net: vlan: sync VLAN features with lower device

After registering a VLAN device and setting its feature flags, we need to
synchronize the VLAN features with the lower device. For example, the VLAN
device does not have the NETIF_F_LRO flag, it should be synchronized with
the lower device based on the NETIF_F_UPPER_DISABLES definition.

As the dev->vlan_features has changed, we need to call
netdev_update_features(). The caller must run after netdev_upper_dev_link()
links the lower devices, so this patch adds the netdev_update_features()
call in register_vlan_dev().

Fixes: fd867d5 ("net/core: generic support for disabling netdev features down stack")
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Link: https://patch.msgid.link/20251030073539.133779-1-liuhangbin@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: liuhangbin

net/8021q/vlan.c

@@ -193,6 +193,8 @@ int register_vlan_dev(struct net_device *dev, struct netlink_ext_ack *extack)
 	vlan_group_set_device(grp, vlan->vlan_proto, vlan_id, dev);
 	grp->nr_vlan_devs++;
 
+	netdev_update_features(dev);
+
 	return 0;
 
 out_unregister_netdev: