XO -> XO ping problem

[Michail Bletsas]

Javier's theory is correct.

I can replicate the issue on both an Apple Airport Express (which 
explicitly supports WDS) and a Linksys WRT54GL (firmware 4.30.7).

With build 406.15 (to get  the latest driver bits) 

http://olpc.download.redhat.com/olpc/streams/development/build406.15/

and firmware 5.220.11.p5, 

XOs associated with the AP via eth0 cannot ping each other. Pinging via 
the mesh interface works fine.

Updating  firmware to 5.110.16.p0 allows the XOs to ping each other via 
the AP.


The is a catch though! Each ping request generates 4 responses!

Apparently, whatever mangling the Linksys and Apple APs are doing to the 
frames before retransmitting must be confusing the bridge code in the 
firmware and make it generate the double duplicate responses.
Pinging the XO from a windows host doesn't generate the duplicate 
responses. Pinging the windows machine from the XO does exhibit the same 
behavior.

For baseline purposes, when associated with our Cisco 1130 APs none of the 
issues mentioned in this thread show up (XO's ping each other and there 
are no duplicate responses).
The Cisco's are WDS-capable but don't do it unless instructed to ;-)

In any case, that's another reason to switch to 5.110.16.p0 asap 
(duplicates are way much better than no packets at all ;-)

M.






"Javier Cardona" <javier at cozybit.com> 
Sent by: libertas-dev-bounces at lists.infradead.org
06/28/2007 11:24 AM

To
"Dan Williams" <dcbw at redhat.com>
cc
libertas-dev at lists.infradead.org, Ronak Chokshi <rchokshi at marvell.com>, 
mbletsas at laptop.org, adrian martin <amart.n at gmail.com>
Subject
Re: XO -> XO ping problem






Dan,

> Linksys WRT54g HW v2, firmware v4.x-something.  I don't think it's
> WDS-enabled at all, WDS doesn't show up anywhere in the interface, but I
> could be wrong.

That fooled us in the past:  although WDS is not mentioned anywhere in
the documentation or the configuration pages, the WRT54g *does*
lazy-WDS.  I have wireshark captures to prove it... :)

Javier


>
> > Javier
> >
> >
> > On 6/27/07, Dan Williams <dcbw at redhat.com> wrote:
> > > Javier,
> > >
> > > We're observing an interesting problem here, replicated in at least 
3
> > > different locations (Waltham (me), Toronto (tamtam), Arlington
> > > (dilinger)) on a bunch of different builds (406.x, 432, 451) with
> > > different hardware (B1, B2, B3) and different firmware (5.220.10.p5,
> > > 5.220.11.p5).  In all 3 locations, nothing is doing mesh networking 
at
> > > all.
> > >
> > > The problem is that when connected in infrastructure mode, two XOs
> > > cannot ping each _other_, but other normal laptops connected to the 
same
> > > AP can ping each XO, and the XO can both ping the normal laptop and
> > > external sites like google.
> > >
> > > For my investigation of this problem, I turned off NetworkManager
> > > completely and booted up in runlevel 3.
> > >
> > > On both laptops I have, I did:
> > >
> > > chkconfig --level 345 NetworkManager off
> > > chkconfig --level 345 dhcdbd off
> > > chkconfig --level 345 network off
> > > nano /etc/inittab (set runlevel 3 as default)
> > > <reboot>
> > > iwconfig eth0 essid foobar key <blah> mode managed
> > > dhclient -1 eth0
> > >
> > > and then tried to ping each other XO from the other, and to ping 
google,
> > > and to ping my ThinkPad T42.  The XOs always failed to ping each 
other,
> > > but could both ping google and my T42.
> > >
> > > Digging further into the issue, I found via wireshark/ethereal on my
> > > thinkpad that I can see the ARP request from XO1 -> XO2, but XO2 
never
> > > sends an ARP reply back (as seen from wireshark).  Turning on RX & 
TX
> > > debugging in the driver on the XO2 shows the "SendSinglePacket 
succeeds"
> > > message for (apparently) each ARP request XO2 receives, which I
> > > interpret to mean that XO2 is actually trying to send the ARP reply, 
but
> > > that the reply gets lost between the host_to_card() function and the
> > > radio.  I can actually try to get the hexdump of the outgoing tx 
packets
> > > if that would help.
> > >
> > > However, running tcpdump on both machines has interesting results. 
The
> > > pinging XO1 shows the pings in the dump, but the dump from the XO2 
being
> > > pinged shows only LLC frames, and no ICMP frames.  tcpdump isn't 
getting
> > > any pings.  If you want the tcpdumps I can send you a link.
> > >
> > > Thoughts?  Can you try to replicate with, say, build 451 and debug 
the
> > > issue as well?
> > >
> > > Thanks,
> > > Dan
> > >
> > >
> > >
> >
> >
>
>


-- 
Javier Cardona
cozybit Inc.
p 415 974 6770
f 415 974 6771
c 415 630 0627
e javier at cozybit.com

_______________________________________________
libertas-dev mailing list
libertas-dev at lists.infradead.org
http://lists.infradead.org/mailman/listinfo/libertas-dev