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Three mobile broadband in Linux¶
Steve Lowry is picking up his Three modem this afternoon and asks on our internal Linux list if it supports Linux.
I’ve ordered the Huawei E220 as it was free. Is it likely to work with Linux? And, if so what should I be looking for to set it up?
I’ve had a Huawei USB modem for about six months now and it works fine in Linux, although it is probably a slightly different model. The box and case for mine claims it is a E160G, whereas lsusb from usbutils claims it is a E220. The manufacturers of these types of products routinely change the components and models without updating the product codes, so you’ll have to wait until you plug it in to see what model it actually is.
As for how to make it work? Simply use a distribution that comes with NetworkManager and NetworkManager’s mobile broadband provider database. When I tested it on a friend’s install with that setup last month it worked out of the box, all you had to do was plug it in and select the network.
The route to fail¶
If, like me, you’d prefer not to install NetworkManager you can manually configure the device using pppd, and life is even easier now than it was when I did it as there is plenty more information available(including this I guess).
Finding the APN¶
The first thing you need is your provider’s APN, and the easiest place to find it is from the NetworkManager database. If yours is not there you’ll have to dig further. When I originally got my device that database was practically empty, so I had to resort to other means to find the APN.
We can extract the APN from the Windows driver that came with the device. The driver can be found on the device itself because it also acts a small SCSI device with a filesystem. It is actually pretty clever, assuming it works as advertised, as it can self-install its own driver when plugged in.
If we find the device name with dmesg we can mount it, and pull the APN from the Windows driver:
mkdir e220_drivers; cd e220_drivers
mount -t vfat /dev/sr2 /mnt/huawei
for file in /mnt/huawei/**/*.cab; do unpack $file; done
The unpack tool from above is just a wrapper around common
archivers, and the tool you actually need to extract the cab files is
unshield. Contrary to my first idea cabextract doesn’t work, as these files
are actually made by installshield.
With the APN in hand all we need to do now is configure our system.
Kernel¶
If you’re using a vendor supplied kernel the options we need are hopefully already enabled. If they’re not, or you build your own kernels, there are few changes we need to make to the kernel configuration.
The dongle itself needs CONFIG_USB_SERIAL_OPTION enabled, which is labelled
as USB driver for GSM and CDMA modems in the kernel’s menuconfig. It
can be found hidden away under the “USB Serial Converters” section in 2.6.31.
We also need CONFIG_PPP and CONFIG_PPP_ASYNC support, which can be
found in the “Network devices” section of the config. Unlike the old-style
dialup you may be used to use there is no point enabling the PPP compression options as they are not supported by
mobile providers in general, partly because the data is already compressed.
Then just rebuild the kernel, and check that the dongle shows up in dmesg output when it is plugged in. If it does we’re ready for the next step.
/etc/chatscripts/three¶
We need a pppd chatscript for the connection, the format and settings of this file can be found in the chat(8) manpage. My chatscript is below:
TIMEOUT 3
ECHO ON
ABORT 'BUSY'
ABORT 'DELAYED'
ABORT 'ERROR'
ABORT 'NO ANSWER'
ABORT 'NO CARRIER'
ABORT 'NO DIALTONE'
ABORT 'VOICE'
'' \rAT
OK 'AT+CGDCONT=1,"IP","3internet"'
OK ATD*99#
CONNECT ""
Exchange 3internet for your APN in the example above, if it differs.
It is also possible, yet unlikely, that you’ll have to call a different number
to *99#. If this was the case you would have found that out from extracting
the data from the drivers or looking your network up in the NetworkManager
database.
Notice the very short value for timeout, I’ve come to that value empirically. If the connection isn’t up after 3 seconds it is not coming up, and you’re just wasting time before you retry.
/etc/ppp/peers/three¶
We also need a peer script, and the format of that file is described in the pppd(8) manpage. Mine can be used as an example:
debug
noauth
connect "/usr/sbin/chat -v -f /etc/chatscripts/three"
noipdefault
usepeerdns
/dev/ttyUSB0
defaultroute
persist
crtscts
lcp-echo-failure 0
You may have to change your device settings if the dongle doesn’t show up as
/dev/ttyUSB0, but other than that the file should be correct.
Note that we don’t set a speed in our peer file, and this may appear unusual to you if you’ve configured pppd manually in the past. The reason is that interface speed for USB modems is set by the kernel, and adding a value here is pointless.
passwords¶
We don’t need to add an entry to chap-secrets or pap-secrets as
authentication isn’t required, but if you’re following along having chosen to
use a configuration tool such as pppconfig just enter any values you wish as
they’re silently ignored.
I’m told the same applies to wvdial, so if it complains about requiring a password just add an empty or random string to stop the errors.
Testing the connection¶
To test the connection all we need to do is issue pon three, or use the
graphical tool in your distro if you wish. The first time you do this you
should watch the output of your syslog to look for errors, the errors can be
found in syslog because we supplied debug in our peer script.
On my system the log can be comfortably viewed with tail -f
/var/log/ppp/current, but it is system dependent and if you don’t use metalog
it will definitely be somewhere else in /var/log.
If the connection worked fine that is all there is to it, now just enable the connection at system startup or configure udev to connect when the device is inserted if it will not always be connected.
Note
These devices can take anywhere between ten and thirty seconds to “settle” once plugged in. So, don’t block on this service if you add it to the system startup scripts as it can significantly slow down the system boot time. On my dongle you can visually check how long the device takes to settle by watching the LED on the case, when it changes from green it has found a network signal and is ready to use.
If the connection didn’t work correctly look at the debugging output in syslog and check the pppd manual page to look up the error codes.
Happy, erm… mobility.
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