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