On Sat, Apr 12, 2025 at 02:24:27PM +0200, Jonas Gorski wrote:
> When adding a bridge vlan that is pvid or untagged after the vlan has
> already been added to any other switchdev backed port, the vlan change
> will be propagated as changed, since the flags change.
>
> This causes the vlan to not be added to the hardware for DSA switches,
> since the DSA handler ignores any vlans for the CPU or DSA ports that
> are changed.
>
> E.g. the following order of operations would work:
>
> $ ip link add swbridge type bridge vlan_filtering 1 vlan_default_pvid 1
> $ ip link set lan1 master swbridge
> $ bridge vlan add dev swbridge vid 1 pvid untagged self
> $ bridge vlan add dev lan1 vid 1 pvid untagged
>
> but this order would brake:
nitpick: s/brake/break/
>
> $ ip link add swbridge type bridge vlan_filtering 1 vlan_default_pvid 1
> $ ip link set lan1 master swbridge
> $ bridge vlan add dev lan1 vid 1 pvid untagged
> $ bridge vlan add dev swbridge vid 1 pvid untagged self
>
> Additionally, the vlan on the bridge itself would become undeletable:
>
> $ bridge vlan
> port vlan-id
> lan1 1 PVID Egress Untagged
> swbridge 1 PVID Egress Untagged
> $ bridge vlan del dev swbridge vid 1 self
> $ bridge vlan
> port vlan-id
> lan1 1 PVID Egress Untagged
> swbridge 1 Egress Untagged
>
> since the vlan was never added to DSA's vlan list, so deleting it will
> cause an error, causing the bridge code to not remove it.
>
> Fix this by checking if flags changed only for vlans that are already
> brentry and pass changed as false for those that become brentries, as
> these are a new vlan (member) from the switchdev point of view.
>
> Fixes: 8d23a54f5bee ("net: bridge: switchdev: differentiate new VLANs from
> changed ones")
> Signed-off-by: Jonas Gorski <jonas.gor...@gmail.com>
> ---
> net/bridge/br_vlan.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/net/bridge/br_vlan.c b/net/bridge/br_vlan.c
> index d9a69ec9affe..939a3aa78d5c 100644
> --- a/net/bridge/br_vlan.c
> +++ b/net/bridge/br_vlan.c
> @@ -715,8 +715,8 @@ static int br_vlan_add_existing(struct net_bridge *br,
> u16 flags, bool *changed,
> struct netlink_ext_ack *extack)
> {
> - bool would_change = __vlan_flags_would_change(vlan, flags);
> bool becomes_brentry = false;
> + bool would_change = false;
> int err;
>
> if (!br_vlan_is_brentry(vlan)) {
> @@ -725,6 +725,8 @@ static int br_vlan_add_existing(struct net_bridge *br,
> return -EINVAL;
>
> becomes_brentry = true;
> + } else {
> + would_change = __vlan_flags_would_change(vlan, flags);
> }
>
> /* Master VLANs that aren't brentries weren't notified before,
> --
> 2.43.0
>
You might want to mention that "bool *changed" is used later in
br_process_vlan_info() to make a decision whether to call
br_vlan_notify(RTM_NEWVLAN) or not. We want to notify switchdev with
changed=false, but we want to keep notifying the change to rtnetlink.
The rtnetlink notification still happens even if we don't set
would_change here, because it depends on this code snippet:
if (becomes_brentry) {
...
*changed = true;
...
}
and not on this one:
if (would_change)
*changed = true;
That was my only concern with this change (I had missed the first snippet
when initially reading the code), and I didn't see in the commit log
some sort of attention paid to this detail.
With that:
Reviewed-by: Vladimir Oltean <vladimir.olt...@nxp.com>
