1. 18 Mar, 2022 34 commits
  2. 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