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/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
+}