netdev - [PATCH net-next 1/9] net: bridge: update BROPT_VLAN_ENABLED before notifying switchdev in br_vlan_filter

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Date:   Mon, 26 Jul 2021 19:55:28 +0300
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     netdev@...r.kernel.org, Jakub Kicinski <kuba@...nel.org>,
        "David S. Miller" <davem@...emloft.net>
Cc:     Florian Fainelli <f.fainelli@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Roopa Prabhu <roopa@...dia.com>,
        Nikolay Aleksandrov <nikolay@...dia.com>,
        Ido Schimmel <idosch@...dia.com>, Jiri Pirko <jiri@...dia.com>
Subject: [PATCH net-next 1/9] net: bridge: update BROPT_VLAN_ENABLED before notifying switchdev in br_vlan_filter_toggle

SWITCHDEV_ATTR_ID_BRIDGE_VLAN_FILTERING is notified by the bridge from
two places:
- nbp_vlan_init(), during bridge port creation
- br_vlan_filter_toggle(), during a netlink/sysfs/ioctl change requested
  by user space

If a switchdev driver uses br_vlan_enabled(br_dev) inside its handler
for the SWITCHDEV_ATTR_ID_BRIDGE_VLAN_FILTERING attribute notifier,
different things will be seen depending on whether the bridge calls from
the first path or the second:
- in nbp_vlan_init(), br_vlan_enabled() reflects the current state of
  the bridge
- in br_vlan_filter_toggle(), br_vlan_enabled() reflects the past state
  of the bridge

This can lead in some cases to complications in driver implementation,
which can be avoided if these could reliably use br_vlan_enabled().

Nothing seems to depend on this behavior, and it seems overall more
straightforward for br_vlan_enabled() to return the proper value even
during the SWITCHDEV_ATTR_ID_BRIDGE_VLAN_FILTERING notifier, so
temporarily enable the bridge option, then revert it if the switchdev
notifier failed.

Cc: Roopa Prabhu <roopa@...dia.com>
Cc: Nikolay Aleksandrov <nikolay@...dia.com>
Cc: Ido Schimmel <idosch@...dia.com>
Cc: Jiri Pirko <jiri@...dia.com>
Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>
---
 net/bridge/br_vlan.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/net/bridge/br_vlan.c b/net/bridge/br_vlan.c
index 325600361487..805206f31795 100644
--- a/net/bridge/br_vlan.c
+++ b/net/bridge/br_vlan.c
@@ -840,11 +840,14 @@ int br_vlan_filter_toggle(struct net_bridge *br, unsigned long val,
 	if (br_opt_get(br, BROPT_VLAN_ENABLED) == !!val)
 		return 0;
 
+	br_opt_toggle(br, BROPT_VLAN_ENABLED, !!val);
+
 	err = switchdev_port_attr_set(br->dev, &attr, extack);
-	if (err && err != -EOPNOTSUPP)
+	if (err && err != -EOPNOTSUPP) {
+		br_opt_toggle(br, BROPT_VLAN_ENABLED, !val);
 		return err;
+	}
 
-	br_opt_toggle(br, BROPT_VLAN_ENABLED, !!val);
 	br_manage_promisc(br);
 	recalculate_group_addr(br);
 	br_recalculate_fwd_mask(br);
-- 
2.25.1