How to share the Internet with Linux and an iPad by Wi-Fi?

[Ralf Mardorf <ralf.mardorf@alice-dsl.net>]

Hi :)

I need to share the Internet for the PC with an iPad. Linux is connected
by PPPoE using eth0 to the Internet and the iPad should get access to
the Internet by a Sempre WU300-1K USB adapter connected to the Linux PC.

$ hwinfo --usb
  [snip]
  Device: usb 0x8172 "RTL8191S WLAN Adapter"
  Revision: "2.00"
  Serial ID: "00e04c000001"
  Driver: "r8712u"
  Driver Modules: "r8712u"
  Device File: wlan0
  [snip]

Using Arch Linux I didn't get the Sempre to run. Using Ubuntu Studio
Oneiric I can connect the iPad to Linux by WLAN, but there's neither a
password required nor access to the Internet.

Is there a way to get Internet access under Debian + a password
protection?

If I run this on Ubuntu ...

$ cat adhoc
#! /bin/sh
# sh ./adhoc
# https://help.ubuntu.com/community/WifiDocs/Adhoc

device=wlan0
sudo service network-manager stop
sudo ip link set $device down
sudo iwconfig $device mode ad-hoc
sudo iwconfig $device channel 4
sudo iwconfig $device essid 'oz'
sudo iwconfig $device key 1324354657
# sudo dhclient $device
sudo ip addr add 169.254.34.2/16 dev $device
exit 0

... the iPad recognized a network "oz". I can connect by selecting the
name "oz", WEP and for the password I just enter a space, but as
mentioned before, I don't get access to the Internet.

A google for "linux masquerade router" found several confusing and not
working howtos.

I would install a minimal Debian, if there should be a usable howto.
Perhaps a small Debian without GUI, since for the moment I would be
glad, just to get access to the Internet for the iPad.

Any hints are welcome,
Ralf

OT:
I didn't buy, but won an iPad 2. Beside all that flashy crap it can do
amazing things, of cause not usable with Linux, but for Mac and Windows
there are e.g. amazing apps that can be used with Mac and Windows DAWs.
Perhaps a jailbreak will enable some possibilities, when using it with a
Linux PC too. I was thinking of selling it and buying an Android tablet,
but a request on Linux audio mailing lists made clear that Android
hasn't the abilities for pro-audio and the Android developers aren't
interested in fixing bugs related to this issue. Another wasted chance
for Linux to become popular and to make more hardware vendors taking
care of Linux. Anyway, I don't own a Mac PC or a Windows PC and I hope I
get access to the Internet using Linux.