net: dsa: flush learned FDB on user port bulk delete

Implement ndo_fdb_del_bulk for DSA so that a bulk RTM_DELNEIGH with NTF_SELF
can flush a switch's learned FDB. This is required by user space applications
implementing MRP (802.1Q).

Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Luke Howard <lukeh@padl.com>

Author: lhoward

net/dsa/port.c

@@ -81,6 +81,23 @@ static int dsa_port_vlan_fast_age(const struct dsa_port *dp, u16 vid)
 	return err;
 }
 
+/* Flush this port's dynamically learned FDB entries, optionally scoped to a
+ * VLAN. Honours an MVRP/MMRP "new" declaration (IEEE 802.1Q 11.2.5): after a
+ * topology change the stale learned entries for the port (and VID) are removed
+ * so traffic re-learns/floods to the new topology. Falls back to flushing every
+ * VLAN when the switch has no VLAN-scoped fast age.
+ */
+int dsa_port_flush_dynamic_fdb(struct dsa_port *dp, u16 vid)
+{
+	struct dsa_switch *ds = dp->ds;
+
+	if (vid && ds->ops->port_vlan_fast_age)
+		return dsa_port_vlan_fast_age(dp, vid);
+
+	dsa_port_fast_age(dp);
+	return 0;
+}
+
 static int dsa_port_msti_fast_age(const struct dsa_port *dp, u16 msti)
 {
 	DECLARE_BITMAP(vids, VLAN_N_VID) = { 0 };

net/dsa/port.h

@@ -19,6 +19,7 @@ bool dsa_port_supports_hwtstamp(struct dsa_port *dp);
 void dsa_port_set_tag_protocol(struct dsa_port *cpu_dp,
 			       const struct dsa_device_ops *tag_ops);
 int dsa_port_set_state(struct dsa_port *dp, u8 state, bool do_fast_age);
+int dsa_port_flush_dynamic_fdb(struct dsa_port *dp, u16 vid);
 int dsa_port_set_mst_state(struct dsa_port *dp,
 			   const struct switchdev_mst_state *state,
 			   struct netlink_ext_ack *extack);

net/dsa/user.c

@@ -575,6 +575,32 @@ dsa_user_fdb_dump(struct sk_buff *skb, struct netlink_callback *cb,
 	return err;
 }
 
+static const struct nla_policy dsa_user_fdb_del_bulk_policy[NDA_MAX + 1] = {
+	[NDA_VLAN]		= NLA_POLICY_RANGE(NLA_U16, 1, VLAN_N_VID - 2),
+	[NDA_IFINDEX]		= NLA_POLICY_MIN(NLA_S32, 1),
+	[NDA_NDM_STATE_MASK]	= { .type = NLA_U16 },
+	[NDA_NDM_FLAGS_MASK]	= { .type = NLA_U8 },
+};
+
+static int dsa_user_fdb_del_bulk(struct nlmsghdr *nlh, struct net_device *dev,
+				 struct netlink_ext_ack *extack)
+{
+	struct dsa_port *dp = dsa_user_to_port(dev);
+	struct nlattr *tb[NDA_MAX + 1];
+	u16 vid = 0;
+	int err;
+
+	err = nlmsg_parse(nlh, sizeof(struct ndmsg), tb, NDA_MAX,
+			  dsa_user_fdb_del_bulk_policy, extack);
+	if (err)
+		return err;
+
+	if (tb[NDA_VLAN])
+		vid = nla_get_u16(tb[NDA_VLAN]);
+
+	return dsa_port_flush_dynamic_fdb(dp, vid);
+}
+
 static int dsa_user_ioctl(struct net_device *dev, struct ifreq *ifr, int cmd)
 {
 	struct dsa_user_priv *p = netdev_priv(dev);
@@ -2704,6 +2730,7 @@ static const struct net_device_ops dsa_user_netdev_ops = {
 	.ndo_set_rx_mode	= dsa_user_set_rx_mode,
 	.ndo_set_mac_address	= dsa_user_set_mac_address,
 	.ndo_fdb_dump		= dsa_user_fdb_dump,
+	.ndo_fdb_del_bulk	= dsa_user_fdb_del_bulk,
 	.ndo_eth_ioctl		= dsa_user_ioctl,
 	.ndo_get_iflink		= dsa_user_get_iflink,
 #ifdef CONFIG_NET_POLL_CONTROLLER