Re: [dpdk-dev] [PATCH 1/2] security: enforce semantics for Tx inline processing

[Nithin Dabilpuram <nithind1988@gmail.com>]

On Tue, Jul 06, 2021 at 10:56:10AM +0000, Ananyev, Konstantin wrote:
> 
> > 
> > From: Nithin Dabilpuram <ndabilpuram@marvell.com>
> > 
> > For Tx inline processing, when RTE_SECURITY_TX_OLOAD_NEED_MDATA is
> > set, rte_security_set_pkt_metadata() needs to be called for pkts
> > to associate a Security session with a mbuf before submitting
> > to Ethdev Tx. This is apart from setting PKT_TX_SEC_OFFLOAD in
> > mbuf.ol_flags. rte_security_set_pkt_metadata() is also used to
> > set some opaque metadata in mbuf for PMD's use.
> > This patch updates documentation that rte_security_set_pkt_metadata()
> > should be called only with mbuf containing Layer 3 and above data.
> > This behaviour is consistent with existing PMD's such as ixgbe.
> > 
> > On Tx, not all net PMD's/HW can parse packet and identify
> > L2 header and L3 header locations on Tx. This is inline with other
> > Tx offloads requirements such as L3 checksum, L4 checksum offload,
> > etc, where mbuf.l2_len, mbuf.l3_len etc, needs to be set for
> > HW to be able to generate checksum. Since Inline IPSec is also
> > such a Tx offload, some PMD's at least need mbuf.l2_len to be
> > valid to find L3 header and perform Outbound IPSec processing.
> > Hence, this patch updates documentation to enforce setting
> > mbuf.l2_len while setting PKT_TX_SEC_OFFLOAD in mbuf.ol_flags
> > for Inline IPSec Crypto / Protocol offload processing to
> > work on Tx.
> > 
> > Signed-off-by: Nithin Dabilpuram <ndabilpuram@marvell.com>
> > Reviewed-by: Akhil Goyal <gakhil@marvell.com>
> > ---
> >  doc/guides/nics/features.rst           | 2 ++
> >  doc/guides/prog_guide/rte_security.rst | 6 +++++-
> >  lib/mbuf/rte_mbuf_core.h               | 2 ++
> >  3 files changed, 9 insertions(+), 1 deletion(-)
> > 
> > diff --git a/doc/guides/nics/features.rst b/doc/guides/nics/features.rst
> > index 403c2b03a..414baf14f 100644
> > --- a/doc/guides/nics/features.rst
> > +++ b/doc/guides/nics/features.rst
> > @@ -430,6 +430,7 @@ of protocol operations. See Security library and PMD documentation for more deta
> > 
> >  * **[uses]       rte_eth_rxconf,rte_eth_rxmode**: ``offloads:DEV_RX_OFFLOAD_SECURITY``,
> >  * **[uses]       rte_eth_txconf,rte_eth_txmode**: ``offloads:DEV_TX_OFFLOAD_SECURITY``.
> > +* **[uses]       mbuf**: ``mbuf.l2_len``.
> >  * **[implements] rte_security_ops**: ``session_create``, ``session_update``,
> >    ``session_stats_get``, ``session_destroy``, ``set_pkt_metadata``, ``capabilities_get``.
> >  * **[provides] rte_eth_dev_info**: ``rx_offload_capa,rx_queue_offload_capa:DEV_RX_OFFLOAD_SECURITY``,
> > @@ -451,6 +452,7 @@ protocol operations. See security library and PMD documentation for more details
> > 
> >  * **[uses]       rte_eth_rxconf,rte_eth_rxmode**: ``offloads:DEV_RX_OFFLOAD_SECURITY``,
> >  * **[uses]       rte_eth_txconf,rte_eth_txmode**: ``offloads:DEV_TX_OFFLOAD_SECURITY``.
> > +* **[uses]       mbuf**: ``mbuf.l2_len``.
> >  * **[implements] rte_security_ops**: ``session_create``, ``session_update``,
> >    ``session_stats_get``, ``session_destroy``, ``set_pkt_metadata``, ``get_userdata``,
> >    ``capabilities_get``.
> > diff --git a/doc/guides/prog_guide/rte_security.rst b/doc/guides/prog_guide/rte_security.rst
> > index f72bc8a78..7b68c698d 100644
> > --- a/doc/guides/prog_guide/rte_security.rst
> > +++ b/doc/guides/prog_guide/rte_security.rst
> > @@ -560,7 +560,11 @@ created by the application is attached to the security session by the API
> > 
> >  For Inline Crypto and Inline protocol offload, device specific defined metadata is
> >  updated in the mbuf using ``rte_security_set_pkt_metadata()`` if
> > -``DEV_TX_OFFLOAD_SEC_NEED_MDATA`` is set.
> > +``RTE_SECURITY_TX_OLOAD_NEED_MDATA`` is set. ``rte_security_set_pkt_metadata()``
> > +should be called on mbuf only with Layer 3 and above data present and
> > +``mbuf.data_off`` should be pointing to Layer 3 Header.
> 
> Hmm... not sure why mbuf.data_off should point to L3 hdr.
> Who will add L2 hdr to the packet in that case?
> Or did you mean ``mbuf.data_off + mbuf.l2_len`` here?

That is the semantics I was trying to define. I think below are the sequence of
operations to be done for ipsec processing,

1. receive_pkt()
2. strip_l2_hdr()
3. Do policy lookup ()
4. Call rte_security_set_pkt_metadata() if pkt needs to be encrypted with a
particular SA. Now pkt only has L3 and above data.
5. Do route_lookup()
6. add_l2hdr() which might be different from stripped l2hdr.
7. Send packet out.

The above sequence is what I believe the current poll mode worker thread in
ipsec-secgw is following. While in event mode, step 2 and step 6 are missing.

This patch is trying to enforce semantics as above so that
rte_security_set_pkt_metadata() can predict what comes in the pkt when he is
called.

I also think above sequence is what Linux kernel stack or other stacks follow.
Does it makes sense ?

> 
> > Once called,
> > +Layer 3 and above data cannot be modified or moved around unless
> > +``rte_security_set_pkt_metadata()`` is called again.
> > 
> >  For inline protocol offloaded ingress traffic, the application can register a
> >  pointer, ``userdata`` , in the security session. When the packet is received,
> > diff --git a/lib/mbuf/rte_mbuf_core.h b/lib/mbuf/rte_mbuf_core.h
> > index bb38d7f58..9d8e3ddc8 100644
> > --- a/lib/mbuf/rte_mbuf_core.h
> > +++ b/lib/mbuf/rte_mbuf_core.h
> > @@ -228,6 +228,8 @@ extern "C" {
> > 
> >  /**
> >   * Request security offload processing on the TX packet.
> > + * To use Tx security offload, the user needs to fill l2_len in mbuf
> > + * indicating L2 header size and where L3 header starts.
> >   */
> >  #define PKT_TX_SEC_OFFLOAD	(1ULL << 43)
> > 
> > --
> > 2.25.1
>