linux/net/netfilter/nf_conntrack_proto_gre.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Connection tracking protocol helper module for GRE.
 *
 * GRE is a generic encapsulation protocol, which is generally not very
 * suited for NAT, as it has no protocol-specific part as port numbers.
 *
 * It has an optional key field, which may help us distinguishing two
 * connections between the same two hosts.
 *
 * GRE is defined in RFC 1701 and RFC 1702, as well as RFC 2784
 *
 * PPTP is built on top of a modified version of GRE, and has a mandatory
 * field called "CallID", which serves us for the same purpose as the key
 * field in plain GRE.
 *
 * Documentation about 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]>
 */

#include <linux/module.h>
#include <linux/types.h>
#include <linux/timer.h>
#include <linux/list.h>
#include <linux/seq_file.h>
#include <linux/in.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <linux/slab.h>
#include <net/dst.h>
#include <net/net_namespace.h>
#include <net/netns/generic.h>
#include <net/netfilter/nf_conntrack_l4proto.h>
#include <net/netfilter/nf_conntrack_helper.h>
#include <net/netfilter/nf_conntrack_core.h>
#include <net/netfilter/nf_conntrack_timeout.h>
#include <linux/netfilter/nf_conntrack_proto_gre.h>
#include <linux/netfilter/nf_conntrack_pptp.h>

static const unsigned int gre_timeouts[GRE_CT_MAX] = …;

/* used when expectation is added */
static DEFINE_SPINLOCK(keymap_lock);

static inline struct nf_gre_net *gre_pernet(struct net *net)
{ … }

static inline int gre_key_cmpfn(const struct nf_ct_gre_keymap *km,
				const struct nf_conntrack_tuple *t)
{ … }

/* look up the source key for a given tuple */
static __be16 gre_keymap_lookup(struct net *net, struct nf_conntrack_tuple *t)
{ … }

/* add a single keymap entry, associate with specified master ct */
int nf_ct_gre_keymap_add(struct nf_conn *ct, enum ip_conntrack_dir dir,
			 struct nf_conntrack_tuple *t)
{ … }
EXPORT_SYMBOL_GPL(…);

/* destroy the keymap entries associated with specified master ct */
void nf_ct_gre_keymap_destroy(struct nf_conn *ct)
{ … }
EXPORT_SYMBOL_GPL(…);

/* PUBLIC CONNTRACK PROTO HELPER FUNCTIONS */

/* gre hdr info to tuple */
bool gre_pkt_to_tuple(const struct sk_buff *skb, unsigned int dataoff,
		      struct net *net, struct nf_conntrack_tuple *tuple)
{ … }

#ifdef CONFIG_NF_CONNTRACK_PROCFS
/* print private data for conntrack */
static void gre_print_conntrack(struct seq_file *s, struct nf_conn *ct)
{ … }
#endif

static unsigned int *gre_get_timeouts(struct net *net)
{ … }

/* Returns verdict for packet, and may modify conntrack */
int nf_conntrack_gre_packet(struct nf_conn *ct,
			    struct sk_buff *skb,
			    unsigned int dataoff,
			    enum ip_conntrack_info ctinfo,
			    const struct nf_hook_state *state)
{ … }

#ifdef CONFIG_NF_CONNTRACK_TIMEOUT

#include <linux/netfilter/nfnetlink.h>
#include <linux/netfilter/nfnetlink_cttimeout.h>

static int gre_timeout_nlattr_to_obj(struct nlattr *tb[],
				     struct net *net, void *data)
{ … }

static int
gre_timeout_obj_to_nlattr(struct sk_buff *skb, const void *data)
{ … }

static const struct nla_policy
gre_timeout_nla_policy[CTA_TIMEOUT_GRE_MAX+1] = …;
#endif /* CONFIG_NF_CONNTRACK_TIMEOUT */

void nf_conntrack_gre_init_net(struct net *net)
{ … }

/* protocol helper struct */
const struct nf_conntrack_l4proto nf_conntrack_l4proto_gre = …;