netdev - [PATCH v3 net-next 03/11] net: bridge: vlan: make __vlan_add

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Message-Id: <20220215170218.2032432-4-vladimir.oltean@nxp.com>
Date:   Tue, 15 Feb 2022 19:02:10 +0200
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     netdev@...r.kernel.org
Cc:     Jakub Kicinski <kuba@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Florian Fainelli <f.fainelli@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        Roopa Prabhu <roopa@...dia.com>,
        Nikolay Aleksandrov <nikolay@...dia.com>,
        Jiri Pirko <jiri@...dia.com>, Ido Schimmel <idosch@...dia.com>,
        Rafael Richter <rafael.richter@....de>,
        Daniel Klauer <daniel.klauer@....de>,
        Tobias Waldekranz <tobias@...dekranz.com>
Subject: [PATCH v3 net-next 03/11] net: bridge: vlan: make __vlan_add_flags react only to PVID and UNTAGGED

Currently there is a very subtle aspect to the behavior of
__vlan_add_flags(): it changes the struct net_bridge_vlan flags and
pvid, yet it returns true ("changed") even if none of those changed,
just a transition of br_vlan_is_brentry(v) took place from false to
true.

This can be seen in br_vlan_add_existing(), however we do not actually
rely on this subtle behavior, since the "if" condition that checks that
the vlan wasn't a brentry before had a useless (until now) assignment:

	*changed = true;

Make things more obvious by actually making __vlan_add_flags() do what's
written on the box, and be more specific about what is actually written
on the box. This is needed because further transformations will be done
to __vlan_add_flags().

Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>
---
v2->v3: patch is new

 net/bridge/br_vlan.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/bridge/br_vlan.c b/net/bridge/br_vlan.c
index 498cc297b492..89e2cfed7bdb 100644
--- a/net/bridge/br_vlan.c
+++ b/net/bridge/br_vlan.c
@@ -58,7 +58,9 @@ static bool __vlan_delete_pvid(struct net_bridge_vlan_group *vg, u16 vid)
 	return true;
 }
 
-/* return true if anything changed, false otherwise */
+/* Returns true if the BRIDGE_VLAN_INFO_PVID and BRIDGE_VLAN_INFO_UNTAGGED bits
+ * of @flags produced any change onto @v, false otherwise
+ */
 static bool __vlan_add_flags(struct net_bridge_vlan *v, u16 flags)
 {
 	struct net_bridge_vlan_group *vg;
@@ -80,7 +82,7 @@ static bool __vlan_add_flags(struct net_bridge_vlan *v, u16 flags)
 	else
 		v->flags &= ~BRIDGE_VLAN_INFO_UNTAGGED;
 
-	return ret || !!(old_flags ^ v->flags);
+	return ret || !!((old_flags ^ v->flags) & BRIDGE_VLAN_INFO_UNTAGGED);
 }
 
 static int __vlan_vid_add(struct net_device *dev, struct net_bridge *br,
-- 
2.25.1