Use a classic thread for UDP server discovery. Closes #545.

gns3server/web/web_server.py

@@ -26,7 +26,7 @@ import socket
 import json
 import ipaddress
 import asyncio
-import select
+import threading
 import aiohttp
 import aiohttp_cors
 import functools
@@ -59,7 +59,6 @@ class WebServer:
         self._handler = None
         self._start_time = time.time()
         self._port_manager = PortManager(host)
-        self._running = False
 
     @staticmethod
     def instance(host=None, port=None):
@@ -195,34 +194,45 @@ class WebServer:
                         ('ipi_addr', in_addr)]
 
         IP_PKTINFO = 8
-        sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
-        membership = socket.inet_aton("239.42.42.1") + socket.inet_aton("0.0.0.0")
-        sock.setsockopt(socket.IPPROTO_IP, socket.IP_ADD_MEMBERSHIP, membership)
-        sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
-        sock.setsockopt(socket.SOL_SOCKET, socket.SO_BROADCAST, 1)
-        sock.setsockopt(socket.SOL_IP, IP_PKTINFO, 1)
-        sock.bind(("0.0.0.0", self._port))
-        log.info("UDP server discovery started on {}:{}".format("0.0.0.0", self._port))
-
-        while self._running:
-            ready_to_read, _, _ = select.select([sock], [], [], 1.0)
-            if ready_to_read:
-                data, ancdata, _, address = sock.recvmsg(255, socket.CMSG_LEN(255))
+        with socket.socket(socket.AF_INET, socket.SOCK_DGRAM) as sock:
+            membership = socket.inet_aton("239.42.42.1") + socket.inet_aton("0.0.0.0")
+            sock.setsockopt(socket.IPPROTO_IP, socket.IP_ADD_MEMBERSHIP, membership)
+            sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+            sock.setsockopt(socket.SOL_SOCKET, socket.SO_BROADCAST, 1)
+            sock.setsockopt(socket.SOL_IP, IP_PKTINFO, 1)
+            try:
+                sock.bind(("", self._port))
+            except OSError as e:
+                log.error("UDP server discovery could not bind on port {}: {}".format(self._port, e))
+                return
+
+            log.info("UDP server discovery started on port {}".format(self._port))
+            while self._loop.is_running():
+                try:
+                    data, ancdata, _, address = sock.recvmsg(255, socket.CMSG_LEN(255))
+                except OSError as e:
+                    log.error("Error while receiving UDP server discovery request: {}".format(e))
+                    continue
                 cmsg_level, cmsg_type, cmsg_data = ancdata[0]
                 if cmsg_level == socket.SOL_IP and cmsg_type == IP_PKTINFO:
                     pktinfo = in_pktinfo.from_buffer_copy(cmsg_data)
                     request_address = ipaddress.IPv4Address(memoryview(pktinfo.ipi_addr).tobytes())
-                    log.debug("UDP server discovery request received on {} using {}".format(socket.if_indextoname(pktinfo.ipi_ifindex),
+                    receiving_interface = socket.if_indextoname(pktinfo.ipi_ifindex)
+                    log.debug("UDP server discovery request received on {} using {}".format(receiving_interface,
                                                                                             request_address))
                     local_address = ipaddress.IPv4Address(memoryview(pktinfo.ipi_spec_dst).tobytes())
+                    if self._host != "0.0.0.0" and self._host != str(local_address):
+                        log.debug("Ignoring UDP discovery request received on {} instead of {}".format(local_address,
+                                                                                                       self._host))
+                        continue
                     server_info = {"version": __version__,
                                    "ip": str(local_address),
                                    "port": self._port}
                     data = json.dumps(server_info)
                     sock.sendto(data.encode(), address)
-                    log.debug("Sent server info to {}: {}".format(local_address, data))
+                    log.debug("Sent server info to {}:{} {}".format(address[0], address[1], data))
                 time.sleep(1) # this is to prevent too many request to slow down the server
-        log.debug("UDP discovery stopped")
+        log.debug("UDP server discovery stopped")
 
     def run(self):
         """
@@ -282,7 +292,6 @@ class WebServer:
         self._handler = app.make_handler(handler=RequestHandler)
         server = self._run_application(self._handler, ssl_context)
         self._loop.run_until_complete(server)
-        self._running = True
         self._signal_handling()
         self._exit_handling()
 
@@ -290,8 +299,9 @@ class WebServer:
             asyncio.async(self.start_shell())
 
         if sys.platform.startswith("linux"):
-           # UDP discovery is only supported on
-           self._loop.run_in_executor(None, self._udp_server_discovery)
+           # UDP discovery is only supported on Linux
+           udp_server_discovery = threading.Thread(target=self._udp_server_discovery, daemon=True)
+           udp_server_discovery.start()
 
         try:
             self._loop.run_forever()
@@ -301,7 +311,7 @@ class WebServer:
             # TypeError: async() takes 1 positional argument but 3 were given
             log.warning("TypeError exception in the loop {}".format(e))
         finally:
-            self._running = False
+
             if self._handler and self._loop.is_running():
                 self._loop.run_until_complete(self._handler.finish_connections())
             server.close()