[Feature] Allow to skip real action and add a header instead

src/libserver/milter.c

@@ -1482,6 +1482,12 @@ rspamd_milter_process_milter_block (struct rspamd_milter_session *session,
 				priv->discard_on_reject = FALSE;
 			}
 		}
+
+		elt = ucl_object_lookup (obj, "no_action");
+
+		if (elt && ucl_object_type (elt) == UCL_BOOLEAN) {
+			priv->no_action = ucl_object_toboolean (elt);
+		}
 	}
 
 	if (action == METRIC_ACTION_ADD_HEADER) {
@@ -1598,6 +1604,21 @@ rspamd_milter_send_task_results (struct rspamd_milter_session *session,
 		goto cleanup;
 	}
 
+	if (priv->no_action) {
+		msg_info_milter ("do not apply action %s, no_action is set",
+				str_action);
+		hname = g_string_new (RSPAMD_MILTER_ACTION_HEADER);
+		hvalue = g_string_new (str_action);
+
+		rspamd_milter_send_action (session, RSPAMD_MILTER_ADDHEADER,
+				hname, hvalue);
+		g_string_free (hname, TRUE);
+		g_string_free (hvalue, TRUE);
+		rspamd_milter_send_action (session, RSPAMD_MILTER_ACCEPT);
+
+		goto cleanup;
+	}
+
 	switch (action) {
 	case METRIC_ACTION_REJECT:
 		if (priv->discard_on_reject) {

src/libserver/milter_internal.h

@@ -66,6 +66,7 @@ struct rspamd_milter_private {
 	enum rspamd_milter_io_state state;
 	int fd;
 	gboolean discard_on_reject;
+	gboolean no_action;
 };
 
 enum rspamd_milter_io_cmd {
@@ -151,4 +152,5 @@ enum rspamd_milter_connect_proto {
 #define RSPAMD_MILTER_TEMPFAIL_MESSAGE "Try again later"
 #define RSPAMD_MILTER_SPAM_HEADER "X-Spam"
 #define RSPAMD_MILTER_DKIM_HEADER "DKIM-Signature"
+#define RSPAMD_MILTER_ACTION_HEADER "X-Rspamd-Action"
 #endif