[RFC PATCH v2 net-next 07/16] net: dsa: sync ageing time when joining the bridge

[Vladimir Oltean <olteanv@gmail.com>]

From: Vladimir Oltean <vladimir.oltean@nxp.com>

The SWITCHDEV_ATTR_ID_BRIDGE_AGEING_TIME attribute is only emitted from:

sysfs/ioctl/netlink
-> br_set_ageing_time
   -> __set_ageing_time

therefore not at bridge port creation time, so:
(a) drivers had to hardcode the initial value for the address ageing time,
    because they didn't get any notification
(b) that hardcoded value can be out of sync, if the user changes the
    ageing time before enslaving the port to the bridge

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
---
 include/linux/if_bridge.h |  6 ++++++
 net/bridge/br_stp.c       | 13 +++++++++++++
 net/dsa/port.c            | 10 ++++++++++
 3 files changed, 29 insertions(+)

diff --git a/include/linux/if_bridge.h b/include/linux/if_bridge.h
index 920d3a02cc68..ebd16495459c 100644
--- a/include/linux/if_bridge.h
+++ b/include/linux/if_bridge.h
@@ -137,6 +137,7 @@ struct net_device *br_fdb_find_port(const struct net_device *br_dev,
 void br_fdb_clear_offload(const struct net_device *dev, u16 vid);
 bool br_port_flag_is_set(const struct net_device *dev, unsigned long flag);
 u8 br_port_get_stp_state(const struct net_device *dev);
+clock_t br_get_ageing_time(struct net_device *br_dev);
 #else
 static inline struct net_device *
 br_fdb_find_port(const struct net_device *br_dev,
@@ -160,6 +161,11 @@ static inline u8 br_port_get_stp_state(const struct net_device *dev)
 {
 	return BR_STATE_DISABLED;
 }
+
+static inline clock_t br_get_ageing_time(struct net_device *br_dev)
+{
+	return 0;
+}
 #endif
 
 #endif
diff --git a/net/bridge/br_stp.c b/net/bridge/br_stp.c
index 86b5e05d3f21..3dafb6143cff 100644
--- a/net/bridge/br_stp.c
+++ b/net/bridge/br_stp.c
@@ -639,6 +639,19 @@ int br_set_ageing_time(struct net_bridge *br, clock_t ageing_time)
 	return 0;
 }
 
+clock_t br_get_ageing_time(struct net_device *br_dev)
+{
+	struct net_bridge *br;
+
+	if (!netif_is_bridge_master(br_dev))
+		return 0;
+
+	br = netdev_priv(br_dev);
+
+	return jiffies_to_clock_t(br->ageing_time);
+}
+EXPORT_SYMBOL_GPL(br_get_ageing_time);
+
 /* called under bridge lock */
 void __br_set_topology_change(struct net_bridge *br, unsigned char val)
 {
diff --git a/net/dsa/port.c b/net/dsa/port.c
index 8380509ee47c..9fde2371e1bc 100644
--- a/net/dsa/port.c
+++ b/net/dsa/port.c
@@ -173,6 +173,7 @@ static int dsa_port_switchdev_sync(struct dsa_port *dp,
 {
 	struct net_device *brport_dev = dsa_port_to_bridge_port(dp);
 	struct net_device *br = dp->bridge_dev;
+	clock_t ageing_time;
 	u8 stp_state;
 	int err;
 
@@ -193,6 +194,11 @@ static int dsa_port_switchdev_sync(struct dsa_port *dp,
 	if (err && err != -EOPNOTSUPP)
 		return err;
 
+	ageing_time = br_get_ageing_time(br);
+	err = dsa_port_ageing_time(dp, ageing_time);
+	if (err && err != -EOPNOTSUPP)
+		return err;
+
 	return 0;
 }
 
@@ -222,6 +228,10 @@ static void dsa_port_switchdev_unsync(struct dsa_port *dp)
 	 * allow this in standalone mode too.
 	 */
 	dsa_port_mrouter(dp->cpu_dp, true, NULL);
+
+	/* Ageing time may be global to the switch chip, so don't change it
+	 * here because we have no good reason (or value) to change it to.
+	 */
 }
 
 int dsa_port_bridge_join(struct dsa_port *dp, struct net_device *br,
-- 
2.25.1