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  1. 18 Mar, 2022 34 commits
  3. 17 Mar, 2022 6 commits
    • Jakub Kicinski's avatar
      Merge branch 'net-bridge-multiple-spanning-trees' · 82e94d41
      Jakub Kicinski authored 
      Tobias Waldekranz says:

====================
net: bridge: Multiple Spanning Trees

The bridge has had per-VLAN STP support for a while now, since:

https://lore.kernel.org/netdev/20200124114022.10883-1-nikolay@cumulusnetworks.com/

The current implementation has some problems:

- The mapping from VLAN to STP state is fixed as 1:1, i.e. each VLAN
  is managed independently. This is awkward from an MSTP (802.1Q-2018,
  Clause 13.5) point of view, where the model is that multiple VLANs
  are grouped into MST instances.

  Because of the way that the standard is written, presumably, this is
  also reflected in hardware implementations. It is not uncommon for a
  switch to support the full 4k range of VIDs, but that the pool of
  MST instances is much smaller. Some examples:

  Marvell LinkStreet (mv88e6xxx): 4k VLANs, but only 64 MSTIs
  Marvell Prestera: 4k VLANs, but only 128 MSTIs
  Microchip SparX-5i: 4k VLANs, but only 128 MSTIs

- By default, the feature is enabled, and there is no way to disable
  it. This makes it hard to add offloading in a backwards compatible
  way, since any underlying switchdevs have no way to refuse the
  function if the hardware does not support it

- The port-global STP state has precedence over per-VLAN states. In
  MSTP, as far as I understand it, all VLANs will use the common
  spanning tree (CST) by default - through traffic engineering you can
  then optimize your network to group subsets of VLANs to use
  different trees (MSTI). To my understanding, the way this is
  typically managed in silicon is roughly:

  Incoming packet:
  .----.----.--------------.----.-------------
  | DA | SA | 802.1Q VID=X | ET | Payload ...
  '----'----'--------------'----'-------------
                        |
                        '->|\     .----------------------------.
                           | +--> | VID | Members | ... | MSTI |
                   PVID -->|/     |-----|---------|-----|------|
                                  |   1 | 0001001 | ... |    0 |
                                  |   2 | 0001010 | ... |   10 |
                                  |   3 | 0001100 | ... |   10 |
                                  '----------------------------'
                                                             |
                               .-----------------------------'
                               |  .------------------------.
                               '->| MSTI | Fwding | Lrning |
                                  |------|--------|--------|
                                  |    0 | 111110 | 111110 |
                                  |   10 | 110111 | 110111 |
                                  '------------------------'

  What this is trying to show is that the STP state (whether MSTP is
  used, or ye olde STP) is always accessed via the VLAN table. If STP
  is running, all MSTI pointers in that table will reference the same
  index in the STP stable - if MSTP is running, some VLANs may point
  to other trees (like in this example).

  The fact that in the Linux bridge, the global state (think: index 0
  in most hardware implementations) is supposed to override the
  per-VLAN state, is very awkward to offload. In effect, this means
  that when the global state changes to blocking, drivers will have to
  iterate over all MSTIs in use, and alter them all to match. This
  also means that you have to cache whether the hardware state is
  currently tracking the global state or the per-VLAN state. In the
  first case, you also have to cache the per-VLAN state so that you
  can restore it if the global state transitions back to forwarding.

This series adds a new mst_enable bridge setting (as suggested by Nik)
that can only be changed when no VLANs are configured on the
bridge. Enabling this mode has the following effect:

- The port-global STP state is used to represent the CST (Common
  Spanning Tree) (1/15)

- Ingress STP filtering is deferred until the frame's VLAN has been
  resolved (1/15)

- The preexisting per-VLAN states can no longer be controlled directly
  (1/15). They are instead placed under the MST module's control,
  which is managed using a new netlink interface (described in 3/15)

- VLANs can br mapped to MSTIs in an arbitrary M:N fashion, using a
  new global VLAN option (2/15)

Switchdev notifications are added so that a driver can track:
- MST enabled state
- VID to MSTI mappings
- MST port states

An offloading implementation is this provided for mv88e6xxx.
====================

Link: https://lore.kernel.org/r/20220316150857.2442916-1-tobias@waldekranz.comSigned-off-by: default avatarJakub Kicinski <kuba@kernel.org>
      82e94d41
    • Tobias Waldekranz's avatar
      net: dsa: mv88e6xxx: MST Offloading · acaf4d2e
      Tobias Waldekranz authored 
      Allocate a SID in the STU for each MSTID in use by a bridge and handle
the mapping of MSTIDs to VLANs using the SID field of each VTU entry.
Signed-off-by: default avatarTobias Waldekranz <tobias@waldekranz.com>
Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
      acaf4d2e
    • Tobias Waldekranz's avatar
      net: dsa: mv88e6xxx: Export STU as devlink region · 7dc96039
      Tobias Waldekranz authored 
      Export the raw STU data in a devlink region so that it can be
inspected from userspace and compared to the current bridge
configuration.
Signed-off-by: default avatarTobias Waldekranz <tobias@waldekranz.com>
Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
      7dc96039
    • Tobias Waldekranz's avatar
      net: dsa: mv88e6xxx: Disentangle STU from VTU · 49c98c1d
      Tobias Waldekranz authored 
      In early LinkStreet silicon (e.g. 6095/6185), the per-VLAN STP states
were kept in the VTU - there was no concept of a SID. Later, the
information was split into two tables, where the VTU only tracked
memberships and deferred the STP state tracking to the STU via a
pointer (SID). This meant that a group of VLANs could share the same
STU entry. Most likely, this was done to align with MSTP (802.1Q-2018,
Clause 13), which is built on this principle.

While the VTU is still 4k lines on most devices, the STU is capped at
64 entries. This means that the current stategy, updating STU info
whenever a VTU entry is updated, can not easily support MSTP because:

- The maximum number of VIDs would also be capped at 64, as we would
  have to allocate one SID for every VTU entry - even if many VLANs
  would effectively share the same MST.

- MSTP updates would be unnecessarily slow as you would have to
  iterate over all VLANs that share the same MST.

In order to support MSTP offloading in the future, manage the STU as a
separate entity from the VTU.

Only add support for newer hardware with separate VTU and
STU. VTU-only devices can also be supported, but essentially this
requires a software implementation of an STU (fanning out state
changed to all VLANs tied to the same MST).
Signed-off-by: default avatarTobias Waldekranz <tobias@waldekranz.com>
Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
      49c98c1d
    • Tobias Waldekranz's avatar
      net: dsa: Handle MST state changes · 7414af30
      Tobias Waldekranz authored 
      Add the usual trampoline functionality from the generic DSA layer down
to the drivers for MST state changes.

When a state changes to disabled/blocking/listening, make sure to fast
age any dynamic entries in the affected VLANs (those controlled by the
MSTI in question).
Signed-off-by: default avatarTobias Waldekranz <tobias@waldekranz.com>
Reviewed-by: default avatarVladimir Oltean <olteanv@gmail.com>
Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
      7414af30
    • Tobias Waldekranz's avatar
      net: dsa: Pass VLAN MSTI migration notifications to driver · 8e6598a7
      Tobias Waldekranz authored 
      Add the usual trampoline functionality from the generic DSA layer down
to the drivers for VLAN MSTI migrations.
Signed-off-by: default avatarTobias Waldekranz <tobias@waldekranz.com>
Reviewed-by: default avatarVladimir Oltean <olteanv@gmail.com>
Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
      8e6598a7
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