net/netfilter/ipvs/ip_vs_ovf.c

   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  */
  24 static struct ip_vs_dest *
  25 ip_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
  60 static 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
  68 static int __init ip_vs_ovf_init(void)
  69 {
  70         return register_ip_vs_scheduler(&ip_vs_ovf_scheduler);
  71 }
  72
  73 static void __exit ip_vs_ovf_cleanup(void)
  74 {
  75         unregister_ip_vs_scheduler(&ip_vs_ovf_scheduler);
  76         synchronize_rcu();
  77 }
  78
  79 module_init(ip_vs_ovf_init);
  80 module_exit(ip_vs_ovf_cleanup);
  81 MODULE_LICENSE("GPL");