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/*
* Device round robin policy for multipath.
*
*
* Version: $Id: multipath_drr.c,v 1.1.2.1 2004/09/16 07:42:34 elueck Exp $
*
* Authors: Einar Lueck <elueck@de.ibm.com><lkml@einar-lueck.de>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
#include <linux/config.h>
#include <asm/system.h>
#include <asm/uaccess.h>
#include <linux/types.h>
#include <linux/sched.h>
#include <linux/errno.h>
#include <linux/timer.h>
#include <linux/mm.h>
#include <linux/kernel.h>
#include <linux/fcntl.h>
#include <linux/stat.h>
#include <linux/socket.h>
#include <linux/in.h>
#include <linux/inet.h>
#include <linux/netdevice.h>
#include <linux/inetdevice.h>
#include <linux/igmp.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/module.h>
#include <linux/mroute.h>
#include <linux/init.h>
#include <net/ip.h>
#include <net/protocol.h>
#include <linux/skbuff.h>
#include <net/sock.h>
#include <net/icmp.h>
#include <net/udp.h>
#include <net/raw.h>
#include <linux/notifier.h>
#include <linux/if_arp.h>
#include <linux/netfilter_ipv4.h>
#include <net/ipip.h>
#include <net/checksum.h>
#include <net/ip_mp_alg.h>
struct multipath_device {
int ifi; /* interface index of device */
atomic_t usecount;
int allocated;
};
#define MULTIPATH_MAX_DEVICECANDIDATES 10
static struct multipath_device state[MULTIPATH_MAX_DEVICECANDIDATES];
static DEFINE_SPINLOCK(state_lock);
static int inline __multipath_findslot(void)
{
int i;
for (i = 0; i < MULTIPATH_MAX_DEVICECANDIDATES; i++) {
if (state[i].allocated == 0)
return i;
}
return -1;
}
static int inline __multipath_finddev(int ifindex)
{
int i;
for (i = 0; i < MULTIPATH_MAX_DEVICECANDIDATES; i++) {
if (state[i].allocated != 0 &&
state[i].ifi == ifindex)
return i;
}
return -1;
}
static int drr_dev_event(struct notifier_block *this,
unsigned long event, void *ptr)
{
struct net_device *dev = ptr;
int devidx;
switch (event) {
case NETDEV_UNREGISTER:
case NETDEV_DOWN:
spin_lock_bh(&state_lock);
devidx = __multipath_finddev(dev->ifindex);
if (devidx != -1) {
state[devidx].allocated = 0;
state[devidx].ifi = 0;
atomic_set(&state[devidx].usecount, 0);
}
spin_unlock_bh(&state_lock);
break;
};
return NOTIFY_DONE;
}
static struct notifier_block drr_dev_notifier = {
.notifier_call = drr_dev_event,
};
static void drr_safe_inc(atomic_t *usecount)
{
int n;
atomic_inc(usecount);
n = atomic_read(usecount);
if (n <= 0) {
int i;
spin_lock_bh(&state_lock);
for (i = 0; i < MULTIPATH_MAX_DEVICECANDIDATES; i++)
atomic_set(&state[i].usecount, 0);
spin_unlock_bh(&state_lock);
}
}
static void drr_select_route(const struct flowi *flp,
struct rtable *first, struct rtable **rp)
{
struct rtable *nh, *result, *cur_min;
int min_usecount = -1;
int devidx = -1;
int cur_min_devidx = -1;
/* 1. make sure all alt. nexthops have the same GC related data */
/* 2. determine the new candidate to be returned */
result = NULL;
cur_min = NULL;
for (nh = rcu_dereference(first); nh;
nh = rcu_dereference(nh->u.rt_next)) {
if ((nh->u.dst.flags & DST_BALANCED) != 0 &&
multipath_comparekeys(&nh->fl, flp)) {
int nh_ifidx = nh->u.dst.dev->ifindex;
nh->u.dst.lastuse = jiffies;
nh->u.dst.__use++;
if (result != NULL)
continue;
/* search for the output interface */
/* this is not SMP safe, only add/remove are
* SMP safe as wrong usecount updates have no big
* impact
*/
devidx = __multipath_finddev(nh_ifidx);
if (devidx == -1) {
/* add the interface to the array
* SMP safe
*/
spin_lock_bh(&state_lock);
/* due to SMP: search again */
devidx = __multipath_finddev(nh_ifidx);
if (devidx == -1) {
/* add entry for device */
devidx = __multipath_findslot();
if (devidx == -1) {
/* unlikely but possible */
continue;
}
state[devidx].allocated = 1;
state[devidx].ifi = nh_ifidx;
atomic_set(&state[devidx].usecount, 0);
min_usecount = 0;
}
spin_unlock_bh(&state_lock);
}
if (min_usecount == 0) {
/* if the device has not been used it is
* the primary target
*/
drr_safe_inc(&state[devidx].usecount);
result = nh;
} else {
int count =
atomic_read(&state[devidx].usecount);
if (min_usecount == -1 ||
count < min_usecount) {
cur_min = nh;
cur_min_devidx = devidx;
min_usecount = count;
}
}
}
}
if (!result) {
if (cur_min) {
drr_safe_inc(&state[cur_min_devidx].usecount);
result = cur_min;
} else {
result = first;
}
}
*rp = result;
}
static struct ip_mp_alg_ops drr_ops = {
.mp_alg_select_route = drr_select_route,
};
static int __init drr_init(void)
{
int err = register_netdevice_notifier(&drr_dev_notifier);
if (err)
return err;
err = multipath_alg_register(&drr_ops, IP_MP_ALG_DRR);
if (err)
goto fail;
return 0;
fail:
unregister_netdevice_notifier(&drr_dev_notifier);
return err;
}
static void __exit drr_exit(void)
{
unregister_netdevice_notifier(&drr_dev_notifier);
multipath_alg_unregister(&drr_ops, IP_MP_ALG_DRR);
}
module_init(drr_init);
module_exit(drr_exit);
MODULE_LICENSE("GPL");
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