fake googlebots

[lists at lazygranch.com]

I got a spoofed googlebot hit. It was easy to detect since there were
probably a hundred requests that triggered my hacker detection map
scheme. Only two requests received a 200 return and both were harmless.

200 118.193.176.53 - - [25/Sep/2016:17:45:23 +0000] "GET / HTTP/1.1" 847 "-" "Mozilla/5.0 (compatible; Googlebot/2.1; +http://www.google.com/bot.html)" "-"

For the fake googlebot:
# host 118.193.176.53
Host 53.176.193.118.in-addr.arpa not found: 3(NXDOMAIN)

For a real googlebot:
# host 66.249.69.184
184.69.249.66.in-addr.arpa domain name pointer crawl-66-249-69-184.googlebot.com.

IP2location shows it is a Chinese ISP:
3(NXDOMAIN)http://www.ip2location.com/118.193.176.53

Nginx has a reverse DNS module:
https://github.com/flant/nginx-http-rdns
I see it has a 10.1 issue:
https://github.com/flant/nginx-http-rdns/issues/8

Presuming this bug gets fixed, does anyone have code to verify
googlebots? Or some other method?