Re: [dpdk-dev] [PATCH] ethdev: allow multiple security sessions to use one rte flow

["Ananyev, Konstantin" <konstantin.ananyev@intel.com>]

> > > > > The rte_security API which enables inline protocol/crypto feature
> > > > > mandates that for every security session an rte_flow is created.
> > > > > This would internally translate to a rule in the hardware which
> > > > > would do packet classification.
> > > > >
> > > > > In rte_securty, one SA would be one security session. And if an
> > > > > rte_flow need to be created for every session, the number of SAs
> > > > > supported by an inline implementation would be limited by the
> > > > > number of rte_flows the PMD would be able to support.
> > > > >
> > > > > If the fields SPI & IP addresses are allowed to be a range, then
> > > > > this limitation can be overcome. Multiple flows will be able to
> > > > > use one rule for SECURITY processing. In this case, the security
> > > > > session provided as conf would be NULL.
> > > >
> > > > Wonder what will be the usage model for it?
> > > > AFAIK,  RFC 4301 clearly states that either SPI value alone or in
> > > > conjunction with dst (and src) IP should clearly identify SA for inbound SAD
> > lookup.
> > > > Am I missing something obvious here?
> > >
> > > [Anoob] Existing SECURITY action type requires application to create
> > > an 'rte_flow' per SA, which is not really required if h/w can use SPI to uniquely
> > identify the security session/SA.
> > >
> > > Existing rte_flow usage: IP (dst,src) + ESP + SPI -> security
> > > processing enabled on one security session (ie on SA)
> > >
> > > The above rule would uniquely identify packets for an SA. But with the
> > > above usage, we would quickly exhaust entries available in h/w lookup
> > > tables (which are limited on our hardware). But if h/w can use SPI field to index
> > into a table (for example), then the above requirement of one rte_flow per SA is
> > not required.
> > >
> > > Proposed rte_flow usage: IP (any) + ESP + SPI (any) -> security
> > > processing enabled on all ESP packets
> > >
> > > Now h/w could use SPI to index into a pre-populated table to get
> > > security session. Please do note that, SPI is not ignored during the actual
> > lookup. Just that it is not used while creating 'rte_flow'.
> >
> > And this table will be prepopulated by user and pointer to it will be somehow
> > passed via rte_flow API?
> > If yes, then what would be the mechanism?
> 
> [Anoob] I'm not sure what exactly you meant by user. But may be I'll explain how it's done in OCTEONTX2 PMD.
> 
> The application would create security_session for every SA. SPI etc would be available to PMD (in conf) when the session is created.
> Now the PMD would populate SA related params in a specific location that h/w would access. This memory is allocated during device
> configure and h/w would have the pointer after the initialization is done.
> 
> PMD uses SPI as index to write into specific locations(during session create) and h/w would use it when it sees an ESP packet eligible
> for SECURITY (in receive path, per packet). As long as session creation could populate at memory locations that h/w would look at, this
> scheme would work.

Thanks for explanation, few more questions:
Ok, so the table will be allocated at device init() somehow (nothing to do with rte_flow).
Then PMD will be able to write/update entries in that table and HW will be able to read (to get SPI, keys, etc), correct?
Now if upper layer (ipsec-secgw for example) would like to create new ESP session on that device, what it would need to do?
Would it still need to use rte_flow API for that?
Or just call rte_security_session_create() and PMD will take update this HW/SW table for it?

> 
> >
> > >
> > > The usage of one 'rte_flow' for multiple SAs is not mandatory. It is
> > > only required when application requires large number of SAs. The proposed
> > change is to allow more efficient usage of h/w resources where it's permitted by
> > the PMD.
> > >
> > > >
> > > > >
> > > > > Application should do an rte_flow_validate() to make sure the flow
> > > > > is supported on the PMD.
> > > > >
> > > > > Signed-off-by: Anoob Joseph <anoobj@marvell.com>
> > > > > ---
> > > > >  lib/librte_ethdev/rte_flow.h | 6 ++++++
> > > > >  1 file changed, 6 insertions(+)
> > > > >
> > > > > diff --git a/lib/librte_ethdev/rte_flow.h
> > > > > b/lib/librte_ethdev/rte_flow.h index 452d359..21fa7ed 100644
> > > > > --- a/lib/librte_ethdev/rte_flow.h
> > > > > +++ b/lib/librte_ethdev/rte_flow.h
> > > > > @@ -2239,6 +2239,12 @@ struct rte_flow_action_meter {
> > > > >   * direction.
> > > > >   *
> > > > >   * Multiple flows can be configured to use the same security session.
> > > > > + *
> > > > > + * The NULL value is allowed for security session. If security
> > > > > + session is NULL,
> > > > > + * then SPI field in ESP flow item and IP addresses in flow items
> > > > > + 'IPv4' and
> > > > > + * 'IPv6' will be allowed to be a range. The rule thus created
> > > > > + can enable
> > > > > + * SECURITY processing on multiple flows.
> > > > > + *
> > > > >   */
> > > > >  struct rte_flow_action_security {
> > > > >  	void *security_session; /**< Pointer to security session structure.
> > > > > */
> > > > > --
> > > > > 2.7.4