team: introduce random mode

As suggested by Eric Dumazet, allow user to select mode which chooses
TX port randomly. Functionality should be more of less similar to
round-robin mode with even lower overhead.

Signed-off-by: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/team/team_mode_random.c

@@ -0,0 +1,71 @@
+/*
+ * drivers/net/team/team_mode_random.c - Random mode for team
+ * Copyright (c) 2013 Jiri Pirko <jiri@resnulli.us>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#include <linux/kernel.h>
+#include <linux/types.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/skbuff.h>
+#include <linux/reciprocal_div.h>
+#include <linux/if_team.h>
+
+static u32 random_N(unsigned int N)
+{
+	return reciprocal_divide(random32(), N);
+}
+
+static bool rnd_transmit(struct team *team, struct sk_buff *skb)
+{
+	struct team_port *port;
+	int port_index;
+
+	port_index = random_N(team->en_port_count);
+	port = team_get_port_by_index_rcu(team, port_index);
+	port = team_get_first_port_txable_rcu(team, port);
+	if (unlikely(!port))
+		goto drop;
+	if (team_dev_queue_xmit(team, port, skb))
+		return false;
+	return true;
+
+drop:
+	dev_kfree_skb_any(skb);
+	return false;
+}
+
+static const struct team_mode_ops rnd_mode_ops = {
+	.transmit		= rnd_transmit,
+	.port_enter		= team_modeop_port_enter,
+	.port_change_dev_addr	= team_modeop_port_change_dev_addr,
+};
+
+static const struct team_mode rnd_mode = {
+	.kind		= "random",
+	.owner		= THIS_MODULE,
+	.ops		= &rnd_mode_ops,
+};
+
+static int __init rnd_init_module(void)
+{
+	return team_mode_register(&rnd_mode);
+}
+
+static void __exit rnd_cleanup_module(void)
+{
+	team_mode_unregister(&rnd_mode);
+}
+
+module_init(rnd_init_module);
+module_exit(rnd_cleanup_module);
+
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Jiri Pirko <jiri@resnulli.us>");
+MODULE_DESCRIPTION("Random mode for team");
+MODULE_ALIAS("team-mode-random");