Re: [dpdk-dev] [RFC] ethdev: add IPv4/IPv6 DSCP rewrite action

[Ori Kam <orika@mellanox.com>]

Hi Stephen,

> -----Original Message-----
> From: Stephen Hemminger <stephen@networkplumber.org>
> Sent: Tuesday, December 10, 2019 8:32 PM
> To: Andrew Rybchenko <arybchenko@solarflare.com>
> Cc: Suanming Mou <suanmingm@mellanox.com>; Adrien Mazarguil
> <adrien.mazarguil@6wind.com>; John McNamara
> <john.mcnamara@intel.com>; Marko Kovacevic
> <marko.kovacevic@intel.com>; Thomas Monjalon <thomas@monjalon.net>;
> Ferruh Yigit <ferruh.yigit@intel.com>; dev@dpdk.org; Shahaf Shuler
> <shahafs@mellanox.com>; Ori Kam <orika@mellanox.com>; Matan Azrad
> <matan@mellanox.com>; Slava Ovsiienko <viacheslavo@mellanox.com>
> Subject: Re: [dpdk-dev] [RFC] ethdev: add IPv4/IPv6 DSCP rewrite action
> 
> On Tue, 10 Dec 2019 10:33:28 +0300
> Andrew Rybchenko <arybchenko@solarflare.com> wrote:
> 
> > > For some overlay network, such as VXLAN, the DSCP field in the new
> outer
> > > IP header after VXLAN decapsulation may need to be updated
> accordingly.
> > >
> > > This commit introduce the DSCP modify action for IPv4 and IPv6.
> > >
> > > Signed-off-by: Suanming Mou <suanmingm@mellanox.com>
> >
> > Acked-by: Andrew Rybchenko <arybchenko@solarflare.com>
> >
> > as usual it requires testpmd support and a driver which
> > supports it (I understand that it may be omitted in RFC).
> 
> And it requires documentation and a software implementation in the flow
> classifier.
> 

Why in the flow classifier?
I don't remember any new code that was added to rte_flow was also added to flow classifier.

> 
> Plus you conveniently exclude defining what happens to reserved bits.
> "What ever our hardware does is correct" is not a useful answer.
> You need to be precise and limited in what is allowed to make this usable.
> 

The action does just what it says nothing more and nothing less. 
It just modify the DSCP value with a value given by the application.
Reserved bits are not touched.

> Sorry, to be so negative. This feature is fine in itself and a useful
> incremental improvement. But nobody has stepped up to address the
> usability
> of rte_flow.

I'm sorry but I don't understand your comment, 
According to my knowledge more and more applications are using rte_flow, and each new feature that is added is based on some 
customer need. 

Thanks,
Ori