lib/rib: enhance the longer iterator

Add an option to bound RIB's longer iterator to the child prefixes
of the parent prefix.

cps/rd.c

@@ -824,7 +824,7 @@ rd_getroute_family(const char *daemon, struct cps_config *cps_conf,
 	int ret;
 
 	spinlock_lock_with_yield(lock, cps_conf);
-	ret = rib_longer_iterator_state_init(&state, rib, NULL, 0);
+	ret = rib_longer_iterator_state_init(&state, rib, NULL, 0, false);
 	if (unlikely(ret < 0)) {
 		rte_spinlock_unlock_tm(lock);
 		G_LOG(ERR, "%s(): failed to initialize the %s RIB iterator (errno=%i): %s\n",

gk/rt.c

@@ -1547,7 +1547,17 @@ check_longer_prefixes(const char *context, const struct rib_head *rib,
 	const char *prefix_str, enum gk_fib_action prefix_action)
 {
 	struct rib_longer_iterator_state state;
-	int ret = rib_longer_iterator_state_init(&state, rib, ip, depth);
+	/*
+	 * @stop_at_children can be true because
+	 *
+	 * (1) if a child is not GK_FWD_GRANTOR, nor GK_DROP,
+	 * 	the test will already fail;
+	 *
+	 * (2) if a child is either GK_FWD_GRANTOR, or GK_DROP,
+	 * 	the grand-children (if they exist) must be safe.
+	 * 	Otherwise, the child would not have been eadded.
+	 */
+	int ret = rib_longer_iterator_state_init(&state, rib, ip, depth, true);
 	if (unlikely(ret < 0)) {
 		G_LOG(ERR, "%s(%s): failed to initialize the %s RIB iterator (errno=%i): %s\n",
 			__func__, prefix_str, context, -ret, strerror(-ret));
@@ -2104,7 +2114,7 @@ list_fib_entries(lua_State *l, const char *context, const struct rib_head *rib,
 	int ret;
 
 	rte_spinlock_lock_tm(lock);
-	ret = rib_longer_iterator_state_init(&state, rib, NULL, 0);
+	ret = rib_longer_iterator_state_init(&state, rib, NULL, 0, false);
 	if (unlikely(ret < 0)) {
 		rte_spinlock_unlock_tm(lock);
 		luaL_error(l, "%s(): failed to initialize the %s RIB iterator (errno=%d): %s",

include/gatekeeper_rib.h

@@ -20,6 +20,7 @@
 #define _GATEKEEPER_GK_RIB_H_
 
 #include <stdint.h>
+#include <stdbool.h>
 #include <setjmp.h>
 
 #include <rte_mempool.h>
@@ -210,6 +211,11 @@ struct rib_longer_iterator_state {
 	struct rib_node_info     start_info;
 	/* The minimum depth of prefix in field @next_address; the scope. */
 	uint8_t                  min_depth;
+	/*
+	 * If true, do not enumerate prefixes longer than the child prefixes
+	 * of the parent prefix.
+	 */
+	bool                     stop_at_children;
 
 	/*
 	 * The following fields are used in between calls of
@@ -229,8 +235,8 @@ struct rib_longer_iterator_state {
 	bool                     has_ended;
 
 	/*
-	 * The following fields are set and only valid while execution is in
-	 * rib_longer_iterator_next().
+	 * The following fields are set and only valid while the execution is
+	 * in rib_longer_iterator_next().
 	 */
 
 	/* When true, keep looking for prefixes greater than @next_address. */
@@ -252,13 +258,27 @@ struct rib_longer_iterator_state {
  * The first call of rib_longer_iterator_next() returns a rule whose prefix
  * is at least as deeper as @depth.
  *
- * Passing @address = NULL (or any other value) and @depth = 0 iterates
- * over the whole RIB; including the default rule
- * (i.e. the zero-length prefix).
+ * Rules are returned such that prefixes are in increasing order
+ * (e.g. 10.2/16 > 10.1/16). Longer prefixes are greater than
+ * shorter sub-prefixes (e.g. 10.2/16 > 10/8).
+ * Notice that 10.2/16 is greater than 10.1.255.255/32.
+ *
+ * Passing @address = NULL (or any other value) and @depth = 0 and
+ * @stop_at_children = false iterates over the whole RIB;
+ * including the default rule (i.e. the zero-length prefix).
  *
  * @address is in network order (big endian).
  * @address == NULL is equivalent to the all-zero address.
  *
+ * When @stop_at_children is true, only the prefix @address/@depth
+ * (if it exists) and its children prefixes are enumerated.
+ * In a RIB with 10/8, 10.1/16, 10.2/16, 10.2.2/24, the longer iterator
+ * will list all prefixes when @address = 10.X.X.X and @depth = 8 and
+ * @stop_at_children = false, but will not list 10.2.2/24 when
+ * @stop_at_children = true.
+ *
+ * The parent prefix is @address/@depth.
+ *
  * If the RIB changes (i.e. rules are added or deleted)
  * between the call of this function and the call of
  * rib_longer_iterator_next(), or between two consecutive calls of
@@ -267,7 +287,8 @@ struct rib_longer_iterator_state {
  * the initial prefix) and that are after the next rule.
  */
 int rib_longer_iterator_state_init(struct rib_longer_iterator_state *state,
-	const struct rib_head *rib, const uint8_t *address, uint8_t depth);
+	const struct rib_head *rib, const uint8_t *address, uint8_t depth,
+	bool stop_at_children);
 
 /*
  * When a rule is found, this function updates @rule and returns zero.

lib/rib.c

@@ -833,7 +833,8 @@ scope_longer_iterator(struct rib_longer_iterator_state *state)
 
 int
 rib_longer_iterator_state_init(struct rib_longer_iterator_state *state,
-	const struct rib_head *rib, const uint8_t *address, uint8_t depth)
+	const struct rib_head *rib, const uint8_t *address, uint8_t depth,
+	bool stop_at_children)
 {
 	int ret;
 
@@ -853,6 +854,7 @@ rib_longer_iterator_state_init(struct rib_longer_iterator_state *state,
 
 	state->rib = rib;
 	state->min_depth = depth;
+	state->stop_at_children = stop_at_children;
 	state->next_depth = depth;
 	state->has_ended = false;
 	scope_longer_iterator(state);
@@ -966,6 +968,13 @@ __rib_longer_iterator_next(struct rib_longer_iterator_state *state,
 		state->rule->depth = info.depth;
 		state->rule->next_hop = cur_node->next_hop;
 		/* Still missing the next rule after the found rule. */
+
+		/*
+		 * The test info.depth > state->min_depth is needed to
+		 * avoid only listing the parent prefix if it exists.
+		 */
+		if (state->stop_at_children && info.depth > state->min_depth)
+			return;
 	}
 
 	__rib_longer_iterator_next(state, cur_node->branch[false], info);