[OLPC Networking] TCP is broken in mesh mode
carrano at laptop.org
Tue Jun 10 18:14:59 EDT 2008
> ~ The invitations are unicast, implemented using TCP. When machine A sends
> an invitation to B, we see the following exchange:
> 1. A broadcasts an ARP request for B
> 2. B sees the ARP request and replies to A
> 3. A receives the ARP reply from B and sends a TCP SYN to B
> 4. B does not see the SYN packet (it does not appear in B's dump)
> 5. A retries a total of three times, but none of the SYN packets are seen
> by B.
> 3b. In parallel, A broadcasts a presence-info update with mDNS, indicating
> that it has shared the activity.
> 4b. B receives this broadcast, updates its presence-info cache, and even
> assigns B's XO icon a new location in the mesh view
I would like to take a look at this traffic (in a capture).
There are some steps between 1 and 2 and between 2 and 3. And this is
the path discovery mechanism that should find a path between B and A
(so B can reply the ARP) and then between A and B, so B can open the
If you are running anything older than build 706, bug #6589 can
explain this behavior. In this case, please update and check if you
still see this.
If you running anything that already brings firmware version 22.p14 we
will investigate this further. Please attach a capture to the ticket.
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