[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 = skb_network_header(skb) + dataoff;

	/* move post-replacement */
	memmove(data + match_offset + rep_len,
		data + match_offset + match_len,
		skb->tail - (skb->network_header + dataoff +
			     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 */
	ip_hdr(skb)->tot_len = htons(skb->len);
	ip_send_check(ip_hdr(skb));
}

/* 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 = ip_hdr(*pskb);
	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(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, ip_hdrlen(*pskb),
					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 = ip_hdr(*pskb);
	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 = ip_hdr(*pskb);
	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 = ip_hdrlen(*pskb) + sizeof(struct tcphdr);
	optend = ip_hdrlen(*pskb) + 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, ip_hdrlen(*pskb) + sizeof(*tcph)))
		return 0;

	tcph = (void *)(*pskb)->data + ip_hdrlen(*pskb);
	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, ip_hdrlen(*pskb), 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));
eddc9ec5	90	data = skb_network_header(skb) + dataoff;
5b1158e9 JK	91
	92	/* move post-replacement */
	93	memmove(data + match_offset + rep_len,
	94	data + match_offset + match_len,
27a884dc ACM	95	skb->tail - (skb->network_header + dataoff +
27a884dc ACM	96	match_offset + match_len));
5b1158e9 JK	97
	98	/* insert data from buffer */
	99	memcpy(data + match_offset, rep_buffer, rep_len);
	100
	101	/* update skb info */
	102	if (rep_len > match_len) {
	103	DEBUGP("nf_nat_mangle_packet: Extending packet by "
	104	"%u from %u bytes\n", rep_len - match_len,
	105	skb->len);
	106	skb_put(skb, rep_len - match_len);
	107	} else {
	108	DEBUGP("nf_nat_mangle_packet: Shrinking packet from "
	109	"%u from %u bytes\n", match_len - rep_len,
	110	skb->len);
	111	__skb_trim(skb, skb->len + rep_len - match_len);
	112	}
	113
	114	/* fix IP hdr checksum information */
eddc9ec5 ACM	115	ip_hdr(skb)->tot_len = htons(skb->len);
eddc9ec5 ACM	116	ip_send_check(ip_hdr(skb));
5b1158e9 JK	117	}
	118
	119	/* Unusual, but possible case. */
	120	static int enlarge_skb(struct sk_buff **pskb, unsigned int extra)
	121	{
	122	struct sk_buff *nskb;
	123
	124	if ((*pskb)->len + extra > 65535)
	125	return 0;
	126
	127	nskb = skb_copy_expand(pskb, skb_headroom(pskb), extra, GFP_ATOMIC);
	128	if (!nskb)
	129	return 0;
	130
	131	/* Transfer socket to new skb. */
	132	if ((*pskb)->sk)
	133	skb_set_owner_w(nskb, (*pskb)->sk);
	134	kfree_skb(*pskb);
	135	*pskb = nskb;
	136	return 1;
	137	}
	138
	139	/* Generic function for mangling variable-length address changes inside
	140	* NATed TCP connections (like the PORT XXX,XXX,XXX,XXX,XXX,XXX
	141	* command in FTP).
	142	*
	143	* Takes care about all the nasty sequence number changes, checksumming,
	144	* skb enlargement, ...
	145	*
	146	* */
	147	int
	148	nf_nat_mangle_tcp_packet(struct sk_buff **pskb,
	149	struct nf_conn *ct,
	150	enum ip_conntrack_info ctinfo,
	151	unsigned int match_offset,
	152	unsigned int match_len,
	153	const char *rep_buffer,
	154	unsigned int rep_len)
	155	{
	156	struct iphdr *iph;
	157	struct tcphdr *tcph;
	158	int oldlen, datalen;
	159
	160	if (!skb_make_writable(pskb, (*pskb)->len))
	161	return 0;
	162
	163	if (rep_len > match_len &&
	164	rep_len - match_len > skb_tailroom(*pskb) &&
	165	!enlarge_skb(pskb, rep_len - match_len))
	166	return 0;
	167
	168	SKB_LINEAR_ASSERT(*pskb);
	169
eddc9ec5	170	iph = ip_hdr(*pskb);
5b1158e9 JK	171	tcph = (void )iph + iph->ihl4;
	172
	173	oldlen = (pskb)->len - iph->ihl4;
	174	mangle_contents(pskb, iph->ihl4 + tcph->doff*4,
	175	match_offset, match_len, rep_buffer, rep_len);
	176
	177	datalen = (pskb)->len - iph->ihl4;
	178	if ((*pskb)->ip_summed != CHECKSUM_PARTIAL) {
	179	tcph->check = 0;
ba7808ea	180	tcph->check = tcp_v4_check(datalen,
5b1158e9 JK	181	iph->saddr, iph->daddr,
5b1158e9 JK	182	csum_partial((char *)tcph,
e905a9ed	183	datalen, 0));
5b1158e9 JK	184	} else
	185	nf_proto_csum_replace2(&tcph->check, *pskb,
	186	htons(oldlen), htons(datalen), 1);
	187
	188	if (rep_len != match_len) {
	189	set_bit(IPS_SEQ_ADJUST_BIT, &ct->status);
	190	adjust_tcp_sequence(ntohl(tcph->seq),
	191	(int)rep_len - (int)match_len,
	192	ct, ctinfo);
	193	/* Tell TCP window tracking about seq change */
c9bdd4b5	194	nf_conntrack_tcp_update(pskb, ip_hdrlen(pskb),
5b1158e9 JK	195	ct, CTINFO2DIR(ctinfo));
	196	}
	197	return 1;
	198	}
	199	EXPORT_SYMBOL(nf_nat_mangle_tcp_packet);
	200
	201	/* Generic function for mangling variable-length address changes inside
	202	* NATed UDP connections (like the CONNECT DATA XXXXX MESG XXXXX INDEX XXXXX
	203	* command in the Amanda protocol)
	204	*
	205	* Takes care about all the nasty sequence number changes, checksumming,
	206	* skb enlargement, ...
	207	*
	208	* XXX - This function could be merged with nf_nat_mangle_tcp_packet which
	209	* should be fairly easy to do.
	210	*/
	211	int
	212	nf_nat_mangle_udp_packet(struct sk_buff **pskb,
	213	struct nf_conn *ct,
	214	enum ip_conntrack_info ctinfo,
	215	unsigned int match_offset,
	216	unsigned int match_len,
	217	const char *rep_buffer,
	218	unsigned int rep_len)
	219	{
	220	struct iphdr *iph;
	221	struct udphdr *udph;
	222	int datalen, oldlen;
	223
	224	/* UDP helpers might accidentally mangle the wrong packet */
eddc9ec5	225	iph = ip_hdr(*pskb);
5b1158e9	226	if ((pskb)->len < iph->ihl4 + sizeof(*udph) +
e905a9ed	227	match_offset + match_len)
5b1158e9 JK	228	return 0;
	229
	230	if (!skb_make_writable(pskb, (*pskb)->len))
	231	return 0;
	232
	233	if (rep_len > match_len &&
	234	rep_len - match_len > skb_tailroom(*pskb) &&
	235	!enlarge_skb(pskb, rep_len - match_len))
	236	return 0;
	237
eddc9ec5	238	iph = ip_hdr(*pskb);
5b1158e9 JK	239	udph = (void )iph + iph->ihl4;
	240
	241	oldlen = (pskb)->len - iph->ihl4;
	242	mangle_contents(pskb, iph->ihl4 + sizeof(*udph),
	243	match_offset, match_len, rep_buffer, rep_len);
	244
	245	/* update the length of the UDP packet */
	246	datalen = (pskb)->len - iph->ihl4;
	247	udph->len = htons(datalen);
	248
	249	/* fix udp checksum if udp checksum was previously calculated */
	250	if (!udph->check && (*pskb)->ip_summed != CHECKSUM_PARTIAL)
	251	return 1;
	252
	253	if ((*pskb)->ip_summed != CHECKSUM_PARTIAL) {
	254	udph->check = 0;
	255	udph->check = csum_tcpudp_magic(iph->saddr, iph->daddr,
e905a9ed YH	256	datalen, IPPROTO_UDP,
	257	csum_partial((char *)udph,
	258	datalen, 0));
5b1158e9 JK	259	if (!udph->check)
	260	udph->check = CSUM_MANGLED_0;
	261	} else
	262	nf_proto_csum_replace2(&udph->check, *pskb,
	263	htons(oldlen), htons(datalen), 1);
	264
	265	return 1;
	266	}
	267	EXPORT_SYMBOL(nf_nat_mangle_udp_packet);
	268
	269	/* Adjust one found SACK option including checksum correction */
	270	static void
	271	sack_adjust(struct sk_buff *skb,
	272	struct tcphdr *tcph,
	273	unsigned int sackoff,
	274	unsigned int sackend,
	275	struct nf_nat_seq *natseq)
	276	{
	277	while (sackoff < sackend) {
	278	struct tcp_sack_block_wire *sack;
	279	__be32 new_start_seq, new_end_seq;
	280
	281	sack = (void *)skb->data + sackoff;
	282	if (after(ntohl(sack->start_seq) - natseq->offset_before,
	283	natseq->correction_pos))
	284	new_start_seq = htonl(ntohl(sack->start_seq)
	285	- natseq->offset_after);
	286	else
	287	new_start_seq = htonl(ntohl(sack->start_seq)
	288	- natseq->offset_before);
	289
	290	if (after(ntohl(sack->end_seq) - natseq->offset_before,
	291	natseq->correction_pos))
	292	new_end_seq = htonl(ntohl(sack->end_seq)
	293	- natseq->offset_after);
	294	else
	295	new_end_seq = htonl(ntohl(sack->end_seq)
	296	- natseq->offset_before);
	297
	298	DEBUGP("sack_adjust: start_seq: %d->%d, end_seq: %d->%d\n",
	299	ntohl(sack->start_seq), new_start_seq,
	300	ntohl(sack->end_seq), new_end_seq);
	301
	302	nf_proto_csum_replace4(&tcph->check, skb,
	303	sack->start_seq, new_start_seq, 0);
	304	nf_proto_csum_replace4(&tcph->check, skb,
	305	sack->end_seq, new_end_seq, 0);
	306	sack->start_seq = new_start_seq;
	307	sack->end_seq = new_end_seq;
	308	sackoff += sizeof(*sack);
	309	}
	310	}
	311
	312	/* TCP SACK sequence number adjustment */
	313	static inline unsigned int
	314	nf_nat_sack_adjust(struct sk_buff **pskb,
	315	struct tcphdr *tcph,
	316	struct nf_conn *ct,
	317	enum ip_conntrack_info ctinfo)
	318	{
	319	unsigned int dir, optoff, optend;
	320	struct nf_conn_nat *nat = nfct_nat(ct);
	321
c9bdd4b5 ACM	322	optoff = ip_hdrlen(*pskb) + sizeof(struct tcphdr);
c9bdd4b5 ACM	323	optend = ip_hdrlen(pskb) + tcph->doff 4;
5b1158e9 JK	324
	325	if (!skb_make_writable(pskb, optend))
	326	return 0;
	327
	328	dir = CTINFO2DIR(ctinfo);
	329
	330	while (optoff < optend) {
	331	/* Usually: option, length. */
	332	unsigned char op = (pskb)->data + optoff;
	333
	334	switch (op[0]) {
	335	case TCPOPT_EOL:
	336	return 1;
	337	case TCPOPT_NOP:
	338	optoff++;
	339	continue;
	340	default:
	341	/* no partial options */
	342	if (optoff + 1 == optend \|\|
	343	optoff + op[1] > optend \|\|
	344	op[1] < 2)
	345	return 0;
	346	if (op[0] == TCPOPT_SACK &&
	347	op[1] >= 2+TCPOLEN_SACK_PERBLOCK &&
	348	((op[1] - 2) % TCPOLEN_SACK_PERBLOCK) == 0)
	349	sack_adjust(*pskb, tcph, optoff+2,
	350	optoff+op[1],
	351	&nat->info.seq[!dir]);
	352	optoff += op[1];
	353	}
	354	}
	355	return 1;
	356	}
	357
	358	/* TCP sequence number adjustment. Returns 1 on success, 0 on failure */
	359	int
	360	nf_nat_seq_adjust(struct sk_buff **pskb,
	361	struct nf_conn *ct,
	362	enum ip_conntrack_info ctinfo)
	363	{
	364	struct tcphdr *tcph;
	365	int dir;
	366	__be32 newseq, newack;
	367	struct nf_conn_nat *nat = nfct_nat(ct);
	368	struct nf_nat_seq this_way, other_way;
	369
	370	dir = CTINFO2DIR(ctinfo);
	371
	372	this_way = &nat->info.seq[dir];
	373	other_way = &nat->info.seq[!dir];
	374
c9bdd4b5	375	if (!skb_make_writable(pskb, ip_hdrlen(pskb) + sizeof(tcph)))
5b1158e9 JK	376	return 0;
5b1158e9 JK	377
c9bdd4b5	378	tcph = (void )(pskb)->data + ip_hdrlen(*pskb);
5b1158e9 JK	379	if (after(ntohl(tcph->seq), this_way->correction_pos))
	380	newseq = htonl(ntohl(tcph->seq) + this_way->offset_after);
	381	else
	382	newseq = htonl(ntohl(tcph->seq) + this_way->offset_before);
	383
	384	if (after(ntohl(tcph->ack_seq) - other_way->offset_before,
	385	other_way->correction_pos))
	386	newack = htonl(ntohl(tcph->ack_seq) - other_way->offset_after);
	387	else
	388	newack = htonl(ntohl(tcph->ack_seq) - other_way->offset_before);
	389
	390	nf_proto_csum_replace4(&tcph->check, *pskb, tcph->seq, newseq, 0);
	391	nf_proto_csum_replace4(&tcph->check, *pskb, tcph->ack_seq, newack, 0);
	392
	393	DEBUGP("Adjusting sequence number from %u->%u, ack from %u->%u\n",
	394	ntohl(tcph->seq), ntohl(newseq), ntohl(tcph->ack_seq),
	395	ntohl(newack));
	396
	397	tcph->seq = newseq;
	398	tcph->ack_seq = newack;
	399
	400	if (!nf_nat_sack_adjust(pskb, tcph, ct, ctinfo))
	401	return 0;
	402
c9bdd4b5	403	nf_conntrack_tcp_update(pskb, ip_hdrlen(pskb), ct, dir);
5b1158e9 JK	404
	405	return 1;
	406	}
	407	EXPORT_SYMBOL(nf_nat_seq_adjust);
	408
	409	/* Setup NAT on this expected conntrack so it follows master. */
	410	/* If we fail to get a free NAT slot, we'll get dropped on confirm */
	411	void nf_nat_follow_master(struct nf_conn *ct,
	412	struct nf_conntrack_expect *exp)
	413	{
	414	struct nf_nat_range range;
	415
	416	/* This must be a fresh one. */
	417	BUG_ON(ct->status & IPS_NAT_DONE_MASK);
	418
	419	/* Change src to where master sends to */
	420	range.flags = IP_NAT_RANGE_MAP_IPS;
	421	range.min_ip = range.max_ip
	422	= ct->master->tuplehash[!exp->dir].tuple.dst.u3.ip;
	423	/* hook doesn't matter, but it has to do source manip */
	424	nf_nat_setup_info(ct, &range, NF_IP_POST_ROUTING);
	425
	426	/* For DST manip, map port here to where it's expected. */
	427	range.flags = (IP_NAT_RANGE_MAP_IPS \| IP_NAT_RANGE_PROTO_SPECIFIED);
	428	range.min = range.max = exp->saved_proto;
	429	range.min_ip = range.max_ip
	430	= ct->master->tuplehash[!exp->dir].tuple.src.u3.ip;
	431	/* hook doesn't matter, but it has to do destination manip */
	432	nf_nat_setup_info(ct, &range, NF_IP_PRE_ROUTING);
	433	}
	434	EXPORT_SYMBOL(nf_nat_follow_master);