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

Vladimir Oltean
2021-03-20T11:13:10Z

On Fri, Mar 19, 2021 at 03:08:46PM -0700, Florian Fainelli wrote:
>
>
> 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

The reworded version has an equal number of lines, but at least it
catches errors now:

static void dsa_port_clear_brport_flags(struct dsa_port *dp,
struct netlink_ext_ack *extack)
{
const unsigned long val = BR_FLOOD | BR_MCAST_FLOOD | BR_BCAST_FLOOD;
const unsigned long mask = BR_LEARNING | BR_FLOOD | BR_MCAST_FLOOD |
BR_BCAST_FLOOD;
int flag, err;

for_each_set_bit(flag, &mask, 32) {
struct switchdev_brport_flags flags = {0};

flags.mask = BIT(flag);
flags.val = val & BIT(flag);

err = dsa_port_bridge_flags(dp, flags, extack);
if (err && err != -EOPNOTSUPP)
dev_err(dp->ds->dev,
"failed to clear bridge port flag %d: %d (%pe)\n",
flag, err, ERR_PTR(err));
}
}