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/*
* 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);
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