port-probe: add a new serial parser filter to detect non-AT strings

We will check each string with our custom filter before even trying to
parse them. A MM_SERIAL_ERROR_PARSE_FAILED error will be issued whenever the
string doesn't match the filter.

src/mm-port-probe-at.c

@@ -50,11 +50,15 @@ mm_port_probe_response_processor_is_at (const gchar *command,
             return FALSE;
         }
 
-        /* If error is NOT known by the parser, request to abort */
-        if (!mm_serial_parser_v1_is_known_error (error)) {
+        /* If error is NOT known by the parser, or if the error is actually
+         * the generic parsing filter error, request to abort */
+        if (!mm_serial_parser_v1_is_known_error (error) ||
+            g_error_matches (error,
+                             MM_SERIAL_ERROR,
+                             MM_SERIAL_ERROR_PARSE_FAILED)) {
             *result_error = g_error_copy (error);
             g_prefix_error (result_error,
-                            "Fatal error parsing AT reply. ");
+                            "Fatal error parsing AT reply: ");
             return FALSE;
         }
 
@@ -91,4 +95,3 @@ mm_port_probe_response_processor_string (const gchar *command,
 
     return TRUE;
 }
-

src/mm-port-probe.c

@@ -954,6 +954,23 @@ serial_buffer_full (MMSerialPort *serial,
     }
 }
 
+static gboolean
+serial_parser_filter_cb (gpointer filter,
+                         gpointer user_data,
+                         GString *response,
+                         GError **error)
+{
+    if (is_non_at_response ((const guint8 *) response->str, response->len)) {
+        g_set_error (error,
+                     MM_SERIAL_ERROR,
+                     MM_SERIAL_ERROR_PARSE_FAILED,
+                     "Not an AT response");
+        return FALSE;
+    }
+
+    return TRUE;
+}
+
 static gboolean
 serial_open_at (MMPortProbe *self)
 {
@@ -968,6 +985,8 @@ serial_open_at (MMPortProbe *self)
 
     /* Create AT serial port if not done before */
     if (!task->serial) {
+        gpointer parser;
+
         task->serial = MM_SERIAL_PORT (mm_at_serial_port_new (g_udev_device_get_name (self->priv->port)));
         if (!task->serial) {
             port_probe_run_task_complete (
@@ -989,9 +1008,13 @@ serial_open_at (MMPortProbe *self)
                       MM_SERIAL_PORT_SPEW_CONTROL,   TRUE,
                       NULL);
 
+        parser = mm_serial_parser_v1_new ();
+        mm_serial_parser_v1_add_filter (parser,
+                                        serial_parser_filter_cb,
+                                        NULL);
         mm_at_serial_port_set_response_parser (MM_AT_SERIAL_PORT (task->serial),
                                                mm_serial_parser_v1_parse,
-                                               mm_serial_parser_v1_new (),
+                                               parser,
                                                mm_serial_parser_v1_destroy);
     }