1 files changed, 128 insertions, 0 deletions
diff --git a/net/ipv4/multipath_random.c b/net/ipv4/multipath_random.c
new file mode 100644
index 000000000000..805a16e47de5
--- /dev/null
+++ b/net/ipv4/multipath_random.c
@@ -0,0 +1,128 @@
+/*
+ *              Random policy for multipath.
+ *
+ *
+ * Version:	$Id: multipath_random.c,v 1.1.2.3 2004/09/21 08:42:11 elueck Exp $
+ *
+ * Authors:	Einar Lueck <elueck@de.ibm.com><lkml@einar-lueck.de>
+ *
+ *		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/config.h>
+#include <asm/system.h>
+#include <asm/uaccess.h>
+#include <linux/types.h>
+#include <linux/sched.h>
+#include <linux/errno.h>
+#include <linux/timer.h>
+#include <linux/mm.h>
+#include <linux/kernel.h>
+#include <linux/fcntl.h>
+#include <linux/stat.h>
+#include <linux/socket.h>
+#include <linux/in.h>
+#include <linux/inet.h>
+#include <linux/netdevice.h>
+#include <linux/inetdevice.h>
+#include <linux/igmp.h>
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
+#include <linux/mroute.h>
+#include <linux/init.h>
+#include <net/ip.h>
+#include <net/protocol.h>
+#include <linux/skbuff.h>
+#include <net/sock.h>
+#include <net/icmp.h>
+#include <net/udp.h>
+#include <net/raw.h>
+#include <linux/notifier.h>
+#include <linux/if_arp.h>
+#include <linux/netfilter_ipv4.h>
+#include <net/ipip.h>
+#include <net/checksum.h>
+#include <net/ip_mp_alg.h>
+
+#define MULTIPATH_MAX_CANDIDATES 40
+
+/* interface to random number generation */
+static unsigned int RANDOM_SEED = 93186752;
+
+static inline unsigned int random(unsigned int ubound)
+{
+	static unsigned int a = 1588635695,
+		q = 2,
+		r = 1117695901;
+
+	RANDOM_SEED = a*(RANDOM_SEED % q) - r*(RANDOM_SEED / q);
+
+	return RANDOM_SEED % ubound;
+}
+
+
+static void random_select_route(const struct flowi *flp,
+				struct rtable *first,
+				struct rtable **rp)
+{
+	struct rtable *rt;
+	struct rtable *decision;
+	unsigned char candidate_count = 0;
+
+	/* count all candidate */
+	for (rt = rcu_dereference(first); rt;
+	     rt = rcu_dereference(rt->u.rt_next)) {
+		if ((rt->u.dst.flags & DST_BALANCED) != 0 &&
+		    multipath_comparekeys(&rt->fl, flp))
+			++candidate_count;
+	}
+
+	/* choose a random candidate */
+	decision = first;
+	if (candidate_count > 1) {
+		unsigned char i = 0;
+		unsigned char candidate_no = (unsigned char)
+			random(candidate_count);
+
+		/* find chosen candidate and adjust GC data for all candidates
+		 * to ensure they stay in cache
+		 */
+		for (rt = first; rt; rt = rt->u.rt_next) {
+			if ((rt->u.dst.flags & DST_BALANCED) != 0 &&
+			    multipath_comparekeys(&rt->fl, flp)) {
+				rt->u.dst.lastuse = jiffies;
+
+				if (i == candidate_no)
+					decision = rt;
+
+				if (i >= candidate_count)
+					break;
+
+				i++;
+			}
+		}
+	}
+
+	decision->u.dst.__use++;
+	*rp = decision;
+}
+
+static struct ip_mp_alg_ops random_ops = {
+	.mp_alg_select_route	=	random_select_route,
+};
+
+static int __init random_init(void)
+{
+	return multipath_alg_register(&random_ops, IP_MP_ALG_RANDOM);
+}
+
+static void __exit random_exit(void)
+{
+	multipath_alg_unregister(&random_ops, IP_MP_ALG_RANDOM);
+}
+
+module_init(random_init);
+module_exit(random_exit);