1 files changed, 265 insertions, 0 deletions

diff --git a/net/ipv4/multipath_drr.c b/net/ipv4/multipath_drr.c
new file mode 100644
index 000000000000..9349686131fc
--- /dev/null
+++ b/net/ipv4/multipath_drr.c
@@ -0,0 +1,265 @@
+/*
+ *              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/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 struct rtable *last_selection = NULL;
+
+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;
+}
+
+struct notifier_block drr_dev_notifier = {
+        .notifier_call  = drr_dev_event,
+};
+
+static void drr_remove(struct rtable *rt)
+{
+        if (last_selection == rt)
+                last_selection = NULL;
+}
+
+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;
+
+        /* if necessary and possible utilize the old alternative */
+        if ((flp->flags & FLOWI_FLAG_MULTIPATHOLDROUTE) != 0 &&
+            last_selection != NULL) {
+                result = last_selection;
+                *rp = result;
+                return;
+        }
+
+        /* 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;
+        last_selection = result;
+}
+
+static struct ip_mp_alg_ops drr_ops = {
+        .mp_alg_select_route    =       drr_select_route,
+        .mp_alg_remove          =       drr_remove,
+};
+
+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_RR);
+        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);