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>
19 #include <net/route.h>
21 #include <linux/netfilter_ipv4.h>
22 #include <net/netfilter/nf_conntrack.h>
23 #include <net/netfilter/nf_conntrack_helper.h>
24 #include <net/netfilter/nf_conntrack_ecache.h>
25 #include <net/netfilter/nf_conntrack_expect.h>
26 #include <net/netfilter/nf_nat.h>
27 #include <net/netfilter/nf_nat_protocol.h>
28 #include <net/netfilter/nf_nat_core.h>
29 #include <net/netfilter/nf_nat_helper.h>
31 #define DUMP_OFFSET(x) \
32 pr_debug("offset_before=%d, offset_after=%d, correction_pos=%u\n", \
33 x->offset_before, x->offset_after, x->correction_pos);
35 static DEFINE_SPINLOCK(nf_nat_seqofs_lock
);
37 /* Setup TCP sequence correction given this change at this sequence */
39 adjust_tcp_sequence(u32 seq
,
42 enum ip_conntrack_info ctinfo
)
45 struct nf_nat_seq
*this_way
, *other_way
;
46 struct nf_conn_nat
*nat
= nfct_nat(ct
);
48 pr_debug("adjust_tcp_sequence: seq = %u, sizediff = %d\n", seq
, seq
);
50 dir
= CTINFO2DIR(ctinfo
);
52 this_way
= &nat
->seq
[dir
];
53 other_way
= &nat
->seq
[!dir
];
55 pr_debug("nf_nat_resize_packet: Seq_offset before: ");
56 DUMP_OFFSET(this_way
);
58 spin_lock_bh(&nf_nat_seqofs_lock
);
60 /* SYN adjust. If it's uninitialized, or this is after last
61 * correction, record it: we don't handle more than one
62 * adjustment in the window, but do deal with common case of a
64 if (this_way
->offset_before
== this_way
->offset_after
||
65 before(this_way
->correction_pos
, seq
)) {
66 this_way
->correction_pos
= seq
;
67 this_way
->offset_before
= this_way
->offset_after
;
68 this_way
->offset_after
+= sizediff
;
70 spin_unlock_bh(&nf_nat_seqofs_lock
);
72 pr_debug("nf_nat_resize_packet: Seq_offset after: ");
73 DUMP_OFFSET(this_way
);
76 /* Get the offset value, for conntrack */
77 s16
nf_nat_get_offset(const struct nf_conn
*ct
,
78 enum ip_conntrack_dir dir
,
81 struct nf_conn_nat
*nat
= nfct_nat(ct
);
82 struct nf_nat_seq
*this_way
;
88 this_way
= &nat
->seq
[dir
];
89 spin_lock_bh(&nf_nat_seqofs_lock
);
90 offset
= after(seq
, this_way
->correction_pos
)
91 ? this_way
->offset_after
: this_way
->offset_before
;
92 spin_unlock_bh(&nf_nat_seqofs_lock
);
96 EXPORT_SYMBOL_GPL(nf_nat_get_offset
);
98 /* Frobs data inside this packet, which is linear. */
99 static void mangle_contents(struct sk_buff
*skb
,
100 unsigned int dataoff
,
101 unsigned int match_offset
,
102 unsigned int match_len
,
103 const char *rep_buffer
,
104 unsigned int rep_len
)
108 BUG_ON(skb_is_nonlinear(skb
));
109 data
= skb_network_header(skb
) + dataoff
;
111 /* move post-replacement */
112 memmove(data
+ match_offset
+ rep_len
,
113 data
+ match_offset
+ match_len
,
114 skb
->tail
- (skb
->network_header
+ dataoff
+
115 match_offset
+ match_len
));
117 /* insert data from buffer */
118 memcpy(data
+ match_offset
, rep_buffer
, rep_len
);
120 /* update skb info */
121 if (rep_len
> match_len
) {
122 pr_debug("nf_nat_mangle_packet: Extending packet by "
123 "%u from %u bytes\n", rep_len
- match_len
, skb
->len
);
124 skb_put(skb
, rep_len
- match_len
);
126 pr_debug("nf_nat_mangle_packet: Shrinking packet from "
127 "%u from %u bytes\n", match_len
- rep_len
, skb
->len
);
128 __skb_trim(skb
, skb
->len
+ rep_len
- match_len
);
131 /* fix IP hdr checksum information */
132 ip_hdr(skb
)->tot_len
= htons(skb
->len
);
133 ip_send_check(ip_hdr(skb
));
136 /* Unusual, but possible case. */
137 static int enlarge_skb(struct sk_buff
*skb
, unsigned int extra
)
139 if (skb
->len
+ extra
> 65535)
142 if (pskb_expand_head(skb
, 0, extra
- skb_tailroom(skb
), GFP_ATOMIC
))
148 /* Generic function for mangling variable-length address changes inside
149 * NATed TCP connections (like the PORT XXX,XXX,XXX,XXX,XXX,XXX
152 * Takes care about all the nasty sequence number changes, checksumming,
153 * skb enlargement, ...
157 nf_nat_mangle_tcp_packet(struct sk_buff
*skb
,
159 enum ip_conntrack_info ctinfo
,
160 unsigned int match_offset
,
161 unsigned int match_len
,
162 const char *rep_buffer
,
163 unsigned int rep_len
)
165 struct rtable
*rt
= skb_rtable(skb
);
170 if (!skb_make_writable(skb
, skb
->len
))
173 if (rep_len
> match_len
&&
174 rep_len
- match_len
> skb_tailroom(skb
) &&
175 !enlarge_skb(skb
, rep_len
- match_len
))
178 SKB_LINEAR_ASSERT(skb
);
181 tcph
= (void *)iph
+ iph
->ihl
*4;
183 oldlen
= skb
->len
- iph
->ihl
*4;
184 mangle_contents(skb
, iph
->ihl
*4 + tcph
->doff
*4,
185 match_offset
, match_len
, rep_buffer
, rep_len
);
187 datalen
= skb
->len
- iph
->ihl
*4;
188 if (skb
->ip_summed
!= CHECKSUM_PARTIAL
) {
189 if (!(rt
->rt_flags
& RTCF_LOCAL
) &&
190 skb
->dev
->features
& NETIF_F_V4_CSUM
) {
191 skb
->ip_summed
= CHECKSUM_PARTIAL
;
192 skb
->csum_start
= skb_headroom(skb
) +
193 skb_network_offset(skb
) +
195 skb
->csum_offset
= offsetof(struct tcphdr
, check
);
196 tcph
->check
= ~tcp_v4_check(datalen
,
197 iph
->saddr
, iph
->daddr
, 0);
200 tcph
->check
= tcp_v4_check(datalen
,
201 iph
->saddr
, iph
->daddr
,
206 inet_proto_csum_replace2(&tcph
->check
, skb
,
207 htons(oldlen
), htons(datalen
), 1);
209 if (rep_len
!= match_len
) {
210 set_bit(IPS_SEQ_ADJUST_BIT
, &ct
->status
);
211 adjust_tcp_sequence(ntohl(tcph
->seq
),
212 (int)rep_len
- (int)match_len
,
214 nf_conntrack_event_cache(IPCT_NATSEQADJ
, ct
);
218 EXPORT_SYMBOL(nf_nat_mangle_tcp_packet
);
220 /* Generic function for mangling variable-length address changes inside
221 * NATed UDP connections (like the CONNECT DATA XXXXX MESG XXXXX INDEX XXXXX
222 * command in the Amanda protocol)
224 * Takes care about all the nasty sequence number changes, checksumming,
225 * skb enlargement, ...
227 * XXX - This function could be merged with nf_nat_mangle_tcp_packet which
228 * should be fairly easy to do.
231 nf_nat_mangle_udp_packet(struct sk_buff
*skb
,
233 enum ip_conntrack_info ctinfo
,
234 unsigned int match_offset
,
235 unsigned int match_len
,
236 const char *rep_buffer
,
237 unsigned int rep_len
)
239 struct rtable
*rt
= skb_rtable(skb
);
244 /* UDP helpers might accidentally mangle the wrong packet */
246 if (skb
->len
< iph
->ihl
*4 + sizeof(*udph
) +
247 match_offset
+ match_len
)
250 if (!skb_make_writable(skb
, skb
->len
))
253 if (rep_len
> match_len
&&
254 rep_len
- match_len
> skb_tailroom(skb
) &&
255 !enlarge_skb(skb
, rep_len
- match_len
))
259 udph
= (void *)iph
+ iph
->ihl
*4;
261 oldlen
= skb
->len
- iph
->ihl
*4;
262 mangle_contents(skb
, iph
->ihl
*4 + sizeof(*udph
),
263 match_offset
, match_len
, rep_buffer
, rep_len
);
265 /* update the length of the UDP packet */
266 datalen
= skb
->len
- iph
->ihl
*4;
267 udph
->len
= htons(datalen
);
269 /* fix udp checksum if udp checksum was previously calculated */
270 if (!udph
->check
&& skb
->ip_summed
!= CHECKSUM_PARTIAL
)
273 if (skb
->ip_summed
!= CHECKSUM_PARTIAL
) {
274 if (!(rt
->rt_flags
& RTCF_LOCAL
) &&
275 skb
->dev
->features
& NETIF_F_V4_CSUM
) {
276 skb
->ip_summed
= CHECKSUM_PARTIAL
;
277 skb
->csum_start
= skb_headroom(skb
) +
278 skb_network_offset(skb
) +
280 skb
->csum_offset
= offsetof(struct udphdr
, check
);
281 udph
->check
= ~csum_tcpudp_magic(iph
->saddr
, iph
->daddr
,
282 datalen
, IPPROTO_UDP
,
286 udph
->check
= csum_tcpudp_magic(iph
->saddr
, iph
->daddr
,
287 datalen
, IPPROTO_UDP
,
291 udph
->check
= CSUM_MANGLED_0
;
294 inet_proto_csum_replace2(&udph
->check
, skb
,
295 htons(oldlen
), htons(datalen
), 1);
299 EXPORT_SYMBOL(nf_nat_mangle_udp_packet
);
301 /* Adjust one found SACK option including checksum correction */
303 sack_adjust(struct sk_buff
*skb
,
305 unsigned int sackoff
,
306 unsigned int sackend
,
307 struct nf_nat_seq
*natseq
)
309 while (sackoff
< sackend
) {
310 struct tcp_sack_block_wire
*sack
;
311 __be32 new_start_seq
, new_end_seq
;
313 sack
= (void *)skb
->data
+ sackoff
;
314 if (after(ntohl(sack
->start_seq
) - natseq
->offset_before
,
315 natseq
->correction_pos
))
316 new_start_seq
= htonl(ntohl(sack
->start_seq
)
317 - natseq
->offset_after
);
319 new_start_seq
= htonl(ntohl(sack
->start_seq
)
320 - natseq
->offset_before
);
322 if (after(ntohl(sack
->end_seq
) - natseq
->offset_before
,
323 natseq
->correction_pos
))
324 new_end_seq
= htonl(ntohl(sack
->end_seq
)
325 - natseq
->offset_after
);
327 new_end_seq
= htonl(ntohl(sack
->end_seq
)
328 - natseq
->offset_before
);
330 pr_debug("sack_adjust: start_seq: %d->%d, end_seq: %d->%d\n",
331 ntohl(sack
->start_seq
), new_start_seq
,
332 ntohl(sack
->end_seq
), new_end_seq
);
334 inet_proto_csum_replace4(&tcph
->check
, skb
,
335 sack
->start_seq
, new_start_seq
, 0);
336 inet_proto_csum_replace4(&tcph
->check
, skb
,
337 sack
->end_seq
, new_end_seq
, 0);
338 sack
->start_seq
= new_start_seq
;
339 sack
->end_seq
= new_end_seq
;
340 sackoff
+= sizeof(*sack
);
344 /* TCP SACK sequence number adjustment */
345 static inline unsigned int
346 nf_nat_sack_adjust(struct sk_buff
*skb
,
349 enum ip_conntrack_info ctinfo
)
351 unsigned int dir
, optoff
, optend
;
352 struct nf_conn_nat
*nat
= nfct_nat(ct
);
354 optoff
= ip_hdrlen(skb
) + sizeof(struct tcphdr
);
355 optend
= ip_hdrlen(skb
) + tcph
->doff
* 4;
357 if (!skb_make_writable(skb
, optend
))
360 dir
= CTINFO2DIR(ctinfo
);
362 while (optoff
< optend
) {
363 /* Usually: option, length. */
364 unsigned char *op
= skb
->data
+ optoff
;
373 /* no partial options */
374 if (optoff
+ 1 == optend
||
375 optoff
+ op
[1] > optend
||
378 if (op
[0] == TCPOPT_SACK
&&
379 op
[1] >= 2+TCPOLEN_SACK_PERBLOCK
&&
380 ((op
[1] - 2) % TCPOLEN_SACK_PERBLOCK
) == 0)
381 sack_adjust(skb
, tcph
, optoff
+2,
382 optoff
+op
[1], &nat
->seq
[!dir
]);
389 /* TCP sequence number adjustment. Returns 1 on success, 0 on failure */
391 nf_nat_seq_adjust(struct sk_buff
*skb
,
393 enum ip_conntrack_info ctinfo
)
397 __be32 newseq
, newack
;
399 struct nf_conn_nat
*nat
= nfct_nat(ct
);
400 struct nf_nat_seq
*this_way
, *other_way
;
402 dir
= CTINFO2DIR(ctinfo
);
404 this_way
= &nat
->seq
[dir
];
405 other_way
= &nat
->seq
[!dir
];
407 if (!skb_make_writable(skb
, ip_hdrlen(skb
) + sizeof(*tcph
)))
410 tcph
= (void *)skb
->data
+ ip_hdrlen(skb
);
411 if (after(ntohl(tcph
->seq
), this_way
->correction_pos
))
412 seqoff
= this_way
->offset_after
;
414 seqoff
= this_way
->offset_before
;
416 if (after(ntohl(tcph
->ack_seq
) - other_way
->offset_before
,
417 other_way
->correction_pos
))
418 ackoff
= other_way
->offset_after
;
420 ackoff
= other_way
->offset_before
;
422 newseq
= htonl(ntohl(tcph
->seq
) + seqoff
);
423 newack
= htonl(ntohl(tcph
->ack_seq
) - ackoff
);
425 inet_proto_csum_replace4(&tcph
->check
, skb
, tcph
->seq
, newseq
, 0);
426 inet_proto_csum_replace4(&tcph
->check
, skb
, tcph
->ack_seq
, newack
, 0);
428 pr_debug("Adjusting sequence number from %u->%u, ack from %u->%u\n",
429 ntohl(tcph
->seq
), ntohl(newseq
), ntohl(tcph
->ack_seq
),
433 tcph
->ack_seq
= newack
;
435 return nf_nat_sack_adjust(skb
, tcph
, ct
, ctinfo
);
438 /* Setup NAT on this expected conntrack so it follows master. */
439 /* If we fail to get a free NAT slot, we'll get dropped on confirm */
440 void nf_nat_follow_master(struct nf_conn
*ct
,
441 struct nf_conntrack_expect
*exp
)
443 struct nf_nat_range range
;
445 /* This must be a fresh one. */
446 BUG_ON(ct
->status
& IPS_NAT_DONE_MASK
);
448 /* Change src to where master sends to */
449 range
.flags
= IP_NAT_RANGE_MAP_IPS
;
450 range
.min_ip
= range
.max_ip
451 = ct
->master
->tuplehash
[!exp
->dir
].tuple
.dst
.u3
.ip
;
452 nf_nat_setup_info(ct
, &range
, IP_NAT_MANIP_SRC
);
454 /* For DST manip, map port here to where it's expected. */
455 range
.flags
= (IP_NAT_RANGE_MAP_IPS
| IP_NAT_RANGE_PROTO_SPECIFIED
);
456 range
.min
= range
.max
= exp
->saved_proto
;
457 range
.min_ip
= range
.max_ip
458 = ct
->master
->tuplehash
[!exp
->dir
].tuple
.src
.u3
.ip
;
459 nf_nat_setup_info(ct
, &range
, IP_NAT_MANIP_DST
);
461 EXPORT_SYMBOL(nf_nat_follow_master
);