mirror of
https://github.com/ethereum/go-ethereum.git
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134 lines
3.2 KiB
Go
134 lines
3.2 KiB
Go
// 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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