/*
* Copyright 2013 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.bitcoinj.net;
import org.bitcoinj.core.Utils;
import org.bitcoinj.utils.Threading;
import com.google.common.annotations.VisibleForTesting;
import com.google.protobuf.ByteString;
import com.google.protobuf.MessageLite;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import javax.annotation.concurrent.GuardedBy;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.util.concurrent.atomic.AtomicReference;
import java.util.concurrent.locks.ReentrantLock;
import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.base.Preconditions.checkState;
/**
* <p>A handler which is used in {@link NioServer} and {@link NioClient} to split up incoming data streams
* into protobufs and provide an interface for writing protobufs to the connections.</p>
*
* <p>Messages are encoded with a 4-byte signed integer (big endian) prefix to indicate their length followed by the
* serialized protobuf</p>
*
* <p>(Used to be called ProtobufParser)</p>
*/
public class ProtobufConnection<MessageType extends MessageLite> extends AbstractTimeoutHandler implements StreamConnection {
private static final Logger log = LoggerFactory.getLogger(ProtobufConnection.class);
/**
* An interface which can be implemented to handle callbacks as new messages are generated and socket events occur.
* @param <MessageType> The protobuf type which is used on this socket.
* This <b>MUST</b> match the MessageType used in the parent {@link ProtobufConnection}
*/
public interface Listener<MessageType extends MessageLite> {
/** Called when a new protobuf is received from the remote side. */
void messageReceived(ProtobufConnection<MessageType> handler, MessageType msg);
/** Called when the connection is opened and available for writing data to. */
void connectionOpen(ProtobufConnection<MessageType> handler);
/** Called when the connection is closed and no more data should be provided. */
void connectionClosed(ProtobufConnection<MessageType> handler);
}
// The callback listener
private final Listener<MessageType> handler;
// The prototype which is used to deserialize messages
private final MessageLite prototype;
// The maximum message size (NOT INCLUDING LENGTH PREFIX)
final int maxMessageSize;
// A temporary buffer used when the message size is larger than the buffer being used by the network code
// Because the networking code uses a constant size buffer and we want to allow for very large message sizes, we use
// a smaller network buffer per client and only allocate more memory when we need it to deserialize large messages.
// Though this is not in of itself a DoS protection, it allows for handling more legitimate clients per server and
// attacking clients can be made to timeout/get blocked if they are sending crap to fill buffers.
@GuardedBy("lock") private int messageBytesOffset = 0;
@GuardedBy("lock") private byte[] messageBytes;
private final ReentrantLock lock = Threading.lock("ProtobufConnection");
@VisibleForTesting final AtomicReference<MessageWriteTarget> writeTarget = new AtomicReference<MessageWriteTarget>();
/**
* Creates a new protobuf handler.
*
* @param handler The callback listener
* @param prototype The default instance of the message type used in both directions of this channel.
* This should be the return value from {@link MessageType#getDefaultInstanceForType()}
* @param maxMessageSize The maximum message size (not including the 4-byte length prefix).
* Note that this has an upper bound of {@link Integer#MAX_VALUE} - 4
* @param timeoutMillis The timeout between messages before the connection is automatically closed. Only enabled
* after the connection is established.
*/
public ProtobufConnection(Listener<MessageType> handler, MessageType prototype, int maxMessageSize, int timeoutMillis) {
this.handler = handler;
this.prototype = prototype;
this.maxMessageSize = Math.min(maxMessageSize, Integer.MAX_VALUE - 4);
setTimeoutEnabled(false);
setSocketTimeout(timeoutMillis);
}
@Override
public void setWriteTarget(MessageWriteTarget writeTarget) {
// Only allow it to be set once.
checkState(this.writeTarget.getAndSet(checkNotNull(writeTarget)) == null);
}
@Override
public int getMaxMessageSize() {
return maxMessageSize;
}
/**
* Closes this connection, eventually triggering a {@link ProtobufConnection.Listener#connectionClosed()} event.
*/
public void closeConnection() {
this.writeTarget.get().closeConnection();
}
@Override
protected void timeoutOccurred() {
log.warn("Timeout occurred for " + handler);
closeConnection();
}
// Deserializes and provides a listener event (buff must not have the length prefix in it)
// Does set the buffers's position to its limit
@SuppressWarnings("unchecked")
// The warning 'unchecked cast' being suppressed here comes from the build() formally returning
// a MessageLite-derived class that cannot be statically guaranteed to be the MessageType.
private void deserializeMessage(ByteBuffer buff) throws Exception {
MessageType msg = (MessageType) prototype.newBuilderForType().mergeFrom(ByteString.copyFrom(buff)).build();
resetTimeout();
handler.messageReceived(this, msg);
}
@Override
public int receiveBytes(ByteBuffer buff) throws Exception {
lock.lock();
try {
if (messageBytes != null) {
// Just keep filling up the currently being worked on message
int bytesToGet = Math.min(messageBytes.length - messageBytesOffset, buff.remaining());
buff.get(messageBytes, messageBytesOffset, bytesToGet);
messageBytesOffset += bytesToGet;
if (messageBytesOffset == messageBytes.length) {
// Filled up our buffer, decode the message
deserializeMessage(ByteBuffer.wrap(messageBytes));
messageBytes = null;
if (buff.hasRemaining())
return bytesToGet + receiveBytes(buff);
}
return bytesToGet;
}
// If we cant read the length prefix yet, give up
if (buff.remaining() < 4)
return 0;
// Read one integer in big endian
buff.order(ByteOrder.BIG_ENDIAN);
final int len = buff.getInt();
// If length is larger than the maximum message size (or is negative/overflows) throw an exception and close the
// connection
if (len > maxMessageSize || len + 4 < 4)
throw new IllegalStateException("Message too large or length underflowed");
// If the buffer's capacity is less than the next messages length + 4 (length prefix), we must use messageBytes
// as a temporary buffer to store the message
if (buff.capacity() < len + 4) {
messageBytes = new byte[len];
// Now copy all remaining bytes into the new buffer, set messageBytesOffset and tell the caller how many
// bytes we consumed
int bytesToRead = buff.remaining();
buff.get(messageBytes, 0, bytesToRead);
messageBytesOffset = bytesToRead;
return bytesToRead + 4;
}
if (buff.remaining() < len) {
// Wait until the whole message is available in the buffer
buff.position(buff.position() - 4); // Make sure the buffer's position is right at the end
return 0;
}
// Temporarily limit the buffer to the size of the message so that the protobuf decode doesn't get messed up
int limit = buff.limit();
buff.limit(buff.position() + len);
deserializeMessage(buff);
checkState(buff.remaining() == 0);
buff.limit(limit); // Reset the limit in case we have to recurse
// If there are still bytes remaining, see if we can pull out another message since we won't get called again
if (buff.hasRemaining())
return len + 4 + receiveBytes(buff);
else
return len + 4;
} finally {
lock.unlock();
}
}
@Override
public void connectionClosed() {
handler.connectionClosed(this);
}
@Override
public void connectionOpened() {
setTimeoutEnabled(true);
handler.connectionOpen(this);
}
/**
* <p>Writes the given message to the other side of the connection, prefixing it with the proper 4-byte prefix.</p>
*
* <p>Provides a write-order guarantee.</p>
*
* @throws IllegalStateException If the encoded message is larger than the maximum message size.
*/
public void write(MessageType msg) throws IllegalStateException {
byte[] messageBytes = msg.toByteArray();
checkState(messageBytes.length <= maxMessageSize);
byte[] messageLength = new byte[4];
Utils.uint32ToByteArrayBE(messageBytes.length, messageLength, 0);
try {
MessageWriteTarget target = writeTarget.get();
target.writeBytes(messageLength);
target.writeBytes(messageBytes);
} catch (IOException e) {
closeConnection();
}
}
}