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  MODULE_DESCRIPTION("ipvs least connection scheduler");
90