Forward error + test

Author: gpotter2

scapy/sendrecv.py

@@ -1401,7 +1401,12 @@ def stop(self, join=True):
         """Stops AsyncSniffer if not in async mode"""
         if self.running:
             self.stop_cb()
-            if not hasattr(self, "continue_sniff") or self.continue_sniff:
+            if not hasattr(self, "continue_sniff"):
+                # Never started -> is there an exception?
+                if self.exception is not None:
+                    raise self.exception
+                return
+            if self.continue_sniff:
                 raise Scapy_Exception(
                     "Unsupported (offline or unsupported socket)"
                 )

test/regression.uts

@@ -1787,6 +1787,14 @@ try:
 except ValueError:
     assert True
 
+try:
+    sniffer = AsyncSniffer(iface="this_interface_does_not_exists")
+    sniffer.start()
+    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():