AsyncSniffer: forward error in stop() if never started (#4800)

* Fix AsyncSniffer Attribute Error
Signed-off-by: Louis Scalbert <[email protected]>

* Forward error + test

---------

Signed-off-by: Louis Scalbert <[email protected]>
Co-authored-by: gpotter2 <[email protected]>

Author: louis-6wind

scapy/sendrecv.py

@@ -1401,6 +1401,11 @@ def stop(self, join=True):
         """Stops AsyncSniffer if not in async mode"""
         if self.running:
             self.stop_cb()
+            if not hasattr(self, "continue_sniff"):
+                # Never started -> is there an exception?
+                if self.exception is not None:
+                    raise self.exception
+                return None
             if self.continue_sniff:
                 raise Scapy_Exception(
                     "Unsupported (offline or unsupported socket)"

test/regression.uts

@@ -1787,6 +1787,15 @@ try:
 except ValueError:
     assert True
 
+try:
+    sniffer = AsyncSniffer(iface="this_interface_does_not_exists")
+    sniffer.start()
+    sniffer.thread.join()
+    sniffer.stop()
+    assert False, "Should have errored by now"
+except ValueError:
+    assert True
+
 = Sending a TCP syn 'forever' at layer 2 and layer 3
 ~ netaccess needs_root IP
 def _test():