9. Generic flow API (rte_flow)

9.1. Overview

This API provides a generic means to configure hardware to match specific ingress or egress traffic, alter its fate and query related counters according to any number of user-defined rules.

It is named rte_flow after the prefix used for all its symbols, and is defined in rte_flow.h.

  • Matching can be performed on packet data (protocol headers, payload) and properties (e.g. associated physical port, virtual device function ID).
  • Possible operations include dropping traffic, diverting it to specific queues, to virtual/physical device functions or ports, performing tunnel offloads, adding marks and so on.

It is slightly higher-level than the legacy filtering framework which it encompasses and supersedes (including all functions and filter types) in order to expose a single interface with an unambiguous behavior that is common to all poll-mode drivers (PMDs).

Several methods to migrate existing applications are described in API migration.

9.2. Flow rule

9.2.1. Description

A flow rule is the combination of attributes with a matching pattern and a list of actions. Flow rules form the basis of this API.

Flow rules can have several distinct actions (such as counting, encapsulating, decapsulating before redirecting packets to a particular queue, etc.), instead of relying on several rules to achieve this and having applications deal with hardware implementation details regarding their order.

Support for different priority levels on a rule basis is provided, for example in order to force a more specific rule to come before a more generic one for packets matched by both. However hardware support for more than a single priority level cannot be guaranteed. When supported, the number of available priority levels is usually low, which is why they can also be implemented in software by PMDs (e.g. missing priority levels may be emulated by reordering rules).

In order to remain as hardware-agnostic as possible, by default all rules are considered to have the same priority, which means that the order between overlapping rules (when a packet is matched by several filters) is undefined.

PMDs may refuse to create overlapping rules at a given priority level when they can be detected (e.g. if a pattern matches an existing filter).

Thus predictable results for a given priority level can only be achieved with non-overlapping rules, using perfect matching on all protocol layers.

Flow rules can also be grouped, the flow rule priority is specific to the group they belong to. All flow rules in a given group are thus processed either before or after another group.

Support for multiple actions per rule may be implemented internally on top of non-default hardware priorities, as a result both features may not be simultaneously available to applications.

Considering that allowed pattern/actions combinations cannot be known in advance and would result in an impractically large number of capabilities to expose, a method is provided to validate a given rule from the current device configuration state.

This enables applications to check if the rule types they need is supported at initialization time, before starting their data path. This method can be used anytime, its only requirement being that the resources needed by a rule should exist (e.g. a target RX queue should be configured first).

Each defined rule is associated with an opaque handle managed by the PMD, applications are responsible for keeping it. These can be used for queries and rules management, such as retrieving counters or other data and destroying them.

To avoid resource leaks on the PMD side, handles must be explicitly destroyed by the application before releasing associated resources such as queues and ports.

The following sections cover:

  • Attributes (represented by struct rte_flow_attr): properties of a flow rule such as its direction (ingress or egress) and priority.
  • Pattern item (represented by struct rte_flow_item): part of a matching pattern that either matches specific packet data or traffic properties. It can also describe properties of the pattern itself, such as inverted matching.
  • Matching pattern: traffic properties to look for, a combination of any number of items.
  • Actions (represented by struct rte_flow_action): operations to perform whenever a packet is matched by a pattern.

9.2.2. Attributes Attribute: Group

Flow rules can be grouped by assigning them a common group number. Lower values have higher priority. Group 0 has the highest priority.

Although optional, applications are encouraged to group similar rules as much as possible to fully take advantage of hardware capabilities (e.g. optimized matching) and work around limitations (e.g. a single pattern type possibly allowed in a given group).

Note that support for more than a single group is not guaranteed. Attribute: Priority

A priority level can be assigned to a flow rule. Like groups, lower values denote higher priority, with 0 as the maximum.

A rule with priority 0 in group 8 is always matched after a rule with priority 8 in group 0.

Group and priority levels are arbitrary and up to the application, they do not need to be contiguous nor start from 0, however the maximum number varies between devices and may be affected by existing flow rules.

If a packet is matched by several rules of a given group for a given priority level, the outcome is undefined. It can take any path, may be duplicated or even cause unrecoverable errors.

Note that support for more than a single priority level is not guaranteed. Attribute: Traffic direction

Flow rules can apply to inbound and/or outbound traffic (ingress/egress).

Several pattern items and actions are valid and can be used in both directions. At least one direction must be specified.

Specifying both directions at once for a given rule is not recommended but may be valid in a few cases (e.g. shared counters).

9.2.3. Pattern item

Pattern items fall in two categories:

  • Matching protocol headers and packet data (ANY, RAW, ETH, VLAN, IPV4, IPV6, ICMP, UDP, TCP, SCTP, VXLAN, MPLS, GRE, ESP and so on), usually associated with a specification structure.
  • Matching meta-data or affecting pattern processing (END, VOID, INVERT, PF, VF, PORT and so on), often without a specification structure.

Item specification structures are used to match specific values among protocol fields (or item properties). Documentation describes for each item whether they are associated with one and their type name if so.

Up to three structures of the same type can be set for a given item:

  • spec: values to match (e.g. a given IPv4 address).
  • last: upper bound for an inclusive range with corresponding fields in spec.
  • mask: bit-mask applied to both spec and last whose purpose is to distinguish the values to take into account and/or partially mask them out (e.g. in order to match an IPv4 address prefix).

Usage restrictions and expected behavior:

  • Setting either mask or last without spec is an error.
  • Field values in last which are either 0 or equal to the corresponding values in spec are ignored; they do not generate a range. Nonzero values lower than those in spec are not supported.
  • Setting spec and optionally last without mask causes the PMD to use the default mask defined for that item (defined as rte_flow_item_{name}_mask constants).
  • Not setting any of them (assuming item type allows it) is equivalent to providing an empty (zeroed) mask for broad (nonspecific) matching.
  • mask is a simple bit-mask applied before interpreting the contents of spec and last, which may yield unexpected results if not used carefully. For example, if for an IPv4 address field, spec provides, last provides and mask provides, the effective range becomes to

Example of an item specification matching an Ethernet header:

Table 9.1 Ethernet item
Field Subfield Value
spec src 00:01:02:03:04
dst 00:2a:66:00:01
type 0x22aa
last unspecified
mask src 00:ff:ff:ff:00
dst 00:00:00:00:ff
type 0x0000

Non-masked bits stand for any value (shown as ? below), Ethernet headers with the following properties are thus matched:

  • src: ??:01:02:03:??
  • dst: ??:??:??:??:01
  • type: 0x????

9.2.4. Matching pattern

A pattern is formed by stacking items starting from the lowest protocol layer to match. This stacking restriction does not apply to meta items which can be placed anywhere in the stack without affecting the meaning of the resulting pattern.

Patterns are terminated by END items.


Table 9.2 TCPv4 as L4
Index Item
0 Ethernet
1 IPv4

Table 9.3 TCPv6 in VXLAN
Index Item
0 Ethernet
1 IPv4
4 Ethernet
5 IPv6

Table 9.4 TCPv4 as L4 with meta items
Index Item
1 Ethernet
3 IPv4

The above example shows how meta items do not affect packet data matching items, as long as those remain stacked properly. The resulting matching pattern is identical to “TCPv4 as L4”.

Table 9.5 UDPv6 anywhere
Index Item
0 IPv6

If supported by the PMD, omitting one or several protocol layers at the bottom of the stack as in the above example (missing an Ethernet specification) enables looking up anywhere in packets.

It is unspecified whether the payload of supported encapsulations (e.g. VXLAN payload) is matched by such a pattern, which may apply to inner, outer or both packets.

Table 9.6 Invalid, missing L3
Index Item
0 Ethernet

The above pattern is invalid due to a missing L3 specification between L2 (Ethernet) and L4 (UDP). Doing so is only allowed at the bottom and at the top of the stack.

9.2.5. Meta item types

They match meta-data or affect pattern processing instead of matching packet data directly, most of them do not need a specification structure. This particularity allows them to be specified anywhere in the stack without causing any side effect. Item: END

End marker for item lists. Prevents further processing of items, thereby ending the pattern.

  • Its numeric value is 0 for convenience.
  • PMD support is mandatory.
  • spec, last and mask are ignored.
Table 9.7 END
Field Value
spec ignored
last ignored
mask ignored Item: VOID

Used as a placeholder for convenience. It is ignored and simply discarded by PMDs.

  • PMD support is mandatory.
  • spec, last and mask are ignored.
Table 9.8 VOID
Field Value
spec ignored
last ignored
mask ignored

One usage example for this type is generating rules that share a common prefix quickly without reallocating memory, only by updating item types:

Table 9.9 TCP, UDP or ICMP as L4
Index Item
0 Ethernet
1 IPv4

Inverted matching, i.e. process packets that do not match the pattern.

  • spec, last and mask are ignored.
Table 9.10 INVERT
Field Value
spec ignored
last ignored
mask ignored

Usage example, matching non-TCPv4 packets only:

Table 9.11 Anything but TCPv4
Index Item
1 Ethernet
2 IPv4
4 END Item: PF

Matches packets addressed to the physical function of the device.

If the underlying device function differs from the one that would normally receive the matched traffic, specifying this item prevents it from reaching that device unless the flow rule contains a Action: PF. Packets are not duplicated between device instances by default.

  • Likely to return an error or never match any traffic if applied to a VF device.
  • Can be combined with any number of Item: VF to match both PF and VF traffic.
  • spec, last and mask must not be set.
Table 9.12 PF
Field Value
spec unset
last unset
mask unset Item: VF

Matches packets addressed to a virtual function ID of the device.

If the underlying device function differs from the one that would normally receive the matched traffic, specifying this item prevents it from reaching that device unless the flow rule contains a Action: VF. Packets are not duplicated between device instances by default.

  • Likely to return an error or never match any traffic if this causes a VF device to match traffic addressed to a different VF.
  • Can be specified multiple times to match traffic addressed to several VF IDs.
  • Can be combined with a PF item to match both PF and VF traffic.
  • Default mask matches any VF ID.
Table 9.13 VF
Field Subfield Value
spec id destination VF ID
last id upper range value
mask id zeroed to match any VF ID Item: PORT

Matches packets coming from the specified physical port of the underlying device.

The first PORT item overrides the physical port normally associated with the specified DPDK input port (port_id). This item can be provided several times to match additional physical ports.

Note that physical ports are not necessarily tied to DPDK input ports (port_id) when those are not under DPDK control. Possible values are specific to each device, they are not necessarily indexed from zero and may not be contiguous.

As a device property, the list of allowed values as well as the value associated with a port_id should be retrieved by other means.

  • Default mask matches any port index.
Table 9.14 PORT
Field Subfield Value
spec index physical port index
last index upper range value
mask index zeroed to match any port index

9.2.6. Data matching item types

Most of these are basically protocol header definitions with associated bit-masks. They must be specified (stacked) from lowest to highest protocol layer to form a matching pattern.

The following list is not exhaustive, new protocols will be added in the future. Item: ANY

Matches any protocol in place of the current layer, a single ANY may also stand for several protocol layers.

This is usually specified as the first pattern item when looking for a protocol anywhere in a packet.

  • Default mask stands for any number of layers.
Table 9.15 ANY
Field Subfield Value
spec num number of layers covered
last num upper range value
mask num zeroed to cover any number of layers

Example for VXLAN TCP payload matching regardless of outer L3 (IPv4 or IPv6) and L4 (UDP) both matched by the first ANY specification, and inner L3 (IPv4 or IPv6) matched by the second ANY specification:

Table 9.16 TCP in VXLAN with wildcards
Index Item Field Subfield Value
0 Ethernet
1 ANY spec num 2
3 Ethernet
4 ANY spec num 1
6 END Item: RAW

Matches a byte string of a given length at a given offset.

Offset is either absolute (using the start of the packet) or relative to the end of the previous matched item in the stack, in which case negative values are allowed.

If search is enabled, offset is used as the starting point. The search area can be delimited by setting limit to a nonzero value, which is the maximum number of bytes after offset where the pattern may start.

Matching a zero-length pattern is allowed, doing so resets the relative offset for subsequent items.

  • This type does not support ranges (last field).
  • Default mask matches all fields exactly.
Table 9.17 RAW
Field Subfield Value
spec relative look for pattern after the previous item
search search pattern from offset (see also limit)
reserved reserved, must be set to zero
offset absolute or relative offset for pattern
limit search area limit for start of pattern
length pattern length
pattern byte string to look for
last if specified, either all 0 or with the same values as spec
mask bit-mask applied to spec values with usual behavior

Example pattern looking for several strings at various offsets of a UDP payload, using combined RAW items:

Table 9.18 UDP payload matching
Index Item Field Subfield Value
0 Ethernet
1 IPv4
3 RAW spec relative 1
search 1
offset 10
limit 0
length 3
pattern “foo”
4 RAW spec relative 1
search 0
offset 20
limit 0
length 3
pattern “bar”
5 RAW spec relative 1
search 0
offset -29
limit 0
length 3
pattern “baz”

This translates to:

  • Locate “foo” at least 10 bytes deep inside UDP payload.
  • Locate “bar” after “foo” plus 20 bytes.
  • Locate “baz” after “bar” minus 29 bytes.

Such a packet may be represented as follows (not to scale):

0                     >= 10 B           == 20 B
|                  |<--------->|     |<--------->|
|                  |           |     |           |
| ETH | IPv4 | UDP | ... | baz | foo | ......... | bar | .... |
                         |                             |
                                     == 29 B

Note that matching subsequent pattern items would resume after “baz”, not “bar” since matching is always performed after the previous item of the stack. Item: ETH

Matches an Ethernet header.

  • dst: destination MAC.
  • src: source MAC.
  • type: EtherType.
  • Default mask matches destination and source addresses only. Item: VLAN

Matches an 802.1Q/ad VLAN tag.

  • tpid: tag protocol identifier.
  • tci: tag control information.
  • Default mask matches TCI only. Item: IPV4

Matches an IPv4 header.

Note: IPv4 options are handled by dedicated pattern items.

  • hdr: IPv4 header definition (rte_ip.h).
  • Default mask matches source and destination addresses only. Item: IPV6

Matches an IPv6 header.

Note: IPv6 options are handled by dedicated pattern items.

  • hdr: IPv6 header definition (rte_ip.h).
  • Default mask matches source and destination addresses only. Item: ICMP

Matches an ICMP header.

  • hdr: ICMP header definition (rte_icmp.h).
  • Default mask matches ICMP type and code only. Item: UDP

Matches a UDP header.

  • hdr: UDP header definition (rte_udp.h).
  • Default mask matches source and destination ports only. Item: TCP

Matches a TCP header.

  • hdr: TCP header definition (rte_tcp.h).
  • Default mask matches source and destination ports only. Item: SCTP

Matches a SCTP header.

  • hdr: SCTP header definition (rte_sctp.h).
  • Default mask matches source and destination ports only. Item: VXLAN

Matches a VXLAN header (RFC 7348).

  • flags: normally 0x08 (I flag).
  • rsvd0: reserved, normally 0x000000.
  • vni: VXLAN network identifier.
  • rsvd1: reserved, normally 0x00.
  • Default mask matches VNI only. Item: E_TAG

Matches an IEEE 802.1BR E-Tag header.

  • tpid: tag protocol identifier (0x893F)
  • epcp_edei_in_ecid_b: E-Tag control information (E-TCI), E-PCP (3b), E-DEI (1b), ingress E-CID base (12b).
  • rsvd_grp_ecid_b: reserved (2b), GRP (2b), E-CID base (12b).
  • in_ecid_e: ingress E-CID ext.
  • ecid_e: E-CID ext.
  • Default mask simultaneously matches GRP and E-CID base. Item: NVGRE

Matches a NVGRE header (RFC 7637).

  • c_k_s_rsvd0_ver: checksum (1b), undefined (1b), key bit (1b), sequence number (1b), reserved 0 (9b), version (3b). This field must have value 0x2000 according to RFC 7637.
  • protocol: protocol type (0x6558).
  • tni: virtual subnet ID.
  • flow_id: flow ID.
  • Default mask matches TNI only. Item: MPLS

Matches a MPLS header.

  • label_tc_s_ttl: label, TC, Bottom of Stack and TTL.
  • Default mask matches label only. Item: GRE

Matches a GRE header.

  • c_rsvd0_ver: checksum, reserved 0 and version.
  • protocol: protocol type.
  • Default mask matches protocol only. Item: FUZZY

Fuzzy pattern match, expect faster than default.

This is for device that support fuzzy match option. Usually a fuzzy match is fast but the cost is accuracy. i.e. Signature Match only match pattern’s hash value, but it is possible two different patterns have the same hash value.

Matching accuracy level can be configured by threshold. Driver can divide the range of threshold and map to different accuracy levels that device support.

Threshold 0 means perfect match (no fuzziness), while threshold 0xffffffff means fuzziest match.

Table 9.19 FUZZY
Field Subfield Value
spec threshold 0 as perfect match, 0xffffffff as fuzziest match
last threshold upper range value
mask threshold bit-mask apply to “spec” and “last”

Usage example, fuzzy match a TCPv4 packets:

Table 9.20 Fuzzy matching
Index Item
1 Ethernet
2 IPv4

Matches a GTPv1 header.

Note: GTP, GTPC and GTPU use the same structure. GTPC and GTPU item are defined for a user-friendly API when creating GTP-C and GTP-U flow rules.

  • v_pt_rsv_flags: version (3b), protocol type (1b), reserved (1b), extension header flag (1b), sequence number flag (1b), N-PDU number flag (1b).
  • msg_type: message type.
  • msg_len: message length.
  • teid: tunnel endpoint identifier.
  • Default mask matches teid only. Item: ESP

Matches an ESP header.

  • hdr: ESP header definition (rte_esp.h).
  • Default mask matches SPI only. Item: GENEVE

Matches a GENEVE header.

  • ver_opt_len_o_c_rsvd0: version (2b), length of the options fields (6b), OAM packet (1b), critical options present (1b), reserved 0 (6b).
  • protocol: protocol type.
  • vni: virtual network identifier.
  • rsvd1: reserved, normally 0x00.
  • Default mask matches VNI only.

9.2.7. Actions

Each possible action is represented by a type. Some have associated configuration structures. Several actions combined in a list can be assigned to a flow rule. That list is not ordered.

They fall in three categories:

  • Terminating actions (such as QUEUE, DROP, RSS, PF, VF) that prevent processing matched packets by subsequent flow rules, unless overridden with PASSTHRU.
  • Non-terminating actions (PASSTHRU, DUP) that leave matched packets up for additional processing by subsequent flow rules.
  • Other non-terminating meta actions that do not affect the fate of packets (END, VOID, MARK, FLAG, COUNT, SECURITY).

When several actions are combined in a flow rule, they should all have different types (e.g. dropping a packet twice is not possible).

Only the last action of a given type is taken into account. PMDs still perform error checking on the entire list.

Like matching patterns, action lists are terminated by END items.

Note that PASSTHRU is the only action able to override a terminating rule.

Example of action that redirects packets to queue index 10:

Table 9.21 Queue action
Field Value
index 10

Action lists examples, their order is not significant, applications must consider all actions to be performed simultaneously:

Table 9.22 Count and drop
Index Action

Table 9.23 Mark, count and redirect
Index Action Field Value
0 MARK mark 0x2a
2 QUEUE queue 10

Table 9.24 Redirect to queue 5
Index Action Field Value
1 QUEUE queue 5

In the above example, considering both actions are performed simultaneously, the end result is that only QUEUE has any effect.

Table 9.25 Redirect to queue 3
Index Action Field Value
0 QUEUE queue 5
2 QUEUE queue 3

As previously described, only the last action of a given type found in the list is taken into account. The above example also shows that VOID is ignored.

9.2.8. Action types

Common action types are described in this section. Like pattern item types, this list is not exhaustive as new actions will be added in the future. Action: END

End marker for action lists. Prevents further processing of actions, thereby ending the list.

  • Its numeric value is 0 for convenience.
  • PMD support is mandatory.
  • No configurable properties.
Table 9.26 END
no properties Action: VOID

Used as a placeholder for convenience. It is ignored and simply discarded by PMDs.

  • PMD support is mandatory.
  • No configurable properties.
Table 9.27 VOID
no properties Action: PASSTHRU

Leaves packets up for additional processing by subsequent flow rules. This is the default when a rule does not contain a terminating action, but can be specified to force a rule to become non-terminating.

  • No configurable properties.
Table 9.28 PASSTHRU
no properties

Example to copy a packet to a queue and continue processing by subsequent flow rules:

Table 9.29 Copy to queue 8
Index Action Field Value
1 QUEUE queue 8
2 END Action: MARK

Attaches an integer value to packets and sets PKT_RX_FDIR and PKT_RX_FDIR_ID mbuf flags.

This value is arbitrary and application-defined. Maximum allowed value depends on the underlying implementation. It is returned in the hash.fdir.hi mbuf field.

Table 9.30 MARK
Field Value
id integer value to return with packets Action: FLAG

Flags packets. Similar to Action: MARK without a specific value; only sets the PKT_RX_FDIR mbuf flag.

  • No configurable properties.
Table 9.31 FLAG
no properties Action: QUEUE

Assigns packets to a given queue index.

  • Terminating by default.
Table 9.32 QUEUE
Field Value
index queue index to use Action: DROP

Drop packets.

  • No configurable properties.
  • Terminating by default.
  • PASSTHRU overrides this action if both are specified.
Table 9.33 DROP
no properties Action: COUNT

Enables counters for this rule.

These counters can be retrieved and reset through rte_flow_query(), see struct rte_flow_query_count.

  • Counters can be retrieved with rte_flow_query().
  • No configurable properties.
Table 9.34 COUNT
no properties

Query structure to retrieve and reset flow rule counters:

Table 9.35 COUNT query
Field I/O Value
reset in reset counter after query
hits_set out hits field is set
bytes_set out bytes field is set
hits out number of hits for this rule
bytes out number of bytes through this rule Action: DUP

Duplicates packets to a given queue index.

This is normally combined with QUEUE, however when used alone, it is actually similar to QUEUE + PASSTHRU.

  • Non-terminating by default.
Table 9.36 DUP
Field Value
index queue index to duplicate packet to Action: RSS

Similar to QUEUE, except RSS is additionally performed on packets to spread them among several queues according to the provided parameters.

Note: RSS hash result is stored in the hash.rss mbuf field which overlaps hash.fdir.lo. Since Action: MARK sets the hash.fdir.hi field only, both can be requested simultaneously.

  • Terminating by default.
Table 9.37 RSS
Field Value
rss_conf RSS parameters
num number of entries in queue[]
queue[] queue indices to use Action: PF

Redirects packets to the physical function (PF) of the current device.

  • No configurable properties.
  • Terminating by default.
Table 9.38 PF
no properties Action: VF

Redirects packets to a virtual function (VF) of the current device.

Packets matched by a VF pattern item can be redirected to their original VF ID instead of the specified one. This parameter may not be available and is not guaranteed to work properly if the VF part is matched by a prior flow rule or if packets are not addressed to a VF in the first place.

  • Terminating by default.
Table 9.39 VF
Field Value
original use original VF ID if possible
vf VF ID to redirect packets to Action: METER

Applies a stage of metering and policing.

The metering and policing (MTR) object has to be first created using the rte_mtr_create() API function. The ID of the MTR object is specified as action parameter. More than one flow can use the same MTR object through the meter action. The MTR object can be further updated or queried using the rte_mtr* API.

  • Non-terminating by default.
Table 9.40 METER
Field Value
mtr_id MTR object ID Action: SECURITY

Perform the security action on flows matched by the pattern items according to the configuration of the security session.

This action modifies the payload of matched flows. For INLINE_CRYPTO, the security protocol headers and IV are fully provided by the application as specified in the flow pattern. The payload of matching packets is encrypted on egress, and decrypted and authenticated on ingress. For INLINE_PROTOCOL, the security protocol is fully offloaded to HW, providing full encapsulation and decapsulation of packets in security protocols. The flow pattern specifies both the outer security header fields and the inner packet fields. The security session specified in the action must match the pattern parameters.

The security session specified in the action must be created on the same port as the flow action that is being specified.

The ingress/egress flow attribute should match that specified in the security session if the security session supports the definition of the direction.

Multiple flows can be configured to use the same security session.

  • Non-terminating by default.
Table 9.41 SECURITY
Field Value
security_session security session to apply

The following is an example of configuring IPsec inline using the INLINE_CRYPTO security session:

The encryption algorithm, keys and salt are part of the opaque rte_security_session. The SA is identified according to the IP and ESP fields in the pattern items.

Table 9.42 IPsec inline crypto flow pattern items.
Index Item
0 Ethernet
1 IPv4
Table 9.43 IPsec inline flow actions.
Index Action

9.2.9. Negative types

All specified pattern items (enum rte_flow_item_type) and actions (enum rte_flow_action_type) use positive identifiers.

The negative space is reserved for dynamic types generated by PMDs during run-time. PMDs may encounter them as a result but must not accept negative identifiers they are not aware of.

A method to generate them remains to be defined.

9.2.10. Planned types

Pattern item types will be added as new protocols are implemented.

Variable headers support through dedicated pattern items, for example in order to match specific IPv4 options and IPv6 extension headers would be stacked after IPv4/IPv6 items.

Other action types are planned but are not defined yet. These include the ability to alter packet data in several ways, such as performing encapsulation/decapsulation of tunnel headers.

9.3. Rules management

A rather simple API with few functions is provided to fully manage flow rules.

Each created flow rule is associated with an opaque, PMD-specific handle pointer. The application is responsible for keeping it until the rule is destroyed.

Flows rules are represented by struct rte_flow objects.

9.3.1. Validation

Given that expressing a definite set of device capabilities is not practical, a dedicated function is provided to check if a flow rule is supported and can be created.

rte_flow_validate(uint16_t port_id,
                  const struct rte_flow_attr *attr,
                  const struct rte_flow_item pattern[],
                  const struct rte_flow_action actions[],
                  struct rte_flow_error *error);

The flow rule is validated for correctness and whether it could be accepted by the device given sufficient resources. The rule is checked against the current device mode and queue configuration. The flow rule may also optionally be validated against existing flow rules and device resources. This function has no effect on the target device.

The returned value is guaranteed to remain valid only as long as no successful calls to rte_flow_create() or rte_flow_destroy() are made in the meantime and no device parameter affecting flow rules in any way are modified, due to possible collisions or resource limitations (although in such cases EINVAL should not be returned).


  • port_id: port identifier of Ethernet device.
  • attr: flow rule attributes.
  • pattern: pattern specification (list terminated by the END pattern item).
  • actions: associated actions (list terminated by the END action).
  • error: perform verbose error reporting if not NULL. PMDs initialize this structure in case of error only.

Return values:

  • 0 if flow rule is valid and can be created. A negative errno value otherwise (rte_errno is also set), the following errors are defined.
  • -ENOSYS: underlying device does not support this functionality.
  • -EINVAL: unknown or invalid rule specification.
  • -ENOTSUP: valid but unsupported rule specification (e.g. partial bit-masks are unsupported).
  • EEXIST: collision with an existing rule. Only returned if device supports flow rule collision checking and there was a flow rule collision. Not receiving this return code is no guarantee that creating the rule will not fail due to a collision.
  • ENOMEM: not enough memory to execute the function, or if the device supports resource validation, resource limitation on the device.
  • -EBUSY: action cannot be performed due to busy device resources, may succeed if the affected queues or even the entire port are in a stopped state (see rte_eth_dev_rx_queue_stop() and rte_eth_dev_stop()).

9.3.2. Creation

Creating a flow rule is similar to validating one, except the rule is actually created and a handle returned.

struct rte_flow *
rte_flow_create(uint16_t port_id,
                const struct rte_flow_attr *attr,
                const struct rte_flow_item pattern[],
                const struct rte_flow_action *actions[],
                struct rte_flow_error *error);


  • port_id: port identifier of Ethernet device.
  • attr: flow rule attributes.
  • pattern: pattern specification (list terminated by the END pattern item).
  • actions: associated actions (list terminated by the END action).
  • error: perform verbose error reporting if not NULL. PMDs initialize this structure in case of error only.

Return values:

A valid handle in case of success, NULL otherwise and rte_errno is set to the positive version of one of the error codes defined for rte_flow_validate().

9.3.3. Destruction

Flow rules destruction is not automatic, and a queue or a port should not be released if any are still attached to them. Applications must take care of performing this step before releasing resources.

rte_flow_destroy(uint16_t port_id,
                 struct rte_flow *flow,
                 struct rte_flow_error *error);

Failure to destroy a flow rule handle may occur when other flow rules depend on it, and destroying it would result in an inconsistent state.

This function is only guaranteed to succeed if handles are destroyed in reverse order of their creation.


  • port_id: port identifier of Ethernet device.
  • flow: flow rule handle to destroy.
  • error: perform verbose error reporting if not NULL. PMDs initialize this structure in case of error only.

Return values:

  • 0 on success, a negative errno value otherwise and rte_errno is set.

9.3.4. Flush

Convenience function to destroy all flow rule handles associated with a port. They are released as with successive calls to rte_flow_destroy().

rte_flow_flush(uint16_t port_id,
               struct rte_flow_error *error);

In the unlikely event of failure, handles are still considered destroyed and no longer valid but the port must be assumed to be in an inconsistent state.


  • port_id: port identifier of Ethernet device.
  • error: perform verbose error reporting if not NULL. PMDs initialize this structure in case of error only.

Return values:

  • 0 on success, a negative errno value otherwise and rte_errno is set.

9.3.5. Query

Query an existing flow rule.

This function allows retrieving flow-specific data such as counters. Data is gathered by special actions which must be present in the flow rule definition.

rte_flow_query(uint16_t port_id,
               struct rte_flow *flow,
               enum rte_flow_action_type action,
               void *data,
               struct rte_flow_error *error);


  • port_id: port identifier of Ethernet device.
  • flow: flow rule handle to query.
  • action: action type to query.
  • data: pointer to storage for the associated query data type.
  • error: perform verbose error reporting if not NULL. PMDs initialize this structure in case of error only.

Return values:

  • 0 on success, a negative errno value otherwise and rte_errno is set.

9.4. Isolated mode

The general expectation for ingress traffic is that flow rules process it first; the remaining unmatched or pass-through traffic usually ends up in a queue (with or without RSS, locally or in some sub-device instance) depending on the global configuration settings of a port.

While fine from a compatibility standpoint, this approach makes drivers more complex as they have to check for possible side effects outside of this API when creating or destroying flow rules. It results in a more limited set of available rule types due to the way device resources are assigned (e.g. no support for the RSS action even on capable hardware).

Given that nonspecific traffic can be handled by flow rules as well, isolated mode is a means for applications to tell a driver that ingress on the underlying port must be injected from the defined flow rules only; that no default traffic is expected outside those rules.

This has the following benefits:

  • Applications get finer-grained control over the kind of traffic they want to receive (no traffic by default).
  • More importantly they control at what point nonspecific traffic is handled relative to other flow rules, by adjusting priority levels.
  • Drivers can assign more hardware resources to flow rules and expand the set of supported rule types.

Because toggling isolated mode may cause profound changes to the ingress processing path of a driver, it may not be possible to leave it once entered. Likewise, existing flow rules or global configuration settings may prevent a driver from entering isolated mode.

Applications relying on this mode are therefore encouraged to toggle it as soon as possible after device initialization, ideally before the first call to rte_eth_dev_configure() to avoid possible failures due to conflicting settings.

Once effective, the following functionality has no effect on the underlying port and may return errors such as ENOTSUP (“not supported”):

  • Toggling promiscuous mode.
  • Toggling allmulticast mode.
  • Configuring MAC addresses.
  • Configuring multicast addresses.
  • Configuring VLAN filters.
  • Configuring Rx filters through the legacy API (e.g. FDIR).
  • Configuring global RSS settings.
rte_flow_isolate(uint16_t port_id, int set, struct rte_flow_error *error);


  • port_id: port identifier of Ethernet device.
  • set: nonzero to enter isolated mode, attempt to leave it otherwise.
  • error: perform verbose error reporting if not NULL. PMDs initialize this structure in case of error only.

Return values:

  • 0 on success, a negative errno value otherwise and rte_errno is set.

9.5. Verbose error reporting

The defined errno values may not be accurate enough for users or application developers who want to investigate issues related to flow rules management. A dedicated error object is defined for this purpose:

enum rte_flow_error_type {
    RTE_FLOW_ERROR_TYPE_NONE, /**< No error. */
    RTE_FLOW_ERROR_TYPE_UNSPECIFIED, /**< Cause unspecified. */
    RTE_FLOW_ERROR_TYPE_HANDLE, /**< Flow rule (handle). */
    RTE_FLOW_ERROR_TYPE_ATTR_GROUP, /**< Group field. */
    RTE_FLOW_ERROR_TYPE_ATTR_PRIORITY, /**< Priority field. */
    RTE_FLOW_ERROR_TYPE_ATTR_INGRESS, /**< Ingress field. */
    RTE_FLOW_ERROR_TYPE_ATTR_EGRESS, /**< Egress field. */
    RTE_FLOW_ERROR_TYPE_ATTR, /**< Attributes structure. */
    RTE_FLOW_ERROR_TYPE_ITEM_NUM, /**< Pattern length. */
    RTE_FLOW_ERROR_TYPE_ITEM, /**< Specific pattern item. */
    RTE_FLOW_ERROR_TYPE_ACTION_NUM, /**< Number of actions. */
    RTE_FLOW_ERROR_TYPE_ACTION, /**< Specific action. */

struct rte_flow_error {
    enum rte_flow_error_type type; /**< Cause field and error types. */
    const void *cause; /**< Object responsible for the error. */
    const char *message; /**< Human-readable error message. */

Error type RTE_FLOW_ERROR_TYPE_NONE stands for no error, in which case remaining fields can be ignored. Other error types describe the type of the object pointed by cause.

If non-NULL, cause points to the object responsible for the error. For a flow rule, this may be a pattern item or an individual action.

If non-NULL, message provides a human-readable error message.

This object is normally allocated by applications and set by PMDs in case of error, the message points to a constant string which does not need to be freed by the application, however its pointer can be considered valid only as long as its associated DPDK port remains configured. Closing the underlying device or unloading the PMD invalidates it.

9.6. Helpers

9.6.1. Error initializer

static inline int
rte_flow_error_set(struct rte_flow_error *error,
                   int code,
                   enum rte_flow_error_type type,
                   const void *cause,
                   const char *message);

This function initializes error (if non-NULL) with the provided parameters and sets rte_errno to code. A negative error code is then returned.

9.7. Caveats

  • DPDK does not keep track of flow rules definitions or flow rule objects automatically. Applications may keep track of the former and must keep track of the latter. PMDs may also do it for internal needs, however this must not be relied on by applications.
  • Flow rules are not maintained between successive port initializations. An application exiting without releasing them and restarting must re-create them from scratch.
  • API operations are synchronous and blocking (EAGAIN cannot be returned).
  • There is no provision for reentrancy/multi-thread safety, although nothing should prevent different devices from being configured at the same time. PMDs may protect their control path functions accordingly.
  • Stopping the data path (TX/RX) should not be necessary when managing flow rules. If this cannot be achieved naturally or with workarounds (such as temporarily replacing the burst function pointers), an appropriate error code must be returned (EBUSY).
  • PMDs, not applications, are responsible for maintaining flow rules configuration when stopping and restarting a port or performing other actions which may affect them. They can only be destroyed explicitly by applications.

For devices exposing multiple ports sharing global settings affected by flow rules:

  • All ports under DPDK control must behave consistently, PMDs are responsible for making sure that existing flow rules on a port are not affected by other ports.
  • Ports not under DPDK control (unaffected or handled by other applications) are user’s responsibility. They may affect existing flow rules and cause undefined behavior. PMDs aware of this may prevent flow rules creation altogether in such cases.

9.8. PMD interface

The PMD interface is defined in rte_flow_driver.h. It is not subject to API/ABI versioning constraints as it is not exposed to applications and may evolve independently.

It is currently implemented on top of the legacy filtering framework through filter type RTE_ETH_FILTER_GENERIC that accepts the single operation RTE_ETH_FILTER_GET to return PMD-specific rte_flow callbacks wrapped inside struct rte_flow_ops.

This overhead is temporarily necessary in order to keep compatibility with the legacy filtering framework, which should eventually disappear.

  • PMD callbacks implement exactly the interface described in Rules management, except for the port ID argument which has already been converted to a pointer to the underlying struct rte_eth_dev.
  • Public API functions do not process flow rules definitions at all before calling PMD functions (no basic error checking, no validation whatsoever). They only make sure these callbacks are non-NULL or return the ENOSYS (function not supported) error.

This interface additionally defines the following helper function:

  • rte_flow_ops_get(): get generic flow operations structure from a port.

More will be added over time.

9.9. Device compatibility

No known implementation supports all the described features.

Unsupported features or combinations are not expected to be fully emulated in software by PMDs for performance reasons. Partially supported features may be completed in software as long as hardware performs most of the work (such as queue redirection and packet recognition).

However PMDs are expected to do their best to satisfy application requests by working around hardware limitations as long as doing so does not affect the behavior of existing flow rules.

The following sections provide a few examples of such cases and describe how PMDs should handle them, they are based on limitations built into the previous APIs.

9.9.1. Global bit-masks

Each flow rule comes with its own, per-layer bit-masks, while hardware may support only a single, device-wide bit-mask for a given layer type, so that two IPv4 rules cannot use different bit-masks.

The expected behavior in this case is that PMDs automatically configure global bit-masks according to the needs of the first flow rule created.

Subsequent rules are allowed only if their bit-masks match those, the EEXIST error code should be returned otherwise.

9.9.2. Unsupported layer types

Many protocols can be simulated by crafting patterns with the Item: RAW type.

PMDs can rely on this capability to simulate support for protocols with headers not directly recognized by hardware.

9.9.3. ANY pattern item

This pattern item stands for anything, which can be difficult to translate to something hardware would understand, particularly if followed by more specific types.

Consider the following pattern:

Table 9.44 Pattern with ANY as L3
Index Item
1 ANY num 1

Knowing that TCP does not make sense with something other than IPv4 and IPv6 as L3, such a pattern may be translated to two flow rules instead:

Table 9.45 ANY replaced with IPV4
Index Item
1 IPV4 (zeroed mask)

Table 9.46 ANY replaced with IPV6
Index Item
1 IPV6 (zeroed mask)

Note that as soon as a ANY rule covers several layers, this approach may yield a large number of hidden flow rules. It is thus suggested to only support the most common scenarios (anything as L2 and/or L3).

9.9.4. Unsupported actions

9.9.5. Flow rules priority

While it would naturally make sense, flow rules cannot be assumed to be processed by hardware in the same order as their creation for several reasons:

  • They may be managed internally as a tree or a hash table instead of a list.
  • Removing a flow rule before adding another one can either put the new rule at the end of the list or reuse a freed entry.
  • Duplication may occur when packets are matched by several rules.

For overlapping rules (particularly in order to use Action: PASSTHRU) predictable behavior is only guaranteed by using different priority levels.

Priority levels are not necessarily implemented in hardware, or may be severely limited (e.g. a single priority bit).

For these reasons, priority levels may be implemented purely in software by PMDs.

  • For devices expecting flow rules to be added in the correct order, PMDs may destroy and re-create existing rules after adding a new one with a higher priority.
  • A configurable number of dummy or empty rules can be created at initialization time to save high priority slots for later.
  • In order to save priority levels, PMDs may evaluate whether rules are likely to collide and adjust their priority accordingly.

9.10. Future evolutions

  • A device profile selection function which could be used to force a permanent profile instead of relying on its automatic configuration based on existing flow rules.
  • A method to optimize rte_flow rules with specific pattern items and action types generated on the fly by PMDs. DPDK should assign negative numbers to these in order to not collide with the existing types. See Negative types.
  • Adding specific egress pattern items and actions as described in Attribute: Traffic direction.
  • Optional software fallback when PMDs are unable to handle requested flow rules so applications do not have to implement their own.

9.11. API migration

Exhaustive list of deprecated filter types (normally prefixed with RTE_ETH_FILTER_) found in rte_eth_ctrl.h and methods to convert them to rte_flow rules.

9.11.1. MACVLAN to ETHVF, PF

MACVLAN can be translated to a basic Item: ETH flow rule with a terminating Action: VF or Action: PF.

Table 9.47 MACVLAN conversion
Pattern Actions
0 ETH spec any VF, PF
last N/A
mask any


ETHERTYPE is basically an Item: ETH flow rule with a terminating Action: QUEUE or Action: DROP.

Table 9.48 ETHERTYPE conversion
Pattern Actions
0 ETH spec any QUEUE, DROP
last N/A
mask any


FLEXIBLE can be translated to one Item: RAW pattern with a terminating Action: QUEUE and a defined priority level.

Table 9.49 FLEXIBLE conversion
Pattern Actions
0 RAW spec any QUEUE
last N/A
mask any

9.11.4. SYN to TCPQUEUE

SYN is a Item: TCP rule with only the syn bit enabled and masked, and a terminating Action: QUEUE.

Priority level can be set to simulate the high priority bit.

Table 9.50 SYN conversion
Pattern Actions
0 ETH spec unset QUEUE
last unset
mask unset
1 IPV4 spec unset END
mask unset
mask unset
2 TCP spec syn 1
mask syn 1


NTUPLE is similar to specifying an empty L2, Item: IPV4 as L3 with Item: TCP or Item: UDP as L4 and a terminating Action: QUEUE.

A priority level can be specified as well.

Table 9.51 NTUPLE conversion
Pattern Actions
0 ETH spec unset QUEUE
last unset
mask unset
1 IPV4 spec any END
last unset
mask any
2 TCP, UDP spec any
last unset
mask any

9.11.6. TUNNEL to ETH, IPV4, IPV6, VXLAN (or other) → QUEUE

TUNNEL matches common IPv4 and IPv6 L3/L4-based tunnel types.

In the following table, Item: ANY is used to cover the optional L4.

Table 9.52 TUNNEL conversion
Pattern Actions
0 ETH spec any QUEUE
last unset
mask any
1 IPV4, IPV6 spec any END
last unset
mask any
2 ANY spec any
last unset
mask num 0
last unset
mask any

9.11.7. FDIR to most item types → QUEUE, DROP, PASSTHRU

FDIR is more complex than any other type, there are several methods to emulate its functionality. It is summarized for the most part in the table below.

A few features are intentionally not supported:

  • The ability to configure the matching input set and masks for the entire device, PMDs should take care of it automatically according to the requested flow rules.

    For example if a device supports only one bit-mask per protocol type, source/address IPv4 bit-masks can be made immutable by the first created rule. Subsequent IPv4 or TCPv4 rules can only be created if they are compatible.

    Note that only protocol bit-masks affected by existing flow rules are immutable, others can be changed later. They become mutable again after the related flow rules are destroyed.

  • Returning four or eight bytes of matched data when using flex bytes filtering. Although a specific action could implement it, it conflicts with the much more useful 32 bits tagging on devices that support it.

  • Side effects on RSS processing of the entire device. Flow rules that conflict with the current device configuration should not be allowed. Similarly, device configuration should not be allowed when it affects existing flow rules.

  • Device modes of operation. “none” is unsupported since filtering cannot be disabled as long as a flow rule is present.

  • “MAC VLAN” or “tunnel” perfect matching modes should be automatically set according to the created flow rules.

  • Signature mode of operation is not defined but could be handled through “FUZZY” item.

Table 9.53 FDIR conversion
Pattern Actions
last N/A
mask any
1 IPV4, IPv6 spec any MARK
last N/A
mask any
2 TCP, UDP, SCTP spec any END
last N/A
mask any
3 VF, PF, FUZZY (optional) spec any
last N/A
mask any

9.11.8. HASH

There is no counterpart to this filter type because it translates to a global device setting instead of a pattern item. Device settings are automatically set according to the created flow rules.

9.11.9. L2_TUNNEL to VOIDVXLAN (or others)

All packets are matched. This type alters incoming packets to encapsulate them in a chosen tunnel type, optionally redirect them to a VF as well.

The destination pool for tag based forwarding can be emulated with other flow rules using Action: DUP.

Table 9.54 L2_TUNNEL conversion
Pattern Actions
0 VOID spec N/A VXLAN, GENEVE, ...
last N/A
mask N/A
1 END VF (optional)