Get Block message: BlockTransferReadBlock validate limit. Fix in startBlockTransfer. New high-level function BlockDownload to download requested blocks.

Transfer Block.go

@@ -67,7 +67,7 @@ func (peer *PeerInfo) startBlockTransfer(BlockchainPublicKey *btcec.PublicKey, L
 			udtConn.Write(blockData)
 
 			sentBlocks++
-			if sentBlocks >= MaxBlockSize {
+			if sentBlocks >= LimitBlockCount {
 				break
 			}
 		}
@@ -115,3 +115,44 @@ func (peer *PeerInfo) BlockTransferRequest(BlockchainPublicKey *btcec.PublicKey,
 
 	return udtConn, virtualConn, nil
 }
+
+// Downloads the requested blocks for the selected blockchain from the remote peer. The callback is called for each result.
+func (peer *PeerInfo) BlockDownload(BlockchainPublicKey *btcec.PublicKey, LimitBlockCount, MaxBlockSize uint64, TargetBlocks []protocol.BlockRange, callback func(data []byte, targetBlock protocol.BlockRange, blockSize uint64, availability uint8)) (err error) {
+	conn, _, err := peer.BlockTransferRequest(BlockchainPublicKey, LimitBlockCount, MaxBlockSize, TargetBlocks)
+	if err != nil {
+		return err
+	}
+	defer conn.Close()
+
+	var limit uint64
+	for _, target := range TargetBlocks {
+		limit += target.Limit
+	}
+
+	for n := uint64(0); n < limit; {
+		data, targetBlock, blockSize, availability, err := protocol.BlockTransferReadBlock(conn, MaxBlockSize)
+		if err != nil {
+			return err
+		} else if !isTargetInRange(TargetBlocks, targetBlock.Offset, targetBlock.Limit) {
+			return errors.New("invalid returned block range")
+		}
+
+		// TODO: Check if the block was already returned in case the block is available. This can be done via simple map.
+
+		callback(data, targetBlock, blockSize, availability)
+
+		n += targetBlock.Limit
+	}
+
+	return nil
+}
+
+func isTargetInRange(targets []protocol.BlockRange, offset, limit uint64) (valid bool) {
+	for _, target := range targets {
+		if offset >= target.Offset && offset+limit <= target.Offset+target.Limit {
+			return true
+		}
+	}
+
+	return false
+}

protocol/Message Encoding Get Block.go

@@ -29,6 +29,8 @@ Offset  Size    Info
                 2 = Block range exceeds size limit.
 1       16      Block range
 17      8       Block size
+
+The limit in block range must be 1 if a block is returned.
 */
 
 package protocol
@@ -197,12 +199,16 @@ func BlockTransferReadBlock(reader io.Reader, maxBlockSize uint64) (data []byte,
 	targetBlock.Limit = binary.LittleEndian.Uint64(header[9:17])
 	blockSize = binary.LittleEndian.Uint64(header[17:25])
 
-	if availability != GetBlockStatusAvailable { // return if status isn't available
+	if targetBlock.Limit == 0 {
+		return nil, targetBlock, blockSize, availability, errors.New("empty target block limit")
+	} else if availability != GetBlockStatusAvailable { // return if status indicates the block is not available
 		return nil, targetBlock, blockSize, availability, nil
 	}
 
 	if blockSize > maxBlockSize {
 		return nil, targetBlock, blockSize, availability, errors.New("remote block size exceeds limit")
+	} else if targetBlock.Limit != 1 {
+		return nil, targetBlock, blockSize, availability, errors.New("invalid target block limit")
 	}
 
 	// read the block