1 .. SPDX-License-Identifier: BSD-3-Clause
2 Copyright(c) 2018 6WIND S.A.
4 .. _switch_representation:
6 Switch Representation within DPDK Applications
7 ==============================================
14 Network adapters with multiple physical ports and/or SR-IOV capabilities
15 usually support the offload of traffic steering rules between their virtual
16 functions (VFs), physical functions (PFs) and ports.
18 Like for standard Ethernet switches, this involves a combination of
19 automatic MAC learning and manual configuration. For most purposes it is
20 managed by the host system and fully transparent to users and applications.
22 On the other hand, applications typically found on hypervisors that process
23 layer 2 (L2) traffic (such as OVS) need to steer traffic themselves
24 according on their own criteria.
26 Without a standard software interface to manage traffic steering rules
27 between VFs, PFs and the various physical ports of a given device,
28 applications cannot take advantage of these offloads; software processing is
29 mandatory even for traffic which ends up re-injected into the device it
32 This document describes how such steering rules can be configured through
33 the DPDK flow API (**rte_flow**), with emphasis on the SR-IOV use case
34 (PF/VF steering) using a single physical port for clarity, however the same
35 logic applies to any number of ports without necessarily involving SR-IOV.
40 In many cases, traffic steering rules cannot be determined in advance;
41 applications usually have to process a bit of traffic in software before
42 thinking about offloading specific flows to hardware.
44 Applications therefore need the ability to receive and inject traffic to
45 various device endpoints (other VFs, PFs or physical ports) before
46 connecting them together. Device drivers must provide means to hook the
47 "other end" of these endpoints and to refer them when configuring flow
50 This role is left to so-called "port representors" (also known as "VF
51 representors" in the specific context of VFs), which are to DPDK what the
52 Ethernet switch device driver model (**switchdev**) [1]_ is to Linux, and
53 which can be thought as a software "patch panel" front-end for applications.
55 - DPDK port representors are implemented as additional virtual Ethernet
56 device (**ethdev**) instances, spawned on an as needed basis through
57 configuration parameters passed to the driver of the underlying
62 -w pci:dbdf,representor=0
63 -w pci:dbdf,representor=[0-3]
64 -w pci:dbdf,representor=[0,5-11]
66 - As virtual devices, they may be more limited than their physical
67 counterparts, for instance by exposing only a subset of device
68 configuration callbacks and/or by not necessarily having Rx/Tx capability.
70 - Among other things, they can be used to assign MAC addresses to the
71 resource they represent.
73 - Applications can tell port representors apart from other physical of virtual
74 port by checking the dev_flags field within their device information
75 structure for the RTE_ETH_DEV_REPRESENTOR bit-field.
79 struct rte_eth_dev_info {
81 uint32_t dev_flags; /**< Device flags */
85 - The device or group relationship of ports can be discovered using the
86 switch ``domain_id`` field within the devices switch information structure. By
87 default the switch ``domain_id`` of a port will be
88 ``RTE_ETH_DEV_SWITCH_DOMAIN_ID_INVALID`` to indicate that the port doesn't
89 support the concept of a switch domain, but ports which do support the concept
90 will be allocated a unique switch ``domain_id``, ports within the same switch
91 domain will share the same ``domain_id``. The switch ``port_id`` is used to
92 specify the port_id in terms of the switch, so in the case of SR-IOV devices
93 the switch ``port_id`` would represent the virtual function identifier of the
99 * Ethernet device associated switch information
101 struct rte_eth_switch_info {
102 const char *name; /**< switch name */
103 uint16_t domain_id; /**< switch domain id */
104 uint16_t port_id; /**< switch port id */
108 .. [1] `Ethernet switch device driver model (switchdev)
109 <https://www.kernel.org/doc/Documentation/networking/switchdev.txt>`_
114 "Basic" in the sense that it is not managed by applications, which
115 nonetheless expect traffic to flow between the various endpoints and the
116 outside as if everything was linked by an Ethernet hub.
118 The following diagram pictures a setup involving a device with one PF, two
119 VFs and one shared physical port
123 .-------------. .-------------. .-------------.
124 | hypervisor | | VM 1 | | VM 2 |
125 | application | | application | | application |
126 `--+----------' `----------+--' `--+----------'
132 .-+--. .---+--. .--+---.
133 | PF | | VF 1 | | VF 2 |
134 `-+--' `---+--' `--+---'
136 `---------. .-----------------------' |
137 | | .-------------------------'
148 - A DPDK application running on the hypervisor owns the PF device, which is
149 arbitrarily assigned port index 3.
151 - Both VFs are assigned to VMs and used by unknown applications; they may be
152 DPDK-based or anything else.
154 - Interconnection is not necessarily done through a true Ethernet switch and
155 may not even exist as a separate entity. The role of this block is to show
156 that something brings PF, VFs and physical ports together and enables
157 communication between them, with a number of built-in restrictions.
159 Subsequent sections in this document describe means for DPDK applications
160 running on the hypervisor to freely assign specific flows between PF, VFs
161 and physical ports based on traffic properties, by managing this
170 When a DPDK application gets assigned a PF device and is deliberately not
171 started in `basic SR-IOV`_ mode, any traffic coming from physical ports is
172 received by PF according to default rules, while VFs remain isolated.
176 .-------------. .-------------. .-------------.
177 | hypervisor | | VM 1 | | VM 2 |
178 | application | | application | | application |
179 `--+----------' `----------+--' `--+----------'
185 .-+--. .---+--. .--+---.
186 | PF | | VF 1 | | VF 2 |
187 `-+--' `------' `------'
191 .--+----------------------.
192 | managed interconnection |
193 `------------+------------'
200 In this mode, interconnection must be configured by the application to
201 enable VF communication, for instance by explicitly directing traffic with a
202 given destination MAC address to VF 1 and allowing that with the same source
203 MAC address to come out of it.
205 For this to work, hypervisor applications need a way to refer to either VF 1
206 or VF 2 in addition to the PF. This is addressed by `VF representors`_.
211 VF representors are virtual but standard DPDK network devices (albeit with
212 limited capabilities) created by PMDs when managing a PF device.
214 Since they represent VF instances used by other applications, configuring
215 them (e.g. assigning a MAC address or setting up promiscuous mode) affects
216 interconnection accordingly. If supported, they may also be used as two-way
217 communication ports with VFs (assuming **switchdev** topology)
222 .-------------. .-------------. .-------------.
223 | hypervisor | | VM 1 | | VM 2 |
224 | application | | application | | application |
225 `--+---+---+--' `----------+--' `--+----------'
227 | | `-------------------. | |
230 .-----+-----. .-----+-----. .-----+-----. | |
231 | port_id 3 | | port_id 4 | | port_id 5 | | |
232 `-----+-----' `-----+-----' `-----+-----' | |
234 .-+--. .-----+-----. .-----+-----. .---+--. .--+---.
235 | PF | | VF 1 rep. | | VF 2 rep. | | VF 1 | | VF 2 |
236 `-+--' `-----+-----' `-----+-----' `---+--' `--+---'
239 `-----. | | .-----------------' |
240 | | | | .---------------------'
242 .--+-------+---+---+---+--.
243 | managed interconnection |
244 `------------+------------'
251 - VF representors are assigned arbitrary port indices 4 and 5 in the
252 hypervisor application and are respectively associated with VF 1 and VF 2.
254 - They can't be dissociated; even if VF 1 and VF 2 were not connected,
255 representors could still be used for configuration.
257 - In this context, port index 3 can be thought as a representor for physical
260 As previously described, the "interconnection" block represents a logical
261 concept. Interconnection occurs when hardware configuration enables traffic
262 flows from one place to another (e.g. physical port 0 to VF 1) according to
265 This is discussed in more detail in `traffic steering`_.
270 In the following diagram, each meaningful traffic origin or endpoint as seen
271 by the hypervisor application is tagged with a unique letter from A to F.
275 .-------------. .-------------. .-------------.
276 | hypervisor | | VM 1 | | VM 2 |
277 | application | | application | | application |
278 `--+---+---+--' `----------+--' `--+----------'
280 | | `-------------------. | |
283 .----(A)----. .----(B)----. .----(C)----. | |
284 | port_id 3 | | port_id 4 | | port_id 5 | | |
285 `-----+-----' `-----+-----' `-----+-----' | |
287 .-+--. .-----+-----. .-----+-----. .---+--. .--+---.
288 | PF | | VF 1 rep. | | VF 2 rep. | | VF 1 | | VF 2 |
289 `-+--' `-----+-----' `-----+-----' `--(D)-' `-(E)--'
292 `-----. | | .-----------------' |
293 | | | | .---------------------'
295 .--+-------+---+---+---+--.
296 | managed interconnection |
297 `------------+------------'
305 - **B**: port representor for VF 1.
306 - **C**: port representor for VF 2.
307 - **D**: VF 1 proper.
308 - **E**: VF 2 proper.
309 - **F**: physical port.
311 Although uncommon, some devices do not enforce a one to one mapping between
312 PF and physical ports. For instance, by default all ports of **mlx4**
313 adapters are available to all their PF/VF instances, in which case
314 additional ports appear next to **F** in the above diagram.
316 Assuming no interconnection is provided by default in this mode, setting up
317 a `basic SR-IOV`_ configuration involving physical port 0 could be broken
322 - **A to F**: let everything through.
323 - **F to A**: PF MAC as destination.
327 - **A to D**, **E to D** and **F to D**: VF 1 MAC as destination.
328 - **D to A**: VF 1 MAC as source and PF MAC as destination.
329 - **D to E**: VF 1 MAC as source and VF 2 MAC as destination.
330 - **D to F**: VF 1 MAC as source.
334 - **A to E**, **D to E** and **F to E**: VF 2 MAC as destination.
335 - **E to A**: VF 2 MAC as source and PF MAC as destination.
336 - **E to D**: VF 2 MAC as source and VF 1 MAC as destination.
337 - **E to F**: VF 2 MAC as source.
339 Devices may additionally support advanced matching criteria such as
340 IPv4/IPv6 addresses or TCP/UDP ports.
342 The combination of matching criteria with target endpoints fits well with
343 **rte_flow** [6]_, which expresses flow rules as combinations of patterns
346 Enhancing **rte_flow** with the ability to make flow rules match and target
347 these endpoints provides a standard interface to manage their
348 interconnection without introducing new concepts and whole new API to
349 implement them. This is described in `flow API (rte_flow)`_.
351 .. [6] `Generic flow API (rte_flow)
352 <http://doc.dpdk.org/guides/prog_guide/rte_flow.html>`_
360 Compared to creating a brand new dedicated interface, **rte_flow** was
361 deemed flexible enough to manage representor traffic only with minor
364 - Using physical ports, PF, VF or port representors as targets.
366 - Affecting traffic that is not necessarily addressed to the DPDK port ID a
367 flow rule is associated with (e.g. forcing VF traffic redirection to PF).
371 - Rule-based packet counters.
373 - The ability to combine several identical actions for traffic duplication
374 (e.g. VF representor in addition to a physical port).
376 - Dedicated actions for traffic encapsulation / decapsulation before
377 reaching an endpoint.
382 From an application standpoint, "ingress" and "egress" flow rule attributes
383 apply to the DPDK port ID they are associated with. They select a traffic
384 direction for matching patterns, but have no impact on actions.
386 When matching traffic coming from or going to a different place than the
387 immediate port ID a flow rule is associated with, these attributes keep
388 their meaning while applying to the chosen origin, as highlighted by the
393 .-------------. .-------------. .-------------.
394 | hypervisor | | VM 1 | | VM 2 |
395 | application | | application | | application |
396 `--+---+---+--' `----------+--' `--+----------'
398 | | `-------------------. | |
401 | | ingress | | ingress | | ingress | |
402 | | egress | | egress | | egress | |
404 .----(A)----. .----(B)----. .----(C)----. | |
405 | port_id 3 | | port_id 4 | | port_id 5 | | |
406 `-----+-----' `-----+-----' `-----+-----' | |
408 .-+--. .-----+-----. .-----+-----. .---+--. .--+---.
409 | PF | | VF 1 rep. | | VF 2 rep. | | VF 1 | | VF 2 |
410 `-+--' `-----+-----' `-----+-----' `--(D)-' `-(E)--'
412 | | | egress | | | | egress
413 | | | ingress | | | | ingress
414 | | .---------' v | | v
415 `-----. | | .-----------------' |
416 | | | | .---------------------'
418 .--+-------+---+---+---+--.
419 | managed interconnection |
420 `------------+------------'
430 Ingress and egress are defined as relative to the application creating the
433 For instance, matching traffic sent by VM 2 would be done through an ingress
434 flow rule on VF 2 (**E**). Likewise for incoming traffic on physical port
435 (**F**). This also applies to **C** and **A** respectively.
440 Without Port Representors
441 ^^^^^^^^^^^^^^^^^^^^^^^^^
443 `Traffic direction`_ describes how an application could match traffic coming
444 from or going to a specific place reachable from a DPDK port ID. This makes
445 sense when the traffic in question is normally seen (i.e. sent or received)
446 by the application creating the flow rule (e.g. as in "redirect all traffic
447 coming from VF 1 to local queue 6").
449 However this does not force such traffic to take a specific route. Creating
450 a flow rule on **A** matching traffic coming from **D** is only meaningful
451 if it can be received by **A** in the first place, otherwise doing so simply
454 A new flow rule attribute named "transfer" is necessary for that. Combining
455 it with "ingress" or "egress" and a specific origin requests a flow rule to
456 be applied at the lowest level
460 ingress only : ingress + transfer
462 .-------------. .-------------. : .-------------. .-------------.
463 | hypervisor | | VM 1 | : | hypervisor | | VM 1 |
464 | application | | application | : | application | | application |
465 `------+------' `--+----------' : `------+------' `--+----------'
466 | | | traffic : | | | traffic
467 .----(A)----. | v : .----(A)----. | v
468 | port_id 3 | | : | port_id 3 | |
469 `-----+-----' | : `-----+-----' |
472 .-+--. .---+--. : .-+--. .---+--.
473 | PF | | VF 1 | : | PF | | VF 1 |
474 `-+--' `--(D)-' : `-+--' `--(D)-'
475 | | | traffic : | ^ | | traffic
476 | | v : | | traffic | v
477 .--+-----------+--. : .--+-----------+--.
478 | interconnection | : | interconnection |
479 `--------+--------' : `--------+--------'
482 .---(F)----. : .---(F)----.
483 | physical | : | physical |
484 | port 0 | : | port 0 |
485 `----------' : `----------'
487 With "ingress" only, traffic is matched on **A** thus still goes to physical
488 port **F** by default
493 testpmd> flow create 3 ingress pattern vf id is 1 / end
494 actions queue index 6 / end
496 With "ingress + transfer", traffic is matched on **D** and is therefore
497 successfully assigned to queue 6 on **A**
502 testpmd> flow create 3 ingress transfer pattern vf id is 1 / end
503 actions queue index 6 / end
506 With Port Representors
507 ^^^^^^^^^^^^^^^^^^^^^^
509 When port representors exist, implicit flow rules with the "transfer"
510 attribute (described in `without port representors`_) are be assumed to
511 exist between them and their represented resources. These may be immutable.
513 In this case, traffic is received by default through the representor and
514 neither the "transfer" attribute nor traffic origin in flow rule patterns
515 are necessary. They simply have to be created on the representor port
516 directly and may target a different representor as described in `PORT_ID
519 Implicit traffic flow with port representor
523 .-------------. .-------------.
524 | hypervisor | | VM 1 |
525 | application | | application |
526 `--+-------+--' `----------+--'
531 .----(A)----. .----(B)----. |
532 | port_id 3 | | port_id 4 | |
533 `-----+-----' `-----+-----' |
535 .-+--. .-----+-----. .---+--.
536 | PF | | VF 1 rep. | | VF 1 |
537 `-+--' `-----+-----' `--(D)-'
539 .--|-------------|-----------|--.
543 `--|----------------------------'
550 Pattern Items And Actions
551 ~~~~~~~~~~~~~~~~~~~~~~~~~
556 Matches traffic originating from (ingress) or going to (egress) a physical
557 port of the underlying device.
559 Using this pattern item without specifying a port index matches the physical
560 port associated with the current DPDK port ID by default. As described in
561 `traffic steering`_, specifying it should be rarely needed.
563 - Matches **F** in `traffic steering`_.
568 Directs matching traffic to a given physical port index.
570 - Targets **F** in `traffic steering`_.
575 Matches traffic originating from (ingress) or going to (egress) a given DPDK
578 Normally only supported if the port ID in question is known by the
579 underlying PMD and related to the device the flow rule is created against.
581 This must not be confused with the `PORT pattern item`_ which refers to the
582 physical port of a device. ``PORT_ID`` refers to a ``struct rte_eth_dev``
583 object on the application side (also known as "port representor" depending
584 on the kind of underlying device).
586 - Matches **A**, **B** or **C** in `traffic steering`_.
591 Directs matching traffic to a given DPDK port ID.
593 Same restrictions as `PORT_ID pattern item`_.
595 - Targets **A**, **B** or **C** in `traffic steering`_.
600 Matches traffic originating from (ingress) or going to (egress) the physical
601 function of the current device.
603 If supported, should work even if the physical function is not managed by
604 the application and thus not associated with a DPDK port ID. Its behavior is
605 otherwise similar to `PORT_ID pattern item`_ using PF port ID.
607 - Matches **A** in `traffic steering`_.
612 Directs matching traffic to the physical function of the current device.
614 Same restrictions as `PF pattern item`_.
616 - Targets **A** in `traffic steering`_.
621 Matches traffic originating from (ingress) or going to (egress) a given
622 virtual function of the current device.
624 If supported, should work even if the virtual function is not managed by
625 the application and thus not associated with a DPDK port ID. Its behavior is
626 otherwise similar to `PORT_ID pattern item`_ using VF port ID.
628 Note this pattern item does not match VF representors traffic which, as
629 separate entities, should be addressed through their own port IDs.
631 - Matches **D** or **E** in `traffic steering`_.
636 Directs matching traffic to a given virtual function of the current device.
638 Same restrictions as `VF pattern item`_.
640 - Targets **D** or **E** in `traffic steering`_.
645 These actions are named according to the protocol they encapsulate traffic
646 with (e.g. ``VXLAN_ENCAP``) and using specific parameters (e.g. VNI for
649 While they modify traffic and can be used multiple times (order matters),
650 unlike `PORT_ID action`_ and friends, they have no impact on steering.
652 As described in `actions order and repetition`_ this means they are useless
653 if used alone in an action list, the resulting traffic gets dropped unless
654 combined with either ``PASSTHRU`` or other endpoint-targeting actions.
659 They perform the reverse of `\*_ENCAP actions`_ by popping protocol headers
660 from traffic instead of pushing them. They can be used multiple times as
663 Note that using these actions on non-matching traffic results in undefined
664 behavior. It is recommended to match the protocol headers to decapsulate on
665 the pattern side of a flow rule in order to use these actions or otherwise
666 make sure only matching traffic goes through.
668 Actions Order and Repetition
669 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
671 Flow rules are currently restricted to at most a single action of each
672 supported type, performed in an unpredictable order (or all at once). To
673 repeat actions in a predictable fashion, applications have to make rules
674 pass-through and use priority levels.
676 It's now clear that PMD support for chaining multiple non-terminating flow
677 rules of varying priority levels is prohibitively difficult to implement
678 compared to simply allowing multiple identical actions performed in a
679 defined order by a single flow rule.
681 - This change is required to support protocol encapsulation offloads and the
682 ability to perform them multiple times (e.g. VLAN then VXLAN).
684 - It makes the ``DUP`` action redundant since multiple ``QUEUE`` actions can
685 be combined for duplication.
687 - The (non-)terminating property of actions must be discarded. Instead, flow
688 rules themselves must be considered terminating by default (i.e. dropping
689 traffic if there is no specific target) unless a ``PASSTHRU`` action is
695 This section provides practical examples based on the established testpmd
696 flow command syntax [2]_, in the context described in `traffic steering`_
700 .-------------. .-------------. .-------------.
701 | hypervisor | | VM 1 | | VM 2 |
702 | application | | application | | application |
703 `--+---+---+--' `----------+--' `--+----------'
705 | | `-------------------. | |
708 .----(A)----. .----(B)----. .----(C)----. | |
709 | port_id 3 | | port_id 4 | | port_id 5 | | |
710 `-----+-----' `-----+-----' `-----+-----' | |
712 .-+--. .-----+-----. .-----+-----. .---+--. .--+---.
713 | PF | | VF 1 rep. | | VF 2 rep. | | VF 1 | | VF 2 |
714 `-+--' `-----+-----' `-----+-----' `--(D)-' `-(E)--'
717 `-----. | | .-----------------' |
718 | | | | .---------------------'
720 .--|-------|---|---|---|--.
724 `------------|------------'
731 By default, PF (**A**) can communicate with the physical port it is
732 associated with (**F**), while VF 1 (**D**) and VF 2 (**E**) are isolated
733 and restricted to communicate with the hypervisor application through their
734 respective representors (**B** and **C**) if supported.
736 Examples in subsequent sections apply to hypervisor applications only and
737 are based on port representors **A**, **B** and **C**.
740 <http://doc.dpdk.org/guides/testpmd_app_ug/testpmd_funcs.html#flow-syntax>`_
742 Associating VF 1 with Physical Port 0
743 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
745 Assign all port traffic (**F**) to VF 1 (**D**) indiscriminately through
750 flow create 3 ingress pattern / end actions port_id id 4 / end
751 flow create 4 ingress pattern / end actions port_id id 3 / end
753 More practical example with MAC address restrictions
757 flow create 3 ingress
758 pattern eth dst is {VF 1 MAC} / end
759 actions port_id id 4 / end
763 flow create 4 ingress
764 pattern eth src is {VF 1 MAC} / end
765 actions port_id id 3 / end
771 From outside to PF and VFs
775 flow create 3 ingress
776 pattern eth dst is ff:ff:ff:ff:ff:ff / end
777 actions port_id id 3 / port_id id 4 / port_id id 5 / end
779 Note ``port_id id 3`` is necessary otherwise only VFs would receive matching
782 From PF to outside and VFs
787 pattern eth dst is ff:ff:ff:ff:ff:ff / end
788 actions port / port_id id 4 / port_id id 5 / end
790 From VFs to outside and PF
794 flow create 4 ingress
795 pattern eth dst is ff:ff:ff:ff:ff:ff src is {VF 1 MAC} / end
796 actions port_id id 3 / port_id id 5 / end
798 flow create 5 ingress
799 pattern eth dst is ff:ff:ff:ff:ff:ff src is {VF 2 MAC} / end
800 actions port_id id 4 / port_id id 4 / end
802 Similar ``33:33:*`` rules based on known MAC addresses should be added for
805 Encapsulating VF 2 Traffic in VXLAN
806 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
808 Assuming pass-through flow rules are supported
812 flow create 5 ingress
814 actions vxlan_encap vni 42 / passthru / end
819 pattern vxlan vni is 42 / end
820 actions vxlan_decap / passthru / end
822 Here ``passthru`` is needed since as described in `actions order and
823 repetition`_, flow rules are otherwise terminating; if supported, a rule
824 without a target endpoint will drop traffic.
826 Without pass-through support, ingress encapsulation on the destination
827 endpoint might not be supported and action list must provide one
831 flow create 5 ingress
832 pattern eth src is {VF 2 MAC} / end
833 actions vxlan_encap vni 42 / port_id id 3 / end
835 flow create 3 ingress
836 pattern vxlan vni is 42 / end
837 actions vxlan_decap / port_id id 5 / end