Correct mDNS TCP/UDP socket flags

* Explicitly mark TCP and UDP as blocking sockets
* Added socket.SO_REUSEADDR to UDP socket
* Added socket.SO_REUSEPORT to TCP+UDP sockets
* Moved socket creation to inside the worker thread's
  start() method.
* Added a socket.close() to the stop() method.
* Enable eventlet patching of the "os" module, required
  to avoid symptoms which look near identical to [1].

[1]: https://github.com/eventlet/eventlet/issues/210

Closes-Bug: 1444384
Change-Id: Iff642673a33d7b8d2e2c1af833f944330001c33b

designate/__init__.py

@@ -15,7 +15,7 @@
 # under the License.
 import eventlet
 
-eventlet.monkey_patch(os=False)
+eventlet.monkey_patch()
 
 import os
 import socket

designate/dnsutils.py

@@ -247,7 +247,9 @@ def bind_tcp(host, port, tcp_backlog):
              {'host': host, 'port': port})
     sock_tcp = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
     sock_tcp.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+    sock_tcp.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT, 1)
     sock_tcp.setsockopt(socket.SOL_SOCKET, socket.SO_KEEPALIVE, 1)
+    sock_tcp.setblocking(True)
     sock_tcp.bind((host, port))
     sock_tcp.listen(tcp_backlog)
 
@@ -259,6 +261,9 @@ def bind_udp(host, port):
     LOG.info(_LI('Opening UDP Listening Socket on %(host)s:%(port)d') %
              {'host': host, 'port': port})
     sock_udp = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+    sock_udp.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+    sock_udp.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT, 1)
+    sock_udp.setblocking(True)
     sock_udp.bind((host, port))
 
     return sock_udp

designate/service.py

@@ -230,8 +230,12 @@ class DNSService(object):
     """
     DNS Service mixin used by all Designate DNS Services
     """
-    def __init__(self, *args, **kwargs):
-        super(DNSService, self).__init__(*args, **kwargs)
+    @abc.abstractproperty
+    def _dns_application(self):
+        pass
+
+    def start(self):
+        super(DNSService, self).start()
 
         self._dns_sock_tcp = dnsutils.bind_tcp(
             self._service_config.host,
@@ -242,13 +246,6 @@ class DNSService(object):
             self._service_config.host,
             self._service_config.port)
 
-    @abc.abstractproperty
-    def _dns_application(self):
-        pass
-
-    def start(self):
-        super(DNSService, self).start()
-
         self.tg.add_thread(self._dns_handle_tcp)
         self.tg.add_thread(self._dns_handle_udp)
 
@@ -260,6 +257,12 @@ class DNSService(object):
         # _handle_udp are stopped too.
         super(DNSService, self).stop()
 
+        if hasattr(self, '_dns_sock_tcp'):
+            self._dns_sock_tcp.close()
+
+        if hasattr(self, '_dns_sock_udp'):
+            self._dns_sock_udp.close()
+
     def _dns_handle_tcp(self):
         LOG.info(_LI("_handle_tcp thread started"))