Re: [dpdk-dev] [PATCH] kni: reduce interface name size

[Michael Pfeiffer <michael.pfeiffer@tu-ilmenau.de>]

Hi Ferruh,

On Fri, 2019-11-15 at 12:49 +0000, Ferruh Yigit wrote:
> On 11/15/2019 12:43 PM, Michael Pfeiffer wrote:
> > Hi Igor,
> > you're right, RTE_KNI_NAMESIZE == IFNAMSIZ is the intention.
> > However,
> > to my understanding linux/if.h (where IFNAMSIZ is defined) is only
> > included when building kernel code. I thought maybe this was
> > intentional to keep rte_kni_common.h free of Linux kernel
> > dependencies
> > (when building userland code).
> > 
> > In practice, it probably won't matter, as the KNI kernel module is
> > available for Linux only at the moment. I will therefore gladly
> > change
> > this to IFNAMSIZ if you and Ferruh think this is the way to go.
> 
> I think better to not add dependency to userland, and I don't expect
> IFNAMSIZ
> changing in kernel side, so safe to keep hardcoded value,
> only perhaps a simple /* IFNAMSIZ  */ comment can be added to
> highlight the
> relation?

perfect, I will update the patch accordingly.

Regards
Michael

> > Regards
> > Michael
> > 
> > On Fri, 2019-11-15 at 15:30 +0300, Igor Ryzhov wrote:
> > > Hi Michael,
> > > 
> > > Isn't it better to set it to IFNAMSIZ instead of 16?
> > > 
> > > Best regards,
> > > Igot
> > > 
> > > On Fri, Nov 15, 2019 at 2:41 PM Michael Pfeiffer <
> > > michael.pfeiffer@tu-ilmenau.de> wrote:
> > > 
> > > > The name in rte_kni_device_info is passed to the kernel, which
> > > > allows
> > > > interface names with at most 16 bytes (IFNAMSIZ). rte_kni_alloc
> > > > with a
> > > > longer name currently trigger a kernel BUG in alloc_netdev_mqs
> > > > in
> > > > net/core/dev.c. Reduce RTE_KNI_NAMESIZE to prevent this
> > > > situation.
> > > > 
> > > > Signed-off-by: Michael Pfeiffer <michael.pfeiffer@tu-ilmenau.de
> > > > >
> > > > ---
> > > >  lib/librte_eal/linux/eal/include/rte_kni_common.h | 2 +-
> > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > > 
> > > > diff --git a/lib/librte_eal/linux/eal/include/rte_kni_common.h
> > > > b/lib/librte_eal/linux/eal/include/rte_kni_common.h
> > > > index 46f75a710..59339271b 100644
> > > > --- a/lib/librte_eal/linux/eal/include/rte_kni_common.h
> > > > +++ b/lib/librte_eal/linux/eal/include/rte_kni_common.h
> > > > @@ -18,7 +18,7 @@
> > > >  /**
> > > >   * KNI name is part of memzone name.
> > > >   */
> > > > -#define RTE_KNI_NAMESIZE 32
> > > > +#define RTE_KNI_NAMESIZE 16
> > > > 
> > > >  #define RTE_CACHE_LINE_MIN_SIZE 64
> > > > 
> > > > --
> > > > 2.20.1
> > > > 
> > > > 
-- 
Michael Pfeiffer

Technische Universität Ilmenau
Fakultät für Informatik und Automatisierung
Fachgebiet Telematik / Rechnernetze

E-Mail: michael.pfeiffer@tu-ilmenau.de
Telefon: +49 3677 69-4854
Web: https://www.tu-ilmenau.de/telematik/mitarbeiter/michael-pfeiffer/