Re: [dpdk-dev] [PATCH v9 1/3] ethdev: add actions to modify TCP header fields

[Adrien Mazarguil <adrien.mazarguil@6wind.com>]

On Tue, Jul 02, 2019 at 09:52:40AM +0000, Dekel Peled wrote:
> Thanks, PSB
> 
> > -----Original Message-----
> > From: Andrew Rybchenko <arybchenko@solarflare.com>
> > Sent: Tuesday, July 2, 2019 11:14 AM
> > To: Dekel Peled <dekelp@mellanox.com>; Adrien Mazarguil
> > <adrien.mazarguil@6wind.com>; wenzhuo.lu@intel.com;
> > jingjing.wu@intel.com; bernard.iremonger@intel.com; Yongseok Koh
> > <yskoh@mellanox.com>; Shahaf Shuler <shahafs@mellanox.com>; Slava
> > Ovsiienko <viacheslavo@mellanox.com>; arybchenko@solarflare.com
> > Cc: dev@dpdk.org; Ori Kam <orika@mellanox.com>
> > Subject: Re: [dpdk-dev] [PATCH v9 1/3] ethdev: add actions to modify TCP
> > header fields
> > 
> > On 01.07.2019 18:43, Dekel Peled wrote:
> > > Add actions:
> > > - INC_TCP_SEQ - Increase sequence number in the outermost TCP header.
> > > - DEC_TCP_SEQ - Decrease sequence number in the outermost TCP
> > header.
> > > - INC_TCP_ACK - Increase acknowledgment number in the outermost TCP
> > > 		header.
> > > - DEC_TCP_ACK - Decrease acknowledgment number in the outermost TCP
> > > 		header.
> > >
> > > Original work by Xiaoyu Min.
> > >
> > > This patch uses the new approach introduced by [1], using a simple
> > > integer instead of using an action-specific structure for each of the
> > > new actions.
> > >
> > > [1]
> > >
> > https://eur03.safelinks.protection.outlook.com/?url=http%3A%2F%2Fpatch
> > >
> > es.dpdk.org%2Fpatch%2F55773%2F&amp;data=02%7C01%7Cdekelp%40mell
> > anox.co
> > >
> > m%7Cae3a2667c3a243a9c1e508d6fec54a22%7Ca652971c7d2e4d9ba6a4d1492
> > 56f461
> > >
> > b%7C0%7C0%7C636976520663069258&amp;sdata=1z3uDQGnnyPZH9NAUuY5
> > 0ZSg3smyZ
> > > nDmc3QZtuNTmyg%3D&amp;reserved=0
> > >
> > > Signed-off-by: Dekel Peled <dekelp@mellanox.com>
> > > Acked-by: Andrew Rybchenko <arybchenko@solarflare.com>
> > > ---
> > >   doc/guides/prog_guide/rte_flow.rst | 32
> > ++++++++++++++++++++++++++++++++
> > >   lib/librte_ethdev/rte_flow.c       |  4 ++++
> > >   lib/librte_ethdev/rte_flow.h       | 32
> > ++++++++++++++++++++++++++++++++
> > >   3 files changed, 68 insertions(+)
> > >
> > > diff --git a/doc/guides/prog_guide/rte_flow.rst
> > > b/doc/guides/prog_guide/rte_flow.rst
> > > index 67deed7..bbe32db 100644
> > > --- a/doc/guides/prog_guide/rte_flow.rst
> > > +++ b/doc/guides/prog_guide/rte_flow.rst
> > > @@ -2346,6 +2346,38 @@ Otherwise, RTE_FLOW_ERROR_TYPE_ACTION
> > error will be returned.
> > >      | ``mac_addr`` | MAC address   |
> > >      +--------------+---------------+
> > >
> > > +Action: ``INC_TCP_SEQ``
> > > +^^^^^^^^^^^^^^^^^^^^^^^
> > > +
> > > +Increase sequence number in the outermost TCP header.
> > > +Value to increase TCP sequence number by is a big-endian 32 bit integer.
> > > +
> > > +Using this action on non-matching traffic will result in undefined behavior.
> > > +
> > > +Action: ``DEC_TCP_SEQ``
> > > +^^^^^^^^^^^^^^^^^^^^^^^
> > > +
> > > +Decrease sequence number in the outermost TCP header.
> > > +Value to decrease TCP sequence number by is a big-endian 32 bit integer.
> > > +
> > > +Using this action on non-matching traffic will result in undefined behavior.
> > > +
> > > +Action: ``INC_TCP_ACK``
> > > +^^^^^^^^^^^^^^^^^^^^^^^
> > > +
> > > +Increase acknowledgment number in the outermost TCP header.
> > > +Value to increase TCP acknowledgment number by is a big-endian 32 bit
> > integer.
> > > +
> > > +Using this action on non-matching traffic will result in undefined behavior.
> > > +
> > > +Action: ``DEC_TCP_ACK``
> > > +^^^^^^^^^^^^^^^^^^^^^^^
> > > +
> > > +Decrease acknowledgment number in the outermost TCP header.
> > > +Value to decrease TCP acknowledgment number by is a big-endian 32 bit
> > integer.
> > > +
> > > +Using this action on non-matching traffic will result in undefined behavior.
> > > +
> > >   Negative types
> > >   ~~~~~~~~~~~~~~
> > >
> > > diff --git a/lib/librte_ethdev/rte_flow.c
> > > b/lib/librte_ethdev/rte_flow.c index 3277be1..0c9f6c6 100644
> > > --- a/lib/librte_ethdev/rte_flow.c
> > > +++ b/lib/librte_ethdev/rte_flow.c
> > > @@ -143,6 +143,10 @@ struct rte_flow_desc_data {
> > >   	MK_FLOW_ACTION(SET_TTL, sizeof(struct rte_flow_action_set_ttl)),
> > >   	MK_FLOW_ACTION(SET_MAC_SRC, sizeof(struct
> > rte_flow_action_set_mac)),
> > >   	MK_FLOW_ACTION(SET_MAC_DST, sizeof(struct
> > > rte_flow_action_set_mac)),
> > > +	MK_FLOW_ACTION(INC_TCP_SEQ, sizeof(rte_be32_t)),
> > > +	MK_FLOW_ACTION(DEC_TCP_SEQ, sizeof(rte_be32_t)),
> > > +	MK_FLOW_ACTION(INC_TCP_ACK, sizeof(rte_be32_t)),
> > > +	MK_FLOW_ACTION(DEC_TCP_ACK, sizeof(rte_be32_t)),
> > >   };
> > >
> > >   static int
> > > diff --git a/lib/librte_ethdev/rte_flow.h
> > > b/lib/librte_ethdev/rte_flow.h index 2232856..28445f4 100644
> > > --- a/lib/librte_ethdev/rte_flow.h
> > > +++ b/lib/librte_ethdev/rte_flow.h
> > > @@ -1651,6 +1651,38 @@ enum rte_flow_action_type {
> > >   	 * See struct rte_flow_action_set_mac.
> > >   	 */
> > >   	RTE_FLOW_ACTION_TYPE_SET_MAC_DST,
> > > +
> > > +	/**
> > > +	 * Increase sequence number in the outermost TCP header.
> > > +	 *
> > > +	 * Using this action on non-matching traffic will result in
> > > +	 * undefined behavior.
> > > +	 */
> > > +	RTE_FLOW_ACTION_TYPE_INC_TCP_SEQ,
> > > +
> > > +	/**
> > > +	 * Decrease sequence number in the outermost TCP header.
> > > +	 *
> > > +	 * Using this action on non-matching traffic will result in
> > > +	 * undefined behavior.
> > > +	 */
> > > +	RTE_FLOW_ACTION_TYPE_DEC_TCP_SEQ,
> > > +
> > > +	/**
> > > +	 * Increase acknowledgment number in the outermost TCP header.
> > > +	 *
> > > +	 * Using this action on non-matching traffic will result in
> > > +	 * undefined behavior.
> > > +	 */
> > > +	RTE_FLOW_ACTION_TYPE_INC_TCP_ACK,
> > > +
> > > +	/**
> > > +	 * Decrease acknowledgment number in the outermost TCP header.
> > > +	 *
> > > +	 * Using this action on non-matching traffic will result in
> > > +	 * undefined behavior.
> > > +	 */
> > > +	RTE_FLOW_ACTION_TYPE_DEC_TCP_ACK,
> > >   };
> > >
> > >   /**
> > 
> > Other actions have type of configuration data description in a comment just
> > before the action enum element. I'm not sure why it is skipped here.
> > It is really vital information.
> > 
> 
> I had the relevant struct name here, and removed it when I changed it to integer.
> In the documentation doc/guides/prog_guide/rte_flow.rst  I added description, please see above.

Yes, still Andrew is right, header documentation must be exhaustive.
Developers might use rte_flow.rst as reference and to understand the
underlying design but will definitely rely on rte_flow.h (and Doxygen) when
writing code.

I suggest something which describes types and how they are used a bit like
enum rte_flow_conv_op, e.g. for RTE_FLOW_ACTION_TYPE_DEC_TCP_ACK:

 [...]
 *
 * Action configuration specifies the value to decrease TCP acknowledgment
 * number as a big-endian 32 bit integer.
 *
 * @p conf type:
 * @code const rte_be32_t * @endcode
 */

I know other actions do not have the same format but we'll update them
eventually.

-- 
Adrien Mazarguil
6WIND