1 /* SIP extension for UDP NAT alteration.
3 * (C) 2005 by Christian Hentschel <chentschel@arnet.com.ar>
4 * based on RR's ip_nat_ftp.c and other modules.
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License version 2 as
8 * published by the Free Software Foundation.
11 #include <linux/module.h>
12 #include <linux/skbuff.h>
15 #include <linux/udp.h>
17 #include <net/netfilter/nf_nat.h>
18 #include <net/netfilter/nf_nat_helper.h>
19 #include <net/netfilter/nf_nat_rule.h>
20 #include <net/netfilter/nf_conntrack_helper.h>
21 #include <net/netfilter/nf_conntrack_expect.h>
22 #include <linux/netfilter/nf_conntrack_sip.h>
24 MODULE_LICENSE("GPL");
25 MODULE_AUTHOR("Christian Hentschel <chentschel@arnet.com.ar>");
26 MODULE_DESCRIPTION("SIP NAT helper");
27 MODULE_ALIAS("ip_nat_sip");
32 #define DEBUGP(format, args...)
37 char src
[sizeof("nnn.nnn.nnn.nnn:nnnnn")];
38 char dst
[sizeof("nnn.nnn.nnn.nnn:nnnnn")];
39 unsigned int srclen
, srciplen
;
40 unsigned int dstlen
, dstiplen
;
41 } addr
[IP_CT_DIR_MAX
];
44 static void addr_map_init(struct nf_conn
*ct
, struct addr_map
*map
)
46 struct nf_conntrack_tuple
*t
;
47 enum ip_conntrack_dir dir
;
50 for (dir
= 0; dir
< IP_CT_DIR_MAX
; dir
++) {
51 t
= &ct
->tuplehash
[dir
].tuple
;
53 n
= sprintf(map
->addr
[dir
].src
, "%u.%u.%u.%u",
54 NIPQUAD(t
->src
.u3
.ip
));
55 map
->addr
[dir
].srciplen
= n
;
56 n
+= sprintf(map
->addr
[dir
].src
+ n
, ":%u",
57 ntohs(t
->src
.u
.udp
.port
));
58 map
->addr
[dir
].srclen
= n
;
60 n
= sprintf(map
->addr
[dir
].dst
, "%u.%u.%u.%u",
61 NIPQUAD(t
->dst
.u3
.ip
));
62 map
->addr
[dir
].dstiplen
= n
;
63 n
+= sprintf(map
->addr
[dir
].dst
+ n
, ":%u",
64 ntohs(t
->dst
.u
.udp
.port
));
65 map
->addr
[dir
].dstlen
= n
;
69 static int map_sip_addr(struct sk_buff
**pskb
, enum ip_conntrack_info ctinfo
,
70 struct nf_conn
*ct
, const char **dptr
, size_t dlen
,
71 enum sip_header_pos pos
, struct addr_map
*map
)
73 enum ip_conntrack_dir dir
= CTINFO2DIR(ctinfo
);
74 unsigned int matchlen
, matchoff
, addrlen
;
77 if (ct_sip_get_info(ct
, *dptr
, dlen
, &matchoff
, &matchlen
, pos
) <= 0)
80 if ((matchlen
== map
->addr
[dir
].srciplen
||
81 matchlen
== map
->addr
[dir
].srclen
) &&
82 memcmp(*dptr
+ matchoff
, map
->addr
[dir
].src
, matchlen
) == 0) {
83 addr
= map
->addr
[!dir
].dst
;
84 addrlen
= map
->addr
[!dir
].dstlen
;
85 } else if ((matchlen
== map
->addr
[dir
].dstiplen
||
86 matchlen
== map
->addr
[dir
].dstlen
) &&
87 memcmp(*dptr
+ matchoff
, map
->addr
[dir
].dst
, matchlen
) == 0) {
88 addr
= map
->addr
[!dir
].src
;
89 addrlen
= map
->addr
[!dir
].srclen
;
93 if (!nf_nat_mangle_udp_packet(pskb
, ct
, ctinfo
,
94 matchoff
, matchlen
, addr
, addrlen
))
96 *dptr
= (*pskb
)->data
+ ip_hdrlen(*pskb
) + sizeof(struct udphdr
);
101 static unsigned int ip_nat_sip(struct sk_buff
**pskb
,
102 enum ip_conntrack_info ctinfo
,
106 enum sip_header_pos pos
;
108 int dataoff
, datalen
;
110 dataoff
= ip_hdrlen(*pskb
) + sizeof(struct udphdr
);
111 datalen
= (*pskb
)->len
- dataoff
;
112 if (datalen
< sizeof("SIP/2.0") - 1)
115 addr_map_init(ct
, &map
);
117 /* Basic rules: requests and responses. */
118 if (strncmp(*dptr
, "SIP/2.0", sizeof("SIP/2.0") - 1) != 0) {
119 /* 10.2: Constructing the REGISTER Request:
121 * The "userinfo" and "@" components of the SIP URI MUST NOT
124 if (datalen
>= sizeof("REGISTER") - 1 &&
125 strncmp(*dptr
, "REGISTER", sizeof("REGISTER") - 1) == 0)
126 pos
= POS_REG_REQ_URI
;
130 if (!map_sip_addr(pskb
, ctinfo
, ct
, dptr
, datalen
, pos
, &map
))
134 if (!map_sip_addr(pskb
, ctinfo
, ct
, dptr
, datalen
, POS_FROM
, &map
) ||
135 !map_sip_addr(pskb
, ctinfo
, ct
, dptr
, datalen
, POS_TO
, &map
) ||
136 !map_sip_addr(pskb
, ctinfo
, ct
, dptr
, datalen
, POS_VIA
, &map
) ||
137 !map_sip_addr(pskb
, ctinfo
, ct
, dptr
, datalen
, POS_CONTACT
, &map
))
142 static unsigned int mangle_sip_packet(struct sk_buff
**pskb
,
143 enum ip_conntrack_info ctinfo
,
145 const char **dptr
, size_t dlen
,
146 char *buffer
, int bufflen
,
147 enum sip_header_pos pos
)
149 unsigned int matchlen
, matchoff
;
151 if (ct_sip_get_info(ct
, *dptr
, dlen
, &matchoff
, &matchlen
, pos
) <= 0)
154 if (!nf_nat_mangle_udp_packet(pskb
, ct
, ctinfo
,
155 matchoff
, matchlen
, buffer
, bufflen
))
158 /* We need to reload this. Thanks Patrick. */
159 *dptr
= (*pskb
)->data
+ ip_hdrlen(*pskb
) + sizeof(struct udphdr
);
163 static int mangle_content_len(struct sk_buff
**pskb
,
164 enum ip_conntrack_info ctinfo
,
168 unsigned int dataoff
, matchoff
, matchlen
;
169 char buffer
[sizeof("65536")];
172 dataoff
= ip_hdrlen(*pskb
) + sizeof(struct udphdr
);
174 /* Get actual SDP lenght */
175 if (ct_sip_get_info(ct
, dptr
, (*pskb
)->len
- dataoff
, &matchoff
,
176 &matchlen
, POS_SDP_HEADER
) > 0) {
178 /* since ct_sip_get_info() give us a pointer passing 'v='
179 we need to add 2 bytes in this count. */
180 int c_len
= (*pskb
)->len
- dataoff
- matchoff
+ 2;
182 /* Now, update SDP length */
183 if (ct_sip_get_info(ct
, dptr
, (*pskb
)->len
- dataoff
, &matchoff
,
184 &matchlen
, POS_CONTENT
) > 0) {
186 bufflen
= sprintf(buffer
, "%u", c_len
);
187 return nf_nat_mangle_udp_packet(pskb
, ct
, ctinfo
,
195 static unsigned int mangle_sdp(struct sk_buff
**pskb
,
196 enum ip_conntrack_info ctinfo
,
198 __be32 newip
, u_int16_t port
,
201 char buffer
[sizeof("nnn.nnn.nnn.nnn")];
202 unsigned int dataoff
, bufflen
;
204 dataoff
= ip_hdrlen(*pskb
) + sizeof(struct udphdr
);
206 /* Mangle owner and contact info. */
207 bufflen
= sprintf(buffer
, "%u.%u.%u.%u", NIPQUAD(newip
));
208 if (!mangle_sip_packet(pskb
, ctinfo
, ct
, &dptr
, (*pskb
)->len
- dataoff
,
209 buffer
, bufflen
, POS_OWNER_IP4
))
212 if (!mangle_sip_packet(pskb
, ctinfo
, ct
, &dptr
, (*pskb
)->len
- dataoff
,
213 buffer
, bufflen
, POS_CONNECTION_IP4
))
216 /* Mangle media port. */
217 bufflen
= sprintf(buffer
, "%u", port
);
218 if (!mangle_sip_packet(pskb
, ctinfo
, ct
, &dptr
, (*pskb
)->len
- dataoff
,
219 buffer
, bufflen
, POS_MEDIA
))
222 return mangle_content_len(pskb
, ctinfo
, ct
, dptr
);
225 /* So, this packet has hit the connection tracking matching code.
226 Mangle it, and change the expectation to match the new version. */
227 static unsigned int ip_nat_sdp(struct sk_buff
**pskb
,
228 enum ip_conntrack_info ctinfo
,
229 struct nf_conntrack_expect
*exp
,
232 struct nf_conn
*ct
= exp
->master
;
233 enum ip_conntrack_dir dir
= CTINFO2DIR(ctinfo
);
237 DEBUGP("ip_nat_sdp():\n");
239 /* Connection will come from reply */
240 newip
= ct
->tuplehash
[!dir
].tuple
.dst
.u3
.ip
;
242 exp
->tuple
.dst
.u3
.ip
= newip
;
243 exp
->saved_proto
.udp
.port
= exp
->tuple
.dst
.u
.udp
.port
;
246 /* When you see the packet, we need to NAT it the same as the
248 exp
->expectfn
= nf_nat_follow_master
;
250 /* Try to get same port: if not, try to change it. */
251 for (port
= ntohs(exp
->saved_proto
.udp
.port
); port
!= 0; port
++) {
252 exp
->tuple
.dst
.u
.udp
.port
= htons(port
);
253 if (nf_conntrack_expect_related(exp
) == 0)
260 if (!mangle_sdp(pskb
, ctinfo
, ct
, newip
, port
, dptr
)) {
261 nf_conntrack_unexpect_related(exp
);
267 static void __exit
nf_nat_sip_fini(void)
269 rcu_assign_pointer(nf_nat_sip_hook
, NULL
);
270 rcu_assign_pointer(nf_nat_sdp_hook
, NULL
);
274 static int __init
nf_nat_sip_init(void)
276 BUG_ON(rcu_dereference(nf_nat_sip_hook
));
277 BUG_ON(rcu_dereference(nf_nat_sdp_hook
));
278 rcu_assign_pointer(nf_nat_sip_hook
, ip_nat_sip
);
279 rcu_assign_pointer(nf_nat_sdp_hook
, ip_nat_sdp
);
283 module_init(nf_nat_sip_init
);
284 module_exit(nf_nat_sip_fini
);
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