180 lines
5.0 KiB
C
180 lines
5.0 KiB
C
/* Same. Just like SNAT, only try to make the connections
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* between client A and server B always have the same source ip.
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*
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* (C) 2000 Paul `Rusty' Russell
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* (C) 2001 Martin Josefsson
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <linux/types.h>
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#include <linux/ip.h>
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#include <linux/timer.h>
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#include <linux/module.h>
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#include <linux/netfilter.h>
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#include <linux/netdevice.h>
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#include <linux/if.h>
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#include <linux/inetdevice.h>
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#include <net/protocol.h>
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#include <net/checksum.h>
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#include <linux/netfilter_ipv4.h>
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#include <linux/netfilter/x_tables.h>
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#include <net/netfilter/nf_nat_rule.h>
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#include <linux/netfilter_ipv4/ipt_SAME.h>
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Martin Josefsson <gandalf@wlug.westbo.se>");
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MODULE_DESCRIPTION("iptables special SNAT module for consistent sourceip");
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static bool
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same_check(const char *tablename,
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const void *e,
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const struct xt_target *target,
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void *targinfo,
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unsigned int hook_mask)
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{
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unsigned int count, countess, rangeip, index = 0;
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struct ipt_same_info *mr = targinfo;
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mr->ipnum = 0;
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if (mr->rangesize < 1) {
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pr_debug("same_check: need at least one dest range.\n");
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return false;
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}
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if (mr->rangesize > IPT_SAME_MAX_RANGE) {
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pr_debug("same_check: too many ranges specified, maximum "
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"is %u ranges\n", IPT_SAME_MAX_RANGE);
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return false;
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}
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for (count = 0; count < mr->rangesize; count++) {
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if (ntohl(mr->range[count].min_ip) >
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ntohl(mr->range[count].max_ip)) {
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pr_debug("same_check: min_ip is larger than max_ip in "
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"range `%u.%u.%u.%u-%u.%u.%u.%u'.\n",
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NIPQUAD(mr->range[count].min_ip),
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NIPQUAD(mr->range[count].max_ip));
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return false;
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}
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if (!(mr->range[count].flags & IP_NAT_RANGE_MAP_IPS)) {
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pr_debug("same_check: bad MAP_IPS.\n");
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return false;
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}
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rangeip = (ntohl(mr->range[count].max_ip) -
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ntohl(mr->range[count].min_ip) + 1);
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mr->ipnum += rangeip;
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pr_debug("same_check: range %u, ipnum = %u\n", count, rangeip);
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}
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pr_debug("same_check: total ipaddresses = %u\n", mr->ipnum);
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mr->iparray = kmalloc((sizeof(u_int32_t) * mr->ipnum), GFP_KERNEL);
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if (!mr->iparray) {
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pr_debug("same_check: Couldn't allocate %Zu bytes "
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"for %u ipaddresses!\n",
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(sizeof(u_int32_t) * mr->ipnum), mr->ipnum);
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return false;
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}
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pr_debug("same_check: Allocated %Zu bytes for %u ipaddresses.\n",
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(sizeof(u_int32_t) * mr->ipnum), mr->ipnum);
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for (count = 0; count < mr->rangesize; count++) {
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for (countess = ntohl(mr->range[count].min_ip);
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countess <= ntohl(mr->range[count].max_ip);
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countess++) {
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mr->iparray[index] = countess;
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pr_debug("same_check: Added ipaddress `%u.%u.%u.%u' "
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"in index %u.\n", HIPQUAD(countess), index);
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index++;
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}
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}
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return true;
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}
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static void
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same_destroy(const struct xt_target *target, void *targinfo)
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{
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struct ipt_same_info *mr = targinfo;
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kfree(mr->iparray);
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pr_debug("same_destroy: Deallocated %Zu bytes for %u ipaddresses.\n",
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(sizeof(u_int32_t) * mr->ipnum), mr->ipnum);
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}
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static unsigned int
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same_target(struct sk_buff *skb,
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const struct net_device *in,
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const struct net_device *out,
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unsigned int hooknum,
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const struct xt_target *target,
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const void *targinfo)
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{
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struct nf_conn *ct;
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enum ip_conntrack_info ctinfo;
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u_int32_t tmpip, aindex;
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__be32 new_ip;
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const struct ipt_same_info *same = targinfo;
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struct nf_nat_range newrange;
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const struct nf_conntrack_tuple *t;
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NF_CT_ASSERT(hooknum == NF_IP_PRE_ROUTING ||
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hooknum == NF_IP_POST_ROUTING);
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ct = nf_ct_get(skb, &ctinfo);
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t = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
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/* Base new source on real src ip and optionally dst ip,
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giving some hope for consistency across reboots.
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Here we calculate the index in same->iparray which
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holds the ipaddress we should use */
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tmpip = ntohl(t->src.u3.ip);
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if (!(same->info & IPT_SAME_NODST))
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tmpip += ntohl(t->dst.u3.ip);
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aindex = tmpip % same->ipnum;
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new_ip = htonl(same->iparray[aindex]);
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pr_debug("ipt_SAME: src=%u.%u.%u.%u dst=%u.%u.%u.%u, "
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"new src=%u.%u.%u.%u\n",
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NIPQUAD(t->src.u3.ip), NIPQUAD(t->dst.u3.ip), NIPQUAD(new_ip));
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/* Transfer from original range. */
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newrange = ((struct nf_nat_range)
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{ same->range[0].flags, new_ip, new_ip,
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/* FIXME: Use ports from correct range! */
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same->range[0].min, same->range[0].max });
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/* Hand modified range to generic setup. */
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return nf_nat_setup_info(ct, &newrange, hooknum);
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}
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static struct xt_target same_reg __read_mostly = {
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.name = "SAME",
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.family = AF_INET,
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.target = same_target,
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.targetsize = sizeof(struct ipt_same_info),
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.table = "nat",
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.hooks = (1 << NF_IP_PRE_ROUTING | 1 << NF_IP_POST_ROUTING),
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.checkentry = same_check,
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.destroy = same_destroy,
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.me = THIS_MODULE,
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};
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static int __init ipt_same_init(void)
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{
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return xt_register_target(&same_reg);
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}
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static void __exit ipt_same_fini(void)
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{
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xt_unregister_target(&same_reg);
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}
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module_init(ipt_same_init);
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module_exit(ipt_same_fini);
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