bug#64937: "who" reports funny dates

[Thorsten Kukuk]

Hi,

On Tue, Aug 01, Bruno Haible wrote:

> Thorsten Kukuk wrote:
> > If you haven't seen yet, I made some time ago a mapping
> > between utmp struct entries and libsystemd functions: 
> > https://github.com/thkukuk/utmpx/blob/main/utmp-to-logind.md
> 
> Thanks. This is helpful.
> 
> The only problem with this mapping is for the ut_line row, which
> used to contain, for inbound ssh, the pty device name. It is not easy
> to find the pty name in this situation; at least, none of the systemd
> APIs and /run/systemd/** files that I looked at helped.

You mean you don't see a TTY on ssh sessions?

openssh is really special: it does not need a TTY for all kind of ssh
sessions, and thus only opens a TTY if needed after creating the
logind session. Thus the logind session does not contain the TTY 
informations.
systemd-logind v254 provides now an interface for this case, which
allows to set the TTY later. For openssh you need this patch:

https://github.com/thkukuk/utmpx/blob/main/patches/openssh/logind-set-tty.patch

> The major changes are:
> * Entries without BOOT_TIME or USER_PROCESS flag are gone. This includes
>   - runlevel and possibly "old time" / "new time" entries, which I don't know
>     how to get from systemd,

systemd has no "runlevel", this entries don't exists.
I haven't found an application which creates "old time" / "new time"
entries, thus I think they can be ignored.

>   - entries for pseudo-terminals (xterm etc.) that are not login shells;
>     I don't know how to get them from systemd either, and (IMO) they were
>     uninteresting anyway,

Yes, this is a problem or not, because on the other side,  it solves a
problem. E.g.
* xterm creates entries for pseudo-terminals
* gnome-terminal does not create entries for pseudo-terminals

That was confusing in the past and is now consistent.

> * The pids now refer to the session leader, which is a parent (or ancestor)
>   of the process which has allocated the pty.

Depends on your application. For the majority of applications, which we
evaluated, the PIDs reported by logind were identical to the PID from utmp.

> * In the ut_line field ("Device" column) I added extra info about the
>   service name, in this case "sshd". I imagine that is at least as useful as
>   knowing the pty name ("pts/4").

See above, this is a special openssh problem, we need to teach openssh
to report the TTY to logind, too.

  Thorsten

-- 
Thorsten Kukuk, Distinguished Engineer, Senior Architect, Future Technologies
SUSE Software Solutions Germany GmbH, Frankenstraße 146, 90461 Nuernberg, 
Germany
Managing Director: Ivo Totev, Andrew McDonald, Werner Knoblich
(HRB 36809, AG Nürnberg)