support: Provide a way to clear the RA bit in DNS server responses

support/resolv_test.h

@@ -148,6 +148,10 @@ struct resolv_response_flags
   /* If true, the AD (authenticated data) flag will be set.  */
   bool ad;
 
+  /* If true, do not set the RA (recursion available) flag in the
+     response.  */
+  bool clear_ra;
+
   /* Initial section count values.  Can be used to artificially
      increase the counts, for malformed packet testing.*/
   unsigned short qdcount;