Disappointment with wifi...

[Mason Loring Bliss]

Hi all. I'm coming to you with a minor existential crisis. :)

I've got a Thinkpad T420, initially purchased as my best bet for FreeBSD
hardware compatibility. For wifi it has Centrino Advanced-N 6205 [Taylor
Peak].

I did a fresh install of 11.0-BETA2 the other day, and that worked well
enough, up to and including finding local wifi and initially connecting.

However, on boot, dhclient keeps saying, repeatedly:

    send_packet: Network is down
    send_packet: No buffer space available

...and of course my network is largely unusable this way. It seems to come
and go, but I can't predict it.

I know it's a volunteer project, and I know that laptops aren't a priority,
especially as compared with servers, but I'd really like for this to work.
The last time I tried to tackle something like this myself, however, it went
badly - I had an onboard Realtek gigabit NIC, and the best I could get was a
brute-force reset of the driver when it would fall over. I made an initial
effort to compare the (functionally flawless, as far as I could see) Linux
driver with ours, but I quickly got lost. I've never attained the lofty
heights of kernel hacking and I completely lacked context to understand the
code.

What would you folks recommend, given a strong interest in seeing FreeBSD
support my T420 well enough for me to be able to use fully? Running FreeBSD
in an interactive role is going to be the best way for me to maintain my
interest in pushing it forward, finding pain points to bring up, etc., and
this laptop is one of my most heavily-used systems, as I'm using it whenever
I'm not at a desk. I could just go back to RHEL on it, but I'd like to take
the opportunity to address this issue and make the world a better place.

It looks like we've had support for this chip for a while... I see it
mentioned a number of times in SVN:

    http://svnweb.freebsd.org/base/head/sys/dev/iwn/if_iwn.c?view=log

Revision 285234 from last year looks interesting... It notes issues with
HT40. I see my local network using HT20, so I would expect this to not
describe my issue, but it does make me wonder if there's anything I can set
to influence driver behaviour. Nothing jumps out at me from iwn(4).

Thanks in advance for ideas and direction.

-- 
Mason Loring Bliss  ((   If I have not seen as far as others, it is because
 mason at blisses.org   ))   giants were standing on my shoulders. - Hal Abelson
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