cmd/devp2p: add discv4 test suite (#21163)

This adds a test suite for discovery v4. The test suite is a port of the Hive suite for
discovery, and will replace the current suite on Hive soon-ish. The tests can be
run locally with this command:

    devp2p discv4 test -remote enode//...

Co-authored-by: Felix Lange <fjl@twurst.com>

cmd/devp2p/discv4cmd.go

@@ -19,11 +19,14 @@ package main
 import (
 	"fmt"
 	"net"
+	"os"
 	"strings"
 	"time"
 
+	"github.com/ethereum/go-ethereum/cmd/devp2p/internal/v4test"
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/crypto"
+	"github.com/ethereum/go-ethereum/internal/utesting"
 	"github.com/ethereum/go-ethereum/p2p/discover"
 	"github.com/ethereum/go-ethereum/p2p/enode"
 	"github.com/ethereum/go-ethereum/params"
@@ -40,6 +43,7 @@ var (
 			discv4ResolveCommand,
 			discv4ResolveJSONCommand,
 			discv4CrawlCommand,
+			discv4TestCommand,
 		},
 	}
 	discv4PingCommand = cli.Command{
@@ -74,6 +78,12 @@ var (
 		Action: discv4Crawl,
 		Flags:  []cli.Flag{bootnodesFlag, crawlTimeoutFlag},
 	}
+	discv4TestCommand = cli.Command{
+		Name:   "test",
+		Usage:  "Runs tests against a node",
+		Action: discv4Test,
+		Flags:  []cli.Flag{remoteEnodeFlag, testPatternFlag, testListen1Flag, testListen2Flag},
+	}
 )
 
 var (
@@ -98,6 +108,25 @@ var (
 		Usage: "Time limit for the crawl.",
 		Value: 30 * time.Minute,
 	}
+	remoteEnodeFlag = cli.StringFlag{
+		Name:   "remote",
+		Usage:  "Enode of the remote node under test",
+		EnvVar: "REMOTE_ENODE",
+	}
+	testPatternFlag = cli.StringFlag{
+		Name:  "run",
+		Usage: "Pattern of test suite(s) to run",
+	}
+	testListen1Flag = cli.StringFlag{
+		Name:  "listen1",
+		Usage: "IP address of the first tester",
+		Value: v4test.Listen1,
+	}
+	testListen2Flag = cli.StringFlag{
+		Name:  "listen2",
+		Usage: "IP address of the second tester",
+		Value: v4test.Listen2,
+	}
 )
 
 func discv4Ping(ctx *cli.Context) error {
@@ -184,6 +213,28 @@ func discv4Crawl(ctx *cli.Context) error {
 	return nil
 }
 
+func discv4Test(ctx *cli.Context) error {
+	// Configure test package globals.
+	if !ctx.IsSet(remoteEnodeFlag.Name) {
+		return fmt.Errorf("Missing -%v", remoteEnodeFlag.Name)
+	}
+	v4test.Remote = ctx.String(remoteEnodeFlag.Name)
+	v4test.Listen1 = ctx.String(testListen1Flag.Name)
+	v4test.Listen2 = ctx.String(testListen2Flag.Name)
+
+	// Filter and run test cases.
+	tests := v4test.AllTests
+	if ctx.IsSet(testPatternFlag.Name) {
+		tests = utesting.MatchTests(tests, ctx.String(testPatternFlag.Name))
+	}
+	results := utesting.RunTests(tests, os.Stdout)
+	if fails := utesting.CountFailures(results); fails > 0 {
+		return fmt.Errorf("%v/%v tests passed.", len(tests)-fails, len(tests))
+	}
+	fmt.Printf("%v/%v passed\n", len(tests), len(tests))
+	return nil
+}
+
 // startV4 starts an ephemeral discovery V4 node.
 func startV4(ctx *cli.Context) *discover.UDPv4 {
 	ln, config := makeDiscoveryConfig(ctx)

cmd/devp2p/internal/v4test/discv4tests.go

@@ -0,0 +1,467 @@
+// Copyright 2020 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 v4test
+
+import (
+	"bytes"
+	"crypto/rand"
+	"fmt"
+	"net"
+	"reflect"
+	"time"
+
+	"github.com/ethereum/go-ethereum/crypto"
+	"github.com/ethereum/go-ethereum/internal/utesting"
+	"github.com/ethereum/go-ethereum/p2p/discover/v4wire"
+)
+
+const (
+	expiration  = 20 * time.Second
+	wrongPacket = 66
+	macSize     = 256 / 8
+)
+
+var (
+	// Remote node under test
+	Remote string
+	// IP where the first tester is listening, port will be assigned
+	Listen1 string = "127.0.0.1"
+	// IP where the second tester is listening, port will be assigned
+	// Before running the test, you may have to `sudo ifconfig lo0 add 127.0.0.2` (on MacOS at least)
+	Listen2 string = "127.0.0.2"
+)
+
+type pingWithJunk struct {
+	Version    uint
+	From, To   v4wire.Endpoint
+	Expiration uint64
+	JunkData1  uint
+	JunkData2  []byte
+}
+
+func (req *pingWithJunk) Name() string { return "PING/v4" }
+func (req *pingWithJunk) Kind() byte   { return v4wire.PingPacket }
+
+type pingWrongType struct {
+	Version    uint
+	From, To   v4wire.Endpoint
+	Expiration uint64
+}
+
+func (req *pingWrongType) Name() string { return "WRONG/v4" }
+func (req *pingWrongType) Kind() byte   { return wrongPacket }
+
+func futureExpiration() uint64 {
+	return uint64(time.Now().Add(expiration).Unix())
+}
+
+// This test just sends a PING packet and expects a response.
+func BasicPing(t *utesting.T) {
+	te := newTestEnv(Remote, Listen1, Listen2)
+	defer te.close()
+
+	pingHash := te.send(te.l1, &v4wire.Ping{
+		Version:    4,
+		From:       te.localEndpoint(te.l1),
+		To:         te.remoteEndpoint(),
+		Expiration: futureExpiration(),
+	})
+
+	reply, _, _ := te.read(te.l1)
+	if err := te.checkPong(reply, pingHash); err != nil {
+		t.Fatal(err)
+	}
+}
+
+// checkPong verifies that reply is a valid PONG matching the given ping hash.
+func (te *testenv) checkPong(reply v4wire.Packet, pingHash []byte) error {
+	if reply == nil || reply.Kind() != v4wire.PongPacket {
+		return fmt.Errorf("expected PONG reply, got %v", reply)
+	}
+	pong := reply.(*v4wire.Pong)
+	if !bytes.Equal(pong.ReplyTok, pingHash) {
+		return fmt.Errorf("PONG reply token mismatch: got %x, want %x", pong.ReplyTok, pingHash)
+	}
+	wantEndpoint := te.localEndpoint(te.l1)
+	if !reflect.DeepEqual(pong.To, wantEndpoint) {
+		return fmt.Errorf("PONG 'to' endpoint mismatch: got %+v, want %+v", pong.To, wantEndpoint)
+	}
+	if v4wire.Expired(pong.Expiration) {
+		return fmt.Errorf("PONG is expired (%v)", pong.Expiration)
+	}
+	return nil
+}
+
+// This test sends a PING packet with wrong 'to' field and expects a PONG response.
+func PingWrongTo(t *utesting.T) {
+	te := newTestEnv(Remote, Listen1, Listen2)
+	defer te.close()
+
+	wrongEndpoint := v4wire.Endpoint{IP: net.ParseIP("192.0.2.0")}
+	pingHash := te.send(te.l1, &v4wire.Ping{
+		Version:    4,
+		From:       te.localEndpoint(te.l1),
+		To:         wrongEndpoint,
+		Expiration: futureExpiration(),
+	})
+
+	reply, _, _ := te.read(te.l1)
+	if err := te.checkPong(reply, pingHash); err != nil {
+		t.Fatal(err)
+	}
+}
+
+// This test sends a PING packet with wrong 'from' field and expects a PONG response.
+func PingWrongFrom(t *utesting.T) {
+	te := newTestEnv(Remote, Listen1, Listen2)
+	defer te.close()
+
+	wrongEndpoint := v4wire.Endpoint{IP: net.ParseIP("192.0.2.0")}
+	pingHash := te.send(te.l1, &v4wire.Ping{
+		Version:    4,
+		From:       wrongEndpoint,
+		To:         te.remoteEndpoint(),
+		Expiration: futureExpiration(),
+	})
+
+	reply, _, _ := te.read(te.l1)
+	if err := te.checkPong(reply, pingHash); err != nil {
+		t.Fatal(err)
+	}
+}
+
+// This test sends a PING packet with additional data at the end and expects a PONG
+// response. The remote node should respond because EIP-8 mandates ignoring additional
+// trailing data.
+func PingExtraData(t *utesting.T) {
+	te := newTestEnv(Remote, Listen1, Listen2)
+	defer te.close()
+
+	pingHash := te.send(te.l1, &pingWithJunk{
+		Version:    4,
+		From:       te.localEndpoint(te.l1),
+		To:         te.remoteEndpoint(),
+		Expiration: futureExpiration(),
+		JunkData1:  42,
+		JunkData2:  []byte{9, 8, 7, 6, 5, 4, 3, 2, 1},
+	})
+
+	reply, _, _ := te.read(te.l1)
+	if err := te.checkPong(reply, pingHash); err != nil {
+		t.Fatal(err)
+	}
+}
+
+// This test sends a PING packet with additional data and wrong 'from' field
+// and expects a PONG response.
+func PingExtraDataWrongFrom(t *utesting.T) {
+	te := newTestEnv(Remote, Listen1, Listen2)
+	defer te.close()
+
+	wrongEndpoint := v4wire.Endpoint{IP: net.ParseIP("192.0.2.0")}
+	req := pingWithJunk{
+		Version:    4,
+		From:       wrongEndpoint,
+		To:         te.remoteEndpoint(),
+		Expiration: futureExpiration(),
+		JunkData1:  42,
+		JunkData2:  []byte{9, 8, 7, 6, 5, 4, 3, 2, 1},
+	}
+	pingHash := te.send(te.l1, &req)
+	reply, _, _ := te.read(te.l1)
+	if err := te.checkPong(reply, pingHash); err != nil {
+		t.Fatal(err)
+	}
+}
+
+// This test sends a PING packet with an expiration in the past.
+// The remote node should not respond.
+func PingPastExpiration(t *utesting.T) {
+	te := newTestEnv(Remote, Listen1, Listen2)
+	defer te.close()
+
+	te.send(te.l1, &v4wire.Ping{
+		Version:    4,
+		From:       te.localEndpoint(te.l1),
+		To:         te.remoteEndpoint(),
+		Expiration: -futureExpiration(),
+	})
+
+	reply, _, _ := te.read(te.l1)
+	if reply != nil {
+		t.Fatal("Expected no reply, got", reply)
+	}
+}
+
+// This test sends an invalid packet. The remote node should not respond.
+func WrongPacketType(t *utesting.T) {
+	te := newTestEnv(Remote, Listen1, Listen2)
+	defer te.close()
+
+	te.send(te.l1, &pingWrongType{
+		Version:    4,
+		From:       te.localEndpoint(te.l1),
+		To:         te.remoteEndpoint(),
+		Expiration: futureExpiration(),
+	})
+
+	reply, _, _ := te.read(te.l1)
+	if reply != nil {
+		t.Fatal("Expected no reply, got", reply)
+	}
+}
+
+// This test verifies that the default behaviour of ignoring 'from' fields is unaffected by
+// the bonding process. After bonding, it pings the target with a different from endpoint.
+func BondThenPingWithWrongFrom(t *utesting.T) {
+	te := newTestEnv(Remote, Listen1, Listen2)
+	defer te.close()
+	bond(t, te)
+
+	wrongEndpoint := v4wire.Endpoint{IP: net.ParseIP("192.0.2.0")}
+	pingHash := te.send(te.l1, &v4wire.Ping{
+		Version:    4,
+		From:       wrongEndpoint,
+		To:         te.remoteEndpoint(),
+		Expiration: futureExpiration(),
+	})
+
+	reply, _, _ := te.read(te.l1)
+	if err := te.checkPong(reply, pingHash); err != nil {
+		t.Fatal(err)
+	}
+}
+
+// This test just sends FINDNODE. The remote node should not reply
+// because the endpoint proof has not completed.
+func FindnodeWithoutEndpointProof(t *utesting.T) {
+	te := newTestEnv(Remote, Listen1, Listen2)
+	defer te.close()
+
+	req := v4wire.Findnode{Expiration: futureExpiration()}
+	rand.Read(req.Target[:])
+	te.send(te.l1, &req)
+
+	reply, _, _ := te.read(te.l1)
+	if reply != nil {
+		t.Fatal("Expected no response, got", reply)
+	}
+}
+
+// BasicFindnode sends a FINDNODE request after performing the endpoint
+// proof. The remote node should respond.
+func BasicFindnode(t *utesting.T) {
+	te := newTestEnv(Remote, Listen1, Listen2)
+	defer te.close()
+	bond(t, te)
+
+	findnode := v4wire.Findnode{Expiration: futureExpiration()}
+	rand.Read(findnode.Target[:])
+	te.send(te.l1, &findnode)
+
+	reply, _, err := te.read(te.l1)
+	if err != nil {
+		t.Fatal("read find nodes", err)
+	}
+	if reply.Kind() != v4wire.NeighborsPacket {
+		t.Fatal("Expected neighbors, got", reply.Name())
+	}
+}
+
+// This test sends an unsolicited NEIGHBORS packet after the endpoint proof, then sends
+// FINDNODE to read the remote table. The remote node should not return the node contained
+// in the unsolicited NEIGHBORS packet.
+func UnsolicitedNeighbors(t *utesting.T) {
+	te := newTestEnv(Remote, Listen1, Listen2)
+	defer te.close()
+	bond(t, te)
+
+	// Send unsolicited NEIGHBORS response.
+	fakeKey, _ := crypto.GenerateKey()
+	encFakeKey := v4wire.EncodePubkey(&fakeKey.PublicKey)
+	neighbors := v4wire.Neighbors{
+		Expiration: futureExpiration(),
+		Nodes: []v4wire.Node{{
+			ID:  encFakeKey,
+			IP:  net.IP{1, 2, 3, 4},
+			UDP: 30303,
+			TCP: 30303,
+		}},
+	}
+	te.send(te.l1, &neighbors)
+
+	// Check if the remote node included the fake node.
+	te.send(te.l1, &v4wire.Findnode{
+		Expiration: futureExpiration(),
+		Target:     encFakeKey,
+	})
+
+	reply, _, err := te.read(te.l1)
+	if err != nil {
+		t.Fatal("read find nodes", err)
+	}
+	if reply.Kind() != v4wire.NeighborsPacket {
+		t.Fatal("Expected neighbors, got", reply.Name())
+	}
+	nodes := reply.(*v4wire.Neighbors).Nodes
+	if contains(nodes, encFakeKey) {
+		t.Fatal("neighbors response contains node from earlier unsolicited neighbors response")
+	}
+}
+
+// This test sends FINDNODE with an expiration timestamp in the past.
+// The remote node should not respond.
+func FindnodePastExpiration(t *utesting.T) {
+	te := newTestEnv(Remote, Listen1, Listen2)
+	defer te.close()
+	bond(t, te)
+
+	findnode := v4wire.Findnode{Expiration: -futureExpiration()}
+	rand.Read(findnode.Target[:])
+	te.send(te.l1, &findnode)
+
+	for {
+		reply, _, _ := te.read(te.l1)
+		if reply == nil {
+			return
+		} else if reply.Kind() == v4wire.NeighborsPacket {
+			t.Fatal("Unexpected NEIGHBORS response for expired FINDNODE request")
+		}
+	}
+}
+
+// bond performs the endpoint proof with the remote node.
+func bond(t *utesting.T, te *testenv) {
+	te.send(te.l1, &v4wire.Ping{
+		Version:    4,
+		From:       te.localEndpoint(te.l1),
+		To:         te.remoteEndpoint(),
+		Expiration: futureExpiration(),
+	})
+
+	var gotPing, gotPong bool
+	for !gotPing || !gotPong {
+		req, hash, err := te.read(te.l1)
+		if err != nil {
+			t.Fatal(err)
+		}
+		switch req.(type) {
+		case *v4wire.Ping:
+			te.send(te.l1, &v4wire.Pong{
+				To:         te.remoteEndpoint(),
+				ReplyTok:   hash,
+				Expiration: futureExpiration(),
+			})
+			gotPing = true
+		case *v4wire.Pong:
+			// TODO: maybe verify pong data here
+			gotPong = true
+		}
+	}
+}
+
+// This test attempts to perform a traffic amplification attack against a
+// 'victim' endpoint using FINDNODE. In this attack scenario, the attacker
+// attempts to complete the endpoint proof non-interactively by sending a PONG
+// with mismatching reply token from the 'victim' endpoint. The attack works if
+// the remote node does not verify the PONG reply token field correctly. The
+// attacker could then perform traffic amplification by sending many FINDNODE
+// requests to the discovery node, which would reply to the 'victim' address.
+func FindnodeAmplificationInvalidPongHash(t *utesting.T) {
+	te := newTestEnv(Remote, Listen1, Listen2)
+	defer te.close()
+
+	// Send PING to start endpoint verification.
+	te.send(te.l1, &v4wire.Ping{
+		Version:    4,
+		From:       te.localEndpoint(te.l1),
+		To:         te.remoteEndpoint(),
+		Expiration: futureExpiration(),
+	})
+
+	var gotPing, gotPong bool
+	for !gotPing || !gotPong {
+		req, _, err := te.read(te.l1)
+		if err != nil {
+			t.Fatal(err)
+		}
+		switch req.(type) {
+		case *v4wire.Ping:
+			// Send PONG from this node ID, but with invalid ReplyTok.
+			te.send(te.l1, &v4wire.Pong{
+				To:         te.remoteEndpoint(),
+				ReplyTok:   make([]byte, macSize),
+				Expiration: futureExpiration(),
+			})
+			gotPing = true
+		case *v4wire.Pong:
+			gotPong = true
+		}
+	}
+
+	// Now send FINDNODE. The remote node should not respond because our
+	// PONG did not reference the PING hash.
+	findnode := v4wire.Findnode{Expiration: futureExpiration()}
+	rand.Read(findnode.Target[:])
+	te.send(te.l1, &findnode)
+
+	// If we receive a NEIGHBORS response, the attack worked and the test fails.
+	reply, _, _ := te.read(te.l1)
+	if reply != nil && reply.Kind() == v4wire.NeighborsPacket {
+		t.Error("Got neighbors")
+	}
+}
+
+// This test attempts to perform a traffic amplification attack using FINDNODE.
+// The attack works if the remote node does not verify the IP address of FINDNODE
+// against the endpoint verification proof done by PING/PONG.
+func FindnodeAmplificationWrongIP(t *utesting.T) {
+	te := newTestEnv(Remote, Listen1, Listen2)
+	defer te.close()
+
+	// Do the endpoint proof from the l1 IP.
+	bond(t, te)
+
+	// Now send FINDNODE from the same node ID, but different IP address.
+	// The remote node should not respond.
+	findnode := v4wire.Findnode{Expiration: futureExpiration()}
+	rand.Read(findnode.Target[:])
+	te.send(te.l2, &findnode)
+
+	// If we receive a NEIGHBORS response, the attack worked and the test fails.
+	reply, _, _ := te.read(te.l2)
+	if reply != nil {
+		t.Error("Got NEIGHORS response for FINDNODE from wrong IP")
+	}
+}
+
+var AllTests = []utesting.Test{
+	{Name: "Ping/Basic", Fn: BasicPing},
+	{Name: "Ping/WrongTo", Fn: PingWrongTo},
+	{Name: "Ping/WrongFrom", Fn: PingWrongFrom},
+	{Name: "Ping/ExtraData", Fn: PingExtraData},
+	{Name: "Ping/ExtraDataWrongFrom", Fn: PingExtraDataWrongFrom},
+	{Name: "Ping/PastExpiration", Fn: PingPastExpiration},
+	{Name: "Ping/WrongPacketType", Fn: WrongPacketType},
+	{Name: "Ping/BondThenPingWithWrongFrom", Fn: BondThenPingWithWrongFrom},
+	{Name: "Findnode/WithoutEndpointProof", Fn: FindnodeWithoutEndpointProof},
+	{Name: "Findnode/BasicFindnode", Fn: BasicFindnode},
+	{Name: "Findnode/UnsolicitedNeighbors", Fn: UnsolicitedNeighbors},
+	{Name: "Findnode/PastExpiration", Fn: FindnodePastExpiration},
+	{Name: "Amplification/InvalidPongHash", Fn: FindnodeAmplificationInvalidPongHash},
+	{Name: "Amplification/WrongIP", Fn: FindnodeAmplificationWrongIP},
+}

cmd/devp2p/internal/v4test/framework.go

@@ -0,0 +1,123 @@
+// Copyright 2020 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 v4test
+
+import (
+	"crypto/ecdsa"
+	"fmt"
+	"net"
+	"time"
+
+	"github.com/ethereum/go-ethereum/crypto"
+	"github.com/ethereum/go-ethereum/p2p/discover/v4wire"
+	"github.com/ethereum/go-ethereum/p2p/enode"
+)
+
+const waitTime = 300 * time.Millisecond
+
+type testenv struct {
+	l1, l2     net.PacketConn
+	key        *ecdsa.PrivateKey
+	remote     *enode.Node
+	remoteAddr *net.UDPAddr
+}
+
+func newTestEnv(remote string, listen1, listen2 string) *testenv {
+	l1, err := net.ListenPacket("udp", fmt.Sprintf("%v:0", listen1))
+	if err != nil {
+		panic(err)
+	}
+	l2, err := net.ListenPacket("udp", fmt.Sprintf("%v:0", listen2))
+	if err != nil {
+		panic(err)
+	}
+	key, err := crypto.GenerateKey()
+	if err != nil {
+		panic(err)
+	}
+	node, err := enode.Parse(enode.ValidSchemes, remote)
+	if err != nil {
+		panic(err)
+	}
+	if node.IP() == nil || node.UDP() == 0 {
+		var ip net.IP
+		var tcpPort, udpPort int
+		if ip = node.IP(); ip == nil {
+			ip = net.ParseIP("127.0.0.1")
+		}
+		if tcpPort = node.TCP(); tcpPort == 0 {
+			tcpPort = 30303
+		}
+		if udpPort = node.TCP(); udpPort == 0 {
+			udpPort = 30303
+		}
+		node = enode.NewV4(node.Pubkey(), ip, tcpPort, udpPort)
+	}
+	addr := &net.UDPAddr{IP: node.IP(), Port: node.UDP()}
+	return &testenv{l1, l2, key, node, addr}
+}
+
+func (te *testenv) close() {
+	te.l1.Close()
+	te.l2.Close()
+}
+
+func (te *testenv) send(c net.PacketConn, req v4wire.Packet) []byte {
+	packet, hash, err := v4wire.Encode(te.key, req)
+	if err != nil {
+		panic(fmt.Errorf("can't encode %v packet: %v", req.Name(), err))
+	}
+	if _, err := c.WriteTo(packet, te.remoteAddr); err != nil {
+		panic(fmt.Errorf("can't send %v: %v", req.Name(), err))
+	}
+	return hash
+}
+
+func (te *testenv) read(c net.PacketConn) (v4wire.Packet, []byte, error) {
+	buf := make([]byte, 2048)
+	if err := c.SetReadDeadline(time.Now().Add(waitTime)); err != nil {
+		return nil, nil, err
+	}
+	n, _, err := c.ReadFrom(buf)
+	if err != nil {
+		return nil, nil, err
+	}
+	p, _, hash, err := v4wire.Decode(buf[:n])
+	return p, hash, err
+}
+
+func (te *testenv) localEndpoint(c net.PacketConn) v4wire.Endpoint {
+	addr := c.LocalAddr().(*net.UDPAddr)
+	return v4wire.Endpoint{
+		IP:  addr.IP.To4(),
+		UDP: uint16(addr.Port),
+		TCP: 0,
+	}
+}
+
+func (te *testenv) remoteEndpoint() v4wire.Endpoint {
+	return v4wire.NewEndpoint(te.remoteAddr, 0)
+}
+
+func contains(ns []v4wire.Node, key v4wire.Pubkey) bool {
+	for _, n := range ns {
+		if n.ID == key {
+			return true
+		}
+	}
+	return false
+}

go.sum

@@ -207,6 +207,7 @@ golang.org/x/sync v0.0.0-20181108010431-42b317875d0f/go.mod h1:RxMgew5VJxzue5/jJ
 golang.org/x/sys v0.0.0-20180909124046-d0be0721c37e/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20181107165924-66b7b1311ac8/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
+golang.org/x/sys v0.0.0-20190405154228-4b34438f7a67/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200323222414-85ca7c5b95cd h1:xhmwyvizuTgC2qz7ZlMluP20uW+C3Rm0FD/WLDX8884=
 golang.org/x/sys v0.0.0-20200323222414-85ca7c5b95cd/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=

internal/utesting/utesting.go

@@ -0,0 +1,190 @@
+// 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 utesting provides a standalone replacement for package testing.
+//
+// This package exists because package testing cannot easily be embedded into a
+// standalone go program. It provides an API that mirrors the standard library
+// testing API.
+package utesting
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"regexp"
+	"runtime"
+	"sync"
+	"time"
+)
+
+// Test represents a single test.
+type Test struct {
+	Name string
+	Fn   func(*T)
+}
+
+// Result is the result of a test execution.
+type Result struct {
+	Name     string
+	Failed   bool
+	Output   string
+	Duration time.Duration
+}
+
+// MatchTests returns the tests whose name matches a regular expression.
+func MatchTests(tests []Test, expr string) []Test {
+	var results []Test
+	re, err := regexp.Compile(expr)
+	if err != nil {
+		return nil
+	}
+	for _, test := range tests {
+		if re.MatchString(test.Name) {
+			results = append(results, test)
+		}
+	}
+	return results
+}
+
+// RunTests executes all given tests in order and returns their results.
+// If the report writer is non-nil, a test report is written to it in real time.
+func RunTests(tests []Test, report io.Writer) []Result {
+	results := make([]Result, len(tests))
+	for i, test := range tests {
+		start := time.Now()
+		results[i].Name = test.Name
+		results[i].Failed, results[i].Output = Run(test)
+		results[i].Duration = time.Since(start)
+		if report != nil {
+			printResult(results[i], report)
+		}
+	}
+	return results
+}
+
+func printResult(r Result, w io.Writer) {
+	pd := r.Duration.Truncate(100 * time.Microsecond)
+	if r.Failed {
+		fmt.Fprintf(w, "-- FAIL %s (%v)\n", r.Name, pd)
+		fmt.Fprintln(w, r.Output)
+	} else {
+		fmt.Fprintf(w, "-- OK %s (%v)\n", r.Name, pd)
+	}
+}
+
+// CountFailures returns the number of failed tests in the result slice.
+func CountFailures(rr []Result) int {
+	count := 0
+	for _, r := range rr {
+		if r.Failed {
+			count++
+		}
+	}
+	return count
+}
+
+// Run executes a single test.
+func Run(test Test) (bool, string) {
+	t := new(T)
+	done := make(chan struct{})
+	go func() {
+		defer close(done)
+		defer func() {
+			if err := recover(); err != nil {
+				buf := make([]byte, 4096)
+				i := runtime.Stack(buf, false)
+				t.Logf("panic: %v\n\n%s", err, buf[:i])
+				t.Fail()
+			}
+		}()
+		test.Fn(t)
+	}()
+	<-done
+	return t.failed, t.output.String()
+}
+
+// T is the value given to the test function. The test can signal failures
+// and log output by calling methods on this object.
+type T struct {
+	mu     sync.Mutex
+	failed bool
+	output bytes.Buffer
+}
+
+// FailNow marks the test as having failed and stops its execution by calling
+// runtime.Goexit (which then runs all deferred calls in the current goroutine).
+func (t *T) FailNow() {
+	t.Fail()
+	runtime.Goexit()
+}
+
+// Fail marks the test as having failed but continues execution.
+func (t *T) Fail() {
+	t.mu.Lock()
+	defer t.mu.Unlock()
+	t.failed = true
+}
+
+// Failed reports whether the test has failed.
+func (t *T) Failed() bool {
+	t.mu.Lock()
+	defer t.mu.Unlock()
+	return t.failed
+}
+
+// Log formats its arguments using default formatting, analogous to Println, and records
+// the text in the error log.
+func (t *T) Log(vs ...interface{}) {
+	t.mu.Lock()
+	defer t.mu.Unlock()
+	fmt.Fprintln(&t.output, vs...)
+}
+
+// Logf formats its arguments according to the format, analogous to Printf, and records
+// the text in the error log. A final newline is added if not provided.
+func (t *T) Logf(format string, vs ...interface{}) {
+	t.mu.Lock()
+	defer t.mu.Unlock()
+	if len(format) == 0 || format[len(format)-1] != '\n' {
+		format += "\n"
+	}
+	fmt.Fprintf(&t.output, format, vs...)
+}
+
+// Error is equivalent to Log followed by Fail.
+func (t *T) Error(vs ...interface{}) {
+	t.Log(vs...)
+	t.Fail()
+}
+
+// Errorf is equivalent to Logf followed by Fail.
+func (t *T) Errorf(format string, vs ...interface{}) {
+	t.Logf(format, vs...)
+	t.Fail()
+}
+
+// Fatal is equivalent to Log followed by FailNow.
+func (t *T) Fatal(vs ...interface{}) {
+	t.Log(vs...)
+	t.FailNow()
+}
+
+// Fatalf is equivalent to Logf followed by FailNow.
+func (t *T) Fatalf(format string, vs ...interface{}) {
+	t.Logf(format, vs...)
+	t.FailNow()
+}

internal/utesting/utesting_test.go

@@ -0,0 +1,55 @@
+// 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 utesting
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestTest(t *testing.T) {
+	tests := []Test{
+		{
+			Name: "successful test",
+			Fn:   func(t *T) {},
+		},
+		{
+			Name: "failing test",
+			Fn: func(t *T) {
+				t.Log("output")
+				t.Error("failed")
+			},
+		},
+		{
+			Name: "panicking test",
+			Fn: func(t *T) {
+				panic("oh no")
+			},
+		},
+	}
+	results := RunTests(tests, nil)
+
+	if results[0].Failed || results[0].Output != "" {
+		t.Fatalf("wrong result for successful test: %#v", results[0])
+	}
+	if !results[1].Failed || results[1].Output != "output\nfailed\n" {
+		t.Fatalf("wrong result for failing test: %#v", results[1])
+	}
+	if !results[2].Failed || !strings.HasPrefix(results[2].Output, "panic: oh no\n") {
+		t.Fatalf("wrong result for panicking test: %#v", results[2])
+	}
+}