#!/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.

source /usr/share/network/lib.sh || exit
source /usr/libexec/ncsid_lib.sh || exit

old_pfx=
old_rtr=

w=60
while true; do
  start=$SECONDS
  while read line; do
    if [ -z "$line" ]; then
      pfx=
      host=
    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)"
      (( t_pfx_b[9] &= 0xf0 ))
      stateless_pfx="$(ip_bytes_to_str t_pfx_b)"
    elif [[ "$line" =~ ^'DNS search list'' '*:' '*([^.-]*)[^.]*[.](.*.google.com)$ ]]; then
      host="${BASH_REMATCH[1]}"
      domain="${BASH_REMATCH[2]}"
    elif [[ "$line" =~ ^from' '(.*)$ ]]; then
      rtr="${BASH_REMATCH[1]}"
      (( "${#pfx}" != 0 )) || continue
      [[ "$pfx" != "$old_pfx" || "$old_rtr" != "$rtr" ]] || continue

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

      # Delete any stale IP Addresses from the primary interface as we won't use them
      UpdateIP xyz.openbmc_project.Network @NCSI_IF@ '0.0.0.0' '0'
      UpdateIP xyz.openbmc_project.Network @NCSI_IF@ '::' '0'

    read -r -d '' contents <<EOF
[Network]
Address=$pfx/128
IPv6PrefixDelegation=yes
[IPv6PrefixDelegation]
RouterLifetimeSec=60
[IPv6Prefix]
Prefix=$stateless_pfx/80
PreferredLifetimeSec=60
ValidLifetimeSec=60
[IPv6RoutePrefix]
Route=$pfx/80
LifetimeSec=60
[Route]
Destination=$stateless_pfx/76
Type=unreachable
Metric=1024
EOF
      for file in /run/systemd/network/{00,}-bmc-gbmcbr.network.d/49-public-ra.conf; do
        mkdir -p -m 755 "$(dirname "$file")"
        printf '%s' "$contents" >"$file"
      done

      contents='[Network]'$'\n'
      contents+="Address=$pfx/128"$'\n'
      contents+="Gateway=$rtr"$'\n'
      for file in /run/systemd/network/{00,}-bmc-@NCSI_IF@.network.d/49-public-ra.conf; do
        mkdir -p -m 755 "$(dirname "$file")"
        printf '%s' "$contents" >"$file"
      done

      # Ensure that systemd-networkd performs a reconfiguration as it doesn't
      # currently check the mtime of drop-in files.
      touch -c /lib/systemd/network/*-bmc-gbmcbr.network
      touch -c /etc/systemd/network/*-bmc-@NCSI_IF@.network

      if [ "$(systemctl is-active systemd-networkd)" != 'inactive' ]; then
        networkctl reload
        networkctl reconfigure gbmcbr
      fi

    read -r -d '' contents <<EOF
table inet filter {
  chain ncsi_input {
    ip6 saddr != $pfx/76 ip6 daddr $pfx/76 goto ncsi_gbmc_br_pub_input
  }
  chain ncsi_forward {
    ip6 saddr != $pfx/76 ip6 daddr $pfx/76 accept
  }
}
EOF
      rfile=/run/nftables/40-gbmc-ncsi-ra.rules
      mkdir -p -m 755 "$(dirname "$rfile")"
      printf '%s' "$contents" >"$rfile"
      systemctl reset-failed nftables
      systemctl --no-block restart nftables

      # Set the machine hostname if discovered
      if [ -n "$host" ]; then
        hostnamectl set-hostname "$host-n$hextet.$domain"
      fi

      old_pfx="$pfx"
      old_rtr="$rtr"
    fi
  done < <(rdisc6 -d -m @NCSI_IF@ -w $(( w * 1000 )) 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