linux/net/netfilter/nf_nat_helper.c

// SPDX-License-Identifier: GPL-2.0-only
/* nf_nat_helper.c - generic support functions for NAT helpers
 *
 * (C) 2000-2002 Harald Welte <[email protected]>
 * (C) 2003-2006 Netfilter Core Team <[email protected]>
 * (C) 2007-2012 Patrick McHardy <[email protected]>
 */
#include <linux/module.h>
#include <linux/gfp.h>
#include <linux/types.h>
#include <linux/skbuff.h>
#include <linux/tcp.h>
#include <linux/udp.h>
#include <net/tcp.h>

#include <net/netfilter/nf_conntrack.h>
#include <net/netfilter/nf_conntrack_helper.h>
#include <net/netfilter/nf_conntrack_ecache.h>
#include <net/netfilter/nf_conntrack_expect.h>
#include <net/netfilter/nf_conntrack_seqadj.h>
#include <net/netfilter/nf_nat.h>
#include <net/netfilter/nf_nat_helper.h>

/* 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)
{ … }

/* Unusual, but possible case. */
static bool enlarge_skb(struct sk_buff *skb, unsigned int extra)
{ … }

/* 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, ...
 *
 * */
bool __nf_nat_mangle_tcp_packet(struct sk_buff *skb,
				struct nf_conn *ct,
				enum ip_conntrack_info ctinfo,
				unsigned int protoff,
				unsigned int match_offset,
				unsigned int match_len,
				const char *rep_buffer,
				unsigned int rep_len, bool adjust)
{ … }
EXPORT_SYMBOL(…);

/* 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.
 */
bool
nf_nat_mangle_udp_packet(struct sk_buff *skb,
			 struct nf_conn *ct,
			 enum ip_conntrack_info ctinfo,
			 unsigned int protoff,
			 unsigned int match_offset,
			 unsigned int match_len,
			 const char *rep_buffer,
			 unsigned int rep_len)
{ … }
EXPORT_SYMBOL(…);

/* 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)
{ … }
EXPORT_SYMBOL(…);

u16 nf_nat_exp_find_port(struct nf_conntrack_expect *exp, u16 port)
{ … }
EXPORT_SYMBOL_GPL(…);