Re: [PATCH] Trivial patch for SIOCGIFCOUNT

Date: Wed Oct 10 2001 - 00:36:29 EST

David S. Miller wrote:

> From: "BALBIR SINGH" <>
> Date: Tue, 09 Oct 2001 18:53:47 +0530
> To make the API orthogonal, I have included a patch for SIOCGIFCOUNT,
> which currently returns -EINVAL. The only reason I am providing this patch
> is to make the API complete and make it easier to port applications from
> other UNIX like OS'es.
>There is no need for this change, and _EVEN_ if we put this
>change in today every APP out there would _STILL_ need to deal with
>all existing kernels which do not have SIOCGIFCOUNT implemented.
>Furthermore, SIOCGIFCOUNT also gives no new functionality that does
>not exist already. SIOCGIFCONF with a zero size with give the
>behavior necessary to get the same answer as a SIOCGIFCOUNT would
>provide. As far as I am aware, every system providing BSD sockets
>provides this SIOCGIFCONF "feature".
>Therefore, it is already quite easy to make applications portable
>between Linux and other BSD socket based systems. Simply use the
>SIOCGIFCONF method throughout.
I had mentioned even earlier, the same functionality can be obtained otherwise.
I was talking about porting from SUN, HP-UX, AIX, etc. I have had people coming
to me and telling me that SIOCGIFNUM (equivalent to SIOCGIFCOUNT) does not exist
and I have had to ask them to use SIOCGIFCONF, if ifc.ifc_len and ifc.ifc_buf set
to '0', to obtain the total size. Again, it is not a must it should be around.
But since the ioctl is there, it might be good to have it work the way some one
reading a man page would expect it to work, or if somebody wanted to port some
application from Sun, HP-UX or AIX would just do


and get his application to compile without changing the code


>Franks a lot,
>David S. Miller

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