[PATCH net 0/2] net: dsa: realtek: rtl8365mb: fix FDB lookups in VLAN-unaware bridges

[Stijn Cleynhens <stijncleynhens@gmail.com>]

In a VLAN-unaware bridge, DSA installs FDB and MDB entries with VID 0,
but the switch classifies untagged frames to the bridge PVID and looks up
VID 0 by FID, while the driver installs IVL entries. Nothing matches, so
a station that roams from behind a user port to behind the CPU port (a
Wi-Fi client moving between access points) stays unreachable until the
learned entry ages out.

Patch 1 makes VID 0 use IVL; patch 2 depends on it. Patch 2 keeps the
neutral PVID (VID 0) on ports of a VLAN-unaware bridge and only programs
the bridge PVID while the port filters VLANs. Tagged frames in a
VLAN-unaware bridge are not covered, see patch 2.

Tested on OpenWrt's 6.18 kernel, which carries the rtl8365mb backports up
to v7.4; the code these patches touch is the same as in net. On an
RTL8367S-VB (TP-Link Deco X50-PoE, with the family D series applied): a
station learned behind the uplink that moves behind the CPU port answers
10/10 pings right away, its stale entry replaced by the CPU one, and
switching VLAN filtering off and on at runtime keeps traffic flowing. An
earlier revision of patch 2, with the same logic, was tested the same way
on an RTL8367S (Deco X50-Outdoor), 0/10 before and 10/10 after. Both
patches build without warnings with W=1 C=1.

Note for Mieczyslaw's RTL8367S-VB series in net-next (v8): patch 2 adds a
vlan_filtering argument to rtl8365mb_vlan_pvid_port_clear(). The family D
path that series adds there reads dsa_port_is_vlan_filtering(), which
still returns the old state while filtering is being turned off, so it
should take the new argument instead; otherwise family D drops untagged
frames after filtering is disabled. Happy to send that as a follow-up
once both are in.

Stijn Cleynhens (2):
  net: dsa: realtek: rtl8365mb: use IVL in VLAN 0
  net: dsa: realtek: rtl8365mb: keep the neutral PVID in VLAN-unaware
    bridges

 drivers/net/dsa/realtek/rtl8365mb_main.c | 147 ++++++++++++++++-------
 drivers/net/dsa/realtek/rtl8365mb_vlan.c |  40 +++++-
 drivers/net/dsa/realtek/rtl8365mb_vlan.h |   4 +-
 3 files changed, 141 insertions(+), 50 deletions(-)


base-commit: 787268686c64be60023743b527645a907e38ccca
-- 
2.56.0