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Always interested in offers/projects/new ideas. Eclectic experience in fields like: numerical computing; Python web; Java enterprise; functional languages; GPGPU; SQL databases; etc. Based in Santiago, Chile; telecommute worldwide. CV; email.

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Linux USB Wifi With TP-Link TL-WN722N

From: andrew cooke <andrew@...>

Date: Wed, 15 Jun 2011 21:31:20 -0400

I've recently been interested in security again.  One consequence of this was
trying to get some handle on how useful wifi antennas (cantennas, pringles
etc) are.

(Incidentally, it turns out that you can make a cantenna by wrapping a plastic
bottle in foil - that makes it much easier to get something the right size)

Anyway, to connect a cantenna to a laptop, you need an aerial socket.  While
my laptop has wifi, it doesn't have an external socket.  And, just as
importantly, it has to be supported well on Linux.

After reading around, it seemed that Atheros chips are as good as anything
these days.  And a local shop had in stock (this is Chile, so you have to take
what you can find) something called a TP-Link TL-WN722N for less than 10
pounds.

So I bought one.

And it works with opensuse 11.4 out of the box, as a simple wifi card.
Unfortunately, if you try to use it with aircrack-ng you get the notorious
"channel -1" error.  The way to fix this is explained at
http://www.aircrack-ng.org/doku.php?id=compat-wireless - follow the
instructions there to install new, patched drivers.  One small caveat - the
driver select script didn't work (ie after using it, my wifi was broken); but
building and installing everything did work.

Also, for the record, if you're seeing some other channel number, clean out
your settings - delete the config for wifi, place it under ifup and don't
configure anything - and then reboot.

Andrew

Stability Issues

From: andrew cooke <andrew@...>

Date: Wed, 22 Jun 2011 23:34:05 -0400

The above was rather unreliable (crashes when using the WiFi card, particular
if hibernating).  So I am now trying with the OpenSuse source.  This includes
the additional pathes added by OpenSuse.

For a good description of the process below see http://
linuxmafia.com/pub/linux/suse-linux-internals/chapter34.html - all we are
doing is downloading the source, unpacking it (and applying the OpenSuse
patches), adding the extra patches, compiling and then installing.

This builds for all kernels at the same time, btw (default, desktop and xen).

 zypper source-install compat-wireless
 tree /usr/src/packages/
 cd /usr/src/packages/SPECS
 rpmbuild -bp compat-wireless.spec
 tree ../BUILD/
 cd ../BUILD/compat-wireless-2.6.38.2-2-ns/source/
 wget
 http://patches.aircrack-ng.org/mac80211.compat08082009.wl_frag+ack_v1.patch
 wget http://patches.aircrack-ng.org/channel-negative-one-maxim.patch
 patch -p1 < mac80211.compat08082009.wl_frag+ack_v1.patch
 patch -p1 < channel-negative-one-maxim.patch
 cd ../../../SPECS/
 rpmbuild -bc --short-circuit compat-wireless.spec
 rpmbuild -bi --short-circuit compat-wireless.spec

That didn't install anything so I then tried

 /usr/src/packages/BUILD/compat-wireless-2.6.38.2-2-ns/obj/default
 make install

which does work (and replaces at least the last line earlier).

Andrew

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