ixgbe: limit small mtu to minimum for ipv4 support

Signed-off-by: NJesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: NJeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: NJeff Garzik <jgarzik@redhat.com>

drivers/net/ixgbe/ixgbe_main.c

@@ -2839,8 +2839,8 @@ static int ixgbe_change_mtu(struct net_device *netdev, int new_mtu)
 	struct ixgbe_adapter *adapter = netdev_priv(netdev);
 	int max_frame = new_mtu + ETH_HLEN + ETH_FCS_LEN;
 
-	if ((max_frame < (ETH_ZLEN + ETH_FCS_LEN)) ||
-	    (max_frame > IXGBE_MAX_JUMBO_FRAME_SIZE))
+	/* MTU < 68 is an error and causes problems on some kernels */
+	if ((new_mtu < 68) || (max_frame > IXGBE_MAX_JUMBO_FRAME_SIZE))
 		return -EINVAL;
 
 	DPRINTK(PROBE, INFO, "changing MTU from %d to %d\n",