p2p: move rlpx into separate package (#21464)

This change moves the RLPx protocol implementation into a separate package,
p2p/rlpx. The new package can be used to establish RLPx connections for
protocol testing purposes.

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

cmd/devp2p/rlpxcmd.go

@@ -0,0 +1,94 @@
+// 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 main
+
+import (
+	"fmt"
+	"net"
+
+	"github.com/ethereum/go-ethereum/common/hexutil"
+	"github.com/ethereum/go-ethereum/crypto"
+	"github.com/ethereum/go-ethereum/p2p"
+	"github.com/ethereum/go-ethereum/p2p/rlpx"
+	"github.com/ethereum/go-ethereum/rlp"
+	"gopkg.in/urfave/cli.v1"
+)
+
+var (
+	rlpxCommand = cli.Command{
+		Name:  "rlpx",
+		Usage: "RLPx Commands",
+		Subcommands: []cli.Command{
+			rlpxPingCommand,
+		},
+	}
+	rlpxPingCommand = cli.Command{
+		Name:      "ping",
+		Usage:     "Perform a RLPx handshake",
+		ArgsUsage: "<node>",
+		Action:    rlpxPing,
+	}
+)
+
+func rlpxPing(ctx *cli.Context) error {
+	n := getNodeArg(ctx)
+
+	fd, err := net.Dial("tcp", fmt.Sprintf("%v:%d", n.IP(), n.TCP()))
+	if err != nil {
+		return err
+	}
+	conn := rlpx.NewConn(fd, n.Pubkey())
+
+	ourKey, _ := crypto.GenerateKey()
+	_, err = conn.Handshake(ourKey)
+	if err != nil {
+		return err
+	}
+
+	code, data, _, err := conn.Read()
+	if err != nil {
+		return err
+	}
+	switch code {
+	case 0:
+		var h devp2pHandshake
+		if err := rlp.DecodeBytes(data, &h); err != nil {
+			return fmt.Errorf("invalid handshake: %v", err)
+		}
+		fmt.Printf("%+v\n", h)
+	case 1:
+		var msg []p2p.DiscReason
+		if rlp.DecodeBytes(data, &msg); len(msg) == 0 {
+			return fmt.Errorf("invalid disconnect message")
+		}
+		return fmt.Errorf("received disconnect message: %v", msg[0])
+	default:
+		return fmt.Errorf("invalid message code %d, expected handshake (code zero)", code)
+	}
+	return nil
+}
+
+// devp2pHandshake is the RLP structure of the devp2p protocol handshake.
+type devp2pHandshake struct {
+	Version    uint64
+	Name       string
+	Caps       []p2p.Cap
+	ListenPort uint64
+	ID         hexutil.Bytes // secp256k1 public key
+	// Ignore additional fields (for forward compatibility).
+	Rest []rlp.RawValue `rlp:"tail"`
+}