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 #include <linux/types.h>
  12 #include <linux/ip.h>
  13 #include <linux/timer.h>
  14 #include <linux/module.h>
  15 #include <linux/netfilter.h>
  16 #include <linux/netdevice.h>
  17 #include <linux/if.h>
  18 #include <linux/inetdevice.h>
  19 #include <net/protocol.h>
  20 #include <net/checksum.h>
  21 #include <linux/netfilter_ipv4.h>
  22 #include <linux/netfilter/x_tables.h>
  23 #include <net/netfilter/nf_nat_rule.h>
  24 #include <linux/netfilter_ipv4/ipt_SAME.h>
  25
  26 MODULE_LICENSE("GPL");
  27 MODULE_AUTHOR("Martin Josefsson <gandalf@wlug.westbo.se>");
  28 MODULE_DESCRIPTION("iptables special SNAT module for consistent sourceip");
  29
  30 #if 0
  31 #define DEBUGP printk
  32 #else
  33 #define DEBUGP(format, args...)
  34 #endif
  35
  36 static bool
  37 same_check(const char *tablename,
  38               const void *e,
  39               const struct xt_target *target,
  40               void *targinfo,
  41               unsigned int hook_mask)
  42 {
  43         unsigned int count, countess, rangeip, index = 0;
  44         struct ipt_same_info *mr = targinfo;
  45
  46         mr->ipnum = 0;
  47
  48         if (mr->rangesize < 1) {
  49                 DEBUGP("same_check: need at least one dest range.\n");
  50                 return false;
  51         }
  52         if (mr->rangesize > IPT_SAME_MAX_RANGE) {
  53                 DEBUGP("same_check: too many ranges specified, maximum "
  54                                 "is %u ranges\n",
  55                                 IPT_SAME_MAX_RANGE);
  56                 return false;
  57         }
  58         for (count = 0; count < mr->rangesize; count++) {
  59                 if (ntohl(mr->range[count].min_ip) >
  60                                 ntohl(mr->range[count].max_ip)) {
  61                         DEBUGP("same_check: min_ip is larger than max_ip in "
  62                                 "range `%u.%u.%u.%u-%u.%u.%u.%u'.\n",
  63                                 NIPQUAD(mr->range[count].min_ip),
  64                                 NIPQUAD(mr->range[count].max_ip));
  65                         return false;
  66                 }
  67                 if (!(mr->range[count].flags & IP_NAT_RANGE_MAP_IPS)) {
  68                         DEBUGP("same_check: bad MAP_IPS.\n");
  69                         return false;
  70                 }
  71                 rangeip = (ntohl(mr->range[count].max_ip) -
  72                                         ntohl(mr->range[count].min_ip) + 1);
  73                 mr->ipnum += rangeip;
  74
  75                 DEBUGP("same_check: range %u, ipnum = %u\n", count, rangeip);
  76         }
  77         DEBUGP("same_check: total ipaddresses = %u\n", mr->ipnum);
  78
  79         mr->iparray = kmalloc((sizeof(u_int32_t) * mr->ipnum), GFP_KERNEL);
  80         if (!mr->iparray) {
  81                 DEBUGP("same_check: Couldn't allocate %u bytes "
  82                         "for %u ipaddresses!\n",
  83                         (sizeof(u_int32_t) * mr->ipnum), mr->ipnum);
  84                 return false;
  85         }
  86         DEBUGP("same_check: Allocated %u bytes for %u ipaddresses.\n",
  87                         (sizeof(u_int32_t) * mr->ipnum), mr->ipnum);
  88
  89         for (count = 0; count < mr->rangesize; count++) {
  90                 for (countess = ntohl(mr->range[count].min_ip);
  91                                 countess <= ntohl(mr->range[count].max_ip);
  92                                         countess++) {
  93                         mr->iparray[index] = countess;
  94                         DEBUGP("same_check: Added ipaddress `%u.%u.%u.%u' "
  95                                 "in index %u.\n",
  96                                 HIPQUAD(countess), index);
  97                         index++;
  98                 }
  99         }
 100         return true;
 101 }
 102
 103 static void
 104 same_destroy(const struct xt_target *target, void *targinfo)
 105 {
 106         struct ipt_same_info *mr = targinfo;
 107
 108         kfree(mr->iparray);
 109
 110         DEBUGP("same_destroy: Deallocated %u bytes for %u ipaddresses.\n",
 111                         (sizeof(u_int32_t) * mr->ipnum), mr->ipnum);
 112 }
 113
 114 static unsigned int
 115 same_target(struct sk_buff **pskb,
 116                 const struct net_device *in,
 117                 const struct net_device *out,
 118                 unsigned int hooknum,
 119                 const struct xt_target *target,
 120                 const void *targinfo)
 121 {
 122         struct nf_conn *ct;
 123         enum ip_conntrack_info ctinfo;
 124         u_int32_t tmpip, aindex;
 125         __be32 new_ip;
 126         const struct ipt_same_info *same = targinfo;
 127         struct nf_nat_range newrange;
 128         const struct nf_conntrack_tuple *t;
 129
 130         NF_CT_ASSERT(hooknum == NF_IP_PRE_ROUTING ||
 131                         hooknum == NF_IP_POST_ROUTING);
 132         ct = nf_ct_get(*pskb, &ctinfo);
 133
 134         t = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
 135
 136         /* Base new source on real src ip and optionally dst ip,
 137            giving some hope for consistency across reboots.
 138            Here we calculate the index in same->iparray which
 139            holds the ipaddress we should use */
 140
 141         tmpip = ntohl(t->src.u3.ip);
 142
 143         if (!(same->info & IPT_SAME_NODST))
 144                 tmpip += ntohl(t->dst.u3.ip);
 145         aindex = tmpip % same->ipnum;
 146
 147         new_ip = htonl(same->iparray[aindex]);
 148
 149         DEBUGP("ipt_SAME: src=%u.%u.%u.%u dst=%u.%u.%u.%u, "
 150                         "new src=%u.%u.%u.%u\n",
 151                         NIPQUAD(t->src.ip), NIPQUAD(t->dst.ip),
 152                         NIPQUAD(new_ip));
 153
 154         /* Transfer from original range. */
 155         newrange = ((struct nf_nat_range)
 156                 { same->range[0].flags, new_ip, new_ip,
 157                   /* FIXME: Use ports from correct range! */
 158                   same->range[0].min, same->range[0].max });
 159
 160         /* Hand modified range to generic setup. */
 161         return nf_nat_setup_info(ct, &newrange, hooknum);
 162 }
 163
 164 static struct xt_target same_reg __read_mostly = {
 165         .name           = "SAME",
 166         .family         = AF_INET,
 167         .target         = same_target,
 168         .targetsize     = sizeof(struct ipt_same_info),
 169         .table          = "nat",
 170         .hooks          = (1 << NF_IP_PRE_ROUTING | 1 << NF_IP_POST_ROUTING),
 171         .checkentry     = same_check,
 172         .destroy        = same_destroy,
 173         .me             = THIS_MODULE,
 174 };
 175
 176 static int __init ipt_same_init(void)
 177 {
 178         return xt_register_target(&same_reg);
 179 }
 180
 181 static void __exit ipt_same_fini(void)
 182 {
 183         xt_unregister_target(&same_reg);
 184 }
 185
 186 module_init(ipt_same_init);
 187 module_exit(ipt_same_fini);
 188