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2 * Random policy for multipath.
5 * Version: $Id: multipath_random.c,v 1.1.2.3 2004/09/21 08:42:11 elueck Exp $
7 * Authors: Einar Lueck <elueck@de.ibm.com><lkml@einar-lueck.de>
9 * This program is free software; you can redistribute it and/or
10 * modify it under the terms of the GNU General Public License
11 * as published by the Free Software Foundation; either version
12 * 2 of the License, or (at your option) any later version.
15 #include <asm/system.h>
16 #include <asm/uaccess.h>
17 #include <linux/types.h>
18 #include <linux/sched.h>
19 #include <linux/errno.h>
20 #include <linux/timer.h>
22 #include <linux/kernel.h>
23 #include <linux/fcntl.h>
24 #include <linux/stat.h>
25 #include <linux/socket.h>
27 #include <linux/inet.h>
28 #include <linux/netdevice.h>
29 #include <linux/inetdevice.h>
30 #include <linux/igmp.h>
31 #include <linux/proc_fs.h>
32 #include <linux/seq_file.h>
33 #include <linux/module.h>
34 #include <linux/mroute.h>
35 #include <linux/init.h>
37 #include <net/protocol.h>
38 #include <linux/skbuff.h>
43 #include <linux/notifier.h>
44 #include <linux/if_arp.h>
45 #include <linux/netfilter_ipv4.h>
47 #include <net/checksum.h>
48 #include <net/ip_mp_alg.h>
50 #define MULTIPATH_MAX_CANDIDATES 40
52 /* interface to random number generation */
53 static unsigned int RANDOM_SEED
= 93186752;
55 static inline unsigned int random(unsigned int ubound
)
57 static unsigned int a
= 1588635695,
61 RANDOM_SEED
= a
*(RANDOM_SEED
% q
) - r
*(RANDOM_SEED
/ q
);
63 return RANDOM_SEED
% ubound
;
67 static void random_select_route(const struct flowi
*flp
,
72 struct rtable
*decision
;
73 unsigned char candidate_count
= 0;
75 /* count all candidate */
76 for (rt
= rcu_dereference(first
); rt
;
77 rt
= rcu_dereference(rt
->u
.rt_next
)) {
78 if ((rt
->u
.dst
.flags
& DST_BALANCED
) != 0 &&
79 multipath_comparekeys(&rt
->fl
, flp
))
83 /* choose a random candidate */
85 if (candidate_count
> 1) {
87 unsigned char candidate_no
= (unsigned char)
88 random(candidate_count
);
90 /* find chosen candidate and adjust GC data for all candidates
91 * to ensure they stay in cache
93 for (rt
= first
; rt
; rt
= rt
->u
.rt_next
) {
94 if ((rt
->u
.dst
.flags
& DST_BALANCED
) != 0 &&
95 multipath_comparekeys(&rt
->fl
, flp
)) {
96 rt
->u
.dst
.lastuse
= jiffies
;
98 if (i
== candidate_no
)
101 if (i
>= candidate_count
)
109 decision
->u
.dst
.__use
++;
113 static struct ip_mp_alg_ops random_ops
= {
114 .mp_alg_select_route
= random_select_route
,
117 static int __init
random_init(void)
119 return multipath_alg_register(&random_ops
, IP_MP_ALG_RANDOM
);
122 static void __exit
random_exit(void)
124 multipath_alg_unregister(&random_ops
, IP_MP_ALG_RANDOM
);
127 module_init(random_init
);
128 module_exit(random_exit
);
129 MODULE_LICENSE("GPL");