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;
76 struct ip_nat_range range;
78 ct_pptp_info = &master->help.ct_pptp_info;
79 nat_pptp_info = &master->nat.help.nat_pptp_info;
81 /* And here goes the grand finale of corrosion... */
83 if (exp->dir == IP_CT_DIR_ORIGINAL) {
84 DEBUGP("we are PNS->PAC\n");
85 /* therefore, build tuple for PAC->PNS */
86 t.src.ip = master->tuplehash[IP_CT_DIR_REPLY].tuple.src.ip;
87 t.src.u.gre.key = htons(master->help.ct_pptp_info.pac_call_id);
88 t.dst.ip = master->tuplehash[IP_CT_DIR_REPLY].tuple.dst.ip;
89 t.dst.u.gre.key = htons(master->help.ct_pptp_info.pns_call_id);
90 t.dst.protonum = IPPROTO_GRE;
92 DEBUGP("we are PAC->PNS\n");
93 /* build tuple for PNS->PAC */
94 t.src.ip = master->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.ip;
96 htons(master->nat.help.nat_pptp_info.pns_call_id);
97 t.dst.ip = master->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.ip;
99 htons(master->nat.help.nat_pptp_info.pac_call_id);
100 t.dst.protonum = IPPROTO_GRE;
103 DEBUGP("trying to unexpect other dir: ");
105 other_exp = ip_conntrack_expect_find(&t);
107 ip_conntrack_unexpect_related(other_exp);
108 ip_conntrack_expect_put(other_exp);
111 DEBUGP("not found!\n");
114 /* This must be a fresh one. */
115 BUG_ON(ct->status & IPS_NAT_DONE_MASK);
117 /* Change src to where master sends to */
118 range.flags = IP_NAT_RANGE_MAP_IPS;
119 range.min_ip = range.max_ip
120 = ct->master->tuplehash[!exp->dir].tuple.dst.ip;
121 if (exp->dir == IP_CT_DIR_ORIGINAL) {
122 range.flags |= IP_NAT_RANGE_PROTO_SPECIFIED;
123 range.min = range.max = exp->saved_proto;
125 /* hook doesn't matter, but it has to do source manip */
126 ip_nat_setup_info(ct, &range, NF_IP_POST_ROUTING);
128 /* For DST manip, map port here to where it's expected. */
129 range.flags = IP_NAT_RANGE_MAP_IPS;
130 range.min_ip = range.max_ip
131 = ct->master->tuplehash[!exp->dir].tuple.src.ip;
132 if (exp->dir == IP_CT_DIR_REPLY) {
133 range.flags |= IP_NAT_RANGE_PROTO_SPECIFIED;
134 range.min = range.max = exp->saved_proto;
136 /* hook doesn't matter, but it has to do destination manip */
137 ip_nat_setup_info(ct, &range, NF_IP_PRE_ROUTING);
140 /* outbound packets == from PNS to PAC */
142 pptp_outbound_pkt(struct sk_buff **pskb,
143 struct ip_conntrack *ct,
144 enum ip_conntrack_info ctinfo,
145 struct PptpControlHeader *ctlh,
146 union pptp_ctrl_union *pptpReq)
149 struct ip_ct_pptp_master *ct_pptp_info = &ct->help.ct_pptp_info;
150 struct ip_nat_pptp *nat_pptp_info = &ct->nat.help.nat_pptp_info;
151 u_int16_t msg, new_callid;
152 unsigned int cid_off;
154 new_callid = htons(ct_pptp_info->pns_call_id);
156 switch (msg = ntohs(ctlh->messageType)) {
157 case PPTP_OUT_CALL_REQUEST:
158 cid_off = offsetof(union pptp_ctrl_union, ocreq.callID);
159 /* FIXME: ideally we would want to reserve a call ID
160 * here. current netfilter NAT core is not able to do
161 * this :( For now we use TCP source port. This breaks
162 * multiple calls within one control session */
164 /* save original call ID in nat_info */
165 nat_pptp_info->pns_call_id = ct_pptp_info->pns_call_id;
167 /* don't use tcph->source since we are at a DSTmanip
168 * hook (e.g. PREROUTING) and pkt is not mangled yet */
169 new_callid = ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u.tcp.port;
171 /* save new call ID in ct info */
172 ct_pptp_info->pns_call_id = ntohs(new_callid);
174 case PPTP_IN_CALL_REPLY:
175 cid_off = offsetof(union pptp_ctrl_union, icreq.callID);
177 case PPTP_CALL_CLEAR_REQUEST:
178 cid_off = offsetof(union pptp_ctrl_union, clrreq.callID);
181 DEBUGP("unknown outbound packet 0x%04x:%s\n", msg,
182 (msg <= PPTP_MSG_MAX)?
183 pptp_msg_name[msg]:pptp_msg_name[0]);
186 case PPTP_SET_LINK_INFO:
187 /* only need to NAT in case PAC is behind NAT box */
188 case PPTP_START_SESSION_REQUEST:
189 case PPTP_START_SESSION_REPLY:
190 case PPTP_STOP_SESSION_REQUEST:
191 case PPTP_STOP_SESSION_REPLY:
192 case PPTP_ECHO_REQUEST:
193 case PPTP_ECHO_REPLY:
194 /* no need to alter packet */
198 /* only OUT_CALL_REQUEST, IN_CALL_REPLY, CALL_CLEAR_REQUEST pass
200 DEBUGP("altering call id from 0x%04x to 0x%04x\n",
201 ntohs(*(u_int16_t *)pptpReq + cid_off), ntohs(new_callid));
204 if (ip_nat_mangle_tcp_packet(pskb, ct, ctinfo,
205 cid_off + sizeof(struct pptp_pkt_hdr) +
206 sizeof(struct PptpControlHeader),
207 sizeof(new_callid), (char *)&new_callid,
208 sizeof(new_callid)) == 0)
215 pptp_exp_gre(struct ip_conntrack_expect *expect_orig,
216 struct ip_conntrack_expect *expect_reply)
218 struct ip_ct_pptp_master *ct_pptp_info =
219 &expect_orig->master->help.ct_pptp_info;
220 struct ip_nat_pptp *nat_pptp_info =
221 &expect_orig->master->nat.help.nat_pptp_info;
223 struct ip_conntrack *ct = expect_orig->master;
225 struct ip_conntrack_tuple inv_t;
226 struct ip_conntrack_tuple *orig_t, *reply_t;
228 /* save original PAC call ID in nat_info */
229 nat_pptp_info->pac_call_id = ct_pptp_info->pac_call_id;
231 /* alter expectation */
232 orig_t = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
233 reply_t = &ct->tuplehash[IP_CT_DIR_REPLY].tuple;
235 /* alter expectation for PNS->PAC direction */
236 invert_tuplepr(&inv_t, &expect_orig->tuple);
237 expect_orig->saved_proto.gre.key = htons(ct_pptp_info->pns_call_id);
238 expect_orig->tuple.src.u.gre.key = htons(nat_pptp_info->pns_call_id);
239 expect_orig->tuple.dst.u.gre.key = htons(ct_pptp_info->pac_call_id);
240 expect_orig->dir = IP_CT_DIR_ORIGINAL;
241 inv_t.src.ip = reply_t->src.ip;
242 inv_t.dst.ip = reply_t->dst.ip;
243 inv_t.src.u.gre.key = htons(nat_pptp_info->pac_call_id);
244 inv_t.dst.u.gre.key = htons(ct_pptp_info->pns_call_id);
246 if (!ip_conntrack_expect_related(expect_orig)) {
247 DEBUGP("successfully registered expect\n");
249 DEBUGP("can't expect_related(expect_orig)\n");
253 /* alter expectation for PAC->PNS direction */
254 invert_tuplepr(&inv_t, &expect_reply->tuple);
255 expect_reply->saved_proto.gre.key = htons(nat_pptp_info->pns_call_id);
256 expect_reply->tuple.src.u.gre.key = htons(nat_pptp_info->pac_call_id);
257 expect_reply->tuple.dst.u.gre.key = htons(ct_pptp_info->pns_call_id);
258 expect_reply->dir = IP_CT_DIR_REPLY;
259 inv_t.src.ip = orig_t->src.ip;
260 inv_t.dst.ip = orig_t->dst.ip;
261 inv_t.src.u.gre.key = htons(nat_pptp_info->pns_call_id);
262 inv_t.dst.u.gre.key = htons(ct_pptp_info->pac_call_id);
264 if (!ip_conntrack_expect_related(expect_reply)) {
265 DEBUGP("successfully registered expect\n");
267 DEBUGP("can't expect_related(expect_reply)\n");
268 ip_conntrack_unexpect_related(expect_orig);
272 if (ip_ct_gre_keymap_add(ct, &expect_reply->tuple, 0) < 0) {
273 DEBUGP("can't register original keymap\n");
274 ip_conntrack_unexpect_related(expect_orig);
275 ip_conntrack_unexpect_related(expect_reply);
279 if (ip_ct_gre_keymap_add(ct, &inv_t, 1) < 0) {
280 DEBUGP("can't register reply keymap\n");
281 ip_conntrack_unexpect_related(expect_orig);
282 ip_conntrack_unexpect_related(expect_reply);
283 ip_ct_gre_keymap_destroy(ct);
290 /* inbound packets == from PAC to PNS */
292 pptp_inbound_pkt(struct sk_buff **pskb,
293 struct ip_conntrack *ct,
294 enum ip_conntrack_info ctinfo,
295 struct PptpControlHeader *ctlh,
296 union pptp_ctrl_union *pptpReq)
298 struct ip_nat_pptp *nat_pptp_info = &ct->nat.help.nat_pptp_info;
299 u_int16_t msg, new_cid = 0, new_pcid;
300 unsigned int pcid_off, cid_off = 0;
302 new_pcid = htons(nat_pptp_info->pns_call_id);
304 switch (msg = ntohs(ctlh->messageType)) {
305 case PPTP_OUT_CALL_REPLY:
306 pcid_off = offsetof(union pptp_ctrl_union, ocack.peersCallID);
307 cid_off = offsetof(union pptp_ctrl_union, ocack.callID);
309 case PPTP_IN_CALL_CONNECT:
310 pcid_off = offsetof(union pptp_ctrl_union, iccon.peersCallID);
312 case PPTP_IN_CALL_REQUEST:
313 /* only need to nat in case PAC is behind NAT box */
315 case PPTP_WAN_ERROR_NOTIFY:
316 pcid_off = offsetof(union pptp_ctrl_union, wanerr.peersCallID);
318 case PPTP_CALL_DISCONNECT_NOTIFY:
319 pcid_off = offsetof(union pptp_ctrl_union, disc.callID);
321 case PPTP_SET_LINK_INFO:
322 pcid_off = offsetof(union pptp_ctrl_union, setlink.peersCallID);
326 DEBUGP("unknown inbound packet %s\n", (msg <= PPTP_MSG_MAX)?
327 pptp_msg_name[msg]:pptp_msg_name[0]);
330 case PPTP_START_SESSION_REQUEST:
331 case PPTP_START_SESSION_REPLY:
332 case PPTP_STOP_SESSION_REQUEST:
333 case PPTP_STOP_SESSION_REPLY:
334 case PPTP_ECHO_REQUEST:
335 case PPTP_ECHO_REPLY:
336 /* no need to alter packet */
340 /* only OUT_CALL_REPLY, IN_CALL_CONNECT, IN_CALL_REQUEST,
341 * WAN_ERROR_NOTIFY, CALL_DISCONNECT_NOTIFY pass down here */
344 DEBUGP("altering peer call id from 0x%04x to 0x%04x\n",
345 ntohs(*(u_int16_t *)pptpReq + pcid_off), ntohs(new_pcid));
347 if (ip_nat_mangle_tcp_packet(pskb, ct, ctinfo,
348 pcid_off + sizeof(struct pptp_pkt_hdr) +
349 sizeof(struct PptpControlHeader),
350 sizeof(new_pcid), (char *)&new_pcid,
351 sizeof(new_pcid)) == 0)
355 DEBUGP("altering call id from 0x%04x to 0x%04x\n",
356 ntohs(*(u_int16_t *)pptpReq + cid_off), ntohs(new_cid));
357 if (ip_nat_mangle_tcp_packet(pskb, ct, ctinfo,
358 cid_off + sizeof(struct pptp_pkt_hdr) +
359 sizeof(struct PptpControlHeader),
360 sizeof(new_cid), (char *)&new_cid,
361 sizeof(new_cid)) == 0)
368 extern int __init ip_nat_proto_gre_init(void);
369 extern void __exit ip_nat_proto_gre_fini(void);
371 static int __init init(void)
375 DEBUGP("%s: registering NAT helper\n", __FILE__);
377 ret = ip_nat_proto_gre_init();
381 BUG_ON(ip_nat_pptp_hook_outbound);
382 ip_nat_pptp_hook_outbound = &pptp_outbound_pkt;
384 BUG_ON(ip_nat_pptp_hook_inbound);
385 ip_nat_pptp_hook_inbound = &pptp_inbound_pkt;
387 BUG_ON(ip_nat_pptp_hook_exp_gre);
388 ip_nat_pptp_hook_exp_gre = &pptp_exp_gre;
390 BUG_ON(ip_nat_pptp_hook_expectfn);
391 ip_nat_pptp_hook_expectfn = &pptp_nat_expected;
393 printk("ip_nat_pptp version %s loaded\n", IP_NAT_PPTP_VERSION);
397 static void __exit fini(void)
399 DEBUGP("cleanup_module\n" );
401 ip_nat_pptp_hook_expectfn = NULL;
402 ip_nat_pptp_hook_exp_gre = NULL;
403 ip_nat_pptp_hook_inbound = NULL;
404 ip_nat_pptp_hook_outbound = NULL;
406 ip_nat_proto_gre_fini();
407 /* Make sure noone calls it, meanwhile */
410 printk("ip_nat_pptp version %s unloaded\n", IP_NAT_PPTP_VERSION);