blob: bdbead8a7a83c60360efe7895d5078aeb2ff23b9 [file] [log] [blame]
/*
* ip_conntrack_proto_gre.c - Version 3.0
*
* 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 <laforge@gnumonks.org>
*
* Development of this code funded by Astaro AG (http://www.astaro.com/)
*
*/
#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/skbuff.h>
#include <net/netfilter/nf_conntrack_l4proto.h>
#include <net/netfilter/nf_conntrack_helper.h>
#include <net/netfilter/nf_conntrack_core.h>
#include <linux/netfilter/nf_conntrack_proto_gre.h>
#include <linux/netfilter/nf_conntrack_pptp.h>
#define GRE_TIMEOUT (30 * HZ)
#define GRE_STREAM_TIMEOUT (180 * HZ)
static DEFINE_RWLOCK(nf_ct_gre_lock);
static LIST_HEAD(gre_keymap_list);
void nf_ct_gre_keymap_flush(void)
{
struct list_head *pos, *n;
write_lock_bh(&nf_ct_gre_lock);
list_for_each_safe(pos, n, &gre_keymap_list) {
list_del(pos);
kfree(pos);
}
write_unlock_bh(&nf_ct_gre_lock);
}
EXPORT_SYMBOL(nf_ct_gre_keymap_flush);
static inline int gre_key_cmpfn(const struct nf_ct_gre_keymap *km,
const struct nf_conntrack_tuple *t)
{
return km->tuple.src.l3num == t->src.l3num &&
!memcmp(&km->tuple.src.u3, &t->src.u3, sizeof(t->src.u3)) &&
!memcmp(&km->tuple.dst.u3, &t->dst.u3, sizeof(t->dst.u3)) &&
km->tuple.dst.protonum == t->dst.protonum &&
km->tuple.dst.u.all == t->dst.u.all;
}
/* look up the source key for a given tuple */
static __be16 gre_keymap_lookup(struct nf_conntrack_tuple *t)
{
struct nf_ct_gre_keymap *km;
__be16 key = 0;
read_lock_bh(&nf_ct_gre_lock);
list_for_each_entry(km, &gre_keymap_list, list) {
if (gre_key_cmpfn(km, t)) {
key = km->tuple.src.u.gre.key;
break;
}
}
read_unlock_bh(&nf_ct_gre_lock);
pr_debug("lookup src key 0x%x for ", key);
NF_CT_DUMP_TUPLE(t);
return key;
}
/* 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)
{
struct nf_conn_help *help = nfct_help(ct);
struct nf_ct_gre_keymap **kmp, *km;
kmp = &help->help.ct_pptp_info.keymap[dir];
if (*kmp) {
/* check whether it's a retransmission */
list_for_each_entry(km, &gre_keymap_list, list) {
if (gre_key_cmpfn(km, t) && km == *kmp)
return 0;
}
pr_debug("trying to override keymap_%s for ct %p\n",
dir == IP_CT_DIR_REPLY ? "reply" : "orig", ct);
return -EEXIST;
}
km = kmalloc(sizeof(*km), GFP_ATOMIC);
if (!km)
return -ENOMEM;
memcpy(&km->tuple, t, sizeof(*t));
*kmp = km;
pr_debug("adding new entry %p: ", km);
NF_CT_DUMP_TUPLE(&km->tuple);
write_lock_bh(&nf_ct_gre_lock);
list_add_tail(&km->list, &gre_keymap_list);
write_unlock_bh(&nf_ct_gre_lock);
return 0;
}
EXPORT_SYMBOL_GPL(nf_ct_gre_keymap_add);
/* destroy the keymap entries associated with specified master ct */
void nf_ct_gre_keymap_destroy(struct nf_conn *ct)
{
struct nf_conn_help *help = nfct_help(ct);
enum ip_conntrack_dir dir;
pr_debug("entering for ct %p\n", ct);
write_lock_bh(&nf_ct_gre_lock);
for (dir = IP_CT_DIR_ORIGINAL; dir < IP_CT_DIR_MAX; dir++) {
if (help->help.ct_pptp_info.keymap[dir]) {
pr_debug("removing %p from list\n",
help->help.ct_pptp_info.keymap[dir]);
list_del(&help->help.ct_pptp_info.keymap[dir]->list);
kfree(help->help.ct_pptp_info.keymap[dir]);
help->help.ct_pptp_info.keymap[dir] = NULL;
}
}
write_unlock_bh(&nf_ct_gre_lock);
}
EXPORT_SYMBOL_GPL(nf_ct_gre_keymap_destroy);
/* PUBLIC CONNTRACK PROTO HELPER FUNCTIONS */
/* invert gre part of tuple */
static int gre_invert_tuple(struct nf_conntrack_tuple *tuple,
const struct nf_conntrack_tuple *orig)
{
tuple->dst.u.gre.key = orig->src.u.gre.key;
tuple->src.u.gre.key = orig->dst.u.gre.key;
return 1;
}
/* gre hdr info to tuple */
static int gre_pkt_to_tuple(const struct sk_buff *skb,
unsigned int dataoff,
struct nf_conntrack_tuple *tuple)
{
struct gre_hdr_pptp _pgrehdr, *pgrehdr;
__be16 srckey;
struct gre_hdr _grehdr, *grehdr;
/* first only delinearize old RFC1701 GRE header */
grehdr = skb_header_pointer(skb, dataoff, sizeof(_grehdr), &_grehdr);
if (!grehdr || grehdr->version != GRE_VERSION_PPTP) {
/* try to behave like "nf_conntrack_proto_generic" */
tuple->src.u.all = 0;
tuple->dst.u.all = 0;
return 1;
}
/* PPTP header is variable length, only need up to the call_id field */
pgrehdr = skb_header_pointer(skb, dataoff, 8, &_pgrehdr);
if (!pgrehdr)
return 1;
if (ntohs(grehdr->protocol) != GRE_PROTOCOL_PPTP) {
pr_debug("GRE_VERSION_PPTP but unknown proto\n");
return 0;
}
tuple->dst.u.gre.key = pgrehdr->call_id;
srckey = gre_keymap_lookup(tuple);
tuple->src.u.gre.key = srckey;
return 1;
}
/* print gre part of tuple */
static int gre_print_tuple(struct seq_file *s,
const struct nf_conntrack_tuple *tuple)
{
return seq_printf(s, "srckey=0x%x dstkey=0x%x ",
ntohs(tuple->src.u.gre.key),
ntohs(tuple->dst.u.gre.key));
}
/* print private data for conntrack */
static int gre_print_conntrack(struct seq_file *s,
const struct nf_conn *ct)
{
return seq_printf(s, "timeout=%u, stream_timeout=%u ",
(ct->proto.gre.timeout / HZ),
(ct->proto.gre.stream_timeout / HZ));
}
/* Returns verdict for packet, and may modify conntrack */
static int gre_packet(struct nf_conn *ct,
const struct sk_buff *skb,
unsigned int dataoff,
enum ip_conntrack_info ctinfo,
int pf,
unsigned int hooknum)
{
/* If we've seen traffic both ways, this is a GRE connection.
* Extend timeout. */
if (ct->status & IPS_SEEN_REPLY) {
nf_ct_refresh_acct(ct, ctinfo, skb,
ct->proto.gre.stream_timeout);
/* Also, more likely to be important, and not a probe. */
set_bit(IPS_ASSURED_BIT, &ct->status);
nf_conntrack_event_cache(IPCT_STATUS, skb);
} else
nf_ct_refresh_acct(ct, ctinfo, skb,
ct->proto.gre.timeout);
return NF_ACCEPT;
}
/* Called when a new connection for this protocol found. */
static int gre_new(struct nf_conn *ct, const struct sk_buff *skb,
unsigned int dataoff)
{
pr_debug(": ");
NF_CT_DUMP_TUPLE(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple);
/* initialize to sane value. Ideally a conntrack helper
* (e.g. in case of pptp) is increasing them */
ct->proto.gre.stream_timeout = GRE_STREAM_TIMEOUT;
ct->proto.gre.timeout = GRE_TIMEOUT;
return 1;
}
/* Called when a conntrack entry has already been removed from the hashes
* and is about to be deleted from memory */
static void gre_destroy(struct nf_conn *ct)
{
struct nf_conn *master = ct->master;
pr_debug(" entering\n");
if (!master)
pr_debug("no master !?!\n");
else
nf_ct_gre_keymap_destroy(master);
}
/* protocol helper struct */
static struct nf_conntrack_l4proto nf_conntrack_l4proto_gre4 __read_mostly = {
.l3proto = AF_INET,
.l4proto = IPPROTO_GRE,
.name = "gre",
.pkt_to_tuple = gre_pkt_to_tuple,
.invert_tuple = gre_invert_tuple,
.print_tuple = gre_print_tuple,
.print_conntrack = gre_print_conntrack,
.packet = gre_packet,
.new = gre_new,
.destroy = gre_destroy,
.me = THIS_MODULE,
#if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
.tuple_to_nfattr = nf_ct_port_tuple_to_nfattr,
.nfattr_to_tuple = nf_ct_port_nfattr_to_tuple,
#endif
};
static int __init nf_ct_proto_gre_init(void)
{
return nf_conntrack_l4proto_register(&nf_conntrack_l4proto_gre4);
}
static void nf_ct_proto_gre_fini(void)
{
nf_conntrack_l4proto_unregister(&nf_conntrack_l4proto_gre4);
nf_ct_gre_keymap_flush();
}
module_init(nf_ct_proto_gre_init);
module_exit(nf_ct_proto_gre_fini);
MODULE_LICENSE("GPL");