Fedora contemplates the driverless printing future

Traditionally, getting a printer working on Linux has involved, among other things, locating and installing the appropriate printer drivers and PostScript printer definition (PPD) files to allow the system to communicate with the printer using whatever special dialect it favors. Often that involves installing a separate package like hplip, often supplied by the printer vendor. Some vendors have traditionally supported Linux better than others, but none of their products seem to work as smoothly as one would like. While printer setup on Linux has definitely improved over the years, it still easy to dread having to make a new printer work.

The Internet Printing Protocol

In this context, it is noteworthy that the maintainers of the CUPS system, which handles printing on Linux, have an outstanding issue (since moved) calling for the removal of its support for printer drivers. The Fedora development list also discussed this idea in late May. There are changes coming in the printing world, and users are naturally curious about when and how those changes will affect them.

Those who have not been following developments in printing may wonder why it would make sense to remove printer drivers, since those are what make the printers actually work. The answer is the Internet Printing Protocol (IPP) and, specifically, a derivative called IPP Everywhere. The idea is simple enough: what if all printers implemented the same protocol so that any software could print to them without the need to install special drivers or, indeed, perform any configuration work at all? Like many things, IPP Everywhere seems to be motivated by the desire to interoperate with smartphones, but it is useful in a wider context as well.

In the IPP Everywhere future, printers simply work. They make themselves known to the network via multicast DNS, allowing other machines on the network to discover them. The protocol allows the printer to communicate its capabilities and accept settings, so features like duplex printing and paper-tray selection work. IPP Everywhere describes a small set of known formats for material to be printed, so there is no need for special drivers for format conversion. Users simply need to indicate their desire to print something, select between the available printers and printing options, install the new toner cartridge that the printer inevitably demands, then file the resulting output in the recycling bin. It's a printing paradise.

Or, at least, it will be a printing paradise one of these days. Given that IPP Everywhere has been around since 2010, one might think that we should have arrived already, but there are some remaining issues.

Does it work?

CUPS has long had support for IPP Everywhere, and distributions have generally enabled that support. But it still doesn't seem to be the default way to use printers on Linux. For example, a search for how to set up your editor's Brother laser printer on Linux results in a visit to Brother's driver page; after a somewhat fraught process the printer can be made to work well — but it's not a transparent or driverless experience.

That printer is supposed to support IPP Everywhere, though, and it can be seen in the output of avahi-browse. Android devices can successfully print to it. That means, with any remotely modern version of Linux, the printer should show up automatically when trying to print a file, without the need to set up a queue at all. It does indeed appear, but an attempt to use it results in the print dialog hanging before the user can even hit the "print" button. That experience may be driverless, and it certainly results in a reduction of wasted paper, but it's also less than fully satisfying.

What about adding a queue explicitly? Firing up the "add a printer" dialog on a freshly installed Fedora 34 system produces a blank window — not the experience a printer user is looking for either. Typing in the IP address for the printer (something most users naturally have at the tips of their fingers) yields the display seen to the right: five options, with no real indication of which one — if any — is correct. In fact, only the final option in the list works at all, and it takes several minutes to print a page, for reasons that are unclear to anybody not initiated into the deep magic of CUPS.

If, instead, one simply tells CUPS to use the printer as an IPP Everywhere device with a command like:

    # lpadmin -p NewPrinter -E -v ipp://10.0.0.16/ipp -m everywhere

The printer works well, immediately. It began, of course, by communicating its appetite for a new toner cartridge to the Fedora system, which duly passed the request on. So IPP Everywhere does work, at some level, on both ends of the connection, but some of the glue is seemingly not yet fully in place.

Most distributors have been working on support for driverless printing. The curious can find instructions online for Arch Linux, Debian (and Ubuntu), Fedora, Gentoo, Red Hat, and others. SUSE and openSUSE seem to be the biggest exception, unless your editor's search skills have failed.

Old printers

In theory, almost all printers made in the last ten years should support IPP Everywhere. It seems that most do, even though the list of certified printers is conspicuously missing a number of vendors. But not everybody has a printer that recent; printers can stay around for a long time. The removal of printer drivers from CUPS (and the distributions using it) means the removal of support for all of those devices. It is fair to say that doesn't sit well with the owners of such hardware.

The intended solution to this problem is "printer applications": programs that can speak to a certain class of printers while implementing the IPP Everywhere protocol to connect those printers to CUPS. Only a handful of those exist now; they include LPrint, which can drive a set of label printers. Work is underway to support others, including the "foo2zjs" devices that show up as IPP Everywhere printers, but which still need special drivers to work. Implementing more printer applications features prominently in the OpenPrinting Google Summer of Code plans this year.

This does not satisfy all users out there, many of whom got their printers working after a fair amount of struggle and do not relish the idea of having to go through that process again with a new system. Some worry that there will be CUPS-supported printers that never get printer-application support; that may well happen, but it's not clear how many users will be affected by the loss of support for some ancient devices. Others complain that this transition is a lot of churn for no real benefit; Solomon Peachy answered that concern this way:

For many of us, that universal printing system can't come soon enough, if it works as well as it is intended to. Should that happen, there is likely to be little lamentation over the loss of printer drivers.

Fake printers

There is one other concern that came up in the Fedora conversation, though. In a world where printers just show up on the net, what is to prevent an attacker from putting up fake printers in the hope of capturing documents with interesting contents? There does not seem to have been much effort put into addressing this scenario; as Zdenek Dohnal put it: "CUPS discovery is designed to run on secure, private LAN, so it is expected that you have a protection against somebody connecting to your WIFI." Peachy added that, if an attacker has a sufficient presence on the local network to advertise a false printer, they can probably do worse things than that.

IPP does have provisions for authentication and such, but employing them would take away much of the convenience that the protocol is meant to provide in the first place. So the general attitude toward security is likely to remain as Dohnal described it: the local network is expected to be secure.

In a related issue, some participants in the discussion expressed concerns that some IPP Everywhere devices work by routing print jobs through cloud-based services. Indeed, the Android print dialog, when printing to the above-mentioned Brother printer, warns that the document may pass through third-party servers — something that does not appear to actually happen in this case. The idea of a local printer that fails when the Internet is down lacks appeal, but somehow we seem to be heading toward that world anyway.

When?

The CUPS project has been working toward a driverless future for many years; the use of PPD files was first deprecated in the 1.4 release in 2009, even though there was no replacement for them at that time. The project finally deprecated printer drivers with the 2.3 release in 2019. "Deprecated" is not the same as "removed", though; this deprecation was intended to draw attention to the forthcoming change. As can be seen with PPD files (which are still supported), there can be a long time between deprecation and removal.

That said, the plan is apparently to remove printer drivers in the next major CUPS release, for which there does not currently appear to be a target date. The project has not made a release since 2.3.3 came out in April 2020, so things do not seem to be moving all that quickly there at the moment. There is probably some time for distributors and users to prepare for this change.

That is a good thing. Even if most printers are supported reasonably well by IPP Everywhere, there will be a lot of users of printer drivers out there, and a lot of users with older printers as well. There will need to be a lot of work and testing done if the first distributions that release with CUPS 2.4 are to not break vast numbers of printing setups. If that can be done, though, perhaps printers can finally join modems as devices that simply work without the need for a lot of messing around.