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 #define REQ_CID(req, off) (*(u_int16_t *)((char *)(req) + (off)))
57 MODULE_LICENSE("GPL");
58 MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
59 MODULE_DESCRIPTION("Netfilter NAT helper module for PPTP");
63 extern const char *pptp_msg_name
[];
64 #define DEBUGP(format, args...) printk(KERN_DEBUG "%s:%s: " format, __FILE__, \
65 __FUNCTION__, ## args)
67 #define DEBUGP(format, args...)
70 static void pptp_nat_expected(struct ip_conntrack
*ct
,
71 struct ip_conntrack_expect
*exp
)
73 struct ip_conntrack
*master
= ct
->master
;
74 struct ip_conntrack_expect
*other_exp
;
75 struct ip_conntrack_tuple t
;
76 struct ip_ct_pptp_master
*ct_pptp_info
;
77 struct ip_nat_pptp
*nat_pptp_info
;
78 struct ip_nat_range range
;
80 ct_pptp_info
= &master
->help
.ct_pptp_info
;
81 nat_pptp_info
= &master
->nat
.help
.nat_pptp_info
;
83 /* And here goes the grand finale of corrosion... */
85 if (exp
->dir
== IP_CT_DIR_ORIGINAL
) {
86 DEBUGP("we are PNS->PAC\n");
87 /* therefore, build tuple for PAC->PNS */
88 t
.src
.ip
= master
->tuplehash
[IP_CT_DIR_REPLY
].tuple
.src
.ip
;
89 t
.src
.u
.gre
.key
= htons(master
->help
.ct_pptp_info
.pac_call_id
);
90 t
.dst
.ip
= master
->tuplehash
[IP_CT_DIR_REPLY
].tuple
.dst
.ip
;
91 t
.dst
.u
.gre
.key
= htons(master
->help
.ct_pptp_info
.pns_call_id
);
92 t
.dst
.protonum
= IPPROTO_GRE
;
94 DEBUGP("we are PAC->PNS\n");
95 /* build tuple for PNS->PAC */
96 t
.src
.ip
= master
->tuplehash
[IP_CT_DIR_ORIGINAL
].tuple
.src
.ip
;
98 htons(master
->nat
.help
.nat_pptp_info
.pns_call_id
);
99 t
.dst
.ip
= master
->tuplehash
[IP_CT_DIR_ORIGINAL
].tuple
.dst
.ip
;
101 htons(master
->nat
.help
.nat_pptp_info
.pac_call_id
);
102 t
.dst
.protonum
= IPPROTO_GRE
;
105 DEBUGP("trying to unexpect other dir: ");
107 other_exp
= ip_conntrack_expect_find(&t
);
109 ip_conntrack_unexpect_related(other_exp
);
110 ip_conntrack_expect_put(other_exp
);
113 DEBUGP("not found!\n");
116 /* This must be a fresh one. */
117 BUG_ON(ct
->status
& IPS_NAT_DONE_MASK
);
119 /* Change src to where master sends to */
120 range
.flags
= IP_NAT_RANGE_MAP_IPS
;
121 range
.min_ip
= range
.max_ip
122 = ct
->master
->tuplehash
[!exp
->dir
].tuple
.dst
.ip
;
123 if (exp
->dir
== IP_CT_DIR_ORIGINAL
) {
124 range
.flags
|= IP_NAT_RANGE_PROTO_SPECIFIED
;
125 range
.min
= range
.max
= exp
->saved_proto
;
127 /* hook doesn't matter, but it has to do source manip */
128 ip_nat_setup_info(ct
, &range
, NF_IP_POST_ROUTING
);
130 /* For DST manip, map port here to where it's expected. */
131 range
.flags
= IP_NAT_RANGE_MAP_IPS
;
132 range
.min_ip
= range
.max_ip
133 = ct
->master
->tuplehash
[!exp
->dir
].tuple
.src
.ip
;
134 if (exp
->dir
== IP_CT_DIR_REPLY
) {
135 range
.flags
|= IP_NAT_RANGE_PROTO_SPECIFIED
;
136 range
.min
= range
.max
= exp
->saved_proto
;
138 /* hook doesn't matter, but it has to do destination manip */
139 ip_nat_setup_info(ct
, &range
, NF_IP_PRE_ROUTING
);
142 /* outbound packets == from PNS to PAC */
144 pptp_outbound_pkt(struct sk_buff
**pskb
,
145 struct ip_conntrack
*ct
,
146 enum ip_conntrack_info ctinfo
,
147 struct PptpControlHeader
*ctlh
,
148 union pptp_ctrl_union
*pptpReq
)
151 struct ip_ct_pptp_master
*ct_pptp_info
= &ct
->help
.ct_pptp_info
;
152 struct ip_nat_pptp
*nat_pptp_info
= &ct
->nat
.help
.nat_pptp_info
;
153 u_int16_t msg
, new_callid
;
154 unsigned int cid_off
;
156 new_callid
= htons(ct_pptp_info
->pns_call_id
);
158 switch (msg
= ntohs(ctlh
->messageType
)) {
159 case PPTP_OUT_CALL_REQUEST
:
160 cid_off
= offsetof(union pptp_ctrl_union
, ocreq
.callID
);
161 /* FIXME: ideally we would want to reserve a call ID
162 * here. current netfilter NAT core is not able to do
163 * this :( For now we use TCP source port. This breaks
164 * multiple calls within one control session */
166 /* save original call ID in nat_info */
167 nat_pptp_info
->pns_call_id
= ct_pptp_info
->pns_call_id
;
169 /* don't use tcph->source since we are at a DSTmanip
170 * hook (e.g. PREROUTING) and pkt is not mangled yet */
171 new_callid
= ct
->tuplehash
[IP_CT_DIR_REPLY
].tuple
.dst
.u
.tcp
.port
;
173 /* save new call ID in ct info */
174 ct_pptp_info
->pns_call_id
= ntohs(new_callid
);
176 case PPTP_IN_CALL_REPLY
:
177 cid_off
= offsetof(union pptp_ctrl_union
, icreq
.callID
);
179 case PPTP_CALL_CLEAR_REQUEST
:
180 cid_off
= offsetof(union pptp_ctrl_union
, clrreq
.callID
);
183 DEBUGP("unknown outbound packet 0x%04x:%s\n", msg
,
184 (msg
<= PPTP_MSG_MAX
)?
185 pptp_msg_name
[msg
]:pptp_msg_name
[0]);
188 case PPTP_SET_LINK_INFO
:
189 /* only need to NAT in case PAC is behind NAT box */
190 case PPTP_START_SESSION_REQUEST
:
191 case PPTP_START_SESSION_REPLY
:
192 case PPTP_STOP_SESSION_REQUEST
:
193 case PPTP_STOP_SESSION_REPLY
:
194 case PPTP_ECHO_REQUEST
:
195 case PPTP_ECHO_REPLY
:
196 /* no need to alter packet */
200 /* only OUT_CALL_REQUEST, IN_CALL_REPLY, CALL_CLEAR_REQUEST pass
202 DEBUGP("altering call id from 0x%04x to 0x%04x\n",
203 ntohs(REQ_CID(pptpReq
, cid_off
)), ntohs(new_callid
));
206 if (ip_nat_mangle_tcp_packet(pskb
, ct
, ctinfo
,
207 cid_off
+ sizeof(struct pptp_pkt_hdr
) +
208 sizeof(struct PptpControlHeader
),
209 sizeof(new_callid
), (char *)&new_callid
,
210 sizeof(new_callid
)) == 0)
217 pptp_exp_gre(struct ip_conntrack_expect
*expect_orig
,
218 struct ip_conntrack_expect
*expect_reply
)
220 struct ip_ct_pptp_master
*ct_pptp_info
=
221 &expect_orig
->master
->help
.ct_pptp_info
;
222 struct ip_nat_pptp
*nat_pptp_info
=
223 &expect_orig
->master
->nat
.help
.nat_pptp_info
;
225 struct ip_conntrack
*ct
= expect_orig
->master
;
227 struct ip_conntrack_tuple inv_t
;
228 struct ip_conntrack_tuple
*orig_t
, *reply_t
;
230 /* save original PAC call ID in nat_info */
231 nat_pptp_info
->pac_call_id
= ct_pptp_info
->pac_call_id
;
233 /* alter expectation */
234 orig_t
= &ct
->tuplehash
[IP_CT_DIR_ORIGINAL
].tuple
;
235 reply_t
= &ct
->tuplehash
[IP_CT_DIR_REPLY
].tuple
;
237 /* alter expectation for PNS->PAC direction */
238 invert_tuplepr(&inv_t
, &expect_orig
->tuple
);
239 expect_orig
->saved_proto
.gre
.key
= htons(ct_pptp_info
->pns_call_id
);
240 expect_orig
->tuple
.src
.u
.gre
.key
= htons(nat_pptp_info
->pns_call_id
);
241 expect_orig
->tuple
.dst
.u
.gre
.key
= htons(ct_pptp_info
->pac_call_id
);
242 expect_orig
->dir
= IP_CT_DIR_ORIGINAL
;
243 inv_t
.src
.ip
= reply_t
->src
.ip
;
244 inv_t
.dst
.ip
= reply_t
->dst
.ip
;
245 inv_t
.src
.u
.gre
.key
= htons(nat_pptp_info
->pac_call_id
);
246 inv_t
.dst
.u
.gre
.key
= htons(ct_pptp_info
->pns_call_id
);
248 if (!ip_conntrack_expect_related(expect_orig
)) {
249 DEBUGP("successfully registered expect\n");
251 DEBUGP("can't expect_related(expect_orig)\n");
255 /* alter expectation for PAC->PNS direction */
256 invert_tuplepr(&inv_t
, &expect_reply
->tuple
);
257 expect_reply
->saved_proto
.gre
.key
= htons(nat_pptp_info
->pns_call_id
);
258 expect_reply
->tuple
.src
.u
.gre
.key
= htons(nat_pptp_info
->pac_call_id
);
259 expect_reply
->tuple
.dst
.u
.gre
.key
= htons(ct_pptp_info
->pns_call_id
);
260 expect_reply
->dir
= IP_CT_DIR_REPLY
;
261 inv_t
.src
.ip
= orig_t
->src
.ip
;
262 inv_t
.dst
.ip
= orig_t
->dst
.ip
;
263 inv_t
.src
.u
.gre
.key
= htons(nat_pptp_info
->pns_call_id
);
264 inv_t
.dst
.u
.gre
.key
= htons(ct_pptp_info
->pac_call_id
);
266 if (!ip_conntrack_expect_related(expect_reply
)) {
267 DEBUGP("successfully registered expect\n");
269 DEBUGP("can't expect_related(expect_reply)\n");
270 ip_conntrack_unexpect_related(expect_orig
);
274 if (ip_ct_gre_keymap_add(ct
, &expect_reply
->tuple
, 0) < 0) {
275 DEBUGP("can't register original keymap\n");
276 ip_conntrack_unexpect_related(expect_orig
);
277 ip_conntrack_unexpect_related(expect_reply
);
281 if (ip_ct_gre_keymap_add(ct
, &inv_t
, 1) < 0) {
282 DEBUGP("can't register reply keymap\n");
283 ip_conntrack_unexpect_related(expect_orig
);
284 ip_conntrack_unexpect_related(expect_reply
);
285 ip_ct_gre_keymap_destroy(ct
);
292 /* inbound packets == from PAC to PNS */
294 pptp_inbound_pkt(struct sk_buff
**pskb
,
295 struct ip_conntrack
*ct
,
296 enum ip_conntrack_info ctinfo
,
297 struct PptpControlHeader
*ctlh
,
298 union pptp_ctrl_union
*pptpReq
)
300 struct ip_nat_pptp
*nat_pptp_info
= &ct
->nat
.help
.nat_pptp_info
;
301 u_int16_t msg
, new_cid
= 0, new_pcid
;
302 unsigned int pcid_off
, cid_off
= 0;
304 new_pcid
= htons(nat_pptp_info
->pns_call_id
);
306 switch (msg
= ntohs(ctlh
->messageType
)) {
307 case PPTP_OUT_CALL_REPLY
:
308 pcid_off
= offsetof(union pptp_ctrl_union
, ocack
.peersCallID
);
309 cid_off
= offsetof(union pptp_ctrl_union
, ocack
.callID
);
311 case PPTP_IN_CALL_CONNECT
:
312 pcid_off
= offsetof(union pptp_ctrl_union
, iccon
.peersCallID
);
314 case PPTP_IN_CALL_REQUEST
:
315 /* only need to nat in case PAC is behind NAT box */
317 case PPTP_WAN_ERROR_NOTIFY
:
318 pcid_off
= offsetof(union pptp_ctrl_union
, wanerr
.peersCallID
);
320 case PPTP_CALL_DISCONNECT_NOTIFY
:
321 pcid_off
= offsetof(union pptp_ctrl_union
, disc
.callID
);
323 case PPTP_SET_LINK_INFO
:
324 pcid_off
= offsetof(union pptp_ctrl_union
, setlink
.peersCallID
);
328 DEBUGP("unknown inbound packet %s\n", (msg
<= PPTP_MSG_MAX
)?
329 pptp_msg_name
[msg
]:pptp_msg_name
[0]);
332 case PPTP_START_SESSION_REQUEST
:
333 case PPTP_START_SESSION_REPLY
:
334 case PPTP_STOP_SESSION_REQUEST
:
335 case PPTP_STOP_SESSION_REPLY
:
336 case PPTP_ECHO_REQUEST
:
337 case PPTP_ECHO_REPLY
:
338 /* no need to alter packet */
342 /* only OUT_CALL_REPLY, IN_CALL_CONNECT, IN_CALL_REQUEST,
343 * WAN_ERROR_NOTIFY, CALL_DISCONNECT_NOTIFY pass down here */
346 DEBUGP("altering peer call id from 0x%04x to 0x%04x\n",
347 ntohs(REQ_CID(pptpReq
, pcid_off
)), ntohs(new_pcid
));
349 if (ip_nat_mangle_tcp_packet(pskb
, ct
, ctinfo
,
350 pcid_off
+ sizeof(struct pptp_pkt_hdr
) +
351 sizeof(struct PptpControlHeader
),
352 sizeof(new_pcid
), (char *)&new_pcid
,
353 sizeof(new_pcid
)) == 0)
357 DEBUGP("altering call id from 0x%04x to 0x%04x\n",
358 ntohs(REQ_CID(pptpReq
, cid_off
)), ntohs(new_cid
));
359 if (ip_nat_mangle_tcp_packet(pskb
, ct
, ctinfo
,
360 cid_off
+ sizeof(struct pptp_pkt_hdr
) +
361 sizeof(struct PptpControlHeader
),
362 sizeof(new_cid
), (char *)&new_cid
,
363 sizeof(new_cid
)) == 0)
370 extern int __init
ip_nat_proto_gre_init(void);
371 extern void __exit
ip_nat_proto_gre_fini(void);
373 static int __init
ip_nat_helper_pptp_init(void)
377 DEBUGP("%s: registering NAT helper\n", __FILE__
);
379 ret
= ip_nat_proto_gre_init();
383 BUG_ON(ip_nat_pptp_hook_outbound
);
384 ip_nat_pptp_hook_outbound
= &pptp_outbound_pkt
;
386 BUG_ON(ip_nat_pptp_hook_inbound
);
387 ip_nat_pptp_hook_inbound
= &pptp_inbound_pkt
;
389 BUG_ON(ip_nat_pptp_hook_exp_gre
);
390 ip_nat_pptp_hook_exp_gre
= &pptp_exp_gre
;
392 BUG_ON(ip_nat_pptp_hook_expectfn
);
393 ip_nat_pptp_hook_expectfn
= &pptp_nat_expected
;
395 printk("ip_nat_pptp version %s loaded\n", IP_NAT_PPTP_VERSION
);
399 static void __exit
ip_nat_helper_pptp_fini(void)
401 DEBUGP("cleanup_module\n" );
403 ip_nat_pptp_hook_expectfn
= NULL
;
404 ip_nat_pptp_hook_exp_gre
= NULL
;
405 ip_nat_pptp_hook_inbound
= NULL
;
406 ip_nat_pptp_hook_outbound
= NULL
;
408 ip_nat_proto_gre_fini();
409 /* Make sure noone calls it, meanwhile */
412 printk("ip_nat_pptp version %s unloaded\n", IP_NAT_PPTP_VERSION
);
415 module_init(ip_nat_helper_pptp_init
);
416 module_exit(ip_nat_helper_pptp_fini
);