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 #include <linux/module.h>
21 #include <linux/tcp.h>
23 #include <net/netfilter/nf_nat.h>
24 #include <net/netfilter/nf_nat_helper.h>
25 #include <net/netfilter/nf_nat_rule.h>
26 #include <net/netfilter/nf_conntrack_helper.h>
27 #include <net/netfilter/nf_conntrack_expect.h>
28 #include <linux/netfilter/nf_conntrack_proto_gre.h>
29 #include <linux/netfilter/nf_conntrack_pptp.h>
31 #define NF_NAT_PPTP_VERSION "3.0"
33 #define REQ_CID(req, off) (*(__be16 *)((char *)(req) + (off)))
35 MODULE_LICENSE("GPL");
36 MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
37 MODULE_DESCRIPTION("Netfilter NAT helper module for PPTP");
38 MODULE_ALIAS("ip_nat_pptp");
40 static void pptp_nat_expected(struct nf_conn
*ct
,
41 struct nf_conntrack_expect
*exp
)
43 struct net
*net
= nf_ct_net(ct
);
44 const struct nf_conn
*master
= ct
->master
;
45 struct nf_conntrack_expect
*other_exp
;
46 struct nf_conntrack_tuple t
;
47 const struct nf_ct_pptp_master
*ct_pptp_info
;
48 const struct nf_nat_pptp
*nat_pptp_info
;
49 struct nf_nat_range range
;
51 ct_pptp_info
= &nfct_help(master
)->help
.ct_pptp_info
;
52 nat_pptp_info
= &nfct_nat(master
)->help
.nat_pptp_info
;
54 /* And here goes the grand finale of corrosion... */
55 if (exp
->dir
== IP_CT_DIR_ORIGINAL
) {
56 pr_debug("we are PNS->PAC\n");
57 /* therefore, build tuple for PAC->PNS */
58 t
.src
.l3num
= AF_INET
;
59 t
.src
.u3
.ip
= master
->tuplehash
[!exp
->dir
].tuple
.src
.u3
.ip
;
60 t
.src
.u
.gre
.key
= ct_pptp_info
->pac_call_id
;
61 t
.dst
.u3
.ip
= master
->tuplehash
[!exp
->dir
].tuple
.dst
.u3
.ip
;
62 t
.dst
.u
.gre
.key
= ct_pptp_info
->pns_call_id
;
63 t
.dst
.protonum
= IPPROTO_GRE
;
65 pr_debug("we are PAC->PNS\n");
66 /* build tuple for PNS->PAC */
67 t
.src
.l3num
= AF_INET
;
68 t
.src
.u3
.ip
= master
->tuplehash
[!exp
->dir
].tuple
.src
.u3
.ip
;
69 t
.src
.u
.gre
.key
= nat_pptp_info
->pns_call_id
;
70 t
.dst
.u3
.ip
= master
->tuplehash
[!exp
->dir
].tuple
.dst
.u3
.ip
;
71 t
.dst
.u
.gre
.key
= nat_pptp_info
->pac_call_id
;
72 t
.dst
.protonum
= IPPROTO_GRE
;
75 pr_debug("trying to unexpect other dir: ");
76 nf_ct_dump_tuple_ip(&t
);
77 other_exp
= nf_ct_expect_find_get(net
, &t
);
79 nf_ct_unexpect_related(other_exp
);
80 nf_ct_expect_put(other_exp
);
81 pr_debug("success\n");
83 pr_debug("not found!\n");
86 /* This must be a fresh one. */
87 BUG_ON(ct
->status
& IPS_NAT_DONE_MASK
);
89 /* Change src to where master sends to */
90 range
.flags
= IP_NAT_RANGE_MAP_IPS
;
91 range
.min_ip
= range
.max_ip
92 = ct
->master
->tuplehash
[!exp
->dir
].tuple
.dst
.u3
.ip
;
93 if (exp
->dir
== IP_CT_DIR_ORIGINAL
) {
94 range
.flags
|= IP_NAT_RANGE_PROTO_SPECIFIED
;
95 range
.min
= range
.max
= exp
->saved_proto
;
97 nf_nat_setup_info(ct
, &range
, IP_NAT_MANIP_SRC
);
99 /* For DST manip, map port here to where it's expected. */
100 range
.flags
= IP_NAT_RANGE_MAP_IPS
;
101 range
.min_ip
= range
.max_ip
102 = ct
->master
->tuplehash
[!exp
->dir
].tuple
.src
.u3
.ip
;
103 if (exp
->dir
== IP_CT_DIR_REPLY
) {
104 range
.flags
|= IP_NAT_RANGE_PROTO_SPECIFIED
;
105 range
.min
= range
.max
= exp
->saved_proto
;
107 nf_nat_setup_info(ct
, &range
, IP_NAT_MANIP_DST
);
110 /* outbound packets == from PNS to PAC */
112 pptp_outbound_pkt(struct sk_buff
*skb
,
114 enum ip_conntrack_info ctinfo
,
115 struct PptpControlHeader
*ctlh
,
116 union pptp_ctrl_union
*pptpReq
)
119 struct nf_ct_pptp_master
*ct_pptp_info
;
120 struct nf_nat_pptp
*nat_pptp_info
;
123 unsigned int cid_off
;
125 ct_pptp_info
= &nfct_help(ct
)->help
.ct_pptp_info
;
126 nat_pptp_info
= &nfct_nat(ct
)->help
.nat_pptp_info
;
128 new_callid
= ct_pptp_info
->pns_call_id
;
130 switch (msg
= ntohs(ctlh
->messageType
)) {
131 case PPTP_OUT_CALL_REQUEST
:
132 cid_off
= offsetof(union pptp_ctrl_union
, ocreq
.callID
);
133 /* FIXME: ideally we would want to reserve a call ID
134 * here. current netfilter NAT core is not able to do
135 * this :( For now we use TCP source port. This breaks
136 * multiple calls within one control session */
138 /* save original call ID in nat_info */
139 nat_pptp_info
->pns_call_id
= ct_pptp_info
->pns_call_id
;
141 /* don't use tcph->source since we are at a DSTmanip
142 * hook (e.g. PREROUTING) and pkt is not mangled yet */
143 new_callid
= ct
->tuplehash
[IP_CT_DIR_REPLY
].tuple
.dst
.u
.tcp
.port
;
145 /* save new call ID in ct info */
146 ct_pptp_info
->pns_call_id
= new_callid
;
148 case PPTP_IN_CALL_REPLY
:
149 cid_off
= offsetof(union pptp_ctrl_union
, icack
.callID
);
151 case PPTP_CALL_CLEAR_REQUEST
:
152 cid_off
= offsetof(union pptp_ctrl_union
, clrreq
.callID
);
155 pr_debug("unknown outbound packet 0x%04x:%s\n", msg
,
156 msg
<= PPTP_MSG_MAX
? pptp_msg_name
[msg
] :
159 case PPTP_SET_LINK_INFO
:
160 /* only need to NAT in case PAC is behind NAT box */
161 case PPTP_START_SESSION_REQUEST
:
162 case PPTP_START_SESSION_REPLY
:
163 case PPTP_STOP_SESSION_REQUEST
:
164 case PPTP_STOP_SESSION_REPLY
:
165 case PPTP_ECHO_REQUEST
:
166 case PPTP_ECHO_REPLY
:
167 /* no need to alter packet */
171 /* only OUT_CALL_REQUEST, IN_CALL_REPLY, CALL_CLEAR_REQUEST pass
173 pr_debug("altering call id from 0x%04x to 0x%04x\n",
174 ntohs(REQ_CID(pptpReq
, cid_off
)), ntohs(new_callid
));
177 if (nf_nat_mangle_tcp_packet(skb
, ct
, ctinfo
,
178 cid_off
+ sizeof(struct pptp_pkt_hdr
) +
179 sizeof(struct PptpControlHeader
),
180 sizeof(new_callid
), (char *)&new_callid
,
181 sizeof(new_callid
)) == 0)
187 pptp_exp_gre(struct nf_conntrack_expect
*expect_orig
,
188 struct nf_conntrack_expect
*expect_reply
)
190 const struct nf_conn
*ct
= expect_orig
->master
;
191 struct nf_ct_pptp_master
*ct_pptp_info
;
192 struct nf_nat_pptp
*nat_pptp_info
;
194 ct_pptp_info
= &nfct_help(ct
)->help
.ct_pptp_info
;
195 nat_pptp_info
= &nfct_nat(ct
)->help
.nat_pptp_info
;
197 /* save original PAC call ID in nat_info */
198 nat_pptp_info
->pac_call_id
= ct_pptp_info
->pac_call_id
;
200 /* alter expectation for PNS->PAC direction */
201 expect_orig
->saved_proto
.gre
.key
= ct_pptp_info
->pns_call_id
;
202 expect_orig
->tuple
.src
.u
.gre
.key
= nat_pptp_info
->pns_call_id
;
203 expect_orig
->tuple
.dst
.u
.gre
.key
= ct_pptp_info
->pac_call_id
;
204 expect_orig
->dir
= IP_CT_DIR_ORIGINAL
;
206 /* alter expectation for PAC->PNS direction */
207 expect_reply
->saved_proto
.gre
.key
= nat_pptp_info
->pns_call_id
;
208 expect_reply
->tuple
.src
.u
.gre
.key
= nat_pptp_info
->pac_call_id
;
209 expect_reply
->tuple
.dst
.u
.gre
.key
= ct_pptp_info
->pns_call_id
;
210 expect_reply
->dir
= IP_CT_DIR_REPLY
;
213 /* inbound packets == from PAC to PNS */
215 pptp_inbound_pkt(struct sk_buff
*skb
,
217 enum ip_conntrack_info ctinfo
,
218 struct PptpControlHeader
*ctlh
,
219 union pptp_ctrl_union
*pptpReq
)
221 const struct nf_nat_pptp
*nat_pptp_info
;
224 unsigned int pcid_off
;
226 nat_pptp_info
= &nfct_nat(ct
)->help
.nat_pptp_info
;
227 new_pcid
= nat_pptp_info
->pns_call_id
;
229 switch (msg
= ntohs(ctlh
->messageType
)) {
230 case PPTP_OUT_CALL_REPLY
:
231 pcid_off
= offsetof(union pptp_ctrl_union
, ocack
.peersCallID
);
233 case PPTP_IN_CALL_CONNECT
:
234 pcid_off
= offsetof(union pptp_ctrl_union
, iccon
.peersCallID
);
236 case PPTP_IN_CALL_REQUEST
:
237 /* only need to nat in case PAC is behind NAT box */
239 case PPTP_WAN_ERROR_NOTIFY
:
240 pcid_off
= offsetof(union pptp_ctrl_union
, wanerr
.peersCallID
);
242 case PPTP_CALL_DISCONNECT_NOTIFY
:
243 pcid_off
= offsetof(union pptp_ctrl_union
, disc
.callID
);
245 case PPTP_SET_LINK_INFO
:
246 pcid_off
= offsetof(union pptp_ctrl_union
, setlink
.peersCallID
);
249 pr_debug("unknown inbound packet %s\n",
250 msg
<= PPTP_MSG_MAX
? pptp_msg_name
[msg
] :
253 case PPTP_START_SESSION_REQUEST
:
254 case PPTP_START_SESSION_REPLY
:
255 case PPTP_STOP_SESSION_REQUEST
:
256 case PPTP_STOP_SESSION_REPLY
:
257 case PPTP_ECHO_REQUEST
:
258 case PPTP_ECHO_REPLY
:
259 /* no need to alter packet */
263 /* only OUT_CALL_REPLY, IN_CALL_CONNECT, IN_CALL_REQUEST,
264 * WAN_ERROR_NOTIFY, CALL_DISCONNECT_NOTIFY pass down here */
267 pr_debug("altering peer call id from 0x%04x to 0x%04x\n",
268 ntohs(REQ_CID(pptpReq
, pcid_off
)), ntohs(new_pcid
));
270 if (nf_nat_mangle_tcp_packet(skb
, ct
, ctinfo
,
271 pcid_off
+ sizeof(struct pptp_pkt_hdr
) +
272 sizeof(struct PptpControlHeader
),
273 sizeof(new_pcid
), (char *)&new_pcid
,
274 sizeof(new_pcid
)) == 0)
279 static int __init
nf_nat_helper_pptp_init(void)
283 BUG_ON(nf_nat_pptp_hook_outbound
!= NULL
);
284 rcu_assign_pointer(nf_nat_pptp_hook_outbound
, pptp_outbound_pkt
);
286 BUG_ON(nf_nat_pptp_hook_inbound
!= NULL
);
287 rcu_assign_pointer(nf_nat_pptp_hook_inbound
, pptp_inbound_pkt
);
289 BUG_ON(nf_nat_pptp_hook_exp_gre
!= NULL
);
290 rcu_assign_pointer(nf_nat_pptp_hook_exp_gre
, pptp_exp_gre
);
292 BUG_ON(nf_nat_pptp_hook_expectfn
!= NULL
);
293 rcu_assign_pointer(nf_nat_pptp_hook_expectfn
, pptp_nat_expected
);
297 static void __exit
nf_nat_helper_pptp_fini(void)
299 rcu_assign_pointer(nf_nat_pptp_hook_expectfn
, NULL
);
300 rcu_assign_pointer(nf_nat_pptp_hook_exp_gre
, NULL
);
301 rcu_assign_pointer(nf_nat_pptp_hook_inbound
, NULL
);
302 rcu_assign_pointer(nf_nat_pptp_hook_outbound
, NULL
);
306 module_init(nf_nat_helper_pptp_init
);
307 module_exit(nf_nat_helper_pptp_fini
);