Re: [RFC] w using logind instead of utmp

On Wed, Jun 21, Craig Small wrote:

> Hi,
>   That all seems fine. I can either commit this change or if you have an
> updated version that version, let me know if there is anything else to add.

No, I'm fine with that version.

  Thanks,
     Thorsten

>  
>  - Craig
> 
> 
> On Tue, 13 Jun 2023 at 17:16, Thorsten Kukuk <[email protected]>
> wrote:
> 
> 
>     Hi,
> 
>     On Tue, Jun 13, Craig Small wrote:
> 
>     > On Fri, 9 Jun 2023 at 23:27, Thorsten Kukuk <[email protected]>
>     > wrote:
>     >
>     >
>     >     with w there is one binary left which only uses utmp, here is a patch
>     to
>     >     add logind support, too.
>     >
>     > OK, thanks for looking into this.
>     > 
>     >
>     >     systemd-logind v245 (or current git) will be necessary for this, as
>     only
>     >     this version has all the APIs to access the data.
>     >
>     > The autoconf only checks for sd_session_get_leader() but I see that you
>     have
>     > ringfenced a few systemd functions with that define. That would imply to
>     me
>     > that either
>     > 1) You can't use those functions without the information from the
>     > sd_session_get_leader(); or
>     > 2) They are introduced at the same time (e.g. in v254
> 
>     sd_session_get_leader() was the last added function, all other functions
>     are older. So if sd_session_get_leader() is present, all other functions
>     should be present, too. I doubt that anybody builds a systemd version
>     and manually removes single, older functions.
> 
>     > What I'm concerned here is the compile time works but those functions are
>     not
>     > present. What happens then? It looks like its doing the right thing here
>     but
>     > confirming it would be great.
> 
>     This are libsystemd functions. They use the same symbol versioning as
>     glibc is using. So if you compile with a newer libsystemd and run it
>     with an older libsystemd, you will get the same function not found errors.
> 
>     If you use a newer libsystemd with an older systemd-logind: also no
>     problem, it will continue to work. systemd-logind provides the data
>     since the beginning, only the libsystemd API was missing.
> 
>     > Also, I think what you're doing here is iterating through what
>     sd_get_sessions
>     > returns which is an array of sessions. For all the subsequent functions,
>     > session==NULL means that sd_get_sessions didn't
>     > have any sessions so we're not running on a systemd system?
> 
>     No, it means nobody is logged in.
>     sd_booted() determines, if systemd is running or not.
> 
>     > Not sure about all the conditional function calls/definitions, it might
>     be
>     > better always to pass the session even when it's NULL (e.g. not compiled
>     with
>     > systemd). On the one hand, it means we aren't meaninglessly passing that
>     > pointer, on the other it makes all the function definitions messier.
> 
>     That what I was thinking about, too, but was unsure. And you would get
>     "unused arguments" warnings/errors.
> 
>       Thorsten
> 
>     > I'll compile it in soon and let you know.
>     >
>     >  - Craig
>     >
>     >
>     >
>     >     Would it be Ok this way? Or what to change?
>     >
>     >      Thorsten
>     >     --
>     >     Thorsten Kukuk, Distinguished Engineer, Senior Architect, Future
>     >     Technologies
>     >     SUSE Software Solutions Germany GmbH, Frankenstraße 146, 90461
>     Nuernberg,
>     >     Germany
>     >     Managing Director: Ivo Totev, Andrew Myers, Andrew McDonald, Martje
>     Boudien
>     >     Moerman
>     >     (HRB 36809, AG Nürnberg)
>     >
> 
>     --
>     Thorsten Kukuk, Distinguished Engineer, Senior Architect, Future
>     Technologies
>     SUSE Software Solutions Germany GmbH, Frankenstraße 146, 90461 Nuernberg,
>     Germany
>     Managing Director: Ivo Totev, Andrew Myers, Andrew McDonald, Martje Boudien
>     Moerman
>     (HRB 36809, AG Nürnberg)
> 
> 

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