]>
Commit | Line | Data |
---|---|---|
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 | ||
9fafcd7b PM |
29 | struct addr_map { |
30 | struct { | |
31 | char src[sizeof("nnn.nnn.nnn.nnn:nnnnn")]; | |
32 | char dst[sizeof("nnn.nnn.nnn.nnn:nnnnn")]; | |
33 | unsigned int srclen, srciplen; | |
34 | unsigned int dstlen, dstiplen; | |
35 | } addr[IP_CT_DIR_MAX]; | |
36 | }; | |
37 | ||
38 | static void addr_map_init(struct nf_conn *ct, struct addr_map *map) | |
39 | { | |
40 | struct nf_conntrack_tuple *t; | |
41 | enum ip_conntrack_dir dir; | |
42 | unsigned int n; | |
43 | ||
44 | for (dir = 0; dir < IP_CT_DIR_MAX; dir++) { | |
45 | t = &ct->tuplehash[dir].tuple; | |
46 | ||
47 | n = sprintf(map->addr[dir].src, "%u.%u.%u.%u", | |
48 | NIPQUAD(t->src.u3.ip)); | |
49 | map->addr[dir].srciplen = n; | |
50 | n += sprintf(map->addr[dir].src + n, ":%u", | |
51 | ntohs(t->src.u.udp.port)); | |
52 | map->addr[dir].srclen = n; | |
53 | ||
54 | n = sprintf(map->addr[dir].dst, "%u.%u.%u.%u", | |
55 | NIPQUAD(t->dst.u3.ip)); | |
56 | map->addr[dir].dstiplen = n; | |
57 | n += sprintf(map->addr[dir].dst + n, ":%u", | |
58 | ntohs(t->dst.u.udp.port)); | |
59 | map->addr[dir].dstlen = n; | |
60 | } | |
61 | } | |
62 | ||
3db05fea | 63 | static int map_sip_addr(struct sk_buff *skb, enum ip_conntrack_info ctinfo, |
9fafcd7b PM |
64 | struct nf_conn *ct, const char **dptr, size_t dlen, |
65 | enum sip_header_pos pos, struct addr_map *map) | |
66 | { | |
67 | enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo); | |
68 | unsigned int matchlen, matchoff, addrlen; | |
69 | char *addr; | |
70 | ||
71 | if (ct_sip_get_info(ct, *dptr, dlen, &matchoff, &matchlen, pos) <= 0) | |
72 | return 1; | |
73 | ||
74 | if ((matchlen == map->addr[dir].srciplen || | |
75 | matchlen == map->addr[dir].srclen) && | |
76 | memcmp(*dptr + matchoff, map->addr[dir].src, matchlen) == 0) { | |
77 | addr = map->addr[!dir].dst; | |
78 | addrlen = map->addr[!dir].dstlen; | |
79 | } else if ((matchlen == map->addr[dir].dstiplen || | |
80 | matchlen == map->addr[dir].dstlen) && | |
81 | memcmp(*dptr + matchoff, map->addr[dir].dst, matchlen) == 0) { | |
82 | addr = map->addr[!dir].src; | |
83 | addrlen = map->addr[!dir].srclen; | |
84 | } else | |
85 | return 1; | |
86 | ||
3db05fea | 87 | if (!nf_nat_mangle_udp_packet(skb, ct, ctinfo, |
e905a9ed | 88 | matchoff, matchlen, addr, addrlen)) |
9fafcd7b | 89 | return 0; |
3db05fea | 90 | *dptr = skb->data + ip_hdrlen(skb) + sizeof(struct udphdr); |
9fafcd7b PM |
91 | return 1; |
92 | ||
93 | } | |
94 | ||
3db05fea | 95 | static unsigned int ip_nat_sip(struct sk_buff *skb, |
9fafcd7b PM |
96 | enum ip_conntrack_info ctinfo, |
97 | struct nf_conn *ct, | |
98 | const char **dptr) | |
99 | { | |
100 | enum sip_header_pos pos; | |
101 | struct addr_map map; | |
102 | int dataoff, datalen; | |
103 | ||
3db05fea HX |
104 | dataoff = ip_hdrlen(skb) + sizeof(struct udphdr); |
105 | datalen = skb->len - dataoff; | |
9fafcd7b | 106 | if (datalen < sizeof("SIP/2.0") - 1) |
45241a7a | 107 | return NF_ACCEPT; |
9fafcd7b PM |
108 | |
109 | addr_map_init(ct, &map); | |
110 | ||
111 | /* Basic rules: requests and responses. */ | |
112 | if (strncmp(*dptr, "SIP/2.0", sizeof("SIP/2.0") - 1) != 0) { | |
113 | /* 10.2: Constructing the REGISTER Request: | |
114 | * | |
115 | * The "userinfo" and "@" components of the SIP URI MUST NOT | |
116 | * be present. | |
117 | */ | |
118 | if (datalen >= sizeof("REGISTER") - 1 && | |
119 | strncmp(*dptr, "REGISTER", sizeof("REGISTER") - 1) == 0) | |
120 | pos = POS_REG_REQ_URI; | |
121 | else | |
122 | pos = POS_REQ_URI; | |
123 | ||
3db05fea | 124 | if (!map_sip_addr(skb, ctinfo, ct, dptr, datalen, pos, &map)) |
9fafcd7b PM |
125 | return NF_DROP; |
126 | } | |
127 | ||
3db05fea HX |
128 | if (!map_sip_addr(skb, ctinfo, ct, dptr, datalen, POS_FROM, &map) || |
129 | !map_sip_addr(skb, ctinfo, ct, dptr, datalen, POS_TO, &map) || | |
130 | !map_sip_addr(skb, ctinfo, ct, dptr, datalen, POS_VIA, &map) || | |
131 | !map_sip_addr(skb, ctinfo, ct, dptr, datalen, POS_CONTACT, &map)) | |
9fafcd7b PM |
132 | return NF_DROP; |
133 | return NF_ACCEPT; | |
134 | } | |
135 | ||
3db05fea | 136 | static unsigned int mangle_sip_packet(struct sk_buff *skb, |
9fafcd7b PM |
137 | enum ip_conntrack_info ctinfo, |
138 | struct nf_conn *ct, | |
139 | const char **dptr, size_t dlen, | |
140 | char *buffer, int bufflen, | |
141 | enum sip_header_pos pos) | |
142 | { | |
143 | unsigned int matchlen, matchoff; | |
144 | ||
145 | if (ct_sip_get_info(ct, *dptr, dlen, &matchoff, &matchlen, pos) <= 0) | |
146 | return 0; | |
147 | ||
3db05fea | 148 | if (!nf_nat_mangle_udp_packet(skb, ct, ctinfo, |
e905a9ed | 149 | matchoff, matchlen, buffer, bufflen)) |
9fafcd7b PM |
150 | return 0; |
151 | ||
152 | /* We need to reload this. Thanks Patrick. */ | |
3db05fea | 153 | *dptr = skb->data + ip_hdrlen(skb) + sizeof(struct udphdr); |
9fafcd7b PM |
154 | return 1; |
155 | } | |
156 | ||
3db05fea | 157 | static int mangle_content_len(struct sk_buff *skb, |
9fafcd7b PM |
158 | enum ip_conntrack_info ctinfo, |
159 | struct nf_conn *ct, | |
160 | const char *dptr) | |
161 | { | |
162 | unsigned int dataoff, matchoff, matchlen; | |
163 | char buffer[sizeof("65536")]; | |
164 | int bufflen; | |
165 | ||
3db05fea | 166 | dataoff = ip_hdrlen(skb) + sizeof(struct udphdr); |
9fafcd7b PM |
167 | |
168 | /* Get actual SDP lenght */ | |
3db05fea | 169 | if (ct_sip_get_info(ct, dptr, skb->len - dataoff, &matchoff, |
e905a9ed | 170 | &matchlen, POS_SDP_HEADER) > 0) { |
9fafcd7b PM |
171 | |
172 | /* since ct_sip_get_info() give us a pointer passing 'v=' | |
173 | we need to add 2 bytes in this count. */ | |
3db05fea | 174 | int c_len = skb->len - dataoff - matchoff + 2; |
9fafcd7b PM |
175 | |
176 | /* Now, update SDP length */ | |
3db05fea | 177 | if (ct_sip_get_info(ct, dptr, skb->len - dataoff, &matchoff, |
e905a9ed | 178 | &matchlen, POS_CONTENT) > 0) { |
9fafcd7b PM |
179 | |
180 | bufflen = sprintf(buffer, "%u", c_len); | |
3db05fea | 181 | return nf_nat_mangle_udp_packet(skb, ct, ctinfo, |
9fafcd7b PM |
182 | matchoff, matchlen, |
183 | buffer, bufflen); | |
184 | } | |
185 | } | |
186 | return 0; | |
187 | } | |
188 | ||
3db05fea | 189 | static unsigned int mangle_sdp(struct sk_buff *skb, |
9fafcd7b PM |
190 | enum ip_conntrack_info ctinfo, |
191 | struct nf_conn *ct, | |
192 | __be32 newip, u_int16_t port, | |
193 | const char *dptr) | |
194 | { | |
195 | char buffer[sizeof("nnn.nnn.nnn.nnn")]; | |
196 | unsigned int dataoff, bufflen; | |
197 | ||
3db05fea | 198 | dataoff = ip_hdrlen(skb) + sizeof(struct udphdr); |
9fafcd7b PM |
199 | |
200 | /* Mangle owner and contact info. */ | |
201 | bufflen = sprintf(buffer, "%u.%u.%u.%u", NIPQUAD(newip)); | |
3db05fea | 202 | if (!mangle_sip_packet(skb, ctinfo, ct, &dptr, skb->len - dataoff, |
e905a9ed | 203 | buffer, bufflen, POS_OWNER_IP4)) |
9fafcd7b PM |
204 | return 0; |
205 | ||
3db05fea | 206 | if (!mangle_sip_packet(skb, ctinfo, ct, &dptr, skb->len - dataoff, |
e905a9ed | 207 | buffer, bufflen, POS_CONNECTION_IP4)) |
9fafcd7b PM |
208 | return 0; |
209 | ||
210 | /* Mangle media port. */ | |
211 | bufflen = sprintf(buffer, "%u", port); | |
3db05fea | 212 | if (!mangle_sip_packet(skb, ctinfo, ct, &dptr, skb->len - dataoff, |
e905a9ed | 213 | buffer, bufflen, POS_MEDIA)) |
9fafcd7b PM |
214 | return 0; |
215 | ||
3db05fea | 216 | return mangle_content_len(skb, ctinfo, ct, dptr); |
9fafcd7b PM |
217 | } |
218 | ||
cfd6c380 HX |
219 | static void ip_nat_sdp_expect(struct nf_conn *ct, |
220 | struct nf_conntrack_expect *exp) | |
221 | { | |
222 | struct nf_nat_range range; | |
223 | ||
224 | /* This must be a fresh one. */ | |
225 | BUG_ON(ct->status & IPS_NAT_DONE_MASK); | |
226 | ||
227 | /* Change src to where master sends to */ | |
228 | range.flags = IP_NAT_RANGE_MAP_IPS; | |
229 | range.min_ip = range.max_ip | |
230 | = ct->master->tuplehash[!exp->dir].tuple.dst.u3.ip; | |
231 | /* hook doesn't matter, but it has to do source manip */ | |
232 | nf_nat_setup_info(ct, &range, NF_IP_POST_ROUTING); | |
233 | ||
234 | /* For DST manip, map port here to where it's expected. */ | |
235 | range.flags = (IP_NAT_RANGE_MAP_IPS | IP_NAT_RANGE_PROTO_SPECIFIED); | |
236 | range.min = range.max = exp->saved_proto; | |
237 | range.min_ip = range.max_ip = exp->saved_ip; | |
238 | /* hook doesn't matter, but it has to do destination manip */ | |
239 | nf_nat_setup_info(ct, &range, NF_IP_PRE_ROUTING); | |
240 | } | |
241 | ||
9fafcd7b PM |
242 | /* So, this packet has hit the connection tracking matching code. |
243 | Mangle it, and change the expectation to match the new version. */ | |
3db05fea | 244 | static unsigned int ip_nat_sdp(struct sk_buff *skb, |
9fafcd7b PM |
245 | enum ip_conntrack_info ctinfo, |
246 | struct nf_conntrack_expect *exp, | |
247 | const char *dptr) | |
248 | { | |
249 | struct nf_conn *ct = exp->master; | |
250 | enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo); | |
251 | __be32 newip; | |
252 | u_int16_t port; | |
253 | ||
9fafcd7b | 254 | /* Connection will come from reply */ |
f4a607bf JB |
255 | if (ct->tuplehash[dir].tuple.src.u3.ip == |
256 | ct->tuplehash[!dir].tuple.dst.u3.ip) | |
257 | newip = exp->tuple.dst.u3.ip; | |
258 | else | |
259 | newip = ct->tuplehash[!dir].tuple.dst.u3.ip; | |
9fafcd7b | 260 | |
cfd6c380 | 261 | exp->saved_ip = exp->tuple.dst.u3.ip; |
9fafcd7b PM |
262 | exp->tuple.dst.u3.ip = newip; |
263 | exp->saved_proto.udp.port = exp->tuple.dst.u.udp.port; | |
264 | exp->dir = !dir; | |
265 | ||
266 | /* When you see the packet, we need to NAT it the same as the | |
267 | this one. */ | |
cfd6c380 | 268 | exp->expectfn = ip_nat_sdp_expect; |
9fafcd7b PM |
269 | |
270 | /* Try to get same port: if not, try to change it. */ | |
271 | for (port = ntohs(exp->saved_proto.udp.port); port != 0; port++) { | |
272 | exp->tuple.dst.u.udp.port = htons(port); | |
6823645d | 273 | if (nf_ct_expect_related(exp) == 0) |
9fafcd7b PM |
274 | break; |
275 | } | |
276 | ||
277 | if (port == 0) | |
278 | return NF_DROP; | |
279 | ||
3db05fea | 280 | if (!mangle_sdp(skb, ctinfo, ct, newip, port, dptr)) { |
6823645d | 281 | nf_ct_unexpect_related(exp); |
9fafcd7b PM |
282 | return NF_DROP; |
283 | } | |
284 | return NF_ACCEPT; | |
285 | } | |
286 | ||
287 | static void __exit nf_nat_sip_fini(void) | |
288 | { | |
289 | rcu_assign_pointer(nf_nat_sip_hook, NULL); | |
290 | rcu_assign_pointer(nf_nat_sdp_hook, NULL); | |
291 | synchronize_rcu(); | |
292 | } | |
293 | ||
294 | static int __init nf_nat_sip_init(void) | |
295 | { | |
296 | BUG_ON(rcu_dereference(nf_nat_sip_hook)); | |
297 | BUG_ON(rcu_dereference(nf_nat_sdp_hook)); | |
298 | rcu_assign_pointer(nf_nat_sip_hook, ip_nat_sip); | |
299 | rcu_assign_pointer(nf_nat_sdp_hook, ip_nat_sdp); | |
300 | return 0; | |
301 | } | |
302 | ||
303 | module_init(nf_nat_sip_init); | |
304 | module_exit(nf_nat_sip_fini); |