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

["Ananyev, Konstantin" <konstantin.ananyev@intel.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.
> >
> > That's just a sample app, it doesn't mean it has to be the only possible way.
> >
> > > While in event mode, step 2 and step 6 are missing.
> >
> > I think this L2 hdr manipulation is totally optional.
> > If your rte_security_set_pkt_metadata() implementation really needs to know L3 hdr offset (not sure why?),
> Since rte_security_set_pkt_metadata() is PMD specific function ptr call, we are currently doing some pre-processing
> here before submitting packet to inline IPSec via rte_eth_tx_burst(). This saves us cycles later in rte_eth_tx_burst().
> If we cannot know for sure, the pkt content at the time of rte_security_set_pkt_metadata() call, then I think
> having a PMD specific callback is not much of use except for saving SA priv data to rte_mbuf.
> 
> > then I suppose we can add a requirement that l2_len has to be set properly before calling rte_security_set_pkt_metadata().
> 
> This is also fine with us.

Ok, so to make sure we are on the same page, you propose:
1. before calling rte_security_set_pkt_metadata() mbuf.l2_len should be properly set.
2. after rte_security_set_pkt_metadata() and before rte_eth_tx_burst() packet contents
    at [mbuf.l2_len, mbuf.pkt_len) can't be modified?

Is that correct understanding?
If yes, I wonder how 2) will correlate with rte_eth_tx_prepare() concept?  

> >
> > >
> > > 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
> > > >