net: bridge: add support for user-controlled bool options

We have been adding many new bridge options, a big number of which are
boolean but still take up netlink attribute ids and waste space in the skb.
Recently we discussed learning from link-local packets[1] and decided
yet another new boolean option will be needed, thus introducing this API
to save some bridge nl space.
The API supports changing the value of multiple boolean options at once
via the br_boolopt_multi struct which has an optmask (which options to
set, bit per opt) and optval (options' new values). Future boolean
options will only be added to the br_boolopt_id enum and then will have
to be handled in br_boolopt_toggle/get. The API will automatically
add the ability to change and export them via netlink, sysfs can use the
single boolopt function versions to do the same. The behaviour with
failing/succeeding is the same as with normal netlink option changing.

If an option requires mapping to internal kernel flag or needs special
configuration to be enabled then it should be handled in
br_boolopt_toggle. It should also be able to retrieve an option's current
state via br_boolopt_get.

v2: WARN_ON() on unsupported option as that shouldn't be possible and
    also will help catch people who add new options without handling
    them for both set and get. Pass down extack so if an option desires
    it could set it on error and be more user-friendly.

[1] https://www.spinics.net/lists/netdev/msg532698.html

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

1 files changed, 71 insertions, 0 deletions

diff --git a/net/bridge/br.c b/net/bridge/br.c
index 360ad66c21e9..c527160c1975 100644
--- a/net/bridge/br.c
+++ b/net/bridge/br.c
@@ -175,6 +175,77 @@ static struct notifier_block br_switchdev_notifier = {
 	.notifier_call = br_switchdev_event,
 };
 
+/* br_boolopt_toggle - change user-controlled boolean option
+ *
+ * @br: bridge device
+ * @opt: id of the option to change
+ * @on: new option value
+ * @extack: extack for error messages
+ *
+ * Changes the value of the respective boolean option to @on taking care of
+ * any internal option value mapping and configuration.
+ */
+int br_boolopt_toggle(struct net_bridge *br, enum br_boolopt_id opt, bool on,
+		      struct netlink_ext_ack *extack)
+{
+	switch (opt) {
+	default:
+		/* shouldn't be called with unsupported options */
+		WARN_ON(1);
+		break;
+	}
+
+	return 0;
+}
+
+int br_boolopt_get(const struct net_bridge *br, enum br_boolopt_id opt)
+{
+	switch (opt) {
+	default:
+		/* shouldn't be called with unsupported options */
+		WARN_ON(1);
+		break;
+	}
+
+	return 0;
+}
+
+int br_boolopt_multi_toggle(struct net_bridge *br,
+			    struct br_boolopt_multi *bm,
+			    struct netlink_ext_ack *extack)
+{
+	unsigned long bitmap = bm->optmask;
+	int err = 0;
+	int opt_id;
+
+	for_each_set_bit(opt_id, &bitmap, BR_BOOLOPT_MAX) {
+		bool on = !!(bm->optval & BIT(opt_id));
+
+		err = br_boolopt_toggle(br, opt_id, on, extack);
+		if (err) {
+			br_debug(br, "boolopt multi-toggle error: option: %d current: %d new: %d error: %d\n",
+				 opt_id, br_boolopt_get(br, opt_id), on, err);
+			break;
+		}
+	}
+
+	return err;
+}
+
+void br_boolopt_multi_get(const struct net_bridge *br,
+			  struct br_boolopt_multi *bm)
+{
+	u32 optval = 0;
+	int opt_id;
+
+	for (opt_id = 0; opt_id < BR_BOOLOPT_MAX; opt_id++)
+		optval |= (br_boolopt_get(br, opt_id) << opt_id);
+
+	bm->optval = optval;
+	bm->optmask = 0;
+}
+
+/* private bridge options, controlled by the kernel */
 void br_opt_toggle(struct net_bridge *br, enum net_bridge_opts opt, bool on)
 {
 	bool cur = !!br_opt_get(br, opt);