Re: Fwd: netdevice.7 SIOCGIFFLAGS/SIOCSIFFLAGS

Re: Fwd: netdevice.7 SIOCGIFFLAGS/SIOCSIFFLAGS

[Oliver Hartkopp]

Hi Alejandro,

we added IFF_ECHO these days on suggestion of Dave Miller - and the 
IFF_LOWER_UP/IFF_DORMANT were already there at that time.

I don't know if there ioctls are still used for retrieving these flags 
as I assume this is done via netlink interface today.

At least there is enough space (in the union) in the ioctl structure for 
longer data structures:

https://elixir.bootlin.com/linux/latest/source/include/uapi/linux/if.h#L265

https://elixir.bootlin.com/linux/latest/source/include/uapi/linux/if.h#L247

https://elixir.bootlin.com/linux/latest/source/net/core/dev_ioctl.c#L114

If you continue discussing about this topic, please remove the 
Volkswagen mail addresses from Urs and me.

I'm still maintaining the CAN subsystem in the Linux kernel - but with a 
private mail address.

And you should better add the netdev ML to your recipients 
netdev@vger.kernel.org where all the netdev guys (including Dave Miller) 
hang out.

Best,
Oliver


> 
> ------------------------------------------------------------------------
> *Von:* Alejandro Colomar (man-pages) <alx.manpages@gmail.com>
> *Gesendet:* Freitag, März 19, 2021 9:00 PM
> *An:* Erik Flodin; mtk.manpages@gmail.com
> *Cc:* linux-man@vger.kernel.org; Stefan Rompf; David S. Miller; Fredrik 
> Arnerup; John Dykstra; David S. Miller; Hartkopp, Oliver, Dr. (EESC/3); 
> Thuermann, Urs, Dr. (K-AERD/M)
> *Betreff:* Re: netdevice.7 SIOCGIFFLAGS/SIOCSIFFLAGS
> [CC += Fredrik, John, David S., Steven, Oliver, Urs]
> 
> Hi,
> 
> On 3/17/21 3:12 PM, Erik Flodin wrote:
>> Hi,
>> 
>> The documentation for SIOCGIFFLAGS/SIOCSIFFLAGS in netdevice.7 lists
>> IFF_LOWER_UP, IFF_DORMANT and IFF_ECHO, but those can't be set in
>> ifr_flags as it is only a short and the flags start at 1<<16.
>> 
>> See also https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=746e6ad23cd6fec2edce056e014a0eabeffa838c 
> <https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=746e6ad23cd6fec2edce056e014a0eabeffa838c>
>> 
> 
> I don't know what's the history of that.
> I researched a bit, and while the struct member is indeed a 'short' [1],
> the flags were added to the kernel for some reason.
> I added a few people to the thread that may know better what to do.Let's
> see if they can comment.
> 
> Links to relevant commits:
> 
> <https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=746e6ad23cd6fec2edce056e014a0eabeffa838c 
> <https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=746e6ad23cd6fec2edce056e014a0eabeffa838c>>
> <https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b00055aacdb172c05067612278ba27265fcd05ce 
> <https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b00055aacdb172c05067612278ba27265fcd05ce>>
> <https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=cd05acfe65ed2cf2db683fa9a6adb8d35635263b 
> <https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=cd05acfe65ed2cf2db683fa9a6adb8d35635263b>>
> <https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/commit/?id=6ecda4d14604d250d385346f4fe9de707f281759 
> <https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/commit/?id=6ecda4d14604d250d385346f4fe9de707f281759>>
> 
> Thanks,
> 
> Alex
> 
> [1]:
> 
> .../linux$ sed -n '/struct ifreq {/,/};/p' include/uapi/linux/if.h
> struct ifreq {
> #define IFHWADDRLEN     6
>          union
>          {
>                  char    ifrn_name[IFNAMSIZ];            /* if name, 
> e.g. "en0" */
>          } ifr_ifrn;
> 
>          union {
>                  struct  sockaddr ifru_addr;
>                  struct  sockaddr ifru_dstaddr;
>                  struct  sockaddr ifru_broadaddr;
>                  struct  sockaddr ifru_netmask;
>                  struct  sockaddr ifru_hwaddr;
>                  short   ifru_flags;
>                  int     ifru_ivalue;
>                  int     ifru_mtu;
>                  struct  ifmap ifru_map;
>                  char    ifru_slave[IFNAMSIZ];   /* Just fits the size */
>                  char    ifru_newname[IFNAMSIZ];
>                  void __user *   ifru_data;
>                  struct  if_settings ifru_settings;
>          } ifr_ifru;
> };
> .../linux$ grep 'define\sifr_flags' include/uapi/linux/if.h
> #define ifr_flags       ifr_ifru.ifru_flags     /* flags                */
> .../linux$
> 
> -- 
> Alejandro Colomar
> Linux man-pages comaintainer; https://www.kernel.org/doc/man-pages/ 
> <https://www.kernel.org/doc/man-pages/>
> http://www.alejandro-colomar.es/ <http://www.alejandro-colomar.es/>

Re: netdevice.7 SIOCGIFFLAGS/SIOCSIFFLAGS

[Alejandro Colomar (man-pages)]

[CC += netdev]

Hi Erik,

On 4/14/21 8:52 PM, Erik Flodin wrote:
> Hi,
> 
> On Fri, 19 Mar 2021 at 20:53, Alejandro Colomar (man-pages)
> <alx.manpages@gmail.com> wrote:
>> On 3/17/21 3:12 PM, Erik Flodin wrote:
>>> The documentation for SIOCGIFFLAGS/SIOCSIFFLAGS in netdevice.7 lists
>>> IFF_LOWER_UP, IFF_DORMANT and IFF_ECHO, but those can't be set in
>>> ifr_flags as it is only a short and the flags start at 1<<16.
>>>
>>> See also https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=746e6ad23cd6fec2edce056e014a0eabeffa838c
>>>
>>
>> I don't know what's the history of that.
> 
> Judging from commit message in the commit linked above it was added by
> mistake. As noted the flags are accessible via netlink, just not via
> SIOCGIFFLAGS.
> 
> // Erik
> 

I should have CCd netdev@ before.  Thanks for the update.  Let's see if 
anyone there can comment.

Thanks,

Alex


-- 
Alejandro Colomar
Linux man-pages comaintainer; https://www.kernel.org/doc/man-pages/
http://www.alejandro-colomar.es/

Re: netdevice.7 SIOCGIFFLAGS/SIOCSIFFLAGS

[Erik Flodin]

Hi again,

Have there been any updates on this one?

// Erik

On Wed, 14 Apr 2021 at 21:56, Alejandro Colomar (man-pages)
<alx.manpages@gmail.com> wrote:
>
> [CC += netdev]
>
> Hi Erik,
>
> On 4/14/21 8:52 PM, Erik Flodin wrote:
> > Hi,
> >
> > On Fri, 19 Mar 2021 at 20:53, Alejandro Colomar (man-pages)
> > <alx.manpages@gmail.com> wrote:
> >> On 3/17/21 3:12 PM, Erik Flodin wrote:
> >>> The documentation for SIOCGIFFLAGS/SIOCSIFFLAGS in netdevice.7 lists
> >>> IFF_LOWER_UP, IFF_DORMANT and IFF_ECHO, but those can't be set in
> >>> ifr_flags as it is only a short and the flags start at 1<<16.
> >>>
> >>> See also https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=746e6ad23cd6fec2edce056e014a0eabeffa838c
> >>>
> >>
> >> I don't know what's the history of that.
> >
> > Judging from commit message in the commit linked above it was added by
> > mistake. As noted the flags are accessible via netlink, just not via
> > SIOCGIFFLAGS.
> >
> > // Erik
> >
>
> I should have CCd netdev@ before.  Thanks for the update.  Let's see if
> anyone there can comment.
>
> Thanks,
>
> Alex
>
>
> --
> Alejandro Colomar
> Linux man-pages comaintainer; https://www.kernel.org/doc/man-pages/
> http://www.alejandro-colomar.es/

Re: netdevice.7 SIOCGIFFLAGS/SIOCSIFFLAGS

[Alejandro Colomar (man-pages)]

[PING mtk, netdev@]
[CC += linux-kernel]

Hi Erik,

On 4/29/21 9:45 PM, Erik Flodin wrote:
> On Wed, 14 Apr 2021 at 21:56, Alejandro Colomar (man-pages)
> <alx.manpages@gmail.com> wrote:
>>
>> [CC += netdev]
>>
>> Hi Erik,
>>
>> On 4/14/21 8:52 PM, Erik Flodin wrote:
>>> Hi,
>>>
>>> On Fri, 19 Mar 2021 at 20:53, Alejandro Colomar (man-pages)
>>> <alx.manpages@gmail.com> wrote:
>>>> On 3/17/21 3:12 PM, Erik Flodin wrote:
>>>>> The documentation for SIOCGIFFLAGS/SIOCSIFFLAGS in netdevice.7 lists
>>>>> IFF_LOWER_UP, IFF_DORMANT and IFF_ECHO, but those can't be set in
>>>>> ifr_flags as it is only a short and the flags start at 1<<16.
>>>>>
>>>>> See also https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=746e6ad23cd6fec2edce056e014a0eabeffa838c
>>>>>
>>>>
>>>> I don't know what's the history of that.
>>>
>>> Judging from commit message in the commit linked above it was added by
>>> mistake. As noted the flags are accessible via netlink, just not via
>>> SIOCGIFFLAGS.
>>>
>>> // Erik
>>>
>>
>> I should have CCd netdev@ before.  Thanks for the update.  Let's see if
>> anyone there can comment.
>>
>> Thanks,
>>
>> Alex
>>

> Hi again,
> 
> Have there been any updates on this one?

No, Noone from the kernel answered.  And I'm sorry, but I'm not sure
what is going on in the code, so I don't want to close this here by just
removing those flags from the manual page, because I worry that the
actual code may be wrong or something.  So I prefer that when Michael
has some time he can maybe review this and say something.  Ideally,
someone from the kernel would also respond, but they haven't.  I've CCd
the LKML; let's see if someone reads this and can help.

Thanks,

Alex

P.S.:  Please, if we haven't responded in a month from now, ping us
again.  Thanks again.

> 
> // Erik
> 
>>
>> --
>> Alejandro Colomar
>> Linux man-pages comaintainer; https://www.kernel.org/doc/man-pages/
>> http://www.alejandro-colomar.es/

-- 
Alejandro Colomar
Linux man-pages comaintainer; https://www.kernel.org/doc/man-pages/
http://www.alejandro-colomar.es/

Re: netdevice.7 SIOCGIFFLAGS/SIOCSIFFLAGS

[Alejandro Colomar (man-pages)]

Hi Erik,

On 10/2/21 18:35, Erik Flodin wrote:
> A bit more than a month has passed so here's a ping :)
> 
> // Erik

Thanks for the ping.

alarm(3600 * 24 * 30);  // :)

> 
> On Fri, 30 Apr 2021 at 21:32, Alejandro Colomar (man-pages) 
> <alx.manpages@gmail.com <mailto:alx.manpages@gmail.com>> wrote:
> 
>     [PING mtk, netdev@]
>     [CC += linux-kernel]
> 
>     Hi Erik,
> 
>     On 4/29/21 9:45 PM, Erik Flodin wrote:
>      > On Wed, 14 Apr 2021 at 21:56, Alejandro Colomar (man-pages)
>      > <alx.manpages@gmail.com <mailto:alx.manpages@gmail.com>> wrote:
>      >>
>      >> [CC += netdev]
>      >>
>      >> Hi Erik,
>      >>
>      >> On 4/14/21 8:52 PM, Erik Flodin wrote:
>      >>> Hi,
>      >>>
>      >>> On Fri, 19 Mar 2021 at 20:53, Alejandro Colomar (man-pages)
>      >>> <alx.manpages@gmail.com <mailto:alx.manpages@gmail.com>> wrote:
>      >>>> On 3/17/21 3:12 PM, Erik Flodin wrote:
>      >>>>> The documentation for SIOCGIFFLAGS/SIOCSIFFLAGS in
>     netdevice.7 lists
>      >>>>> IFF_LOWER_UP, IFF_DORMANT and IFF_ECHO, but those can't be set in
>      >>>>> ifr_flags as it is only a short and the flags start at 1<<16.
>      >>>>>
>      >>>>> See also
>     https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=746e6ad23cd6fec2edce056e014a0eabeffa838c
>     <https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=746e6ad23cd6fec2edce056e014a0eabeffa838c>
>      >>>>>
>      >>>>
>      >>>> I don't know what's the history of that.
>      >>>
>      >>> Judging from commit message in the commit linked above it was
>     added by
>      >>> mistake. As noted the flags are accessible via netlink, just
>     not via
>      >>> SIOCGIFFLAGS.
>      >>>
>      >>> // Erik
>      >>>
>      >>
>      >> I should have CCd netdev@ before.  Thanks for the update.  Let's
>     see if
>      >> anyone there can comment.
>      >>
>      >> Thanks,
>      >>
>      >> Alex
>      >>
> 
>      > Hi again,
>      >
>      > Have there been any updates on this one?
> 
>     No, Noone from the kernel answered.  And I'm sorry, but I'm not sure
>     what is going on in the code, so I don't want to close this here by just
>     removing those flags from the manual page, because I worry that the
>     actual code may be wrong or something.  So I prefer that when Michael
>     has some time he can maybe review this and say something.  Ideally,
>     someone from the kernel would also respond, but they haven't.  I've CCd
>     the LKML; let's see if someone reads this and can help.
> 
>     Thanks,
> 
>     Alex
> 
>     P.S.:  Please, if we haven't responded in a month from now, ping us
>     again.  Thanks again.
> 
>      >
>      > // Erik
>      >
>      >>
>      >> --
>      >> Alejandro Colomar
>      >> Linux man-pages comaintainer;
>     https://www.kernel.org/doc/man-pages/
>     <https://www.kernel.org/doc/man-pages/>
>      >> http://www.alejandro-colomar.es/ <http://www.alejandro-colomar.es/>
> 
>     -- 
>     Alejandro Colomar
>     Linux man-pages comaintainer; https://www.kernel.org/doc/man-pages/
>     <https://www.kernel.org/doc/man-pages/>
>     http://www.alejandro-colomar.es/ <http://www.alejandro-colomar.es/>
> 

-- 
Alejandro Colomar
Linux man-pages comaintainer; http://www.kernel.org/doc/man-pages/
http://www.alejandro-colomar.es/