Allow the API and Websocket queries to be restricted to specific IPs

[edhelas]

This feature is useful for projects that wraps Galene and only need to access it locally for security reasons.

[jech]

Please describe in more detail (feel free to edit your summary above, no need to follow up).

1. What should the UI look like? A list of IPs in the global configuration file? Or do you need subnetting support? Or do you need the ability to change the list at runtime without restarting the server?
2. How should it interact with reverse proxies? Should we just use the TCP connection's remote address, or should we trust HTTP headers inserted by reverse proxies?
3. Anything else I need to know?

[edhelas]

I was thinking of something like the bind-address parameter of MySQL https://dev.mysql.com/blog-archive/the-bind-address-option-now-supports-multiple-addresses/
Or simply listen to a local UNIX socket file or port by choice, also works :)

[jech]

That's not going to work for us. We use a single socket for the built-in webserver, the protocol WebSocket, and the admin API. This socket is bound to whatever is specified in the -listen command-line parameter.

What we can do is refuse admin requests depending on the remote IP. So how do we specify the allowed remote IPs?