cmd/devp2p: add devp2p debug tool (#19657)

* p2p/discover: export Ping and RequestENR

These two are useful for checking the status of a node.

* cmd/devp2p: add devp2p debug tool

This is a new tool for debugging p2p issues. It supports a few
basic tasks for now, but many more things can and will be added
in the near future.

   devp2p enrdump            -- prints ENRs readably
   devp2p discv4 ping        -- checks if a node is up
   devp2p discv4 requestenr  -- gets a node's record
   devp2p discv4 resolve     -- finds a node through the DHT

6 files changed, 446 insertions, 8 deletions

diff --git a/cmd/devp2p/discv4cmd.go b/cmd/devp2p/discv4cmd.go
new file mode 100644
index 000000000..1e56687a6
--- /dev/null
+++ b/cmd/devp2p/discv4cmd.go
@@ -0,0 +1,166 @@
+// 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"
+	"net"
+	"sort"
+	"strings"
+	"time"
+
+	"github.com/ethereum/go-ethereum/crypto"
+	"github.com/ethereum/go-ethereum/p2p/discover"
+	"github.com/ethereum/go-ethereum/p2p/enode"
+	"github.com/ethereum/go-ethereum/params"
+	"gopkg.in/urfave/cli.v1"
+)
+
+var (
+	discv4Command = cli.Command{
+		Name:  "discv4",
+		Usage: "Node Discovery v4 tools",
+		Subcommands: []cli.Command{
+			discv4PingCommand,
+			discv4RequestRecordCommand,
+			discv4ResolveCommand,
+		},
+	}
+	discv4PingCommand = cli.Command{
+		Name:   "ping",
+		Usage:  "Sends ping to a node",
+		Action: discv4Ping,
+	}
+	discv4RequestRecordCommand = cli.Command{
+		Name:   "requestenr",
+		Usage:  "Requests a node record using EIP-868 enrRequest",
+		Action: discv4RequestRecord,
+	}
+	discv4ResolveCommand = cli.Command{
+		Name:   "resolve",
+		Usage:  "Finds a node in the DHT",
+		Action: discv4Resolve,
+		Flags:  []cli.Flag{bootnodesFlag},
+	}
+)
+
+var bootnodesFlag = cli.StringFlag{
+	Name:  "bootnodes",
+	Usage: "Comma separated nodes used for bootstrapping",
+}
+
+func discv4Ping(ctx *cli.Context) error {
+	n, disc, err := getNodeArgAndStartV4(ctx)
+	if err != nil {
+		return err
+	}
+	defer disc.Close()
+
+	start := time.Now()
+	if err := disc.Ping(n); err != nil {
+		return fmt.Errorf("node didn't respond: %v", err)
+	}
+	fmt.Printf("node responded to ping (RTT %v).\n", time.Since(start))
+	return nil
+}
+
+func discv4RequestRecord(ctx *cli.Context) error {
+	n, disc, err := getNodeArgAndStartV4(ctx)
+	if err != nil {
+		return err
+	}
+	defer disc.Close()
+
+	respN, err := disc.RequestENR(n)
+	if err != nil {
+		return fmt.Errorf("can't retrieve record: %v", err)
+	}
+	fmt.Println(respN.String())
+	return nil
+}
+
+func discv4Resolve(ctx *cli.Context) error {
+	n, disc, err := getNodeArgAndStartV4(ctx)
+	if err != nil {
+		return err
+	}
+	defer disc.Close()
+
+	fmt.Println(disc.Resolve(n).String())
+	return nil
+}
+
+func getNodeArgAndStartV4(ctx *cli.Context) (*enode.Node, *discover.UDPv4, error) {
+	if ctx.NArg() != 1 {
+		return nil, nil, fmt.Errorf("missing node as command-line argument")
+	}
+	n, err := parseNode(ctx.Args()[0])
+	if err != nil {
+		return nil, nil, err
+	}
+	var bootnodes []*enode.Node
+	if commandHasFlag(ctx, bootnodesFlag) {
+		bootnodes, err = parseBootnodes(ctx)
+		if err != nil {
+			return nil, nil, err
+		}
+	}
+	disc, err := startV4(bootnodes)
+	return n, disc, err
+}
+
+func parseBootnodes(ctx *cli.Context) ([]*enode.Node, error) {
+	s := params.RinkebyBootnodes
+	if ctx.IsSet(bootnodesFlag.Name) {
+		s = strings.Split(ctx.String(bootnodesFlag.Name), ",")
+	}
+	nodes := make([]*enode.Node, len(s))
+	var err error
+	for i, record := range s {
+		nodes[i], err = parseNode(record)
+		if err != nil {
+			return nil, fmt.Errorf("invalid bootstrap node: %v", err)
+		}
+	}
+	return nodes, nil
+}
+
+// commandHasFlag returns true if the current command supports the given flag.
+func commandHasFlag(ctx *cli.Context, flag cli.Flag) bool {
+	flags := ctx.FlagNames()
+	sort.Strings(flags)
+	i := sort.SearchStrings(flags, flag.GetName())
+	return i != len(flags) && flags[i] == flag.GetName()
+}
+
+// startV4 starts an ephemeral discovery V4 node.
+func startV4(bootnodes []*enode.Node) (*discover.UDPv4, error) {
+	var cfg discover.Config
+	cfg.Bootnodes = bootnodes
+	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 {
+		return nil, err
+	}
+	addr := socket.LocalAddr().(*net.UDPAddr)
+	ln.SetFallbackIP(net.IP{127, 0, 0, 1})
+	ln.SetFallbackUDP(addr.Port)
+	return discover.ListenUDP(socket, ln, cfg)
+}
diff --git a/cmd/devp2p/enrcmd.go b/cmd/devp2p/enrcmd.go
new file mode 100644
index 000000000..15d77dd01
--- /dev/null
+++ b/cmd/devp2p/enrcmd.go
@@ -0,0 +1,198 @@
+// 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 (
+	"bytes"
+	"encoding/base64"
+	"encoding/hex"
+	"fmt"
+	"io/ioutil"
+	"net"
+	"os"
+	"strconv"
+	"strings"
+
+	"github.com/ethereum/go-ethereum/p2p/enode"
+	"github.com/ethereum/go-ethereum/p2p/enr"
+	"github.com/ethereum/go-ethereum/rlp"
+	"gopkg.in/urfave/cli.v1"
+)
+
+var enrdumpCommand = cli.Command{
+	Name:   "enrdump",
+	Usage:  "Pretty-prints node records",
+	Action: enrdump,
+	Flags: []cli.Flag{
+		cli.StringFlag{Name: "file"},
+	},
+}
+
+func enrdump(ctx *cli.Context) error {
+	var source string
+	if file := ctx.String("file"); file != "" {
+		if ctx.NArg() != 0 {
+			return fmt.Errorf("can't dump record from command-line argument in -file mode")
+		}
+		var b []byte
+		var err error
+		if file == "-" {
+			b, err = ioutil.ReadAll(os.Stdin)
+		} else {
+			b, err = ioutil.ReadFile(file)
+		}
+		if err != nil {
+			return err
+		}
+		source = string(b)
+	} else if ctx.NArg() == 1 {
+		source = ctx.Args()[0]
+	} else {
+		return fmt.Errorf("need record as argument")
+	}
+
+	r, err := parseRecord(source)
+	if err != nil {
+		return fmt.Errorf("INVALID: %v", err)
+	}
+	fmt.Print(dumpRecord(r))
+	return nil
+}
+
+// dumpRecord creates a human-readable description of the given node record.
+func dumpRecord(r *enr.Record) string {
+	out := new(bytes.Buffer)
+	if n, err := enode.New(enode.ValidSchemes, r); err != nil {
+		fmt.Fprintf(out, "INVALID: %v\n", err)
+	} else {
+		fmt.Fprintf(out, "Node ID: %v\n", n.ID())
+	}
+	kv := r.AppendElements(nil)[1:]
+	fmt.Fprintf(out, "Record has sequence number %d and %d key/value pairs.\n", r.Seq(), len(kv)/2)
+	fmt.Fprint(out, dumpRecordKV(kv, 2))
+	return out.String()
+}
+
+func dumpRecordKV(kv []interface{}, indent int) string {
+	// Determine the longest key name for alignment.
+	var out string
+	var longestKey = 0
+	for i := 0; i < len(kv); i += 2 {
+		key := kv[i].(string)
+		if len(key) > longestKey {
+			longestKey = len(key)
+		}
+	}
+	// Print the keys, invoking formatters for known keys.
+	for i := 0; i < len(kv); i += 2 {
+		key := kv[i].(string)
+		val := kv[i+1].(rlp.RawValue)
+		pad := longestKey - len(key)
+		out += strings.Repeat(" ", indent) + strconv.Quote(key) + strings.Repeat(" ", pad+1)
+		formatter := attrFormatters[key]
+		if formatter == nil {
+			formatter = formatAttrRaw
+		}
+		fmtval, ok := formatter(val)
+		if ok {
+			out += fmtval + "\n"
+		} else {
+			out += hex.EncodeToString(val) + " (!)\n"
+		}
+	}
+	return out
+}
+
+// parseNode parses a node record and verifies its signature.
+func parseNode(source string) (*enode.Node, error) {
+	if strings.HasPrefix(source, "enode://") {
+		return enode.ParseV4(source)
+	}
+	r, err := parseRecord(source)
+	if err != nil {
+		return nil, err
+	}
+	return enode.New(enode.ValidSchemes, r)
+}
+
+// parseRecord parses a node record from hex, base64, or raw binary input.
+func parseRecord(source string) (*enr.Record, error) {
+	bin := []byte(source)
+	if d, ok := decodeRecordHex(bytes.TrimSpace(bin)); ok {
+		bin = d
+	} else if d, ok := decodeRecordBase64(bytes.TrimSpace(bin)); ok {
+		bin = d
+	}
+	var r enr.Record
+	err := rlp.DecodeBytes(bin, &r)
+	return &r, err
+}
+
+func decodeRecordHex(b []byte) ([]byte, bool) {
+	if bytes.HasPrefix(b, []byte("0x")) {
+		b = b[2:]
+	}
+	dec := make([]byte, hex.DecodedLen(len(b)))
+	_, err := hex.Decode(dec, b)
+	return dec, err == nil
+}
+
+func decodeRecordBase64(b []byte) ([]byte, bool) {
+	if bytes.HasPrefix(b, []byte("enr:")) {
+		b = b[4:]
+	}
+	dec := make([]byte, base64.RawURLEncoding.DecodedLen(len(b)))
+	n, err := base64.RawURLEncoding.Decode(dec, b)
+	return dec[:n], err == nil
+}
+
+// attrFormatters contains formatting functions for well-known ENR keys.
+var attrFormatters = map[string]func(rlp.RawValue) (string, bool){
+	"id":   formatAttrString,
+	"ip":   formatAttrIP,
+	"ip6":  formatAttrIP,
+	"tcp":  formatAttrUint,
+	"tcp6": formatAttrUint,
+	"udp":  formatAttrUint,
+	"udp6": formatAttrUint,
+}
+
+func formatAttrRaw(v rlp.RawValue) (string, bool) {
+	s := hex.EncodeToString(v)
+	return s, true
+}
+
+func formatAttrString(v rlp.RawValue) (string, bool) {
+	content, _, err := rlp.SplitString(v)
+	return strconv.Quote(string(content)), err == nil
+}
+
+func formatAttrIP(v rlp.RawValue) (string, bool) {
+	content, _, err := rlp.SplitString(v)
+	if err != nil || len(content) != 4 && len(content) != 6 {
+		return "", false
+	}
+	return net.IP(content).String(), true
+}
+
+func formatAttrUint(v rlp.RawValue) (string, bool) {
+	var x uint64
+	if err := rlp.DecodeBytes(v, &x); err != nil {
+		return "", false
+	}
+	return strconv.FormatUint(x, 10), true
+}
diff --git a/cmd/devp2p/main.go b/cmd/devp2p/main.go
new file mode 100644
index 000000000..4532ab968
--- /dev/null
+++ b/cmd/devp2p/main.go
@@ -0,0 +1,68 @@
+// 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"
+	"os"
+	"path/filepath"
+
+	"github.com/ethereum/go-ethereum/internal/debug"
+	"github.com/ethereum/go-ethereum/params"
+	"gopkg.in/urfave/cli.v1"
+)
+
+var (
+	// Git information set by linker when building with ci.go.
+	gitCommit string
+	gitDate   string
+	app       = &cli.App{
+		Name:        filepath.Base(os.Args[0]),
+		Usage:       "go-ethereum devp2p tool",
+		Version:     params.VersionWithCommit(gitCommit, gitDate),
+		Writer:      os.Stdout,
+		HideVersion: true,
+	}
+)
+
+func init() {
+	// Set up the CLI app.
+	app.Flags = append(app.Flags, debug.Flags...)
+	app.Before = func(ctx *cli.Context) error {
+		return debug.Setup(ctx, "")
+	}
+	app.After = func(ctx *cli.Context) error {
+		debug.Exit()
+		return nil
+	}
+	app.CommandNotFound = func(ctx *cli.Context, cmd string) {
+		fmt.Fprintf(os.Stderr, "No such command: %s\n", cmd)
+		os.Exit(1)
+	}
+	// Add subcommands.
+	app.Commands = []cli.Command{
+		enrdumpCommand,
+		discv4Command,
+	}
+}
+
+func main() {
+	if err := app.Run(os.Args); err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(1)
+	}
+}
diff --git a/p2p/discover/table.go b/p2p/discover/table.go
index 3460e8377..e0a46792b 100644
--- a/p2p/discover/table.go
+++ b/p2p/discover/table.go
@@ -85,10 +85,10 @@ type Table struct {
 // transport is implemented by the UDP transports.
 type transport interface {
 	Self() *enode.Node
+	RequestENR(*enode.Node) (*enode.Node, error)
 	lookupRandom() []*enode.Node
 	lookupSelf() []*enode.Node
 	ping(*enode.Node) (seq uint64, err error)
-	requestENR(*enode.Node) (*enode.Node, error)
 }
 
 // bucket contains nodes, ordered by their last activity. the entry
@@ -344,7 +344,7 @@ func (tab *Table) doRevalidate(done chan<- struct{}) {
 
 	// Also fetch record if the node replied and returned a higher sequence number.
 	if last.Seq() < remoteSeq {
-		n, err := tab.net.requestENR(unwrapNode(last))
+		n, err := tab.net.RequestENR(unwrapNode(last))
 		if err != nil {
 			tab.log.Debug("ENR request failed", "id", last.ID(), "addr", last.addr(), "err", err)
 		} else {
diff --git a/p2p/discover/table_util_test.go b/p2p/discover/table_util_test.go
index 3075c4340..8e5fc7374 100644
--- a/p2p/discover/table_util_test.go
+++ b/p2p/discover/table_util_test.go
@@ -145,7 +145,7 @@ func (t *pingRecorder) ping(n *enode.Node) (seq uint64, err error) {
 }
 
 // requestENR simulates an ENR request.
-func (t *pingRecorder) requestENR(n *enode.Node) (*enode.Node, error) {
+func (t *pingRecorder) RequestENR(n *enode.Node) (*enode.Node, error) {
 	t.mu.Lock()
 	defer t.mu.Unlock()
 
diff --git a/p2p/discover/v4_udp.go b/p2p/discover/v4_udp.go
index b3569b671..b2a5d85cf 100644
--- a/p2p/discover/v4_udp.go
+++ b/p2p/discover/v4_udp.go
@@ -415,13 +415,13 @@ func (t *UDPv4) lookupWorker(n *node, targetKey encPubkey, reply chan<- []*node)
 // version of the node record for it. It returns n if the node could not be resolved.
 func (t *UDPv4) Resolve(n *enode.Node) *enode.Node {
 	// Try asking directly. This works if the node is still responding on the endpoint we have.
-	if rn, err := t.requestENR(n); err == nil {
+	if rn, err := t.RequestENR(n); err == nil {
 		return rn
 	}
 	// Check table for the ID, we might have a newer version there.
 	if intable := t.tab.getNode(n.ID()); intable != nil && intable.Seq() > n.Seq() {
 		n = intable
-		if rn, err := t.requestENR(n); err == nil {
+		if rn, err := t.RequestENR(n); err == nil {
 			return rn
 		}
 	}
@@ -433,7 +433,7 @@ func (t *UDPv4) Resolve(n *enode.Node) *enode.Node {
 	result := t.LookupPubkey((*ecdsa.PublicKey)(&key))
 	for _, rn := range result {
 		if rn.ID() == n.ID() {
-			if rn, err := t.requestENR(rn); err == nil {
+			if rn, err := t.RequestENR(rn); err == nil {
 				return rn
 			}
 		}
@@ -447,6 +447,12 @@ func (t *UDPv4) ourEndpoint() rpcEndpoint {
 	return makeEndpoint(a, uint16(n.TCP()))
 }
 
+// Ping sends a ping message to the given node.
+func (t *UDPv4) Ping(n *enode.Node) error {
+	_, err := t.ping(n)
+	return err
+}
+
 // ping sends a ping message to the given node and waits for a reply.
 func (t *UDPv4) ping(n *enode.Node) (seq uint64, err error) {
 	rm := t.sendPing(n.ID(), &net.UDPAddr{IP: n.IP(), Port: n.UDP()}, nil)
@@ -521,8 +527,8 @@ func (t *UDPv4) findnode(toid enode.ID, toaddr *net.UDPAddr, target encPubkey) (
 	return nodes, <-rm.errc
 }
 
-// requestENR sends enrRequest to the given node and waits for a response.
-func (t *UDPv4) requestENR(n *enode.Node) (*enode.Node, error) {
+// RequestENR sends enrRequest to the given node and waits for a response.
+func (t *UDPv4) RequestENR(n *enode.Node) (*enode.Node, error) {
 	addr := &net.UDPAddr{IP: n.IP(), Port: n.UDP()}
 	t.ensureBond(n.ID(), addr)