Internet Sharing with the N810, or “How to make a $400 WLAN adapter”

I’m currently living in the top floor of a house, with the basement rented to another tenant.  Being the poor student that I am at the moment, I couldn’t afford Internets for the whole summer (*gasp*), but my neighbour agreed to let me share hers.  The problem was that my desktop has no wireless card, and as mentioned, I’m currently poor, so I can’t buy a USB dongle.  Thanks to Macer and Luke-Jr on #maemo, I got this my N810 set up to share its wireless connection with my desktop over USB networking.

This guide assumes a Linux desktop with usbnet  support available (try running modprobe usbnet as root to find out if you have the module), and an N810 with root access enabled.  I’m going to also assume you have the PC Connection Manager installed on your tablet, as it makes things simpler for most people, and also quicker to configure on the fly.

- On the Desktop: as root, run

modprobe usbnet

ifconfig -a

this should list several network interfaces, and one of them should be called usb0 (or some other number, if you are already using USB networking for something else).  Write down the address listed under wlan0

- On the N810: plug your Nokia USB cable into the N8x0, and into your desktop.  Then run the PC Connection Manager applet from your tablet’s control panel.  Click “Advanced”, then the ellipsis (…) button at the top.  Click “New”, and name our profile something like “HappySharing”.  (It really doesn’t matter what you call it.) Select that profile, and click “Select”.  Under the Tool Manager tab, uncheck anything you don’t want.  If you don’t know what it is, just uncheck it – it shouldn’t affect what we’re doing, but if you don’t know how it works, you probably don’t want it on .  Under the Network Manager tab, under “USB Network”, select “Network” from the combo box.  Then enter the following in the text boxes:

IP address: [same as your N810's wlan0 address, noted in the first step]

Gateway: [Whatever your router/gateway's IP address is]

Network mask: [for most people, 255.255.255.0]

Click “Save”, and then “Apply”.

- On the Desktop: as root, run

ifconfig usb0 192.168.x.y up

route add default dev usb0

Where x is the same subnet as your wireless router (usually 1 or 0 for consumer models), and y is an unused static IP address on your network (check your router settings to find out where the DHCP-assigned addresses start, and choose a number lower than that).

- On the N810: as root, run

route add -net 192.168.x.y netmask 255.255.255.255 dev usb0

echo 1 > /proc/sys/net/ipv4/ip_forward

echo 1 > /proc/sys/net/ipv4/conf/all/proxy_arp

Where x and y are the same as in the previous step.

After this is done, everything should work.  Try pinging something from your desktop (you’ll need to set up static DNS servers – 4.2.2.1 and 4.2.2.2 work fine, if you don’t know any others off the top of your head).  Each time you unplug your N810, you’ll want to use PC Connection Manager to select the “None” profile, and every time you want this set up again, you’ll have to switch back to the profile you created, and then redo the last two steps.

I may well have forgotten some detail, or made some assumptions in writing this other than what I mentioned, so if you notice anything that doesn’t look right, or doesn’t work, please let me know in the comments.

Happy forwarding,

- The Ffej