net/netfilter/ipvs/ip_vs_lc.c

   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 *
  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
  75 static int __init ip_vs_lc_init(void)
  76 {
  77         return register_ip_vs_scheduler(&ip_vs_lc_scheduler) ;
  78 }
  79
  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");