#!/bin/sh
# script called from /etc/qemu-ifup to bridge a tap network
# interface to an ethernet interface.
# 
# Usage: qemu_bridge [-dhcp] tap_interface eth_interface 
#
#        qemu_bridge [-dhcp] tap_interface
#            (find eth interface automatically)
#
# if -dhcp is specified, use dhcp to get bridge ip, otherwise
# reuse ethernet interface settings.

DHCP=""
if [ "$1" = "-dhcp" ]; then
  shift
  DHCP=yes
fi

# tap interface
TAP_IF="$1"
if ! ifconfig -a | grep -q "^$TAP_IF"; then
  echo "qemu_bridge: Tap interface '$TAP_IF' doesn't exist, aborting."
  exit 1
fi

# The network interface to attach the network bridge to.
IF="$2"
if [ -z "$IF" ]; then
  # use default route's interface if possible
  IF=`route -n | grep '^0.0.0.0' | xargs echo | cut -d\  -f8`
  if [ -z "$IF" ]; then 
    # otherwise get first configured interface
    IF=`ifconfig -s | tail +2 | grep -v '^lo\|^tun\|^tap\|^br0' | head -1 | cut -d\  -f1`
  fi
fi

if ! ifconfig -a | grep -q "^$IF"; then
  echo "qemu_bridge: couldn't find ethernet interface, aborting."
  exit 1
fi

# create bridge if it doesn't exist already
if ! ifconfig -a | grep -q '^br0'; then

  if [ -n "$DHCP" ]; then
    echo "Creating bridge br0 for interfaces $IF, $TAP_IF (dhcp)"
  else
    # If not using DHCP, get eth interface settings
    IP=`ifconfig $IF | head -2 | tail -1 |  sed -e 's/.*addr:\([0-9.]*\).*/\1/'`
    BROADCAST=`ifconfig $IF | head -2 | tail -1 | sed -e 's/.*cast:\([0-9.]*\).*/\1/'`
    NETMASK=`ifconfig $IF | head -2 | tail -1 | sed -e 's/.*Mask:\([0-9.]*\).*/\1/'`
    GATEWAY=`route -n | grep $IF | sed -e 's/[0-9.]* *\([0-9.]*\).*/\1/' | grep -v '0\.0\.0\.0' | head -1`
    echo "Creating bridge br0 for interfaces $IF, $TAP_IF (ip $IP, bcast $BROADCAST, gw $GATEWAY)"
  fi
  # Warning: if the host is a diskless setup (knoppix terminal server),
  # bringing down the interface will hang the pc ...
  ifconfig $IF down
  brctl addbr br0
  ifconfig $IF 0.0.0.0 promisc up
  
  echo "Configuring bridge..."
  brctl stp br0 off
  brctl setfd br0 1
  brctl sethello br0 1
  brctl addif br0 $IF
  
  if [ -n "$DHCP" ]; then
    echo "Bringing up br0 (dhcp)..."
    [ -x /sbin/pump ] && PUMP="/sbin/pump -i"
    [ -x /sbin/dhclient ] && PUMP="/sbin/dhclient"
    $PUMP br0
  else
    echo "Bringing up br0 ($IP)..."
    ifconfig br0 $IP netmask $NETMASK broadcast $BROADCAST up
    
    if [ -n "$GATEWAY" ]; then
      route add default gw $GATEWAY
    fi
  fi
fi

# add tap interface to bridge
ifconfig $TAP_IF 0.0.0.0 promisc up
brctl addif br0 $TAP_IF