zebra: fix update protocol nexthop-group fib flag value

A nexthop-group does not display the 'fib' flag
value of its nexthops.

> nexthop-group A
>  nexthop 192.168.1.55 loop1
> exit

observed:

> ubuntu2204# show nexthop-group rib 181818168 json
> {
>   "181818168":{
>     "type":"sharp",
>     "refCount":1,
>     "uptime":"00:00:17",
>     "vrf":"default",
>     "valid":true,
>     "installed":true,
>     "depends":[
>       528
>     ],
>     "nexthops":[
>       {
>         "flags":1,
>         "ip":"192.168.1.55",
>         "afi":"ipv4",
>         "interfaceIndex":3,
>         "interfaceName":"loop1",
>         "vrf":"default",
>         "active":true,
>         "weight":1
>       }
>     ]
>   }
> }

The FIB flag is used to inform the user that a given nexthop
is installed in the system, which is the case when using
iproute2:

> # ip nexthop show id 181818168
> id 181818168 group 15 proto 194
> # ip nexthop show id 15
> id 15 via 192.168.1.55 dev loop1 scope link proto 194

Fix this by refreshing the FIB flag value of its nexthops,
when the dataplane result indicate the nexthop-group is
installed.

> ubuntu2204# show nexthop-group rib 181818168  json
> {
>   "181818168":{
>     "type":"sharp",
>     "refCount":1,
>     "uptime":"00:00:25",
>     "vrf":"default",
>     "valid":true,
>     "installed":true,
>     "depends":[
>       574
>     ],
>     "nexthops":[
>       {
>         "flags":3,
>         "fib":true,
>         "ip":"192.168.1.55",
>         "afi":"ipv4",
>         "interfaceIndex":3,
>         "interfaceName":"loop1",
>         "vrf":"default",
>         "active":true,
>         "weight":1
>       }
>     ]
>   }
> }
>

Link: FRRouting#16332
Signed-off-by: Philippe Guibert <philippe.guibert@6wind.com>

zebra/zebra_nhg.c

@@ -3253,6 +3253,7 @@ void zebra_nhg_dplane_result(struct zebra_dplane_ctx *ctx)
 	enum zebra_dplane_result status;
 	uint32_t id = 0;
 	struct nhg_hash_entry *nhe = NULL;
+	struct nexthop *nhop;
 
 	op = dplane_ctx_get_op(ctx);
 	status = dplane_ctx_get_status(ctx);
@@ -3289,6 +3290,16 @@ void zebra_nhg_dplane_result(struct zebra_dplane_ctx *ctx)
 		case ZEBRA_DPLANE_REQUEST_SUCCESS:
 			SET_FLAG(nhe->flags, NEXTHOP_GROUP_INSTALLED);
 			zebra_nhg_handle_install(nhe, true);
+			/* update FIB flag of nexthop-group */
+			for (ALL_NEXTHOPS(nhe->nhg, nhop)) {
+				if (!CHECK_FLAG(nhop->flags,
+						NEXTHOP_FLAG_ACTIVE))
+					continue;
+				if (CHECK_FLAG(nhop->flags,
+					       NEXTHOP_FLAG_RECURSIVE))
+					continue;
+				SET_FLAG(nhop->flags, NEXTHOP_FLAG_FIB);
+			}
 
 			/* If daemon nhg, send it an update */
 			if (PROTO_OWNED(nhe))