#!/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.

[[ -n ${gbmc_br_gw_src_lib-} ]] && return

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

gbmc_br_gw_src_ip_stateful=
gbmc_br_gw_src_ip_stateless=
declare -A gbmc_br_gw_src_routes=()
gbmc_br_gw_defgw=

gbmc_br_set_router() {
  local defgw=
  local route
  for route in "${!gbmc_br_gw_src_routes[@]}"; do
    if [[ $route != *' dev gbmcbr '* ]]; then
      defgw=1
      break
    fi
  done
  [[ $defgw == "$gbmc_br_gw_defgw" ]] && return
  gbmc_br_gw_defgw="$defgw"

  local files=(/run/systemd/network/{00,}-bmc-gbmcbr.network.d/50-defgw.conf)
  if [[ -n $defgw ]]; then
    local file
    for file in "${files[@]}"; do
      mkdir -p "$(dirname "$file")"
      printf '[IPv6PrefixDelegation]\nRouterLifetimeSec=30\n' >"$file"
    done
  else
    rm -f "${files[@]}"
  fi

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

gbmc_br_gw_src_update() {
  local gbmc_br_gw_src_ip="${gbmc_br_gw_src_ip_stateful:-$gbmc_br_gw_src_ip_stateless}"
  [[ -n $gbmc_br_gw_src_ip ]] || return

  local route
  for route in "${!gbmc_br_gw_src_routes[@]}"; do
    [[ $route != *" src $gbmc_br_gw_src_ip "* ]] || continue
    echo "gBMC Bridge Updating GW source [$gbmc_br_gw_src_ip]: $route" >&2
    # shellcheck disable=SC2086
    ip route change $route src "$gbmc_br_gw_src_ip" && \
      unset 'gbmc_br_gw_src_routes[$route]'
  done
}

gbmc_br_gw_src_hook() {
  # We only want to match default gateway routes that are dynamic
  # (have an expiration time). These will be updated with our preferred
  # source.
  # shellcheck disable=SC2154
  if [[ $change == route && $route == 'default '*':'* ]]; then
    if [[ $route =~ ^(.*)( +expires +[^ ]+)(.*)$ ]]; then
      route="${BASH_REMATCH[1]}${BASH_REMATCH[3]}"
    fi
    if [[ $action == add && -z ${gbmc_br_gw_src_routes["$route"]} ]]; then
      gbmc_br_gw_src_routes["$route"]=1
      gbmc_br_gw_src_update
      gbmc_br_set_router
    elif [[ $action == del && -n "${gbmc_br_gw_src_routes["$route"]}" ]]; then
      unset 'gbmc_br_gw_src_routes[$route]'
      gbmc_br_gw_src_update
      gbmc_br_set_router
    fi
  # Match only global IP addresses on the bridge that match the BMC stateless
  # prefix (<mpfx>:fd00:). So 2002:af4:3480:2248:fd00:6345:3069:9186 would be
  # matched as the preferred source IP for outoging traffic.
  elif [[ $change == addr && $intf == gbmcbr && $scope == global ]] &&
       [[ $fam == inet6 && $flags != *tentative* ]]; then
    local ip_bytes=()
    if ! ip_to_bytes ip_bytes "$ip"; then
      echo "gBMC Bridge Ensure RA Invalid IP: $ip" >&2
      return 1
    fi
    # Ignore ULAs and non-gBMC addresses
    if (( ip_bytes[0] & 0xfe == 0xfc || ip_bytes[8] != 0xfd )); then
      return 0
    fi
    if (( ip_bytes[9] & 0x0f != 0 )); then
      local -n gbmc_br_gw_src_ip=gbmc_br_gw_src_ip_stateful
    else
      local -n gbmc_br_gw_src_ip=gbmc_br_gw_src_ip_stateless
    fi
    if [[ $action == add && $ip != "$gbmc_br_gw_src_ip" ]]; then
      gbmc_br_gw_src_ip="$ip"
      gbmc_br_gw_src_update
    fi
    if [[ $action == del && $ip == "$gbmc_br_gw_src_ip" ]]; then
      gbmc_br_gw_src_ip=
    fi
  fi
}

GBMC_IP_MONITOR_HOOKS+=(gbmc_br_gw_src_hook)

gbmc_br_gw_src_lib=1