In 8.1.9 you'll be able to opt-in to a setting on the gateway that has the gateway do a reverse DNS lookup to attempt to verify the hostname based on the provided IP:
"When enabled, Ignition's web server will attempt to resolve the remote HTTP client's hostname by performing a reverse DNS lookup using the remote HTTP client's IP address where appropriate, which could have a performance impact for each request which attempts a hostname lookup. When disabled, Ignition's web server will not attempt to resolve hostnames and any queries for the remote HTTP client's hostname will result in their IP address instead."