cups-browsed does not use encryption

[Stone2GIT]

Describe the bug
First of all - I am not sure wether it is a bug or more a feature request.

Settings up cups 2.2.7 to use encryption with GnuTLS certificate (self-signed) and cups-filters 1.25-10 (SuSE SLES15SP5 packages) using cups-browsed to discover remote printers / CUPS servers on the net leads to error message in /var/log/cups/error_log "[Client 65] Unable to encrypt connection: An unexpected TLS packet was received.".

Using gnutls-cli accessing the CUPS server with encryption leads to "[Client 231] Connection now encrypted." which shows the connection could be encrypted.

Using curl with curl http://: shows a connection not possible, whereas curl https has success.

Same in browser while accessing CUPS web ui.

This leads to the assumption that cups-browsed cannot be forced to discover printers or CUPS servers by encrypted connection at first and always doing a unencrypted HTTP request at first.

To Reproduce
Steps to reproduce the behavior:

1. set up CUPS 2.2.7 with encryption
2. add DefaultEncrption required to /etc/cups/cupsd.conf
3. add CreateSelfSignedCerts no to /etc/cups/cups-files.conf
4. configure cups-browsed on a client
5. start cups-browsed

Expected behavior
Expected behavior is to use encrypted requests to discover printers / CUPS servers.

Screenshots
If applicable, add screenshots to help explain your problem.

System Information:

• OS: SLES15SP5
• Firefox, Chrome, Safari
• Version cups 2.2.7, cups-filters 1.25-10

Additional context
Context is evaluating a CUPS cluster with cups-browsed and using encrypted connections.

[Stone2GIT]

p.s:

Is there any flowchart around showing connections and data flow of CUPS, cups-browsed and e.g. usage of implicitclass etc.? And if a link would be nice