meta-google/recipes-google/ncsi/files/gbmc-ncsi-nft.sh.in

# 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.

[ -z "${gbmc_ncsi_nft_lib-}" ] || return

gbmc_ncsi_nft_init=
gbmc_ncsi_nft_lastip4=
gbmc_ncsi_nft_lastip6=

gbmc_ncsi_nft_update() {
  [ -n "$gbmc_ncsi_nft_init" ] || return

  printf 'NCSI firewall for IPv4(%s) IPv6(%s)\n' \
    "${gbmc_ncsi_nft_lastip4:-(deleted)}" \
    "${gbmc_ncsi_nft_lastip6:-(deleted)}" >&2

  local contents=
  contents+='table inet filter {'$'\n'
  contents+='    chain ncsi_input {'$'\n'

  local ip4="$gbmc_ncsi_nft_lastip4"
  if [ -n "$ip4" ]; then
    contents+="        ip daddr $ip4 goto ncsi_legacy_input"$'\n'
  fi

  local ip6="$gbmc_ncsi_nft_lastip6"
  if [ -n "$ip6" ]; then
    contents+="        ip6 daddr $ip6/128 goto ncsi_legacy_input"$'\n'

    # Pad out to 4 hextets with no trailing semicolons
    local pfx=
    pfx="${ip6%::}"
    while true; do
      # Count `:` in `pfx` by removing them and diffing their lengths
      local nos="${pfx//:/}"
      (( ${#pfx} - ${#nos} >= 3 )) && break
      pfx+=":0"
    done

    # If our address has enough spare bits for appending the BMC suffix
    # then we add a rule that allows the BMC subnet. That is, we need a /64
    # as input.
    if (( ${#pfx} - ${#nos} == 3 )); then
      contents+="        ip6 saddr != ${pfx}:fd00::/72 ip6 daddr"
      contents+=" ${pfx}:fd00::/72 goto ncsi_gbmc_br_pub_input"$'\n'
    fi
  fi

  contents+='    }'$'\n'
  contents+='}'$'\n'

  local rfile=/run/nftables/40-gbmc-ncsi-in.rules
  mkdir -p -m 755 "$(dirname "$rfile")"
  printf '%s' "$contents" >"$rfile"

  echo 'Restarting nftables' >&2
  systemctl reset-failed nftables
  systemctl --no-block restart nftables
}

gbmc_ncsi_nft_hook() {
  if [ "$change" = 'init' ]; then
    gbmc_ncsi_nft_init=1
    gbmc_ncsi_nft_update
  elif [ "$change" = 'addr' -a "$intf" = '@NCSI_IF@' -a "$scope" = 'global' ]; then
    if [ "$fam" = 'inet6' ]; then
      local -n lastip='gbmc_ncsi_nft_lastip6'
    else
      local -n lastip='gbmc_ncsi_nft_lastip4'
    fi
    if [ "$action" = 'add' -a "$ip" != "$lastip" ]; then
      lastip="$ip"
      gbmc_ncsi_nft_update
    fi
    if [ "$action" = 'del' -a "$ip" = "$lastip" ]; then
      lastip=
      gbmc_ncsi_nft_update
    fi
  fi
}

GBMC_IP_MONITOR_HOOKS+=(gbmc_ncsi_nft_hook)

gbmc_ncsi_nft_lib=1