Re: [RFC PATCH v2 net-next 03/16] net: dsa: inherit the actual bridge port flags at join time

Florian Fainelli
2021-03-19T22:10:05Z

On 3/18/2021 4:18 PM, Vladimir Oltean wrote:
> From: Vladimir Oltean <vladimir.oltean@nxp.com>
>
> DSA currently assumes that the bridge port starts off with this
> constellation of bridge port flags:
>
> - learning on
> - unicast flooding on
> - multicast flooding on
> - broadcast flooding on
>
> just by virtue of code copy-pasta from the bridge layer (new_nbp).
> This was a simple enough strategy thus far, because the 'bridge join'
> moment always coincided with the 'bridge port creation' moment.
>
> But with sandwiched interfaces, such as:
>
> br0
> |
> bond0
> |
> swp0
>
> it may happen that the user has had time to change the bridge port flags
> of bond0 before enslaving swp0 to it. In that case, swp0 will falsely
> assume that the bridge port flags are those determined by new_nbp, when
> in fact this can happen:
>
> ip link add br0 type bridge
> ip link add bond0 type bond
> ip link set bond0 master br0
> ip link set bond0 type bridge_slave learning off
> ip link set swp0 master br0
>
> Now swp0 has learning enabled, bond0 has learning disabled. Not nice.
>
> Fix this by "dumpster diving" through the actual bridge port flags with
> br_port_flag_is_set, at bridge join time.
>
> We use this opportunity to split dsa_port_change_brport_flags into two
> distinct functions called dsa_port_inherit_brport_flags and
> dsa_port_clear_brport_flags, now that the implementation for the two
> cases is no longer similar.
>
> Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
> ---
> net/dsa/port.c | 123 ++++++++++++++++++++++++++++++++-----------------
> 1 file changed, 82 insertions(+), 41 deletions(-)
>
> diff --git a/net/dsa/port.c b/net/dsa/port.c
> index fcbe5b1545b8..346c50467810 100644
> --- a/net/dsa/port.c
> +++ b/net/dsa/port.c
> @@ -122,26 +122,82 @@ void dsa_port_disable(struct dsa_port *dp)
> rtnl_unlock();
> }
>
> -static void dsa_port_change_brport_flags(struct dsa_port *dp,
> - bool bridge_offload)
> +static void dsa_port_clear_brport_flags(struct dsa_port *dp,
> + struct netlink_ext_ack *extack)
> {
> struct switchdev_brport_flags flags;
> - int flag;
>
> - flags.mask = BR_LEARNING | BR_FLOOD | BR_MCAST_FLOOD | BR_BCAST_FLOOD;
> - if (bridge_offload)
> - flags.val = flags.mask;
> - else
> - flags.val = flags.mask & ~BR_LEARNING;
> + flags.mask = BR_LEARNING;
> + flags.val = 0;
> + dsa_port_bridge_flags(dp, flags, extack);

Would not you want to use the same for_each_set_bit() loop that
dsa_port_change_br_flags() uses, that would be a tad more compact.
--
Florian