net: bridge: mdb: add support to extend add/del commands

Since the MDB add/del code expects an exact struct br_mdb_entry we can't
really add any extensions, thus add a new nested attribute at the level of
MDBA_SET_ENTRY called MDBA_SET_ENTRY_ATTRS which will be used to pass
all new options via netlink attributes. This patch doesn't change
anything functionally since the new attribute is not used yet, only
parsed.
Signed-off-by: Nikolay Aleksandrov <nikolay@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/uapi/linux/if_bridge.h

@@ -530,10 +530,22 @@ struct br_mdb_entry {
 enum {
 	MDBA_SET_ENTRY_UNSPEC,
 	MDBA_SET_ENTRY,
+	MDBA_SET_ENTRY_ATTRS,
 	__MDBA_SET_ENTRY_MAX,
 };
 #define MDBA_SET_ENTRY_MAX (__MDBA_SET_ENTRY_MAX - 1)
 
+/* [MDBA_SET_ENTRY_ATTRS] = {
+ *    [MDBE_ATTR_xxx]
+ *    ...
+ * }
+ */
+enum {
+	MDBE_ATTR_UNSPEC,
+	__MDBE_ATTR_MAX,
+};
+#define MDBE_ATTR_MAX (__MDBE_ATTR_MAX - 1)
+
 /* Embedded inside LINK_XSTATS_TYPE_BRIDGE */
 enum {
 	BRIDGE_XSTATS_UNSPEC,

net/bridge/br_mdb.c

@@ -670,9 +670,12 @@ static bool is_valid_mdb_entry(struct br_mdb_entry *entry,
 	return true;
 }
 
+static const struct nla_policy br_mdbe_attrs_pol[MDBE_ATTR_MAX + 1] = {
+};
+
 static int br_mdb_parse(struct sk_buff *skb, struct nlmsghdr *nlh,
 			struct net_device **pdev, struct br_mdb_entry **pentry,
-			struct netlink_ext_ack *extack)
+			struct nlattr **mdb_attrs, struct netlink_ext_ack *extack)
 {
 	struct net *net = sock_net(skb->sk);
 	struct br_mdb_entry *entry;
@@ -719,6 +722,17 @@ static int br_mdb_parse(struct sk_buff *skb, struct nlmsghdr *nlh,
 		return -EINVAL;
 	*pentry = entry;
 
+	if (tb[MDBA_SET_ENTRY_ATTRS]) {
+		err = nla_parse_nested(mdb_attrs, MDBE_ATTR_MAX,
+				       tb[MDBA_SET_ENTRY_ATTRS],
+				       br_mdbe_attrs_pol, extack);
+		if (err)
+			return err;
+	} else {
+		memset(mdb_attrs, 0,
+		       sizeof(struct nlattr *) * (MDBE_ATTR_MAX + 1));
+	}
+
 	return 0;
 }
 
@@ -803,6 +817,7 @@ static int __br_mdb_add(struct net *net, struct net_bridge *br,
 static int br_mdb_add(struct sk_buff *skb, struct nlmsghdr *nlh,
 		      struct netlink_ext_ack *extack)
 {
+	struct nlattr *mdb_attrs[MDBE_ATTR_MAX + 1];
 	struct net *net = sock_net(skb->sk);
 	struct net_bridge_vlan_group *vg;
 	struct net_bridge_port *p = NULL;
@@ -812,7 +827,7 @@ static int br_mdb_add(struct sk_buff *skb, struct nlmsghdr *nlh,
 	struct net_bridge *br;
 	int err;
 
-	err = br_mdb_parse(skb, nlh, &dev, &entry, extack);
+	err = br_mdb_parse(skb, nlh, &dev, &entry, mdb_attrs, extack);
 	if (err < 0)
 		return err;
 
@@ -921,6 +936,7 @@ static int __br_mdb_del(struct net_bridge *br, struct br_mdb_entry *entry)
 static int br_mdb_del(struct sk_buff *skb, struct nlmsghdr *nlh,
 		      struct netlink_ext_ack *extack)
 {
+	struct nlattr *mdb_attrs[MDBE_ATTR_MAX + 1];
 	struct net *net = sock_net(skb->sk);
 	struct net_bridge_vlan_group *vg;
 	struct net_bridge_port *p = NULL;
@@ -930,7 +946,7 @@ static int br_mdb_del(struct sk_buff *skb, struct nlmsghdr *nlh,
 	struct net_bridge *br;
 	int err;
 
-	err = br_mdb_parse(skb, nlh, &dev, &entry, extack);
+	err = br_mdb_parse(skb, nlh, &dev, &entry, mdb_attrs, extack);
 	if (err < 0)
 		return err;