IPv6: fix race between cleanup and add/delete address
[linux-2.6.git] / net / netfilter / ipvs / ip_vs_rr.c
1 /*
2  * IPVS:        Round-Robin Scheduling module
3  *
4  * Authors:     Wensong Zhang <wensong@linuxvirtualserver.org>
5  *              Peter Kese <peter.kese@ijs.si>
6  *
7  *              This program is free software; you can redistribute it and/or
8  *              modify it under the terms of the GNU General Public License
9  *              as published by the Free Software Foundation; either version
10  *              2 of the License, or (at your option) any later version.
11  *
12  * Fixes/Changes:
13  *     Wensong Zhang            :     changed the ip_vs_rr_schedule to return dest
14  *     Julian Anastasov         :     fixed the NULL pointer access bug in debugging
15  *     Wensong Zhang            :     changed some comestics things for debugging
16  *     Wensong Zhang            :     changed for the d-linked destination list
17  *     Wensong Zhang            :     added the ip_vs_rr_update_svc
18  *     Wensong Zhang            :     added any dest with weight=0 is quiesced
19  *
20  */
21
22 #define KMSG_COMPONENT "IPVS"
23 #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
24
25 #include <linux/module.h>
26 #include <linux/kernel.h>
27
28 #include <net/ip_vs.h>
29
30
31 static int ip_vs_rr_init_svc(struct ip_vs_service *svc)
32 {
33         svc->sched_data = &svc->destinations;
34         return 0;
35 }
36
37
38 static int ip_vs_rr_update_svc(struct ip_vs_service *svc)
39 {
40         svc->sched_data = &svc->destinations;
41         return 0;
42 }
43
44
45 /*
46  * Round-Robin Scheduling
47  */
48 static struct ip_vs_dest *
49 ip_vs_rr_schedule(struct ip_vs_service *svc, const struct sk_buff *skb)
50 {
51         struct list_head *p, *q;
52         struct ip_vs_dest *dest;
53
54         IP_VS_DBG(6, "%s(): Scheduling...\n", __func__);
55
56         write_lock(&svc->sched_lock);
57         p = (struct list_head *)svc->sched_data;
58         p = p->next;
59         q = p;
60         do {
61                 /* skip list head */
62                 if (q == &svc->destinations) {
63                         q = q->next;
64                         continue;
65                 }
66
67                 dest = list_entry(q, struct ip_vs_dest, n_list);
68                 if (!(dest->flags & IP_VS_DEST_F_OVERLOAD) &&
69                     atomic_read(&dest->weight) > 0)
70                         /* HIT */
71                         goto out;
72                 q = q->next;
73         } while (q != p);
74         write_unlock(&svc->sched_lock);
75         IP_VS_ERR_RL("RR: no destination available\n");
76         return NULL;
77
78   out:
79         svc->sched_data = q;
80         write_unlock(&svc->sched_lock);
81         IP_VS_DBG_BUF(6, "RR: server %s:%u "
82                       "activeconns %d refcnt %d weight %d\n",
83                       IP_VS_DBG_ADDR(svc->af, &dest->addr), ntohs(dest->port),
84                       atomic_read(&dest->activeconns),
85                       atomic_read(&dest->refcnt), atomic_read(&dest->weight));
86
87         return dest;
88 }
89
90
91 static struct ip_vs_scheduler ip_vs_rr_scheduler = {
92         .name =                 "rr",                   /* name */
93         .refcnt =               ATOMIC_INIT(0),
94         .module =               THIS_MODULE,
95         .n_list =               LIST_HEAD_INIT(ip_vs_rr_scheduler.n_list),
96         .init_service =         ip_vs_rr_init_svc,
97         .update_service =       ip_vs_rr_update_svc,
98         .schedule =             ip_vs_rr_schedule,
99 };
100
101 static int __init ip_vs_rr_init(void)
102 {
103         return register_ip_vs_scheduler(&ip_vs_rr_scheduler);
104 }
105
106 static void __exit ip_vs_rr_cleanup(void)
107 {
108         unregister_ip_vs_scheduler(&ip_vs_rr_scheduler);
109 }
110
111 module_init(ip_vs_rr_init);
112 module_exit(ip_vs_rr_cleanup);
113 MODULE_LICENSE("GPL");