[linux-block.git] / net / ipv4 / netfilter / ip_nat_helper.c

/* ip_nat_helper.c - generic support functions for NAT helpers 
 *
 * (C) 2000-2002 Harald Welte <laforge@netfilter.org>
 * (C) 2003-2004 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.
 *
 * 	14 Jan 2002 Harald Welte <laforge@gnumonks.org>:
 *		- add support for SACK adjustment 
 *	14 Mar 2002 Harald Welte <laforge@gnumonks.org>:
 *		- merge SACK support into newnat API
 *	16 Aug 2002 Brian J. Murrell <netfilter@interlinx.bc.ca>:
 *		- make ip_nat_resize_packet more generic (TCP and UDP)
 *		- add ip_nat_mangle_udp_packet
 */
#include <linux/config.h>
#include <linux/module.h>
#include <linux/kmod.h>
#include <linux/types.h>
#include <linux/timer.h>
#include <linux/skbuff.h>
#include <linux/netfilter_ipv4.h>
#include <net/checksum.h>
#include <net/icmp.h>
#include <net/ip.h>
#include <net/tcp.h>
#include <net/udp.h>

#define ASSERT_READ_LOCK(x)
#define ASSERT_WRITE_LOCK(x)

#include <linux/netfilter_ipv4/ip_conntrack.h>
#include <linux/netfilter_ipv4/ip_conntrack_helper.h>
#include <linux/netfilter_ipv4/ip_nat.h>
#include <linux/netfilter_ipv4/ip_nat_protocol.h>
#include <linux/netfilter_ipv4/ip_nat_core.h>
#include <linux/netfilter_ipv4/ip_nat_helper.h>
#include <linux/netfilter_ipv4/listhelp.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(ip_nat_seqofs_lock);

/* Setup TCP sequence correction given this change at this sequence */
static inline void 
adjust_tcp_sequence(u32 seq,
		    int sizediff,
		    struct ip_conntrack *ct, 
		    enum ip_conntrack_info ctinfo)
{
	int dir;
	struct ip_nat_seq *this_way, *other_way;

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

	dir = CTINFO2DIR(ctinfo);

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

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

	spin_lock_bh(&ip_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(&ip_nat_seqofs_lock);

	DEBUGP("ip_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("ip_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("ip_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 
ip_nat_mangle_tcp_packet(struct sk_buff **pskb,
			 struct ip_conntrack *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 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;

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

	datalen = (*pskb)->len - iph->ihl*4;
	tcph->check = 0;
	tcph->check = tcp_v4_check(tcph, datalen, iph->saddr, iph->daddr,
				   csum_partial((char *)tcph, datalen, 0));

	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 */
		ip_conntrack_tcp_update(*pskb, ct, CTINFO2DIR(ctinfo));
	}
	return 1;
}
			
/* 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 ip_nat_mangle_tcp_packet which
 *       should be fairly easy to do.
 */
int 
ip_nat_mangle_udp_packet(struct sk_buff **pskb,
			 struct ip_conntrack *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;

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

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

	/* fix udp checksum if udp checksum was previously calculated */
	if (udph->check) {
		int datalen = (*pskb)->len - iph->ihl * 4;
		udph->check = 0;
		udph->check = csum_tcpudp_magic(iph->saddr, iph->daddr,
		                                datalen, IPPROTO_UDP,
		                                csum_partial((char *)udph,
		                                             datalen, 0));
	}

	return 1;
}

/* 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 ip_nat_seq *natseq)
{
	while (sackoff < sackend) {
		struct tcp_sack_block *sack;
		u_int32_t 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 = ntohl(sack->start_seq) 
					- natseq->offset_after;
		else
			new_start_seq = ntohl(sack->start_seq) 
					- natseq->offset_before;
		new_start_seq = htonl(new_start_seq);

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

		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);

		tcph->check = 
			ip_nat_cheat_check(~sack->start_seq, new_start_seq,
					   ip_nat_cheat_check(~sack->end_seq, 
						   	      new_end_seq,
							      tcph->check));
		sack->start_seq = new_start_seq;
		sack->end_seq = new_end_seq;
		sackoff += sizeof(*sack);
	}
}

/* TCP SACK sequence number adjustment */
static inline unsigned int
ip_nat_sack_adjust(struct sk_buff **pskb,
		   struct tcphdr *tcph,
		   struct ip_conntrack *ct,
		   enum ip_conntrack_info ctinfo)
{
	unsigned int dir, optoff, optend;

	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],
					    &ct->nat.info.seq[!dir]);
			optoff += op[1];
		}
	}
	return 1;
}

/* TCP sequence number adjustment.  Returns 1 on success, 0 on failure */
int
ip_nat_seq_adjust(struct sk_buff **pskb, 
		  struct ip_conntrack *ct, 
		  enum ip_conntrack_info ctinfo)
{
	struct tcphdr *tcph;
	int dir, newseq, newack;
	struct ip_nat_seq *this_way, *other_way;	

	dir = CTINFO2DIR(ctinfo);

	this_way = &ct->nat.info.seq[dir];
	other_way = &ct->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 = ntohl(tcph->seq) + this_way->offset_after;
	else
		newseq = ntohl(tcph->seq) + this_way->offset_before;
	newseq = htonl(newseq);

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

	tcph->check = ip_nat_cheat_check(~tcph->seq, newseq,
					 ip_nat_cheat_check(~tcph->ack_seq, 
					 		    newack, 
							    tcph->check));

	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 (!ip_nat_sack_adjust(pskb, tcph, ct, ctinfo))
		return 0;

	ip_conntrack_tcp_update(*pskb, ct, dir);

	return 1;
}

/* 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 ip_nat_follow_master(struct ip_conntrack *ct,
			  struct ip_conntrack_expect *exp)
{
	struct ip_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.ip;
	/* hook doesn't matter, but it has to do source manip */
	ip_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.ip;
	/* hook doesn't matter, but it has to do destination manip */
	ip_nat_setup_info(ct, &range, NF_IP_PRE_ROUTING);
}
Commit	Line	Data
1da177e4 LT	1	/* ip_nat_helper.c - generic support functions for NAT helpers
	2	*
	3	* (C) 2000-2002 Harald Welte <laforge@netfilter.org>
	4	* (C) 2003-2004 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	* 14 Jan 2002 Harald Welte <laforge@gnumonks.org>:
	11	* - add support for SACK adjustment
	12	* 14 Mar 2002 Harald Welte <laforge@gnumonks.org>:
	13	* - merge SACK support into newnat API
	14	* 16 Aug 2002 Brian J. Murrell <netfilter@interlinx.bc.ca>:
	15	* - make ip_nat_resize_packet more generic (TCP and UDP)
	16	* - add ip_nat_mangle_udp_packet
	17	*/
	18	#include <linux/config.h>
	19	#include <linux/module.h>
	20	#include <linux/kmod.h>
	21	#include <linux/types.h>
	22	#include <linux/timer.h>
	23	#include <linux/skbuff.h>
	24	#include <linux/netfilter_ipv4.h>
	25	#include <net/checksum.h>
	26	#include <net/icmp.h>
	27	#include <net/ip.h>
	28	#include <net/tcp.h>
	29	#include <net/udp.h>
	30
e45b1be8 PM	31	#define ASSERT_READ_LOCK(x)
e45b1be8 PM	32	#define ASSERT_WRITE_LOCK(x)
1da177e4 LT	33
	34	#include <linux/netfilter_ipv4/ip_conntrack.h>
	35	#include <linux/netfilter_ipv4/ip_conntrack_helper.h>
	36	#include <linux/netfilter_ipv4/ip_nat.h>
	37	#include <linux/netfilter_ipv4/ip_nat_protocol.h>
	38	#include <linux/netfilter_ipv4/ip_nat_core.h>
	39	#include <linux/netfilter_ipv4/ip_nat_helper.h>
	40	#include <linux/netfilter_ipv4/listhelp.h>
	41
	42	#if 0
	43	#define DEBUGP printk
	44	#define DUMP_OFFSET(x) printk("offset_before=%d, offset_after=%d, correction_pos=%u\n", x->offset_before, x->offset_after, x->correction_pos);
	45	#else
	46	#define DEBUGP(format, args...)
	47	#define DUMP_OFFSET(x)
	48	#endif
	49
e45b1be8	50	static DEFINE_SPINLOCK(ip_nat_seqofs_lock);
1da177e4 LT	51
	52	/* Setup TCP sequence correction given this change at this sequence */
	53	static inline void
	54	adjust_tcp_sequence(u32 seq,
	55	int sizediff,
	56	struct ip_conntrack *ct,
	57	enum ip_conntrack_info ctinfo)
	58	{
	59	int dir;
	60	struct ip_nat_seq this_way, other_way;
	61
	62	DEBUGP("ip_nat_resize_packet: old_size = %u, new_size = %u\n",
	63	(*skb)->len, new_size);
	64
	65	dir = CTINFO2DIR(ctinfo);
	66
	67	this_way = &ct->nat.info.seq[dir];
	68	other_way = &ct->nat.info.seq[!dir];
	69
	70	DEBUGP("ip_nat_resize_packet: Seq_offset before: ");
	71	DUMP_OFFSET(this_way);
	72
e45b1be8	73	spin_lock_bh(&ip_nat_seqofs_lock);
1da177e4 LT	74
	75	/* SYN adjust. If it's uninitialized, or this is after last
	76	* correction, record it: we don't handle more than one
	77	* adjustment in the window, but do deal with common case of a
	78	* retransmit */
	79	if (this_way->offset_before == this_way->offset_after
	80	\|\| before(this_way->correction_pos, seq)) {
	81	this_way->correction_pos = seq;
	82	this_way->offset_before = this_way->offset_after;
	83	this_way->offset_after += sizediff;
	84	}
e45b1be8	85	spin_unlock_bh(&ip_nat_seqofs_lock);
1da177e4 LT	86
	87	DEBUGP("ip_nat_resize_packet: Seq_offset after: ");
	88	DUMP_OFFSET(this_way);
	89	}
	90
	91	/* Frobs data inside this packet, which is linear. */
	92	static void mangle_contents(struct sk_buff *skb,
	93	unsigned int dataoff,
	94	unsigned int match_offset,
	95	unsigned int match_len,
	96	const char *rep_buffer,
	97	unsigned int rep_len)
	98	{
	99	unsigned char *data;
	100
	101	BUG_ON(skb_is_nonlinear(skb));
	102	data = (unsigned char *)skb->nh.iph + dataoff;
	103
	104	/* move post-replacement */
	105	memmove(data + match_offset + rep_len,
	106	data + match_offset + match_len,
	107	skb->tail - (data + match_offset + match_len));
	108
	109	/* insert data from buffer */
	110	memcpy(data + match_offset, rep_buffer, rep_len);
	111
	112	/* update skb info */
	113	if (rep_len > match_len) {
	114	DEBUGP("ip_nat_mangle_packet: Extending packet by "
	115	"%u from %u bytes\n", rep_len - match_len,
	116	skb->len);
	117	skb_put(skb, rep_len - match_len);
	118	} else {
	119	DEBUGP("ip_nat_mangle_packet: Shrinking packet from "
	120	"%u from %u bytes\n", match_len - rep_len,
	121	skb->len);
	122	__skb_trim(skb, skb->len + rep_len - match_len);
	123	}
	124
	125	/* fix IP hdr checksum information */
	126	skb->nh.iph->tot_len = htons(skb->len);
	127	ip_send_check(skb->nh.iph);
	128	}
	129
	130	/* Unusual, but possible case. */
	131	static int enlarge_skb(struct sk_buff **pskb, unsigned int extra)
	132	{
	133	struct sk_buff *nskb;
	134
	135	if ((*pskb)->len + extra > 65535)
	136	return 0;
	137
	138	nskb = skb_copy_expand(pskb, skb_headroom(pskb), extra, GFP_ATOMIC);
	139	if (!nskb)
	140	return 0;
	141
	142	/* Transfer socket to new skb. */
	143	if ((*pskb)->sk)
	144	skb_set_owner_w(nskb, (*pskb)->sk);
1da177e4 LT	145	kfree_skb(*pskb);
	146	*pskb = nskb;
	147	return 1;
	148	}
	149
	150	/* Generic function for mangling variable-length address changes inside
	151	* NATed TCP connections (like the PORT XXX,XXX,XXX,XXX,XXX,XXX
	152	* command in FTP).
	153	*
	154	* Takes care about all the nasty sequence number changes, checksumming,
	155	* skb enlargement, ...
	156	*
	157	* */
	158	int
	159	ip_nat_mangle_tcp_packet(struct sk_buff **pskb,
	160	struct ip_conntrack *ct,
	161	enum ip_conntrack_info ctinfo,
	162	unsigned int match_offset,
	163	unsigned int match_len,
	164	const char *rep_buffer,
	165	unsigned int rep_len)
	166	{
	167	struct iphdr *iph;
	168	struct tcphdr *tcph;
	169	int datalen;
	170
089af26c	171	if (!skb_make_writable(pskb, (*pskb)->len))
1da177e4 LT	172	return 0;
	173
	174	if (rep_len > match_len
	175	&& rep_len - match_len > skb_tailroom(*pskb)
	176	&& !enlarge_skb(pskb, rep_len - match_len))
	177	return 0;
	178
	179	SKB_LINEAR_ASSERT(*pskb);
	180
	181	iph = (*pskb)->nh.iph;
	182	tcph = (void )iph + iph->ihl4;
	183
	184	mangle_contents(pskb, iph->ihl4 + tcph->doff*4,
	185	match_offset, match_len, rep_buffer, rep_len);
	186
	187	datalen = (pskb)->len - iph->ihl4;
	188	tcph->check = 0;
	189	tcph->check = tcp_v4_check(tcph, datalen, iph->saddr, iph->daddr,
	190	csum_partial((char *)tcph, datalen, 0));
	191
	192	if (rep_len != match_len) {
	193	set_bit(IPS_SEQ_ADJUST_BIT, &ct->status);
	194	adjust_tcp_sequence(ntohl(tcph->seq),
	195	(int)rep_len - (int)match_len,
	196	ct, ctinfo);
	197	/* Tell TCP window tracking about seq change */
	198	ip_conntrack_tcp_update(*pskb, ct, CTINFO2DIR(ctinfo));
	199	}
	200	return 1;
	201	}
	202
	203	/* Generic function for mangling variable-length address changes inside
	204	* NATed UDP connections (like the CONNECT DATA XXXXX MESG XXXXX INDEX XXXXX
	205	* command in the Amanda protocol)
	206	*
	207	* Takes care about all the nasty sequence number changes, checksumming,
	208	* skb enlargement, ...
	209	*
	210	* XXX - This function could be merged with ip_nat_mangle_tcp_packet which
	211	* should be fairly easy to do.
	212	*/
	213	int
	214	ip_nat_mangle_udp_packet(struct sk_buff **pskb,
	215	struct ip_conntrack *ct,
	216	enum ip_conntrack_info ctinfo,
	217	unsigned int match_offset,
	218	unsigned int match_len,
	219	const char *rep_buffer,
	220	unsigned int rep_len)
	221	{
	222	struct iphdr *iph;
	223	struct udphdr *udph;
	224
	225	/* UDP helpers might accidentally mangle the wrong packet */
	226	iph = (*pskb)->nh.iph;
	227	if ((pskb)->len < iph->ihl4 + sizeof(*udph) +
	228	match_offset + match_len)
	229	return 0;
	230
089af26c	231	if (!skb_make_writable(pskb, (*pskb)->len))
1da177e4 LT	232	return 0;
	233
	234	if (rep_len > match_len
	235	&& rep_len - match_len > skb_tailroom(*pskb)
	236	&& !enlarge_skb(pskb, rep_len - match_len))
	237	return 0;
	238
	239	iph = (*pskb)->nh.iph;
	240	udph = (void )iph + 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	udph->len = htons((pskb)->len - iph->ihl4);
	246
	247	/* fix udp checksum if udp checksum was previously calculated */
	248	if (udph->check) {
	249	int datalen = (pskb)->len - iph->ihl 4;
	250	udph->check = 0;
	251	udph->check = csum_tcpudp_magic(iph->saddr, iph->daddr,
	252	datalen, IPPROTO_UDP,
	253	csum_partial((char *)udph,
	254	datalen, 0));
	255	}
	256
	257	return 1;
	258	}
	259
	260	/* Adjust one found SACK option including checksum correction */
	261	static void
	262	sack_adjust(struct sk_buff *skb,
	263	struct tcphdr *tcph,
	264	unsigned int sackoff,
	265	unsigned int sackend,
	266	struct ip_nat_seq *natseq)
	267	{
	268	while (sackoff < sackend) {
	269	struct tcp_sack_block *sack;
	270	u_int32_t new_start_seq, new_end_seq;
	271
	272	sack = (void *)skb->data + sackoff;
	273	if (after(ntohl(sack->start_seq) - natseq->offset_before,
	274	natseq->correction_pos))
	275	new_start_seq = ntohl(sack->start_seq)
	276	- natseq->offset_after;
	277	else
	278	new_start_seq = ntohl(sack->start_seq)
	279	- natseq->offset_before;
	280	new_start_seq = htonl(new_start_seq);
	281
	282	if (after(ntohl(sack->end_seq) - natseq->offset_before,
	283	natseq->correction_pos))
	284	new_end_seq = ntohl(sack->end_seq)
	285	- natseq->offset_after;
	286	else
	287	new_end_seq = ntohl(sack->end_seq)
	288	- natseq->offset_before;
	289	new_end_seq = htonl(new_end_seq);
	290
	291	DEBUGP("sack_adjust: start_seq: %d->%d, end_seq: %d->%d\n",
	292	ntohl(sack->start_seq), new_start_seq,
	293	ntohl(sack->end_seq), new_end_seq);
	294
	295	tcph->check =
296	ip_nat_cheat_check(~sack->start_seq, new_start_seq,
297	ip_nat_cheat_check(~sack->end_seq,
298	new_end_seq,
299	tcph->check));
300	sack->start_seq = new_start_seq;
301	sack->end_seq = new_end_seq;
302	sackoff += sizeof(*sack);
303	}
304	}
305
306	/* TCP SACK sequence number adjustment */
307	static inline unsigned int
308	ip_nat_sack_adjust(struct sk_buff **pskb,
309	struct tcphdr *tcph,
310	struct ip_conntrack *ct,
311	enum ip_conntrack_info ctinfo)
312	{
313	unsigned int dir, optoff, optend;
314
315	optoff = (pskb)->nh.iph->ihl4 + sizeof(struct tcphdr);
316	optend = (pskb)->nh.iph->ihl4 + tcph->doff*4;
317
089af26c	318	if (!skb_make_writable(pskb, optend))
1da177e4 LT	319	return 0;
	320
	321	dir = CTINFO2DIR(ctinfo);
	322
	323	while (optoff < optend) {
	324	/* Usually: option, length. */
	325	unsigned char op = (pskb)->data + optoff;
	326
	327	switch (op[0]) {
	328	case TCPOPT_EOL:
	329	return 1;
	330	case TCPOPT_NOP:
	331	optoff++;
	332	continue;
	333	default:
	334	/* no partial options */
	335	if (optoff + 1 == optend
	336	\|\| optoff + op[1] > optend
	337	\|\| op[1] < 2)
	338	return 0;
	339	if (op[0] == TCPOPT_SACK
	340	&& op[1] >= 2+TCPOLEN_SACK_PERBLOCK
	341	&& ((op[1] - 2) % TCPOLEN_SACK_PERBLOCK) == 0)
	342	sack_adjust(*pskb, tcph, optoff+2,
	343	optoff+op[1],
	344	&ct->nat.info.seq[!dir]);
	345	optoff += op[1];
	346	}
	347	}
	348	return 1;
	349	}
	350
	351	/* TCP sequence number adjustment. Returns 1 on success, 0 on failure */
	352	int
	353	ip_nat_seq_adjust(struct sk_buff **pskb,
	354	struct ip_conntrack *ct,
	355	enum ip_conntrack_info ctinfo)
	356	{
	357	struct tcphdr *tcph;
	358	int dir, newseq, newack;
	359	struct ip_nat_seq this_way, other_way;
	360
	361	dir = CTINFO2DIR(ctinfo);
	362
	363	this_way = &ct->nat.info.seq[dir];
	364	other_way = &ct->nat.info.seq[!dir];
	365
089af26c	366	if (!skb_make_writable(pskb, (pskb)->nh.iph->ihl4+sizeof(*tcph)))
1da177e4 LT	367	return 0;
	368
	369	tcph = (void )(pskb)->data + (pskb)->nh.iph->ihl4;
	370	if (after(ntohl(tcph->seq), this_way->correction_pos))
	371	newseq = ntohl(tcph->seq) + this_way->offset_after;
	372	else
	373	newseq = ntohl(tcph->seq) + this_way->offset_before;
	374	newseq = htonl(newseq);
	375
	376	if (after(ntohl(tcph->ack_seq) - other_way->offset_before,
	377	other_way->correction_pos))
	378	newack = ntohl(tcph->ack_seq) - other_way->offset_after;
	379	else
	380	newack = ntohl(tcph->ack_seq) - other_way->offset_before;
	381	newack = htonl(newack);
	382
	383	tcph->check = ip_nat_cheat_check(~tcph->seq, newseq,
	384	ip_nat_cheat_check(~tcph->ack_seq,
	385	newack,
	386	tcph->check));
	387
	388	DEBUGP("Adjusting sequence number from %u->%u, ack from %u->%u\n",
	389	ntohl(tcph->seq), ntohl(newseq), ntohl(tcph->ack_seq),
	390	ntohl(newack));
	391
	392	tcph->seq = newseq;
	393	tcph->ack_seq = newack;
	394
	395	if (!ip_nat_sack_adjust(pskb, tcph, ct, ctinfo))
	396	return 0;
	397
	398	ip_conntrack_tcp_update(*pskb, ct, dir);
	399
	400	return 1;
	401	}
	402
	403	/* Setup NAT on this expected conntrack so it follows master. */
	404	/* If we fail to get a free NAT slot, we'll get dropped on confirm */
	405	void ip_nat_follow_master(struct ip_conntrack *ct,
	406	struct ip_conntrack_expect *exp)
	407	{
	408	struct ip_nat_range range;
	409
	410	/* This must be a fresh one. */
	411	BUG_ON(ct->status & IPS_NAT_DONE_MASK);
	412
	413	/* Change src to where master sends to */
	414	range.flags = IP_NAT_RANGE_MAP_IPS;
	415	range.min_ip = range.max_ip
	416	= ct->master->tuplehash[!exp->dir].tuple.dst.ip;
	417	/* hook doesn't matter, but it has to do source manip */
	418	ip_nat_setup_info(ct, &range, NF_IP_POST_ROUTING);
	419
	420	/* For DST manip, map port here to where it's expected. */
	421	range.flags = (IP_NAT_RANGE_MAP_IPS \| IP_NAT_RANGE_PROTO_SPECIFIED);
	422	range.min = range.max = exp->saved_proto;
	423	range.min_ip = range.max_ip
	424	= ct->master->tuplehash[!exp->dir].tuple.src.ip;
	425	/* hook doesn't matter, but it has to do destination manip */
	426	ip_nat_setup_info(ct, &range, NF_IP_PRE_ROUTING);
	427	}