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* (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
/* Everything about the rules for NAT. */
#include <linux/types.h>
#include <linux/ip.h>
#include <linux/netfilter.h>
#include <linux/netfilter_ipv4.h>
#include <linux/module.h>
#include <linux/kmod.h>
#include <linux/skbuff.h>
#include <linux/proc_fs.h>
#include <net/checksum.h>
#include <net/route.h>
#include <linux/bitops.h>
#include <linux/netfilter_ipv4/ip_tables.h>
#include <net/netfilter/nf_nat.h>
#include <net/netfilter/nf_nat_core.h>
#include <net/netfilter/nf_nat_rule.h>
#define NAT_VALID_HOOKS ((1 << NF_INET_PRE_ROUTING) | \
(1 << NF_INET_POST_ROUTING) | \
(1 << NF_INET_LOCAL_OUT))
static struct
{
struct ipt_replace repl;
struct ipt_standard entries[3];
struct ipt_error term;
} nat_initial_table __initdata = {
.repl = {
.name = "nat",
.valid_hooks = NAT_VALID_HOOKS,
.num_entries = 4,
.size = sizeof(struct ipt_standard) * 3 + sizeof(struct ipt_error),
.hook_entry = {
[NF_INET_PRE_ROUTING] = 0,
[NF_INET_POST_ROUTING] = sizeof(struct ipt_standard),
[NF_INET_LOCAL_OUT] = sizeof(struct ipt_standard) * 2
},
.underflow = {
[NF_INET_PRE_ROUTING] = 0,
[NF_INET_POST_ROUTING] = sizeof(struct ipt_standard),
[NF_INET_LOCAL_OUT] = sizeof(struct ipt_standard) * 2
},
},
.entries = {
IPT_STANDARD_INIT(NF_ACCEPT), /* PRE_ROUTING */
IPT_STANDARD_INIT(NF_ACCEPT), /* POST_ROUTING */
IPT_STANDARD_INIT(NF_ACCEPT), /* LOCAL_OUT */
},
.term = IPT_ERROR_INIT, /* ERROR */
};
static struct xt_table __nat_table = {
.name = "nat",
.valid_hooks = NAT_VALID_HOOKS,
.lock = __RW_LOCK_UNLOCKED(__nat_table.lock),
.me = THIS_MODULE,
.af = AF_INET,
};
static struct xt_table *nat_table;
/* Source NAT */
static unsigned int ipt_snat_target(struct sk_buff *skb,
const struct net_device *in,
const struct net_device *out,
unsigned int hooknum,
const struct xt_target *target,
const void *targinfo)
{
struct nf_conn *ct;
enum ip_conntrack_info ctinfo;
const struct nf_nat_multi_range_compat *mr = targinfo;
NF_CT_ASSERT(hooknum == NF_INET_POST_ROUTING);
ct = nf_ct_get(skb, &ctinfo);
/* Connection must be valid and new. */
NF_CT_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED ||
ctinfo == IP_CT_RELATED + IP_CT_IS_REPLY));
NF_CT_ASSERT(out);
return nf_nat_setup_info(ct, &mr->range[0], IP_NAT_MANIP_SRC);
}
/* Before 2.6.11 we did implicit source NAT if required. Warn about change. */
static void warn_if_extra_mangle(__be32 dstip, __be32 srcip)
{
static int warned = 0;
struct flowi fl = { .nl_u = { .ip4_u = { .daddr = dstip } } };
struct rtable *rt;
if (ip_route_output_key(&init_net, &rt, &fl) != 0)
return;
if (rt->rt_src != srcip && !warned) {
printk("NAT: no longer support implicit source local NAT\n");
printk("NAT: packet src %u.%u.%u.%u -> dst %u.%u.%u.%u\n",
NIPQUAD(srcip), NIPQUAD(dstip));
warned = 1;
}
ip_rt_put(rt);
}
static unsigned int ipt_dnat_target(struct sk_buff *skb,
const struct net_device *in,
const struct net_device *out,
unsigned int hooknum,
const struct xt_target *target,
const void *targinfo)
{
struct nf_conn *ct;
enum ip_conntrack_info ctinfo;
const struct nf_nat_multi_range_compat *mr = targinfo;
NF_CT_ASSERT(hooknum == NF_INET_PRE_ROUTING ||
hooknum == NF_INET_LOCAL_OUT);
ct = nf_ct_get(skb, &ctinfo);
/* Connection must be valid and new. */
NF_CT_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED));
if (hooknum == NF_INET_LOCAL_OUT &&
mr->range[0].flags & IP_NAT_RANGE_MAP_IPS)
warn_if_extra_mangle(ip_hdr(skb)->daddr,
mr->range[0].min_ip);
return nf_nat_setup_info(ct, &mr->range[0], IP_NAT_MANIP_DST);
}
static bool ipt_snat_checkentry(const char *tablename,
const void *entry,
const struct xt_target *target,
void *targinfo,
unsigned int hook_mask)
{
const struct nf_nat_multi_range_compat *mr = targinfo;
/* Must be a valid range */
if (mr->rangesize != 1) {
printk("SNAT: multiple ranges no longer supported\n");
return false;
}
return true;
}
static bool ipt_dnat_checkentry(const char *tablename,
const void *entry,
const struct xt_target *target,
void *targinfo,
unsigned int hook_mask)
{
const struct nf_nat_multi_range_compat *mr = targinfo;
/* Must be a valid range */
if (mr->rangesize != 1) {
printk("DNAT: multiple ranges no longer supported\n");
return false;
}
return true;
}
unsigned int
alloc_null_binding(struct nf_conn *ct, unsigned int hooknum)
{
/* Force range to this IP; let proto decide mapping for
per-proto parts (hence not IP_NAT_RANGE_PROTO_SPECIFIED).
Use reply in case it's already been mangled (eg local packet).
*/
__be32 ip
= (HOOK2MANIP(hooknum) == IP_NAT_MANIP_SRC
? ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3.ip
: ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3.ip);
struct nf_nat_range range
= { IP_NAT_RANGE_MAP_IPS, ip, ip, { 0 }, { 0 } };
pr_debug("Allocating NULL binding for %p (%u.%u.%u.%u)\n",
ct, NIPQUAD(ip));
return nf_nat_setup_info(ct, &range, HOOK2MANIP(hooknum));
}
int nf_nat_rule_find(struct sk_buff *skb,
unsigned int hooknum,
const struct net_device *in,
const struct net_device *out,
struct nf_conn *ct)
{
int ret;
ret = ipt_do_table(skb, hooknum, in, out, nat_table);
if (ret == NF_ACCEPT) {
if (!nf_nat_initialized(ct, HOOK2MANIP(hooknum)))
/* NUL mapping */
ret = alloc_null_binding(ct, hooknum);
}
return ret;
}
static struct xt_target ipt_snat_reg __read_mostly = {
.name = "SNAT",
.target = ipt_snat_target,
.targetsize = sizeof(struct nf_nat_multi_range_compat),
.table = "nat",
.hooks = 1 << NF_INET_POST_ROUTING,
.checkentry = ipt_snat_checkentry,
.family = AF_INET,
};
static struct xt_target ipt_dnat_reg __read_mostly = {
.name = "DNAT",
.target = ipt_dnat_target,
.targetsize = sizeof(struct nf_nat_multi_range_compat),
.table = "nat",
.hooks = (1 << NF_INET_PRE_ROUTING) | (1 << NF_INET_LOCAL_OUT),
.checkentry = ipt_dnat_checkentry,
.family = AF_INET,
};
int __init nf_nat_rule_init(void)
{
int ret;
nat_table = ipt_register_table(&init_net, &__nat_table,
&nat_initial_table.repl);
if (IS_ERR(nat_table))
return PTR_ERR(nat_table);
ret = xt_register_target(&ipt_snat_reg);
if (ret != 0)
goto unregister_table;
ret = xt_register_target(&ipt_dnat_reg);
if (ret != 0)
goto unregister_snat;
return ret;
unregister_snat:
xt_unregister_target(&ipt_snat_reg);
unregister_table:
ipt_unregister_table(nat_table);
return ret;
}
void nf_nat_rule_cleanup(void)
{
xt_unregister_target(&ipt_dnat_reg);
xt_unregister_target(&ipt_snat_reg);
ipt_unregister_table(nat_table);
}
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