net/sched: cls_u32: fix cls_u32 on filter replace

The following sequence is currently broken:

 # tc qdisc add dev foo ingress
 # tc filter replace dev foo protocol all ingress \
   u32 match u8 0 0 action mirred egress mirror dev bar1
 # tc filter replace dev foo protocol all ingress \
   handle 800::800 pref 49152 \
   u32 match u8 0 0 action mirred egress mirror dev bar2
 Error: cls_u32: Key node flags do not match passed flags.
 We have an error talking to the kernel, -1

The error comes from u32_change() when comparing new and
existing flags. The existing ones always contains one of
TCA_CLS_FLAGS_{,NOT}_IN_HW flag depending on offloading state.
These flags cannot be passed from userspace so the condition
(n->flags != flags) in u32_change() always fails.

Fix the condition so the flags TCA_CLS_FLAGS_NOT_IN_HW and
TCA_CLS_FLAGS_IN_HW are not taken into account.

Fixes: 24d3dc6d ("net/sched: cls_u32: Reflect HW offload status")
Signed-off-by: NIvan Vecera <ivecera@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/sched/cls_u32.c

@@ -955,7 +955,8 @@ static int u32_change(struct net *net, struct sk_buff *in_skb,
 			return -EINVAL;
 		}
 
-		if (n->flags != flags) {
+		if ((n->flags ^ flags) &
+		    ~(TCA_CLS_FLAGS_IN_HW | TCA_CLS_FLAGS_NOT_IN_HW)) {
 			NL_SET_ERR_MSG_MOD(extack, "Key node flags do not match passed flags");
 			return -EINVAL;
 		}