Nest: Implement locking of prefix tries during walks

The prune loop may may rebuild the prefix trie and therefore invalidate
walk state for asynchronous walks (used in 'show route in' cmd). Fix it
by adding locking that keeps the old trie in memory until current walks
are done.

In future this could be improved by rebuilding trie walk states (by
lookup for last found prefix) after the prefix trie rebuild.

1 files changed, 6 insertions, 0 deletions

diff --git a/nest/route.h b/nest/route.h
index c4e0d2c6..7930058a 100644
--- a/nest/route.h
+++ b/nest/route.h
@@ -191,6 +191,9 @@ typedef struct rtable {
   struct fib_iterator prune_fit;	/* Rtable prune FIB iterator */
   struct fib_iterator nhu_fit;		/* Next Hop Update FIB iterator */
   struct f_trie *trie_new;		/* New prefix trie defined during pruning */
+  struct f_trie *trie_old;		/* Old prefix trie waiting to be freed */
+  u32 trie_lock_count;			/* Prefix trie locked by walks */
+  u32 trie_old_lock_count;		/* Old prefix trie locked by walks */
 
   list subscribers;			/* Subscribers for notifications */
   struct timer *settle_timer;		/* Settle time for notifications */
@@ -332,6 +335,8 @@ void rt_preconfig(struct config *);
 void rt_commit(struct config *new, struct config *old);
 void rt_lock_table(rtable *);
 void rt_unlock_table(rtable *);
+struct f_trie * rt_lock_trie(rtable *tab);
+void rt_unlock_trie(rtable *tab, struct f_trie *trie);
 void rt_subscribe(rtable *tab, struct rt_subscription *s);
 void rt_unsubscribe(struct rt_subscription *s);
 void rt_flowspec_link(rtable *src, rtable *dst);
@@ -405,6 +410,7 @@ struct rt_show_data {
   struct rt_show_data_rtable *last_table; /* Last table in output */
   struct fib_iterator fit;		/* Iterator over networks in table */
   struct f_trie_walk_state *walk_state;	/* Iterator over networks in trie */
+  struct f_trie *walk_lock;		/* Locked trie for walking */
   int verbose, tables_defined_by;
   const struct filter *filter;
   struct proto *show_protocol;