[linux-block.git] / net / ipv4 / netfilter / nf_nat_pptp.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * 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/)
 *
 * (C) 2006-2012 Patrick McHardy <kaber@trash.net>
 *
 * 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_conntrack_helper.h>
#include <net/netfilter/nf_conntrack_expect.h>
#include <net/netfilter/nf_conntrack_zones.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_NF_NAT_HELPER("pptp");

static void pptp_nat_expected(struct nf_conn *ct,
			      struct nf_conntrack_expect *exp)
{
	struct net *net = nf_ct_net(ct);
	const struct nf_conn *master = ct->master;
	struct nf_conntrack_expect *other_exp;
	struct nf_conntrack_tuple t = {};
	const struct nf_ct_pptp_master *ct_pptp_info;
	const struct nf_nat_pptp *nat_pptp_info;
	struct nf_nat_range2 range;
	struct nf_conn_nat *nat;

	nat = nf_ct_nat_ext_add(ct);
	if (WARN_ON_ONCE(!nat))
		return;

	nat_pptp_info = &nat->help.nat_pptp_info;
	ct_pptp_info = nfct_help_data(master);

	/* And here goes the grand finale of corrosion... */
	if (exp->dir == IP_CT_DIR_ORIGINAL) {
		pr_debug("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 {
		pr_debug("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;
	}

	pr_debug("trying to unexpect other dir: ");
	nf_ct_dump_tuple_ip(&t);
	other_exp = nf_ct_expect_find_get(net, nf_ct_zone(ct), &t);
	if (other_exp) {
		nf_ct_unexpect_related(other_exp);
		nf_ct_expect_put(other_exp);
		pr_debug("success\n");
	} else {
		pr_debug("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 = NF_NAT_RANGE_MAP_IPS;
	range.min_addr = range.max_addr
		= ct->master->tuplehash[!exp->dir].tuple.dst.u3;
	if (exp->dir == IP_CT_DIR_ORIGINAL) {
		range.flags |= NF_NAT_RANGE_PROTO_SPECIFIED;
		range.min_proto = range.max_proto = exp->saved_proto;
	}
	nf_nat_setup_info(ct, &range, NF_NAT_MANIP_SRC);

	/* For DST manip, map port here to where it's expected. */
	range.flags = NF_NAT_RANGE_MAP_IPS;
	range.min_addr = range.max_addr
		= ct->master->tuplehash[!exp->dir].tuple.src.u3;
	if (exp->dir == IP_CT_DIR_REPLY) {
		range.flags |= NF_NAT_RANGE_PROTO_SPECIFIED;
		range.min_proto = range.max_proto = exp->saved_proto;
	}
	nf_nat_setup_info(ct, &range, NF_NAT_MANIP_DST);
}

/* outbound packets == from PNS to PAC */
static int
pptp_outbound_pkt(struct sk_buff *skb,
		  struct nf_conn *ct,
		  enum ip_conntrack_info ctinfo,
		  unsigned int protoff,
		  struct PptpControlHeader *ctlh,
		  union pptp_ctrl_union *pptpReq)

{
	struct nf_ct_pptp_master *ct_pptp_info;
	struct nf_conn_nat *nat = nfct_nat(ct);
	struct nf_nat_pptp *nat_pptp_info;
	u_int16_t msg;
	__be16 new_callid;
	unsigned int cid_off;

	if (WARN_ON_ONCE(!nat))
		return NF_DROP;

	nat_pptp_info = &nat->help.nat_pptp_info;
	ct_pptp_info = nfct_help_data(ct);

	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:
		pr_debug("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 */
	pr_debug("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(skb, ct, ctinfo, protoff,
				      cid_off + sizeof(struct pptp_pkt_hdr) +
				      sizeof(struct PptpControlHeader),
				      sizeof(new_callid), (char *)&new_callid,
				      sizeof(new_callid)))
		return NF_DROP;
	return NF_ACCEPT;
}

static void
pptp_exp_gre(struct nf_conntrack_expect *expect_orig,
	     struct nf_conntrack_expect *expect_reply)
{
	const struct nf_conn *ct = expect_orig->master;
	struct nf_conn_nat *nat = nfct_nat(ct);
	struct nf_ct_pptp_master *ct_pptp_info;
	struct nf_nat_pptp *nat_pptp_info;

	if (WARN_ON_ONCE(!nat))
		return;

	nat_pptp_info = &nat->help.nat_pptp_info;
	ct_pptp_info = nfct_help_data(ct);

	/* 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 *skb,
		 struct nf_conn *ct,
		 enum ip_conntrack_info ctinfo,
		 unsigned int protoff,
		 struct PptpControlHeader *ctlh,
		 union pptp_ctrl_union *pptpReq)
{
	const struct nf_nat_pptp *nat_pptp_info;
	struct nf_conn_nat *nat = nfct_nat(ct);
	u_int16_t msg;
	__be16 new_pcid;
	unsigned int pcid_off;

	if (WARN_ON_ONCE(!nat))
		return NF_DROP;

	nat_pptp_info = &nat->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:
		pr_debug("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 */
	pr_debug("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(skb, ct, ctinfo, protoff,
				      pcid_off + sizeof(struct pptp_pkt_hdr) +
				      sizeof(struct PptpControlHeader),
				      sizeof(new_pcid), (char *)&new_pcid,
				      sizeof(new_pcid)))
		return NF_DROP;
	return NF_ACCEPT;
}

static int __init nf_nat_helper_pptp_init(void)
{
	BUG_ON(nf_nat_pptp_hook_outbound != NULL);
	RCU_INIT_POINTER(nf_nat_pptp_hook_outbound, pptp_outbound_pkt);

	BUG_ON(nf_nat_pptp_hook_inbound != NULL);
	RCU_INIT_POINTER(nf_nat_pptp_hook_inbound, pptp_inbound_pkt);

	BUG_ON(nf_nat_pptp_hook_exp_gre != NULL);
	RCU_INIT_POINTER(nf_nat_pptp_hook_exp_gre, pptp_exp_gre);

	BUG_ON(nf_nat_pptp_hook_expectfn != NULL);
	RCU_INIT_POINTER(nf_nat_pptp_hook_expectfn, pptp_nat_expected);
	return 0;
}

static void __exit nf_nat_helper_pptp_fini(void)
{
	RCU_INIT_POINTER(nf_nat_pptp_hook_expectfn, NULL);
	RCU_INIT_POINTER(nf_nat_pptp_hook_exp_gre, NULL);
	RCU_INIT_POINTER(nf_nat_pptp_hook_inbound, NULL);
	RCU_INIT_POINTER(nf_nat_pptp_hook_outbound, NULL);
	synchronize_rcu();
}

module_init(nf_nat_helper_pptp_init);
module_exit(nf_nat_helper_pptp_fini);
Commit	Line	Data
09c434b8	1	// SPDX-License-Identifier: GPL-2.0-only
f09943fe PM	2	/*
	3	* nf_nat_pptp.c
	4	*
	5	* NAT support for PPTP (Point to Point Tunneling Protocol).
	6	* PPTP is a a protocol for creating virtual private networks.
	7	* It is a specification defined by Microsoft and some vendors
	8	* working with Microsoft. PPTP is built on top of a modified
	9	* version of the Internet Generic Routing Encapsulation Protocol.
	10	* GRE is defined in RFC 1701 and RFC 1702. Documentation of
	11	* PPTP can be found in RFC 2637
	12	*
	13	* (C) 2000-2005 by Harald Welte <laforge@gnumonks.org>
	14	*
	15	* Development of this code funded by Astaro AG (http://www.astaro.com/)
	16	*
f229f6ce PM	17	* (C) 2006-2012 Patrick McHardy <kaber@trash.net>
f229f6ce PM	18	*
f09943fe PM	19	* TODO: - NAT to a unique tuple, not to TCP source port
	20	* (needs netfilter tuple reservation)
	21	*/
	22
	23	#include <linux/module.h>
	24	#include <linux/tcp.h>
	25
	26	#include <net/netfilter/nf_nat.h>
	27	#include <net/netfilter/nf_nat_helper.h>
f09943fe PM	28	#include <net/netfilter/nf_conntrack_helper.h>
f09943fe PM	29	#include <net/netfilter/nf_conntrack_expect.h>
5d0aa2cc	30	#include <net/netfilter/nf_conntrack_zones.h>
f09943fe PM	31	#include <linux/netfilter/nf_conntrack_proto_gre.h>
	32	#include <linux/netfilter/nf_conntrack_pptp.h>
	33
	34	#define NF_NAT_PPTP_VERSION "3.0"
	35
	36	#define REQ_CID(req, off) ((__be16 )((char *)(req) + (off)))
	37
	38	MODULE_LICENSE("GPL");
	39	MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
	40	MODULE_DESCRIPTION("Netfilter NAT helper module for PPTP");
e1f172e1	41	MODULE_ALIAS_NF_NAT_HELPER("pptp");
f09943fe	42
f09943fe PM	43	static void pptp_nat_expected(struct nf_conn *ct,
	44	struct nf_conntrack_expect *exp)
	45	{
cfd6e3d7	46	struct net *net = nf_ct_net(ct);
9ddd0ed0	47	const struct nf_conn *master = ct->master;
f09943fe	48	struct nf_conntrack_expect *other_exp;
c255cb2e	49	struct nf_conntrack_tuple t = {};
9ddd0ed0 JE	50	const struct nf_ct_pptp_master *ct_pptp_info;
9ddd0ed0 JE	51	const struct nf_nat_pptp *nat_pptp_info;
2eb0f624	52	struct nf_nat_range2 range;
2fe7c321	53	struct nf_conn_nat *nat;
f09943fe	54
2fe7c321 FW	55	nat = nf_ct_nat_ext_add(ct);
	56	if (WARN_ON_ONCE(!nat))
	57	return;
	58
	59	nat_pptp_info = &nat->help.nat_pptp_info;
1afc5679	60	ct_pptp_info = nfct_help_data(master);
f09943fe PM	61
	62	/* And here goes the grand finale of corrosion... */
	63	if (exp->dir == IP_CT_DIR_ORIGINAL) {
0d53778e	64	pr_debug("we are PNS->PAC\n");
f09943fe PM	65	/* therefore, build tuple for PAC->PNS */
	66	t.src.l3num = AF_INET;
	67	t.src.u3.ip = master->tuplehash[!exp->dir].tuple.src.u3.ip;
	68	t.src.u.gre.key = ct_pptp_info->pac_call_id;
	69	t.dst.u3.ip = master->tuplehash[!exp->dir].tuple.dst.u3.ip;
	70	t.dst.u.gre.key = ct_pptp_info->pns_call_id;
	71	t.dst.protonum = IPPROTO_GRE;
	72	} else {
0d53778e	73	pr_debug("we are PAC->PNS\n");
f09943fe PM	74	/* build tuple for PNS->PAC */
f09943fe PM	75	t.src.l3num = AF_INET;
a46bf7d5	76	t.src.u3.ip = master->tuplehash[!exp->dir].tuple.src.u3.ip;
f09943fe	77	t.src.u.gre.key = nat_pptp_info->pns_call_id;
a46bf7d5	78	t.dst.u3.ip = master->tuplehash[!exp->dir].tuple.dst.u3.ip;
f09943fe PM	79	t.dst.u.gre.key = nat_pptp_info->pac_call_id;
	80	t.dst.protonum = IPPROTO_GRE;
	81	}
	82
0d53778e	83	pr_debug("trying to unexpect other dir: ");
3c9fba65	84	nf_ct_dump_tuple_ip(&t);
5d0aa2cc	85	other_exp = nf_ct_expect_find_get(net, nf_ct_zone(ct), &t);
f09943fe	86	if (other_exp) {
6823645d PM	87	nf_ct_unexpect_related(other_exp);
6823645d PM	88	nf_ct_expect_put(other_exp);
0d53778e	89	pr_debug("success\n");
f09943fe	90	} else {
0d53778e	91	pr_debug("not found!\n");
f09943fe PM	92	}
	93
	94	/* This must be a fresh one. */
	95	BUG_ON(ct->status & IPS_NAT_DONE_MASK);
	96
	97	/* Change src to where master sends to */
cbc9f2f4	98	range.flags = NF_NAT_RANGE_MAP_IPS;
c7232c99 PM	99	range.min_addr = range.max_addr
c7232c99 PM	100	= ct->master->tuplehash[!exp->dir].tuple.dst.u3;
f09943fe	101	if (exp->dir == IP_CT_DIR_ORIGINAL) {
cbc9f2f4	102	range.flags \|= NF_NAT_RANGE_PROTO_SPECIFIED;
c7232c99	103	range.min_proto = range.max_proto = exp->saved_proto;
f09943fe	104	}
cbc9f2f4	105	nf_nat_setup_info(ct, &range, NF_NAT_MANIP_SRC);
f09943fe PM	106
f09943fe PM	107	/* For DST manip, map port here to where it's expected. */
cbc9f2f4	108	range.flags = NF_NAT_RANGE_MAP_IPS;
c7232c99 PM	109	range.min_addr = range.max_addr
c7232c99 PM	110	= ct->master->tuplehash[!exp->dir].tuple.src.u3;
f09943fe	111	if (exp->dir == IP_CT_DIR_REPLY) {
cbc9f2f4	112	range.flags \|= NF_NAT_RANGE_PROTO_SPECIFIED;
c7232c99	113	range.min_proto = range.max_proto = exp->saved_proto;
f09943fe	114	}
cbc9f2f4	115	nf_nat_setup_info(ct, &range, NF_NAT_MANIP_DST);
f09943fe PM	116	}
	117
	118	/* outbound packets == from PNS to PAC */
	119	static int
3db05fea	120	pptp_outbound_pkt(struct sk_buff *skb,
f09943fe PM	121	struct nf_conn *ct,
f09943fe PM	122	enum ip_conntrack_info ctinfo,
051966c0	123	unsigned int protoff,
f09943fe PM	124	struct PptpControlHeader *ctlh,
	125	union pptp_ctrl_union *pptpReq)
	126
	127	{
	128	struct nf_ct_pptp_master *ct_pptp_info;
2fe7c321	129	struct nf_conn_nat *nat = nfct_nat(ct);
f09943fe PM	130	struct nf_nat_pptp *nat_pptp_info;
	131	u_int16_t msg;
	132	__be16 new_callid;
	133	unsigned int cid_off;
	134
2fe7c321 FW	135	if (WARN_ON_ONCE(!nat))
	136	return NF_DROP;
	137
	138	nat_pptp_info = &nat->help.nat_pptp_info;
1afc5679	139	ct_pptp_info = nfct_help_data(ct);
f09943fe PM	140
	141	new_callid = ct_pptp_info->pns_call_id;
	142
	143	switch (msg = ntohs(ctlh->messageType)) {
	144	case PPTP_OUT_CALL_REQUEST:
	145	cid_off = offsetof(union pptp_ctrl_union, ocreq.callID);
	146	/* FIXME: ideally we would want to reserve a call ID
	147	* here. current netfilter NAT core is not able to do
	148	* this :( For now we use TCP source port. This breaks
	149	* multiple calls within one control session */
	150
	151	/* save original call ID in nat_info */
	152	nat_pptp_info->pns_call_id = ct_pptp_info->pns_call_id;
	153
	154	/* don't use tcph->source since we are at a DSTmanip
	155	* hook (e.g. PREROUTING) and pkt is not mangled yet */
	156	new_callid = ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u.tcp.port;
	157
	158	/* save new call ID in ct info */
	159	ct_pptp_info->pns_call_id = new_callid;
	160	break;
	161	case PPTP_IN_CALL_REPLY:
	162	cid_off = offsetof(union pptp_ctrl_union, icack.callID);
	163	break;
	164	case PPTP_CALL_CLEAR_REQUEST:
	165	cid_off = offsetof(union pptp_ctrl_union, clrreq.callID);
	166	break;
	167	default:
0d53778e PM	168	pr_debug("unknown outbound packet 0x%04x:%s\n", msg,
	169	msg <= PPTP_MSG_MAX ? pptp_msg_name[msg] :
	170	pptp_msg_name[0]);
f09943fe PM	171	/* fall through */
	172	case PPTP_SET_LINK_INFO:
	173	/* only need to NAT in case PAC is behind NAT box */
	174	case PPTP_START_SESSION_REQUEST:
	175	case PPTP_START_SESSION_REPLY:
	176	case PPTP_STOP_SESSION_REQUEST:
	177	case PPTP_STOP_SESSION_REPLY:
	178	case PPTP_ECHO_REQUEST:
	179	case PPTP_ECHO_REPLY:
	180	/* no need to alter packet */
	181	return NF_ACCEPT;
	182	}
	183
	184	/* only OUT_CALL_REQUEST, IN_CALL_REPLY, CALL_CLEAR_REQUEST pass
	185	* down to here */
0d53778e PM	186	pr_debug("altering call id from 0x%04x to 0x%04x\n",
0d53778e PM	187	ntohs(REQ_CID(pptpReq, cid_off)), ntohs(new_callid));
f09943fe PM	188
f09943fe PM	189	/* mangle packet */
cba81cc4 GF	190	if (!nf_nat_mangle_tcp_packet(skb, ct, ctinfo, protoff,
	191	cid_off + sizeof(struct pptp_pkt_hdr) +
	192	sizeof(struct PptpControlHeader),
	193	sizeof(new_callid), (char *)&new_callid,
	194	sizeof(new_callid)))
f09943fe PM	195	return NF_DROP;
	196	return NF_ACCEPT;
	197	}
	198
	199	static void
	200	pptp_exp_gre(struct nf_conntrack_expect *expect_orig,
	201	struct nf_conntrack_expect *expect_reply)
	202	{
9ddd0ed0	203	const struct nf_conn *ct = expect_orig->master;
2fe7c321	204	struct nf_conn_nat *nat = nfct_nat(ct);
f09943fe PM	205	struct nf_ct_pptp_master *ct_pptp_info;
	206	struct nf_nat_pptp *nat_pptp_info;
	207
2fe7c321 FW	208	if (WARN_ON_ONCE(!nat))
	209	return;
	210
	211	nat_pptp_info = &nat->help.nat_pptp_info;
1afc5679	212	ct_pptp_info = nfct_help_data(ct);
f09943fe PM	213
	214	/* save original PAC call ID in nat_info */
	215	nat_pptp_info->pac_call_id = ct_pptp_info->pac_call_id;
	216
	217	/* alter expectation for PNS->PAC direction */
	218	expect_orig->saved_proto.gre.key = ct_pptp_info->pns_call_id;
	219	expect_orig->tuple.src.u.gre.key = nat_pptp_info->pns_call_id;
	220	expect_orig->tuple.dst.u.gre.key = ct_pptp_info->pac_call_id;
	221	expect_orig->dir = IP_CT_DIR_ORIGINAL;
	222
	223	/* alter expectation for PAC->PNS direction */
	224	expect_reply->saved_proto.gre.key = nat_pptp_info->pns_call_id;
	225	expect_reply->tuple.src.u.gre.key = nat_pptp_info->pac_call_id;
	226	expect_reply->tuple.dst.u.gre.key = ct_pptp_info->pns_call_id;
	227	expect_reply->dir = IP_CT_DIR_REPLY;
	228	}
	229
	230	/* inbound packets == from PAC to PNS */
	231	static int
3db05fea	232	pptp_inbound_pkt(struct sk_buff *skb,
f09943fe PM	233	struct nf_conn *ct,
f09943fe PM	234	enum ip_conntrack_info ctinfo,
051966c0	235	unsigned int protoff,
f09943fe PM	236	struct PptpControlHeader *ctlh,
	237	union pptp_ctrl_union *pptpReq)
	238	{
9ddd0ed0	239	const struct nf_nat_pptp *nat_pptp_info;
2fe7c321	240	struct nf_conn_nat *nat = nfct_nat(ct);
f09943fe PM	241	u_int16_t msg;
	242	__be16 new_pcid;
	243	unsigned int pcid_off;
	244
2fe7c321 FW	245	if (WARN_ON_ONCE(!nat))
	246	return NF_DROP;
	247
	248	nat_pptp_info = &nat->help.nat_pptp_info;
f09943fe PM	249	new_pcid = nat_pptp_info->pns_call_id;
	250
	251	switch (msg = ntohs(ctlh->messageType)) {
	252	case PPTP_OUT_CALL_REPLY:
	253	pcid_off = offsetof(union pptp_ctrl_union, ocack.peersCallID);
	254	break;
	255	case PPTP_IN_CALL_CONNECT:
	256	pcid_off = offsetof(union pptp_ctrl_union, iccon.peersCallID);
	257	break;
	258	case PPTP_IN_CALL_REQUEST:
	259	/* only need to nat in case PAC is behind NAT box */
	260	return NF_ACCEPT;
	261	case PPTP_WAN_ERROR_NOTIFY:
	262	pcid_off = offsetof(union pptp_ctrl_union, wanerr.peersCallID);
	263	break;
	264	case PPTP_CALL_DISCONNECT_NOTIFY:
	265	pcid_off = offsetof(union pptp_ctrl_union, disc.callID);
	266	break;
	267	case PPTP_SET_LINK_INFO:
	268	pcid_off = offsetof(union pptp_ctrl_union, setlink.peersCallID);
	269	break;
	270	default:
0d53778e PM	271	pr_debug("unknown inbound packet %s\n",
	272	msg <= PPTP_MSG_MAX ? pptp_msg_name[msg] :
	273	pptp_msg_name[0]);
f09943fe PM	274	/* fall through */
	275	case PPTP_START_SESSION_REQUEST:
	276	case PPTP_START_SESSION_REPLY:
	277	case PPTP_STOP_SESSION_REQUEST:
	278	case PPTP_STOP_SESSION_REPLY:
	279	case PPTP_ECHO_REQUEST:
	280	case PPTP_ECHO_REPLY:
	281	/* no need to alter packet */
	282	return NF_ACCEPT;
	283	}
	284
	285	/* only OUT_CALL_REPLY, IN_CALL_CONNECT, IN_CALL_REQUEST,
	286	* WAN_ERROR_NOTIFY, CALL_DISCONNECT_NOTIFY pass down here */
	287
	288	/* mangle packet */
0d53778e PM	289	pr_debug("altering peer call id from 0x%04x to 0x%04x\n",
0d53778e PM	290	ntohs(REQ_CID(pptpReq, pcid_off)), ntohs(new_pcid));
f09943fe	291
cba81cc4 GF	292	if (!nf_nat_mangle_tcp_packet(skb, ct, ctinfo, protoff,
	293	pcid_off + sizeof(struct pptp_pkt_hdr) +
	294	sizeof(struct PptpControlHeader),
	295	sizeof(new_pcid), (char *)&new_pcid,
	296	sizeof(new_pcid)))
f09943fe PM	297	return NF_DROP;
	298	return NF_ACCEPT;
	299	}
	300
	301	static int __init nf_nat_helper_pptp_init(void)
	302	{
d1332e0a	303	BUG_ON(nf_nat_pptp_hook_outbound != NULL);
a9b3cd7f	304	RCU_INIT_POINTER(nf_nat_pptp_hook_outbound, pptp_outbound_pkt);
f09943fe	305
d1332e0a	306	BUG_ON(nf_nat_pptp_hook_inbound != NULL);
a9b3cd7f	307	RCU_INIT_POINTER(nf_nat_pptp_hook_inbound, pptp_inbound_pkt);
f09943fe	308
d1332e0a	309	BUG_ON(nf_nat_pptp_hook_exp_gre != NULL);
a9b3cd7f	310	RCU_INIT_POINTER(nf_nat_pptp_hook_exp_gre, pptp_exp_gre);
f09943fe	311
d1332e0a	312	BUG_ON(nf_nat_pptp_hook_expectfn != NULL);
a9b3cd7f	313	RCU_INIT_POINTER(nf_nat_pptp_hook_expectfn, pptp_nat_expected);
f09943fe PM	314	return 0;
	315	}
	316
	317	static void __exit nf_nat_helper_pptp_fini(void)
	318	{
a9b3cd7f SH	319	RCU_INIT_POINTER(nf_nat_pptp_hook_expectfn, NULL);
	320	RCU_INIT_POINTER(nf_nat_pptp_hook_exp_gre, NULL);
	321	RCU_INIT_POINTER(nf_nat_pptp_hook_inbound, NULL);
	322	RCU_INIT_POINTER(nf_nat_pptp_hook_outbound, NULL);
f09943fe PM	323	synchronize_rcu();
	324	}
	325
	326	module_init(nf_nat_helper_pptp_init);
	327	module_exit(nf_nat_helper_pptp_fini);