https://www.open-mesh.org/https://www.open-mesh.org/favicon.ico?16699090422018-08-31T10:42:30ZOpen Meshbatman-adv - Bug #363: Broadcast ELP smaller than specified in documentionhttps://www.open-mesh.org/issues/363?journal_id=14602018-08-31T10:42:30ZSven Eckelmann
<ul><li><strong>Description</strong> updated (<a title="View differences" href="/journals/1460/diff?detail_id=904">diff</a>)</li></ul> batman-adv - Bug #363: Broadcast ELP smaller than specified in documentionhttps://www.open-mesh.org/issues/363?journal_id=14612018-08-31T10:56:25ZSven Eckelmann
<ul><li><strong>Description</strong> updated (<a title="View differences" href="/journals/1461/diff?detail_id=905">diff</a>)</li></ul> batman-adv - Bug #363: Broadcast ELP smaller than specified in documentionhttps://www.open-mesh.org/issues/363?journal_id=14622018-08-31T11:01:03ZSven Eckelmann
<ul></ul><p>The underlying drivers will add some padding when it is required (60 bytes for ethernet). Here for example from visornic.</p>
<pre>
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;
}
</pre>
<p>But still, the <a class="wiki-page" href="https://www.open-mesh.org/projects/batman-adv/wiki/ELP#section-9">ELP</a> documentation talks about a lot more (300 bytes) and not only 60 bytes.</p> batman-adv - Bug #363: Broadcast ELP smaller than specified in documentionhttps://www.open-mesh.org/issues/363?journal_id=14632018-09-01T07:57:21ZAntonio Quartulli
<ul></ul><p>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".</p>
<p>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.</p> batman-adv - Bug #363: Broadcast ELP smaller than specified in documentionhttps://www.open-mesh.org/issues/363?journal_id=14642018-09-01T09:01:41ZSven Eckelmann
<ul><li><strong>Subject</strong> changed from <i>Broadcast ELP smaller than minimal ethernet packet size</i> to <i>Broadcast ELP smaller than specified in documention</i></li><li><strong>Description</strong> updated (<a title="View differences" href="/journals/1464/diff?detail_id=907">diff</a>)</li></ul><p>Ok, changed the bug description to only talk about the specification. The minimal ethernet size should not be relevant here.</p>