is "volatile" the cause of ifconfig flags not matching sysfs flags?

is "volatile" the cause of ifconfig flags not matching sysfs flags?

[Robert P. J. Day]

  almost certainly another dumb question, but i was poking around the
sysfs, particularly /sys/class/net/<ifname>/*, to familiarize myself
with what i can glean (or set) re interfaces under /sys, and i noticed
"flags", but what i get there doesn't match what i get by running
ifconfig.

  specifically, if i list the flags for my wireless interface under
/sys:

$ cat flags
0x1003
$

  but with ifconfig:

$ ifconfig wlp2s0
wlp2s0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
              ^^^^

  do those two "flags" values represent the same set of flags? and
does the obvious difference have to do with some of those flags being
"volatile" as dewscribed in include/uapi/linux/if.h? or am i just
totally misreading this?

rday

-- 

========================================================================
Robert P. J. Day                                 Ottawa, Ontario, CANADA
                  http://crashcourse.ca/dokuwiki

Twitter:                                       http://twitter.com/rpjday
LinkedIn:                               http://ca.linkedin.com/in/rpjday
========================================================================

Re: is "volatile" the cause of ifconfig flags not matching sysfs flags?

[Stephen Hemminger]

On Wed, 22 Aug 2018 18:32:36 -0400 (EDT)
"Robert P. J. Day" <rpjday@crashcourse.ca> wrote:

>   almost certainly another dumb question, but i was poking around the
> sysfs, particularly /sys/class/net/<ifname>/*, to familiarize myself
> with what i can glean (or set) re interfaces under /sys, and i noticed
> "flags", but what i get there doesn't match what i get by running
> ifconfig.
> 
>   specifically, if i list the flags for my wireless interface under
> /sys:
> 
> $ cat flags
> 0x1003
> $
> 
>   but with ifconfig:
> 
> $ ifconfig wlp2s0
> wlp2s0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
>               ^^^^
> 
>   do those two "flags" values represent the same set of flags? and
> does the obvious difference have to do with some of those flags being
> "volatile" as dewscribed in include/uapi/linux/if.h? or am i just
> totally misreading this?
> 
> rday
> 

sysfs reports netdevice->if_flags where as ifconfig is getting hex
value from SIOCGIFFLAGS which does:
	dev_get_flags(dev)

The value in sysfs is more intended for internal debugging, where all the
normal userspace API's return a more limited set of historical values.

Re: is "volatile" the cause of ifconfig flags not matching sysfs flags?

[Robert P. J. Day]

On Wed, 22 Aug 2018, Stephen Hemminger wrote:

> On Wed, 22 Aug 2018 18:32:36 -0400 (EDT)
> "Robert P. J. Day" <rpjday@crashcourse.ca> wrote:
>
> >   almost certainly another dumb question, but i was poking around the
> > sysfs, particularly /sys/class/net/<ifname>/*, to familiarize myself
> > with what i can glean (or set) re interfaces under /sys, and i noticed
> > "flags", but what i get there doesn't match what i get by running
> > ifconfig.
> >
> >   specifically, if i list the flags for my wireless interface under
> > /sys:
> >
> > $ cat flags
> > 0x1003
> > $
> >
> >   but with ifconfig:
> >
> > $ ifconfig wlp2s0
> > wlp2s0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
> >               ^^^^
> >
> >   do those two "flags" values represent the same set of flags? and
> > does the obvious difference have to do with some of those flags being
> > "volatile" as dewscribed in include/uapi/linux/if.h? or am i just
> > totally misreading this?
> >
> > rday
> >
>
> sysfs reports netdevice->if_flags where as ifconfig is getting hex
> value from SIOCGIFFLAGS which does:
> 	dev_get_flags(dev)
>
> The value in sysfs is more intended for internal debugging, where
> all the normal userspace API's return a more limited set of
> historical values.

  so the history aside, those values ultimately represent the same
flags?

rday

-- 

========================================================================
Robert P. J. Day                                 Ottawa, Ontario, CANADA
                  http://crashcourse.ca/dokuwiki

Twitter:                                       http://twitter.com/rpjday
LinkedIn:                               http://ca.linkedin.com/in/rpjday
========================================================================