5.15-stable review patch. If anyone has any objections, please let me know.
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From: Vladimir Oltean vladimir.oltean@nxp.com
[ Upstream commit 498625a8ab2c8e1c9ab5105744310e8d6952cc01 ]
It has been reported that when under a bridge with stp_state=1, the logs get spammed with this message:
[ 251.734607] fsl_dpaa2_eth dpni.5 eth0: Couldn't decode source port
Further debugging shows the following info associated with packets: source_port=-1, switch_id=-1, vid=-1, vbid=1
In other words, they are data plane packets which are supposed to be decoded by dsa_tag_8021q_find_port_by_vbid(), but the latter (correctly) refuses to do so, because no switch port is currently in BR_STATE_LEARNING or BR_STATE_FORWARDING - so the packet is effectively unexpected.
The error goes away after the port progresses to BR_STATE_LEARNING in 15 seconds (the default forward_time of the bridge), because then, dsa_tag_8021q_find_port_by_vbid() can correctly associate the data plane packets with a plausible bridge port in a plausible STP state.
Re-reading IEEE 802.1D-1990, I see the following:
"4.4.2 Learning: (...) The Forwarding Process shall discard received frames."
IEEE 802.1D-2004 further clarifies:
"DISABLED, BLOCKING, LISTENING, and BROKEN all correspond to the DISCARDING port state. While those dot1dStpPortStates serve to distinguish reasons for discarding frames, the operation of the Forwarding and Learning processes is the same for all of them. (...) LISTENING represents a port that the spanning tree algorithm has selected to be part of the active topology (computing a Root Port or Designated Port role) but is temporarily discarding frames to guard against loops or incorrect learning."
Well, this is not what the driver does - instead it sets mac[port].ingress = true.
To get rid of the log spam, prevent unexpected data plane packets to be received by software by discarding them on ingress in the LISTENING state.
In terms of blame attribution: the prints only date back to commit d7f9787a763f ("net: dsa: tag_8021q: add support for imprecise RX based on the VBID"). However, the settings would permit a LISTENING port to forward to a FORWARDING port, and the standard suggests that's not OK.
Fixes: 640f763f98c2 ("net: dsa: sja1105: Add support for Spanning Tree Protocol") Signed-off-by: Vladimir Oltean vladimir.oltean@nxp.com Link: https://patch.msgid.link/20250509113816.2221992-1-vladimir.oltean@nxp.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/net/dsa/sja1105/sja1105_main.c | 6 +----- 1 file changed, 1 insertion(+), 5 deletions(-)
diff --git a/drivers/net/dsa/sja1105/sja1105_main.c b/drivers/net/dsa/sja1105/sja1105_main.c index 888f10d93b9ab..ec1c0ad591184 100644 --- a/drivers/net/dsa/sja1105/sja1105_main.c +++ b/drivers/net/dsa/sja1105/sja1105_main.c @@ -1969,6 +1969,7 @@ static void sja1105_bridge_stp_state_set(struct dsa_switch *ds, int port, switch (state) { case BR_STATE_DISABLED: case BR_STATE_BLOCKING: + case BR_STATE_LISTENING: /* From UM10944 description of DRPDTAG (why put this there?): * "Management traffic flows to the port regardless of the state * of the INGRESS flag". So BPDUs are still be allowed to pass. @@ -1978,11 +1979,6 @@ static void sja1105_bridge_stp_state_set(struct dsa_switch *ds, int port, mac[port].egress = false; mac[port].dyn_learn = false; break; - case BR_STATE_LISTENING: - mac[port].ingress = true; - mac[port].egress = false; - mac[port].dyn_learn = false; - break; case BR_STATE_LEARNING: mac[port].ingress = true; mac[port].egress = false;