1 /* ip_nat_helper.c - generic support functions for NAT helpers
3 * (C) 2000-2002 Harald Welte <laforge@netfilter.org>
4 * (C) 2003-2006 Netfilter Core Team <coreteam@netfilter.org>
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.
10 #include <linux/module.h>
11 #include <linux/kmod.h>
12 #include <linux/types.h>
13 #include <linux/timer.h>
14 #include <linux/skbuff.h>
15 #include <linux/tcp.h>
16 #include <linux/udp.h>
17 #include <net/checksum.h>
20 #include <linux/netfilter_ipv4.h>
21 #include <net/netfilter/nf_conntrack.h>
22 #include <net/netfilter/nf_conntrack_helper.h>
23 #include <net/netfilter/nf_conntrack_expect.h>
24 #include <net/netfilter/nf_nat.h>
25 #include <net/netfilter/nf_nat_protocol.h>
26 #include <net/netfilter/nf_nat_core.h>
27 #include <net/netfilter/nf_nat_helper.h>
31 #define DUMP_OFFSET(x) printk("offset_before=%d, offset_after=%d, correction_pos=%u\n", x->offset_before, x->offset_after, x->correction_pos);
33 #define DEBUGP(format, args...)
34 #define DUMP_OFFSET(x)
37 static DEFINE_SPINLOCK(nf_nat_seqofs_lock
);
39 /* Setup TCP sequence correction given this change at this sequence */
41 adjust_tcp_sequence(u32 seq
,
44 enum ip_conntrack_info ctinfo
)
47 struct nf_nat_seq
*this_way
, *other_way
;
48 struct nf_conn_nat
*nat
= nfct_nat(ct
);
50 DEBUGP("nf_nat_resize_packet: old_size = %u, new_size = %u\n",
51 (*skb
)->len
, new_size
);
53 dir
= CTINFO2DIR(ctinfo
);
55 this_way
= &nat
->info
.seq
[dir
];
56 other_way
= &nat
->info
.seq
[!dir
];
58 DEBUGP("nf_nat_resize_packet: Seq_offset before: ");
59 DUMP_OFFSET(this_way
);
61 spin_lock_bh(&nf_nat_seqofs_lock
);
63 /* SYN adjust. If it's uninitialized, or this is after last
64 * correction, record it: we don't handle more than one
65 * adjustment in the window, but do deal with common case of a
67 if (this_way
->offset_before
== this_way
->offset_after
||
68 before(this_way
->correction_pos
, seq
)) {
69 this_way
->correction_pos
= seq
;
70 this_way
->offset_before
= this_way
->offset_after
;
71 this_way
->offset_after
+= sizediff
;
73 spin_unlock_bh(&nf_nat_seqofs_lock
);
75 DEBUGP("nf_nat_resize_packet: Seq_offset after: ");
76 DUMP_OFFSET(this_way
);
79 /* Frobs data inside this packet, which is linear. */
80 static void mangle_contents(struct sk_buff
*skb
,
82 unsigned int match_offset
,
83 unsigned int match_len
,
84 const char *rep_buffer
,
89 BUG_ON(skb_is_nonlinear(skb
));
90 data
= skb_network_header(skb
) + dataoff
;
92 /* move post-replacement */
93 memmove(data
+ match_offset
+ rep_len
,
94 data
+ match_offset
+ match_len
,
95 skb
->tail
- (skb
->network_header
+ dataoff
+
96 match_offset
+ match_len
));
98 /* insert data from buffer */
99 memcpy(data
+ match_offset
, rep_buffer
, rep_len
);
101 /* update skb info */
102 if (rep_len
> match_len
) {
103 DEBUGP("nf_nat_mangle_packet: Extending packet by "
104 "%u from %u bytes\n", rep_len
- match_len
,
106 skb_put(skb
, rep_len
- match_len
);
108 DEBUGP("nf_nat_mangle_packet: Shrinking packet from "
109 "%u from %u bytes\n", match_len
- rep_len
,
111 __skb_trim(skb
, skb
->len
+ rep_len
- match_len
);
114 /* fix IP hdr checksum information */
115 ip_hdr(skb
)->tot_len
= htons(skb
->len
);
116 ip_send_check(ip_hdr(skb
));
119 /* Unusual, but possible case. */
120 static int enlarge_skb(struct sk_buff
**pskb
, unsigned int extra
)
122 struct sk_buff
*nskb
;
124 if ((*pskb
)->len
+ extra
> 65535)
127 nskb
= skb_copy_expand(*pskb
, skb_headroom(*pskb
), extra
, GFP_ATOMIC
);
131 /* Transfer socket to new skb. */
133 skb_set_owner_w(nskb
, (*pskb
)->sk
);
139 /* Generic function for mangling variable-length address changes inside
140 * NATed TCP connections (like the PORT XXX,XXX,XXX,XXX,XXX,XXX
143 * Takes care about all the nasty sequence number changes, checksumming,
144 * skb enlargement, ...
148 nf_nat_mangle_tcp_packet(struct sk_buff
**pskb
,
150 enum ip_conntrack_info ctinfo
,
151 unsigned int match_offset
,
152 unsigned int match_len
,
153 const char *rep_buffer
,
154 unsigned int rep_len
)
156 struct rtable
*rt
= (struct rtable
*)(*pskb
)->dst
;
161 if (!skb_make_writable(pskb
, (*pskb
)->len
))
164 if (rep_len
> match_len
&&
165 rep_len
- match_len
> skb_tailroom(*pskb
) &&
166 !enlarge_skb(pskb
, rep_len
- match_len
))
169 SKB_LINEAR_ASSERT(*pskb
);
172 tcph
= (void *)iph
+ iph
->ihl
*4;
174 oldlen
= (*pskb
)->len
- iph
->ihl
*4;
175 mangle_contents(*pskb
, iph
->ihl
*4 + tcph
->doff
*4,
176 match_offset
, match_len
, rep_buffer
, rep_len
);
178 datalen
= (*pskb
)->len
- iph
->ihl
*4;
179 if ((*pskb
)->ip_summed
!= CHECKSUM_PARTIAL
) {
180 if (!(rt
->rt_flags
& RTCF_LOCAL
) &&
181 (*pskb
)->dev
->features
& NETIF_F_V4_CSUM
) {
182 (*pskb
)->ip_summed
= CHECKSUM_PARTIAL
;
183 (*pskb
)->csum_start
= skb_headroom(*pskb
) +
184 skb_network_offset(*pskb
) +
186 (*pskb
)->csum_offset
= offsetof(struct tcphdr
, check
);
187 tcph
->check
= ~tcp_v4_check(datalen
,
188 iph
->saddr
, iph
->daddr
, 0);
191 tcph
->check
= tcp_v4_check(datalen
,
192 iph
->saddr
, iph
->daddr
,
193 csum_partial((char *)tcph
,
197 nf_proto_csum_replace2(&tcph
->check
, *pskb
,
198 htons(oldlen
), htons(datalen
), 1);
200 if (rep_len
!= match_len
) {
201 set_bit(IPS_SEQ_ADJUST_BIT
, &ct
->status
);
202 adjust_tcp_sequence(ntohl(tcph
->seq
),
203 (int)rep_len
- (int)match_len
,
205 /* Tell TCP window tracking about seq change */
206 nf_conntrack_tcp_update(*pskb
, ip_hdrlen(*pskb
),
207 ct
, CTINFO2DIR(ctinfo
));
211 EXPORT_SYMBOL(nf_nat_mangle_tcp_packet
);
213 /* Generic function for mangling variable-length address changes inside
214 * NATed UDP connections (like the CONNECT DATA XXXXX MESG XXXXX INDEX XXXXX
215 * command in the Amanda protocol)
217 * Takes care about all the nasty sequence number changes, checksumming,
218 * skb enlargement, ...
220 * XXX - This function could be merged with nf_nat_mangle_tcp_packet which
221 * should be fairly easy to do.
224 nf_nat_mangle_udp_packet(struct sk_buff
**pskb
,
226 enum ip_conntrack_info ctinfo
,
227 unsigned int match_offset
,
228 unsigned int match_len
,
229 const char *rep_buffer
,
230 unsigned int rep_len
)
232 struct rtable
*rt
= (struct rtable
*)(*pskb
)->dst
;
237 /* UDP helpers might accidentally mangle the wrong packet */
239 if ((*pskb
)->len
< iph
->ihl
*4 + sizeof(*udph
) +
240 match_offset
+ match_len
)
243 if (!skb_make_writable(pskb
, (*pskb
)->len
))
246 if (rep_len
> match_len
&&
247 rep_len
- match_len
> skb_tailroom(*pskb
) &&
248 !enlarge_skb(pskb
, rep_len
- match_len
))
252 udph
= (void *)iph
+ iph
->ihl
*4;
254 oldlen
= (*pskb
)->len
- iph
->ihl
*4;
255 mangle_contents(*pskb
, iph
->ihl
*4 + sizeof(*udph
),
256 match_offset
, match_len
, rep_buffer
, rep_len
);
258 /* update the length of the UDP packet */
259 datalen
= (*pskb
)->len
- iph
->ihl
*4;
260 udph
->len
= htons(datalen
);
262 /* fix udp checksum if udp checksum was previously calculated */
263 if (!udph
->check
&& (*pskb
)->ip_summed
!= CHECKSUM_PARTIAL
)
266 if ((*pskb
)->ip_summed
!= CHECKSUM_PARTIAL
) {
267 if (!(rt
->rt_flags
& RTCF_LOCAL
) &&
268 (*pskb
)->dev
->features
& NETIF_F_V4_CSUM
) {
269 (*pskb
)->ip_summed
= CHECKSUM_PARTIAL
;
270 (*pskb
)->csum_start
= skb_headroom(*pskb
) +
271 skb_network_offset(*pskb
) +
273 (*pskb
)->csum_offset
= offsetof(struct udphdr
, check
);
274 udph
->check
= ~csum_tcpudp_magic(iph
->saddr
, iph
->daddr
,
275 datalen
, IPPROTO_UDP
,
279 udph
->check
= csum_tcpudp_magic(iph
->saddr
, iph
->daddr
,
280 datalen
, IPPROTO_UDP
,
281 csum_partial((char *)udph
,
284 udph
->check
= CSUM_MANGLED_0
;
287 nf_proto_csum_replace2(&udph
->check
, *pskb
,
288 htons(oldlen
), htons(datalen
), 1);
292 EXPORT_SYMBOL(nf_nat_mangle_udp_packet
);
294 /* Adjust one found SACK option including checksum correction */
296 sack_adjust(struct sk_buff
*skb
,
298 unsigned int sackoff
,
299 unsigned int sackend
,
300 struct nf_nat_seq
*natseq
)
302 while (sackoff
< sackend
) {
303 struct tcp_sack_block_wire
*sack
;
304 __be32 new_start_seq
, new_end_seq
;
306 sack
= (void *)skb
->data
+ sackoff
;
307 if (after(ntohl(sack
->start_seq
) - natseq
->offset_before
,
308 natseq
->correction_pos
))
309 new_start_seq
= htonl(ntohl(sack
->start_seq
)
310 - natseq
->offset_after
);
312 new_start_seq
= htonl(ntohl(sack
->start_seq
)
313 - natseq
->offset_before
);
315 if (after(ntohl(sack
->end_seq
) - natseq
->offset_before
,
316 natseq
->correction_pos
))
317 new_end_seq
= htonl(ntohl(sack
->end_seq
)
318 - natseq
->offset_after
);
320 new_end_seq
= htonl(ntohl(sack
->end_seq
)
321 - natseq
->offset_before
);
323 DEBUGP("sack_adjust: start_seq: %d->%d, end_seq: %d->%d\n",
324 ntohl(sack
->start_seq
), new_start_seq
,
325 ntohl(sack
->end_seq
), new_end_seq
);
327 nf_proto_csum_replace4(&tcph
->check
, skb
,
328 sack
->start_seq
, new_start_seq
, 0);
329 nf_proto_csum_replace4(&tcph
->check
, skb
,
330 sack
->end_seq
, new_end_seq
, 0);
331 sack
->start_seq
= new_start_seq
;
332 sack
->end_seq
= new_end_seq
;
333 sackoff
+= sizeof(*sack
);
337 /* TCP SACK sequence number adjustment */
338 static inline unsigned int
339 nf_nat_sack_adjust(struct sk_buff
**pskb
,
342 enum ip_conntrack_info ctinfo
)
344 unsigned int dir
, optoff
, optend
;
345 struct nf_conn_nat
*nat
= nfct_nat(ct
);
347 optoff
= ip_hdrlen(*pskb
) + sizeof(struct tcphdr
);
348 optend
= ip_hdrlen(*pskb
) + tcph
->doff
* 4;
350 if (!skb_make_writable(pskb
, optend
))
353 dir
= CTINFO2DIR(ctinfo
);
355 while (optoff
< optend
) {
356 /* Usually: option, length. */
357 unsigned char *op
= (*pskb
)->data
+ optoff
;
366 /* no partial options */
367 if (optoff
+ 1 == optend
||
368 optoff
+ op
[1] > optend
||
371 if (op
[0] == TCPOPT_SACK
&&
372 op
[1] >= 2+TCPOLEN_SACK_PERBLOCK
&&
373 ((op
[1] - 2) % TCPOLEN_SACK_PERBLOCK
) == 0)
374 sack_adjust(*pskb
, tcph
, optoff
+2,
376 &nat
->info
.seq
[!dir
]);
383 /* TCP sequence number adjustment. Returns 1 on success, 0 on failure */
385 nf_nat_seq_adjust(struct sk_buff
**pskb
,
387 enum ip_conntrack_info ctinfo
)
391 __be32 newseq
, newack
;
392 struct nf_conn_nat
*nat
= nfct_nat(ct
);
393 struct nf_nat_seq
*this_way
, *other_way
;
395 dir
= CTINFO2DIR(ctinfo
);
397 this_way
= &nat
->info
.seq
[dir
];
398 other_way
= &nat
->info
.seq
[!dir
];
400 if (!skb_make_writable(pskb
, ip_hdrlen(*pskb
) + sizeof(*tcph
)))
403 tcph
= (void *)(*pskb
)->data
+ ip_hdrlen(*pskb
);
404 if (after(ntohl(tcph
->seq
), this_way
->correction_pos
))
405 newseq
= htonl(ntohl(tcph
->seq
) + this_way
->offset_after
);
407 newseq
= htonl(ntohl(tcph
->seq
) + this_way
->offset_before
);
409 if (after(ntohl(tcph
->ack_seq
) - other_way
->offset_before
,
410 other_way
->correction_pos
))
411 newack
= htonl(ntohl(tcph
->ack_seq
) - other_way
->offset_after
);
413 newack
= htonl(ntohl(tcph
->ack_seq
) - other_way
->offset_before
);
415 nf_proto_csum_replace4(&tcph
->check
, *pskb
, tcph
->seq
, newseq
, 0);
416 nf_proto_csum_replace4(&tcph
->check
, *pskb
, tcph
->ack_seq
, newack
, 0);
418 DEBUGP("Adjusting sequence number from %u->%u, ack from %u->%u\n",
419 ntohl(tcph
->seq
), ntohl(newseq
), ntohl(tcph
->ack_seq
),
423 tcph
->ack_seq
= newack
;
425 if (!nf_nat_sack_adjust(pskb
, tcph
, ct
, ctinfo
))
428 nf_conntrack_tcp_update(*pskb
, ip_hdrlen(*pskb
), ct
, dir
);
432 EXPORT_SYMBOL(nf_nat_seq_adjust
);
434 /* Setup NAT on this expected conntrack so it follows master. */
435 /* If we fail to get a free NAT slot, we'll get dropped on confirm */
436 void nf_nat_follow_master(struct nf_conn
*ct
,
437 struct nf_conntrack_expect
*exp
)
439 struct nf_nat_range range
;
441 /* This must be a fresh one. */
442 BUG_ON(ct
->status
& IPS_NAT_DONE_MASK
);
444 /* Change src to where master sends to */
445 range
.flags
= IP_NAT_RANGE_MAP_IPS
;
446 range
.min_ip
= range
.max_ip
447 = ct
->master
->tuplehash
[!exp
->dir
].tuple
.dst
.u3
.ip
;
448 /* hook doesn't matter, but it has to do source manip */
449 nf_nat_setup_info(ct
, &range
, NF_IP_POST_ROUTING
);
451 /* For DST manip, map port here to where it's expected. */
452 range
.flags
= (IP_NAT_RANGE_MAP_IPS
| IP_NAT_RANGE_PROTO_SPECIFIED
);
453 range
.min
= range
.max
= exp
->saved_proto
;
454 range
.min_ip
= range
.max_ip
455 = ct
->master
->tuplehash
[!exp
->dir
].tuple
.src
.u3
.ip
;
456 /* hook doesn't matter, but it has to do destination manip */
457 nf_nat_setup_info(ct
, &range
, NF_IP_PRE_ROUTING
);
459 EXPORT_SYMBOL(nf_nat_follow_master
);