Better error feedback for flush interface.

configuration.c

@@ -897,6 +897,8 @@ parse_config_line(int c, gnc_t gnc, void *closure,
         if(c < -1 || !action_return)
             goto fail;
         *action_return = CONFIG_ACTION_NO;
+        if(message_return)
+            *message_return = "Permission denied";
     } else if(strcmp(token, "in") == 0) {
         struct filter *filter;
         c = parse_filter(c, gnc, closure, &filter);
@@ -946,13 +948,24 @@ parse_config_line(int c, gnc_t gnc, void *closure,
             goto fail;
         if(strcmp(token2, "interface") == 0) {
             char *ifname;
+            int rc;
             c = getword(c, &ifname, gnc, closure);
             c = skip_eol(c, gnc, closure);
             if(c < -1) {
                 free(token2);
                 goto fail;
             }
-            flush_interface(ifname);
+            rc = flush_interface(ifname);
+            if(rc <= 0) {
+                if(action_return)
+                    *action_return = CONFIG_ACTION_NO;
+                if(message_return) {
+                    if(rc < 0)
+                        *message_return = "Couldn't flush interface";
+                    else
+                        *message_return = "No such interface";
+                }
+            }
             free(token2);
             free(ifname);
         } else {