import logging import socket import errno from twisted.internet import protocol, defer from lbrynet.core.call_later_manager import CallLaterManager import constants import encoding import msgtypes import msgformat from contact import Contact from error import BUILTIN_EXCEPTIONS, UnknownRemoteException, TimeoutError log = logging.getLogger(__name__) class KademliaProtocol(protocol.DatagramProtocol): """ Implements all low-level network-related functions of a Kademlia node """ msgSizeLimit = constants.udpDatagramMaxSize - 26 def __init__(self, node): self._node = node self._encoder = encoding.Bencode() self._translator = msgformat.DefaultFormat() self._sentMessages = {} self._partialMessages = {} self._partialMessagesProgress = {} def sendRPC(self, contact, method, args, rawResponse=False): """ Sends an RPC to the specified contact @param contact: The contact (remote node) to send the RPC to @type contact: kademlia.contacts.Contact @param method: The name of remote method to invoke @type method: str @param args: A list of (non-keyword) arguments to pass to the remote method, in the correct order @type args: tuple @param rawResponse: If this is set to C{True}, the caller of this RPC will receive a tuple containing the actual response message object and the originating address tuple as a result; in other words, it will not be interpreted by this class. Unless something special needs to be done with the metadata associated with the message, this should remain C{False}. @type rawResponse: bool @return: This immediately returns a deferred object, which will return the result of the RPC call, or raise the relevant exception if the remote node raised one. If C{rawResponse} is set to C{True}, however, it will always return the actual response message (which may be a C{ResponseMessage} or an C{ErrorMessage}). @rtype: twisted.internet.defer.Deferred """ msg = msgtypes.RequestMessage(self._node.node_id, method, args) msgPrimitive = self._translator.toPrimitive(msg) encodedMsg = self._encoder.encode(msgPrimitive) if args: log.debug("DHT SEND CALL %s(%s)", method, args[0].encode('hex')) else: log.debug("DHT SEND CALL %s", method) df = defer.Deferred() if rawResponse: df._rpcRawResponse = True # Set the RPC timeout timer timeoutCall, cancelTimeout = self._node.reactor_callLater(constants.rpcTimeout, self._msgTimeout, msg.id) # Transmit the data self._send(encodedMsg, msg.id, (contact.address, contact.port)) self._sentMessages[msg.id] = (contact.id, df, timeoutCall, method, args) df.addErrback(cancelTimeout) return df def startProtocol(self): log.info("DHT listening on UDP %i", self._node.port) def datagramReceived(self, datagram, address): """ Handles and parses incoming RPC messages (and responses) @note: This is automatically called by Twisted when the protocol receives a UDP datagram """ if datagram[0] == '\x00' and datagram[25] == '\x00': totalPackets = (ord(datagram[1]) << 8) | ord(datagram[2]) msgID = datagram[5:25] seqNumber = (ord(datagram[3]) << 8) | ord(datagram[4]) if msgID not in self._partialMessages: self._partialMessages[msgID] = {} self._partialMessages[msgID][seqNumber] = datagram[26:] if len(self._partialMessages[msgID]) == totalPackets: keys = self._partialMessages[msgID].keys() keys.sort() data = '' for key in keys: data += self._partialMessages[msgID][key] datagram = data del self._partialMessages[msgID] else: return try: msgPrimitive = self._encoder.decode(datagram) message = self._translator.fromPrimitive(msgPrimitive) except (encoding.DecodeError, ValueError) as err: # We received some rubbish here log.warning("Error decoding datagram %s from %s:%i - %s", datagram.encode('hex'), address[0], address[1], err) return except (IndexError, KeyError): log.warning("Couldn't decode dht datagram from %s", address) return remoteContact = Contact(message.nodeID, address[0], address[1], self) # Refresh the remote node's details in the local node's k-buckets self._node.addContact(remoteContact) if isinstance(message, msgtypes.RequestMessage): # This is an RPC method request self._handleRPC(remoteContact, message.id, message.request, message.args) elif isinstance(message, msgtypes.ResponseMessage): # Find the message that triggered this response if message.id in self._sentMessages: # Cancel timeout timer for this RPC df, timeoutCall = self._sentMessages[message.id][1:3] timeoutCall.cancel() del self._sentMessages[message.id] if hasattr(df, '_rpcRawResponse'): # The RPC requested that the raw response message # and originating address be returned; do not # interpret it df.callback((message, address)) elif isinstance(message, msgtypes.ErrorMessage): # The RPC request raised a remote exception; raise it locally if message.exceptionType in BUILTIN_EXCEPTIONS: exception_type = BUILTIN_EXCEPTIONS[message.exceptionType] else: exception_type = UnknownRemoteException remoteException = exception_type(message.response) # this error is returned by nodes that can be contacted but have an old # and broken version of the ping command, if they return it the node can # be contacted, so we'll treat it as a successful ping old_ping_error = "ping() got an unexpected keyword argument '_rpcNodeContact'" if isinstance(remoteException, TypeError) and \ remoteException.message == old_ping_error: log.debug("old pong error") df.callback('pong') else: log.error("DHT RECV REMOTE EXCEPTION FROM %s:%i: %s", address[0], address[1], remoteException) df.errback(remoteException) else: # We got a result from the RPC df.callback(message.response) else: # If the original message isn't found, it must have timed out # TODO: we should probably do something with this... pass def _send(self, data, rpcID, address): """ Transmit the specified data over UDP, breaking it up into several packets if necessary If the data is spread over multiple UDP datagrams, the packets have the following structure:: | | | | | |||||||||||| 0x00 | |Transmision|Total number|Sequence number| RPC ID |Header end| | type ID | of packets |of this packet | | indicator| | (1 byte) | (2 bytes) | (2 bytes) |(20 bytes)| (1 byte) | | | | | | |||||||||||| | @note: The header used for breaking up large data segments will possibly be moved out of the KademliaProtocol class in the future, into something similar to a message translator/encoder class (see C{kademlia.msgformat} and C{kademlia.encoding}). """ if len(data) > self.msgSizeLimit: # We have to spread the data over multiple UDP datagrams, # and provide sequencing information # # 1st byte is transmission type id, bytes 2 & 3 are the # total number of packets in this transmission, bytes 4 & # 5 are the sequence number for this specific packet totalPackets = len(data) / self.msgSizeLimit if len(data) % self.msgSizeLimit > 0: totalPackets += 1 encTotalPackets = chr(totalPackets >> 8) + chr(totalPackets & 0xff) seqNumber = 0 startPos = 0 while seqNumber < totalPackets: packetData = data[startPos:startPos + self.msgSizeLimit] encSeqNumber = chr(seqNumber >> 8) + chr(seqNumber & 0xff) txData = '\x00%s%s%s\x00%s' % (encTotalPackets, encSeqNumber, rpcID, packetData) self._scheduleSendNext(txData, address) startPos += self.msgSizeLimit seqNumber += 1 else: self._scheduleSendNext(data, address) def _scheduleSendNext(self, txData, address): """Schedule the sending of the next UDP packet """ delayed_call, _ = self._node.reactor_callSoon(self._write, txData, address) def _write(self, txData, address): if self.transport: try: self.transport.write(txData, address) except socket.error as err: if err.errno == errno.EWOULDBLOCK: # i'm scared this may swallow important errors, but i get a million of these # on Linux and it doesnt seem to affect anything -grin log.warning("Can't send data to dht: EWOULDBLOCK") elif err.errno == errno.ENETUNREACH: # this should probably try to retransmit when the network connection is back log.error("Network is unreachable") else: log.error("DHT socket error: %s (%i)", err.message, err.errno) raise err else: log.warning("transport not connected!") def _sendResponse(self, contact, rpcID, response): """ Send a RPC response to the specified contact """ msg = msgtypes.ResponseMessage(rpcID, self._node.node_id, response) msgPrimitive = self._translator.toPrimitive(msg) encodedMsg = self._encoder.encode(msgPrimitive) self._send(encodedMsg, rpcID, (contact.address, contact.port)) def _sendError(self, contact, rpcID, exceptionType, exceptionMessage): """ Send an RPC error message to the specified contact """ msg = msgtypes.ErrorMessage(rpcID, self._node.node_id, exceptionType, exceptionMessage) msgPrimitive = self._translator.toPrimitive(msg) encodedMsg = self._encoder.encode(msgPrimitive) self._send(encodedMsg, rpcID, (contact.address, contact.port)) def _handleRPC(self, senderContact, rpcID, method, args): """ Executes a local function in response to an RPC request """ # Set up the deferred callchain def handleError(f): self._sendError(senderContact, rpcID, f.type, f.getErrorMessage()) def handleResult(result): self._sendResponse(senderContact, rpcID, result) df = defer.Deferred() df.addCallback(handleResult) df.addErrback(handleError) # Execute the RPC func = getattr(self._node, method, None) if callable(func) and hasattr(func, 'rpcmethod'): # Call the exposed Node method and return the result to the deferred callback chain if args: log.debug("DHT RECV CALL %s(%s) %s:%i", method, args[0].encode('hex'), senderContact.address, senderContact.port) else: log.debug("DHT RECV CALL %s %s:%i", method, senderContact.address, senderContact.port) try: if method != 'ping': kwargs = {'_rpcNodeID': senderContact.id, '_rpcNodeContact': senderContact} result = func(*args, **kwargs) else: result = func() except Exception, e: log.exception("error handling request for %s: %s", senderContact.address, method) df.errback(e) else: df.callback(result) else: # No such exposed method df.errback(AttributeError('Invalid method: %s' % method)) def _msgTimeout(self, messageID): """ Called when an RPC request message times out """ # Find the message that timed out if messageID not in self._sentMessages: # This should never be reached log.error("deferred timed out, but is not present in sent messages list!") return remoteContactID, df, timeout_call, method, args = self._sentMessages[messageID] if self._partialMessages.has_key(messageID): # We are still receiving this message self._msgTimeoutInProgress(messageID, remoteContactID, df, method, args) return del self._sentMessages[messageID] # The message's destination node is now considered to be dead; # raise an (asynchronous) TimeoutError exception and update the host node self._node.removeContact(remoteContactID) df.errback(TimeoutError(remoteContactID)) def _msgTimeoutInProgress(self, messageID, remoteContactID, df, method, args): # See if any progress has been made; if not, kill the message if self._hasProgressBeenMade(messageID): # Reset the RPC timeout timer timeoutCall, _ = self._node.reactor_callLater(constants.rpcTimeout, self._msgTimeout, messageID) self._sentMessages[messageID] = (remoteContactID, df, timeoutCall, method, args) else: # No progress has been made if messageID in self._partialMessagesProgress: del self._partialMessagesProgress[messageID] if messageID in self._partialMessages: del self._partialMessages[messageID] df.errback(TimeoutError(remoteContactID)) def _hasProgressBeenMade(self, messageID): return ( self._partialMessagesProgress.has_key(messageID) and ( len(self._partialMessagesProgress[messageID]) != len(self._partialMessages[messageID]) ) ) def stopProtocol(self): """ Called when the transport is disconnected. Will only be called once, after all ports are disconnected. """ log.info('Stopping DHT') CallLaterManager.stop() log.info('DHT stopped')