discovery/rendezvous.go
package discovery
import (
"context"
"crypto/ecdsa"
"errors"
"math/rand"
"net"
"sync"
"time"
ma "github.com/multiformats/go-multiaddr"
"github.com/status-im/rendezvous"
"github.com/ethereum/go-ethereum/log"
"github.com/ethereum/go-ethereum/p2p/discv5"
"github.com/ethereum/go-ethereum/p2p/enode"
"github.com/ethereum/go-ethereum/p2p/enr"
)
const (
registrationPeriod = 10 * time.Second
requestTimeout = 5 * time.Second
bucketSize = 10
)
var (
errNodeIsNil = errors.New("node cannot be nil")
errIdentityIsNil = errors.New("identity cannot be nil")
errDiscoveryIsStopped = errors.New("discovery is stopped")
)
func NewRendezvous(servers []ma.Multiaddr, identity *ecdsa.PrivateKey, node *enode.Node) (*Rendezvous, error) {
r := new(Rendezvous)
r.node = node
r.identity = identity
r.servers = servers
r.registrationPeriod = registrationPeriod
r.bucketSize = bucketSize
return r, nil
}
func NewRendezvousWithENR(servers []ma.Multiaddr, record enr.Record) *Rendezvous {
r := new(Rendezvous)
r.servers = servers
r.registrationPeriod = registrationPeriod
r.bucketSize = bucketSize
r.record = &record
return r
}
// Rendezvous is an implementation of discovery interface that uses
// rendezvous client.
type Rendezvous struct {
mu sync.RWMutex
client *rendezvous.Client
// Root context is used to cancel running requests
// when Rendezvous is stopped.
rootCtx context.Context
cancelRootCtx context.CancelFunc
servers []ma.Multiaddr
registrationPeriod time.Duration
bucketSize int
node *enode.Node
identity *ecdsa.PrivateKey
recordMu sync.Mutex
record *enr.Record // record is set directly if rendezvous is used in proxy mode
}
func (r *Rendezvous) Running() bool {
r.mu.RLock()
defer r.mu.RUnlock()
return r.client != nil
}
// Start creates client with ephemeral identity.
func (r *Rendezvous) Start() error {
r.mu.Lock()
defer r.mu.Unlock()
client, err := rendezvous.NewEphemeral()
if err != nil {
return err
}
r.client = &client
r.rootCtx, r.cancelRootCtx = context.WithCancel(context.Background())
return nil
}
// Stop removes client reference.
func (r *Rendezvous) Stop() error {
r.mu.Lock()
defer r.mu.Unlock()
if r.client == nil {
return nil
}
r.cancelRootCtx()
if err := r.client.Close(); err != nil {
return err
}
r.client = nil
return nil
}
func (r *Rendezvous) MakeRecord(srv *ma.Multiaddr) (record enr.Record, err error) {
r.recordMu.Lock()
defer r.recordMu.Unlock()
if r.record != nil {
return *r.record, nil
}
if r.node == nil {
return record, errNodeIsNil
}
if r.identity == nil {
return record, errIdentityIsNil
}
ip := r.node.IP()
if srv != nil && (ip.IsLoopback() || IsPrivate(ip)) { // If AdvertiseAddr is not specified, 127.0.0.1 might be returned
ctx, cancel := context.WithTimeout(r.rootCtx, requestTimeout)
defer cancel()
ipAddr, err := r.client.RemoteIp(ctx, *srv)
if err != nil {
log.Error("could not obtain the external ip address", "err", err)
} else {
parsedIP := net.ParseIP(ipAddr)
if parsedIP != nil {
ip = parsedIP
log.Info("node's external IP address", "ipAddr", ipAddr)
} else {
log.Error("invalid ip address obtained from rendezvous server", "ipaddr", ipAddr, "err", err)
}
}
}
record.Set(enr.IP(ip))
record.Set(enr.TCP(r.node.TCP()))
record.Set(enr.UDP(r.node.UDP()))
// public key is added to ENR when ENR is signed
if err := enode.SignV4(&record, r.identity); err != nil {
return record, err
}
r.record = &record
return record, nil
}
func (r *Rendezvous) register(srv ma.Multiaddr, topic string, record enr.Record) error {
ctx, cancel := context.WithTimeout(r.rootCtx, requestTimeout)
defer cancel()
r.mu.RLock()
defer r.mu.RUnlock()
if r.client == nil {
return errDiscoveryIsStopped
}
err := r.client.Register(ctx, srv, topic, record, r.registrationPeriod)
if err != nil {
log.Error("error registering", "topic", topic, "rendezvous server", srv, "err", err)
}
return err
}
// Register renews registration in the specified server.
func (r *Rendezvous) Register(topic string, stop chan struct{}) error {
srv := r.getRandomServer()
record, err := r.MakeRecord(&srv)
if err != nil {
return err
}
// sending registration more often than the whole registraton period
// will ensure that it won't be accidentally removed
ticker := time.NewTicker(r.registrationPeriod / 2)
defer ticker.Stop()
if err := r.register(srv, topic, record); err == context.Canceled {
return err
}
for {
select {
case <-stop:
return nil
case <-ticker.C:
if err := r.register(r.getRandomServer(), topic, record); err == context.Canceled {
return err
} else if err == errDiscoveryIsStopped {
return nil
}
}
}
}
func (r *Rendezvous) discoverRequest(srv ma.Multiaddr, topic string) ([]enr.Record, error) {
ctx, cancel := context.WithTimeout(r.rootCtx, requestTimeout)
defer cancel()
r.mu.RLock()
defer r.mu.RUnlock()
if r.client == nil {
return nil, errDiscoveryIsStopped
}
return r.client.Discover(ctx, srv, topic, r.bucketSize)
}
// Discover will search for new records every time period fetched from period channel.
func (r *Rendezvous) Discover(
topic string, period <-chan time.Duration, found chan<- *discv5.Node, lookup chan<- bool,
) error {
ticker := time.NewTicker(<-period)
for {
select {
case newPeriod, ok := <-period:
ticker.Stop()
if !ok {
return nil
}
ticker = time.NewTicker(newPeriod)
case <-ticker.C:
srv := r.servers[rand.Intn(len(r.servers))] // nolint: gosec
records, err := r.discoverRequest(srv, topic)
if err == context.Canceled {
return err
} else if err == errDiscoveryIsStopped {
return nil
} else if err != nil {
log.Debug("error fetching records", "topic", topic, "rendezvous server", srv, "err", err)
} else {
for i := range records {
n, err := enrToNode(records[i])
if err != nil {
log.Warn("error converting enr record to node", "err", err)
} else {
log.Debug("converted enr to", "ENODE", n.String())
select {
case found <- n:
case newPeriod, ok := <-period:
// closing a period channel is a signal to producer that consumer exited
ticker.Stop()
if !ok {
return nil
}
ticker = time.NewTicker(newPeriod)
}
}
}
}
}
}
}
func (r *Rendezvous) getRandomServer() ma.Multiaddr {
return r.servers[rand.Intn(len(r.servers))] // nolint: gosec
}
func enrToNode(record enr.Record) (*discv5.Node, error) {
var (
key enode.Secp256k1
ip enr.IPv4
tport enr.TCP
uport enr.UDP
nodeID discv5.NodeID
)
if err := record.Load(&key); err != nil {
return nil, err
}
ecdsaKey := ecdsa.PublicKey(key)
nodeID = discv5.PubkeyID(&ecdsaKey)
if err := record.Load(&ip); err != nil {
return nil, err
}
if err := record.Load(&tport); err != nil {
return nil, err
}
// ignore absence of udp port, as it is optional
_ = record.Load(&uport)
return discv5.NewNode(nodeID, net.IP(ip), uint16(uport), uint16(tport)), nil
}
// IsPrivate reports whether ip is a private address, according to
// RFC 1918 (IPv4 addresses) and RFC 4193 (IPv6 addresses).
// Copied/Adapted from https://go-review.googlesource.com/c/go/+/272668/11/src/net/ip.go
// Copyright (c) The Go Authors. All rights reserved.
// @TODO: once Go 1.17 is released in Q42021, remove this function as it will become part of the language
func IsPrivate(ip net.IP) bool {
if ip4 := ip.To4(); ip4 != nil {
// Following RFC 4193, Section 3. Local IPv6 Unicast Addresses which says:
// The Internet Assigned Numbers Authority (IANA) has reserved the
// following three blocks of the IPv4 address space for private internets:
// 10.0.0.0 - 10.255.255.255 (10/8 prefix)
// 172.16.0.0 - 172.31.255.255 (172.16/12 prefix)
// 192.168.0.0 - 192.168.255.255 (192.168/16 prefix)
return ip4[0] == 10 ||
(ip4[0] == 172 && ip4[1]&0xf0 == 16) ||
(ip4[0] == 192 && ip4[1] == 168)
}
// Following RFC 4193, Section 3. Private Address Space which says:
// The Internet Assigned Numbers Authority (IANA) has reserved the
// following block of the IPv6 address space for local internets:
// FC00:: - FDFF:FFFF:FFFF:FFFF:FFFF:FFFF:FFFF:FFFF (FC00::/7 prefix)
return len(ip) == net.IPv6len && ip[0]&0xfe == 0xfc
}