kni: check abi version between kmod and lib

[Stephen Hemminger]

On Thu, 21 Apr 2022 11:40:00 -0400
Ray Kinsella <mdr at ashroe.eu> wrote:

> Stephen Hemminger <stephen at networkplumber.org> writes:
> 
> > On Thu, 21 Apr 2022 12:38:26 +0800
> > Stephen Coleman <omegacoleman at gmail.com> wrote:
> >  
> >> KNI ioctl functions copy data from userspace lib, and this interface
> >> of kmod is not compatible indeed. If the user use incompatible rte_kni.ko
> >> bad things happen: sometimes various fields contain garbage value,
> >> sometimes it cause a kmod soft lockup.
> >> 
> >> Some common distros ship their own rte_kni.ko, so this is likely to
> >> happen.
> >> 
> >> This patch add abi version checking between userland lib and kmod so
> >> that:
> >> 
> >> * if kmod ioctl got a wrong abi magic, it refuse to go on
> >> * if userland lib, probed a wrong abi version via newly added ioctl, it
> >>   also refuse to go on
> >> 
> >> Bugzilla ID: 998  
> >
> >
> > Kernel API's are supposed to be 99% stable.
> > If this driver was playing by the upstream kernel rules this would not
> > have happened.  
> 
> Well look, it is out-of-tree and never likely to be in-tree, so those
> rules don't apply. Making sure the ABI doesn't change during the ABI
> stablity period, should be good enough?
> 

I think if KNI changes, it should just add more ioctl numbers and
be compatible, it is not that hard.