129 lines
3.0 KiB
C
129 lines
3.0 KiB
C
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/*
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* Random policy for multipath.
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*
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*
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* Version: $Id: multipath_random.c,v 1.1.2.3 2004/09/21 08:42:11 elueck Exp $
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*
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* Authors: Einar Lueck <elueck@de.ibm.com><lkml@einar-lueck.de>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#include <linux/config.h>
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#include <asm/system.h>
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#include <asm/uaccess.h>
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#include <linux/types.h>
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#include <linux/sched.h>
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#include <linux/errno.h>
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#include <linux/timer.h>
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#include <linux/mm.h>
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#include <linux/kernel.h>
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#include <linux/fcntl.h>
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#include <linux/stat.h>
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#include <linux/socket.h>
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#include <linux/in.h>
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#include <linux/inet.h>
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#include <linux/netdevice.h>
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#include <linux/inetdevice.h>
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#include <linux/igmp.h>
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#include <linux/proc_fs.h>
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#include <linux/seq_file.h>
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#include <linux/mroute.h>
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#include <linux/init.h>
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#include <net/ip.h>
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#include <net/protocol.h>
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#include <linux/skbuff.h>
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#include <net/sock.h>
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#include <net/icmp.h>
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#include <net/udp.h>
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#include <net/raw.h>
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#include <linux/notifier.h>
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#include <linux/if_arp.h>
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#include <linux/netfilter_ipv4.h>
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#include <net/ipip.h>
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#include <net/checksum.h>
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#include <net/ip_mp_alg.h>
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#define MULTIPATH_MAX_CANDIDATES 40
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/* interface to random number generation */
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static unsigned int RANDOM_SEED = 93186752;
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static inline unsigned int random(unsigned int ubound)
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{
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static unsigned int a = 1588635695,
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q = 2,
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r = 1117695901;
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RANDOM_SEED = a*(RANDOM_SEED % q) - r*(RANDOM_SEED / q);
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return RANDOM_SEED % ubound;
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}
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static void random_select_route(const struct flowi *flp,
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struct rtable *first,
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struct rtable **rp)
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{
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struct rtable *rt;
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struct rtable *decision;
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unsigned char candidate_count = 0;
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/* count all candidate */
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for (rt = rcu_dereference(first); rt;
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rt = rcu_dereference(rt->u.rt_next)) {
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if ((rt->u.dst.flags & DST_BALANCED) != 0 &&
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multipath_comparekeys(&rt->fl, flp))
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++candidate_count;
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}
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/* choose a random candidate */
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decision = first;
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if (candidate_count > 1) {
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unsigned char i = 0;
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unsigned char candidate_no = (unsigned char)
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random(candidate_count);
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/* find chosen candidate and adjust GC data for all candidates
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* to ensure they stay in cache
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*/
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for (rt = first; rt; rt = rt->u.rt_next) {
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if ((rt->u.dst.flags & DST_BALANCED) != 0 &&
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multipath_comparekeys(&rt->fl, flp)) {
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rt->u.dst.lastuse = jiffies;
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if (i == candidate_no)
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decision = rt;
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if (i >= candidate_count)
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break;
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i++;
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}
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}
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}
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decision->u.dst.__use++;
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*rp = decision;
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}
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static struct ip_mp_alg_ops random_ops = {
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.mp_alg_select_route = random_select_route,
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};
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static int __init random_init(void)
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{
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return multipath_alg_register(&random_ops, IP_MP_ALG_RANDOM);
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}
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static void __exit random_exit(void)
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{
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multipath_alg_unregister(&random_ops, IP_MP_ALG_RANDOM);
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}
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module_init(random_init);
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module_exit(random_exit);
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