linux/net/netfilter/ipvs/ip_vs_wrr.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * IPVS:        Weighted Round-Robin Scheduling module
 *
 * Authors:     Wensong Zhang <[email protected]>
 *
 * Changes:
 *     Wensong Zhang            :     changed the ip_vs_wrr_schedule to return dest
 *     Wensong Zhang            :     changed some comestics things for debugging
 *     Wensong Zhang            :     changed for the d-linked destination list
 *     Wensong Zhang            :     added the ip_vs_wrr_update_svc
 *     Julian Anastasov         :     fixed the bug of returning destination
 *                                    with weight 0 when all weights are zero
 */

#define KMSG_COMPONENT …
#define pr_fmt(fmt) …

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/net.h>
#include <linux/gcd.h>

#include <net/ip_vs.h>

/* The WRR algorithm depends on some caclulations:
 * - mw: maximum weight
 * - di: weight step, greatest common divisor from all weights
 * - cw: current required weight
 * As result, all weights are in the [di..mw] range with a step=di.
 *
 * First, we start with cw = mw and select dests with weight >= cw.
 * Then cw is reduced with di and all dests are checked again.
 * Last pass should be with cw = di. We have mw/di passes in total:
 *
 * pass 1: cw = max weight
 * pass 2: cw = max weight - di
 * pass 3: cw = max weight - 2 * di
 * ...
 * last pass: cw = di
 *
 * Weights are supposed to be >= di but we run in parallel with
 * weight changes, it is possible some dest weight to be reduced
 * below di, bad if it is the only available dest.
 *
 * So, we modify how mw is calculated, now it is reduced with (di - 1),
 * so that last cw is 1 to catch such dests with weight below di:
 * pass 1: cw = max weight - (di - 1)
 * pass 2: cw = max weight - di - (di - 1)
 * pass 3: cw = max weight - 2 * di - (di - 1)
 * ...
 * last pass: cw = 1
 *
 */

/*
 * current destination pointer for weighted round-robin scheduling
 */
struct ip_vs_wrr_mark { … };


static int ip_vs_wrr_gcd_weight(struct ip_vs_service *svc)
{ … }


/*
 *    Get the maximum weight of the service destinations.
 */
static int ip_vs_wrr_max_weight(struct ip_vs_service *svc)
{ … }


static int ip_vs_wrr_init_svc(struct ip_vs_service *svc)
{ … }


static void ip_vs_wrr_done_svc(struct ip_vs_service *svc)
{ … }


static int ip_vs_wrr_dest_changed(struct ip_vs_service *svc,
				  struct ip_vs_dest *dest)
{ … }


/*
 *    Weighted Round-Robin Scheduling
 */
static struct ip_vs_dest *
ip_vs_wrr_schedule(struct ip_vs_service *svc, const struct sk_buff *skb,
		   struct ip_vs_iphdr *iph)
{ … }


static struct ip_vs_scheduler ip_vs_wrr_scheduler = …;

static int __init ip_vs_wrr_init(void)
{ … }

static void __exit ip_vs_wrr_cleanup(void)
{ … }

module_init(…) …;
module_exit(ip_vs_wrr_cleanup);
MODULE_LICENSE(…) …;
MODULE_DESCRIPTION(…) …;