Re: [dpdk-dev] [PATCH v6 2/4] examples/ipsec-secgw: add fallback session feature

[Akhil Goyal <akhil.goyal@nxp.com>]

Hi Konstantin,
> 
> Hi Akhil,
> 
> > >
> > > Inline processing is limited to a specified subset of traffic. It is
> > > often unable to handle more complicated situations, such as fragmented
> > > traffic. When using inline processing such traffic is dropped.
> > >
> > > Introduce fallback session for inline processing allowing processing
> > > packets that normally would be dropped. A fallback session is
> > > configured by adding 'fallback' keyword with 'lookaside-none' or
> > > 'lookaside-protocol' parameter to an SA configuration.
> > >
> > > Using IPsec anti-replay window or ESN feature with fallback session is
> > > not yet supported when primary session is of type
> > > 'inline-protocol-offload' or fallback session is 'lookaside-protocol'
> > > because SA sequence number is not synchronized between software and
> > > hardware sessions. Fallback sessions are also limited to ingress IPsec
> > > traffic.
> > >
> > > Fallback session feature is not available in the legacy mode.
> > >
> > I started looking this patch, but some initial thoughts looking at the patch
> description.
> >
> > When you say a fallback session will be a lookaside none or lookaside protocol,
> > the packet will be processed asynchronously and might as well reorder.
> 
> Yes, we documented it as one of limitations.
> Though as I already mentioned for some use-cases some reordering it is
> acceptable.

Which usecases allow reordering. I think most stacks have replay window of less than 256/128 frames.
> 
>  > The best possible solution for this would be the synchronous API which are in
> talks
> 
> Agree, that would be a way to avoid reordering, but it is not there yet.
> 
> > in another patchset or use a SW PMD(eg. Openssl etc.) session and wait till you
> get the packet dequeued.
> > So effectively async APIs will be used to behave synchronously.
> > You can not use hardware PMD session as it will perform very badly for
> fallback packets
> > Because you have to wait till the packet is not getting dequeued back.
> 
> We don't plan to support that model because of great performance penalty you
> mentioned.

So what is currently supported with this patchset.
- cpu crypto is not there yet.
- SW PMD you are not supporting that model.

> 
> >
> > Having said that, you won't find a device or a scenario where you can use
> > Inline crypto as primary and lookaside proto as fallback.
> > It can only be like inline crypto as primary and lookaside none as fallback.
> 
> Yes, correct.
> I thought that we already removed lookaside-proto from supported types.
> If we didn't - will certainly do that.
> 
> >
> > BTW, I am ok with Patch 1/4 and 3/4. If no objections from the community, I
> can pick those.
> 
> Great to hear.
> What obstacles do you see with others two?
I believe there are some discussion going on between you and Anoob.


> Konstantin
> 
> >
> > -Akhil
> >
> > > Acked-by: Konstantin Ananyev <konstantin.ananyev@intel.com>
> > > Tested-by: Bernard Iremonger <bernard.iremonger@intel.com>
> > > Signed-off-by: Marcin Smoczynski <marcinx.smoczynski@intel.com>
> > > ---