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

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