#!/bin/bash
source ~/.bashrc



main() {

  fqdn=$(hostname -f)
  domaintmp=${fqdn#*.}
  hostnametmp=${fqdn%%.*}
  # i for internet
  fqdn=${hostnametmp}i.${domaintmp}

  up4=false

  if ! read -r _ _  gateway _ ifdev _ < <(ip -4 route get 85.119.83.50 2>/dev/null); then
    # if our internet is down, just give up, no need to have an error
    if [[ ! $INVOCATION_ID ]]; then
      echo $0: failed to get route, giving up
    fi
    exit 0
  fi

  case $gateway in
    10.2.0.1)
      dynhost=i.b8.nz
      ;;
    *)
      return 0
      ;;
  esac

  athome=false
  if [[ -s /dev/shm/dynamic-ip-update-state ]]; then
    oldbytes=$(cat /dev/shm/dynamic-ip-update-state)
    newbytes=$(awk '$1 == "'$ifdev':" {print $2 + $10}' /proc/net/dev)
    if [[ $oldbytes == [1-9]* ]] && (( newbytes >= oldbytes )); then
      athome=true
      printf "%s\n" "$newbytes" >/dev/shm/dynamic-ip-update-state
    fi
  fi
  if ! $athome && timeout -s 9 5 ssh-keyscan -p 2220 -t rsa $gateway 2>/dev/null | grep -qFx "[$gateway]:2220 ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQCH+/h1dGEfKEusBblndU2e6QT4wLCm5+yqr/sqh/0X9YfjR7BfWWm8nNmuP55cYc+Wuf5ljB1H1acXEcsl1y8e0j3agHfF0V74FE1N1zz5nn2Ep8NHnmqgEhza38ZxMPh+4p3X7zklEKU7+3SzybKBi8sg0wLzlS2LM0JaUN80zR2sK11Kye3dURUXPk78u5wodOkgcEYRwSYaDMJlUzWP+poRXIDJwFaMQnwmxbl/c84yOyaU0x/d6hFwoRscWecihX+vvBNeSyxR4xr2HDOyUWwJkctyAgt2p7w3tfkXOKcCRzTAjGVIMQLTvo0sG/yJbcyHoEFdFybCsgDvfyYn"; then
    athome=true
    awk '$1 == "'$ifdev':" {print $2 + $10}' /proc/net/dev > /dev/shm/dynamic-ip-update-state
  fi


  if $athome; then
    cur4="$(dig +short $dynhost @iankelling.org | tail -1)"
    if ip4=$(curl -s4 https://iankelling.org/cgi/pubip); then
      if [[ $cur4 && $ip4 && $cur4 != $ip4 ]]; then
        up4=true # update ipv4
      fi
    fi
  fi

  # may not be set yet so allow fail
  cur6="$(host -4 -t aaaa $fqdn iankelling.org | sed -rn 's/.*has IPv6 address (.*)/\1/p;T;q')" ||:

  up6=false

  out6=$(curl -s6 https://iankelling.org/cgi/pubip) ||: # failure allowed if we have no ipv6

  if [[ $out6 ]]; then
    dev=$(ip -o a show to $out6 | awk '{print $2}')
    # we use slaac with privacy extension, so get our less private more permanent address
    mac=$(cat /sys/class/net/$dev/address)

    IFS=: read -a f <<<$mac; set -- ${f[@]}
    ip6=${out6%:*:*:*:*}:$(printf %x $((0x$1 + 2)))$2:$3'ff:fe'$4:$5$6
    # in case we aren't using slaac
    if ! ip a | grep "^ *inet6 $ip6/" &>/dev/null; then
      ip6=$out6
    fi
  fi

  if [[ $cur6 != $ip6 ]]; then
    up6=true
  fi

  if ! $up4 && ! $up6; then
    return 0
  fi

  # note, a simpler way to do this would be to ssh and use
  # "${SSH_CLIENT%% *}
  # to update bind if needed.

  f=$(mktemp)
  cat >>$f <<EOF
server iankelling.org
zone b8.nz
EOF

  if $up4; then
    cat >>$f <<EOF
update delete $dynhost. A
update add $dynhost. 300 A $ip4
EOF
  fi

  if $up6; then
    if [[ $ip6 ]]; then
      cat >>$f <<EOF
update delete $fqdn. AAAA
update add $fqdn. 60 AAAA $ip6
EOF
    else
      cat >>$f <<EOF
update delete $fqdn. AAAA
EOF
    fi
  fi

  cat >>$f <<EOF
show
send
answer
quit
EOF

  nsupdate -k /p/c/machine_specific/vps/filesystem/etc/bind/Kb8.nz.*.private <$f
  sed -i 's/^server .*/server bk.b8.nz/' $f
  nsupdate -k /p/c/machine_specific/vps/filesystem/etc/bind/Kb8.nz.*.private <$f


}

if [[ $INVOCATION_ID ]]; then
  # this is to prevent systemd from filling up the journal
  for (( runcount=0; runcount < 100; runcount++ )); do
    main
    sleep 30
  done
else
  main
fi





exit 0


#   # # persistent initial setup for this:
#   # # create files in /a/c/machine_specific/vps/filesystem/etc/bind
#   # # note, conflink also does some group ownership stuff.
#   mkc /p/c/machine_specific/vps/filesystem/etc/bind
#   sudo dnssec-keygen -a HMAC-SHA512 -b 512 -n HOST b8.nz
#   user=$(id -un)
#   sudo chown $user:$user *


#   f=key.b8.nz
#   cat >$f <<EOF
# key b8.nz. {
# algorithm HMAC-SHA512;
# secret "$(awk '$1 == "Key:" {print $2}' Kb8.nz.*.private)";
# };
# EOF

#   chmod 640 [kK]*

#   # push here?
#   #myunison -ob li
#   #ssh li conflink
#   ssh li.b8.nz systemctl reload bind9


#   # b8.nz has address 65.96.178.16
#   # b8.nz has IPv6 address 2601:197:600:6efb:82fa:5bff:fe1c:6ecf