1#!/bin/bash
2# Copyright 2021 Google LLC
3#
4# Licensed under the Apache License, Version 2.0 (the "License");
5# you may not use this file except in compliance with the License.
6# You may obtain a copy of the License at
7#
8#      http://www.apache.org/licenses/LICENSE-2.0
9#
10# Unless required by applicable law or agreed to in writing, software
11# distributed under the License is distributed on an "AS IS" BASIS,
12# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13# See the License for the specific language governing permissions and
14# limitations under the License.
15
16[[ -n ${gbmc_br_nft_lib-} ]] && return
17
18# shellcheck source=meta-google/recipes-google/networking/network-sh/lib.sh
19source /usr/share/network/lib.sh || exit
20
21gbmc_br_nft_pfx=
22
23gbmc_br_nft_update() {
24  printf 'gBMC Bridge input firewall for %s\n' \
25    "${gbmc_br_nft_pfx:-(deleted)}" >&2
26
27  local contents=
28  contents+='table inet filter {'$'\n'
29  contents+='    chain gbmc_br_int_input {'$'\n'
30  if [[ -n ${gbmc_br_nft_pfx-} ]]; then
31    contents+="        ip6 saddr $gbmc_br_nft_pfx"
32    contents+=" ip6 daddr $gbmc_br_nft_pfx accept"$'\n'
33  fi
34  contents+='    }'$'\n'
35  contents+='}'$'\n'
36
37  local rfile=/run/nftables/40-gbmc-br-int.rules
38  mkdir -p "$(dirname "$rfile")"
39  printf '%s' "$contents" >"$rfile"
40
41  # shellcheck disable=SC2015
42  systemctl reset-failed nftables && systemctl --no-block reload-or-restart nftables || true
43}
44
45gbmc_br_nft_hook() {
46  # Match only global IP addresses on the bridge that match the BMC prefix
47  # (<mpfx>:fdxx:). So 2002:af4:3480:2248:fd02:6345:3069:9186 would become
48  # a 2002:af4:3480:2248:fd00/76 rule.
49  # shellcheck disable=SC2154
50  if [[ $change == addr && $intf == gbmcbr && $scope == global ]] &&
51       [[ $fam == inet6 && $flags != *tentative* ]]; then
52    local ip_bytes=()
53    if ! ip_to_bytes ip_bytes "$ip"; then
54      echo "gBMC Bridge NFT Invalid IP: $ip" >&2
55      return 1
56    fi
57    if (( ip_bytes[8] != 0xfd )); then
58      return 0
59    fi
60    local i
61    for (( i=9; i<16; i++ )); do
62      ip_bytes["$i"]=0
63    done
64    pfx="$(ip_bytes_to_str ip_bytes)/76"
65    if [[ $action == add && $pfx != "$gbmc_br_nft_pfx" ]]; then
66      gbmc_br_nft_pfx="$pfx"
67      gbmc_br_nft_update
68    fi
69  fi
70}
71
72GBMC_IP_MONITOR_HOOKS+=(gbmc_br_nft_hook)
73
74gbmc_br_nft_lib=1
75