Add base communication framework.

1 files changed, 140 insertions, 0 deletions

diff --git a/src/leap/bitmask/backend/signaler.py b/src/leap/bitmask/backend/signaler.py
new file mode 100644
index 00000000..d96015f4
--- /dev/null
+++ b/src/leap/bitmask/backend/signaler.py
@@ -0,0 +1,140 @@
+#!/usr/bin/env python
+# encoding: utf-8
+import Queue
+import threading
+import time
+
+import zmq
+
+from leap.bitmask.backend.api import SIGNALS
+from leap.bitmask.backend.utils import get_frontend_certificates
+
+import logging
+logger = logging.getLogger(__name__)
+
+
+class Signaler(object):
+    """
+    Signaler client.
+    Receives signals from the backend and sends to the signaling server.
+    """
+    PORT = "5667"
+    SERVER = "tcp://localhost:%s" % PORT
+
+    def __init__(self):
+        """
+        Initialize the ZMQ socket to talk to the signaling server.
+        """
+        context = zmq.Context()
+        logger.debug("Connecting to signaling server...")
+        socket = context.socket(zmq.REQ)
+
+        # public, secret = zmq.curve_keypair()
+        client_keys = zmq.curve_keypair()
+        socket.curve_publickey = client_keys[0]
+        socket.curve_secretkey = client_keys[1]
+
+        # The client must know the server's public key to make a CURVE
+        # connection.
+        public, _ = get_frontend_certificates()
+        socket.curve_serverkey = public
+
+        socket.setsockopt(zmq.RCVTIMEO, 1000)
+        socket.connect(self.SERVER)
+        self._socket = socket
+
+        self._signal_queue = Queue.Queue()
+
+        self._do_work = threading.Event()  # used to stop the worker thread.
+        self._worker_signaler = threading.Thread(target=self._worker)
+
+    def __getattribute__(self, name):
+        """
+        This allows the user to do:
+            S = Signaler()
+            S.SOME_SIGNAL
+
+        Just by having defined 'some_signal' in _SIGNALS
+
+        :param name: the attribute name that is requested.
+        :type name: str
+        """
+        if name in SIGNALS:
+            return name
+        else:
+            return object.__getattribute__(self, name)
+
+    def signal(self, signal, data=None):
+        """
+        Sends a signal to the signaling server.
+
+        :param signal: the signal to send.
+        :type signal: str
+        """
+        if signal not in SIGNALS:
+            raise Exception("Unknown signal: '{0}'".format(signal))
+
+        request = {
+            'signal': signal,
+            'data': data,
+        }
+
+        try:
+            request_json = zmq.utils.jsonapi.dumps(request)
+        except Exception as e:
+            msg = ("Error serializing request into JSON.\n"
+                   "Exception: {0} Data: {1}")
+            msg = msg.format(e, request)
+            logger.critical(msg)
+            raise
+
+        # queue the call in order to handle the request in a thread safe way.
+        self._signal_queue.put(request_json)
+
+    def _worker(self):
+        """
+        Worker loop that processes the Queue of pending requests to do.
+        """
+        while self._do_work.is_set():
+            try:
+                request = self._signal_queue.get(block=False)
+                self._send_request(request)
+            except Queue.Empty:
+                pass
+            time.sleep(0.01)
+
+        logger.debug("Signaler thread stopped.")
+
+    def start(self):
+        """
+        Start the Signaler worker.
+        """
+        self._do_work.set()
+        self._worker_signaler.start()
+
+    def stop(self):
+        """
+        Stop the Signaler worker.
+        """
+        self._do_work.clear()
+
+    def _send_request(self, request):
+        """
+        Send the given request to the server.
+        This is used from a thread safe loop in order to avoid sending a
+        request without receiving a response from a previous one.
+
+        :param request: the request to send.
+        :type request: str
+        """
+        logger.debug("Signaling '{0}'".format(request))
+        self._socket.send(request)
+
+        # Get the reply.
+        try:
+            response = self._socket.recv()
+            msg = "Received reply for '{0}' -> '{1}'".format(request, response)
+            logger.debug(msg)
+        except zmq.error.Again as e:
+            msg = "Timeout error contacting signaler. {0!r}".format(e)
+            logger.critical(msg)