Handle unsupported IKEv1 exchange types more specifically.

src/libcharon/encoding/message.c

@@ -1896,7 +1896,7 @@ METHOD(message_t, parse_body, status_t,
 		DBG1(DBG_ENC, "no message rules specified for a %N %s",
 			 exchange_type_names, this->exchange_type,
 			 this->is_request ? "request" : "response");
-		return PARSE_ERROR;
+		return NOT_SUPPORTED;
 	}
 
 	status = parse_payloads(this);

src/libcharon/sa/task_manager_v1.c

@@ -699,6 +699,11 @@ static status_t parse_message(private_task_manager_t *this, message_t *msg)
 	{
 		switch (status)
 		{
+			case NOT_SUPPORTED:
+				DBG1(DBG_IKE, "unsupported exchange type");
+				send_notify_response(this, msg,
+									 INVALID_EXCHANGE_TYPE, chunk_empty);
+				break;
 			case PARSE_ERROR:
 				DBG1(DBG_IKE, "message parsing failed");
 				send_notify_response(this, msg,