[net-next-2.6.git] / net / ipv4 / netfilter / nf_nat_pptp.c

/*
 * 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 <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("ip_nat_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_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) {
		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 = 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;
	}
	nf_nat_setup_info(ct, &range, IP_NAT_MANIP_SRC);

	/* 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;
	}
	nf_nat_setup_info(ct, &range, IP_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,
		  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:
		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,
				     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)
{
	const 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 *skb,
		 struct nf_conn *ct,
		 enum ip_conntrack_info ctinfo,
		 struct PptpControlHeader *ctlh,
		 union pptp_ctrl_union *pptpReq)
{
	const 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:
		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,
				     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(nf_nat_pptp_hook_outbound != NULL);
	rcu_assign_pointer(nf_nat_pptp_hook_outbound, pptp_outbound_pkt);

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

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

	BUG_ON(nf_nat_pptp_hook_expectfn != NULL);
	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);
Commit	Line	Data
f09943fe PM	1	/*
	2	* nf_nat_pptp.c
	3	*
	4	* NAT support for PPTP (Point to Point Tunneling Protocol).
	5	* PPTP is a a protocol for creating virtual private networks.
	6	* It is a specification defined by Microsoft and some vendors
	7	* working with Microsoft. PPTP is built on top of a modified
	8	* version of the Internet Generic Routing Encapsulation Protocol.
	9	* GRE is defined in RFC 1701 and RFC 1702. Documentation of
	10	* PPTP can be found in RFC 2637
	11	*
	12	* (C) 2000-2005 by Harald Welte <laforge@gnumonks.org>
	13	*
	14	* Development of this code funded by Astaro AG (http://www.astaro.com/)
	15	*
	16	* TODO: - NAT to a unique tuple, not to TCP source port
	17	* (needs netfilter tuple reservation)
	18	*/
	19
	20	#include <linux/module.h>
	21	#include <linux/tcp.h>
	22
	23	#include <net/netfilter/nf_nat.h>
	24	#include <net/netfilter/nf_nat_helper.h>
	25	#include <net/netfilter/nf_nat_rule.h>
	26	#include <net/netfilter/nf_conntrack_helper.h>
	27	#include <net/netfilter/nf_conntrack_expect.h>
5d0aa2cc	28	#include <net/netfilter/nf_conntrack_zones.h>
f09943fe PM	29	#include <linux/netfilter/nf_conntrack_proto_gre.h>
	30	#include <linux/netfilter/nf_conntrack_pptp.h>
	31
	32	#define NF_NAT_PPTP_VERSION "3.0"
	33
	34	#define REQ_CID(req, off) ((__be16 )((char *)(req) + (off)))
	35
	36	MODULE_LICENSE("GPL");
	37	MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
	38	MODULE_DESCRIPTION("Netfilter NAT helper module for PPTP");
	39	MODULE_ALIAS("ip_nat_pptp");
	40
f09943fe PM	41	static void pptp_nat_expected(struct nf_conn *ct,
	42	struct nf_conntrack_expect *exp)
	43	{
cfd6e3d7	44	struct net *net = nf_ct_net(ct);
9ddd0ed0	45	const struct nf_conn *master = ct->master;
f09943fe PM	46	struct nf_conntrack_expect *other_exp;
f09943fe PM	47	struct nf_conntrack_tuple t;
9ddd0ed0 JE	48	const struct nf_ct_pptp_master *ct_pptp_info;
9ddd0ed0 JE	49	const struct nf_nat_pptp *nat_pptp_info;
587aa641	50	struct nf_nat_range range;
f09943fe PM	51
	52	ct_pptp_info = &nfct_help(master)->help.ct_pptp_info;
	53	nat_pptp_info = &nfct_nat(master)->help.nat_pptp_info;
	54
	55	/* And here goes the grand finale of corrosion... */
	56	if (exp->dir == IP_CT_DIR_ORIGINAL) {
0d53778e	57	pr_debug("we are PNS->PAC\n");
f09943fe PM	58	/* therefore, build tuple for PAC->PNS */
	59	t.src.l3num = AF_INET;
	60	t.src.u3.ip = master->tuplehash[!exp->dir].tuple.src.u3.ip;
	61	t.src.u.gre.key = ct_pptp_info->pac_call_id;
	62	t.dst.u3.ip = master->tuplehash[!exp->dir].tuple.dst.u3.ip;
	63	t.dst.u.gre.key = ct_pptp_info->pns_call_id;
	64	t.dst.protonum = IPPROTO_GRE;
	65	} else {
0d53778e	66	pr_debug("we are PAC->PNS\n");
f09943fe PM	67	/* build tuple for PNS->PAC */
f09943fe PM	68	t.src.l3num = AF_INET;
a46bf7d5	69	t.src.u3.ip = master->tuplehash[!exp->dir].tuple.src.u3.ip;
f09943fe	70	t.src.u.gre.key = nat_pptp_info->pns_call_id;
a46bf7d5	71	t.dst.u3.ip = master->tuplehash[!exp->dir].tuple.dst.u3.ip;
f09943fe PM	72	t.dst.u.gre.key = nat_pptp_info->pac_call_id;
	73	t.dst.protonum = IPPROTO_GRE;
	74	}
	75
0d53778e	76	pr_debug("trying to unexpect other dir: ");
3c9fba65	77	nf_ct_dump_tuple_ip(&t);
5d0aa2cc	78	other_exp = nf_ct_expect_find_get(net, nf_ct_zone(ct), &t);
f09943fe	79	if (other_exp) {
6823645d PM	80	nf_ct_unexpect_related(other_exp);
6823645d PM	81	nf_ct_expect_put(other_exp);
0d53778e	82	pr_debug("success\n");
f09943fe	83	} else {
0d53778e	84	pr_debug("not found!\n");
f09943fe PM	85	}
	86
	87	/* This must be a fresh one. */
	88	BUG_ON(ct->status & IPS_NAT_DONE_MASK);
	89
	90	/* Change src to where master sends to */
	91	range.flags = IP_NAT_RANGE_MAP_IPS;
	92	range.min_ip = range.max_ip
	93	= ct->master->tuplehash[!exp->dir].tuple.dst.u3.ip;
	94	if (exp->dir == IP_CT_DIR_ORIGINAL) {
	95	range.flags \|= IP_NAT_RANGE_PROTO_SPECIFIED;
	96	range.min = range.max = exp->saved_proto;
	97	}
cc01dcbd	98	nf_nat_setup_info(ct, &range, IP_NAT_MANIP_SRC);
f09943fe PM	99
	100	/* For DST manip, map port here to where it's expected. */
	101	range.flags = IP_NAT_RANGE_MAP_IPS;
	102	range.min_ip = range.max_ip
	103	= ct->master->tuplehash[!exp->dir].tuple.src.u3.ip;
	104	if (exp->dir == IP_CT_DIR_REPLY) {
	105	range.flags \|= IP_NAT_RANGE_PROTO_SPECIFIED;
	106	range.min = range.max = exp->saved_proto;
	107	}
cc01dcbd	108	nf_nat_setup_info(ct, &range, IP_NAT_MANIP_DST);
f09943fe PM	109	}
	110
	111	/* outbound packets == from PNS to PAC */
	112	static int
3db05fea	113	pptp_outbound_pkt(struct sk_buff *skb,
f09943fe PM	114	struct nf_conn *ct,
	115	enum ip_conntrack_info ctinfo,
	116	struct PptpControlHeader *ctlh,
	117	union pptp_ctrl_union *pptpReq)
	118
	119	{
	120	struct nf_ct_pptp_master *ct_pptp_info;
	121	struct nf_nat_pptp *nat_pptp_info;
	122	u_int16_t msg;
	123	__be16 new_callid;
	124	unsigned int cid_off;
	125
	126	ct_pptp_info = &nfct_help(ct)->help.ct_pptp_info;
	127	nat_pptp_info = &nfct_nat(ct)->help.nat_pptp_info;
	128
	129	new_callid = ct_pptp_info->pns_call_id;
	130
	131	switch (msg = ntohs(ctlh->messageType)) {
	132	case PPTP_OUT_CALL_REQUEST:
	133	cid_off = offsetof(union pptp_ctrl_union, ocreq.callID);
	134	/* FIXME: ideally we would want to reserve a call ID
	135	* here. current netfilter NAT core is not able to do
	136	* this :( For now we use TCP source port. This breaks
	137	* multiple calls within one control session */
	138
	139	/* save original call ID in nat_info */
	140	nat_pptp_info->pns_call_id = ct_pptp_info->pns_call_id;
	141
	142	/* don't use tcph->source since we are at a DSTmanip
	143	* hook (e.g. PREROUTING) and pkt is not mangled yet */
	144	new_callid = ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u.tcp.port;
	145
	146	/* save new call ID in ct info */
	147	ct_pptp_info->pns_call_id = new_callid;
	148	break;
	149	case PPTP_IN_CALL_REPLY:
	150	cid_off = offsetof(union pptp_ctrl_union, icack.callID);
	151	break;
	152	case PPTP_CALL_CLEAR_REQUEST:
	153	cid_off = offsetof(union pptp_ctrl_union, clrreq.callID);
	154	break;
	155	default:
0d53778e PM	156	pr_debug("unknown outbound packet 0x%04x:%s\n", msg,
	157	msg <= PPTP_MSG_MAX ? pptp_msg_name[msg] :
	158	pptp_msg_name[0]);
f09943fe PM	159	/* fall through */
	160	case PPTP_SET_LINK_INFO:
	161	/* only need to NAT in case PAC is behind NAT box */
	162	case PPTP_START_SESSION_REQUEST:
	163	case PPTP_START_SESSION_REPLY:
	164	case PPTP_STOP_SESSION_REQUEST:
	165	case PPTP_STOP_SESSION_REPLY:
	166	case PPTP_ECHO_REQUEST:
	167	case PPTP_ECHO_REPLY:
	168	/* no need to alter packet */
	169	return NF_ACCEPT;
	170	}
	171
	172	/* only OUT_CALL_REQUEST, IN_CALL_REPLY, CALL_CLEAR_REQUEST pass
	173	* down to here */
0d53778e PM	174	pr_debug("altering call id from 0x%04x to 0x%04x\n",
0d53778e PM	175	ntohs(REQ_CID(pptpReq, cid_off)), ntohs(new_callid));
f09943fe PM	176
f09943fe PM	177	/* mangle packet */
3db05fea	178	if (nf_nat_mangle_tcp_packet(skb, ct, ctinfo,
e905a9ed YH	179	cid_off + sizeof(struct pptp_pkt_hdr) +
	180	sizeof(struct PptpControlHeader),
	181	sizeof(new_callid), (char *)&new_callid,
	182	sizeof(new_callid)) == 0)
f09943fe PM	183	return NF_DROP;
	184	return NF_ACCEPT;
	185	}
	186
	187	static void
	188	pptp_exp_gre(struct nf_conntrack_expect *expect_orig,
	189	struct nf_conntrack_expect *expect_reply)
	190	{
9ddd0ed0	191	const struct nf_conn *ct = expect_orig->master;
f09943fe PM	192	struct nf_ct_pptp_master *ct_pptp_info;
	193	struct nf_nat_pptp *nat_pptp_info;
	194
	195	ct_pptp_info = &nfct_help(ct)->help.ct_pptp_info;
	196	nat_pptp_info = &nfct_nat(ct)->help.nat_pptp_info;
	197
	198	/* save original PAC call ID in nat_info */
	199	nat_pptp_info->pac_call_id = ct_pptp_info->pac_call_id;
	200
	201	/* alter expectation for PNS->PAC direction */
	202	expect_orig->saved_proto.gre.key = ct_pptp_info->pns_call_id;
	203	expect_orig->tuple.src.u.gre.key = nat_pptp_info->pns_call_id;
	204	expect_orig->tuple.dst.u.gre.key = ct_pptp_info->pac_call_id;
	205	expect_orig->dir = IP_CT_DIR_ORIGINAL;
	206
	207	/* alter expectation for PAC->PNS direction */
	208	expect_reply->saved_proto.gre.key = nat_pptp_info->pns_call_id;
	209	expect_reply->tuple.src.u.gre.key = nat_pptp_info->pac_call_id;
	210	expect_reply->tuple.dst.u.gre.key = ct_pptp_info->pns_call_id;
	211	expect_reply->dir = IP_CT_DIR_REPLY;
	212	}
	213
	214	/* inbound packets == from PAC to PNS */
	215	static int
3db05fea	216	pptp_inbound_pkt(struct sk_buff *skb,
f09943fe PM	217	struct nf_conn *ct,
	218	enum ip_conntrack_info ctinfo,
	219	struct PptpControlHeader *ctlh,
	220	union pptp_ctrl_union *pptpReq)
	221	{
9ddd0ed0	222	const struct nf_nat_pptp *nat_pptp_info;
f09943fe PM	223	u_int16_t msg;
	224	__be16 new_pcid;
	225	unsigned int pcid_off;
	226
	227	nat_pptp_info = &nfct_nat(ct)->help.nat_pptp_info;
	228	new_pcid = nat_pptp_info->pns_call_id;
	229
	230	switch (msg = ntohs(ctlh->messageType)) {
	231	case PPTP_OUT_CALL_REPLY:
	232	pcid_off = offsetof(union pptp_ctrl_union, ocack.peersCallID);
	233	break;
	234	case PPTP_IN_CALL_CONNECT:
	235	pcid_off = offsetof(union pptp_ctrl_union, iccon.peersCallID);
	236	break;
	237	case PPTP_IN_CALL_REQUEST:
	238	/* only need to nat in case PAC is behind NAT box */
	239	return NF_ACCEPT;
	240	case PPTP_WAN_ERROR_NOTIFY:
	241	pcid_off = offsetof(union pptp_ctrl_union, wanerr.peersCallID);
	242	break;
	243	case PPTP_CALL_DISCONNECT_NOTIFY:
	244	pcid_off = offsetof(union pptp_ctrl_union, disc.callID);
	245	break;
	246	case PPTP_SET_LINK_INFO:
	247	pcid_off = offsetof(union pptp_ctrl_union, setlink.peersCallID);
	248	break;
	249	default:
0d53778e PM	250	pr_debug("unknown inbound packet %s\n",
	251	msg <= PPTP_MSG_MAX ? pptp_msg_name[msg] :
	252	pptp_msg_name[0]);
f09943fe PM	253	/* fall through */
	254	case PPTP_START_SESSION_REQUEST:
	255	case PPTP_START_SESSION_REPLY:
	256	case PPTP_STOP_SESSION_REQUEST:
	257	case PPTP_STOP_SESSION_REPLY:
	258	case PPTP_ECHO_REQUEST:
	259	case PPTP_ECHO_REPLY:
	260	/* no need to alter packet */
	261	return NF_ACCEPT;
	262	}
	263
	264	/* only OUT_CALL_REPLY, IN_CALL_CONNECT, IN_CALL_REQUEST,
	265	* WAN_ERROR_NOTIFY, CALL_DISCONNECT_NOTIFY pass down here */
	266
	267	/* mangle packet */
0d53778e PM	268	pr_debug("altering peer call id from 0x%04x to 0x%04x\n",
0d53778e PM	269	ntohs(REQ_CID(pptpReq, pcid_off)), ntohs(new_pcid));
f09943fe	270
3db05fea	271	if (nf_nat_mangle_tcp_packet(skb, ct, ctinfo,
e905a9ed	272	pcid_off + sizeof(struct pptp_pkt_hdr) +
f09943fe PM	273	sizeof(struct PptpControlHeader),
	274	sizeof(new_pcid), (char *)&new_pcid,
	275	sizeof(new_pcid)) == 0)
	276	return NF_DROP;
	277	return NF_ACCEPT;
	278	}
	279
	280	static int __init nf_nat_helper_pptp_init(void)
	281	{
	282	nf_nat_need_gre();
	283
d1332e0a	284	BUG_ON(nf_nat_pptp_hook_outbound != NULL);
f09943fe PM	285	rcu_assign_pointer(nf_nat_pptp_hook_outbound, pptp_outbound_pkt);
f09943fe PM	286
d1332e0a	287	BUG_ON(nf_nat_pptp_hook_inbound != NULL);
f09943fe PM	288	rcu_assign_pointer(nf_nat_pptp_hook_inbound, pptp_inbound_pkt);
f09943fe PM	289
d1332e0a	290	BUG_ON(nf_nat_pptp_hook_exp_gre != NULL);
f09943fe PM	291	rcu_assign_pointer(nf_nat_pptp_hook_exp_gre, pptp_exp_gre);
f09943fe PM	292
d1332e0a	293	BUG_ON(nf_nat_pptp_hook_expectfn != NULL);
f09943fe PM	294	rcu_assign_pointer(nf_nat_pptp_hook_expectfn, pptp_nat_expected);
	295	return 0;
	296	}
	297
	298	static void __exit nf_nat_helper_pptp_fini(void)
	299	{
	300	rcu_assign_pointer(nf_nat_pptp_hook_expectfn, NULL);
	301	rcu_assign_pointer(nf_nat_pptp_hook_exp_gre, NULL);
	302	rcu_assign_pointer(nf_nat_pptp_hook_inbound, NULL);
	303	rcu_assign_pointer(nf_nat_pptp_hook_outbound, NULL);
	304	synchronize_rcu();
	305	}
	306
	307	module_init(nf_nat_helper_pptp_init);
	308	module_exit(nf_nat_helper_pptp_fini);