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) (*(__be16 *)((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 = 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 = 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;
96 t.src.u.gre.key = master->nat.help.nat_pptp_info.pns_call_id;
97 t.dst.ip = master->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.ip;
98 t.dst.u.gre.key = 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 /* This must be a fresh one. */
114 BUG_ON(ct->status & IPS_NAT_DONE_MASK);
116 /* Change src to where master sends to */
117 range.flags = IP_NAT_RANGE_MAP_IPS;
118 range.min_ip = range.max_ip
119 = ct->master->tuplehash[!exp->dir].tuple.dst.ip;
120 if (exp->dir == IP_CT_DIR_ORIGINAL) {
121 range.flags |= IP_NAT_RANGE_PROTO_SPECIFIED;
122 range.min = range.max = exp->saved_proto;
124 /* hook doesn't matter, but it has to do source manip */
125 ip_nat_setup_info(ct, &range, NF_IP_POST_ROUTING);
127 /* For DST manip, map port here to where it's expected. */
128 range.flags = IP_NAT_RANGE_MAP_IPS;
129 range.min_ip = range.max_ip
130 = ct->master->tuplehash[!exp->dir].tuple.src.ip;
131 if (exp->dir == IP_CT_DIR_REPLY) {
132 range.flags |= IP_NAT_RANGE_PROTO_SPECIFIED;
133 range.min = range.max = exp->saved_proto;
135 /* hook doesn't matter, but it has to do destination manip */
136 ip_nat_setup_info(ct, &range, NF_IP_PRE_ROUTING);
139 /* outbound packets == from PNS to PAC */
141 pptp_outbound_pkt(struct sk_buff **pskb,
142 struct ip_conntrack *ct,
143 enum ip_conntrack_info ctinfo,
144 struct PptpControlHeader *ctlh,
145 union pptp_ctrl_union *pptpReq)
148 struct ip_ct_pptp_master *ct_pptp_info = &ct->help.ct_pptp_info;
149 struct ip_nat_pptp *nat_pptp_info = &ct->nat.help.nat_pptp_info;
152 unsigned int cid_off;
154 new_callid = 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 = new_callid;
174 case PPTP_IN_CALL_REPLY:
175 cid_off = offsetof(union pptp_ctrl_union, icack.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(REQ_CID(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_conntrack *ct = expect_orig->master;
219 struct ip_ct_pptp_master *ct_pptp_info = &ct->help.ct_pptp_info;
220 struct ip_nat_pptp *nat_pptp_info = &ct->nat.help.nat_pptp_info;
222 /* save original PAC call ID in nat_info */
223 nat_pptp_info->pac_call_id = ct_pptp_info->pac_call_id;
225 /* alter expectation for PNS->PAC direction */
226 expect_orig->saved_proto.gre.key = ct_pptp_info->pns_call_id;
227 expect_orig->tuple.src.u.gre.key = nat_pptp_info->pns_call_id;
228 expect_orig->tuple.dst.u.gre.key = ct_pptp_info->pac_call_id;
229 expect_orig->dir = IP_CT_DIR_ORIGINAL;
231 /* alter expectation for PAC->PNS direction */
232 expect_reply->saved_proto.gre.key = nat_pptp_info->pns_call_id;
233 expect_reply->tuple.src.u.gre.key = nat_pptp_info->pac_call_id;
234 expect_reply->tuple.dst.u.gre.key = ct_pptp_info->pns_call_id;
235 expect_reply->dir = IP_CT_DIR_REPLY;
238 /* inbound packets == from PAC to PNS */
240 pptp_inbound_pkt(struct sk_buff **pskb,
241 struct ip_conntrack *ct,
242 enum ip_conntrack_info ctinfo,
243 struct PptpControlHeader *ctlh,
244 union pptp_ctrl_union *pptpReq)
246 struct ip_nat_pptp *nat_pptp_info = &ct->nat.help.nat_pptp_info;
249 unsigned int pcid_off;
251 new_pcid = nat_pptp_info->pns_call_id;
253 switch (msg = ntohs(ctlh->messageType)) {
254 case PPTP_OUT_CALL_REPLY:
255 pcid_off = offsetof(union pptp_ctrl_union, ocack.peersCallID);
257 case PPTP_IN_CALL_CONNECT:
258 pcid_off = offsetof(union pptp_ctrl_union, iccon.peersCallID);
260 case PPTP_IN_CALL_REQUEST:
261 /* only need to nat in case PAC is behind NAT box */
263 case PPTP_WAN_ERROR_NOTIFY:
264 pcid_off = offsetof(union pptp_ctrl_union, wanerr.peersCallID);
266 case PPTP_CALL_DISCONNECT_NOTIFY:
267 pcid_off = offsetof(union pptp_ctrl_union, disc.callID);
269 case PPTP_SET_LINK_INFO:
270 pcid_off = offsetof(union pptp_ctrl_union, setlink.peersCallID);
274 DEBUGP("unknown inbound packet %s\n", (msg <= PPTP_MSG_MAX)?
275 pptp_msg_name[msg]:pptp_msg_name[0]);
278 case PPTP_START_SESSION_REQUEST:
279 case PPTP_START_SESSION_REPLY:
280 case PPTP_STOP_SESSION_REQUEST:
281 case PPTP_STOP_SESSION_REPLY:
282 case PPTP_ECHO_REQUEST:
283 case PPTP_ECHO_REPLY:
284 /* no need to alter packet */
288 /* only OUT_CALL_REPLY, IN_CALL_CONNECT, IN_CALL_REQUEST,
289 * WAN_ERROR_NOTIFY, CALL_DISCONNECT_NOTIFY pass down here */
292 DEBUGP("altering peer call id from 0x%04x to 0x%04x\n",
293 ntohs(REQ_CID(pptpReq, pcid_off)), ntohs(new_pcid));
295 if (ip_nat_mangle_tcp_packet(pskb, ct, ctinfo,
296 pcid_off + sizeof(struct pptp_pkt_hdr) +
297 sizeof(struct PptpControlHeader),
298 sizeof(new_pcid), (char *)&new_pcid,
299 sizeof(new_pcid)) == 0)
305 extern int __init ip_nat_proto_gre_init(void);
306 extern void __exit ip_nat_proto_gre_fini(void);
308 static int __init ip_nat_helper_pptp_init(void)
312 DEBUGP("%s: registering NAT helper\n", __FILE__);
314 ret = ip_nat_proto_gre_init();
318 BUG_ON(ip_nat_pptp_hook_outbound);
319 ip_nat_pptp_hook_outbound = &pptp_outbound_pkt;
321 BUG_ON(ip_nat_pptp_hook_inbound);
322 ip_nat_pptp_hook_inbound = &pptp_inbound_pkt;
324 BUG_ON(ip_nat_pptp_hook_exp_gre);
325 ip_nat_pptp_hook_exp_gre = &pptp_exp_gre;
327 BUG_ON(ip_nat_pptp_hook_expectfn);
328 ip_nat_pptp_hook_expectfn = &pptp_nat_expected;
330 printk("ip_nat_pptp version %s loaded\n", IP_NAT_PPTP_VERSION);
334 static void __exit ip_nat_helper_pptp_fini(void)
336 DEBUGP("cleanup_module\n" );
338 ip_nat_pptp_hook_expectfn = NULL;
339 ip_nat_pptp_hook_exp_gre = NULL;
340 ip_nat_pptp_hook_inbound = NULL;
341 ip_nat_pptp_hook_outbound = NULL;
343 ip_nat_proto_gre_fini();
344 /* Make sure noone calls it, meanwhile */
347 printk("ip_nat_pptp version %s unloaded\n", IP_NAT_PPTP_VERSION);
350 module_init(ip_nat_helper_pptp_init);
351 module_exit(ip_nat_helper_pptp_fini);