2 * (C) 1999-2001 Paul `Rusty' Russell
3 * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
4 * (C) 2011 Patrick McHardy <kaber@trash.net>
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License version 2 as
8 * published by the Free Software Foundation.
11 #include <linux/types.h>
12 #include <linux/module.h>
13 #include <linux/skbuff.h>
15 #include <linux/icmp.h>
16 #include <linux/netfilter.h>
17 #include <linux/netfilter_ipv4.h>
18 #include <net/secure_seq.h>
19 #include <net/checksum.h>
20 #include <net/route.h>
23 #include <net/netfilter/nf_conntrack_core.h>
24 #include <net/netfilter/nf_conntrack.h>
25 #include <net/netfilter/nf_nat_core.h>
26 #include <net/netfilter/nf_nat_l3proto.h>
27 #include <net/netfilter/nf_nat_l4proto.h>
29 static const struct nf_nat_l3proto nf_nat_l3proto_ipv4
;
32 static void nf_nat_ipv4_decode_session(struct sk_buff
*skb
,
33 const struct nf_conn
*ct
,
34 enum ip_conntrack_dir dir
,
35 unsigned long statusbit
,
38 const struct nf_conntrack_tuple
*t
= &ct
->tuplehash
[dir
].tuple
;
39 struct flowi4
*fl4
= &fl
->u
.ip4
;
41 if (ct
->status
& statusbit
) {
42 fl4
->daddr
= t
->dst
.u3
.ip
;
43 if (t
->dst
.protonum
== IPPROTO_TCP
||
44 t
->dst
.protonum
== IPPROTO_UDP
||
45 t
->dst
.protonum
== IPPROTO_UDPLITE
||
46 t
->dst
.protonum
== IPPROTO_DCCP
||
47 t
->dst
.protonum
== IPPROTO_SCTP
)
48 fl4
->fl4_dport
= t
->dst
.u
.all
;
51 statusbit
^= IPS_NAT_MASK
;
53 if (ct
->status
& statusbit
) {
54 fl4
->saddr
= t
->src
.u3
.ip
;
55 if (t
->dst
.protonum
== IPPROTO_TCP
||
56 t
->dst
.protonum
== IPPROTO_UDP
||
57 t
->dst
.protonum
== IPPROTO_UDPLITE
||
58 t
->dst
.protonum
== IPPROTO_DCCP
||
59 t
->dst
.protonum
== IPPROTO_SCTP
)
60 fl4
->fl4_sport
= t
->src
.u
.all
;
63 #endif /* CONFIG_XFRM */
65 static bool nf_nat_ipv4_in_range(const struct nf_conntrack_tuple
*t
,
66 const struct nf_nat_range
*range
)
68 return ntohl(t
->src
.u3
.ip
) >= ntohl(range
->min_addr
.ip
) &&
69 ntohl(t
->src
.u3
.ip
) <= ntohl(range
->max_addr
.ip
);
72 static u32
nf_nat_ipv4_secure_port(const struct nf_conntrack_tuple
*t
,
75 return secure_ipv4_port_ephemeral(t
->src
.u3
.ip
, t
->dst
.u3
.ip
, dport
);
78 static bool nf_nat_ipv4_manip_pkt(struct sk_buff
*skb
,
79 unsigned int iphdroff
,
80 const struct nf_nat_l4proto
*l4proto
,
81 const struct nf_conntrack_tuple
*target
,
82 enum nf_nat_manip_type maniptype
)
87 if (!skb_make_writable(skb
, iphdroff
+ sizeof(*iph
)))
90 iph
= (void *)skb
->data
+ iphdroff
;
91 hdroff
= iphdroff
+ iph
->ihl
* 4;
93 if (!l4proto
->manip_pkt(skb
, &nf_nat_l3proto_ipv4
, iphdroff
, hdroff
,
96 iph
= (void *)skb
->data
+ iphdroff
;
98 if (maniptype
== NF_NAT_MANIP_SRC
) {
99 csum_replace4(&iph
->check
, iph
->saddr
, target
->src
.u3
.ip
);
100 iph
->saddr
= target
->src
.u3
.ip
;
102 csum_replace4(&iph
->check
, iph
->daddr
, target
->dst
.u3
.ip
);
103 iph
->daddr
= target
->dst
.u3
.ip
;
108 static void nf_nat_ipv4_csum_update(struct sk_buff
*skb
,
109 unsigned int iphdroff
, __sum16
*check
,
110 const struct nf_conntrack_tuple
*t
,
111 enum nf_nat_manip_type maniptype
)
113 struct iphdr
*iph
= (struct iphdr
*)(skb
->data
+ iphdroff
);
116 if (maniptype
== NF_NAT_MANIP_SRC
) {
118 newip
= t
->src
.u3
.ip
;
121 newip
= t
->dst
.u3
.ip
;
123 inet_proto_csum_replace4(check
, skb
, oldip
, newip
, true);
126 static void nf_nat_ipv4_csum_recalc(struct sk_buff
*skb
,
127 u8 proto
, void *data
, __sum16
*check
,
128 int datalen
, int oldlen
)
130 if (skb
->ip_summed
!= CHECKSUM_PARTIAL
) {
131 const struct iphdr
*iph
= ip_hdr(skb
);
133 skb
->ip_summed
= CHECKSUM_PARTIAL
;
134 skb
->csum_start
= skb_headroom(skb
) + skb_network_offset(skb
) +
136 skb
->csum_offset
= (void *)check
- data
;
137 *check
= ~csum_tcpudp_magic(iph
->saddr
, iph
->daddr
, datalen
,
140 inet_proto_csum_replace2(check
, skb
,
141 htons(oldlen
), htons(datalen
), true);
144 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
145 static int nf_nat_ipv4_nlattr_to_range(struct nlattr
*tb
[],
146 struct nf_nat_range
*range
)
148 if (tb
[CTA_NAT_V4_MINIP
]) {
149 range
->min_addr
.ip
= nla_get_be32(tb
[CTA_NAT_V4_MINIP
]);
150 range
->flags
|= NF_NAT_RANGE_MAP_IPS
;
153 if (tb
[CTA_NAT_V4_MAXIP
])
154 range
->max_addr
.ip
= nla_get_be32(tb
[CTA_NAT_V4_MAXIP
]);
156 range
->max_addr
.ip
= range
->min_addr
.ip
;
162 static const struct nf_nat_l3proto nf_nat_l3proto_ipv4
= {
163 .l3proto
= NFPROTO_IPV4
,
164 .in_range
= nf_nat_ipv4_in_range
,
165 .secure_port
= nf_nat_ipv4_secure_port
,
166 .manip_pkt
= nf_nat_ipv4_manip_pkt
,
167 .csum_update
= nf_nat_ipv4_csum_update
,
168 .csum_recalc
= nf_nat_ipv4_csum_recalc
,
169 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
170 .nlattr_to_range
= nf_nat_ipv4_nlattr_to_range
,
173 .decode_session
= nf_nat_ipv4_decode_session
,
177 int nf_nat_icmp_reply_translation(struct sk_buff
*skb
,
179 enum ip_conntrack_info ctinfo
,
180 unsigned int hooknum
)
186 enum ip_conntrack_dir dir
= CTINFO2DIR(ctinfo
);
187 enum nf_nat_manip_type manip
= HOOK2MANIP(hooknum
);
188 unsigned int hdrlen
= ip_hdrlen(skb
);
189 const struct nf_nat_l4proto
*l4proto
;
190 struct nf_conntrack_tuple target
;
191 unsigned long statusbit
;
193 NF_CT_ASSERT(ctinfo
== IP_CT_RELATED
|| ctinfo
== IP_CT_RELATED_REPLY
);
195 if (!skb_make_writable(skb
, hdrlen
+ sizeof(*inside
)))
197 if (nf_ip_checksum(skb
, hooknum
, hdrlen
, 0))
200 inside
= (void *)skb
->data
+ hdrlen
;
201 if (inside
->icmp
.type
== ICMP_REDIRECT
) {
202 if ((ct
->status
& IPS_NAT_DONE_MASK
) != IPS_NAT_DONE_MASK
)
204 if (ct
->status
& IPS_NAT_MASK
)
208 if (manip
== NF_NAT_MANIP_SRC
)
209 statusbit
= IPS_SRC_NAT
;
211 statusbit
= IPS_DST_NAT
;
213 /* Invert if this is reply direction */
214 if (dir
== IP_CT_DIR_REPLY
)
215 statusbit
^= IPS_NAT_MASK
;
217 if (!(ct
->status
& statusbit
))
220 l4proto
= __nf_nat_l4proto_find(NFPROTO_IPV4
, inside
->ip
.protocol
);
221 if (!nf_nat_ipv4_manip_pkt(skb
, hdrlen
+ sizeof(inside
->icmp
),
222 l4proto
, &ct
->tuplehash
[!dir
].tuple
, !manip
))
225 if (skb
->ip_summed
!= CHECKSUM_PARTIAL
) {
226 /* Reloading "inside" here since manip_pkt may reallocate */
227 inside
= (void *)skb
->data
+ hdrlen
;
228 inside
->icmp
.checksum
= 0;
229 inside
->icmp
.checksum
=
230 csum_fold(skb_checksum(skb
, hdrlen
,
231 skb
->len
- hdrlen
, 0));
234 /* Change outer to look like the reply to an incoming packet */
235 nf_ct_invert_tuplepr(&target
, &ct
->tuplehash
[!dir
].tuple
);
236 l4proto
= __nf_nat_l4proto_find(NFPROTO_IPV4
, 0);
237 if (!nf_nat_ipv4_manip_pkt(skb
, 0, l4proto
, &target
, manip
))
242 EXPORT_SYMBOL_GPL(nf_nat_icmp_reply_translation
);
245 nf_nat_ipv4_fn(void *priv
, struct sk_buff
*skb
,
246 const struct nf_hook_state
*state
,
247 unsigned int (*do_chain
)(void *priv
,
249 const struct nf_hook_state
*state
,
253 enum ip_conntrack_info ctinfo
;
254 struct nf_conn_nat
*nat
;
255 /* maniptype == SRC for postrouting. */
256 enum nf_nat_manip_type maniptype
= HOOK2MANIP(state
->hook
);
258 ct
= nf_ct_get(skb
, &ctinfo
);
259 /* Can't track? It's not due to stress, or conntrack would
260 * have dropped it. Hence it's the user's responsibilty to
261 * packet filter it out, or implement conntrack/NAT for that
267 /* Don't try to NAT if this packet is not conntracked */
268 if (nf_ct_is_untracked(ct
))
271 nat
= nf_ct_nat_ext_add(ct
);
277 case IP_CT_RELATED_REPLY
:
278 if (ip_hdr(skb
)->protocol
== IPPROTO_ICMP
) {
279 if (!nf_nat_icmp_reply_translation(skb
, ct
, ctinfo
,
285 /* Fall thru... (Only ICMPs can be IP_CT_IS_REPLY) */
287 /* Seen it before? This can happen for loopback, retrans,
290 if (!nf_nat_initialized(ct
, maniptype
)) {
293 ret
= do_chain(priv
, skb
, state
, ct
);
294 if (ret
!= NF_ACCEPT
)
297 if (nf_nat_initialized(ct
, HOOK2MANIP(state
->hook
)))
300 ret
= nf_nat_alloc_null_binding(ct
, state
->hook
);
301 if (ret
!= NF_ACCEPT
)
304 pr_debug("Already setup manip %s for ct %p\n",
305 maniptype
== NF_NAT_MANIP_SRC
? "SRC" : "DST",
307 if (nf_nat_oif_changed(state
->hook
, ctinfo
, nat
,
315 NF_CT_ASSERT(ctinfo
== IP_CT_ESTABLISHED
||
316 ctinfo
== IP_CT_ESTABLISHED_REPLY
);
317 if (nf_nat_oif_changed(state
->hook
, ctinfo
, nat
, state
->out
))
321 return nf_nat_packet(ct
, ctinfo
, state
->hook
, skb
);
324 nf_ct_kill_acct(ct
, ctinfo
, skb
);
327 EXPORT_SYMBOL_GPL(nf_nat_ipv4_fn
);
330 nf_nat_ipv4_in(void *priv
, struct sk_buff
*skb
,
331 const struct nf_hook_state
*state
,
332 unsigned int (*do_chain
)(void *priv
,
334 const struct nf_hook_state
*state
,
338 __be32 daddr
= ip_hdr(skb
)->daddr
;
340 ret
= nf_nat_ipv4_fn(priv
, skb
, state
, do_chain
);
341 if (ret
!= NF_DROP
&& ret
!= NF_STOLEN
&&
342 daddr
!= ip_hdr(skb
)->daddr
)
347 EXPORT_SYMBOL_GPL(nf_nat_ipv4_in
);
350 nf_nat_ipv4_out(void *priv
, struct sk_buff
*skb
,
351 const struct nf_hook_state
*state
,
352 unsigned int (*do_chain
)(void *priv
,
354 const struct nf_hook_state
*state
,
358 const struct nf_conn
*ct
;
359 enum ip_conntrack_info ctinfo
;
364 /* root is playing with raw sockets. */
365 if (skb
->len
< sizeof(struct iphdr
) ||
366 ip_hdrlen(skb
) < sizeof(struct iphdr
))
369 ret
= nf_nat_ipv4_fn(priv
, skb
, state
, do_chain
);
371 if (ret
!= NF_DROP
&& ret
!= NF_STOLEN
&&
372 !(IPCB(skb
)->flags
& IPSKB_XFRM_TRANSFORMED
) &&
373 (ct
= nf_ct_get(skb
, &ctinfo
)) != NULL
) {
374 enum ip_conntrack_dir dir
= CTINFO2DIR(ctinfo
);
376 if ((ct
->tuplehash
[dir
].tuple
.src
.u3
.ip
!=
377 ct
->tuplehash
[!dir
].tuple
.dst
.u3
.ip
) ||
378 (ct
->tuplehash
[dir
].tuple
.dst
.protonum
!= IPPROTO_ICMP
&&
379 ct
->tuplehash
[dir
].tuple
.src
.u
.all
!=
380 ct
->tuplehash
[!dir
].tuple
.dst
.u
.all
)) {
381 err
= nf_xfrm_me_harder(state
->net
, skb
, AF_INET
);
383 ret
= NF_DROP_ERR(err
);
389 EXPORT_SYMBOL_GPL(nf_nat_ipv4_out
);
392 nf_nat_ipv4_local_fn(void *priv
, struct sk_buff
*skb
,
393 const struct nf_hook_state
*state
,
394 unsigned int (*do_chain
)(void *priv
,
396 const struct nf_hook_state
*state
,
399 const struct nf_conn
*ct
;
400 enum ip_conntrack_info ctinfo
;
404 /* root is playing with raw sockets. */
405 if (skb
->len
< sizeof(struct iphdr
) ||
406 ip_hdrlen(skb
) < sizeof(struct iphdr
))
409 ret
= nf_nat_ipv4_fn(priv
, skb
, state
, do_chain
);
410 if (ret
!= NF_DROP
&& ret
!= NF_STOLEN
&&
411 (ct
= nf_ct_get(skb
, &ctinfo
)) != NULL
) {
412 enum ip_conntrack_dir dir
= CTINFO2DIR(ctinfo
);
414 if (ct
->tuplehash
[dir
].tuple
.dst
.u3
.ip
!=
415 ct
->tuplehash
[!dir
].tuple
.src
.u3
.ip
) {
416 err
= ip_route_me_harder(state
->net
, skb
, RTN_UNSPEC
);
418 ret
= NF_DROP_ERR(err
);
421 else if (!(IPCB(skb
)->flags
& IPSKB_XFRM_TRANSFORMED
) &&
422 ct
->tuplehash
[dir
].tuple
.dst
.protonum
!= IPPROTO_ICMP
&&
423 ct
->tuplehash
[dir
].tuple
.dst
.u
.all
!=
424 ct
->tuplehash
[!dir
].tuple
.src
.u
.all
) {
425 err
= nf_xfrm_me_harder(state
->net
, skb
, AF_INET
);
427 ret
= NF_DROP_ERR(err
);
433 EXPORT_SYMBOL_GPL(nf_nat_ipv4_local_fn
);
435 static int __init
nf_nat_l3proto_ipv4_init(void)
439 err
= nf_nat_l4proto_register(NFPROTO_IPV4
, &nf_nat_l4proto_icmp
);
442 err
= nf_nat_l3proto_register(&nf_nat_l3proto_ipv4
);
448 nf_nat_l4proto_unregister(NFPROTO_IPV4
, &nf_nat_l4proto_icmp
);
453 static void __exit
nf_nat_l3proto_ipv4_exit(void)
455 nf_nat_l3proto_unregister(&nf_nat_l3proto_ipv4
);
456 nf_nat_l4proto_unregister(NFPROTO_IPV4
, &nf_nat_l4proto_icmp
);
459 MODULE_LICENSE("GPL");
460 MODULE_ALIAS("nf-nat-" __stringify(AF_INET
));
462 module_init(nf_nat_l3proto_ipv4_init
);
463 module_exit(nf_nat_l3proto_ipv4_exit
);