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