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Jun 25, 2014, 03:53 PM
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Cell Phone broadband again

So Virgin sent out a hidden update which disabled the wifi tethering again. It also disabled bluetooth networking. Merely changing phone numbers caused it to download the update. The update didn't affect the Android core.

For many years, people networked using bluetooth + ppp. They opened a serial console over bluetooth which required some AT commands to get the console to go into PPP mode. Then Android introduced PPP over ADB. Then a new standard for networking over bluetooth appeared called PAN.

Now some random notes for PAN.

# enable bluetooth dongle on the laptop
hciconfig hci0 up
# A menu option is required to allow the phone to be discovered by the laptop
hcitool scan
# Connect the phone to a /dev/rfcomm node
rfcomm bind 0 BC:F5:AC:2B:34:96
rfcomm show 0
# test connection
l2ping BC:F5:AC:2B:34:96
# Allow the PC to be discovered by the phone
hciconfig hci0 piscan
# Show status of PC
# allow phone to pair
bluetooth-agent 1234

# change class to networking device
Class = 0x020100
# restart bluetoothd
killall bluetoothd

# bluetooth networking module
modprobe bnep
pand --connect BC:F5:AC:2B:34:96
ifconfig bnep0
route add default gw

# on the phone
iptables -t nat -A POSTROUTING -j MASQUERADE
echo "1" > /proc/sys/net/ipv4/ip_forward

PAN was the closest to working. It forwarded ICMP & UDP, but upon the 1st TCP connection, disabled the bnep0 device.

Another idea was to use the PC as an access point, set the phone as a station, but use the phone as the gateway. The phone can't do simultaneous Wifi & LTE on the GUI, but it can on the command line. Enable, then disable Wifi on the GUI to get an IP address from your PC. Enable LTE on the GUI. Copy the wpa glue from your PC to the phone. On the phone command line, a random combination of the following is required:

Run the Portable wifi hotspot program to set an unknown configuration bit.
/system/xbin/ifconfig wlan0 up
wpa_supplicant -iwlan0 -c/storage/external_SD/wpa.marcy
/system/xbin/ifconfig wlan0

to get it to connect again to your PC while keeping LTE alive. Manually set the IP address it got last time. After all the standard IP masquerading glue, it seems to work yet again.

The old Pi is deployed for yet another task as the mobile hotspot for the crippled mobile hotspot. There is only 1 RT8192 dongle left.

It's become quite clear that tethered broadband through a rooted phone has lost popularity in recent years, since the phone companies are able to devote a lot more manpower to the most minute kernel archana, there are less people interested in the networking internals & the extra $500 per year for a formal tethering plan has a lot less of an impact than it used to. An entire team in Singapore gets $10 million/year just to scan the Jack Crossfire blog for holes in the networking stack.
Last edited by Jack Crossfire; Jun 25, 2014 at 09:34 PM.
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