// Copyright 2015 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library 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 Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
package enode
import (
"bytes"
"crypto/rand"
"encoding/binary"
"fmt"
"net"
"os"
"sync"
"time"
"github.com/dexon-foundation/dexon/rlp"
"github.com/syndtr/goleveldb/leveldb"
"github.com/syndtr/goleveldb/leveldb/errors"
"github.com/syndtr/goleveldb/leveldb/iterator"
"github.com/syndtr/goleveldb/leveldb/opt"
"github.com/syndtr/goleveldb/leveldb/storage"
"github.com/syndtr/goleveldb/leveldb/util"
)
// Keys in the node database.
const (
dbVersionKey = "version" // Version of the database to flush if changes
dbNodePrefix = "n:" // Identifier to prefix node entries with
dbLocalPrefix = "local:"
dbDiscoverRoot = "v4"
// These fields are stored per ID and IP, the full key is "n:<ID>:v4:<IP>:findfail".
// Use nodeItemKey to create those keys.
dbNodeFindFails = "findfail"
dbNodePing = "lastping"
dbNodePong = "lastpong"
dbNodeSeq = "seq"
// Local information is keyed by ID only, the full key is "local:<ID>:seq".
// Use localItemKey to create those keys.
dbLocalSeq = "seq"
)
const (
dbNodeExpiration = 24 * time.Hour // Time after which an unseen node should be dropped.
dbCleanupCycle = time.Hour // Time period for running the expiration task.
dbVersion = 8
)
var zeroIP = make(net.IP, 16)
// DB is the node database, storing previously seen nodes and any collected metadata about
// them for QoS purposes.
type DB struct {
lvl *leveldb.DB // Interface to the database itself
runner sync.Once // Ensures we can start at most one expirer
quit chan struct{} // Channel to signal the expiring thread to stop
}
// OpenDB opens a node database for storing and retrieving infos about known peers in the
// network. If no path is given an in-memory, temporary database is constructed.
func OpenDB(path string) (*DB, error) {
if path == "" {
return newMemoryDB()
}
return newPersistentDB(path)
}
// newMemoryNodeDB creates a new in-memory node database without a persistent backend.
func newMemoryDB() (*DB, error) {
db, err := leveldb.Open(storage.NewMemStorage(), nil)
if err != nil {
return nil, err
}
return &DB{lvl: db, quit: make(chan struct{})}, nil
}
// newPersistentNodeDB creates/opens a leveldb backed persistent node database,
// also flushing its contents in case of a version mismatch.
func newPersistentDB(path string) (*DB, error) {
opts := &opt.Options{OpenFilesCacheCapacity: 5}
db, err := leveldb.OpenFile(path, opts)
if _, iscorrupted := err.(*errors.ErrCorrupted); iscorrupted {
db, err = leveldb.RecoverFile(path, nil)
}
if err != nil {
return nil, err
}
// The nodes contained in the cache correspond to a certain protocol version.
// Flush all nodes if the version doesn't match.
currentVer := make([]byte, binary.MaxVarintLen64)
currentVer = currentVer[:binary.PutVarint(currentVer, int64(dbVersion))]
blob, err := db.Get([]byte(dbVersionKey), nil)
switch err {
case leveldb.ErrNotFound:
// Version not found (i.e. empty cache), insert it
if err := db.Put([]byte(dbVersionKey), currentVer, nil); err != nil {
db.Close()
return nil, err
}
case nil:
// Version present, flush if different
if !bytes.Equal(blob, currentVer) {
db.Close()
if err = os.RemoveAll(path); err != nil {
return nil, err
}
return newPersistentDB(path)
}
}
return &DB{lvl: db, quit: make(chan struct{})}, nil
}
// nodeKey returns the database key for a node record.
func nodeKey(id ID) []byte {
key := append([]byte(dbNodePrefix), id[:]...)
key = append(key, ':')
key = append(key, dbDiscoverRoot...)
return key
}
// splitNodeKey returns the node ID of a key created by nodeKey.
func splitNodeKey(key []byte) (id ID, rest []byte) {
if !bytes.HasPrefix(key, []byte(dbNodePrefix)) {
return ID{}, nil
}
item := key[len(dbNodePrefix):]
copy(id[:], item[:len(id)])
return id, item[len(id)+1:]
}
// nodeItemKey returns the database key for a node metadata field.
func nodeItemKey(id ID, ip net.IP, field string) []byte {
ip16 := ip.To16()
if ip16 == nil {
panic(fmt.Errorf("invalid IP (length %d)", len(ip)))
}
return bytes.Join([][]byte{nodeKey(id), ip16, []byte(field)}, []byte{':'})
}
// splitNodeItemKey returns the components of a key created by nodeItemKey.
func splitNodeItemKey(key []byte) (id ID, ip net.IP, field string) {
id, key = splitNodeKey(key)
// Skip discover root.
if string(key) == dbDiscoverRoot {
return id, nil, ""
}
key = key[len(dbDiscoverRoot)+1:]
// Split out the IP.
ip = net.IP(key[:16])
if ip4 := ip.To4(); ip4 != nil {
ip = ip4
}
key = key[16+1:]
// Field is the remainder of key.
field = string(key)
return id, ip, field
}
// localItemKey returns the key of a local node item.
func localItemKey(id ID, field string) []byte {
key := append([]byte(dbLocalPrefix), id[:]...)
key = append(key, ':')
key = append(key, field...)
return key
}
// fetchInt64 retrieves an integer associated with a particular key.
func (db *DB) fetchInt64(key []byte) int64 {
blob, err := db.lvl.Get(key, nil)
if err != nil {
return 0
}
val, read := binary.Varint(blob)
if read <= 0 {
return 0
}
return val
}
// storeInt64 stores an integer in the given key.
func (db *DB) storeInt64(key []byte, n int64) error {
blob := make([]byte, binary.MaxVarintLen64)
blob = blob[:binary.PutVarint(blob, n)]
return db.lvl.Put(key, blob, nil)
}
// fetchUint64 retrieves an integer associated with a particular key.
func (db *DB) fetchUint64(key []byte) uint64 {
blob, err := db.lvl.Get(key, nil)
if err != nil {
return 0
}
val, _ := binary.Uvarint(blob)
return val
}
// storeUint64 stores an integer in the given key.
func (db *DB) storeUint64(key []byte, n uint64) error {
blob := make([]byte, binary.MaxVarintLen64)
blob = blob[:binary.PutUvarint(blob, n)]
return db.lvl.Put(key, blob, nil)
}
// Node retrieves a node with a given id from the database.
func (db *DB) Node(id ID) *Node {
blob, err := db.lvl.Get(nodeKey(id), nil)
if err != nil {
return nil
}
return mustDecodeNode(id[:], blob)
}
func mustDecodeNode(id, data []byte) *Node {
node := new(Node)
if err := rlp.DecodeBytes(data, &node.r); err != nil {
panic(fmt.Errorf("p2p/enode: can't decode node %x in DB: %v", id, err))
}
// Restore node id cache.
copy(node.id[:], id)
return node
}
// UpdateNode inserts - potentially overwriting - a node into the peer database.
func (db *DB) UpdateNode(node *Node) error {
if node.Seq() < db.NodeSeq(node.ID()) {
return nil
}
blob, err := rlp.EncodeToBytes(&node.r)
if err != nil {
return err
}
if err := db.lvl.Put(nodeKey(node.ID()), blob, nil); err != nil {
return err
}
return db.storeUint64(nodeItemKey(node.ID(), zeroIP, dbNodeSeq), node.Seq())
}
// NodeSeq returns the stored record sequence number of the given node.
func (db *DB) NodeSeq(id ID) uint64 {
return db.fetchUint64(nodeItemKey(id, zeroIP, dbNodeSeq))
}
// Resolve returns the stored record of the node if it has a larger sequence
// number than n.
func (db *DB) Resolve(n *Node) *Node {
if n.Seq() > db.NodeSeq(n.ID()) {
return n
}
return db.Node(n.ID())
}
// DeleteNode deletes all information associated with a node.
func (db *DB) DeleteNode(id ID) {
deleteRange(db.lvl, nodeKey(id))
}
func deleteRange(db *leveldb.DB, prefix []byte) {
it := db.NewIterator(util.BytesPrefix(prefix), nil)
defer it.Release()
for it.Next() {
db.Delete(it.Key(), nil)
}
}
// ensureExpirer is a small helper method ensuring that the data expiration
// mechanism is running. If the expiration goroutine is already running, this
// method simply returns.
//
// The goal is to start the data evacuation only after the network successfully
// bootstrapped itself (to prevent dumping potentially useful seed nodes). Since
// it would require significant overhead to exactly trace the first successful
// convergence, it's simpler to "ensure" the correct state when an appropriate
// condition occurs (i.e. a successful bonding), and discard further events.
func (db *DB) ensureExpirer() {
db.runner.Do(func() { go db.expirer() })
}
// expirer should be started in a go routine, and is responsible for looping ad
// infinitum and dropping stale data from the database.
func (db *DB) expirer() {
tick := time.NewTicker(dbCleanupCycle)
defer tick.Stop()
for {
select {
case <-tick.C:
db.expireNodes()
case <-db.quit:
return
}
}
}
// expireNodes iterates over the database and deletes all nodes that have not
// been seen (i.e. received a pong from) for some time.
func (db *DB) expireNodes() {
it := db.lvl.NewIterator(util.BytesPrefix([]byte(dbNodePrefix)), nil)
defer it.Release()
if !it.Next() {
return
}
var (
threshold = time.Now().Add(-dbNodeExpiration).Unix()
youngestPong int64
atEnd = false
)
for !atEnd {
id, ip, field := splitNodeItemKey(it.Key())
if field == dbNodePong {
time, _ := binary.Varint(it.Value())
if time > youngestPong {
youngestPong = time
}
if time < threshold {
// Last pong from this IP older than threshold, remove fields belonging to it.
deleteRange(db.lvl, nodeItemKey(id, ip, ""))
}
}
atEnd = !it.Next()
nextID, _ := splitNodeKey(it.Key())
if atEnd || nextID != id {
// We've moved beyond the last entry of the current ID.
// Remove everything if there was no recent enough pong.
if youngestPong > 0 && youngestPong < threshold {
deleteRange(db.lvl, nodeKey(id))
}
youngestPong = 0
}
}
}
// LastPingReceived retrieves the time of the last ping packet received from
// a remote node.
func (db *DB) LastPingReceived(id ID, ip net.IP) time.Time {
return time.Unix(db.fetchInt64(nodeItemKey(id, ip, dbNodePing)), 0)
}
// UpdateLastPingReceived updates the last time we tried contacting a remote node.
func (db *DB) UpdateLastPingReceived(id ID, ip net.IP, instance time.Time) error {
return db.storeInt64(nodeItemKey(id, ip, dbNodePing), instance.Unix())
}
// LastPongReceived retrieves the time of the last successful pong from remote node.
func (db *DB) LastPongReceived(id ID, ip net.IP) time.Time {
// Launch expirer
db.ensureExpirer()
return time.Unix(db.fetchInt64(nodeItemKey(id, ip, dbNodePong)), 0)
}
// UpdateLastPongReceived updates the last pong time of a node.
func (db *DB) UpdateLastPongReceived(id ID, ip net.IP, instance time.Time) error {
return db.storeInt64(nodeItemKey(id, ip, dbNodePong), instance.Unix())
}
// FindFails retrieves the number of findnode failures since bonding.
func (db *DB) FindFails(id ID, ip net.IP) int {
return int(db.fetchInt64(nodeItemKey(id, ip, dbNodeFindFails)))
}
// UpdateFindFails updates the number of findnode failures since bonding.
func (db *DB) UpdateFindFails(id ID, ip net.IP, fails int) error {
return db.storeInt64(nodeItemKey(id, ip, dbNodeFindFails), int64(fails))
}
// LocalSeq retrieves the local record sequence counter.
func (db *DB) localSeq(id ID) uint64 {
return db.fetchUint64(nodeItemKey(id, zeroIP, dbLocalSeq))
}
// storeLocalSeq stores the local record sequence counter.
func (db *DB) storeLocalSeq(id ID, n uint64) {
db.storeUint64(nodeItemKey(id, zeroIP, dbLocalSeq), n)
}
// QuerySeeds retrieves random nodes to be used as potential seed nodes
// for bootstrapping.
func (db *DB) QuerySeeds(n int, maxAge time.Duration) []*Node {
var (
now = time.Now()
nodes = make([]*Node, 0, n)
it = db.lvl.NewIterator(nil, nil)
id ID
)
defer it.Release()
seek:
for seeks := 0; len(nodes) < n && seeks < n*5; seeks++ {
// Seek to a random entry. The first byte is incremented by a
// random amount each time in order to increase the likelihood
// of hitting all existing nodes in very small databases.
ctr := id[0]
rand.Read(id[:])
id[0] = ctr + id[0]%16
it.Seek(nodeKey(id))
n := nextNode(it)
if n == nil {
id[0] = 0
continue seek // iterator exhausted
}
if now.Sub(db.LastPongReceived(n.ID(), n.IP())) > maxAge {
continue seek
}
for i := range nodes {
if nodes[i].ID() == n.ID() {
continue seek // duplicate
}
}
nodes = append(nodes, n)
}
return nodes
}
// reads the next node record from the iterator, skipping over other
// database entries.
func nextNode(it iterator.Iterator) *Node {
for end := false; !end; end = !it.Next() {
id, rest := splitNodeKey(it.Key())
if string(rest) != dbDiscoverRoot {
continue
}
return mustDecodeNode(id[:], it.Value())
}
return nil
}
// close flushes and closes the database files.
func (db *DB) Close() {
close(db.quit)
db.lvl.Close()
}
