Re: [PATCH net-next] Remove DECnet support from kernel

On 09. 01. 23, 9:14, Jan Engelhardt wrote:

On Monday 2023-01-09 08:04, Jiri Slaby wrote:

quoted

On 18. 08. 22, 2:43, Stephen Hemminger wrote:

quoted

DECnet is an obsolete network protocol

this breaks userspace. Some projects include linux/dn.h:

  https://codesearch.debian.net/search?q=include.*linux%2Fdn.h&literal=0

I found Trinity fails to build:
net/proto-decnet.c:5:10: fatal error: linux/dn.h: No such file or directory
     5 | #include <linux/dn.h>

Should we provide the above as empty files?

Not a good idea. There may be configure tests / code that merely checks for
dn.h existence without checking for specific contents/defines. If you provide
empty files, this would fail to build:

#include "config.h"
#ifdef HAVE_LINUX_DN_H
#	include <linux/dn.h>
#endif
int main() {
#ifdef HAVE_LINUX_DN_H
	socket(AF_DECNET, 0, DNPROTO_NSP); // or whatever
#else
	...
#endif
}

So, with my distro hat on, outright removing header files feels like the
slightly lesser of two evils. Given the task to port $arbitrary software
between operating systems, absent header files is something more or less
"regularly" encountered, so one could argue we are "trained" to deal with it.
But missing individual defines is a much deeper dive into the APIs and
software to patch it out.

Right, we used to keep providing also defines and structs in uapi 
headers of removed functionality. So that the above socket would 
compile, but fail during runtime.

I am not biased to any solution. In fact, I found out trinity was fixed 
already. So either path networking takes, it's fine by me. I'm not sure 
about the chromium users, though (and I don't care).

thanks,
-- 
js
suse labs