pfSense

Pull request: https://github.com/pfsense/pfsense/pull/3198
That makes the "Please match the requested format:" text more helpful.

It would also be nice to automagically convert to lowercase as the characters are typed or pasted into the field.

While I think it is cool to convert the characters as you type, the GUI has to accept upper case letters as well.

Once the IPv6 address is sanitized, all the IPv6 address in pfSense must use/print only lower case letters.

This one also automatically converts the input to lowercase as the user leaves the IP Address field, or presses a button somewhere else (like Save):
https://github.com/pfsense/pfsense/pull/3199

Note: The pull request generated discussion about whether users should have the option to record IPv6 addresses with their choice of upper or lower case A-F,a-f, and store it in the config as the user has entered it. Then the back-end code would convert to lower case on the fly when making use of the addresses to drive the system.

Regardless of that, the existing behaviour is requiring that lower case be entered. The pull request simply automates this process and gives some help text to give the user more clue about what to enter. So the PR does not change existing underlying behaviour.

If someone wants to discuss the overall policy of stored format of IPv6 addresses in the config, then fine. But the PR is not about that.

This appears to have broken the use of Aliases that have names using capital letters. See #6918

See #6918
A new function has been provided to force IPv6 to lower case on save. This is being added to GUI pages as required

interfaces.php also has addrtolower()