net: bridge: add no_linklocal_learn bool option

Use the new boolopt API to add an option which disables learning from
link-local packets. The default is kept as before and learning is
enabled. This is a simple map from a boolopt bit to a bridge private
flag that is tested before learning.

v2: pass NULL for extack via sysfs

Signed-off-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

Author: Nikolay Aleksandrov

include/uapi/linux/if_bridge.h

@@ -294,10 +294,13 @@ struct br_mcast_stats {
 };
 
 /* bridge boolean options
+ * BR_BOOLOPT_NO_LL_LEARN - disable learning from link-local packets
+ *
  * IMPORTANT: if adding a new option do not forget to handle
  *            it in br_boolopt_toggle/get and bridge sysfs
  */
 enum br_boolopt_id {
+	BR_BOOLOPT_NO_LL_LEARN,
 	BR_BOOLOPT_MAX
 };
 

net/bridge/br.c

@@ -189,6 +189,9 @@ int br_boolopt_toggle(struct net_bridge *br, enum br_boolopt_id opt, bool on,
 		      struct netlink_ext_ack *extack)
 {
 	switch (opt) {
+	case BR_BOOLOPT_NO_LL_LEARN:
+		br_opt_toggle(br, BROPT_NO_LL_LEARN, on);
+		break;
 	default:
 		/* shouldn't be called with unsupported options */
 		WARN_ON(1);
@@ -201,6 +204,8 @@ int br_boolopt_toggle(struct net_bridge *br, enum br_boolopt_id opt, bool on,
 int br_boolopt_get(const struct net_bridge *br, enum br_boolopt_id opt)
 {
 	switch (opt) {
+	case BR_BOOLOPT_NO_LL_LEARN:
+		return br_opt_get(br, BROPT_NO_LL_LEARN);
 	default:
 		/* shouldn't be called with unsupported options */
 		WARN_ON(1);

net/bridge/br_input.c

@@ -188,7 +188,9 @@ static void __br_handle_local_finish(struct sk_buff *skb)
 	u16 vid = 0;
 
 	/* check if vlan is allowed, to avoid spoofing */
-	if (p->flags & BR_LEARNING && br_should_learn(p, skb, &vid))
+	if ((p->flags & BR_LEARNING) &&
+	    !br_opt_get(p->br, BROPT_NO_LL_LEARN) &&
+	    br_should_learn(p, skb, &vid))
 		br_fdb_update(p->br, p, eth_hdr(skb)->h_source, vid, false);
 }
 

net/bridge/br_private.h

@@ -328,6 +328,7 @@ enum net_bridge_opts {
 	BROPT_NEIGH_SUPPRESS_ENABLED,
 	BROPT_MTU_SET_BY_USER,
 	BROPT_VLAN_STATS_PER_PORT,
+	BROPT_NO_LL_LEARN,
 };
 
 struct net_bridge {

net/bridge/br_sysfs_br.c

@@ -328,6 +328,27 @@ static ssize_t flush_store(struct device *d,
 }
 static DEVICE_ATTR_WO(flush);
 
+static ssize_t no_linklocal_learn_show(struct device *d,
+				       struct device_attribute *attr,
+				       char *buf)
+{
+	struct net_bridge *br = to_bridge(d);
+	return sprintf(buf, "%d\n", br_boolopt_get(br, BR_BOOLOPT_NO_LL_LEARN));
+}
+
+static int set_no_linklocal_learn(struct net_bridge *br, unsigned long val)
+{
+	return br_boolopt_toggle(br, BR_BOOLOPT_NO_LL_LEARN, !!val, NULL);
+}
+
+static ssize_t no_linklocal_learn_store(struct device *d,
+					struct device_attribute *attr,
+					const char *buf, size_t len)
+{
+	return store_bridge_parm(d, buf, len, set_no_linklocal_learn);
+}
+static DEVICE_ATTR_RW(no_linklocal_learn);
+
 #ifdef CONFIG_BRIDGE_IGMP_SNOOPING
 static ssize_t multicast_router_show(struct device *d,
 				     struct device_attribute *attr, char *buf)
@@ -841,6 +862,7 @@ static struct attribute *bridge_attrs[] = {
 	&dev_attr_gc_timer.attr,
 	&dev_attr_group_addr.attr,
 	&dev_attr_flush.attr,
+	&dev_attr_no_linklocal_learn.attr,
 #ifdef CONFIG_BRIDGE_IGMP_SNOOPING
 	&dev_attr_multicast_router.attr,
 	&dev_attr_multicast_snooping.attr,