1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * IPVS: Round-Robin Scheduling module
4 *
5 * Authors: Wensong Zhang <wensong@linuxvirtualserver.org>
6 * Peter Kese <peter.kese@ijs.si>
7 *
8 * Fixes/Changes:
9 * Wensong Zhang : changed the ip_vs_rr_schedule to return dest
10 * Julian Anastasov : fixed the NULL pointer access bug in debugging
11 * Wensong Zhang : changed some comestics things for debugging
12 * Wensong Zhang : changed for the d-linked destination list
13 * Wensong Zhang : added the ip_vs_rr_update_svc
14 * Wensong Zhang : added any dest with weight=0 is quiesced
15 */
16
17#define KMSG_COMPONENT "IPVS"
18#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
19
20#include <linux/module.h>
21#include <linux/kernel.h>
22
23#include <net/ip_vs.h>
24
25
26static int ip_vs_rr_init_svc(struct ip_vs_service *svc)
27{
28 svc->sched_data = &svc->destinations;
29 return 0;
30}
31
32
33static int ip_vs_rr_del_dest(struct ip_vs_service *svc, struct ip_vs_dest *dest)
34{
35 struct list_head *p;
36
37 spin_lock_bh(lock: &svc->sched_lock);
38 p = (struct list_head *) svc->sched_data;
39 /* dest is already unlinked, so p->prev is not valid but
40 * p->next is valid, use it to reach previous entry.
41 */
42 if (p == &dest->n_list)
43 svc->sched_data = p->next->prev;
44 spin_unlock_bh(lock: &svc->sched_lock);
45 return 0;
46}
47
48
49/*
50 * Round-Robin Scheduling
51 */
52static struct ip_vs_dest *
53ip_vs_rr_schedule(struct ip_vs_service *svc, const struct sk_buff *skb,
54 struct ip_vs_iphdr *iph)
55{
56 struct list_head *p;
57 struct ip_vs_dest *dest, *last;
58 int pass = 0;
59
60 IP_VS_DBG(6, "%s(): Scheduling...\n", __func__);
61
62 spin_lock_bh(lock: &svc->sched_lock);
63 p = (struct list_head *) svc->sched_data;
64 last = dest = list_entry(p, struct ip_vs_dest, n_list);
65
66 do {
67 list_for_each_entry_continue_rcu(dest,
68 &svc->destinations,
69 n_list) {
70 if (!(dest->flags & IP_VS_DEST_F_OVERLOAD) &&
71 atomic_read(v: &dest->weight) > 0)
72 /* HIT */
73 goto out;
74 if (dest == last)
75 goto stop;
76 }
77 pass++;
78 /* Previous dest could be unlinked, do not loop forever.
79 * If we stay at head there is no need for 2nd pass.
80 */
81 } while (pass < 2 && p != &svc->destinations);
82
83stop:
84 spin_unlock_bh(lock: &svc->sched_lock);
85 ip_vs_scheduler_err(svc, msg: "no destination available");
86 return NULL;
87
88 out:
89 svc->sched_data = &dest->n_list;
90 spin_unlock_bh(lock: &svc->sched_lock);
91 IP_VS_DBG_BUF(6, "RR: server %s:%u "
92 "activeconns %d refcnt %d weight %d\n",
93 IP_VS_DBG_ADDR(dest->af, &dest->addr), ntohs(dest->port),
94 atomic_read(&dest->activeconns),
95 refcount_read(&dest->refcnt), atomic_read(&dest->weight));
96
97 return dest;
98}
99
100
101static struct ip_vs_scheduler ip_vs_rr_scheduler = {
102 .name = "rr", /* name */
103 .refcnt = ATOMIC_INIT(0),
104 .module = THIS_MODULE,
105 .n_list = LIST_HEAD_INIT(ip_vs_rr_scheduler.n_list),
106 .init_service = ip_vs_rr_init_svc,
107 .add_dest = NULL,
108 .del_dest = ip_vs_rr_del_dest,
109 .schedule = ip_vs_rr_schedule,
110};
111
112static int __init ip_vs_rr_init(void)
113{
114 return register_ip_vs_scheduler(scheduler: &ip_vs_rr_scheduler);
115}
116
117static void __exit ip_vs_rr_cleanup(void)
118{
119 unregister_ip_vs_scheduler(scheduler: &ip_vs_rr_scheduler);
120 synchronize_rcu();
121}
122
123module_init(ip_vs_rr_init);
124module_exit(ip_vs_rr_cleanup);
125MODULE_DESCRIPTION("ipvs round-robin scheduler");
126MODULE_LICENSE("GPL");
127

source code of linux/net/netfilter/ipvs/ip_vs_rr.c