#!/bin/sh

PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin

# The list of Google networks.
src="https://www.gstatic.com/ipranges/goog.json"

dir="/var/db/google"
dest="$dir/goog.json"
netlist="$dir/nets"
temp="$dest.$$"

set -e
install -d "$dir"

[ "$1" = "-f" ] && rm -f "$dest" "$netlist"
trap 'rm -f "$temp" "$netlist.new"' EXIT

# Download the list with time modification check.
[ -e "$dest" ] || touch -t 197001010000 "$dest"
fetch --no-verify-peer -qai "$dest" -o "$temp" "$src" 2>/dev/null
[ -s "$temp" ]

# The list has been updated.
mv "$temp" "$dest"

# Get plain list of IPv4 prefixes out of JSON
awk -F'"' '/ipv4Prefix/ {print $4}' "$dest" | sort -u > "$netlist.new"
[ -e "$netlist" ] || touch "$netlist"
cmp -sz "$netlist" "$netlist.new" && exit 0

# Apply changes.
gw=$(route -n get default | awk '/gateway: / {print $2}')
[ -n "$gw" ]
diff "$netlist" "$netlist.new" | {
  echo 'conf t'
  sed -Ee '/^[<>]/!d'				\
       -e 's/^>(.+)/ip route\1 '${gw}/		\
       -e 's/^<(.+)/no ip route\1 '${gw}/
  echo end
} | vtysh 2>&1 | logger -t applynets -p user.info

mv $netlist.new $netlist