replace .send() with async events

mitmproxy/proxy/protocol2/server_async.py

@@ -18,7 +18,7 @@ class ConnectionHandler:
         self.client = Client(addr)
         self.context = Context(self.client)
 
-        self.layer = ReverseProxy(self.context, ("towel.blinkenlights.nl", 23))
+        self.layer = ReverseProxy(self.context, ("example.com", 80))
 
         self.transports = {}  # type: MutableMapping[Connection, StreamIO]
         self.transports[self.client] = StreamIO(reader, writer)
@@ -26,8 +26,6 @@ class ConnectionHandler:
         self.lock = asyncio.Lock()
 
     async def handle_client(self):
-        await self.server_event(events.Start())
-
         await self.handle_connection(self.client)
 
         for connection in self.transports:
@@ -48,16 +46,28 @@ class ConnectionHandler:
 
     async def handle_connection(self, connection):
         connection.connected = True
+        await self.server_event(events.OpenConnection(connection))
         reader, writer = self.transports[connection]
         while True:
+            try:
                 data = await reader.read(4096)
+            except socket.error:
+                data = b""
             if data:
                 await self.server_event(events.ReceiveData(connection, data))
             else:
                 connection.connected = False
                 await self.close(connection)
+                await self.server_event(events.CloseConnection(connection))
                 break
 
+    async def open_connection(self, event: events.OpenConnection):
+        reader, writer = await asyncio.open_connection(
+            *event.connection.address
+        )
+        self.transports[event.connection] = StreamIO(reader, writer)
+        await self.handle_connection(event.connection)
+
     async def server_event(self, event: events.Event):
         print("*", event)
         async with self.lock:
@@ -66,13 +76,7 @@ class ConnectionHandler:
             for event in layer_events:
                 print("<<", event)
                 if isinstance(event, events.OpenConnection):
-                    reader, writer = await asyncio.open_connection(
-                        *event.connection.address
-                    )
-                    self.transports[event.connection] = StreamIO(reader, writer)
-                    asyncio.ensure_future(self.handle_connection(event.connection))
-                    layer_events.send(42)
-
+                    asyncio.ensure_future(self.open_connection(event))
                 elif isinstance(event, events.SendData):
                     self.transports[event.connection].w.write(event.data)
                 else:

mitmproxy/proxy/protocol2/tcp.py

@@ -1,25 +1,96 @@
+import functools
+
 from mitmproxy.proxy.protocol2 import events
 from mitmproxy.proxy.protocol2.context import ClientServerContext
 from mitmproxy.proxy.protocol2.events import TEventGenerator
 from mitmproxy.proxy.protocol2.layer import Layer
 
+"""
+Utility decorators that help build state machines
+"""
+
+
+def defer(event_type):
+    """
+    Queue up the events matching the specified event type and emit them immediately
+    after the state has changed.
+    """
+
+    def decorator(f):
+        deferred = []
+
+        @functools.wraps(f)
+        def wrapper(self, event: events.Event):
+            if isinstance(event, event_type):
+                deferred.append(event)
+            else:
+                yield from f(self, event)
+                if self.state != f:
+                    for event in deferred:
+                        yield from self.state(event)
+                    deferred.clear()
+
+        return wrapper
+
+    return decorator
+
+
+def exit_on_close(f):
+    """
+    Stop all further interaction once a single close event has been observed.
+    """
+    closed = False
+
+    @functools.wraps(f)
+    def wrapper(self, event: events.Event):
+        nonlocal closed
+        if isinstance(event, events.CloseConnection):
+            closed = True
+        if not closed:
+            yield from f(self, event)
+
+    return wrapper
+
 
 class TCPLayer(Layer):
     context = None  # type: ClientServerContext
 
-    def handle_event(self, event: events.Event) -> TEventGenerator:
-        if isinstance(event, events.Start):
-            if not self.context.server.connected:
-                try:
-                    t = yield events.OpenConnection(self.context.server)
-                    yield
-                    print("opening took {}s".format(t))  # example on how we can implement .ask()
-                except Exception as e:
-                    print("Could not connect to server: {}".format(e))
+    def __init__(self, context: ClientServerContext):
+        super().__init__(context)
+        self.state = self.start
 
+    def handle_event(self, event: events.Event) -> TEventGenerator:
+        yield from self.state(event)
+
+    def start(self, event: events.Event) -> TEventGenerator:
+        if isinstance(event, events.OpenConnection):
+            if not self.context.server.connected:
+                yield events.OpenConnection(self.context.server)
+                self.state = self.wait_for_open
+            else:
+                self.state = self.relay_messages
+        else:
+            raise TypeError("Unexpected event: {}".format(event))
+
+    @defer(events.ReceiveData)
+    @exit_on_close
+    def wait_for_open(self, event: events.Event) -> TEventGenerator:
+        if isinstance(event, events.OpenConnection):
+            # connection is now open
+            self.state = self.relay_messages
+        else:
+            raise TypeError("Unexpected event: {}".format(event))
+            # noinspection PyUnreachableCode
+            yield
+
+    def relay_messages(self, event: events.Event) -> TEventGenerator:
         if isinstance(event, events.ReceiveData):
             if event.connection == self.context.client:
                 dst = self.context.server
             else:
                 dst = self.context.client
             yield events.SendData(dst, event.data)
+        if isinstance(event, events.CloseConnection):
+            pass  # TODO: close other connection here.
+        else:
+            raise TypeError("Unexpected event: {}".format(event))