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/gfp.h>
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>
20 #include <net/route.h>
22 #include <linux/netfilter_ipv4.h>
23 #include <net/netfilter/nf_conntrack.h>
24 #include <net/netfilter/nf_conntrack_helper.h>
25 #include <net/netfilter/nf_conntrack_ecache.h>
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>
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);
36 static DEFINE_SPINLOCK(nf_nat_seqofs_lock);
38 /* Setup TCP sequence correction given this change at this sequence */
40 adjust_tcp_sequence(u32 seq,
43 enum ip_conntrack_info ctinfo)
45 enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
46 struct nf_conn_nat *nat = nfct_nat(ct);
47 struct nf_nat_seq *this_way = &nat->seq[dir];
49 pr_debug("adjust_tcp_sequence: seq = %u, sizediff = %d\n",
52 pr_debug("adjust_tcp_sequence: Seq_offset before: ");
53 DUMP_OFFSET(this_way);
55 spin_lock_bh(&nf_nat_seqofs_lock);
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
61 if (this_way->offset_before == this_way->offset_after ||
62 before(this_way->correction_pos, seq)) {
63 this_way->correction_pos = seq;
64 this_way->offset_before = this_way->offset_after;
65 this_way->offset_after += sizediff;
67 spin_unlock_bh(&nf_nat_seqofs_lock);
69 pr_debug("adjust_tcp_sequence: Seq_offset after: ");
70 DUMP_OFFSET(this_way);
73 /* Get the offset value, for conntrack */
74 s16 nf_nat_get_offset(const struct nf_conn *ct,
75 enum ip_conntrack_dir dir,
78 struct nf_conn_nat *nat = nfct_nat(ct);
79 struct nf_nat_seq *this_way;
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);
93 EXPORT_SYMBOL_GPL(nf_nat_get_offset);
95 /* Frobs data inside this packet, which is linear. */
96 static void mangle_contents(struct sk_buff *skb,
98 unsigned int match_offset,
99 unsigned int match_len,
100 const char *rep_buffer,
101 unsigned int rep_len)
105 BUG_ON(skb_is_nonlinear(skb));
106 data = skb_network_header(skb) + dataoff;
108 /* move post-replacement */
109 memmove(data + match_offset + rep_len,
110 data + match_offset + match_len,
111 skb->tail - (skb->network_header + dataoff +
112 match_offset + match_len));
114 /* insert data from buffer */
115 memcpy(data + match_offset, rep_buffer, rep_len);
117 /* update skb info */
118 if (rep_len > match_len) {
119 pr_debug("nf_nat_mangle_packet: Extending packet by "
120 "%u from %u bytes\n", rep_len - match_len, skb->len);
121 skb_put(skb, rep_len - match_len);
123 pr_debug("nf_nat_mangle_packet: Shrinking packet from "
124 "%u from %u bytes\n", match_len - rep_len, skb->len);
125 __skb_trim(skb, skb->len + rep_len - match_len);
128 /* fix IP hdr checksum information */
129 ip_hdr(skb)->tot_len = htons(skb->len);
130 ip_send_check(ip_hdr(skb));
133 /* Unusual, but possible case. */
134 static int enlarge_skb(struct sk_buff *skb, unsigned int extra)
136 if (skb->len + extra > 65535)
139 if (pskb_expand_head(skb, 0, extra - skb_tailroom(skb), GFP_ATOMIC))
145 void nf_nat_set_seq_adjust(struct nf_conn *ct, enum ip_conntrack_info ctinfo,
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);
154 EXPORT_SYMBOL_GPL(nf_nat_set_seq_adjust);
156 /* Generic function for mangling variable-length address changes inside
157 * NATed TCP connections (like the PORT XXX,XXX,XXX,XXX,XXX,XXX
160 * Takes care about all the nasty sequence number changes, checksumming,
161 * skb enlargement, ...
164 int __nf_nat_mangle_tcp_packet(struct sk_buff *skb,
166 enum ip_conntrack_info ctinfo,
167 unsigned int match_offset,
168 unsigned int match_len,
169 const char *rep_buffer,
170 unsigned int rep_len, bool adjust)
172 struct rtable *rt = skb_rtable(skb);
177 if (!skb_make_writable(skb, skb->len))
180 if (rep_len > match_len &&
181 rep_len - match_len > skb_tailroom(skb) &&
182 !enlarge_skb(skb, rep_len - match_len))
185 SKB_LINEAR_ASSERT(skb);
188 tcph = (void *)iph + iph->ihl*4;
190 oldlen = skb->len - iph->ihl*4;
191 mangle_contents(skb, iph->ihl*4 + tcph->doff*4,
192 match_offset, match_len, rep_buffer, rep_len);
194 datalen = skb->len - iph->ihl*4;
195 if (skb->ip_summed != CHECKSUM_PARTIAL) {
196 if (!(rt->rt_flags & RTCF_LOCAL) &&
197 skb->dev->features & NETIF_F_V4_CSUM) {
198 skb->ip_summed = CHECKSUM_PARTIAL;
199 skb->csum_start = skb_headroom(skb) +
200 skb_network_offset(skb) +
202 skb->csum_offset = offsetof(struct tcphdr, check);
203 tcph->check = ~tcp_v4_check(datalen,
204 iph->saddr, iph->daddr, 0);
207 tcph->check = tcp_v4_check(datalen,
208 iph->saddr, iph->daddr,
213 inet_proto_csum_replace2(&tcph->check, skb,
214 htons(oldlen), htons(datalen), 1);
216 if (adjust && rep_len != match_len)
217 nf_nat_set_seq_adjust(ct, ctinfo, tcph->seq,
218 (int)rep_len - (int)match_len);
222 EXPORT_SYMBOL(__nf_nat_mangle_tcp_packet);
224 /* Generic function for mangling variable-length address changes inside
225 * NATed UDP connections (like the CONNECT DATA XXXXX MESG XXXXX INDEX XXXXX
226 * command in the Amanda protocol)
228 * Takes care about all the nasty sequence number changes, checksumming,
229 * skb enlargement, ...
231 * XXX - This function could be merged with nf_nat_mangle_tcp_packet which
232 * should be fairly easy to do.
235 nf_nat_mangle_udp_packet(struct sk_buff *skb,
237 enum ip_conntrack_info ctinfo,
238 unsigned int match_offset,
239 unsigned int match_len,
240 const char *rep_buffer,
241 unsigned int rep_len)
243 struct rtable *rt = skb_rtable(skb);
248 /* UDP helpers might accidentally mangle the wrong packet */
250 if (skb->len < iph->ihl*4 + sizeof(*udph) +
251 match_offset + match_len)
254 if (!skb_make_writable(skb, skb->len))
257 if (rep_len > match_len &&
258 rep_len - match_len > skb_tailroom(skb) &&
259 !enlarge_skb(skb, rep_len - match_len))
263 udph = (void *)iph + iph->ihl*4;
265 oldlen = skb->len - iph->ihl*4;
266 mangle_contents(skb, iph->ihl*4 + sizeof(*udph),
267 match_offset, match_len, rep_buffer, rep_len);
269 /* update the length of the UDP packet */
270 datalen = skb->len - iph->ihl*4;
271 udph->len = htons(datalen);
273 /* fix udp checksum if udp checksum was previously calculated */
274 if (!udph->check && skb->ip_summed != CHECKSUM_PARTIAL)
277 if (skb->ip_summed != CHECKSUM_PARTIAL) {
278 if (!(rt->rt_flags & RTCF_LOCAL) &&
279 skb->dev->features & NETIF_F_V4_CSUM) {
280 skb->ip_summed = CHECKSUM_PARTIAL;
281 skb->csum_start = skb_headroom(skb) +
282 skb_network_offset(skb) +
284 skb->csum_offset = offsetof(struct udphdr, check);
285 udph->check = ~csum_tcpudp_magic(iph->saddr, iph->daddr,
286 datalen, IPPROTO_UDP,
290 udph->check = csum_tcpudp_magic(iph->saddr, iph->daddr,
291 datalen, IPPROTO_UDP,
295 udph->check = CSUM_MANGLED_0;
298 inet_proto_csum_replace2(&udph->check, skb,
299 htons(oldlen), htons(datalen), 1);
303 EXPORT_SYMBOL(nf_nat_mangle_udp_packet);
305 /* Adjust one found SACK option including checksum correction */
307 sack_adjust(struct sk_buff *skb,
309 unsigned int sackoff,
310 unsigned int sackend,
311 struct nf_nat_seq *natseq)
313 while (sackoff < sackend) {
314 struct tcp_sack_block_wire *sack;
315 __be32 new_start_seq, new_end_seq;
317 sack = (void *)skb->data + sackoff;
318 if (after(ntohl(sack->start_seq) - natseq->offset_before,
319 natseq->correction_pos))
320 new_start_seq = htonl(ntohl(sack->start_seq)
321 - natseq->offset_after);
323 new_start_seq = htonl(ntohl(sack->start_seq)
324 - natseq->offset_before);
326 if (after(ntohl(sack->end_seq) - natseq->offset_before,
327 natseq->correction_pos))
328 new_end_seq = htonl(ntohl(sack->end_seq)
329 - natseq->offset_after);
331 new_end_seq = htonl(ntohl(sack->end_seq)
332 - natseq->offset_before);
334 pr_debug("sack_adjust: start_seq: %d->%d, end_seq: %d->%d\n",
335 ntohl(sack->start_seq), new_start_seq,
336 ntohl(sack->end_seq), new_end_seq);
338 inet_proto_csum_replace4(&tcph->check, skb,
339 sack->start_seq, new_start_seq, 0);
340 inet_proto_csum_replace4(&tcph->check, skb,
341 sack->end_seq, new_end_seq, 0);
342 sack->start_seq = new_start_seq;
343 sack->end_seq = new_end_seq;
344 sackoff += sizeof(*sack);
348 /* TCP SACK sequence number adjustment */
349 static inline unsigned int
350 nf_nat_sack_adjust(struct sk_buff *skb,
353 enum ip_conntrack_info ctinfo)
355 unsigned int dir, optoff, optend;
356 struct nf_conn_nat *nat = nfct_nat(ct);
358 optoff = ip_hdrlen(skb) + sizeof(struct tcphdr);
359 optend = ip_hdrlen(skb) + tcph->doff * 4;
361 if (!skb_make_writable(skb, optend))
364 dir = CTINFO2DIR(ctinfo);
366 while (optoff < optend) {
367 /* Usually: option, length. */
368 unsigned char *op = skb->data + optoff;
377 /* no partial options */
378 if (optoff + 1 == optend ||
379 optoff + op[1] > optend ||
382 if (op[0] == TCPOPT_SACK &&
383 op[1] >= 2+TCPOLEN_SACK_PERBLOCK &&
384 ((op[1] - 2) % TCPOLEN_SACK_PERBLOCK) == 0)
385 sack_adjust(skb, tcph, optoff+2,
386 optoff+op[1], &nat->seq[!dir]);
393 /* TCP sequence number adjustment. Returns 1 on success, 0 on failure */
395 nf_nat_seq_adjust(struct sk_buff *skb,
397 enum ip_conntrack_info ctinfo)
401 __be32 newseq, newack;
403 struct nf_conn_nat *nat = nfct_nat(ct);
404 struct nf_nat_seq *this_way, *other_way;
406 dir = CTINFO2DIR(ctinfo);
408 this_way = &nat->seq[dir];
409 other_way = &nat->seq[!dir];
411 if (!skb_make_writable(skb, ip_hdrlen(skb) + sizeof(*tcph)))
414 tcph = (void *)skb->data + ip_hdrlen(skb);
415 if (after(ntohl(tcph->seq), this_way->correction_pos))
416 seqoff = this_way->offset_after;
418 seqoff = this_way->offset_before;
420 if (after(ntohl(tcph->ack_seq) - other_way->offset_before,
421 other_way->correction_pos))
422 ackoff = other_way->offset_after;
424 ackoff = other_way->offset_before;
426 newseq = htonl(ntohl(tcph->seq) + seqoff);
427 newack = htonl(ntohl(tcph->ack_seq) - ackoff);
429 inet_proto_csum_replace4(&tcph->check, skb, tcph->seq, newseq, 0);
430 inet_proto_csum_replace4(&tcph->check, skb, tcph->ack_seq, newack, 0);
432 pr_debug("Adjusting sequence number from %u->%u, ack from %u->%u\n",
433 ntohl(tcph->seq), ntohl(newseq), ntohl(tcph->ack_seq),
437 tcph->ack_seq = newack;
439 return nf_nat_sack_adjust(skb, tcph, ct, ctinfo);
442 /* Setup NAT on this expected conntrack so it follows master. */
443 /* If we fail to get a free NAT slot, we'll get dropped on confirm */
444 void nf_nat_follow_master(struct nf_conn *ct,
445 struct nf_conntrack_expect *exp)
447 struct nf_nat_range range;
449 /* This must be a fresh one. */
450 BUG_ON(ct->status & IPS_NAT_DONE_MASK);
452 /* Change src to where master sends to */
453 range.flags = IP_NAT_RANGE_MAP_IPS;
454 range.min_ip = range.max_ip
455 = ct->master->tuplehash[!exp->dir].tuple.dst.u3.ip;
456 nf_nat_setup_info(ct, &range, IP_NAT_MANIP_SRC);
458 /* For DST manip, map port here to where it's expected. */
459 range.flags = (IP_NAT_RANGE_MAP_IPS | IP_NAT_RANGE_PROTO_SPECIFIED);
460 range.min = range.max = exp->saved_proto;
461 range.min_ip = range.max_ip
462 = ct->master->tuplehash[!exp->dir].tuple.src.u3.ip;
463 nf_nat_setup_info(ct, &range, IP_NAT_MANIP_DST);
465 EXPORT_SYMBOL(nf_nat_follow_master);