LMXF-specification/LXMF/LXMRouter.py

import os
import sys
import time
import math
import random
import base64
import atexit
import signal
import threading

from collections import deque

import RNS
import RNS.vendor.umsgpack as msgpack

from .LXMF import APP_NAME
from .LXMF import FIELD_TICKET
from .LXMF import PN_META_NAME
from .LXMF import pn_announce_data_is_valid

from .LXMPeer import LXMPeer
from .LXMessage import LXMessage
from .Handlers import LXMFDeliveryAnnounceHandler
from .Handlers import LXMFPropagationAnnounceHandler

import LXMF.LXStamper as LXStamper

class LXMRouter:
    MAX_DELIVERY_ATTEMPTS = 5
    PROCESSING_INTERVAL   = 4
    DELIVERY_RETRY_WAIT   = 10
    PATH_REQUEST_WAIT     = 7
    MAX_PATHLESS_TRIES    = 1
    LINK_MAX_INACTIVITY   = 10*60
    P_LINK_MAX_INACTIVITY = 3*60

    MESSAGE_EXPIRY        = 30*24*60*60
    STAMP_COST_EXPIRY     = 45*24*60*60

    NODE_ANNOUNCE_DELAY   = 20

    MAX_PEERS             = 20
    AUTOPEER              = True
    AUTOPEER_MAXDEPTH     = 4
    FASTEST_N_RANDOM_POOL = 2
    ROTATION_HEADROOM_PCT = 10
    ROTATION_AR_MAX       = 0.5

    PEERING_COST          = 18
    MAX_PEERING_COST      = 24
    PROPAGATION_COST_MIN  = 13
    PROPAGATION_COST_FLEX = 3
    PROPAGATION_COST      = 16
    PROPAGATION_LIMIT     = 256
    SYNC_LIMIT            = PROPAGATION_LIMIT*40
    DELIVERY_LIMIT        = 1000

    PR_PATH_TIMEOUT       = 10
    PN_STAMP_THROTTLE     = 180

    PR_IDLE               = 0x00
    PR_PATH_REQUESTED     = 0x01
    PR_LINK_ESTABLISHING  = 0x02
    PR_LINK_ESTABLISHED   = 0x03
    PR_REQUEST_SENT       = 0x04
    PR_RECEIVING          = 0x05
    PR_RESPONSE_RECEIVED  = 0x06
    PR_COMPLETE           = 0x07
    PR_NO_PATH            = 0xf0
    PR_LINK_FAILED        = 0xf1
    PR_TRANSFER_FAILED    = 0xf2
    PR_NO_IDENTITY_RCVD   = 0xf3
    PR_NO_ACCESS          = 0xf4
    PR_FAILED             = 0xfe

    PR_ALL_MESSAGES       = 0x00

    DUPLICATE_SIGNAL      = "lxmf_duplicate"

    STATS_GET_PATH        = "/pn/get/stats"
    SYNC_REQUEST_PATH     = "/pn/peer/sync"
    UNPEER_REQUEST_PATH   = "/pn/peer/unpeer"


    ### Developer-facing API ##############################
    #######################################################

    def __init__(self, identity=None, storagepath=None, autopeer=AUTOPEER, autopeer_maxdepth=None,
                 propagation_limit=PROPAGATION_LIMIT, delivery_limit=DELIVERY_LIMIT, sync_limit=SYNC_LIMIT,
                 enforce_ratchets=False, enforce_stamps=False, static_peers = [], max_peers=None,
                 from_static_only=False, sync_strategy=LXMPeer.STRATEGY_PERSISTENT,
                 propagation_cost=PROPAGATION_COST, propagation_cost_flexibility=PROPAGATION_COST_FLEX,
                 peering_cost=PEERING_COST, max_peering_cost=MAX_PEERING_COST, name=None):

        random.seed(os.urandom(10))

        self.pending_inbound       = []
        self.pending_outbound      = []
        self.failed_outbound       = []
        self.direct_links          = {}
        self.backchannel_links     = {}
        self.delivery_destinations = {}

        self.prioritised_list      = []
        self.ignored_list          = []
        self.allowed_list          = []
        self.control_allowed_list  = []
        self.auth_required         = False
        self.retain_synced_on_node = False

        self.default_sync_strategy = sync_strategy
        self.processing_outbound   = False
        self.processing_inbound    = False
        self.processing_count      = 0
        self.name                  = name

        self.propagation_node = False
        self.propagation_node_start_time = None        

        if storagepath == None: raise ValueError("LXMF cannot be initialised without a storage path")
        else:
            self.storagepath = storagepath+"/lxmf"
            self.ratchetpath = self.storagepath+"/ratchets"

        self.outbound_propagation_node = None
        self.outbound_propagation_link = None

        if delivery_limit == None: delivery_limit = LXMRouter.DELIVERY_LIMIT
        if propagation_cost < LXMRouter.PROPAGATION_COST_MIN: propagation_cost = LXMRouter.PROPAGATION_COST_MIN

        self.message_storage_limit              = None
        self.information_storage_limit          = None
        self.propagation_per_transfer_limit     = propagation_limit
        self.propagation_per_sync_limit         = sync_limit
        self.delivery_per_transfer_limit        = delivery_limit
        self.propagation_stamp_cost             = propagation_cost
        self.propagation_stamp_cost_flexibility = propagation_cost_flexibility
        self.peering_cost                       = peering_cost
        self.max_peering_cost                   = max_peering_cost
        self.enforce_ratchets                   = enforce_ratchets
        self._enforce_stamps                    = enforce_stamps
        self.pending_deferred_stamps            = {}
        self.throttled_peers                    = {}

        if sync_limit == None or self.propagation_per_sync_limit < self.propagation_per_transfer_limit:
            self.propagation_per_sync_limit = self.propagation_per_transfer_limit

        self.wants_download_on_path_available_from = None
        self.wants_download_on_path_available_to = None
        self.propagation_transfer_state = LXMRouter.PR_IDLE
        self.propagation_transfer_progress = 0.0
        self.propagation_transfer_last_result = None
        self.propagation_transfer_last_duplicates = None
        self.propagation_transfer_max_messages = None
        self.prioritise_rotating_unreachable_peers = False
        self.active_propagation_links = []
        self.validated_peer_links = {}
        self.locally_delivered_transient_ids = {}
        self.locally_processed_transient_ids = {}
        self.outbound_stamp_costs = {}
        self.available_tickets = {"outbound": {}, "inbound": {}, "last_deliveries": {}}

        self.cost_file_lock = threading.Lock()
        self.ticket_file_lock = threading.Lock()
        self.stamp_gen_lock = threading.Lock()
        self.exit_handler_running = False

        if identity == None:
            identity = RNS.Identity()

        self.identity = identity
        self.propagation_destination = RNS.Destination(self.identity, RNS.Destination.IN, RNS.Destination.SINGLE, APP_NAME, "propagation")
        self.propagation_destination.set_default_app_data(self.get_propagation_node_app_data)
        self.control_destination = None
        self.client_propagation_messages_received = 0
        self.client_propagation_messages_served = 0
        self.unpeered_propagation_incoming = 0
        self.unpeered_propagation_rx_bytes = 0

        if autopeer != None: self.autopeer = autopeer
        else:                self.autopeer = LXMRouter.AUTOPEER

        if autopeer_maxdepth != None: self.autopeer_maxdepth = autopeer_maxdepth
        else:                         self.autopeer_maxdepth = LXMRouter.AUTOPEER_MAXDEPTH

        if max_peers == None: self.max_peers = LXMRouter.MAX_PEERS
        else:
            if type(max_peers) == int and max_peers >= 0: self.max_peers = max_peers
            else: raise ValueError(f"Invalid value for max_peers: {max_peers}")

        self.from_static_only = from_static_only
        if type(static_peers) != list: raise ValueError(f"Invalid type supplied for static peer list: {type(static_peers)}")
        else:
            for static_peer in static_peers:
                if type(static_peer) != bytes: raise ValueError(f"Invalid static peer destination hash: {static_peer}")
                else:
                    if len(static_peer) != RNS.Reticulum.TRUNCATED_HASHLENGTH//8: raise ValueError(f"Invalid static peer destination hash: {static_peer}")

            self.static_peers = static_peers

        self.peers = {}
        self.propagation_entries = {}

        self.peer_distribution_queue = deque()

        RNS.Transport.register_announce_handler(LXMFDeliveryAnnounceHandler(self))
        RNS.Transport.register_announce_handler(LXMFPropagationAnnounceHandler(self))

        self.__delivery_callback = None

        try:
            if os.path.isfile(self.storagepath+"/local_deliveries"):
                locally_delivered_file = open(self.storagepath+"/local_deliveries", "rb")
                data = locally_delivered_file.read()
                locally_delivered_file.close()
                self.locally_delivered_transient_ids = msgpack.unpackb(data)
                if not type(self.locally_delivered_transient_ids) == dict:
                    RNS.log("Invalid data format for loaded locally delivered transient IDs, recreating...", RNS.LOG_ERROR)
                    self.locally_delivered_transient_ids = {}

        except Exception as e:
            RNS.log("Could not load locally delivered message ID cache from storage. The contained exception was: "+str(e), RNS.LOG_ERROR)
            self.locally_delivered_transient_ids = {}

        try:
            if os.path.isfile(self.storagepath+"/locally_processed"):
                locally_processed_file = open(self.storagepath+"/locally_processed", "rb")
                data = locally_processed_file.read()
                locally_processed_file.close()
                self.locally_processed_transient_ids = msgpack.unpackb(data)
                if not type(self.locally_processed_transient_ids) == dict:
                    RNS.log("Invalid data format for loaded locally processed transient IDs, recreating...", RNS.LOG_ERROR)
                    self.locally_processed_transient_ids = {}


        except Exception as e:
            RNS.log("Could not load locally processed message ID cache from storage. The contained exception was: "+str(e), RNS.LOG_ERROR)
            self.locally_processed_transient_ids = {}

        try:
            self.clean_transient_id_caches()

        except Exception as e:
            RNS.log("Could not clean transient ID caches. The contained exception was : "+str(e), RNS.LOG_ERROR)
            self.locally_delivered_transient_ids = {}
            self.locally_processed_transient_ids = {}

        try:
            if os.path.isfile(self.storagepath+"/outbound_stamp_costs"):
                with self.cost_file_lock:
                    with open(self.storagepath+"/outbound_stamp_costs", "rb") as outbound_stamp_cost_file:
                        data = outbound_stamp_cost_file.read()
                        self.outbound_stamp_costs = msgpack.unpackb(data)
                        if not type(self.outbound_stamp_costs) == dict:
                            RNS.log("Invalid data format for loaded outbound stamp costs, recreating...", RNS.LOG_ERROR)
                            self.outbound_stamp_costs = {}

                self.clean_outbound_stamp_costs()
                self.save_outbound_stamp_costs()

        except Exception as e:
            RNS.log("Could not load outbound stamp costs from storage. The contained exception was: "+str(e), RNS.LOG_ERROR)

        try:
            if os.path.isfile(self.storagepath+"/available_tickets"):
                with self.ticket_file_lock:
                    with open(self.storagepath+"/available_tickets", "rb") as available_tickets_file:
                        data = available_tickets_file.read()
                        self.available_tickets = msgpack.unpackb(data)
                        if not type(self.available_tickets) == dict:
                            RNS.log("Invalid data format for loaded available tickets, recreating...", RNS.LOG_ERROR)
                            self.available_tickets = {"outbound": {}, "inbound": {}, "last_deliveries": {}}
                        if not "outbound" in self.available_tickets:
                            RNS.log("Missing outbound entry in loaded available tickets, recreating...", RNS.LOG_ERROR)
                            self.available_tickets["outbound"] = {}
                        if not "inbound" in self.available_tickets:
                            RNS.log("Missing inbound entry in loaded available tickets, recreating...", RNS.LOG_ERROR)
                            self.available_tickets["inbound"] = {}
                        if not "last_deliveries" in self.available_tickets:
                            RNS.log("Missing local_deliveries entry in loaded available tickets, recreating...", RNS.LOG_ERROR)
                            self.available_tickets["last_deliveries"] = {}

                self.clean_available_tickets()
                self.save_available_tickets()

        except Exception as e:
            RNS.log("Could not load outbound stamp costs from storage. The contained exception was: "+str(e), RNS.LOG_ERROR)

        atexit.register(self.exit_handler)
        signal.signal(signal.SIGINT, self.sigint_handler)
        signal.signal(signal.SIGTERM, self.sigterm_handler)

        job_thread = threading.Thread(target=self.jobloop)
        job_thread.setDaemon(True)
        job_thread.start()

    def announce(self, destination_hash, attached_interface=None):
        if destination_hash in self.delivery_destinations:
            self.delivery_destinations[destination_hash].announce(app_data=self.get_announce_app_data(destination_hash), attached_interface=attached_interface)

    def get_propagation_node_announce_metadata(self):
        metadata = {}
        if self.name: metadata[PN_META_NAME] = str(self.name).encode("utf-8")
        return metadata

    def get_propagation_node_app_data(self):
        metadata      = self.get_propagation_node_announce_metadata()
        node_state    = self.propagation_node and not self.from_static_only
        stamp_cost    = [self.propagation_stamp_cost, self.propagation_stamp_cost_flexibility, self.peering_cost]
        announce_data = [ False,                                  # 0: Legacy LXMF PN support
                          int(time.time()),                       # 1: Current node timebase
                          node_state,                             # 2: Boolean flag signalling propagation node state
                          self.propagation_per_transfer_limit,    # 3: Per-transfer limit for message propagation in kilobytes
                          self.propagation_per_sync_limit,        # 4: Limit for incoming propagation node syncs
                          stamp_cost,                             # 5: Propagation stamp cost for this node
                          metadata ]                              # 6: Node metadata

        return msgpack.packb(announce_data)

    def announce_propagation_node(self):
        def delayed_announce():
            time.sleep(LXMRouter.NODE_ANNOUNCE_DELAY)
            self.propagation_destination.announce(app_data=self.get_propagation_node_app_data())

        da_thread = threading.Thread(target=delayed_announce)
        da_thread.setDaemon(True)
        da_thread.start()

    def register_delivery_identity(self, identity, display_name = None, stamp_cost = None):
        if len(self.delivery_destinations) != 0:
            RNS.log("Currently only one delivery identity is supported per LXMF router instance", RNS.LOG_ERROR)
            return None

        if not os.path.isdir(self.ratchetpath):
            os.makedirs(self.ratchetpath)

        delivery_destination = RNS.Destination(identity, RNS.Destination.IN, RNS.Destination.SINGLE, APP_NAME, "delivery")
        delivery_destination.enable_ratchets(f"{self.ratchetpath}/{RNS.hexrep(delivery_destination.hash, delimit=False)}.ratchets")
        delivery_destination.set_packet_callback(self.delivery_packet)
        delivery_destination.set_link_established_callback(self.delivery_link_established)
        delivery_destination.display_name = display_name

        if self.enforce_ratchets:
            delivery_destination.enforce_ratchets()

        if display_name != None:
            def get_app_data():
                return self.get_announce_app_data(delivery_destination.hash)
            delivery_destination.set_default_app_data(get_app_data)

        self.delivery_destinations[delivery_destination.hash] = delivery_destination
        self.set_inbound_stamp_cost(delivery_destination.hash, stamp_cost)

        return delivery_destination

    def register_delivery_callback(self, callback):
        self.__delivery_callback = callback

    def set_inbound_stamp_cost(self, destination_hash, stamp_cost):
        if destination_hash in self.delivery_destinations:
            delivery_destination = self.delivery_destinations[destination_hash]
            if stamp_cost == None:
                delivery_destination.stamp_cost = None
                return True
            elif type(stamp_cost) == int:
                if stamp_cost < 1:
                    delivery_destination.stamp_cost = None
                elif stamp_cost < 255:
                    delivery_destination.stamp_cost = stamp_cost
                else:
                    return False
    
                return True

        return False

    def get_outbound_stamp_cost(self, destination_hash):
        if destination_hash in self.outbound_stamp_costs:
            stamp_cost = self.outbound_stamp_costs[destination_hash][1]
            return stamp_cost
        else:
            return None

    def set_active_propagation_node(self, destination_hash):
        self.set_outbound_propagation_node(destination_hash)
        # self.set_inbound_propagation_node(destination_hash)

    def set_outbound_propagation_node(self, destination_hash):
        if len(destination_hash) != RNS.Identity.TRUNCATED_HASHLENGTH//8 or type(destination_hash) != bytes:
            raise ValueError("Invalid destination hash for outbound propagation node")
        else:
            if self.outbound_propagation_node != destination_hash:
                self.outbound_propagation_node = destination_hash
                if self.outbound_propagation_link != None:
                    if self.outbound_propagation_link.destination.hash != destination_hash:
                        self.outbound_propagation_link.teardown()
                        self.outbound_propagation_link = None

    def get_outbound_propagation_node(self):
        return self.outbound_propagation_node

    def get_outbound_propagation_cost(self):
        target_propagation_cost = None
        pn_destination_hash = self.get_outbound_propagation_node()
        pn_app_data = RNS.Identity.recall_app_data(pn_destination_hash)
        if pn_announce_data_is_valid(pn_app_data):
            pn_config = msgpack.unpackb(pn_app_data)
            target_propagation_cost = pn_config[5][0]

        if not target_propagation_cost:
            RNS.log(f"Could not retrieve cached propagation node config. Requesting path to propagation node to get target propagation cost...", RNS.LOG_DEBUG)
            RNS.Transport.request_path(pn_destination_hash)
            timeout = time.time() + LXMRouter.PATH_REQUEST_WAIT
            while not RNS.Identity.recall_app_data(pn_destination_hash) and time.time() < timeout:
                time.sleep(0.5)

            pn_app_data = RNS.Identity.recall_app_data(pn_destination_hash)
            if pn_announce_data_is_valid(pn_app_data):
                pn_config = msgpack.unpackb(pn_app_data)
                target_propagation_cost = pn_config[5][0]

        if not target_propagation_cost: RNS.log("Propagation node stamp cost still unavailable after path request", RNS.LOG_ERROR)
        return target_propagation_cost

    def set_inbound_propagation_node(self, destination_hash):
        # TODO: Implement
        raise NotImplementedError("Inbound/outbound propagation node differentiation is currently not implemented")

    def get_inbound_propagation_node(self):
        return self.get_outbound_propagation_node()

    def set_retain_node_lxms(self, retain):
        if retain == True:
            self.retain_synced_on_node = True
        else:
            self.retain_synced_on_node = False

    def set_authentication(self, required=None):
        if required != None:
            self.auth_required = required

    def requires_authentication(self):
        return self.auth_required

    def allow(self, identity_hash=None):
        if isinstance(identity_hash, bytes) and len(identity_hash) == RNS.Identity.TRUNCATED_HASHLENGTH//8:
            if not identity_hash in self.allowed_list:
                self.allowed_list.append(identity_hash)
        else:
            raise ValueError("Allowed identity hash must be "+str(RNS.Identity.TRUNCATED_HASHLENGTH//8)+" bytes")

    def disallow(self, identity_hash=None):
        if isinstance(identity_hash, bytes) and len(identity_hash) == RNS.Identity.TRUNCATED_HASHLENGTH//8:
            if identity_hash in self.allowed_list:
                self.allowed_list.pop(identity_hash)
        else:
            raise ValueError("Disallowed identity hash must be "+str(RNS.Identity.TRUNCATED_HASHLENGTH//8)+" bytes")

    def allow_control(self, identity_hash=None):
        if isinstance(identity_hash, bytes) and len(identity_hash) == RNS.Identity.TRUNCATED_HASHLENGTH//8:
            if not identity_hash in self.control_allowed_list: self.control_allowed_list.append(identity_hash)
        else: raise ValueError("Allowed identity hash must be "+str(RNS.Identity.TRUNCATED_HASHLENGTH//8)+" bytes")

    def disallow_control(self, identity_hash=None):
        if isinstance(identity_hash, bytes) and len(identity_hash) == RNS.Identity.TRUNCATED_HASHLENGTH//8:
            if identity_hash in self.control_allowed_list: self.control_allowed_list.pop(identity_hash)
        else: raise ValueError("Disallowed identity hash must be "+str(RNS.Identity.TRUNCATED_HASHLENGTH//8)+" bytes")

    def prioritise(self, destination_hash=None):
        if isinstance(destination_hash, bytes) and len(destination_hash) == RNS.Reticulum.TRUNCATED_HASHLENGTH//8:
            if not destination_hash in self.prioritised_list:
                self.prioritised_list.append(destination_hash)
        else:
            raise ValueError("Prioritised destination hash must be "+str(RNS.Reticulum.TRUNCATED_HASHLENGTH//8)+" bytes")

    def unprioritise(self, identity_hash=None):
        if isinstance(destination_hash, bytes) and len(destination_hash) == RNS.Reticulum.TRUNCATED_HASHLENGTH//8:
            if destination_hash in self.prioritised_list:
                self.prioritised_list.pop(destination_hash)
        else:
            raise ValueError("Prioritised destination hash must be "+str(RNS.Reticulum.TRUNCATED_HASHLENGTH//8)+" bytes")

    def request_messages_from_propagation_node(self, identity, max_messages = PR_ALL_MESSAGES):
        if max_messages == None:
            max_messages = LXMRouter.PR_ALL_MESSAGES

        self.propagation_transfer_progress = 0.0
        self.propagation_transfer_max_messages = max_messages
        if self.outbound_propagation_node != None:
            if self.outbound_propagation_link != None and self.outbound_propagation_link.status == RNS.Link.ACTIVE:
                self.propagation_transfer_state = LXMRouter.PR_LINK_ESTABLISHED
                RNS.log("Requesting message list from propagation node", RNS.LOG_DEBUG)
                self.outbound_propagation_link.identify(identity)
                self.outbound_propagation_link.request(
                    LXMPeer.MESSAGE_GET_PATH,
                    [None, None], # Set both want and have fields to None to get message list
                    response_callback=self.message_list_response,
                    failed_callback=self.message_get_failed
                )
                self.propagation_transfer_state = LXMRouter.PR_REQUEST_SENT
            else:
                if self.outbound_propagation_link == None:
                    if RNS.Transport.has_path(self.outbound_propagation_node):
                        self.wants_download_on_path_available_from = None
                        self.propagation_transfer_state = LXMRouter.PR_LINK_ESTABLISHING
                        RNS.log("Establishing link to "+RNS.prettyhexrep(self.outbound_propagation_node)+" for message download", RNS.LOG_DEBUG)
                        propagation_node_identity = RNS.Identity.recall(self.outbound_propagation_node)
                        propagation_node_destination = RNS.Destination(propagation_node_identity, RNS.Destination.OUT, RNS.Destination.SINGLE, APP_NAME, "propagation")
                        def msg_request_established_callback(link):
                            self.request_messages_from_propagation_node(identity, self.propagation_transfer_max_messages)

                        self.outbound_propagation_link = RNS.Link(propagation_node_destination, established_callback=msg_request_established_callback)
                    else:
                        RNS.log("No path known for message download from propagation node "+RNS.prettyhexrep(self.outbound_propagation_node)+". Requesting path...", RNS.LOG_DEBUG)
                        RNS.Transport.request_path(self.outbound_propagation_node)
                        self.wants_download_on_path_available_from = self.outbound_propagation_node
                        self.wants_download_on_path_available_to = identity
                        self.wants_download_on_path_available_timeout = time.time() + LXMRouter.PR_PATH_TIMEOUT
                        self.propagation_transfer_state = LXMRouter.PR_PATH_REQUESTED
                        self.request_messages_path_job()
                else:
                    RNS.log("Waiting for propagation node link to become active", RNS.LOG_EXTREME)
        else:
            RNS.log("Cannot request LXMF propagation node sync, no default propagation node configured", RNS.LOG_WARNING)

    def cancel_propagation_node_requests(self):
        if self.outbound_propagation_link != None:
            self.outbound_propagation_link.teardown()
            self.outbound_propagation_link = None

        self.acknowledge_sync_completion(reset_state=True)

    def enable_propagation(self):
        try:
            self.messagepath = self.storagepath+"/messagestore"

            if not os.path.isdir(self.storagepath):
                os.makedirs(self.storagepath)

            if not os.path.isdir(self.messagepath):
                os.makedirs(self.messagepath)

            self.propagation_entries = {}

            st = time.time(); RNS.log("Indexing messagestore...", RNS.LOG_NOTICE)
            for filename in os.listdir(self.messagepath):
                components = filename.split("_")
                if len(components) >= 3:
                    if float(components[1]) > 0:
                        if len(components[0]) == RNS.Identity.HASHLENGTH//8*2:
                            try:
                                transient_id       = bytes.fromhex(components[0])
                                received           = float(components[1])
                                stamp_value        = int(components[2])
                                filepath           = self.messagepath+"/"+filename
                                msg_size           = os.path.getsize(filepath)
                                file               = open(filepath, "rb")
                                destination_hash   = file.read(LXMessage.DESTINATION_LENGTH)
                                file.close()

                                self.propagation_entries[transient_id] = [
                                    destination_hash,   # 0: Destination hash
                                    filepath,           # 1: Storage location
                                    received,           # 2: Receive timestamp
                                    msg_size,           # 3: Message size
                                    [],                 # 4: Handled peers
                                    [],                 # 5: Unhandled peers
                                    stamp_value,        # 6: Stamp value
                                ]

                            except Exception as e:
                                RNS.log("Could not read LXM from message store. The contained exception was: "+str(e), RNS.LOG_ERROR)
            
            et = time.time(); mps = 0 if et-st == 0 else math.floor(len(self.propagation_entries)/(et-st))
            RNS.log(f"Indexed {len(self.propagation_entries)} messages in {RNS.prettytime(et-st)}, {mps} msgs/s", RNS.LOG_NOTICE)
            RNS.log("Rebuilding peer synchronisation states...", RNS.LOG_NOTICE)
            st = time.time()

            if os.path.isfile(self.storagepath+"/peers"):
                peers_file = open(self.storagepath+"/peers", "rb")
                peers_data = peers_file.read()
                peers_file.close()

                if len(peers_data) > 0:
                    serialised_peers = msgpack.unpackb(peers_data)
                    del peers_data

                    while len(serialised_peers) > 0:
                        serialised_peer = serialised_peers.pop()
                        peer = LXMPeer.from_bytes(serialised_peer, self)
                        del serialised_peer
                        if peer.destination_hash in self.static_peers and peer.last_heard == 0:
                            RNS.Transport.request_path(peer.destination_hash)
                        if peer.identity != None:
                            self.peers[peer.destination_hash] = peer
                            lim_str = ", no transfer limit"
                            if peer.propagation_transfer_limit != None:
                                lim_str = ", "+RNS.prettysize(peer.propagation_transfer_limit*1000)+" transfer limit"
                            RNS.log("Rebuilt peer "+RNS.prettyhexrep(peer.destination_hash)+" with "+str(peer.unhandled_message_count)+" unhandled messages"+lim_str, RNS.LOG_DEBUG)
                        else:
                            RNS.log("Peer "+RNS.prettyhexrep(peer.destination_hash)+" could not be loaded, because its identity could not be recalled. Dropping peer.", RNS.LOG_DEBUG)
                            del peer

                    del serialised_peers

            if len(self.static_peers) > 0:
                for static_peer in self.static_peers:
                    if not static_peer in self.peers:
                        RNS.log(f"Activating static peering with {RNS.prettyhexrep(static_peer)}", RNS.LOG_NOTICE)
                        self.peers[static_peer] = LXMPeer(self, static_peer, sync_strategy=self.default_sync_strategy)
                        if self.peers[static_peer].last_heard == 0:
                            # TODO: Allow path request responses through announce handler
                            # momentarily here, so peering config can be updated even if
                            # the static peer is not available to directly send an announce.
                            RNS.Transport.request_path(static_peer)

            RNS.log(f"Rebuilt synchronisation state for {len(self.peers)} peers in {RNS.prettytime(time.time()-st)}", RNS.LOG_NOTICE)

            try:
                if os.path.isfile(self.storagepath+"/node_stats"):
                    node_stats_file = open(self.storagepath+"/node_stats", "rb")
                    data = node_stats_file.read()
                    node_stats_file.close()
                    node_stats = msgpack.unpackb(data)

                    if not type(node_stats) == dict:
                        RNS.log("Invalid data format for loaded local node stats, node stats will be reset", RNS.LOG_ERROR)
                    else:
                        self.client_propagation_messages_received = node_stats["client_propagation_messages_received"]
                        self.client_propagation_messages_served = node_stats["client_propagation_messages_served"]
                        self.unpeered_propagation_incoming = node_stats["unpeered_propagation_incoming"]
                        self.unpeered_propagation_rx_bytes = node_stats["unpeered_propagation_rx_bytes"]

            except Exception as e:
                RNS.log("Could not load local node stats. The contained exception was: "+str(e), RNS.LOG_ERROR)

            self.propagation_node = True
            self.propagation_node_start_time = time.time()
            self.propagation_destination.set_link_established_callback(self.propagation_link_established)
            self.propagation_destination.set_packet_callback(self.propagation_packet)

            self.propagation_destination.register_request_handler(LXMPeer.OFFER_REQUEST_PATH, self.offer_request, allow = RNS.Destination.ALLOW_ALL)
            self.propagation_destination.register_request_handler(LXMPeer.MESSAGE_GET_PATH, self.message_get_request, allow = RNS.Destination.ALLOW_ALL)

            self.control_allowed_list = [self.identity.hash]
            self.control_destination  = RNS.Destination(self.identity, RNS.Destination.IN, RNS.Destination.SINGLE, APP_NAME, "propagation", "control")
            self.control_destination.register_request_handler(LXMRouter.STATS_GET_PATH, self.stats_get_request, allow = RNS.Destination.ALLOW_LIST, allowed_list=self.control_allowed_list)
            self.control_destination.register_request_handler(LXMRouter.SYNC_REQUEST_PATH, self.peer_sync_request, allow = RNS.Destination.ALLOW_LIST, allowed_list=self.control_allowed_list)
            self.control_destination.register_request_handler(LXMRouter.UNPEER_REQUEST_PATH, self.peer_unpeer_request, allow = RNS.Destination.ALLOW_LIST, allowed_list=self.control_allowed_list)

            if self.message_storage_limit != None:
                limit_str = ", limit is "+RNS.prettysize(self.message_storage_limit)
            else:
                limit_str = ""

            RNS.log("LXMF Propagation Node message store size is "+RNS.prettysize(self.message_storage_size())+limit_str, RNS.LOG_DEBUG)

            self.announce_propagation_node()

        except Exception as e:
            RNS.log("Could not enable propagation node. The contained exception was: "+str(e), RNS.LOG_ERROR)
            raise e
            RNS.panic()

    def disable_propagation(self):
        self.propagation_node = False
        self.announce_propagation_node()

    def enforce_stamps(self):
        self._enforce_stamps = True

    def ignore_stamps(self):
        self._enforce_stamps = False

    def ignore_destination(self, destination_hash):
        if not destination_hash in self.ignored_list:
            self.ignored_list.append(destination_hash)

    def unignore_destination(self, destination_hash):
        if destination_hash in self.ignored_list:
            self.ignored_list.remove(destination_hash)

    def set_message_storage_limit(self, kilobytes = None, megabytes = None, gigabytes = None):
        limit_bytes = 0

        if kilobytes != None:
            limit_bytes += kilobytes*1000

        if megabytes != None:
            limit_bytes += megabytes*1000*1000

        if gigabytes != None:
            limit_bytes += gigabytes*1000*1000*1000

        if limit_bytes == 0:
            limit_bytes = None

        try:
            if limit_bytes == None or int(limit_bytes) > 0:
                self.message_storage_limit = int(limit_bytes)
            else:
                raise ValueError("Cannot set LXMF information storage limit to "+str(limit_bytes))
        
        except Exception as e:
            raise ValueError("Cannot set LXMF information storage limit to "+str(limit_bytes))

    def message_storage_limit(self):
        return self.message_storage_limit

    def message_storage_size(self):
        if self.propagation_node:
            return sum(self.propagation_entries[f][3] for f in self.propagation_entries)
        else:
            return None

    def set_information_storage_limit(self, kilobytes = None, megabytes = None, gigabytes = None):
        limit_bytes = 0
        if kilobytes != None: limit_bytes += kilobytes*1000
        if megabytes != None: limit_bytes += megabytes*1000*1000
        if gigabytes != None: limit_bytes += gigabytes*1000*1000*1000
        if limit_bytes == 0:  limit_bytes = None

        try:
            if limit_bytes == None or int(limit_bytes) > 0: self.information_storage_limit = int(limit_bytes)
            else: raise ValueError("Cannot set LXMF information storage limit to "+str(limit_bytes))
        except Exception as e: raise ValueError("Cannot set LXMF information storage limit to "+str(limit_bytes))

    def information_storage_limit(self):
        return self.information_storage_limit

    def information_storage_size(self):
        pass

    def delivery_link_available(self, destination_hash):
        if destination_hash in self.direct_links or destination_hash in self.backchannel_links: return True
        else: return False


    ### Propagation Node Control ##########################
    #######################################################

    def compile_stats(self):
        if not self.propagation_node: return None
        else:
            peer_stats = {}
            for peer_id in self.peers.copy():
                peer = self.peers[peer_id]
                peer_stats[peer_id] = {
                    "type": "static" if peer_id in self.static_peers else "discovered",
                    "state": peer.state,
                    "alive": peer.alive,
                    "name":  peer.name,
                    "last_heard": int(peer.last_heard),
                    "next_sync_attempt": peer.next_sync_attempt,
                    "last_sync_attempt": peer.last_sync_attempt,
                    "sync_backoff": peer.sync_backoff,
                    "peering_timebase": peer.peering_timebase,
                    "ler": int(peer.link_establishment_rate),
                    "str": int(peer.sync_transfer_rate),
                    "transfer_limit": peer.propagation_transfer_limit,
                    "sync_limit": peer.propagation_sync_limit,
                    "target_stamp_cost": peer.propagation_stamp_cost,
                    "stamp_cost_flexibility": peer.propagation_stamp_cost_flexibility,
                    "peering_cost": peer.peering_cost,
                    "peering_key": peer.peering_key_value(),
                    "network_distance": RNS.Transport.hops_to(peer_id),
                    "rx_bytes": peer.rx_bytes,
                    "tx_bytes": peer.tx_bytes,
                    "acceptance_rate": peer.acceptance_rate,
                    "messages": {
                        "offered": peer.offered,
                        "outgoing": peer.outgoing,
                        "incoming": peer.incoming,
                        "unhandled": peer.unhandled_message_count
                    },
                }

            node_stats = {
                "identity_hash": self.identity.hash,
                "destination_hash": self.propagation_destination.hash,
                "uptime": time.time()-self.propagation_node_start_time,
                "delivery_limit": self.delivery_per_transfer_limit,
                "propagation_limit": self.propagation_per_transfer_limit,
                "sync_limit": self.propagation_per_sync_limit,
                "target_stamp_cost": self.propagation_stamp_cost,
                "stamp_cost_flexibility": self.propagation_stamp_cost_flexibility,
                "peering_cost": self.peering_cost,
                "max_peering_cost": self.max_peering_cost,
                "autopeer_maxdepth": self.autopeer_maxdepth,
                "from_static_only": self.from_static_only,
                "messagestore": {
                    "count": len(self.propagation_entries),
                    "bytes": self.message_storage_size(),
                    "limit": self.message_storage_limit,
                },
                "clients" : {
                    "client_propagation_messages_received": self.client_propagation_messages_received,
                    "client_propagation_messages_served": self.client_propagation_messages_served,
                },
                "unpeered_propagation_incoming": self.unpeered_propagation_incoming,
                "unpeered_propagation_rx_bytes": self.unpeered_propagation_rx_bytes,
                "static_peers": len(self.static_peers),
                "discovered_peers": len(self.peers)-len(self.static_peers),
                "total_peers": len(self.peers),
                "max_peers": self.max_peers,
                "peers": peer_stats,
            }

            return node_stats

    def stats_get_request(self, path, data, request_id, remote_identity, requested_at):
        if   remote_identity == None:                               return LXMPeer.ERROR_NO_IDENTITY
        elif remote_identity.hash not in self.control_allowed_list: return LXMPeer.ERROR_NO_ACCESS
        else:                                                       return self.compile_stats()

    def peer_sync_request(self, path, data, request_id, remote_identity, requested_at):
        if   remote_identity == None:                               return LXMPeer.ERROR_NO_IDENTITY
        elif remote_identity.hash not in self.control_allowed_list: return LXMPeer.ERROR_NO_ACCESS
        else:
            if type(data)  != bytes:                                return LXMPeer.ERROR_INVALID_DATA
            elif len(data) != RNS.Identity.TRUNCATED_HASHLENGTH//8: return LXMPeer.ERROR_INVALID_DATA
            else:
                if not data in self.peers: return LXMPeer.ERROR_NOT_FOUND
                else:
                    self.peers[data].sync()
                    return True

    def peer_unpeer_request(self, path, data, request_id, remote_identity, requested_at):
        if   remote_identity == None:                               return LXMPeer.ERROR_NO_IDENTITY
        elif remote_identity.hash not in self.control_allowed_list: return LXMPeer.ERROR_NO_ACCESS
        else:
            if type(data)  != bytes:                                return LXMPeer.ERROR_INVALID_DATA
            elif len(data) != RNS.Identity.TRUNCATED_HASHLENGTH//8: return LXMPeer.ERROR_INVALID_DATA
            else:
                if not data in self.peers: return LXMPeer.ERROR_NOT_FOUND
                else:
                    self.unpeer(data)
                    return True


    ### Utility & Maintenance #############################
    #######################################################

    JOB_OUTBOUND_INTERVAL  = 1
    JOB_STAMPS_INTERVAL    = 1
    JOB_LINKS_INTERVAL     = 1
    JOB_TRANSIENT_INTERVAL = 60
    JOB_STORE_INTERVAL     = 120
    JOB_PEERSYNC_INTERVAL  = 6
    JOB_PEERINGEST_INTERVAL= JOB_PEERSYNC_INTERVAL
    JOB_ROTATE_INTERVAL    = 56*JOB_PEERINGEST_INTERVAL
    def jobs(self):
        if not self.exit_handler_running:
            self.processing_count += 1

            if self.processing_count % LXMRouter.JOB_OUTBOUND_INTERVAL == 0:
                self.process_outbound()

            if self.processing_count % LXMRouter.JOB_STAMPS_INTERVAL == 0:
                threading.Thread(target=self.process_deferred_stamps, daemon=True).start()

            if self.processing_count % LXMRouter.JOB_LINKS_INTERVAL == 0:
                self.clean_links()

            if self.processing_count % LXMRouter.JOB_TRANSIENT_INTERVAL == 0:
                self.clean_transient_id_caches()

            if self.processing_count % LXMRouter.JOB_STORE_INTERVAL == 0:
                if self.propagation_node == True: self.clean_message_store()

            if self.processing_count % LXMRouter.JOB_PEERINGEST_INTERVAL == 0:
                if self.propagation_node == True: self.flush_queues()

            if self.processing_count % LXMRouter.JOB_ROTATE_INTERVAL == 0:
                if self.propagation_node == True: self.rotate_peers()

            if self.processing_count % LXMRouter.JOB_PEERSYNC_INTERVAL == 0:
                if self.propagation_node == True: self.sync_peers()
                self.clean_throttled_peers()

    def jobloop(self):
        while (True):
            # TODO: Improve this to scheduling, so manual
            # triggers can delay next run
            try:
                self.jobs()
            except Exception as e:
                RNS.log("An error ocurred while running LXMF Router jobs.", RNS.LOG_ERROR)
                RNS.log("The contained exception was: "+str(e), RNS.LOG_ERROR)
                RNS.trace_exception(e)
            time.sleep(LXMRouter.PROCESSING_INTERVAL)

    def flush_queues(self):
        if len(self.peers) > 0:
            self.flush_peer_distribution_queue()
            RNS.log("Calculating peer distribution queue mappings...", RNS.LOG_DEBUG); st = time.time()
            for peer_id in self.peers.copy():
                if peer_id in self.peers:
                    peer = self.peers[peer_id]
                    if peer.queued_items():
                        peer.process_queues()

            RNS.log(f"Distribution queue mapping completed in {RNS.prettytime(time.time()-st)}", RNS.LOG_DEBUG)

    def clean_links(self):
        closed_links = []
        for link_hash in self.direct_links:
            link = self.direct_links[link_hash]
            inactive_time = link.no_data_for()

            if inactive_time > LXMRouter.LINK_MAX_INACTIVITY:
                link.teardown()
                closed_links.append(link_hash)
                if link.link_id in self.validated_peer_links:
                    self.validated_peer_links.pop(link.link_id)

        for link_hash in closed_links:
            cleaned_link = self.direct_links.pop(link_hash)
            RNS.log("Cleaned link "+str(cleaned_link), RNS.LOG_DEBUG)

        try:
            inactive_links = []
            for link in self.active_propagation_links:
                if link.no_data_for() > LXMRouter.P_LINK_MAX_INACTIVITY:
                    inactive_links.append(link)

            for link in inactive_links:
                self.active_propagation_links.remove(link)
                link.teardown()
        
        except Exception as e:
            RNS.log("An error occurred while cleaning inbound propagation links. The contained exception was: "+str(e), RNS.LOG_ERROR)

        if self.outbound_propagation_link != None and self.outbound_propagation_link.status == RNS.Link.CLOSED:
            self.outbound_propagation_link = None
            if self.propagation_transfer_state == LXMRouter.PR_COMPLETE:
                self.acknowledge_sync_completion()
            elif self.propagation_transfer_state < LXMRouter.PR_LINK_ESTABLISHED:
                self.acknowledge_sync_completion(failure_state=LXMRouter.PR_LINK_FAILED)
            elif self.propagation_transfer_state >= LXMRouter.PR_LINK_ESTABLISHED and self.propagation_transfer_state < LXMRouter.PR_COMPLETE:
                self.acknowledge_sync_completion(failure_state=LXMRouter.PR_TRANSFER_FAILED)
            else:
                RNS.log(f"Unknown propagation transfer state on link cleaning: {self.propagation_transfer_state}", RNS.LOG_DEBUG)
                self.acknowledge_sync_completion()

            RNS.log("Cleaned outbound propagation link", RNS.LOG_DEBUG)

    def clean_transient_id_caches(self):
        now = time.time()
        removed_entries = []
        for transient_id in self.locally_delivered_transient_ids:
            timestamp = self.locally_delivered_transient_ids[transient_id]
            if now > timestamp+LXMRouter.MESSAGE_EXPIRY*6.0:
                removed_entries.append(transient_id)

        for transient_id in removed_entries:
            self.locally_delivered_transient_ids.pop(transient_id)
            RNS.log("Cleaned "+RNS.prettyhexrep(transient_id)+" from local delivery cache", RNS.LOG_DEBUG)

        removed_entries = []
        for transient_id in self.locally_processed_transient_ids:
            timestamp = self.locally_processed_transient_ids[transient_id]
            if now > timestamp+LXMRouter.MESSAGE_EXPIRY*6.0:
                removed_entries.append(transient_id)

        for transient_id in removed_entries:
            self.locally_processed_transient_ids.pop(transient_id)
            RNS.log("Cleaned "+RNS.prettyhexrep(transient_id)+" from locally processed cache", RNS.LOG_DEBUG)

    def update_stamp_cost(self, destination_hash, stamp_cost):
        RNS.log(f"Updating outbound stamp cost for {RNS.prettyhexrep(destination_hash)} to {stamp_cost}", RNS.LOG_DEBUG)
        self.outbound_stamp_costs[destination_hash] = [time.time(), stamp_cost]
        
        def job(): self.save_outbound_stamp_costs()
        threading.Thread(target=self.save_outbound_stamp_costs, daemon=True).start()

    def get_announce_app_data(self, destination_hash):
        if destination_hash in self.delivery_destinations:
            delivery_destination = self.delivery_destinations[destination_hash]
            
            display_name = None
            if delivery_destination.display_name != None:
                display_name = delivery_destination.display_name.encode("utf-8")

            stamp_cost = None
            if delivery_destination.stamp_cost != None and type(delivery_destination.stamp_cost) == int:
                if delivery_destination.stamp_cost > 0 and delivery_destination.stamp_cost < 255:
                    stamp_cost = delivery_destination.stamp_cost

            peer_data = [display_name, stamp_cost]

            return msgpack.packb(peer_data)

    def get_size(self, transient_id):
        lxm_size = self.propagation_entries[transient_id][3]
        return lxm_size

    def get_weight(self, transient_id):
        dst_hash   = self.propagation_entries[transient_id][0]
        lxm_rcvd   = self.propagation_entries[transient_id][2]
        lxm_size   = self.propagation_entries[transient_id][3]

        now        = time.time()
        age_weight = max(1, (now - lxm_rcvd)/60/60/24/4)

        if dst_hash in self.prioritised_list: priority_weight = 0.1
        else:                                 priority_weight = 1.0
        
        return priority_weight * age_weight * lxm_size

    def get_stamp_value(self, transient_id):
        if not transient_id in self.propagation_entries: return None
        else:                                            return self.propagation_entries[transient_id][6]

    def generate_ticket(self, destination_hash, expiry=LXMessage.TICKET_EXPIRY):
        now = time.time()
        ticket = None
        if destination_hash in self.available_tickets["last_deliveries"]:
            last_delivery = self.available_tickets["last_deliveries"][destination_hash]
            elapsed = now - last_delivery
            if elapsed < LXMessage.TICKET_INTERVAL:
                RNS.log(f"A ticket for {RNS.prettyhexrep(destination_hash)} was already delivered {RNS.prettytime(elapsed)} ago, not including another ticket yet", RNS.LOG_DEBUG)
                return None

        if destination_hash in self.available_tickets["inbound"]:
            for ticket in self.available_tickets["inbound"][destination_hash]:
                ticket_entry = self.available_tickets["inbound"][destination_hash][ticket]
                expires = ticket_entry[0]; validity_left = expires - now
                if validity_left > LXMessage.TICKET_RENEW:
                    RNS.log(f"Found generated ticket for {RNS.prettyhexrep(destination_hash)} with {RNS.prettytime(validity_left)} of validity left, re-using this one", RNS.LOG_DEBUG)
                    return [expires, ticket]
        
        else:
            self.available_tickets["inbound"][destination_hash] = {}

        RNS.log(f"No generated tickets for {RNS.prettyhexrep(destination_hash)} with enough validity found, generating a new one", RNS.LOG_DEBUG)
        expires = now+expiry
        ticket  = os.urandom(LXMessage.TICKET_LENGTH)
        self.available_tickets["inbound"][destination_hash][ticket] = [expires]
        self.save_available_tickets()

        return [expires, ticket]

    def remember_ticket(self, destination_hash, ticket_entry):
        expires = ticket_entry[0]-time.time()
        RNS.log(f"Remembering ticket for {RNS.prettyhexrep(destination_hash)}, expires in {RNS.prettytime(expires)}", RNS.LOG_DEBUG)
        self.available_tickets["outbound"][destination_hash] = [ticket_entry[0], ticket_entry[1]]

    def get_outbound_ticket(self, destination_hash):
        if destination_hash in self.available_tickets["outbound"]:
            entry = self.available_tickets["outbound"][destination_hash]
            if entry[0] > time.time():
                return entry[1]

        return None

    def get_outbound_ticket_expiry(self, destination_hash):
        if destination_hash in self.available_tickets["outbound"]:
            entry = self.available_tickets["outbound"][destination_hash]
            if entry[0] > time.time():
                return entry[0]

        return None

    def get_inbound_tickets(self, destination_hash):
        now = time.time()
        available_tickets = []
        if destination_hash in self.available_tickets["inbound"]:
            for inbound_ticket in self.available_tickets["inbound"][destination_hash]:
                if now < self.available_tickets["inbound"][destination_hash][inbound_ticket][0]:
                    available_tickets.append(inbound_ticket)

        if len(available_tickets) == 0:
            return None
        else:
            return available_tickets

    def clean_throttled_peers(self):
        expired_entries = []
        now = time.time()
        for peer_hash in self.throttled_peers:
            if now > self.throttled_peers[peer_hash]: expired_entries.append(peer_hash)

        for peer_hash in expired_entries: self.throttled_peers.pop(peer_hash)

    def clean_message_store(self):
        RNS.log("Cleaning message store", RNS.LOG_VERBOSE)
        # Check and remove expired messages
        now = time.time()
        removed_entries = {}
        for transient_id in self.propagation_entries.copy():
            entry       = self.propagation_entries[transient_id]
            filepath    = entry[1]
            stamp_value = entry[6]
            filename    = os.path.split(filepath)[-1]
            components  = filename.split("_")

            if len(components) == 3 and float(components[1]) > 0 and len(os.path.split(components[0])[1]) == (RNS.Identity.HASHLENGTH//8)*2 and int(components[2]) == stamp_value:
                timestamp = float(components[1])
                if now > timestamp+LXMRouter.MESSAGE_EXPIRY:
                    RNS.log("Purging message "+RNS.prettyhexrep(transient_id)+" due to expiry", RNS.LOG_EXTREME)
                    removed_entries[transient_id] = filepath
            else:
                RNS.log("Purging message "+RNS.prettyhexrep(transient_id)+" due to invalid file path", RNS.LOG_WARNING)
                removed_entries[transient_id] = filepath
        
        removed_count = 0
        for transient_id in removed_entries:
            try:
                filepath = removed_entries[transient_id]
                self.propagation_entries.pop(transient_id)
                if os.path.isfile(filepath):
                        os.unlink(filepath)
                removed_count += 1
            except Exception as e:
                RNS.log("Could not remove "+RNS.prettyhexrep(transient_id)+" from message store. The contained exception was: "+str(e), RNS.LOG_ERROR)

        if removed_count > 0:
            RNS.log("Cleaned "+str(removed_count)+" entries from the message store", RNS.LOG_VERBOSE)

        # Check size of message store and cull if needed
        try:
            message_storage_size = self.message_storage_size()
            if message_storage_size != None:
                if self.message_storage_limit != None and message_storage_size > self.message_storage_limit:
                    # Clean the message storage according to priorities
                    bytes_needed = message_storage_size - self.message_storage_limit
                    bytes_cleaned = 0

                    weighted_entries = []
                    for transient_id in self.propagation_entries.copy():
                        weighted_entries.append([
                            self.propagation_entries[transient_id],
                            self.get_weight(transient_id),
                            transient_id
                        ])

                    weighted_entries.sort(key=lambda we: we[1], reverse=True)

                    i = 0
                    while i < len(weighted_entries) and bytes_cleaned < bytes_needed:
                        try:
                            w = weighted_entries[i]
                            entry = w[0]
                            transient_id = w[2]
                            filepath = entry[1]

                            if os.path.isfile(filepath):
                                os.unlink(filepath)
                            
                            self.propagation_entries.pop(transient_id)
                            bytes_cleaned += entry[3]

                            RNS.log("Removed "+RNS.prettyhexrep(transient_id)+" with weight "+str(w[1])+" to clear up "+RNS.prettysize(entry[3])+", now cleaned "+RNS.prettysize(bytes_cleaned)+" out of "+RNS.prettysize(bytes_needed)+" needed", RNS.LOG_EXTREME)
    
                        except Exception as e:
                            RNS.log("Error while cleaning LXMF message from message store. The contained exception was: "+str(e), RNS.LOG_ERROR)
    
                        finally:
                            i += 1

                    RNS.log("LXMF message store size is now "+RNS.prettysize(self.message_storage_size())+" for "+str(len(self.propagation_entries))+" items", RNS.LOG_EXTREME)


        except Exception as e:
            RNS.log("Could not clean the LXMF message store. The contained exception was: "+str(e), RNS.LOG_ERROR)

    def save_locally_delivered_transient_ids(self):
        try:
            if len(self.locally_delivered_transient_ids) > 0:
                if not os.path.isdir(self.storagepath):
                    os.makedirs(self.storagepath)

                with open(self.storagepath+"/local_deliveries", "wb") as locally_delivered_file:
                    locally_delivered_file.write(msgpack.packb(self.locally_delivered_transient_ids))

        except Exception as e:
            RNS.log("Could not save locally delivered message ID cache to storage. The contained exception was: "+str(e), RNS.LOG_ERROR)

    def save_locally_processed_transient_ids(self):
        try:
            if len(self.locally_processed_transient_ids) > 0:
                if not os.path.isdir(self.storagepath):
                    os.makedirs(self.storagepath)

                with open(self.storagepath+"/locally_processed", "wb") as locally_processed_file:
                    locally_processed_file.write(msgpack.packb(self.locally_processed_transient_ids))

        except Exception as e:
            RNS.log("Could not save locally processed transient ID cache to storage. The contained exception was: "+str(e), RNS.LOG_ERROR)

    def save_node_stats(self):
        try:
            if not os.path.isdir(self.storagepath):
                os.makedirs(self.storagepath)

            with open(self.storagepath+"/node_stats", "wb") as stats_file:
                node_stats = {
                    "client_propagation_messages_received": self.client_propagation_messages_received,
                    "client_propagation_messages_served": self.client_propagation_messages_served,
                    "unpeered_propagation_incoming": self.unpeered_propagation_incoming,
                    "unpeered_propagation_rx_bytes": self.unpeered_propagation_rx_bytes,
                }
                stats_file.write(msgpack.packb(node_stats))

        except Exception as e:
            RNS.log("Could not save local node stats to storage. The contained exception was: "+str(e), RNS.LOG_ERROR)
        

    def clean_outbound_stamp_costs(self):
        try:
            expired = []
            for destination_hash in self.outbound_stamp_costs:
                entry = self.outbound_stamp_costs[destination_hash]
                if time.time() > entry[0] + LXMRouter.STAMP_COST_EXPIRY:
                    expired.append(destination_hash)

            for destination_hash in expired:
                self.outbound_stamp_costs.pop(destination_hash)
        
        except Exception as e:
            RNS.log(f"Error while cleaning outbound stamp costs. The contained exception was: {e}", RNS.LOG_ERROR)
            RNS.trace_exception(e)

    def save_outbound_stamp_costs(self):
        with self.cost_file_lock:
            try:
                if not os.path.isdir(self.storagepath):
                        os.makedirs(self.storagepath)

                outbound_stamp_costs_file = open(self.storagepath+"/outbound_stamp_costs", "wb")
                outbound_stamp_costs_file.write(msgpack.packb(self.outbound_stamp_costs))
                outbound_stamp_costs_file.close()

            except Exception as e:
                RNS.log("Could not save outbound stamp costs to storage. The contained exception was: "+str(e), RNS.LOG_ERROR)

    def clean_available_tickets(self):
        try:
            # Clean outbound tickets
            expired_outbound = []
            for destination_hash in self.available_tickets["outbound"]:
                entry = self.available_tickets["outbound"][destination_hash]
                if time.time() > entry[0]:
                    expired_outbound.append(destination_hash)

            for destination_hash in expired_outbound:
                self.available_tickets["outbound"].pop(destination_hash)

            # Clean inbound tickets
            for destination_hash in self.available_tickets["inbound"]:
                expired_inbound = []
                for inbound_ticket in self.available_tickets["inbound"][destination_hash]:
                    entry = self.available_tickets["inbound"][destination_hash][inbound_ticket]
                    ticket_expiry = entry[0]
                    if time.time() > ticket_expiry+LXMessage.TICKET_GRACE:
                        expired_inbound.append(inbound_ticket)

                for inbound_ticket in expired_inbound:
                    self.available_tickets["inbound"][destination_hash].pop(inbound_ticket)
        
        except Exception as e:
            RNS.log(f"Error while cleaning available tickets. The contained exception was: {e}", RNS.LOG_ERROR)
            RNS.trace_exception(e)

    def save_available_tickets(self):
        with self.ticket_file_lock:
            try:
                if not os.path.isdir(self.storagepath):
                        os.makedirs(self.storagepath)

                available_tickets_file = open(self.storagepath+"/available_tickets", "wb")
                available_tickets_file.write(msgpack.packb(self.available_tickets))
                available_tickets_file.close()

            except Exception as e:
                RNS.log("Could not save available tickets to storage. The contained exception was: "+str(e), RNS.LOG_ERROR)

    def reload_available_tickets(self):
        RNS.log("Reloading available tickets from storage", RNS.LOG_DEBUG)
        try:
            with self.ticket_file_lock:
                with open(self.storagepath+"/available_tickets", "rb") as available_tickets_file:
                    data = available_tickets_file.read()
                    self.available_tickets = msgpack.unpackb(data)
                    if not type(self.available_tickets) == dict:
                        RNS.log("Invalid data format for loaded available tickets, recreating...", RNS.LOG_ERROR)
                        self.available_tickets = {"outbound": {}, "inbound": {}, "last_deliveries": {}}
                    if not "outbound" in self.available_tickets:
                        RNS.log("Missing outbound entry in loaded available tickets, recreating...", RNS.LOG_ERROR)
                        self.available_tickets["outbound"] = {}
                    if not "inbound" in self.available_tickets:
                        RNS.log("Missing inbound entry in loaded available tickets, recreating...", RNS.LOG_ERROR)
                        self.available_tickets["inbound"] = {}
                    if not "last_deliveries" in self.available_tickets:
                        RNS.log("Missing local_deliveries entry in loaded available tickets, recreating...", RNS.LOG_ERROR)
                        self.available_tickets["last_deliveries"] = {}
        
        except Exception as e:
            RNS.log(f"An error occurred while reloading available tickets from storage: {e}", RNS.LOG_ERROR)

    def exit_handler(self):
        if self.exit_handler_running:
            return

        self.exit_handler_running = True

        RNS.log("Tearing down delivery destinations...", RNS.LOG_NOTICE)
        for destination_hash in self.delivery_destinations:
            delivery_destination = self.delivery_destinations[destination_hash]
            delivery_destination.set_packet_callback(None)
            delivery_destination.set_link_established_callback(None)
            for link in delivery_destination.links:
                try:
                    if link.status == RNS.Link.ACTIVE:
                        link.teardown()
                except Exception as e:
                    RNS.log("Error while tearing down propagation link: {e}", RNS.LOG_ERROR)

        if self.propagation_node:
            RNS.log("Tearing down propagation node destination...", RNS.LOG_NOTICE)
            self.propagation_destination.set_link_established_callback(None)
            self.propagation_destination.set_packet_callback(None)
            self.propagation_destination.deregister_request_handler(LXMPeer.OFFER_REQUEST_PATH)
            self.propagation_destination.deregister_request_handler(LXMPeer.MESSAGE_GET_PATH)
            self.propagation_destination.deregister_request_handler(LXMRouter.STATS_GET_PATH)
            self.propagation_destination.deregister_request_handler(LXMRouter.SYNC_REQUEST_PATH)
            self.propagation_destination.deregister_request_handler(LXMRouter.UNPEER_REQUEST_PATH)
            for link in self.active_propagation_links:
                try:
                    if link.status == RNS.Link.ACTIVE:
                        link.teardown()
                except Exception as e:
                    RNS.log("Error while tearing down propagation link: {e}", RNS.LOG_ERROR)

        RNS.log("Persisting LXMF state data to storage...", RNS.LOG_NOTICE)
        self.flush_queues()
        if self.propagation_node:
            try:
                st = time.time(); RNS.log(f"Saving {len(self.peers)} peer synchronisation states to storage...", RNS.LOG_NOTICE)
                serialised_peers = []
                peer_dict = self.peers.copy()
                for peer_id in peer_dict:
                    peer = self.peers[peer_id]
                    serialised_peers.append(peer.to_bytes())

                peers_file = open(self.storagepath+"/peers", "wb")
                peers_file.write(msgpack.packb(serialised_peers))
                peers_file.close()

                RNS.log(f"Saved {len(serialised_peers)} peers to storage in {RNS.prettyshorttime(time.time()-st)}", RNS.LOG_NOTICE)

            except Exception as e:
                RNS.log("Could not save propagation node peers to storage. The contained exception was: "+str(e), RNS.LOG_ERROR)

        self.save_locally_delivered_transient_ids()
        self.save_locally_processed_transient_ids()
        self.save_node_stats()

    def sigint_handler(self, signal, frame):
        if not self.exit_handler_running:
            RNS.log("Received SIGINT, shutting down now!", RNS.LOG_WARNING)
            sys.exit(0)
        else:
            RNS.log("Received SIGINT, but exit handler is running, keeping process alive until storage persist is complete", RNS.LOG_WARNING)

    def sigterm_handler(self, signal, frame):
        if not self.exit_handler_running:
            RNS.log("Received SIGTERM, shutting down now!", RNS.LOG_WARNING)
            sys.exit(0)
        else:
            RNS.log("Received SIGTERM, but exit handler is running, keeping process alive until storage persist is complete", RNS.LOG_WARNING)

    def __str__(self):
        return "<LXMRouter "+RNS.hexrep(self.identity.hash, delimit=False)+">"


    ### Message Download ##################################
    #######################################################
    
    def request_messages_path_job(self):
        job_thread = threading.Thread(target=self.__request_messages_path_job)
        job_thread.setDaemon(True)
        job_thread.start()

    def __request_messages_path_job(self):
        path_timeout = self.wants_download_on_path_available_timeout
        while not RNS.Transport.has_path(self.wants_download_on_path_available_from) and time.time() < path_timeout:
            time.sleep(0.1)

        if RNS.Transport.has_path(self.wants_download_on_path_available_from):
            self.request_messages_from_propagation_node(self.wants_download_on_path_available_to, self.propagation_transfer_max_messages)
        else:
            RNS.log("Propagation node path request timed out", RNS.LOG_DEBUG)
            self.acknowledge_sync_completion(failure_state=LXMRouter.PR_NO_PATH)
    
    def identity_allowed(self, identity):
        if self.auth_required:
            if identity.hash in self.allowed_list:
                return True
            else:
                return False
        
        else:
            return True

    def message_get_request(self, path, data, request_id, remote_identity, requested_at):
        if remote_identity == None:                      return LXMPeer.ERROR_NO_IDENTITY
        elif not self.identity_allowed(remote_identity): return LXMPeer.ERROR_NO_ACCESS
        else:
            try:
                remote_destination = RNS.Destination(remote_identity, RNS.Destination.OUT, RNS.Destination.SINGLE, APP_NAME, "delivery")

                # If both want and have fields are empty, send a list of
                # available messages.
                if data[0] == None and data[1] == None:
                    available_messages = []
                    for transient_id in self.propagation_entries:
                        message_entry = self.propagation_entries[transient_id]
                        if message_entry[0] == remote_destination.hash:
                            message_size = os.path.getsize(message_entry[1])
                            available_entry = [transient_id, message_size]
                            available_messages.append(available_entry)

                    available_messages.sort(key=lambda e: e[1], reverse=False)

                    transient_ids = []
                    for available_entry in available_messages: transient_ids.append(available_entry[0])
                    return transient_ids

                else:
                    # Process messages the client already have
                    if data[1] != None and len(data[1]) > 0:
                        for transient_id in data[1]:
                            if transient_id in self.propagation_entries and self.propagation_entries[transient_id][0] == remote_destination.hash:
                                try:
                                    filepath = self.propagation_entries[transient_id][1]
                                    self.propagation_entries.pop(transient_id)
                                    os.unlink(filepath)
                                    # TODO: Remove debug
                                    # RNS.log("Client "+RNS.prettyhexrep(remote_destination.hash)+" purged message "+RNS.prettyhexrep(transient_id)+" at "+str(filepath), RNS.LOG_DEBUG)
                                
                                except Exception as e:
                                    RNS.log("Error while processing message purge request from "+RNS.prettyhexrep(remote_destination.hash)+". The contained exception was: "+str(e), RNS.LOG_ERROR)


                    # Process wanted messages
                    response_messages = []
                    if data[0] != None and len(data[0]) > 0:
                        client_transfer_limit = None
                        if len(data) >= 3:
                            try:
                                client_transfer_limit = float(data[2])*1000
                                RNS.log("Client indicates transfer limit of "+RNS.prettysize(client_transfer_limit), RNS.LOG_DEBUG)
                            except: pass

                        per_message_overhead = 16 # Really only 2 bytes, but set a bit higher for now
                        cumulative_size = 24 # Initialised to highest reasonable binary structure overhead
                        for transient_id in data[0]:
                            if transient_id in self.propagation_entries and self.propagation_entries[transient_id][0] == remote_destination.hash:
                                try:
                                    filepath = self.propagation_entries[transient_id][1]
                                    RNS.log("Client "+RNS.prettyhexrep(remote_destination.hash)+" requested message "+RNS.prettyhexrep(transient_id)+" at "+str(filepath), RNS.LOG_DEBUG)

                                    message_file = open(filepath, "rb")
                                    lxmf_data = message_file.read()
                                    message_file.close()

                                    lxm_size = len(lxmf_data)
                                    next_size = cumulative_size + (lxm_size+per_message_overhead)

                                    if client_transfer_limit != None and next_size > client_transfer_limit: pass
                                    else:
                                        response_messages.append(lxmf_data[:-LXStamper.STAMP_SIZE])
                                        cumulative_size += (lxm_size+per_message_overhead)

                                except Exception as e:
                                    RNS.log("Error while processing message download request from "+RNS.prettyhexrep(remote_destination.hash)+". The contained exception was: "+str(e), RNS.LOG_ERROR)

                    self.client_propagation_messages_served += len(response_messages)
                    return response_messages

            except Exception as e:
                RNS.log("Error occurred while generating response for download request, the contained exception was: "+str(e), RNS.LOG_DEBUG)
                return None

    def message_list_response(self, request_receipt):
        if request_receipt.response == LXMPeer.ERROR_NO_IDENTITY:
            RNS.log("Propagation node indicated missing identification on list request, tearing down link.", RNS.LOG_DEBUG)
            if self.outbound_propagation_link != None:
                self.outbound_propagation_link.teardown()
            self.propagation_transfer_state = LXMRouter.PR_NO_IDENTITY_RCVD

        elif request_receipt.response == LXMPeer.ERROR_NO_ACCESS:
            RNS.log("Propagation node did not allow list request, tearing down link.", RNS.LOG_DEBUG)
            if self.outbound_propagation_link != None:
                self.outbound_propagation_link.teardown()
            self.propagation_transfer_state = LXMRouter.PR_NO_ACCESS

        else:
            if request_receipt.response != None and isinstance(request_receipt.response, list):
                haves = []
                wants = []
                if len(request_receipt.response) > 0:
                    for transient_id in request_receipt.response:
                        if self.has_message(transient_id):
                            if not self.retain_synced_on_node:
                                haves.append(transient_id)
                        else:
                            if self.propagation_transfer_max_messages == LXMRouter.PR_ALL_MESSAGES or len(wants) < self.propagation_transfer_max_messages:
                                wants.append(transient_id)

                    ms = "" if len(wants) == 1 else "s"
                    RNS.log(f"Requesting {len(wants)} message{ms} from propagation node", RNS.LOG_DEBUG)
                    request_receipt.link.request(
                        LXMPeer.MESSAGE_GET_PATH,
                        [wants, haves, self.delivery_per_transfer_limit],
                        response_callback=self.message_get_response,
                        failed_callback=self.message_get_failed,
                        progress_callback=self.message_get_progress)

                else:
                    self.propagation_transfer_state = LXMRouter.PR_COMPLETE
                    self.propagation_transfer_progress = 1.0
                    self.propagation_transfer_last_result = 0

            else:
                RNS.log("Invalid message list data received from propagation node", RNS.LOG_DEBUG)
                if self.outbound_propagation_link != None:
                    self.outbound_propagation_link.teardown()

    def message_get_response(self, request_receipt):
        if request_receipt.response == LXMPeer.ERROR_NO_IDENTITY:
            RNS.log("Propagation node indicated missing identification on get request, tearing down link.", RNS.LOG_DEBUG)
            if self.outbound_propagation_link != None:
                self.outbound_propagation_link.teardown()
            self.propagation_transfer_state = LXMRouter.PR_NO_IDENTITY_RCVD

        elif request_receipt.response == LXMPeer.ERROR_NO_ACCESS:
            RNS.log("Propagation node did not allow get request, tearing down link.", RNS.LOG_DEBUG)
            if self.outbound_propagation_link != None:
                self.outbound_propagation_link.teardown()
            self.propagation_transfer_state = LXMRouter.PR_NO_ACCESS

        else:
            duplicates = 0
            if request_receipt.response != None and len(request_receipt.response) > 0:
                haves = []
                for lxmf_data in request_receipt.response:
                    result = self.lxmf_propagation(lxmf_data, signal_duplicate=LXMRouter.DUPLICATE_SIGNAL)
                    if result == LXMRouter.DUPLICATE_SIGNAL: duplicates += 1
                    haves.append(RNS.Identity.full_hash(lxmf_data))

                # Return a list of successfully received messages to the node.
                # This deletes the messages on the propagation node.
                # TODO: Add option to keep messages on node.
                request_receipt.link.request(
                    LXMPeer.MESSAGE_GET_PATH,
                    [None, haves],
                    # response_callback=self.message_syncfinal_response,
                    failed_callback=self.message_get_failed,
                    # progress_callback=self.message_get_progress
                )

            self.propagation_transfer_state = LXMRouter.PR_COMPLETE
            self.propagation_transfer_progress = 1.0
            self.propagation_transfer_last_duplicates = duplicates
            self.propagation_transfer_last_result = len(request_receipt.response)
            self.save_locally_delivered_transient_ids()

    def message_get_progress(self, request_receipt):
        self.propagation_transfer_state = LXMRouter.PR_RECEIVING
        self.propagation_transfer_progress = request_receipt.get_progress()

    def message_get_failed(self, request_receipt):
        RNS.log("Message list/get request failed", RNS.LOG_DEBUG)
        if self.outbound_propagation_link != None:
            self.outbound_propagation_link.teardown()

    def acknowledge_sync_completion(self, reset_state=False, failure_state=None):
        self.propagation_transfer_last_result = None
        if reset_state or self.propagation_transfer_state <= LXMRouter.PR_COMPLETE:
            if failure_state == None:
                self.propagation_transfer_state = LXMRouter.PR_IDLE
            else:
                self.propagation_transfer_state = failure_state

        self.propagation_transfer_progress = 0.0
        self.wants_download_on_path_available_from = None
        self.wants_download_on_path_available_to = None

    def has_message(self, transient_id):
        if transient_id in self.locally_delivered_transient_ids:
            return True
        else:
            return False
    
    def cancel_outbound(self, message_id, cancel_state=LXMessage.CANCELLED):
        try:
            if message_id in self.pending_deferred_stamps:
                lxm = self.pending_deferred_stamps[message_id]
                RNS.log(f"Cancelling deferred stamp generation for {lxm}", RNS.LOG_DEBUG)
                lxm.state = cancel_state
                LXStamper.cancel_work(message_id)

            lxmessage = None
            for lxm in self.pending_outbound:
                if lxm.message_id == message_id:
                    lxmessage = lxm

            if lxmessage != None:
                lxmessage.state = cancel_state
                if lxmessage in self.pending_outbound:
                    RNS.log(f"Cancelling {lxmessage} in outbound queue", RNS.LOG_DEBUG)
                    if lxmessage.representation == LXMessage.RESOURCE:
                        if lxmessage.resource_representation != None:
                            lxmessage.resource_representation.cancel()

                    self.process_outbound()

        except Exception as e:
            RNS.log(f"An error occurred while cancelling {lxmessage}: {e}", RNS.LOG_ERROR)
            RNS.trace_exception(e)

    def handle_outbound(self, lxmessage):
        destination_hash = lxmessage.get_destination().hash

        if lxmessage.stamp_cost == None:
            if destination_hash in self.outbound_stamp_costs:
                stamp_cost = self.outbound_stamp_costs[destination_hash][1]
                lxmessage.stamp_cost = stamp_cost
                RNS.log(f"No stamp cost set on LXM to {RNS.prettyhexrep(destination_hash)}, autoconfigured to {stamp_cost}, as required by latest announce", RNS.LOG_DEBUG)

        lxmessage.state = LXMessage.OUTBOUND

        # If an outbound ticket is available for this
        # destination, attach it to the message.
        lxmessage.outbound_ticket = self.get_outbound_ticket(destination_hash)
        if lxmessage.outbound_ticket != None and lxmessage.defer_stamp:
            RNS.log(f"Deferred stamp generation was requested for {lxmessage}, but outbound ticket was applied, processing immediately", RNS.LOG_DEBUG)
            lxmessage.defer_stamp = False

        # If requested, include a ticket to allow the
        # destination to reply without generating a stamp.
        if lxmessage.include_ticket:
            ticket = self.generate_ticket(lxmessage.destination_hash)
            if ticket: lxmessage.fields[FIELD_TICKET] = ticket

        if not lxmessage.packed: lxmessage.pack()

        unknown_path_requested = False
        if not RNS.Transport.has_path(destination_hash) and lxmessage.method == LXMessage.OPPORTUNISTIC:
            RNS.log(f"Pre-emptively requesting unknown path for opportunistic {lxmessage}", RNS.LOG_DEBUG)
            RNS.Transport.request_path(destination_hash)
            lxmessage.next_delivery_attempt = time.time() + LXMRouter.PATH_REQUEST_WAIT
            unknown_path_requested = True

        lxmessage.determine_transport_encryption()

        if lxmessage.defer_stamp and lxmessage.stamp_cost == None:
            RNS.log(f"Deferred stamp generation was requested for {lxmessage}, but no stamp is required, processing immediately", RNS.LOG_DEBUG)
            lxmessage.defer_stamp = False

        if not lxmessage.defer_stamp and not (lxmessage.desired_method == LXMessage.PROPAGATED and lxmessage.defer_propagation_stamp):
            while not unknown_path_requested and self.processing_outbound: time.sleep(0.05)

            self.pending_outbound.append(lxmessage)
            if not unknown_path_requested: self.process_outbound()

        else: self.pending_deferred_stamps[lxmessage.message_id] = lxmessage

    def get_outbound_progress(self, lxm_hash):
        for lxm in self.pending_outbound:
            if lxm.hash == lxm_hash:
                return lxm.progress

        for lxm_id in self.pending_deferred_stamps:
            if self.pending_deferred_stamps[lxm_id].hash == lxm_hash:
                return self.pending_deferred_stamps[lxm_id].progress
        
        return None

    def get_outbound_lxm_stamp_cost(self, lxm_hash):
        for lxm in self.pending_outbound:
            if lxm.hash == lxm_hash:
                if lxm.outbound_ticket: return None
                else:                   return lxm.stamp_cost

        for lxm_id in self.pending_deferred_stamps:
            if self.pending_deferred_stamps[lxm_id].hash == lxm_hash:
                lxm = self.pending_deferred_stamps[lxm_id]
                if lxm.outbound_ticket: return None
                else:                   return lxm.stamp_cost
        
        return None

    def get_outbound_lxm_propagation_stamp_cost(self, lxm_hash):
        for lxm in self.pending_outbound:
            if lxm.hash == lxm_hash:
                return lxm.propagation_target_cost

        for lxm_id in self.pending_deferred_stamps:
            if self.pending_deferred_stamps[lxm_id].hash == lxm_hash:
                return self.pending_deferred_stamps[lxm_id].propagation_target_cost
        
        return None


    ### Message Routing & Delivery ########################
    #######################################################

    def lxmf_delivery(self, lxmf_data, destination_type = None, phy_stats = None, ratchet_id = None, method = None, no_stamp_enforcement=False, allow_duplicate=False):
        try:
            message = LXMessage.unpack_from_bytes(lxmf_data)
            if ratchet_id and not message.ratchet_id:
                message.ratchet_id = ratchet_id

            if method:
                message.method = method

            if message.signature_validated and FIELD_TICKET in message.fields:
                ticket_entry = message.fields[FIELD_TICKET]
                if type(ticket_entry) == list and len(ticket_entry) > 1:
                    expires = ticket_entry[0]
                    ticket  = ticket_entry[1]

                    if time.time() < expires:
                        if type(ticket) == bytes and len(ticket) == LXMessage.TICKET_LENGTH:
                            self.remember_ticket(message.source_hash, ticket_entry)
                            def save_job():
                                self.save_available_tickets()
                            threading.Thread(target=save_job, daemon=True).start()

            required_stamp_cost = self.delivery_destinations[message.destination_hash].stamp_cost
            if required_stamp_cost != None:
                destination_tickets = self.get_inbound_tickets(message.source_hash)
                if message.validate_stamp(required_stamp_cost, tickets=destination_tickets):
                    message.stamp_valid = True
                    message.stamp_checked = True
                else:
                    message.stamp_valid = False
                    message.stamp_checked = True

                if not message.stamp_valid:
                    if no_stamp_enforcement:
                        RNS.log(f"Received {message} with invalid stamp, but allowing anyway, since stamp enforcement was temporarily disabled", RNS.LOG_NOTICE)
                    else:
                        if self._enforce_stamps:
                            RNS.log(f"Dropping {message} with invalid stamp", RNS.LOG_NOTICE)
                            return False
                        else:
                            RNS.log(f"Received {message} with invalid stamp, but allowing anyway, since stamp enforcement is disabled", RNS.LOG_NOTICE)
                else:
                    RNS.log(f"Received {message} with valid stamp", RNS.LOG_DEBUG)

            if phy_stats != None:
                if "rssi" in phy_stats: message.rssi = phy_stats["rssi"]
                if "snr" in phy_stats: message.snr = phy_stats["snr"]
                if "q" in phy_stats: message.q = phy_stats["q"]

            # TODO: Update these descriptions to account for ratchets
            if destination_type == RNS.Destination.SINGLE:
                message.transport_encrypted = True
                message.transport_encryption = LXMessage.ENCRYPTION_DESCRIPTION_EC
            elif destination_type == RNS.Destination.GROUP:
                message.transport_encrypted = True
                message.transport_encryption = LXMessage.ENCRYPTION_DESCRIPTION_AES
            elif destination_type == RNS.Destination.LINK:
                message.transport_encrypted = True
                message.transport_encryption = LXMessage.ENCRYPTION_DESCRIPTION_EC
            else:
                message.transport_encrypted = False
                message.transport_encryption = None

            if message.source_hash in self.ignored_list:
                RNS.log(str(self)+" ignored message from "+RNS.prettyhexrep(message.source_hash), RNS.LOG_DEBUG)
                return False

            if not allow_duplicate and self.has_message(message.hash):
                RNS.log(str(self)+" ignored already received message from "+RNS.prettyhexrep(message.source_hash), RNS.LOG_DEBUG)
                return False
            else:
                self.locally_delivered_transient_ids[message.hash] = time.time()

            if self.__delivery_callback != None and callable(self.__delivery_callback):
                try:
                    self.__delivery_callback(message)
                except Exception as e:
                    RNS.log("An error occurred in the external delivery callback for "+str(message), RNS.LOG_ERROR)
                    RNS.trace_exception(e)

            return True

        except Exception as e:
            RNS.log("Could not assemble LXMF message from received data", RNS.LOG_NOTICE)
            RNS.log("The contained exception was: "+str(e), RNS.LOG_DEBUG)
            return False

    def delivery_packet(self, data, packet):
        packet.prove()
        try:
            method = None
            if packet.destination_type != RNS.Destination.LINK:
                method = LXMessage.OPPORTUNISTIC
                lxmf_data  = b""
                lxmf_data += packet.destination.hash
                lxmf_data += data
            else:
                method = LXMessage.DIRECT
                lxmf_data = data

            try:
                reticulum = RNS.Reticulum.get_instance()
                if packet.rssi == None: packet.rssi = reticulum.get_packet_rssi(packet.packet_hash)
                if packet.snr  == None: packet.snr  = reticulum.get_packet_snr(packet.packet_hash)
                if packet.q    == None: packet.q    = reticulum.get_packet_q(packet.packet_hash)
            except Exception as e:
                RNS.log("Error while retrieving physical link stats for LXMF delivery packet: "+str(e), RNS.LOG_ERROR)

            phy_stats = {"rssi": packet.rssi, "snr": packet.snr, "q": packet.q}

            self.lxmf_delivery(lxmf_data, packet.destination_type, phy_stats=phy_stats, ratchet_id=packet.ratchet_id, method=method)

        except Exception as e:
            RNS.log("Exception occurred while parsing incoming LXMF data.", RNS.LOG_ERROR)
            RNS.log("The contained exception was: "+str(e), RNS.LOG_ERROR)

    def delivery_link_established(self, link):
        link.track_phy_stats(True)
        link.set_packet_callback(self.delivery_packet)
        link.set_resource_strategy(RNS.Link.ACCEPT_APP)
        link.set_resource_callback(self.delivery_resource_advertised)
        link.set_resource_started_callback(self.resource_transfer_began)
        link.set_resource_concluded_callback(self.delivery_resource_concluded)
        link.set_remote_identified_callback(self.delivery_remote_identified)

    def delivery_link_closed(self, link):
        pass

    def resource_transfer_began(self, resource):
        RNS.log("Transfer began for LXMF delivery resource "+str(resource), RNS.LOG_DEBUG)

    def delivery_resource_advertised(self, resource):
        size = resource.get_data_size()
        limit = self.delivery_per_transfer_limit*1000
        if limit != None and size > limit:
            RNS.log("Rejecting "+RNS.prettysize(size)+" incoming LXMF delivery resource, since it exceeds the limit of "+RNS.prettysize(limit), RNS.LOG_DEBUG)
            return False
        else:
            return True

    def delivery_resource_concluded(self, resource):
        RNS.log("Transfer concluded for LXMF delivery resource "+str(resource), RNS.LOG_DEBUG)
        if resource.status == RNS.Resource.COMPLETE:
            ratchet_id = None
            # Set ratchet ID to link ID if available
            if resource.link and hasattr(resource.link, "link_id"):
                ratchet_id = resource.link.link_id
            phy_stats = {"rssi": resource.link.rssi, "snr": resource.link.snr, "q": resource.link.q}
            self.lxmf_delivery(resource.data.read(), resource.link.type, phy_stats=phy_stats, ratchet_id=ratchet_id, method=LXMessage.DIRECT)

    def delivery_remote_identified(self, link, identity):
        destination_hash = RNS.Destination.hash_from_name_and_identity("lxmf.delivery", identity)
        self.backchannel_links[destination_hash] = link
        RNS.log(f"Backchannel became available for {RNS.prettyhexrep(destination_hash)} on delivery link {link}", RNS.LOG_DEBUG)


    ### Peer Sync & Propagation ###########################
    #######################################################

    def peer(self, destination_hash, timestamp, propagation_transfer_limit, propagation_sync_limit, propagation_stamp_cost, propagation_stamp_cost_flexibility, peering_cost, metadata):
        if peering_cost > self.max_peering_cost:
            if destination_hash in self.peers:
                RNS.log(f"Peer {RNS.prettyhexrep(destination_hash)} increased peering cost beyond local accepted maximum, breaking peering...", RNS.LOG_NOTICE)
                self.unpeer(destination_hash, timestamp)
            else:
                RNS.log(f"Not peering with {RNS.prettyhexrep(destination_hash)}, since its peering cost of {peering_cost} exceeds local maximum of {self.max_peering_cost}", RNS.LOG_NOTICE)

        else:
            if destination_hash in self.peers:
                peer = self.peers[destination_hash]
                if timestamp > peer.peering_timebase:
                    peer.alive = True
                    peer.metadata = metadata
                    peer.sync_backoff = 0
                    peer.next_sync_attempt = 0
                    peer.peering_timebase = timestamp
                    peer.last_heard = time.time()
                    peer.propagation_stamp_cost = propagation_stamp_cost
                    peer.propagation_stamp_cost_flexibility = propagation_stamp_cost_flexibility
                    peer.peering_cost = peering_cost
                    peer.propagation_transfer_limit = propagation_transfer_limit
                    if propagation_sync_limit != None: peer.propagation_sync_limit = propagation_sync_limit
                    else:                              peer.propagation_sync_limit = propagation_transfer_limit
                    
                    RNS.log(f"Peering config updated for {RNS.prettyhexrep(destination_hash)}", RNS.LOG_VERBOSE)
                
            else:
                if len(self.peers) >= self.max_peers: RNS.log(f"Max peers reached, not peering with {RNS.prettyhexrep(destination_hash)}", RNS.LOG_DEBUG)
                else:
                    peer = LXMPeer(self, destination_hash, sync_strategy=self.default_sync_strategy)
                    peer.alive = True
                    peer.metadata = metadata
                    peer.last_heard = time.time()
                    peer.propagation_stamp_cost = propagation_stamp_cost
                    peer.propagation_stamp_cost_flexibility = propagation_stamp_cost_flexibility
                    peer.peering_cost = peering_cost
                    peer.propagation_transfer_limit = propagation_transfer_limit
                    if propagation_sync_limit != None: peer.propagation_sync_limit = propagation_sync_limit
                    else:                              peer.propagation_sync_limit = propagation_transfer_limit
                    
                    self.peers[destination_hash] = peer
                    RNS.log(f"Peered with {RNS.prettyhexrep(destination_hash)}", RNS.LOG_NOTICE)


    def unpeer(self, destination_hash, timestamp = None):
        if timestamp == None:
            timestamp = int(time.time())

        if destination_hash in self.peers:
            peer = self.peers[destination_hash]

            if timestamp >= peer.peering_timebase:
                self.peers.pop(destination_hash)
                RNS.log("Broke peering with "+str(peer.destination))

    def rotate_peers(self):
        try:
            rotation_headroom = max(1, math.floor(self.max_peers*(LXMRouter.ROTATION_HEADROOM_PCT/100.0)))
            required_drops = len(self.peers) - (self.max_peers - rotation_headroom)
            if required_drops > 0 and len(self.peers) - required_drops > 1:
                peers = self.peers.copy()
                untested_peers = []
                for peer_id in self.peers:
                    peer = self.peers[peer_id]
                    if peer.last_sync_attempt == 0:
                        untested_peers.append(peer)

                if len(untested_peers) >= rotation_headroom:
                    RNS.log("Newly added peer threshold reached, postponing peer rotation", RNS.LOG_DEBUG)
                    return
                
                fully_synced_peers = {}
                for peer_id in peers:
                    peer = peers[peer_id]
                    if peer.unhandled_message_count == 0:
                        fully_synced_peers[peer_id] = peer

                if len(fully_synced_peers) > 0:
                    peers = fully_synced_peers
                    ms = "" if len(fully_synced_peers) == 1 else "s"
                    RNS.log(f"Found {len(fully_synced_peers)} fully synced peer{ms}, using as peer rotation pool basis", RNS.LOG_DEBUG)

                culled_peers  = []
                waiting_peers = []
                unresponsive_peers = []
                for peer_id in peers:
                    peer = peers[peer_id]
                    if not peer_id in self.static_peers and peer.state == LXMPeer.IDLE:
                        if peer.alive:
                            if peer.offered == 0:
                                # Don't consider for unpeering until at
                                # least one message has been offered
                                pass
                            else:
                                waiting_peers.append(peer)
                        else:
                            unresponsive_peers.append(peer)

                drop_pool = []
                if len(unresponsive_peers) > 0:
                    drop_pool.extend(unresponsive_peers)
                    if not self.prioritise_rotating_unreachable_peers:
                        drop_pool.extend(waiting_peers)

                else:
                    drop_pool.extend(waiting_peers)

                if len(drop_pool) > 0:
                    drop_count = min(required_drops, len(drop_pool))
                    low_acceptance_rate_peers = sorted(
                        drop_pool,
                        key=lambda p: ( 0 if p.offered == 0 else (p.outgoing/p.offered) ),
                        reverse=False
                    )[0:drop_count]

                    dropped_peers = 0
                    for peer in low_acceptance_rate_peers:
                        ar = 0 if peer.offered == 0 else round((peer.outgoing/peer.offered)*100, 2)
                        if ar < LXMRouter.ROTATION_AR_MAX*100:
                            reachable_str = "reachable" if peer.alive else "unreachable"
                            RNS.log(f"Acceptance rate for {reachable_str} peer {RNS.prettyhexrep(peer.destination_hash)} was: {ar}% ({peer.outgoing}/{peer.offered}, {peer.unhandled_message_count} unhandled messages)", RNS.LOG_DEBUG)
                            self.unpeer(peer.destination_hash)
                            dropped_peers += 1

                    ms = "" if dropped_peers == 1 else "s"
                    RNS.log(f"Dropped {dropped_peers} low acceptance rate peer{ms} to increase peering headroom", RNS.LOG_DEBUG)

        except Exception as e:
            RNS.log(f"An error occurred during peer rotation: {e}", RNS.LOG_ERROR)
            RNS.trace_exception(e)

    def sync_peers(self):
        culled_peers  = []
        waiting_peers = []
        unresponsive_peers = []
        peers = self.peers.copy()
        for peer_id in peers:
            peer = peers[peer_id]
            if time.time() > peer.last_heard + LXMPeer.MAX_UNREACHABLE:
                if not peer_id in self.static_peers: culled_peers.append(peer_id)
            
            else:
                if peer.state == LXMPeer.IDLE and len(peer.unhandled_messages) > 0:
                    if peer.alive: waiting_peers.append(peer)
                    else:
                        if hasattr(peer, "next_sync_attempt") and time.time() > peer.next_sync_attempt: unresponsive_peers.append(peer)
                        else: pass # RNS.log("Not adding peer "+str(peer)+" since it is in sync backoff", RNS.LOG_DEBUG)

        peer_pool = []
        if len(waiting_peers) > 0:
            fastest_peers = sorted(
                waiting_peers,
                key=lambda p: p.sync_transfer_rate,
                reverse=True
            )[0:min(LXMRouter.FASTEST_N_RANDOM_POOL, len(waiting_peers))]
            peer_pool.extend(fastest_peers)
            
            unknown_speed_peers = [p for p in waiting_peers if p.sync_transfer_rate == 0]
            if len(unknown_speed_peers) > 0:
                peer_pool.extend(
                    unknown_speed_peers[
                        0:min(
                            len(unknown_speed_peers),
                            len(fastest_peers)
                        )]
                )

            RNS.log("Selecting peer to sync from "+str(len(waiting_peers))+" waiting peers.", RNS.LOG_DEBUG)
            
        elif len(unresponsive_peers) > 0:
            RNS.log("No active peers available, randomly selecting peer to sync from "+str(len(unresponsive_peers))+" unresponsive peers.", RNS.LOG_DEBUG)
            peer_pool = unresponsive_peers
        
        if len(peer_pool) > 0:
            selected_index = random.randint(0,len(peer_pool)-1)
            selected_peer = peer_pool[selected_index]
            RNS.log("Selected waiting peer "+str(selected_index)+": "+RNS.prettyhexrep(selected_peer.destination.hash), RNS.LOG_DEBUG)
            selected_peer.sync()

        for peer_id in culled_peers:
            RNS.log("Removing peer "+RNS.prettyhexrep(peer_id)+" due to excessive unreachability", RNS.LOG_WARNING)
            try:
                if peer_id in self.peers:
                    self.peers.pop(peer_id)
            except Exception as e:
                RNS.log("Error while removing peer "+RNS.prettyhexrep(peer_id)+". The contained exception was: "+str(e), RNS.LOG_ERROR)

    def propagation_link_established(self, link):
        link.set_packet_callback(self.propagation_packet)
        link.set_resource_strategy(RNS.Link.ACCEPT_APP)
        link.set_resource_callback(self.propagation_resource_advertised)
        link.set_resource_started_callback(self.resource_transfer_began)
        link.set_resource_concluded_callback(self.propagation_resource_concluded)
        self.active_propagation_links.append(link)

    def propagation_resource_advertised(self, resource):
        if self.from_static_only:
            remote_identity = resource.link.get_remote_identity()
            if remote_identity == None:
                RNS.log(f"Rejecting propagation resource from unidentified peer", RNS.LOG_DEBUG)
                return False
            else:
                remote_destination = RNS.Destination(remote_identity, RNS.Destination.OUT, RNS.Destination.SINGLE, APP_NAME, "propagation")
                remote_hash = remote_destination.hash
                remote_str  = RNS.prettyhexrep(remote_hash)
                if not remote_hash in self.static_peers:
                    RNS.log(f"Rejecting propagation resource from {remote_str} not in static peers list", RNS.LOG_DEBUG)
                    return False

        size = resource.get_data_size()
        limit = self.propagation_per_sync_limit*1000
        if limit != None and size > limit:
            RNS.log(f"Rejecting {RNS.prettysize(size)} incoming propagation resource, since it exceeds the limit of {RNS.prettysize(limit)}", RNS.LOG_DEBUG)
            return False
        else:
            return True

    def propagation_packet(self, data, packet):
        try:
            if packet.destination_type != RNS.Destination.LINK: return
            else:
                data               = msgpack.unpackb(data)
                remote_timebase    = data[0]
                messages           = data[1]

                min_accepted_cost  = max(0, self.propagation_stamp_cost-self.propagation_stamp_cost_flexibility)
                validated_messages = LXStamper.validate_pn_stamps(messages, min_accepted_cost)

                for validated_entry in validated_messages:
                    lxmf_data    = validated_entry[1]
                    stamp_value  = validated_entry[2]
                    stamp_data   = validated_entry[3]
                    self.lxmf_propagation(lxmf_data, stamp_value=stamp_value, stamp_data=stamp_data)
                    self.client_propagation_messages_received += 1

                if len(validated_messages) == len(messages):
                    ms = "" if len(messages) == 1 else "s"
                    RNS.log(f"Received {len(messages)} propagation message{ms} from client with valid stamp{ms}", RNS.LOG_DEBUG)
                    packet.prove()
                else:
                    RNS.log("Propagation transfer from client contained messages with invalid stamps", RNS.LOG_NOTICE)
                    reject_data = msgpack.packb([LXMPeer.ERROR_INVALID_STAMP])
                    RNS.Packet(packet.link, reject_data).send()
                    packet.link.teardown()

        except Exception as e:
            RNS.log("Exception occurred while parsing incoming LXMF propagation data.", RNS.LOG_ERROR)
            RNS.log("The contained exception was: "+str(e), RNS.LOG_ERROR)

    def offer_request(self, path, data, request_id, link_id, remote_identity, requested_at):
        if remote_identity == None:
            return LXMPeer.ERROR_NO_IDENTITY
        else:
            remote_destination = RNS.Destination(remote_identity, RNS.Destination.OUT, RNS.Destination.SINGLE, APP_NAME, "propagation")
            remote_hash = remote_destination.hash
            remote_str  = RNS.prettyhexrep(remote_hash)

            if remote_hash in self.throttled_peers:
                throttle_remaining = self.throttled_peers[remote_hash]-time.time()
                if throttle_remaining > 0:
                    RNS.log(f"Propagation offer from node {remote_str} rejected, throttled for {RNS.prettytime(throttle_remaining)} more", RNS.LOG_NOTICE)
                    return LXMPeer.ERROR_THROTTLED
                else: self.throttled_peers.pop(remote_hash)

            if self.from_static_only:
                if not remote_hash in self.static_peers:
                    RNS.log(f"Rejecting propagation request from {remote_str} not in static peers list", RNS.LOG_DEBUG)
                    return LXMPeer.ERROR_NO_ACCESS

            try:
                if type(data) != list and len(data) < 2: return LXMPeer.ERROR_INVALID_DATA

                peering_id         = self.identity.hash+remote_identity.hash
                target_cost        = self.peering_cost
                peering_key        = data[0]
                transient_ids      = data[1]
                wanted_ids         = []

                ts                 = time.time()
                peering_key_valid  = LXStamper.validate_peering_key(peering_id, peering_key, target_cost)
                td                 = time.time() - ts

                if not peering_key_valid:
                    RNS.log(f"Invalid peering key for incoming sync offer", RNS.LOG_DEBUG)
                    return LXMPeer.ERROR_INVALID_KEY

                else:
                    RNS.log(f"Peering key validated for incoming offer in {RNS.prettytime(td)}", RNS.LOG_DEBUG)
                    self.validated_peer_links[link_id] = True
                    for transient_id in transient_ids:
                        if not transient_id in self.propagation_entries: wanted_ids.append(transient_id)

                    if len(wanted_ids)   == 0:                  return False
                    elif len(wanted_ids) == len(transient_ids): return True
                    else:                                       return wanted_ids

            except Exception as e:
                RNS.log("Error occurred while generating response for sync request, the contained exception was: "+str(e), RNS.LOG_DEBUG)
                RNS.trace_exception(e)
                return None

    def propagation_resource_concluded(self, resource):
        if resource.status == RNS.Resource.COMPLETE:
            try:
                data = msgpack.unpackb(resource.data.read())

                if type(data) == list and len(data) == 2 and type(data[0] == float) and type(data[1]) == list:
                    # This is a series of propagation messages from a peer or originator
                    remote_identity = resource.link.get_remote_identity()
                    remote_timebase = data[0]
                    messages        = data[1]
                    remote_hash     = None
                    remote_str      = "unknown client"

                    if remote_identity != None:
                        remote_destination = RNS.Destination(remote_identity, RNS.Destination.OUT, RNS.Destination.SINGLE, APP_NAME, "propagation")
                        remote_hash        = remote_destination.hash
                        remote_app_data    = RNS.Identity.recall_app_data(remote_hash)
                        remote_str         = RNS.prettyhexrep(remote_hash)

                        if remote_hash in self.peers: remote_str = f"peer {remote_str}"
                        else:
                            if pn_announce_data_is_valid(remote_app_data):
                                # 1: Current node timebase
                                # 2: Boolean flag signalling propagation node state
                                # 3: Per-transfer limit for message propagation in kilobytes
                                # 4: Limit for incoming propagation node syncs
                                # 5: Propagation stamp costs for this node
                                # 6: Node metadata
                                if remote_app_data[2] and self.autopeer and RNS.Transport.hops_to(remote_hash) <= self.autopeer_maxdepth:
                                    remote_timebase       = remote_app_data[1]
                                    remote_transfer_limit = remote_app_data[3]
                                    remote_sync_limit     = remote_app_data[4]
                                    remote_stamp_cost     = remote_app_data[5][0]
                                    remote_stamp_flex     = remote_app_data[5][1]
                                    remote_peering_cost   = remote_app_data[5][2]
                                    remote_metadata       = remote_app_data[6]

                                    RNS.log(f"Auto-peering with {remote_str} discovered via incoming sync", RNS.LOG_DEBUG) # TODO: Remove debug
                                    self.peer(remote_hash, remote_timebase, remote_transfer_limit, remote_sync_limit, remote_stamp_cost, remote_stamp_flex, remote_peering_cost, remote_metadata)

                    peering_key_valid = False
                    if remote_identity != None:
                        if resource.link.link_id in self.validated_peer_links and self.validated_peer_links[resource.link.link_id] == True:
                            peering_key_valid = True

                    if not peering_key_valid and len(messages) > 1:
                        resource.link.teardown()
                        RNS.log(f"Received multiple propagation messages from {remote_str} without valid peering key presentation. This is not supposed to happen, ignoring.", RNS.LOG_WARNING)
                        RNS.log(f"Clients and peers without a valid peering key can only deliver 1 message per transfer.", RNS.LOG_WARNING)
                    else:
                        ms = "" if len(messages) == 1 else "s"
                        RNS.log(f"Received {len(messages)} message{ms} from {remote_str}, validating stamps...", RNS.LOG_VERBOSE)

                        min_accepted_cost  = max(0, self.propagation_stamp_cost-self.propagation_stamp_cost_flexibility)
                        validated_messages = LXStamper.validate_pn_stamps(messages, min_accepted_cost)
                        invalid_stamps     = len(messages)-len(validated_messages)
                        ms                 = "" if invalid_stamps == 1 else "s"
                        if len(validated_messages) == len(messages): RNS.log(f"All message stamps validated from {remote_str}", RNS.LOG_VERBOSE)
                        else:                                        RNS.log(f"Transfer from {remote_str} contained {invalid_stamps} invalid stamp{ms}", RNS.LOG_WARNING)

                        for validated_entry in validated_messages:
                            transient_id = validated_entry[0]
                            lxmf_data    = validated_entry[1]
                            stamp_value  = validated_entry[2]
                            stamp_data   = validated_entry[3]
                            peer         = None
                            
                            if remote_hash != None and remote_hash in self.peers:
                                peer = self.peers[remote_hash]
                                peer.incoming += 1
                                peer.rx_bytes += len(lxmf_data)
                            else:
                                if remote_identity != None:
                                    self.unpeered_propagation_incoming += 1
                                    self.unpeered_propagation_rx_bytes += len(lxmf_data)
                                else:
                                    self.client_propagation_messages_received += 1

                            self.lxmf_propagation(lxmf_data, from_peer=peer, stamp_value=stamp_value, stamp_data=stamp_data)
                            if peer != None: peer.queue_handled_message(transient_id)

                        invalid_message_count = len(messages) - len(validated_messages)
                        if invalid_message_count > 0:
                            resource.link.teardown()
                            if remote_identity != None:
                                throttle_time = LXMRouter.PN_STAMP_THROTTLE
                                self.throttled_peers[remote_hash] = time.time()+throttle_time
                                ms = "" if invalid_message_count == 1 else "s"
                                RNS.log(f"Propagation transfer from {remote_str} contained {invalid_message_count} message{ms} with invalid stamps, throttled for {RNS.prettytime(throttle_time)}", RNS.LOG_NOTICE)

                else:
                    RNS.log("Invalid data structure received at propagation destination, ignoring", RNS.LOG_DEBUG)
    
            except Exception as e:
                RNS.log("Error while unpacking received propagation resource", RNS.LOG_DEBUG)
                RNS.trace_exception(e)

    def enqueue_peer_distribution(self, transient_id, from_peer):
        self.peer_distribution_queue.append([transient_id, from_peer])

    def flush_peer_distribution_queue(self):
        if len(self.peer_distribution_queue) > 0:
            entries = []
            while len(self.peer_distribution_queue) > 0:
                entries.append(self.peer_distribution_queue.pop())

            for peer_id in self.peers.copy():
                if peer_id in self.peers:
                    peer = self.peers[peer_id]
                    for entry in entries:
                        transient_id = entry[0]
                        from_peer = entry[1]
                        if peer != from_peer:
                            peer.queue_unhandled_message(transient_id)

    def lxmf_propagation(self, lxmf_data, signal_local_delivery=None, signal_duplicate=None, allow_duplicate=False, is_paper_message=False,
                         from_peer=None, stamp_value=None, stamp_data=None):
        if is_paper_message: no_stamp_enforcement = True
        else:                no_stamp_enforcement = False

        try:
            if len(lxmf_data) >= LXMessage.LXMF_OVERHEAD:
                transient_id = RNS.Identity.full_hash(lxmf_data)

                if (not transient_id in self.propagation_entries and not transient_id in self.locally_processed_transient_ids) or allow_duplicate == True:
                    received = time.time()
                    destination_hash  = lxmf_data[:LXMessage.DESTINATION_LENGTH]

                    self.locally_processed_transient_ids[transient_id] = received

                    if destination_hash in self.delivery_destinations:
                        delivery_destination = self.delivery_destinations[destination_hash]
                        encrypted_lxmf_data = lxmf_data[LXMessage.DESTINATION_LENGTH:]
                        decrypted_lxmf_data = delivery_destination.decrypt(encrypted_lxmf_data)
                        if decrypted_lxmf_data != None:
                            delivery_data = lxmf_data[:LXMessage.DESTINATION_LENGTH]+decrypted_lxmf_data
                            self.lxmf_delivery(delivery_data, delivery_destination.type, ratchet_id=delivery_destination.latest_ratchet_id, method=LXMessage.PROPAGATED, no_stamp_enforcement=no_stamp_enforcement, allow_duplicate=allow_duplicate)
                            self.locally_delivered_transient_ids[transient_id] = time.time()

                            if signal_local_delivery != None:
                                return signal_local_delivery

                    else:
                        if self.propagation_node:
                            stamped_data    = lxmf_data+stamp_data
                            value_component = f"_{stamp_value}" if stamp_value and stamp_value > 0 else ""
                            file_path       = f"{self.messagepath}/{RNS.hexrep(transient_id, delimit=False)}_{received}{value_component}"
                            msg_file        = open(file_path, "wb")
                            msg_file.write(stamped_data); msg_file.close()

                            RNS.log(f"Received propagated LXMF message {RNS.prettyhexrep(transient_id)} with stamp value {stamp_value}, adding to peer distribution queues...", RNS.LOG_EXTREME)
                            self.propagation_entries[transient_id] = [destination_hash, file_path, time.time(), len(stamped_data), [], [], stamp_value]
                            self.enqueue_peer_distribution(transient_id, from_peer)

                        else:
                            # TODO: Add message to sneakernet queues when implemented
                            RNS.log(f"Received propagated LXMF message {RNS.prettyhexrep(transient_id)}, but this instance is not hosting a propagation node, discarding message.", RNS.LOG_DEBUG)

                    return True

                else:
                    if signal_duplicate != None:
                        return signal_duplicate

                    else:
                        return False

            return False

        except Exception as e:
            RNS.log("Could not assemble propagated LXMF message from received data", RNS.LOG_DEBUG)
            RNS.log("The contained exception was: "+str(e), RNS.LOG_DEBUG)
            RNS.trace_exception(e)
            return False

    def ingest_lxm_uri(self, uri, signal_local_delivery=None, signal_duplicate=None, allow_duplicate=False):
        try:
            if not uri.lower().startswith(LXMessage.URI_SCHEMA+"://"):
                RNS.log("Cannot ingest LXM, invalid URI provided.", RNS.LOG_ERROR)
                return False

            else:
                lxmf_data = base64.urlsafe_b64decode(uri.replace(LXMessage.URI_SCHEMA+"://", "").replace("/", "")+"==")
                transient_id = RNS.Identity.full_hash(lxmf_data)
                
                router_propagation_result = self.lxmf_propagation(lxmf_data, signal_local_delivery=signal_local_delivery, signal_duplicate=signal_duplicate, allow_duplicate=allow_duplicate, is_paper_message=True)
                if router_propagation_result != False:
                    RNS.log("LXM with transient ID "+RNS.prettyhexrep(transient_id)+" was ingested.", RNS.LOG_DEBUG)
                    return router_propagation_result
                else:
                    RNS.log("No valid LXM could be ingested from the provided URI", RNS.LOG_DEBUG)
                    return False

        except Exception as e:
            RNS.log("Error while decoding URI-encoded LXMF message. The contained exception was: "+str(e), RNS.LOG_ERROR)
            return False

    def fail_message(self, lxmessage):
        RNS.log(str(lxmessage)+" failed to send", RNS.LOG_DEBUG)

        if lxmessage in self.pending_outbound:
            self.pending_outbound.remove(lxmessage)

        self.failed_outbound.append(lxmessage)

        if lxmessage.state != LXMessage.REJECTED:
            lxmessage.state = LXMessage.FAILED

        if lxmessage.failed_callback != None and callable(lxmessage.failed_callback):
            lxmessage.failed_callback(lxmessage)

    def process_deferred_stamps(self):
        if len(self.pending_deferred_stamps) > 0:

            if self.stamp_gen_lock.locked():
                return

            else:
                with self.stamp_gen_lock:
                    selected_lxm = None
                    selected_message_id = None
                    for message_id in self.pending_deferred_stamps:
                        lxmessage = self.pending_deferred_stamps[message_id]
                        if selected_lxm == None:
                            selected_lxm = lxmessage
                            selected_message_id = message_id

                    if selected_lxm != None:
                        if selected_lxm.state == LXMessage.CANCELLED:
                            RNS.log(f"Message cancelled during deferred stamp generation for {selected_lxm}.", RNS.LOG_DEBUG)
                            selected_lxm.stamp_generation_failed = True
                            self.pending_deferred_stamps.pop(selected_message_id)
                            if selected_lxm.failed_callback != None and callable(selected_lxm.failed_callback):
                                selected_lxm.failed_callback(lxmessage)
                            
                            return

                        if selected_lxm.defer_stamp:
                            if selected_lxm.stamp == None: stamp_generation_success = False
                            else:                          stamp_generation_success = True
                        else:                              stamp_generation_success = True

                        if selected_lxm.desired_method == LXMessage.PROPAGATED:
                            if selected_lxm.propagation_stamp == None: propagation_stamp_generation_success = False
                            else:                                      propagation_stamp_generation_success = True
                        else:                                          propagation_stamp_generation_success = True

                        if stamp_generation_success == False:
                            RNS.log(f"Starting stamp generation for {selected_lxm}...", RNS.LOG_DEBUG)
                            generated_stamp = selected_lxm.get_stamp()
                            if generated_stamp:
                                selected_lxm.stamp = generated_stamp
                                selected_lxm.defer_stamp = False
                                selected_lxm.packed = None
                                selected_lxm.pack()
                                stamp_generation_success = True
                                RNS.log(f"Stamp generation completed for {selected_lxm}", RNS.LOG_DEBUG)
                            else:
                                if selected_lxm.state == LXMessage.CANCELLED:
                                    RNS.log(f"Message cancelled during deferred stamp generation for {selected_lxm}.", RNS.LOG_DEBUG)
                                    selected_lxm.stamp_generation_failed = True
                                    self.pending_deferred_stamps.pop(selected_message_id)
                                    if selected_lxm.failed_callback != None and callable(selected_lxm.failed_callback):
                                        selected_lxm.failed_callback(lxmessage)
                                else:
                                    RNS.log(f"Deferred stamp generation did not succeed. Failing {selected_lxm}.", RNS.LOG_ERROR)
                                    selected_lxm.stamp_generation_failed = True
                                    self.pending_deferred_stamps.pop(selected_message_id)
                                    self.fail_message(selected_lxm)

                        if propagation_stamp_generation_success == False:
                            RNS.log(f"Starting propagation stamp generation for {selected_lxm}...", RNS.LOG_DEBUG)
                            pn_target_cost = self.get_outbound_propagation_cost()
                            if pn_target_cost == None:
                                RNS.log("Failed to get propagation node stamp cost, cannot generate propagation stamp", RNS.LOG_ERROR)
                                selected_lxm.stamp_generation_failed = True
                                self.pending_deferred_stamps.pop(selected_message_id)
                                self.fail_message(selected_lxm)

                            else:
                                propagation_stamp = selected_lxm.get_propagation_stamp(target_cost=pn_target_cost)
                                if propagation_stamp:
                                    selected_lxm.propagation_stamp = propagation_stamp
                                    selected_lxm.defer_propagation_stamp = False
                                    selected_lxm.packed = None
                                    selected_lxm.pack()
                                    propagation_stamp_generation_success = True
                                    RNS.log(f"Propagation stamp generation completed for {selected_lxm}", RNS.LOG_DEBUG)
                                else:
                                    if selected_lxm.state == LXMessage.CANCELLED:
                                        RNS.log(f"Message cancelled during deferred propagation stamp generation for {selected_lxm}.", RNS.LOG_DEBUG)
                                        selected_lxm.stamp_generation_failed = True
                                        self.pending_deferred_stamps.pop(selected_message_id)
                                        if selected_lxm.failed_callback != None and callable(selected_lxm.failed_callback):
                                            selected_lxm.failed_callback(lxmessage)
                                    else:
                                        RNS.log(f"Deferred propagation stamp generation did not succeed. Failing {selected_lxm}.", RNS.LOG_ERROR)
                                        selected_lxm.stamp_generation_failed = True
                                        self.pending_deferred_stamps.pop(selected_message_id)
                                        self.fail_message(selected_lxm)

                        if stamp_generation_success and propagation_stamp_generation_success:
                            self.pending_deferred_stamps.pop(selected_message_id)
                            self.pending_outbound.append(selected_lxm)

    def propagation_transfer_signalling_packet(self, data, packet):
        try:
            unpacked = msgpack.unpackb(data)
            if type(unpacked) == list and len(unpacked) >= 1:
                signal = unpacked[0]
                if signal == LXMPeer.ERROR_INVALID_STAMP:
                    RNS.log("Message rejected by propagation node", RNS.LOG_ERROR)
                    if hasattr(packet, "link") and hasattr(packet.link, "for_lxmessage"):
                        lxm = packet.link.for_lxmessage
                        RNS.log(f"Invalid propagation stamp on {lxm}", RNS.LOG_ERROR)
                        self.cancel_outbound(lxm.message_id, cancel_state=LXMessage.REJECTED)

        except Exception as e:
            RNS.log(f"An error occurred while processing propagation transfer signalling. The contained exception was: {e}", RNS.LOG_ERROR)

    def process_outbound(self, sender = None):
        if self.processing_outbound:
            return

        for lxmessage in self.pending_outbound:
            if lxmessage.state == LXMessage.DELIVERED:
                RNS.log("Delivery has occurred for "+str(lxmessage)+", removing from outbound queue", RNS.LOG_DEBUG)
                self.pending_outbound.remove(lxmessage)

                # Udate ticket delivery stats
                if lxmessage.include_ticket and FIELD_TICKET in lxmessage.fields:
                    RNS.log(f"Updating latest ticket delivery for {RNS.prettyhexrep(lxmessage.destination_hash)}", RNS.LOG_DEBUG)
                    self.available_tickets["last_deliveries"][lxmessage.destination_hash] = time.time()
                    self.save_available_tickets()

                # Prepare link for backchannel communications
                delivery_destination_hash = lxmessage.get_destination().hash
                if lxmessage.method == LXMessage.DIRECT and delivery_destination_hash in self.direct_links:
                    direct_link = self.direct_links[delivery_destination_hash]
                    if not hasattr(direct_link, "backchannel_identified") or direct_link.backchannel_identified == False:
                        if direct_link.initiator == True:
                            source_destination_hash = lxmessage.get_source().hash
                            if source_destination_hash in self.delivery_destinations:
                                backchannel_identity = self.delivery_destinations[source_destination_hash].identity
                                backchannel_desthash = RNS.Destination.hash_from_name_and_identity("lxmf.delivery", backchannel_identity)
                                direct_link.identify(backchannel_identity)
                                direct_link.backchannel_identified = True
                                self.delivery_link_established(direct_link)
                                RNS.log(f"Performed backchannel identification as {RNS.prettyhexrep(backchannel_desthash)} on {direct_link}", RNS.LOG_DEBUG)

            elif lxmessage.method == LXMessage.PROPAGATED and lxmessage.state == LXMessage.SENT:
                RNS.log("Propagation has occurred for "+str(lxmessage)+", removing from outbound queue", RNS.LOG_DEBUG)
                self.pending_outbound.remove(lxmessage)

            elif lxmessage.state == LXMessage.CANCELLED:
                RNS.log("Cancellation requested for "+str(lxmessage)+", removing from outbound queue", RNS.LOG_DEBUG)
                self.pending_outbound.remove(lxmessage)
                if lxmessage.failed_callback != None and callable(lxmessage.failed_callback):
                    lxmessage.failed_callback(lxmessage)

            elif lxmessage.state == LXMessage.REJECTED:
                RNS.log("Receiver rejected "+str(lxmessage)+", removing from outbound queue", RNS.LOG_DEBUG)
                if lxmessage in self.pending_outbound: self.pending_outbound.remove(lxmessage)
                if lxmessage.failed_callback != None and callable(lxmessage.failed_callback):
                    lxmessage.failed_callback(lxmessage)

            else:
                RNS.log("Outbound processing for "+str(lxmessage)+" to "+RNS.prettyhexrep(lxmessage.get_destination().hash), RNS.LOG_DEBUG)

                if lxmessage.progress == None or lxmessage.progress < 0.01: lxmessage.progress = 0.01

                # Outbound handling for opportunistic messages
                if lxmessage.method == LXMessage.OPPORTUNISTIC:
                    if lxmessage.delivery_attempts <= LXMRouter.MAX_DELIVERY_ATTEMPTS:
                        if lxmessage.delivery_attempts >= LXMRouter.MAX_PATHLESS_TRIES and not RNS.Transport.has_path(lxmessage.get_destination().hash):
                            RNS.log(f"Requesting path to {RNS.prettyhexrep(lxmessage.get_destination().hash)} after {lxmessage.delivery_attempts} pathless tries for {lxmessage}", RNS.LOG_DEBUG)
                            lxmessage.delivery_attempts += 1
                            RNS.Transport.request_path(lxmessage.get_destination().hash)
                            lxmessage.next_delivery_attempt = time.time() + LXMRouter.PATH_REQUEST_WAIT
                            lxmessage.progress = 0.01
                        elif lxmessage.delivery_attempts == LXMRouter.MAX_PATHLESS_TRIES+1 and RNS.Transport.has_path(lxmessage.get_destination().hash):
                            RNS.log(f"Opportunistic delivery for {lxmessage} still unsuccessful after {lxmessage.delivery_attempts} attempts, trying to rediscover path to {RNS.prettyhexrep(lxmessage.get_destination().hash)}", RNS.LOG_DEBUG)
                            lxmessage.delivery_attempts += 1
                            RNS.Reticulum.get_instance().drop_path(lxmessage.get_destination().hash)
                            def rediscover_job():
                                time.sleep(0.5)
                                RNS.Transport.request_path(lxmessage.get_destination().hash)
                            threading.Thread(target=rediscover_job, daemon=True).start()
                            lxmessage.next_delivery_attempt = time.time() + LXMRouter.PATH_REQUEST_WAIT
                            lxmessage.progress = 0.01
                        else:
                            if not hasattr(lxmessage, "next_delivery_attempt") or time.time() > lxmessage.next_delivery_attempt:
                                lxmessage.delivery_attempts += 1
                                lxmessage.next_delivery_attempt = time.time() + LXMRouter.DELIVERY_RETRY_WAIT
                                RNS.log("Opportunistic delivery attempt "+str(lxmessage.delivery_attempts)+" for "+str(lxmessage)+" to "+RNS.prettyhexrep(lxmessage.get_destination().hash), RNS.LOG_DEBUG)
                                lxmessage.send()
                    else:
                        RNS.log("Max delivery attempts reached for oppertunistic "+str(lxmessage)+" to "+RNS.prettyhexrep(lxmessage.get_destination().hash), RNS.LOG_DEBUG)
                        self.fail_message(lxmessage)

                # Outbound handling for messages transferred
                # over a direct link to the final recipient
                elif lxmessage.method == LXMessage.DIRECT:
                    if lxmessage.delivery_attempts <= LXMRouter.MAX_DELIVERY_ATTEMPTS:
                        delivery_destination_hash = lxmessage.get_destination().hash
                        direct_link = None
                        
                        if delivery_destination_hash in self.direct_links:
                            # An established direct link already exists to
                            # the destination, so we'll try to use it for
                            # delivering the message
                            direct_link = self.direct_links[delivery_destination_hash]
                            RNS.log(f"Using available direct link {direct_link} to {RNS.prettyhexrep(delivery_destination_hash)}", RNS.LOG_DEBUG)

                        elif delivery_destination_hash in self.backchannel_links:
                            # An established backchannel link exists to
                            # the destination, so we'll try to use it for
                            # delivering the message
                            direct_link = self.backchannel_links[delivery_destination_hash]
                            RNS.log(f"Using available backchannel link {direct_link} to {RNS.prettyhexrep(delivery_destination_hash)}", RNS.LOG_DEBUG)

                        if direct_link != None:
                            if direct_link.status == RNS.Link.ACTIVE:
                                if lxmessage.progress == None or lxmessage.progress < 0.05:
                                    lxmessage.progress = 0.05
                                if lxmessage.state != LXMessage.SENDING:
                                    RNS.log("Starting transfer of "+str(lxmessage)+" to "+RNS.prettyhexrep(lxmessage.get_destination().hash)+" on link "+str(direct_link), RNS.LOG_DEBUG)
                                    lxmessage.set_delivery_destination(direct_link)
                                    lxmessage.send()
                                else:
                                    if lxmessage.representation == LXMessage.RESOURCE:
                                        RNS.log("The transfer of "+str(lxmessage)+" is in progress ("+str(round(lxmessage.progress*100, 1))+"%)", RNS.LOG_DEBUG)
                                    else:
                                        RNS.log("Waiting for proof for "+str(lxmessage)+" sent as link packet", RNS.LOG_DEBUG)
                            elif direct_link.status == RNS.Link.CLOSED:
                                if direct_link.activated_at != None:
                                    RNS.log("The link to "+RNS.prettyhexrep(lxmessage.get_destination().hash)+" was closed unexpectedly, retrying path request...", RNS.LOG_DEBUG)
                                    RNS.Transport.request_path(lxmessage.get_destination().hash)
                                else:
                                    if not hasattr(lxmessage, "path_request_retried"):
                                        RNS.log("The link to "+RNS.prettyhexrep(lxmessage.get_destination().hash)+" was never activated, retrying path request...", RNS.LOG_DEBUG)
                                        RNS.Transport.request_path(lxmessage.get_destination().hash)
                                        lxmessage.path_request_retried = True
                                    else:
                                        RNS.log("The link to "+RNS.prettyhexrep(lxmessage.get_destination().hash)+" was never activated", RNS.LOG_DEBUG)

                                    lxmessage.next_delivery_attempt = time.time() + LXMRouter.PATH_REQUEST_WAIT

                                lxmessage.set_delivery_destination(None)
                                if delivery_destination_hash in self.direct_links:
                                    self.direct_links.pop(delivery_destination_hash)
                                if delivery_destination_hash in self.backchannel_links:
                                    self.backchannel_links.pop(delivery_destination_hash)
                                lxmessage.next_delivery_attempt = time.time() + LXMRouter.DELIVERY_RETRY_WAIT
                            else:
                                # Simply wait for the link to become active or close
                                RNS.log("The link to "+RNS.prettyhexrep(lxmessage.get_destination().hash)+" is pending, waiting for link to become active", RNS.LOG_DEBUG)
                        else:
                            # No link exists, so we'll try to establish one, but
                            # only if we've never tried before, or the retry wait
                            # period has elapsed.
                            if not hasattr(lxmessage, "next_delivery_attempt") or time.time() > lxmessage.next_delivery_attempt:
                                lxmessage.delivery_attempts += 1
                                lxmessage.next_delivery_attempt = time.time() + LXMRouter.DELIVERY_RETRY_WAIT

                                if lxmessage.delivery_attempts < LXMRouter.MAX_DELIVERY_ATTEMPTS:
                                    if RNS.Transport.has_path(lxmessage.get_destination().hash):
                                        RNS.log("Establishing link to "+RNS.prettyhexrep(lxmessage.get_destination().hash)+" for delivery attempt "+str(lxmessage.delivery_attempts)+" to "+RNS.prettyhexrep(lxmessage.get_destination().hash), RNS.LOG_DEBUG)
                                        delivery_link = RNS.Link(lxmessage.get_destination())
                                        delivery_link.set_link_established_callback(self.process_outbound)
                                        self.direct_links[delivery_destination_hash] = delivery_link
                                        lxmessage.progress = 0.03
                                    else:
                                        RNS.log("No path known for delivery attempt "+str(lxmessage.delivery_attempts)+" to "+RNS.prettyhexrep(lxmessage.get_destination().hash)+". Requesting path...", RNS.LOG_DEBUG)
                                        RNS.Transport.request_path(lxmessage.get_destination().hash)
                                        lxmessage.next_delivery_attempt = time.time() + LXMRouter.PATH_REQUEST_WAIT
                                        lxmessage.progress = 0.01
                    else:
                        RNS.log("Max delivery attempts reached for direct "+str(lxmessage)+" to "+RNS.prettyhexrep(lxmessage.get_destination().hash), RNS.LOG_DEBUG)
                        self.fail_message(lxmessage)

                # Outbound handling for messages transported via
                # propagation to a LXMF router network.
                elif lxmessage.method == LXMessage.PROPAGATED:
                    RNS.log("Attempting propagated delivery for "+str(lxmessage)+" to "+RNS.prettyhexrep(lxmessage.get_destination().hash), RNS.LOG_DEBUG)

                    if self.outbound_propagation_node == None:
                        RNS.log("No outbound propagation node specified for propagated "+str(lxmessage)+" to "+RNS.prettyhexrep(lxmessage.get_destination().hash), RNS.LOG_ERROR)
                        self.fail_message(lxmessage)
                    else:
                        if lxmessage.delivery_attempts <= LXMRouter.MAX_DELIVERY_ATTEMPTS:

                            if self.outbound_propagation_link != None:
                                # A link already exists, so we'll try to use it
                                # to deliver the message
                                if self.outbound_propagation_link.status == RNS.Link.ACTIVE:
                                    if lxmessage.state != LXMessage.SENDING:
                                        RNS.log("Starting propagation transfer of "+str(lxmessage)+" to "+RNS.prettyhexrep(lxmessage.get_destination().hash)+" via "+RNS.prettyhexrep(self.outbound_propagation_node), RNS.LOG_DEBUG)
                                        lxmessage.set_delivery_destination(self.outbound_propagation_link)
                                        lxmessage.send()
                                    else:
                                        if lxmessage.representation == LXMessage.RESOURCE:
                                            RNS.log("The transfer of "+str(lxmessage)+" is in progress ("+str(round(lxmessage.progress*100, 1))+"%)", RNS.LOG_DEBUG)
                                        else:
                                            RNS.log("Waiting for proof for "+str(lxmessage)+" sent as link packet", RNS.LOG_DEBUG)
                                elif self.outbound_propagation_link.status == RNS.Link.CLOSED:
                                    RNS.log("The link to "+RNS.prettyhexrep(self.outbound_propagation_node)+" was closed", RNS.LOG_DEBUG)
                                    self.outbound_propagation_link = None
                                    lxmessage.next_delivery_attempt = time.time() + LXMRouter.DELIVERY_RETRY_WAIT
                                else:
                                    # Simply wait for the link to become
                                    # active or close
                                    RNS.log("The propagation link to "+RNS.prettyhexrep(self.outbound_propagation_node)+" is pending, waiting for link to become active", RNS.LOG_DEBUG)
                            else:
                                # No link exists, so we'll try to establish one, but
                                # only if we've never tried before, or the retry wait
                                # period has elapsed.
                                if not hasattr(lxmessage, "next_delivery_attempt") or time.time() > lxmessage.next_delivery_attempt:
                                    lxmessage.delivery_attempts += 1
                                    lxmessage.next_delivery_attempt = time.time() + LXMRouter.DELIVERY_RETRY_WAIT

                                    if lxmessage.delivery_attempts < LXMRouter.MAX_DELIVERY_ATTEMPTS:
                                        if RNS.Transport.has_path(self.outbound_propagation_node):
                                            RNS.log("Establishing link to "+RNS.prettyhexrep(self.outbound_propagation_node)+" for propagation attempt "+str(lxmessage.delivery_attempts)+" to "+RNS.prettyhexrep(lxmessage.get_destination().hash), RNS.LOG_DEBUG)
                                            propagation_node_identity = RNS.Identity.recall(self.outbound_propagation_node)
                                            propagation_node_destination = RNS.Destination(propagation_node_identity, RNS.Destination.OUT, RNS.Destination.SINGLE, APP_NAME, "propagation")
                                            self.outbound_propagation_link = RNS.Link(propagation_node_destination, established_callback=self.process_outbound)
                                            self.outbound_propagation_link.set_packet_callback(self.propagation_transfer_signalling_packet)
                                            self.outbound_propagation_link.for_lxmessage = lxmessage
                                        else:
                                            RNS.log("No path known for propagation attempt "+str(lxmessage.delivery_attempts)+" to "+RNS.prettyhexrep(self.outbound_propagation_node)+". Requesting path...", RNS.LOG_DEBUG)
                                            RNS.Transport.request_path(self.outbound_propagation_node)
                                            lxmessage.next_delivery_attempt = time.time() + LXMRouter.PATH_REQUEST_WAIT

                        else:
                            RNS.log("Max delivery attempts reached for propagated "+str(lxmessage)+" to "+RNS.prettyhexrep(lxmessage.get_destination().hash), RNS.LOG_DEBUG)
                            self.fail_message(lxmessage)