blob: 9349686131fcf2552a748913675dab743f6bc733 [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
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>
22#include <linux/mm.h>
23#include <linux/kernel.h>
24#include <linux/fcntl.h>
25#include <linux/stat.h>
26#include <linux/socket.h>
27#include <linux/in.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>
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);
60static struct rtable *last_selection = NULL;
61
62static int inline __multipath_findslot(void)
63{
64 int i;
65
66 for (i = 0; i < MULTIPATH_MAX_DEVICECANDIDATES; i++) {
67 if (state[i].allocated == 0)
68 return i;
69 }
70 return -1;
71}
72
73static int inline __multipath_finddev(int ifindex)
74{
75 int i;
76
77 for (i = 0; i < MULTIPATH_MAX_DEVICECANDIDATES; i++) {
78 if (state[i].allocated != 0 &&
79 state[i].ifi == ifindex)
80 return i;
81 }
82 return -1;
83}
84
85static int drr_dev_event(struct notifier_block *this,
86 unsigned long event, void *ptr)
87{
88 struct net_device *dev = ptr;
89 int devidx;
90
91 switch (event) {
92 case NETDEV_UNREGISTER:
93 case NETDEV_DOWN:
94 spin_lock_bh(&state_lock);
95
96 devidx = __multipath_finddev(dev->ifindex);
97 if (devidx != -1) {
98 state[devidx].allocated = 0;
99 state[devidx].ifi = 0;
100 atomic_set(&state[devidx].usecount, 0);
101 }
102
103 spin_unlock_bh(&state_lock);
104 break;
105 };
106
107 return NOTIFY_DONE;
108}
109
110struct notifier_block drr_dev_notifier = {
111 .notifier_call = drr_dev_event,
112};
113
114static void drr_remove(struct rtable *rt)
115{
116 if (last_selection == rt)
117 last_selection = NULL;
118}
119
120static void drr_safe_inc(atomic_t *usecount)
121{
122 int n;
123
124 atomic_inc(usecount);
125
126 n = atomic_read(usecount);
127 if (n <= 0) {
128 int i;
129
130 spin_lock_bh(&state_lock);
131
132 for (i = 0; i < MULTIPATH_MAX_DEVICECANDIDATES; i++)
133 atomic_set(&state[i].usecount, 0);
134
135 spin_unlock_bh(&state_lock);
136 }
137}
138
139static void drr_select_route(const struct flowi *flp,
140 struct rtable *first, struct rtable **rp)
141{
142 struct rtable *nh, *result, *cur_min;
143 int min_usecount = -1;
144 int devidx = -1;
145 int cur_min_devidx = -1;
146
147 /* if necessary and possible utilize the old alternative */
148 if ((flp->flags & FLOWI_FLAG_MULTIPATHOLDROUTE) != 0 &&
149 last_selection != NULL) {
150 result = last_selection;
151 *rp = result;
152 return;
153 }
154
155 /* 1. make sure all alt. nexthops have the same GC related data */
156 /* 2. determine the new candidate to be returned */
157 result = NULL;
158 cur_min = NULL;
159 for (nh = rcu_dereference(first); nh;
160 nh = rcu_dereference(nh->u.rt_next)) {
161 if ((nh->u.dst.flags & DST_BALANCED) != 0 &&
162 multipath_comparekeys(&nh->fl, flp)) {
163 int nh_ifidx = nh->u.dst.dev->ifindex;
164
165 nh->u.dst.lastuse = jiffies;
166 nh->u.dst.__use++;
167 if (result != NULL)
168 continue;
169
170 /* search for the output interface */
171
172 /* this is not SMP safe, only add/remove are
173 * SMP safe as wrong usecount updates have no big
174 * impact
175 */
176 devidx = __multipath_finddev(nh_ifidx);
177 if (devidx == -1) {
178 /* add the interface to the array
179 * SMP safe
180 */
181 spin_lock_bh(&state_lock);
182
183 /* due to SMP: search again */
184 devidx = __multipath_finddev(nh_ifidx);
185 if (devidx == -1) {
186 /* add entry for device */
187 devidx = __multipath_findslot();
188 if (devidx == -1) {
189 /* unlikely but possible */
190 continue;
191 }
192
193 state[devidx].allocated = 1;
194 state[devidx].ifi = nh_ifidx;
195 atomic_set(&state[devidx].usecount, 0);
196 min_usecount = 0;
197 }
198
199 spin_unlock_bh(&state_lock);
200 }
201
202 if (min_usecount == 0) {
203 /* if the device has not been used it is
204 * the primary target
205 */
206 drr_safe_inc(&state[devidx].usecount);
207 result = nh;
208 } else {
209 int count =
210 atomic_read(&state[devidx].usecount);
211
212 if (min_usecount == -1 ||
213 count < min_usecount) {
214 cur_min = nh;
215 cur_min_devidx = devidx;
216 min_usecount = count;
217 }
218 }
219 }
220 }
221
222 if (!result) {
223 if (cur_min) {
224 drr_safe_inc(&state[cur_min_devidx].usecount);
225 result = cur_min;
226 } else {
227 result = first;
228 }
229 }
230
231 *rp = result;
232 last_selection = result;
233}
234
235static struct ip_mp_alg_ops drr_ops = {
236 .mp_alg_select_route = drr_select_route,
237 .mp_alg_remove = drr_remove,
238};
239
240static int __init drr_init(void)
241{
242 int err = register_netdevice_notifier(&drr_dev_notifier);
243
244 if (err)
245 return err;
246
247 err = multipath_alg_register(&drr_ops, IP_MP_ALG_RR);
248 if (err)
249 goto fail;
250
251 return 0;
252
253fail:
254 unregister_netdevice_notifier(&drr_dev_notifier);
255 return err;
256}
257
258static void __exit drr_exit(void)
259{
260 unregister_netdevice_notifier(&drr_dev_notifier);
261 multipath_alg_unregister(&drr_ops, IP_MP_ALG_DRR);
262}
263
264module_init(drr_init);
265module_exit(drr_exit);