linux-stable/Documentation/networking/dsa
Vladimir Oltean d27656d02d docs: net: dsa: sja1105: document limitations of tc-flower rule VLAN awareness
After change "net: dsa: tag_8021q: replace the SVL bridging with
VLAN-unaware IVL bridging", tag_8021q enforces two different pvids on a
port, depending on whether it is standalone or in a VLAN-unaware bridge.

Up until now, there was a single pvid, represented by
dsa_tag_8021q_rx_vid(), and that was used as the VLAN for VLAN-unaware
virtual link rules, regardless of whether the port was bridged or
standalone.

To keep VLAN-unaware virtual links working, we need to follow whether
the port is in a bridge or not, and update the VLAN ID from those rules.

In fact we can't fully do that. Depending on whether the switch is
VLAN-aware or not, we can accept Virtual Link rules with just the MAC
DA, or with a MAC DA and a VID. So we already deny changes to the VLAN
awareness of the switch. But the VLAN awareness may also change as a
result of joining or leaving a bridge.

One might say we could just allow the following: a port may leave a
VLAN-unaware bridge while it has VLAN-unaware VL (tc-flower) rules, and
the driver will update those with the new tag_8021q pvid for standalone
mode, but the driver won't accept joining a bridge at all while VL rules
were installed in standalone mode. This is sort of a compromise made
because leaving a bridge is an operation that cannot be vetoed.
But this sort of setup change is not fully supported, either: as
mentioned, VLAN filtering changes can also be triggered by leaving a
bridge, therefore, the existing veto we have in place for turning VLAN
filtering off with VLAN-aware VL rules active still isn't fully
effective.

I really don't know how to deal with this in a way that produces
predictable behavior for user space. Since at the moment, keeping this
feature fully functional on constellation changes (not changing the
tag_8021q port pvid when joining a bridge) is blocking progress for the
DSA FDB isolation, I'd rather document it as a (potentially temporary)
limitation and go on without it.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2022-02-27 11:06:13 +00:00
..
b53.rst Documentation: net: dsa: b53: Describe b53 configuration 2019-07-08 15:30:13 -07:00
bcm_sf2.rst Documentation: net: dsa: transition to the rst format 2019-04-12 16:48:35 -07:00
configuration.rst net: dsa: delete dsa_legacy_fdb_add and dsa_legacy_fdb_del 2021-06-29 10:46:23 -07:00
dsa.rst docs: net: dsa: document the new methods for bridge TX forwarding offload 2021-08-22 09:49:04 +01:00
index.rst Documentation: net: dsa: b53: Describe b53 configuration 2019-07-08 15:30:13 -07:00
lan9303.rst Documentation: net: dsa: transition to the rst format 2019-04-12 16:48:35 -07:00
sja1105.rst docs: net: dsa: sja1105: document limitations of tc-flower rule VLAN awareness 2022-02-27 11:06:13 +00:00