lib: Introducing a 3rd state for route-map match cmd: RMAP_NOOP

Introducing a 3rd state for route_map_apply library function: RMAP_NOOP

Traditionally route map MATCH rule apis  were designed to return
a binary response, consisting of either RMAP_MATCH or RMAP_NOMATCH.
(Route-map SET rule apis return RMAP_OKAY or RMAP_ERROR).
Depending on this response, the following statemachine decided the
course of action:

Action: Apply route-map match and return the result (RMAP_MATCH/RMAP_NOMATCH)
State1: Receveived RMAP_MATCH
THEN: If Routemap type is PERMIT, execute other rules if applicable,
otherwise we PERMIT!
Else: If Routemap type is DENY, we DENYMATCH right away

State2: Received RMAP_NOMATCH, continue on to next route-map, otherwise,
return DENYMATCH by default if nothing matched.

With reference to PR 4078 (https://github.com/FRRouting/frr/pull/4078),
we require a 3rd state because of the following situation:

The issue - what if, the rule api needs to abort or ignore a rule?:
"match evpn vni xx" route-map filter can be applied to incoming routes
regardless of whether the tunnel type is vxlan or mpls.
This rule should be N/A for mpls based evpn route, but applicable to only
vxlan based evpn route.

Today, the filter produces either a match or nomatch response regardless of
whether it is mpls/vxlan, resulting in either permitting or denying the
route.. So an mpls evpn route may get filtered out incorrectly.
Eg: "route-map RM1 permit 10 ; match evpn vni 20" or
"route-map RM2 deny 20 ; match vni 20"

With the introduction of the 3rd state, we can abort this rule check safely.
How? The rules api can now return RMAP_NOOP (or another enum) to indicate
that it encountered an invalid check, and needs to abort just that rule,
but continue with other rules.

Question: Do we repurpose an existing enum RMAP_OKAY or RMAP_ERROR
as the 3rd state (or create a new enum like RMAP_NOOP)?
RMAP_OKAY and RMAP_ERROR are used to return the result of set cmd.

We chose to go with RMAP_NOOP (but open to ideas),
as a way to bypass the rmap filter

As a result we have a 3rd state:
State3: Received RMAP_NOOP
Then, proceed to other route-map, otherwise return RMAP_PERMITMATCH by default.

Signed-off-by:Lakshman Krishnamoorthy <lkrishnamoor@vmware.com>

1 files changed, 12 insertions, 14 deletions

diff --git a/ospf6d/ospf6_asbr.c b/ospf6d/ospf6_asbr.c
index 946bbf8cc..4fbf70c9d 100644
--- a/ospf6d/ospf6_asbr.c
+++ b/ospf6d/ospf6_asbr.c
@@ -1018,7 +1018,7 @@ void ospf6_asbr_redistribute_add(int type, ifindex_t ifindex,
 				 unsigned int nexthop_num,
 				 struct in6_addr *nexthop, route_tag_t tag)
 {
-	int ret;
+	route_map_result_t ret;
 	struct ospf6_route troute;
 	struct ospf6_external_info tinfo;
 	struct ospf6_route *route, *match;
@@ -1355,7 +1355,7 @@ static void ospf6_redistribute_show_config(struct vty *vty)
 
 
 /* Routemap Functions */
-static route_map_result_t
+static enum route_map_match_result_t
 ospf6_routemap_rule_match_address_prefixlist(void *rule,
 					     const struct prefix *prefix,
 					     route_map_object_t type,
@@ -1395,7 +1395,7 @@ struct route_map_rule_cmd ospf6_routemap_rule_match_address_prefixlist_cmd = {
 /* `match interface IFNAME' */
 /* Match function should return 1 if match is success else return
    zero. */
-static route_map_result_t
+static enum route_map_match_result_t
 ospf6_routemap_rule_match_interface(void *rule, const struct prefix *prefix,
 				    route_map_object_t type, void *object)
 {
@@ -1433,10 +1433,9 @@ struct route_map_rule_cmd ospf6_routemap_rule_match_interface_cmd = {
 	ospf6_routemap_rule_match_interface_free};
 
 /* Match function for matching route tags */
-static route_map_result_t ospf6_routemap_rule_match_tag(void *rule,
-							const struct prefix *p,
-							route_map_object_t type,
-							void *object)
+static enum route_map_match_result_t
+ospf6_routemap_rule_match_tag(void *rule, const struct prefix *p,
+			      route_map_object_t type, void *object)
 {
 	route_tag_t *tag = rule;
 	struct ospf6_route *route = object;
@@ -1453,7 +1452,7 @@ static struct route_map_rule_cmd ospf6_routemap_rule_match_tag_cmd = {
 	route_map_rule_tag_free,
 };
 
-static route_map_result_t
+static enum route_map_match_result_t
 ospf6_routemap_rule_set_metric_type(void *rule, const struct prefix *prefix,
 				    route_map_object_t type, void *object)
 {
@@ -1489,7 +1488,7 @@ struct route_map_rule_cmd ospf6_routemap_rule_set_metric_type_cmd = {
 	ospf6_routemap_rule_set_metric_type_free,
 };
 
-static route_map_result_t
+static enum route_map_match_result_t
 ospf6_routemap_rule_set_metric(void *rule, const struct prefix *prefix,
 			       route_map_object_t type, void *object)
 {
@@ -1524,7 +1523,7 @@ struct route_map_rule_cmd ospf6_routemap_rule_set_metric_cmd = {
 	ospf6_routemap_rule_set_metric_free,
 };
 
-static route_map_result_t
+static enum route_map_match_result_t
 ospf6_routemap_rule_set_forwarding(void *rule, const struct prefix *prefix,
 				   route_map_object_t type, void *object)
 {
@@ -1562,10 +1561,9 @@ struct route_map_rule_cmd ospf6_routemap_rule_set_forwarding_cmd = {
 	ospf6_routemap_rule_set_forwarding_free,
 };
 
-static route_map_result_t ospf6_routemap_rule_set_tag(void *rule,
-						      const struct prefix *p,
-						      route_map_object_t type,
-						      void *object)
+static enum route_map_match_result_t
+ospf6_routemap_rule_set_tag(void *rule, const struct prefix *p,
+			    route_map_object_t type, void *object)
 {
 	route_tag_t *tag = rule;
 	struct ospf6_route *route = object;