path: root/cmd/devp2p/discv4cmd.go

// 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)
}