net: dsa: sja1105: fix leakage of flooded frames outside bridging domain

Quite embarrasingly, I managed to fool myself into thinking that the
flooding domain of sja1105 source ports is restricted by the forwarding
domain, which it isn't. Frames which match an FDB entry are forwarded
towards that entry's DESTPORTS restricted by REACH_PORT[SRC_PORT], while
frames that don't match any FDB entry are forwarded towards
FL_DOMAIN[SRC_PORT] or BC_DOMAIN[SRC_PORT].

This means we can't get away with doing the simple thing, and we must
manage the flooding domain ourselves such that it is restricted by the
forwarding domain. This new function must be called from the
.port_bridge_join and .port_bridge_leave methods too, not just from
.port_bridge_flags as we did before.

Fixes: 4d942354 ("net: dsa: sja1105: offload bridge port flags to device")
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/sja1105/sja1105.h

@@ -206,6 +206,8 @@ struct sja1105_private {
 	bool rgmii_tx_delay[SJA1105_NUM_PORTS];
 	bool best_effort_vlan_filtering;
 	unsigned long learn_ena;
+	unsigned long ucast_egress_floods;
+	unsigned long bcast_egress_floods;
 	const struct sja1105_info *info;
 	struct gpio_desc *reset_gpio;
 	struct spi_device *spidev;

drivers/net/dsa/sja1105/sja1105_main.c

@@ -50,6 +50,12 @@ sja1105_port_allow_traffic(struct sja1105_l2_forwarding_entry *l2_fwd,
 		l2_fwd[from].reach_port &= ~BIT(to);
 }
 
+static bool sja1105_can_forward(struct sja1105_l2_forwarding_entry *l2_fwd,
+				int from, int to)
+{
+	return !!(l2_fwd[from].reach_port & BIT(to));
+}
+
 /* Structure used to temporarily transport device tree
  * settings into sja1105_setup
  */
@@ -408,6 +414,12 @@ static int sja1105_init_l2_forwarding(struct sja1105_private *priv)
 		for (j = 0; j < SJA1105_NUM_TC; j++)
 			l2fwd[i].vlan_pmap[j] = j;
 
+		/* All ports start up with egress flooding enabled,
+		 * including the CPU port.
+		 */
+		priv->ucast_egress_floods |= BIT(i);
+		priv->bcast_egress_floods |= BIT(i);
+
 		if (i == upstream)
 			continue;
 
@@ -1571,6 +1583,50 @@ static int sja1105_mdb_del(struct dsa_switch *ds, int port,
 	return sja1105_fdb_del(ds, port, mdb->addr, mdb->vid);
 }
 
+/* Common function for unicast and broadcast flood configuration.
+ * Flooding is configured between each {ingress, egress} port pair, and since
+ * the bridge's semantics are those of "egress flooding", it means we must
+ * enable flooding towards this port from all ingress ports that are in the
+ * same forwarding domain.
+ */
+static int sja1105_manage_flood_domains(struct sja1105_private *priv)
+{
+	struct sja1105_l2_forwarding_entry *l2_fwd;
+	struct dsa_switch *ds = priv->ds;
+	int from, to, rc;
+
+	l2_fwd = priv->static_config.tables[BLK_IDX_L2_FORWARDING].entries;
+
+	for (from = 0; from < ds->num_ports; from++) {
+		u64 fl_domain = 0, bc_domain = 0;
+
+		for (to = 0; to < priv->ds->num_ports; to++) {
+			if (!sja1105_can_forward(l2_fwd, from, to))
+				continue;
+
+			if (priv->ucast_egress_floods & BIT(to))
+				fl_domain |= BIT(to);
+			if (priv->bcast_egress_floods & BIT(to))
+				bc_domain |= BIT(to);
+		}
+
+		/* Nothing changed, nothing to do */
+		if (l2_fwd[from].fl_domain == fl_domain &&
+		    l2_fwd[from].bc_domain == bc_domain)
+			continue;
+
+		l2_fwd[from].fl_domain = fl_domain;
+		l2_fwd[from].bc_domain = bc_domain;
+
+		rc = sja1105_dynamic_config_write(priv, BLK_IDX_L2_FORWARDING,
+						  from, &l2_fwd[from], true);
+		if (rc < 0)
+			return rc;
+	}
+
+	return 0;
+}
+
 static int sja1105_bridge_member(struct dsa_switch *ds, int port,
 				 struct net_device *br, bool member)
 {
@@ -1608,8 +1664,12 @@ static int sja1105_bridge_member(struct dsa_switch *ds, int port,
 			return rc;
 	}
 
-	return sja1105_dynamic_config_write(priv, BLK_IDX_L2_FORWARDING,
-					    port, &l2_fwd[port], true);
+	rc = sja1105_dynamic_config_write(priv, BLK_IDX_L2_FORWARDING,
+					  port, &l2_fwd[port], true);
+	if (rc)
+		return rc;
+
+	return sja1105_manage_flood_domains(priv);
 }
 
 static void sja1105_bridge_stp_state_set(struct dsa_switch *ds, int port,
@@ -3302,51 +3362,24 @@ static int sja1105_port_set_learning(struct sja1105_private *priv, int port,
 	return 0;
 }
 
-/* Common function for unicast and broadcast flood configuration.
- * Flooding is configured between each {ingress, egress} port pair, and since
- * the bridge's semantics are those of "egress flooding", it means we must
- * enable flooding towards this port from all ingress ports that are in the
- * same bridge. In practice, we just enable flooding from all possible ingress
- * ports regardless of whether they're in the same bridge or not, since the
- * reach_port configuration will not allow flooded frames to leak across
- * bridging domains anyway.
- */
 static int sja1105_port_ucast_bcast_flood(struct sja1105_private *priv, int to,
 					  struct switchdev_brport_flags flags)
 {
-	struct sja1105_l2_forwarding_entry *l2_fwd;
-	int from, rc;
-
-	l2_fwd = priv->static_config.tables[BLK_IDX_L2_FORWARDING].entries;
-
-	for (from = 0; from < priv->ds->num_ports; from++) {
-		if (dsa_is_unused_port(priv->ds, from))
-			continue;
-		if (from == to)
-			continue;
-
-		/* Unicast */
-		if (flags.mask & BR_FLOOD) {
-			if (flags.val & BR_FLOOD)
-				l2_fwd[from].fl_domain |= BIT(to);
-			else
-				l2_fwd[from].fl_domain &= ~BIT(to);
-		}
-		/* Broadcast */
-		if (flags.mask & BR_BCAST_FLOOD) {
-			if (flags.val & BR_BCAST_FLOOD)
-				l2_fwd[from].bc_domain |= BIT(to);
-			else
-				l2_fwd[from].bc_domain &= ~BIT(to);
-		}
+	if (flags.mask & BR_FLOOD) {
+		if (flags.val & BR_FLOOD)
+			priv->ucast_egress_floods |= BIT(to);
+		else
+			priv->ucast_egress_floods |= BIT(to);
+	}
 
-		rc = sja1105_dynamic_config_write(priv, BLK_IDX_L2_FORWARDING,
-						  from, &l2_fwd[from], true);
-		if (rc < 0)
-			return rc;
+	if (flags.mask & BR_BCAST_FLOOD) {
+		if (flags.val & BR_BCAST_FLOOD)
+			priv->bcast_egress_floods |= BIT(to);
+		else
+			priv->bcast_egress_floods |= BIT(to);
 	}
 
-	return 0;
+	return sja1105_manage_flood_domains(priv);
 }
 
 static int sja1105_port_mcast_flood(struct sja1105_private *priv, int to,