From: Florian Fainelli <f.faine...@gmail.com> This patch provides details on the expected behavior of switchdev enabled network devices when operating in a "stand alone" mode, as well as when being bridge members. This clarifies a number of things that recently came up during a bug fixing session on the b53 DSA switch driver.
Signed-off-by: Florian Fainelli <f.faine...@gmail.com> Signed-off-by: Vladimir Oltean <vladimir.olt...@nxp.com> --- Documentation/networking/switchdev.rst | 120 +++++++++++++++++++++++++ 1 file changed, 120 insertions(+) diff --git a/Documentation/networking/switchdev.rst b/Documentation/networking/switchdev.rst index ddc3f35775dc..9fb3e0fd39dc 100644 --- a/Documentation/networking/switchdev.rst +++ b/Documentation/networking/switchdev.rst @@ -385,3 +385,123 @@ The driver can monitor for updates to arp_tbl using the netevent notifier NETEVENT_NEIGH_UPDATE. The device can be programmed with resolved nexthops for the routes as arp_tbl updates. The driver implements ndo_neigh_destroy to know when arp_tbl neighbor entries are purged from the port. + +Device driver expected behavior +------------------------------- + +Below is a set of defined behavior that switchdev enabled network devices must +adhere to. + +Configuration-less state +^^^^^^^^^^^^^^^^^^^^^^^^ + +Upon driver bring up, the network devices must be fully operational, and the +backing driver must configure the network device such that it is possible to +send and receive traffic to this network device and it is properly separated +from other network devices/ports (e.g.: as is frequent with a switch ASIC). How +this is achieved is heavily hardware dependent, but a simple solution can be to +use per-port VLAN identifiers unless a better mechanism is available +(proprietary metadata for each network port for instance). + +The network device must be capable of running a full IP protocol stack +including multicast, DHCP, IPv4/6, etc. If necessary, it should program the +appropriate filters for VLAN, multicast, unicast etc. The underlying device +driver must effectively be configured in a similar fashion to what it would do +when IGMP snooping is enabled for IP multicast over these switchdev network +devices and unsolicited multicast must be filtered as early as possible into +the hardware. + +When configuring VLANs on top of the network device, all VLANs must be working, +irrespective of the state of other network devices (e.g.: other ports being part +of a VLAN-aware bridge doing ingress VID checking). See below for details. + +If the device implements e.g.: VLAN filtering, putting the interface in +promiscuous mode should allow the reception of all VLAN tags (including those +not present in the filter(s)). + +Bridged switch ports +^^^^^^^^^^^^^^^^^^^^ + +When a switchdev enabled network device is added as a bridge member, it should +not disrupt any functionality of non-bridged network devices and they +should continue to behave as normal network devices. Depending on the bridge +configuration knobs below, the expected behavior is documented. + +Bridge VLAN filtering +^^^^^^^^^^^^^^^^^^^^^ + +The Linux bridge allows the configuration of a VLAN filtering mode (statically, +at device creation time, and dynamically, during run time) which must be +observed by the underlying switchdev network device/hardware: + +- with VLAN filtering turned off: the bridge is strictly VLAN unaware and its + data path will only process untagged Ethernet frames. Frames ingressing the + device with a VID that is not programmed into the bridge/switch's VLAN table + must be forwarded and may be processed using a VLAN device (see below). + +- with VLAN filtering turned on: the bridge is VLAN-aware and frames ingressing + the device with a VID that is not programmed into the bridges/switch's VLAN + table must be dropped (strict VID checking). + +Non-bridged network ports of the same switch fabric must not be disturbed in any +way by the enabling of VLAN filtering on the bridge device(s). + +VLAN devices configured on top of a switchdev network device (e.g: sw0p1.100) +which is a bridge port member must also observe the following behavior: + +- with VLAN filtering turned off, enslaving VLAN devices into the bridge might + be allowed provided that there is sufficient separation using e.g.: a + reserved VLAN ID (4095 for instance) for untagged traffic. The VLAN data path + is used to pop/push the VLAN tag such that the bridge's data path only + processes untagged traffic. + +- with VLAN filtering turned on, these VLAN devices can be created as long as + there is not an existing VLAN entry into the bridge with an identical VID and + port membership. These VLAN devices cannot be enslaved into the bridge since + they duplicate functionality/use case with the bridge's VLAN data path + processing. + +Because VLAN filtering can be turned on/off at runtime, the switchdev driver +must be able to reconfigure the underlying hardware on the fly to honor the +toggling of that option and behave appropriately. + +A switchdev driver can also refuse to support dynamic toggling of the VLAN +filtering knob at runtime and require a destruction of the bridge device(s) and +creation of new bridge device(s) with a different VLAN filtering value to +ensure VLAN awareness is pushed down to the hardware. + +Finally, even when VLAN filtering in the bridge is turned off, the underlying +switch hardware and driver may still configured itself in a VLAN-aware mode +provided that the behavior described above is observed. + +Bridge IGMP snooping +^^^^^^^^^^^^^^^^^^^^ + +The Linux bridge allows the configuration of IGMP snooping (statically, at +interface creation time, or dynamically, during runtime) which must be observed +by the underlying switchdev network device/hardware in the following way: + +- when IGMP snooping is turned off, multicast traffic must be flooded to all + ports within the same bridge that have mcast_flood=true. The CPU/management + port should ideally not be flooded (unless the ingress interface has + IFF_ALLMULTI or IFF_PROMISC) and continue to learn multicast traffic through + the network stack notifications. If the hardware is not capable of doing that + then the CPU/management port must also be flooded and multicast filtering + happens in software. + +- when IGMP snooping is turned on, multicast traffic must selectively flow + to the appropriate network ports (including CPU/management port). Flooding of + unknown multicast should be only towards the ports connected to a multicast + router (the local device may also act as a multicast router). + +The switch must adhere to RFC 4541 and flood multicast traffic accordingly +since that is what the Linux bridge implementation does. + +Because IGMP snooping can be turned on/off at runtime, the switchdev driver +must be able to reconfigure the underlying hardware on the fly to honor the +toggling of that option and behave appropriately. + +A switchdev driver can also refuse to support dynamic toggling of the multicast +snooping knob at runtime and require the destruction of the bridge device(s) +and creation of a new bridge device(s) with a different multicast snooping +value. -- 2.25.1
