// SPDX-License-Identifier: GPL-2.0-only
/* (C) 1999-2001 Paul `Rusty' Russell
* (C) 2002-2006 Netfilter Core Team <[email protected]>
*/
#include <linux/types.h>
#include <linux/export.h>
#include <linux/init.h>
#include <linux/udp.h>
#include <linux/tcp.h>
#include <linux/icmp.h>
#include <linux/icmpv6.h>
#include <linux/dccp.h>
#include <linux/sctp.h>
#include <net/sctp/checksum.h>
#include <linux/netfilter.h>
#include <net/netfilter/nf_nat.h>
#include <linux/ipv6.h>
#include <linux/netfilter_ipv6.h>
#include <net/checksum.h>
#include <net/ip6_checksum.h>
#include <net/ip6_route.h>
#include <net/xfrm.h>
#include <net/ipv6.h>
#include <net/netfilter/nf_conntrack_core.h>
#include <net/netfilter/nf_conntrack.h>
#include <linux/netfilter/nfnetlink_conntrack.h>
static void nf_csum_update(struct sk_buff *skb,
unsigned int iphdroff, __sum16 *check,
const struct nf_conntrack_tuple *t,
enum nf_nat_manip_type maniptype);
static void
__udp_manip_pkt(struct sk_buff *skb,
unsigned int iphdroff, struct udphdr *hdr,
const struct nf_conntrack_tuple *tuple,
enum nf_nat_manip_type maniptype, bool do_csum)
{
__be16 *portptr, newport;
if (maniptype == NF_NAT_MANIP_SRC) {
/* Get rid of src port */
newport = tuple->src.u.udp.port;
portptr = &hdr->source;
} else {
/* Get rid of dst port */
newport = tuple->dst.u.udp.port;
portptr = &hdr->dest;
}
if (do_csum) {
nf_csum_update(skb, iphdroff, &hdr->check, tuple, maniptype);
inet_proto_csum_replace2(&hdr->check, skb, *portptr, newport,
false);
if (!hdr->check)
hdr->check = CSUM_MANGLED_0;
}
*portptr = newport;
}
static bool udp_manip_pkt(struct sk_buff *skb,
unsigned int iphdroff, unsigned int hdroff,
const struct nf_conntrack_tuple *tuple,
enum nf_nat_manip_type maniptype)
{
struct udphdr *hdr;
if (skb_ensure_writable(skb, hdroff + sizeof(*hdr)))
return false;
hdr = (struct udphdr *)(skb->data + hdroff);
__udp_manip_pkt(skb, iphdroff, hdr, tuple, maniptype, !!hdr->check);
return true;
}
static bool udplite_manip_pkt(struct sk_buff *skb,
unsigned int iphdroff, unsigned int hdroff,
const struct nf_conntrack_tuple *tuple,
enum nf_nat_manip_type maniptype)
{
#ifdef CONFIG_NF_CT_PROTO_UDPLITE
struct udphdr *hdr;
if (skb_ensure_writable(skb, hdroff + sizeof(*hdr)))
return false;
hdr = (struct udphdr *)(skb->data + hdroff);
__udp_manip_pkt(skb, iphdroff, hdr, tuple, maniptype, true);
#endif
return true;
}
static bool
sctp_manip_pkt(struct sk_buff *skb,
unsigned int iphdroff, unsigned int hdroff,
const struct nf_conntrack_tuple *tuple,
enum nf_nat_manip_type maniptype)
{
#ifdef CONFIG_NF_CT_PROTO_SCTP
struct sctphdr *hdr;
int hdrsize = 8;
/* This could be an inner header returned in imcp packet; in such
* cases we cannot update the checksum field since it is outside
* of the 8 bytes of transport layer headers we are guaranteed.
*/
if (skb->len >= hdroff + sizeof(*hdr))
hdrsize = sizeof(*hdr);
if (skb_ensure_writable(skb, hdroff + hdrsize))
return false;
hdr = (struct sctphdr *)(skb->data + hdroff);
if (maniptype == NF_NAT_MANIP_SRC) {
/* Get rid of src port */
hdr->source = tuple->src.u.sctp.port;
} else {
/* Get rid of dst port */
hdr->dest = tuple->dst.u.sctp.port;
}
if (hdrsize < sizeof(*hdr))
return true;
if (skb->ip_summed != CHECKSUM_PARTIAL) {
hdr->checksum = sctp_compute_cksum(skb, hdroff);
skb->ip_summed = CHECKSUM_NONE;
}
#endif
return true;
}
static bool
tcp_manip_pkt(struct sk_buff *skb,
unsigned int iphdroff, unsigned int hdroff,
const struct nf_conntrack_tuple *tuple,
enum nf_nat_manip_type maniptype)
{
struct tcphdr *hdr;
__be16 *portptr, newport, oldport;
int hdrsize = 8; /* TCP connection tracking guarantees this much */
/* this could be a inner header returned in icmp packet; in such
cases we cannot update the checksum field since it is outside of
the 8 bytes of transport layer headers we are guaranteed */
if (skb->len >= hdroff + sizeof(struct tcphdr))
hdrsize = sizeof(struct tcphdr);
if (skb_ensure_writable(skb, hdroff + hdrsize))
return false;
hdr = (struct tcphdr *)(skb->data + hdroff);
if (maniptype == NF_NAT_MANIP_SRC) {
/* Get rid of src port */
newport = tuple->src.u.tcp.port;
portptr = &hdr->source;
} else {
/* Get rid of dst port */
newport = tuple->dst.u.tcp.port;
portptr = &hdr->dest;
}
oldport = *portptr;
*portptr = newport;
if (hdrsize < sizeof(*hdr))
return true;
nf_csum_update(skb, iphdroff, &hdr->check, tuple, maniptype);
inet_proto_csum_replace2(&hdr->check, skb, oldport, newport, false);
return true;
}
static bool
dccp_manip_pkt(struct sk_buff *skb,
unsigned int iphdroff, unsigned int hdroff,
const struct nf_conntrack_tuple *tuple,
enum nf_nat_manip_type maniptype)
{
#ifdef CONFIG_NF_CT_PROTO_DCCP
struct dccp_hdr *hdr;
__be16 *portptr, oldport, newport;
int hdrsize = 8; /* DCCP connection tracking guarantees this much */
if (skb->len >= hdroff + sizeof(struct dccp_hdr))
hdrsize = sizeof(struct dccp_hdr);
if (skb_ensure_writable(skb, hdroff + hdrsize))
return false;
hdr = (struct dccp_hdr *)(skb->data + hdroff);
if (maniptype == NF_NAT_MANIP_SRC) {
newport = tuple->src.u.dccp.port;
portptr = &hdr->dccph_sport;
} else {
newport = tuple->dst.u.dccp.port;
portptr = &hdr->dccph_dport;
}
oldport = *portptr;
*portptr = newport;
if (hdrsize < sizeof(*hdr))
return true;
nf_csum_update(skb, iphdroff, &hdr->dccph_checksum, tuple, maniptype);
inet_proto_csum_replace2(&hdr->dccph_checksum, skb, oldport, newport,
false);
#endif
return true;
}
static bool
icmp_manip_pkt(struct sk_buff *skb,
unsigned int iphdroff, unsigned int hdroff,
const struct nf_conntrack_tuple *tuple,
enum nf_nat_manip_type maniptype)
{
struct icmphdr *hdr;
if (skb_ensure_writable(skb, hdroff + sizeof(*hdr)))
return false;
hdr = (struct icmphdr *)(skb->data + hdroff);
switch (hdr->type) {
case ICMP_ECHO:
case ICMP_ECHOREPLY:
case ICMP_TIMESTAMP:
case ICMP_TIMESTAMPREPLY:
case ICMP_INFO_REQUEST:
case ICMP_INFO_REPLY:
case ICMP_ADDRESS:
case ICMP_ADDRESSREPLY:
break;
default:
return true;
}
inet_proto_csum_replace2(&hdr->checksum, skb,
hdr->un.echo.id, tuple->src.u.icmp.id, false);
hdr->un.echo.id = tuple->src.u.icmp.id;
return true;
}
static bool
icmpv6_manip_pkt(struct sk_buff *skb,
unsigned int iphdroff, unsigned int hdroff,
const struct nf_conntrack_tuple *tuple,
enum nf_nat_manip_type maniptype)
{
struct icmp6hdr *hdr;
if (skb_ensure_writable(skb, hdroff + sizeof(*hdr)))
return false;
hdr = (struct icmp6hdr *)(skb->data + hdroff);
nf_csum_update(skb, iphdroff, &hdr->icmp6_cksum, tuple, maniptype);
if (hdr->icmp6_type == ICMPV6_ECHO_REQUEST ||
hdr->icmp6_type == ICMPV6_ECHO_REPLY) {
inet_proto_csum_replace2(&hdr->icmp6_cksum, skb,
hdr->icmp6_identifier,
tuple->src.u.icmp.id, false);
hdr->icmp6_identifier = tuple->src.u.icmp.id;
}
return true;
}
/* manipulate a GRE packet according to maniptype */
static bool
gre_manip_pkt(struct sk_buff *skb,
unsigned int iphdroff, unsigned int hdroff,
const struct nf_conntrack_tuple *tuple,
enum nf_nat_manip_type maniptype)
{
#if IS_ENABLED(CONFIG_NF_CT_PROTO_GRE)
const struct gre_base_hdr *greh;
struct pptp_gre_header *pgreh;
/* pgreh includes two optional 32bit fields which are not required
* to be there. That's where the magic '8' comes from */
if (skb_ensure_writable(skb, hdroff + sizeof(*pgreh) - 8))
return false;
greh = (void *)skb->data + hdroff;
pgreh = (struct pptp_gre_header *)greh;
/* we only have destination manip of a packet, since 'source key'
* is not present in the packet itself */
if (maniptype != NF_NAT_MANIP_DST)
return true;
switch (greh->flags & GRE_VERSION) {
case GRE_VERSION_0:
/* We do not currently NAT any GREv0 packets.
* Try to behave like "nf_nat_proto_unknown" */
break;
case GRE_VERSION_1:
pr_debug("call_id -> 0x%04x\n", ntohs(tuple->dst.u.gre.key));
pgreh->call_id = tuple->dst.u.gre.key;
break;
default:
pr_debug("can't nat unknown GRE version\n");
return false;
}
#endif
return true;
}
static bool l4proto_manip_pkt(struct sk_buff *skb,
unsigned int iphdroff, unsigned int hdroff,
const struct nf_conntrack_tuple *tuple,
enum nf_nat_manip_type maniptype)
{
switch (tuple->dst.protonum) {
case IPPROTO_TCP:
return tcp_manip_pkt(skb, iphdroff, hdroff,
tuple, maniptype);
case IPPROTO_UDP:
return udp_manip_pkt(skb, iphdroff, hdroff,
tuple, maniptype);
case IPPROTO_UDPLITE:
return udplite_manip_pkt(skb, iphdroff, hdroff,
tuple, maniptype);
case IPPROTO_SCTP:
return sctp_manip_pkt(skb, iphdroff, hdroff,
tuple, maniptype);
case IPPROTO_ICMP:
return icmp_manip_pkt(skb, iphdroff, hdroff,
tuple, maniptype);
case IPPROTO_ICMPV6:
return icmpv6_manip_pkt(skb, iphdroff, hdroff,
tuple, maniptype);
case IPPROTO_DCCP:
return dccp_manip_pkt(skb, iphdroff, hdroff,
tuple, maniptype);
case IPPROTO_GRE:
return gre_manip_pkt(skb, iphdroff, hdroff,
tuple, maniptype);
}
/* If we don't know protocol -- no error, pass it unmodified. */
return true;
}
static bool nf_nat_ipv4_manip_pkt(struct sk_buff *skb,
unsigned int iphdroff,
const struct nf_conntrack_tuple *target,
enum nf_nat_manip_type maniptype)
{
struct iphdr *iph;
unsigned int hdroff;
if (skb_ensure_writable(skb, iphdroff + sizeof(*iph)))
return false;
iph = (void *)skb->data + iphdroff;
hdroff = iphdroff + iph->ihl * 4;
if (!l4proto_manip_pkt(skb, iphdroff, hdroff, target, maniptype))
return false;
iph = (void *)skb->data + iphdroff;
if (maniptype == NF_NAT_MANIP_SRC) {
csum_replace4(&iph->check, iph->saddr, target->src.u3.ip);
iph->saddr = target->src.u3.ip;
} else {
csum_replace4(&iph->check, iph->daddr, target->dst.u3.ip);
iph->daddr = target->dst.u3.ip;
}
return true;
}
static bool nf_nat_ipv6_manip_pkt(struct sk_buff *skb,
unsigned int iphdroff,
const struct nf_conntrack_tuple *target,
enum nf_nat_manip_type maniptype)
{
#if IS_ENABLED(CONFIG_IPV6)
struct ipv6hdr *ipv6h;
__be16 frag_off;
int hdroff;
u8 nexthdr;
if (skb_ensure_writable(skb, iphdroff + sizeof(*ipv6h)))
return false;
ipv6h = (void *)skb->data + iphdroff;
nexthdr = ipv6h->nexthdr;
hdroff = ipv6_skip_exthdr(skb, iphdroff + sizeof(*ipv6h),
&nexthdr, &frag_off);
if (hdroff < 0)
goto manip_addr;
if ((frag_off & htons(~0x7)) == 0 &&
!l4proto_manip_pkt(skb, iphdroff, hdroff, target, maniptype))
return false;
/* must reload, offset might have changed */
ipv6h = (void *)skb->data + iphdroff;
manip_addr:
if (maniptype == NF_NAT_MANIP_SRC)
ipv6h->saddr = target->src.u3.in6;
else
ipv6h->daddr = target->dst.u3.in6;
#endif
return true;
}
unsigned int nf_nat_manip_pkt(struct sk_buff *skb, struct nf_conn *ct,
enum nf_nat_manip_type mtype,
enum ip_conntrack_dir dir)
{
struct nf_conntrack_tuple target;
/* We are aiming to look like inverse of other direction. */
nf_ct_invert_tuple(&target, &ct->tuplehash[!dir].tuple);
switch (target.src.l3num) {
case NFPROTO_IPV6:
if (nf_nat_ipv6_manip_pkt(skb, 0, &target, mtype))
return NF_ACCEPT;
break;
case NFPROTO_IPV4:
if (nf_nat_ipv4_manip_pkt(skb, 0, &target, mtype))
return NF_ACCEPT;
break;
default:
WARN_ON_ONCE(1);
break;
}
return NF_DROP;
}
static void nf_nat_ipv4_csum_update(struct sk_buff *skb,
unsigned int iphdroff, __sum16 *check,
const struct nf_conntrack_tuple *t,
enum nf_nat_manip_type maniptype)
{
struct iphdr *iph = (struct iphdr *)(skb->data + iphdroff);
__be32 oldip, newip;
if (maniptype == NF_NAT_MANIP_SRC) {
oldip = iph->saddr;
newip = t->src.u3.ip;
} else {
oldip = iph->daddr;
newip = t->dst.u3.ip;
}
inet_proto_csum_replace4(check, skb, oldip, newip, true);
}
static void nf_nat_ipv6_csum_update(struct sk_buff *skb,
unsigned int iphdroff, __sum16 *check,
const struct nf_conntrack_tuple *t,
enum nf_nat_manip_type maniptype)
{
#if IS_ENABLED(CONFIG_IPV6)
const struct ipv6hdr *ipv6h = (struct ipv6hdr *)(skb->data + iphdroff);
const struct in6_addr *oldip, *newip;
if (maniptype == NF_NAT_MANIP_SRC) {
oldip = &ipv6h->saddr;
newip = &t->src.u3.in6;
} else {
oldip = &ipv6h->daddr;
newip = &t->dst.u3.in6;
}
inet_proto_csum_replace16(check, skb, oldip->s6_addr32,
newip->s6_addr32, true);
#endif
}
static void nf_csum_update(struct sk_buff *skb,
unsigned int iphdroff, __sum16 *check,
const struct nf_conntrack_tuple *t,
enum nf_nat_manip_type maniptype)
{
switch (t->src.l3num) {
case NFPROTO_IPV4:
nf_nat_ipv4_csum_update(skb, iphdroff, check, t, maniptype);
return;
case NFPROTO_IPV6:
nf_nat_ipv6_csum_update(skb, iphdroff, check, t, maniptype);
return;
}
}
static void nf_nat_ipv4_csum_recalc(struct sk_buff *skb,
u8 proto, void *data, __sum16 *check,
int datalen, int oldlen)
{
if (skb->ip_summed != CHECKSUM_PARTIAL) {
const struct iphdr *iph = ip_hdr(skb);
skb->ip_summed = CHECKSUM_PARTIAL;
skb->csum_start = skb_headroom(skb) + skb_network_offset(skb) +
ip_hdrlen(skb);
skb->csum_offset = (void *)check - data;
*check = ~csum_tcpudp_magic(iph->saddr, iph->daddr, datalen,
proto, 0);
} else {
inet_proto_csum_replace2(check, skb,
htons(oldlen), htons(datalen), true);
}
}
#if IS_ENABLED(CONFIG_IPV6)
static void nf_nat_ipv6_csum_recalc(struct sk_buff *skb,
u8 proto, void *data, __sum16 *check,
int datalen, int oldlen)
{
if (skb->ip_summed != CHECKSUM_PARTIAL) {
const struct ipv6hdr *ipv6h = ipv6_hdr(skb);
skb->ip_summed = CHECKSUM_PARTIAL;
skb->csum_start = skb_headroom(skb) + skb_network_offset(skb) +
(data - (void *)skb->data);
skb->csum_offset = (void *)check - data;
*check = ~csum_ipv6_magic(&ipv6h->saddr, &ipv6h->daddr,
datalen, proto, 0);
} else {
inet_proto_csum_replace2(check, skb,
htons(oldlen), htons(datalen), true);
}
}
#endif
void nf_nat_csum_recalc(struct sk_buff *skb,
u8 nfproto, u8 proto, void *data, __sum16 *check,
int datalen, int oldlen)
{
switch (nfproto) {
case NFPROTO_IPV4:
nf_nat_ipv4_csum_recalc(skb, proto, data, check,
datalen, oldlen);
return;
#if IS_ENABLED(CONFIG_IPV6)
case NFPROTO_IPV6:
nf_nat_ipv6_csum_recalc(skb, proto, data, check,
datalen, oldlen);
return;
#endif
}
WARN_ON_ONCE(1);
}
int nf_nat_icmp_reply_translation(struct sk_buff *skb,
struct nf_conn *ct,
enum ip_conntrack_info ctinfo,
unsigned int hooknum)
{
struct {
struct icmphdr icmp;
struct iphdr ip;
} *inside;
enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
enum nf_nat_manip_type manip = HOOK2MANIP(hooknum);
unsigned int hdrlen = ip_hdrlen(skb);
struct nf_conntrack_tuple target;
unsigned long statusbit;
WARN_ON(ctinfo != IP_CT_RELATED && ctinfo != IP_CT_RELATED_REPLY);
if (skb_ensure_writable(skb, hdrlen + sizeof(*inside)))
return 0;
if (nf_ip_checksum(skb, hooknum, hdrlen, IPPROTO_ICMP))
return 0;
inside = (void *)skb->data + hdrlen;
if (inside->icmp.type == ICMP_REDIRECT) {
if ((ct->status & IPS_NAT_DONE_MASK) != IPS_NAT_DONE_MASK)
return 0;
if (ct->status & IPS_NAT_MASK)
return 0;
}
if (manip == NF_NAT_MANIP_SRC)
statusbit = IPS_SRC_NAT;
else
statusbit = IPS_DST_NAT;
/* Invert if this is reply direction */
if (dir == IP_CT_DIR_REPLY)
statusbit ^= IPS_NAT_MASK;
if (!(ct->status & statusbit))
return 1;
if (!nf_nat_ipv4_manip_pkt(skb, hdrlen + sizeof(inside->icmp),
&ct->tuplehash[!dir].tuple, !manip))
return 0;
if (skb->ip_summed != CHECKSUM_PARTIAL) {
/* Reloading "inside" here since manip_pkt may reallocate */
inside = (void *)skb->data + hdrlen;
inside->icmp.checksum = 0;
inside->icmp.checksum =
csum_fold(skb_checksum(skb, hdrlen,
skb->len - hdrlen, 0));
}
/* Change outer to look like the reply to an incoming packet */
nf_ct_invert_tuple(&target, &ct->tuplehash[!dir].tuple);
target.dst.protonum = IPPROTO_ICMP;
if (!nf_nat_ipv4_manip_pkt(skb, 0, &target, manip))
return 0;
return 1;
}
EXPORT_SYMBOL_GPL(nf_nat_icmp_reply_translation);
static unsigned int
nf_nat_ipv4_fn(void *priv, struct sk_buff *skb,
const struct nf_hook_state *state)
{
struct nf_conn *ct;
enum ip_conntrack_info ctinfo;
ct = nf_ct_get(skb, &ctinfo);
if (!ct)
return NF_ACCEPT;
if (ctinfo == IP_CT_RELATED || ctinfo == IP_CT_RELATED_REPLY) {
if (ip_hdr(skb)->protocol == IPPROTO_ICMP) {
if (!nf_nat_icmp_reply_translation(skb, ct, ctinfo,
state->hook))
return NF_DROP;
else
return NF_ACCEPT;
}
}
return nf_nat_inet_fn(priv, skb, state);
}
static unsigned int
nf_nat_ipv4_pre_routing(void *priv, struct sk_buff *skb,
const struct nf_hook_state *state)
{
unsigned int ret;
__be32 daddr = ip_hdr(skb)->daddr;
ret = nf_nat_ipv4_fn(priv, skb, state);
if (ret == NF_ACCEPT && daddr != ip_hdr(skb)->daddr)
skb_dst_drop(skb);
return ret;
}
#ifdef CONFIG_XFRM
static int nf_xfrm_me_harder(struct net *net, struct sk_buff *skb, unsigned int family)
{
struct sock *sk = skb->sk;
struct dst_entry *dst;
unsigned int hh_len;
struct flowi fl;
int err;
err = xfrm_decode_session(net, skb, &fl, family);
if (err < 0)
return err;
dst = skb_dst(skb);
if (dst->xfrm)
dst = ((struct xfrm_dst *)dst)->route;
if (!dst_hold_safe(dst))
return -EHOSTUNREACH;
if (sk && !net_eq(net, sock_net(sk)))
sk = NULL;
dst = xfrm_lookup(net, dst, &fl, sk, 0);
if (IS_ERR(dst))
return PTR_ERR(dst);
skb_dst_drop(skb);
skb_dst_set(skb, dst);
/* Change in oif may mean change in hh_len. */
hh_len = skb_dst(skb)->dev->hard_header_len;
if (skb_headroom(skb) < hh_len &&
pskb_expand_head(skb, hh_len - skb_headroom(skb), 0, GFP_ATOMIC))
return -ENOMEM;
return 0;
}
#endif
static bool nf_nat_inet_port_was_mangled(const struct sk_buff *skb, __be16 sport)
{
enum ip_conntrack_info ctinfo;
enum ip_conntrack_dir dir;
const struct nf_conn *ct;
ct = nf_ct_get(skb, &ctinfo);
if (!ct)
return false;
switch (nf_ct_protonum(ct)) {
case IPPROTO_TCP:
case IPPROTO_UDP:
break;
default:
return false;
}
dir = CTINFO2DIR(ctinfo);
if (dir != IP_CT_DIR_ORIGINAL)
return false;
return ct->tuplehash[!dir].tuple.dst.u.all != sport;
}
static unsigned int
nf_nat_ipv4_local_in(void *priv, struct sk_buff *skb,
const struct nf_hook_state *state)
{
__be32 saddr = ip_hdr(skb)->saddr;
struct sock *sk = skb->sk;
unsigned int ret;
ret = nf_nat_ipv4_fn(priv, skb, state);
if (ret != NF_ACCEPT || !sk || inet_sk_transparent(sk))
return ret;
/* skb has a socket assigned via tcp edemux. We need to check
* if nf_nat_ipv4_fn() has mangled the packet in a way that
* edemux would not have found this socket.
*
* This includes both changes to the source address and changes
* to the source port, which are both handled by the
* nf_nat_ipv4_fn() call above -- long after tcp/udp early demux
* might have found a socket for the old (pre-snat) address.
*/
if (saddr != ip_hdr(skb)->saddr ||
nf_nat_inet_port_was_mangled(skb, sk->sk_dport))
skb_orphan(skb); /* TCP edemux obtained wrong socket */
return ret;
}
static unsigned int
nf_nat_ipv4_out(void *priv, struct sk_buff *skb,
const struct nf_hook_state *state)
{
#ifdef CONFIG_XFRM
const struct nf_conn *ct;
enum ip_conntrack_info ctinfo;
int err;
#endif
unsigned int ret;
ret = nf_nat_ipv4_fn(priv, skb, state);
#ifdef CONFIG_XFRM
if (ret != NF_ACCEPT)
return ret;
if (IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED)
return ret;
ct = nf_ct_get(skb, &ctinfo);
if (ct) {
enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
if (ct->tuplehash[dir].tuple.src.u3.ip !=
ct->tuplehash[!dir].tuple.dst.u3.ip ||
(ct->tuplehash[dir].tuple.dst.protonum != IPPROTO_ICMP &&
ct->tuplehash[dir].tuple.src.u.all !=
ct->tuplehash[!dir].tuple.dst.u.all)) {
err = nf_xfrm_me_harder(state->net, skb, AF_INET);
if (err < 0)
ret = NF_DROP_ERR(err);
}
}
#endif
return ret;
}
static unsigned int
nf_nat_ipv4_local_fn(void *priv, struct sk_buff *skb,
const struct nf_hook_state *state)
{
const struct nf_conn *ct;
enum ip_conntrack_info ctinfo;
unsigned int ret;
int err;
ret = nf_nat_ipv4_fn(priv, skb, state);
if (ret != NF_ACCEPT)
return ret;
ct = nf_ct_get(skb, &ctinfo);
if (ct) {
enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
if (ct->tuplehash[dir].tuple.dst.u3.ip !=
ct->tuplehash[!dir].tuple.src.u3.ip) {
err = ip_route_me_harder(state->net, state->sk, skb, RTN_UNSPEC);
if (err < 0)
ret = NF_DROP_ERR(err);
}
#ifdef CONFIG_XFRM
else if (!(IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED) &&
ct->tuplehash[dir].tuple.dst.protonum != IPPROTO_ICMP &&
ct->tuplehash[dir].tuple.dst.u.all !=
ct->tuplehash[!dir].tuple.src.u.all) {
err = nf_xfrm_me_harder(state->net, skb, AF_INET);
if (err < 0)
ret = NF_DROP_ERR(err);
}
#endif
}
return ret;
}
static const struct nf_hook_ops nf_nat_ipv4_ops[] = {
/* Before packet filtering, change destination */
{
.hook = nf_nat_ipv4_pre_routing,
.pf = NFPROTO_IPV4,
.hooknum = NF_INET_PRE_ROUTING,
.priority = NF_IP_PRI_NAT_DST,
},
/* After packet filtering, change source */
{
.hook = nf_nat_ipv4_out,
.pf = NFPROTO_IPV4,
.hooknum = NF_INET_POST_ROUTING,
.priority = NF_IP_PRI_NAT_SRC,
},
/* Before packet filtering, change destination */
{
.hook = nf_nat_ipv4_local_fn,
.pf = NFPROTO_IPV4,
.hooknum = NF_INET_LOCAL_OUT,
.priority = NF_IP_PRI_NAT_DST,
},
/* After packet filtering, change source */
{
.hook = nf_nat_ipv4_local_in,
.pf = NFPROTO_IPV4,
.hooknum = NF_INET_LOCAL_IN,
.priority = NF_IP_PRI_NAT_SRC,
},
};
int nf_nat_ipv4_register_fn(struct net *net, const struct nf_hook_ops *ops)
{
return nf_nat_register_fn(net, ops->pf, ops, nf_nat_ipv4_ops,
ARRAY_SIZE(nf_nat_ipv4_ops));
}
EXPORT_SYMBOL_GPL(nf_nat_ipv4_register_fn);
void nf_nat_ipv4_unregister_fn(struct net *net, const struct nf_hook_ops *ops)
{
nf_nat_unregister_fn(net, ops->pf, ops, ARRAY_SIZE(nf_nat_ipv4_ops));
}
EXPORT_SYMBOL_GPL(nf_nat_ipv4_unregister_fn);
#if IS_ENABLED(CONFIG_IPV6)
int nf_nat_icmpv6_reply_translation(struct sk_buff *skb,
struct nf_conn *ct,
enum ip_conntrack_info ctinfo,
unsigned int hooknum,
unsigned int hdrlen)
{
struct {
struct icmp6hdr icmp6;
struct ipv6hdr ip6;
} *inside;
enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
enum nf_nat_manip_type manip = HOOK2MANIP(hooknum);
struct nf_conntrack_tuple target;
unsigned long statusbit;
WARN_ON(ctinfo != IP_CT_RELATED && ctinfo != IP_CT_RELATED_REPLY);
if (skb_ensure_writable(skb, hdrlen + sizeof(*inside)))
return 0;
if (nf_ip6_checksum(skb, hooknum, hdrlen, IPPROTO_ICMPV6))
return 0;
inside = (void *)skb->data + hdrlen;
if (inside->icmp6.icmp6_type == NDISC_REDIRECT) {
if ((ct->status & IPS_NAT_DONE_MASK) != IPS_NAT_DONE_MASK)
return 0;
if (ct->status & IPS_NAT_MASK)
return 0;
}
if (manip == NF_NAT_MANIP_SRC)
statusbit = IPS_SRC_NAT;
else
statusbit = IPS_DST_NAT;
/* Invert if this is reply direction */
if (dir == IP_CT_DIR_REPLY)
statusbit ^= IPS_NAT_MASK;
if (!(ct->status & statusbit))
return 1;
if (!nf_nat_ipv6_manip_pkt(skb, hdrlen + sizeof(inside->icmp6),
&ct->tuplehash[!dir].tuple, !manip))
return 0;
if (skb->ip_summed != CHECKSUM_PARTIAL) {
struct ipv6hdr *ipv6h = ipv6_hdr(skb);
inside = (void *)skb->data + hdrlen;
inside->icmp6.icmp6_cksum = 0;
inside->icmp6.icmp6_cksum =
csum_ipv6_magic(&ipv6h->saddr, &ipv6h->daddr,
skb->len - hdrlen, IPPROTO_ICMPV6,
skb_checksum(skb, hdrlen,
skb->len - hdrlen, 0));
}
nf_ct_invert_tuple(&target, &ct->tuplehash[!dir].tuple);
target.dst.protonum = IPPROTO_ICMPV6;
if (!nf_nat_ipv6_manip_pkt(skb, 0, &target, manip))
return 0;
return 1;
}
EXPORT_SYMBOL_GPL(nf_nat_icmpv6_reply_translation);
static unsigned int
nf_nat_ipv6_fn(void *priv, struct sk_buff *skb,
const struct nf_hook_state *state)
{
struct nf_conn *ct;
enum ip_conntrack_info ctinfo;
__be16 frag_off;
int hdrlen;
u8 nexthdr;
ct = nf_ct_get(skb, &ctinfo);
/* Can't track? It's not due to stress, or conntrack would
* have dropped it. Hence it's the user's responsibilty to
* packet filter it out, or implement conntrack/NAT for that
* protocol. 8) --RR
*/
if (!ct)
return NF_ACCEPT;
if (ctinfo == IP_CT_RELATED || ctinfo == IP_CT_RELATED_REPLY) {
nexthdr = ipv6_hdr(skb)->nexthdr;
hdrlen = ipv6_skip_exthdr(skb, sizeof(struct ipv6hdr),
&nexthdr, &frag_off);
if (hdrlen >= 0 && nexthdr == IPPROTO_ICMPV6) {
if (!nf_nat_icmpv6_reply_translation(skb, ct, ctinfo,
state->hook,
hdrlen))
return NF_DROP;
else
return NF_ACCEPT;
}
}
return nf_nat_inet_fn(priv, skb, state);
}
static unsigned int
nf_nat_ipv6_local_in(void *priv, struct sk_buff *skb,
const struct nf_hook_state *state)
{
struct in6_addr saddr = ipv6_hdr(skb)->saddr;
struct sock *sk = skb->sk;
unsigned int ret;
ret = nf_nat_ipv6_fn(priv, skb, state);
if (ret != NF_ACCEPT || !sk || inet_sk_transparent(sk))
return ret;
/* see nf_nat_ipv4_local_in */
if (ipv6_addr_cmp(&saddr, &ipv6_hdr(skb)->saddr) ||
nf_nat_inet_port_was_mangled(skb, sk->sk_dport))
skb_orphan(skb);
return ret;
}
static unsigned int
nf_nat_ipv6_in(void *priv, struct sk_buff *skb,
const struct nf_hook_state *state)
{
unsigned int ret, verdict;
struct in6_addr daddr = ipv6_hdr(skb)->daddr;
ret = nf_nat_ipv6_fn(priv, skb, state);
verdict = ret & NF_VERDICT_MASK;
if (verdict != NF_DROP && verdict != NF_STOLEN &&
ipv6_addr_cmp(&daddr, &ipv6_hdr(skb)->daddr))
skb_dst_drop(skb);
return ret;
}
static unsigned int
nf_nat_ipv6_out(void *priv, struct sk_buff *skb,
const struct nf_hook_state *state)
{
#ifdef CONFIG_XFRM
const struct nf_conn *ct;
enum ip_conntrack_info ctinfo;
int err;
#endif
unsigned int ret;
ret = nf_nat_ipv6_fn(priv, skb, state);
#ifdef CONFIG_XFRM
if (ret != NF_ACCEPT)
return ret;
if (IP6CB(skb)->flags & IP6SKB_XFRM_TRANSFORMED)
return ret;
ct = nf_ct_get(skb, &ctinfo);
if (ct) {
enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
if (!nf_inet_addr_cmp(&ct->tuplehash[dir].tuple.src.u3,
&ct->tuplehash[!dir].tuple.dst.u3) ||
(ct->tuplehash[dir].tuple.dst.protonum != IPPROTO_ICMPV6 &&
ct->tuplehash[dir].tuple.src.u.all !=
ct->tuplehash[!dir].tuple.dst.u.all)) {
err = nf_xfrm_me_harder(state->net, skb, AF_INET6);
if (err < 0)
ret = NF_DROP_ERR(err);
}
}
#endif
return ret;
}
static unsigned int
nf_nat_ipv6_local_fn(void *priv, struct sk_buff *skb,
const struct nf_hook_state *state)
{
const struct nf_conn *ct;
enum ip_conntrack_info ctinfo;
unsigned int ret;
int err;
ret = nf_nat_ipv6_fn(priv, skb, state);
if (ret != NF_ACCEPT)
return ret;
ct = nf_ct_get(skb, &ctinfo);
if (ct) {
enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
if (!nf_inet_addr_cmp(&ct->tuplehash[dir].tuple.dst.u3,
&ct->tuplehash[!dir].tuple.src.u3)) {
err = nf_ip6_route_me_harder(state->net, state->sk, skb);
if (err < 0)
ret = NF_DROP_ERR(err);
}
#ifdef CONFIG_XFRM
else if (!(IP6CB(skb)->flags & IP6SKB_XFRM_TRANSFORMED) &&
ct->tuplehash[dir].tuple.dst.protonum != IPPROTO_ICMPV6 &&
ct->tuplehash[dir].tuple.dst.u.all !=
ct->tuplehash[!dir].tuple.src.u.all) {
err = nf_xfrm_me_harder(state->net, skb, AF_INET6);
if (err < 0)
ret = NF_DROP_ERR(err);
}
#endif
}
return ret;
}
static const struct nf_hook_ops nf_nat_ipv6_ops[] = {
/* Before packet filtering, change destination */
{
.hook = nf_nat_ipv6_in,
.pf = NFPROTO_IPV6,
.hooknum = NF_INET_PRE_ROUTING,
.priority = NF_IP6_PRI_NAT_DST,
},
/* After packet filtering, change source */
{
.hook = nf_nat_ipv6_out,
.pf = NFPROTO_IPV6,
.hooknum = NF_INET_POST_ROUTING,
.priority = NF_IP6_PRI_NAT_SRC,
},
/* Before packet filtering, change destination */
{
.hook = nf_nat_ipv6_local_fn,
.pf = NFPROTO_IPV6,
.hooknum = NF_INET_LOCAL_OUT,
.priority = NF_IP6_PRI_NAT_DST,
},
/* After packet filtering, change source */
{
.hook = nf_nat_ipv6_local_in,
.pf = NFPROTO_IPV6,
.hooknum = NF_INET_LOCAL_IN,
.priority = NF_IP6_PRI_NAT_SRC,
},
};
int nf_nat_ipv6_register_fn(struct net *net, const struct nf_hook_ops *ops)
{
return nf_nat_register_fn(net, ops->pf, ops, nf_nat_ipv6_ops,
ARRAY_SIZE(nf_nat_ipv6_ops));
}
EXPORT_SYMBOL_GPL(nf_nat_ipv6_register_fn);
void nf_nat_ipv6_unregister_fn(struct net *net, const struct nf_hook_ops *ops)
{
nf_nat_unregister_fn(net, ops->pf, ops, ARRAY_SIZE(nf_nat_ipv6_ops));
}
EXPORT_SYMBOL_GPL(nf_nat_ipv6_unregister_fn);
#endif /* CONFIG_IPV6 */
#if defined(CONFIG_NF_TABLES_INET) && IS_ENABLED(CONFIG_NFT_NAT)
int nf_nat_inet_register_fn(struct net *net, const struct nf_hook_ops *ops)
{
int ret;
if (WARN_ON_ONCE(ops->pf != NFPROTO_INET))
return -EINVAL;
ret = nf_nat_register_fn(net, NFPROTO_IPV6, ops, nf_nat_ipv6_ops,
ARRAY_SIZE(nf_nat_ipv6_ops));
if (ret)
return ret;
ret = nf_nat_register_fn(net, NFPROTO_IPV4, ops, nf_nat_ipv4_ops,
ARRAY_SIZE(nf_nat_ipv4_ops));
if (ret)
nf_nat_unregister_fn(net, NFPROTO_IPV6, ops,
ARRAY_SIZE(nf_nat_ipv6_ops));
return ret;
}
EXPORT_SYMBOL_GPL(nf_nat_inet_register_fn);
void nf_nat_inet_unregister_fn(struct net *net, const struct nf_hook_ops *ops)
{
nf_nat_unregister_fn(net, NFPROTO_IPV4, ops, ARRAY_SIZE(nf_nat_ipv4_ops));
nf_nat_unregister_fn(net, NFPROTO_IPV6, ops, ARRAY_SIZE(nf_nat_ipv6_ops));
}
EXPORT_SYMBOL_GPL(nf_nat_inet_unregister_fn);
#endif /* NFT INET NAT */
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