#!/usr/bin/env bash
set -Eeuo pipefail

# Docker environment variables

: ${DHCP:='N'}
: ${MAC:='02:11:32:AA:BB:CC'}

: ${VM_NET_TAP:='dsm'}
: ${VM_NET_DEV:='eth0'}
: ${VM_NET_MAC:="$MAC"}
: ${VM_NET_HOST:='VirtualDSM'}

: ${DNSMASQ_OPTS:=''}
: ${DNSMASQ:='/usr/sbin/dnsmasq'}
: ${DNSMASQ_CONF_DIR:='/etc/dnsmasq.d'}

ADD_ERR="Please add the following setting to your container:"

# ######################################
#  Functions
# ######################################

configureDHCP() {

  # Create a macvtap network for the VM guest

  { ip link add link "$VM_NET_DEV" name "$VM_NET_TAP" address "$VM_NET_MAC" type macvtap mode bridge ; rc=$?; } || :

  if (( rc != 0 )); then
    error "Cannot create macvtap interface. Please make sure the network type is 'macvlan' and not 'ipvlan',"
    error "and that the NET_ADMIN capability has been added to the container: --cap-add NET_ADMIN" && exit 16
  fi

  while ! ip link set "$VM_NET_TAP" up; do
    info "Waiting for address to become available..."
    sleep 2
  done

  local TAP_NR TAP_PATH MAJOR MINOR
  TAP_NR=$(</sys/class/net/"$VM_NET_TAP"/ifindex)
  TAP_PATH="/dev/tap${TAP_NR}"

  # Create dev file (there is no udev in container: need to be done manually)
  IFS=: read -r MAJOR MINOR < <(cat /sys/devices/virtual/net/"$VM_NET_TAP"/tap*/dev)
  (( MAJOR < 1)) && error "Cannot find: sys/devices/virtual/net/$VM_NET_TAP" && exit 18

  [[ ! -e "$TAP_PATH" ]] && [[ -e "/dev0/${TAP_PATH##*/}" ]] && ln -s "/dev0/${TAP_PATH##*/}" "$TAP_PATH"

  if [[ ! -e "$TAP_PATH" ]]; then
    { mknod "$TAP_PATH" c "$MAJOR" "$MINOR" ; rc=$?; } || :
    (( rc != 0 )) && error "Cannot mknod: $TAP_PATH ($rc)" && exit 20
  fi

  { exec 30>>"$TAP_PATH"; rc=$?; } 2>/dev/null || :

  if (( rc != 0 )); then
    error "Cannot create TAP interface ($rc). $ADD_ERR --device-cgroup-rule='c *:* rwm'" && exit 21
  fi

  { exec 40>>/dev/vhost-net; rc=$?; } 2>/dev/null || :

  if (( rc != 0 )); then
    error "VHOST can not be found ($rc). $ADD_ERR --device=/dev/vhost-net" && exit 22
  fi

  NET_OPTS="-netdev tap,id=hostnet0,vhost=on,vhostfd=40,fd=30"

  return 0
}

configureDNS () {

  # dnsmasq configuration:
  DNSMASQ_OPTS="$DNSMASQ_OPTS --dhcp-range=$VM_NET_IP,$VM_NET_IP --dhcp-host=$VM_NET_MAC,,$VM_NET_IP,$VM_NET_HOST,infinite --dhcp-option=option:netmask,255.255.255.0"

  # Create lease file for faster resolve
  echo "0 $VM_NET_MAC $VM_NET_IP $VM_NET_HOST 01:$VM_NET_MAC" > /var/lib/misc/dnsmasq.leases
  chmod 644 /var/lib/misc/dnsmasq.leases

  # Set DNS server and gateway
  DNSMASQ_OPTS="$DNSMASQ_OPTS --dhcp-option=option:dns-server,${VM_NET_IP%.*}.1 --dhcp-option=option:router,${VM_NET_IP%.*}.1"
  DNSMASQ_OPTS=$(echo "$DNSMASQ_OPTS" | sed 's/\t/ /g' | tr -s ' ' | sed 's/^ *//')

  [[ "$DEBUG" == [Yy1]* ]] && set -x
  $DNSMASQ ${DNSMASQ_OPTS:+ $DNSMASQ_OPTS}
  { set +x; } 2>/dev/null
  [[ "$DEBUG" == [Yy1]* ]] && echo

  return 0
}

configureNAT () {

  # Create a bridge with a static IP for the VM guest

  VM_NET_IP='20.20.20.21'
  [[ "$DEBUG" == [Yy1]* ]] && set -x

  { ip link add dev dockerbridge type bridge ; rc=$?; } || :

  if (( rc != 0 )); then
    error "Failed to create bridge. $ADD_ERR --cap-add NET_ADMIN" && exit 23
  fi

  ip address add ${VM_NET_IP%.*}.1/24 broadcast ${VM_NET_IP%.*}.255 dev dockerbridge

  while ! ip link set dockerbridge up; do
    info "Waiting for address to become available..."
    sleep 2
  done

  # QEMU Works with taps, set tap to the bridge created
  ip tuntap add dev "$VM_NET_TAP" mode tap

  while ! ip link set "$VM_NET_TAP" up promisc on; do
    info "Waiting for tap to become available..."
    sleep 2
  done

  ip link set dev "$VM_NET_TAP" master dockerbridge

  # Add internet connection to the VM
  iptables -t nat -A POSTROUTING -o "$VM_NET_DEV" -j MASQUERADE
  iptables -t nat -A PREROUTING -i "$VM_NET_DEV" -d "$IP" -p tcp  -j DNAT --to "$VM_NET_IP"
  iptables -t nat -A PREROUTING -i "$VM_NET_DEV" -d "$IP" -p udp  -j DNAT --to "$VM_NET_IP"

  if (( KERNEL > 4 )); then
    # Hack for guest VMs complaining about "bad udp checksums in 5 packets"
    iptables -A POSTROUTING -t mangle -p udp --dport bootpc -j CHECKSUM --checksum-fill || true
  fi

  { set +x; } 2>/dev/null
  [[ "$DEBUG" == [Yy1]* ]] && echo

  # Check port forwarding flag
  if [[ $(< /proc/sys/net/ipv4/ip_forward) -eq 0 ]]; then
    { sysctl -w net.ipv4.ip_forward=1 ; rc=$?; } || :
    if (( rc != 0 )); then
      error "IP forwarding is disabled. $ADD_ERR --sysctl net.ipv4.ip_forward=1" && exit 24
    fi
  fi

  NET_OPTS="-netdev tap,ifname=$VM_NET_TAP,script=no,downscript=no,id=hostnet0"

  { exec 40>>/dev/vhost-net; rc=$?; } 2>/dev/null || :
  (( rc == 0 )) && NET_OPTS="$NET_OPTS,vhost=on,vhostfd=40"

  configureDNS

  return 0
}

closeNetwork () {

  exec 30<&- || true
  exec 40<&- || true

  if [[ "$DHCP" == [Yy1]* ]]; then

    fKill "server.sh"

    ip link set "$VM_NET_TAP" down || true
    ip link delete "$VM_NET_TAP" || true

  else

    fKill "dnsmasq"

    ip link set "$VM_NET_TAP" down promisc off || true
    ip link delete "$VM_NET_TAP" || true

    ip link set dockerbridge down || true
    ip link delete dockerbridge || true

  fi
}

# ######################################
#  Configure Network
# ######################################

fKill "server.sh"

# Create the necessary file structure for /dev/net/tun
if [ ! -c /dev/net/tun ]; then
  [ ! -d /dev/net ] && mkdir -m 755 /dev/net
  if mknod /dev/net/tun c 10 200; then
    chmod 666 /dev/net/tun
  fi
fi

if [ ! -c /dev/net/tun ]; then
  error "TUN device missing. $ADD_ERR --cap-add NET_ADMIN" && exit 25
fi

# Create the necessary file structure for /dev/vhost-net
if [ ! -c /dev/vhost-net ]; then
  if mknod /dev/vhost-net c 10 238; then
    chmod 660 /dev/vhost-net
  fi
fi

update-alternatives --set iptables /usr/sbin/iptables-legacy > /dev/null
update-alternatives --set ip6tables /usr/sbin/ip6tables-legacy > /dev/null

VM_NET_MAC="${VM_NET_MAC//-/:}"
GATEWAY=$(ip r | grep default | awk '{print $3}')
IP=$(ip address show dev "$VM_NET_DEV" | grep inet | awk '/inet / { print $2 }' | cut -f1 -d/)

if [[ "$DEBUG" == [Yy1]* ]]; then
  info "Container IP is $IP with gateway $GATEWAY" && echo
fi

if [[ "$DHCP" == [Yy1]* ]]; then

  if [[ "$GATEWAY" == "172."* ]]; then
    if [[ "$DEBUG" != [Yy1]* ]]; then
      error "You can only enable DHCP while the container is on a macvlan network!" && exit 26
    fi
  fi

  # Configuration for DHCP IP
  configureDHCP

  # Display IP on port 80 and 5000
  /run/server.sh 5000 /run/ip.sh &

else

  # Configuration for static IP
  configureNAT

fi

NET_OPTS="$NET_OPTS -device virtio-net-pci,romfile=,netdev=hostnet0,mac=$VM_NET_MAC,id=net0"

return 0