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1 | .. SPDX-License-Identifier: GPL-2.0 |
2 | .. include:: <isonum.txt> | |
3 | ||
4 | =============================================== | |
4ceec22d SF |
5 | Ethernet switch device driver model (switchdev) |
6 | =============================================== | |
32c0f0be MCC |
7 | |
8 | Copyright |copy| 2014 Jiri Pirko <jiri@resnulli.us> | |
9 | ||
10 | Copyright |copy| 2014-2015 Scott Feldman <sfeldma@gmail.com> | |
4ceec22d SF |
11 | |
12 | ||
13 | The Ethernet switch device driver model (switchdev) is an in-kernel driver | |
14 | model for switch devices which offload the forwarding (data) plane from the | |
15 | kernel. | |
16 | ||
17 | Figure 1 is a block diagram showing the components of the switchdev model for | |
18 | an example setup using a data-center-class switch ASIC chip. Other setups | |
19 | with SR-IOV or soft switches, such as OVS, are possible. | |
20 | ||
32c0f0be | 21 | :: |
4ceec22d | 22 | |
32c0f0be MCC |
23 | |
24 | User-space tools | |
51513748 RD |
25 | |
26 | user space | | |
27 | +-------------------------------------------------------------------+ | |
28 | kernel | Netlink | |
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29 | | |
30 | +--------------+-------------------------------+ | |
31 | | Network stack | | |
32 | | (Linux) | | |
33 | | | | |
34 | +----------------------------------------------+ | |
35 | ||
36 | sw1p2 sw1p4 sw1p6 | |
37 | sw1p1 + sw1p3 + sw1p5 + eth1 | |
38 | + | + | + | + | |
39 | | | | | | | | | |
40 | +--+----+----+----+----+----+---+ +-----+-----+ | |
41 | | Switch driver | | mgmt | | |
42 | | (this document) | | driver | | |
43 | | | | | | |
44 | +--------------+----------------+ +-----------+ | |
45 | | | |
51513748 RD |
46 | kernel | HW bus (eg PCI) |
47 | +-------------------------------------------------------------------+ | |
48 | hardware | | |
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49 | +--------------+----------------+ |
50 | | Switch device (sw1) | | |
51 | | +----+ +--------+ | |
52 | | | v offloaded data path | mgmt port | |
53 | | | | | | |
54 | +--|----|----+----+----+----+---+ | |
55 | | | | | | | | |
56 | + + + + + + | |
57 | p1 p2 p3 p4 p5 p6 | |
51513748 | 58 | |
32c0f0be | 59 | front-panel ports |
d5066c46 | 60 | |
4ceec22d | 61 | |
32c0f0be | 62 | Fig 1. |
4ceec22d SF |
63 | |
64 | ||
65 | Include Files | |
66 | ------------- | |
67 | ||
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68 | :: |
69 | ||
70 | #include <linux/netdevice.h> | |
71 | #include <net/switchdev.h> | |
4ceec22d SF |
72 | |
73 | ||
74 | Configuration | |
75 | ------------- | |
76 | ||
77 | Use "depends NET_SWITCHDEV" in driver's Kconfig to ensure switchdev model | |
78 | support is built for driver. | |
79 | ||
80 | ||
81 | Switch Ports | |
82 | ------------ | |
83 | ||
84 | On switchdev driver initialization, the driver will allocate and register a | |
85 | struct net_device (using register_netdev()) for each enumerated physical switch | |
86 | port, called the port netdev. A port netdev is the software representation of | |
87 | the physical port and provides a conduit for control traffic to/from the | |
88 | controller (the kernel) and the network, as well as an anchor point for higher | |
89 | level constructs such as bridges, bonds, VLANs, tunnels, and L3 routers. Using | |
90 | standard netdev tools (iproute2, ethtool, etc), the port netdev can also | |
91 | provide to the user access to the physical properties of the switch port such | |
92 | as PHY link state and I/O statistics. | |
93 | ||
94 | There is (currently) no higher-level kernel object for the switch beyond the | |
95 | port netdevs. All of the switchdev driver ops are netdev ops or switchdev ops. | |
96 | ||
97 | A switch management port is outside the scope of the switchdev driver model. | |
98 | Typically, the management port is not participating in offloaded data plane and | |
99 | is loaded with a different driver, such as a NIC driver, on the management port | |
100 | device. | |
101 | ||
75f3a101 IS |
102 | Switch ID |
103 | ^^^^^^^^^ | |
104 | ||
80d79ad2 FF |
105 | The switchdev driver must implement the net_device operation |
106 | ndo_get_port_parent_id for each port netdev, returning the same physical ID for | |
107 | each port of a switch. The ID must be unique between switches on the same | |
108 | system. The ID does not need to be unique between switches on different | |
109 | systems. | |
75f3a101 IS |
110 | |
111 | The switch ID is used to locate ports on a switch and to know if aggregated | |
112 | ports belong to the same switch. | |
113 | ||
4ceec22d SF |
114 | Port Netdev Naming |
115 | ^^^^^^^^^^^^^^^^^^ | |
116 | ||
117 | Udev rules should be used for port netdev naming, using some unique attribute | |
118 | of the port as a key, for example the port MAC address or the port PHYS name. | |
119 | Hard-coding of kernel netdev names within the driver is discouraged; let the | |
120 | kernel pick the default netdev name, and let udev set the final name based on a | |
121 | port attribute. | |
122 | ||
123 | Using port PHYS name (ndo_get_phys_port_name) for the key is particularly | |
1f5dc44c | 124 | useful for dynamically-named ports where the device names its ports based on |
4ceec22d SF |
125 | external configuration. For example, if a physical 40G port is split logically |
126 | into 4 10G ports, resulting in 4 port netdevs, the device can give a unique | |
32c0f0be | 127 | name for each port using port PHYS name. The udev rule would be:: |
4ceec22d | 128 | |
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129 | SUBSYSTEM=="net", ACTION=="add", ATTR{phys_switch_id}=="<phys_switch_id>", \ |
130 | ATTR{phys_port_name}!="", NAME="swX$attr{phys_port_name}" | |
4ceec22d SF |
131 | |
132 | Suggested naming convention is "swXpYsZ", where X is the switch name or ID, Y | |
133 | is the port name or ID, and Z is the sub-port name or ID. For example, sw1p1s0 | |
134 | would be sub-port 0 on port 1 on switch 1. | |
135 | ||
4ceec22d SF |
136 | Port Features |
137 | ^^^^^^^^^^^^^ | |
138 | ||
139 | NETIF_F_NETNS_LOCAL | |
140 | ||
141 | If the switchdev driver (and device) only supports offloading of the default | |
142 | network namespace (netns), the driver should set this feature flag to prevent | |
143 | the port netdev from being moved out of the default netns. A netns-aware | |
1f5dc44c | 144 | driver/device would not set this flag and be responsible for partitioning |
4ceec22d SF |
145 | hardware to preserve netns containment. This means hardware cannot forward |
146 | traffic from a port in one namespace to another port in another namespace. | |
147 | ||
148 | Port Topology | |
149 | ^^^^^^^^^^^^^ | |
150 | ||
151 | The port netdevs representing the physical switch ports can be organized into | |
152 | higher-level switching constructs. The default construct is a standalone | |
153 | router port, used to offload L3 forwarding. Two or more ports can be bonded | |
154 | together to form a LAG. Two or more ports (or LAGs) can be bridged to bridge | |
d290f1fc | 155 | L2 networks. VLANs can be applied to sub-divide L2 networks. L2-over-L3 |
4ceec22d SF |
156 | tunnels can be built on ports. These constructs are built using standard Linux |
157 | tools such as the bridge driver, the bonding/team drivers, and netlink-based | |
158 | tools such as iproute2. | |
159 | ||
160 | The switchdev driver can know a particular port's position in the topology by | |
161 | monitoring NETDEV_CHANGEUPPER notifications. For example, a port moved into a | |
162 | bond will see it's upper master change. If that bond is moved into a bridge, | |
163 | the bond's upper master will change. And so on. The driver will track such | |
164 | movements to know what position a port is in in the overall topology by | |
165 | registering for netdevice events and acting on NETDEV_CHANGEUPPER. | |
166 | ||
167 | L2 Forwarding Offload | |
168 | --------------------- | |
169 | ||
170 | The idea is to offload the L2 data forwarding (switching) path from the kernel | |
171 | to the switchdev device by mirroring bridge FDB entries down to the device. An | |
172 | FDB entry is the {port, MAC, VLAN} tuple forwarding destination. | |
173 | ||
174 | To offloading L2 bridging, the switchdev driver/device should support: | |
175 | ||
176 | - Static FDB entries installed on a bridge port | |
177 | - Notification of learned/forgotten src mac/vlans from device | |
178 | - STP state changes on the port | |
179 | - VLAN flooding of multicast/broadcast and unknown unicast packets | |
180 | ||
181 | Static FDB Entries | |
182 | ^^^^^^^^^^^^^^^^^^ | |
183 | ||
787a4109 VO |
184 | A driver which implements the ``ndo_fdb_add``, ``ndo_fdb_del`` and |
185 | ``ndo_fdb_dump`` operations is able to support the command below, which adds a | |
186 | static bridge FDB entry:: | |
187 | ||
188 | bridge fdb add dev DEV ADDRESS [vlan VID] [self] static | |
189 | ||
190 | (the "static" keyword is non-optional: if not specified, the entry defaults to | |
191 | being "local", which means that it should not be forwarded) | |
192 | ||
193 | The "self" keyword (optional because it is implicit) has the role of | |
194 | instructing the kernel to fulfill the operation through the ``ndo_fdb_add`` | |
195 | implementation of the ``DEV`` device itself. If ``DEV`` is a bridge port, this | |
196 | will bypass the bridge and therefore leave the software database out of sync | |
197 | with the hardware one. | |
198 | ||
199 | To avoid this, the "master" keyword can be used:: | |
200 | ||
201 | bridge fdb add dev DEV ADDRESS [vlan VID] master static | |
202 | ||
203 | The above command instructs the kernel to search for a master interface of | |
204 | ``DEV`` and fulfill the operation through the ``ndo_fdb_add`` method of that. | |
205 | This time, the bridge generates a ``SWITCHDEV_FDB_ADD_TO_DEVICE`` notification | |
206 | which the port driver can handle and use it to program its hardware table. This | |
207 | way, the software and the hardware database will both contain this static FDB | |
208 | entry. | |
209 | ||
210 | Note: for new switchdev drivers that offload the Linux bridge, implementing the | |
211 | ``ndo_fdb_add`` and ``ndo_fdb_del`` bridge bypass methods is strongly | |
212 | discouraged: all static FDB entries should be added on a bridge port using the | |
213 | "master" flag. The ``ndo_fdb_dump`` is an exception and can be implemented to | |
214 | visualize the hardware tables, if the device does not have an interrupt for | |
215 | notifying the operating system of newly learned/forgotten dynamic FDB | |
216 | addresses. In that case, the hardware FDB might end up having entries that the | |
217 | software FDB does not, and implementing ``ndo_fdb_dump`` is the only way to see | |
218 | them. | |
1f5dc44c | 219 | |
4ceec22d | 220 | Note: by default, the bridge does not filter on VLAN and only bridges untagged |
32c0f0be | 221 | traffic. To enable VLAN support, turn on VLAN filtering:: |
4ceec22d SF |
222 | |
223 | echo 1 >/sys/class/net/<bridge>/bridge/vlan_filtering | |
224 | ||
225 | Notification of Learned/Forgotten Source MAC/VLANs | |
226 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | |
227 | ||
228 | The switch device will learn/forget source MAC address/VLAN on ingress packets | |
229 | and notify the switch driver of the mac/vlan/port tuples. The switch driver, | |
32c0f0be | 230 | in turn, will notify the bridge driver using the switchdev notifier call:: |
4ceec22d | 231 | |
6685987c | 232 | err = call_switchdev_notifiers(val, dev, info, extack); |
4ceec22d | 233 | |
f5ed2feb SF |
234 | Where val is SWITCHDEV_FDB_ADD when learning and SWITCHDEV_FDB_DEL when |
235 | forgetting, and info points to a struct switchdev_notifier_fdb_info. On | |
236 | SWITCHDEV_FDB_ADD, the bridge driver will install the FDB entry into the | |
237 | bridge's FDB and mark the entry as NTF_EXT_LEARNED. The iproute2 bridge | |
32c0f0be | 238 | command will label these entries "offload":: |
4ceec22d SF |
239 | |
240 | $ bridge fdb | |
241 | 52:54:00:12:35:01 dev sw1p1 master br0 permanent | |
242 | 00:02:00:00:02:00 dev sw1p1 master br0 offload | |
243 | 00:02:00:00:02:00 dev sw1p1 self | |
244 | 52:54:00:12:35:02 dev sw1p2 master br0 permanent | |
245 | 00:02:00:00:03:00 dev sw1p2 master br0 offload | |
246 | 00:02:00:00:03:00 dev sw1p2 self | |
247 | 33:33:00:00:00:01 dev eth0 self permanent | |
248 | 01:00:5e:00:00:01 dev eth0 self permanent | |
249 | 33:33:ff:00:00:00 dev eth0 self permanent | |
250 | 01:80:c2:00:00:0e dev eth0 self permanent | |
251 | 33:33:00:00:00:01 dev br0 self permanent | |
252 | 01:00:5e:00:00:01 dev br0 self permanent | |
253 | 33:33:ff:12:35:01 dev br0 self permanent | |
254 | ||
32c0f0be | 255 | Learning on the port should be disabled on the bridge using the bridge command:: |
4ceec22d SF |
256 | |
257 | bridge link set dev DEV learning off | |
258 | ||
32c0f0be | 259 | Learning on the device port should be enabled, as well as learning_sync:: |
4ceec22d SF |
260 | |
261 | bridge link set dev DEV learning on self | |
262 | bridge link set dev DEV learning_sync on self | |
263 | ||
5a784498 | 264 | Learning_sync attribute enables syncing of the learned/forgotten FDB entry to |
4ceec22d SF |
265 | the bridge's FDB. It's possible, but not optimal, to enable learning on the |
266 | device port and on the bridge port, and disable learning_sync. | |
267 | ||
cc0c207a | 268 | To support learning, the driver implements switchdev op |
010c8f01 | 269 | switchdev_port_attr_set for SWITCHDEV_ATTR_PORT_ID_{PRE}_BRIDGE_FLAGS. |
4ceec22d SF |
270 | |
271 | FDB Ageing | |
272 | ^^^^^^^^^^ | |
273 | ||
45ffda75 SF |
274 | The bridge will skip ageing FDB entries marked with NTF_EXT_LEARNED and it is |
275 | the responsibility of the port driver/device to age out these entries. If the | |
276 | port device supports ageing, when the FDB entry expires, it will notify the | |
277 | driver which in turn will notify the bridge with SWITCHDEV_FDB_DEL. If the | |
278 | device does not support ageing, the driver can simulate ageing using a | |
5a784498 | 279 | garbage collection timer to monitor FDB entries. Expired entries will be |
45ffda75 SF |
280 | notified to the bridge using SWITCHDEV_FDB_DEL. See rocker driver for |
281 | example of driver running ageing timer. | |
282 | ||
283 | To keep an NTF_EXT_LEARNED entry "alive", the driver should refresh the FDB | |
284 | entry by calling call_switchdev_notifiers(SWITCHDEV_FDB_ADD, ...). The | |
4ceec22d SF |
285 | notification will reset the FDB entry's last-used time to now. The driver |
286 | should rate limit refresh notifications, for example, no more than once a | |
45ffda75 | 287 | second. (The last-used time is visible using the bridge -s fdb option). |
4ceec22d SF |
288 | |
289 | STP State Change on Port | |
290 | ^^^^^^^^^^^^^^^^^^^^^^^^ | |
291 | ||
292 | Internally or with a third-party STP protocol implementation (e.g. mstpd), the | |
293 | bridge driver maintains the STP state for ports, and will notify the switch | |
f5ed2feb | 294 | driver of STP state change on a port using the switchdev op |
1f868398 | 295 | switchdev_attr_port_set for SWITCHDEV_ATTR_PORT_ID_STP_UPDATE. |
4ceec22d SF |
296 | |
297 | State is one of BR_STATE_*. The switch driver can use STP state updates to | |
298 | update ingress packet filter list for the port. For example, if port is | |
299 | DISABLED, no packets should pass, but if port moves to BLOCKED, then STP BPDUs | |
300 | and other IEEE 01:80:c2:xx:xx:xx link-local multicast packets can pass. | |
301 | ||
302 | Note that STP BDPUs are untagged and STP state applies to all VLANs on the port | |
303 | so packet filters should be applied consistently across untagged and tagged | |
304 | VLANs on the port. | |
305 | ||
306 | Flooding L2 domain | |
307 | ^^^^^^^^^^^^^^^^^^ | |
308 | ||
309 | For a given L2 VLAN domain, the switch device should flood multicast/broadcast | |
310 | and unknown unicast packets to all ports in domain, if allowed by port's | |
311 | current STP state. The switch driver, knowing which ports are within which | |
371e59ad IS |
312 | vlan L2 domain, can program the switch device for flooding. The packet may |
313 | be sent to the port netdev for processing by the bridge driver. The | |
a48037e7 SF |
314 | bridge should not reflood the packet to the same ports the device flooded, |
315 | otherwise there will be duplicate packets on the wire. | |
316 | ||
6bc506b4 IS |
317 | To avoid duplicate packets, the switch driver should mark a packet as already |
318 | forwarded by setting the skb->offload_fwd_mark bit. The bridge driver will mark | |
319 | the skb using the ingress bridge port's mark and prevent it from being forwarded | |
320 | through any bridge port with the same mark. | |
4ceec22d SF |
321 | |
322 | It is possible for the switch device to not handle flooding and push the | |
323 | packets up to the bridge driver for flooding. This is not ideal as the number | |
324 | of ports scale in the L2 domain as the device is much more efficient at | |
325 | flooding packets that software. | |
326 | ||
741af005 IS |
327 | If supported by the device, flood control can be offloaded to it, preventing |
328 | certain netdevs from flooding unicast traffic for which there is no FDB entry. | |
329 | ||
4ceec22d SF |
330 | IGMP Snooping |
331 | ^^^^^^^^^^^^^ | |
332 | ||
4f5590f8 ER |
333 | In order to support IGMP snooping, the port netdevs should trap to the bridge |
334 | driver all IGMP join and leave messages. | |
335 | The bridge multicast module will notify port netdevs on every multicast group | |
336 | changed whether it is static configured or dynamically joined/leave. | |
337 | The hardware implementation should be forwarding all registered multicast | |
338 | traffic groups only to the configured ports. | |
4ceec22d | 339 | |
7616dcbb SF |
340 | L3 Routing Offload |
341 | ------------------ | |
4ceec22d SF |
342 | |
343 | Offloading L3 routing requires that device be programmed with FIB entries from | |
344 | the kernel, with the device doing the FIB lookup and forwarding. The device | |
345 | does a longest prefix match (LPM) on FIB entries matching route prefix and | |
7616dcbb SF |
346 | forwards the packet to the matching FIB entry's nexthop(s) egress ports. |
347 | ||
fd41b0ea JP |
348 | To program the device, the driver has to register a FIB notifier handler |
349 | using register_fib_notifier. The following events are available: | |
7616dcbb | 350 | |
32c0f0be MCC |
351 | =================== =================================================== |
352 | FIB_EVENT_ENTRY_ADD used for both adding a new FIB entry to the device, | |
353 | or modifying an existing entry on the device. | |
354 | FIB_EVENT_ENTRY_DEL used for removing a FIB entry | |
355 | FIB_EVENT_RULE_ADD, | |
356 | FIB_EVENT_RULE_DEL used to propagate FIB rule changes | |
357 | =================== =================================================== | |
358 | ||
359 | FIB_EVENT_ENTRY_ADD and FIB_EVENT_ENTRY_DEL events pass:: | |
7616dcbb | 360 | |
fd41b0ea JP |
361 | struct fib_entry_notifier_info { |
362 | struct fib_notifier_info info; /* must be first */ | |
7616dcbb SF |
363 | u32 dst; |
364 | int dst_len; | |
365 | struct fib_info *fi; | |
366 | u8 tos; | |
367 | u8 type; | |
7616dcbb | 368 | u32 tb_id; |
fd41b0ea JP |
369 | u32 nlflags; |
370 | }; | |
7616dcbb | 371 | |
32c0f0be MCC |
372 | to add/modify/delete IPv4 dst/dest_len prefix on table tb_id. The ``*fi`` |
373 | structure holds details on the route and route's nexthops. ``*dev`` is one | |
374 | of the port netdevs mentioned in the route's next hop list. | |
4ceec22d SF |
375 | |
376 | Routes offloaded to the device are labeled with "offload" in the ip route | |
32c0f0be | 377 | listing:: |
4ceec22d SF |
378 | |
379 | $ ip route show | |
380 | default via 192.168.0.2 dev eth0 | |
381 | 11.0.0.0/30 dev sw1p1 proto kernel scope link src 11.0.0.2 offload | |
382 | 11.0.0.4/30 via 11.0.0.1 dev sw1p1 proto zebra metric 20 offload | |
383 | 11.0.0.8/30 dev sw1p2 proto kernel scope link src 11.0.0.10 offload | |
384 | 11.0.0.12/30 via 11.0.0.9 dev sw1p2 proto zebra metric 20 offload | |
385 | 12.0.0.2 proto zebra metric 30 offload | |
386 | nexthop via 11.0.0.1 dev sw1p1 weight 1 | |
387 | nexthop via 11.0.0.9 dev sw1p2 weight 1 | |
388 | 12.0.0.3 via 11.0.0.1 dev sw1p1 proto zebra metric 20 offload | |
389 | 12.0.0.4 via 11.0.0.9 dev sw1p2 proto zebra metric 20 offload | |
390 | 192.168.0.0/24 dev eth0 proto kernel scope link src 192.168.0.15 | |
391 | ||
fd41b0ea JP |
392 | The "offload" flag is set in case at least one device offloads the FIB entry. |
393 | ||
7616dcbb | 394 | XXX: add/mod/del IPv6 FIB API |
4ceec22d SF |
395 | |
396 | Nexthop Resolution | |
397 | ^^^^^^^^^^^^^^^^^^ | |
398 | ||
399 | The FIB entry's nexthop list contains the nexthop tuple (gateway, dev), but for | |
400 | the switch device to forward the packet with the correct dst mac address, the | |
401 | nexthop gateways must be resolved to the neighbor's mac address. Neighbor mac | |
402 | address discovery comes via the ARP (or ND) process and is available via the | |
403 | arp_tbl neighbor table. To resolve the routes nexthop gateways, the driver | |
404 | should trigger the kernel's neighbor resolution process. See the rocker | |
405 | driver's rocker_port_ipv4_resolve() for an example. | |
406 | ||
407 | The driver can monitor for updates to arp_tbl using the netevent notifier | |
408 | NETEVENT_NEIGH_UPDATE. The device can be programmed with resolved nexthops | |
dd19f83d SF |
409 | for the routes as arp_tbl updates. The driver implements ndo_neigh_destroy |
410 | to know when arp_tbl neighbor entries are purged from the port. | |
0f22ad45 FF |
411 | |
412 | Device driver expected behavior | |
413 | ------------------------------- | |
414 | ||
415 | Below is a set of defined behavior that switchdev enabled network devices must | |
416 | adhere to. | |
417 | ||
418 | Configuration-less state | |
419 | ^^^^^^^^^^^^^^^^^^^^^^^^ | |
420 | ||
421 | Upon driver bring up, the network devices must be fully operational, and the | |
422 | backing driver must configure the network device such that it is possible to | |
423 | send and receive traffic to this network device and it is properly separated | |
424 | from other network devices/ports (e.g.: as is frequent with a switch ASIC). How | |
425 | this is achieved is heavily hardware dependent, but a simple solution can be to | |
426 | use per-port VLAN identifiers unless a better mechanism is available | |
427 | (proprietary metadata for each network port for instance). | |
428 | ||
429 | The network device must be capable of running a full IP protocol stack | |
430 | including multicast, DHCP, IPv4/6, etc. If necessary, it should program the | |
431 | appropriate filters for VLAN, multicast, unicast etc. The underlying device | |
432 | driver must effectively be configured in a similar fashion to what it would do | |
433 | when IGMP snooping is enabled for IP multicast over these switchdev network | |
434 | devices and unsolicited multicast must be filtered as early as possible in | |
435 | the hardware. | |
436 | ||
437 | When configuring VLANs on top of the network device, all VLANs must be working, | |
438 | irrespective of the state of other network devices (e.g.: other ports being part | |
439 | of a VLAN-aware bridge doing ingress VID checking). See below for details. | |
440 | ||
441 | If the device implements e.g.: VLAN filtering, putting the interface in | |
442 | promiscuous mode should allow the reception of all VLAN tags (including those | |
443 | not present in the filter(s)). | |
444 | ||
445 | Bridged switch ports | |
446 | ^^^^^^^^^^^^^^^^^^^^ | |
447 | ||
448 | When a switchdev enabled network device is added as a bridge member, it should | |
449 | not disrupt any functionality of non-bridged network devices and they | |
450 | should continue to behave as normal network devices. Depending on the bridge | |
451 | configuration knobs below, the expected behavior is documented. | |
452 | ||
453 | Bridge VLAN filtering | |
454 | ^^^^^^^^^^^^^^^^^^^^^ | |
455 | ||
456 | The Linux bridge allows the configuration of a VLAN filtering mode (statically, | |
457 | at device creation time, and dynamically, during run time) which must be | |
458 | observed by the underlying switchdev network device/hardware: | |
459 | ||
460 | - with VLAN filtering turned off: the bridge is strictly VLAN unaware and its | |
461 | data path will process all Ethernet frames as if they are VLAN-untagged. | |
462 | The bridge VLAN database can still be modified, but the modifications should | |
463 | have no effect while VLAN filtering is turned off. Frames ingressing the | |
464 | device with a VID that is not programmed into the bridge/switch's VLAN table | |
465 | must be forwarded and may be processed using a VLAN device (see below). | |
466 | ||
467 | - with VLAN filtering turned on: the bridge is VLAN-aware and frames ingressing | |
468 | the device with a VID that is not programmed into the bridges/switch's VLAN | |
469 | table must be dropped (strict VID checking). | |
470 | ||
471 | When there is a VLAN device (e.g: sw0p1.100) configured on top of a switchdev | |
472 | network device which is a bridge port member, the behavior of the software | |
473 | network stack must be preserved, or the configuration must be refused if that | |
474 | is not possible. | |
475 | ||
476 | - with VLAN filtering turned off, the bridge will process all ingress traffic | |
477 | for the port, except for the traffic tagged with a VLAN ID destined for a | |
478 | VLAN upper. The VLAN upper interface (which consumes the VLAN tag) can even | |
479 | be added to a second bridge, which includes other switch ports or software | |
480 | interfaces. Some approaches to ensure that the forwarding domain for traffic | |
481 | belonging to the VLAN upper interfaces are managed properly: | |
cfeb961a | 482 | |
0f22ad45 FF |
483 | * If forwarding destinations can be managed per VLAN, the hardware could be |
484 | configured to map all traffic, except the packets tagged with a VID | |
485 | belonging to a VLAN upper interface, to an internal VID corresponding to | |
486 | untagged packets. This internal VID spans all ports of the VLAN-unaware | |
487 | bridge. The VID corresponding to the VLAN upper interface spans the | |
488 | physical port of that VLAN interface, as well as the other ports that | |
489 | might be bridged with it. | |
490 | * Treat bridge ports with VLAN upper interfaces as standalone, and let | |
491 | forwarding be handled in the software data path. | |
492 | ||
493 | - with VLAN filtering turned on, these VLAN devices can be created as long as | |
494 | the bridge does not have an existing VLAN entry with the same VID on any | |
495 | bridge port. These VLAN devices cannot be enslaved into the bridge since they | |
496 | duplicate functionality/use case with the bridge's VLAN data path processing. | |
497 | ||
498 | Non-bridged network ports of the same switch fabric must not be disturbed in any | |
499 | way by the enabling of VLAN filtering on the bridge device(s). If the VLAN | |
500 | filtering setting is global to the entire chip, then the standalone ports | |
501 | should indicate to the network stack that VLAN filtering is required by setting | |
502 | 'rx-vlan-filter: on [fixed]' in the ethtool features. | |
503 | ||
504 | Because VLAN filtering can be turned on/off at runtime, the switchdev driver | |
505 | must be able to reconfigure the underlying hardware on the fly to honor the | |
506 | toggling of that option and behave appropriately. If that is not possible, the | |
507 | switchdev driver can also refuse to support dynamic toggling of the VLAN | |
508 | filtering knob at runtime and require a destruction of the bridge device(s) and | |
509 | creation of new bridge device(s) with a different VLAN filtering value to | |
510 | ensure VLAN awareness is pushed down to the hardware. | |
511 | ||
512 | Even when VLAN filtering in the bridge is turned off, the underlying switch | |
513 | hardware and driver may still configure itself in a VLAN-aware mode provided | |
514 | that the behavior described above is observed. | |
515 | ||
516 | The VLAN protocol of the bridge plays a role in deciding whether a packet is | |
517 | treated as tagged or not: a bridge using the 802.1ad protocol must treat both | |
518 | VLAN-untagged packets, as well as packets tagged with 802.1Q headers, as | |
519 | untagged. | |
520 | ||
521 | The 802.1p (VID 0) tagged packets must be treated in the same way by the device | |
522 | as untagged packets, since the bridge device does not allow the manipulation of | |
523 | VID 0 in its database. | |
524 | ||
525 | When the bridge has VLAN filtering enabled and a PVID is not configured on the | |
6b38c571 | 526 | ingress port, untagged and 802.1p tagged packets must be dropped. When the bridge |
0f22ad45 FF |
527 | has VLAN filtering enabled and a PVID exists on the ingress port, untagged and |
528 | priority-tagged packets must be accepted and forwarded according to the | |
529 | bridge's port membership of the PVID VLAN. When the bridge has VLAN filtering | |
530 | disabled, the presence/lack of a PVID should not influence the packet | |
531 | forwarding decision. | |
532 | ||
533 | Bridge IGMP snooping | |
534 | ^^^^^^^^^^^^^^^^^^^^ | |
535 | ||
536 | The Linux bridge allows the configuration of IGMP snooping (statically, at | |
537 | interface creation time, or dynamically, during runtime) which must be observed | |
538 | by the underlying switchdev network device/hardware in the following way: | |
539 | ||
540 | - when IGMP snooping is turned off, multicast traffic must be flooded to all | |
541 | ports within the same bridge that have mcast_flood=true. The CPU/management | |
542 | port should ideally not be flooded (unless the ingress interface has | |
543 | IFF_ALLMULTI or IFF_PROMISC) and continue to learn multicast traffic through | |
544 | the network stack notifications. If the hardware is not capable of doing that | |
545 | then the CPU/management port must also be flooded and multicast filtering | |
546 | happens in software. | |
547 | ||
548 | - when IGMP snooping is turned on, multicast traffic must selectively flow | |
549 | to the appropriate network ports (including CPU/management port). Flooding of | |
550 | unknown multicast should be only towards the ports connected to a multicast | |
551 | router (the local device may also act as a multicast router). | |
552 | ||
553 | The switch must adhere to RFC 4541 and flood multicast traffic accordingly | |
554 | since that is what the Linux bridge implementation does. | |
555 | ||
556 | Because IGMP snooping can be turned on/off at runtime, the switchdev driver | |
557 | must be able to reconfigure the underlying hardware on the fly to honor the | |
558 | toggling of that option and behave appropriately. | |
559 | ||
560 | A switchdev driver can also refuse to support dynamic toggling of the multicast | |
561 | snooping knob at runtime and require the destruction of the bridge device(s) | |
562 | and creation of a new bridge device(s) with a different multicast snooping | |
563 | value. |