ipvs: add a 'default' case in do_ip_vs_set_ctl()

It is better to return the default switch case with
'-EINVAL', in case new commands are added. otherwise,
return a uninitialized value of ret.
Signed-off-by: NLi Qiong <liqiong@nfschina.com>
Reviewed-by: NSimon Horman <horms@verge.net.au>
Acked-by: NJulian Anastasov <ja@ssi.bg>
Signed-off-by: NPablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/ipvs/ip_vs_ctl.c

@@ -2590,6 +2590,11 @@ do_ip_vs_set_ctl(struct sock *sk, int cmd, sockptr_t ptr, unsigned int len)
 		break;
 	case IP_VS_SO_SET_DELDEST:
 		ret = ip_vs_del_dest(svc, &udest);
+		break;
+	default:
+		WARN_ON_ONCE(1);
+		ret = -EINVAL;
+		break;
 	}
 
   out_unlock: