1/*
2 * IPVS:        Round-Robin Scheduling module
3 *
4 * Version:     $Id: ip_vs_rr.c,v 1.1.1.1 2007/08/03 18:53:52 Exp $
5 *
6 * Authors:     Wensong Zhang <wensong@linuxvirtualserver.org>
7 *              Peter Kese <peter.kese@ijs.si>
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 * Fixes/Changes:
15 *     Wensong Zhang            :     changed the ip_vs_rr_schedule to return dest
16 *     Julian Anastasov         :     fixed the NULL pointer access bug in debugging
17 *     Wensong Zhang            :     changed some comestics things for debugging
18 *     Wensong Zhang            :     changed for the d-linked destination list
19 *     Wensong Zhang            :     added the ip_vs_rr_update_svc
20 *     Wensong Zhang            :     added any dest with weight=0 is quiesced
21 *
22 */
23
24#include <linux/module.h>
25#include <linux/kernel.h>
26
27#include <net/ip_vs.h>
28
29
30static int ip_vs_rr_init_svc(struct ip_vs_service *svc)
31{
32	svc->sched_data = &svc->destinations;
33	return 0;
34}
35
36
37static int ip_vs_rr_done_svc(struct ip_vs_service *svc)
38{
39	return 0;
40}
41
42
43static int ip_vs_rr_update_svc(struct ip_vs_service *svc)
44{
45	svc->sched_data = &svc->destinations;
46	return 0;
47}
48
49
50/*
51 * Round-Robin Scheduling
52 */
53static struct ip_vs_dest *
54ip_vs_rr_schedule(struct ip_vs_service *svc, const struct sk_buff *skb)
55{
56	struct list_head *p, *q;
57	struct ip_vs_dest *dest;
58
59	IP_VS_DBG(6, "ip_vs_rr_schedule(): Scheduling...\n");
60
61	write_lock(&svc->sched_lock);
62	p = (struct list_head *)svc->sched_data;
63	p = p->next;
64	q = p;
65	do {
66		/* skip list head */
67		if (q == &svc->destinations) {
68			q = q->next;
69			continue;
70		}
71
72		dest = list_entry(q, struct ip_vs_dest, n_list);
73		if (!(dest->flags & IP_VS_DEST_F_OVERLOAD) &&
74		    atomic_read(&dest->weight) > 0)
75			/* HIT */
76			goto out;
77		q = q->next;
78	} while (q != p);
79	write_unlock(&svc->sched_lock);
80	return NULL;
81
82  out:
83	svc->sched_data = q;
84	write_unlock(&svc->sched_lock);
85	IP_VS_DBG(6, "RR: server %u.%u.%u.%u:%u "
86		  "activeconns %d refcnt %d weight %d\n",
87		  NIPQUAD(dest->addr), ntohs(dest->port),
88		  atomic_read(&dest->activeconns),
89		  atomic_read(&dest->refcnt), atomic_read(&dest->weight));
90
91	return dest;
92}
93
94
95static struct ip_vs_scheduler ip_vs_rr_scheduler = {
96	.name =			"rr",			/* name */
97	.refcnt =		ATOMIC_INIT(0),
98	.module =		THIS_MODULE,
99	.init_service =		ip_vs_rr_init_svc,
100	.done_service =		ip_vs_rr_done_svc,
101	.update_service =	ip_vs_rr_update_svc,
102	.schedule =		ip_vs_rr_schedule,
103};
104
105static int __init ip_vs_rr_init(void)
106{
107	INIT_LIST_HEAD(&ip_vs_rr_scheduler.n_list);
108	return register_ip_vs_scheduler(&ip_vs_rr_scheduler);
109}
110
111static void __exit ip_vs_rr_cleanup(void)
112{
113	unregister_ip_vs_scheduler(&ip_vs_rr_scheduler);
114}
115
116module_init(ip_vs_rr_init);
117module_exit(ip_vs_rr_cleanup);
118MODULE_LICENSE("GPL");
119