(listenAddrFlag.Name))
+	disc, err := discover.ListenV4(socket, ln, config)
+	if err != nil {
+		exit(err)
+	}
+	return disc
+}
+
+func makeDiscoveryConfig(ctx *cli.Context) (*enode.LocalNode, discover.Config) {
+	var cfg discover.Config
+
+	if ctx.IsSet(nodekeyFlag.Name) {
+		key, err := crypto.HexToECDSA(ctx.String(nodekeyFlag.Name))
+		if err != nil {
+			exit(fmt.Errorf("-%s: %v", nodekeyFlag.Name, err))
+		}
+		cfg.PrivateKey = key
+	} else {
+		cfg.PrivateKey, _ = crypto.GenerateKey()
+	}
+
+	if commandHasFlag(ctx, bootnodesFlag) {
+		bn, err := parseBootnodes(ctx)
+		if err != nil {
+			exit(err)
+		}
+		cfg.Bootnodes = bn
+	}
+
+	dbpath := ctx.String(nodedbFlag.Name)
+	db, err := enode.OpenDB(dbpath)
+	if err != nil {
+		exit(err)
+	}
+	ln := enode.NewLocalNode(db, cfg.PrivateKey)
+	return ln, cfg
+}
+
+func listen(ln *enode.LocalNode, addr string) *net.UDPConn {
+	if addr == "" {
+		addr = "0.0.0.0:0"
+	}
+	socket, err := net.ListenPacket("udp4", addr)
+	if err != nil {
+		exit(err)
+	}
+	usocket := socket.(*net.UDPConn)
+	uaddr := socket.LocalAddr().(*net.UDPAddr)
+	ln.SetFallbackIP(net.IP{127, 0, 0, 1})
+	ln.SetFallbackUDP(uaddr.Port)
+	return usocket
+}
+
 func parseBootnodes(ctx *cli.Context) ([]*enode.Node, error) {
 	s := params.RinkebyBootnodes
 	if ctx.IsSet(bootnodesFlag.Name) {
@@ -187,40 +255,3 @@ func parseBootnodes(ctx *cli.Context) ([]*enode.Node, error) {
 	}
 	return nodes, nil
 }
-
-// startV4 starts an ephemeral discovery V4 node.
-func startV4(ctx *cli.Context) *discover.UDPv4 {
-	socket, ln, cfg, err := listen()
-	if err != nil {
-		exit(err)
-	}
-	if commandHasFlag(ctx, bootnodesFlag) {
-		bn, err := parseBootnodes(ctx)
-		if err != nil {
-			exit(err)
-		}
-		cfg.Bootnodes = bn
-	}
-	disc, err := discover.ListenV4(socket, ln, cfg)
-	if err != nil {
-		exit(err)
-	}
-	return disc
-}
-
-func listen() (*net.UDPConn, *enode.LocalNode, discover.Config, error) {
-	var cfg discover.Config
-	cfg.PrivateKey, _ = crypto.GenerateKey()
-	db, _ := enode.OpenDB("")
-	ln := enode.NewLocalNode(db, cfg.PrivateKey)
-
-	socket, err := net.ListenUDP("udp4", &net.UDPAddr{IP: net.IP{0, 0, 0, 0}})
-	if err != nil {
-		db.Close()
-		return nil, nil, cfg, err
-	}
-	addr := socket.LocalAddr().(*net.UDPAddr)
-	ln.SetFallbackIP(net.IP{127, 0, 0, 1})
-	ln.SetFallbackUDP(addr.Port)
-	return socket, ln, cfg, nil
-}

cmd/devp2p/discv5cmd.go

@@ -0,0 +1,123 @@
+// Copyright 2019 The go-ethereum Authors
+// This file is part of go-ethereum.
+//
+// go-ethereum is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// go-ethereum 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 General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with go-ethereum. If not, see <http://www.gnu.org/licenses/>.
+
+package main
+
+import (
+	"fmt"
+	"time"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/p2p/discover"
+	"gopkg.in/urfave/cli.v1"
+)
+
+var (
+	discv5Command = cli.Command{
+		Name:  "discv5",
+		Usage: "Node Discovery v5 tools",
+		Subcommands: []cli.Command{
+			discv5PingCommand,
+			discv5ResolveCommand,
+			discv5CrawlCommand,
+			discv5ListenCommand,
+		},
+	}
+	discv5PingCommand = cli.Command{
+		Name:   "ping",
+		Usage:  "Sends ping to a node",
+		Action: discv5Ping,
+	}
+	discv5ResolveCommand = cli.Command{
+		Name:   "resolve",
+		Usage:  "Finds a node in the DHT",
+		Action: discv5Resolve,
+		Flags:  []cli.Flag{bootnodesFlag},
+	}
+	discv5CrawlCommand = cli.Command{
+		Name:   "crawl",
+		Usage:  "Updates a nodes.json file with random nodes found in the DHT",
+		Action: discv5Crawl,
+		Flags:  []cli.Flag{bootnodesFlag, crawlTimeoutFlag},
+	}
+	discv5ListenCommand = cli.Command{
+		Name:   "listen",
+		Usage:  "Runs a node",
+		Action: discv5Listen,
+		Flags: []cli.Flag{
+			bootnodesFlag,
+			nodekeyFlag,
+			nodedbFlag,
+			listenAddrFlag,
+		},
+	}
+)
+
+func discv5Ping(ctx *cli.Context) error {
+	n := getNodeArg(ctx)
+	disc := startV5(ctx)
+	defer disc.Close()
+
+	fmt.Println(disc.Ping(n))
+	return nil
+}
+
+func discv5Resolve(ctx *cli.Context) error {
+	n := getNodeArg(ctx)
+	disc := startV5(ctx)
+	defer disc.Close()
+
+	fmt.Println(disc.Resolve(n))
+	return nil
+}
+
+func discv5Crawl(ctx *cli.Context) error {
+	if ctx.NArg() < 1 {
+		return fmt.Errorf("need nodes file as argument")
+	}
+	nodesFile := ctx.Args().First()
+	var inputSet nodeSet
+	if common.FileExist(nodesFile) {
+		inputSet = loadNodesJSON(nodesFile)
+	}
+
+	disc := startV5(ctx)
+	defer disc.Close()
+	c := newCrawler(inputSet, disc, disc.RandomNodes())
+	c.revalidateInterval = 10 * time.Minute
+	output := c.run(ctx.Duration(crawlTimeoutFlag.Name))
+	writeNodesJSON(nodesFile, output)
+	return nil
+}
+
+func discv5Listen(ctx *cli.Context) error {
+	disc := startV5(ctx)
+	defer disc.Close()
+
+	fmt.Println(disc.Self())
+	select {}
+}
+
+// startV5 starts an ephemeral discovery v5 node.
+func startV5(ctx *cli.Context) *discover.UDPv5 {
+	ln, config := makeDiscoveryConfig(ctx)
+	socket := listen(ln, ctx.String(listenAddrFlag.Name))
+	disc, err := discover.ListenV5(socket, ln, config)
+	if err != nil {
+		exit(err)
+	}
+	return disc
+}

cmd/devp2p/main.go

@@ -59,6 +59,7 @@ func init() {
 	app.Commands = []cli.Command{
 		enrdumpCommand,
 		discv4Command,
+		discv5Command,
 		dnsCommand,
 		nodesetCommand,
 	}

p2p/discover/common.go

@@ -20,8 +20,10 @@ import (
 	"crypto/ecdsa"
 	"net"
 
+	"github.com/ethereum/go-ethereum/common/mclock"
 	"github.com/ethereum/go-ethereum/log"
 	"github.com/ethereum/go-ethereum/p2p/enode"
+	"github.com/ethereum/go-ethereum/p2p/enr"
 	"github.com/ethereum/go-ethereum/p2p/netutil"
 )
 
@@ -43,6 +45,21 @@ type Config struct {
 	Bootnodes    []*enode.Node      // list of bootstrap nodes
 	Unhandled    chan<- ReadPacket  // unhandled packets are sent on this channel
 	Log          log.Logger         // if set, log messages go here
+	ValidSchemes enr.IdentityScheme // allowed identity schemes
+	Clock        mclock.Clock
+}
+
+func (cfg Config) withDefaults() Config {
+	if cfg.Log == nil {
+		cfg.Log = log.Root()
+	}
+	if cfg.ValidSchemes == nil {
+		cfg.ValidSchemes = enode.ValidSchemes
+	}
+	if cfg.Clock == nil {
+		cfg.Clock = mclock.System{}
+	}
+	return cfg
 }
 
 // ListenUDP starts listening for discovery packets on the given UDP socket.
@@ -51,8 +68,15 @@ func ListenUDP(c UDPConn, ln *enode.LocalNode, cfg Config) (*UDPv4, error) {
 }
 
 // ReadPacket is a packet that couldn't be handled. Those packets are sent to the unhandled
-// channel if configured. This is exported for internal use, do not use this type.
+// channel if configured.
 type ReadPacket struct {
 	Data []byte
 	Addr *net.UDPAddr
 }
+
+func min(x, y int) int {
+	if x > y {
+		return y
+	}
+	return x
+}

p2p/discover/lookup.go

@@ -150,7 +150,7 @@ func (it *lookup) query(n *node, reply chan<- []*node) {
 	} else if len(r) == 0 {
 		fails++
 		it.tab.db.UpdateFindFails(n.ID(), n.IP(), fails)
-		it.tab.log.Trace("Findnode failed", "id", n.ID(), "failcount", fails, "err", err)
+		it.tab.log.Trace("Findnode failed", "id", n.ID(), "failcount", fails, "results", len(r), "err", err)
 		if fails >= maxFindnodeFailures {
 			it.tab.log.Trace("Too many findnode failures, dropping", "id", n.ID(), "failcount", fails)
 			it.tab.delete(n)

p2p/discover/node.go

@@ -18,6 +18,7 @@ package discover
 
 import (
 	"crypto/ecdsa"
+	"crypto/elliptic"
 	"errors"
 	"math/big"
 	"net"
@@ -45,13 +46,13 @@ func encodePubkey(key *ecdsa.PublicKey) encPubkey {
 	return e
 }
 
-func decodePubkey(e encPubkey) (*ecdsa.PublicKey, error) {
-	p := &ecdsa.PublicKey{Curve: crypto.S256(), X: new(big.Int), Y: new(big.Int)}
+func decodePubkey(curve elliptic.Curve, e encPubkey) (*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, errors.New("invalid secp256k1 curve point")
+		return nil, errors.New("invalid curve point")
 	}
 	return p, nil
 }

p2p/discover/table.go

@@ -424,6 +424,10 @@ func (tab *Table) len() (n int) {
 // bucket returns the bucket for the given node ID hash.
 func (tab *Table) bucket(id enode.ID) *bucket {
 	d := enode.LogDist(tab.self().ID(), id)
+	return tab.bucketAtDistance(d)
+}
+
+func (tab *Table) bucketAtDistance(d int) *bucket {
 	if d <= bucketMinDistance {
 		return tab.buckets[0]
 	}

p2p/discover/table_util_test.go

@@ -24,7 +24,6 @@ import (
 	"fmt"
 	"math/rand"
 	"net"
-	"reflect"
 	"sort"
 	"sync"
 
@@ -56,6 +55,23 @@ func nodeAtDistance(base enode.ID, ld int, ip net.IP) *node {
 	return wrapNode(enode.SignNull(&r, idAtDistance(base, ld)))
 }
 
+// nodesAtDistance creates n nodes for which enode.LogDist(base, node.ID()) == ld.
+func nodesAtDistance(base enode.ID, ld int, n int) []*enode.Node {
+	results := make([]*enode.Node, n)
+	for i := range results {
+		results[i] = unwrapNode(nodeAtDistance(base, ld, intIP(i)))
+	}
+	return results
+}
+
+func nodesToRecords(nodes []*enode.Node) []*enr.Record {
+	records := make([]*enr.Record, len(nodes))
+	for i := range nodes {
+		records[i] = nodes[i].Record()
+	}
+	return records
+}
+
 // idAtDistance returns a random hash such that enode.LogDist(a, b) == n
 func idAtDistance(a enode.ID, n int) (b enode.ID) {
 	if n == 0 {
@@ -173,9 +189,16 @@ func hasDuplicates(slice []*node) bool {
 }
 
 func checkNodesEqual(got, want []*enode.Node) error {
-	if reflect.DeepEqual(got, want) {
+	if len(got) == len(want) {
+		for i := range got {
+			if !nodeEqual(got[i], want[i]) {
+				goto NotEqual
+			}
 			return nil
 		}
+	}
+
+NotEqual:
 	output := new(bytes.Buffer)
 	fmt.Fprintf(output, "got %d nodes:\n", len(got))
 	for _, n := range got {
@@ -188,6 +211,10 @@ func checkNodesEqual(got, want []*enode.Node) error {
 	return errors.New(output.String())
 }
 
+func nodeEqual(n1 *enode.Node, n2 *enode.Node) bool {
+	return n1.ID() == n2.ID() && n1.IP().Equal(n2.IP())
+}
+
 func sortByID(nodes []*enode.Node) {
 	sort.Slice(nodes, func(i, j int) bool {
 		return string(nodes[i].ID().Bytes()) < string(nodes[j].ID().Bytes())

p2p/discover/v4_lookup_test.go

@@ -25,6 +25,7 @@ import (
 
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/p2p/enode"
+	"github.com/ethereum/go-ethereum/p2p/enr"
 )
 
 func TestUDPv4_Lookup(t *testing.T) {
@@ -32,7 +33,7 @@ func TestUDPv4_Lookup(t *testing.T) {
 	test := newUDPTest(t)
 
 	// Lookup on empty table returns no nodes.
-	targetKey, _ := decodePubkey(lookupTestnet.target)
+	targetKey, _ := decodePubkey(crypto.S256(), lookupTestnet.target)
 	if results := test.udp.LookupPubkey(targetKey); len(results) > 0 {
 		t.Fatalf("lookup on empty table returned %d results: %#v", len(results), results)
 	}
@@ -59,15 +60,7 @@ func TestUDPv4_Lookup(t *testing.T) {
 	if len(results) != bucketSize {
 		t.Errorf("wrong number of results: got %d, want %d", len(results), bucketSize)
 	}
-	if hasDuplicates(wrapNodes(results)) {
-		t.Errorf("result set contains duplicate entries")
-	}
-	if !sortedByDistanceTo(lookupTestnet.target.id(), wrapNodes(results)) {
-		t.Errorf("result set not sorted by distance to target")
-	}
-	if err := checkNodesEqual(results, lookupTestnet.closest(bucketSize)); err != nil {
-		t.Errorf("results aren't the closest %d nodes\n%v", bucketSize, err)
-	}
+	checkLookupResults(t, lookupTestnet, results)
 }
 
 func TestUDPv4_LookupIterator(t *testing.T) {
@@ -156,6 +149,26 @@ func serveTestnet(test *udpTest, testnet *preminedTestnet) {
 	}
 }
 
+// checkLookupResults verifies that the results of a lookup are the closest nodes to
+// the testnet's target.
+func checkLookupResults(t *testing.T, tn *preminedTestnet, results []*enode.Node) {
+	t.Helper()
+	t.Logf("results:")
+	for _, e := range results {
+		t.Logf("  ld=%d, %x", enode.LogDist(tn.target.id(), e.ID()), e.ID().Bytes())
+	}
+	if hasDuplicates(wrapNodes(results)) {
+		t.Errorf("result set contains duplicate entries")
+	}
+	if !sortedByDistanceTo(tn.target.id(), wrapNodes(results)) {
+		t.Errorf("result set not sorted by distance to target")
+	}
+	wantNodes := tn.closest(len(results))
+	if err := checkNodesEqual(results, wantNodes); err != nil {
+		t.Error(err)
+	}
+}
+
 // This is the test network for the Lookup test.
 // The nodes were obtained by running lookupTestnet.mine with a random NodeID as target.
 var lookupTestnet = &preminedTestnet{
@@ -242,8 +255,12 @@ func (tn *preminedTestnet) nodes() []*enode.Node {
 
 func (tn *preminedTestnet) node(dist, index int) *enode.Node {
 	key := tn.dists[dist][index]
-	ip := net.IP{127, byte(dist >> 8), byte(dist), byte(index)}
-	return enode.NewV4(&key.PublicKey, ip, 0, 5000)
+	rec := new(enr.Record)
+	rec.Set(enr.IP{127, byte(dist >> 8), byte(dist), byte(index)})
+	rec.Set(enr.UDP(5000))
+	enode.SignV4(rec, key)
+	n, _ := enode.New(enode.ValidSchemes, rec)
+	return n
 }
 
 func (tn *preminedTestnet) nodeByAddr(addr *net.UDPAddr) (*enode.Node, *ecdsa.PrivateKey) {
@@ -261,6 +278,19 @@ func (tn *preminedTestnet) nodesAtDistance(dist int) []rpcNode {
 	return result
 }
 
+func (tn *preminedTestnet) neighborsAtDistance(base *enode.Node, distance uint, elems int) []*enode.Node {
+	nodes := nodesByDistance{target: base.ID()}
+	for d := range lookupTestnet.dists {
+		for i := range lookupTestnet.dists[d] {
+			n := lookupTestnet.node(d, i)
+			if uint(enode.LogDist(n.ID(), base.ID())) == distance {
+				nodes.push(wrapNode(n), elems)
+			}
+		}
+	}
+	return unwrapNodes(nodes.entries)
+}
+
 func (tn *preminedTestnet) closest(n int) (nodes []*enode.Node) {
 	for d := range tn.dists {
 		for i := range tn.dists[d] {

p2p/discover/v4_udp.go

@@ -47,6 +47,7 @@ var (
 	errTimeout          = errors.New("RPC timeout")
 	errClockWarp        = errors.New("reply deadline too far in the future")
 	errClosed           = errors.New("socket closed")
+	errLowPort          = errors.New("low port")
 )
 
 const (
@@ -176,7 +177,7 @@ func (t *UDPv4) nodeFromRPC(sender *net.UDPAddr, rn rpcNode) (*node, error) {
 	if t.netrestrict != nil && !t.netrestrict.Contains(rn.IP) {
 		return nil, errors.New("not contained in netrestrict whitelist")
 	}
-	key, err := decodePubkey(rn.ID)
+	key, err := decodePubkey(crypto.S256(), rn.ID)
 	if err != nil {
 		return nil, err
 	}
@@ -209,7 +210,7 @@ type UDPv4 struct {
 	addReplyMatcher chan *replyMatcher
 	gotreply        chan reply
 	closeCtx        context.Context
-	cancelCloseCtx  func()
+	cancelCloseCtx  context.CancelFunc
 }
 
 // replyMatcher represents a pending reply.
@@ -258,6 +259,7 @@ type reply struct {
 }
 
 func ListenV4(c UDPConn, ln *enode.LocalNode, cfg Config) (*UDPv4, error) {
+	cfg = cfg.withDefaults()
 	closeCtx, cancel := context.WithCancel(context.Background())
 	t := &UDPv4{
 		conn:            c,
@@ -271,9 +273,6 @@ func ListenV4(c UDPConn, ln *enode.LocalNode, cfg Config) (*UDPv4, error) {
 		cancelCloseCtx:  cancel,
 		log:             cfg.Log,
 	}
-	if t.log == nil {
-		t.log = log.Root()
-	}
 
 	tab, err := newTable(t, ln.Database(), cfg.Bootnodes, t.log)
 	if err != nil {
@@ -812,7 +811,7 @@ func (req *pingV4) preverify(t *UDPv4, from *net.UDPAddr, fromID enode.ID, fromK
 	if expired(req.Expiration) {
 		return errExpired
 	}
-	key, err := decodePubkey(fromKey)
+	key, err := decodePubkey(crypto.S256(), fromKey)
 	if err != nil {
 		return errors.New("invalid public key")
 	}

p2p/discover/v4_udp_test.go

@@ -41,10 +41,6 @@ import (
 	"github.com/ethereum/go-ethereum/rlp"
 )
 
-func init() {
-	spew.Config.DisableMethods = true
-}
-
 // shared test variables
 var (
 	futureExp          = uint64(time.Now().Add(10 * time.Hour).Unix())
@@ -117,9 +113,12 @@ func (test *udpTest) packetInFrom(wantError error, key *ecdsa.PrivateKey, addr *
 func (test *udpTest) waitPacketOut(validate interface{}) (closed bool) {
 	test.t.Helper()
 
-	dgram, ok := test.pipe.receive()
-	if !ok {
+	dgram, err := test.pipe.receive()
+	if err == errClosed {
 		return true
+	} else if err != nil {
+		test.t.Error("packet receive error:", err)
+		return false
 	}
 	p, _, hash, err := decodeV4(dgram.data)
 	if err != nil {
@@ -671,17 +670,30 @@ func (c *dgramPipe) LocalAddr() net.Addr {
 	return &net.UDPAddr{IP: testLocal.IP, Port: int(testLocal.UDP)}
 }
 
-func (c *dgramPipe) receive() (dgram, bool) {
+func (c *dgramPipe) receive() (dgram, error) {
 	c.mu.Lock()
 	defer c.mu.Unlock()
-	for len(c.queue) == 0 && !c.closed {
+
+	var timedOut bool
+	timer := time.AfterFunc(3*time.Second, func() {
+		c.mu.Lock()
+		timedOut = true
+		c.mu.Unlock()
+		c.cond.Broadcast()
+	})
+	defer timer.Stop()
+
+	for len(c.queue) == 0 && !c.closed && !timedOut {
 		c.cond.Wait()
 	}
 	if c.closed {
-		return dgram{}, false
+		return dgram{}, errClosed
+	}
+	if timedOut {
+		return dgram{}, errTimeout
 	}
 	p := c.queue[0]
 	copy(c.queue, c.queue[1:])
 	c.queue = c.queue[:len(c.queue)-1]
-	return p, true
+	return p, nil
 }

p2p/discover/v5_encoding.go

@@ -0,0 +1,659 @@
+// 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 discover
+
+import (
+	"bytes"
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	crand "crypto/rand"
+	"crypto/sha256"
+	"errors"
+	"fmt"
+	"hash"
+	"net"
+	"time"
+
+	"github.com/ethereum/go-ethereum/common/math"
+	"github.com/ethereum/go-ethereum/common/mclock"
+	"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"
+	"golang.org/x/crypto/hkdf"
+)
+
+// TODO concurrent WHOAREYOU tie-breaker
+// TODO deal with WHOAREYOU amplification factor (min packet size?)
+// TODO add counter to nonce
+// TODO rehandshake after X packets
+
+// Discovery v5 packet types.
+const (
+	p_pingV5 byte = iota + 1
+	p_pongV5
+	p_findnodeV5
+	p_nodesV5
+	p_requestTicketV5
+	p_ticketV5
+	p_regtopicV5
+	p_regconfirmationV5
+	p_topicqueryV5
+	p_unknownV5   = byte(255) // any non-decryptable packet
+	p_whoareyouV5 = byte(254) // the WHOAREYOU packet
+)
+
+// Discovery v5 packet structures.
+type (
+	// unknownV5 represents any packet that can't be decrypted.
+	unknownV5 struct {
+		AuthTag []byte
+	}
+
+	// WHOAREYOU contains the handshake challenge.
+	whoareyouV5 struct {
+		AuthTag   []byte
+		IDNonce   [32]byte // To be signed by recipient.
+		RecordSeq uint64   // ENR sequence number of recipient
+
+		node *enode.Node
+		sent mclock.AbsTime
+	}
+
+	// PING is sent during liveness checks.
+	pingV5 struct {
+		ReqID  []byte
+		ENRSeq uint64
+	}
+
+	// PONG is the reply to PING.
+	pongV5 struct {
+		ReqID  []byte
+		ENRSeq uint64
+		ToIP   net.IP // These fields should mirror the UDP envelope address of the ping
+		ToPort uint16 // packet, which provides a way to discover the the external address (after NAT).
+	}
+
+	// FINDNODE is a query for nodes in the given bucket.
+	findnodeV5 struct {
+		ReqID    []byte
+		Distance uint
+	}
+
+	// NODES is the reply to FINDNODE and TOPICQUERY.
+	nodesV5 struct {
+		ReqID []byte
+		Total uint8
+		Nodes []*enr.Record
+	}
+
+	// REQUESTTICKET requests a ticket for a topic queue.
+	requestTicketV5 struct {
+		ReqID []byte
+		Topic []byte
+	}
+
+	// TICKET is the response to REQUESTTICKET.
+	ticketV5 struct {
+		ReqID  []byte
+		Ticket []byte
+	}
+
+	// REGTOPIC registers the sender in a topic queue using a ticket.
+	regtopicV5 struct {
+		ReqID  []byte
+		Ticket []byte
+		ENR    *enr.Record
+	}
+
+	// REGCONFIRMATION is the reply to REGTOPIC.
+	regconfirmationV5 struct {
+		ReqID      []byte
+		Registered bool
+	}
+
+	// TOPICQUERY asks for nodes with the given topic.
+	topicqueryV5 struct {
+		ReqID []byte
+		Topic []byte
+	}
+)
+
+const (
+	// Encryption/authentication parameters.
+	authSchemeName   = "gcm"
+	aesKeySize       = 16
+	gcmNonceSize     = 12
+	idNoncePrefix    = "discovery-id-nonce"
+	handshakeTimeout = time.Second
+)
+
+var (
+	errTooShort               = errors.New("packet too short")
+	errUnexpectedHandshake    = errors.New("unexpected auth response, not in handshake")
+	errHandshakeNonceMismatch = errors.New("wrong nonce in auth response")
+	errInvalidAuthKey         = errors.New("invalid ephemeral pubkey")
+	errUnknownAuthScheme      = errors.New("unknown auth scheme in handshake")
+	errNoRecord               = errors.New("expected ENR in handshake but none sent")
+	errInvalidNonceSig        = errors.New("invalid ID nonce signature")
+	zeroNonce                 = make([]byte, gcmNonceSize)
+)
+
+// wireCodec encodes and decodes discovery v5 packets.
+type wireCodec struct {
+	sha256           hash.Hash
+	localnode        *enode.LocalNode
+	privkey          *ecdsa.PrivateKey
+	myChtagHash      enode.ID
+	myWhoareyouMagic []byte
+
+	sc *sessionCache
+}
+
+type handshakeSecrets struct {
+	writeKey, readKey, authRespKey []byte
+}
+
+type authHeader struct {
+	authHeaderList
+	isHandshake bool
+}
+
+type authHeaderList struct {
+	Auth         []byte   // authentication info of packet
+	IDNonce      [32]byte // IDNonce of WHOAREYOU
+	Scheme       string   // name of encryption/authentication scheme
+	EphemeralKey []byte   // ephemeral public key
+	Response     []byte   // encrypted authResponse
+}
+
+type authResponse struct {
+	Version   uint
+	Signature []byte
+	Record    *enr.Record `rlp:"nil"` // sender's record
+}
+
+func (h *authHeader) DecodeRLP(r *rlp.Stream) error {
+	k, _, err := r.Kind()
+	if err != nil {
+		return err
+	}
+	if k == rlp.Byte || k == rlp.String {
+		return r.Decode(&h.Auth)
+	}
+	h.isHandshake = true
+	return r.Decode(&h.authHeaderList)
+}
+
+// ephemeralKey decodes the ephemeral public key in the header.
+func (h *authHeaderList) ephemeralKey(curve elliptic.Curve) *ecdsa.PublicKey {
+	var key encPubkey
+	copy(key[:], h.EphemeralKey)
+	pubkey, _ := decodePubkey(curve, key)
+	return pubkey
+}
+
+// newWireCodec creates a wire codec.
+func newWireCodec(ln *enode.LocalNode, key *ecdsa.PrivateKey, clock mclock.Clock) *wireCodec {
+	c := &wireCodec{
+		sha256:    sha256.New(),
+		localnode: ln,
+		privkey:   key,
+		sc:        newSessionCache(1024, clock),
+	}
+	// Create magic strings for packet matching.
+	self := ln.ID()
+	c.myWhoareyouMagic = c.sha256sum(self[:], []byte("WHOAREYOU"))
+	copy(c.myChtagHash[:], c.sha256sum(self[:]))
+	return c
+}
+
+// encode encodes a packet to a node. 'id' and 'addr' specify the destination node. The
+// 'challenge' parameter should be the most recently received WHOAREYOU packet from that
+// node.
+func (c *wireCodec) encode(id enode.ID, addr string, packet packetV5, challenge *whoareyouV5) ([]byte, []byte, error) {
+	if packet.kind() == p_whoareyouV5 {
+		p := packet.(*whoareyouV5)
+		enc, err := c.encodeWhoareyou(id, p)
+		if err == nil {
+			c.sc.storeSentHandshake(id, addr, p)
+		}
+		return enc, nil, err
+	}
+	// Ensure calling code sets node if needed.
+	if challenge != nil && challenge.node == nil {
+		panic("BUG: missing challenge.node in encode")
+	}
+	writeKey := c.sc.writeKey(id, addr)
+	if writeKey != nil || challenge != nil {
+		return c.encodeEncrypted(id, addr, packet, writeKey, challenge)
+	}
+	return c.encodeRandom(id)
+}
+
+// encodeRandom encodes a random packet.
+func (c *wireCodec) encodeRandom(toID enode.ID) ([]byte, []byte, error) {
+	tag := xorTag(c.sha256sum(toID[:]), c.localnode.ID())
+	r := make([]byte, 44) // TODO randomize size
+	if _, err := crand.Read(r); err != nil {
+		return nil, nil, err
+	}
+	nonce := make([]byte, gcmNonceSize)
+	if _, err := crand.Read(nonce); err != nil {
+		return nil, nil, fmt.Errorf("can't get random data: %v", err)
+	}
+	b := new(bytes.Buffer)
+	b.Write(tag[:])
+	rlp.Encode(b, nonce)
+	b.Write(r)
+	return b.Bytes(), nonce, nil
+}
+
+// encodeWhoareyou encodes WHOAREYOU.
+func (c *wireCodec) encodeWhoareyou(toID enode.ID, packet *whoareyouV5) ([]byte, error) {
+	// Sanity check node field to catch misbehaving callers.
+	if packet.RecordSeq > 0 && packet.node == nil {
+		panic("BUG: missing node in whoareyouV5 with non-zero seq")
+	}
+	b := new(bytes.Buffer)
+	b.Write(c.sha256sum(toID[:], []byte("WHOAREYOU")))
+	err := rlp.Encode(b, packet)
+	return b.Bytes(), err
+}
+
+// encodeEncrypted encodes an encrypted packet.
+func (c *wireCodec) encodeEncrypted(toID enode.ID, toAddr string, packet packetV5, writeKey []byte, challenge *whoareyouV5) (enc []byte, authTag []byte, err error) {
+	nonce := make([]byte, gcmNonceSize)
+	if _, err := crand.Read(nonce); err != nil {
+		return nil, nil, fmt.Errorf("can't get random data: %v", err)
+	}
+
+	var headEnc []byte
+	if challenge == nil {
+		// Regular packet, use existing key and simply encode nonce.
+		headEnc, _ = rlp.EncodeToBytes(nonce)
+	} else {
+		// We're answering WHOAREYOU, generate new keys and encrypt with those.
+		header, sec, err := c.makeAuthHeader(nonce, challenge)
+		if err != nil {
+			return nil, nil, err
+		}
+		if headEnc, err = rlp.EncodeToBytes(header); err != nil {
+			return nil, nil, err
+		}
+		c.sc.storeNewSession(toID, toAddr, sec.readKey, sec.writeKey)
+		writeKey = sec.writeKey
+	}
+
+	// Encode the packet.
+	body := new(bytes.Buffer)
+	body.WriteByte(packet.kind())
+	if err := rlp.Encode(body, packet); err != nil {
+		return nil, nil, err
+	}
+	tag := xorTag(c.sha256sum(toID[:]), c.localnode.ID())
+	headsize := len(tag) + len(headEnc)
+	headbuf := make([]byte, headsize)
+	copy(headbuf[:], tag[:])
+	copy(headbuf[len(tag):], headEnc)
+
+	// Encrypt the body.
+	enc, err = encryptGCM(headbuf, writeKey, nonce, body.Bytes(), tag[:])
+	return enc, nonce, err
+}
+
+// encodeAuthHeader creates the auth header on a call packet following WHOAREYOU.
+func (c *wireCodec) makeAuthHeader(nonce []byte, challenge *whoareyouV5) (*authHeaderList, *handshakeSecrets, error) {
+	resp := &authResponse{Version: 5}
+
+	// Add our record to response if it's newer than what remote
+	// side has.
+	ln := c.localnode.Node()
+	if challenge.RecordSeq < ln.Seq() {
+		resp.Record = ln.Record()
+	}
+
+	// Create the ephemeral key. This needs to be first because the
+	// key is part of the ID nonce signature.
+	var remotePubkey = new(ecdsa.PublicKey)
+	if err := challenge.node.Load((*enode.Secp256k1)(remotePubkey)); err != nil {
+		return nil, nil, fmt.Errorf("can't find secp256k1 key for recipient")
+	}
+	ephkey, err := crypto.GenerateKey()
+	if err != nil {
+		return nil, nil, fmt.Errorf("can't generate ephemeral key")
+	}
+	ephpubkey := encodePubkey(&ephkey.PublicKey)
+
+	// Add ID nonce signature to response.
+	idsig, err := c.signIDNonce(challenge.IDNonce[:], ephpubkey[:])
+	if err != nil {
+		return nil, nil, fmt.Errorf("can't sign: %v", err)
+	}
+	resp.Signature = idsig
+
+	// Create session keys.
+	sec := c.deriveKeys(c.localnode.ID(), challenge.node.ID(), ephkey, remotePubkey, challenge)
+	if sec == nil {
+		return nil, nil, fmt.Errorf("key derivation failed")
+	}
+
+	// Encrypt the authentication response and assemble the auth header.
+	respRLP, err := rlp.EncodeToBytes(resp)
+	if err != nil {
+		return nil, nil, fmt.Errorf("can't encode auth response: %v", err)
+	}
+	respEnc, err := encryptGCM(nil, sec.authRespKey, zeroNonce, respRLP, nil)
+	if err != nil {
+		return nil, nil, fmt.Errorf("can't encrypt auth response: %v", err)
+	}
+	head := &authHeaderList{
+		Auth:         nonce,
+		Scheme:       authSchemeName,
+		IDNonce:      challenge.IDNonce,
+		EphemeralKey: ephpubkey[:],
+		Response:     respEnc,
+	}
+	return head, sec, err
+}
+
+// deriveKeys generates session keys using elliptic-curve Diffie-Hellman key agreement.
+func (c *wireCodec) deriveKeys(n1, n2 enode.ID, priv *ecdsa.PrivateKey, pub *ecdsa.PublicKey, challenge *whoareyouV5) *handshakeSecrets {
+	eph := ecdh(priv, pub)
+	if eph == nil {
+		return nil
+	}
+
+	info := []byte("discovery v5 key agreement")
+	info = append(info, n1[:]...)
+	info = append(info, n2[:]...)
+	kdf := hkdf.New(c.sha256reset, eph, challenge.IDNonce[:], info)
+	sec := handshakeSecrets{
+		writeKey:    make([]byte, aesKeySize),
+		readKey:     make([]byte, aesKeySize),
+		authRespKey: make([]byte, aesKeySize),
+	}
+	kdf.Read(sec.writeKey)
+	kdf.Read(sec.readKey)
+	kdf.Read(sec.authRespKey)
+	for i := range eph {
+		eph[i] = 0
+	}
+	return &sec
+}
+
+// signIDNonce creates the ID nonce signature.
+func (c *wireCodec) signIDNonce(nonce, ephkey []byte) ([]byte, error) {
+	idsig, err := crypto.Sign(c.idNonceHash(nonce, ephkey), c.privkey)
+	if err != nil {
+		return nil, fmt.Errorf("can't sign: %v", err)
+	}
+	return idsig[:len(idsig)-1], nil // remove recovery ID
+}
+
+// idNonceHash computes the hash of id nonce with prefix.
+func (c *wireCodec) idNonceHash(nonce, ephkey []byte) []byte {
+	h := c.sha256reset()
+	h.Write([]byte(idNoncePrefix))
+	h.Write(nonce)
+	h.Write(ephkey)
+	return h.Sum(nil)
+}
+
+// decode decodes a discovery packet.
+func (c *wireCodec) decode(input []byte, addr string) (enode.ID, *enode.Node, packetV5, error) {
+	// Delete timed-out handshakes. This must happen before decoding to avoid
+	// processing the same handshake twice.
+	c.sc.handshakeGC()
+
+	if len(input) < 32 {
+		return enode.ID{}, nil, nil, errTooShort
+	}
+	if bytes.HasPrefix(input, c.myWhoareyouMagic) {
+		p, err := c.decodeWhoareyou(input)
+		return enode.ID{}, nil, p, err
+	}
+	sender := xorTag(input[:32], c.myChtagHash)
+	p, n, err := c.decodeEncrypted(sender, addr, input)
+	return sender, n, p, err
+}
+
+// decodeWhoareyou decode a WHOAREYOU packet.
+func (c *wireCodec) decodeWhoareyou(input []byte) (packetV5, error) {
+	packet := new(whoareyouV5)
+	err := rlp.DecodeBytes(input[32:], packet)
+	return packet, err
+}
+
+// decodeEncrypted decodes an encrypted discovery packet.
+func (c *wireCodec) decodeEncrypted(fromID enode.ID, fromAddr string, input []byte) (packetV5, *enode.Node, error) {
+	// Decode packet header.
+	var head authHeader
+	r := bytes.NewReader(input[32:])
+	err := rlp.Decode(r, &head)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	// Decrypt and process auth response.
+	readKey, node, err := c.decodeAuth(fromID, fromAddr, &head)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	// Decrypt and decode the packet body.
+	headsize := len(input) - r.Len()
+	bodyEnc := input[headsize:]
+	body, err := decryptGCM(readKey, head.Auth, bodyEnc, input[:32])
+	if err != nil {
+		if !head.isHandshake {
+			// Can't decrypt, start handshake.
+			return &unknownV5{AuthTag: head.Auth}, nil, nil
+		}
+		return nil, nil, fmt.Errorf("handshake failed: %v", err)
+	}
+	if len(body) == 0 {
+		return nil, nil, errTooShort
+	}
+	p, err := decodePacketBodyV5(body[0], body[1:])
+	return p, node, err
+}
+
+// decodeAuth processes an auth header.
+func (c *wireCodec) decodeAuth(fromID enode.ID, fromAddr string, head *authHeader) ([]byte, *enode.Node, error) {
+	if !head.isHandshake {
+		return c.sc.readKey(fromID, fromAddr), nil, nil
+	}
+
+	// Remote is attempting handshake. Verify against our last WHOAREYOU.
+	challenge := c.sc.getHandshake(fromID, fromAddr)
+	if challenge == nil {
+		return nil, nil, errUnexpectedHandshake
+	}
+	if head.IDNonce != challenge.IDNonce {
+		return nil, nil, errHandshakeNonceMismatch
+	}
+	sec, n, err := c.decodeAuthResp(fromID, fromAddr, &head.authHeaderList, challenge)
+	if err != nil {
+		return nil, n, err
+	}
+	// Swap keys to match remote.
+	sec.readKey, sec.writeKey = sec.writeKey, sec.readKey
+	c.sc.storeNewSession(fromID, fromAddr, sec.readKey, sec.writeKey)
+	c.sc.deleteHandshake(fromID, fromAddr)
+	return sec.readKey, n, err
+}
+
+// decodeAuthResp decodes and verifies an authentication response.
+func (c *wireCodec) decodeAuthResp(fromID enode.ID, fromAddr string, head *authHeaderList, challenge *whoareyouV5) (*handshakeSecrets, *enode.Node, error) {
+	// Decrypt / decode the response.
+	if head.Scheme != authSchemeName {
+		return nil, nil, errUnknownAuthScheme
+	}
+	ephkey := head.ephemeralKey(c.privkey.Curve)
+	if ephkey == nil {
+		return nil, nil, errInvalidAuthKey
+	}
+	sec := c.deriveKeys(fromID, c.localnode.ID(), c.privkey, ephkey, challenge)
+	respPT, err := decryptGCM(sec.authRespKey, zeroNonce, head.Response, nil)
+	if err != nil {
+		return nil, nil, fmt.Errorf("can't decrypt auth response header: %v", err)
+	}
+	var resp authResponse
+	if err := rlp.DecodeBytes(respPT, &resp); err != nil {
+		return nil, nil, fmt.Errorf("invalid auth response: %v", err)
+	}
+
+	// Verify response node record. The remote node should include the record
+	// if we don't have one or if ours is older than the latest version.
+	node := challenge.node
+	if resp.Record != nil {
+		if node == nil || node.Seq() < resp.Record.Seq() {
+			n, err := enode.New(enode.ValidSchemes, resp.Record)
+			if err != nil {
+				return nil, nil, fmt.Errorf("invalid node record: %v", err)
+			}
+			if n.ID() != fromID {
+				return nil, nil, fmt.Errorf("record in auth respose has wrong ID: %v", n.ID())
+			}
+			node = n
+		}
+	}
+	if node == nil {
+		return nil, nil, errNoRecord
+	}
+
+	// Verify ID nonce signature.
+	err = c.verifyIDSignature(challenge.IDNonce[:], head.EphemeralKey, resp.Signature, node)
+	if err != nil {
+		return nil, nil, err
+	}
+	return sec, node, nil
+}
+
+// verifyIDSignature checks that signature over idnonce was made by the node with given record.
+func (c *wireCodec) verifyIDSignature(nonce, ephkey, sig []byte, n *enode.Node) error {
+	switch idscheme := n.Record().IdentityScheme(); idscheme {
+	case "v4":
+		var pk ecdsa.PublicKey
+		n.Load((*enode.Secp256k1)(&pk)) // cannot fail because record is valid
+		if !crypto.VerifySignature(crypto.FromECDSAPub(&pk), c.idNonceHash(nonce, ephkey), sig) {
+			return errInvalidNonceSig
+		}
+		return nil
+	default:
+		return fmt.Errorf("can't verify ID nonce signature against scheme %q", idscheme)
+	}
+}
+
+// decodePacketBody decodes the body of an encrypted discovery packet.
+func decodePacketBodyV5(ptype byte, body []byte) (packetV5, error) {
+	var dec packetV5
+	switch ptype {
+	case p_pingV5:
+		dec = new(pingV5)
+	case p_pongV5:
+		dec = new(pongV5)
+	case p_findnodeV5:
+		dec = new(findnodeV5)
+	case p_nodesV5:
+		dec = new(nodesV5)
+	case p_requestTicketV5:
+		dec = new(requestTicketV5)
+	case p_ticketV5:
+		dec = new(ticketV5)
+	case p_regtopicV5:
+		dec = new(regtopicV5)
+	case p_regconfirmationV5:
+		dec = new(regconfirmationV5)
+	case p_topicqueryV5:
+		dec = new(topicqueryV5)
+	default:
+		return nil, fmt.Errorf("unknown packet type %d", ptype)
+	}
+	if err := rlp.DecodeBytes(body, dec); err != nil {
+		return nil, err
+	}
+	return dec, nil
+}
+
+// sha256reset returns the shared hash instance.
+func (c *wireCodec) sha256reset() hash.Hash {
+	c.sha256.Reset()
+	return c.sha256
+}
+
+// sha256sum computes sha256 on the concatenation of inputs.
+func (c *wireCodec) sha256sum(inputs ...[]byte) []byte {
+	c.sha256.Reset()
+	for _, b := range inputs {
+		c.sha256.Write(b)
+	}
+	return c.sha256.Sum(nil)
+}
+
+func xorTag(a []byte, b enode.ID) enode.ID {
+	var r enode.ID
+	for i := range r {
+		r[i] = a[i] ^ b[i]
+	}
+	return r
+}
+
+// ecdh creates a shared secret.
+func ecdh(privkey *ecdsa.PrivateKey, pubkey *ecdsa.PublicKey) []byte {
+	secX, secY := pubkey.ScalarMult(pubkey.X, pubkey.Y, privkey.D.Bytes())
+	if secX == nil {
+		return nil
+	}
+	sec := make([]byte, 33)
+	sec[0] = 0x02 | byte(secY.Bit(0))
+	math.ReadBits(secX, sec[1:])
+	return sec
+}
+
+// encryptGCM encrypts pt using AES-GCM with the given key and nonce.
+func encryptGCM(dest, key, nonce, pt, authData []byte) ([]byte, error) {
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		panic(fmt.Errorf("can't create block cipher: %v", err))
+	}
+	aesgcm, err := cipher.NewGCMWithNonceSize(block, gcmNonceSize)
+	if err != nil {
+		panic(fmt.Errorf("can't create GCM: %v", err))
+	}
+	return aesgcm.Seal(dest, nonce, pt, authData), nil
+}
+
+// decryptGCM decrypts ct using AES-GCM with the given key and nonce.
+func decryptGCM(key, nonce, ct, authData []byte) ([]byte, error) {
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		return nil, fmt.Errorf("can't create block cipher: %v", err)
+	}
+	if len(nonce) != gcmNonceSize {
+		return nil, fmt.Errorf("invalid GCM nonce size: %d", len(nonce))
+	}
+	aesgcm, err := cipher.NewGCMWithNonceSize(block, gcmNonceSize)
+	if err != nil {
+		return nil, fmt.Errorf("can't create GCM: %v", err)
+	}
+	pt := make([]byte, 0, len(ct))
+	return aesgcm.Open(pt, nonce, ct, authData)
+}

p2p/discover/v5_encoding_test.go

@@ -0,0 +1,373 @@
+// 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 discover
+
+import (
+	"bytes"
+	"crypto/ecdsa"
+	"encoding/hex"
+	"fmt"
+	"net"
+	"reflect"
+	"testing"
+
+	"github.com/davecgh/go-spew/spew"
+	"github.com/ethereum/go-ethereum/common/mclock"
+	"github.com/ethereum/go-ethereum/crypto"
+	"github.com/ethereum/go-ethereum/p2p/enode"
+)
+
+var (
+	testKeyA, _ = crypto.HexToECDSA("eef77acb6c6a6eebc5b363a475ac583ec7eccdb42b6481424c60f59aa326547f")
+	testKeyB, _ = crypto.HexToECDSA("66fb62bfbd66b9177a138c1e5cddbe4f7c30c343e94e68df8769459cb1cde628")
+	testIDnonce = [32]byte{5, 6, 7, 8, 9, 10, 11, 12}
+)
+
+func TestDeriveKeysV5(t *testing.T) {
+	t.Parallel()
+
+	var (
+		n1        = enode.ID{1}
+		n2        = enode.ID{2}
+		challenge = &whoareyouV5{}
+		db, _     = enode.OpenDB("")
+		ln        = enode.NewLocalNode(db, testKeyA)
+		c         = newWireCodec(ln, testKeyA, mclock.System{})
+	)
+	defer db.Close()
+
+	sec1 := c.deriveKeys(n1, n2, testKeyA, &testKeyB.PublicKey, challenge)
+	sec2 := c.deriveKeys(n1, n2, testKeyB, &testKeyA.PublicKey, challenge)
+	if sec1 == nil || sec2 == nil {
+		t.Fatal("key agreement failed")
+	}
+	if !reflect.DeepEqual(sec1, sec2) {
+		t.Fatalf("keys not equal:\n  %+v\n  %+v", sec1, sec2)
+	}
+}
+
+// This test checks the basic handshake flow where A talks to B and A has no secrets.
+func TestHandshakeV5(t *testing.T) {
+	t.Parallel()
+	net := newHandshakeTest()
+	defer net.close()
+
+	// A -> B   RANDOM PACKET
+	packet, _ := net.nodeA.encode(t, net.nodeB, &findnodeV5{})
+	resp := net.nodeB.expectDecode(t, p_unknownV5, packet)
+
+	// A <- B   WHOAREYOU
+	challenge := &whoareyouV5{
+		AuthTag:   resp.(*unknownV5).AuthTag,
+		IDNonce:   testIDnonce,
+		RecordSeq: 0,
+	}
+	whoareyou, _ := net.nodeB.encode(t, net.nodeA, challenge)
+	net.nodeA.expectDecode(t, p_whoareyouV5, whoareyou)
+
+	// A -> B   FINDNODE
+	findnode, _ := net.nodeA.encodeWithChallenge(t, net.nodeB, challenge, &findnodeV5{})
+	net.nodeB.expectDecode(t, p_findnodeV5, findnode)
+	if len(net.nodeB.c.sc.handshakes) > 0 {
+		t.Fatalf("node B didn't remove handshake from challenge map")
+	}
+
+	// A <- B   NODES
+	nodes, _ := net.nodeB.encode(t, net.nodeA, &nodesV5{Total: 1})
+	net.nodeA.expectDecode(t, p_nodesV5, nodes)
+}
+
+// This test checks that handshake attempts are removed within the timeout.
+func TestHandshakeV5_timeout(t *testing.T) {
+	t.Parallel()
+	net := newHandshakeTest()
+	defer net.close()
+
+	// A -> B   RANDOM PACKET
+	packet, _ := net.nodeA.encode(t, net.nodeB, &findnodeV5{})
+	resp := net.nodeB.expectDecode(t, p_unknownV5, packet)
+
+	// A <- B   WHOAREYOU
+	challenge := &whoareyouV5{
+		AuthTag:   resp.(*unknownV5).AuthTag,
+		IDNonce:   testIDnonce,
+		RecordSeq: 0,
+	}
+	whoareyou, _ := net.nodeB.encode(t, net.nodeA, challenge)
+	net.nodeA.expectDecode(t, p_whoareyouV5, whoareyou)
+
+	// A -> B   FINDNODE after timeout
+	net.clock.Run(handshakeTimeout + 1)
+	findnode, _ := net.nodeA.encodeWithChallenge(t, net.nodeB, challenge, &findnodeV5{})
+	net.nodeB.expectDecodeErr(t, errUnexpectedHandshake, findnode)
+}
+
+// This test checks handshake behavior when no record is sent in the auth response.
+func TestHandshakeV5_norecord(t *testing.T) {
+	t.Parallel()
+	net := newHandshakeTest()
+	defer net.close()
+
+	// A -> B   RANDOM PACKET
+	packet, _ := net.nodeA.encode(t, net.nodeB, &findnodeV5{})
+	resp := net.nodeB.expectDecode(t, p_unknownV5, packet)
+
+	// A <- B   WHOAREYOU
+	nodeA := net.nodeA.n()
+	if nodeA.Seq() == 0 {
+		t.Fatal("need non-zero sequence number")
+	}
+	challenge := &whoareyouV5{
+		AuthTag:   resp.(*unknownV5).AuthTag,
+		IDNonce:   testIDnonce,
+		RecordSeq: nodeA.Seq(),
+		node:      nodeA,
+	}
+	whoareyou, _ := net.nodeB.encode(t, net.nodeA, challenge)
+	net.nodeA.expectDecode(t, p_whoareyouV5, whoareyou)
+
+	// A -> B   FINDNODE
+	findnode, _ := net.nodeA.encodeWithChallenge(t, net.nodeB, challenge, &findnodeV5{})
+	net.nodeB.expectDecode(t, p_findnodeV5, findnode)
+
+	// A <- B   NODES
+	nodes, _ := net.nodeB.encode(t, net.nodeA, &nodesV5{Total: 1})
+	net.nodeA.expectDecode(t, p_nodesV5, nodes)
+}
+
+// In this test, A tries to send FINDNODE with existing secrets but B doesn't know
+// anything about A.
+func TestHandshakeV5_rekey(t *testing.T) {
+	t.Parallel()
+	net := newHandshakeTest()
+	defer net.close()
+
+	initKeys := &handshakeSecrets{
+		readKey:  []byte("BBBBBBBBBBBBBBBB"),
+		writeKey: []byte("AAAAAAAAAAAAAAAA"),
+	}
+	net.nodeA.c.sc.storeNewSession(net.nodeB.id(), net.nodeB.addr(), initKeys.readKey, initKeys.writeKey)
+
+	// A -> B   FINDNODE (encrypted with zero keys)
+	findnode, authTag := net.nodeA.encode(t, net.nodeB, &findnodeV5{})
+	net.nodeB.expectDecode(t, p_unknownV5, findnode)
+
+	// A <- B   WHOAREYOU
+	challenge := &whoareyouV5{AuthTag: authTag, IDNonce: testIDnonce}
+	whoareyou, _ := net.nodeB.encode(t, net.nodeA, challenge)
+	net.nodeA.expectDecode(t, p_whoareyouV5, whoareyou)
+
+	// Check that new keys haven't been stored yet.
+	if s := net.nodeA.c.sc.session(net.nodeB.id(), net.nodeB.addr()); !bytes.Equal(s.writeKey, initKeys.writeKey) || !bytes.Equal(s.readKey, initKeys.readKey) {
+		t.Fatal("node A stored keys too early")
+	}
+	if s := net.nodeB.c.sc.session(net.nodeA.id(), net.nodeA.addr()); s != nil {
+		t.Fatal("node B stored keys too early")
+	}
+
+	// A -> B   FINDNODE encrypted with new keys
+	findnode, _ = net.nodeA.encodeWithChallenge(t, net.nodeB, challenge, &findnodeV5{})
+	net.nodeB.expectDecode(t, p_findnodeV5, findnode)
+
+	// A <- B   NODES
+	nodes, _ := net.nodeB.encode(t, net.nodeA, &nodesV5{Total: 1})
+	net.nodeA.expectDecode(t, p_nodesV5, nodes)
+}
+
+// In this test A and B have different keys before the handshake.
+func TestHandshakeV5_rekey2(t *testing.T) {
+	t.Parallel()
+	net := newHandshakeTest()
+	defer net.close()
+
+	initKeysA := &handshakeSecrets{
+		readKey:  []byte("BBBBBBBBBBBBBBBB"),
+		writeKey: []byte("AAAAAAAAAAAAAAAA"),
+	}
+	initKeysB := &handshakeSecrets{
+		readKey:  []byte("CCCCCCCCCCCCCCCC"),
+		writeKey: []byte("DDDDDDDDDDDDDDDD"),
+	}
+	net.nodeA.c.sc.storeNewSession(net.nodeB.id(), net.nodeB.addr(), initKeysA.readKey, initKeysA.writeKey)
+	net.nodeB.c.sc.storeNewSession(net.nodeA.id(), net.nodeA.addr(), initKeysB.readKey, initKeysA.writeKey)
+
+	// A -> B   FINDNODE encrypted with initKeysA
+	findnode, authTag := net.nodeA.encode(t, net.nodeB, &findnodeV5{Distance: 3})
+	net.nodeB.expectDecode(t, p_unknownV5, findnode)
+
+	// A <- B   WHOAREYOU
+	challenge := &whoareyouV5{AuthTag: authTag, IDNonce: testIDnonce}
+	whoareyou, _ := net.nodeB.encode(t, net.nodeA, challenge)
+	net.nodeA.expectDecode(t, p_whoareyouV5, whoareyou)
+
+	// A -> B   FINDNODE encrypted with new keys
+	findnode, _ = net.nodeA.encodeWithChallenge(t, net.nodeB, challenge, &findnodeV5{})
+	net.nodeB.expectDecode(t, p_findnodeV5, findnode)
+
+	// A <- B   NODES
+	nodes, _ := net.nodeB.encode(t, net.nodeA, &nodesV5{Total: 1})
+	net.nodeA.expectDecode(t, p_nodesV5, nodes)
+}
+
+// This test checks some malformed packets.
+func TestDecodeErrorsV5(t *testing.T) {
+	t.Parallel()
+	net := newHandshakeTest()
+	defer net.close()
+
+	net.nodeA.expectDecodeErr(t, errTooShort, []byte{})
+	// TODO some more tests would be nice :)
+}
+
+// This benchmark checks performance of authHeader decoding, verification and key derivation.
+func BenchmarkV5_DecodeAuthSecp256k1(b *testing.B) {
+	net := newHandshakeTest()
+	defer net.close()
+
+	var (
+		idA       = net.nodeA.id()
+		addrA     = net.nodeA.addr()
+		challenge = &whoareyouV5{AuthTag: []byte("authresp"), RecordSeq: 0, node: net.nodeB.n()}
+		nonce     = make([]byte, gcmNonceSize)
+	)
+	header, _, _ := net.nodeA.c.makeAuthHeader(nonce, challenge)
+	challenge.node = nil // force ENR signature verification in decoder
+	b.ResetTimer()
+
+	for i := 0; i < b.N; i++ {
+		_, _, err := net.nodeB.c.decodeAuthResp(idA, addrA, header, challenge)
+		if err != nil {
+			b.Fatal(err)
+		}
+	}
+}
+
+// This benchmark checks how long it takes to decode an encrypted ping packet.
+func BenchmarkV5_DecodePing(b *testing.B) {
+	net := newHandshakeTest()
+	defer net.close()
+
+	r := []byte{233, 203, 93, 195, 86, 47, 177, 186, 227, 43, 2, 141, 244, 230, 120, 17}
+	w := []byte{79, 145, 252, 171, 167, 216, 252, 161, 208, 190, 176, 106, 214, 39, 178, 134}
+	net.nodeA.c.sc.storeNewSession(net.nodeB.id(), net.nodeB.addr(), r, w)
+	net.nodeB.c.sc.storeNewSession(net.nodeA.id(), net.nodeA.addr(), w, r)
+	addrB := net.nodeA.addr()
+	ping := &pingV5{ReqID: []byte("reqid"), ENRSeq: 5}
+	enc, _, err := net.nodeA.c.encode(net.nodeB.id(), addrB, ping, nil)
+	if err != nil {
+		b.Fatalf("can't encode: %v", err)
+	}
+	b.ResetTimer()
+
+	for i := 0; i < b.N; i++ {
+		_, _, p, _ := net.nodeB.c.decode(enc, addrB)
+		if _, ok := p.(*pingV5); !ok {
+			b.Fatalf("wrong packet type %T", p)
+		}
+	}
+}
+
+var pp = spew.NewDefaultConfig()
+
+type handshakeTest struct {
+	nodeA, nodeB handshakeTestNode
+	clock        mclock.Simulated
+}
+
+type handshakeTestNode struct {
+	ln *enode.LocalNode
+	c  *wireCodec
+}
+
+func newHandshakeTest() *handshakeTest {
+	t := new(handshakeTest)
+	t.nodeA.init(testKeyA, net.IP{127, 0, 0, 1}, &t.clock)
+	t.nodeB.init(testKeyB, net.IP{127, 0, 0, 1}, &t.clock)
+	return t
+}
+
+func (t *handshakeTest) close() {
+	t.nodeA.ln.Database().Close()
+	t.nodeB.ln.Database().Close()
+}
+
+func (n *handshakeTestNode) init(key *ecdsa.PrivateKey, ip net.IP, clock mclock.Clock) {
+	db, _ := enode.OpenDB("")
+	n.ln = enode.NewLocalNode(db, key)
+	n.ln.SetStaticIP(ip)
+	n.c = newWireCodec(n.ln, key, clock)
+}
+
+func (n *handshakeTestNode) encode(t testing.TB, to handshakeTestNode, p packetV5) ([]byte, []byte) {
+	t.Helper()
+	return n.encodeWithChallenge(t, to, nil, p)
+}
+
+func (n *handshakeTestNode) encodeWithChallenge(t testing.TB, to handshakeTestNode, c *whoareyouV5, p packetV5) ([]byte, []byte) {
+	t.Helper()
+	// Copy challenge and add destination node. This avoids sharing 'c' among the two codecs.
+	var challenge *whoareyouV5
+	if c != nil {
+		challengeCopy := *c
+		challenge = &challengeCopy
+		challenge.node = to.n()
+	}
+	// Encode to destination.
+	enc, authTag, err := n.c.encode(to.id(), to.addr(), p, challenge)
+	if err != nil {
+		t.Fatal(fmt.Errorf("(%s) %v", n.ln.ID().TerminalString(), err))
+	}
+	t.Logf("(%s) -> (%s)   %s\n%s", n.ln.ID().TerminalString(), to.id().TerminalString(), p.name(), hex.Dump(enc))
+	return enc, authTag
+}
+
+func (n *handshakeTestNode) expectDecode(t *testing.T, ptype byte, p []byte) packetV5 {
+	t.Helper()
+	dec, err := n.decode(p)
+	if err != nil {
+		t.Fatal(fmt.Errorf("(%s) %v", n.ln.ID().TerminalString(), err))
+	}
+	t.Logf("(%s) %#v", n.ln.ID().TerminalString(), pp.NewFormatter(dec))
+	if dec.kind() != ptype {
+		t.Fatalf("expected packet type %d, got %d", ptype, dec.kind())
+	}
+	return dec
+}
+
+func (n *handshakeTestNode) expectDecodeErr(t *testing.T, wantErr error, p []byte) {
+	t.Helper()
+	if _, err := n.decode(p); !reflect.DeepEqual(err, wantErr) {
+		t.Fatal(fmt.Errorf("(%s) got err %q, want %q", n.ln.ID().TerminalString(), err, wantErr))
+	}
+}
+
+func (n *handshakeTestNode) decode(input []byte) (packetV5, error) {
+	_, _, p, err := n.c.decode(input, "127.0.0.1")
+	return p, err
+}
+
+func (n *handshakeTestNode) n() *enode.Node {
+	return n.ln.Node()
+}
+
+func (n *handshakeTestNode) addr() string {
+	return n.ln.Node().IP().String()
+}
+
+func (n *handshakeTestNode) id() enode.ID {
+	return n.ln.ID()
+}

p2p/discover/v5_session.go

@@ -0,0 +1,123 @@
+// Copyright 2020 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 discover
+
+import (
+	crand "crypto/rand"
+
+	"github.com/ethereum/go-ethereum/common/mclock"
+	"github.com/ethereum/go-ethereum/p2p/enode"
+	"github.com/hashicorp/golang-lru/simplelru"
+)
+
+// The sessionCache keeps negotiated encryption keys and
+// state for in-progress handshakes in the Discovery v5 wire protocol.
+type sessionCache struct {
+	sessions   *simplelru.LRU
+	handshakes map[sessionID]*whoareyouV5
+	clock      mclock.Clock
+}
+
+// sessionID identifies a session or handshake.
+type sessionID struct {
+	id   enode.ID
+	addr string
+}
+
+// session contains session information
+type session struct {
+	writeKey     []byte
+	readKey      []byte
+	nonceCounter uint32
+}
+
+func newSessionCache(maxItems int, clock mclock.Clock) *sessionCache {
+	cache, err := simplelru.NewLRU(maxItems, nil)
+	if err != nil {
+		panic("can't create session cache")
+	}
+	return &sessionCache{
+		sessions:   cache,
+		handshakes: make(map[sessionID]*whoareyouV5),
+		clock:      clock,
+	}
+}
+
+// nextNonce creates a nonce for encrypting a message to the given session.
+func (sc *sessionCache) nextNonce(id enode.ID, addr string) []byte {
+	n := make([]byte, gcmNonceSize)
+	crand.Read(n)
+	return n
+}
+
+// session returns the current session for the given node, if any.
+func (sc *sessionCache) session(id enode.ID, addr string) *session {
+	item, ok := sc.sessions.Get(sessionID{id, addr})
+	if !ok {
+		return nil
+	}
+	return item.(*session)
+}
+
+// readKey returns the current read key for the given node.
+func (sc *sessionCache) readKey(id enode.ID, addr string) []byte {
+	if s := sc.session(id, addr); s != nil {
+		return s.readKey
+	}
+	return nil
+}
+
+// writeKey returns the current read key for the given node.
+func (sc *sessionCache) writeKey(id enode.ID, addr string) []byte {
+	if s := sc.session(id, addr); s != nil {
+		return s.writeKey
+	}
+	return nil
+}
+
+// storeNewSession stores new encryption keys in the cache.
+func (sc *sessionCache) storeNewSession(id enode.ID, addr string, r, w []byte) {
+	sc.sessions.Add(sessionID{id, addr}, &session{
+		readKey: r, writeKey: w,
+	})
+}
+
+// getHandshake gets the handshake challenge we previously sent to the given remote node.
+func (sc *sessionCache) getHandshake(id enode.ID, addr string) *whoareyouV5 {
+	return sc.handshakes[sessionID{id, addr}]
+}
+
+// storeSentHandshake stores the handshake challenge sent to the given remote node.
+func (sc *sessionCache) storeSentHandshake(id enode.ID, addr string, challenge *whoareyouV5) {
+	challenge.sent = sc.clock.Now()
+	sc.handshakes[sessionID{id, addr}] = challenge
+}
+
+// deleteHandshake deletes handshake data for the given node.
+func (sc *sessionCache) deleteHandshake(id enode.ID, addr string) {
+	delete(sc.handshakes, sessionID{id, addr})
+}
+
+// handshakeGC deletes timed-out handshakes.
+func (sc *sessionCache) handshakeGC() {
+	deadline := sc.clock.Now().Add(-handshakeTimeout)
+	for key, challenge := range sc.handshakes {
+		if challenge.sent < deadline {
+			delete(sc.handshakes, key)
+		}
+	}
+}

p2p/discover/v5_udp.go

@@ -0,0 +1,832 @@
+// 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 discover
+
+import (
+	"bytes"
+	"context"
+	"crypto/ecdsa"
+	crand "crypto/rand"
+	"errors"
+	"fmt"
+	"io"
+	"math"
+	"net"
+	"sync"
+	"time"
+
+	"github.com/ethereum/go-ethereum/common/mclock"
+	"github.com/ethereum/go-ethereum/log"
+	"github.com/ethereum/go-ethereum/p2p/enode"
+	"github.com/ethereum/go-ethereum/p2p/enr"
+	"github.com/ethereum/go-ethereum/p2p/netutil"
+)
+
+const (
+	lookupRequestLimit      = 3  // max requests against a single node during lookup
+	findnodeResultLimit     = 15 // applies in FINDNODE handler
+	totalNodesResponseLimit = 5  // applies in waitForNodes
+	nodesResponseItemLimit  = 3  // applies in sendNodes
+
+	respTimeoutV5 = 700 * time.Millisecond
+)
+
+// codecV5 is implemented by wireCodec (and testCodec).
+//
+// The UDPv5 transport is split into two objects: the codec object deals with
+// encoding/decoding and with the handshake; the UDPv5 object handles higher-level concerns.
+type codecV5 interface {
+	// encode encodes a packet. The 'challenge' parameter is non-nil for calls which got a
+	// WHOAREYOU response.
+	encode(fromID enode.ID, fromAddr string, p packetV5, challenge *whoareyouV5) (enc []byte, authTag []byte, err error)
+
+	// decode decodes a packet. It returns an *unknownV5 packet if decryption fails.
+	// The fromNode return value is non-nil when the input contains a handshake response.
+	decode(input []byte, fromAddr string) (fromID enode.ID, fromNode *enode.Node, p packetV5, err error)
+}
+
+// packetV5 is implemented by all discv5 packet type structs.
+type packetV5 interface {
+	// These methods provide information and set the request ID.
+	name() string
+	kind() byte
+	setreqid([]byte)
+	// handle should perform the appropriate action to handle the packet, i.e. this is the
+	// place to send the response.
+	handle(t *UDPv5, fromID enode.ID, fromAddr *net.UDPAddr)
+}
+
+// UDPv5 is the implementation of protocol version 5.
+type UDPv5 struct {
+	// static fields
+	conn         UDPConn
+	tab          *Table
+	netrestrict  *netutil.Netlist
+	priv         *ecdsa.PrivateKey
+	localNode    *enode.LocalNode
+	db           *enode.DB
+	log          log.Logger
+	clock        mclock.Clock
+	validSchemes enr.IdentityScheme
+
+	// channels into dispatch
+	packetInCh    chan ReadPacket
+	readNextCh    chan struct{}
+	callCh        chan *callV5
+	callDoneCh    chan *callV5
+	respTimeoutCh chan *callTimeout
+
+	// state of dispatch
+	codec            codecV5
+	activeCallByNode map[enode.ID]*callV5
+	activeCallByAuth map[string]*callV5
+	callQueue        map[enode.ID][]*callV5
+
+	// shutdown stuff
+	closeOnce      sync.Once
+	closeCtx       context.Context
+	cancelCloseCtx context.CancelFunc
+	wg             sync.WaitGroup
+}
+
+// callV5 represents a remote procedure call against another node.
+type callV5 struct {
+	node         *enode.Node
+	packet       packetV5
+	responseType byte // expected packet type of response
+	reqid        []byte
+	ch           chan packetV5 // responses sent here
+	err          chan error    // errors sent here
+
+	// Valid for active calls only:
+	authTag        []byte       // authTag of request packet
+	handshakeCount int          // # times we attempted handshake for this call
+	challenge      *whoareyouV5 // last sent handshake challenge
+	timeout        mclock.Timer
+}
+
+// callTimeout is the response timeout event of a call.
+type callTimeout struct {
+	c     *callV5
+	timer mclock.Timer
+}
+
+// ListenV5 listens on the given connection.
+func ListenV5(conn UDPConn, ln *enode.LocalNode, cfg Config) (*UDPv5, error) {
+	t, err := newUDPv5(conn, ln, cfg)
+	if err != nil {
+		return nil, err
+	}
+	go t.tab.loop()
+	t.wg.Add(2)
+	go t.readLoop()
+	go t.dispatch()
+	return t, nil
+}
+
+// newUDPv5 creates a UDPv5 transport, but doesn't start any goroutines.
+func newUDPv5(conn UDPConn, ln *enode.LocalNode, cfg Config) (*UDPv5, error) {
+	closeCtx, cancelCloseCtx := context.WithCancel(context.Background())
+	cfg = cfg.withDefaults()
+	t := &UDPv5{
+		// static fields
+		conn:         conn,
+		localNode:    ln,
+		db:           ln.Database(),
+		netrestrict:  cfg.NetRestrict,
+		priv:         cfg.PrivateKey,
+		log:          cfg.Log,
+		validSchemes: cfg.ValidSchemes,
+		clock:        cfg.Clock,
+		// channels into dispatch
+		packetInCh:    make(chan ReadPacket, 1),
+		readNextCh:    make(chan struct{}, 1),
+		callCh:        make(chan *callV5),
+		callDoneCh:    make(chan *callV5),
+		respTimeoutCh: make(chan *callTimeout),
+		// state of dispatch
+		codec:            newWireCodec(ln, cfg.PrivateKey, cfg.Clock),
+		activeCallByNode: make(map[enode.ID]*callV5),
+		activeCallByAuth: make(map[string]*callV5),
+		callQueue:        make(map[enode.ID][]*callV5),
+		// shutdown
+		closeCtx:       closeCtx,
+		cancelCloseCtx: cancelCloseCtx,
+	}
+	tab, err := newTable(t, t.db, cfg.Bootnodes, cfg.Log)
+	if err != nil {
+		return nil, err
+	}
+	t.tab = tab
+	return t, nil
+}
+
+// Self returns the local node record.
+func (t *UDPv5) Self() *enode.Node {
+	return t.localNode.Node()
+}
+
+// Close shuts down packet processing.
+func (t *UDPv5) Close() {
+	t.closeOnce.Do(func() {
+		t.cancelCloseCtx()
+		t.conn.Close()
+		t.wg.Wait()
+		t.tab.close()
+	})
+}
+
+// Ping sends a ping message to the given node.
+func (t *UDPv5) Ping(n *enode.Node) error {
+	_, err := t.ping(n)
+	return err
+}
+
+// Resolve searches for a specific node with the given ID and tries to get the most recent
+// version of the node record for it. It returns n if the node could not be resolved.
+func (t *UDPv5) Resolve(n *enode.Node) *enode.Node {
+	if intable := t.tab.getNode(n.ID()); intable != nil && intable.Seq() > n.Seq() {
+		n = intable
+	}
+	// Try asking directly. This works if the node is still responding on the endpoint we have.
+	if resp, err := t.RequestENR(n); err == nil {
+		return resp
+	}
+	// Otherwise do a network lookup.
+	result := t.Lookup(n.ID())
+	for _, rn := range result {
+		if rn.ID() == n.ID() && rn.Seq() > n.Seq() {
+			return rn
+		}
+	}
+	return n
+}
+
+func (t *UDPv5) RandomNodes() enode.Iterator {
+	if t.tab.len() == 0 {
+		// All nodes were dropped, refresh. The very first query will hit this
+		// case and run the bootstrapping logic.
+		<-t.tab.refresh()
+	}
+
+	return newLookupIterator(t.closeCtx, t.newRandomLookup)
+}
+
+// Lookup performs a recursive lookup for the given target.
+// It returns the closest nodes to target.
+func (t *UDPv5) Lookup(target enode.ID) []*enode.Node {
+	return t.newLookup(t.closeCtx, target).run()
+}
+
+// lookupRandom looks up a random target.
+// This is needed to satisfy the transport interface.
+func (t *UDPv5) lookupRandom() []*enode.Node {
+	return t.newRandomLookup(t.closeCtx).run()
+}
+
+// lookupSelf looks up our own node ID.
+// This is needed to satisfy the transport interface.
+func (t *UDPv5) lookupSelf() []*enode.Node {
+	return t.newLookup(t.closeCtx, t.Self().ID()).run()
+}
+
+func (t *UDPv5) newRandomLookup(ctx context.Context) *lookup {
+	var target enode.ID
+	crand.Read(target[:])
+	return t.newLookup(ctx, target)
+}
+
+func (t *UDPv5) newLookup(ctx context.Context, target enode.ID) *lookup {
+	return newLookup(ctx, t.tab, target, func(n *node) ([]*node, error) {
+		return t.lookupWorker(n, target)
+	})
+}
+
+// lookupWorker performs FINDNODE calls against a single node during lookup.
+func (t *UDPv5) lookupWorker(destNode *node, target enode.ID) ([]*node, error) {
+	var (
+		dists = lookupDistances(target, destNode.ID())
+		nodes = nodesByDistance{target: target}
+		err   error
+	)
+	for i := 0; i < lookupRequestLimit && len(nodes.entries) < findnodeResultLimit; i++ {
+		var r []*enode.Node
+		r, err = t.findnode(unwrapNode(destNode), dists[i])
+		if err == errClosed {
+			return nil, err
+		}
+		for _, n := range r {
+			if n.ID() != t.Self().ID() {
+				nodes.push(wrapNode(n), findnodeResultLimit)
+			}
+		}
+	}
+	return nodes.entries, err
+}
+
+// lookupDistances computes the distance parameter for FINDNODE calls to dest.
+// It chooses distances adjacent to logdist(target, dest), e.g. for a target
+// with logdist(target, dest) = 255 the result is [255, 256, 254].
+func lookupDistances(target, dest enode.ID) (dists []int) {
+	td := enode.LogDist(target, dest)
+	dists = append(dists, td)
+	for i := 1; len(dists) < lookupRequestLimit; i++ {
+		if td+i < 256 {
+			dists = append(dists, td+i)
+		}
+		if td-i > 0 {
+			dists = append(dists, td-i)
+		}
+	}
+	return dists
+}
+
+// ping calls PING on a node and waits for a PONG response.
+func (t *UDPv5) ping(n *enode.Node) (uint64, error) {
+	resp := t.call(n, p_pongV5, &pingV5{ENRSeq: t.localNode.Node().Seq()})
+	defer t.callDone(resp)
+	select {
+	case pong := <-resp.ch:
+		return pong.(*pongV5).ENRSeq, nil
+	case err := <-resp.err:
+		return 0, err
+	}
+}
+
+// requestENR requests n's record.
+func (t *UDPv5) RequestENR(n *enode.Node) (*enode.Node, error) {
+	nodes, err := t.findnode(n, 0)
+	if err != nil {
+		return nil, err
+	}
+	if len(nodes) != 1 {
+		return nil, fmt.Errorf("%d nodes in response for distance zero", len(nodes))
+	}
+	return nodes[0], nil
+}
+
+// requestTicket calls REQUESTTICKET on a node and waits for a TICKET response.
+func (t *UDPv5) requestTicket(n *enode.Node) ([]byte, error) {
+	resp := t.call(n, p_ticketV5, &pingV5{})
+	defer t.callDone(resp)
+	select {
+	case response := <-resp.ch:
+		return response.(*ticketV5).Ticket, nil
+	case err := <-resp.err:
+		return nil, err
+	}
+}
+
+// findnode calls FINDNODE on a node and waits for responses.
+func (t *UDPv5) findnode(n *enode.Node, distance int) ([]*enode.Node, error) {
+	resp := t.call(n, p_nodesV5, &findnodeV5{Distance: uint(distance)})
+	return t.waitForNodes(resp, distance)
+}
+
+// waitForNodes waits for NODES responses to the given call.
+func (t *UDPv5) waitForNodes(c *callV5, distance int) ([]*enode.Node, error) {
+	defer t.callDone(c)
+
+	var (
+		nodes           []*enode.Node
+		seen            = make(map[enode.ID]struct{})
+		received, total = 0, -1
+	)
+	for {
+		select {
+		case responseP := <-c.ch:
+			response := responseP.(*nodesV5)
+			for _, record := range response.Nodes {
+				node, err := t.verifyResponseNode(c, record, distance, seen)
+				if err != nil {
+					t.log.Debug("Invalid record in "+response.name(), "id", c.node.ID(), "err", err)
+					continue
+				}
+				nodes = append(nodes, node)
+			}
+			if total == -1 {
+				total = min(int(response.Total), totalNodesResponseLimit)
+			}
+			if received++; received == total {
+				return nodes, nil
+			}
+		case err := <-c.err:
+			return nodes, err
+		}
+	}
+}
+
+// verifyResponseNode checks validity of a record in a NODES response.
+func (t *UDPv5) verifyResponseNode(c *callV5, r *enr.Record, distance int, seen map[enode.ID]struct{}) (*enode.Node, error) {
+	node, err := enode.New(t.validSchemes, r)
+	if err != nil {
+		return nil, err
+	}
+	if err := netutil.CheckRelayIP(c.node.IP(), node.IP()); err != nil {
+		return nil, err
+	}
+	if c.node.UDP() <= 1024 {
+		return nil, errLowPort
+	}
+	if distance != -1 {
+		if d := enode.LogDist(c.node.ID(), node.ID()); d != distance {
+			return nil, fmt.Errorf("wrong distance %d", d)
+		}
+	}
+	if _, ok := seen[node.ID()]; ok {
+		return nil, fmt.Errorf("duplicate record")
+	}
+	seen[node.ID()] = struct{}{}
+	return node, nil
+}
+
+// call sends the given call and sets up a handler for response packets (of type c.responseType).
+// Responses are dispatched to the call's response channel.
+func (t *UDPv5) call(node *enode.Node, responseType byte, packet packetV5) *callV5 {
+	c := &callV5{
+		node:         node,
+		packet:       packet,
+		responseType: responseType,
+		reqid:        make([]byte, 8),
+		ch:           make(chan packetV5, 1),
+		err:          make(chan error, 1),
+	}
+	// Assign request ID.
+	crand.Read(c.reqid)
+	packet.setreqid(c.reqid)
+	// Send call to dispatch.
+	select {
+	case t.callCh <- c:
+	case <-t.closeCtx.Done():
+		c.err <- errClosed
+	}
+	return c
+}
+
+// callDone tells dispatch that the active call is done.
+func (t *UDPv5) callDone(c *callV5) {
+	select {
+	case t.callDoneCh <- c:
+	case <-t.closeCtx.Done():
+	}
+}
+
+// dispatch runs in its own goroutine, handles incoming packets and deals with calls.
+//
+// For any destination node there is at most one 'active call', stored in the t.activeCall*
+// maps. A call is made active when it is sent. The active call can be answered by a
+// matching response, in which case c.ch receives the response; or by timing out, in which case
+// c.err receives the error. When the function that created the call signals the active
+// call is done through callDone, the next call from the call queue is started.
+//
+// Calls may also be answered by a WHOAREYOU packet referencing the call packet's authTag.
+// When that happens the call is simply re-sent to complete the handshake. We allow one
+// handshake attempt per call.
+func (t *UDPv5) dispatch() {
+	defer t.wg.Done()
+
+	// Arm first read.
+	t.readNextCh <- struct{}{}
+
+	for {
+		select {
+		case c := <-t.callCh:
+			id := c.node.ID()
+			t.callQueue[id] = append(t.callQueue[id], c)
+			t.sendNextCall(id)
+
+		case ct := <-t.respTimeoutCh:
+			active := t.activeCallByNode[ct.c.node.ID()]
+			if ct.c == active && ct.timer == active.timeout {
+				ct.c.err <- errTimeout
+			}
+
+		case c := <-t.callDoneCh:
+			id := c.node.ID()
+			active := t.activeCallByNode[id]
+			if active != c {
+				panic("BUG: callDone for inactive call")
+			}
+			c.timeout.Stop()
+			delete(t.activeCallByAuth, string(c.authTag))
+			delete(t.activeCallByNode, id)
+			t.sendNextCall(id)
+
+		case p := <-t.packetInCh:
+			t.handlePacket(p.Data, p.Addr)
+			// Arm next read.
+			t.readNextCh <- struct{}{}
+
+		case <-t.closeCtx.Done():
+			close(t.readNextCh)
+			for id, queue := range t.callQueue {
+				for _, c := range queue {
+					c.err <- errClosed
+				}
+				delete(t.callQueue, id)
+			}
+			for id, c := range t.activeCallByNode {
+				c.err <- errClosed
+				delete(t.activeCallByNode, id)
+				delete(t.activeCallByAuth, string(c.authTag))
+			}
+			return
+		}
+	}
+}
+
+// startResponseTimeout sets the response timer for a call.
+func (t *UDPv5) startResponseTimeout(c *callV5) {
+	if c.timeout != nil {
+		c.timeout.Stop()
+	}
+	var (
+		timer mclock.Timer
+		done  = make(chan struct{})
+	)
+	timer = t.clock.AfterFunc(respTimeoutV5, func() {
+		<-done
+		select {
+		case t.respTimeoutCh <- &callTimeout{c, timer}:
+		case <-t.closeCtx.Done():
+		}
+	})
+	c.timeout = timer
+	close(done)
+}
+
+// sendNextCall sends the next call in the call queue if there is no active call.
+func (t *UDPv5) sendNextCall(id enode.ID) {
+	queue := t.callQueue[id]
+	if len(queue) == 0 || t.activeCallByNode[id] != nil {
+		return
+	}
+	t.activeCallByNode[id] = queue[0]
+	t.sendCall(t.activeCallByNode[id])
+	if len(queue) == 1 {
+		delete(t.callQueue, id)
+	} else {
+		copy(queue, queue[1:])
+		t.callQueue[id] = queue[:len(queue)-1]
+	}
+}
+
+// sendCall encodes and sends a request packet to the call's recipient node.
+// This performs a handshake if needed.
+func (t *UDPv5) sendCall(c *callV5) {
+	if len(c.authTag) > 0 {
+		// The call already has an authTag from a previous handshake attempt. Remove the
+		// entry for the authTag because we're about to generate a new authTag for this
+		// call.
+		delete(t.activeCallByAuth, string(c.authTag))
+	}
+
+	addr := &net.UDPAddr{IP: c.node.IP(), Port: c.node.UDP()}
+	newTag, _ := t.send(c.node.ID(), addr, c.packet, c.challenge)
+	c.authTag = newTag
+	t.activeCallByAuth[string(c.authTag)] = c
+	t.startResponseTimeout(c)
+}
+
+// sendResponse sends a response packet to the given node.
+// This doesn't trigger a handshake even if no keys are available.
+func (t *UDPv5) sendResponse(toID enode.ID, toAddr *net.UDPAddr, packet packetV5) error {
+	_, err := t.send(toID, toAddr, packet, nil)
+	return err
+}
+
+// send sends a packet to the given node.
+func (t *UDPv5) send(toID enode.ID, toAddr *net.UDPAddr, packet packetV5, c *whoareyouV5) ([]byte, error) {
+	addr := toAddr.String()
+	enc, authTag, err := t.codec.encode(toID, addr, packet, c)
+	if err != nil {
+		t.log.Warn(">> "+packet.name(), "id", toID, "addr", addr, "err", err)
+		return authTag, err
+	}
+	_, err = t.conn.WriteToUDP(enc, toAddr)
+	t.log.Trace(">> "+packet.name(), "id", toID, "addr", addr)
+	return authTag, err
+}
+
+// readLoop runs in its own goroutine and reads packets from the network.
+func (t *UDPv5) readLoop() {
+	defer t.wg.Done()
+
+	buf := make([]byte, maxPacketSize)
+	for range t.readNextCh {
+		nbytes, from, err := t.conn.ReadFromUDP(buf)
+		if netutil.IsTemporaryError(err) {
+			// Ignore temporary read errors.
+			t.log.Debug("Temporary UDP read error", "err", err)
+			continue
+		} else if err != nil {
+			// Shut down the loop for permament errors.
+			if err != io.EOF {
+				t.log.Debug("UDP read error", "err", err)
+			}
+			return
+		}
+		t.dispatchReadPacket(from, buf[:nbytes])
+	}
+}
+
+// dispatchReadPacket sends a packet into the dispatch loop.
+func (t *UDPv5) dispatchReadPacket(from *net.UDPAddr, content []byte) bool {
+	select {
+	case t.packetInCh <- ReadPacket{content, from}:
+		return true
+	case <-t.closeCtx.Done():
+		return false
+	}
+}
+
+// handlePacket decodes and processes an incoming packet from the network.
+func (t *UDPv5) handlePacket(rawpacket []byte, fromAddr *net.UDPAddr) error {
+	addr := fromAddr.String()
+	fromID, fromNode, packet, err := t.codec.decode(rawpacket, addr)
+	if err != nil {
+		t.log.Debug("Bad discv5 packet", "id", fromID, "addr", addr, "err", err)
+		return err
+	}
+	if fromNode != nil {
+		// Handshake succeeded, add to table.
+		t.tab.addSeenNode(wrapNode(fromNode))
+	}
+	if packet.kind() != p_whoareyouV5 {
+		// WHOAREYOU logged separately to report the sender ID.
+		t.log.Trace("<< "+packet.name(), "id", fromID, "addr", addr)
+	}
+	packet.handle(t, fromID, fromAddr)
+	return nil
+}
+
+// handleCallResponse dispatches a response packet to the call waiting for it.
+func (t *UDPv5) handleCallResponse(fromID enode.ID, fromAddr *net.UDPAddr, reqid []byte, p packetV5) {
+	ac := t.activeCallByNode[fromID]
+	if ac == nil || !bytes.Equal(reqid, ac.reqid) {
+		t.log.Debug(fmt.Sprintf("Unsolicited/late %s response", p.name()), "id", fromID, "addr", fromAddr)
+		return
+	}
+	if !fromAddr.IP.Equal(ac.node.IP()) || fromAddr.Port != ac.node.UDP() {
+		t.log.Debug(fmt.Sprintf("%s from wrong endpoint", p.name()), "id", fromID, "addr", fromAddr)
+		return
+	}
+	if p.kind() != ac.responseType {
+		t.log.Debug(fmt.Sprintf("Wrong disv5 response type %s", p.name()), "id", fromID, "addr", fromAddr)
+		return
+	}
+	t.startResponseTimeout(ac)
+	ac.ch <- p
+}
+
+// getNode looks for a node record in table and database.
+func (t *UDPv5) getNode(id enode.ID) *enode.Node {
+	if n := t.tab.getNode(id); n != nil {
+		return n
+	}
+	if n := t.localNode.Database().Node(id); n != nil {
+		return n
+	}
+	return nil
+}
+
+// UNKNOWN
+
+func (p *unknownV5) name() string       { return "UNKNOWN/v5" }
+func (p *unknownV5) kind() byte         { return p_unknownV5 }
+func (p *unknownV5) setreqid(id []byte) {}
+
+func (p *unknownV5) handle(t *UDPv5, fromID enode.ID, fromAddr *net.UDPAddr) {
+	challenge := &whoareyouV5{AuthTag: p.AuthTag}
+	crand.Read(challenge.IDNonce[:])
+	if n := t.getNode(fromID); n != nil {
+		challenge.node = n
+		challenge.RecordSeq = n.Seq()
+	}
+	t.sendResponse(fromID, fromAddr, challenge)
+}
+
+// WHOAREYOU
+
+func (p *whoareyouV5) name() string       { return "WHOAREYOU/v5" }
+func (p *whoareyouV5) kind() byte         { return p_whoareyouV5 }
+func (p *whoareyouV5) setreqid(id []byte) {}
+
+func (p *whoareyouV5) handle(t *UDPv5, fromID enode.ID, fromAddr *net.UDPAddr) {
+	c, err := p.matchWithCall(t, p.AuthTag)
+	if err != nil {
+		t.log.Debug("Invalid WHOAREYOU/v5", "addr", fromAddr, "err", err)
+		return
+	}
+	// Resend the call that was answered by WHOAREYOU.
+	t.log.Trace("<< "+p.name(), "id", c.node.ID(), "addr", fromAddr)
+	c.handshakeCount++
+	c.challenge = p
+	p.node = c.node
+	t.sendCall(c)
+}
+
+var (
+	errChallengeNoCall = errors.New("no matching call")
+	errChallengeTwice  = errors.New("second handshake")
+)
+
+// matchWithCall checks whether the handshake attempt matches the active call.
+func (p *whoareyouV5) matchWithCall(t *UDPv5, authTag []byte) (*callV5, error) {
+	c := t.activeCallByAuth[string(authTag)]
+	if c == nil {
+		return nil, errChallengeNoCall
+	}
+	if c.handshakeCount > 0 {
+		return nil, errChallengeTwice
+	}
+	return c, nil
+}
+
+// PING
+
+func (p *pingV5) name() string       { return "PING/v5" }
+func (p *pingV5) kind() byte         { return p_pingV5 }
+func (p *pingV5) setreqid(id []byte) { p.ReqID = id }
+
+func (p *pingV5) handle(t *UDPv5, fromID enode.ID, fromAddr *net.UDPAddr) {
+	t.sendResponse(fromID, fromAddr, &pongV5{
+		ReqID:  p.ReqID,
+		ToIP:   fromAddr.IP,
+		ToPort: uint16(fromAddr.Port),
+		ENRSeq: t.localNode.Node().Seq(),
+	})
+}
+
+// PONG
+
+func (p *pongV5) name() string       { return "PONG/v5" }
+func (p *pongV5) kind() byte         { return p_pongV5 }
+func (p *pongV5) setreqid(id []byte) { p.ReqID = id }
+
+func (p *pongV5) handle(t *UDPv5, fromID enode.ID, fromAddr *net.UDPAddr) {
+	t.localNode.UDPEndpointStatement(fromAddr, &net.UDPAddr{IP: p.ToIP, Port: int(p.ToPort)})
+	t.handleCallResponse(fromID, fromAddr, p.ReqID, p)
+}
+
+// FINDNODE
+
+func (p *findnodeV5) name() string       { return "FINDNODE/v5" }
+func (p *findnodeV5) kind() byte         { return p_findnodeV5 }
+func (p *findnodeV5) setreqid(id []byte) { p.ReqID = id }
+
+func (p *findnodeV5) handle(t *UDPv5, fromID enode.ID, fromAddr *net.UDPAddr) {
+	if p.Distance == 0 {
+		t.sendNodes(fromID, fromAddr, p.ReqID, []*enode.Node{t.Self()})
+		return
+	}
+	if p.Distance > 256 {
+		p.Distance = 256
+	}
+	// Get bucket entries.
+	t.tab.mutex.Lock()
+	nodes := unwrapNodes(t.tab.bucketAtDistance(int(p.Distance)).entries)
+	t.tab.mutex.Unlock()
+	if len(nodes) > findnodeResultLimit {
+		nodes = nodes[:findnodeResultLimit]
+	}
+	t.sendNodes(fromID, fromAddr, p.ReqID, nodes)
+}
+
+// sendNodes sends the given records in one or more NODES packets.
+func (t *UDPv5) sendNodes(toID enode.ID, toAddr *net.UDPAddr, reqid []byte, nodes []*enode.Node) {
+	// TODO livenessChecks > 1
+	// TODO CheckRelayIP
+	total := uint8(math.Ceil(float64(len(nodes)) / 3))
+	resp := &nodesV5{ReqID: reqid, Total: total, Nodes: make([]*enr.Record, 3)}
+	sent := false
+	for len(nodes) > 0 {
+		items := min(nodesResponseItemLimit, len(nodes))
+		resp.Nodes = resp.Nodes[:items]
+		for i := 0; i < items; i++ {
+			resp.Nodes[i] = nodes[i].Record()
+		}
+		t.sendResponse(toID, toAddr, resp)
+		nodes = nodes[items:]
+		sent = true
+	}
+	// Ensure at least one response is sent.
+	if !sent {
+		resp.Total = 1
+		resp.Nodes = nil
+		t.sendResponse(toID, toAddr, resp)
+	}
+}
+
+// NODES
+
+func (p *nodesV5) name() string       { return "NODES/v5" }
+func (p *nodesV5) kind() byte         { return p_nodesV5 }
+func (p *nodesV5) setreqid(id []byte) { p.ReqID = id }
+
+func (p *nodesV5) handle(t *UDPv5, fromID enode.ID, fromAddr *net.UDPAddr) {
+	t.handleCallResponse(fromID, fromAddr, p.ReqID, p)
+}
+
+// REQUESTTICKET
+
+func (p *requestTicketV5) name() string       { return "REQUESTTICKET/v5" }
+func (p *requestTicketV5) kind() byte         { return p_requestTicketV5 }
+func (p *requestTicketV5) setreqid(id []byte) { p.ReqID = id }
+
+func (p *requestTicketV5) handle(t *UDPv5, fromID enode.ID, fromAddr *net.UDPAddr) {
+	t.sendResponse(fromID, fromAddr, &ticketV5{ReqID: p.ReqID})
+}
+
+// TICKET
+
+func (p *ticketV5) name() string       { return "TICKET/v5" }
+func (p *ticketV5) kind() byte         { return p_ticketV5 }
+func (p *ticketV5) setreqid(id []byte) { p.ReqID = id }
+
+func (p *ticketV5) handle(t *UDPv5, fromID enode.ID, fromAddr *net.UDPAddr) {
+	t.handleCallResponse(fromID, fromAddr, p.ReqID, p)
+}
+
+// REGTOPIC
+
+func (p *regtopicV5) name() string       { return "REGTOPIC/v5" }
+func (p *regtopicV5) kind() byte         { return p_regtopicV5 }
+func (p *regtopicV5) setreqid(id []byte) { p.ReqID = id }
+
+func (p *regtopicV5) handle(t *UDPv5, fromID enode.ID, fromAddr *net.UDPAddr) {
+	t.sendResponse(fromID, fromAddr, &regconfirmationV5{ReqID: p.ReqID, Registered: false})
+}
+
+// REGCONFIRMATION
+
+func (p *regconfirmationV5) name() string       { return "REGCONFIRMATION/v5" }
+func (p *regconfirmationV5) kind() byte         { return p_regconfirmationV5 }
+func (p *regconfirmationV5) setreqid(id []byte) { p.ReqID = id }
+
+func (p *regconfirmationV5) handle(t *UDPv5, fromID enode.ID, fromAddr *net.UDPAddr) {
+	t.handleCallResponse(fromID, fromAddr, p.ReqID, p)
+}
+
+// TOPICQUERY
+
+func (p *topicqueryV5) name() string       { return "TOPICQUERY/v5" }
+func (p *topicqueryV5) kind() byte         { return p_topicqueryV5 }
+func (p *topicqueryV5) setreqid(id []byte) { p.ReqID = id }
+
+func (p *topicqueryV5) handle(t *UDPv5, fromID enode.ID, fromAddr *net.UDPAddr) {
+}

p2p/discover/v5_udp_test.go

@@ -0,0 +1,622 @@
+// 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 discover
+
+import (
+	"bytes"
+	"crypto/ecdsa"
+	"encoding/binary"
+	"fmt"
+	"math/rand"
+	"net"
+	"reflect"
+	"testing"
+	"time"
+
+	"github.com/ethereum/go-ethereum/internal/testlog"
+	"github.com/ethereum/go-ethereum/log"
+	"github.com/ethereum/go-ethereum/p2p/enode"
+	"github.com/ethereum/go-ethereum/p2p/enr"
+	"github.com/ethereum/go-ethereum/rlp"
+)
+
+// Real sockets, real crypto: this test checks end-to-end connectivity for UDPv5.
+func TestEndToEndV5(t *testing.T) {
+	t.Parallel()
+
+	var nodes []*UDPv5
+	for i := 0; i < 5; i++ {
+		var cfg Config
+		if len(nodes) > 0 {
+			bn := nodes[0].Self()
+			cfg.Bootnodes = []*enode.Node{bn}
+		}
+		node := startLocalhostV5(t, cfg)
+		nodes = append(nodes, node)
+		defer node.Close()
+	}
+
+	last := nodes[len(nodes)-1]
+	target := nodes[rand.Intn(len(nodes)-2)].Self()
+	results := last.Lookup(target.ID())
+	if len(results) == 0 || results[0].ID() != target.ID() {
+		t.Fatalf("lookup returned wrong results: %v", results)
+	}
+}
+
+func startLocalhostV5(t *testing.T, cfg Config) *UDPv5 {
+	cfg.PrivateKey = newkey()
+	db, _ := enode.OpenDB("")
+	ln := enode.NewLocalNode(db, cfg.PrivateKey)
+
+	// Prefix logs with node ID.
+	lprefix := fmt.Sprintf("(%s)", ln.ID().TerminalString())
+	lfmt := log.TerminalFormat(false)
+	cfg.Log = testlog.Logger(t, log.LvlTrace)
+	cfg.Log.SetHandler(log.FuncHandler(func(r *log.Record) error {
+		t.Logf("%s %s", lprefix, lfmt.Format(r))
+		return nil
+	}))
+
+	// Listen.
+	socket, err := net.ListenUDP("udp4", &net.UDPAddr{IP: net.IP{127, 0, 0, 1}})
+	if err != nil {
+		t.Fatal(err)
+	}
+	realaddr := socket.LocalAddr().(*net.UDPAddr)
+	ln.SetStaticIP(realaddr.IP)
+	ln.Set(enr.UDP(realaddr.Port))
+	udp, err := ListenV5(socket, ln, cfg)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return udp
+}
+
+// This test checks that incoming PING calls are handled correctly.
+func TestUDPv5_pingHandling(t *testing.T) {
+	t.Parallel()
+	test := newUDPV5Test(t)
+	defer test.close()
+
+	test.packetIn(&pingV5{ReqID: []byte("foo")})
+	test.waitPacketOut(func(p *pongV5, addr *net.UDPAddr, authTag []byte) {
+		if !bytes.Equal(p.ReqID, []byte("foo")) {
+			t.Error("wrong request ID in response:", p.ReqID)
+		}
+		if p.ENRSeq != test.table.self().Seq() {
+			t.Error("wrong ENR sequence number in response:", p.ENRSeq)
+		}
+	})
+}
+
+// This test checks that incoming 'unknown' packets trigger the handshake.
+func TestUDPv5_unknownPacket(t *testing.T) {
+	t.Parallel()
+	test := newUDPV5Test(t)
+	defer test.close()
+
+	authTag := [12]byte{1, 2, 3}
+	check := func(p *whoareyouV5, wantSeq uint64) {
+		t.Helper()
+		if !bytes.Equal(p.AuthTag, authTag[:]) {
+			t.Error("wrong token in WHOAREYOU:", p.AuthTag, authTag[:])
+		}
+		if p.IDNonce == ([32]byte{}) {
+			t.Error("all zero ID nonce")
+		}
+		if p.RecordSeq != wantSeq {
+			t.Errorf("wrong record seq %d in WHOAREYOU, want %d", p.RecordSeq, wantSeq)
+		}
+	}
+
+	// Unknown packet from unknown node.
+	test.packetIn(&unknownV5{AuthTag: authTag[:]})
+	test.waitPacketOut(func(p *whoareyouV5, addr *net.UDPAddr, _ []byte) {
+		check(p, 0)
+	})
+
+	// Make node known.
+	n := test.getNode(test.remotekey, test.remoteaddr).Node()
+	test.table.addSeenNode(wrapNode(n))
+
+	test.packetIn(&unknownV5{AuthTag: authTag[:]})
+	test.waitPacketOut(func(p *whoareyouV5, addr *net.UDPAddr, _ []byte) {
+		check(p, n.Seq())
+	})
+}
+
+// This test checks that incoming FINDNODE calls are handled correctly.
+func TestUDPv5_findnodeHandling(t *testing.T) {
+	t.Parallel()
+	test := newUDPV5Test(t)
+	defer test.close()
+
+	// Create test nodes and insert them into the table.
+	nodes := nodesAtDistance(test.table.self().ID(), 253, 10)
+	fillTable(test.table, wrapNodes(nodes))
+
+	// Requesting with distance zero should return the node's own record.
+	test.packetIn(&findnodeV5{ReqID: []byte{0}, Distance: 0})
+	test.expectNodes([]byte{0}, 1, []*enode.Node{test.udp.Self()})
+
+	// Requesting with distance > 256 caps it at 256.
+	test.packetIn(&findnodeV5{ReqID: []byte{1}, Distance: 4234098})
+	test.expectNodes([]byte{1}, 1, nil)
+
+	// This request gets no nodes because the corresponding bucket is empty.
+	test.packetIn(&findnodeV5{ReqID: []byte{2}, Distance: 254})
+	test.expectNodes([]byte{2}, 1, nil)
+
+	// This request gets all test nodes.
+	test.packetIn(&findnodeV5{ReqID: []byte{3}, Distance: 253})
+	test.expectNodes([]byte{3}, 4, nodes)
+}
+
+func (test *udpV5Test) expectNodes(wantReqID []byte, wantTotal uint8, wantNodes []*enode.Node) {
+	nodeSet := make(map[enode.ID]*enr.Record)
+	for _, n := range wantNodes {
+		nodeSet[n.ID()] = n.Record()
+	}
+	for {
+		test.waitPacketOut(func(p *nodesV5, addr *net.UDPAddr, authTag []byte) {
+			if len(p.Nodes) > 3 {
+				test.t.Fatalf("too many nodes in response")
+			}
+			if p.Total != wantTotal {
+				test.t.Fatalf("wrong total response count %d", p.Total)
+			}
+			if !bytes.Equal(p.ReqID, wantReqID) {
+				test.t.Fatalf("wrong request ID in response: %v", p.ReqID)
+			}
+			for _, record := range p.Nodes {
+				n, _ := enode.New(enode.ValidSchemesForTesting, record)
+				want := nodeSet[n.ID()]
+				if want == nil {
+					test.t.Fatalf("unexpected node in response: %v", n)
+				}
+				if !reflect.DeepEqual(record, want) {
+					test.t.Fatalf("wrong record in response: %v", n)
+				}
+				delete(nodeSet, n.ID())
+			}
+		})
+		if len(nodeSet) == 0 {
+			return
+		}
+	}
+}
+
+// This test checks that outgoing PING calls work.
+func TestUDPv5_pingCall(t *testing.T) {
+	t.Parallel()
+	test := newUDPV5Test(t)
+	defer test.close()
+
+	remote := test.getNode(test.remotekey, test.remoteaddr).Node()
+	done := make(chan error, 1)
+
+	// This ping times out.
+	go func() {
+		_, err := test.udp.ping(remote)
+		done <- err
+	}()
+	test.waitPacketOut(func(p *pingV5, addr *net.UDPAddr, authTag []byte) {})
+	if err := <-done; err != errTimeout {
+		t.Fatalf("want errTimeout, got %q", err)
+	}
+
+	// This ping works.
+	go func() {
+		_, err := test.udp.ping(remote)
+		done <- err
+	}()
+	test.waitPacketOut(func(p *pingV5, addr *net.UDPAddr, authTag []byte) {
+		test.packetInFrom(test.remotekey, test.remoteaddr, &pongV5{ReqID: p.ReqID})
+	})
+	if err := <-done; err != nil {
+		t.Fatal(err)
+	}
+
+	// This ping gets a reply from the wrong endpoint.
+	go func() {
+		_, err := test.udp.ping(remote)
+		done <- err
+	}()
+	test.waitPacketOut(func(p *pingV5, addr *net.UDPAddr, authTag []byte) {
+		wrongAddr := &net.UDPAddr{IP: net.IP{33, 44, 55, 22}, Port: 10101}
+		test.packetInFrom(test.remotekey, wrongAddr, &pongV5{ReqID: p.ReqID})
+	})
+	if err := <-done; err != errTimeout {
+		t.Fatalf("want errTimeout for reply from wrong IP, got %q", err)
+	}
+}
+
+// This test checks that outgoing FINDNODE calls work and multiple NODES
+// replies are aggregated.
+func TestUDPv5_findnodeCall(t *testing.T) {
+	t.Parallel()
+	test := newUDPV5Test(t)
+	defer test.close()
+
+	// Launch the request:
+	var (
+		distance = 230
+		remote   = test.getNode(test.remotekey, test.remoteaddr).Node()
+		nodes    = nodesAtDistance(remote.ID(), distance, 8)
+		done     = make(chan error, 1)
+		response []*enode.Node
+	)
+	go func() {
+		var err error
+		response, err = test.udp.findnode(remote, distance)
+		done <- err
+	}()
+
+	// Serve the responses:
+	test.waitPacketOut(func(p *findnodeV5, addr *net.UDPAddr, authTag []byte) {
+		if p.Distance != uint(distance) {
+			t.Fatalf("wrong bucket: %d", p.Distance)
+		}
+		test.packetIn(&nodesV5{
+			ReqID: p.ReqID,
+			Total: 2,
+			Nodes: nodesToRecords(nodes[:4]),
+		})
+		test.packetIn(&nodesV5{
+			ReqID: p.ReqID,
+			Total: 2,
+			Nodes: nodesToRecords(nodes[4:]),
+		})
+	})
+
+	// Check results:
+	if err := <-done; err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if !reflect.DeepEqual(response, nodes) {
+		t.Fatalf("wrong nodes in response")
+	}
+
+	// TODO: check invalid IPs
+	// TODO: check invalid/unsigned record
+}
+
+// This test checks that pending calls are re-sent when a handshake happens.
+func TestUDPv5_callResend(t *testing.T) {
+	t.Parallel()
+	test := newUDPV5Test(t)
+	defer test.close()
+
+	remote := test.getNode(test.remotekey, test.remoteaddr).Node()
+	done := make(chan error, 2)
+	go func() {
+		_, err := test.udp.ping(remote)
+		done <- err
+	}()
+	go func() {
+		_, err := test.udp.ping(remote)
+		done <- err
+	}()
+
+	// Ping answered by WHOAREYOU.
+	test.waitPacketOut(func(p *pingV5, addr *net.UDPAddr, authTag []byte) {
+		test.packetIn(&whoareyouV5{AuthTag: authTag})
+	})
+	// Ping should be re-sent.
+	test.waitPacketOut(func(p *pingV5, addr *net.UDPAddr, authTag []byte) {
+		test.packetIn(&pongV5{ReqID: p.ReqID})
+	})
+	// Answer the other ping.
+	test.waitPacketOut(func(p *pingV5, addr *net.UDPAddr, authTag []byte) {
+		test.packetIn(&pongV5{ReqID: p.ReqID})
+	})
+	if err := <-done; err != nil {
+		t.Fatalf("unexpected ping error: %v", err)
+	}
+	if err := <-done; err != nil {
+		t.Fatalf("unexpected ping error: %v", err)
+	}
+}
+
+// This test ensures we don't allow multiple rounds of WHOAREYOU for a single call.
+func TestUDPv5_multipleHandshakeRounds(t *testing.T) {
+	t.Parallel()
+	test := newUDPV5Test(t)
+	defer test.close()
+
+	remote := test.getNode(test.remotekey, test.remoteaddr).Node()
+	done := make(chan error, 1)
+	go func() {
+		_, err := test.udp.ping(remote)
+		done <- err
+	}()
+
+	// Ping answered by WHOAREYOU.
+	test.waitPacketOut(func(p *pingV5, addr *net.UDPAddr, authTag []byte) {
+		test.packetIn(&whoareyouV5{AuthTag: authTag})
+	})
+	// Ping answered by WHOAREYOU again.
+	test.waitPacketOut(func(p *pingV5, addr *net.UDPAddr, authTag []byte) {
+		test.packetIn(&whoareyouV5{AuthTag: authTag})
+	})
+	if err := <-done; err != errTimeout {
+		t.Fatalf("unexpected ping error: %q", err)
+	}
+}
+
+// This test checks that calls with n replies may take up to n * respTimeout.
+func TestUDPv5_callTimeoutReset(t *testing.T) {
+	t.Parallel()
+	test := newUDPV5Test(t)
+	defer test.close()
+
+	// Launch the request:
+	var (
+		distance = 230
+		remote   = test.getNode(test.remotekey, test.remoteaddr).Node()
+		nodes    = nodesAtDistance(remote.ID(), distance, 8)
+		done     = make(chan error, 1)
+	)
+	go func() {
+		_, err := test.udp.findnode(remote, distance)
+		done <- err
+	}()
+
+	// Serve two responses, slowly.
+	test.waitPacketOut(func(p *findnodeV5, addr *net.UDPAddr, authTag []byte) {
+		time.Sleep(respTimeout - 50*time.Millisecond)
+		test.packetIn(&nodesV5{
+			ReqID: p.ReqID,
+			Total: 2,
+			Nodes: nodesToRecords(nodes[:4]),
+		})
+
+		time.Sleep(respTimeout - 50*time.Millisecond)
+		test.packetIn(&nodesV5{
+			ReqID: p.ReqID,
+			Total: 2,
+			Nodes: nodesToRecords(nodes[4:]),
+		})
+	})
+	if err := <-done; err != nil {
+		t.Fatalf("unexpected error: %q", err)
+	}
+}
+
+// This test checks that lookup works.
+func TestUDPv5_lookup(t *testing.T) {
+	t.Parallel()
+	test := newUDPV5Test(t)
+
+	// Lookup on empty table returns no nodes.
+	if results := test.udp.Lookup(lookupTestnet.target.id()); len(results) > 0 {
+		t.Fatalf("lookup on empty table returned %d results: %#v", len(results), results)
+	}
+
+	// Ensure the tester knows all nodes in lookupTestnet by IP.
+	for d, nn := range lookupTestnet.dists {
+		for i, key := range nn {
+			n := lookupTestnet.node(d, i)
+			test.getNode(key, &net.UDPAddr{IP: n.IP(), Port: n.UDP()})
+		}
+	}
+
+	// Seed table with initial node.
+	fillTable(test.table, []*node{wrapNode(lookupTestnet.node(256, 0))})
+
+	// Start the lookup.
+	resultC := make(chan []*enode.Node, 1)
+	go func() {
+		resultC <- test.udp.Lookup(lookupTestnet.target.id())
+		test.close()
+	}()
+
+	// Answer lookup packets.
+	for done := false; !done; {
+		done = test.waitPacketOut(func(p packetV5, to *net.UDPAddr, authTag []byte) {
+			recipient, key := lookupTestnet.nodeByAddr(to)
+			switch p := p.(type) {
+			case *pingV5:
+				test.packetInFrom(key, to, &pongV5{ReqID: p.ReqID})
+			case *findnodeV5:
+				nodes := lookupTestnet.neighborsAtDistance(recipient, p.Distance, 3)
+				response := &nodesV5{ReqID: p.ReqID, Total: 1, Nodes: nodesToRecords(nodes)}
+				test.packetInFrom(key, to, response)
+			}
+		})
+	}
+
+	// Verify result nodes.
+	checkLookupResults(t, lookupTestnet, <-resultC)
+}
+
+// udpV5Test is the framework for all tests above.
+// It runs the UDPv5 transport on a virtual socket and allows testing outgoing packets.
+type udpV5Test struct {
+	t                   *testing.T
+	pipe                *dgramPipe
+	table               *Table
+	db                  *enode.DB
+	udp                 *UDPv5
+	localkey, remotekey *ecdsa.PrivateKey
+	remoteaddr          *net.UDPAddr
+	nodesByID           map[enode.ID]*enode.LocalNode
+	nodesByIP           map[string]*enode.LocalNode
+}
+
+type testCodec struct {
+	test *udpV5Test
+	id   enode.ID
+	ctr  uint64
+}
+
+type testCodecFrame struct {
+	NodeID  enode.ID
+	AuthTag []byte
+	Ptype   byte
+	Packet  rlp.RawValue
+}
+
+func (c *testCodec) encode(toID enode.ID, addr string, p packetV5, _ *whoareyouV5) ([]byte, []byte, error) {
+	c.ctr++
+	authTag := make([]byte, 8)
+	binary.BigEndian.PutUint64(authTag, c.ctr)
+	penc, _ := rlp.EncodeToBytes(p)
+	frame, err := rlp.EncodeToBytes(testCodecFrame{c.id, authTag, p.kind(), penc})
+	return frame, authTag, err
+}
+
+func (c *testCodec) decode(input []byte, addr string) (enode.ID, *enode.Node, packetV5, error) {
+	frame, p, err := c.decodeFrame(input)
+	if err != nil {
+		return enode.ID{}, nil, nil, err
+	}
+	if p.kind() == p_whoareyouV5 {
+		frame.NodeID = enode.ID{} // match wireCodec behavior
+	}
+	return frame.NodeID, nil, p, nil
+}
+
+func (c *testCodec) decodeFrame(input []byte) (frame testCodecFrame, p packetV5, err error) {
+	if err = rlp.DecodeBytes(input, &frame); err != nil {
+		return frame, nil, fmt.Errorf("invalid frame: %v", err)
+	}
+	switch frame.Ptype {
+	case p_unknownV5:
+		dec := new(unknownV5)
+		err = rlp.DecodeBytes(frame.Packet, &dec)
+		p = dec
+	case p_whoareyouV5:
+		dec := new(whoareyouV5)
+		err = rlp.DecodeBytes(frame.Packet, &dec)
+		p = dec
+	default:
+		p, err = decodePacketBodyV5(frame.Ptype, frame.Packet)
+	}
+	return frame, p, err
+}
+
+func newUDPV5Test(t *testing.T) *udpV5Test {
+	test := &udpV5Test{
+		t:          t,
+		pipe:       newpipe(),
+		localkey:   newkey(),
+		remotekey:  newkey(),
+		remoteaddr: &net.UDPAddr{IP: net.IP{10, 0, 1, 99}, Port: 30303},
+		nodesByID:  make(map[enode.ID]*enode.LocalNode),
+		nodesByIP:  make(map[string]*enode.LocalNode),
+	}
+	test.db, _ = enode.OpenDB("")
+	ln := enode.NewLocalNode(test.db, test.localkey)
+	ln.SetStaticIP(net.IP{10, 0, 0, 1})
+	ln.Set(enr.UDP(30303))
+	test.udp, _ = ListenV5(test.pipe, ln, Config{
+		PrivateKey:   test.localkey,
+		Log:          testlog.Logger(t, log.LvlTrace),
+		ValidSchemes: enode.ValidSchemesForTesting,
+	})
+	test.udp.codec = &testCodec{test: test, id: ln.ID()}
+	test.table = test.udp.tab
+	test.nodesByID[ln.ID()] = ln
+	// Wait for initial refresh so the table doesn't send unexpected findnode.
+	<-test.table.initDone
+	return test
+}
+
+// handles a packet as if it had been sent to the transport.
+func (test *udpV5Test) packetIn(packet packetV5) {
+	test.t.Helper()
+	test.packetInFrom(test.remotekey, test.remoteaddr, packet)
+}
+
+// handles a packet as if it had been sent to the transport by the key/endpoint.
+func (test *udpV5Test) packetInFrom(key *ecdsa.PrivateKey, addr *net.UDPAddr, packet packetV5) {
+	test.t.Helper()
+
+	ln := test.getNode(key, addr)
+	codec := &testCodec{test: test, id: ln.ID()}
+	enc, _, err := codec.encode(test.udp.Self().ID(), addr.String(), packet, nil)
+	if err != nil {
+		test.t.Errorf("%s encode error: %v", packet.name(), err)
+	}
+	if test.udp.dispatchReadPacket(addr, enc) {
+		<-test.udp.readNextCh // unblock UDPv5.dispatch
+	}
+}
+
+// getNode ensures the test knows about a node at the given endpoint.
+func (test *udpV5Test) getNode(key *ecdsa.PrivateKey, addr *net.UDPAddr) *enode.LocalNode {
+	id := encodePubkey(&key.PublicKey).id()
+	ln := test.nodesByID[id]
+	if ln == nil {
+		db, _ := enode.OpenDB("")
+		ln = enode.NewLocalNode(db, key)
+		ln.SetStaticIP(addr.IP)
+		ln.Set(enr.UDP(addr.Port))
+		test.nodesByID[id] = ln
+	}
+	test.nodesByIP[string(addr.IP)] = ln
+	return ln
+}
+
+func (test *udpV5Test) waitPacketOut(validate interface{}) (closed bool) {
+	test.t.Helper()
+	fn := reflect.ValueOf(validate)
+	exptype := fn.Type().In(0)
+
+	dgram, err := test.pipe.receive()
+	if err == errClosed {
+		return true
+	}
+	if err == errTimeout {
+		test.t.Fatalf("timed out waiting for %v", exptype)
+		return false
+	}
+	ln := test.nodesByIP[string(dgram.to.IP)]
+	if ln == nil {
+		test.t.Fatalf("attempt to send to non-existing node %v", &dgram.to)
+		return false
+	}
+	codec := &testCodec{test: test, id: ln.ID()}
+	frame, p, err := codec.decodeFrame(dgram.data)
+	if err != nil {
+		test.t.Errorf("sent packet decode error: %v", err)
+		return false
+	}
+	if !reflect.TypeOf(p).AssignableTo(exptype) {
+		test.t.Errorf("sent packet type mismatch, got: %v, want: %v", reflect.TypeOf(p), exptype)
+		return false
+	}
+	fn.Call([]reflect.Value{reflect.ValueOf(p), reflect.ValueOf(&dgram.to), reflect.ValueOf(frame.AuthTag)})
+	return false
+}
+
+func (test *udpV5Test) close() {
+	test.t.Helper()
+
+	test.udp.Close()
+	test.db.Close()
+	for id, n := range test.nodesByID {
+		if id != test.udp.Self().ID() {
+			n.Database().Close()
+		}
+	}
+	if len(test.pipe.queue) != 0 {
+		test.t.Fatalf("%d unmatched UDP packets in queue", len(test.pipe.queue))
+	}
+}

p2p/enode/nodedb.go

@@ -41,6 +41,7 @@ const (
 	dbNodePrefix   = "n:"      // Identifier to prefix node entries with
 	dbLocalPrefix  = "local:"
 	dbDiscoverRoot = "v4"
+	dbDiscv5Root   = "v5"
 
 	// These fields are stored per ID and IP, the full key is "n:<ID>:v4:<IP>:findfail".
 	// Use nodeItemKey to create those keys.
@@ -172,6 +173,16 @@ func splitNodeItemKey(key []byte) (id ID, ip net.IP, field string) {
 	return id, ip, field
 }
 
+func v5Key(id ID, ip net.IP, field string) []byte {
+	return bytes.Join([][]byte{
+		[]byte(dbNodePrefix),
+		id[:],
+		[]byte(dbDiscv5Root),
+		ip.To16(),
+		[]byte(field),
+	}, []byte{':'})
+}
+
 // localItemKey returns the key of a local node item.
 func localItemKey(id ID, field string) []byte {
 	key := append([]byte(dbLocalPrefix), id[:]...)
@@ -378,6 +389,16 @@ func (db *DB) UpdateFindFails(id ID, ip net.IP, fails int) error {
 	return db.storeInt64(nodeItemKey(id, ip, dbNodeFindFails), int64(fails))
 }
 
+// FindFailsV5 retrieves the discv5 findnode failure counter.
+func (db *DB) FindFailsV5(id ID, ip net.IP) int {
+	return int(db.fetchInt64(v5Key(id, ip, dbNodeFindFails)))
+}
+
+// UpdateFindFailsV5 stores the discv5 findnode failure counter.
+func (db *DB) UpdateFindFailsV5(id ID, ip net.IP, fails int) error {
+	return db.storeInt64(v5Key(id, ip, dbNodeFindFails), int64(fails))
+}
+
 // LocalSeq retrieves the local record sequence counter.
 func (db *DB) localSeq(id ID) uint64 {
 	return db.fetchUint64(localItemKey(id, dbLocalSeq))

p2p/enode/nodedb_test.go

@@ -462,3 +462,14 @@ func TestDBExpiration(t *testing.T) {
 		}
 	}
 }
+
+// This test checks that expiration works when discovery v5 data is present
+// in the database.
+func TestDBExpireV5(t *testing.T) {
+	db, _ := OpenDB("")
+	defer db.Close()
+
+	ip := net.IP{127, 0, 0, 1}
+	db.UpdateFindFailsV5(ID{}, ip, 4)
+	db.expireNodes()
+}