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>

1 files changed, 4 insertions, 24 deletions

diff --git a/net/dsa/tag_sja1105.c b/net/dsa/tag_sja1105.c
index 9c2df9ece01b..7c92c329a092 100644
--- a/net/dsa/tag_sja1105.c
+++ b/net/dsa/tag_sja1105.c
@@ -358,20 +358,6 @@ static struct sk_buff
 	return skb;
 }
 
-static void sja1105_decode_subvlan(struct sk_buff *skb, u16 subvlan)
-{
-	struct dsa_port *dp = dsa_slave_to_port(skb->dev);
-	struct sja1105_port *sp = dp->priv;
-	u16 vid = sp->subvlan_map[subvlan];
-	u16 vlan_tci;
-
-	if (vid == VLAN_N_VID)
-		return;
-
-	vlan_tci = (skb->priority << VLAN_PRIO_SHIFT) | vid;
-	__vlan_hwaccel_put_tag(skb, htons(ETH_P_8021Q), vlan_tci);
-}
-
 static bool sja1105_skb_has_tag_8021q(const struct sk_buff *skb)
 {
 	u16 tpid = ntohs(eth_hdr(skb)->h_proto);
@@ -389,8 +375,8 @@ static struct sk_buff *sja1105_rcv(struct sk_buff *skb,
 				   struct net_device *netdev,
 				   struct packet_type *pt)
 {
-	int source_port, switch_id, subvlan = 0;
 	struct sja1105_meta meta = {0};
+	int source_port, switch_id;
 	struct ethhdr *hdr;
 	bool is_link_local;
 	bool is_meta;
@@ -403,7 +389,7 @@ static struct sk_buff *sja1105_rcv(struct sk_buff *skb,
 
 	if (sja1105_skb_has_tag_8021q(skb)) {
 		/* Normal traffic path. */
-		dsa_8021q_rcv(skb, &source_port, &switch_id, &subvlan);
+		dsa_8021q_rcv(skb, &source_port, &switch_id);
 	} else if (is_link_local) {
 		/* Management traffic path. Switch embeds the switch ID and
 		 * port ID into bytes of the destination MAC, courtesy of
@@ -428,9 +414,6 @@ static struct sk_buff *sja1105_rcv(struct sk_buff *skb,
 		return NULL;
 	}
 
-	if (subvlan)
-		sja1105_decode_subvlan(skb, subvlan);
-
 	return sja1105_rcv_meta_state_machine(skb, &meta, is_link_local,
 					      is_meta);
 }
@@ -538,7 +521,7 @@ static struct sk_buff *sja1110_rcv(struct sk_buff *skb,
 				   struct net_device *netdev,
 				   struct packet_type *pt)
 {
-	int source_port = -1, switch_id = -1, subvlan = 0;
+	int source_port = -1, switch_id = -1;
 
 	skb->offload_fwd_mark = 1;
 
@@ -551,7 +534,7 @@ static struct sk_buff *sja1110_rcv(struct sk_buff *skb,
 
 	/* Packets with in-band control extensions might still have RX VLANs */
 	if (likely(sja1105_skb_has_tag_8021q(skb)))
-		dsa_8021q_rcv(skb, &source_port, &switch_id, &subvlan);
+		dsa_8021q_rcv(skb, &source_port, &switch_id);
 
 	skb->dev = dsa_master_find_slave(netdev, switch_id, source_port);
 	if (!skb->dev) {
@@ -561,9 +544,6 @@ static struct sk_buff *sja1110_rcv(struct sk_buff *skb,
 		return NULL;
 	}
 
-	if (subvlan)
-		sja1105_decode_subvlan(skb, subvlan);
-
 	return skb;
 }