ripd: Implement `allow-ecmp X` command

Allow setting an arbitrary number of paths to be installed instead of ALL.

Signed-off-by: Donatas Abraitis <donatas@opensourcerouting.org>

4 files changed, 102 insertions, 12 deletions

diff --git a/ripd/rip_cli.c b/ripd/rip_cli.c
index ac9fc4b1a..6f45bb5d9 100644
--- a/ripd/rip_cli.c
+++ b/ripd/rip_cli.c
@@ -85,14 +85,33 @@ void cli_show_router_rip(struct vty *vty, const struct lyd_node *dnode,
 /*
  * XPath: /frr-ripd:ripd/instance/allow-ecmp
  */
-DEFPY_YANG (rip_allow_ecmp,
+DEFUN_YANG (rip_allow_ecmp,
        rip_allow_ecmp_cmd,
-       "[no] allow-ecmp",
+       "allow-ecmp [" CMD_RANGE_STR(1, MULTIPATH_NUM) "]",
+       "Allow Equal Cost MultiPath\n"
+       "Number of paths\n")
+{
+	int idx_number = 1;
+	char mpaths[3] = {};
+	uint32_t paths = MULTIPATH_NUM;
+
+	if (argv[idx_number])
+		paths = strtol(argv[idx_number]->arg, NULL, 10);
+	snprintf(mpaths, sizeof(mpaths), "%u", paths);
+
+	nb_cli_enqueue_change(vty, "./allow-ecmp", NB_OP_MODIFY, mpaths);
+
+	return nb_cli_apply_changes(vty, NULL);
+}
+
+DEFUN_YANG (no_rip_allow_ecmp,
+       no_rip_allow_ecmp_cmd,
+       "no allow-ecmp [" CMD_RANGE_STR(1, MULTIPATH_NUM) "]",
        NO_STR
-       "Allow Equal Cost MultiPath\n")
+       "Allow Equal Cost MultiPath\n"
+       "Number of paths\n")
 {
-	nb_cli_enqueue_change(vty, "./allow-ecmp", NB_OP_MODIFY,
-			      no ? "false" : "true");
+	nb_cli_enqueue_change(vty, "./allow-ecmp", NB_OP_MODIFY, 0);
 
 	return nb_cli_apply_changes(vty, NULL);
 }
@@ -100,10 +119,14 @@ DEFPY_YANG (rip_allow_ecmp,
 void cli_show_rip_allow_ecmp(struct vty *vty, const struct lyd_node *dnode,
 			     bool show_defaults)
 {
-	if (!yang_dnode_get_bool(dnode, NULL))
-		vty_out(vty, " no");
+	uint8_t paths;
+
+	paths = yang_dnode_get_uint8(dnode, NULL);
 
-	vty_out(vty, " allow-ecmp\n");
+	if (!paths)
+		vty_out(vty, " no allow-ecmp\n");
+	else
+		vty_out(vty, " allow-ecmp %d\n", paths);
 }
 
 /*
@@ -1156,6 +1179,7 @@ void rip_cli_init(void)
 	install_element(RIP_NODE, &rip_no_distribute_list_cmd);
 
 	install_element(RIP_NODE, &rip_allow_ecmp_cmd);
+	install_element(RIP_NODE, &no_rip_allow_ecmp_cmd);
 	install_element(RIP_NODE, &rip_default_information_originate_cmd);
 	install_element(RIP_NODE, &rip_default_metric_cmd);
 	install_element(RIP_NODE, &no_rip_default_metric_cmd);
diff --git a/ripd/rip_nb_config.c b/ripd/rip_nb_config.c
index 8fe34705c..19578d56c 100644
--- a/ripd/rip_nb_config.c
+++ b/ripd/rip_nb_config.c
@@ -101,9 +101,13 @@ int ripd_instance_allow_ecmp_modify(struct nb_cb_modify_args *args)
 		return NB_OK;
 
 	rip = nb_running_get_entry(args->dnode, NULL, true);
-	rip->ecmp = yang_dnode_get_bool(args->dnode, NULL);
-	if (!rip->ecmp)
+	rip->ecmp = yang_dnode_get_uint8(args->dnode, NULL);
+	if (!rip->ecmp) {
 		rip_ecmp_disable(rip);
+		return NB_OK;
+	}
+
+	rip_ecmp_change(rip);
 
 	return NB_OK;
 }
diff --git a/ripd/ripd.c b/ripd/ripd.c
index cb8dd4945..3e8f8a934 100644
--- a/ripd/ripd.c
+++ b/ripd/ripd.c
@@ -155,7 +155,10 @@ struct rip_info *rip_ecmp_add(struct rip *rip, struct rip_info *rinfo_new)
 {
 	struct route_node *rp = rinfo_new->rp;
 	struct rip_info *rinfo = NULL;
+	struct rip_info *rinfo_exist = NULL;
 	struct list *list = NULL;
+	struct listnode *node = NULL;
+	struct listnode *nnode = NULL;
 
 	if (rp->info == NULL)
 		rp->info = list_new();
@@ -166,6 +169,33 @@ struct rip_info *rip_ecmp_add(struct rip *rip, struct rip_info *rinfo_new)
 	if (listcount(list) && !rip->ecmp)
 		return NULL;
 
+	/* Add or replace an existing ECMP path with lower neighbor IP */
+	if (listcount(list) && listcount(list) >= rip->ecmp) {
+		struct rip_info *from_highest = NULL;
+
+		/* Find the rip_info struct that has the highest nexthop IP */
+		for (ALL_LIST_ELEMENTS(list, node, nnode, rinfo_exist))
+			if (!from_highest ||
+			    (from_highest &&
+			     IPV4_ADDR_CMP(&rinfo_exist->from,
+					   &from_highest->from) > 0)) {
+				from_highest = rinfo_exist;
+			}
+
+		/* If we have a route in ECMP group, delete the old
+		 * one that has a higher next-hop address. Lower IP is
+		 * preferred.
+		 */
+		if (rip->ecmp > 1 && from_highest &&
+		    IPV4_ADDR_CMP(&from_highest->from, &rinfo_new->from) > 0) {
+			rip_ecmp_delete(rip, from_highest);
+			goto add_or_replace;
+		}
+
+		return NULL;
+	}
+
+add_or_replace:
 	rinfo = rip_info_new();
 	memcpy(rinfo, rinfo_new, sizeof(struct rip_info));
 	listnode_add(list, rinfo);
@@ -2631,6 +2661,36 @@ struct rip *rip_lookup_by_vrf_name(const char *vrf_name)
 	return RB_FIND(rip_instance_head, &rip_instances, &rip);
 }
 
+/* Update ECMP routes to zebra when `allow-ecmp` changed. */
+void rip_ecmp_change(struct rip *rip)
+{
+	struct route_node *rp;
+	struct rip_info *rinfo;
+	struct list *list;
+	struct listnode *node, *nextnode;
+
+	for (rp = route_top(rip->table); rp; rp = route_next(rp)) {
+		list = rp->info;
+		if (list && listcount(list) > 1) {
+			while (listcount(list) > rip->ecmp) {
+				struct rip_info *from_highest = NULL;
+
+				for (ALL_LIST_ELEMENTS(list, node, nextnode,
+						       rinfo)) {
+					if (!from_highest ||
+					    (from_highest &&
+					     IPV4_ADDR_CMP(
+						     &rinfo->from,
+						     &from_highest->from) > 0))
+						from_highest = rinfo;
+				}
+
+				rip_ecmp_delete(rip, from_highest);
+			}
+		}
+	}
+}
+
 /* Create new RIP instance and set it to global variable. */
 struct rip *rip_create(const char *vrf_name, struct vrf *vrf, int socket)
 {
@@ -2640,7 +2700,7 @@ struct rip *rip_create(const char *vrf_name, struct vrf *vrf, int socket)
 	rip->vrf_name = XSTRDUP(MTYPE_RIP_VRF_NAME, vrf_name);
 
 	/* Set initial value. */
-	rip->ecmp = yang_get_default_bool("%s/allow-ecmp", RIP_INSTANCE);
+	rip->ecmp = yang_get_default_uint8("%s/allow-ecmp", RIP_INSTANCE);
 	rip->default_metric =
 		yang_get_default_uint8("%s/default-metric", RIP_INSTANCE);
 	rip->distance =
diff --git a/ripd/ripd.h b/ripd/ripd.h
index bba3c2806..2db1e5a6b 100644
--- a/ripd/ripd.h
+++ b/ripd/ripd.h
@@ -141,7 +141,7 @@ struct rip {
 	struct route_table *distance_table;
 
 	/* RIP ECMP flag */
-	bool ecmp;
+	uint8_t ecmp;
 
 	/* Are we in passive-interface default mode? */
 	bool passive_default;
@@ -537,4 +537,6 @@ extern struct event_loop *master;
 DECLARE_HOOK(rip_ifaddr_add, (struct connected * ifc), (ifc));
 DECLARE_HOOK(rip_ifaddr_del, (struct connected * ifc), (ifc));
 
+extern void rip_ecmp_change(struct rip *rip);
+
 #endif /* _ZEBRA_RIP_H */