Route table cork: Indicate whether the export queues are congested.

These routines detect the export congestion (as defined by configurable
thresholds) and propagate the state to readers. There are no readers for
now, they will be added in following commits.

1 files changed, 42 insertions, 0 deletions

diff --git a/nest/rt.h b/nest/rt.h
index 5acbded6..58c6ec33 100644
--- a/nest/rt.h
+++ b/nest/rt.h
@@ -18,6 +18,7 @@
 #include "lib/fib.h"
 #include "lib/route.h"
 #include "lib/event.h"
+#include "lib/rcu.h"
 
 #include <stdatomic.h>
 
@@ -33,6 +34,10 @@ struct f_trie;
 struct f_trie_walk_state;
 struct cli;
 
+struct rt_cork_threshold {
+  u64 low, high;
+};
+
 /*
  *	Master Routing Tables. Generally speaking, each of them contains a FIB
  *	with each entry pointing to a list of route entries representing routes
@@ -57,6 +62,7 @@ struct rtable_config {
   btime min_settle_time;		/* Minimum settle time for notifications */
   btime max_settle_time;		/* Maximum settle time for notifications */
   btime export_settle_time;		/* Delay before exports are announced */
+  struct rt_cork_threshold cork_threshold;	/* Cork threshold values */
 };
 
 struct rt_export_hook;
@@ -111,6 +117,8 @@ typedef struct rtable {
   byte hcu_scheduled;			/* Hostcache update is scheduled */
   byte nhu_state;			/* Next Hop Update state */
   byte export_used;			/* Pending Export pruning is scheduled */
+  byte cork_active;			/* Cork has been activated */
+  struct rt_cork_threshold cork_threshold;	/* Threshold for table cork */
   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 */
@@ -139,6 +147,40 @@ struct rt_flowspec_link {
   u32 uc;
 };
 
+extern struct rt_cork {
+  _Atomic uint active;
+  event_list queue;
+  event run;
+} rt_cork;
+
+static inline void rt_cork_acquire(void)
+{
+  atomic_fetch_add_explicit(&rt_cork.active, 1, memory_order_acq_rel);
+}
+
+static inline void rt_cork_release(void)
+{
+  if (atomic_fetch_sub_explicit(&rt_cork.active, 1, memory_order_acq_rel) == 1)
+  {
+    synchronize_rcu();
+    ev_schedule_work(&rt_cork.run);
+  }
+}
+
+static inline int rt_cork_check(event *e)
+{
+  rcu_read_lock();
+
+  int corked = (atomic_load_explicit(&rt_cork.active, memory_order_acquire) > 0);
+  if (corked)
+    ev_send(&rt_cork.queue, e);
+
+  rcu_read_unlock();
+
+  return corked;
+}
+
+
 #define NHU_CLEAN	0
 #define NHU_SCHEDULED	1
 #define NHU_RUNNING	2