net: cls_u32: be more strict about skip-sw flag for knodes

Return an error if user requested skip-sw and the underlaying
hardware cannot handle tc offloads (or offloads are disabled).
This patch fixes the knode handling.
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sched/cls_u32.c

@@ -508,7 +508,9 @@ static int u32_replace_hw_knode(struct tcf_proto *tp,
 	offload.type = TC_SETUP_CLSU32;
 	offload.cls_u32 = &u32_offload;
 
-	if (tc_should_offload(dev, tp, flags)) {
+	if (!tc_should_offload(dev, tp, flags))
+		return tc_skip_sw(flags) ? -EINVAL : 0;
+
 	offload.cls_u32->command = TC_CLSU32_REPLACE_KNODE;
 	offload.cls_u32->knode.handle = n->handle;
 	offload.cls_u32->knode.fshift = n->fshift;
@@ -528,7 +530,6 @@ static int u32_replace_hw_knode(struct tcf_proto *tp,
 					    tp->protocol, &offload);
 	if (tc_skip_sw(flags))
 		return err;
-	}
 
 	return 0;
 }