pure routing.... generating a sane mac addr on the wndr3700 in cerowrt?

pure routing.... generating a sane mac addr on the wndr3700 in cerowrt?

[Dave Taht]

I really want to stop bridging on cerowrt[1], entirely, at least for now.

Coping with multicast, doing saner traffic shaping, trying to come up
with an qdisc estimator that handles multicast right in the presence
of multicast's monsterous effects, and especially - *only seeing
traffic generated from the wireless network while looking at the
problems therein*, is what's driving me.

I don't care about the performance impact of routing vs bridging right
now. In fact I think the performance impact of bridging a  GigE wired
network to a 54Mbit  wireless impact is rather easily demonstrated
with things like IPTv or any even modest level of multicast traffic,
but the latter is hard to prove without testing.

1) What's stopping me is figuring out the depths of the openwrt code
to generate a valid, usable mac address for the undefined wndr wired
card on first boot. I figure it should come from the second wireless
interface, get the local bit defined, and go to the top of the
allowable range that the wireless interface pulls from to generate
it's SSIDs, then slam the generated address into
/etc/config/network....

2) I generate a non-bridged network on the nano-m5s (which has valid
mac addrs for all interfaces, I think) and babel loses the ability to
send mc packets to any interface. Other normal network behavior (eg,
the interfaces work for normal connects) ensues, however.

I've managed to get similar behavior on the wndr when I assign an
arbitrary mac addr to the ethernet interface and unbridge them. With
the vlan enabled, wired networking stops working entirely, with the
vlan disabled, networking worked, but babel stopped. So my assumption
is that there is code buried in the bridging and/or firewall code that
enables some kernel feature or another.

(I'd run into similar problems a year back:
  http://answerpot.com/showthread.php?1484403-IFF_RUNNING%20and%20hostapd
which I thought were solved
)

Just to add to my test set, I've got a kvm and dreamplug build popping out soon.

-- 
Dave Täht
http://www.bufferbloat.net

1: http://www.bufferbloat.net/projects/uberwrt

Re: pure routing.... generating a sane mac addr on the wndr3700 in cerowrt?

[Juliusz Chroboczek]

> I figure it should come from the second wireless interface, get the
> local bit defined, and go to the top of the allowable range that the
> wireless interface pulls from to generate it's SSIDs

Nah.  Just pull 6 bytes from /dev/random, set the local bit, and unset
the group bit.

> 2) I generate a non-bridged network on the nano-m5s (which has valid
> mac addrs for all interfaces, I think) and babel loses the ability to
> send mc packets to any interface.

Do you have link-local v6 addresses on all interfaces?

What does babeld have to say?  (Hint: it uses its own log file.)

-- Juliusz

Re: pure routing.... generating a sane mac addr on the wndr3700 in cerowrt?

[Stephen Hemminger]

On Fri, 24 Jun 2011 00:58:31 +0200
Juliusz Chroboczek <jch@pps.jussieu.fr> wrote:

> > I figure it should come from the second wireless interface, get the
> > local bit defined, and go to the top of the allowable range that the
> > wireless interface pulls from to generate it's SSIDs
> 
> Nah.  Just pull 6 bytes from /dev/random, set the local bit, and unset
> the group bit.

There is nice random_ether_addr in kernel to meet your needs.