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 */
23static struct ip_vs_dest *
24ip_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
66static 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
75static int __init ip_vs_lc_init(void)
76{
77	return register_ip_vs_scheduler(&ip_vs_lc_scheduler) ;
78}
79
80static void __exit ip_vs_lc_cleanup(void)
81{
82	unregister_ip_vs_scheduler(&ip_vs_lc_scheduler);
83	synchronize_rcu();
84}
85
86module_init(ip_vs_lc_init);
87module_exit(ip_vs_lc_cleanup);
88MODULE_LICENSE("GPL");
89MODULE_DESCRIPTION("ipvs least connection scheduler");
90