import logging from twisted.internet import defer from distance import Distance from error import TimeoutError import constants log = logging.getLogger(__name__) def get_contact(contact_list, node_id, address, port): for contact in contact_list: if contact.id == node_id and contact.address == address and contact.port == port: return contact raise IndexError(node_id) class _IterativeFind(object): # TODO: use polymorphism to search for a value or node # instead of using a find_value flag def __init__(self, node, shortlist, key, rpc): self.node = node self.finished_deferred = defer.Deferred() # all distance operations in this class only care about the distance # to self.key, so this makes it easier to calculate those self.distance = Distance(key) # The closest known and active node yet found self.closest_node = None if not shortlist else shortlist[0] self.prev_closest_node = None # Shortlist of contact objects (the k closest known contacts to the key from the routing table) self.shortlist = shortlist # The search key self.key = str(key) # The rpc method name (findValue or findNode) self.rpc = rpc # List of active queries; len() indicates number of active probes self.active_probes = [] # List of contact (address, port) tuples that have already been queried, includes contacts that didn't reply self.already_contacted = [] # A list of found and known-to-be-active remote nodes (Contact objects) self.active_contacts = [] # Ensure only one searchIteration call is running at a time self._search_iteration_semaphore = defer.DeferredSemaphore(1) self._iteration_count = 0 self.find_value_result = {} self.pending_iteration_calls = [] @property def is_find_node_request(self): return self.rpc == "findNode" @property def is_find_value_request(self): return self.rpc == "findValue" def is_closer(self, contact): if not self.closest_node: return True return self.distance.is_closer(contact.id, self.closest_node.id) def getContactTriples(self, result): if self.is_find_value_request: contact_triples = result['contacts'] else: contact_triples = result for contact_tup in contact_triples: if not isinstance(contact_tup, (list, tuple)) or len(contact_tup) != 3: raise ValueError("invalid contact triple") return contact_triples def sortByDistance(self, contact_list): """Sort the list of contacts in order by distance from key""" contact_list.sort(key=lambda c: self.distance(c.id)) @defer.inlineCallbacks def extendShortlist(self, contact, result): # The "raw response" tuple contains the response message and the originating address info originAddress = (contact.address, contact.port) if self.finished_deferred.called: defer.returnValue(contact.id) if self.node.contact_manager.is_ignored(originAddress): raise ValueError("contact is ignored") if contact.id == self.node.node_id: defer.returnValue(contact.id) if contact not in self.active_contacts: self.active_contacts.append(contact) if contact not in self.shortlist: self.shortlist.append(contact) # Now grow extend the (unverified) shortlist with the returned contacts # TODO: some validation on the result (for guarding against attacks) # If we are looking for a value, first see if this result is the value # we are looking for before treating it as a list of contact triples if self.is_find_value_request and self.key in result: # We have found the value self.find_value_result[self.key] = result[self.key] self.finished_deferred.callback(self.find_value_result) else: if self.is_find_value_request: # We are looking for a value, and the remote node didn't have it # - mark it as the closest "empty" node, if it is # TODO: store to this peer after finding the value as per the kademlia spec if 'closestNodeNoValue' in self.find_value_result: if self.is_closer(contact): self.find_value_result['closestNodeNoValue'] = contact else: self.find_value_result['closestNodeNoValue'] = contact contactTriples = self.getContactTriples(result) for contactTriple in contactTriples: if (contactTriple[1], contactTriple[2]) in ((c.address, c.port) for c in self.already_contacted): continue elif self.node.contact_manager.is_ignored((contactTriple[1], contactTriple[2])): continue else: found_contact = self.node.contact_manager.make_contact(contactTriple[0], contactTriple[1], contactTriple[2], self.node._protocol) if found_contact not in self.shortlist: self.shortlist.append(found_contact) if not self.finished_deferred.called and self.should_stop(): self.sortByDistance(self.active_contacts) self.finished_deferred.callback(self.active_contacts[:min(constants.k, len(self.active_contacts))]) defer.returnValue(contact.id) @defer.inlineCallbacks def probeContact(self, contact): fn = getattr(contact, self.rpc) try: response = yield fn(self.key) result = yield self.extendShortlist(contact, response) defer.returnValue(result) except (TimeoutError, defer.CancelledError, ValueError, IndexError): defer.returnValue(contact.id) def should_stop(self): if self.is_find_value_request: # search stops when it finds a value, let it run return False if self.prev_closest_node and self.closest_node and self.distance.is_closer(self.prev_closest_node.id, self.closest_node.id): # we're getting further away return True if len(self.active_contacts) >= constants.k: # we have enough results return True return False # Send parallel, asynchronous FIND_NODE RPCs to the shortlist of contacts def _searchIteration(self): # Sort the discovered active nodes from closest to furthest if len(self.active_contacts): self.sortByDistance(self.active_contacts) self.prev_closest_node = self.closest_node self.closest_node = self.active_contacts[0] # Sort the current shortList before contacting other nodes self.sortByDistance(self.shortlist) probes = [] already_contacted_addresses = {(c.address, c.port) for c in self.already_contacted} to_remove = [] for contact in self.shortlist: if self.node.contact_manager.is_ignored((contact.address, contact.port)): to_remove.append(contact) # a contact became bad during iteration continue if (contact.address, contact.port) not in already_contacted_addresses: self.already_contacted.append(contact) to_remove.append(contact) probe = self.probeContact(contact) probes.append(probe) self.active_probes.append(probe) if len(probes) == constants.alpha: break for contact in to_remove: # these contacts will be re-added to the shortlist when they reply successfully self.shortlist.remove(contact) # run the probes if probes: # Schedule the next iteration if there are any active # calls (Kademlia uses loose parallelism) self.searchIteration() d = defer.DeferredList(probes, consumeErrors=True) def _remove_probes(results): for probe in probes: self.active_probes.remove(probe) return results d.addCallback(_remove_probes) elif not self.finished_deferred.called and not self.active_probes or self.should_stop(): # If no probes were sent, there will not be any improvement, so we're done self.sortByDistance(self.active_contacts) self.finished_deferred.callback(self.active_contacts[:min(constants.k, len(self.active_contacts))]) elif not self.finished_deferred.called: # Force the next iteration self.searchIteration() def searchIteration(self, delay=constants.iterativeLookupDelay): def _cancel_pending_iterations(result): while self.pending_iteration_calls: canceller = self.pending_iteration_calls.pop() canceller() return result self.finished_deferred.addBoth(_cancel_pending_iterations) self._iteration_count += 1 call, cancel = self.node.reactor_callLater(delay, self._search_iteration_semaphore.run, self._searchIteration) self.pending_iteration_calls.append(cancel) def iterativeFind(node, shortlist, key, rpc): helper = _IterativeFind(node, shortlist, key, rpc) helper.searchIteration(0) return helper.finished_deferred