net: dsa: felix: manage host flooding using a specific driver callback

At the time - commit 7569459a52c9 ("net: dsa: manage flooding on the CPU
ports") - not introducing a dedicated switch callback for host flooding
made sense, because for the only user, the felix driver, there was
nothing different to do for the CPU port than set the flood flags on the
CPU port just like on any other bridge port.

There are 2 reasons why this approach is not good enough, however.

(1) Other drivers, like sja1105, support configuring flooding as a
    function of {ingress port, egress port}, whereas the DSA
    ->port_bridge_flags() function only operates on an egress port.
    So with that driver we'd have useless host flooding from user ports
    which don't need it.

(2) Even with the felix driver, support for multiple CPU ports makes it
    difficult to piggyback on ->port_bridge_flags(). The way in which
    the felix driver is going to support host-filtered addresses with
    multiple CPU ports is that it will direct these addresses towards
    both CPU ports (in a sort of multicast fashion), then restrict the
    forwarding to only one of the two using the forwarding masks.
    Consequently, flooding will also be enabled towards both CPU ports.
    However, ->port_bridge_flags() gets passed the index of a single CPU
    port, and that leaves the flood settings out of sync between the 2
    CPU ports.

This is to say, it's better to have a specific driver method for host
flooding, which takes the user port as argument. This solves problem (1)
by allowing the driver to do different things for different user ports,
and problem (2) by abstracting the operation and letting the driver do
whatever, rather than explicitly making the DSA core point to the CPU
port it thinks needs to be touched.

This new method also creates a problem, which is that cross-chip setups
are not handled. However I don't have hardware right now where I can
test what is the proper thing to do, and there isn't hardware compatible
with multi-switch trees that supports host flooding. So it remains a
problem to be tackled in the future.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

3 files changed, 15 insertions, 30 deletions

diff --git a/net/dsa/dsa_priv.h b/net/dsa/dsa_priv.h
index 7c9abd5a0ab9..d9722e49864b 100644
--- a/net/dsa/dsa_priv.h
+++ b/net/dsa/dsa_priv.h
@@ -291,6 +291,7 @@ int dsa_port_hsr_join(struct dsa_port *dp, struct net_device *hsr);
 void dsa_port_hsr_leave(struct dsa_port *dp, struct net_device *hsr);
 int dsa_port_tag_8021q_vlan_add(struct dsa_port *dp, u16 vid, bool broadcast);
 void dsa_port_tag_8021q_vlan_del(struct dsa_port *dp, u16 vid, bool broadcast);
+void dsa_port_set_host_flood(struct dsa_port *dp, bool uc, bool mc);
 
 /* slave.c */
 extern const struct dsa_device_ops notag_netdev_ops;
diff --git a/net/dsa/port.c b/net/dsa/port.c
index ecf0395cbddd..3738f2d40a0b 100644
--- a/net/dsa/port.c
+++ b/net/dsa/port.c
@@ -920,6 +920,14 @@ int dsa_port_bridge_flags(struct dsa_port *dp,
 	return 0;
 }
 
+void dsa_port_set_host_flood(struct dsa_port *dp, bool uc, bool mc)
+{
+	struct dsa_switch *ds = dp->ds;
+
+	if (ds->ops->port_set_host_flood)
+		ds->ops->port_set_host_flood(ds, dp->index, uc, mc);
+}
+
 int dsa_port_vlan_msti(struct dsa_port *dp,
 		       const struct switchdev_vlan_msti *msti)
 {
diff --git a/net/dsa/slave.c b/net/dsa/slave.c
index 5ee0aced9410..801a5d445833 100644
--- a/net/dsa/slave.c
+++ b/net/dsa/slave.c
@@ -262,37 +262,13 @@ static int dsa_slave_close(struct net_device *dev)
 	return 0;
 }
 
-/* Keep flooding enabled towards this port's CPU port as long as it serves at
- * least one port in the tree that requires it.
- */
-static void dsa_port_manage_cpu_flood(struct dsa_port *dp)
+static void dsa_slave_manage_host_flood(struct net_device *dev)
 {
-	struct switchdev_brport_flags flags = {
-		.mask = BR_FLOOD | BR_MCAST_FLOOD,
-	};
-	struct dsa_switch_tree *dst = dp->ds->dst;
-	struct dsa_port *cpu_dp = dp->cpu_dp;
-	struct dsa_port *other_dp;
-	int err;
-
-	list_for_each_entry(other_dp, &dst->ports, list) {
-		if (!dsa_port_is_user(other_dp))
-			continue;
-
-		if (other_dp->cpu_dp != cpu_dp)
-			continue;
-
-		if (other_dp->slave->flags & IFF_ALLMULTI)
-			flags.val |= BR_MCAST_FLOOD;
-		if (other_dp->slave->flags & IFF_PROMISC)
-			flags.val |= BR_FLOOD | BR_MCAST_FLOOD;
-	}
-
-	err = dsa_port_pre_bridge_flags(dp, flags, NULL);
-	if (err)
-		return;
+	bool mc = dev->flags & (IFF_PROMISC | IFF_ALLMULTI);
+	struct dsa_port *dp = dsa_slave_to_port(dev);
+	bool uc = dev->flags & IFF_PROMISC;
 
-	dsa_port_bridge_flags(cpu_dp, flags, NULL);
+	dsa_port_set_host_flood(dp, uc, mc);
 }
 
 static void dsa_slave_change_rx_flags(struct net_device *dev, int change)
@@ -310,7 +286,7 @@ static void dsa_slave_change_rx_flags(struct net_device *dev, int change)
 
 	if (dsa_switch_supports_uc_filtering(ds) &&
 	    dsa_switch_supports_mc_filtering(ds))
-		dsa_port_manage_cpu_flood(dp);
+		dsa_slave_manage_host_flood(dev);
 }
 
 static void dsa_slave_set_rx_mode(struct net_device *dev)