help in using eth_change_mtu

[Harsh <hanemade@xxxxxxxxx>]

Hello,
         If some extra information is required to be sent with each
packet then does that require to change Ethernet MTU 1500 to
1500-(Bytes in extra info) or its ok with 1500 value of MTU? While
checking source code of net_init.c in drivers/net dir i found one
function eth_change_mtu. I want to know does that helps? why its given
there in source code?
regards,
Harsh.

static int eth_change_mtu(struct net_device *dev, int new_mtu)
 {
        if ((new_mtu < 68) || (new_mtu > 1500))
                 return -EINVAL;
        dev->mtu = new_mtu;
        return 0;
 }