Look up filters from p2p GetCBF message

blockchain/indexers/cbfindex.go

@@ -156,6 +156,17 @@ func (idx *CBFIndex) DisconnectBlock(dbTx database.Tx, block *btcutil.Block, vie
 	return nil
 }
 
+func (idx *CBFIndex) GetFilterByBlockHash(hash *chainhash.Hash) ([]byte,
+    error) {
+	var filterBytes []byte
+	err := idx.db.View(func(dbTx database.Tx) error {
+		var err error
+		filterBytes, err = dbFetchCBFIndexEntry(dbTx, hash)
+		return err
+	})
+	return filterBytes, err
+}
+
 // NewCBFIndex returns a new instance of an indexer that is used to create a
 // mapping of the hashes of all blocks in the blockchain to their respective
 // committed bloom filters.

server.go

@@ -746,8 +746,14 @@ func (sp *serverPeer) OnGetCBFilter(_ *peer.Peer, msg *wire.MsgGetCBFilter) {
 		return
 	}
 
-	// XXX work in progress
-	peerLog.Warnf("received OnGetCBFilter: not yet")
+	filterBytes, err := sp.server.cbfIndex.GetFilterByBlockHash(&msg.BlockHash)
+
+	if len(filterBytes) > 0 {
+		peerLog.Infof("Obtained CB filter for %v", msg.BlockHash)
+	} else {
+		peerLog.Infof("Could not obtain CB filter for %v: %v",
+		    msg.BlockHash, err)
+	}
 }
 
 // enforceNodeBloomFlag disconnects the peer if the server is not configured to