[NETFILTER]: nf_conntrack/nf_nat: add PPTP helper port

Add nf_conntrack port of the PPtP conntrack/NAT helper. Since there seems
to be no IPv6-capable PPtP implementation the helper only support IPv4.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

9 files changed, 1449 insertions, 0 deletions

diff --git a/net/ipv4/netfilter/Kconfig b/net/ipv4/netfilter/Kconfig
index 4555f721dfc1..c3327ac024de 100644
--- a/net/ipv4/netfilter/Kconfig
+++ b/net/ipv4/netfilter/Kconfig
@@ -484,6 +484,10 @@ config IP_NF_NAT_SNMP_BASIC
 #           <expr> '&&' <expr>                   (6)
 #
 # (6) Returns the result of min(/expr/, /expr/).
+config NF_NAT_PROTO_GRE
+	tristate
+	depends on NF_NAT && NF_CT_PROTO_GRE
+
 config IP_NF_NAT_FTP
 	tristate
 	depends on IP_NF_IPTABLES && IP_NF_CONNTRACK && IP_NF_NAT
@@ -528,6 +532,12 @@ config IP_NF_NAT_PPTP
 	default IP_NF_NAT if IP_NF_PPTP=y
 	default m if IP_NF_PPTP=m
 
+config NF_NAT_PPTP
+	tristate
+	depends on IP_NF_IPTABLES && NF_CONNTRACK && NF_NAT
+	default NF_NAT && NF_CONNTRACK_PPTP
+	select NF_NAT_PROTO_GRE
+
 config IP_NF_NAT_H323
 	tristate
 	depends on IP_NF_IPTABLES!=n && IP_NF_CONNTRACK!=n && IP_NF_NAT!=n
diff --git a/net/ipv4/netfilter/Makefile b/net/ipv4/netfilter/Makefile
index 56733c370327..ef33ff2cdda9 100644
--- a/net/ipv4/netfilter/Makefile
+++ b/net/ipv4/netfilter/Makefile
@@ -54,6 +54,10 @@ obj-$(CONFIG_NF_NAT_AMANDA) += nf_nat_amanda.o
 obj-$(CONFIG_NF_NAT_FTP) += nf_nat_ftp.o
 obj-$(CONFIG_NF_NAT_H323) += nf_nat_h323.o
 obj-$(CONFIG_NF_NAT_IRC) += nf_nat_irc.o
+obj-$(CONFIG_NF_NAT_PPTP) += nf_nat_pptp.o
+
+# NAT protocols (nf_nat)
+obj-$(CONFIG_NF_NAT_PROTO_GRE) += nf_nat_proto_gre.o
 
 # generic IP tables 
 obj-$(CONFIG_IP_NF_IPTABLES) += ip_tables.o
diff --git a/net/ipv4/netfilter/nf_nat_pptp.c b/net/ipv4/netfilter/nf_nat_pptp.c
new file mode 100644
index 000000000000..0ae45b79a4eb
--- /dev/null
+++ b/net/ipv4/netfilter/nf_nat_pptp.c
@@ -0,0 +1,315 @@
+/*
+ * nf_nat_pptp.c
+ *
+ * NAT support for PPTP (Point to Point Tunneling Protocol).
+ * PPTP is a 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 <laforge@gnumonks.org>
+ *
+ * Development of this code funded by Astaro AG (http://www.astaro.com/)
+ *
+ * TODO: - NAT to a unique tuple, not to TCP source port
+ * 	   (needs netfilter tuple reservation)
+ */
+
+#include <linux/module.h>
+#include <linux/tcp.h>
+
+#include <net/netfilter/nf_nat.h>
+#include <net/netfilter/nf_nat_helper.h>
+#include <net/netfilter/nf_nat_rule.h>
+#include <net/netfilter/nf_conntrack_helper.h>
+#include <net/netfilter/nf_conntrack_expect.h>
+#include <linux/netfilter/nf_conntrack_proto_gre.h>
+#include <linux/netfilter/nf_conntrack_pptp.h>
+
+#define NF_NAT_PPTP_VERSION "3.0"
+
+#define REQ_CID(req, off)		(*(__be16 *)((char *)(req) + (off)))
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
+MODULE_DESCRIPTION("Netfilter NAT helper module for PPTP");
+MODULE_ALIAS("ip_nat_pptp");
+
+#if 0
+extern const char *pptp_msg_name[];
+#define DEBUGP(format, args...) printk(KERN_DEBUG "%s:%s: " format, __FILE__, \
+				       __FUNCTION__, ## args)
+#else
+#define DEBUGP(format, args...)
+#endif
+
+static void pptp_nat_expected(struct nf_conn *ct,
+			      struct nf_conntrack_expect *exp)
+{
+	struct nf_conn *master = ct->master;
+	struct nf_conntrack_expect *other_exp;
+	struct nf_conntrack_tuple t;
+	struct nf_ct_pptp_master *ct_pptp_info;
+	struct nf_nat_pptp *nat_pptp_info;
+	struct ip_nat_range range;
+
+	ct_pptp_info = &nfct_help(master)->help.ct_pptp_info;
+	nat_pptp_info = &nfct_nat(master)->help.nat_pptp_info;
+
+	/* And here goes the grand finale of corrosion... */
+	if (exp->dir == IP_CT_DIR_ORIGINAL) {
+		DEBUGP("we are PNS->PAC\n");
+		/* therefore, build tuple for PAC->PNS */
+		t.src.l3num = AF_INET;
+		t.src.u3.ip = master->tuplehash[!exp->dir].tuple.src.u3.ip;
+		t.src.u.gre.key = ct_pptp_info->pac_call_id;
+		t.dst.u3.ip = master->tuplehash[!exp->dir].tuple.dst.u3.ip;
+		t.dst.u.gre.key = ct_pptp_info->pns_call_id;
+		t.dst.protonum = IPPROTO_GRE;
+	} else {
+		DEBUGP("we are PAC->PNS\n");
+		/* build tuple for PNS->PAC */
+		t.src.l3num = AF_INET;
+		t.src.u3.ip = master->tuplehash[exp->dir].tuple.src.u3.ip;
+		t.src.u.gre.key = nat_pptp_info->pns_call_id;
+		t.dst.u3.ip = master->tuplehash[exp->dir].tuple.dst.u3.ip;
+		t.dst.u.gre.key = nat_pptp_info->pac_call_id;
+		t.dst.protonum = IPPROTO_GRE;
+	}
+
+	DEBUGP("trying to unexpect other dir: ");
+	NF_CT_DUMP_TUPLE(&t);
+	other_exp = nf_conntrack_expect_find_get(&t);
+	if (other_exp) {
+		nf_conntrack_unexpect_related(other_exp);
+		nf_conntrack_expect_put(other_exp);
+		DEBUGP("success\n");
+	} else {
+		DEBUGP("not found!\n");
+	}
+
+	/* This must be a fresh one. */
+	BUG_ON(ct->status & IPS_NAT_DONE_MASK);
+
+	/* Change src to where master sends to */
+	range.flags = IP_NAT_RANGE_MAP_IPS;
+	range.min_ip = range.max_ip
+		= ct->master->tuplehash[!exp->dir].tuple.dst.u3.ip;
+	if (exp->dir == IP_CT_DIR_ORIGINAL) {
+		range.flags |= IP_NAT_RANGE_PROTO_SPECIFIED;
+		range.min = range.max = exp->saved_proto;
+	}
+	/* hook doesn't matter, but it has to do source manip */
+	nf_nat_setup_info(ct, &range, NF_IP_POST_ROUTING);
+
+	/* For DST manip, map port here to where it's expected. */
+	range.flags = IP_NAT_RANGE_MAP_IPS;
+	range.min_ip = range.max_ip
+		= ct->master->tuplehash[!exp->dir].tuple.src.u3.ip;
+	if (exp->dir == IP_CT_DIR_REPLY) {
+		range.flags |= IP_NAT_RANGE_PROTO_SPECIFIED;
+		range.min = range.max = exp->saved_proto;
+	}
+	/* hook doesn't matter, but it has to do destination manip */
+	nf_nat_setup_info(ct, &range, NF_IP_PRE_ROUTING);
+}
+
+/* outbound packets == from PNS to PAC */
+static int
+pptp_outbound_pkt(struct sk_buff **pskb,
+		  struct nf_conn *ct,
+		  enum ip_conntrack_info ctinfo,
+		  struct PptpControlHeader *ctlh,
+		  union pptp_ctrl_union *pptpReq)
+
+{
+	struct nf_ct_pptp_master *ct_pptp_info;
+	struct nf_nat_pptp *nat_pptp_info;
+	u_int16_t msg;
+	__be16 new_callid;
+	unsigned int cid_off;
+
+	ct_pptp_info  = &nfct_help(ct)->help.ct_pptp_info;
+	nat_pptp_info = &nfct_nat(ct)->help.nat_pptp_info;
+
+	new_callid = ct_pptp_info->pns_call_id;
+
+	switch (msg = ntohs(ctlh->messageType)) {
+	case PPTP_OUT_CALL_REQUEST:
+		cid_off = offsetof(union pptp_ctrl_union, ocreq.callID);
+		/* FIXME: ideally we would want to reserve a call ID
+		 * here.  current netfilter NAT core is not able to do
+		 * this :( For now we use TCP source port. This breaks
+		 * multiple calls within one control session */
+
+		/* save original call ID in nat_info */
+		nat_pptp_info->pns_call_id = ct_pptp_info->pns_call_id;
+
+		/* don't use tcph->source since we are at a DSTmanip
+		 * hook (e.g. PREROUTING) and pkt is not mangled yet */
+		new_callid = ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u.tcp.port;
+
+		/* save new call ID in ct info */
+		ct_pptp_info->pns_call_id = new_callid;
+		break;
+	case PPTP_IN_CALL_REPLY:
+		cid_off = offsetof(union pptp_ctrl_union, icack.callID);
+		break;
+	case PPTP_CALL_CLEAR_REQUEST:
+		cid_off = offsetof(union pptp_ctrl_union, clrreq.callID);
+		break;
+	default:
+		DEBUGP("unknown outbound packet 0x%04x:%s\n", msg,
+		      (msg <= PPTP_MSG_MAX)?
+		      pptp_msg_name[msg]:pptp_msg_name[0]);
+		/* fall through */
+	case PPTP_SET_LINK_INFO:
+		/* only need to NAT in case PAC is behind NAT box */
+	case PPTP_START_SESSION_REQUEST:
+	case PPTP_START_SESSION_REPLY:
+	case PPTP_STOP_SESSION_REQUEST:
+	case PPTP_STOP_SESSION_REPLY:
+	case PPTP_ECHO_REQUEST:
+	case PPTP_ECHO_REPLY:
+		/* no need to alter packet */
+		return NF_ACCEPT;
+	}
+
+	/* only OUT_CALL_REQUEST, IN_CALL_REPLY, CALL_CLEAR_REQUEST pass
+	 * down to here */
+	DEBUGP("altering call id from 0x%04x to 0x%04x\n",
+		ntohs(REQ_CID(pptpReq, cid_off)), ntohs(new_callid));
+
+	/* mangle packet */
+	if (nf_nat_mangle_tcp_packet(pskb, ct, ctinfo,
+	                             cid_off + sizeof(struct pptp_pkt_hdr) +
+	                             sizeof(struct PptpControlHeader),
+	                             sizeof(new_callid), (char *)&new_callid,
+	                             sizeof(new_callid)) == 0)
+		return NF_DROP;
+	return NF_ACCEPT;
+}
+
+static void
+pptp_exp_gre(struct nf_conntrack_expect *expect_orig,
+	     struct nf_conntrack_expect *expect_reply)
+{
+	struct nf_conn *ct = expect_orig->master;
+	struct nf_ct_pptp_master *ct_pptp_info;
+	struct nf_nat_pptp *nat_pptp_info;
+
+	ct_pptp_info  = &nfct_help(ct)->help.ct_pptp_info;
+	nat_pptp_info = &nfct_nat(ct)->help.nat_pptp_info;
+
+	/* save original PAC call ID in nat_info */
+	nat_pptp_info->pac_call_id = ct_pptp_info->pac_call_id;
+
+	/* alter expectation for PNS->PAC direction */
+	expect_orig->saved_proto.gre.key = ct_pptp_info->pns_call_id;
+	expect_orig->tuple.src.u.gre.key = nat_pptp_info->pns_call_id;
+	expect_orig->tuple.dst.u.gre.key = ct_pptp_info->pac_call_id;
+	expect_orig->dir = IP_CT_DIR_ORIGINAL;
+
+	/* alter expectation for PAC->PNS direction */
+	expect_reply->saved_proto.gre.key = nat_pptp_info->pns_call_id;
+	expect_reply->tuple.src.u.gre.key = nat_pptp_info->pac_call_id;
+	expect_reply->tuple.dst.u.gre.key = ct_pptp_info->pns_call_id;
+	expect_reply->dir = IP_CT_DIR_REPLY;
+}
+
+/* inbound packets == from PAC to PNS */
+static int
+pptp_inbound_pkt(struct sk_buff **pskb,
+		 struct nf_conn *ct,
+		 enum ip_conntrack_info ctinfo,
+		 struct PptpControlHeader *ctlh,
+		 union pptp_ctrl_union *pptpReq)
+{
+	struct nf_nat_pptp *nat_pptp_info;
+	u_int16_t msg;
+	__be16 new_pcid;
+	unsigned int pcid_off;
+
+	nat_pptp_info = &nfct_nat(ct)->help.nat_pptp_info;
+	new_pcid = nat_pptp_info->pns_call_id;
+
+	switch (msg = ntohs(ctlh->messageType)) {
+	case PPTP_OUT_CALL_REPLY:
+		pcid_off = offsetof(union pptp_ctrl_union, ocack.peersCallID);
+		break;
+	case PPTP_IN_CALL_CONNECT:
+		pcid_off = offsetof(union pptp_ctrl_union, iccon.peersCallID);
+		break;
+	case PPTP_IN_CALL_REQUEST:
+		/* only need to nat in case PAC is behind NAT box */
+		return NF_ACCEPT;
+	case PPTP_WAN_ERROR_NOTIFY:
+		pcid_off = offsetof(union pptp_ctrl_union, wanerr.peersCallID);
+		break;
+	case PPTP_CALL_DISCONNECT_NOTIFY:
+		pcid_off = offsetof(union pptp_ctrl_union, disc.callID);
+		break;
+	case PPTP_SET_LINK_INFO:
+		pcid_off = offsetof(union pptp_ctrl_union, setlink.peersCallID);
+		break;
+	default:
+		DEBUGP("unknown inbound packet %s\n", (msg <= PPTP_MSG_MAX)?
+			pptp_msg_name[msg]:pptp_msg_name[0]);
+		/* fall through */
+	case PPTP_START_SESSION_REQUEST:
+	case PPTP_START_SESSION_REPLY:
+	case PPTP_STOP_SESSION_REQUEST:
+	case PPTP_STOP_SESSION_REPLY:
+	case PPTP_ECHO_REQUEST:
+	case PPTP_ECHO_REPLY:
+		/* no need to alter packet */
+		return NF_ACCEPT;
+	}
+
+	/* only OUT_CALL_REPLY, IN_CALL_CONNECT, IN_CALL_REQUEST,
+	 * WAN_ERROR_NOTIFY, CALL_DISCONNECT_NOTIFY pass down here */
+
+	/* mangle packet */
+	DEBUGP("altering peer call id from 0x%04x to 0x%04x\n",
+		ntohs(REQ_CID(pptpReq, pcid_off)), ntohs(new_pcid));
+
+	if (nf_nat_mangle_tcp_packet(pskb, ct, ctinfo,
+	                             pcid_off + sizeof(struct pptp_pkt_hdr) +
+				     sizeof(struct PptpControlHeader),
+				     sizeof(new_pcid), (char *)&new_pcid,
+				     sizeof(new_pcid)) == 0)
+		return NF_DROP;
+	return NF_ACCEPT;
+}
+
+static int __init nf_nat_helper_pptp_init(void)
+{
+	nf_nat_need_gre();
+
+	BUG_ON(rcu_dereference(nf_nat_pptp_hook_outbound));
+	rcu_assign_pointer(nf_nat_pptp_hook_outbound, pptp_outbound_pkt);
+
+	BUG_ON(rcu_dereference(nf_nat_pptp_hook_inbound));
+	rcu_assign_pointer(nf_nat_pptp_hook_inbound, pptp_inbound_pkt);
+
+	BUG_ON(rcu_dereference(nf_nat_pptp_hook_exp_gre));
+	rcu_assign_pointer(nf_nat_pptp_hook_exp_gre, pptp_exp_gre);
+
+	BUG_ON(rcu_dereference(nf_nat_pptp_hook_expectfn));
+	rcu_assign_pointer(nf_nat_pptp_hook_expectfn, pptp_nat_expected);
+	return 0;
+}
+
+static void __exit nf_nat_helper_pptp_fini(void)
+{
+	rcu_assign_pointer(nf_nat_pptp_hook_expectfn, NULL);
+	rcu_assign_pointer(nf_nat_pptp_hook_exp_gre, NULL);
+	rcu_assign_pointer(nf_nat_pptp_hook_inbound, NULL);
+	rcu_assign_pointer(nf_nat_pptp_hook_outbound, NULL);
+	synchronize_rcu();
+}
+
+module_init(nf_nat_helper_pptp_init);
+module_exit(nf_nat_helper_pptp_fini);
diff --git a/net/ipv4/netfilter/nf_nat_proto_gre.c b/net/ipv4/netfilter/nf_nat_proto_gre.c
new file mode 100644
index 000000000000..d3de579e09d2
--- /dev/null
+++ b/net/ipv4/netfilter/nf_nat_proto_gre.c
@@ -0,0 +1,179 @@
+/*
+ * nf_nat_proto_gre.c
+ *
+ * NAT 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/skbuff.h>
+#include <linux/ip.h>
+
+#include <net/netfilter/nf_nat.h>
+#include <net/netfilter/nf_nat_rule.h>
+#include <net/netfilter/nf_nat_protocol.h>
+#include <linux/netfilter/nf_conntrack_proto_gre.h>
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
+MODULE_DESCRIPTION("Netfilter NAT protocol helper module for GRE");
+
+#if 0
+#define DEBUGP(format, args...) printk(KERN_DEBUG "%s:%s: " format, __FILE__, \
+				       __FUNCTION__, ## args)
+#else
+#define DEBUGP(x, args...)
+#endif
+
+/* is key in given range between min and max */
+static int
+gre_in_range(const struct nf_conntrack_tuple *tuple,
+	     enum nf_nat_manip_type maniptype,
+	     const union nf_conntrack_man_proto *min,
+	     const union nf_conntrack_man_proto *max)
+{
+	__be16 key;
+
+	if (maniptype == IP_NAT_MANIP_SRC)
+		key = tuple->src.u.gre.key;
+	else
+		key = tuple->dst.u.gre.key;
+
+	return ntohs(key) >= ntohs(min->gre.key) &&
+	       ntohs(key) <= ntohs(max->gre.key);
+}
+
+/* generate unique tuple ... */
+static int
+gre_unique_tuple(struct nf_conntrack_tuple *tuple,
+		 const struct nf_nat_range *range,
+		 enum nf_nat_manip_type maniptype,
+		 const struct nf_conn *conntrack)
+{
+	static u_int16_t key;
+	__be16 *keyptr;
+	unsigned int min, i, range_size;
+
+	if (maniptype == IP_NAT_MANIP_SRC)
+		keyptr = &tuple->src.u.gre.key;
+	else
+		keyptr = &tuple->dst.u.gre.key;
+
+	if (!(range->flags & IP_NAT_RANGE_PROTO_SPECIFIED)) {
+		DEBUGP("%p: NATing GRE PPTP\n", conntrack);
+		min = 1;
+		range_size = 0xffff;
+	} else {
+		min = ntohs(range->min.gre.key);
+		range_size = ntohs(range->max.gre.key) - min + 1;
+	}
+
+	DEBUGP("min = %u, range_size = %u\n", min, range_size);
+
+	for (i = 0; i < range_size; i++, key++) {
+		*keyptr = htons(min + key % range_size);
+		if (!nf_nat_used_tuple(tuple, conntrack))
+			return 1;
+	}
+
+	DEBUGP("%p: no NAT mapping\n", conntrack);
+	return 0;
+}
+
+/* manipulate a GRE packet according to maniptype */
+static int
+gre_manip_pkt(struct sk_buff **pskb, unsigned int iphdroff,
+	      const struct nf_conntrack_tuple *tuple,
+	      enum nf_nat_manip_type maniptype)
+{
+	struct gre_hdr *greh;
+	struct gre_hdr_pptp *pgreh;
+	struct iphdr *iph = (struct iphdr *)((*pskb)->data + iphdroff);
+	unsigned int hdroff = iphdroff + iph->ihl * 4;
+
+	/* pgreh includes two optional 32bit fields which are not required
+	 * to be there.  That's where the magic '8' comes from */
+	if (!skb_make_writable(pskb, hdroff + sizeof(*pgreh) - 8))
+		return 0;
+
+	greh = (void *)(*pskb)->data + hdroff;
+	pgreh = (struct gre_hdr_pptp *)greh;
+
+	/* we only have destination manip of a packet, since 'source key'
+	 * is not present in the packet itself */
+	if (maniptype != IP_NAT_MANIP_DST)
+		return 1;
+	switch (greh->version) {
+	case 0:
+		if (!greh->key) {
+			DEBUGP("can't nat GRE w/o key\n");
+			break;
+		}
+		if (greh->csum) {
+			/* FIXME: Never tested this code... */
+			nf_proto_csum_replace4(gre_csum(greh), *pskb,
+					       *(gre_key(greh)),
+					       tuple->dst.u.gre.key, 0);
+		}
+		*(gre_key(greh)) = tuple->dst.u.gre.key;
+		break;
+	case GRE_VERSION_PPTP:
+		DEBUGP("call_id -> 0x%04x\n", ntohs(tuple->dst.u.gre.key));
+		pgreh->call_id = tuple->dst.u.gre.key;
+		break;
+	default:
+		DEBUGP("can't nat unknown GRE version\n");
+		return 0;
+	}
+	return 1;
+}
+
+static struct nf_nat_protocol gre __read_mostly = {
+	.name			= "GRE",
+	.protonum		= IPPROTO_GRE,
+	.manip_pkt		= gre_manip_pkt,
+	.in_range		= gre_in_range,
+	.unique_tuple		= gre_unique_tuple,
+#if defined(CONFIG_IP_NF_CONNTRACK_NETLINK) || \
+    defined(CONFIG_IP_NF_CONNTRACK_NETLINK_MODULE)
+	.range_to_nfattr	= nf_nat_port_range_to_nfattr,
+	.nfattr_to_range	= nf_nat_port_nfattr_to_range,
+#endif
+};
+
+int __init nf_nat_proto_gre_init(void)
+{
+	return nf_nat_protocol_register(&gre);
+}
+
+void __exit nf_nat_proto_gre_fini(void)
+{
+	nf_nat_protocol_unregister(&gre);
+}
+
+module_init(nf_nat_proto_gre_init);
+module_exit(nf_nat_proto_gre_fini);
+
+void nf_nat_need_gre(void)
+{
+	return;
+}
+EXPORT_SYMBOL_GPL(nf_nat_need_gre);
diff --git a/net/netfilter/Kconfig b/net/netfilter/Kconfig
index d1a365d83c53..6b2eb26ae03f 100644
--- a/net/netfilter/Kconfig
+++ b/net/netfilter/Kconfig
@@ -120,6 +120,10 @@ config NF_CONNTRACK_EVENTS
 
 	  If unsure, say `N'.
 
+config NF_CT_PROTO_GRE
+	tristate
+	depends on EXPERIMENTAL && NF_CONNTRACK
+
 config NF_CT_PROTO_SCTP
 	tristate 'SCTP protocol on new connection tracking support (EXPERIMENTAL)'
 	depends on EXPERIMENTAL && NF_CONNTRACK
@@ -213,6 +217,25 @@ config NF_CONNTRACK_NETBIOS_NS
 
 	  To compile it as a module, choose M here.  If unsure, say N.
 
+config NF_CONNTRACK_PPTP
+	tristate "PPtP protocol support (EXPERIMENTAL)"
+	depends on EXPERIMENTAL && NF_CONNTRACK
+	select NF_CT_PROTO_GRE
+	help
+	  This module adds support for PPTP (Point to Point Tunnelling
+	  Protocol, RFC2637) connection tracking and NAT.
+
+	  If you are running PPTP sessions over a stateful firewall or NAT
+	  box, you may want to enable this feature.
+
+	  Please note that not all PPTP modes of operation are supported yet.
+	  Specifically these limitations exist:
+	    - Blindy assumes that control connections are always established
+	      in PNS->PAC direction. This is a violation of RFC2637.
+	    - Only supports a single call within each session
+
+	  To compile it as a module, choose M here.  If unsure, say N.
+
 config NF_CT_NETLINK
 	tristate 'Connection tracking netlink interface (EXPERIMENTAL)'
 	depends on EXPERIMENTAL && NF_CONNTRACK && NETFILTER_NETLINK
diff --git a/net/netfilter/Makefile b/net/netfilter/Makefile
index 67144b2af647..897bed4cbd79 100644
--- a/net/netfilter/Makefile
+++ b/net/netfilter/Makefile
@@ -14,6 +14,7 @@ obj-$(CONFIG_NETFILTER_NETLINK_LOG) += nfnetlink_log.o
 obj-$(CONFIG_NF_CONNTRACK) += nf_conntrack.o
 
 # SCTP protocol connection tracking
+obj-$(CONFIG_NF_CT_PROTO_GRE) += nf_conntrack_proto_gre.o
 obj-$(CONFIG_NF_CT_PROTO_SCTP) += nf_conntrack_proto_sctp.o
 
 # netlink interface for nf_conntrack
@@ -27,6 +28,7 @@ obj-$(CONFIG_NF_CONNTRACK_FTP) += nf_conntrack_ftp.o
 obj-$(CONFIG_NF_CONNTRACK_H323) += nf_conntrack_h323.o
 obj-$(CONFIG_NF_CONNTRACK_IRC) += nf_conntrack_irc.o
 obj-$(CONFIG_NF_CONNTRACK_NETBIOS_NS) += nf_conntrack_netbios_ns.o
+obj-$(CONFIG_NF_CONNTRACK_PPTP) += nf_conntrack_pptp.o
 
 # generic X tables 
 obj-$(CONFIG_NETFILTER_XTABLES) += x_tables.o xt_tcpudp.o
diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index aa8beabfeebb..ed756c928bc4 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -300,6 +300,7 @@ static void
 destroy_conntrack(struct nf_conntrack *nfct)
 {
 	struct nf_conn *ct = (struct nf_conn *)nfct;
+	struct nf_conn_help *help = nfct_help(ct);
 	struct nf_conntrack_l3proto *l3proto;
 	struct nf_conntrack_l4proto *l4proto;
 
@@ -310,6 +311,9 @@ destroy_conntrack(struct nf_conntrack *nfct)
 	nf_conntrack_event(IPCT_DESTROY, ct);
 	set_bit(IPS_DYING_BIT, &ct->status);
 
+	if (help && help->helper && help->helper->destroy)
+		help->helper->destroy(ct);
+
 	/* To make sure we don't get any weird locking issues here:
 	 * destroy_conntrack() MUST NOT be called with a write lock
 	 * to nf_conntrack_lock!!! -HW */
diff --git a/net/netfilter/nf_conntrack_pptp.c b/net/netfilter/nf_conntrack_pptp.c
new file mode 100644
index 000000000000..f0ff00e0d052
--- /dev/null
+++ b/net/netfilter/nf_conntrack_pptp.c
@@ -0,0 +1,607 @@
+/*
+ * Connection tracking support for PPTP (Point to Point Tunneling Protocol).
+ * PPTP is a 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 <laforge@gnumonks.org>
+ *
+ * Development of this code funded by Astaro AG (http://www.astaro.com/)
+ *
+ * Limitations:
+ * 	 - We blindly assume that control connections are always
+ * 	   established in PNS->PAC direction.  This is a violation
+ * 	   of RFFC2673
+ * 	 - 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 <linux/netfilter/nf_conntrack_proto_gre.h>
+#include <linux/netfilter/nf_conntrack_pptp.h>
+
+#define NF_CT_PPTP_VERSION "3.1"
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
+MODULE_DESCRIPTION("Netfilter connection tracking helper module for PPTP");
+MODULE_ALIAS("ip_conntrack_pptp");
+
+static DEFINE_SPINLOCK(nf_pptp_lock);
+
+int
+(*nf_nat_pptp_hook_outbound)(struct sk_buff **pskb,
+			     struct nf_conn *ct, enum ip_conntrack_info ctinfo,
+			     struct PptpControlHeader *ctlh,
+			     union pptp_ctrl_union *pptpReq) __read_mostly;
+EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_outbound);
+
+int
+(*nf_nat_pptp_hook_inbound)(struct sk_buff **pskb,
+			    struct nf_conn *ct, enum ip_conntrack_info ctinfo,
+			    struct PptpControlHeader *ctlh,
+			    union pptp_ctrl_union *pptpReq) __read_mostly;
+EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_inbound);
+
+void
+(*nf_nat_pptp_hook_exp_gre)(struct nf_conntrack_expect *expect_orig,
+			    struct nf_conntrack_expect *expect_reply)
+			    __read_mostly;
+EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_exp_gre);
+
+void
+(*nf_nat_pptp_hook_expectfn)(struct nf_conn *ct,
+			     struct nf_conntrack_expect *exp) __read_mostly;
+EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_expectfn);
+
+#if 0
+/* PptpControlMessageType names */
+const char *pptp_msg_name[] = {
+	"UNKNOWN_MESSAGE",
+	"START_SESSION_REQUEST",
+	"START_SESSION_REPLY",
+	"STOP_SESSION_REQUEST",
+	"STOP_SESSION_REPLY",
+	"ECHO_REQUEST",
+	"ECHO_REPLY",
+	"OUT_CALL_REQUEST",
+	"OUT_CALL_REPLY",
+	"IN_CALL_REQUEST",
+	"IN_CALL_REPLY",
+	"IN_CALL_CONNECT",
+	"CALL_CLEAR_REQUEST",
+	"CALL_DISCONNECT_NOTIFY",
+	"WAN_ERROR_NOTIFY",
+	"SET_LINK_INFO"
+};
+EXPORT_SYMBOL(pptp_msg_name);
+#define DEBUGP(format, args...)	printk(KERN_DEBUG "%s:%s: " format, __FILE__, __FUNCTION__, ## args)
+#else
+#define DEBUGP(format, args...)
+#endif
+
+#define SECS *HZ
+#define MINS * 60 SECS
+#define HOURS * 60 MINS
+
+#define PPTP_GRE_TIMEOUT 		(10 MINS)
+#define PPTP_GRE_STREAM_TIMEOUT 	(5 HOURS)
+
+static void pptp_expectfn(struct nf_conn *ct,
+			 struct nf_conntrack_expect *exp)
+{
+	typeof(nf_nat_pptp_hook_expectfn) nf_nat_pptp_expectfn;
+	DEBUGP("increasing timeouts\n");
+
+	/* increase timeout of GRE data channel conntrack entry */
+	ct->proto.gre.timeout	     = PPTP_GRE_TIMEOUT;
+	ct->proto.gre.stream_timeout = PPTP_GRE_STREAM_TIMEOUT;
+
+	/* Can you see how rusty this code is, compared with the pre-2.6.11
+	 * one? That's what happened to my shiny newnat of 2002 ;( -HW */
+
+	rcu_read_lock();
+	nf_nat_pptp_expectfn = rcu_dereference(nf_nat_pptp_hook_expectfn);
+	if (nf_nat_pptp_expectfn && ct->status & IPS_NAT_MASK)
+		nf_nat_pptp_expectfn(ct, exp);
+	else {
+		struct nf_conntrack_tuple inv_t;
+		struct nf_conntrack_expect *exp_other;
+
+		/* obviously this tuple inversion only works until you do NAT */
+		nf_ct_invert_tuplepr(&inv_t, &exp->tuple);
+		DEBUGP("trying to unexpect other dir: ");
+		NF_CT_DUMP_TUPLE(&inv_t);
+
+		exp_other = nf_conntrack_expect_find_get(&inv_t);
+		if (exp_other) {
+			/* delete other expectation.  */
+			DEBUGP("found\n");
+			nf_conntrack_unexpect_related(exp_other);
+			nf_conntrack_expect_put(exp_other);
+		} else {
+			DEBUGP("not found\n");
+		}
+	}
+	rcu_read_unlock();
+}
+
+static int destroy_sibling_or_exp(const struct nf_conntrack_tuple *t)
+{
+	struct nf_conntrack_tuple_hash *h;
+	struct nf_conntrack_expect *exp;
+	struct nf_conn *sibling;
+
+	DEBUGP("trying to timeout ct or exp for tuple ");
+	NF_CT_DUMP_TUPLE(t);
+
+	h = nf_conntrack_find_get(t, NULL);
+	if (h)  {
+		sibling = nf_ct_tuplehash_to_ctrack(h);
+		DEBUGP("setting timeout of conntrack %p to 0\n", sibling);
+		sibling->proto.gre.timeout	  = 0;
+		sibling->proto.gre.stream_timeout = 0;
+		if (del_timer(&sibling->timeout))
+			sibling->timeout.function((unsigned long)sibling);
+		nf_ct_put(sibling);
+		return 1;
+	} else {
+		exp = nf_conntrack_expect_find_get(t);
+		if (exp) {
+			DEBUGP("unexpect_related of expect %p\n", exp);
+			nf_conntrack_unexpect_related(exp);
+			nf_conntrack_expect_put(exp);
+			return 1;
+		}
+	}
+	return 0;
+}
+
+/* timeout GRE data connections */
+static void pptp_destroy_siblings(struct nf_conn *ct)
+{
+	struct nf_conn_help *help = nfct_help(ct);
+	struct nf_conntrack_tuple t;
+
+	nf_ct_gre_keymap_destroy(ct);
+
+	/* try original (pns->pac) tuple */
+	memcpy(&t, &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple, sizeof(t));
+	t.dst.protonum = IPPROTO_GRE;
+	t.src.u.gre.key = help->help.ct_pptp_info.pns_call_id;
+	t.dst.u.gre.key = help->help.ct_pptp_info.pac_call_id;
+	if (!destroy_sibling_or_exp(&t))
+		DEBUGP("failed to timeout original pns->pac ct/exp\n");
+
+	/* try reply (pac->pns) tuple */
+	memcpy(&t, &ct->tuplehash[IP_CT_DIR_REPLY].tuple, sizeof(t));
+	t.dst.protonum = IPPROTO_GRE;
+	t.src.u.gre.key = help->help.ct_pptp_info.pac_call_id;
+	t.dst.u.gre.key = help->help.ct_pptp_info.pns_call_id;
+	if (!destroy_sibling_or_exp(&t))
+		DEBUGP("failed to timeout reply pac->pns ct/exp\n");
+}
+
+/* expect GRE connections (PNS->PAC and PAC->PNS direction) */
+static int exp_gre(struct nf_conn *ct, __be16 callid, __be16 peer_callid)
+{
+	struct nf_conntrack_expect *exp_orig, *exp_reply;
+	enum ip_conntrack_dir dir;
+	int ret = 1;
+	typeof(nf_nat_pptp_hook_exp_gre) nf_nat_pptp_exp_gre;
+
+	exp_orig = nf_conntrack_expect_alloc(ct);
+	if (exp_orig == NULL)
+		goto out;
+
+	exp_reply = nf_conntrack_expect_alloc(ct);
+	if (exp_reply == NULL)
+		goto out_put_orig;
+
+	/* original direction, PNS->PAC */
+	dir = IP_CT_DIR_ORIGINAL;
+	nf_conntrack_expect_init(exp_orig, ct->tuplehash[dir].tuple.src.l3num,
+				 &ct->tuplehash[dir].tuple.src.u3,
+				 &ct->tuplehash[dir].tuple.dst.u3,
+				 IPPROTO_GRE, &peer_callid, &callid);
+	exp_orig->expectfn = pptp_expectfn;
+
+	/* reply direction, PAC->PNS */
+	dir = IP_CT_DIR_REPLY;
+	nf_conntrack_expect_init(exp_reply, ct->tuplehash[dir].tuple.src.l3num,
+				 &ct->tuplehash[dir].tuple.src.u3,
+				 &ct->tuplehash[dir].tuple.dst.u3,
+				 IPPROTO_GRE, &callid, &peer_callid);
+	exp_reply->expectfn = pptp_expectfn;
+
+	nf_nat_pptp_exp_gre = rcu_dereference(nf_nat_pptp_hook_exp_gre);
+	if (nf_nat_pptp_exp_gre && ct->status & IPS_NAT_MASK)
+		nf_nat_pptp_exp_gre(exp_orig, exp_reply);
+	if (nf_conntrack_expect_related(exp_orig) != 0)
+		goto out_put_both;
+	if (nf_conntrack_expect_related(exp_reply) != 0)
+		goto out_unexpect_orig;
+
+	/* Add GRE keymap entries */
+	if (nf_ct_gre_keymap_add(ct, IP_CT_DIR_ORIGINAL, &exp_orig->tuple) != 0)
+		goto out_unexpect_both;
+	if (nf_ct_gre_keymap_add(ct, IP_CT_DIR_REPLY, &exp_reply->tuple) != 0) {
+		nf_ct_gre_keymap_destroy(ct);
+		goto out_unexpect_both;
+	}
+	ret = 0;
+
+out_put_both:
+	nf_conntrack_expect_put(exp_reply);
+out_put_orig:
+	nf_conntrack_expect_put(exp_orig);
+out:
+	return ret;
+
+out_unexpect_both:
+	nf_conntrack_unexpect_related(exp_reply);
+out_unexpect_orig:
+	nf_conntrack_unexpect_related(exp_orig);
+	goto out_put_both;
+}
+
+static inline int
+pptp_inbound_pkt(struct sk_buff **pskb,
+		 struct PptpControlHeader *ctlh,
+		 union pptp_ctrl_union *pptpReq,
+		 unsigned int reqlen,
+		 struct nf_conn *ct,
+		 enum ip_conntrack_info ctinfo)
+{
+	struct nf_ct_pptp_master *info = &nfct_help(ct)->help.ct_pptp_info;
+	u_int16_t msg;
+	__be16 cid = 0, pcid = 0;
+	typeof(nf_nat_pptp_hook_inbound) nf_nat_pptp_inbound;
+
+	msg = ntohs(ctlh->messageType);
+	DEBUGP("inbound control message %s\n", pptp_msg_name[msg]);
+
+	switch (msg) {
+	case PPTP_START_SESSION_REPLY:
+		/* server confirms new control session */
+		if (info->sstate < PPTP_SESSION_REQUESTED)
+			goto invalid;
+		if (pptpReq->srep.resultCode == PPTP_START_OK)
+			info->sstate = PPTP_SESSION_CONFIRMED;
+		else
+			info->sstate = PPTP_SESSION_ERROR;
+		break;
+
+	case PPTP_STOP_SESSION_REPLY:
+		/* server confirms end of control session */
+		if (info->sstate > PPTP_SESSION_STOPREQ)
+			goto invalid;
+		if (pptpReq->strep.resultCode == PPTP_STOP_OK)
+			info->sstate = PPTP_SESSION_NONE;
+		else
+			info->sstate = PPTP_SESSION_ERROR;
+		break;
+
+	case PPTP_OUT_CALL_REPLY:
+		/* server accepted call, we now expect GRE frames */
+		if (info->sstate != PPTP_SESSION_CONFIRMED)
+			goto invalid;
+		if (info->cstate != PPTP_CALL_OUT_REQ &&
+		    info->cstate != PPTP_CALL_OUT_CONF)
+			goto invalid;
+
+		cid = pptpReq->ocack.callID;
+		pcid = pptpReq->ocack.peersCallID;
+		if (info->pns_call_id != pcid)
+			goto invalid;
+		DEBUGP("%s, CID=%X, PCID=%X\n", pptp_msg_name[msg],
+			ntohs(cid), ntohs(pcid));
+
+		if (pptpReq->ocack.resultCode == PPTP_OUTCALL_CONNECT) {
+			info->cstate = PPTP_CALL_OUT_CONF;
+			info->pac_call_id = cid;
+			exp_gre(ct, cid, pcid);
+		} else
+			info->cstate = PPTP_CALL_NONE;
+		break;
+
+	case PPTP_IN_CALL_REQUEST:
+		/* server tells us about incoming call request */
+		if (info->sstate != PPTP_SESSION_CONFIRMED)
+			goto invalid;
+
+		cid = pptpReq->icreq.callID;
+		DEBUGP("%s, CID=%X\n", pptp_msg_name[msg], ntohs(cid));
+		info->cstate = PPTP_CALL_IN_REQ;
+		info->pac_call_id = cid;
+		break;
+
+	case PPTP_IN_CALL_CONNECT:
+		/* server tells us about incoming call established */
+		if (info->sstate != PPTP_SESSION_CONFIRMED)
+			goto invalid;
+		if (info->cstate != PPTP_CALL_IN_REP &&
+		    info->cstate != PPTP_CALL_IN_CONF)
+			goto invalid;
+
+		pcid = pptpReq->iccon.peersCallID;
+		cid = info->pac_call_id;
+
+		if (info->pns_call_id != pcid)
+			goto invalid;
+
+		DEBUGP("%s, PCID=%X\n", pptp_msg_name[msg], ntohs(pcid));
+		info->cstate = PPTP_CALL_IN_CONF;
+
+		/* we expect a GRE connection from PAC to PNS */
+		exp_gre(ct, cid, pcid);
+		break;
+
+	case PPTP_CALL_DISCONNECT_NOTIFY:
+		/* server confirms disconnect */
+		cid = pptpReq->disc.callID;
+		DEBUGP("%s, CID=%X\n", pptp_msg_name[msg], ntohs(cid));
+		info->cstate = PPTP_CALL_NONE;
+
+		/* untrack this call id, unexpect GRE packets */
+		pptp_destroy_siblings(ct);
+		break;
+
+	case PPTP_WAN_ERROR_NOTIFY:
+	case PPTP_ECHO_REQUEST:
+	case PPTP_ECHO_REPLY:
+		/* I don't have to explain these ;) */