net/ipv4/netfilter/ipt_SAME.c

   1 /* Same.  Just like SNAT, only try to make the connections
   2  *        between client A and server B always have the same source ip.
   3  *
   4  * (C) 2000 Paul `Rusty' Russell
   5  * (C) 2001 Martin Josefsson
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  *
  11  * 010320 Martin Josefsson <gandalf@wlug.westbo.se>
  12  *      * copied ipt_BALANCE.c to ipt_SAME.c and changed a few things.
  13  * 010728 Martin Josefsson <gandalf@wlug.westbo.se>
  14  *      * added --nodst to not include destination-ip in new source
  15  *        calculations.
  16  *      * added some more sanity-checks.
  17  * 010729 Martin Josefsson <gandalf@wlug.westbo.se>
  18  *      * fixed a buggy if-statement in same_check(), should have
  19  *        used ntohl() but didn't.
  20  *      * added support for multiple ranges. IPT_SAME_MAX_RANGE is
  21  *        defined in linux/include/linux/netfilter_ipv4/ipt_SAME.h
  22  *        and is currently set to 10.
  23  *      * added support for 1-address range, nice to have now that
  24  *        we have multiple ranges.
  25  */
  26 #include <linux/types.h>
  27 #include <linux/ip.h>
  28 #include <linux/timer.h>
  29 #include <linux/module.h>
  30 #include <linux/netfilter.h>
  31 #include <linux/netdevice.h>
  32 #include <linux/if.h>
  33 #include <linux/inetdevice.h>
  34 #include <net/protocol.h>
  35 #include <net/checksum.h>
  36 #include <linux/netfilter_ipv4.h>
  37 #ifdef CONFIG_NF_NAT_NEEDED
  38 #include <net/netfilter/nf_nat_rule.h>
  39 #else
  40 #include <linux/netfilter_ipv4/ip_nat_rule.h>
  41 #endif
  42 #include <linux/netfilter_ipv4/ipt_SAME.h>
  43
  44 MODULE_LICENSE("GPL");
  45 MODULE_AUTHOR("Martin Josefsson <gandalf@wlug.westbo.se>");
  46 MODULE_DESCRIPTION("iptables special SNAT module for consistent sourceip");
  47
  48 #if 0
  49 #define DEBUGP printk
  50 #else
  51 #define DEBUGP(format, args...)
  52 #endif
  53
  54 static int
  55 same_check(const char *tablename,
  56               const void *e,
  57               const struct xt_target *target,
  58               void *targinfo,
  59               unsigned int hook_mask)
  60 {
  61         unsigned int count, countess, rangeip, index = 0;
  62         struct ipt_same_info *mr = targinfo;
  63
  64         mr->ipnum = 0;
  65
  66         if (mr->rangesize < 1) {
  67                 DEBUGP("same_check: need at least one dest range.\n");
  68                 return 0;
  69         }
  70         if (mr->rangesize > IPT_SAME_MAX_RANGE) {
  71                 DEBUGP("same_check: too many ranges specified, maximum "
  72                                 "is %u ranges\n",
  73                                 IPT_SAME_MAX_RANGE);
  74                 return 0;
  75         }
  76         for (count = 0; count < mr->rangesize; count++) {
  77                 if (ntohl(mr->range[count].min_ip) >
  78                                 ntohl(mr->range[count].max_ip)) {
  79                         DEBUGP("same_check: min_ip is larger than max_ip in "
  80                                 "range `%u.%u.%u.%u-%u.%u.%u.%u'.\n",
  81                                 NIPQUAD(mr->range[count].min_ip),
  82                                 NIPQUAD(mr->range[count].max_ip));
  83                         return 0;
  84                 }
  85                 if (!(mr->range[count].flags & IP_NAT_RANGE_MAP_IPS)) {
  86                         DEBUGP("same_check: bad MAP_IPS.\n");
  87                         return 0;
  88                 }
  89                 rangeip = (ntohl(mr->range[count].max_ip) -
  90                                         ntohl(mr->range[count].min_ip) + 1);
  91                 mr->ipnum += rangeip;
  92
  93                 DEBUGP("same_check: range %u, ipnum = %u\n", count, rangeip);
  94         }
  95         DEBUGP("same_check: total ipaddresses = %u\n", mr->ipnum);
  96
  97         mr->iparray = kmalloc((sizeof(u_int32_t) * mr->ipnum), GFP_KERNEL);
  98         if (!mr->iparray) {
  99                 DEBUGP("same_check: Couldn't allocate %u bytes "
 100                         "for %u ipaddresses!\n",
 101                         (sizeof(u_int32_t) * mr->ipnum), mr->ipnum);
 102                 return 0;
 103         }
 104         DEBUGP("same_check: Allocated %u bytes for %u ipaddresses.\n",
 105                         (sizeof(u_int32_t) * mr->ipnum), mr->ipnum);
 106
 107         for (count = 0; count < mr->rangesize; count++) {
 108                 for (countess = ntohl(mr->range[count].min_ip);
 109                                 countess <= ntohl(mr->range[count].max_ip);
 110                                         countess++) {
 111                         mr->iparray[index] = countess;
 112                         DEBUGP("same_check: Added ipaddress `%u.%u.%u.%u' "
 113                                 "in index %u.\n",
 114                                 HIPQUAD(countess), index);
 115                         index++;
 116                 }
 117         }
 118         return 1;
 119 }
 120
 121 static void
 122 same_destroy(const struct xt_target *target, void *targinfo)
 123 {
 124         struct ipt_same_info *mr = targinfo;
 125
 126         kfree(mr->iparray);
 127
 128         DEBUGP("same_destroy: Deallocated %u bytes for %u ipaddresses.\n",
 129                         (sizeof(u_int32_t) * mr->ipnum), mr->ipnum);
 130 }
 131
 132 static unsigned int
 133 same_target(struct sk_buff **pskb,
 134                 const struct net_device *in,
 135                 const struct net_device *out,
 136                 unsigned int hooknum,
 137                 const struct xt_target *target,
 138                 const void *targinfo)
 139 {
 140         struct ip_conntrack *ct;
 141         enum ip_conntrack_info ctinfo;
 142         u_int32_t tmpip, aindex;
 143         __be32 new_ip;
 144         const struct ipt_same_info *same = targinfo;
 145         struct ip_nat_range newrange;
 146         const struct ip_conntrack_tuple *t;
 147
 148         IP_NF_ASSERT(hooknum == NF_IP_PRE_ROUTING ||
 149                         hooknum == NF_IP_POST_ROUTING);
 150         ct = ip_conntrack_get(*pskb, &ctinfo);
 151
 152         t = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
 153
 154         /* Base new source on real src ip and optionally dst ip,
 155            giving some hope for consistency across reboots.
 156            Here we calculate the index in same->iparray which
 157            holds the ipaddress we should use */
 158
 159 #ifdef CONFIG_NF_NAT_NEEDED
 160         tmpip = ntohl(t->src.u3.ip);
 161
 162         if (!(same->info & IPT_SAME_NODST))
 163                 tmpip += ntohl(t->dst.u3.ip);
 164 #else
 165         tmpip = ntohl(t->src.ip);
 166
 167         if (!(same->info & IPT_SAME_NODST))
 168                 tmpip += ntohl(t->dst.ip);
 169 #endif
 170         aindex = tmpip % same->ipnum;
 171
 172         new_ip = htonl(same->iparray[aindex]);
 173
 174         DEBUGP("ipt_SAME: src=%u.%u.%u.%u dst=%u.%u.%u.%u, "
 175                         "new src=%u.%u.%u.%u\n",
 176                         NIPQUAD(t->src.ip), NIPQUAD(t->dst.ip),
 177                         NIPQUAD(new_ip));
 178
 179         /* Transfer from original range. */
 180         newrange = ((struct ip_nat_range)
 181                 { same->range[0].flags, new_ip, new_ip,
 182                   /* FIXME: Use ports from correct range! */
 183                   same->range[0].min, same->range[0].max });
 184
 185         /* Hand modified range to generic setup. */
 186         return ip_nat_setup_info(ct, &newrange, hooknum);
 187 }
 188
 189 static struct ipt_target same_reg = {
 190         .name           = "SAME",
 191         .target         = same_target,
 192         .targetsize     = sizeof(struct ipt_same_info),
 193         .table          = "nat",
 194         .hooks          = (1 << NF_IP_PRE_ROUTING | 1 << NF_IP_POST_ROUTING),
 195         .checkentry     = same_check,
 196         .destroy        = same_destroy,
 197         .me             = THIS_MODULE,
 198 };
 199
 200 static int __init ipt_same_init(void)
 201 {
 202         return ipt_register_target(&same_reg);
 203 }
 204
 205 static void __exit ipt_same_fini(void)
 206 {
 207         ipt_unregister_target(&same_reg);
 208 }
 209
 210 module_init(ipt_same_init);
 211 module_exit(ipt_same_fini);
 212