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// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (c) 2011, 2012 Patrick McHardy <kaber@trash.net>
*/
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/ipv6.h>
#include <net/ipv6.h>
#include <linux/netfilter.h>
#include <linux/netfilter_ipv6.h>
#include <linux/netfilter_ipv6/ip6t_NPT.h>
#include <linux/netfilter/x_tables.h>
static int ip6t_npt_checkentry(const struct xt_tgchk_param *par)
{
struct ip6t_npt_tginfo *npt = par->targinfo;
struct in6_addr pfx;
__wsum src_sum, dst_sum;
if (npt->src_pfx_len > 64 || npt->dst_pfx_len > 64)
return -EINVAL;
/* Ensure that LSB of prefix is zero */
ipv6_addr_prefix(&pfx, &npt->src_pfx.in6, npt->src_pfx_len);
if (!ipv6_addr_equal(&pfx, &npt->src_pfx.in6))
return -EINVAL;
ipv6_addr_prefix(&pfx, &npt->dst_pfx.in6, npt->dst_pfx_len);
if (!ipv6_addr_equal(&pfx, &npt->dst_pfx.in6))
return -EINVAL;
src_sum = csum_partial(&npt->src_pfx.in6, sizeof(npt->src_pfx.in6), 0);
dst_sum = csum_partial(&npt->dst_pfx.in6, sizeof(npt->dst_pfx.in6), 0);
npt->adjustment = ~csum_fold(csum_sub(src_sum, dst_sum));
return 0;
}
static bool ip6t_npt_map_pfx(const struct ip6t_npt_tginfo *npt,
struct in6_addr *addr)
{
unsigned int pfx_len;
unsigned int i, idx;
__be32 mask;
__sum16 sum;
pfx_len = max(npt->src_pfx_len, npt->dst_pfx_len);
for (i = 0; i < pfx_len; i += 32) {
if (pfx_len - i >= 32)
mask = 0;
else
mask = htonl((1 << (i - pfx_len + 32)) - 1);
idx = i / 32;
addr->s6_addr32[idx] &= mask;
addr->s6_addr32[idx] |= ~mask & npt->dst_pfx.in6.s6_addr32[idx];
}
if (pfx_len <= 48)
idx = 3;
else {
for (idx = 4; idx < ARRAY_SIZE(addr->s6_addr16); idx++) {
if ((__force __sum16)addr->s6_addr16[idx] !=
CSUM_MANGLED_0)
break;
}
if (idx == ARRAY_SIZE(addr->s6_addr16))
return false;
}
sum = ~csum_fold(csum_add(csum_unfold((__force __sum16)addr->s6_addr16[idx]),
csum_unfold(npt->adjustment)));
if (sum == CSUM_MANGLED_0)
sum = 0;
*(__force __sum16 *)&addr->s6_addr16[idx] = sum;
return true;
}
static struct ipv6hdr *icmpv6_bounced_ipv6hdr(struct sk_buff *skb,
struct ipv6hdr *_bounced_hdr)
{
if (ipv6_hdr(skb)->nexthdr != IPPROTO_ICMPV6)
return NULL;
if (!icmpv6_is_err(icmp6_hdr(skb)->icmp6_type))
return NULL;
return skb_header_pointer(skb,
skb_transport_offset(skb) + sizeof(struct icmp6hdr),
sizeof(struct ipv6hdr),
_bounced_hdr);
}
static unsigned int
ip6t_snpt_tg(struct sk_buff *skb, const struct xt_action_param *par)
{
const struct ip6t_npt_tginfo *npt = par->targinfo;
struct ipv6hdr _bounced_hdr;
struct ipv6hdr *bounced_hdr;
struct in6_addr bounced_pfx;
if (!ip6t_npt_map_pfx(npt, &ipv6_hdr(skb)->saddr)) {
icmpv6_send(skb, ICMPV6_PARAMPROB, ICMPV6_HDR_FIELD,
offsetof(struct ipv6hdr, saddr));
return NF_DROP;
}
/* rewrite dst addr of bounced packet which was sent to dst range */
bounced_hdr = icmpv6_bounced_ipv6hdr(skb, &_bounced_hdr);
if (bounced_hdr) {
ipv6_addr_prefix(&bounced_pfx, &bounced_hdr->daddr, npt->src_pfx_len);
if (ipv6_addr_cmp(&bounced_pfx, &npt->src_pfx.in6) == 0)
ip6t_npt_map_pfx(npt, &bounced_hdr->daddr);
}
return XT_CONTINUE;
}
static unsigned int
ip6t_dnpt_tg(struct sk_buff *skb, const struct xt_action_param *par)
{
const struct ip6t_npt_tginfo *npt = par->targinfo;
struct ipv6hdr _bounced_hdr;
struct ipv6hdr *bounced_hdr;
struct in6_addr bounced_pfx;
if (!ip6t_npt_map_pfx(npt, &ipv6_hdr(skb)->daddr)) {
icmpv6_send(skb, ICMPV6_PARAMPROB, ICMPV6_HDR_FIELD,
offsetof(struct ipv6hdr, daddr));
return NF_DROP;
}
/* rewrite src addr of bounced packet which was sent from dst range */
bounced_hdr = icmpv6_bounced_ipv6hdr(skb, &_bounced_hdr);
if (bounced_hdr) {
ipv6_addr_prefix(&bounced_pfx, &bounced_hdr->saddr, npt->src_pfx_len);
if (ipv6_addr_cmp(&bounced_pfx, &npt->src_pfx.in6) == 0)
ip6t_npt_map_pfx(npt, &bounced_hdr->saddr);
}
return XT_CONTINUE;
}
static struct xt_target ip6t_npt_target_reg[] __read_mostly = {
{
.name = "SNPT",
.table = "mangle",
.target = ip6t_snpt_tg,
.targetsize = sizeof(struct ip6t_npt_tginfo),
.usersize = offsetof(struct ip6t_npt_tginfo, adjustment),
.checkentry = ip6t_npt_checkentry,
.family = NFPROTO_IPV6,
.hooks = (1 << NF_INET_LOCAL_IN) |
(1 << NF_INET_POST_ROUTING),
.me = THIS_MODULE,
},
{
.name = "DNPT",
.table = "mangle",
.target = ip6t_dnpt_tg,
.targetsize = sizeof(struct ip6t_npt_tginfo),
.usersize = offsetof(struct ip6t_npt_tginfo, adjustment),
.checkentry = ip6t_npt_checkentry,
.family = NFPROTO_IPV6,
.hooks = (1 << NF_INET_PRE_ROUTING) |
(1 << NF_INET_LOCAL_OUT),
.me = THIS_MODULE,
},
};
static int __init ip6t_npt_init(void)
{
return xt_register_targets(ip6t_npt_target_reg,
ARRAY_SIZE(ip6t_npt_target_reg));
}
static void __exit ip6t_npt_exit(void)
{
xt_unregister_targets(ip6t_npt_target_reg,
ARRAY_SIZE(ip6t_npt_target_reg));
}
module_init(ip6t_npt_init);
module_exit(ip6t_npt_exit);
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("IPv6-to-IPv6 Network Prefix Translation (RFC 6296)");
MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
MODULE_ALIAS("ip6t_SNPT");
MODULE_ALIAS("ip6t_DNPT");
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