linux/net/netfilter/nf_conntrack_pptp.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Connection tracking support for PPTP (Point to Point Tunneling Protocol).
 * PPTP is a protocol for creating virtual private networks.
 * It is a specification defined by Microsoft and some vendors
 * working with Microsoft.  PPTP is built on top of a modified
 * version of the Internet Generic Routing Encapsulation Protocol.
 * GRE is defined in RFC 1701 and RFC 1702.  Documentation of
 * PPTP can be found in RFC 2637
 *
 * (C) 2000-2005 by Harald Welte <[email protected]>
 *
 * Development of this code funded by Astaro AG (http://www.astaro.com/)
 *
 * (C) 2006-2012 Patrick McHardy <[email protected]>
 *
 * Limitations:
 * 	 - We blindly assume that control connections are always
 * 	   established in PNS->PAC direction.  This is a violation
 *	   of RFC 2637
 * 	 - We can only support one single call within each session
 * TODO:
 *	 - testing of incoming PPTP calls
 */

#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/in.h>
#include <linux/tcp.h>

#include <net/netfilter/nf_conntrack.h>
#include <net/netfilter/nf_conntrack_core.h>
#include <net/netfilter/nf_conntrack_helper.h>
#include <net/netfilter/nf_conntrack_zones.h>
#include <linux/netfilter/nf_conntrack_proto_gre.h>
#include <linux/netfilter/nf_conntrack_pptp.h>

#define NF_CT_PPTP_VERSION …

MODULE_LICENSE(…) …;
MODULE_AUTHOR(…) …;
MODULE_DESCRIPTION(…) …;
MODULE_ALIAS(…) …;
MODULE_ALIAS_NFCT_HELPER(…) …;

static DEFINE_SPINLOCK(nf_pptp_lock);

const struct nf_nat_pptp_hook __rcu *nf_nat_pptp_hook;
EXPORT_SYMBOL_GPL(…);

#if defined(DEBUG) || defined(CONFIG_DYNAMIC_DEBUG)
/* PptpControlMessageType names */
static const char *const pptp_msg_name_array[PPTP_MSG_MAX + 1] = …;

const char *pptp_msg_name(u_int16_t msg)
{ … }
EXPORT_SYMBOL(…);
#endif

#define SECS …
#define MINS …
#define HOURS …

#define PPTP_GRE_TIMEOUT …
#define PPTP_GRE_STREAM_TIMEOUT …

static void pptp_expectfn(struct nf_conn *ct,
			 struct nf_conntrack_expect *exp)
{ … }

static int destroy_sibling_or_exp(struct net *net, struct nf_conn *ct,
				  const struct nf_conntrack_tuple *t)
{ … }

/* timeout GRE data connections */
static void pptp_destroy_siblings(struct nf_conn *ct)
{ … }

/* expect GRE connections (PNS->PAC and PAC->PNS direction) */
static int exp_gre(struct nf_conn *ct, __be16 callid, __be16 peer_callid)
{ … }

static int
pptp_inbound_pkt(struct sk_buff *skb, unsigned int protoff,
		 struct PptpControlHeader *ctlh,
		 union pptp_ctrl_union *pptpReq,
		 unsigned int reqlen,
		 struct nf_conn *ct,
		 enum ip_conntrack_info ctinfo)
{ … }

static int
pptp_outbound_pkt(struct sk_buff *skb, unsigned int protoff,
		  struct PptpControlHeader *ctlh,
		  union pptp_ctrl_union *pptpReq,
		  unsigned int reqlen,
		  struct nf_conn *ct,
		  enum ip_conntrack_info ctinfo)
{ … }

static const unsigned int pptp_msg_size[] = …;

/* track caller id inside control connection, call expect_related */
static int
conntrack_pptp_help(struct sk_buff *skb, unsigned int protoff,
		    struct nf_conn *ct, enum ip_conntrack_info ctinfo)

{ … }

static const struct nf_conntrack_expect_policy pptp_exp_policy = …;

/* control protocol helper */
static struct nf_conntrack_helper pptp __read_mostly = …;

static int __init nf_conntrack_pptp_init(void)
{ … }

static void __exit nf_conntrack_pptp_fini(void)
{ … }

module_init(…) …;
module_exit(nf_conntrack_pptp_fini);