netdev - [PATCH net 4/4] net: dsa: mv88e6xxx: Limit rsvd2cpu policy to user ports on 6393X

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Message-ID: <20241206130824.3784213-5-tobias@waldekranz.com>
Date: Fri,  6 Dec 2024 14:07:36 +0100
From: Tobias Waldekranz <tobias@...dekranz.com>
To: davem@...emloft.net,
	kuba@...nel.org
Cc: andrew@...n.ch,
	f.fainelli@...il.com,
	olteanv@...il.com,
	netdev@...r.kernel.org,
	linux@...linux.org.uk,
	chris.packham@...iedtelesis.co.nz
Subject: [PATCH net 4/4] net: dsa: mv88e6xxx: Limit rsvd2cpu policy to user ports on 6393X

For packets with a DA in the IEEE reserved L2 group range, originating
from a CPU, forward it as normal, rather than classifying it as
management.

Example use-case:

     bridge (group_fwd_mask 0x4000)
     / |  \
 swp1 swp2 tap0
   \   /
(mv88e6xxx)

We've created a bridge with a non-zero group_fwd_mask (allowing LLDP
in this example) containing a set of ports managed by mv88e6xxx and
some foreign interface (e.g. an L2 VPN tunnel).

Since an LLDP packet coming in to the bridge from the other side of
tap0 is eligable for tx forward offloading, a FORWARD frame destined
for swp1 and swp2 would be send to the conduit interface.

Before this change, due to rsvd2cpu being enabled on the CPU port, the
switch would try to trap it back to the CPU. Given that the CPU is
trusted, instead assume that it indeed meant for the packet to be
forwarded like any other.

Signed-off-by: Tobias Waldekranz <tobias@...dekranz.com>
---
 drivers/net/dsa/mv88e6xxx/port.c | 31 +++++++++++++++++++++++++------
 1 file changed, 25 insertions(+), 6 deletions(-)

diff --git a/drivers/net/dsa/mv88e6xxx/port.c b/drivers/net/dsa/mv88e6xxx/port.c
index 56ed2f57fef8..bf6d558c112c 100644
--- a/drivers/net/dsa/mv88e6xxx/port.c
+++ b/drivers/net/dsa/mv88e6xxx/port.c
@@ -1416,6 +1416,23 @@ static int mv88e6393x_port_policy_write_all(struct mv88e6xxx_chip *chip,
 	return 0;
 }
 
+static int mv88e6393x_port_policy_write_user(struct mv88e6xxx_chip *chip,
+					     u16 pointer, u8 data)
+{
+	int err, port;
+
+	for (port = 0; port < mv88e6xxx_num_ports(chip); port++) {
+		if (!dsa_is_user_port(chip->ds, port))
+			continue;
+
+		err = mv88e6393x_port_policy_write(chip, port, pointer, data);
+		if (err)
+			return err;
+	}
+
+	return 0;
+}
+
 int mv88e6393x_set_egress_port(struct mv88e6xxx_chip *chip,
 			       enum mv88e6xxx_egress_direction direction,
 			       int port)
@@ -1457,26 +1474,28 @@ int mv88e6393x_port_mgmt_rsvd2cpu(struct mv88e6xxx_chip *chip)
 	int err;
 
 	/* Consider the frames with reserved multicast destination
-	 * addresses matching 01:80:c2:00:00:00 and
-	 * 01:80:c2:00:00:02 as MGMT.
+	 * addresses matching 01:80:c2:00:00:00 and 01:80:c2:00:00:02
+	 * as MGMT when received on user ports. Forward as normal on
+	 * CPU/DSA ports, to support bridges with non-zero
+	 * group_fwd_masks.
 	 */
 	ptr = MV88E6393X_PORT_POLICY_MGMT_CTL_PTR_01C280000000XLO;
-	err = mv88e6393x_port_policy_write_all(chip, ptr, 0xff);
+	err = mv88e6393x_port_policy_write_user(chip, ptr, 0xff);
 	if (err)
 		return err;
 
 	ptr = MV88E6393X_PORT_POLICY_MGMT_CTL_PTR_01C280000000XHI;
-	err = mv88e6393x_port_policy_write_all(chip, ptr, 0xff);
+	err = mv88e6393x_port_policy_write_user(chip, ptr, 0xff);
 	if (err)
 		return err;
 
 	ptr = MV88E6393X_PORT_POLICY_MGMT_CTL_PTR_01C280000002XLO;
-	err = mv88e6393x_port_policy_write_all(chip, ptr, 0xff);
+	err = mv88e6393x_port_policy_write_user(chip, ptr, 0xff);
 	if (err)
 		return err;
 
 	ptr = MV88E6393X_PORT_POLICY_MGMT_CTL_PTR_01C280000002XHI;
-	err = mv88e6393x_port_policy_write_all(chip, ptr, 0xff);
+	err = mv88e6393x_port_policy_write_user(chip, ptr, 0xff);
 	if (err)
 		return err;
 
-- 
2.43.0