linux/net/netfilter/xt_l2tp.c

// SPDX-License-Identifier: GPL-2.0-only
/* Kernel module to match L2TP header parameters. */

/* (C) 2013      James Chapman <[email protected]>
 */

#define pr_fmt(fmt) …
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/if_ether.h>
#include <net/ip.h>
#include <linux/ipv6.h>
#include <net/ipv6.h>
#include <net/udp.h>
#include <linux/l2tp.h>

#include <linux/netfilter_ipv4.h>
#include <linux/netfilter_ipv6.h>
#include <linux/netfilter_ipv4/ip_tables.h>
#include <linux/netfilter_ipv6/ip6_tables.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter/xt_tcpudp.h>
#include <linux/netfilter/xt_l2tp.h>

/* L2TP header masks */
#define L2TP_HDR_T_BIT …
#define L2TP_HDR_L_BIT …
#define L2TP_HDR_VER …

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

/* The L2TP fields that can be matched */
struct l2tp_data { … };

l2tp_val;

static bool l2tp_match(const struct xt_l2tp_info *info, struct l2tp_data *data)
{ … }

/* Parse L2TP header fields when UDP encapsulation is used. Handles
 * L2TPv2 and L2TPv3. Note the L2TPv3 control and data packets have a
 * different format. See
 * RFC2661, Section 3.1, L2TPv2 Header Format
 * RFC3931, Section 3.2.1, L2TPv3 Control Message Header
 * RFC3931, Section 3.2.2, L2TPv3 Data Message Header
 * RFC3931, Section 4.1.2.1, L2TPv3 Session Header over UDP
 */
static bool l2tp_udp_mt(const struct sk_buff *skb, struct xt_action_param *par, u16 thoff)
{ … }

/* Parse L2TP header fields for IP encapsulation (no UDP header).
 * L2TPv3 data packets have a different form with IP encap. See
 * RC3931, Section 4.1.1.1, L2TPv3 Session Header over IP.
 * RC3931, Section 4.1.1.2, L2TPv3 Control and Data Traffic over IP.
 */
static bool l2tp_ip_mt(const struct sk_buff *skb, struct xt_action_param *par, u16 thoff)
{ … }

static bool l2tp_mt4(const struct sk_buff *skb, struct xt_action_param *par)
{ … }

#if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
static bool l2tp_mt6(const struct sk_buff *skb, struct xt_action_param *par)
{ … }
#endif

static int l2tp_mt_check(const struct xt_mtchk_param *par)
{ … }

static int l2tp_mt_check4(const struct xt_mtchk_param *par)
{ … }

#if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
static int l2tp_mt_check6(const struct xt_mtchk_param *par)
{ … }
#endif

static struct xt_match l2tp_mt_reg[] __read_mostly = …;

static int __init l2tp_mt_init(void)
{ … }

static void __exit l2tp_mt_exit(void)
{ … }

module_init(…) …;
module_exit(l2tp_mt_exit);