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/module.h>
40 #include <linux/tcp.h>
43 #include <linux/netfilter_ipv4/ip_nat.h>
44 #include <linux/netfilter_ipv4/ip_nat_rule.h>
45 #include <linux/netfilter_ipv4/ip_nat_helper.h>
46 #include <linux/netfilter_ipv4/ip_nat_pptp.h>
47 #include <linux/netfilter_ipv4/ip_conntrack_core.h>
48 #include <linux/netfilter_ipv4/ip_conntrack_helper.h>
49 #include <linux/netfilter_ipv4/ip_conntrack_proto_gre.h>
50 #include <linux/netfilter_ipv4/ip_conntrack_pptp.h>
52 #define IP_NAT_PPTP_VERSION "3.0"
54 #define REQ_CID(req, off) (*(u_int16_t *)((char *)(req) + (off)))
56 MODULE_LICENSE("GPL");
57 MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
58 MODULE_DESCRIPTION("Netfilter NAT helper module for PPTP");
62 extern const char *pptp_msg_name[];
63 #define DEBUGP(format, args...) printk(KERN_DEBUG "%s:%s: " format, __FILE__, \
64 __FUNCTION__, ## args)
66 #define DEBUGP(format, args...)
69 static void pptp_nat_expected(struct ip_conntrack *ct,
70 struct ip_conntrack_expect *exp)
72 struct ip_conntrack *master = ct->master;
73 struct ip_conntrack_expect *other_exp;
74 struct ip_conntrack_tuple t;
75 struct ip_ct_pptp_master *ct_pptp_info;
76 struct ip_nat_pptp *nat_pptp_info;
77 struct ip_nat_range range;
79 ct_pptp_info = &master->help.ct_pptp_info;
80 nat_pptp_info = &master->nat.help.nat_pptp_info;
82 /* And here goes the grand finale of corrosion... */
84 if (exp->dir == IP_CT_DIR_ORIGINAL) {
85 DEBUGP("we are PNS->PAC\n");
86 /* therefore, build tuple for PAC->PNS */
87 t.src.ip = master->tuplehash[IP_CT_DIR_REPLY].tuple.src.ip;
88 t.src.u.gre.key = htons(master->help.ct_pptp_info.pac_call_id);
89 t.dst.ip = master->tuplehash[IP_CT_DIR_REPLY].tuple.dst.ip;
90 t.dst.u.gre.key = htons(master->help.ct_pptp_info.pns_call_id);
91 t.dst.protonum = IPPROTO_GRE;
93 DEBUGP("we are PAC->PNS\n");
94 /* build tuple for PNS->PAC */
95 t.src.ip = master->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.ip;
97 htons(master->nat.help.nat_pptp_info.pns_call_id);
98 t.dst.ip = master->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.ip;
100 htons(master->nat.help.nat_pptp_info.pac_call_id);
101 t.dst.protonum = IPPROTO_GRE;
104 DEBUGP("trying to unexpect other dir: ");
106 other_exp = ip_conntrack_expect_find(&t);
108 ip_conntrack_unexpect_related(other_exp);
109 ip_conntrack_expect_put(other_exp);
112 DEBUGP("not found!\n");
115 /* This must be a fresh one. */
116 BUG_ON(ct->status & IPS_NAT_DONE_MASK);
118 /* Change src to where master sends to */
119 range.flags = IP_NAT_RANGE_MAP_IPS;
120 range.min_ip = range.max_ip
121 = ct->master->tuplehash[!exp->dir].tuple.dst.ip;
122 if (exp->dir == IP_CT_DIR_ORIGINAL) {
123 range.flags |= IP_NAT_RANGE_PROTO_SPECIFIED;
124 range.min = range.max = exp->saved_proto;
126 /* hook doesn't matter, but it has to do source manip */
127 ip_nat_setup_info(ct, &range, NF_IP_POST_ROUTING);
129 /* For DST manip, map port here to where it's expected. */
130 range.flags = IP_NAT_RANGE_MAP_IPS;
131 range.min_ip = range.max_ip
132 = ct->master->tuplehash[!exp->dir].tuple.src.ip;
133 if (exp->dir == IP_CT_DIR_REPLY) {
134 range.flags |= IP_NAT_RANGE_PROTO_SPECIFIED;
135 range.min = range.max = exp->saved_proto;
137 /* hook doesn't matter, but it has to do destination manip */
138 ip_nat_setup_info(ct, &range, NF_IP_PRE_ROUTING);
141 /* outbound packets == from PNS to PAC */
143 pptp_outbound_pkt(struct sk_buff **pskb,
144 struct ip_conntrack *ct,
145 enum ip_conntrack_info ctinfo,
146 struct PptpControlHeader *ctlh,
147 union pptp_ctrl_union *pptpReq)
150 struct ip_ct_pptp_master *ct_pptp_info = &ct->help.ct_pptp_info;
151 struct ip_nat_pptp *nat_pptp_info = &ct->nat.help.nat_pptp_info;
152 u_int16_t msg, new_callid;
153 unsigned int cid_off;
155 new_callid = htons(ct_pptp_info->pns_call_id);
157 switch (msg = ntohs(ctlh->messageType)) {
158 case PPTP_OUT_CALL_REQUEST:
159 cid_off = offsetof(union pptp_ctrl_union, ocreq.callID);
160 /* FIXME: ideally we would want to reserve a call ID
161 * here. current netfilter NAT core is not able to do
162 * this :( For now we use TCP source port. This breaks
163 * multiple calls within one control session */
165 /* save original call ID in nat_info */
166 nat_pptp_info->pns_call_id = ct_pptp_info->pns_call_id;
168 /* don't use tcph->source since we are at a DSTmanip
169 * hook (e.g. PREROUTING) and pkt is not mangled yet */
170 new_callid = ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u.tcp.port;
172 /* save new call ID in ct info */
173 ct_pptp_info->pns_call_id = ntohs(new_callid);
175 case PPTP_IN_CALL_REPLY:
176 cid_off = offsetof(union pptp_ctrl_union, icreq.callID);
178 case PPTP_CALL_CLEAR_REQUEST:
179 cid_off = offsetof(union pptp_ctrl_union, clrreq.callID);
182 DEBUGP("unknown outbound packet 0x%04x:%s\n", msg,
183 (msg <= PPTP_MSG_MAX)?
184 pptp_msg_name[msg]:pptp_msg_name[0]);
187 case PPTP_SET_LINK_INFO:
188 /* only need to NAT in case PAC is behind NAT box */
189 case PPTP_START_SESSION_REQUEST:
190 case PPTP_START_SESSION_REPLY:
191 case PPTP_STOP_SESSION_REQUEST:
192 case PPTP_STOP_SESSION_REPLY:
193 case PPTP_ECHO_REQUEST:
194 case PPTP_ECHO_REPLY:
195 /* no need to alter packet */
199 /* only OUT_CALL_REQUEST, IN_CALL_REPLY, CALL_CLEAR_REQUEST pass
201 DEBUGP("altering call id from 0x%04x to 0x%04x\n",
202 ntohs(REQ_CID(pptpReq, cid_off)), ntohs(new_callid));
205 if (ip_nat_mangle_tcp_packet(pskb, ct, ctinfo,
206 cid_off + sizeof(struct pptp_pkt_hdr) +
207 sizeof(struct PptpControlHeader),
208 sizeof(new_callid), (char *)&new_callid,
209 sizeof(new_callid)) == 0)
216 pptp_exp_gre(struct ip_conntrack_expect *expect_orig,
217 struct ip_conntrack_expect *expect_reply)
219 struct ip_ct_pptp_master *ct_pptp_info =
220 &expect_orig->master->help.ct_pptp_info;
221 struct ip_nat_pptp *nat_pptp_info =
222 &expect_orig->master->nat.help.nat_pptp_info;
224 struct ip_conntrack *ct = expect_orig->master;
226 struct ip_conntrack_tuple inv_t;
227 struct ip_conntrack_tuple *orig_t, *reply_t;
229 /* save original PAC call ID in nat_info */
230 nat_pptp_info->pac_call_id = ct_pptp_info->pac_call_id;
232 /* alter expectation */
233 orig_t = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
234 reply_t = &ct->tuplehash[IP_CT_DIR_REPLY].tuple;
236 /* alter expectation for PNS->PAC direction */
237 invert_tuplepr(&inv_t, &expect_orig->tuple);
238 expect_orig->saved_proto.gre.key = htons(ct_pptp_info->pns_call_id);
239 expect_orig->tuple.src.u.gre.key = htons(nat_pptp_info->pns_call_id);
240 expect_orig->tuple.dst.u.gre.key = htons(ct_pptp_info->pac_call_id);
241 expect_orig->dir = IP_CT_DIR_ORIGINAL;
242 inv_t.src.ip = reply_t->src.ip;
243 inv_t.dst.ip = reply_t->dst.ip;
244 inv_t.src.u.gre.key = htons(nat_pptp_info->pac_call_id);
245 inv_t.dst.u.gre.key = htons(ct_pptp_info->pns_call_id);
247 if (!ip_conntrack_expect_related(expect_orig)) {
248 DEBUGP("successfully registered expect\n");
250 DEBUGP("can't expect_related(expect_orig)\n");
254 /* alter expectation for PAC->PNS direction */
255 invert_tuplepr(&inv_t, &expect_reply->tuple);
256 expect_reply->saved_proto.gre.key = htons(nat_pptp_info->pns_call_id);
257 expect_reply->tuple.src.u.gre.key = htons(nat_pptp_info->pac_call_id);
258 expect_reply->tuple.dst.u.gre.key = htons(ct_pptp_info->pns_call_id);
259 expect_reply->dir = IP_CT_DIR_REPLY;
260 inv_t.src.ip = orig_t->src.ip;
261 inv_t.dst.ip = orig_t->dst.ip;
262 inv_t.src.u.gre.key = htons(nat_pptp_info->pns_call_id);
263 inv_t.dst.u.gre.key = htons(ct_pptp_info->pac_call_id);
265 if (!ip_conntrack_expect_related(expect_reply)) {
266 DEBUGP("successfully registered expect\n");
268 DEBUGP("can't expect_related(expect_reply)\n");
269 ip_conntrack_unexpect_related(expect_orig);
273 if (ip_ct_gre_keymap_add(ct, &expect_reply->tuple, 0) < 0) {
274 DEBUGP("can't register original keymap\n");
275 ip_conntrack_unexpect_related(expect_orig);
276 ip_conntrack_unexpect_related(expect_reply);
280 if (ip_ct_gre_keymap_add(ct, &inv_t, 1) < 0) {
281 DEBUGP("can't register reply keymap\n");
282 ip_conntrack_unexpect_related(expect_orig);
283 ip_conntrack_unexpect_related(expect_reply);
284 ip_ct_gre_keymap_destroy(ct);
291 /* inbound packets == from PAC to PNS */
293 pptp_inbound_pkt(struct sk_buff **pskb,
294 struct ip_conntrack *ct,
295 enum ip_conntrack_info ctinfo,
296 struct PptpControlHeader *ctlh,
297 union pptp_ctrl_union *pptpReq)
299 struct ip_nat_pptp *nat_pptp_info = &ct->nat.help.nat_pptp_info;
300 u_int16_t msg, new_cid = 0, new_pcid;
301 unsigned int pcid_off, cid_off = 0;
303 new_pcid = htons(nat_pptp_info->pns_call_id);
305 switch (msg = ntohs(ctlh->messageType)) {
306 case PPTP_OUT_CALL_REPLY:
307 pcid_off = offsetof(union pptp_ctrl_union, ocack.peersCallID);
308 cid_off = offsetof(union pptp_ctrl_union, ocack.callID);
310 case PPTP_IN_CALL_CONNECT:
311 pcid_off = offsetof(union pptp_ctrl_union, iccon.peersCallID);
313 case PPTP_IN_CALL_REQUEST:
314 /* only need to nat in case PAC is behind NAT box */
316 case PPTP_WAN_ERROR_NOTIFY:
317 pcid_off = offsetof(union pptp_ctrl_union, wanerr.peersCallID);
319 case PPTP_CALL_DISCONNECT_NOTIFY:
320 pcid_off = offsetof(union pptp_ctrl_union, disc.callID);
322 case PPTP_SET_LINK_INFO:
323 pcid_off = offsetof(union pptp_ctrl_union, setlink.peersCallID);
327 DEBUGP("unknown inbound packet %s\n", (msg <= PPTP_MSG_MAX)?
328 pptp_msg_name[msg]:pptp_msg_name[0]);
331 case PPTP_START_SESSION_REQUEST:
332 case PPTP_START_SESSION_REPLY:
333 case PPTP_STOP_SESSION_REQUEST:
334 case PPTP_STOP_SESSION_REPLY:
335 case PPTP_ECHO_REQUEST:
336 case PPTP_ECHO_REPLY:
337 /* no need to alter packet */
341 /* only OUT_CALL_REPLY, IN_CALL_CONNECT, IN_CALL_REQUEST,
342 * WAN_ERROR_NOTIFY, CALL_DISCONNECT_NOTIFY pass down here */
345 DEBUGP("altering peer call id from 0x%04x to 0x%04x\n",
346 ntohs(REQ_CID(pptpReq, pcid_off)), ntohs(new_pcid));
348 if (ip_nat_mangle_tcp_packet(pskb, ct, ctinfo,
349 pcid_off + sizeof(struct pptp_pkt_hdr) +
350 sizeof(struct PptpControlHeader),
351 sizeof(new_pcid), (char *)&new_pcid,
352 sizeof(new_pcid)) == 0)
356 DEBUGP("altering call id from 0x%04x to 0x%04x\n",
357 ntohs(REQ_CID(pptpReq, cid_off)), ntohs(new_cid));
358 if (ip_nat_mangle_tcp_packet(pskb, ct, ctinfo,
359 cid_off + sizeof(struct pptp_pkt_hdr) +
360 sizeof(struct PptpControlHeader),
361 sizeof(new_cid), (char *)&new_cid,
362 sizeof(new_cid)) == 0)
369 extern int __init ip_nat_proto_gre_init(void);
370 extern void __exit ip_nat_proto_gre_fini(void);
372 static int __init ip_nat_helper_pptp_init(void)
376 DEBUGP("%s: registering NAT helper\n", __FILE__);
378 ret = ip_nat_proto_gre_init();
382 BUG_ON(ip_nat_pptp_hook_outbound);
383 ip_nat_pptp_hook_outbound = &pptp_outbound_pkt;
385 BUG_ON(ip_nat_pptp_hook_inbound);
386 ip_nat_pptp_hook_inbound = &pptp_inbound_pkt;
388 BUG_ON(ip_nat_pptp_hook_exp_gre);
389 ip_nat_pptp_hook_exp_gre = &pptp_exp_gre;
391 BUG_ON(ip_nat_pptp_hook_expectfn);
392 ip_nat_pptp_hook_expectfn = &pptp_nat_expected;
394 printk("ip_nat_pptp version %s loaded\n", IP_NAT_PPTP_VERSION);
398 static void __exit ip_nat_helper_pptp_fini(void)
400 DEBUGP("cleanup_module\n" );
402 ip_nat_pptp_hook_expectfn = NULL;
403 ip_nat_pptp_hook_exp_gre = NULL;
404 ip_nat_pptp_hook_inbound = NULL;
405 ip_nat_pptp_hook_outbound = NULL;
407 ip_nat_proto_gre_fini();
408 /* Make sure noone calls it, meanwhile */
411 printk("ip_nat_pptp version %s unloaded\n", IP_NAT_PPTP_VERSION);
414 module_init(ip_nat_helper_pptp_init);
415 module_exit(ip_nat_helper_pptp_fini);