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, 23 insertions, 27 deletions

diff --git a/ospfd/ospf_routemap.c b/ospfd/ospf_routemap.c
index ab2d5ae58..d725837fe 100644
--- a/ospfd/ospf_routemap.c
+++ b/ospfd/ospf_routemap.c
@@ -126,10 +126,9 @@ static void ospf_route_map_event(const char *name)
 
 /* `match ip netxthop ' */
 /* Match function return 1 if match is success else return zero. */
-static route_map_result_t route_match_ip_nexthop(void *rule,
-						 const struct prefix *prefix,
-						 route_map_object_t type,
-						 void *object)
+static enum route_map_match_result_t
+route_match_ip_nexthop(void *rule, const struct prefix *prefix,
+		       route_map_object_t type, void *object)
 {
 	struct access_list *alist;
 	struct external_info *ei = object;
@@ -171,7 +170,7 @@ struct route_map_rule_cmd route_match_ip_nexthop_cmd = {
 
 /* `match ip next-hop prefix-list PREFIX_LIST' */
 
-static route_map_result_t
+static enum route_map_match_result_t
 route_match_ip_next_hop_prefix_list(void *rule, const struct prefix *prefix,
 				    route_map_object_t type, void *object)
 {
@@ -213,10 +212,9 @@ struct route_map_rule_cmd route_match_ip_next_hop_prefix_list_cmd = {
 /* `match ip address IP_ACCESS_LIST' */
 /* Match function should return 1 if match is success else return
    zero. */
-static route_map_result_t route_match_ip_address(void *rule,
-						 const struct prefix *prefix,
-						 route_map_object_t type,
-						 void *object)
+static enum route_map_match_result_t
+route_match_ip_address(void *rule, const struct prefix *prefix,
+		       route_map_object_t type, void *object)
 {
 	struct access_list *alist;
 	/* struct prefix_ipv4 match; */
@@ -252,7 +250,7 @@ struct route_map_rule_cmd route_match_ip_address_cmd = {
 	route_match_ip_address_free};
 
 /* `match ip address prefix-list PREFIX_LIST' */
-static route_map_result_t
+static enum route_map_match_result_t
 route_match_ip_address_prefix_list(void *rule, const struct prefix *prefix,
 				   route_map_object_t type, void *object)
 {
@@ -288,10 +286,9 @@ struct route_map_rule_cmd route_match_ip_address_prefix_list_cmd = {
 /* `match interface IFNAME' */
 /* Match function should return 1 if match is success else return
    zero. */
-static route_map_result_t route_match_interface(void *rule,
-						const struct prefix *prefix,
-						route_map_object_t type,
-						void *object)
+static enum route_map_match_result_t
+route_match_interface(void *rule, const struct prefix *prefix,
+		      route_map_object_t type, void *object)
 {
 	struct interface *ifp;
 	struct external_info *ei;
@@ -327,9 +324,9 @@ struct route_map_rule_cmd route_match_interface_cmd = {
 	route_match_interface_free};
 
 /* Match function return 1 if match is success else return zero. */
-static route_map_result_t route_match_tag(void *rule,
-					  const struct prefix *prefix,
-					  route_map_object_t type, void *object)
+static enum route_map_match_result_t
+route_match_tag(void *rule, const struct prefix *prefix,
+		route_map_object_t type, void *object)
 {
 	route_tag_t *tag;
 	struct external_info *ei;
@@ -358,10 +355,9 @@ struct ospf_metric {
 
 /* `set metric METRIC' */
 /* Set metric to attribute. */
-static route_map_result_t route_set_metric(void *rule,
-					   const struct prefix *prefix,
-					   route_map_object_t type,
-					   void *object)
+static enum route_map_match_result_t
+route_set_metric(void *rule, const struct prefix *prefix,
+		 route_map_object_t type, void *object)
 {
 	struct ospf_metric *metric;
 	struct external_info *ei;
@@ -439,10 +435,9 @@ struct route_map_rule_cmd route_set_metric_cmd = {
 
 /* `set metric-type TYPE' */
 /* Set metric-type to attribute. */
-static route_map_result_t route_set_metric_type(void *rule,
-						const struct prefix *prefix,
-						route_map_object_t type,
-						void *object)
+static enum route_map_match_result_t
+route_set_metric_type(void *rule, const struct prefix *prefix,
+		      route_map_object_t type, void *object)
 {
 	uint32_t *metric_type;
 	struct external_info *ei;
@@ -489,8 +484,9 @@ struct route_map_rule_cmd route_set_metric_type_cmd = {
 	route_set_metric_type_free,
 };
 
-static route_map_result_t route_set_tag(void *rule, const struct prefix *prefix,
-					route_map_object_t type, void *object)
+static enum route_map_match_result_t
+route_set_tag(void *rule, const struct prefix *prefix, route_map_object_t type,
+	      void *object)
 {
 	route_tag_t *tag;
 	struct external_info *ei;