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, 12 insertions, 65 deletions

diff --git a/net/dsa/tag_8021q.c b/net/dsa/tag_8021q.c
index 4aa29f90ecea..d657864969d4 100644
--- a/net/dsa/tag_8021q.c
+++ b/net/dsa/tag_8021q.c
@@ -17,7 +17,7 @@
  *
  * | 11  | 10  |  9  |  8  |  7  |  6  |  5  |  4  |  3  |  2  |  1  |  0  |
  * +-----------+-----+-----------------+-----------+-----------------------+
- * |    DIR    | SVL |    SWITCH_ID    |  SUBVLAN  |          PORT         |
+ * |    DIR    | RSV |    SWITCH_ID    |    RSV    |          PORT         |
  * +-----------+-----+-----------------+-----------+-----------------------+
  *
  * DIR - VID[11:10]:
@@ -27,24 +27,13 @@
  *	These values make the special VIDs of 0, 1 and 4095 to be left
  *	unused by this coding scheme.
  *
- * SVL/SUBVLAN - { VID[9], VID[5:4] }:
- *	Sub-VLAN encoding. Valid only when DIR indicates an RX VLAN.
- *	* 0 (0b000): Field does not encode a sub-VLAN, either because
- *	received traffic is untagged, PVID-tagged or because a second
- *	VLAN tag is present after this tag and not inside of it.
- *	* 1 (0b001): Received traffic is tagged with a VID value private
- *	to the host. This field encodes the index in the host's lookup
- *	table through which the value of the ingress VLAN ID can be
- *	recovered.
- *	* 2 (0b010): Field encodes a sub-VLAN.
- *	...
- *	* 7 (0b111): Field encodes a sub-VLAN.
- *	When DIR indicates a TX VLAN, SUBVLAN must be transmitted as zero
- *	(by the host) and ignored on receive (by the switch).
- *
  * SWITCH_ID - VID[8:6]:
  *	Index of switch within DSA tree. Must be between 0 and 7.
  *
+ * RSV - VID[5:4]:
+ *	To be used for further expansion of PORT or for other purposes.
+ *	Must be transmitted as zero and ignored on receive.
+ *
  * PORT - VID[3:0]:
  *	Index of switch port. Must be between 0 and 15.
  */
@@ -61,18 +50,6 @@
 #define DSA_8021Q_SWITCH_ID(x)		(((x) << DSA_8021Q_SWITCH_ID_SHIFT) & \
 						 DSA_8021Q_SWITCH_ID_MASK)
 
-#define DSA_8021Q_SUBVLAN_HI_SHIFT	9
-#define DSA_8021Q_SUBVLAN_HI_MASK	GENMASK(9, 9)
-#define DSA_8021Q_SUBVLAN_LO_SHIFT	4
-#define DSA_8021Q_SUBVLAN_LO_MASK	GENMASK(5, 4)
-#define DSA_8021Q_SUBVLAN_HI(x)		(((x) & GENMASK(2, 2)) >> 2)
-#define DSA_8021Q_SUBVLAN_LO(x)		((x) & GENMASK(1, 0))
-#define DSA_8021Q_SUBVLAN(x)		\
-		(((DSA_8021Q_SUBVLAN_LO(x) << DSA_8021Q_SUBVLAN_LO_SHIFT) & \
-		  DSA_8021Q_SUBVLAN_LO_MASK) | \
-		 ((DSA_8021Q_SUBVLAN_HI(x) << DSA_8021Q_SUBVLAN_HI_SHIFT) & \
-		  DSA_8021Q_SUBVLAN_HI_MASK))
-
 #define DSA_8021Q_PORT_SHIFT		0
 #define DSA_8021Q_PORT_MASK		GENMASK(3, 0)
 #define DSA_8021Q_PORT(x)		(((x) << DSA_8021Q_PORT_SHIFT) & \
@@ -98,13 +75,6 @@ u16 dsa_8021q_rx_vid(struct dsa_switch *ds, int port)
 }
 EXPORT_SYMBOL_GPL(dsa_8021q_rx_vid);
 
-u16 dsa_8021q_rx_vid_subvlan(struct dsa_switch *ds, int port, u16 subvlan)
-{
-	return DSA_8021Q_DIR_RX | DSA_8021Q_SWITCH_ID(ds->index) |
-	       DSA_8021Q_PORT(port) | DSA_8021Q_SUBVLAN(subvlan);
-}
-EXPORT_SYMBOL_GPL(dsa_8021q_rx_vid_subvlan);
-
 /* Returns the decoded switch ID from the RX VID. */
 int dsa_8021q_rx_switch_id(u16 vid)
 {
@@ -119,20 +89,6 @@ int dsa_8021q_rx_source_port(u16 vid)
 }
 EXPORT_SYMBOL_GPL(dsa_8021q_rx_source_port);
 
-/* Returns the decoded subvlan from the RX VID. */
-u16 dsa_8021q_rx_subvlan(u16 vid)
-{
-	u16 svl_hi, svl_lo;
-
-	svl_hi = (vid & DSA_8021Q_SUBVLAN_HI_MASK) >>
-		 DSA_8021Q_SUBVLAN_HI_SHIFT;
-	svl_lo = (vid & DSA_8021Q_SUBVLAN_LO_MASK) >>
-		 DSA_8021Q_SUBVLAN_LO_SHIFT;
-
-	return (svl_hi << 2) | svl_lo;
-}
-EXPORT_SYMBOL_GPL(dsa_8021q_rx_subvlan);
-
 bool vid_is_dsa_8021q_rxvlan(u16 vid)
 {
 	return (vid & DSA_8021Q_DIR_MASK) == DSA_8021Q_DIR_RX;
@@ -227,7 +183,7 @@ static int dsa_8021q_setup_port(struct dsa_8021q_context *ctx, int port,
 	u16 rx_vid = dsa_8021q_rx_vid(ctx->ds, port);
 	u16 tx_vid = dsa_8021q_tx_vid(ctx->ds, port);
 	struct net_device *master;
-	int i, err, subvlan;
+	int i, err;
 
 	/* The CPU port is implicitly configured by
 	 * configuring the front-panel ports
@@ -275,18 +231,11 @@ static int dsa_8021q_setup_port(struct dsa_8021q_context *ctx, int port,
 		return err;
 	}
 
-	/* Add to the master's RX filter not only @rx_vid, but in fact
-	 * the entire subvlan range, just in case this DSA switch might
-	 * want to use sub-VLANs.
-	 */
-	for (subvlan = 0; subvlan < DSA_8021Q_N_SUBVLAN; subvlan++) {
-		u16 vid = dsa_8021q_rx_vid_subvlan(ctx->ds, port, subvlan);
-
-		if (enabled)
-			vlan_vid_add(master, ctx->proto, vid);
-		else
-			vlan_vid_del(master, ctx->proto, vid);
-	}
+	/* Add @rx_vid to the master's RX filter. */
+	if (enabled)
+		vlan_vid_add(master, ctx->proto, rx_vid);
+	else
+		vlan_vid_del(master, ctx->proto, rx_vid);
 
 	/* Finally apply the TX VID on this port and on the CPU port */
 	err = dsa_8021q_vid_apply(ctx, port, tx_vid, BRIDGE_VLAN_INFO_UNTAGGED,
@@ -471,8 +420,7 @@ struct sk_buff *dsa_8021q_xmit(struct sk_buff *skb, struct net_device *netdev,
 }
 EXPORT_SYMBOL_GPL(dsa_8021q_xmit);
 
-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 vid, tci;
 
@@ -489,7 +437,6 @@ void dsa_8021q_rcv(struct sk_buff *skb, int *source_port, int *switch_id,
 
 	*source_port = dsa_8021q_rx_source_port(vid);
 	*switch_id = dsa_8021q_rx_switch_id(vid);
-	*subvlan = dsa_8021q_rx_subvlan(vid);
 	skb->priority = (tci & VLAN_PRIO_MASK) >> VLAN_PRIO_SHIFT;
 }
 EXPORT_SYMBOL_GPL(dsa_8021q_rcv);