[dpdk-dev] [PATCH] examples/l3fwd: force CRC stripping for i40evf

Ananyev, Konstantin konstantin.ananyev at intel.com
Wed Nov 9 13:13:45 CET 2016

> -----Original Message-----
> From: Topel, Bjorn
> Sent: Wednesday, November 9, 2016 11:28 AM
> To: Ananyev, Konstantin <konstantin.ananyev at intel.com>; dev at dpdk.org; Zhang, Helin <helin.zhang at intel.com>
> Cc: Xu, Qian Q <qian.q.xu at intel.com>; Yao, Lei A <lei.a.yao at intel.com>; Wu, Jingjing <jingjing.wu at intel.com>;
> thomas.monjalon at 6wind.com
> Subject: Re: [dpdk-dev] [PATCH] examples/l3fwd: force CRC stripping for i40evf
> >> Correct, so the broader question would be "what is the correct
> >> behavior for an example application, when a port configuration
> >> isn't supported by the hardware?".
> >>
> >> My stand, FWIW, is that igb and ixgbe should have the same
> >> semantics as i40e currently has, i.e. return an error to the user
> >> if the port is mis-configured, NOT changing the setting behind the
> >> users back.
> >>
> >
> > Fine by me, but then it means that the fix haw to include changes
> > for all apps plus ixgbe and igb PMDs, correct? :)
> Ugh. Correct, I guess. :-)
> As for ixgbe and igb - they need a patch changing from silent ignore to
> explicit error. Regarding the apps, I guess all the apps that rely on
> that disabling CRC stripping always work, need some work. Or should all
> the example applications have CRC stripping *enabled* by default? I'd
> assume that all DPDK supported NICs has support for CRC stripping

From the sources, it seems that only nfp doesn't support HW CRC stripping.
In fact, as I can see some non-Intel PMDs just ignore hw_stip_crc value
and assume that CRC strip is always on. 

> and I
> guess this is the rational for having it on by default for Intel VFs.
> In general, for the example applications, if an application relies on a
> property for a port, that the hardware doesn't support -- what would be
> the desired behavior? Or is it implied that the example applications
> only use a common, minimal set of features that are know to be supported
> by all DPDK supported hardware?
> Isn't it perfectly valid that some example applications wont run for all
> hardware?
> Finally, why doesn't l3fwd have the CRC stripped?

I don’t know any good reason for that for l3fwd or any other sample app.
I think it is just a 'historical' reason.

> Björn

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