1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * IPVS: Least-Connection Scheduling module
4 *
5 * Authors: Wensong Zhang <wensong@linuxvirtualserver.org>
6 *
7 * Changes:
8 * Wensong Zhang : added the ip_vs_lc_update_svc
9 * Wensong Zhang : added any dest with weight=0 is quiesced
10 */
11
12 #define KMSG_COMPONENT "IPVS"
13 #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
14
15 #include <linux/module.h>
16 #include <linux/kernel.h>
17
18 #include <net/ip_vs.h>
19
20 /*
21 * Least Connection scheduling
22 */
23 static struct ip_vs_dest *
ip_vs_lc_schedule(struct ip_vs_service * svc,const struct sk_buff * skb,struct ip_vs_iphdr * iph)24 ip_vs_lc_schedule(struct ip_vs_service *svc, const struct sk_buff *skb,
25 struct ip_vs_iphdr *iph)
26 {
27 struct ip_vs_dest *dest, *least = NULL;
28 unsigned int loh = 0, doh;
29
30 IP_VS_DBG(6, "%s(): Scheduling...\n", __func__);
31
32 /*
33 * Simply select the server with the least number of
34 * (activeconns<<5) + inactconns
35 * Except whose weight is equal to zero.
36 * If the weight is equal to zero, it means that the server is
37 * quiesced, the existing connections to the server still get
38 * served, but no new connection is assigned to the server.
39 */
40
41 list_for_each_entry_rcu(dest, &svc->destinations, n_list) {
42 if ((dest->flags & IP_VS_DEST_F_OVERLOAD) ||
43 atomic_read(&dest->weight) == 0)
44 continue;
45 doh = ip_vs_dest_conn_overhead(dest);
46 if (!least || doh < loh) {
47 least = dest;
48 loh = doh;
49 }
50 }
51
52 if (!least)
53 ip_vs_scheduler_err(svc, "no destination available");
54 else
55 IP_VS_DBG_BUF(6, "LC: server %s:%u activeconns %d "
56 "inactconns %d\n",
57 IP_VS_DBG_ADDR(least->af, &least->addr),
58 ntohs(least->port),
59 atomic_read(&least->activeconns),
60 atomic_read(&least->inactconns));
61
62 return least;
63 }
64
65
66 static struct ip_vs_scheduler ip_vs_lc_scheduler = {
67 .name = "lc",
68 .refcnt = ATOMIC_INIT(0),
69 .module = THIS_MODULE,
70 .n_list = LIST_HEAD_INIT(ip_vs_lc_scheduler.n_list),
71 .schedule = ip_vs_lc_schedule,
72 };
73
74
ip_vs_lc_init(void)75 static int __init ip_vs_lc_init(void)
76 {
77 return register_ip_vs_scheduler(&ip_vs_lc_scheduler) ;
78 }
79
ip_vs_lc_cleanup(void)80 static void __exit ip_vs_lc_cleanup(void)
81 {
82 unregister_ip_vs_scheduler(&ip_vs_lc_scheduler);
83 synchronize_rcu();
84 }
85
86 module_init(ip_vs_lc_init);
87 module_exit(ip_vs_lc_cleanup);
88 MODULE_LICENSE("GPL");
89