Check socket host availability before binding

pywalfox/__main__.py

@@ -61,7 +61,6 @@ def run_daemon():
 
     daemon = Daemon(python_version.major)
     daemon.start()
-    daemon.close()
 
 def handle_args(args):
     """Handles CLI arguments."""
@@ -76,7 +75,6 @@ def handle_args(args):
     if args.action == 'daemon':
         setup_logging(args.verbose, args.print_mode)
         run_daemon()
-        sys.exit(0)
 
     if args.action == 'log':
         open_log_file()

pywalfox/channel/connector.py

@@ -1,7 +1,7 @@
+import os
 import socket
 import logging
-from ..config import UNIX_SOCKET_PATH, WIN_SOCKET_HOST
-
+from ..config import UNIX_SOCKET_PATH, WIN_SOCKET_HOST, UNIX_SOCKET_PATH_ALT, WIN_SOCKET_HOST_ALT
 
 class Connector:
     """
@@ -13,14 +13,51 @@ class Connector:
     """
     def __init__(self, platform_id):
         if platform_id == 'win32':
-            self.host = WIN_SOCKET_HOST
+            self.host = self.get_win_socket_host()
             self.socket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
             logging.debug('Setup socket server using AF_INET (win32)')
         else:
-            self.host = UNIX_SOCKET_PATH
+            self.host = self.get_unix_socket_path()
             self.socket = socket.socket(socket.AF_UNIX, socket.SOCK_DGRAM)
             logging.debug('Setup socket server using AF_UNIX (linux/darwin)')
 
+    def get_unix_socket_path(self):
+        """
+        Get an available path to bind the UNIX-socket to.
+
+        :return: the path to be used when binding the UNIX-socket
+        :rType: str
+        """
+        if os.path.exists(UNIX_SOCKET_PATH):
+            logging.debug('Default UNIX-socket is already in use')
+            return UNIX_SOCKET_PATH_ALT
+
+        return UNIX_SOCKET_PATH
+
+    def get_win_socket_host(self):
+        """
+        Get an available host and port to bind the UDP-socket to.
+
+        :return: the host and port to be used when binding the UDP-socket
+        :rType: (host, port)
+        """
+        is_valid = True
+        test_socket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+        try:
+            test_socket.bind(WIN_SOCKET_HOST)
+            test_socket.close()
+        except OSError as e:
+            is_valid = False
+            if e.errno == 98: # errno 98 means that address is already bound
+                logging.debug('Default UDP-socket host is already in use')
+            else:
+                logging.error('Failed to test UDP-socket host availability: %s' % str(e))
+
+        if is_valid is True:
+            return WIN_SOCKET_HOST
+
+        return WIN_SOCKET_HOST_ALT
+
     def encode_message(self, message):
         """
         Encodes a message to be sent using the socket.

pywalfox/channel/unix/server.py

@@ -33,4 +33,14 @@ def start(self):
     def close(self):
         """Unbinds the socket and deletes the file."""
         self.socket.close()
-        os.remove(self.host)
+
+        try:
+            """
+            UNIX-sockets can be overwritten by other processes even if another process
+            is already using it. This may lead to the file not existing and will
+            cause a crash if not handled properly.
+            """
+            os.remove(self.host)
+            logging.debug('UNIX-socket deleted')
+        except OSError as e:
+            logging.debug('UNIX-socket has already been deleted, skipping')

pywalfox/config.py

@@ -3,7 +3,9 @@
 DAEMON_VERSION = '2.5'
 
 UNIX_SOCKET_PATH = '/tmp/pywalfox_socket'
+UNIX_SOCKET_PATH_ALT = '/tmp/pywalfox_socket_alt'
 WIN_SOCKET_HOST = ('127.0.0.1', 56744)
+WIN_SOCKET_HOST_ALT = ('127.0.0.1', 56745)
 
 SUPPORTED_BROWSERS = ['firefox']
 

pywalfox/daemon.py

@@ -1,4 +1,5 @@
 import sys
+import signal
 import logging
 from threading import Thread
 
@@ -28,6 +29,9 @@ def __init__(self, python_version):
         self.socket_server = Server()
         self.is_running = False
 
+        signal.signal(signal.SIGINT, self.close)
+        signal.signal(signal.SIGTERM, self.close)
+
     def set_chrome_path(self):
         """Tries to set the path to the chrome directory."""
         self.chrome_path = get_firefox_chrome_path()
@@ -198,16 +202,15 @@ def start(self):
         """Starts the daemon and listens for incoming messages."""
         self.is_running = True
         self.start_socket_server()
-        try:
-            while True:
-                message = self.messenger.get_message()
-                logging.debug('Received message from extension: %s' % message)
-                self.handle_message(message)
-        except KeyboardInterrupt:
-            return
-
-    def close(self):
+
+        while self.is_running:
+            message = self.messenger.get_message()
+            logging.debug('Received message from extension: %s' % message)
+            self.handle_message(message)
+
+    def close(self, signal, frame):
         """Application cleanup."""
-        self.socket_server.close()
+        logging.debug('Running cleanup')
         self.is_running = False
-        logging.debug('Cleanup')
+        self.socket_server.close()
+        sys.exit(0)