vlan: use a valid default mtu value for vlan over macsec

[cascardo/linux.git] / net / 8021q / vlan_dev.c

diff --git a/net/8021q/vlan_dev.c b/net/8021q/vlan_dev.c
index 86ae75b..516b0e7 100644 (file)
--- a/net/8021q/vlan_dev.c
+++ b/net/8021q/vlan_dev.c
@@ -146,10 +146,12 @@ static netdev_tx_t vlan_dev_hard_start_xmit(struct sk_buff *skb,
 
 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;