forked from mirror/go-ethereum
Péter Szilágyi
10 years ago
parent
971702e7a1
commit
6def110c37
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// Contains the discovery cache, storing previously seen nodes to act as seed
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// servers during bootstrapping the network.
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package discover |
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import ( |
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"bytes" |
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"encoding/binary" |
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"net" |
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"os" |
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"github.com/ethereum/go-ethereum/rlp" |
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"github.com/syndtr/goleveldb/leveldb" |
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"github.com/syndtr/goleveldb/leveldb/storage" |
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) |
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// Cache stores all nodes we know about.
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type Cache struct { |
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db *leveldb.DB |
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} |
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// Cache version to allow dumping old data if it changes.
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var cacheVersionKey = []byte("pv") |
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// NewMemoryCache creates a new in-memory peer cache without a persistent backend.
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func NewMemoryCache() (*Cache, error) { |
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db, err := leveldb.Open(storage.NewMemStorage(), nil) |
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if err != nil { |
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return nil, err |
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} |
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return &Cache{db: db}, nil |
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} |
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// NewPersistentCache creates/opens a leveldb backed persistent peer cache, also
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// flushing its contents in case of a version mismatch.
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func NewPersistentCache(path string) (*Cache, error) { |
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// Try to open the cache, recovering any corruption
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db, err := leveldb.OpenFile(path, nil) |
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if _, iscorrupted := err.(leveldb.ErrCorrupted); iscorrupted { |
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db, err = leveldb.RecoverFile(path, nil) |
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} |
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if err != nil { |
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return nil, err |
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} |
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// The nodes contained in the cache correspond to a certain protocol version.
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// Flush all nodes if the version doesn't match.
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currentVer := make([]byte, binary.MaxVarintLen64) |
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currentVer = currentVer[:binary.PutVarint(currentVer, Version)] |
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blob, err := db.Get(cacheVersionKey, nil) |
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switch err { |
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case leveldb.ErrNotFound: |
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// Version not found (i.e. empty cache), insert it
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err = db.Put(cacheVersionKey, currentVer, nil) |
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case nil: |
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// Version present, flush if different
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if !bytes.Equal(blob, currentVer) { |
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db.Close() |
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if err = os.RemoveAll(path); err != nil { |
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return nil, err |
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} |
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return NewPersistentCache(path) |
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} |
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} |
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// Clean up in case of an error
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if err != nil { |
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db.Close() |
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return nil, err |
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} |
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return &Cache{db: db}, nil |
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} |
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// get retrieves a node with a given id from the seed da
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func (c *Cache) get(id NodeID) *Node { |
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blob, err := c.db.Get(id[:], nil) |
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if err != nil { |
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return nil |
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} |
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node := new(Node) |
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if err := rlp.DecodeBytes(blob, node); err != nil { |
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return nil |
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} |
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return node |
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} |
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// list retrieves a batch of nodes from the database.
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func (c *Cache) list(n int) []*Node { |
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it := c.db.NewIterator(nil, nil) |
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defer it.Release() |
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nodes := make([]*Node, 0, n) |
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for i := 0; i < n && it.Next(); i++ { |
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var id NodeID |
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copy(id[:], it.Key()) |
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if node := c.get(id); node != nil { |
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nodes = append(nodes, node) |
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} |
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} |
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return nodes |
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} |
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// update inserts - potentially overwriting - a node in the seed database.
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func (c *Cache) update(node *Node) error { |
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blob, err := rlp.EncodeToBytes(node) |
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if err != nil { |
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return err |
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} |
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return c.db.Put(node.ID[:], blob, nil) |
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} |
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// add inserts a new node into the seed database.
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func (c *Cache) add(id NodeID, addr *net.UDPAddr, tcpPort uint16) *Node { |
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node := &Node{ |
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ID: id, |
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IP: addr.IP, |
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DiscPort: addr.Port, |
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TCPPort: int(tcpPort), |
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} |
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c.update(node) |
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return node |
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} |
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// delete removes a node from the database.
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func (c *Cache) delete(id NodeID) error { |
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return c.db.Delete(id[:], nil) |
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} |
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// Close flushes and closes the database files.
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func (c *Cache) Close() { |
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c.db.Close() |
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} |
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