[net-next-2.6.git] / net / ipv4 / netfilter / nf_nat_helper.c

/* ip_nat_helper.c - generic support functions for NAT helpers
 *
 * (C) 2000-2002 Harald Welte <laforge@netfilter.org>
 * (C) 2003-2006 Netfilter Core Team <coreteam@netfilter.org>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */
#include <linux/module.h>
#include <linux/kmod.h>
#include <linux/types.h>
#include <linux/timer.h>
#include <linux/skbuff.h>
#include <linux/tcp.h>
#include <linux/udp.h>
#include <net/checksum.h>
#include <net/tcp.h>

#include <linux/netfilter_ipv4.h>
#include <net/netfilter/nf_conntrack.h>
#include <net/netfilter/nf_conntrack_helper.h>
#include <net/netfilter/nf_conntrack_expect.h>
#include <net/netfilter/nf_nat.h>
#include <net/netfilter/nf_nat_protocol.h>
#include <net/netfilter/nf_nat_core.h>
#include <net/netfilter/nf_nat_helper.h>

#if 0
#define DEBUGP printk
#define DUMP_OFFSET(x)	printk("offset_before=%d, offset_after=%d, correction_pos=%u\n", x->offset_before, x->offset_after, x->correction_pos);
#else
#define DEBUGP(format, args...)
#define DUMP_OFFSET(x)
#endif

static DEFINE_SPINLOCK(nf_nat_seqofs_lock);

/* Setup TCP sequence correction given this change at this sequence */
static inline void
adjust_tcp_sequence(u32 seq,
		    int sizediff,
		    struct nf_conn *ct,
		    enum ip_conntrack_info ctinfo)
{
	int dir;
	struct nf_nat_seq *this_way, *other_way;
	struct nf_conn_nat *nat = nfct_nat(ct);

	DEBUGP("nf_nat_resize_packet: old_size = %u, new_size = %u\n",
		(*skb)->len, new_size);

	dir = CTINFO2DIR(ctinfo);

	this_way = &nat->info.seq[dir];
	other_way = &nat->info.seq[!dir];

	DEBUGP("nf_nat_resize_packet: Seq_offset before: ");
	DUMP_OFFSET(this_way);

	spin_lock_bh(&nf_nat_seqofs_lock);

	/* SYN adjust. If it's uninitialized, or this is after last
	 * correction, record it: we don't handle more than one
	 * adjustment in the window, but do deal with common case of a
	 * retransmit */
	if (this_way->offset_before == this_way->offset_after ||
	    before(this_way->correction_pos, seq)) {
		   this_way->correction_pos = seq;
		   this_way->offset_before = this_way->offset_after;
		   this_way->offset_after += sizediff;
	}
	spin_unlock_bh(&nf_nat_seqofs_lock);

	DEBUGP("nf_nat_resize_packet: Seq_offset after: ");
	DUMP_OFFSET(this_way);
}

/* Frobs data inside this packet, which is linear. */
static void mangle_contents(struct sk_buff *skb,
			    unsigned int dataoff,
			    unsigned int match_offset,
			    unsigned int match_len,
			    const char *rep_buffer,
			    unsigned int rep_len)
{
	unsigned char *data;

	BUG_ON(skb_is_nonlinear(skb));
	data = (unsigned char *)skb->nh.iph + dataoff;

	/* move post-replacement */
	memmove(data + match_offset + rep_len,
		data + match_offset + match_len,
		skb->tail - (data + match_offset + match_len));

	/* insert data from buffer */
	memcpy(data + match_offset, rep_buffer, rep_len);

	/* update skb info */
	if (rep_len > match_len) {
		DEBUGP("nf_nat_mangle_packet: Extending packet by "
		       "%u from %u bytes\n", rep_len - match_len,
		       skb->len);
		skb_put(skb, rep_len - match_len);
	} else {
		DEBUGP("nf_nat_mangle_packet: Shrinking packet from "
		       "%u from %u bytes\n", match_len - rep_len,
		       skb->len);
		__skb_trim(skb, skb->len + rep_len - match_len);
	}

	/* fix IP hdr checksum information */
	skb->nh.iph->tot_len = htons(skb->len);
	ip_send_check(skb->nh.iph);
}

/* Unusual, but possible case. */
static int enlarge_skb(struct sk_buff **pskb, unsigned int extra)
{
	struct sk_buff *nskb;

	if ((*pskb)->len + extra > 65535)
		return 0;

	nskb = skb_copy_expand(*pskb, skb_headroom(*pskb), extra, GFP_ATOMIC);
	if (!nskb)
		return 0;

	/* Transfer socket to new skb. */
	if ((*pskb)->sk)
		skb_set_owner_w(nskb, (*pskb)->sk);
	kfree_skb(*pskb);
	*pskb = nskb;
	return 1;
}

/* Generic function for mangling variable-length address changes inside
 * NATed TCP connections (like the PORT XXX,XXX,XXX,XXX,XXX,XXX
 * command in FTP).
 *
 * Takes care about all the nasty sequence number changes, checksumming,
 * skb enlargement, ...
 *
 * */
int
nf_nat_mangle_tcp_packet(struct sk_buff **pskb,
			 struct nf_conn *ct,
			 enum ip_conntrack_info ctinfo,
			 unsigned int match_offset,
			 unsigned int match_len,
			 const char *rep_buffer,
			 unsigned int rep_len)
{
	struct iphdr *iph;
	struct tcphdr *tcph;
	int oldlen, datalen;

	if (!skb_make_writable(pskb, (*pskb)->len))
		return 0;

	if (rep_len > match_len &&
	    rep_len - match_len > skb_tailroom(*pskb) &&
	    !enlarge_skb(pskb, rep_len - match_len))
		return 0;

	SKB_LINEAR_ASSERT(*pskb);

	iph = (*pskb)->nh.iph;
	tcph = (void *)iph + iph->ihl*4;

	oldlen = (*pskb)->len - iph->ihl*4;
	mangle_contents(*pskb, iph->ihl*4 + tcph->doff*4,
			match_offset, match_len, rep_buffer, rep_len);

	datalen = (*pskb)->len - iph->ihl*4;
	if ((*pskb)->ip_summed != CHECKSUM_PARTIAL) {
		tcph->check = 0;
		tcph->check = tcp_v4_check(tcph, datalen,
					   iph->saddr, iph->daddr,
					   csum_partial((char *)tcph,
					   		datalen, 0));
	} else
		nf_proto_csum_replace2(&tcph->check, *pskb,
				       htons(oldlen), htons(datalen), 1);

	if (rep_len != match_len) {
		set_bit(IPS_SEQ_ADJUST_BIT, &ct->status);
		adjust_tcp_sequence(ntohl(tcph->seq),
				    (int)rep_len - (int)match_len,
				    ct, ctinfo);
		/* Tell TCP window tracking about seq change */
		nf_conntrack_tcp_update(*pskb, (*pskb)->nh.iph->ihl*4,
					ct, CTINFO2DIR(ctinfo));
	}
	return 1;
}
EXPORT_SYMBOL(nf_nat_mangle_tcp_packet);

/* Generic function for mangling variable-length address changes inside
 * NATed UDP connections (like the CONNECT DATA XXXXX MESG XXXXX INDEX XXXXX
 * command in the Amanda protocol)
 *
 * Takes care about all the nasty sequence number changes, checksumming,
 * skb enlargement, ...
 *
 * XXX - This function could be merged with nf_nat_mangle_tcp_packet which
 *       should be fairly easy to do.
 */
int
nf_nat_mangle_udp_packet(struct sk_buff **pskb,
			 struct nf_conn *ct,
			 enum ip_conntrack_info ctinfo,
			 unsigned int match_offset,
			 unsigned int match_len,
			 const char *rep_buffer,
			 unsigned int rep_len)
{
	struct iphdr *iph;
	struct udphdr *udph;
	int datalen, oldlen;

	/* UDP helpers might accidentally mangle the wrong packet */
	iph = (*pskb)->nh.iph;
	if ((*pskb)->len < iph->ihl*4 + sizeof(*udph) +
	                       match_offset + match_len)
		return 0;

	if (!skb_make_writable(pskb, (*pskb)->len))
		return 0;

	if (rep_len > match_len &&
	    rep_len - match_len > skb_tailroom(*pskb) &&
	    !enlarge_skb(pskb, rep_len - match_len))
		return 0;

	iph = (*pskb)->nh.iph;
	udph = (void *)iph + iph->ihl*4;

	oldlen = (*pskb)->len - iph->ihl*4;
	mangle_contents(*pskb, iph->ihl*4 + sizeof(*udph),
			match_offset, match_len, rep_buffer, rep_len);

	/* update the length of the UDP packet */
	datalen = (*pskb)->len - iph->ihl*4;
	udph->len = htons(datalen);

	/* fix udp checksum if udp checksum was previously calculated */
	if (!udph->check && (*pskb)->ip_summed != CHECKSUM_PARTIAL)
		return 1;

	if ((*pskb)->ip_summed != CHECKSUM_PARTIAL) {
		udph->check = 0;
		udph->check = csum_tcpudp_magic(iph->saddr, iph->daddr,
		                                datalen, IPPROTO_UDP,
		                                csum_partial((char *)udph,
		                                             datalen, 0));
		if (!udph->check)
			udph->check = CSUM_MANGLED_0;
	} else
		nf_proto_csum_replace2(&udph->check, *pskb,
				       htons(oldlen), htons(datalen), 1);

	return 1;
}
EXPORT_SYMBOL(nf_nat_mangle_udp_packet);

/* Adjust one found SACK option including checksum correction */
static void
sack_adjust(struct sk_buff *skb,
	    struct tcphdr *tcph,
	    unsigned int sackoff,
	    unsigned int sackend,
	    struct nf_nat_seq *natseq)
{
	while (sackoff < sackend) {
		struct tcp_sack_block_wire *sack;
		__be32 new_start_seq, new_end_seq;

		sack = (void *)skb->data + sackoff;
		if (after(ntohl(sack->start_seq) - natseq->offset_before,
			  natseq->correction_pos))
			new_start_seq = htonl(ntohl(sack->start_seq)
					- natseq->offset_after);
		else
			new_start_seq = htonl(ntohl(sack->start_seq)
					- natseq->offset_before);

		if (after(ntohl(sack->end_seq) - natseq->offset_before,
			  natseq->correction_pos))
			new_end_seq = htonl(ntohl(sack->end_seq)
				      - natseq->offset_after);
		else
			new_end_seq = htonl(ntohl(sack->end_seq)
				      - natseq->offset_before);

		DEBUGP("sack_adjust: start_seq: %d->%d, end_seq: %d->%d\n",
			ntohl(sack->start_seq), new_start_seq,
			ntohl(sack->end_seq), new_end_seq);

		nf_proto_csum_replace4(&tcph->check, skb,
				       sack->start_seq, new_start_seq, 0);
		nf_proto_csum_replace4(&tcph->check, skb,
				       sack->end_seq, new_end_seq, 0);
		sack->start_seq = new_start_seq;
		sack->end_seq = new_end_seq;
		sackoff += sizeof(*sack);
	}
}

/* TCP SACK sequence number adjustment */
static inline unsigned int
nf_nat_sack_adjust(struct sk_buff **pskb,
		   struct tcphdr *tcph,
		   struct nf_conn *ct,
		   enum ip_conntrack_info ctinfo)
{
	unsigned int dir, optoff, optend;
	struct nf_conn_nat *nat = nfct_nat(ct);

	optoff = (*pskb)->nh.iph->ihl*4 + sizeof(struct tcphdr);
	optend = (*pskb)->nh.iph->ihl*4 + tcph->doff*4;

	if (!skb_make_writable(pskb, optend))
		return 0;

	dir = CTINFO2DIR(ctinfo);

	while (optoff < optend) {
		/* Usually: option, length. */
		unsigned char *op = (*pskb)->data + optoff;

		switch (op[0]) {
		case TCPOPT_EOL:
			return 1;
		case TCPOPT_NOP:
			optoff++;
			continue;
		default:
			/* no partial options */
			if (optoff + 1 == optend ||
			    optoff + op[1] > optend ||
			    op[1] < 2)
				return 0;
			if (op[0] == TCPOPT_SACK &&
			    op[1] >= 2+TCPOLEN_SACK_PERBLOCK &&
			    ((op[1] - 2) % TCPOLEN_SACK_PERBLOCK) == 0)
				sack_adjust(*pskb, tcph, optoff+2,
					    optoff+op[1],
					    &nat->info.seq[!dir]);
			optoff += op[1];
		}
	}
	return 1;
}

/* TCP sequence number adjustment.  Returns 1 on success, 0 on failure */
int
nf_nat_seq_adjust(struct sk_buff **pskb,
		  struct nf_conn *ct,
		  enum ip_conntrack_info ctinfo)
{
	struct tcphdr *tcph;
	int dir;
	__be32 newseq, newack;
	struct nf_conn_nat *nat = nfct_nat(ct);
	struct nf_nat_seq *this_way, *other_way;

	dir = CTINFO2DIR(ctinfo);

	this_way = &nat->info.seq[dir];
	other_way = &nat->info.seq[!dir];

	if (!skb_make_writable(pskb, (*pskb)->nh.iph->ihl*4+sizeof(*tcph)))
		return 0;

	tcph = (void *)(*pskb)->data + (*pskb)->nh.iph->ihl*4;
	if (after(ntohl(tcph->seq), this_way->correction_pos))
		newseq = htonl(ntohl(tcph->seq) + this_way->offset_after);
	else
		newseq = htonl(ntohl(tcph->seq) + this_way->offset_before);

	if (after(ntohl(tcph->ack_seq) - other_way->offset_before,
		  other_way->correction_pos))
		newack = htonl(ntohl(tcph->ack_seq) - other_way->offset_after);
	else
		newack = htonl(ntohl(tcph->ack_seq) - other_way->offset_before);

	nf_proto_csum_replace4(&tcph->check, *pskb, tcph->seq, newseq, 0);
	nf_proto_csum_replace4(&tcph->check, *pskb, tcph->ack_seq, newack, 0);

	DEBUGP("Adjusting sequence number from %u->%u, ack from %u->%u\n",
		ntohl(tcph->seq), ntohl(newseq), ntohl(tcph->ack_seq),
		ntohl(newack));

	tcph->seq = newseq;
	tcph->ack_seq = newack;

	if (!nf_nat_sack_adjust(pskb, tcph, ct, ctinfo))
		return 0;

	nf_conntrack_tcp_update(*pskb, (*pskb)->nh.iph->ihl*4, ct, dir);

	return 1;
}
EXPORT_SYMBOL(nf_nat_seq_adjust);

/* Setup NAT on this expected conntrack so it follows master. */
/* If we fail to get a free NAT slot, we'll get dropped on confirm */
void nf_nat_follow_master(struct nf_conn *ct,
			  struct nf_conntrack_expect *exp)
{
	struct nf_nat_range range;

	/* This must be a fresh one. */
	BUG_ON(ct->status & IPS_NAT_DONE_MASK);

	/* Change src to where master sends to */
	range.flags = IP_NAT_RANGE_MAP_IPS;
	range.min_ip = range.max_ip
		= ct->master->tuplehash[!exp->dir].tuple.dst.u3.ip;
	/* hook doesn't matter, but it has to do source manip */
	nf_nat_setup_info(ct, &range, NF_IP_POST_ROUTING);

	/* For DST manip, map port here to where it's expected. */
	range.flags = (IP_NAT_RANGE_MAP_IPS | IP_NAT_RANGE_PROTO_SPECIFIED);
	range.min = range.max = exp->saved_proto;
	range.min_ip = range.max_ip
		= ct->master->tuplehash[!exp->dir].tuple.src.u3.ip;
	/* hook doesn't matter, but it has to do destination manip */
	nf_nat_setup_info(ct, &range, NF_IP_PRE_ROUTING);
}
EXPORT_SYMBOL(nf_nat_follow_master);
Commit	Line	Data
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>
	19
	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>
	28
	29	#if 0
	30	#define DEBUGP printk
	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);
	32	#else
	33	#define DEBUGP(format, args...)
	34	#define DUMP_OFFSET(x)
	35	#endif
	36
	37	static DEFINE_SPINLOCK(nf_nat_seqofs_lock);
	38
	39	/* Setup TCP sequence correction given this change at this sequence */
	40	static inline void
	41	adjust_tcp_sequence(u32 seq,
	42	int sizediff,
	43	struct nf_conn *ct,
	44	enum ip_conntrack_info ctinfo)
	45	{
	46	int dir;
	47	struct nf_nat_seq this_way, other_way;
	48	struct nf_conn_nat *nat = nfct_nat(ct);
	49
	50	DEBUGP("nf_nat_resize_packet: old_size = %u, new_size = %u\n",
	51	(*skb)->len, new_size);
	52
	53	dir = CTINFO2DIR(ctinfo);
	54
	55	this_way = &nat->info.seq[dir];
	56	other_way = &nat->info.seq[!dir];
	57
	58	DEBUGP("nf_nat_resize_packet: Seq_offset before: ");
	59	DUMP_OFFSET(this_way);
	60
	61	spin_lock_bh(&nf_nat_seqofs_lock);
	62
	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
66	* retransmit */
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;
72	}
73	spin_unlock_bh(&nf_nat_seqofs_lock);
74
75	DEBUGP("nf_nat_resize_packet: Seq_offset after: ");
76	DUMP_OFFSET(this_way);
77	}
78
79	/* Frobs data inside this packet, which is linear. */
80	static void mangle_contents(struct sk_buff *skb,
81	unsigned int dataoff,
82	unsigned int match_offset,
83	unsigned int match_len,
84	const char *rep_buffer,
85	unsigned int rep_len)
86	{
87	unsigned char *data;
88
89	BUG_ON(skb_is_nonlinear(skb));
90	data = (unsigned char *)skb->nh.iph + dataoff;
91
92	/* move post-replacement */
93	memmove(data + match_offset + rep_len,
94	data + match_offset + match_len,
95	skb->tail - (data + match_offset + match_len));
96
97	/* insert data from buffer */
98	memcpy(data + match_offset, rep_buffer, rep_len);
99
100	/* update skb info */
101	if (rep_len > match_len) {
102	DEBUGP("nf_nat_mangle_packet: Extending packet by "
103	"%u from %u bytes\n", rep_len - match_len,
104	skb->len);
105	skb_put(skb, rep_len - match_len);
106	} else {
107	DEBUGP("nf_nat_mangle_packet: Shrinking packet from "
108	"%u from %u bytes\n", match_len - rep_len,
109	skb->len);
110	__skb_trim(skb, skb->len + rep_len - match_len);
111	}
112
113	/* fix IP hdr checksum information */
114	skb->nh.iph->tot_len = htons(skb->len);
115	ip_send_check(skb->nh.iph);
116	}
117
118	/* Unusual, but possible case. */
119	static int enlarge_skb(struct sk_buff **pskb, unsigned int extra)
120	{
121	struct sk_buff *nskb;
122
123	if ((*pskb)->len + extra > 65535)
124	return 0;
125
126	nskb = skb_copy_expand(pskb, skb_headroom(pskb), extra, GFP_ATOMIC);
127	if (!nskb)
128	return 0;
129
130	/* Transfer socket to new skb. */
131	if ((*pskb)->sk)
132	skb_set_owner_w(nskb, (*pskb)->sk);
133	kfree_skb(*pskb);
134	*pskb = nskb;
135	return 1;
136	}
137
138	/* Generic function for mangling variable-length address changes inside
139	* NATed TCP connections (like the PORT XXX,XXX,XXX,XXX,XXX,XXX
140	* command in FTP).
141	*
142	* Takes care about all the nasty sequence number changes, checksumming,
143	* skb enlargement, ...
144	*
145	* */
146	int
147	nf_nat_mangle_tcp_packet(struct sk_buff **pskb,
148	struct nf_conn *ct,
149	enum ip_conntrack_info ctinfo,
150	unsigned int match_offset,
151	unsigned int match_len,
152	const char *rep_buffer,
153	unsigned int rep_len)
154	{
155	struct iphdr *iph;
156	struct tcphdr *tcph;
157	int oldlen, datalen;
158
159	if (!skb_make_writable(pskb, (*pskb)->len))
160	return 0;
161
162	if (rep_len > match_len &&
163	rep_len - match_len > skb_tailroom(*pskb) &&
164	!enlarge_skb(pskb, rep_len - match_len))
165	return 0;
166
167	SKB_LINEAR_ASSERT(*pskb);
168
169	iph = (*pskb)->nh.iph;
170	tcph = (void )iph + iph->ihl4;
171
172	oldlen = (pskb)->len - iph->ihl4;
173	mangle_contents(pskb, iph->ihl4 + tcph->doff*4,
174	match_offset, match_len, rep_buffer, rep_len);
175
176	datalen = (pskb)->len - iph->ihl4;
177	if ((*pskb)->ip_summed != CHECKSUM_PARTIAL) {
178	tcph->check = 0;
179	tcph->check = tcp_v4_check(tcph, datalen,
180	iph->saddr, iph->daddr,
181	csum_partial((char *)tcph,
182	datalen, 0));
183	} else
184	nf_proto_csum_replace2(&tcph->check, *pskb,
185	htons(oldlen), htons(datalen), 1);
186
187	if (rep_len != match_len) {
188	set_bit(IPS_SEQ_ADJUST_BIT, &ct->status);
189	adjust_tcp_sequence(ntohl(tcph->seq),
190	(int)rep_len - (int)match_len,
191	ct, ctinfo);
192	/* Tell TCP window tracking about seq change */
193	nf_conntrack_tcp_update(pskb, (pskb)->nh.iph->ihl*4,
194	ct, CTINFO2DIR(ctinfo));
195	}
196	return 1;
197	}
198	EXPORT_SYMBOL(nf_nat_mangle_tcp_packet);
199
200	/* Generic function for mangling variable-length address changes inside
201	* NATed UDP connections (like the CONNECT DATA XXXXX MESG XXXXX INDEX XXXXX
202	* command in the Amanda protocol)
203	*
204	* Takes care about all the nasty sequence number changes, checksumming,
205	* skb enlargement, ...
206	*
207	* XXX - This function could be merged with nf_nat_mangle_tcp_packet which
208	* should be fairly easy to do.
209	*/
210	int
211	nf_nat_mangle_udp_packet(struct sk_buff **pskb,
212	struct nf_conn *ct,
213	enum ip_conntrack_info ctinfo,
214	unsigned int match_offset,
215	unsigned int match_len,
216	const char *rep_buffer,
217	unsigned int rep_len)
218	{
219	struct iphdr *iph;
220	struct udphdr *udph;
221	int datalen, oldlen;
222
223	/* UDP helpers might accidentally mangle the wrong packet */
224	iph = (*pskb)->nh.iph;
225	if ((pskb)->len < iph->ihl4 + sizeof(*udph) +
226	match_offset + match_len)
227	return 0;
228
229	if (!skb_make_writable(pskb, (*pskb)->len))
230	return 0;
231
232	if (rep_len > match_len &&
233	rep_len - match_len > skb_tailroom(*pskb) &&
234	!enlarge_skb(pskb, rep_len - match_len))
235	return 0;
236
237	iph = (*pskb)->nh.iph;
238	udph = (void )iph + iph->ihl4;
239
240	oldlen = (pskb)->len - iph->ihl4;
241	mangle_contents(pskb, iph->ihl4 + sizeof(*udph),
242	match_offset, match_len, rep_buffer, rep_len);
243
244	/* update the length of the UDP packet */
245	datalen = (pskb)->len - iph->ihl4;
246	udph->len = htons(datalen);
247
248	/* fix udp checksum if udp checksum was previously calculated */
249	if (!udph->check && (*pskb)->ip_summed != CHECKSUM_PARTIAL)
250	return 1;
251
252	if ((*pskb)->ip_summed != CHECKSUM_PARTIAL) {
253	udph->check = 0;
254	udph->check = csum_tcpudp_magic(iph->saddr, iph->daddr,
255	datalen, IPPROTO_UDP,
256	csum_partial((char *)udph,
257	datalen, 0));
258	if (!udph->check)
259	udph->check = CSUM_MANGLED_0;
260	} else
261	nf_proto_csum_replace2(&udph->check, *pskb,
262	htons(oldlen), htons(datalen), 1);
263
264	return 1;
265	}
266	EXPORT_SYMBOL(nf_nat_mangle_udp_packet);
267
268	/* Adjust one found SACK option including checksum correction */
269	static void
270	sack_adjust(struct sk_buff *skb,
271	struct tcphdr *tcph,
272	unsigned int sackoff,
273	unsigned int sackend,
274	struct nf_nat_seq *natseq)
275	{
276	while (sackoff < sackend) {
277	struct tcp_sack_block_wire *sack;
278	__be32 new_start_seq, new_end_seq;
279
280	sack = (void *)skb->data + sackoff;
281	if (after(ntohl(sack->start_seq) - natseq->offset_before,
282	natseq->correction_pos))
283	new_start_seq = htonl(ntohl(sack->start_seq)
284	- natseq->offset_after);
285	else
286	new_start_seq = htonl(ntohl(sack->start_seq)
287	- natseq->offset_before);
288
289	if (after(ntohl(sack->end_seq) - natseq->offset_before,
290	natseq->correction_pos))
291	new_end_seq = htonl(ntohl(sack->end_seq)
292	- natseq->offset_after);
293	else
294	new_end_seq = htonl(ntohl(sack->end_seq)
295	- natseq->offset_before);
296
297	DEBUGP("sack_adjust: start_seq: %d->%d, end_seq: %d->%d\n",
298	ntohl(sack->start_seq), new_start_seq,
299	ntohl(sack->end_seq), new_end_seq);
300
301	nf_proto_csum_replace4(&tcph->check, skb,
302	sack->start_seq, new_start_seq, 0);
303	nf_proto_csum_replace4(&tcph->check, skb,
304	sack->end_seq, new_end_seq, 0);
305	sack->start_seq = new_start_seq;
306	sack->end_seq = new_end_seq;
307	sackoff += sizeof(*sack);
308	}
309	}
310
311	/* TCP SACK sequence number adjustment */
312	static inline unsigned int
313	nf_nat_sack_adjust(struct sk_buff **pskb,
314	struct tcphdr *tcph,
315	struct nf_conn *ct,
316	enum ip_conntrack_info ctinfo)
317	{
318	unsigned int dir, optoff, optend;
319	struct nf_conn_nat *nat = nfct_nat(ct);
320
321	optoff = (pskb)->nh.iph->ihl4 + sizeof(struct tcphdr);
322	optend = (pskb)->nh.iph->ihl4 + tcph->doff*4;
323
324	if (!skb_make_writable(pskb, optend))
325	return 0;
326
327	dir = CTINFO2DIR(ctinfo);
328
329	while (optoff < optend) {
330	/* Usually: option, length. */
331	unsigned char op = (pskb)->data + optoff;
332
333	switch (op[0]) {
334	case TCPOPT_EOL:
335	return 1;
336	case TCPOPT_NOP:
337	optoff++;
338	continue;
339	default:
340	/* no partial options */
341	if (optoff + 1 == optend \|\|
342	optoff + op[1] > optend \|\|
343	op[1] < 2)
344	return 0;
345	if (op[0] == TCPOPT_SACK &&
346	op[1] >= 2+TCPOLEN_SACK_PERBLOCK &&
347	((op[1] - 2) % TCPOLEN_SACK_PERBLOCK) == 0)
348	sack_adjust(*pskb, tcph, optoff+2,
349	optoff+op[1],
350	&nat->info.seq[!dir]);
351	optoff += op[1];
352	}
353	}
354	return 1;
355	}
356
357	/* TCP sequence number adjustment. Returns 1 on success, 0 on failure */
358	int
359	nf_nat_seq_adjust(struct sk_buff **pskb,
360	struct nf_conn *ct,
361	enum ip_conntrack_info ctinfo)
362	{
363	struct tcphdr *tcph;
364	int dir;
365	__be32 newseq, newack;
366	struct nf_conn_nat *nat = nfct_nat(ct);
367	struct nf_nat_seq this_way, other_way;
368
369	dir = CTINFO2DIR(ctinfo);
370
371	this_way = &nat->info.seq[dir];
372	other_way = &nat->info.seq[!dir];
373
374	if (!skb_make_writable(pskb, (pskb)->nh.iph->ihl4+sizeof(*tcph)))
375	return 0;
376
377	tcph = (void )(pskb)->data + (pskb)->nh.iph->ihl4;
378	if (after(ntohl(tcph->seq), this_way->correction_pos))
379	newseq = htonl(ntohl(tcph->seq) + this_way->offset_after);
380	else
381	newseq = htonl(ntohl(tcph->seq) + this_way->offset_before);
382
383	if (after(ntohl(tcph->ack_seq) - other_way->offset_before,
384	other_way->correction_pos))
385	newack = htonl(ntohl(tcph->ack_seq) - other_way->offset_after);
386	else
387	newack = htonl(ntohl(tcph->ack_seq) - other_way->offset_before);
388
389	nf_proto_csum_replace4(&tcph->check, *pskb, tcph->seq, newseq, 0);
390	nf_proto_csum_replace4(&tcph->check, *pskb, tcph->ack_seq, newack, 0);
391
392	DEBUGP("Adjusting sequence number from %u->%u, ack from %u->%u\n",
393	ntohl(tcph->seq), ntohl(newseq), ntohl(tcph->ack_seq),
394	ntohl(newack));
395
396	tcph->seq = newseq;
397	tcph->ack_seq = newack;
398
399	if (!nf_nat_sack_adjust(pskb, tcph, ct, ctinfo))
400	return 0;
401
402	nf_conntrack_tcp_update(pskb, (pskb)->nh.iph->ihl*4, ct, dir);
403
404	return 1;
405	}
406	EXPORT_SYMBOL(nf_nat_seq_adjust);
407
408	/* Setup NAT on this expected conntrack so it follows master. */
409	/* If we fail to get a free NAT slot, we'll get dropped on confirm */
410	void nf_nat_follow_master(struct nf_conn *ct,
411	struct nf_conntrack_expect *exp)
412	{
413	struct nf_nat_range range;
414
415	/* This must be a fresh one. */
416	BUG_ON(ct->status & IPS_NAT_DONE_MASK);
417
418	/* Change src to where master sends to */
419	range.flags = IP_NAT_RANGE_MAP_IPS;
420	range.min_ip = range.max_ip
421	= ct->master->tuplehash[!exp->dir].tuple.dst.u3.ip;
422	/* hook doesn't matter, but it has to do source manip */
423	nf_nat_setup_info(ct, &range, NF_IP_POST_ROUTING);
424
425	/* For DST manip, map port here to where it's expected. */
426	range.flags = (IP_NAT_RANGE_MAP_IPS \| IP_NAT_RANGE_PROTO_SPECIFIED);
427	range.min = range.max = exp->saved_proto;
428	range.min_ip = range.max_ip
429	= ct->master->tuplehash[!exp->dir].tuple.src.u3.ip;
430	/* hook doesn't matter, but it has to do destination manip */
431	nf_nat_setup_info(ct, &range, NF_IP_PRE_ROUTING);
432	}
433	EXPORT_SYMBOL(nf_nat_follow_master);