net/ipv4/multipath_rr.c

   1 /*
   2  *              Round robin policy for multipath.
   3  *
   4  *
   5  * Version:     $Id: multipath_rr.c,v 1.1.2.2 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/mroute.h>
  35 #include <linux/init.h>
  36 #include <net/ip.h>
  37 #include <net/protocol.h>
  38 #include <linux/skbuff.h>
  39 #include <net/sock.h>
  40 #include <net/icmp.h>
  41 #include <net/udp.h>
  42 #include <net/raw.h>
  43 #include <linux/notifier.h>
  44 #include <linux/if_arp.h>
  45 #include <linux/netfilter_ipv4.h>
  46 #include <net/ipip.h>
  47 #include <net/checksum.h>
  48 #include <net/ip_mp_alg.h>
  49
  50 #define MULTIPATH_MAX_CANDIDATES 40
  51
  52 static struct rtable* last_used = NULL;
  53
  54 static void rr_remove(struct rtable *rt)
  55 {
  56         if (last_used == rt)
  57                 last_used = NULL;
  58 }
  59
  60 static void rr_select_route(const struct flowi *flp,
  61                             struct rtable *first, struct rtable **rp)
  62 {
  63         struct rtable *nh, *result, *min_use_cand = NULL;
  64         int min_use = -1;
  65
  66         /* if necessary and possible utilize the old alternative */
  67         if ((flp->flags & FLOWI_FLAG_MULTIPATHOLDROUTE) != 0 &&
  68             last_used != NULL) {
  69                 result = last_used;
  70                 goto out;
  71         }
  72
  73         /* 1. make sure all alt. nexthops have the same GC related data
  74          * 2. determine the new candidate to be returned
  75          */
  76         result = NULL;
  77         for (nh = rcu_dereference(first); nh;
  78              nh = rcu_dereference(nh->u.rt_next)) {
  79                 if ((nh->u.dst.flags & DST_BALANCED) != 0 &&
  80                     multipath_comparekeys(&nh->fl, flp)) {
  81                         nh->u.dst.lastuse = jiffies;
  82
  83                         if (min_use == -1 || nh->u.dst.__use < min_use) {
  84                                 min_use = nh->u.dst.__use;
  85                                 min_use_cand = nh;
  86                         }
  87                 }
  88         }
  89         result = min_use_cand;
  90         if (!result)
  91                 result = first;
  92
  93 out:
  94         last_used = result;
  95         result->u.dst.__use++;
  96         *rp = result;
  97 }
  98
  99 static struct ip_mp_alg_ops rr_ops = {
 100         .mp_alg_select_route    =       rr_select_route,
 101         .mp_alg_remove          =       rr_remove,
 102 };
 103
 104 static int __init rr_init(void)
 105 {
 106         return multipath_alg_register(&rr_ops, IP_MP_ALG_RR);
 107 }
 108
 109 static void __exit rr_exit(void)
 110 {
 111         multipath_alg_unregister(&rr_ops, IP_MP_ALG_RR);
 112 }
 113
 114 module_init(rr_init);
 115 module_exit(rr_exit);