[dpdk-dev] [RFC] ethdev: introduce conntrack flow action and item

[Bing Zhao]

Hi Andrew,
Sorry for the late reply.

> -----Original Message-----
> From: Andrew Rybchenko <andrew.rybchenko at oktetlabs.ru>
> Sent: Monday, March 22, 2021 11:17 PM
> To: Bing Zhao <bingz at nvidia.com>; Ori Kam <orika at nvidia.com>; NBU-
> Contact-Thomas Monjalon <thomas at monjalon.net>;
> ferruh.yigit at intel.com
> Cc: dev at dpdk.org
> Subject: Re: [RFC] ethdev: introduce conntrack flow action and item
> 
> External email: Use caution opening links or attachments
> 
> 
> On 3/18/21 10:30 AM, Bing Zhao wrote:
> > This commit introduced the conntrack action and item.
> >
> > Usually the HW offloading is stateless. For some stateful
> offloading
> > like a TCP connection, HW module will help provide the ability of
> a
> > full offloading w/o SW participation after the connection was
> > established.
> >
> > The basic usage is that in the first flow the application should
> add
> > the conntrack action and in the following flow(s) the application
> > should use the conntrack item to match on the result.
> >
> > A TCP connection has two directions traffic. To set a conntrack
> action
> > context correctly, information from packets of both directions are
> > required.
> >
> > The conntrack action should be created on one port and supply the
> peer
> > port as a parameter to the action. After context creating, it
> could
> > only be used between the ports (dual-port mode) or a single port.
> The
> > application should modify the action via action_ctx_update
> interface
> > before each use in dual-port mode, in order to set the correct
> > direction for the following rte flow.
> 
> Sorry, but "update interface before each use" sounds frightening.
> May be I simply don't understand all reasons behind.

Sorry for the uncleared description and the "each use in dual-port mode" should be "single-port mode". It is a suggestion but not a must, depending on the HW. But usually, since connection tracking is a bi-directional action and should be used by original and reply direction flows.
For dual-ports mode, usually the original traffic and reply traffic will come from different ports, the SW could distinguish them implicitly.
But in single-port mode, like in a gateway scenario, all the traffic are ingress and go into the same port, it is hard to distinguish the direction.
The update of the action will be just in SW level, or maybe in the HW level, depends on the NIC features.
If the next several flows to be created with this action context are for the same direction, then there is no need to call such API. Only when using it for an opposite direction, the interface will be called.
Also, if some changing of the action context is needed, like the seq/ACK/window, then the interface is also needed.

> 
> > Query will be supported via action_ctx_query interface, about the
> > current packets information and connection status.
> >
> > For the packets received during the conntrack setup, it is
> suggested
> > to re-inject the packets in order to take full advantage of the
> > conntrack. Only the valid packets should pass the conntrack,
> packets
> > with invalid TCP information, like out of window, or with invalid
> > header, like malformed, should not pass.
> >
> > Testpmd command line example:
> >
> > set conntrack [index] enable is 1 last_seq is xxx last ack is xxx
> /
> > ... / orig_dir win_scale is xxx sent_end is xxx max_win is xxx ...
> /
> > rply_dir ... / end flow action_ctx [CTX] create ingress ... /
> > conntrack is [index] / end flow create 0 group X ingress
> patterns ...
> > / tcp / end actions action_ctx [CTX] / jump group Y / end flow
> create
> > 0 group Y ingress patterns ... / ct is [Valid] / end actions queue
> > index [hairpin queue] / end

@Andrew @Ori
Is such command line interface OK from your points of view?

> >
> > Signed-off-by: Bing Zhao <bingz at nvidia.com>
> > ---
> >  lib/librte_ethdev/rte_flow.h | 191
> > +++++++++++++++++++++++++++++++++++
> >  1 file changed, 191 insertions(+)
> >
> > diff --git a/lib/librte_ethdev/rte_flow.h
> > b/lib/librte_ethdev/rte_flow.h index 669e677e91..b2e4f0751a 100644
> > --- a/lib/librte_ethdev/rte_flow.h
> > +++ b/lib/librte_ethdev/rte_flow.h
> > @@ -550,6 +550,15 @@ enum rte_flow_item_type {
> >        * See struct rte_flow_item_geneve_opt
> >        */
> >       RTE_FLOW_ITEM_TYPE_GENEVE_OPT,
> > +
> > +     /**
> > +      * [META]
> > +      *
> > +      * Matches conntrack state.
> > +      *
> > +      * See struct rte_flow_item_conntrack.
> > +      */
> > +     RTE_FLOW_ITEM_TYPE_CONNTRACK,
> >  };
> >
> >  /**
> > @@ -1654,6 +1663,49 @@ rte_flow_item_geneve_opt_mask = {  };
> #endif
> >
> > +/**
> > + * The packet is with valid.
> > + */
> > +#define RTE_FLOW_CONNTRACK_FLAG_STATE_VALID (1 << 0)
> 
> It sounds like conntrack state is valid, but not packet is valid
> from conntrack point of view. May be:
> RTE_FLOW_CONNTRACK_FLAG_PKT_VALID? Or _VALID_PKT to go with _BAD_PKT.

The original idea of this is the state is valid after the packet integrity checking.
1. if some fields of the packet itself has an error, _BAD_PKT, and the packet will not be checked by the HW.
Then
2. if passed the HW connection tracking module, it should be considered _VALID.
3. if not passed the HW module checking, e.g., out of window, then it should be considered INVALID state or ERROR state.
But yes, the name should be more clear to describe themselves.

> 
> > +/**
> > + * The state of the connection was changed.
> > + */
> > +#define RTE_FLOW_CONNTRACK_FLAG_STATE_CHANGED (1 << 1)
> > +/**
> > + * Error state was detected on this packet for this connection.
> > + */
> > +#define RTE_FLOW_CONNTRACK_FLAG_ERROR (1 << 2)
> > +/**
> > + * The HW connection tracking module is disabled.
> > + * It can be due to application command or an invalid state.
> > + */
> > +#define RTE_FLOW_CONNTRACK_FLAG_DISABLED (1 << 3)
> > +/**
> > + * The packet contains some bad field(s).
> > + */
> > +#define RTE_FLOW_CONNTRACK_FLAG_BAD_PKT (1 << 4)
> > +
> > +/**
> > + * @warning
> > + * @b EXPERIMENTAL: this structure may change without prior
> notice
> > + *
> > + * RTE_FLOW_ITEM_TYPE_CONNTRACK
> > + *
> > + * Matches the state of a packet after it passed the connection
> > +tracking
> > + * examination. The state is a bit mask of one
> > +RTE_FLOW_CONNTRACK_FLAG*
> > + * or a reasonable combination of these bits.
> > + */
> > +struct rte_flow_item_conntrack {
> > +     uint32_t flags;
> > +};
> > +
> > +/** Default mask for RTE_FLOW_ITEM_TYPE_CONNTRACK. */ #ifndef
> > +__cplusplus static const struct rte_flow_item_conntrack
> > +rte_flow_item_conntrack_mask = {
> > +     .flags = 0xffffffff,
> > +};
> > +#endif
> > +
> >  /**
> >   * Matching pattern item definition.
> >   *
> > @@ -2236,6 +2288,17 @@ enum rte_flow_action_type {
> >        * See struct rte_flow_action_modify_field.
> >        */
> >       RTE_FLOW_ACTION_TYPE_MODIFY_FIELD,
> > +
> > +     /**
> > +      * [META]
> > +      *
> > +      * Enable tracking a TCP connection state.
> > +      *
> > +      * Send packet to HW connection tracking module for
> examination.
> > +      *
> > +      * See struct rte_flow_action_conntrack.
> > +      */
> > +     RTE_FLOW_ACTION_TYPE_CONNTRACK,
> >  };
> >
> >  /**
> > @@ -2828,6 +2891,134 @@ struct rte_flow_action_set_dscp {
> >   */
> >  struct rte_flow_shared_action;
> >
> > +/**
> > + * The state of a TCP connection.
> > + */
> > +enum rte_flow_conntrack_state {
> > +     RTE_FLOW_CONNTRACK_STATE_SYN_RECV,
> > +     /**< SYN-ACK packet was seen. */
> 
> May I suggest to put comments before enum member. IMHO it is more
> readable. Comment after makes sense if it is on the same line,
> otherwise, it is better to use comments before code.

Sure, I will change it in the patch itself.

> 
> > +     RTE_FLOW_CONNTRACK_STATE_ESTABLISHED,
> > +     /**< 3-way handshark was done. */
> > +     RTE_FLOW_CONNTRACK_STATE_FIN_WAIT,
> > +     /**< First FIN packet was received to close the connection.
> */
> > +     RTE_FLOW_CONNTRACK_STATE_CLOSE_WAIT,
> > +     /**< First FIN was ACKed. */
> > +     RTE_FLOW_CONNTRACK_STATE_LAST_ACK,
> > +     /**< After second FIN, waiting for the last ACK. */
> > +     RTE_FLOW_CONNTRACK_STATE_TIME_WAIT,
> > +     /**< Second FIN was ACKed, connection was closed. */ };
> > +
> > +/**
> > + * The last passed TCP packet flags of a connection.
> > + */
> > +enum rte_flow_conntrack_index {
> 
> Sorry, I don't understand why it is named conntrack_index.

May flag will be a better name instead of index? Or any other suggestion?

> 
> > +     RTE_FLOW_CONNTRACK_INDEX_NONE = 0, /**< No Flag. */
> > +     RTE_FLOW_CONNTRACK_INDEX_SYN = (1 << 0), /**< With SYN flag.
> */
> > +     RTE_FLOW_CONNTRACK_INDEX_SYN_ACK = (1 << 1), /**< With
> SYN+ACK flag. */
> > +     RTE_FLOW_CONNTRACK_INDEX_FIN = (1 << 2), /**< With FIN flag.
> */
> > +     RTE_FLOW_CONNTRACK_INDEX_ACK = (1 << 3), /**< With ACK flag.
> */
> > +     RTE_FLOW_CONNTRACK_INDEX_RST = (1 << 4), /**< With RST flag.
> */
> > +};
> > +
> > +/**
> > + * @warning
> > + * @b EXPERIMENTAL: this structure may change without prior
> notice
> > + *
> > + * Configuration parameters for each direction of a TCP
> connection.
> > + */
> > +struct rte_flow_tcp_dir_param {
> > +     uint32_t scale:4; /**< TCP window scaling factor, 0xF to
> disable. */
> > +     uint32_t close_initiated:1; /**< The FIN was sent by this
> direction. */
> > +     uint32_t last_ack_seen:1;
> > +     /**< An ACK packet has been received by this side. */
> 
> Same here about comments after fields.

Will change them all.

> 
> > +     uint32_t data_unacked:1;
> > +     /**< If set, indicates that there is unacked data of the
> connection. */
> > +     uint32_t sent_end;
> > +     /**< Maximal value of sequence + payload length over sent
> > +      * packets (next ACK from the opposite direction).
> > +      */
> > +     uint32_t reply_end;
> > +     /**< Maximal value of (ACK + window size) over received
> packet + length
> > +      * over sent packet (maximal sequence could be sent).
> > +      */
> > +     uint32_t max_win;
> > +     /**< Maximal value of actual window size over sent packets.
> */
> > +     uint32_t max_ack;
> > +     /**< Maximal value of ACK over sent packets. */ };
> > +
> > +/**
> > + * @warning
> > + * @b EXPERIMENTAL: this structure may change without prior
> notice
> > + *
> > + * RTE_FLOW_ACTION_TYPE_CONNTRACK
> > + *
> > + * Configuration and initial state for the connection tracking
> module.
> > + * This structure could be used for both setting and query.
> > + */
> > +struct rte_flow_action_conntrack {
> > +     uint16_t peer_port; /**< The peer port number, can be the
> same port. */
> > +     uint32_t is_original_dir:1;
> > +     /**< Direction of this connection when creating a flow, the
> value only
> > +      * affects the subsequent flows creation.
> > +      */
> 
> and here tool

Will change them all in the patch.

> 
> > +     uint32_t enable:1;
> > +     /**< Enable / disable the conntrack HW module. When disabled,
> the
> > +      * result will always be RTE_FLOW_CONNTRACK_FLAG_DISABLED.
> > +      * In this state the HW will act as passthrough.
> > +      */
> 
> Does it disable entire conntrack HW module for all flows?
> It sounds like this. If so - confusing.

Yes, for all the flows that using this connection tracking context. But for the remaining flows which use other CT contexts, they will not be impacted.

> 
> > +     uint32_t live_connection:1;
> > +     /**< At least one ack was seen, after the connection was
> established. */
> > +     uint32_t selective_ack:1;
> > +     /**< Enable selective ACK on this connection. */
> > +     uint32_t challenge_ack_passed:1;
> > +     /**< A challenge ack has passed. */
> > +     uint32_t last_direction:1;
> > +     /**< 1: The last packet is seen that comes from the original
> direction.
> > +      * 0: From the reply direction.
> > +      */
> > +     uint32_t liberal_mode:1;
> > +     /**< No TCP check will be done except the state change. */
> > +     enum rte_flow_conntrack_state state;
> > +     /**< The current state of the connection. */
> > +     uint8_t max_ack_window;
> > +     /**< Scaling factor for maximal allowed ACK window. */
> > +     uint8_t retransmission_limit;
> > +     /**< Maximal allowed number of retransmission times. */
> > +     struct rte_flow_tcp_dir_param original_dir;
> > +     /**< TCP parameters of the original direction. */
> > +     struct rte_flow_tcp_dir_param reply_dir;
> > +     /**< TCP parameters of the reply direction. */
> > +     uint16_t last_window;
> > +     /**< The window value of the last packet passed this
> conntrack. */
> > +     enum rte_flow_conntrack_index last_index;
> > +     uint32_t last_seq;
> > +     /**< The sequence of the last packet passed this conntrack.
> */
> > +     uint32_t last_ack;
> > +     /**< The acknowledgement of the last packet passed this
> conntrack. */
> > +     uint32_t last_end;
> > +     /**< The total value ACK + payload length of the last packet
> passed
> > +      * this conntrack.
> > +      */
> > +};
> > +
> > +/**
> > + * RTE_FLOW_ACTION_TYPE_CONNTRACK
> > + *
> > + * Wrapper structure for the context update interface.
> > + * Ports cannot support updating, and the only valid solution is
> to
> > + * destroy the old context and create a new one instead.
> > + */
> > +struct rte_flow_modify_conntrack {
> > +     struct rte_flow_action_conntrack new_ct;
> > +     /**< New connection tracking parameters to be updated. */
> 
> and here

Will change them all in the formal patch.

> 
> > +     uint32_t direction:1; /**< The direction field will be
> updated. */
> > +     uint32_t state:1;
> > +     /**< All the other fields except direction will be updated.
> */
> > +     uint32_t reserved:30; /**< Reserved bits for the future
> usage.
> > +*/ };
> > +
> >  /**
> >   * Field IDs for MODIFY_FIELD action.
> >   */
> >