// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * IPVS:        Weighted Fail Over module
 *
 * Authors:     Kenny Mathis <kmathis@chokepoint.net>
 *
 * Changes:
 *     Kenny Mathis            :     added initial functionality based on weight
 */

#define pr_fmt(fmt) "IPVS: " fmt

#include <linux/module.h>
#include <linux/kernel.h>

#include <net/ip_vs.h>

/* Weighted Fail Over Module */
static struct ip_vs_dest *
ip_vs_fo_schedule(struct ip_vs_service *svc, const struct sk_buff *skb,
                  struct ip_vs_iphdr *iph)
{
        struct ip_vs_dest *dest, *hweight = NULL;
        int hw = 0; /* Track highest weight */

        IP_VS_DBG(6, "ip_vs_fo_schedule(): Scheduling...\n");

        /* Basic failover functionality
         * Find virtual server with highest weight and send it traffic
         */
        list_for_each_entry_rcu(dest, &svc->destinations, n_list) {
                if (!(dest->flags & IP_VS_DEST_F_OVERLOAD) &&
                    atomic_read(&dest->weight) > hw) {
                        hweight = dest;
                        hw = atomic_read(&dest->weight);
                }
        }

        if (hweight) {
                IP_VS_DBG_BUF(6, "FO: server %s:%u activeconns %d weight %d\n",
                              IP_VS_DBG_ADDR(hweight->af, &hweight->addr),
                              ntohs(hweight->port),
                              atomic_read(&hweight->activeconns),
                              atomic_read(&hweight->weight));
                return hweight;
        }

        ip_vs_scheduler_err(svc, "no destination available");
        return NULL;
}

static struct ip_vs_scheduler ip_vs_fo_scheduler = {
        .name =                 "fo",
        .refcnt =               ATOMIC_INIT(0),
        .module =               THIS_MODULE,
        .n_list =               LIST_HEAD_INIT(ip_vs_fo_scheduler.n_list),
        .schedule =             ip_vs_fo_schedule,
};

static int __init ip_vs_fo_init(void)
{
        return register_ip_vs_scheduler(&ip_vs_fo_scheduler);
}

static void __exit ip_vs_fo_cleanup(void)
{
        unregister_ip_vs_scheduler(&ip_vs_fo_scheduler);
        synchronize_rcu();
}

module_init(ip_vs_fo_init);
module_exit(ip_vs_fo_cleanup);
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("ipvs weighted failover scheduler");