net: netdevsim: mimic tc-taprio offload

To be able to use netdevsim for tc-testing with an offloaded tc-taprio
schedule, it needs to report a PTP clock (which it now does), and to
accept ndo_setup_tc(TC_SETUP_QDISC_TAPRIO) calls.

Since netdevsim has no packet I/O, this doesn't do anything intelligent,
it only allows taprio offload code paths to go through some level of
automated testing.

Signed-off-by: Vladimir Oltean <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

drivers/net/netdevsim/netdev.c

···
 	return 0;
 }
 
+static void nsim_taprio_stats(struct tc_taprio_qopt_stats *stats)
+{
+	stats->window_drops = 0;
+	stats->tx_overruns = 0;
+}
+
+static int nsim_setup_tc_taprio(struct net_device *dev,
+				struct tc_taprio_qopt_offload *offload)
+{
+	int err = 0;
+
+	switch (offload->cmd) {
+	case TAPRIO_CMD_REPLACE:
+	case TAPRIO_CMD_DESTROY:
+		break;
+	case TAPRIO_CMD_STATS:
+		nsim_taprio_stats(&offload->stats);
+		break;
+	default:
+		err = -EOPNOTSUPP;
+	}
+
+	return err;
+}
+
 static LIST_HEAD(nsim_block_cb_list);
 
 static int
···
 	struct netdevsim *ns = netdev_priv(dev);
 
 	switch (type) {
+	case TC_SETUP_QDISC_TAPRIO:
+		return nsim_setup_tc_taprio(dev, type_data);
 	case TC_SETUP_BLOCK:
 		return flow_block_cb_setup_simple(type_data,
 						  &nsim_block_cb_list,