--- /dev/null
+/*
+ * 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)
+
+#if 0
+#define DEBUGP(format, args...) printk(KERN_DEBUG "%s:%s: " format, __FILE__, __FUNCTION__, ## args)
+#else
+#define DEBUGP(x, args...)
+#endif
+
+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);
+
+ DEBUGP("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;
+
+ BUG_ON(strcmp(help->helper->name, "pptp"));
+ 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;
+ }
+ DEBUGP("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;
+
+ DEBUGP("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;
+
+ DEBUGP("entering for ct %p\n", ct);
+ BUG_ON(strcmp(help->helper->name, "pptp"));
+
+ 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]) {
+ DEBUGP("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) {
+ DEBUGP("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)
+{
+ DEBUGP(": ");
+ 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;
+ DEBUGP(" entering\n");
+
+ if (!master)
+ DEBUGP("no master !?!\n");
+ else
+ nf_ct_gre_keymap_destroy(master);
+}
+
+/* protocol helper struct */
+static struct nf_conntrack_l4proto nf_conntrack_l4proto_gre4 = {
+ .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");
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