[5494bc]: extensions / xt_RAWNAT.c  Maximize  Restore  History

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/*
* "RAWNAT" target extension for Xtables - untracked NAT
* Copyright Š Jan Engelhardt, 2008 - 2009
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License; either
* version 2 of the License, or any later version, as published by the
* Free Software Foundation.
*/
#include <linux/ip.h>
#include <linux/ipv6.h>
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/tcp.h>
#include <linux/udp.h>
#include <linux/version.h>
#include <linux/netfilter.h>
#include <linux/netfilter/nf_conntrack_common.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter_ipv6/ip6_tables.h>
#include <net/ip.h>
#include <net/ipv6.h>
#include "compat_xtables.h"
#include "xt_RAWNAT.h"
#if defined(CONFIG_IP6_NF_IPTABLES) || defined(CONFIG_IP6_NF_IPTABLES_MODULE)
# define WITH_IPV6 1
#endif
static inline __be32
remask(__be32 addr, __be32 repl, unsigned int shift)
{
uint32_t mask = (shift == 32) ? 0 : (~(uint32_t)0 >> shift);
return htonl((ntohl(addr) & mask) | (ntohl(repl) & ~mask));
}
#ifdef WITH_IPV6
static void
rawnat_ipv6_mask(__be32 *addr, const __be32 *repl, unsigned int mask)
{
switch (mask) {
case 0:
break;
case 1 ... 31:
addr[0] = remask(addr[0], repl[0], mask);
break;
case 32:
addr[0] = repl[0];
break;
case 33 ... 63:
addr[0] = repl[0];
addr[1] = remask(addr[1], repl[1], mask - 32);
break;
case 64:
addr[0] = repl[0];
addr[1] = repl[1];
break;
case 65 ... 95:
addr[0] = repl[0];
addr[1] = repl[1];
addr[2] = remask(addr[2], repl[2], mask - 64);
case 96:
addr[0] = repl[0];
addr[1] = repl[1];
addr[2] = repl[2];
break;
case 97 ... 127:
addr[0] = repl[0];
addr[1] = repl[1];
addr[2] = repl[2];
addr[3] = remask(addr[3], repl[3], mask - 96);
break;
case 128:
addr[0] = repl[0];
addr[1] = repl[1];
addr[2] = repl[2];
addr[3] = repl[3];
break;
}
}
#endif
static void rawnat4_update_l4(struct sk_buff *skb, __be32 oldip, __be32 newip)
{
struct iphdr *iph = ip_hdr(skb);
void *transport_hdr = (void *)iph + ip_hdrlen(skb);
struct tcphdr *tcph;
struct udphdr *udph;
bool cond;
switch (iph->protocol) {
case IPPROTO_TCP:
tcph = transport_hdr;
inet_proto_csum_replace4(&tcph->check, skb, oldip, newip, true);
break;
case IPPROTO_UDP:
case IPPROTO_UDPLITE:
udph = transport_hdr;
cond = udph->check != 0;
cond |= skb->ip_summed == CHECKSUM_PARTIAL;
if (cond) {
inet_proto_csum_replace4(&udph->check, skb,
oldip, newip, true);
if (udph->check == 0)
udph->check = CSUM_MANGLED_0;
}
break;
}
}
static unsigned int rawnat4_writable_part(const struct iphdr *iph)
{
unsigned int wlen = sizeof(*iph);
switch (iph->protocol) {
case IPPROTO_TCP:
wlen += sizeof(struct tcphdr);
break;
case IPPROTO_UDP:
wlen += sizeof(struct udphdr);
break;
}
return wlen;
}
static unsigned int
rawsnat_tg4(struct sk_buff **pskb, const struct xt_action_param *par)
{
const struct xt_rawnat_tginfo *info = par->targinfo;
struct iphdr *iph;
__be32 new_addr;
iph = ip_hdr(*pskb);
new_addr = remask(iph->saddr, info->addr.ip, info->mask);
if (iph->saddr == new_addr)
return XT_CONTINUE;
if (!skb_make_writable(pskb, rawnat4_writable_part(iph)))
return NF_DROP;
iph = ip_hdr(*pskb);
csum_replace4(&iph->check, iph->saddr, new_addr);
rawnat4_update_l4(*pskb, iph->saddr, new_addr);
iph->saddr = new_addr;
return XT_CONTINUE;
}
static unsigned int
rawdnat_tg4(struct sk_buff **pskb, const struct xt_action_param *par)
{
const struct xt_rawnat_tginfo *info = par->targinfo;
struct iphdr *iph;
__be32 new_addr;
iph = ip_hdr(*pskb);
new_addr = remask(iph->daddr, info->addr.ip, info->mask);
if (iph->daddr == new_addr)
return XT_CONTINUE;
if (!skb_make_writable(pskb, rawnat4_writable_part(iph)))
return NF_DROP;
iph = ip_hdr(*pskb);
csum_replace4(&iph->check, iph->daddr, new_addr);
rawnat4_update_l4(*pskb, iph->daddr, new_addr);
iph->daddr = new_addr;
return XT_CONTINUE;
}
#ifdef WITH_IPV6
static bool rawnat6_prepare_l4(struct sk_buff **pskb, unsigned int *l4offset,
unsigned int *l4proto)
{
static const unsigned int types[] =
{IPPROTO_TCP, IPPROTO_UDP, IPPROTO_UDPLITE};
unsigned int i;
int err;
*l4proto = NEXTHDR_MAX;
for (i = 0; i < ARRAY_SIZE(types); ++i) {
err = ipv6_find_hdr(*pskb, l4offset, types[i], NULL, NULL);
if (err >= 0) {
*l4proto = types[i];
break;
}
if (err != -ENOENT)
return false;
}
switch (*l4proto) {
case IPPROTO_TCP:
if (!skb_make_writable(pskb, *l4offset + sizeof(struct tcphdr)))
return false;
break;
case IPPROTO_UDP:
case IPPROTO_UDPLITE:
if (!skb_make_writable(pskb, *l4offset + sizeof(struct udphdr)))
return false;
break;
}
return true;
}
static void rawnat6_update_l4(struct sk_buff *skb, unsigned int l4proto,
unsigned int l4offset, const struct in6_addr *oldip,
const struct in6_addr *newip)
{
const struct ipv6hdr *iph = ipv6_hdr(skb);
struct tcphdr *tcph;
struct udphdr *udph;
unsigned int i;
bool cond;
switch (l4proto) {
case IPPROTO_TCP:
tcph = (void *)iph + l4offset;
for (i = 0; i < 4; ++i)
inet_proto_csum_replace4(&tcph->check, skb,
oldip->s6_addr32[i], newip->s6_addr32[i], true);
break;
case IPPROTO_UDP:
case IPPROTO_UDPLITE:
udph = (void *)iph + l4offset;
cond = udph->check;
cond |= skb->ip_summed == CHECKSUM_PARTIAL;
if (cond) {
for (i = 0; i < 4; ++i)
inet_proto_csum_replace4(&udph->check, skb,
oldip->s6_addr32[i],
newip->s6_addr32[i], true);
if (udph->check == 0)
udph->check = CSUM_MANGLED_0;
}
break;
}
}
static unsigned int
rawsnat_tg6(struct sk_buff **pskb, const struct xt_action_param *par)
{
const struct xt_rawnat_tginfo *info = par->targinfo;
unsigned int l4offset = 0, l4proto;
struct ipv6hdr *iph;
struct in6_addr new_addr;
iph = ipv6_hdr(*pskb);
memcpy(&new_addr, &iph->saddr, sizeof(new_addr));
rawnat_ipv6_mask(new_addr.s6_addr32, info->addr.ip6, info->mask);
if (ipv6_addr_cmp(&iph->saddr, &new_addr) == 0)
return XT_CONTINUE;
if (!rawnat6_prepare_l4(pskb, &l4offset, &l4proto))
return NF_DROP;
iph = ipv6_hdr(*pskb);
rawnat6_update_l4(*pskb, l4proto, l4offset, &iph->saddr, &new_addr);
memcpy(&iph->saddr, &new_addr, sizeof(new_addr));
return XT_CONTINUE;
}
static unsigned int
rawdnat_tg6(struct sk_buff **pskb, const struct xt_action_param *par)
{
const struct xt_rawnat_tginfo *info = par->targinfo;
unsigned int l4offset = 0, l4proto;
struct ipv6hdr *iph;
struct in6_addr new_addr;
iph = ipv6_hdr(*pskb);
memcpy(&new_addr, &iph->daddr, sizeof(new_addr));
rawnat_ipv6_mask(new_addr.s6_addr32, info->addr.ip6, info->mask);
if (ipv6_addr_cmp(&iph->daddr, &new_addr) == 0)
return XT_CONTINUE;
if (!rawnat6_prepare_l4(pskb, &l4offset, &l4proto))
return NF_DROP;
iph = ipv6_hdr(*pskb);
rawnat6_update_l4(*pskb, l4proto, l4offset, &iph->daddr, &new_addr);
memcpy(&iph->daddr, &new_addr, sizeof(new_addr));
return XT_CONTINUE;
}
#endif
static int rawnat_tg_check(const struct xt_tgchk_param *par)
{
if (strcmp(par->table, "raw") == 0 ||
strcmp(par->table, "rawpost") == 0)
return 0;
printk(KERN_ERR KBUILD_MODNAME " may only be used in the \"raw\" or "
"\"rawpost\" table.\n");
return -EINVAL;
}
static struct xt_target rawnat_tg_reg[] __read_mostly = {
{
.name = "RAWSNAT",
.revision = 0,
.family = NFPROTO_IPV4,
.target = rawsnat_tg4,
.targetsize = sizeof(struct xt_rawnat_tginfo),
.checkentry = rawnat_tg_check,
.me = THIS_MODULE,
},
#ifdef WITH_IPV6
{
.name = "RAWSNAT",
.revision = 0,
.family = NFPROTO_IPV6,
.target = rawsnat_tg6,
.targetsize = sizeof(struct xt_rawnat_tginfo),
.checkentry = rawnat_tg_check,
.me = THIS_MODULE,
},
#endif
{
.name = "RAWDNAT",
.revision = 0,
.family = NFPROTO_IPV4,
.target = rawdnat_tg4,
.targetsize = sizeof(struct xt_rawnat_tginfo),
.checkentry = rawnat_tg_check,
.me = THIS_MODULE,
},
#ifdef WITH_IPV6
{
.name = "RAWDNAT",
.revision = 0,
.family = NFPROTO_IPV6,
.target = rawdnat_tg6,
.targetsize = sizeof(struct xt_rawnat_tginfo),
.checkentry = rawnat_tg_check,
.me = THIS_MODULE,
},
#endif
};
static int __init rawnat_tg_init(void)
{
return xt_register_targets(rawnat_tg_reg, ARRAY_SIZE(rawnat_tg_reg));
}
static void __exit rawnat_tg_exit(void)
{
xt_unregister_targets(rawnat_tg_reg, ARRAY_SIZE(rawnat_tg_reg));
}
module_init(rawnat_tg_init);
module_exit(rawnat_tg_exit);
MODULE_AUTHOR("Jan Engelhardt ");
MODULE_DESCRIPTION("Xtables: conntrack-less raw NAT");
MODULE_LICENSE("GPL");
MODULE_ALIAS("ipt_RAWSNAT");
MODULE_ALIAS("ipt_RAWDNAT");
MODULE_ALIAS("ip6t_RAWSNAT");
MODULE_ALIAS("ip6t_RAWDNAT");

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