linux/net/netfilter/nf_nat_sip.c

// SPDX-License-Identifier: GPL-2.0-only
/* SIP extension for NAT alteration.
 *
 * (C) 2005 by Christian Hentschel <[email protected]>
 * based on RR's ip_nat_ftp.c and other modules.
 * (C) 2007 United Security Providers
 * (C) 2007, 2008, 2011, 2012 Patrick McHardy <[email protected]>
 */

#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/inet.h>
#include <linux/udp.h>
#include <linux/tcp.h>

#include <net/netfilter/nf_nat.h>
#include <net/netfilter/nf_nat_helper.h>
#include <net/netfilter/nf_conntrack_core.h>
#include <net/netfilter/nf_conntrack_helper.h>
#include <net/netfilter/nf_conntrack_expect.h>
#include <net/netfilter/nf_conntrack_seqadj.h>
#include <linux/netfilter/nf_conntrack_sip.h>

#define NAT_HELPER_NAME …

MODULE_LICENSE(…) …;
MODULE_AUTHOR(…) …;
MODULE_DESCRIPTION(…) …;
MODULE_ALIAS_NF_NAT_HELPER(…);

static struct nf_conntrack_nat_helper nat_helper_sip = …;

static unsigned int mangle_packet(struct sk_buff *skb, unsigned int protoff,
				  unsigned int dataoff,
				  const char **dptr, unsigned int *datalen,
				  unsigned int matchoff, unsigned int matchlen,
				  const char *buffer, unsigned int buflen)
{ … }

static int sip_sprintf_addr(const struct nf_conn *ct, char *buffer,
			    const union nf_inet_addr *addr, bool delim)
{ … }

static int sip_sprintf_addr_port(const struct nf_conn *ct, char *buffer,
				 const union nf_inet_addr *addr, u16 port)
{ … }

static int map_addr(struct sk_buff *skb, unsigned int protoff,
		    unsigned int dataoff,
		    const char **dptr, unsigned int *datalen,
		    unsigned int matchoff, unsigned int matchlen,
		    union nf_inet_addr *addr, __be16 port)
{ … }

static int map_sip_addr(struct sk_buff *skb, unsigned int protoff,
			unsigned int dataoff,
			const char **dptr, unsigned int *datalen,
			enum sip_header_types type)
{ … }

static unsigned int nf_nat_sip(struct sk_buff *skb, unsigned int protoff,
			       unsigned int dataoff,
			       const char **dptr, unsigned int *datalen)
{ … }

static void nf_nat_sip_seq_adjust(struct sk_buff *skb, unsigned int protoff,
				  s16 off)
{ … }

/* Handles expected signalling connections and media streams */
static void nf_nat_sip_expected(struct nf_conn *ct,
				struct nf_conntrack_expect *exp)
{ … }

static unsigned int nf_nat_sip_expect(struct sk_buff *skb, unsigned int protoff,
				      unsigned int dataoff,
				      const char **dptr, unsigned int *datalen,
				      struct nf_conntrack_expect *exp,
				      unsigned int matchoff,
				      unsigned int matchlen)
{ … }

static int mangle_content_len(struct sk_buff *skb, unsigned int protoff,
			      unsigned int dataoff,
			      const char **dptr, unsigned int *datalen)
{ … }

static int mangle_sdp_packet(struct sk_buff *skb, unsigned int protoff,
			     unsigned int dataoff,
			     const char **dptr, unsigned int *datalen,
			     unsigned int sdpoff,
			     enum sdp_header_types type,
			     enum sdp_header_types term,
			     char *buffer, int buflen)
{ … }

static unsigned int nf_nat_sdp_addr(struct sk_buff *skb, unsigned int protoff,
				    unsigned int dataoff,
				    const char **dptr, unsigned int *datalen,
				    unsigned int sdpoff,
				    enum sdp_header_types type,
				    enum sdp_header_types term,
				    const union nf_inet_addr *addr)
{ … }

static unsigned int nf_nat_sdp_port(struct sk_buff *skb, unsigned int protoff,
				    unsigned int dataoff,
				    const char **dptr, unsigned int *datalen,
				    unsigned int matchoff,
				    unsigned int matchlen,
				    u_int16_t port)
{ … }

static unsigned int nf_nat_sdp_session(struct sk_buff *skb, unsigned int protoff,
				       unsigned int dataoff,
				       const char **dptr, unsigned int *datalen,
				       unsigned int sdpoff,
				       const union nf_inet_addr *addr)
{ … }

/* So, this packet has hit the connection tracking matching code.
   Mangle it, and change the expectation to match the new version. */
static unsigned int nf_nat_sdp_media(struct sk_buff *skb, unsigned int protoff,
				     unsigned int dataoff,
				     const char **dptr, unsigned int *datalen,
				     struct nf_conntrack_expect *rtp_exp,
				     struct nf_conntrack_expect *rtcp_exp,
				     unsigned int mediaoff,
				     unsigned int medialen,
				     union nf_inet_addr *rtp_addr)
{ … }

static struct nf_ct_helper_expectfn sip_nat = …;

static void __exit nf_nat_sip_fini(void)
{ … }

static const struct nf_nat_sip_hooks sip_hooks = …;

static int __init nf_nat_sip_init(void)
{ … }

module_init(…) …;
module_exit(nf_nat_sip_fini);