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/errno.h>
19 #include <linux/timer.h>
21 #include <linux/kernel.h>
22 #include <linux/fcntl.h>
23 #include <linux/stat.h>
24 #include <linux/socket.h>
26 #include <linux/inet.h>
27 #include <linux/netdevice.h>
28 #include <linux/inetdevice.h>
29 #include <linux/igmp.h>
30 #include <linux/proc_fs.h>
31 #include <linux/seq_file.h>
32 #include <linux/module.h>
33 #include <linux/mroute.h>
34 #include <linux/init.h>
36 #include <net/protocol.h>
37 #include <linux/skbuff.h>
42 #include <linux/notifier.h>
43 #include <linux/if_arp.h>
44 #include <linux/netfilter_ipv4.h>
46 #include <net/checksum.h>
47 #include <net/ip_mp_alg.h>
49 #define MULTIPATH_MAX_CANDIDATES 40
51 /* interface to random number generation */
52 static unsigned int RANDOM_SEED
= 93186752;
54 static inline unsigned int random(unsigned int ubound
)
56 static unsigned int a
= 1588635695,
60 RANDOM_SEED
= a
*(RANDOM_SEED
% q
) - r
*(RANDOM_SEED
/ q
);
62 return RANDOM_SEED
% ubound
;
66 static void random_select_route(const struct flowi
*flp
,
71 struct rtable
*decision
;
72 unsigned char candidate_count
= 0;
74 /* count all candidate */
75 for (rt
= rcu_dereference(first
); rt
;
76 rt
= rcu_dereference(rt
->u
.dst
.rt_next
)) {
77 if ((rt
->u
.dst
.flags
& DST_BALANCED
) != 0 &&
78 multipath_comparekeys(&rt
->fl
, flp
))
82 /* choose a random candidate */
84 if (candidate_count
> 1) {
86 unsigned char candidate_no
= (unsigned char)
87 random(candidate_count
);
89 /* find chosen candidate and adjust GC data for all candidates
90 * to ensure they stay in cache
92 for (rt
= first
; rt
; rt
= rt
->u
.dst
.rt_next
) {
93 if ((rt
->u
.dst
.flags
& DST_BALANCED
) != 0 &&
94 multipath_comparekeys(&rt
->fl
, flp
)) {
95 rt
->u
.dst
.lastuse
= jiffies
;
97 if (i
== candidate_no
)
100 if (i
>= candidate_count
)
108 decision
->u
.dst
.__use
++;
112 static struct ip_mp_alg_ops random_ops
= {
113 .mp_alg_select_route
= random_select_route
,
116 static int __init
random_init(void)
118 return multipath_alg_register(&random_ops
, IP_MP_ALG_RANDOM
);
121 static void __exit
random_exit(void)
123 multipath_alg_unregister(&random_ops
, IP_MP_ALG_RANDOM
);
126 module_init(random_init
);
127 module_exit(random_exit
);
128 MODULE_LICENSE("GPL");