Lock the dynamips reader an writer

Fix #103

gns3server/modules/dynamips/dynamips_hypervisor.py

@@ -59,6 +59,8 @@ class DynamipsHypervisor:
         self._reader = None
         self._writer = None
 
+        self._io_lock = asyncio.Lock()
+
     @asyncio.coroutine
     def connect(self, timeout=10):
         """
@@ -80,6 +82,7 @@ class DynamipsHypervisor:
         while time.time() - begin < timeout:
             yield from asyncio.sleep(0.01)
             try:
+                with (yield from self._io_lock):
                     self._reader, self._writer = yield from asyncio.open_connection(host, self._port)
             except OSError as e:
                 last_exception = e
@@ -120,6 +123,7 @@ class DynamipsHypervisor:
         """
 
         yield from self.send("hypervisor close")
+        with (yield from self._io_lock):
             self._writer.close()
             self._reader, self._writer = None
 
@@ -129,6 +133,7 @@ class DynamipsHypervisor:
         Stops this hypervisor (will no longer run).
         """
 
+        with (yield from self._io_lock):
             try:
                 # try to properly stop the hypervisor
                 yield from self.send("hypervisor stop")
@@ -255,6 +260,7 @@ class DynamipsHypervisor:
         # but still have more data. The only thing we know for sure is the last line
         # will begin with '100-' or a '2xx-' and end with '\r\n'
 
+        with (yield from self._io_lock):
             if self._writer is None or self._reader is None:
                 raise DynamipsError("Not connected")