#!/bin/bash
# Copyright 2021 Google LLC
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#      http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

[ ! -e /usr/share/gbmc-br-lib.sh ] && exit

# shellcheck source=meta-google/recipes-google/networking/network-sh/lib.sh
source /usr/share/network/lib.sh || exit
# shellcheck source=meta-google/recipes-google/networking/gbmc-bridge/gbmc-br-lib.sh
source /usr/share/gbmc-br-lib.sh || exit

NCSI_IF='@NCSI_IF@'

old_pfx=
old_fqdn=
old_rtr=

set_host() {
  [[ -n "$host" && -n "$domain" && -n "$hextet" ]] || return

  local fqdn="$host-n$hextet.$domain"
  [ "$fqdn" != "$old_fqdn" ] || return
  old_fqdn="$fqdn"

  echo "Found hostname $fqdn" >&2
  hostnamectl set-hostname "$fqdn" || true
}

set_net() {
  [[ -n "$pfx" && -n "$rtr" ]] || return
  [[ "$pfx" != "$old_pfx" || "$rtr" != "$old_rtr" ]] || return
  old_pfx="$pfx"
  old_rtr="$rtr"

  echo "Found prefix $pfx from $rtr" >&2

  # We no longer need NCSId if we are in this configuration
  systemctl stop --no-block ncsid@"$NCSI_IF" || true

  # Save the IP address for the interface
  gbmc_br_set_ip "$pfx" || true

  # DHCP Relay workaround until alternate source port is supported
  # TODO: Remove this once internal relaying cleanups land
  gbmc-ncsi-smartnic-wa.sh || true
}

w=60
while true; do
  start=$SECONDS
  while read -r line; do
    # `script` terminates all lines with a CRLF, remove it
    line="${line:0:-1}"
    if [ -z "$line" ]; then
      hextet=
      pfx=
      host=
      domain=
    elif [[ "$line" =~ ^Prefix' '*:' '*(.*)/([0-9]+)$ ]]; then
      t_pfx="${BASH_REMATCH[1]}"
      t_pfx_len="${BASH_REMATCH[2]}"
      ip_to_bytes t_pfx_b "$t_pfx" || continue
      (( t_pfx_len == 76 && (t_pfx_b[8] & 0xfd) == 0xfd )) || continue
      (( t_pfx_b[9] |= 1 ))
      hextet="fd$(printf '%02x' "${t_pfx_b[9]}")"
      pfx="$(ip_bytes_to_str t_pfx_b)"
    elif [[ "$line" =~ ^'DNS search list'' '*:' '*([^.]+)(.*[.]google[.]com)' '*$ ]]; then
      # Ideally, we use PCRE and with lookahead and can do this in a single regex
      #   ^([a-zA-Z0-9-]+(?=-n[a-fA-F0-9]{1,4})|[a-zA-Z0-9-]+(?!-n[a-fA-F0-9]{1,4}))[^.]*[.]((?:[a-zA-Z0-9]*[.])*google[.]com)$
      # Instead we do multiple steps to extract the needed info
      host="${BASH_REMATCH[1]}"
      domain="${BASH_REMATCH[2]#.}"
      if [[ "$host" =~ (-n[a-fA-F0-9]{1,4})$ ]]; then
        host="${host%"${BASH_REMATCH[1]}"}"
      fi
    elif [[ "$line" =~ ^from' '(.*)$ ]]; then
      rtr="${BASH_REMATCH[1]}"
      set_net || true
      set_host || true
    fi
  done < <(exec script -q -c "rdisc6 -d -m $NCSI_IF -w $(( w * 1000 ))" /dev/null 2>/dev/null)
  # If rdisc6 exits early we still want to wait the full `w` time before
  # starting again.
  (( timeout = start + w - SECONDS ))
  sleep $(( timeout < 0 ? 0 : timeout ))
done