ipv4: Notify newly added route if should be offloaded

When a route is added, it should only be notified in case it is the
first route in the FIB alias list with the given {prefix, prefix length,
table ID}. Otherwise, it is not used in the data path and should not be
considered by switch drivers.

v2:
* Convert to use fib_find_alias() instead of fib_find_first_alias()

Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Reviewed-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/fib_trie.c

@@ -1295,6 +1295,16 @@ int fib_table_insert(struct net *net, struct fib_table *tb,
 	if (WARN_ON_ONCE(!l))
 		goto out_free_new_fa;
 
+	if (fib_find_alias(&l->leaf, new_fa->fa_slen, 0, 0, tb->tb_id, true) ==
+	    new_fa) {
+		enum fib_event_type fib_event;
+
+		fib_event = FIB_EVENT_ENTRY_REPLACE_TMP;
+		err = call_fib_entry_notifiers(net, fib_event, key, plen,
+					       new_fa, extack);
+		if (err)
+			goto out_remove_new_fa;
+	}
 	err = call_fib_entry_notifiers(net, event, key, plen, new_fa, extack);
 	if (err)
 		goto out_remove_new_fa;