net: dsa: sja1105: delete the best_effort_vlan_filtering mode

Simply put, the best-effort VLAN filtering mode relied on VLAN retagging
from a bridge VLAN towards a tag_8021q sub-VLAN in order to be able to
decode the source port in the tagger, but the VLAN retagging
implementation inside the sja1105 chips is not the best and we were
relying on marginal operating conditions.

The most notable limitation of the best-effort VLAN filtering mode is
its incapacity to treat this case properly:

ip link add br0 type bridge vlan_filtering 1
ip link set swp2 master br0
ip link set swp4 master br0
bridge vlan del dev swp4 vid 1
bridge vlan add dev swp4 vid 1 pvid

When sending an untagged packet through swp2, the expectation is for it
to be forwarded to swp4 as egress-tagged (so it will contain VLAN ID 1
on egress). But the switch will send it as egress-untagged.

There was an attempt to fix this here:
https://patchwork.kernel.org/project/netdevbpf/patch/20210407201452.1703261-2-olteanv@gmail.com/

but it failed miserably because it broke PTP RX timestamping, in a way
that cannot be corrected due to hardware issues related to VLAN
retagging.

So with either PTP broken or pushing VLAN headers on egress for untagged
packets being broken, the sad reality is that the best-effort VLAN
filtering code is broken. Delete it.

Note that this means there will be a temporary loss of functionality in
this driver until it is replaced with something better (network stack
RX/TX capability for "mode 2" as described in
Documentation/networking/dsa/sja1105.rst, the "port under VLAN-aware
bridge" case). We simply cannot keep this code until that driver rework
is done, it is super bloated and tangled with tag_8021q.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 1 insertions, 9 deletions

diff --git a/include/linux/dsa/8021q.h b/include/linux/dsa/8021q.h
index 1587961f1a7b..608607f904a5 100644
--- a/include/linux/dsa/8021q.h
+++ b/include/linux/dsa/8021q.h
@@ -35,8 +35,6 @@ struct dsa_8021q_context {
 	__be16 proto;
 };
 
-#define DSA_8021Q_N_SUBVLAN			8
-
 int dsa_8021q_setup(struct dsa_8021q_context *ctx, bool enabled);
 
 int dsa_8021q_crosschip_bridge_join(struct dsa_8021q_context *ctx, int port,
@@ -50,21 +48,16 @@ int dsa_8021q_crosschip_bridge_leave(struct dsa_8021q_context *ctx, int port,
 struct sk_buff *dsa_8021q_xmit(struct sk_buff *skb, struct net_device *netdev,
 			       u16 tpid, u16 tci);
 
-void dsa_8021q_rcv(struct sk_buff *skb, int *source_port, int *switch_id,
-		   int *subvlan);
+void dsa_8021q_rcv(struct sk_buff *skb, int *source_port, int *switch_id);
 
 u16 dsa_8021q_tx_vid(struct dsa_switch *ds, int port);
 
 u16 dsa_8021q_rx_vid(struct dsa_switch *ds, int port);
 
-u16 dsa_8021q_rx_vid_subvlan(struct dsa_switch *ds, int port, u16 subvlan);
-
 int dsa_8021q_rx_switch_id(u16 vid);
 
 int dsa_8021q_rx_source_port(u16 vid);
 
-u16 dsa_8021q_rx_subvlan(u16 vid);
-
 bool vid_is_dsa_8021q_rxvlan(u16 vid);
 
 bool vid_is_dsa_8021q_txvlan(u16 vid);
diff --git a/include/linux/dsa/sja1105.h b/include/linux/dsa/sja1105.h
index b6089b88314c..0eadc7ac44ec 100644
--- a/include/linux/dsa/sja1105.h
+++ b/include/linux/dsa/sja1105.h
@@ -59,7 +59,6 @@ struct sja1105_skb_cb {
 	((struct sja1105_skb_cb *)((skb)->cb))
 
 struct sja1105_port {
-	u16 subvlan_map[DSA_8021Q_N_SUBVLAN];
 	struct kthread_worker *xmit_worker;
 	struct kthread_work xmit_work;
 	struct sk_buff_head xmit_queue;