[NCLUG] Perplexing wireless issue - Voodoo accepted

[Matt Taggart]

>  My other devices were working fine on the network
> (PS3, Xbox, other laptops/desktops).

Are any of these devices wireless? Or are they wired on the WRT54GL ports 
or elsewhere on the network?

It would help to determine:
* If any other wireless devices are getting DHCP and working.
* If any other wired devices on the WRT54GL are getting DHCP and working.

Then you can determine if the problem is just the laptop, just the router, 
just Tomato, or some combination.

> I then hooked up another router through the WRT54GL (a
> Buffalo WHR-HP-G54 with dd-wrt) and then laptop connected right up.

You connected the buffalo to one of the client ports on the WRT54GL and 
then the laptop was able to get a wireless link to the buffalo? And it got 
an address via DHCP? from the buffalo or from the wrt?

So far I think the problem is either the laptop or the wrt hardware itself, 
but answers to the above might narrow it down some more.

>   The logs on the laptop indicate that it sends the DHCPREQUEST but
> receives no DHCPOFFER.  The logs on the router indicate a DHCPOFFER was
> sent, but no DHCPACK is received. I tried using wireshark and tcpdump
> to see if the laptop was just ignoring the DHCPOFFER packet.  I couldn't
> get anything conclusive, but maybe my flags were wrong, or I wasn't
> looking close enough.

Here's another total stab in the dark, but since your symptoms match those 
of a problem I once had I thought I'd mention it...

Make sure Explicit Congestion Notfication is turned off on the laptop.

cat /proc/sys/net/ipv4/tcp_ecn

should return zero. If you are using a distro kernel then it should be off 
already, but if you built your own maybe you thought this sounded like a 
nice feature and turned it on (like I did when I ran into a similar 
problem).

-- 
Matt Taggart
matt at lackof.org