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9fafcd7b PM |
1 | /* SIP extension for UDP NAT alteration. |
2 | * | |
3 | * (C) 2005 by Christian Hentschel <chentschel@arnet.com.ar> | |
4 | * based on RR's ip_nat_ftp.c and other modules. | |
5 | * | |
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. | |
9 | */ | |
10 | ||
11 | #include <linux/module.h> | |
12 | #include <linux/skbuff.h> | |
13 | #include <linux/ip.h> | |
c9bdd4b5 | 14 | #include <net/ip.h> |
9fafcd7b PM |
15 | #include <linux/udp.h> |
16 | ||
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> | |
23 | ||
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"); | |
28 | ||
29 | #if 0 | |
30 | #define DEBUGP printk | |
31 | #else | |
32 | #define DEBUGP(format, args...) | |
33 | #endif | |
34 | ||
35 | struct addr_map { | |
36 | struct { | |
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]; | |
42 | }; | |
43 | ||
44 | static void addr_map_init(struct nf_conn *ct, struct addr_map *map) | |
45 | { | |
46 | struct nf_conntrack_tuple *t; | |
47 | enum ip_conntrack_dir dir; | |
48 | unsigned int n; | |
49 | ||
50 | for (dir = 0; dir < IP_CT_DIR_MAX; dir++) { | |
51 | t = &ct->tuplehash[dir].tuple; | |
52 | ||
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; | |
59 | ||
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; | |
66 | } | |
67 | } | |
68 | ||
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) | |
72 | { | |
73 | enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo); | |
74 | unsigned int matchlen, matchoff, addrlen; | |
75 | char *addr; | |
76 | ||
77 | if (ct_sip_get_info(ct, *dptr, dlen, &matchoff, &matchlen, pos) <= 0) | |
78 | return 1; | |
79 | ||
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; | |
90 | } else | |
91 | return 1; | |
92 | ||
93 | if (!nf_nat_mangle_udp_packet(pskb, ct, ctinfo, | |
e905a9ed | 94 | matchoff, matchlen, addr, addrlen)) |
9fafcd7b | 95 | return 0; |
c9bdd4b5 | 96 | *dptr = (*pskb)->data + ip_hdrlen(*pskb) + sizeof(struct udphdr); |
9fafcd7b PM |
97 | return 1; |
98 | ||
99 | } | |
100 | ||
101 | static unsigned int ip_nat_sip(struct sk_buff **pskb, | |
102 | enum ip_conntrack_info ctinfo, | |
103 | struct nf_conn *ct, | |
104 | const char **dptr) | |
105 | { | |
106 | enum sip_header_pos pos; | |
107 | struct addr_map map; | |
108 | int dataoff, datalen; | |
109 | ||
c9bdd4b5 | 110 | dataoff = ip_hdrlen(*pskb) + sizeof(struct udphdr); |
9fafcd7b PM |
111 | datalen = (*pskb)->len - dataoff; |
112 | if (datalen < sizeof("SIP/2.0") - 1) | |
113 | return NF_DROP; | |
114 | ||
115 | addr_map_init(ct, &map); | |
116 | ||
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: | |
120 | * | |
121 | * The "userinfo" and "@" components of the SIP URI MUST NOT | |
122 | * be present. | |
123 | */ | |
124 | if (datalen >= sizeof("REGISTER") - 1 && | |
125 | strncmp(*dptr, "REGISTER", sizeof("REGISTER") - 1) == 0) | |
126 | pos = POS_REG_REQ_URI; | |
127 | else | |
128 | pos = POS_REQ_URI; | |
129 | ||
130 | if (!map_sip_addr(pskb, ctinfo, ct, dptr, datalen, pos, &map)) | |
131 | return NF_DROP; | |
132 | } | |
133 | ||
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)) | |
138 | return NF_DROP; | |
139 | return NF_ACCEPT; | |
140 | } | |
141 | ||
142 | static unsigned int mangle_sip_packet(struct sk_buff **pskb, | |
143 | enum ip_conntrack_info ctinfo, | |
144 | struct nf_conn *ct, | |
145 | const char **dptr, size_t dlen, | |
146 | char *buffer, int bufflen, | |
147 | enum sip_header_pos pos) | |
148 | { | |
149 | unsigned int matchlen, matchoff; | |
150 | ||
151 | if (ct_sip_get_info(ct, *dptr, dlen, &matchoff, &matchlen, pos) <= 0) | |
152 | return 0; | |
153 | ||
154 | if (!nf_nat_mangle_udp_packet(pskb, ct, ctinfo, | |
e905a9ed | 155 | matchoff, matchlen, buffer, bufflen)) |
9fafcd7b PM |
156 | return 0; |
157 | ||
158 | /* We need to reload this. Thanks Patrick. */ | |
c9bdd4b5 | 159 | *dptr = (*pskb)->data + ip_hdrlen(*pskb) + sizeof(struct udphdr); |
9fafcd7b PM |
160 | return 1; |
161 | } | |
162 | ||
163 | static int mangle_content_len(struct sk_buff **pskb, | |
164 | enum ip_conntrack_info ctinfo, | |
165 | struct nf_conn *ct, | |
166 | const char *dptr) | |
167 | { | |
168 | unsigned int dataoff, matchoff, matchlen; | |
169 | char buffer[sizeof("65536")]; | |
170 | int bufflen; | |
171 | ||
c9bdd4b5 | 172 | dataoff = ip_hdrlen(*pskb) + sizeof(struct udphdr); |
9fafcd7b PM |
173 | |
174 | /* Get actual SDP lenght */ | |
175 | if (ct_sip_get_info(ct, dptr, (*pskb)->len - dataoff, &matchoff, | |
e905a9ed | 176 | &matchlen, POS_SDP_HEADER) > 0) { |
9fafcd7b PM |
177 | |
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; | |
181 | ||
182 | /* Now, update SDP length */ | |
183 | if (ct_sip_get_info(ct, dptr, (*pskb)->len - dataoff, &matchoff, | |
e905a9ed | 184 | &matchlen, POS_CONTENT) > 0) { |
9fafcd7b PM |
185 | |
186 | bufflen = sprintf(buffer, "%u", c_len); | |
187 | return nf_nat_mangle_udp_packet(pskb, ct, ctinfo, | |
188 | matchoff, matchlen, | |
189 | buffer, bufflen); | |
190 | } | |
191 | } | |
192 | return 0; | |
193 | } | |
194 | ||
195 | static unsigned int mangle_sdp(struct sk_buff **pskb, | |
196 | enum ip_conntrack_info ctinfo, | |
197 | struct nf_conn *ct, | |
198 | __be32 newip, u_int16_t port, | |
199 | const char *dptr) | |
200 | { | |
201 | char buffer[sizeof("nnn.nnn.nnn.nnn")]; | |
202 | unsigned int dataoff, bufflen; | |
203 | ||
c9bdd4b5 | 204 | dataoff = ip_hdrlen(*pskb) + sizeof(struct udphdr); |
9fafcd7b PM |
205 | |
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, | |
e905a9ed | 209 | buffer, bufflen, POS_OWNER_IP4)) |
9fafcd7b PM |
210 | return 0; |
211 | ||
212 | if (!mangle_sip_packet(pskb, ctinfo, ct, &dptr, (*pskb)->len - dataoff, | |
e905a9ed | 213 | buffer, bufflen, POS_CONNECTION_IP4)) |
9fafcd7b PM |
214 | return 0; |
215 | ||
216 | /* Mangle media port. */ | |
217 | bufflen = sprintf(buffer, "%u", port); | |
218 | if (!mangle_sip_packet(pskb, ctinfo, ct, &dptr, (*pskb)->len - dataoff, | |
e905a9ed | 219 | buffer, bufflen, POS_MEDIA)) |
9fafcd7b PM |
220 | return 0; |
221 | ||
222 | return mangle_content_len(pskb, ctinfo, ct, dptr); | |
223 | } | |
224 | ||
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, | |
230 | const char *dptr) | |
231 | { | |
232 | struct nf_conn *ct = exp->master; | |
233 | enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo); | |
234 | __be32 newip; | |
235 | u_int16_t port; | |
236 | ||
237 | DEBUGP("ip_nat_sdp():\n"); | |
238 | ||
239 | /* Connection will come from reply */ | |
240 | newip = ct->tuplehash[!dir].tuple.dst.u3.ip; | |
241 | ||
242 | exp->tuple.dst.u3.ip = newip; | |
243 | exp->saved_proto.udp.port = exp->tuple.dst.u.udp.port; | |
244 | exp->dir = !dir; | |
245 | ||
246 | /* When you see the packet, we need to NAT it the same as the | |
247 | this one. */ | |
248 | exp->expectfn = nf_nat_follow_master; | |
249 | ||
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) | |
254 | break; | |
255 | } | |
256 | ||
257 | if (port == 0) | |
258 | return NF_DROP; | |
259 | ||
260 | if (!mangle_sdp(pskb, ctinfo, ct, newip, port, dptr)) { | |
261 | nf_conntrack_unexpect_related(exp); | |
262 | return NF_DROP; | |
263 | } | |
264 | return NF_ACCEPT; | |
265 | } | |
266 | ||
267 | static void __exit nf_nat_sip_fini(void) | |
268 | { | |
269 | rcu_assign_pointer(nf_nat_sip_hook, NULL); | |
270 | rcu_assign_pointer(nf_nat_sdp_hook, NULL); | |
271 | synchronize_rcu(); | |
272 | } | |
273 | ||
274 | static int __init nf_nat_sip_init(void) | |
275 | { | |
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); | |
280 | return 0; | |
281 | } | |
282 | ||
283 | module_init(nf_nat_sip_init); | |
284 | module_exit(nf_nat_sip_fini); |