blob: 252e837b17a52d54079db9c1eb5a1f62d5889a4c [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * Device round robin policy for multipath.
3 *
4 *
5 * Version: $Id: multipath_drr.c,v 1.1.2.1 2004/09/16 07:42:34 elueck Exp $
6 *
7 * Authors: Einar Lueck <elueck@de.ibm.com><lkml@einar-lueck.de>
8 *
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.
13 */
14
Linus Torvalds1da177e2005-04-16 15:20:36 -070015#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>
21#include <linux/mm.h>
22#include <linux/kernel.h>
23#include <linux/fcntl.h>
24#include <linux/stat.h>
25#include <linux/socket.h>
26#include <linux/in.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>
Randy Dunlap6efd8452005-06-13 14:29:06 -070033#include <linux/module.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070034#include <linux/mroute.h>
35#include <linux/init.h>
36#include <net/ip.h>
37#include <net/protocol.h>
38#include <linux/skbuff.h>
39#include <net/sock.h>
40#include <net/icmp.h>
41#include <net/udp.h>
42#include <net/raw.h>
43#include <linux/notifier.h>
44#include <linux/if_arp.h>
45#include <linux/netfilter_ipv4.h>
46#include <net/ipip.h>
47#include <net/checksum.h>
48#include <net/ip_mp_alg.h>
49
50struct multipath_device {
51 int ifi; /* interface index of device */
52 atomic_t usecount;
53 int allocated;
54};
55
56#define MULTIPATH_MAX_DEVICECANDIDATES 10
57
58static struct multipath_device state[MULTIPATH_MAX_DEVICECANDIDATES];
59static DEFINE_SPINLOCK(state_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -070060
61static int inline __multipath_findslot(void)
62{
63 int i;
64
65 for (i = 0; i < MULTIPATH_MAX_DEVICECANDIDATES; i++) {
66 if (state[i].allocated == 0)
67 return i;
68 }
69 return -1;
70}
71
72static int inline __multipath_finddev(int ifindex)
73{
74 int i;
75
76 for (i = 0; i < MULTIPATH_MAX_DEVICECANDIDATES; i++) {
77 if (state[i].allocated != 0 &&
78 state[i].ifi == ifindex)
79 return i;
80 }
81 return -1;
82}
83
84static int drr_dev_event(struct notifier_block *this,
85 unsigned long event, void *ptr)
86{
87 struct net_device *dev = ptr;
88 int devidx;
89
90 switch (event) {
91 case NETDEV_UNREGISTER:
92 case NETDEV_DOWN:
93 spin_lock_bh(&state_lock);
94
95 devidx = __multipath_finddev(dev->ifindex);
96 if (devidx != -1) {
97 state[devidx].allocated = 0;
98 state[devidx].ifi = 0;
99 atomic_set(&state[devidx].usecount, 0);
100 }
101
102 spin_unlock_bh(&state_lock);
103 break;
104 };
105
106 return NOTIFY_DONE;
107}
108
Adrian Bunk0742fd52005-08-09 19:35:47 -0700109static struct notifier_block drr_dev_notifier = {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700110 .notifier_call = drr_dev_event,
111};
112
Linus Torvalds1da177e2005-04-16 15:20:36 -0700113
114static void drr_safe_inc(atomic_t *usecount)
115{
116 int n;
117
118 atomic_inc(usecount);
119
120 n = atomic_read(usecount);
121 if (n <= 0) {
122 int i;
123
124 spin_lock_bh(&state_lock);
125
126 for (i = 0; i < MULTIPATH_MAX_DEVICECANDIDATES; i++)
127 atomic_set(&state[i].usecount, 0);
128
129 spin_unlock_bh(&state_lock);
130 }
131}
132
133static void drr_select_route(const struct flowi *flp,
134 struct rtable *first, struct rtable **rp)
135{
136 struct rtable *nh, *result, *cur_min;
137 int min_usecount = -1;
138 int devidx = -1;
139 int cur_min_devidx = -1;
140
Linus Torvalds1da177e2005-04-16 15:20:36 -0700141 /* 1. make sure all alt. nexthops have the same GC related data */
142 /* 2. determine the new candidate to be returned */
143 result = NULL;
144 cur_min = NULL;
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;
150
151 nh->u.dst.lastuse = jiffies;
152 nh->u.dst.__use++;
153 if (result != NULL)
154 continue;
155
156 /* search for the output interface */
157
158 /* this is not SMP safe, only add/remove are
159 * SMP safe as wrong usecount updates have no big
160 * impact
161 */
162 devidx = __multipath_finddev(nh_ifidx);
163 if (devidx == -1) {
164 /* add the interface to the array
165 * SMP safe
166 */
167 spin_lock_bh(&state_lock);
168
169 /* due to SMP: search again */
170 devidx = __multipath_finddev(nh_ifidx);
171 if (devidx == -1) {
172 /* add entry for device */
173 devidx = __multipath_findslot();
174 if (devidx == -1) {
175 /* unlikely but possible */
176 continue;
177 }
178
179 state[devidx].allocated = 1;
180 state[devidx].ifi = nh_ifidx;
181 atomic_set(&state[devidx].usecount, 0);
182 min_usecount = 0;
183 }
184
185 spin_unlock_bh(&state_lock);
186 }
187
188 if (min_usecount == 0) {
189 /* if the device has not been used it is
190 * the primary target
191 */
192 drr_safe_inc(&state[devidx].usecount);
193 result = nh;
194 } else {
195 int count =
196 atomic_read(&state[devidx].usecount);
197
198 if (min_usecount == -1 ||
199 count < min_usecount) {
200 cur_min = nh;
201 cur_min_devidx = devidx;
202 min_usecount = count;
203 }
204 }
205 }
206 }
207
208 if (!result) {
209 if (cur_min) {
210 drr_safe_inc(&state[cur_min_devidx].usecount);
211 result = cur_min;
212 } else {
213 result = first;
214 }
215 }
216
217 *rp = result;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700218}
219
220static struct ip_mp_alg_ops drr_ops = {
221 .mp_alg_select_route = drr_select_route,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700222};
223
224static int __init drr_init(void)
225{
226 int err = register_netdevice_notifier(&drr_dev_notifier);
227
228 if (err)
229 return err;
230
Pravin B. Shelar37e20a62005-05-29 20:26:44 -0700231 err = multipath_alg_register(&drr_ops, IP_MP_ALG_DRR);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700232 if (err)
233 goto fail;
234
235 return 0;
236
237fail:
238 unregister_netdevice_notifier(&drr_dev_notifier);
239 return err;
240}
241
242static void __exit drr_exit(void)
243{
244 unregister_netdevice_notifier(&drr_dev_notifier);
245 multipath_alg_unregister(&drr_ops, IP_MP_ALG_DRR);
246}
247
248module_init(drr_init);
249module_exit(drr_exit);
Randy Dunlap6efd8452005-06-13 14:29:06 -0700250MODULE_LICENSE("GPL");