static int vlan_dev_change_mtu(struct net_device *dev, int new_mtu)
{
- /* TODO: gotta make sure the underlying layer can handle it,
- * maybe an IFF_VLAN_CAPABLE flag for devices?
- */
- if (vlan_dev_priv(dev)->real_dev->mtu < new_mtu)
+ struct net_device *real_dev = vlan_dev_priv(dev)->real_dev;
+ unsigned int max_mtu = real_dev->mtu;
+
+ if (netif_reduces_vlan_mtu(real_dev))
+ max_mtu -= VLAN_HLEN;
+ if (max_mtu < new_mtu)
return -ERANGE;
dev->mtu = new_mtu;