1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * IPVS:        Overflow-Connection Scheduling module
4 *
5 * Authors:     Raducu Deaconu <rhadoo_io@yahoo.com>
6 *
7 * Scheduler implements "overflow" loadbalancing according to number of active
8 * connections , will keep all connections to the node with the highest weight
9 * and overflow to the next node if the number of connections exceeds the node's
10 * weight.
11 * Note that this scheduler might not be suitable for UDP because it only uses
12 * active connections
13 */
14
15#define KMSG_COMPONENT "IPVS"
16#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
17
18#include <linux/module.h>
19#include <linux/kernel.h>
20
21#include <net/ip_vs.h>
22
23/* OVF Connection scheduling  */
24static struct ip_vs_dest *
25ip_vs_ovf_schedule(struct ip_vs_service *svc, const struct sk_buff *skb,
26		   struct ip_vs_iphdr *iph)
27{
28	struct ip_vs_dest *dest, *h = NULL;
29	int hw = 0, w;
30
31	IP_VS_DBG(6, "ip_vs_ovf_schedule(): Scheduling...\n");
32	/* select the node with highest weight, go to next in line if active
33	* connections exceed weight
34	*/
35	list_for_each_entry_rcu(dest, &svc->destinations, n_list) {
36		w = atomic_read(&dest->weight);
37		if ((dest->flags & IP_VS_DEST_F_OVERLOAD) ||
38		    atomic_read(&dest->activeconns) > w ||
39		    w == 0)
40			continue;
41		if (!h || w > hw) {
42			h = dest;
43			hw = w;
44		}
45	}
46
47	if (h) {
48		IP_VS_DBG_BUF(6, "OVF: server %s:%u active %d w %d\n",
49			      IP_VS_DBG_ADDR(h->af, &h->addr),
50			      ntohs(h->port),
51			      atomic_read(&h->activeconns),
52			      atomic_read(&h->weight));
53		return h;
54	}
55
56	ip_vs_scheduler_err(svc, "no destination available");
57	return NULL;
58}
59
60static struct ip_vs_scheduler ip_vs_ovf_scheduler = {
61	.name =			"ovf",
62	.refcnt =		ATOMIC_INIT(0),
63	.module =		THIS_MODULE,
64	.n_list =		LIST_HEAD_INIT(ip_vs_ovf_scheduler.n_list),
65	.schedule =		ip_vs_ovf_schedule,
66};
67
68static int __init ip_vs_ovf_init(void)
69{
70	return register_ip_vs_scheduler(&ip_vs_ovf_scheduler);
71}
72
73static void __exit ip_vs_ovf_cleanup(void)
74{
75	unregister_ip_vs_scheduler(&ip_vs_ovf_scheduler);
76	synchronize_rcu();
77}
78
79module_init(ip_vs_ovf_init);
80module_exit(ip_vs_ovf_cleanup);
81MODULE_LICENSE("GPL");
82MODULE_DESCRIPTION("ipvs overflow connection scheduler");
83