Open-Mesh » batman-adv

The underlying drivers will add some padding when it is required (60 bytes for ethernet). Here for example from visornic.

    if (len < ETH_MIN_PACKET_SIZE &&
        ((skb_end_pointer(skb) - skb->data) >= ETH_MIN_PACKET_SIZE)) {
        /* pad the packet out to minimum size */
        padlen = ETH_MIN_PACKET_SIZE - len;
        memset(&skb->data[len], 0, padlen);
        skb->tail += padlen;
        skb->len += padlen;
        len += padlen;
        firstfraglen += padlen;
    }

But still, the ELP documentation talks about a lot more (300 bytes) and not only 60 bytes.

I am not sure about what was the goal of that section. For sure, smaller broadcast packets should have a higher chance of being received (and avoid collisions). This is probably why we don't pad and we "let the underneath driver take care of it".

Now I am surprised that some drivers don't do that. After all, the minimum packet size is a driver/hw constraint, so why should an upper layer protocol takecare of it? As you said, between batman-adv and the HW there could be other layers which we are not aware of.