ripng: Implement `allow-ecmp X` command

A port of ripd implementation for ripngd implemented by 75fce4645a.

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

ripngd/ripng_cli.c

@@ -85,14 +85,32 @@ void cli_show_router_ripng(struct vty *vty, const struct lyd_node *dnode,
 /*
  * XPath: /frr-ripngd:ripngd/instance/allow-ecmp
  */
-DEFPY_YANG (ripng_allow_ecmp,
+DEFUN_YANG (ripng_allow_ecmp,
-       ripng_allow_ecmp_cmd,
+            ripng_allow_ecmp_cmd,
-       "[no] allow-ecmp",
+            "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,
+	int idx_number = 0;
-			      no ? "false" : "true");
+	char mpaths[3] = {};
+	uint32_t paths = MULTIPATH_NUM;
+
+    if (argv_find(argv, argc, CMD_RANGE_STR(1, MULTIPATH_NUM), &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_ripng_allow_ecmp,
+            no_ripng_allow_ecmp_cmd,
+            "no allow-ecmp [" CMD_RANGE_STR(1, MULTIPATH_NUM) "]", NO_STR
+            "Allow Equal Cost MultiPath\n"
+            "Number of paths\n")
+{
+	nb_cli_enqueue_change(vty, "./allow-ecmp", NB_OP_MODIFY, 0);
 
 	return nb_cli_apply_changes(vty, NULL);
 }
@@ -100,10 +118,14 @@ DEFPY_YANG (ripng_allow_ecmp,
 void cli_show_ripng_allow_ecmp(struct vty *vty, const struct lyd_node *dnode,
 			       bool show_defaults)
 {
-	if (!yang_dnode_get_bool(dnode, NULL))
+	uint8_t paths;
-		vty_out(vty, " no");
 
-	vty_out(vty, " allow-ecmp\n");
+	paths = yang_dnode_get_uint8(dnode, NULL);
+
+	if (!paths)
+		vty_out(vty, " no allow-ecmp\n");
+	else
+		vty_out(vty, " allow-ecmp %d\n", paths);
 }
 
 /*
@@ -547,6 +569,7 @@ void ripng_cli_init(void)
 	install_element(RIPNG_NODE, &ripng_no_ipv6_distribute_list_cmd);
 
 	install_element(RIPNG_NODE, &ripng_allow_ecmp_cmd);
+	install_element(RIPNG_NODE, &no_ripng_allow_ecmp_cmd);
 	install_element(RIPNG_NODE, &ripng_default_information_originate_cmd);
 	install_element(RIPNG_NODE, &ripng_default_metric_cmd);
 	install_element(RIPNG_NODE, &no_ripng_default_metric_cmd);

ripngd/ripng_nb_config.c

@@ -129,9 +129,13 @@ int ripngd_instance_allow_ecmp_modify(struct nb_cb_modify_args *args)
 		return NB_OK;
 
 	ripng = nb_running_get_entry(args->dnode, NULL, true);
-	ripng->ecmp = yang_dnode_get_bool(args->dnode, NULL);
+	ripng->ecmp = yang_dnode_get_uint8(args->dnode, NULL);
-	if (!ripng->ecmp)
+	if (!ripng->ecmp) {
 		ripng_ecmp_disable(ripng);
+		return NB_OK;
+	}
+
+	ripng_ecmp_change(ripng);
 
 	return NB_OK;
 }

ripngd/ripng_zebra.c

@@ -20,6 +20,7 @@
 
 /* All information about zebra. */
 struct zclient *zclient = NULL;
+uint32_t zebra_ecmp_count = MULTIPATH_NUM;
 
 /* Send ECMP routes to zebra. */
 static void ripng_zebra_ipv6_send(struct ripng *ripng, struct agg_node *rp,
@@ -30,7 +31,7 @@ static void ripng_zebra_ipv6_send(struct ripng *ripng, struct agg_node *rp,
 	struct zapi_nexthop *api_nh;
 	struct listnode *listnode = NULL;
 	struct ripng_info *rinfo = NULL;
-	int count = 0;
+	uint32_t count = 0;
 	const struct prefix *p = agg_node_get_prefix(rp);
 
 	memset(&api, 0, sizeof(api));
@@ -41,7 +42,7 @@ static void ripng_zebra_ipv6_send(struct ripng *ripng, struct agg_node *rp,
 
 	SET_FLAG(api.message, ZAPI_MESSAGE_NEXTHOP);
 	for (ALL_LIST_ELEMENTS_RO(list, listnode, rinfo)) {
-		if (count >= MULTIPATH_NUM)
+		if (count >= zebra_ecmp_count)
 			break;
 		api_nh = &api.nexthops[count];
 		api_nh->vrf_id = ripng->vrf->vrf_id;
@@ -227,6 +228,11 @@ static zclient_handler *const ripng_handlers[] = {
 	[ZEBRA_REDISTRIBUTE_ROUTE_DEL] = ripng_zebra_read_route,
 };
 
+static void ripng_zebra_capabilities(struct zclient_capabilities *cap)
+{
+	zebra_ecmp_count = MIN(cap->ecmp, zebra_ecmp_count);
+}
+
 /* Initialize zebra structure and it's commands. */
 void zebra_init(struct event_loop *master)
 {
@@ -236,6 +242,7 @@ void zebra_init(struct event_loop *master)
 	zclient_init(zclient, ZEBRA_ROUTE_RIPNG, 0, &ripngd_privs);
 
 	zclient->zebra_connected = ripng_zebra_connected;
+	zclient->zebra_capabilities = ripng_zebra_capabilities;
 }
 
 void ripng_zebra_stop(void)

ripngd/ripngd.c

@@ -443,7 +443,10 @@ struct ripng_info *ripng_ecmp_add(struct ripng *ripng,
 {
 	struct agg_node *rp = rinfo_new->rp;
 	struct ripng_info *rinfo = NULL;
+	struct ripng_info *rinfo_exist = NULL;
 	struct list *list = NULL;
+	struct listnode *node = NULL;
+	struct listnode *nnode = NULL;
 
 	if (rp->info == NULL)
 		rp->info = list_new();
@@ -454,6 +457,33 @@ struct ripng_info *ripng_ecmp_add(struct ripng *ripng,
 	if (listcount(list) && !ripng->ecmp)
 		return NULL;
 
+	/* Add or replace an existing ECMP path with lower neighbor IP */
+	if (listcount(list) && listcount(list) >= ripng->ecmp) {
+		struct ripng_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 &&
+			     IPV6_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 (ripng->ecmp > 1 && from_highest &&
+		    IPV6_ADDR_CMP(&from_highest->from, &rinfo_new->from) > 0) {
+			ripng_ecmp_delete(ripng, from_highest);
+			goto add_or_replace;
+		}
+
+		return NULL;
+	}
+
+add_or_replace:
 	rinfo = ripng_info_new();
 	memcpy(rinfo, rinfo_new, sizeof(struct ripng_info));
 	listnode_add(list, rinfo);
@@ -475,6 +505,36 @@ struct ripng_info *ripng_ecmp_add(struct ripng *ripng,
 	return rinfo;
 }
 
+/* Update ECMP routes to zebra when `allow-ecmp` changed. */
+void ripng_ecmp_change(struct ripng *ripng)
+{
+	struct agg_node *rp;
+	struct ripng_info *rinfo;
+	struct list *list;
+	struct listnode *node, *nextnode;
+
+	for (rp = agg_route_top(ripng->table); rp; rp = agg_route_next(rp)) {
+		list = rp->info;
+		if (list && listcount(list) > 1) {
+			while (listcount(list) > ripng->ecmp) {
+				struct ripng_info *from_highest = NULL;
+
+				for (ALL_LIST_ELEMENTS(list, node, nextnode,
+						       rinfo)) {
+					if (!from_highest ||
+					    (from_highest &&
+					     IPV6_ADDR_CMP(
+						     &rinfo->from,
+						     &from_highest->from) > 0))
+						from_highest = rinfo;
+				}
+
+				ripng_ecmp_delete(ripng, from_highest);
+			}
+		}
+	}
+}
+
 /* Replace the ECMP list with the new route.
  * RETURN: the new entry added in the list
  */
@@ -1814,7 +1874,7 @@ struct ripng *ripng_create(const char *vrf_name, struct vrf *vrf, int socket)
 		"%s/timers/flush-interval", RIPNG_INSTANCE);
 	ripng->default_metric =
 		yang_get_default_uint8("%s/default-metric", RIPNG_INSTANCE);
-	ripng->ecmp = yang_get_default_bool("%s/allow-ecmp", RIPNG_INSTANCE);
+	ripng->ecmp = yang_get_default_uint8("%s/allow-ecmp", RIPNG_INSTANCE);
 
 	/* Make buffer.  */
 	ripng->ibuf = stream_new(RIPNG_MAX_PACKET_SIZE * 5);

ripngd/ripngd.h

@@ -130,7 +130,7 @@ struct ripng {
 	struct event *t_triggered_interval;
 
 	/* RIPng ECMP flag */
-	bool ecmp;
+	uint8_t ecmp;
 
 	/* RIPng redistribute configuration. */
 	struct {
@@ -429,6 +429,7 @@ extern struct ripng_info *ripng_ecmp_replace(struct ripng *ripng,
 					     struct ripng_info *rinfo);
 extern struct ripng_info *ripng_ecmp_delete(struct ripng *ripng,
 					    struct ripng_info *rinfo);
+extern void ripng_ecmp_change(struct ripng *ripng);
 
 extern void ripng_vrf_init(void);
 extern void ripng_vrf_terminate(void);

yang/frr-ripngd.yang

@@ -86,8 +86,8 @@ module frr-ripngd {
           "VRF name.";
       }
       leaf allow-ecmp {
-        type boolean;
+        type uint8;
-        default "false";
+        default 0;
         description
           "Allow equal-cost multi-path.";
       }