1 files changed, 134 insertions, 0 deletions
diff --git a/p2p/discover/cache.go b/p2p/discover/cache.go
new file mode 100644
index 000000000..f6bab4591
--- /dev/null
+++ b/p2p/discover/cache.go
@@ -0,0 +1,134 @@
+// Contains the discovery cache, storing previously seen nodes to act as seed
+// servers during bootstrapping the network.
+
+package discover
+
+import (
+	"bytes"
+	"encoding/binary"
+	"net"
+	"os"
+
+	"github.com/ethereum/go-ethereum/rlp"
+	"github.com/syndtr/goleveldb/leveldb"
+	"github.com/syndtr/goleveldb/leveldb/storage"
+)
+
+// Cache stores all nodes we know about.
+type Cache struct {
+	db *leveldb.DB
+}
+
+// Cache version to allow dumping old data if it changes.
+var cacheVersionKey = []byte("pv")
+
+// NewMemoryCache creates a new in-memory peer cache without a persistent backend.
+func NewMemoryCache() (*Cache, error) {
+	db, err := leveldb.Open(storage.NewMemStorage(), nil)
+	if err != nil {
+		return nil, err
+	}
+	return &Cache{db: db}, nil
+}
+
+// NewPersistentCache creates/opens a leveldb backed persistent peer cache, also
+// flushing its contents in case of a version mismatch.
+func NewPersistentCache(path string) (*Cache, error) {
+	// Try to open the cache, recovering any corruption
+	db, err := leveldb.OpenFile(path, nil)
+	if _, iscorrupted := err.(leveldb.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, Version)]
+
+	blob, err := db.Get(cacheVersionKey, nil)
+	switch err {
+	case leveldb.ErrNotFound:
+		// Version not found (i.e. empty cache), insert it
+		err = db.Put(cacheVersionKey, currentVer, nil)
+
+	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 NewPersistentCache(path)
+		}
+	}
+	// Clean up in case of an error
+	if err != nil {
+		db.Close()
+		return nil, err
+	}
+	return &Cache{db: db}, nil
+}
+
+// get retrieves a node with a given id from the seed da
+func (c *Cache) get(id NodeID) *Node {
+	blob, err := c.db.Get(id[:], nil)
+	if err != nil {
+		return nil
+	}
+	node := new(Node)
+	if err := rlp.DecodeBytes(blob, node); err != nil {
+		return nil
+	}
+	return node
+}
+
+// list retrieves a batch of nodes from the database.
+func (c *Cache) list(n int) []*Node {
+	it := c.db.NewIterator(nil, nil)
+	defer it.Release()
+
+	nodes := make([]*Node, 0, n)
+	for i := 0; i < n && it.Next(); i++ {
+		var id NodeID
+		copy(id[:], it.Key())
+
+		if node := c.get(id); node != nil {
+			nodes = append(nodes, node)
+		}
+	}
+	return nodes
+}
+
+// update inserts - potentially overwriting - a node in the seed database.
+func (c *Cache) update(node *Node) error {
+	blob, err := rlp.EncodeToBytes(node)
+	if err != nil {
+		return err
+	}
+	return c.db.Put(node.ID[:], blob, nil)
+}
+
+// add inserts a new node into the seed database.
+func (c *Cache) add(id NodeID, addr *net.UDPAddr, tcpPort uint16) *Node {
+	node := &Node{
+		ID:       id,
+		IP:       addr.IP,
+		DiscPort: addr.Port,
+		TCPPort:  int(tcpPort),
+	}
+	c.update(node)
+
+	return node
+}
+
+// delete removes a node from the database.
+func (c *Cache) delete(id NodeID) error {
+	return c.db.Delete(id[:], nil)
+}
+
+// Close flushes and closes the database files.
+func (c *Cache) Close() {
+	c.db.Close()
+}