A quick tip for Vodacom 3G / GPRS / EDGE users in South Africa.

There is a special APN called “internetvpn” for laptop users who connect to corporate VPNs. While this probably doesn’t interest most readers, it is a useful APN to use because:

• You get a real Public IP address, not a private NATted one.
• You get lower latency.
• The cost is the same. (i.e. regular data bundles work fine)

If you use a VPN, this will probably make it more reliable, and if you don’t it will at least make your ssh use more comfortable.

Unfortunately, the following vodacom issues will still be present:

• No incoming TCP connections (i.e. you can’t serve web pages from or ssh into your laptop)
• Often you get “martian” DNS servers (10.11.12.13 and 10.11.12.14). Either reconnect, or manually set your DNS servers to 196.43.46.190 (SAIX) and 196.207.40.165 (Vodacom).
• TCP connections are regularly reset. (Overloaded NAT/Firewall hardware?)

How to get it:

1. Call vodacom customer care (111).
2. Follow the IVR menu options in the directions of data cards.
3. Ask them to enable the “internetvpn APN” (you might have to explain it to them)
4. Reconfigure your phone / chat script / “data card driver” to use “internetvpn” instead of “internet”
5. Profit! :-)

Tectonic has spotted a new GUI for 3G Datacards.

You can see it in action.

Vodafone Spain sponsored it’s writing, and they made the right choices: it’s GPL, Python-GTK, and pretty well written. It looks like a clone of the Windows Vodafone client, but using libnotify, and other cool GTKisms. I highly approve.

Installing it was as simple as downloading the deb, and installing it with gdebi.

The first thing I did was add the support for my Option 3G GT Quad Fusion Datacard, which was as simple as finding out the USB IDs, and modifying another card’s driver:

class OptionGTFusionQuadLite(Device):
    __properties__ = {
          'usb_device.vendor_id' : 0x0af0,
          'usb_device.product_id': 0x6300,
    }
    __name__ = "Option GT Fusion Quad Lite"
    conn_dict = OPTION_DICT

simple eh?

This should be incorporated in default Ubuntu installs. It should also be extended to support talking to phones over bluetooth / IRDA. (At the moment, it seems to only like talking to things that HAL knows about)

Seeing as I carry around a vast array of equipment, in my massive, 10Ton backpack, I normally have a 3G card at hand. If I’m visiting someone who doesn’t have broadband themselves, or I’m sitting in a Coffee Shop with other laptop-lugging friends I might want to share my 3G connection with friends, via WiFi. (assuming I have a data bundle that month, or they understand the horrific 3G data pricing)

I wrote a little script to make this easy

• It’s clearly Atheros-specific, but I’ve included more generic commands in comments. Obviously interface names would need to be changed
• I dial the 3G connection before I run this, and disconnect afterwards, but it would be trivial to change that…
• My dnsmasq.conf contains only the line dhcp-range=10.42.42.10,10.42.42.254,12h
• Dnsmasq is configured not to run on startup, via update-rc.d

/usr/local/sbin/3g-ap:

#!/bin/sh

/etc/dbus-1/event.d/25NetworkManager stop
# Atheros:
wlanconfig ath0 destroy
wlanconfig ath0 create wlandev wifi0 wlanmode ap
# Other:
#iwconfig ath1 mode master

iwconfig ath0 chan 3
iwconfig ath0 essid SR
iwconfig ath0 enc s:13Char-Passwd

ifconfig ath0 up 10.42.42.1 netmask 255.255.255.0
/etc/init.d/dnsmasq start

iptables -t nat -F POSTROUTING
iptables -t nat -A POSTROUTING -o ppp0 -s 10.42.42.0/24 -j MASQUERADE
sysctl -w net/ipv4/ip_forward=1

echo "Done - when finished, hit enter"
read ignoreme

/etc/init.d/dnsmasq stop
iptables -t nat -F POSTROUTING
sysctl -w net/ipv4/ip_forward=0

# Atheros:    
wlanconfig ath0 destroy
wlanconfig ath0 create wlandev wifi0 wlanmode sta
# Other:
#iwconfig ath0 mode managed

/etc/dbus-1/event.d/25NetworkManager start

I’ve touched up the CLUG wiki GPRS/3G page today. It’s now a complete dump of my knowledge on the subject - a page I wish had existed when I started mucking with mobile data.

Now I’m just waiting for the 3G card that I bought on eBay to turn up, so I can get a slightly more usable connection than asthmatic GPRS when I’m on the run.