meta-google/recipes-google/networking/gbmc-bridge/50-gbmc-br.rules

table bridge filter {
  chain gbmc_br_prerouting {
    type filter hook prerouting priority 0;
    iifname != gbmcbr accept
    # Sometimes our links are over NCSI and we don't want to broadcast
    # those packets over the entire bridge. They are only relevant P2P.
    ether type 0x88F8 drop
  }
}

table inet filter {
  chain gbmc_br_input {
    type filter hook input priority 0; policy drop;
    iifname != gbmcbr accept
    ct state established accept
    jump gbmc_br_int_input
    jump gbmc_br_pub_input
    reject
  }
  set gbmc_br_int_addrs {
    type ipv6_addr;
    flags interval
    elements = {
      ff00::/8,
      fe80::/64,
      fdb5:0481:10ce::/64,
    }
  }
  chain gbmc_br_int_input {
    ip6 daddr @gbmc_br_int_addrs accept
    ip6 saddr @gbmc_br_int_addrs accept
  }
  chain gbmc_br_pub_input {
    ip6 nexthdr icmpv6 accept
  }
}