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5b1158e9 JK |
1 | /* ip_nat_helper.c - generic support functions for NAT helpers |
2 | * | |
3 | * (C) 2000-2002 Harald Welte <laforge@netfilter.org> | |
4 | * (C) 2003-2006 Netfilter Core Team <coreteam@netfilter.org> | |
5 | * | |
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. | |
9 | */ | |
10 | #include <linux/module.h> | |
5a0e3ad6 | 11 | #include <linux/gfp.h> |
5b1158e9 JK |
12 | #include <linux/kmod.h> |
13 | #include <linux/types.h> | |
14 | #include <linux/timer.h> | |
15 | #include <linux/skbuff.h> | |
16 | #include <linux/tcp.h> | |
17 | #include <linux/udp.h> | |
18 | #include <net/checksum.h> | |
19 | #include <net/tcp.h> | |
1668e010 | 20 | #include <net/route.h> |
5b1158e9 JK |
21 | |
22 | #include <linux/netfilter_ipv4.h> | |
23 | #include <net/netfilter/nf_conntrack.h> | |
24 | #include <net/netfilter/nf_conntrack_helper.h> | |
13eae15a | 25 | #include <net/netfilter/nf_conntrack_ecache.h> |
5b1158e9 JK |
26 | #include <net/netfilter/nf_conntrack_expect.h> |
27 | #include <net/netfilter/nf_nat.h> | |
28 | #include <net/netfilter/nf_nat_protocol.h> | |
29 | #include <net/netfilter/nf_nat_core.h> | |
30 | #include <net/netfilter/nf_nat_helper.h> | |
31 | ||
0d53778e PM |
32 | #define DUMP_OFFSET(x) \ |
33 | pr_debug("offset_before=%d, offset_after=%d, correction_pos=%u\n", \ | |
34 | x->offset_before, x->offset_after, x->correction_pos); | |
5b1158e9 JK |
35 | |
36 | static DEFINE_SPINLOCK(nf_nat_seqofs_lock); | |
37 | ||
38 | /* Setup TCP sequence correction given this change at this sequence */ | |
39 | static inline void | |
40 | adjust_tcp_sequence(u32 seq, | |
41 | int sizediff, | |
42 | struct nf_conn *ct, | |
43 | enum ip_conntrack_info ctinfo) | |
44 | { | |
76ac8940 | 45 | enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo); |
5b1158e9 | 46 | struct nf_conn_nat *nat = nfct_nat(ct); |
76ac8940 | 47 | struct nf_nat_seq *this_way = &nat->seq[dir]; |
5b1158e9 | 48 | |
76ac8940 HE |
49 | pr_debug("adjust_tcp_sequence: seq = %u, sizediff = %d\n", |
50 | seq, sizediff); | |
5b1158e9 | 51 | |
76ac8940 | 52 | pr_debug("adjust_tcp_sequence: Seq_offset before: "); |
5b1158e9 JK |
53 | DUMP_OFFSET(this_way); |
54 | ||
55 | spin_lock_bh(&nf_nat_seqofs_lock); | |
56 | ||
57 | /* SYN adjust. If it's uninitialized, or this is after last | |
58 | * correction, record it: we don't handle more than one | |
59 | * adjustment in the window, but do deal with common case of a | |
60 | * retransmit */ | |
61 | if (this_way->offset_before == this_way->offset_after || | |
62 | before(this_way->correction_pos, seq)) { | |
76ac8940 HE |
63 | this_way->correction_pos = seq; |
64 | this_way->offset_before = this_way->offset_after; | |
65 | this_way->offset_after += sizediff; | |
5b1158e9 JK |
66 | } |
67 | spin_unlock_bh(&nf_nat_seqofs_lock); | |
68 | ||
76ac8940 | 69 | pr_debug("adjust_tcp_sequence: Seq_offset after: "); |
5b1158e9 JK |
70 | DUMP_OFFSET(this_way); |
71 | } | |
72 | ||
f9dd09c7 JK |
73 | /* Get the offset value, for conntrack */ |
74 | s16 nf_nat_get_offset(const struct nf_conn *ct, | |
75 | enum ip_conntrack_dir dir, | |
76 | u32 seq) | |
77 | { | |
78 | struct nf_conn_nat *nat = nfct_nat(ct); | |
79 | struct nf_nat_seq *this_way; | |
80 | s16 offset; | |
81 | ||
82 | if (!nat) | |
83 | return 0; | |
84 | ||
85 | this_way = &nat->seq[dir]; | |
86 | spin_lock_bh(&nf_nat_seqofs_lock); | |
87 | offset = after(seq, this_way->correction_pos) | |
88 | ? this_way->offset_after : this_way->offset_before; | |
89 | spin_unlock_bh(&nf_nat_seqofs_lock); | |
90 | ||
91 | return offset; | |
92 | } | |
93 | EXPORT_SYMBOL_GPL(nf_nat_get_offset); | |
94 | ||
5b1158e9 JK |
95 | /* Frobs data inside this packet, which is linear. */ |
96 | static void mangle_contents(struct sk_buff *skb, | |
97 | unsigned int dataoff, | |
98 | unsigned int match_offset, | |
99 | unsigned int match_len, | |
100 | const char *rep_buffer, | |
101 | unsigned int rep_len) | |
102 | { | |
103 | unsigned char *data; | |
104 | ||
105 | BUG_ON(skb_is_nonlinear(skb)); | |
eddc9ec5 | 106 | data = skb_network_header(skb) + dataoff; |
5b1158e9 JK |
107 | |
108 | /* move post-replacement */ | |
109 | memmove(data + match_offset + rep_len, | |
110 | data + match_offset + match_len, | |
27a884dc ACM |
111 | skb->tail - (skb->network_header + dataoff + |
112 | match_offset + match_len)); | |
5b1158e9 JK |
113 | |
114 | /* insert data from buffer */ | |
115 | memcpy(data + match_offset, rep_buffer, rep_len); | |
116 | ||
117 | /* update skb info */ | |
118 | if (rep_len > match_len) { | |
0d53778e PM |
119 | pr_debug("nf_nat_mangle_packet: Extending packet by " |
120 | "%u from %u bytes\n", rep_len - match_len, skb->len); | |
5b1158e9 JK |
121 | skb_put(skb, rep_len - match_len); |
122 | } else { | |
0d53778e PM |
123 | pr_debug("nf_nat_mangle_packet: Shrinking packet from " |
124 | "%u from %u bytes\n", match_len - rep_len, skb->len); | |
5b1158e9 JK |
125 | __skb_trim(skb, skb->len + rep_len - match_len); |
126 | } | |
127 | ||
128 | /* fix IP hdr checksum information */ | |
eddc9ec5 ACM |
129 | ip_hdr(skb)->tot_len = htons(skb->len); |
130 | ip_send_check(ip_hdr(skb)); | |
5b1158e9 JK |
131 | } |
132 | ||
133 | /* Unusual, but possible case. */ | |
3db05fea | 134 | static int enlarge_skb(struct sk_buff *skb, unsigned int extra) |
5b1158e9 | 135 | { |
3db05fea | 136 | if (skb->len + extra > 65535) |
5b1158e9 JK |
137 | return 0; |
138 | ||
3db05fea | 139 | if (pskb_expand_head(skb, 0, extra - skb_tailroom(skb), GFP_ATOMIC)) |
5b1158e9 JK |
140 | return 0; |
141 | ||
5b1158e9 JK |
142 | return 1; |
143 | } | |
144 | ||
010c0b9f PM |
145 | void nf_nat_set_seq_adjust(struct nf_conn *ct, enum ip_conntrack_info ctinfo, |
146 | __be32 seq, s16 off) | |
147 | { | |
148 | if (!off) | |
149 | return; | |
150 | set_bit(IPS_SEQ_ADJUST_BIT, &ct->status); | |
151 | adjust_tcp_sequence(ntohl(seq), off, ct, ctinfo); | |
152 | nf_conntrack_event_cache(IPCT_NATSEQADJ, ct); | |
153 | } | |
154 | EXPORT_SYMBOL_GPL(nf_nat_set_seq_adjust); | |
155 | ||
b71d1d42 | 156 | static void nf_nat_csum(struct sk_buff *skb, const struct iphdr *iph, void *data, |
0abee526 CG |
157 | int datalen, __sum16 *check, int oldlen) |
158 | { | |
159 | struct rtable *rt = skb_rtable(skb); | |
160 | ||
161 | if (skb->ip_summed != CHECKSUM_PARTIAL) { | |
162 | if (!(rt->rt_flags & RTCF_LOCAL) && | |
163 | skb->dev->features & NETIF_F_V4_CSUM) { | |
164 | skb->ip_summed = CHECKSUM_PARTIAL; | |
165 | skb->csum_start = skb_headroom(skb) + | |
166 | skb_network_offset(skb) + | |
167 | iph->ihl * 4; | |
168 | skb->csum_offset = (void *)check - data; | |
169 | *check = ~csum_tcpudp_magic(iph->saddr, iph->daddr, | |
170 | datalen, iph->protocol, 0); | |
171 | } else { | |
172 | *check = 0; | |
173 | *check = csum_tcpudp_magic(iph->saddr, iph->daddr, | |
174 | datalen, iph->protocol, | |
175 | csum_partial(data, datalen, | |
176 | 0)); | |
177 | if (iph->protocol == IPPROTO_UDP && !*check) | |
178 | *check = CSUM_MANGLED_0; | |
179 | } | |
180 | } else | |
181 | inet_proto_csum_replace2(check, skb, | |
182 | htons(oldlen), htons(datalen), 1); | |
183 | } | |
184 | ||
5b1158e9 JK |
185 | /* Generic function for mangling variable-length address changes inside |
186 | * NATed TCP connections (like the PORT XXX,XXX,XXX,XXX,XXX,XXX | |
187 | * command in FTP). | |
188 | * | |
189 | * Takes care about all the nasty sequence number changes, checksumming, | |
190 | * skb enlargement, ... | |
191 | * | |
192 | * */ | |
010c0b9f PM |
193 | int __nf_nat_mangle_tcp_packet(struct sk_buff *skb, |
194 | struct nf_conn *ct, | |
195 | enum ip_conntrack_info ctinfo, | |
196 | unsigned int match_offset, | |
197 | unsigned int match_len, | |
198 | const char *rep_buffer, | |
199 | unsigned int rep_len, bool adjust) | |
5b1158e9 JK |
200 | { |
201 | struct iphdr *iph; | |
202 | struct tcphdr *tcph; | |
203 | int oldlen, datalen; | |
204 | ||
3db05fea | 205 | if (!skb_make_writable(skb, skb->len)) |
5b1158e9 JK |
206 | return 0; |
207 | ||
208 | if (rep_len > match_len && | |
3db05fea HX |
209 | rep_len - match_len > skb_tailroom(skb) && |
210 | !enlarge_skb(skb, rep_len - match_len)) | |
5b1158e9 JK |
211 | return 0; |
212 | ||
3db05fea | 213 | SKB_LINEAR_ASSERT(skb); |
5b1158e9 | 214 | |
3db05fea | 215 | iph = ip_hdr(skb); |
5b1158e9 JK |
216 | tcph = (void *)iph + iph->ihl*4; |
217 | ||
3db05fea HX |
218 | oldlen = skb->len - iph->ihl*4; |
219 | mangle_contents(skb, iph->ihl*4 + tcph->doff*4, | |
5b1158e9 JK |
220 | match_offset, match_len, rep_buffer, rep_len); |
221 | ||
3db05fea | 222 | datalen = skb->len - iph->ihl*4; |
0abee526 | 223 | nf_nat_csum(skb, iph, tcph, datalen, &tcph->check, oldlen); |
5b1158e9 | 224 | |
010c0b9f PM |
225 | if (adjust && rep_len != match_len) |
226 | nf_nat_set_seq_adjust(ct, ctinfo, tcph->seq, | |
227 | (int)rep_len - (int)match_len); | |
228 | ||
5b1158e9 JK |
229 | return 1; |
230 | } | |
010c0b9f | 231 | EXPORT_SYMBOL(__nf_nat_mangle_tcp_packet); |
5b1158e9 JK |
232 | |
233 | /* Generic function for mangling variable-length address changes inside | |
234 | * NATed UDP connections (like the CONNECT DATA XXXXX MESG XXXXX INDEX XXXXX | |
235 | * command in the Amanda protocol) | |
236 | * | |
237 | * Takes care about all the nasty sequence number changes, checksumming, | |
238 | * skb enlargement, ... | |
239 | * | |
240 | * XXX - This function could be merged with nf_nat_mangle_tcp_packet which | |
241 | * should be fairly easy to do. | |
242 | */ | |
243 | int | |
3db05fea | 244 | nf_nat_mangle_udp_packet(struct sk_buff *skb, |
5b1158e9 JK |
245 | struct nf_conn *ct, |
246 | enum ip_conntrack_info ctinfo, | |
247 | unsigned int match_offset, | |
248 | unsigned int match_len, | |
249 | const char *rep_buffer, | |
250 | unsigned int rep_len) | |
251 | { | |
252 | struct iphdr *iph; | |
253 | struct udphdr *udph; | |
254 | int datalen, oldlen; | |
255 | ||
256 | /* UDP helpers might accidentally mangle the wrong packet */ | |
3db05fea HX |
257 | iph = ip_hdr(skb); |
258 | if (skb->len < iph->ihl*4 + sizeof(*udph) + | |
e905a9ed | 259 | match_offset + match_len) |
5b1158e9 JK |
260 | return 0; |
261 | ||
3db05fea | 262 | if (!skb_make_writable(skb, skb->len)) |
5b1158e9 JK |
263 | return 0; |
264 | ||
265 | if (rep_len > match_len && | |
3db05fea HX |
266 | rep_len - match_len > skb_tailroom(skb) && |
267 | !enlarge_skb(skb, rep_len - match_len)) | |
5b1158e9 JK |
268 | return 0; |
269 | ||
3db05fea | 270 | iph = ip_hdr(skb); |
5b1158e9 JK |
271 | udph = (void *)iph + iph->ihl*4; |
272 | ||
3db05fea HX |
273 | oldlen = skb->len - iph->ihl*4; |
274 | mangle_contents(skb, iph->ihl*4 + sizeof(*udph), | |
5b1158e9 JK |
275 | match_offset, match_len, rep_buffer, rep_len); |
276 | ||
277 | /* update the length of the UDP packet */ | |
3db05fea | 278 | datalen = skb->len - iph->ihl*4; |
5b1158e9 JK |
279 | udph->len = htons(datalen); |
280 | ||
281 | /* fix udp checksum if udp checksum was previously calculated */ | |
3db05fea | 282 | if (!udph->check && skb->ip_summed != CHECKSUM_PARTIAL) |
5b1158e9 JK |
283 | return 1; |
284 | ||
0abee526 | 285 | nf_nat_csum(skb, iph, udph, datalen, &udph->check, oldlen); |
5b1158e9 JK |
286 | |
287 | return 1; | |
288 | } | |
289 | EXPORT_SYMBOL(nf_nat_mangle_udp_packet); | |
290 | ||
291 | /* Adjust one found SACK option including checksum correction */ | |
292 | static void | |
293 | sack_adjust(struct sk_buff *skb, | |
294 | struct tcphdr *tcph, | |
295 | unsigned int sackoff, | |
296 | unsigned int sackend, | |
297 | struct nf_nat_seq *natseq) | |
298 | { | |
299 | while (sackoff < sackend) { | |
300 | struct tcp_sack_block_wire *sack; | |
301 | __be32 new_start_seq, new_end_seq; | |
302 | ||
303 | sack = (void *)skb->data + sackoff; | |
304 | if (after(ntohl(sack->start_seq) - natseq->offset_before, | |
305 | natseq->correction_pos)) | |
306 | new_start_seq = htonl(ntohl(sack->start_seq) | |
307 | - natseq->offset_after); | |
308 | else | |
309 | new_start_seq = htonl(ntohl(sack->start_seq) | |
310 | - natseq->offset_before); | |
311 | ||
312 | if (after(ntohl(sack->end_seq) - natseq->offset_before, | |
313 | natseq->correction_pos)) | |
314 | new_end_seq = htonl(ntohl(sack->end_seq) | |
315 | - natseq->offset_after); | |
316 | else | |
317 | new_end_seq = htonl(ntohl(sack->end_seq) | |
318 | - natseq->offset_before); | |
319 | ||
0d53778e PM |
320 | pr_debug("sack_adjust: start_seq: %d->%d, end_seq: %d->%d\n", |
321 | ntohl(sack->start_seq), new_start_seq, | |
322 | ntohl(sack->end_seq), new_end_seq); | |
5b1158e9 | 323 | |
be0ea7d5 PM |
324 | inet_proto_csum_replace4(&tcph->check, skb, |
325 | sack->start_seq, new_start_seq, 0); | |
326 | inet_proto_csum_replace4(&tcph->check, skb, | |
327 | sack->end_seq, new_end_seq, 0); | |
5b1158e9 JK |
328 | sack->start_seq = new_start_seq; |
329 | sack->end_seq = new_end_seq; | |
330 | sackoff += sizeof(*sack); | |
331 | } | |
332 | } | |
333 | ||
334 | /* TCP SACK sequence number adjustment */ | |
335 | static inline unsigned int | |
3db05fea | 336 | nf_nat_sack_adjust(struct sk_buff *skb, |
5b1158e9 JK |
337 | struct tcphdr *tcph, |
338 | struct nf_conn *ct, | |
339 | enum ip_conntrack_info ctinfo) | |
340 | { | |
341 | unsigned int dir, optoff, optend; | |
342 | struct nf_conn_nat *nat = nfct_nat(ct); | |
343 | ||
3db05fea HX |
344 | optoff = ip_hdrlen(skb) + sizeof(struct tcphdr); |
345 | optend = ip_hdrlen(skb) + tcph->doff * 4; | |
5b1158e9 | 346 | |
3db05fea | 347 | if (!skb_make_writable(skb, optend)) |
5b1158e9 JK |
348 | return 0; |
349 | ||
350 | dir = CTINFO2DIR(ctinfo); | |
351 | ||
352 | while (optoff < optend) { | |
353 | /* Usually: option, length. */ | |
3db05fea | 354 | unsigned char *op = skb->data + optoff; |
5b1158e9 JK |
355 | |
356 | switch (op[0]) { | |
357 | case TCPOPT_EOL: | |
358 | return 1; | |
359 | case TCPOPT_NOP: | |
360 | optoff++; | |
361 | continue; | |
362 | default: | |
363 | /* no partial options */ | |
364 | if (optoff + 1 == optend || | |
365 | optoff + op[1] > optend || | |
366 | op[1] < 2) | |
367 | return 0; | |
368 | if (op[0] == TCPOPT_SACK && | |
369 | op[1] >= 2+TCPOLEN_SACK_PERBLOCK && | |
370 | ((op[1] - 2) % TCPOLEN_SACK_PERBLOCK) == 0) | |
3db05fea | 371 | sack_adjust(skb, tcph, optoff+2, |
b6b84d4a | 372 | optoff+op[1], &nat->seq[!dir]); |
5b1158e9 JK |
373 | optoff += op[1]; |
374 | } | |
375 | } | |
376 | return 1; | |
377 | } | |
378 | ||
379 | /* TCP sequence number adjustment. Returns 1 on success, 0 on failure */ | |
380 | int | |
3db05fea | 381 | nf_nat_seq_adjust(struct sk_buff *skb, |
5b1158e9 JK |
382 | struct nf_conn *ct, |
383 | enum ip_conntrack_info ctinfo) | |
384 | { | |
385 | struct tcphdr *tcph; | |
386 | int dir; | |
387 | __be32 newseq, newack; | |
a3a9f79e | 388 | s16 seqoff, ackoff; |
5b1158e9 JK |
389 | struct nf_conn_nat *nat = nfct_nat(ct); |
390 | struct nf_nat_seq *this_way, *other_way; | |
391 | ||
392 | dir = CTINFO2DIR(ctinfo); | |
393 | ||
b6b84d4a YK |
394 | this_way = &nat->seq[dir]; |
395 | other_way = &nat->seq[!dir]; | |
5b1158e9 | 396 | |
3db05fea | 397 | if (!skb_make_writable(skb, ip_hdrlen(skb) + sizeof(*tcph))) |
5b1158e9 JK |
398 | return 0; |
399 | ||
3db05fea | 400 | tcph = (void *)skb->data + ip_hdrlen(skb); |
5b1158e9 | 401 | if (after(ntohl(tcph->seq), this_way->correction_pos)) |
a3a9f79e | 402 | seqoff = this_way->offset_after; |
5b1158e9 | 403 | else |
a3a9f79e | 404 | seqoff = this_way->offset_before; |
5b1158e9 JK |
405 | |
406 | if (after(ntohl(tcph->ack_seq) - other_way->offset_before, | |
407 | other_way->correction_pos)) | |
a3a9f79e | 408 | ackoff = other_way->offset_after; |
5b1158e9 | 409 | else |
a3a9f79e PM |
410 | ackoff = other_way->offset_before; |
411 | ||
412 | newseq = htonl(ntohl(tcph->seq) + seqoff); | |
413 | newack = htonl(ntohl(tcph->ack_seq) - ackoff); | |
5b1158e9 | 414 | |
be0ea7d5 PM |
415 | inet_proto_csum_replace4(&tcph->check, skb, tcph->seq, newseq, 0); |
416 | inet_proto_csum_replace4(&tcph->check, skb, tcph->ack_seq, newack, 0); | |
5b1158e9 | 417 | |
0d53778e PM |
418 | pr_debug("Adjusting sequence number from %u->%u, ack from %u->%u\n", |
419 | ntohl(tcph->seq), ntohl(newseq), ntohl(tcph->ack_seq), | |
420 | ntohl(newack)); | |
5b1158e9 JK |
421 | |
422 | tcph->seq = newseq; | |
423 | tcph->ack_seq = newack; | |
424 | ||
f9dd09c7 | 425 | return nf_nat_sack_adjust(skb, tcph, ct, ctinfo); |
5b1158e9 | 426 | } |
5b1158e9 JK |
427 | |
428 | /* Setup NAT on this expected conntrack so it follows master. */ | |
429 | /* If we fail to get a free NAT slot, we'll get dropped on confirm */ | |
430 | void nf_nat_follow_master(struct nf_conn *ct, | |
431 | struct nf_conntrack_expect *exp) | |
432 | { | |
433 | struct nf_nat_range range; | |
434 | ||
435 | /* This must be a fresh one. */ | |
436 | BUG_ON(ct->status & IPS_NAT_DONE_MASK); | |
437 | ||
438 | /* Change src to where master sends to */ | |
439 | range.flags = IP_NAT_RANGE_MAP_IPS; | |
440 | range.min_ip = range.max_ip | |
441 | = ct->master->tuplehash[!exp->dir].tuple.dst.u3.ip; | |
cc01dcbd | 442 | nf_nat_setup_info(ct, &range, IP_NAT_MANIP_SRC); |
5b1158e9 JK |
443 | |
444 | /* For DST manip, map port here to where it's expected. */ | |
445 | range.flags = (IP_NAT_RANGE_MAP_IPS | IP_NAT_RANGE_PROTO_SPECIFIED); | |
446 | range.min = range.max = exp->saved_proto; | |
447 | range.min_ip = range.max_ip | |
448 | = ct->master->tuplehash[!exp->dir].tuple.src.u3.ip; | |
cc01dcbd | 449 | nf_nat_setup_info(ct, &range, IP_NAT_MANIP_DST); |
5b1158e9 JK |
450 | } |
451 | EXPORT_SYMBOL(nf_nat_follow_master); |