setup_network.sh

#!/system/bin/sh

set -e

TAP_IFACE=crosvm_tap
TAP_ADDR=192.168.1.1
TAP_NET=192.168.1.0

function setup_network() {
  local WAN_IFACE=$(ip route get 8.8.8.8 2> /dev/null | awk -- '{printf $5}')
  if [ "${WAN_IFACE}" == "" ]; then
    echo "No network. Connect to a WiFi network and start again"
    return 1
  fi

  if ip link show ${TAP_IFACE} &> /dev/null ; then
    echo "TAP interface ${TAP_IFACE} already exists"
    return 1
  fi

  ip tuntap add mode tap group virtualmachine vnet_hdr ${TAP_IFACE}
  ip addr add ${TAP_ADDR}/24 dev ${TAP_IFACE}
  ip link set ${TAP_IFACE} up
  ip rule flush
  ip rule add from all lookup ${WAN_IFACE}
  ip route add ${TAP_NET}/24 dev ${TAP_IFACE} table ${WAN_IFACE}
  sysctl net.ipv4.ip_forward=1
  iptables -t filter -F
  iptables -t nat -A POSTROUTING -s ${TAP_NET}/24 -j MASQUERADE
}

function setup_if_necessary() {
  if [ "$(getprop ro.crosvm.network.setup.done)" == 1 ]; then
    return
  fi
  echo "Setting up..."
  check_privilege
  setup_network
  setenforce 0
  chmod 666 /dev/tun
  setprop ro.crosvm.network.setup.done 1
}

function check_privilege() {
  if [ "$(id -u)" -ne 0 ]; then
    echo "Run 'adb root' first"
    return 1
  fi
}

setup_if_necessary