Initial work on Channel

RNS/Channel.py

@@ -0,0 +1,350 @@
+from __future__ import annotations
+import collections
+import enum
+import threading
+import time
+from types import TracebackType
+from typing import Type, Callable, TypeVar
+import abc
+import contextlib
+import struct
+import RNS
+from abc import ABC, abstractmethod
+_TPacket = TypeVar("_TPacket")
+
+
+class ChannelOutletBase(ABC):
+    @abstractmethod
+    def send(self, raw: bytes) -> _TPacket:
+        raise NotImplemented()
+
+    @abstractmethod
+    def resend(self, packet: _TPacket) -> _TPacket:
+        raise NotImplemented()
+
+    @property
+    @abstractmethod
+    def mdu(self):
+        raise NotImplemented()
+
+    @property
+    @abstractmethod
+    def rtt(self):
+        raise NotImplemented()
+
+    @property
+    @abstractmethod
+    def is_usable(self):
+        raise NotImplemented()
+
+    @abstractmethod
+    def get_packet_state(self, packet: _TPacket) -> MessageState:
+        raise NotImplemented()
+
+    @abstractmethod
+    def timed_out(self):
+        raise NotImplemented()
+
+    @abstractmethod
+    def __str__(self):
+        raise NotImplemented()
+
+    @abstractmethod
+    def set_packet_timeout_callback(self, packet: _TPacket, callback: Callable[[_TPacket], None] | None,
+                                    timeout: float | None = None):
+        raise NotImplemented()
+
+    @abstractmethod
+    def set_packet_delivered_callback(self, packet: _TPacket, callback: Callable[[_TPacket], None] | None):
+        raise NotImplemented()
+
+    @abstractmethod
+    def get_packet_id(self, packet: _TPacket) -> any:
+        raise NotImplemented()
+
+
+class CEType(enum.IntEnum):
+    ME_NO_MSG_TYPE      = 0
+    ME_INVALID_MSG_TYPE = 1
+    ME_NOT_REGISTERED   = 2
+    ME_LINK_NOT_READY   = 3
+    ME_ALREADY_SENT     = 4
+    ME_TOO_BIG          = 5
+
+
+class ChannelException(Exception):
+    def __init__(self, ce_type: CEType, *args):
+        super().__init__(args)
+        self.type = ce_type
+
+
+class MessageState(enum.IntEnum):
+    MSGSTATE_NEW       = 0
+    MSGSTATE_SENT      = 1
+    MSGSTATE_DELIVERED = 2
+    MSGSTATE_FAILED    = 3
+
+
+class MessageBase(abc.ABC):
+    MSGTYPE = None
+
+    @abstractmethod
+    def pack(self) -> bytes:
+        raise NotImplemented()
+
+    @abstractmethod
+    def unpack(self, raw):
+        raise NotImplemented()
+
+
+class Envelope:
+    def unpack(self, message_factories: dict[int, Type]) -> MessageBase:
+        msgtype, self.sequence, length = struct.unpack(">HHH", self.raw[:6])
+        raw = self.raw[6:]
+        ctor = message_factories.get(msgtype, None)
+        if ctor is None:
+            raise ChannelException(CEType.ME_NOT_REGISTERED, f"Unable to find constructor for Channel MSGTYPE {hex(msgtype)}")
+        message = ctor()
+        message.unpack(raw)
+        return message
+
+    def pack(self) -> bytes:
+        if self.message.__class__.MSGTYPE is None:
+            raise ChannelException(CEType.ME_NO_MSG_TYPE, f"{self.message.__class__} lacks MSGTYPE")
+        data = self.message.pack()
+        self.raw = struct.pack(">HHH", self.message.MSGTYPE, self.sequence, len(data)) + data
+        return self.raw
+
+    def __init__(self, outlet: ChannelOutletBase, message: MessageBase = None, raw: bytes = None, sequence: int = None):
+        self.ts = time.time()
+        self.id = id(self)
+        self.message = message
+        self.raw = raw
+        self.packet: _TPacket = None
+        self.sequence = sequence
+        self.outlet = outlet
+        self.tries = 0
+        self.tracked = False
+
+
+class Channel(contextlib.AbstractContextManager):
+    def __init__(self, outlet: ChannelOutletBase):
+        self._outlet = outlet
+        self._lock = threading.RLock()
+        self._tx_ring: collections.deque[Envelope] = collections.deque()
+        self._rx_ring: collections.deque[Envelope] = collections.deque()
+        self._message_callback: Callable[[MessageBase], None] | None = None
+        self._next_sequence = 0
+        self._message_factories: dict[int, Type[MessageBase]] = self._get_msg_constructors()
+        self._max_tries = 5
+
+    def __enter__(self) -> Channel:
+        return self
+
+    def __exit__(self, __exc_type: Type[BaseException] | None, __exc_value: BaseException | None,
+                 __traceback: TracebackType | None) -> bool | None:
+        self.shutdown()
+        return False
+
+    @staticmethod
+    def _get_msg_constructors() -> (int, Type[MessageBase]):
+        subclass_tuples = []
+        for subclass in MessageBase.__subclasses__():
+            with contextlib.suppress(Exception):
+                subclass()  # verify constructor works with no arguments, needed for unpacking
+                subclass_tuples.append((subclass.MSGTYPE, subclass))
+        message_factories = dict(subclass_tuples)
+        return message_factories
+
+    def register_message_type(self, message_class: Type[MessageBase]):
+        if not issubclass(message_class, MessageBase):
+            raise ChannelException(CEType.ME_INVALID_MSG_TYPE, f"{message_class} is not a subclass of {MessageBase}.")
+        if message_class.MSGTYPE is None:
+            raise ChannelException(CEType.ME_INVALID_MSG_TYPE, f"{message_class} has invalid MSGTYPE class attribute.")
+        try:
+            message_class()
+        except Exception as ex:
+            raise ChannelException(CEType.ME_INVALID_MSG_TYPE,
+                                     f"{message_class} raised an exception when constructed with no arguments: {ex}")
+
+        self._message_factories[message_class.MSGTYPE] = message_class
+
+    def set_message_callback(self, callback: Callable[[MessageBase], None]):
+        self._message_callback = callback
+
+    def shutdown(self):
+        self.clear_rings()
+
+    def clear_rings(self):
+        with self._lock:
+            for envelope in self._tx_ring:
+                if envelope.packet is not None:
+                    self._outlet.set_packet_timeout_callback(envelope.packet, None)
+                    self._outlet.set_packet_delivered_callback(envelope.packet, None)
+            self._tx_ring.clear()
+            self._rx_ring.clear()
+
+    def emplace_envelope(self, envelope: Envelope, ring: collections.deque[Envelope]) -> bool:
+        with self._lock:
+            i = 0
+            for env in ring:
+                if env.sequence < envelope.sequence:
+                    ring.insert(i, envelope)
+                    return True
+                if env.sequence == envelope.sequence:
+                    RNS.log(f"Envelope: Emplacement of duplicate envelope sequence.", RNS.LOG_EXTREME)
+                    return False
+                i += 1
+            envelope.tracked = True
+            ring.append(envelope)
+            return True
+
+    def prune_rx_ring(self):
+        with self._lock:
+            # Implementation for fixed window = 1
+            stale = list(sorted(self._rx_ring, key=lambda env: env.sequence, reverse=True))[1:]
+            for env in stale:
+                env.tracked = False
+                self._rx_ring.remove(env)
+
+    def receive(self, raw: bytes):
+        try:
+            envelope = Envelope(outlet=self._outlet, raw=raw)
+            message = envelope.unpack(self._message_factories)
+            with self._lock:
+                is_new = self.emplace_envelope(envelope, self._rx_ring)
+                self.prune_rx_ring()
+            if not is_new:
+                RNS.log("Channel: Duplicate message received", RNS.LOG_DEBUG)
+                return
+            RNS.log(f"Message received: {message}", RNS.LOG_DEBUG)
+            if self._message_callback:
+                threading.Thread(target=self._message_callback, name="Message Callback", args=[message], daemon=True)\
+                    .start()
+        except Exception as ex:
+            RNS.log(f"Channel: Error receiving data: {ex}")
+
+    def is_ready_to_send(self) -> bool:
+        if not self._outlet.is_usable:
+            RNS.log("Channel: Link is not usable.", RNS.LOG_EXTREME)
+            return False
+
+        with self._lock:
+            for envelope in self._tx_ring:
+                if envelope.outlet == self._outlet and (not envelope.packet
+                                                        or self._outlet.get_packet_state(envelope.packet) == MessageState.MSGSTATE_SENT):
+                    RNS.log("Channel: Link has a pending message.", RNS.LOG_EXTREME)
+                    return False
+        return True
+
+    def _packet_tx_op(self, packet: _TPacket, op: Callable[[_TPacket], bool]):
+        with self._lock:
+            envelope = next(filter(lambda e: self._outlet.get_packet_id(e.packet) == self._outlet.get_packet_id(packet),
+                                   self._tx_ring), None)
+            if envelope and op(envelope):
+                envelope.tracked = False
+                if envelope in self._tx_ring:
+                    self._tx_ring.remove(envelope)
+                else:
+                    RNS.log("Channel: Envelope not found in TX ring", RNS.LOG_DEBUG)
+        if not envelope:
+            RNS.log("Channel: Spurious message received.", RNS.LOG_EXTREME)
+
+    def _packet_delivered(self, packet: _TPacket):
+        self._packet_tx_op(packet, lambda env: True)
+
+    def _packet_timeout(self, packet: _TPacket):
+        def retry_envelope(envelope: Envelope) -> bool:
+            if envelope.tries >= self._max_tries:
+                RNS.log("Channel: Retry count exceeded, tearing down Link.", RNS.LOG_ERROR)
+                self.shutdown()  # start on separate thread?
+                self._outlet.timed_out()
+                return True
+            envelope.tries += 1
+            self._outlet.resend(envelope.packet)
+            return False
+
+        self._packet_tx_op(packet, retry_envelope)
+
+    def send(self, message: MessageBase) -> Envelope:
+        envelope: Envelope | None = None
+        with self._lock:
+            if not self.is_ready_to_send():
+                raise ChannelException(CEType.ME_LINK_NOT_READY, f"Link is not ready")
+            envelope = Envelope(self._outlet, message=message, sequence=self._next_sequence)
+            self._next_sequence = (self._next_sequence + 1) % 0x10000
+            self.emplace_envelope(envelope, self._tx_ring)
+        if envelope is None:
+            raise BlockingIOError()
+
+        envelope.pack()
+        if len(envelope.raw) > self._outlet.mdu:
+            raise ChannelException(CEType.ME_TOO_BIG, f"Packed message too big for packet: {len(envelope.raw)} > {self._outlet.mdu}")
+        envelope.packet = self._outlet.send(envelope.raw)
+        envelope.tries += 1
+        self._outlet.set_packet_delivered_callback(envelope.packet, self._packet_delivered)
+        self._outlet.set_packet_timeout_callback(envelope.packet, self._packet_timeout)
+        return envelope
+
+
+class LinkChannelOutlet(ChannelOutletBase):
+    def __init__(self, link: RNS.Link):
+        self.link = link
+
+    def send(self, raw: bytes) -> RNS.Packet:
+        packet = RNS.Packet(self.link, raw, context=RNS.Packet.CHANNEL)
+        packet.send()
+        return packet
+
+    def resend(self, packet: RNS.Packet) -> RNS.Packet:
+        if not packet.resend():
+            RNS.log("Failed to resend packet", RNS.LOG_ERROR)
+        return packet
+
+    @property
+    def mdu(self):
+        return self.link.MDU
+
+    @property
+    def rtt(self):
+        return self.link.rtt
+
+    @property
+    def is_usable(self):
+        return True  # had issues looking at Link.status
+
+    def get_packet_state(self, packet: _TPacket) -> MessageState:
+        status = packet.receipt.get_status()
+        if status == RNS.PacketReceipt.SENT:
+            return MessageState.MSGSTATE_SENT
+        if status == RNS.PacketReceipt.DELIVERED:
+            return MessageState.MSGSTATE_DELIVERED
+        if status == RNS.PacketReceipt.FAILED:
+            return MessageState.MSGSTATE_FAILED
+        else:
+            raise Exception(f"Unexpected receipt state: {status}")
+
+    def timed_out(self):
+        self.link.teardown()
+
+    def __str__(self):
+        return f"{self.__class__.__name__}({self.link})"
+
+    def set_packet_timeout_callback(self, packet: RNS.Packet, callback: Callable[[RNS.Packet], None] | None,
+                                    timeout: float | None = None):
+        if timeout:
+            packet.receipt.set_timeout(timeout)
+
+        def inner(receipt: RNS.PacketReceipt):
+            callback(packet)
+
+        packet.receipt.set_timeout_callback(inner if callback else None)
+
+    def set_packet_delivered_callback(self, packet: RNS.Packet, callback: Callable[[RNS.Packet], None] | None):
+        def inner(receipt: RNS.PacketReceipt):
+            callback(packet)
+
+        packet.receipt.set_delivery_callback(inner if callback else None)
+
+    def get_packet_id(self, packet: RNS.Packet) -> any:
+        return packet.get_hash()

RNS/Link.py

@@ -22,7 +22,7 @@
 
 from RNS.Cryptography import X25519PrivateKey, X25519PublicKey, Ed25519PrivateKey, Ed25519PublicKey
 from RNS.Cryptography import Fernet
-
+from RNS.Channel import Channel, LinkChannelOutlet
 from time import sleep
 from .vendor import umsgpack as umsgpack
 import threading
@@ -163,6 +163,7 @@ class Link:
         self.destination = destination
         self.attached_interface = None
         self.__remote_identity = None
+        self._channel = None
         if self.destination == None:
             self.initiator = False
             self.prv     = X25519PrivateKey.generate()
@@ -462,6 +463,8 @@ class Link:
             resource.cancel()
         for resource in self.outgoing_resources:
             resource.cancel()
+        if self._channel:
+            self._channel.shutdown()
             
         self.prv = None
         self.pub = None
@@ -642,6 +645,27 @@ class Link:
                 if pending_request.request_id == resource.request_id:
                     pending_request.request_timed_out(None)
 
+    def _ensure_channel(self):
+        if self._channel is None:
+            self._channel = Channel(LinkChannelOutlet(self))
+        return self._channel
+
+    def set_message_callback(self, callback, message_types=None):
+        if not callback:
+            if self._channel:
+                self._channel.set_message_callback(None)
+                return
+
+        self._ensure_channel()
+
+        if message_types:
+            for msg_type in message_types:
+                self._channel.register_message_type(msg_type)
+        self._channel.set_message_callback(callback)
+
+    def send_message(self, message: RNS.Channel.MessageBase):
+        self._ensure_channel().send(message)
+
     def receive(self, packet):
         self.watchdog_lock = True
         if not self.status == Link.CLOSED and not (self.initiator and packet.context == RNS.Packet.KEEPALIVE and packet.data == bytes([0xFF])):
@@ -788,6 +812,14 @@ class Link:
                         for resource in self.incoming_resources:
                             resource.receive_part(packet)
 
+                    elif packet.context == RNS.Packet.CHANNEL:
+                        if not self._channel:
+                            RNS.log(f"Channel data received without open channel", RNS.LOG_DEBUG)
+                        else:
+                            plaintext = self.decrypt(packet.data)
+                            self._channel.receive(plaintext)
+                            packet.prove()
+
                 elif packet.packet_type == RNS.Packet.PROOF:
                     if packet.context == RNS.Packet.RESOURCE_PRF:
                         resource_hash = packet.data[0:RNS.Identity.HASHLENGTH//8]

RNS/Packet.py

@@ -75,6 +75,7 @@ class Packet:
     PATH_RESPONSE  = 0x0B   # Packet is a response to a path request
     COMMAND        = 0x0C   # Packet is a command
     COMMAND_STATUS = 0x0D   # Packet is a status of an executed command
+    CHANNEL        = 0x0E   # Packet contains link channel data
     KEEPALIVE      = 0xFA   # Packet is a keepalive packet
     LINKIDENTIFY   = 0xFB   # Packet is a link peer identification proof
     LINKCLOSE      = 0xFC   # Packet is a link close message

tests/channel.py

@@ -0,0 +1,316 @@
+from __future__ import annotations
+import threading
+import RNS
+from RNS.Channel import MessageState, ChannelOutletBase, Channel, MessageBase
+from RNS.vendor import umsgpack
+from typing import Callable
+import contextlib
+import typing
+import types
+import time
+import uuid
+import unittest
+
+
+class Packet:
+    timeout = 1.0
+
+    def __init__(self, raw: bytes):
+        self.state = MessageState.MSGSTATE_NEW
+        self.raw = raw
+        self.packet_id = uuid.uuid4()
+        self.tries = 0
+        self.timeout_id = None
+        self.lock = threading.RLock()
+        self.instances = 0
+        self.timeout_callback: Callable[[Packet], None] | None = None
+        self.delivered_callback: Callable[[Packet], None] | None = None
+
+    def set_timeout(self, callback: Callable[[Packet], None] | None, timeout: float):
+        with self.lock:
+            if timeout is not None:
+                self.timeout = timeout
+            self.timeout_callback = callback
+
+
+    def send(self):
+        self.tries += 1
+        self.state = MessageState.MSGSTATE_SENT
+
+        def elapsed(timeout: float, timeout_id: uuid.uuid4):
+            with self.lock:
+                self.instances += 1
+            try:
+                time.sleep(timeout)
+                with self.lock:
+                    if self.timeout_id == timeout_id:
+                        self.timeout_id = None
+                        self.state = MessageState.MSGSTATE_FAILED
+                        if self.timeout_callback:
+                            self.timeout_callback(self)
+            finally:
+                with self.lock:
+                    self.instances -= 1
+
+        self.timeout_id = uuid.uuid4()
+        threading.Thread(target=elapsed, name="Packet Timeout", args=[self.timeout, self.timeout_id],
+                         daemon=True).start()
+
+    def clear_timeout(self):
+        self.timeout_id = None
+
+    def set_delivered_callback(self, callback: Callable[[Packet], None]):
+        self.delivered_callback = callback
+        
+    def delivered(self):
+        with self.lock:
+            self.state = MessageState.MSGSTATE_DELIVERED
+            self.timeout_id = None
+        if self.delivered_callback:
+            self.delivered_callback(self)
+
+
+class ChannelOutletTest(ChannelOutletBase):
+    def get_packet_state(self, packet: Packet) -> MessageState:
+        return packet.state
+
+    def set_packet_timeout_callback(self, packet: Packet, callback: Callable[[Packet], None] | None,
+                                    timeout: float | None = None):
+        packet.set_timeout(callback, timeout)
+
+    def set_packet_delivered_callback(self, packet: Packet, callback: Callable[[Packet], None] | None):
+        packet.set_delivered_callback(callback)
+
+    def get_packet_id(self, packet: Packet) -> any:
+        return packet.packet_id
+
+    def __init__(self, mdu: int, rtt: float):
+        self.link_id = uuid.uuid4()
+        self.timeout_callbacks = 0
+        self._mdu = mdu
+        self._rtt = rtt
+        self._usable = True
+        self.packets = []
+        self.packet_callback: Callable[[ChannelOutletBase, bytes], None] | None = None
+
+    def send(self, raw: bytes) -> Packet:
+        packet = Packet(raw)
+        packet.send()
+        self.packets.append(packet)
+        return packet
+
+    def resend(self, packet: Packet) -> Packet:
+        packet.send()
+        return packet
+
+    @property
+    def mdu(self):
+        return self._mdu
+
+    @property
+    def rtt(self):
+        return self._rtt
+
+    @property
+    def is_usable(self):
+        return self._usable
+
+    def timed_out(self):
+        self.timeout_callbacks += 1
+
+    def __str__(self):
+        return str(self.link_id)
+
+
+class MessageTest(MessageBase):
+    MSGTYPE = 0xabcd
+
+    def __init__(self):
+        self.id = str(uuid.uuid4())
+        self.data = "test"
+        self.not_serialized = str(uuid.uuid4())
+
+    def pack(self) -> bytes:
+        return umsgpack.packb((self.id, self.data))
+
+    def unpack(self, raw):
+        self.id, self.data = umsgpack.unpackb(raw)
+
+
+class ProtocolHarness(contextlib.AbstractContextManager):
+    def __init__(self, rtt: float):
+        self.outlet = ChannelOutletTest(mdu=500, rtt=rtt)
+        self.channel = Channel(self.outlet)
+
+    def cleanup(self):
+        self.channel.shutdown()
+
+    def __exit__(self, __exc_type: typing.Type[BaseException], __exc_value: BaseException,
+                 __traceback: types.TracebackType) -> bool:
+        # self._log.debug(f"__exit__({__exc_type}, {__exc_value}, {__traceback})")
+        self.cleanup()
+        return False
+
+
+class TestChannel(unittest.TestCase):
+    def setUp(self) -> None:
+        self.rtt = 0.001
+        self.retry_interval = self.rtt * 150
+        Packet.timeout = self.retry_interval
+        self.h = ProtocolHarness(self.rtt)
+
+    def tearDown(self) -> None:
+        self.h.cleanup()
+
+    def test_send_one_retry(self):
+        message = MessageTest()
+
+        self.assertEqual(0, len(self.h.outlet.packets))
+
+        envelope = self.h.channel.send(message)
+
+        self.assertIsNotNone(envelope)
+        self.assertIsNotNone(envelope.raw)
+        self.assertEqual(1, len(self.h.outlet.packets))
+        self.assertIsNotNone(envelope.packet)
+        self.assertTrue(envelope in self.h.channel._tx_ring)
+        self.assertTrue(envelope.tracked)
+
+        packet = self.h.outlet.packets[0]
+
+        self.assertEqual(envelope.packet, packet)
+        self.assertEqual(1, envelope.tries)
+        self.assertEqual(1, packet.tries)
+        self.assertEqual(1, packet.instances)
+        self.assertEqual(MessageState.MSGSTATE_SENT, packet.state)
+        self.assertEqual(envelope.raw, packet.raw)
+
+        time.sleep(self.retry_interval * 1.5)
+
+        self.assertEqual(1, len(self.h.outlet.packets))
+        self.assertEqual(2, envelope.tries)
+        self.assertEqual(2, packet.tries)
+        self.assertEqual(1, packet.instances)
+
+        time.sleep(self.retry_interval)
+
+        self.assertEqual(1, len(self.h.outlet.packets))
+        self.assertEqual(self.h.outlet.packets[0], packet)
+        self.assertEqual(3, envelope.tries)
+        self.assertEqual(3, packet.tries)
+        self.assertEqual(1, packet.instances)
+        self.assertEqual(MessageState.MSGSTATE_SENT, packet.state)
+
+        packet.delivered()
+
+        self.assertEqual(MessageState.MSGSTATE_DELIVERED, packet.state)
+
+        time.sleep(self.retry_interval)
+
+        self.assertEqual(1, len(self.h.outlet.packets))
+        self.assertEqual(3, envelope.tries)
+        self.assertEqual(3, packet.tries)
+        self.assertEqual(0, packet.instances)
+        self.assertFalse(envelope.tracked)
+
+    def test_send_timeout(self):
+        message = MessageTest()
+
+        self.assertEqual(0, len(self.h.outlet.packets))
+
+        envelope = self.h.channel.send(message)
+
+        self.assertIsNotNone(envelope)
+        self.assertIsNotNone(envelope.raw)
+        self.assertEqual(1, len(self.h.outlet.packets))
+        self.assertIsNotNone(envelope.packet)
+        self.assertTrue(envelope in self.h.channel._tx_ring)
+        self.assertTrue(envelope.tracked)
+
+        packet = self.h.outlet.packets[0]
+
+        self.assertEqual(envelope.packet, packet)
+        self.assertEqual(1, envelope.tries)
+        self.assertEqual(1, packet.tries)
+        self.assertEqual(1, packet.instances)
+        self.assertEqual(MessageState.MSGSTATE_SENT, packet.state)
+        self.assertEqual(envelope.raw, packet.raw)
+
+        time.sleep(self.retry_interval * 7.5)
+
+        self.assertEqual(1, len(self.h.outlet.packets))
+        self.assertEqual(5, envelope.tries)
+        self.assertEqual(5, packet.tries)
+        self.assertEqual(0, packet.instances)
+        self.assertEqual(MessageState.MSGSTATE_FAILED, packet.state)
+        self.assertFalse(envelope.tracked)
+
+    def eat_own_dog_food(self, message: MessageBase, checker: typing.Callable[[MessageBase], None]):
+        decoded: [MessageBase] = []
+
+        def handle_message(message: MessageBase):
+            decoded.append(message)
+
+        self.h.channel.set_message_callback(handle_message)
+        self.assertEqual(len(self.h.outlet.packets), 0)
+
+        envelope = self.h.channel.send(message)
+        time.sleep(self.retry_interval * 0.5)
+
+        self.assertIsNotNone(envelope)
+        self.assertIsNotNone(envelope.raw)
+        self.assertEqual(1, len(self.h.outlet.packets))
+        self.assertIsNotNone(envelope.packet)
+        self.assertTrue(envelope in self.h.channel._tx_ring)
+        self.assertTrue(envelope.tracked)
+
+        packet = self.h.outlet.packets[0]
+
+        self.assertEqual(envelope.packet, packet)
+        self.assertEqual(1, envelope.tries)
+        self.assertEqual(1, packet.tries)
+        self.assertEqual(1, packet.instances)
+        self.assertEqual(MessageState.MSGSTATE_SENT, packet.state)
+        self.assertEqual(envelope.raw, packet.raw)
+
+        packet.delivered()
+
+        self.assertEqual(MessageState.MSGSTATE_DELIVERED, packet.state)
+
+        time.sleep(self.retry_interval * 2)
+
+        self.assertEqual(1, len(self.h.outlet.packets))
+        self.assertEqual(1, envelope.tries)
+        self.assertEqual(1, packet.tries)
+        self.assertEqual(0, packet.instances)
+        self.assertFalse(envelope.tracked)
+
+        self.assertEqual(len(self.h.outlet.packets), 1)
+        self.assertEqual(MessageState.MSGSTATE_DELIVERED, packet.state)
+        self.assertFalse(envelope.tracked)
+        self.assertEqual(0, len(decoded))
+
+        self.h.channel.receive(packet.raw)
+
+        self.assertEqual(1, len(decoded))
+
+        rx_message = decoded[0]
+
+        self.assertIsNotNone(rx_message)
+        self.assertIsInstance(rx_message, message.__class__)
+        checker(rx_message)
+
+    def test_send_receive_message_test(self):
+        message = MessageTest()
+
+        def check(rx_message: MessageBase):
+            self.assertIsInstance(rx_message, message.__class__)
+            self.assertEqual(message.id, rx_message.id)
+            self.assertEqual(message.data, rx_message.data)
+            self.assertNotEqual(message.not_serialized, rx_message.not_serialized)
+
+        self.eat_own_dog_food(message, check)
+
+
+if __name__ == '__main__':
+    unittest.main(verbosity=2)

tests/link.py

@@ -6,6 +6,9 @@ import threading
 import time
 import RNS
 import os
+from tests.channel import MessageTest
+from RNS.Channel import MessageBase
+
 
 APP_NAME = "rns_unit_tests"
 
@@ -46,6 +49,11 @@ def close_rns():
     global c_rns
     if c_rns != None:
         c_rns.m_proc.kill()
+        # stdout, stderr = c_rns.m_proc.communicate()
+        # if stdout:
+        #     print(stdout.decode("utf-8"))
+        # if stderr:
+        #     print(stderr.decode("utf-8"))
 
 class TestLink(unittest.TestCase):
     def setUp(self):
@@ -346,6 +354,52 @@ class TestLink(unittest.TestCase):
         time.sleep(0.5)
         self.assertEqual(l1.status, RNS.Link.CLOSED)
 
+    def test_10_channel_round_trip(self):
+        global c_rns
+        init_rns(self)
+        print("")
+        print("Channel round trip test")
+
+        # TODO: Load this from public bytes only
+        id1 = RNS.Identity.from_bytes(bytes.fromhex(fixed_keys[0][0]))
+        self.assertEqual(id1.hash, bytes.fromhex(fixed_keys[0][1]))
+
+        dest = RNS.Destination(id1, RNS.Destination.OUT, RNS.Destination.SINGLE, APP_NAME, "link", "establish")
+
+        self.assertEqual(dest.hash, bytes.fromhex("fb48da0e82e6e01ba0c014513f74540d"))
+
+        l1 = RNS.Link(dest)
+        time.sleep(1)
+        self.assertEqual(l1.status, RNS.Link.ACTIVE)
+
+        received = []
+
+        def handle_message(message: MessageBase):
+            received.append(message)
+
+        test_message = MessageTest()
+        test_message.data = "Hello"
+
+        l1.set_message_callback(handle_message)
+        l1.send_message(test_message)
+
+        time.sleep(0.5)
+
+        self.assertEqual(1, len(received))
+
+        rx_message = received[0]
+
+        self.assertIsInstance(rx_message, MessageTest)
+        self.assertEqual("Hello back", rx_message.data)
+        self.assertEqual(test_message.id, rx_message.id)
+        self.assertNotEqual(test_message.not_serialized, rx_message.not_serialized)
+        self.assertEqual(1, len(l1._channel._rx_ring))
+
+        l1.teardown()
+        time.sleep(0.5)
+        self.assertEqual(l1.status, RNS.Link.CLOSED)
+        self.assertEqual(0, len(l1._channel._rx_ring))
+
 
     def size_str(self, num, suffix='B'):
         units = ['','K','M','G','T','P','E','Z']
@@ -405,6 +459,11 @@ def targets(yp=False):
         link.set_resource_started_callback(resource_started)
         link.set_resource_concluded_callback(resource_concluded)
 
+        def handle_message(message):
+            message.data = message.data + " back"
+            link.send_message(message)
+        link.set_message_callback(handle_message, [MessageTest])
+
     m_rns = RNS.Reticulum("./tests/rnsconfig")
     id1 = RNS.Identity.from_bytes(bytes.fromhex(fixed_keys[0][0]))
     d1 = RNS.Destination(id1, RNS.Destination.IN, RNS.Destination.SINGLE, APP_NAME, "link", "establish")