2 * Device round robin policy for multipath.
5 * Version: $Id: multipath_drr.c,v 1.1.2.1 2004/09/16 07:42:34 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 <linux/config.h>
16 #include <asm/system.h>
17 #include <asm/uaccess.h>
18 #include <linux/types.h>
19 #include <linux/sched.h>
20 #include <linux/errno.h>
21 #include <linux/timer.h>
23 #include <linux/kernel.h>
24 #include <linux/fcntl.h>
25 #include <linux/stat.h>
26 #include <linux/socket.h>
28 #include <linux/inet.h>
29 #include <linux/netdevice.h>
30 #include <linux/inetdevice.h>
31 #include <linux/igmp.h>
32 #include <linux/proc_fs.h>
33 #include <linux/seq_file.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 struct multipath_device
{
51 int ifi
; /* interface index of device */
56 #define MULTIPATH_MAX_DEVICECANDIDATES 10
58 static struct multipath_device state
[MULTIPATH_MAX_DEVICECANDIDATES
];
59 static DEFINE_SPINLOCK(state_lock
);
61 static int inline __multipath_findslot(void)
65 for (i
= 0; i
< MULTIPATH_MAX_DEVICECANDIDATES
; i
++) {
66 if (state
[i
].allocated
== 0)
72 static int inline __multipath_finddev(int ifindex
)
76 for (i
= 0; i
< MULTIPATH_MAX_DEVICECANDIDATES
; i
++) {
77 if (state
[i
].allocated
!= 0 &&
78 state
[i
].ifi
== ifindex
)
84 static int drr_dev_event(struct notifier_block
*this,
85 unsigned long event
, void *ptr
)
87 struct net_device
*dev
= ptr
;
91 case NETDEV_UNREGISTER
:
93 spin_lock_bh(&state_lock
);
95 devidx
= __multipath_finddev(dev
->ifindex
);
97 state
[devidx
].allocated
= 0;
98 state
[devidx
].ifi
= 0;
99 atomic_set(&state
[devidx
].usecount
, 0);
102 spin_unlock_bh(&state_lock
);
109 struct notifier_block drr_dev_notifier
= {
110 .notifier_call
= drr_dev_event
,
114 static void drr_safe_inc(atomic_t
*usecount
)
118 atomic_inc(usecount
);
120 n
= atomic_read(usecount
);
124 spin_lock_bh(&state_lock
);
126 for (i
= 0; i
< MULTIPATH_MAX_DEVICECANDIDATES
; i
++)
127 atomic_set(&state
[i
].usecount
, 0);
129 spin_unlock_bh(&state_lock
);
133 static void drr_select_route(const struct flowi
*flp
,
134 struct rtable
*first
, struct rtable
**rp
)
136 struct rtable
*nh
, *result
, *cur_min
;
137 int min_usecount
= -1;
139 int cur_min_devidx
= -1;
141 /* 1. make sure all alt. nexthops have the same GC related data */
142 /* 2. determine the new candidate to be returned */
145 for (nh
= rcu_dereference(first
); nh
;
146 nh
= rcu_dereference(nh
->u
.rt_next
)) {
147 if ((nh
->u
.dst
.flags
& DST_BALANCED
) != 0 &&
148 multipath_comparekeys(&nh
->fl
, flp
)) {
149 int nh_ifidx
= nh
->u
.dst
.dev
->ifindex
;
151 nh
->u
.dst
.lastuse
= jiffies
;
156 /* search for the output interface */
158 /* this is not SMP safe, only add/remove are
159 * SMP safe as wrong usecount updates have no big
162 devidx
= __multipath_finddev(nh_ifidx
);
164 /* add the interface to the array
167 spin_lock_bh(&state_lock
);
169 /* due to SMP: search again */
170 devidx
= __multipath_finddev(nh_ifidx
);
172 /* add entry for device */
173 devidx
= __multipath_findslot();
175 /* unlikely but possible */
179 state
[devidx
].allocated
= 1;
180 state
[devidx
].ifi
= nh_ifidx
;
181 atomic_set(&state
[devidx
].usecount
, 0);
185 spin_unlock_bh(&state_lock
);
188 if (min_usecount
== 0) {
189 /* if the device has not been used it is
192 drr_safe_inc(&state
[devidx
].usecount
);
196 atomic_read(&state
[devidx
].usecount
);
198 if (min_usecount
== -1 ||
199 count
< min_usecount
) {
201 cur_min_devidx
= devidx
;
202 min_usecount
= count
;
210 drr_safe_inc(&state
[cur_min_devidx
].usecount
);
220 static struct ip_mp_alg_ops drr_ops
= {
221 .mp_alg_select_route
= drr_select_route
,
224 static int __init
drr_init(void)
226 int err
= register_netdevice_notifier(&drr_dev_notifier
);
231 err
= multipath_alg_register(&drr_ops
, IP_MP_ALG_DRR
);
238 unregister_netdevice_notifier(&drr_dev_notifier
);
242 static void __exit
drr_exit(void)
244 unregister_netdevice_notifier(&drr_dev_notifier
);
245 multipath_alg_unregister(&drr_ops
, IP_MP_ALG_DRR
);
248 module_init(drr_init
);
249 module_exit(drr_exit
);