Fix #981 Use -webserverip to set http listen address

[leuc]

Followed the HTTP port code with an extra IP address validation in the router.

It works via command line flag, but not sure what is needed for configuration from the admin web UI.

Literally my first Go code :)

[gabek]

Thank you! Just one comment about the default.

[leuc]

default listen address changed.

Added admin REST API endpoint, with type validation. Only tested with curl, not against the actual admin UI.

This should validate the IP, so people can't brick the config. Not sure about the UI interaction in case of an error, so left out for now.

[gabek]

Thanks for adding this check! Instead of asserting the type once here to check it, and then another time to actually use it, could this be swaped around a bit (excuse the bad code inside a comment box):

if port, ok := configValue.Value.(float64); ok {
...setHttpPort(port)
} else {
BadRequestHandler(w, "bad request or some message")
}

And the same can probably be done with the SetWebServerIP check/use as well.

[leuc]

Gotcha, will do.

[leuc]

71aca7e should have a better logic and also checks port range and validates given IP

[gabek]

@leuc Would you mind commenting on the issue at #981 so I can make sure you get credit for closing it? :) It won't let me assign somebody who hasn't been involved in the discussion haha.

[gabek]

Thanks for working on this! I'm not sure yet if we want this configurable in the admin or not (I'm kind of leaning to it being a cli flag only), so I'll probably pull out the APIs if that's the case, but I'll leave it for now so we have the option. Thanks again!