Conf: Free stored old config before parsing new one

BIRD keeps a previous (old) configuration for the purpose of undo. The
existing code frees it after a new configuration is successfully parsed
during reconfiguration. That causes memory usage spikes as there are
temporarily three configurations (old, current, and new). The patch
changes it to free the old one before parsing the new one (as user
already requested a new config). The disadvantage is that undo is
not available after failed reconfiguration.

2 files changed, 18 insertions, 0 deletions

diff --git a/conf/conf.c b/conf/conf.c
index 11c136e7..4e31de29 100644
--- a/conf/conf.c
+++ b/conf/conf.c
@@ -201,6 +201,23 @@ config_free(struct config *c)
     rfree(c->pool);
 }
 
+/**
+ * config_free_old - free stored old configuration
+ *
+ * This function frees the old configuration (%old_config) that is saved for the
+ * purpose of undo. It is useful before parsing a new config when reconfig is
+ * requested, to avoid keeping three (perhaps memory-heavy) configs together.
+ */
+void
+config_free_old(void)
+{
+  tm_stop(config_timer);
+  undo_available = 0;
+
+  config_free(old_config);
+  old_config = NULL;
+}
+
 void
 config_add_obstacle(struct config *c)
 {
diff --git a/conf/conf.h b/conf/conf.h
index 5ec924b0..b409750e 100644
--- a/conf/conf.h
+++ b/conf/conf.h
@@ -70,6 +70,7 @@ struct config *config_alloc(const char *name);
 int config_parse(struct config *);
 int cli_parse(struct config *);
 void config_free(struct config *);
+void config_free_old(void);
 int config_commit(struct config *, int type, uint timeout);
 int config_confirm(void);
 int config_undo(void);