[mirror_ubuntu-artful-kernel.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 rtable *rt = (struct rtable *)(*pskb)->dst;
	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) {
		if (!(rt->rt_flags & RTCF_LOCAL) &&
		    (*pskb)->dev->features & NETIF_F_V4_CSUM) {
			(*pskb)->ip_summed = CHECKSUM_PARTIAL;
			(*pskb)->csum_start = skb_headroom(*pskb) +
					      skb_network_offset(*pskb) +
					      iph->ihl * 4;
			(*pskb)->csum_offset = offsetof(struct tcphdr, check);
			tcph->check = ~tcp_v4_check(datalen,
						    iph->saddr, iph->daddr, 0);
		} else {
			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 rtable *rt = (struct rtable *)(*pskb)->dst;
	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) {
		if (!(rt->rt_flags & RTCF_LOCAL) &&
		    (*pskb)->dev->features & NETIF_F_V4_CSUM) {
			(*pskb)->ip_summed = CHECKSUM_PARTIAL;
			(*pskb)->csum_start = skb_headroom(*pskb) +
					      skb_network_offset(*pskb) +
					      iph->ihl * 4;
			(*pskb)->csum_offset = offsetof(struct udphdr, check);
			udph->check = ~csum_tcpudp_magic(iph->saddr, iph->daddr,
							 datalen, IPPROTO_UDP,
							 0);
		} else {
			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	{
fe6092ea	156	struct rtable rt = (struct rtable )(*pskb)->dst;
5b1158e9 JK	157	struct iphdr *iph;
	158	struct tcphdr *tcph;
	159	int oldlen, datalen;
	160
	161	if (!skb_make_writable(pskb, (*pskb)->len))
	162	return 0;
	163
	164	if (rep_len > match_len &&
	165	rep_len - match_len > skb_tailroom(*pskb) &&
	166	!enlarge_skb(pskb, rep_len - match_len))
	167	return 0;
	168
	169	SKB_LINEAR_ASSERT(*pskb);
	170
eddc9ec5	171	iph = ip_hdr(*pskb);
5b1158e9 JK	172	tcph = (void )iph + iph->ihl4;
	173
	174	oldlen = (pskb)->len - iph->ihl4;
	175	mangle_contents(pskb, iph->ihl4 + tcph->doff*4,
	176	match_offset, match_len, rep_buffer, rep_len);
	177
	178	datalen = (pskb)->len - iph->ihl4;
	179	if ((*pskb)->ip_summed != CHECKSUM_PARTIAL) {
fe6092ea	180	if (!(rt->rt_flags & RTCF_LOCAL) &&
d212f87b	181	(*pskb)->dev->features & NETIF_F_V4_CSUM) {
fe6092ea PM	182	(*pskb)->ip_summed = CHECKSUM_PARTIAL;
	183	(pskb)->csum_start = skb_headroom(pskb) +
	184	skb_network_offset(*pskb) +
	185	iph->ihl * 4;
	186	(*pskb)->csum_offset = offsetof(struct tcphdr, check);
	187	tcph->check = ~tcp_v4_check(datalen,
	188	iph->saddr, iph->daddr, 0);
	189	} else {
	190	tcph->check = 0;
	191	tcph->check = tcp_v4_check(datalen,
	192	iph->saddr, iph->daddr,
	193	csum_partial((char *)tcph,
	194	datalen, 0));
	195	}
5b1158e9 JK	196	} else
	197	nf_proto_csum_replace2(&tcph->check, *pskb,
	198	htons(oldlen), htons(datalen), 1);
	199
	200	if (rep_len != match_len) {
	201	set_bit(IPS_SEQ_ADJUST_BIT, &ct->status);
	202	adjust_tcp_sequence(ntohl(tcph->seq),
	203	(int)rep_len - (int)match_len,
	204	ct, ctinfo);
	205	/* Tell TCP window tracking about seq change */
c9bdd4b5	206	nf_conntrack_tcp_update(pskb, ip_hdrlen(pskb),
5b1158e9 JK	207	ct, CTINFO2DIR(ctinfo));
	208	}
	209	return 1;
	210	}
	211	EXPORT_SYMBOL(nf_nat_mangle_tcp_packet);
	212
	213	/* Generic function for mangling variable-length address changes inside
	214	* NATed UDP connections (like the CONNECT DATA XXXXX MESG XXXXX INDEX XXXXX
	215	* command in the Amanda protocol)
	216	*
	217	* Takes care about all the nasty sequence number changes, checksumming,
	218	* skb enlargement, ...
	219	*
	220	* XXX - This function could be merged with nf_nat_mangle_tcp_packet which
	221	* should be fairly easy to do.
	222	*/
	223	int
	224	nf_nat_mangle_udp_packet(struct sk_buff **pskb,
	225	struct nf_conn *ct,
	226	enum ip_conntrack_info ctinfo,
	227	unsigned int match_offset,
	228	unsigned int match_len,
	229	const char *rep_buffer,
	230	unsigned int rep_len)
	231	{
fe6092ea	232	struct rtable rt = (struct rtable )(*pskb)->dst;
5b1158e9 JK	233	struct iphdr *iph;
	234	struct udphdr *udph;
	235	int datalen, oldlen;
	236
	237	/* UDP helpers might accidentally mangle the wrong packet */
eddc9ec5	238	iph = ip_hdr(*pskb);
5b1158e9	239	if ((pskb)->len < iph->ihl4 + sizeof(*udph) +
e905a9ed	240	match_offset + match_len)
5b1158e9 JK	241	return 0;
	242
	243	if (!skb_make_writable(pskb, (*pskb)->len))
	244	return 0;
	245
	246	if (rep_len > match_len &&
	247	rep_len - match_len > skb_tailroom(*pskb) &&
	248	!enlarge_skb(pskb, rep_len - match_len))
	249	return 0;
	250
eddc9ec5	251	iph = ip_hdr(*pskb);
5b1158e9 JK	252	udph = (void )iph + iph->ihl4;
	253
	254	oldlen = (pskb)->len - iph->ihl4;
	255	mangle_contents(pskb, iph->ihl4 + sizeof(*udph),
	256	match_offset, match_len, rep_buffer, rep_len);
	257
	258	/* update the length of the UDP packet */
	259	datalen = (pskb)->len - iph->ihl4;
	260	udph->len = htons(datalen);
	261
	262	/* fix udp checksum if udp checksum was previously calculated */
	263	if (!udph->check && (*pskb)->ip_summed != CHECKSUM_PARTIAL)
	264	return 1;
	265
	266	if ((*pskb)->ip_summed != CHECKSUM_PARTIAL) {
fe6092ea	267	if (!(rt->rt_flags & RTCF_LOCAL) &&
d212f87b	268	(*pskb)->dev->features & NETIF_F_V4_CSUM) {
fe6092ea PM	269	(*pskb)->ip_summed = CHECKSUM_PARTIAL;
	270	(pskb)->csum_start = skb_headroom(pskb) +
	271	skb_network_offset(*pskb) +
	272	iph->ihl * 4;
	273	(*pskb)->csum_offset = offsetof(struct udphdr, check);
	274	udph->check = ~csum_tcpudp_magic(iph->saddr, iph->daddr,
	275	datalen, IPPROTO_UDP,
	276	0);
	277	} else {
	278	udph->check = 0;
	279	udph->check = csum_tcpudp_magic(iph->saddr, iph->daddr,
	280	datalen, IPPROTO_UDP,
	281	csum_partial((char *)udph,
	282	datalen, 0));
	283	if (!udph->check)
	284	udph->check = CSUM_MANGLED_0;
	285	}
5b1158e9 JK	286	} else
	287	nf_proto_csum_replace2(&udph->check, *pskb,
	288	htons(oldlen), htons(datalen), 1);
	289
	290	return 1;
	291	}
	292	EXPORT_SYMBOL(nf_nat_mangle_udp_packet);
	293
	294	/* Adjust one found SACK option including checksum correction */
	295	static void
	296	sack_adjust(struct sk_buff *skb,
	297	struct tcphdr *tcph,
	298	unsigned int sackoff,
	299	unsigned int sackend,
	300	struct nf_nat_seq *natseq)
	301	{
	302	while (sackoff < sackend) {
	303	struct tcp_sack_block_wire *sack;
	304	__be32 new_start_seq, new_end_seq;
	305
	306	sack = (void *)skb->data + sackoff;
	307	if (after(ntohl(sack->start_seq) - natseq->offset_before,
	308	natseq->correction_pos))
	309	new_start_seq = htonl(ntohl(sack->start_seq)
	310	- natseq->offset_after);
	311	else
	312	new_start_seq = htonl(ntohl(sack->start_seq)
	313	- natseq->offset_before);
	314
	315	if (after(ntohl(sack->end_seq) - natseq->offset_before,
	316	natseq->correction_pos))
	317	new_end_seq = htonl(ntohl(sack->end_seq)
	318	- natseq->offset_after);
	319	else
	320	new_end_seq = htonl(ntohl(sack->end_seq)
	321	- natseq->offset_before);
	322
	323	DEBUGP("sack_adjust: start_seq: %d->%d, end_seq: %d->%d\n",
	324	ntohl(sack->start_seq), new_start_seq,
	325	ntohl(sack->end_seq), new_end_seq);
	326
	327	nf_proto_csum_replace4(&tcph->check, skb,
	328	sack->start_seq, new_start_seq, 0);
	329	nf_proto_csum_replace4(&tcph->check, skb,
	330	sack->end_seq, new_end_seq, 0);
	331	sack->start_seq = new_start_seq;
	332	sack->end_seq = new_end_seq;
	333	sackoff += sizeof(*sack);
	334	}
	335	}
	336
	337	/* TCP SACK sequence number adjustment */
	338	static inline unsigned int
	339	nf_nat_sack_adjust(struct sk_buff **pskb,
	340	struct tcphdr *tcph,
	341	struct nf_conn *ct,
	342	enum ip_conntrack_info ctinfo)
	343	{
	344	unsigned int dir, optoff, optend;
	345	struct nf_conn_nat *nat = nfct_nat(ct);
	346
c9bdd4b5 ACM	347	optoff = ip_hdrlen(*pskb) + sizeof(struct tcphdr);
c9bdd4b5 ACM	348	optend = ip_hdrlen(pskb) + tcph->doff 4;
5b1158e9 JK	349
	350	if (!skb_make_writable(pskb, optend))
	351	return 0;
	352
	353	dir = CTINFO2DIR(ctinfo);
	354
	355	while (optoff < optend) {
	356	/* Usually: option, length. */
	357	unsigned char op = (pskb)->data + optoff;
	358
	359	switch (op[0]) {
	360	case TCPOPT_EOL:
	361	return 1;
	362	case TCPOPT_NOP:
	363	optoff++;
	364	continue;
	365	default:
	366	/* no partial options */
	367	if (optoff + 1 == optend \|\|
	368	optoff + op[1] > optend \|\|
	369	op[1] < 2)
	370	return 0;
	371	if (op[0] == TCPOPT_SACK &&
	372	op[1] >= 2+TCPOLEN_SACK_PERBLOCK &&
	373	((op[1] - 2) % TCPOLEN_SACK_PERBLOCK) == 0)
	374	sack_adjust(*pskb, tcph, optoff+2,
	375	optoff+op[1],
	376	&nat->info.seq[!dir]);
	377	optoff += op[1];
	378	}
	379	}
	380	return 1;
	381	}
	382
	383	/* TCP sequence number adjustment. Returns 1 on success, 0 on failure */
	384	int
	385	nf_nat_seq_adjust(struct sk_buff **pskb,
	386	struct nf_conn *ct,
	387	enum ip_conntrack_info ctinfo)
	388	{
	389	struct tcphdr *tcph;
	390	int dir;
	391	__be32 newseq, newack;
	392	struct nf_conn_nat *nat = nfct_nat(ct);
	393	struct nf_nat_seq this_way, other_way;
	394
	395	dir = CTINFO2DIR(ctinfo);
	396
	397	this_way = &nat->info.seq[dir];
	398	other_way = &nat->info.seq[!dir];
	399
c9bdd4b5	400	if (!skb_make_writable(pskb, ip_hdrlen(pskb) + sizeof(tcph)))
5b1158e9 JK	401	return 0;
5b1158e9 JK	402
c9bdd4b5	403	tcph = (void )(pskb)->data + ip_hdrlen(*pskb);
5b1158e9 JK	404	if (after(ntohl(tcph->seq), this_way->correction_pos))
	405	newseq = htonl(ntohl(tcph->seq) + this_way->offset_after);
	406	else
	407	newseq = htonl(ntohl(tcph->seq) + this_way->offset_before);
	408
	409	if (after(ntohl(tcph->ack_seq) - other_way->offset_before,
	410	other_way->correction_pos))
	411	newack = htonl(ntohl(tcph->ack_seq) - other_way->offset_after);
	412	else
	413	newack = htonl(ntohl(tcph->ack_seq) - other_way->offset_before);
	414
	415	nf_proto_csum_replace4(&tcph->check, *pskb, tcph->seq, newseq, 0);
	416	nf_proto_csum_replace4(&tcph->check, *pskb, tcph->ack_seq, newack, 0);
	417
	418	DEBUGP("Adjusting sequence number from %u->%u, ack from %u->%u\n",
	419	ntohl(tcph->seq), ntohl(newseq), ntohl(tcph->ack_seq),
	420	ntohl(newack));
	421
	422	tcph->seq = newseq;
	423	tcph->ack_seq = newack;
	424
	425	if (!nf_nat_sack_adjust(pskb, tcph, ct, ctinfo))
	426	return 0;
	427
c9bdd4b5	428	nf_conntrack_tcp_update(pskb, ip_hdrlen(pskb), ct, dir);
5b1158e9 JK	429
	430	return 1;
	431	}
	432	EXPORT_SYMBOL(nf_nat_seq_adjust);
	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;
	448	/* hook doesn't matter, but it has to do source manip */
	449	nf_nat_setup_info(ct, &range, NF_IP_POST_ROUTING);
	450
	451	/* For DST manip, map port here to where it's expected. */
	452	range.flags = (IP_NAT_RANGE_MAP_IPS \| IP_NAT_RANGE_PROTO_SPECIFIED);
	453	range.min = range.max = exp->saved_proto;
	454	range.min_ip = range.max_ip
	455	= ct->master->tuplehash[!exp->dir].tuple.src.u3.ip;
	456	/* hook doesn't matter, but it has to do destination manip */
	457	nf_nat_setup_info(ct, &range, NF_IP_PRE_ROUTING);
	458	}
	459	EXPORT_SYMBOL(nf_nat_follow_master);