Hi, Florian,
> +}
> +
> +static int aq_ndev_change_mtu(struct net_device *ndev, int new_mtu)
> +{
> + struct aq_nic_s *aq_nic = (struct aq_nic_s *)netdev_priv(ndev);
> + int err = 0;
> +
> + if (new_mtu == ndev->mtu) {
> + err = 0;
> + goto err_exit;
> + }
> + if (new_mtu < 68) {
> + err = -EINVAL;
> + goto err_exit;
> + }
> What's so special about 68 here?
I think that the check that the passed MTU is at least 68 bytes is
justified and correct.
This convention is followed by a large number of Ethernet drivers; for example,
http://lxr.free-electrons.com/source/drivers/net/ethernet/intel/i40e/i40e_main.c#L2246
http://lxr.free-electrons.com/source/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c#L6049
The size of 68 bytes is originated from RFC 791:
https://tools.ietf.org/html/rfc791
...
Every internet module must be able to forward a datagram of 68 octets
without further fragmentation.
This is because an internet header may be up to 60 octets, and the
minimum fragment is 8 octets.
...
Regards,
Rami Rosen
