27. Flow Classification Library

DPDK provides a Flow Classification library that provides the ability to classify an input packet by matching it against a set of Flow rules.

The initial implementation supports counting of IPv4 5-tuple packets which match a particular Flow rule only.

Please refer to the Generic flow API (rte_flow) for more information.

The Flow Classification library uses the librte_table API for managing Flow rules and matching packets against the Flow rules. The library is table agnostic and can use the following tables: Access Control List, Hash and Longest Prefix Match(LPM). The Access Control List table is used in the initial implementation.

Please refer to the Packet Framework for more information.on librte_table.

DPDK provides an Access Control List library that provides the ability to classify an input packet based on a set of classification rules.

Please refer to the Packet Classification and Access Control library for more information on librte_acl.

There is also a Flow Classify sample application which demonstrates the use of the Flow Classification Library API’s.

Please refer to the Flow Classify Sample Application for more information on the flow_classify sample application.

27.1. Overview

The library has the following API’s

/**
 * Flow classifier create
 *
 * @param params
 *   Parameters for flow classifier creation
 * @return
 *   Handle to flow classifier instance on success or NULL otherwise
 */
struct rte_flow_classifier *
rte_flow_classifier_create(struct rte_flow_classifier_params *params);

/**
 * Flow classifier free
 *
 * @param cls
 *   Handle to flow classifier instance
 * @return
 *   0 on success, error code otherwise
 */
int
rte_flow_classifier_free(struct rte_flow_classifier *cls);

/**
 * Flow classify table create
 *
 * @param cls
 *   Handle to flow classifier instance
 * @param params
 *   Parameters for flow_classify table creation
 * @return
 *   0 on success, error code otherwise
 */
int
rte_flow_classify_table_create(struct rte_flow_classifier *cls,
       struct rte_flow_classify_table_params *params);

/**
 * Validate the flow classify rule
 *
 * @param[in] cls
 *   Handle to flow classifier instance
 * @param[in] attr
 *   Flow rule attributes
 * @param[in] pattern
 *   Pattern specification (list terminated by the END pattern item).
 * @param[in] actions
 *   Associated actions (list terminated by the END pattern item).
 * @param[out] error
 *   Perform verbose error reporting if not NULL. Structure
 *   initialised in case of error only.
 * @return
 *   0 on success, error code otherwise
 */
int
rte_flow_classify_validate(struct rte_flow_classifier *cls,
        const struct rte_flow_attr *attr,
        const struct rte_flow_item pattern[],
        const struct rte_flow_action actions[],
        struct rte_flow_error *error);

/**
 * Add a flow classify rule to the flow_classifier table.
 *
 * @param[in] cls
 *   Flow classifier handle
 * @param[in] attr
 *   Flow rule attributes
 * @param[in] pattern
 *   Pattern specification (list terminated by the END pattern item).
 * @param[in] actions
 *   Associated actions (list terminated by the END pattern item).
 * @param[out] key_found
 *   returns 1 if rule present already, 0 otherwise.
 * @param[out] error
 *   Perform verbose error reporting if not NULL. Structure
 *   initialised in case of error only.
 * @return
 *   A valid handle in case of success, NULL otherwise.
 */
struct rte_flow_classify_rule *
rte_flow_classify_table_entry_add(struct rte_flow_classifier *cls,
        const struct rte_flow_attr *attr,
        const struct rte_flow_item pattern[],
        const struct rte_flow_action actions[],
        int *key_found;
        struct rte_flow_error *error);

/**
 * Delete a flow classify rule from the flow_classifier table.
 *
 * @param[in] cls
 *   Flow classifier handle
 * @param[in] rule
 *   Flow classify rule
 * @return
 *   0 on success, error code otherwise.
 */
int
rte_flow_classify_table_entry_delete(struct rte_flow_classifier *cls,
        struct rte_flow_classify_rule *rule);

/**
 * Query flow classifier for given rule.
 *
 * @param[in] cls
 *   Flow classifier handle
 * @param[in] pkts
 *   Pointer to packets to process
 * @param[in] nb_pkts
 *   Number of packets to process
 * @param[in] rule
 *   Flow classify rule
 * @param[in] stats
 *   Flow classify stats
 *
 * @return
 *   0 on success, error code otherwise.
 */
int
rte_flow_classifier_query(struct rte_flow_classifier *cls,
        struct rte_mbuf **pkts,
        const uint16_t nb_pkts,
        struct rte_flow_classify_rule *rule,
        struct rte_flow_classify_stats *stats);

27.1.1. Classifier creation

The application creates the Classifier using the rte_flow_classifier_create API. The rte_flow_classify_params structure must be initialised by the application before calling the API.

struct rte_flow_classifier_params {
    /** flow classifier name */
    const char *name;

    /** CPU socket ID where memory for the flow classifier and its */
    /** elements (tables) should be allocated */
    int socket_id;
};

The Classifier has the following internal structures:

struct rte_cls_table {
    /* Input parameters */
    struct rte_table_ops ops;
    uint32_t entry_size;
    enum rte_flow_classify_table_type type;

    /* Handle to the low-level table object */
    void *h_table;
};

#define RTE_FLOW_CLASSIFIER_MAX_NAME_SZ 256

struct rte_flow_classifier {
    /* Input parameters */
    char name[RTE_FLOW_CLASSIFIER_MAX_NAME_SZ];
    int socket_id;

    /* Internal */
    /* ntuple_filter */
    struct rte_eth_ntuple_filter ntuple_filter;

    /* classifier tables */
    struct rte_cls_table tables[RTE_FLOW_CLASSIFY_TABLE_MAX];
    uint32_t table_mask;
    uint32_t num_tables;

    uint16_t nb_pkts;
    struct rte_flow_classify_table_entry
        *entries[RTE_PORT_IN_BURST_SIZE_MAX];
} __rte_cache_aligned;

27.1.2. Adding a table to the Classifier

The application adds a table to the Classifier using the rte_flow_classify_table_create API. The rte_flow_classify_table_params structure must be initialised by the application before calling the API.

struct rte_flow_classify_table_params {
    /** Table operations (specific to each table type) */
    struct rte_table_ops *ops;

    /** Opaque param to be passed to the table create operation */
    void *arg_create;

    /** Classifier table type */
    enum rte_flow_classify_table_type type;
 };

To create an ACL table the rte_table_acl_params structure must be initialised and assigned to arg_create in the rte_flow_classify_table_params structure.

struct rte_table_acl_params {
    /** Name */
    const char *name;

    /** Maximum number of ACL rules in the table */
    uint32_t n_rules;

    /** Number of fields in the ACL rule specification */
    uint32_t n_rule_fields;

    /** Format specification of the fields of the ACL rule */
    struct rte_acl_field_def field_format[RTE_ACL_MAX_FIELDS];
};

The fields for the ACL rule must also be initialised by the application.

An ACL table can be added to the Classifier for each ACL rule, for example another table could be added for the IPv6 5-tuple rule.

27.1.3. Flow Parsing

The library currently supports three IPv4 5-tuple flow patterns, for UDP, TCP and SCTP.

/* Pattern for IPv4 5-tuple UDP filter */
static enum rte_flow_item_type pattern_ntuple_1[] = {
    RTE_FLOW_ITEM_TYPE_ETH,
    RTE_FLOW_ITEM_TYPE_IPV4,
    RTE_FLOW_ITEM_TYPE_UDP,
    RTE_FLOW_ITEM_TYPE_END,
};

/* Pattern for IPv4 5-tuple TCP filter */
static enum rte_flow_item_type pattern_ntuple_2[] = {
    RTE_FLOW_ITEM_TYPE_ETH,
    RTE_FLOW_ITEM_TYPE_IPV4,
    RTE_FLOW_ITEM_TYPE_TCP,
    RTE_FLOW_ITEM_TYPE_END,
};

/* Pattern for IPv4 5-tuple SCTP filter */
static enum rte_flow_item_type pattern_ntuple_3[] = {
    RTE_FLOW_ITEM_TYPE_ETH,
    RTE_FLOW_ITEM_TYPE_IPV4,
    RTE_FLOW_ITEM_TYPE_SCTP,
    RTE_FLOW_ITEM_TYPE_END,
};

The API function rte_flow_classify_validate parses the IPv4 5-tuple pattern, attributes and actions and returns the 5-tuple data in the rte_eth_ntuple_filter structure.

static int
rte_flow_classify_validate(struct rte_flow_classifier *cls,
               const struct rte_flow_attr *attr,
               const struct rte_flow_item pattern[],
               const struct rte_flow_action actions[],
               struct rte_flow_error *error)

27.1.4. Adding Flow Rules

The rte_flow_classify_table_entry_add API creates an rte_flow_classify object which contains the flow_classify id and type, the action, a union of add and delete keys and a union of rules. It uses the rte_flow_classify_validate API function for parsing the flow parameters. The 5-tuple ACL key data is obtained from the rte_eth_ntuple_filter structure populated by the classify_parse_ntuple_filter function which parses the Flow rule.

struct acl_keys {
    struct rte_table_acl_rule_add_params key_add; /* add key */
    struct rte_table_acl_rule_delete_params key_del; /* delete key */
};

struct classify_rules {
    enum rte_flow_classify_rule_type type;
    union {
        struct rte_flow_classify_ipv4_5tuple ipv4_5tuple;
    } u;
};

struct rte_flow_classify {
    uint32_t id;  /* unique ID of classify object */
    enum rte_flow_classify_table_type tbl_type; /* rule table */
    struct classify_rules rules; /* union of rules */
    union {
        struct acl_keys key;
    } u;
    int key_found; /* rule key found in table */
    struct rte_flow_classify_table_entry entry;  /* rule meta data */
    void *entry_ptr; /* handle to the table entry for rule meta data */
};

It then calls the table.ops.f_add API to add the rule to the ACL table.

27.1.5. Deleting Flow Rules

The rte_flow_classify_table_entry_delete API calls the table.ops.f_delete API to delete a rule from the ACL table.

27.1.6. Packet Matching

The rte_flow_classifier_query API is used to find packets which match a given flow rule in the table. This API calls the flow_classify_run internal function which calls the table.ops.f_lookup API to see if any packets in a burst match any of the Flow rules in the table. The meta data for the highest priority rule matched for each packet is returned in the entries array in the rte_flow_classify object. The internal function action_apply implements the Count action which is used to return data which matches a particular Flow rule.

The rte_flow_classifier_query API uses the following structures to return data to the application.

/** IPv4 5-tuple data */
struct rte_flow_classify_ipv4_5tuple {
    uint32_t dst_ip;         /**< Destination IP address in big endian. */
    uint32_t dst_ip_mask;    /**< Mask of destination IP address. */
    uint32_t src_ip;         /**< Source IP address in big endian. */
    uint32_t src_ip_mask;    /**< Mask of destination IP address. */
    uint16_t dst_port;       /**< Destination port in big endian. */
    uint16_t dst_port_mask;  /**< Mask of destination port. */
    uint16_t src_port;       /**< Source Port in big endian. */
    uint16_t src_port_mask;  /**< Mask of source port. */
    uint8_t proto;           /**< L4 protocol. */
    uint8_t proto_mask;      /**< Mask of L4 protocol. */
};

/**
 * Flow stats
 *
 * For the count action, stats can be returned by the query API.
 *
 * Storage for stats is provided by the application.
 *
 *
 */
struct rte_flow_classify_stats {
    void *stats;
};

struct rte_flow_classify_5tuple_stats {
    /** count of packets that match IPv4 5tuple pattern */
    uint64_t counter1;
    /** IPv4 5tuple data */
    struct rte_flow_classify_ipv4_5tuple ipv4_5tuple;
};