github.com/pslzym/go-ethereum@v1.8.17-0.20180926104442-4b6824e07b1b/p2p/enode/nodedb.go (about)

     1  // Copyright 2015 The go-ethereum Authors
     2  // This file is part of the go-ethereum library.
     3  //
     4  // The go-ethereum library is free software: you can redistribute it and/or modify
     5  // it under the terms of the GNU Lesser General Public License as published by
     6  // the Free Software Foundation, either version 3 of the License, or
     7  // (at your option) any later version.
     8  //
     9  // The go-ethereum library is distributed in the hope that it will be useful,
    10  // but WITHOUT ANY WARRANTY; without even the implied warranty of
    11  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
    12  // GNU Lesser General Public License for more details.
    13  //
    14  // You should have received a copy of the GNU Lesser General Public License
    15  // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
    16  
    17  package enode
    18  
    19  import (
    20  	"bytes"
    21  	"crypto/rand"
    22  	"encoding/binary"
    23  	"fmt"
    24  	"os"
    25  	"sync"
    26  	"time"
    27  
    28  	"github.com/ethereum/go-ethereum/log"
    29  	"github.com/ethereum/go-ethereum/rlp"
    30  	"github.com/syndtr/goleveldb/leveldb"
    31  	"github.com/syndtr/goleveldb/leveldb/errors"
    32  	"github.com/syndtr/goleveldb/leveldb/iterator"
    33  	"github.com/syndtr/goleveldb/leveldb/opt"
    34  	"github.com/syndtr/goleveldb/leveldb/storage"
    35  	"github.com/syndtr/goleveldb/leveldb/util"
    36  )
    37  
    38  var (
    39  	nodeDBNilID          = ID{}           // Special node ID to use as a nil element.
    40  	nodeDBNodeExpiration = 24 * time.Hour // Time after which an unseen node should be dropped.
    41  	nodeDBCleanupCycle   = time.Hour      // Time period for running the expiration task.
    42  	nodeDBVersion        = 6
    43  )
    44  
    45  // DB is the node database, storing previously seen nodes and any collected metadata about
    46  // them for QoS purposes.
    47  type DB struct {
    48  	lvl    *leveldb.DB   // Interface to the database itself
    49  	runner sync.Once     // Ensures we can start at most one expirer
    50  	quit   chan struct{} // Channel to signal the expiring thread to stop
    51  }
    52  
    53  // Schema layout for the node database
    54  var (
    55  	nodeDBVersionKey = []byte("version") // Version of the database to flush if changes
    56  	nodeDBItemPrefix = []byte("n:")      // Identifier to prefix node entries with
    57  
    58  	nodeDBDiscoverRoot      = ":discover"
    59  	nodeDBDiscoverPing      = nodeDBDiscoverRoot + ":lastping"
    60  	nodeDBDiscoverPong      = nodeDBDiscoverRoot + ":lastpong"
    61  	nodeDBDiscoverFindFails = nodeDBDiscoverRoot + ":findfail"
    62  )
    63  
    64  // OpenDB opens a node database for storing and retrieving infos about known peers in the
    65  // network. If no path is given an in-memory, temporary database is constructed.
    66  func OpenDB(path string) (*DB, error) {
    67  	if path == "" {
    68  		return newMemoryDB()
    69  	}
    70  	return newPersistentDB(path)
    71  }
    72  
    73  // newMemoryNodeDB creates a new in-memory node database without a persistent backend.
    74  func newMemoryDB() (*DB, error) {
    75  	db, err := leveldb.Open(storage.NewMemStorage(), nil)
    76  	if err != nil {
    77  		return nil, err
    78  	}
    79  	return &DB{lvl: db, quit: make(chan struct{})}, nil
    80  }
    81  
    82  // newPersistentNodeDB creates/opens a leveldb backed persistent node database,
    83  // also flushing its contents in case of a version mismatch.
    84  func newPersistentDB(path string) (*DB, error) {
    85  	opts := &opt.Options{OpenFilesCacheCapacity: 5}
    86  	db, err := leveldb.OpenFile(path, opts)
    87  	if _, iscorrupted := err.(*errors.ErrCorrupted); iscorrupted {
    88  		db, err = leveldb.RecoverFile(path, nil)
    89  	}
    90  	if err != nil {
    91  		return nil, err
    92  	}
    93  	// The nodes contained in the cache correspond to a certain protocol version.
    94  	// Flush all nodes if the version doesn't match.
    95  	currentVer := make([]byte, binary.MaxVarintLen64)
    96  	currentVer = currentVer[:binary.PutVarint(currentVer, int64(nodeDBVersion))]
    97  
    98  	blob, err := db.Get(nodeDBVersionKey, nil)
    99  	switch err {
   100  	case leveldb.ErrNotFound:
   101  		// Version not found (i.e. empty cache), insert it
   102  		if err := db.Put(nodeDBVersionKey, currentVer, nil); err != nil {
   103  			db.Close()
   104  			return nil, err
   105  		}
   106  
   107  	case nil:
   108  		// Version present, flush if different
   109  		if !bytes.Equal(blob, currentVer) {
   110  			db.Close()
   111  			if err = os.RemoveAll(path); err != nil {
   112  				return nil, err
   113  			}
   114  			return newPersistentDB(path)
   115  		}
   116  	}
   117  	return &DB{lvl: db, quit: make(chan struct{})}, nil
   118  }
   119  
   120  // makeKey generates the leveldb key-blob from a node id and its particular
   121  // field of interest.
   122  func makeKey(id ID, field string) []byte {
   123  	if bytes.Equal(id[:], nodeDBNilID[:]) {
   124  		return []byte(field)
   125  	}
   126  	return append(nodeDBItemPrefix, append(id[:], field...)...)
   127  }
   128  
   129  // splitKey tries to split a database key into a node id and a field part.
   130  func splitKey(key []byte) (id ID, field string) {
   131  	// If the key is not of a node, return it plainly
   132  	if !bytes.HasPrefix(key, nodeDBItemPrefix) {
   133  		return ID{}, string(key)
   134  	}
   135  	// Otherwise split the id and field
   136  	item := key[len(nodeDBItemPrefix):]
   137  	copy(id[:], item[:len(id)])
   138  	field = string(item[len(id):])
   139  
   140  	return id, field
   141  }
   142  
   143  // fetchInt64 retrieves an integer instance associated with a particular
   144  // database key.
   145  func (db *DB) fetchInt64(key []byte) int64 {
   146  	blob, err := db.lvl.Get(key, nil)
   147  	if err != nil {
   148  		return 0
   149  	}
   150  	val, read := binary.Varint(blob)
   151  	if read <= 0 {
   152  		return 0
   153  	}
   154  	return val
   155  }
   156  
   157  // storeInt64 update a specific database entry to the current time instance as a
   158  // unix timestamp.
   159  func (db *DB) storeInt64(key []byte, n int64) error {
   160  	blob := make([]byte, binary.MaxVarintLen64)
   161  	blob = blob[:binary.PutVarint(blob, n)]
   162  
   163  	return db.lvl.Put(key, blob, nil)
   164  }
   165  
   166  // Node retrieves a node with a given id from the database.
   167  func (db *DB) Node(id ID) *Node {
   168  	blob, err := db.lvl.Get(makeKey(id, nodeDBDiscoverRoot), nil)
   169  	if err != nil {
   170  		return nil
   171  	}
   172  	return mustDecodeNode(id[:], blob)
   173  }
   174  
   175  func mustDecodeNode(id, data []byte) *Node {
   176  	node := new(Node)
   177  	if err := rlp.DecodeBytes(data, &node.r); err != nil {
   178  		panic(fmt.Errorf("p2p/enode: can't decode node %x in DB: %v", id, err))
   179  	}
   180  	// Restore node id cache.
   181  	copy(node.id[:], id)
   182  	return node
   183  }
   184  
   185  // UpdateNode inserts - potentially overwriting - a node into the peer database.
   186  func (db *DB) UpdateNode(node *Node) error {
   187  	blob, err := rlp.EncodeToBytes(&node.r)
   188  	if err != nil {
   189  		return err
   190  	}
   191  	return db.lvl.Put(makeKey(node.ID(), nodeDBDiscoverRoot), blob, nil)
   192  }
   193  
   194  // DeleteNode deletes all information/keys associated with a node.
   195  func (db *DB) DeleteNode(id ID) error {
   196  	deleter := db.lvl.NewIterator(util.BytesPrefix(makeKey(id, "")), nil)
   197  	for deleter.Next() {
   198  		if err := db.lvl.Delete(deleter.Key(), nil); err != nil {
   199  			return err
   200  		}
   201  	}
   202  	return nil
   203  }
   204  
   205  // ensureExpirer is a small helper method ensuring that the data expiration
   206  // mechanism is running. If the expiration goroutine is already running, this
   207  // method simply returns.
   208  //
   209  // The goal is to start the data evacuation only after the network successfully
   210  // bootstrapped itself (to prevent dumping potentially useful seed nodes). Since
   211  // it would require significant overhead to exactly trace the first successful
   212  // convergence, it's simpler to "ensure" the correct state when an appropriate
   213  // condition occurs (i.e. a successful bonding), and discard further events.
   214  func (db *DB) ensureExpirer() {
   215  	db.runner.Do(func() { go db.expirer() })
   216  }
   217  
   218  // expirer should be started in a go routine, and is responsible for looping ad
   219  // infinitum and dropping stale data from the database.
   220  func (db *DB) expirer() {
   221  	tick := time.NewTicker(nodeDBCleanupCycle)
   222  	defer tick.Stop()
   223  	for {
   224  		select {
   225  		case <-tick.C:
   226  			if err := db.expireNodes(); err != nil {
   227  				log.Error("Failed to expire nodedb items", "err", err)
   228  			}
   229  		case <-db.quit:
   230  			return
   231  		}
   232  	}
   233  }
   234  
   235  // expireNodes iterates over the database and deletes all nodes that have not
   236  // been seen (i.e. received a pong from) for some allotted time.
   237  func (db *DB) expireNodes() error {
   238  	threshold := time.Now().Add(-nodeDBNodeExpiration)
   239  
   240  	// Find discovered nodes that are older than the allowance
   241  	it := db.lvl.NewIterator(nil, nil)
   242  	defer it.Release()
   243  
   244  	for it.Next() {
   245  		// Skip the item if not a discovery node
   246  		id, field := splitKey(it.Key())
   247  		if field != nodeDBDiscoverRoot {
   248  			continue
   249  		}
   250  		// Skip the node if not expired yet (and not self)
   251  		if seen := db.LastPongReceived(id); seen.After(threshold) {
   252  			continue
   253  		}
   254  		// Otherwise delete all associated information
   255  		db.DeleteNode(id)
   256  	}
   257  	return nil
   258  }
   259  
   260  // LastPingReceived retrieves the time of the last ping packet received from
   261  // a remote node.
   262  func (db *DB) LastPingReceived(id ID) time.Time {
   263  	return time.Unix(db.fetchInt64(makeKey(id, nodeDBDiscoverPing)), 0)
   264  }
   265  
   266  // UpdateLastPingReceived updates the last time we tried contacting a remote node.
   267  func (db *DB) UpdateLastPingReceived(id ID, instance time.Time) error {
   268  	return db.storeInt64(makeKey(id, nodeDBDiscoverPing), instance.Unix())
   269  }
   270  
   271  // LastPongReceived retrieves the time of the last successful pong from remote node.
   272  func (db *DB) LastPongReceived(id ID) time.Time {
   273  	// Launch expirer
   274  	db.ensureExpirer()
   275  	return time.Unix(db.fetchInt64(makeKey(id, nodeDBDiscoverPong)), 0)
   276  }
   277  
   278  // UpdateLastPongReceived updates the last pong time of a node.
   279  func (db *DB) UpdateLastPongReceived(id ID, instance time.Time) error {
   280  	return db.storeInt64(makeKey(id, nodeDBDiscoverPong), instance.Unix())
   281  }
   282  
   283  // FindFails retrieves the number of findnode failures since bonding.
   284  func (db *DB) FindFails(id ID) int {
   285  	return int(db.fetchInt64(makeKey(id, nodeDBDiscoverFindFails)))
   286  }
   287  
   288  // UpdateFindFails updates the number of findnode failures since bonding.
   289  func (db *DB) UpdateFindFails(id ID, fails int) error {
   290  	return db.storeInt64(makeKey(id, nodeDBDiscoverFindFails), int64(fails))
   291  }
   292  
   293  // QuerySeeds retrieves random nodes to be used as potential seed nodes
   294  // for bootstrapping.
   295  func (db *DB) QuerySeeds(n int, maxAge time.Duration) []*Node {
   296  	var (
   297  		now   = time.Now()
   298  		nodes = make([]*Node, 0, n)
   299  		it    = db.lvl.NewIterator(nil, nil)
   300  		id    ID
   301  	)
   302  	defer it.Release()
   303  
   304  seek:
   305  	for seeks := 0; len(nodes) < n && seeks < n*5; seeks++ {
   306  		// Seek to a random entry. The first byte is incremented by a
   307  		// random amount each time in order to increase the likelihood
   308  		// of hitting all existing nodes in very small databases.
   309  		ctr := id[0]
   310  		rand.Read(id[:])
   311  		id[0] = ctr + id[0]%16
   312  		it.Seek(makeKey(id, nodeDBDiscoverRoot))
   313  
   314  		n := nextNode(it)
   315  		if n == nil {
   316  			id[0] = 0
   317  			continue seek // iterator exhausted
   318  		}
   319  		if now.Sub(db.LastPongReceived(n.ID())) > maxAge {
   320  			continue seek
   321  		}
   322  		for i := range nodes {
   323  			if nodes[i].ID() == n.ID() {
   324  				continue seek // duplicate
   325  			}
   326  		}
   327  		nodes = append(nodes, n)
   328  	}
   329  	return nodes
   330  }
   331  
   332  // reads the next node record from the iterator, skipping over other
   333  // database entries.
   334  func nextNode(it iterator.Iterator) *Node {
   335  	for end := false; !end; end = !it.Next() {
   336  		id, field := splitKey(it.Key())
   337  		if field != nodeDBDiscoverRoot {
   338  			continue
   339  		}
   340  		return mustDecodeNode(id[:], it.Value())
   341  	}
   342  	return nil
   343  }
   344  
   345  // close flushes and closes the database files.
   346  func (db *DB) Close() {
   347  	close(db.quit)
   348  	db.lvl.Close()
   349  }