blob: f8aad03d674b05008edb5b9883b3a26b2fa7461f [file] [log] [blame]
/*
* (C) 1999-2001 Paul `Rusty' Russell
* (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
* (C) 2011 Patrick McHardy <kaber@trash.net>
*
* 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.
*/
#include <linux/types.h>
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/ip.h>
#include <linux/icmp.h>
#include <linux/netfilter.h>
#include <linux/netfilter_ipv4.h>
#include <net/secure_seq.h>
#include <net/checksum.h>
#include <net/route.h>
#include <net/ip.h>
#include <net/netfilter/nf_conntrack_core.h>
#include <net/netfilter/nf_conntrack.h>
#include <net/netfilter/nf_nat_core.h>
#include <net/netfilter/nf_nat_l3proto.h>
#include <net/netfilter/nf_nat_l4proto.h>
static const struct nf_nat_l3proto nf_nat_l3proto_ipv4;
#ifdef CONFIG_XFRM
static void nf_nat_ipv4_decode_session(struct sk_buff *skb,
const struct nf_conn *ct,
enum ip_conntrack_dir dir,
unsigned long statusbit,
struct flowi *fl)
{
const struct nf_conntrack_tuple *t = &ct->tuplehash[dir].tuple;
struct flowi4 *fl4 = &fl->u.ip4;
if (ct->status & statusbit) {
fl4->daddr = t->dst.u3.ip;
if (t->dst.protonum == IPPROTO_TCP ||
t->dst.protonum == IPPROTO_UDP ||
t->dst.protonum == IPPROTO_UDPLITE ||
t->dst.protonum == IPPROTO_DCCP ||
t->dst.protonum == IPPROTO_SCTP)
fl4->fl4_dport = t->dst.u.all;
}
statusbit ^= IPS_NAT_MASK;
if (ct->status & statusbit) {
fl4->saddr = t->src.u3.ip;
if (t->dst.protonum == IPPROTO_TCP ||
t->dst.protonum == IPPROTO_UDP ||
t->dst.protonum == IPPROTO_UDPLITE ||
t->dst.protonum == IPPROTO_DCCP ||
t->dst.protonum == IPPROTO_SCTP)
fl4->fl4_sport = t->src.u.all;
}
}
#endif /* CONFIG_XFRM */
static bool nf_nat_ipv4_in_range(const struct nf_conntrack_tuple *t,
const struct nf_nat_range *range)
{
return ntohl(t->src.u3.ip) >= ntohl(range->min_addr.ip) &&
ntohl(t->src.u3.ip) <= ntohl(range->max_addr.ip);
}
static u32 nf_nat_ipv4_secure_port(const struct nf_conntrack_tuple *t,
__be16 dport)
{
return secure_ipv4_port_ephemeral(t->src.u3.ip, t->dst.u3.ip, dport);
}
static bool nf_nat_ipv4_manip_pkt(struct sk_buff *skb,
unsigned int iphdroff,
const struct nf_nat_l4proto *l4proto,
const struct nf_conntrack_tuple *target,
enum nf_nat_manip_type maniptype)
{
struct iphdr *iph;
unsigned int hdroff;
if (!skb_make_writable(skb, iphdroff + sizeof(*iph)))
return false;
iph = (void *)skb->data + iphdroff;
hdroff = iphdroff + iph->ihl * 4;
if (!l4proto->manip_pkt(skb, &nf_nat_l3proto_ipv4, 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 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_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_NF_CT_NETLINK)
static int nf_nat_ipv4_nlattr_to_range(struct nlattr *tb[],
struct nf_nat_range *range)
{
if (tb[CTA_NAT_V4_MINIP]) {
range->min_addr.ip = nla_get_be32(tb[CTA_NAT_V4_MINIP]);
range->flags |= NF_NAT_RANGE_MAP_IPS;
}
if (tb[CTA_NAT_V4_MAXIP])
range->max_addr.ip = nla_get_be32(tb[CTA_NAT_V4_MAXIP]);
else
range->max_addr.ip = range->min_addr.ip;
return 0;
}
#endif
static const struct nf_nat_l3proto nf_nat_l3proto_ipv4 = {
.l3proto = NFPROTO_IPV4,
.in_range = nf_nat_ipv4_in_range,
.secure_port = nf_nat_ipv4_secure_port,
.manip_pkt = nf_nat_ipv4_manip_pkt,
.csum_update = nf_nat_ipv4_csum_update,
.csum_recalc = nf_nat_ipv4_csum_recalc,
#if IS_ENABLED(CONFIG_NF_CT_NETLINK)
.nlattr_to_range = nf_nat_ipv4_nlattr_to_range,
#endif
#ifdef CONFIG_XFRM
.decode_session = nf_nat_ipv4_decode_session,
#endif
};
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);
const struct nf_nat_l4proto *l4proto;
struct nf_conntrack_tuple target;
unsigned long statusbit;
NF_CT_ASSERT(ctinfo == IP_CT_RELATED || ctinfo == IP_CT_RELATED_REPLY);
if (!skb_make_writable(skb, hdrlen + sizeof(*inside)))
return 0;
if (nf_ip_checksum(skb, hooknum, hdrlen, 0))
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;
l4proto = __nf_nat_l4proto_find(NFPROTO_IPV4, inside->ip.protocol);
if (!nf_nat_ipv4_manip_pkt(skb, hdrlen + sizeof(inside->icmp),
l4proto, &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_tuplepr(&target, &ct->tuplehash[!dir].tuple);
l4proto = __nf_nat_l4proto_find(NFPROTO_IPV4, 0);
if (!nf_nat_ipv4_manip_pkt(skb, 0, l4proto, &target, manip))
return 0;
return 1;
}
EXPORT_SYMBOL_GPL(nf_nat_icmp_reply_translation);
unsigned int
nf_nat_ipv4_fn(void *priv, struct sk_buff *skb,
const struct nf_hook_state *state,
unsigned int (*do_chain)(void *priv,
struct sk_buff *skb,
const struct nf_hook_state *state,
struct nf_conn *ct))
{
struct nf_conn *ct;
enum ip_conntrack_info ctinfo;
struct nf_conn_nat *nat;
/* maniptype == SRC for postrouting. */
enum nf_nat_manip_type maniptype = HOOK2MANIP(state->hook);
/* We never see fragments: conntrack defrags on pre-routing
* and local-out, and nf_nat_out protects post-routing.
*/
NF_CT_ASSERT(!ip_is_fragment(ip_hdr(skb)));
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;
/* Don't try to NAT if this packet is not conntracked */
if (nf_ct_is_untracked(ct))
return NF_ACCEPT;
nat = nf_ct_nat_ext_add(ct);
if (nat == NULL)
return NF_ACCEPT;
switch (ctinfo) {
case IP_CT_RELATED:
case 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;
}
/* Fall thru... (Only ICMPs can be IP_CT_IS_REPLY) */
case IP_CT_NEW:
/* Seen it before? This can happen for loopback, retrans,
* or local packets.
*/
if (!nf_nat_initialized(ct, maniptype)) {
unsigned int ret;
ret = do_chain(priv, skb, state, ct);
if (ret != NF_ACCEPT)
return ret;
if (nf_nat_initialized(ct, HOOK2MANIP(state->hook)))
break;
ret = nf_nat_alloc_null_binding(ct, state->hook);
if (ret != NF_ACCEPT)
return ret;
} else {
pr_debug("Already setup manip %s for ct %p\n",
maniptype == NF_NAT_MANIP_SRC ? "SRC" : "DST",
ct);
if (nf_nat_oif_changed(state->hook, ctinfo, nat,
state->out))
goto oif_changed;
}
break;
default:
/* ESTABLISHED */
NF_CT_ASSERT(ctinfo == IP_CT_ESTABLISHED ||
ctinfo == IP_CT_ESTABLISHED_REPLY);
if (nf_nat_oif_changed(state->hook, ctinfo, nat, state->out))
goto oif_changed;
}
return nf_nat_packet(ct, ctinfo, state->hook, skb);
oif_changed:
nf_ct_kill_acct(ct, ctinfo, skb);
return NF_DROP;
}
EXPORT_SYMBOL_GPL(nf_nat_ipv4_fn);
unsigned int
nf_nat_ipv4_in(void *priv, struct sk_buff *skb,
const struct nf_hook_state *state,
unsigned int (*do_chain)(void *priv,
struct sk_buff *skb,
const struct nf_hook_state *state,
struct nf_conn *ct))
{
unsigned int ret;
__be32 daddr = ip_hdr(skb)->daddr;
ret = nf_nat_ipv4_fn(priv, skb, state, do_chain);
if (ret != NF_DROP && ret != NF_STOLEN &&
daddr != ip_hdr(skb)->daddr)
skb_dst_drop(skb);
return ret;
}
EXPORT_SYMBOL_GPL(nf_nat_ipv4_in);
unsigned int
nf_nat_ipv4_out(void *priv, struct sk_buff *skb,
const struct nf_hook_state *state,
unsigned int (*do_chain)(void *priv,
struct sk_buff *skb,
const struct nf_hook_state *state,
struct nf_conn *ct))
{
#ifdef CONFIG_XFRM
const struct nf_conn *ct;
enum ip_conntrack_info ctinfo;
int err;
#endif
unsigned int ret;
/* root is playing with raw sockets. */
if (skb->len < sizeof(struct iphdr) ||
ip_hdrlen(skb) < sizeof(struct iphdr))
return NF_ACCEPT;
ret = nf_nat_ipv4_fn(priv, skb, state, do_chain);
#ifdef CONFIG_XFRM
if (ret != NF_DROP && ret != NF_STOLEN &&
!(IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED) &&
(ct = nf_ct_get(skb, &ctinfo)) != NULL) {
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;
}
EXPORT_SYMBOL_GPL(nf_nat_ipv4_out);
unsigned int
nf_nat_ipv4_local_fn(void *priv, struct sk_buff *skb,
const struct nf_hook_state *state,
unsigned int (*do_chain)(void *priv,
struct sk_buff *skb,
const struct nf_hook_state *state,
struct nf_conn *ct))
{
const struct nf_conn *ct;
enum ip_conntrack_info ctinfo;
unsigned int ret;
int err;
/* root is playing with raw sockets. */
if (skb->len < sizeof(struct iphdr) ||
ip_hdrlen(skb) < sizeof(struct iphdr))
return NF_ACCEPT;
ret = nf_nat_ipv4_fn(priv, skb, state, do_chain);
if (ret != NF_DROP && ret != NF_STOLEN &&
(ct = nf_ct_get(skb, &ctinfo)) != NULL) {
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, 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;
}
EXPORT_SYMBOL_GPL(nf_nat_ipv4_local_fn);
static int __init nf_nat_l3proto_ipv4_init(void)
{
int err;
err = nf_nat_l4proto_register(NFPROTO_IPV4, &nf_nat_l4proto_icmp);
if (err < 0)
goto err1;
err = nf_nat_l3proto_register(&nf_nat_l3proto_ipv4);
if (err < 0)
goto err2;
return err;
err2:
nf_nat_l4proto_unregister(NFPROTO_IPV4, &nf_nat_l4proto_icmp);
err1:
return err;
}
static void __exit nf_nat_l3proto_ipv4_exit(void)
{
nf_nat_l3proto_unregister(&nf_nat_l3proto_ipv4);
nf_nat_l4proto_unregister(NFPROTO_IPV4, &nf_nat_l4proto_icmp);
}
MODULE_LICENSE("GPL");
MODULE_ALIAS("nf-nat-" __stringify(AF_INET));
module_init(nf_nat_l3proto_ipv4_init);
module_exit(nf_nat_l3proto_ipv4_exit);