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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> | |
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> | |
18 | #include <net/tcp.h> | |
1668e010 | 19 | #include <net/route.h> |
5b1158e9 JK |
20 | |
21 | #include <linux/netfilter_ipv4.h> | |
22 | #include <net/netfilter/nf_conntrack.h> | |
23 | #include <net/netfilter/nf_conntrack_helper.h> | |
13eae15a | 24 | #include <net/netfilter/nf_conntrack_ecache.h> |
5b1158e9 JK |
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> | |
30 | ||
0d53778e PM |
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); | |
5b1158e9 JK |
34 | |
35 | static DEFINE_SPINLOCK(nf_nat_seqofs_lock); | |
36 | ||
37 | /* Setup TCP sequence correction given this change at this sequence */ | |
38 | static inline void | |
39 | adjust_tcp_sequence(u32 seq, | |
40 | int sizediff, | |
41 | struct nf_conn *ct, | |
42 | enum ip_conntrack_info ctinfo) | |
43 | { | |
76ac8940 | 44 | enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo); |
5b1158e9 | 45 | struct nf_conn_nat *nat = nfct_nat(ct); |
76ac8940 | 46 | struct nf_nat_seq *this_way = &nat->seq[dir]; |
5b1158e9 | 47 | |
76ac8940 HE |
48 | pr_debug("adjust_tcp_sequence: seq = %u, sizediff = %d\n", |
49 | seq, sizediff); | |
5b1158e9 | 50 | |
76ac8940 | 51 | pr_debug("adjust_tcp_sequence: Seq_offset before: "); |
5b1158e9 JK |
52 | DUMP_OFFSET(this_way); |
53 | ||
54 | spin_lock_bh(&nf_nat_seqofs_lock); | |
55 | ||
56 | /* SYN adjust. If it's uninitialized, or this is after last | |
57 | * correction, record it: we don't handle more than one | |
58 | * adjustment in the window, but do deal with common case of a | |
59 | * retransmit */ | |
60 | if (this_way->offset_before == this_way->offset_after || | |
61 | before(this_way->correction_pos, seq)) { | |
76ac8940 HE |
62 | this_way->correction_pos = seq; |
63 | this_way->offset_before = this_way->offset_after; | |
64 | this_way->offset_after += sizediff; | |
5b1158e9 JK |
65 | } |
66 | spin_unlock_bh(&nf_nat_seqofs_lock); | |
67 | ||
76ac8940 | 68 | pr_debug("adjust_tcp_sequence: Seq_offset after: "); |
5b1158e9 JK |
69 | DUMP_OFFSET(this_way); |
70 | } | |
71 | ||
f9dd09c7 JK |
72 | /* Get the offset value, for conntrack */ |
73 | s16 nf_nat_get_offset(const struct nf_conn *ct, | |
74 | enum ip_conntrack_dir dir, | |
75 | u32 seq) | |
76 | { | |
77 | struct nf_conn_nat *nat = nfct_nat(ct); | |
78 | struct nf_nat_seq *this_way; | |
79 | s16 offset; | |
80 | ||
81 | if (!nat) | |
82 | return 0; | |
83 | ||
84 | this_way = &nat->seq[dir]; | |
85 | spin_lock_bh(&nf_nat_seqofs_lock); | |
86 | offset = after(seq, this_way->correction_pos) | |
87 | ? this_way->offset_after : this_way->offset_before; | |
88 | spin_unlock_bh(&nf_nat_seqofs_lock); | |
89 | ||
90 | return offset; | |
91 | } | |
92 | EXPORT_SYMBOL_GPL(nf_nat_get_offset); | |
93 | ||
5b1158e9 JK |
94 | /* Frobs data inside this packet, which is linear. */ |
95 | static void mangle_contents(struct sk_buff *skb, | |
96 | unsigned int dataoff, | |
97 | unsigned int match_offset, | |
98 | unsigned int match_len, | |
99 | const char *rep_buffer, | |
100 | unsigned int rep_len) | |
101 | { | |
102 | unsigned char *data; | |
103 | ||
104 | BUG_ON(skb_is_nonlinear(skb)); | |
eddc9ec5 | 105 | data = skb_network_header(skb) + dataoff; |
5b1158e9 JK |
106 | |
107 | /* move post-replacement */ | |
108 | memmove(data + match_offset + rep_len, | |
109 | data + match_offset + match_len, | |
27a884dc ACM |
110 | skb->tail - (skb->network_header + dataoff + |
111 | match_offset + match_len)); | |
5b1158e9 JK |
112 | |
113 | /* insert data from buffer */ | |
114 | memcpy(data + match_offset, rep_buffer, rep_len); | |
115 | ||
116 | /* update skb info */ | |
117 | if (rep_len > match_len) { | |
0d53778e PM |
118 | pr_debug("nf_nat_mangle_packet: Extending packet by " |
119 | "%u from %u bytes\n", rep_len - match_len, skb->len); | |
5b1158e9 JK |
120 | skb_put(skb, rep_len - match_len); |
121 | } else { | |
0d53778e PM |
122 | pr_debug("nf_nat_mangle_packet: Shrinking packet from " |
123 | "%u from %u bytes\n", match_len - rep_len, skb->len); | |
5b1158e9 JK |
124 | __skb_trim(skb, skb->len + rep_len - match_len); |
125 | } | |
126 | ||
127 | /* fix IP hdr checksum information */ | |
eddc9ec5 ACM |
128 | ip_hdr(skb)->tot_len = htons(skb->len); |
129 | ip_send_check(ip_hdr(skb)); | |
5b1158e9 JK |
130 | } |
131 | ||
132 | /* Unusual, but possible case. */ | |
3db05fea | 133 | static int enlarge_skb(struct sk_buff *skb, unsigned int extra) |
5b1158e9 | 134 | { |
3db05fea | 135 | if (skb->len + extra > 65535) |
5b1158e9 JK |
136 | return 0; |
137 | ||
3db05fea | 138 | if (pskb_expand_head(skb, 0, extra - skb_tailroom(skb), GFP_ATOMIC)) |
5b1158e9 JK |
139 | return 0; |
140 | ||
5b1158e9 JK |
141 | return 1; |
142 | } | |
143 | ||
144 | /* Generic function for mangling variable-length address changes inside | |
145 | * NATed TCP connections (like the PORT XXX,XXX,XXX,XXX,XXX,XXX | |
146 | * command in FTP). | |
147 | * | |
148 | * Takes care about all the nasty sequence number changes, checksumming, | |
149 | * skb enlargement, ... | |
150 | * | |
151 | * */ | |
152 | int | |
3db05fea | 153 | nf_nat_mangle_tcp_packet(struct sk_buff *skb, |
5b1158e9 JK |
154 | struct nf_conn *ct, |
155 | enum ip_conntrack_info ctinfo, | |
156 | unsigned int match_offset, | |
157 | unsigned int match_len, | |
158 | const char *rep_buffer, | |
159 | unsigned int rep_len) | |
160 | { | |
511c3f92 | 161 | struct rtable *rt = skb_rtable(skb); |
5b1158e9 JK |
162 | struct iphdr *iph; |
163 | struct tcphdr *tcph; | |
164 | int oldlen, datalen; | |
165 | ||
3db05fea | 166 | if (!skb_make_writable(skb, skb->len)) |
5b1158e9 JK |
167 | return 0; |
168 | ||
169 | if (rep_len > match_len && | |
3db05fea HX |
170 | rep_len - match_len > skb_tailroom(skb) && |
171 | !enlarge_skb(skb, rep_len - match_len)) | |
5b1158e9 JK |
172 | return 0; |
173 | ||
3db05fea | 174 | SKB_LINEAR_ASSERT(skb); |
5b1158e9 | 175 | |
3db05fea | 176 | iph = ip_hdr(skb); |
5b1158e9 JK |
177 | tcph = (void *)iph + iph->ihl*4; |
178 | ||
3db05fea HX |
179 | oldlen = skb->len - iph->ihl*4; |
180 | mangle_contents(skb, iph->ihl*4 + tcph->doff*4, | |
5b1158e9 JK |
181 | match_offset, match_len, rep_buffer, rep_len); |
182 | ||
3db05fea HX |
183 | datalen = skb->len - iph->ihl*4; |
184 | if (skb->ip_summed != CHECKSUM_PARTIAL) { | |
fe6092ea | 185 | if (!(rt->rt_flags & RTCF_LOCAL) && |
3db05fea HX |
186 | skb->dev->features & NETIF_F_V4_CSUM) { |
187 | skb->ip_summed = CHECKSUM_PARTIAL; | |
188 | skb->csum_start = skb_headroom(skb) + | |
189 | skb_network_offset(skb) + | |
190 | iph->ihl * 4; | |
191 | skb->csum_offset = offsetof(struct tcphdr, check); | |
fe6092ea PM |
192 | tcph->check = ~tcp_v4_check(datalen, |
193 | iph->saddr, iph->daddr, 0); | |
194 | } else { | |
195 | tcph->check = 0; | |
196 | tcph->check = tcp_v4_check(datalen, | |
197 | iph->saddr, iph->daddr, | |
a47362a2 | 198 | csum_partial(tcph, |
fe6092ea PM |
199 | datalen, 0)); |
200 | } | |
5b1158e9 | 201 | } else |
be0ea7d5 PM |
202 | inet_proto_csum_replace2(&tcph->check, skb, |
203 | htons(oldlen), htons(datalen), 1); | |
5b1158e9 JK |
204 | |
205 | if (rep_len != match_len) { | |
206 | set_bit(IPS_SEQ_ADJUST_BIT, &ct->status); | |
207 | adjust_tcp_sequence(ntohl(tcph->seq), | |
208 | (int)rep_len - (int)match_len, | |
209 | ct, ctinfo); | |
a71996fc | 210 | nf_conntrack_event_cache(IPCT_NATSEQADJ, ct); |
5b1158e9 JK |
211 | } |
212 | return 1; | |
213 | } | |
214 | EXPORT_SYMBOL(nf_nat_mangle_tcp_packet); | |
215 | ||
216 | /* Generic function for mangling variable-length address changes inside | |
217 | * NATed UDP connections (like the CONNECT DATA XXXXX MESG XXXXX INDEX XXXXX | |
218 | * command in the Amanda protocol) | |
219 | * | |
220 | * Takes care about all the nasty sequence number changes, checksumming, | |
221 | * skb enlargement, ... | |
222 | * | |
223 | * XXX - This function could be merged with nf_nat_mangle_tcp_packet which | |
224 | * should be fairly easy to do. | |
225 | */ | |
226 | int | |
3db05fea | 227 | nf_nat_mangle_udp_packet(struct sk_buff *skb, |
5b1158e9 JK |
228 | struct nf_conn *ct, |
229 | enum ip_conntrack_info ctinfo, | |
230 | unsigned int match_offset, | |
231 | unsigned int match_len, | |
232 | const char *rep_buffer, | |
233 | unsigned int rep_len) | |
234 | { | |
511c3f92 | 235 | struct rtable *rt = skb_rtable(skb); |
5b1158e9 JK |
236 | struct iphdr *iph; |
237 | struct udphdr *udph; | |
238 | int datalen, oldlen; | |
239 | ||
240 | /* UDP helpers might accidentally mangle the wrong packet */ | |
3db05fea HX |
241 | iph = ip_hdr(skb); |
242 | if (skb->len < iph->ihl*4 + sizeof(*udph) + | |
e905a9ed | 243 | match_offset + match_len) |
5b1158e9 JK |
244 | return 0; |
245 | ||
3db05fea | 246 | if (!skb_make_writable(skb, skb->len)) |
5b1158e9 JK |
247 | return 0; |
248 | ||
249 | if (rep_len > match_len && | |
3db05fea HX |
250 | rep_len - match_len > skb_tailroom(skb) && |
251 | !enlarge_skb(skb, rep_len - match_len)) | |
5b1158e9 JK |
252 | return 0; |
253 | ||
3db05fea | 254 | iph = ip_hdr(skb); |
5b1158e9 JK |
255 | udph = (void *)iph + iph->ihl*4; |
256 | ||
3db05fea HX |
257 | oldlen = skb->len - iph->ihl*4; |
258 | mangle_contents(skb, iph->ihl*4 + sizeof(*udph), | |
5b1158e9 JK |
259 | match_offset, match_len, rep_buffer, rep_len); |
260 | ||
261 | /* update the length of the UDP packet */ | |
3db05fea | 262 | datalen = skb->len - iph->ihl*4; |
5b1158e9 JK |
263 | udph->len = htons(datalen); |
264 | ||
265 | /* fix udp checksum if udp checksum was previously calculated */ | |
3db05fea | 266 | if (!udph->check && skb->ip_summed != CHECKSUM_PARTIAL) |
5b1158e9 JK |
267 | return 1; |
268 | ||
3db05fea | 269 | if (skb->ip_summed != CHECKSUM_PARTIAL) { |
fe6092ea | 270 | if (!(rt->rt_flags & RTCF_LOCAL) && |
3db05fea HX |
271 | skb->dev->features & NETIF_F_V4_CSUM) { |
272 | skb->ip_summed = CHECKSUM_PARTIAL; | |
273 | skb->csum_start = skb_headroom(skb) + | |
274 | skb_network_offset(skb) + | |
275 | iph->ihl * 4; | |
276 | skb->csum_offset = offsetof(struct udphdr, check); | |
fe6092ea PM |
277 | udph->check = ~csum_tcpudp_magic(iph->saddr, iph->daddr, |
278 | datalen, IPPROTO_UDP, | |
279 | 0); | |
280 | } else { | |
281 | udph->check = 0; | |
282 | udph->check = csum_tcpudp_magic(iph->saddr, iph->daddr, | |
283 | datalen, IPPROTO_UDP, | |
a47362a2 | 284 | csum_partial(udph, |
fe6092ea PM |
285 | datalen, 0)); |
286 | if (!udph->check) | |
287 | udph->check = CSUM_MANGLED_0; | |
288 | } | |
5b1158e9 | 289 | } else |
be0ea7d5 PM |
290 | inet_proto_csum_replace2(&udph->check, skb, |
291 | htons(oldlen), htons(datalen), 1); | |
5b1158e9 JK |
292 | |
293 | return 1; | |
294 | } | |
295 | EXPORT_SYMBOL(nf_nat_mangle_udp_packet); | |
296 | ||
297 | /* Adjust one found SACK option including checksum correction */ | |
298 | static void | |
299 | sack_adjust(struct sk_buff *skb, | |
300 | struct tcphdr *tcph, | |
301 | unsigned int sackoff, | |
302 | unsigned int sackend, | |
303 | struct nf_nat_seq *natseq) | |
304 | { | |
305 | while (sackoff < sackend) { | |
306 | struct tcp_sack_block_wire *sack; | |
307 | __be32 new_start_seq, new_end_seq; | |
308 | ||
309 | sack = (void *)skb->data + sackoff; | |
310 | if (after(ntohl(sack->start_seq) - natseq->offset_before, | |
311 | natseq->correction_pos)) | |
312 | new_start_seq = htonl(ntohl(sack->start_seq) | |
313 | - natseq->offset_after); | |
314 | else | |
315 | new_start_seq = htonl(ntohl(sack->start_seq) | |
316 | - natseq->offset_before); | |
317 | ||
318 | if (after(ntohl(sack->end_seq) - natseq->offset_before, | |
319 | natseq->correction_pos)) | |
320 | new_end_seq = htonl(ntohl(sack->end_seq) | |
321 | - natseq->offset_after); | |
322 | else | |
323 | new_end_seq = htonl(ntohl(sack->end_seq) | |
324 | - natseq->offset_before); | |
325 | ||
0d53778e PM |
326 | pr_debug("sack_adjust: start_seq: %d->%d, end_seq: %d->%d\n", |
327 | ntohl(sack->start_seq), new_start_seq, | |
328 | ntohl(sack->end_seq), new_end_seq); | |
5b1158e9 | 329 | |
be0ea7d5 PM |
330 | inet_proto_csum_replace4(&tcph->check, skb, |
331 | sack->start_seq, new_start_seq, 0); | |
332 | inet_proto_csum_replace4(&tcph->check, skb, | |
333 | sack->end_seq, new_end_seq, 0); | |
5b1158e9 JK |
334 | sack->start_seq = new_start_seq; |
335 | sack->end_seq = new_end_seq; | |
336 | sackoff += sizeof(*sack); | |
337 | } | |
338 | } | |
339 | ||
340 | /* TCP SACK sequence number adjustment */ | |
341 | static inline unsigned int | |
3db05fea | 342 | nf_nat_sack_adjust(struct sk_buff *skb, |
5b1158e9 JK |
343 | struct tcphdr *tcph, |
344 | struct nf_conn *ct, | |
345 | enum ip_conntrack_info ctinfo) | |
346 | { | |
347 | unsigned int dir, optoff, optend; | |
348 | struct nf_conn_nat *nat = nfct_nat(ct); | |
349 | ||
3db05fea HX |
350 | optoff = ip_hdrlen(skb) + sizeof(struct tcphdr); |
351 | optend = ip_hdrlen(skb) + tcph->doff * 4; | |
5b1158e9 | 352 | |
3db05fea | 353 | if (!skb_make_writable(skb, optend)) |
5b1158e9 JK |
354 | return 0; |
355 | ||
356 | dir = CTINFO2DIR(ctinfo); | |
357 | ||
358 | while (optoff < optend) { | |
359 | /* Usually: option, length. */ | |
3db05fea | 360 | unsigned char *op = skb->data + optoff; |
5b1158e9 JK |
361 | |
362 | switch (op[0]) { | |
363 | case TCPOPT_EOL: | |
364 | return 1; | |
365 | case TCPOPT_NOP: | |
366 | optoff++; | |
367 | continue; | |
368 | default: | |
369 | /* no partial options */ | |
370 | if (optoff + 1 == optend || | |
371 | optoff + op[1] > optend || | |
372 | op[1] < 2) | |
373 | return 0; | |
374 | if (op[0] == TCPOPT_SACK && | |
375 | op[1] >= 2+TCPOLEN_SACK_PERBLOCK && | |
376 | ((op[1] - 2) % TCPOLEN_SACK_PERBLOCK) == 0) | |
3db05fea | 377 | sack_adjust(skb, tcph, optoff+2, |
b6b84d4a | 378 | optoff+op[1], &nat->seq[!dir]); |
5b1158e9 JK |
379 | optoff += op[1]; |
380 | } | |
381 | } | |
382 | return 1; | |
383 | } | |
384 | ||
385 | /* TCP sequence number adjustment. Returns 1 on success, 0 on failure */ | |
386 | int | |
3db05fea | 387 | nf_nat_seq_adjust(struct sk_buff *skb, |
5b1158e9 JK |
388 | struct nf_conn *ct, |
389 | enum ip_conntrack_info ctinfo) | |
390 | { | |
391 | struct tcphdr *tcph; | |
392 | int dir; | |
393 | __be32 newseq, newack; | |
a3a9f79e | 394 | s16 seqoff, ackoff; |
5b1158e9 JK |
395 | struct nf_conn_nat *nat = nfct_nat(ct); |
396 | struct nf_nat_seq *this_way, *other_way; | |
397 | ||
398 | dir = CTINFO2DIR(ctinfo); | |
399 | ||
b6b84d4a YK |
400 | this_way = &nat->seq[dir]; |
401 | other_way = &nat->seq[!dir]; | |
5b1158e9 | 402 | |
3db05fea | 403 | if (!skb_make_writable(skb, ip_hdrlen(skb) + sizeof(*tcph))) |
5b1158e9 JK |
404 | return 0; |
405 | ||
3db05fea | 406 | tcph = (void *)skb->data + ip_hdrlen(skb); |
5b1158e9 | 407 | if (after(ntohl(tcph->seq), this_way->correction_pos)) |
a3a9f79e | 408 | seqoff = this_way->offset_after; |
5b1158e9 | 409 | else |
a3a9f79e | 410 | seqoff = this_way->offset_before; |
5b1158e9 JK |
411 | |
412 | if (after(ntohl(tcph->ack_seq) - other_way->offset_before, | |
413 | other_way->correction_pos)) | |
a3a9f79e | 414 | ackoff = other_way->offset_after; |
5b1158e9 | 415 | else |
a3a9f79e PM |
416 | ackoff = other_way->offset_before; |
417 | ||
418 | newseq = htonl(ntohl(tcph->seq) + seqoff); | |
419 | newack = htonl(ntohl(tcph->ack_seq) - ackoff); | |
5b1158e9 | 420 | |
be0ea7d5 PM |
421 | inet_proto_csum_replace4(&tcph->check, skb, tcph->seq, newseq, 0); |
422 | inet_proto_csum_replace4(&tcph->check, skb, tcph->ack_seq, newack, 0); | |
5b1158e9 | 423 | |
0d53778e PM |
424 | pr_debug("Adjusting sequence number from %u->%u, ack from %u->%u\n", |
425 | ntohl(tcph->seq), ntohl(newseq), ntohl(tcph->ack_seq), | |
426 | ntohl(newack)); | |
5b1158e9 JK |
427 | |
428 | tcph->seq = newseq; | |
429 | tcph->ack_seq = newack; | |
430 | ||
f9dd09c7 | 431 | return nf_nat_sack_adjust(skb, tcph, ct, ctinfo); |
5b1158e9 | 432 | } |
5b1158e9 JK |
433 | |
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) | |
438 | { | |
439 | struct nf_nat_range range; | |
440 | ||
441 | /* This must be a fresh one. */ | |
442 | BUG_ON(ct->status & IPS_NAT_DONE_MASK); | |
443 | ||
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; | |
cc01dcbd | 448 | nf_nat_setup_info(ct, &range, IP_NAT_MANIP_SRC); |
5b1158e9 JK |
449 | |
450 | /* For DST manip, map port here to where it's expected. */ | |
451 | range.flags = (IP_NAT_RANGE_MAP_IPS | IP_NAT_RANGE_PROTO_SPECIFIED); | |
452 | range.min = range.max = exp->saved_proto; | |
453 | range.min_ip = range.max_ip | |
454 | = ct->master->tuplehash[!exp->dir].tuple.src.u3.ip; | |
cc01dcbd | 455 | nf_nat_setup_info(ct, &range, IP_NAT_MANIP_DST); |
5b1158e9 JK |
456 | } |
457 | EXPORT_SYMBOL(nf_nat_follow_master); |