This script uses iptable forwarding and dnsmasq to share an internet connection with full relay of remote DNS servers and a local DHCP server. Before trying the script, here is the over all steps:

• You connect to the internet in your normal fashion. For instance with a 3G dongle and your network manager applet.

• Make sure that nothing is running on port 53, run netstat -tlnp to debug

• READ THE SCRIPT before starting and know which interfaces you are using. EXTERNAL is the one connected to the internet and INTERNAL is the one you are sharing the connection via.

• Do not let network-manager mange the INTERNAL interface!

• You might have to adjust the script, especially the iwconfig part, as different interfaces may have different ways of configuring the WEP key

  !/bin/bash

  if [ ! whoami = "root" ]
  then
  echo "Only root"
  exit
  fi

  DHCP='yes'
  EXTERNAL=ppp0
  INTERNAL=wlan0
  INTERNAL_HOST_IP='192.168.10.1'
  SHARE_TO_WLAN='yes'
  WEPKEY=abe1234567
  SSID='mynetwork'
  DNSMASQ_CONFIG='dhcp-range=192.168.10.20,192.168.10.255,12h'
  DNSMASQ_CONFIG_FILE='/etc/dnsmasq.d/shareconnection'

  if [[ $DHCP -eq 'yes' ]]
  then

  DHCP SERVER (enable below lines)

  apt-get install dnsmasq  
  echo $DNSMASQ_CONFIG > $DNSMASQ_CONFIG_FILE  
      echo "listen-address=192.168.10.1" >> $DNSMASQ_CONFIG_FILE  
      echo interface=$INTERNAL >> $DNSMASQ_CONFIG_FILE  
  /etc/init.d/dnsmasq stop
  

  fi

  echo 1 > /proc/sys/net/ipv4/ip_forward
  /sbin/iptables -t nat -A POSTROUTING -o $EXTERNAL -j MASQUERADE
  /sbin/iptables -A FORWARD -i $EXTERNAL -o $INTERNAL -m state --state RELATED,ESTABLISHED -j ACCEPT
  /sbin/iptables -A FORWARD -i $INTERNAL -o $EXTERNAL -j ACCEPT

  ifconfig $INTERNAL down
  ifconfig $INTERNAL $INTERNAL_HOST_IP
  iwconfig wlan0 mode ad-hoc
  iwconfig wlan0 essid $SSID
  iwconfig wlan0 key $WEPKEY
  ifconfig $INTERNAL up

  if [[ $DHCP -eq 'yes' ]]
  then
  /etc/init.d/dnsmasq start
  fi