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(v: &dest->weight);
37 if ((dest->flags & IP_VS_DEST_F_OVERLOAD) ||
38 atomic_read(v: &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, msg: "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(scheduler: &ip_vs_ovf_scheduler);
71}
72
73static void __exit ip_vs_ovf_cleanup(void)
74{
75 unregister_ip_vs_scheduler(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

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