gnetworkaddress: Implement parallel ipv4 and ipv6 dns lookups

As RFC 8305 recommends we can start multiple DNS queries in parallel
to more quickly make an initial response, especially when one is
particularly slow/broken.

gio/tests/mock-resolver.h

@@ -0,0 +1,35 @@
+/* GIO - GLib Input, Output and Streaming Library
+ *
+ * Copyright (C) 2018 Igalia S.L.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General
+ * Public License along with this library; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <gio/gio.h>
+
+G_BEGIN_DECLS
+
+#define MOCK_TYPE_RESOLVER (mock_resolver_get_type())
+G_DECLARE_FINAL_TYPE (MockResolver, mock_resolver, MOCK, RESOLVER, GResolver)
+
+MockResolver *mock_resolver_new (void);
+void mock_resolver_set_ipv4_delay_ms (MockResolver *self, guint delay_ms);
+void mock_resolver_set_ipv4_results (MockResolver *self, GList *results);
+void mock_resolver_set_ipv4_error (MockResolver *self, GError *error);
+void mock_resolver_set_ipv6_delay_ms (MockResolver *self, guint delay_ms);
+void mock_resolver_set_ipv6_results (MockResolver *self, GList *results);
+void mock_resolver_set_ipv6_error (MockResolver *self, GError *error);
+G_END_DECLS