Application specific VTY attributes

[Harald Welte]

Sorry for the late response,

On Wed, Sep 23, 2020 at 03:58:31PM +0200, Neels Hofmeyr wrote:
> On Wed, Sep 23, 2020 at 05:40:39PM +0700, Vadim Yanitskiy wrote:
> >   struct cmd_node foo_node = {
> >     .usrattr = (1 << FOO_VTY_ATTR_RESTART_FULL),  // (!)
> >   };
> 
> this way we could no longer see that a newly added command failed to set the
> correct user attribute. i.e. I add a new DEFUN, I fail to remember setting
> attributes, and thus it shows some attribute which is wrong. If each command
> gets explicit attributes, errors like that are unlikely: If I add a DEFUN and
> forget to set the right attribute, there will be no attribute, and a user
> reading the vty reference will ask us to fix, without the need to try and fail
> first.

we could have a checker script that issues warnings, similar to the value_string
checker?  We could indeed also deprecate DEFUN (make it print a warning for now)
while things are migrated to those with attributes...

> libosmocore defined attrs would be useful. 

ACK.

> I know that the VTY code disregards osmo_ completely, but I'd still favor
> prepending OSMO_* to new enum values.

I'm -as usual - in favor of consistency.  So if the old code has no prefix, any
additions should also not have prefixes.

> btw, each and every osmo_fsm caller and now also each and every vty attribute
> defining code defines a left-shift macro like
> 
> 	#define S(x) (1 << (x))
> 
> it's a bit silly to repeat this definition all over the place.
> Added to libosmocore, it would have to be called OSMO_S()...
> makes everything longer. maybe nevermind, just thinking aloud.
> }

Yes, that is a known issue..

> > dexter wrote:
> > > Maybe we could have some standard letters defined in libosmocore
> > > for standard situations:
> > > F = Full restart required
> > > I = Applied Immediately
> > 
> > ACK.  We can also agree that generic (pre-defined) attributes use upper
> > case letters, while the application specific ones use lower case?

I like that approach

> Then again, 'F' should mean the same thing in various osmo-* programs?

yes.

> But consider, having attributes of upper case and lower case of the same letter
> could be somewhat confusing to users. 

Well, given that in iptables, lowercase are matches and uppercase are targets, I guess
it's clear I don't share such a concern.  But maybe it is confusing to Windows users
who are taught for decades that there is no distinction between upper and lower case?
I'm willing to accept that there is a concern.

> libosmocore assigns letters, applications assign numbers and special
> characters??

I would go for the other way around, as I would expect libosmocore to define
fewer 'common' attributes, while applications may have more different flags.
So as there are fewer numbers than lstters, I'd go for libosmocore=numbers.

Please note that in the end it's not just libosmcoore, but also
libosmogb, libosmo-abis, libosmo-sccp, ...

Regards,
	Harald
-- 
- Harald Welte <hwelte at sysmocom.de>             http://www.sysmocom.de/
=======================================================================
* sysmocom - systems for mobile communications GmbH
* Alt-Moabit 93
* 10559 Berlin, Germany
* Sitz / Registered office: Berlin, HRB 134158 B
* Geschaeftsfuehrer / Managing Director: Harald Welte