#!/bin/bash -x
# Niels Elgaard Larsen
# script to use eeePC 701 with USB 3g modem as accesspoint
# requires iptables, udhcpd, hostapd
# License: GPL or BSD.

# usage netshare my_network  shrared_as
# I.e. the first argument is how you connect to the internet
# the second argument is how others connect through you.

# networks are: 3g, wifi, ether, e.g:
# netshare 3g wifi
# netshare 3g wired
# netshare wifi wired
# netshare wired wifi

if [ -z "$1" ]; then
  echo usage netshare my_network  shrared_as
  echo networks are: 3g, wifi, ether, e.g:
  echo netshare 3g wifi
  echo netshare 3g wired
  echo netshare wifi wired
  echo netshare wired wifi
  exit 0
fi

ESSID="itpol freedom"
#FORCEGDEV=ppp0
#FORCEGDEV=hso0
CHANNEL=11

HWMODE=g
#FORCEAPDRIVER=nl80211

echo 1 > /proc/sys/net/ipv4/ip_forward
if [ "xwired" = "x$1" ] || [ "xwired" = "x$2" ]; then
  WIREDDEV=${FORCEWIRED-$(grep eth /proc/net/dev|cut -d: -f1)}
fi

if [ "x3g" = "x$1" ] || [ "x3g" = "x$2" ]; then
  GDEV=${FORCEGDEV-$(grep -e  '\(hso\|ppp\)' /proc/net/dev|cut -d: -f1)}
fi


if [ "xwifi" = "x$2" ]; then
  # set FORCEWIFIDEV if you do not want the first device
  APDEV=${FORCEWIFIDEV-$(iw dev|grep Interface|grep -v 'mon\.'|head -1|awk '{print $2}')}
  ifconfig ${APDEV} down
  if [ -z "$1" ]; then
    echo did not find device for WWIFI access point
  fi
  APMODE=$(iwconfig $APDEV|grep IEEE|awk '{print $3}')
  if [ ${APMODE} = "802.1b" ]; then
    HWMODE=b
  fi
  echo using AP device ${APDEV}
  APDRIVER=${FORCEAPDRVER}
  if [ -z "$FORCEAPDRIVER" ]; then
    APDRIVER=${FORCEAPDRVER-hostap}
    APDRIVER=hostap
    if (lsmod|grep mac80211); then
      echo saw mac80211 module, guessing on nl80211 driver for devive $APDEV
      echo set FORCEAPDRIVER if necessary
      APDRIVER=nl80211
    fi
  fi
  echo stop dhcp clients
  /etc/init.d/wicd stop
  killall -9 wpa_supplicant
  killall hostapd 
  TFILE=$(mktemp)
  cat > "$TFILE" << ZZZ
interface=$APDEV
driver=${APDRIVER}
ssid=${ESSID}
hw_mode=${HWMODE}
channel=${CHANNEL}
ZZZ
  hostapd $TFILE & 
fi
 
case "$1" in
  "3g" )
  FROMDEV=${GDEV} ;;
  "wired" )
  FROMDEV=${WIREDDEV} ;;
  "wifi" )
  FROMDEV=${FORCEWIFIDEV-$(iw dev|grep Interface|grep -v 'mon\.'|head -1|awk '{print $2}')}
esac
echo sharing ${FROMDEV}

case "$2" in
  "x3g" )
  echo can not share on 3g
  exit 3 ;;
  "wired" )
  TODEV=${WIREDDEV} ;;	
  "wifi" )
  TODEV=${APDEV} ;;
esac
echo sharing on ${TODEV}

killall udhcpd
ifconfig $TODEV down
UDHCPCONFIG=$(mktemp)
cat > "$UDHCPCONFIG" << ZZZ
start 		192.168.42.20
end		192.168.42.254
interface	${TODEV}
opt     router  192.168.42.1 
opt dns 212.60.120.244
ZZZ

iptables -t nat -F; iptables -t mangle -F
#ifconfig $TODEV up
ifconfig $TODEV 192.168.42.1 netmask 255.255.255.0 up
iptables -t nat -A POSTROUTING -s 192.168.42.0/24 -o ${FROMDEV} -j MASQUERADE
/sbin/iptables -A FORWARD -i ${TODEV} -o ${FROMDEV} -j ACCEPT
/sbin/iptables -A FORWARD -i ${FROMDEV} -o ${TODEV} -j ACCEPT

udhcpd $UDHCPCONFIG
echo make sure your GPRS connection is up