net/netfilter/ipvs/ip_vs_rr.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * IPVS:        Round-Robin Scheduling module
   4  *
   5  * Authors:     Wensong Zhang <wensong@linuxvirtualserver.org>
   6  *              Peter Kese <peter.kese@ijs.si>
   7  *
   8  * Fixes/Changes:
   9  *     Wensong Zhang            :     changed the ip_vs_rr_schedule to return dest
  10  *     Julian Anastasov         :     fixed the NULL pointer access bug in debugging
  11  *     Wensong Zhang            :     changed some comestics things for debugging
  12  *     Wensong Zhang            :     changed for the d-linked destination list
  13  *     Wensong Zhang            :     added the ip_vs_rr_update_svc
  14  *     Wensong Zhang            :     added any dest with weight=0 is quiesced
  15  */
  16
  17 #define KMSG_COMPONENT "IPVS"
  18 #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
  19
  20 #include <linux/module.h>
  21 #include <linux/kernel.h>
  22
  23 #include <net/ip_vs.h>
  24
  25
  26 static int ip_vs_rr_init_svc(struct ip_vs_service *svc)
  27 {
  28         svc->sched_data = &svc->destinations;
  29         return 0;
  30 }
  31
  32
  33 static int ip_vs_rr_del_dest(struct ip_vs_service *svc, struct ip_vs_dest *dest)
  34 {
  35         struct list_head *p;
  36
  37         spin_lock_bh(&svc->sched_lock);
  38         p = (struct list_head *) svc->sched_data;
  39         /* dest is already unlinked, so p->prev is not valid but
  40          * p->next is valid, use it to reach previous entry.
  41          */
  42         if (p == &dest->n_list)
  43                 svc->sched_data = p->next->prev;
  44         spin_unlock_bh(&svc->sched_lock);
  45         return 0;
  46 }
  47
  48
  49 /*
  50  * Round-Robin Scheduling
  51  */
  52 static struct ip_vs_dest *
  53 ip_vs_rr_schedule(struct ip_vs_service *svc, const struct sk_buff *skb,
  54                   struct ip_vs_iphdr *iph)
  55 {
  56         struct list_head *p;
  57         struct ip_vs_dest *dest, *last;
  58         int pass = 0;
  59
  60         IP_VS_DBG(6, "%s(): Scheduling...\n", __func__);
  61
  62         spin_lock_bh(&svc->sched_lock);
  63         p = (struct list_head *) svc->sched_data;
  64         last = dest = list_entry(p, struct ip_vs_dest, n_list);
  65
  66         do {
  67                 list_for_each_entry_continue_rcu(dest,
  68                                                  &svc->destinations,
  69                                                  n_list) {
  70                         if (!(dest->flags & IP_VS_DEST_F_OVERLOAD) &&
  71                             atomic_read(&dest->weight) > 0)
  72                                 /* HIT */
  73                                 goto out;
  74                         if (dest == last)
  75                                 goto stop;
  76                 }
  77                 pass++;
  78                 /* Previous dest could be unlinked, do not loop forever.
  79                  * If we stay at head there is no need for 2nd pass.
  80                  */
  81         } while (pass < 2 && p != &svc->destinations);
  82
  83 stop:
  84         spin_unlock_bh(&svc->sched_lock);
  85         ip_vs_scheduler_err(svc, "no destination available");
  86         return NULL;
  87
  88   out:
  89         svc->sched_data = &dest->n_list;
  90         spin_unlock_bh(&svc->sched_lock);
  91         IP_VS_DBG_BUF(6, "RR: server %s:%u "
  92                       "activeconns %d refcnt %d weight %d\n",
  93                       IP_VS_DBG_ADDR(dest->af, &dest->addr), ntohs(dest->port),
  94                       atomic_read(&dest->activeconns),
  95                       refcount_read(&dest->refcnt), atomic_read(&dest->weight));
  96
  97         return dest;
  98 }
  99
 100
 101 static struct ip_vs_scheduler ip_vs_rr_scheduler = {
 102         .name =                 "rr",                   /* name */
 103         .refcnt =               ATOMIC_INIT(0),
 104         .module =               THIS_MODULE,
 105         .n_list =               LIST_HEAD_INIT(ip_vs_rr_scheduler.n_list),
 106         .init_service =         ip_vs_rr_init_svc,
 107         .add_dest =             NULL,
 108         .del_dest =             ip_vs_rr_del_dest,
 109         .schedule =             ip_vs_rr_schedule,
 110 };
 111
 112 static int __init ip_vs_rr_init(void)
 113 {
 114         return register_ip_vs_scheduler(&ip_vs_rr_scheduler);
 115 }
 116
 117 static void __exit ip_vs_rr_cleanup(void)
 118 {
 119         unregister_ip_vs_scheduler(&ip_vs_rr_scheduler);
 120         synchronize_rcu();
 121 }
 122
 123 module_init(ip_vs_rr_init);
 124 module_exit(ip_vs_rr_cleanup);
 125 MODULE_LICENSE("GPL");