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 #include <linux/netfilter_ipv4/ip_nat_rule.h>
  38 #include <linux/netfilter_ipv4/ipt_SAME.h>
  39
  40 MODULE_LICENSE("GPL");
  41 MODULE_AUTHOR("Martin Josefsson <gandalf@wlug.westbo.se>");
  42 MODULE_DESCRIPTION("iptables special SNAT module for consistent sourceip");
  43
  44 #if 0
  45 #define DEBUGP printk
  46 #else
  47 #define DEBUGP(format, args...)
  48 #endif
  49
  50 static int
  51 same_check(const char *tablename,
  52               const void *e,
  53               const struct xt_target *target,
  54               void *targinfo,
  55               unsigned int hook_mask)
  56 {
  57         unsigned int count, countess, rangeip, index = 0;
  58         struct ipt_same_info *mr = targinfo;
  59
  60         mr->ipnum = 0;
  61
  62         if (mr->rangesize < 1) {
  63                 DEBUGP("same_check: need at least one dest range.\n");
  64                 return 0;
  65         }
  66         if (mr->rangesize > IPT_SAME_MAX_RANGE) {
  67                 DEBUGP("same_check: too many ranges specified, maximum "
  68                                 "is %u ranges\n",
  69                                 IPT_SAME_MAX_RANGE);
  70                 return 0;
  71         }
  72         for (count = 0; count < mr->rangesize; count++) {
  73                 if (ntohl(mr->range[count].min_ip) >
  74                                 ntohl(mr->range[count].max_ip)) {
  75                         DEBUGP("same_check: min_ip is larger than max_ip in "
  76                                 "range `%u.%u.%u.%u-%u.%u.%u.%u'.\n",
  77                                 NIPQUAD(mr->range[count].min_ip),
  78                                 NIPQUAD(mr->range[count].max_ip));
  79                         return 0;
  80                 }
  81                 if (!(mr->range[count].flags & IP_NAT_RANGE_MAP_IPS)) {
  82                         DEBUGP("same_check: bad MAP_IPS.\n");
  83                         return 0;
  84                 }
  85                 rangeip = (ntohl(mr->range[count].max_ip) -
  86                                         ntohl(mr->range[count].min_ip) + 1);
  87                 mr->ipnum += rangeip;
  88
  89                 DEBUGP("same_check: range %u, ipnum = %u\n", count, rangeip);
  90         }
  91         DEBUGP("same_check: total ipaddresses = %u\n", mr->ipnum);
  92
  93         mr->iparray = kmalloc((sizeof(u_int32_t) * mr->ipnum), GFP_KERNEL);
  94         if (!mr->iparray) {
  95                 DEBUGP("same_check: Couldn't allocate %u bytes "
  96                         "for %u ipaddresses!\n",
  97                         (sizeof(u_int32_t) * mr->ipnum), mr->ipnum);
  98                 return 0;
  99         }
 100         DEBUGP("same_check: Allocated %u bytes for %u ipaddresses.\n",
 101                         (sizeof(u_int32_t) * mr->ipnum), mr->ipnum);
 102
 103         for (count = 0; count < mr->rangesize; count++) {
 104                 for (countess = ntohl(mr->range[count].min_ip);
 105                                 countess <= ntohl(mr->range[count].max_ip);
 106                                         countess++) {
 107                         mr->iparray[index] = countess;
 108                         DEBUGP("same_check: Added ipaddress `%u.%u.%u.%u' "
 109                                 "in index %u.\n",
 110                                 HIPQUAD(countess), index);
 111                         index++;
 112                 }
 113         }
 114         return 1;
 115 }
 116
 117 static void
 118 same_destroy(const struct xt_target *target, void *targinfo)
 119 {
 120         struct ipt_same_info *mr = targinfo;
 121
 122         kfree(mr->iparray);
 123
 124         DEBUGP("same_destroy: Deallocated %u bytes for %u ipaddresses.\n",
 125                         (sizeof(u_int32_t) * mr->ipnum), mr->ipnum);
 126 }
 127
 128 static unsigned int
 129 same_target(struct sk_buff **pskb,
 130                 const struct net_device *in,
 131                 const struct net_device *out,
 132                 unsigned int hooknum,
 133                 const struct xt_target *target,
 134                 const void *targinfo)
 135 {
 136         struct ip_conntrack *ct;
 137         enum ip_conntrack_info ctinfo;
 138         u_int32_t tmpip, aindex, new_ip;
 139         const struct ipt_same_info *same = targinfo;
 140         struct ip_nat_range newrange;
 141         const struct ip_conntrack_tuple *t;
 142
 143         IP_NF_ASSERT(hooknum == NF_IP_PRE_ROUTING ||
 144                         hooknum == NF_IP_POST_ROUTING);
 145         ct = ip_conntrack_get(*pskb, &ctinfo);
 146
 147         t = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
 148
 149         /* Base new source on real src ip and optionally dst ip,
 150            giving some hope for consistency across reboots.
 151            Here we calculate the index in same->iparray which
 152            holds the ipaddress we should use */
 153
 154         tmpip = ntohl(t->src.ip);
 155
 156         if (!(same->info & IPT_SAME_NODST))
 157                 tmpip += ntohl(t->dst.ip);
 158
 159         aindex = tmpip % same->ipnum;
 160
 161         new_ip = htonl(same->iparray[aindex]);
 162
 163         DEBUGP("ipt_SAME: src=%u.%u.%u.%u dst=%u.%u.%u.%u, "
 164                         "new src=%u.%u.%u.%u\n",
 165                         NIPQUAD(t->src.ip), NIPQUAD(t->dst.ip),
 166                         NIPQUAD(new_ip));
 167
 168         /* Transfer from original range. */
 169         newrange = ((struct ip_nat_range)
 170                 { same->range[0].flags, new_ip, new_ip,
 171                   /* FIXME: Use ports from correct range! */
 172                   same->range[0].min, same->range[0].max });
 173
 174         /* Hand modified range to generic setup. */
 175         return ip_nat_setup_info(ct, &newrange, hooknum);
 176 }
 177
 178 static struct ipt_target same_reg = {
 179         .name           = "SAME",
 180         .target         = same_target,
 181         .targetsize     = sizeof(struct ipt_same_info),
 182         .table          = "nat",
 183         .hooks          = (1 << NF_IP_PRE_ROUTING | 1 << NF_IP_POST_ROUTING),
 184         .checkentry     = same_check,
 185         .destroy        = same_destroy,
 186         .me             = THIS_MODULE,
 187 };
 188
 189 static int __init ipt_same_init(void)
 190 {
 191         return ipt_register_target(&same_reg);
 192 }
 193
 194 static void __exit ipt_same_fini(void)
 195 {
 196         ipt_unregister_target(&same_reg);
 197 }
 198
 199 module_init(ipt_same_init);
 200 module_exit(ipt_same_fini);
 201