1 /*
2 * Copyright 2011 Daniel Drown
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 *
16 * config.c - configuration settings
17 */
18
19 #include <string.h>
20 #include <stdlib.h>
21 #include <arpa/inet.h>
22 #include <stdio.h>
23 #include <limits.h>
24 #include <errno.h>
25 #include <unistd.h>
26
27 #include <cutils/config_utils.h>
28 #include <netutils/ifc.h>
29
30 #include "config.h"
31 #include "dns64.h"
32 #include "logging.h"
33 #include "getaddr.h"
34 #include "clatd.h"
35 #include "checksum.h"
36
37 struct clat_config Global_Clatd_Config;
38
39 /* function: config_item_str
40 * locates the config item and returns the pointer to a string, or NULL on failure. Caller frees pointer
41 * root - parsed configuration
42 * item_name - name of config item to locate
43 * defaultvar - value to use if config item isn't present
44 */
config_item_str(cnode * root,const char * item_name,const char * defaultvar)45 char *config_item_str(cnode *root, const char *item_name, const char *defaultvar) {
46 const char *tmp;
47
48 if(!(tmp = config_str(root, item_name, defaultvar))) {
49 logmsg(ANDROID_LOG_FATAL,"%s config item needed",item_name);
50 return NULL;
51 }
52 return strdup(tmp);
53 }
54
55 /* function: config_item_int16_t
56 * locates the config item, parses the integer, and returns the pointer ret_val_ptr, or NULL on failure
57 * root - parsed configuration
58 * item_name - name of config item to locate
59 * defaultvar - value to use if config item isn't present
60 * ret_val_ptr - pointer for return value storage
61 */
config_item_int16_t(cnode * root,const char * item_name,const char * defaultvar,int16_t * ret_val_ptr)62 int16_t *config_item_int16_t(cnode *root, const char *item_name, const char *defaultvar, int16_t *ret_val_ptr) {
63 const char *tmp;
64 char *endptr;
65 long int conf_int;
66
67 if(!(tmp = config_str(root, item_name, defaultvar))) {
68 logmsg(ANDROID_LOG_FATAL,"%s config item needed",item_name);
69 return NULL;
70 }
71
72 errno = 0;
73 conf_int = strtol(tmp,&endptr,10);
74 if(errno > 0) {
75 logmsg(ANDROID_LOG_FATAL,"%s config item is not numeric: %s (error=%s)",item_name,tmp,strerror(errno));
76 return NULL;
77 }
78 if(endptr == tmp || *tmp == '\0') {
79 logmsg(ANDROID_LOG_FATAL,"%s config item is not numeric: %s",item_name,tmp);
80 return NULL;
81 }
82 if(*endptr != '\0') {
83 logmsg(ANDROID_LOG_FATAL,"%s config item contains non-numeric characters: %s",item_name,endptr);
84 return NULL;
85 }
86 if(conf_int > INT16_MAX || conf_int < INT16_MIN) {
87 logmsg(ANDROID_LOG_FATAL,"%s config item is too big/small: %d",item_name,conf_int);
88 return NULL;
89 }
90 *ret_val_ptr = conf_int;
91 return ret_val_ptr;
92 }
93
94 /* function: config_item_ip
95 * locates the config item, parses the ipv4 address, and returns the pointer ret_val_ptr, or NULL on failure
96 * root - parsed configuration
97 * item_name - name of config item to locate
98 * defaultvar - value to use if config item isn't present
99 * ret_val_ptr - pointer for return value storage
100 */
config_item_ip(cnode * root,const char * item_name,const char * defaultvar,struct in_addr * ret_val_ptr)101 struct in_addr *config_item_ip(cnode *root, const char *item_name, const char *defaultvar, struct in_addr *ret_val_ptr) {
102 const char *tmp;
103 int status;
104
105 if(!(tmp = config_str(root, item_name, defaultvar))) {
106 logmsg(ANDROID_LOG_FATAL,"%s config item needed",item_name);
107 return NULL;
108 }
109
110 status = inet_pton(AF_INET, tmp, ret_val_ptr);
111 if(status <= 0) {
112 logmsg(ANDROID_LOG_FATAL,"invalid IPv4 address specified for %s: %s", item_name, tmp);
113 return NULL;
114 }
115
116 return ret_val_ptr;
117 }
118
119 /* function: config_item_ip6
120 * locates the config item, parses the ipv6 address, and returns the pointer ret_val_ptr, or NULL on failure
121 * root - parsed configuration
122 * item_name - name of config item to locate
123 * defaultvar - value to use if config item isn't present
124 * ret_val_ptr - pointer for return value storage
125 */
config_item_ip6(cnode * root,const char * item_name,const char * defaultvar,struct in6_addr * ret_val_ptr)126 struct in6_addr *config_item_ip6(cnode *root, const char *item_name, const char *defaultvar, struct in6_addr *ret_val_ptr) {
127 const char *tmp;
128 int status;
129
130 if(!(tmp = config_str(root, item_name, defaultvar))) {
131 logmsg(ANDROID_LOG_FATAL,"%s config item needed",item_name);
132 return NULL;
133 }
134
135 status = inet_pton(AF_INET6, tmp, ret_val_ptr);
136 if(status <= 0) {
137 logmsg(ANDROID_LOG_FATAL,"invalid IPv6 address specified for %s: %s", item_name, tmp);
138 return NULL;
139 }
140
141 return ret_val_ptr;
142 }
143
144 /* function: free_config
145 * frees the memory used by the global config variable
146 */
free_config()147 void free_config() {
148 if(Global_Clatd_Config.plat_from_dns64_hostname) {
149 free(Global_Clatd_Config.plat_from_dns64_hostname);
150 Global_Clatd_Config.plat_from_dns64_hostname = NULL;
151 }
152 }
153
154 /* function: ipv6_prefix_equal
155 * compares the prefixes two ipv6 addresses. assumes the prefix lengths are both /64.
156 * a1 - first address
157 * a2 - second address
158 * returns: 0 if the subnets are different, 1 if they are the same.
159 */
ipv6_prefix_equal(struct in6_addr * a1,struct in6_addr * a2)160 int ipv6_prefix_equal(struct in6_addr *a1, struct in6_addr *a2) {
161 return !memcmp(a1, a2, 8);
162 }
163
164 /* function: dns64_detection
165 * does dns lookups to set the plat subnet or exits on failure, waits forever for a dns response with a query backoff timer
166 * net_id - (optional) netId to use, NETID_UNSET indicates use of default network
167 */
dns64_detection(unsigned net_id)168 void dns64_detection(unsigned net_id) {
169 int backoff_sleep, status;
170 struct in6_addr tmp_ptr;
171
172 backoff_sleep = 1;
173
174 while(1) {
175 status = plat_prefix(Global_Clatd_Config.plat_from_dns64_hostname,net_id,&tmp_ptr);
176 if(status > 0) {
177 memcpy(&Global_Clatd_Config.plat_subnet, &tmp_ptr, sizeof(struct in6_addr));
178 return;
179 }
180 logmsg(ANDROID_LOG_WARN, "dns64_detection -- error, sleeping for %d seconds", backoff_sleep);
181 sleep(backoff_sleep);
182 backoff_sleep *= 2;
183 if(backoff_sleep >= 1800) {
184 // Scale down to one DNS query per half hour. Unnecessary DNS queries waste power, and the
185 // benefit is minimal (basically, only limited to the case where a network goes from IPv6-only
186 // to IPv6 with NAT64).
187 backoff_sleep = 1800;
188 }
189 }
190 }
191
192 /* function: gen_random_iid
193 * picks a random interface ID that is checksum neutral with the IPv4 address and the NAT64 prefix
194 * myaddr - IPv6 address to write to
195 * ipv4_local_subnet - clat IPv4 address
196 * plat_subnet - NAT64 prefix
197 */
gen_random_iid(struct in6_addr * myaddr,struct in_addr * ipv4_local_subnet,struct in6_addr * plat_subnet)198 void gen_random_iid(struct in6_addr *myaddr, struct in_addr *ipv4_local_subnet,
199 struct in6_addr *plat_subnet) {
200 // Fill last 8 bytes of IPv6 address with random bits.
201 arc4random_buf(&myaddr->s6_addr[8], 8);
202
203 // Make the IID checksum-neutral. That is, make it so that:
204 // checksum(Local IPv4 | Remote IPv4) = checksum(Local IPv6 | Remote IPv6)
205 // in other words (because remote IPv6 = NAT64 prefix | Remote IPv4):
206 // checksum(Local IPv4) = checksum(Local IPv6 | NAT64 prefix)
207 // Do this by adjusting the two bytes in the middle of the IID.
208
209 uint16_t middlebytes = (myaddr->s6_addr[11] << 8) + myaddr->s6_addr[12];
210
211 uint32_t c1 = ip_checksum_add(0, ipv4_local_subnet, sizeof(*ipv4_local_subnet));
212 uint32_t c2 = ip_checksum_add(0, plat_subnet, sizeof(*plat_subnet)) +
213 ip_checksum_add(0, myaddr, sizeof(*myaddr));
214
215 uint16_t delta = ip_checksum_adjust(middlebytes, c1, c2);
216 myaddr->s6_addr[11] = delta >> 8;
217 myaddr->s6_addr[12] = delta & 0xff;
218 }
219
220 // Factored out to a separate function for testability.
connect_is_ipv4_address_free(in_addr_t addr)221 int connect_is_ipv4_address_free(in_addr_t addr) {
222 int s = socket(AF_INET, SOCK_DGRAM, 0);
223 if (s == -1) {
224 return 0;
225 }
226
227 // Attempt to connect to the address. If the connection succeeds and getsockname returns the same
228 // the address then the address is already assigned to the system and we can't use it.
229 struct sockaddr_in sin = { .sin_family = AF_INET, .sin_addr = { addr }, .sin_port = 53 };
230 socklen_t len = sizeof(sin);
231 int inuse = connect(s, (struct sockaddr *) &sin, sizeof(sin)) == 0 &&
232 getsockname(s, (struct sockaddr *) &sin, &len) == 0 &&
233 (size_t) len >= sizeof(sin) &&
234 sin.sin_addr.s_addr == addr;
235
236 close(s);
237 return !inuse;
238 }
239
240 addr_free_func config_is_ipv4_address_free = connect_is_ipv4_address_free;
241
242 /* function: config_select_ipv4_address
243 * picks a free IPv4 address, starting from ip and trying all addresses in the prefix in order
244 * ip - the IP address from the configuration file
245 * prefixlen - the length of the prefix from which addresses may be selected.
246 * returns: the IPv4 address, or INADDR_NONE if no addresses were available
247 */
config_select_ipv4_address(const struct in_addr * ip,int16_t prefixlen)248 in_addr_t config_select_ipv4_address(const struct in_addr *ip, int16_t prefixlen) {
249 in_addr_t chosen = INADDR_NONE;
250
251 // Don't accept prefixes that are too large because we scan addresses one by one.
252 if (prefixlen < 16 || prefixlen > 32) {
253 return chosen;
254 }
255
256 // All these are in host byte order.
257 in_addr_t mask = 0xffffffff >> (32 - prefixlen) << (32 - prefixlen);
258 in_addr_t ipv4 = ntohl(ip->s_addr);
259 in_addr_t first_ipv4 = ipv4;
260 in_addr_t prefix = ipv4 & mask;
261
262 // Pick the first IPv4 address in the pool, wrapping around if necessary.
263 // So, for example, 192.0.0.4 -> 192.0.0.5 -> 192.0.0.6 -> 192.0.0.7 -> 192.0.0.0.
264 do {
265 if (config_is_ipv4_address_free(htonl(ipv4))) {
266 chosen = htonl(ipv4);
267 break;
268 }
269 ipv4 = prefix | ((ipv4 + 1) & ~mask);
270 } while (ipv4 != first_ipv4);
271
272 return chosen;
273 }
274
275 /* function: config_generate_local_ipv6_subnet
276 * generates the local ipv6 subnet when given the interface ip
277 * requires config.ipv6_host_id
278 * interface_ip - in: interface ip, out: local ipv6 host address
279 */
config_generate_local_ipv6_subnet(struct in6_addr * interface_ip)280 void config_generate_local_ipv6_subnet(struct in6_addr *interface_ip) {
281 int i;
282
283 if (Global_Clatd_Config.use_dynamic_iid) {
284 /* Generate a random interface ID. */
285 gen_random_iid(interface_ip,
286 &Global_Clatd_Config.ipv4_local_subnet,
287 &Global_Clatd_Config.plat_subnet);
288 } else {
289 /* Use the specified interface ID. */
290 for(i = 2; i < 4; i++) {
291 interface_ip->s6_addr32[i] = Global_Clatd_Config.ipv6_host_id.s6_addr32[i];
292 }
293 }
294 }
295
296 /* function: read_config
297 * reads the config file and parses it into the global variable Global_Clatd_Config. returns 0 on failure, 1 on success
298 * file - filename to parse
299 * uplink_interface - interface to use to reach the internet and supplier of address space
300 * plat_prefix - (optional) plat prefix to use, otherwise follow config file
301 * net_id - (optional) netId to use, NETID_UNSET indicates use of default network
302 */
read_config(const char * file,const char * uplink_interface,const char * plat_prefix,unsigned net_id)303 int read_config(const char *file, const char *uplink_interface, const char *plat_prefix,
304 unsigned net_id) {
305 cnode *root = config_node("", "");
306 void *tmp_ptr = NULL;
307 unsigned flags;
308
309 if(!root) {
310 logmsg(ANDROID_LOG_FATAL,"out of memory");
311 return 0;
312 }
313
314 memset(&Global_Clatd_Config, '\0', sizeof(Global_Clatd_Config));
315
316 config_load_file(root, file);
317 if(root->first_child == NULL) {
318 logmsg(ANDROID_LOG_FATAL,"Could not read config file %s", file);
319 goto failed;
320 }
321
322 Global_Clatd_Config.default_pdp_interface = strdup(uplink_interface);
323 if (!Global_Clatd_Config.default_pdp_interface)
324 goto failed;
325
326 if(!config_item_int16_t(root, "mtu", "-1", &Global_Clatd_Config.mtu))
327 goto failed;
328
329 if(!config_item_int16_t(root, "ipv4mtu", "-1", &Global_Clatd_Config.ipv4mtu))
330 goto failed;
331
332 if(!config_item_ip(root, "ipv4_local_subnet", DEFAULT_IPV4_LOCAL_SUBNET,
333 &Global_Clatd_Config.ipv4_local_subnet))
334 goto failed;
335
336 if(!config_item_int16_t(root, "ipv4_local_prefixlen", DEFAULT_IPV4_LOCAL_PREFIXLEN,
337 &Global_Clatd_Config.ipv4_local_prefixlen))
338 goto failed;
339
340 if(plat_prefix) { // plat subnet is coming from the command line
341 if(inet_pton(AF_INET6, plat_prefix, &Global_Clatd_Config.plat_subnet) <= 0) {
342 logmsg(ANDROID_LOG_FATAL,"invalid IPv6 address specified for plat prefix: %s", plat_prefix);
343 goto failed;
344 }
345 } else {
346 tmp_ptr = (void *)config_item_str(root, "plat_from_dns64", "yes");
347 if(!tmp_ptr || strcmp(tmp_ptr, "no") == 0) {
348 free(tmp_ptr);
349
350 if(!config_item_ip6(root, "plat_subnet", NULL, &Global_Clatd_Config.plat_subnet)) {
351 logmsg(ANDROID_LOG_FATAL, "plat_from_dns64 disabled, but no plat_subnet specified");
352 goto failed;
353 }
354 } else {
355 free(tmp_ptr);
356
357 if(!(Global_Clatd_Config.plat_from_dns64_hostname = config_item_str(root, "plat_from_dns64_hostname", DEFAULT_DNS64_DETECTION_HOSTNAME)))
358 goto failed;
359 dns64_detection(net_id);
360 }
361 }
362
363 if (!config_item_ip6(root, "ipv6_host_id", "::", &Global_Clatd_Config.ipv6_host_id))
364 goto failed;
365
366 /* In order to prevent multiple devices attempting to use the same clat address, never use a
367 statically-configured interface ID on a broadcast interface such as wifi. */
368 if (!IN6_IS_ADDR_UNSPECIFIED(&Global_Clatd_Config.ipv6_host_id)) {
369 ifc_init();
370 ifc_get_info(Global_Clatd_Config.default_pdp_interface, NULL, NULL, &flags);
371 ifc_close();
372 Global_Clatd_Config.use_dynamic_iid = (flags & IFF_BROADCAST) != 0;
373 } else {
374 Global_Clatd_Config.use_dynamic_iid = 1;
375 }
376
377 return 1;
378
379 failed:
380 free(root);
381 free_config();
382 return 0;
383 }
384
385 /* function; dump_config
386 * prints the current config
387 */
dump_config()388 void dump_config() {
389 char charbuffer[INET6_ADDRSTRLEN];
390
391 logmsg(ANDROID_LOG_DEBUG,"mtu = %d",Global_Clatd_Config.mtu);
392 logmsg(ANDROID_LOG_DEBUG,"ipv4mtu = %d",Global_Clatd_Config.ipv4mtu);
393 logmsg(ANDROID_LOG_DEBUG,"ipv6_local_subnet = %s",inet_ntop(AF_INET6, &Global_Clatd_Config.ipv6_local_subnet, charbuffer, sizeof(charbuffer)));
394 logmsg(ANDROID_LOG_DEBUG,"ipv4_local_subnet = %s",inet_ntop(AF_INET, &Global_Clatd_Config.ipv4_local_subnet, charbuffer, sizeof(charbuffer)));
395 logmsg(ANDROID_LOG_DEBUG,"ipv4_local_prefixlen = %d", Global_Clatd_Config.ipv4_local_prefixlen);
396 logmsg(ANDROID_LOG_DEBUG,"plat_subnet = %s",inet_ntop(AF_INET6, &Global_Clatd_Config.plat_subnet, charbuffer, sizeof(charbuffer)));
397 logmsg(ANDROID_LOG_DEBUG,"default_pdp_interface = %s",Global_Clatd_Config.default_pdp_interface);
398 }
399