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 struct ipt_entry *e,
  53               void *targinfo,
  54               unsigned int targinfosize,
  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 (strcmp(tablename, "nat") != 0) {
  63                 DEBUGP("same_check: bad table `%s'.\n", tablename);
  64                 return 0;
  65         }
  66         if (targinfosize != IPT_ALIGN(sizeof(*mr))) {
  67                 DEBUGP("same_check: size %u.\n", targinfosize);
  68                 return 0;
  69         }
  70         if (hook_mask & ~(1 << NF_IP_PRE_ROUTING | 1 << NF_IP_POST_ROUTING)) {
  71                 DEBUGP("same_check: bad hooks %x.\n", hook_mask);
  72                 return 0;
  73         }
  74         if (mr->rangesize < 1) {
  75                 DEBUGP("same_check: need at least one dest range.\n");
  76                 return 0;
  77         }
  78         if (mr->rangesize > IPT_SAME_MAX_RANGE) {
  79                 DEBUGP("same_check: too many ranges specified, maximum "
  80                                 "is %u ranges\n",
  81                                 IPT_SAME_MAX_RANGE);
  82                 return 0;
  83         }
  84         for (count = 0; count < mr->rangesize; count++) {
  85                 if (ntohl(mr->range[count].min_ip) >
  86                                 ntohl(mr->range[count].max_ip)) {
  87                         DEBUGP("same_check: min_ip is larger than max_ip in "
  88                                 "range `%u.%u.%u.%u-%u.%u.%u.%u'.\n",
  89                                 NIPQUAD(mr->range[count].min_ip),
  90                                 NIPQUAD(mr->range[count].max_ip));
  91                         return 0;
  92                 }
  93                 if (!(mr->range[count].flags & IP_NAT_RANGE_MAP_IPS)) {
  94                         DEBUGP("same_check: bad MAP_IPS.\n");
  95                         return 0;
  96                 }
  97                 rangeip = (ntohl(mr->range[count].max_ip) -
  98                                         ntohl(mr->range[count].min_ip) + 1);
  99                 mr->ipnum += rangeip;
 100
 101                 DEBUGP("same_check: range %u, ipnum = %u\n", count, rangeip);
 102         }
 103         DEBUGP("same_check: total ipaddresses = %u\n", mr->ipnum);
 104
 105         mr->iparray = kmalloc((sizeof(u_int32_t) * mr->ipnum), GFP_KERNEL);
 106         if (!mr->iparray) {
 107                 DEBUGP("same_check: Couldn't allocate %u bytes "
 108                         "for %u ipaddresses!\n",
 109                         (sizeof(u_int32_t) * mr->ipnum), mr->ipnum);
 110                 return 0;
 111         }
 112         DEBUGP("same_check: Allocated %u bytes for %u ipaddresses.\n",
 113                         (sizeof(u_int32_t) * mr->ipnum), mr->ipnum);
 114
 115         for (count = 0; count < mr->rangesize; count++) {
 116                 for (countess = ntohl(mr->range[count].min_ip);
 117                                 countess <= ntohl(mr->range[count].max_ip);
 118                                         countess++) {
 119                         mr->iparray[index] = countess;
 120                         DEBUGP("same_check: Added ipaddress `%u.%u.%u.%u' "
 121                                 "in index %u.\n",
 122                                 HIPQUAD(countess), index);
 123                         index++;
 124                 }
 125         }
 126         return 1;
 127 }
 128
 129 static void
 130 same_destroy(void *targinfo,
 131                 unsigned int targinfosize)
 132 {
 133         struct ipt_same_info *mr = targinfo;
 134
 135         kfree(mr->iparray);
 136
 137         DEBUGP("same_destroy: Deallocated %u bytes for %u ipaddresses.\n",
 138                         (sizeof(u_int32_t) * mr->ipnum), mr->ipnum);
 139 }
 140
 141 static unsigned int
 142 same_target(struct sk_buff **pskb,
 143                 const struct net_device *in,
 144                 const struct net_device *out,
 145                 unsigned int hooknum,
 146                 const void *targinfo,
 147                 void *userinfo)
 148 {
 149         struct ip_conntrack *ct;
 150         enum ip_conntrack_info ctinfo;
 151         u_int32_t tmpip, aindex, new_ip;
 152         const struct ipt_same_info *same = targinfo;
 153         struct ip_nat_range newrange;
 154         const struct ip_conntrack_tuple *t;
 155
 156         IP_NF_ASSERT(hooknum == NF_IP_PRE_ROUTING ||
 157                         hooknum == NF_IP_POST_ROUTING);
 158         ct = ip_conntrack_get(*pskb, &ctinfo);
 159
 160         t = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
 161
 162         /* Base new source on real src ip and optionally dst ip,
 163            giving some hope for consistency across reboots.
 164            Here we calculate the index in same->iparray which
 165            holds the ipaddress we should use */
 166
 167         tmpip = ntohl(t->src.ip);
 168
 169         if (!(same->info & IPT_SAME_NODST))
 170                 tmpip += ntohl(t->dst.ip);
 171
 172         aindex = tmpip % same->ipnum;
 173
 174         new_ip = htonl(same->iparray[aindex]);
 175
 176         DEBUGP("ipt_SAME: src=%u.%u.%u.%u dst=%u.%u.%u.%u, "
 177                         "new src=%u.%u.%u.%u\n",
 178                         NIPQUAD(t->src.ip), NIPQUAD(t->dst.ip),
 179                         NIPQUAD(new_ip));
 180
 181         /* Transfer from original range. */
 182         newrange = ((struct ip_nat_range)
 183                 { same->range[0].flags, new_ip, new_ip,
 184                   /* FIXME: Use ports from correct range! */
 185                   same->range[0].min, same->range[0].max });
 186
 187         /* Hand modified range to generic setup. */
 188         return ip_nat_setup_info(ct, &newrange, hooknum);
 189 }
 190
 191 static struct ipt_target same_reg = {
 192         .name           = "SAME",
 193         .target         = same_target,
 194         .checkentry     = same_check,
 195         .destroy        = same_destroy,
 196         .me             = THIS_MODULE,
 197 };
 198
 199 static int __init init(void)
 200 {
 201         return ipt_register_target(&same_reg);
 202 }
 203
 204 static void __exit fini(void)
 205 {
 206         ipt_unregister_target(&same_reg);
 207 }
 208
 209 module_init(init);
 210 module_exit(fini);
 211