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
;
152 u_int16_t msg
, *cid
= NULL
, new_callid
;
154 new_callid
= htons(ct_pptp_info
->pns_call_id
);
156 switch (msg
= ntohs(ctlh
->messageType
)) {
157 case PPTP_OUT_CALL_REQUEST
:
158 cid
= &pptpReq
->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
= &pptpReq
->icreq
.callID
;
177 case PPTP_CALL_CLEAR_REQUEST
:
178 cid
= &pptpReq
->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
203 DEBUGP("altering call id from 0x%04x to 0x%04x\n",
204 ntohs(*cid
), ntohs(new_callid
));
207 if (ip_nat_mangle_tcp_packet(pskb
, ct
, ctinfo
,
208 (void *)cid
- ((void *)ctlh
- sizeof(struct pptp_pkt_hdr
)),
211 sizeof(new_callid
)) == 0)
218 pptp_exp_gre(struct ip_conntrack_expect
*expect_orig
,
219 struct ip_conntrack_expect
*expect_reply
)
221 struct ip_ct_pptp_master
*ct_pptp_info
=
222 &expect_orig
->master
->help
.ct_pptp_info
;
223 struct ip_nat_pptp
*nat_pptp_info
=
224 &expect_orig
->master
->nat
.help
.nat_pptp_info
;
226 struct ip_conntrack
*ct
= expect_orig
->master
;
228 struct ip_conntrack_tuple inv_t
;
229 struct ip_conntrack_tuple
*orig_t
, *reply_t
;
231 /* save original PAC call ID in nat_info */
232 nat_pptp_info
->pac_call_id
= ct_pptp_info
->pac_call_id
;
234 /* alter expectation */
235 orig_t
= &ct
->tuplehash
[IP_CT_DIR_ORIGINAL
].tuple
;
236 reply_t
= &ct
->tuplehash
[IP_CT_DIR_REPLY
].tuple
;
238 /* alter expectation for PNS->PAC direction */
239 invert_tuplepr(&inv_t
, &expect_orig
->tuple
);
240 expect_orig
->saved_proto
.gre
.key
= htons(ct_pptp_info
->pns_call_id
);
241 expect_orig
->tuple
.src
.u
.gre
.key
= htons(nat_pptp_info
->pns_call_id
);
242 expect_orig
->tuple
.dst
.u
.gre
.key
= htons(ct_pptp_info
->pac_call_id
);
243 expect_orig
->dir
= IP_CT_DIR_ORIGINAL
;
244 inv_t
.src
.ip
= reply_t
->src
.ip
;
245 inv_t
.dst
.ip
= reply_t
->dst
.ip
;
246 inv_t
.src
.u
.gre
.key
= htons(nat_pptp_info
->pac_call_id
);
247 inv_t
.dst
.u
.gre
.key
= htons(ct_pptp_info
->pns_call_id
);
249 if (!ip_conntrack_expect_related(expect_orig
)) {
250 DEBUGP("successfully registered expect\n");
252 DEBUGP("can't expect_related(expect_orig)\n");
256 /* alter expectation for PAC->PNS direction */
257 invert_tuplepr(&inv_t
, &expect_reply
->tuple
);
258 expect_reply
->saved_proto
.gre
.key
= htons(nat_pptp_info
->pns_call_id
);
259 expect_reply
->tuple
.src
.u
.gre
.key
= htons(nat_pptp_info
->pac_call_id
);
260 expect_reply
->tuple
.dst
.u
.gre
.key
= htons(ct_pptp_info
->pns_call_id
);
261 expect_reply
->dir
= IP_CT_DIR_REPLY
;
262 inv_t
.src
.ip
= orig_t
->src
.ip
;
263 inv_t
.dst
.ip
= orig_t
->dst
.ip
;
264 inv_t
.src
.u
.gre
.key
= htons(nat_pptp_info
->pns_call_id
);
265 inv_t
.dst
.u
.gre
.key
= htons(ct_pptp_info
->pac_call_id
);
267 if (!ip_conntrack_expect_related(expect_reply
)) {
268 DEBUGP("successfully registered expect\n");
270 DEBUGP("can't expect_related(expect_reply)\n");
271 ip_conntrack_unexpect_related(expect_orig
);
275 if (ip_ct_gre_keymap_add(ct
, &expect_reply
->tuple
, 0) < 0) {
276 DEBUGP("can't register original keymap\n");
277 ip_conntrack_unexpect_related(expect_orig
);
278 ip_conntrack_unexpect_related(expect_reply
);
282 if (ip_ct_gre_keymap_add(ct
, &inv_t
, 1) < 0) {
283 DEBUGP("can't register reply keymap\n");
284 ip_conntrack_unexpect_related(expect_orig
);
285 ip_conntrack_unexpect_related(expect_reply
);
286 ip_ct_gre_keymap_destroy(ct
);
293 /* inbound packets == from PAC to PNS */
295 pptp_inbound_pkt(struct sk_buff
**pskb
,
296 struct ip_conntrack
*ct
,
297 enum ip_conntrack_info ctinfo
,
298 struct PptpControlHeader
*ctlh
,
299 union pptp_ctrl_union
*pptpReq
)
301 struct ip_nat_pptp
*nat_pptp_info
= &ct
->nat
.help
.nat_pptp_info
;
302 u_int16_t msg
, new_cid
= 0, new_pcid
, *pcid
= NULL
, *cid
= NULL
;
304 int ret
= NF_ACCEPT
, rv
;
306 new_pcid
= htons(nat_pptp_info
->pns_call_id
);
308 switch (msg
= ntohs(ctlh
->messageType
)) {
309 case PPTP_OUT_CALL_REPLY
:
310 pcid
= &pptpReq
->ocack
.peersCallID
;
311 cid
= &pptpReq
->ocack
.callID
;
313 case PPTP_IN_CALL_CONNECT
:
314 pcid
= &pptpReq
->iccon
.peersCallID
;
316 case PPTP_IN_CALL_REQUEST
:
317 /* only need to nat in case PAC is behind NAT box */
319 case PPTP_WAN_ERROR_NOTIFY
:
320 pcid
= &pptpReq
->wanerr
.peersCallID
;
322 case PPTP_CALL_DISCONNECT_NOTIFY
:
323 pcid
= &pptpReq
->disc
.callID
;
325 case PPTP_SET_LINK_INFO
:
326 pcid
= &pptpReq
->setlink
.peersCallID
;
330 DEBUGP("unknown inbound packet %s\n", (msg
<= PPTP_MSG_MAX
)?
331 pptp_msg_name
[msg
]:pptp_msg_name
[0]);
334 case PPTP_START_SESSION_REQUEST
:
335 case PPTP_START_SESSION_REPLY
:
336 case PPTP_STOP_SESSION_REQUEST
:
337 case PPTP_STOP_SESSION_REPLY
:
338 case PPTP_ECHO_REQUEST
:
339 case PPTP_ECHO_REPLY
:
340 /* no need to alter packet */
344 /* only OUT_CALL_REPLY, IN_CALL_CONNECT, IN_CALL_REQUEST,
345 * WAN_ERROR_NOTIFY, CALL_DISCONNECT_NOTIFY pass down here */
349 DEBUGP("altering peer call id from 0x%04x to 0x%04x\n",
350 ntohs(*pcid
), ntohs(new_pcid
));
352 rv
= ip_nat_mangle_tcp_packet(pskb
, ct
, ctinfo
,
353 (void *)pcid
- ((void *)ctlh
- sizeof(struct pptp_pkt_hdr
)),
354 sizeof(new_pcid
), (char *)&new_pcid
,
361 DEBUGP("altering call id from 0x%04x to 0x%04x\n",
362 ntohs(*cid
), ntohs(new_cid
));
363 rv
= ip_nat_mangle_tcp_packet(pskb
, ct
, ctinfo
,
364 (void *)cid
- ((void *)ctlh
- sizeof(struct pptp_pkt_hdr
)),
372 /* check for earlier return value of 'switch' above */
373 if (ret
!= NF_ACCEPT
)
376 /* great, at least we don't need to resize packets */
381 extern int __init
ip_nat_proto_gre_init(void);
382 extern void __exit
ip_nat_proto_gre_fini(void);
384 static int __init
init(void)
388 DEBUGP("%s: registering NAT helper\n", __FILE__
);
390 ret
= ip_nat_proto_gre_init();
394 BUG_ON(ip_nat_pptp_hook_outbound
);
395 ip_nat_pptp_hook_outbound
= &pptp_outbound_pkt
;
397 BUG_ON(ip_nat_pptp_hook_inbound
);
398 ip_nat_pptp_hook_inbound
= &pptp_inbound_pkt
;
400 BUG_ON(ip_nat_pptp_hook_exp_gre
);
401 ip_nat_pptp_hook_exp_gre
= &pptp_exp_gre
;
403 BUG_ON(ip_nat_pptp_hook_expectfn
);
404 ip_nat_pptp_hook_expectfn
= &pptp_nat_expected
;
406 printk("ip_nat_pptp version %s loaded\n", IP_NAT_PPTP_VERSION
);
410 static void __exit
fini(void)
412 DEBUGP("cleanup_module\n" );
414 ip_nat_pptp_hook_expectfn
= NULL
;
415 ip_nat_pptp_hook_exp_gre
= NULL
;
416 ip_nat_pptp_hook_inbound
= NULL
;
417 ip_nat_pptp_hook_outbound
= NULL
;
419 ip_nat_proto_gre_fini();
420 /* Make sure noone calls it, meanwhile */
423 printk("ip_nat_pptp version %s unloaded\n", IP_NAT_PPTP_VERSION
);