net/ipv4/multipath_drr.c

   1 /*
   2  *              Device round robin policy for multipath.
   3  *
   4  *
   5  * Version:     $Id: multipath_drr.c,v 1.1.2.1 2004/09/16 07:42:34 elueck Exp $
   6  *
   7  * Authors:     Einar Lueck <elueck@de.ibm.com><lkml@einar-lueck.de>
   8  *
   9  *              This program is free software; you can redistribute it and/or
  10  *              modify it under the terms of the GNU General Public License
  11  *              as published by the Free Software Foundation; either version
  12  *              2 of the License, or (at your option) any later version.
  13  */
  14
  15 #include <linux/config.h>
  16 #include <asm/system.h>
  17 #include <asm/uaccess.h>
  18 #include <linux/types.h>
  19 #include <linux/sched.h>
  20 #include <linux/errno.h>
  21 #include <linux/timer.h>
  22 #include <linux/mm.h>
  23 #include <linux/kernel.h>
  24 #include <linux/fcntl.h>
  25 #include <linux/stat.h>
  26 #include <linux/socket.h>
  27 #include <linux/in.h>
  28 #include <linux/inet.h>
  29 #include <linux/netdevice.h>
  30 #include <linux/inetdevice.h>
  31 #include <linux/igmp.h>
  32 #include <linux/proc_fs.h>
  33 #include <linux/seq_file.h>
  34 #include <linux/module.h>
  35 #include <linux/mroute.h>
  36 #include <linux/init.h>
  37 #include <net/ip.h>
  38 #include <net/protocol.h>
  39 #include <linux/skbuff.h>
  40 #include <net/sock.h>
  41 #include <net/icmp.h>
  42 #include <net/udp.h>
  43 #include <net/raw.h>
  44 #include <linux/notifier.h>
  45 #include <linux/if_arp.h>
  46 #include <linux/netfilter_ipv4.h>
  47 #include <net/ipip.h>
  48 #include <net/checksum.h>
  49 #include <net/ip_mp_alg.h>
  50
  51 struct multipath_device {
  52         int             ifi; /* interface index of device */
  53         atomic_t        usecount;
  54         int             allocated;
  55 };
  56
  57 #define MULTIPATH_MAX_DEVICECANDIDATES 10
  58
  59 static struct multipath_device state[MULTIPATH_MAX_DEVICECANDIDATES];
  60 static DEFINE_SPINLOCK(state_lock);
  61
  62 static int inline __multipath_findslot(void)
  63 {
  64         int i;
  65
  66         for (i = 0; i < MULTIPATH_MAX_DEVICECANDIDATES; i++) {
  67                 if (state[i].allocated == 0)
  68                         return i;
  69         }
  70         return -1;
  71 }
  72
  73 static int inline __multipath_finddev(int ifindex)
  74 {
  75         int i;
  76
  77         for (i = 0; i < MULTIPATH_MAX_DEVICECANDIDATES; i++) {
  78                 if (state[i].allocated != 0 &&
  79                     state[i].ifi == ifindex)
  80                         return i;
  81         }
  82         return -1;
  83 }
  84
  85 static int drr_dev_event(struct notifier_block *this,
  86                          unsigned long event, void *ptr)
  87 {
  88         struct net_device *dev = ptr;
  89         int devidx;
  90
  91         switch (event) {
  92         case NETDEV_UNREGISTER:
  93         case NETDEV_DOWN:
  94                 spin_lock_bh(&state_lock);
  95
  96                 devidx = __multipath_finddev(dev->ifindex);
  97                 if (devidx != -1) {
  98                         state[devidx].allocated = 0;
  99                         state[devidx].ifi = 0;
 100                         atomic_set(&state[devidx].usecount, 0);
 101                 }
 102
 103                 spin_unlock_bh(&state_lock);
 104                 break;
 105         };
 106
 107         return NOTIFY_DONE;
 108 }
 109
 110 static struct notifier_block drr_dev_notifier = {
 111         .notifier_call  = drr_dev_event,
 112 };
 113
 114
 115 static void drr_safe_inc(atomic_t *usecount)
 116 {
 117         int n;
 118
 119         atomic_inc(usecount);
 120
 121         n = atomic_read(usecount);
 122         if (n <= 0) {
 123                 int i;
 124
 125                 spin_lock_bh(&state_lock);
 126
 127                 for (i = 0; i < MULTIPATH_MAX_DEVICECANDIDATES; i++)
 128                         atomic_set(&state[i].usecount, 0);
 129
 130                 spin_unlock_bh(&state_lock);
 131         }
 132 }
 133
 134 static void drr_select_route(const struct flowi *flp,
 135                              struct rtable *first, struct rtable **rp)
 136 {
 137         struct rtable *nh, *result, *cur_min;
 138         int min_usecount = -1;
 139         int devidx = -1;
 140         int cur_min_devidx = -1;
 141
 142         /* 1. make sure all alt. nexthops have the same GC related data */
 143         /* 2. determine the new candidate to be returned */
 144         result = NULL;
 145         cur_min = NULL;
 146         for (nh = rcu_dereference(first); nh;
 147              nh = rcu_dereference(nh->u.rt_next)) {
 148                 if ((nh->u.dst.flags & DST_BALANCED) != 0 &&
 149                     multipath_comparekeys(&nh->fl, flp)) {
 150                         int nh_ifidx = nh->u.dst.dev->ifindex;
 151
 152                         nh->u.dst.lastuse = jiffies;
 153                         nh->u.dst.__use++;
 154                         if (result != NULL)
 155                                 continue;
 156
 157                         /* search for the output interface */
 158
 159                         /* this is not SMP safe, only add/remove are
 160                          * SMP safe as wrong usecount updates have no big
 161                          * impact
 162                          */
 163                         devidx = __multipath_finddev(nh_ifidx);
 164                         if (devidx == -1) {
 165                                 /* add the interface to the array
 166                                  * SMP safe
 167                                  */
 168                                 spin_lock_bh(&state_lock);
 169
 170                                 /* due to SMP: search again */
 171                                 devidx = __multipath_finddev(nh_ifidx);
 172                                 if (devidx == -1) {
 173                                         /* add entry for device */
 174                                         devidx = __multipath_findslot();
 175                                         if (devidx == -1) {
 176                                                 /* unlikely but possible */
 177                                                 continue;
 178                                         }
 179
 180                                         state[devidx].allocated = 1;
 181                                         state[devidx].ifi = nh_ifidx;
 182                                         atomic_set(&state[devidx].usecount, 0);
 183                                         min_usecount = 0;
 184                                 }
 185
 186                                 spin_unlock_bh(&state_lock);
 187                         }
 188
 189                         if (min_usecount == 0) {
 190                                 /* if the device has not been used it is
 191                                  * the primary target
 192                                  */
 193                                 drr_safe_inc(&state[devidx].usecount);
 194                                 result = nh;
 195                         } else {
 196                                 int count =
 197                                         atomic_read(&state[devidx].usecount);
 198
 199                                 if (min_usecount == -1 ||
 200                                     count < min_usecount) {
 201                                         cur_min = nh;
 202                                         cur_min_devidx = devidx;
 203                                         min_usecount = count;
 204                                 }
 205                         }
 206                 }
 207         }
 208
 209         if (!result) {
 210                 if (cur_min) {
 211                         drr_safe_inc(&state[cur_min_devidx].usecount);
 212                         result = cur_min;
 213                 } else {
 214                         result = first;
 215                 }
 216         }
 217
 218         *rp = result;
 219 }
 220
 221 static struct ip_mp_alg_ops drr_ops = {
 222         .mp_alg_select_route    =       drr_select_route,
 223 };
 224
 225 static int __init drr_init(void)
 226 {
 227         int err = register_netdevice_notifier(&drr_dev_notifier);
 228
 229         if (err)
 230                 return err;
 231
 232         err = multipath_alg_register(&drr_ops, IP_MP_ALG_DRR);
 233         if (err)
 234                 goto fail;
 235
 236         return 0;
 237
 238 fail:
 239         unregister_netdevice_notifier(&drr_dev_notifier);
 240         return err;
 241 }
 242
 243 static void __exit drr_exit(void)
 244 {
 245         unregister_netdevice_notifier(&drr_dev_notifier);
 246         multipath_alg_unregister(&drr_ops, IP_MP_ALG_DRR);
 247 }
 248
 249 module_init(drr_init);
 250 module_exit(drr_exit);
 251 MODULE_LICENSE("GPL");