// 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/>.
// Contains the node database, storing previously seen nodes and any collected
// metadata about them for QoS purposes.
package discover
import (
"bytes"
"crypto/rand"
"encoding/binary"
"os"
"sync"
"time"
"github.com/ethereum/go-ethereum/crypto"
"github.com/ethereum/go-ethereum/log"
"github.com/ethereum/go-ethereum/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"
)
var (
nodeDBNilNodeID = NodeID{} // Special node ID to use as a nil element.
nodeDBNodeExpiration = 24 * time.Hour // Time after which an unseen node should be dropped.
nodeDBCleanupCycle = time.Hour // Time period for running the expiration task.
)
// nodeDB stores all nodes we know about.
type nodeDB struct {
lvl *leveldb.DB // Interface to the database itself
self NodeID // Own node id to prevent adding it into the database
runner sync.Once // Ensures we can start at most one expirer
quit chan struct{} // Channel to signal the expiring thread to stop
}
// Schema layout for the node database
var (
nodeDBVersionKey = []byte("version") // Version of the database to flush if changes
nodeDBItemPrefix = []byte("n:") // Identifier to prefix node entries with
nodeDBDiscoverRoot = ":discover"
nodeDBDiscoverPing = nodeDBDiscoverRoot + ":lastping"
nodeDBDiscoverPong = nodeDBDiscoverRoot + ":lastpong"
nodeDBDiscoverFindFails = nodeDBDiscoverRoot + ":findfail"
)
// newNodeDB creates a new 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 newNodeDB(path string, version int, self NodeID) (*nodeDB, error) {
if path == "" {
return newMemoryNodeDB(self)
}
return newPersistentNodeDB(path, version, self)
}
// newMemoryNodeDB creates a new in-memory node database without a persistent
// backend.
func newMemoryNodeDB(self NodeID) (*nodeDB, error) {
db, err := leveldb.Open(storage.NewMemStorage(), nil)
if err != nil {
return nil, err
}
return &nodeDB{
lvl: db,
self: self,
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 newPersistentNodeDB(path string, version int, self NodeID) (*nodeDB, 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(version))]
blob, err := db.Get(nodeDBVersionKey, nil)
switch err {
case leveldb.ErrNotFound:
// Version not found (i.e. empty cache), insert it
if err := db.Put(nodeDBVersionKey, 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 newPersistentNodeDB(path, version, self)
}
}
return &nodeDB{
lvl: db,
self: self,
quit: make(chan struct{}),
}, nil
}
// makeKey generates the leveldb key-blob from a node id and its particular
// field of interest.
func makeKey(id NodeID, field string) []byte {
if bytes.Equal(id[:], nodeDBNilNodeID[:]) {
return []byte(field)
}
return append(nodeDBItemPrefix, append(id[:], field...)...)
}
// splitKey tries to split a database key into a node id and a field part.
func splitKey(key []byte) (id NodeID, field string) {
// If the key is not of a node, return it plainly
if !bytes.HasPrefix(key, nodeDBItemPrefix) {
return NodeID{}, string(key)
}
// Otherwise split the id and field
item := key[len(nodeDBItemPrefix):]
copy(id[:], item[:len(id)])
field = string(item[len(id):])
return id, field
}
// fetchInt64 retrieves an integer instance associated with a particular
// database key.
func (db *nodeDB) 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 update a specific database entry to the current time instance as a
// unix timestamp.
func (db *nodeDB) storeInt64(key []byte, n int64) error {
blob := make([]byte, binary.MaxVarintLen64)
blob = blob[:binary.PutVarint(blob, n)]
return db.lvl.Put(key, blob, nil)
}
// node retrieves a node with a given id from the database.
func (db *nodeDB) node(id NodeID) *Node {
blob, err := db.lvl.Get(makeKey(id, nodeDBDiscoverRoot), nil)
if err != nil {
return nil
}
node := new(Node)
if err := rlp.DecodeBytes(blob, node); err != nil {
log.Error("Failed to decode node RLP", "err", err)
return nil
}
node.sha = crypto.Keccak256Hash(node.ID[:])
return node
}
// updateNode inserts - potentially overwriting - a node into the peer database.
func (db *nodeDB) updateNode(node *Node) error {
blob, err := rlp.EncodeToBytes(node)
if err != nil {
return err
}
return db.lvl.Put(makeKey(node.ID, nodeDBDiscoverRoot), blob, nil)
}
// deleteNode deletes all information/keys associated with a node.
func (db *nodeDB) deleteNode(id NodeID) error {
deleter := db.lvl.NewIterator(util.BytesPrefix(makeKey(id, "")), nil)
for deleter.Next() {
if err := db.lvl.Delete(deleter.Key(), nil); err != nil {
return err
}
}
return 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 *nodeDB) 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 *nodeDB) expirer() {
tick := time.NewTicker(nodeDBCleanupCycle)
defer tick.Stop()
for {
select {
case <-tick.C:
if err := db.expireNodes(); err != nil {
log.Error("Failed to expire nodedb items", "err", err)
}
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 allotted time.
func (db *nodeDB) expireNodes() error {
threshold := time.Now().Add(-nodeDBNodeExpiration)
// Find discovered nodes that are older than the allowance
it := db.lvl.NewIterator(nil, nil)
defer it.Release()
for it.Next() {
// Skip the item if not a discovery node
id, field := splitKey(it.Key())
if field != nodeDBDiscoverRoot {
continue
}
// Skip the node if not expired yet (and not self)
if !bytes.Equal(id[:], db.self[:]) {
if seen := db.lastPong(id); seen.After(threshold) {
continue
}
}
// Otherwise delete all associated information
db.deleteNode(id)
}
return nil
}
// lastPing retrieves the time of the last ping packet send to a remote node,
// requesting binding.
func (db *nodeDB) lastPing(id NodeID) time.Time {
return time.Unix(db.fetchInt64(makeKey(id, nodeDBDiscoverPing)), 0)
}
// updateLastPing updates the last time we tried contacting a remote node.
func (db *nodeDB) updateLastPing(id NodeID, instance time.Time) error {
return db.storeInt64(makeKey(id, nodeDBDiscoverPing), instance.Unix())
}
// lastPong retrieves the time of the last successful contact from remote node.
func (db *nodeDB) lastPong(id NodeID) time.Time {
return time.Unix(db.fetchInt64(makeKey(id, nodeDBDiscoverPong)), 0)
}
// updateLastPong updates the last time a remote node successfully contacted.
func (db *nodeDB) updateLastPong(id NodeID, instance time.Time) error {
return db.storeInt64(makeKey(id, nodeDBDiscoverPong), instance.Unix())
}
// findFails retrieves the number of findnode failures since bonding.
func (db *nodeDB) findFails(id NodeID) int {
return int(db.fetchInt64(makeKey(id, nodeDBDiscoverFindFails)))
}
// updateFindFails updates the number of findnode failures since bonding.
func (db *nodeDB) updateFindFails(id NodeID, fails int) error {
return db.storeInt64(makeKey(id, nodeDBDiscoverFindFails), int64(fails))
}
// querySeeds retrieves random nodes to be used as potential seed nodes
// for bootstrapping.
func (db *nodeDB) querySeeds(n int, maxAge time.Duration) []*Node {
var (
now = time.Now()
nodes = make([]*Node, 0, n)
it = db.lvl.NewIterator(nil, nil)
id NodeID
)
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(makeKey(id, nodeDBDiscoverRoot))
n := nextNode(it)
if n == nil {
id[0] = 0
continue seek // iterator exhausted
}
if n.ID == db.self {
continue seek
}
if now.Sub(db.lastPong(n.ID)) > 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, field := splitKey(it.Key())
if field != nodeDBDiscoverRoot {
continue
}
var n Node
if err := rlp.DecodeBytes(it.Value(), &n); err != nil {
log.Warn("Failed to decode node RLP", "id", id, "err", err)
continue
}
return &n
}
return nil
}
// close flushes and closes the database files.
func (db *nodeDB) close() {
close(db.quit)
db.lvl.Close()
}
