2 * ip_nat_pptp.c - Version 3.0
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
12 * (C) 2000-2005 by Harald Welte <laforge@gnumonks.org>
14 * Development of this code funded by Astaro AG (http://www.astaro.com/)
16 * TODO: - NAT to a unique tuple, not to TCP source port
17 * (needs netfilter tuple reservation)
20 * 2002-02-10 - Version 1.3
21 * - Use ip_nat_mangle_tcp_packet() because of cloned skb's
22 * in local connections (Philip Craig <philipc@snapgear.com>)
23 * - add checks for magicCookie and pptp version
24 * - make argument list of pptp_{out,in}bound_packet() shorter
25 * - move to C99 style initializers
26 * - print version number at module loadtime
27 * 2003-09-22 - Version 1.5
28 * - use SNATed tcp sourceport as callid, since we get called before
29 * TCP header is mangled (Philip Craig <philipc@snapgear.com>)
30 * 2004-10-22 - Version 2.0
31 * - kernel 2.6.x version
32 * 2005-06-10 - Version 3.0
33 * - kernel >= 2.6.11 version,
34 * funded by Oxcoda NetBox Blue (http://www.netboxblue.com/)
38 #include <linux/config.h>
39 #include <linux/module.h>
41 #include <linux/tcp.h>
44 #include <linux/netfilter_ipv4/ip_nat.h>
45 #include <linux/netfilter_ipv4/ip_nat_rule.h>
46 #include <linux/netfilter_ipv4/ip_nat_helper.h>
47 #include <linux/netfilter_ipv4/ip_nat_pptp.h>
48 #include <linux/netfilter_ipv4/ip_conntrack_core.h>
49 #include <linux/netfilter_ipv4/ip_conntrack_helper.h>
50 #include <linux/netfilter_ipv4/ip_conntrack_proto_gre.h>
51 #include <linux/netfilter_ipv4/ip_conntrack_pptp.h>
53 #define IP_NAT_PPTP_VERSION "3.0"
55 MODULE_LICENSE("GPL");
56 MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
57 MODULE_DESCRIPTION("Netfilter NAT helper module for PPTP");
61 extern const char *pptp_msg_name[];
62 #define DEBUGP(format, args...) printk(KERN_DEBUG "%s:%s: " format, __FILE__, \
63 __FUNCTION__, ## args)
65 #define DEBUGP(format, args...)
68 static void pptp_nat_expected(struct ip_conntrack *ct,
69 struct ip_conntrack_expect *exp)
71 struct ip_conntrack *master = ct->master;
72 struct ip_conntrack_expect *other_exp;
73 struct ip_conntrack_tuple t;
74 struct ip_ct_pptp_master *ct_pptp_info;
75 struct ip_nat_pptp *nat_pptp_info;
77 ct_pptp_info = &master->help.ct_pptp_info;
78 nat_pptp_info = &master->nat.help.nat_pptp_info;
80 /* And here goes the grand finale of corrosion... */
82 if (exp->dir == IP_CT_DIR_ORIGINAL) {
83 DEBUGP("we are PNS->PAC\n");
84 /* therefore, build tuple for PAC->PNS */
85 t.src.ip = master->tuplehash[IP_CT_DIR_REPLY].tuple.src.ip;
86 t.src.u.gre.key = htons(master->help.ct_pptp_info.pac_call_id);
87 t.dst.ip = master->tuplehash[IP_CT_DIR_REPLY].tuple.dst.ip;
88 t.dst.u.gre.key = htons(master->help.ct_pptp_info.pns_call_id);
89 t.dst.protonum = IPPROTO_GRE;
91 DEBUGP("we are PAC->PNS\n");
92 /* build tuple for PNS->PAC */
93 t.src.ip = master->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.ip;
95 htons(master->nat.help.nat_pptp_info.pns_call_id);
96 t.dst.ip = master->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.ip;
98 htons(master->nat.help.nat_pptp_info.pac_call_id);
99 t.dst.protonum = IPPROTO_GRE;
102 DEBUGP("trying to unexpect other dir: ");
104 other_exp = ip_conntrack_expect_find(&t);
106 ip_conntrack_unexpect_related(other_exp);
107 ip_conntrack_expect_put(other_exp);
110 DEBUGP("not found!\n");
113 ip_nat_follow_master(ct, exp);
116 /* outbound packets == from PNS to PAC */
118 pptp_outbound_pkt(struct sk_buff **pskb,
119 struct ip_conntrack *ct,
120 enum ip_conntrack_info ctinfo,
121 struct PptpControlHeader *ctlh,
122 union pptp_ctrl_union *pptpReq)
125 struct ip_ct_pptp_master *ct_pptp_info = &ct->help.ct_pptp_info;
126 struct ip_nat_pptp *nat_pptp_info = &ct->nat.help.nat_pptp_info;
128 u_int16_t msg, *cid = NULL, new_callid;
130 new_callid = htons(ct_pptp_info->pns_call_id);
132 switch (msg = ntohs(ctlh->messageType)) {
133 case PPTP_OUT_CALL_REQUEST:
134 cid = &pptpReq->ocreq.callID;
135 /* FIXME: ideally we would want to reserve a call ID
136 * here. current netfilter NAT core is not able to do
137 * this :( For now we use TCP source port. This breaks
138 * multiple calls within one control session */
140 /* save original call ID in nat_info */
141 nat_pptp_info->pns_call_id = ct_pptp_info->pns_call_id;
143 /* don't use tcph->source since we are at a DSTmanip
144 * hook (e.g. PREROUTING) and pkt is not mangled yet */
145 new_callid = ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u.tcp.port;
147 /* save new call ID in ct info */
148 ct_pptp_info->pns_call_id = ntohs(new_callid);
150 case PPTP_IN_CALL_REPLY:
151 cid = &pptpReq->icreq.callID;
153 case PPTP_CALL_CLEAR_REQUEST:
154 cid = &pptpReq->clrreq.callID;
157 DEBUGP("unknown outbound packet 0x%04x:%s\n", msg,
158 (msg <= PPTP_MSG_MAX)?
159 pptp_msg_name[msg]:pptp_msg_name[0]);
162 case PPTP_SET_LINK_INFO:
163 /* only need to NAT in case PAC is behind NAT box */
164 case PPTP_START_SESSION_REQUEST:
165 case PPTP_START_SESSION_REPLY:
166 case PPTP_STOP_SESSION_REQUEST:
167 case PPTP_STOP_SESSION_REPLY:
168 case PPTP_ECHO_REQUEST:
169 case PPTP_ECHO_REPLY:
170 /* no need to alter packet */
174 /* only OUT_CALL_REQUEST, IN_CALL_REPLY, CALL_CLEAR_REQUEST pass
179 DEBUGP("altering call id from 0x%04x to 0x%04x\n",
180 ntohs(*cid), ntohs(new_callid));
183 if (ip_nat_mangle_tcp_packet(pskb, ct, ctinfo,
184 (void *)cid - ((void *)ctlh - sizeof(struct pptp_pkt_hdr)),
187 sizeof(new_callid)) == 0)
194 pptp_exp_gre(struct ip_conntrack_expect *expect_orig,
195 struct ip_conntrack_expect *expect_reply)
197 struct ip_ct_pptp_master *ct_pptp_info =
198 &expect_orig->master->help.ct_pptp_info;
199 struct ip_nat_pptp *nat_pptp_info =
200 &expect_orig->master->nat.help.nat_pptp_info;
202 struct ip_conntrack *ct = expect_orig->master;
204 struct ip_conntrack_tuple inv_t;
205 struct ip_conntrack_tuple *orig_t, *reply_t;
207 /* save original PAC call ID in nat_info */
208 nat_pptp_info->pac_call_id = ct_pptp_info->pac_call_id;
210 /* alter expectation */
211 orig_t = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
212 reply_t = &ct->tuplehash[IP_CT_DIR_REPLY].tuple;
214 /* alter expectation for PNS->PAC direction */
215 invert_tuplepr(&inv_t, &expect_orig->tuple);
216 expect_orig->saved_proto.gre.key = htons(nat_pptp_info->pac_call_id);
217 expect_orig->tuple.src.u.gre.key = htons(nat_pptp_info->pns_call_id);
218 expect_orig->tuple.dst.u.gre.key = htons(ct_pptp_info->pac_call_id);
219 expect_orig->dir = IP_CT_DIR_ORIGINAL;
220 inv_t.src.ip = reply_t->src.ip;
221 inv_t.dst.ip = reply_t->dst.ip;
222 inv_t.src.u.gre.key = htons(nat_pptp_info->pac_call_id);
223 inv_t.dst.u.gre.key = htons(ct_pptp_info->pns_call_id);
225 if (!ip_conntrack_expect_related(expect_orig)) {
226 DEBUGP("successfully registered expect\n");
228 DEBUGP("can't expect_related(expect_orig)\n");
232 /* alter expectation for PAC->PNS direction */
233 invert_tuplepr(&inv_t, &expect_reply->tuple);
234 expect_reply->saved_proto.gre.key = htons(nat_pptp_info->pns_call_id);
235 expect_reply->tuple.src.u.gre.key = htons(nat_pptp_info->pac_call_id);
236 expect_reply->tuple.dst.u.gre.key = htons(ct_pptp_info->pns_call_id);
237 expect_reply->dir = IP_CT_DIR_REPLY;
238 inv_t.src.ip = orig_t->src.ip;
239 inv_t.dst.ip = orig_t->dst.ip;
240 inv_t.src.u.gre.key = htons(nat_pptp_info->pns_call_id);
241 inv_t.dst.u.gre.key = htons(ct_pptp_info->pac_call_id);
243 if (!ip_conntrack_expect_related(expect_reply)) {
244 DEBUGP("successfully registered expect\n");
246 DEBUGP("can't expect_related(expect_reply)\n");
247 ip_conntrack_unexpect_related(expect_orig);
251 if (ip_ct_gre_keymap_add(ct, &expect_reply->tuple, 0) < 0) {
252 DEBUGP("can't register original keymap\n");
253 ip_conntrack_unexpect_related(expect_orig);
254 ip_conntrack_unexpect_related(expect_reply);
258 if (ip_ct_gre_keymap_add(ct, &inv_t, 1) < 0) {
259 DEBUGP("can't register reply keymap\n");
260 ip_conntrack_unexpect_related(expect_orig);
261 ip_conntrack_unexpect_related(expect_reply);
262 ip_ct_gre_keymap_destroy(ct);
269 /* inbound packets == from PAC to PNS */
271 pptp_inbound_pkt(struct sk_buff **pskb,
272 struct ip_conntrack *ct,
273 enum ip_conntrack_info ctinfo,
274 struct PptpControlHeader *ctlh,
275 union pptp_ctrl_union *pptpReq)
277 struct ip_nat_pptp *nat_pptp_info = &ct->nat.help.nat_pptp_info;
278 u_int16_t msg, new_cid = 0, new_pcid, *pcid = NULL, *cid = NULL;
280 int ret = NF_ACCEPT, rv;
282 new_pcid = htons(nat_pptp_info->pns_call_id);
284 switch (msg = ntohs(ctlh->messageType)) {
285 case PPTP_OUT_CALL_REPLY:
286 pcid = &pptpReq->ocack.peersCallID;
287 cid = &pptpReq->ocack.callID;
289 case PPTP_IN_CALL_CONNECT:
290 pcid = &pptpReq->iccon.peersCallID;
292 case PPTP_IN_CALL_REQUEST:
293 /* only need to nat in case PAC is behind NAT box */
295 case PPTP_WAN_ERROR_NOTIFY:
296 pcid = &pptpReq->wanerr.peersCallID;
298 case PPTP_CALL_DISCONNECT_NOTIFY:
299 pcid = &pptpReq->disc.callID;
301 case PPTP_SET_LINK_INFO:
302 pcid = &pptpReq->setlink.peersCallID;
306 DEBUGP("unknown inbound packet %s\n", (msg <= PPTP_MSG_MAX)?
307 pptp_msg_name[msg]:pptp_msg_name[0]);
310 case PPTP_START_SESSION_REQUEST:
311 case PPTP_START_SESSION_REPLY:
312 case PPTP_STOP_SESSION_REQUEST:
313 case PPTP_STOP_SESSION_REPLY:
314 case PPTP_ECHO_REQUEST:
315 case PPTP_ECHO_REPLY:
316 /* no need to alter packet */
320 /* only OUT_CALL_REPLY, IN_CALL_CONNECT, IN_CALL_REQUEST,
321 * WAN_ERROR_NOTIFY, CALL_DISCONNECT_NOTIFY pass down here */
325 DEBUGP("altering peer call id from 0x%04x to 0x%04x\n",
326 ntohs(*pcid), ntohs(new_pcid));
328 rv = ip_nat_mangle_tcp_packet(pskb, ct, ctinfo,
329 (void *)pcid - ((void *)ctlh - sizeof(struct pptp_pkt_hdr)),
330 sizeof(new_pcid), (char *)&new_pcid,
337 DEBUGP("altering call id from 0x%04x to 0x%04x\n",
338 ntohs(*cid), ntohs(new_cid));
339 rv = ip_nat_mangle_tcp_packet(pskb, ct, ctinfo,
340 (void *)cid - ((void *)ctlh - sizeof(struct pptp_pkt_hdr)),
348 /* check for earlier return value of 'switch' above */
349 if (ret != NF_ACCEPT)
352 /* great, at least we don't need to resize packets */
357 extern int __init ip_nat_proto_gre_init(void);
358 extern void __exit ip_nat_proto_gre_fini(void);
360 static int __init init(void)
364 DEBUGP("%s: registering NAT helper\n", __FILE__);
366 ret = ip_nat_proto_gre_init();
370 BUG_ON(ip_nat_pptp_hook_outbound);
371 ip_nat_pptp_hook_outbound = &pptp_outbound_pkt;
373 BUG_ON(ip_nat_pptp_hook_inbound);
374 ip_nat_pptp_hook_inbound = &pptp_inbound_pkt;
376 BUG_ON(ip_nat_pptp_hook_exp_gre);
377 ip_nat_pptp_hook_exp_gre = &pptp_exp_gre;
379 BUG_ON(ip_nat_pptp_hook_expectfn);
380 ip_nat_pptp_hook_expectfn = &pptp_nat_expected;
382 printk("ip_nat_pptp version %s loaded\n", IP_NAT_PPTP_VERSION);
386 static void __exit fini(void)
388 DEBUGP("cleanup_module\n" );
390 ip_nat_pptp_hook_expectfn = NULL;
391 ip_nat_pptp_hook_exp_gre = NULL;
392 ip_nat_pptp_hook_inbound = NULL;
393 ip_nat_pptp_hook_outbound = NULL;
395 ip_nat_proto_gre_fini();
396 /* Make sure noone calls it, meanwhile */
399 printk("ip_nat_pptp version %s unloaded\n", IP_NAT_PPTP_VERSION);