1 /*
2 * Copyright 2008, The Android Open Source Project
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
17 #define LOG_TAG "DHCP"
18
19 #include <dirent.h>
20 #include <errno.h>
21 #include <poll.h>
22 #include <netinet/in.h>
23 #include <stdarg.h>
24 #include <stdlib.h>
25 #include <stdio.h>
26 #include <string.h>
27 #include <sys/select.h>
28 #include <sys/socket.h>
29 #include <sys/time.h>
30 #include <sys/types.h>
31 #include <time.h>
32 #include <unistd.h>
33
34 #include <cutils/properties.h>
35 #include <log/log.h>
36
37 #include <netutils/ifc.h>
38 #include "dhcpmsg.h"
39 #include "packet.h"
40
41 #define VERBOSE 2
42
43 static int verbose = 1;
44 static char errmsg[2048];
45
46 typedef unsigned long long msecs_t;
47 #if VERBOSE
48 void dump_dhcp_msg();
49 #endif
50
get_msecs(void)51 msecs_t get_msecs(void)
52 {
53 struct timespec ts;
54
55 if (clock_gettime(CLOCK_MONOTONIC, &ts)) {
56 return 0;
57 } else {
58 return (((msecs_t) ts.tv_sec) * ((msecs_t) 1000)) +
59 (((msecs_t) ts.tv_nsec) / ((msecs_t) 1000000));
60 }
61 }
62
printerr(char * fmt,...)63 void printerr(char *fmt, ...)
64 {
65 va_list ap;
66
67 va_start(ap, fmt);
68 vsnprintf(errmsg, sizeof(errmsg), fmt, ap);
69 va_end(ap);
70
71 ALOGD("%s", errmsg);
72 }
73
dhcp_lasterror()74 const char *dhcp_lasterror()
75 {
76 return errmsg;
77 }
78
fatal(const char * reason)79 int fatal(const char *reason)
80 {
81 printerr("%s: %s\n", reason, strerror(errno));
82 return -1;
83 // exit(1);
84 }
85
ipaddr(in_addr_t addr)86 const char *ipaddr(in_addr_t addr)
87 {
88 struct in_addr in_addr;
89
90 in_addr.s_addr = addr;
91 return inet_ntoa(in_addr);
92 }
93
94 extern int ipv4NetmaskToPrefixLength(in_addr_t mask);
95
96 typedef struct dhcp_info dhcp_info;
97
98 struct dhcp_info {
99 uint32_t type;
100
101 uint32_t ipaddr;
102 uint32_t gateway;
103 uint32_t prefixLength;
104
105 uint32_t dns1;
106 uint32_t dns2;
107
108 uint32_t serveraddr;
109 uint32_t lease;
110 };
111
112 dhcp_info last_good_info;
113
get_dhcp_info(uint32_t * ipaddr,uint32_t * gateway,uint32_t * prefixLength,uint32_t * dns1,uint32_t * dns2,uint32_t * server,uint32_t * lease)114 void get_dhcp_info(uint32_t *ipaddr, uint32_t *gateway, uint32_t *prefixLength,
115 uint32_t *dns1, uint32_t *dns2, uint32_t *server,
116 uint32_t *lease)
117 {
118 *ipaddr = last_good_info.ipaddr;
119 *gateway = last_good_info.gateway;
120 *prefixLength = last_good_info.prefixLength;
121 *dns1 = last_good_info.dns1;
122 *dns2 = last_good_info.dns2;
123 *server = last_good_info.serveraddr;
124 *lease = last_good_info.lease;
125 }
126
dhcp_configure(const char * ifname,dhcp_info * info)127 static int dhcp_configure(const char *ifname, dhcp_info *info)
128 {
129 last_good_info = *info;
130 return ifc_configure(ifname, info->ipaddr, info->prefixLength, info->gateway,
131 info->dns1, info->dns2);
132 }
133
dhcp_type_to_name(uint32_t type)134 static const char *dhcp_type_to_name(uint32_t type)
135 {
136 switch(type) {
137 case DHCPDISCOVER: return "discover";
138 case DHCPOFFER: return "offer";
139 case DHCPREQUEST: return "request";
140 case DHCPDECLINE: return "decline";
141 case DHCPACK: return "ack";
142 case DHCPNAK: return "nak";
143 case DHCPRELEASE: return "release";
144 case DHCPINFORM: return "inform";
145 default: return "???";
146 }
147 }
148
dump_dhcp_info(dhcp_info * info)149 void dump_dhcp_info(dhcp_info *info)
150 {
151 char addr[20], gway[20];
152 ALOGD("--- dhcp %s (%d) ---",
153 dhcp_type_to_name(info->type), info->type);
154 strcpy(addr, ipaddr(info->ipaddr));
155 strcpy(gway, ipaddr(info->gateway));
156 ALOGD("ip %s gw %s prefixLength %d", addr, gway, info->prefixLength);
157 if (info->dns1) ALOGD("dns1: %s", ipaddr(info->dns1));
158 if (info->dns2) ALOGD("dns2: %s", ipaddr(info->dns2));
159 ALOGD("server %s, lease %d seconds",
160 ipaddr(info->serveraddr), info->lease);
161 }
162
163
decode_dhcp_msg(dhcp_msg * msg,int len,dhcp_info * info)164 int decode_dhcp_msg(dhcp_msg *msg, int len, dhcp_info *info)
165 {
166 uint8_t *x;
167 unsigned int opt;
168 int optlen;
169
170 memset(info, 0, sizeof(dhcp_info));
171 if (len < (DHCP_MSG_FIXED_SIZE + 4)) return -1;
172
173 len -= (DHCP_MSG_FIXED_SIZE + 4);
174
175 if (msg->options[0] != OPT_COOKIE1) return -1;
176 if (msg->options[1] != OPT_COOKIE2) return -1;
177 if (msg->options[2] != OPT_COOKIE3) return -1;
178 if (msg->options[3] != OPT_COOKIE4) return -1;
179
180 x = msg->options + 4;
181
182 while (len > 2) {
183 opt = *x++;
184 if (opt == OPT_PAD) {
185 len--;
186 continue;
187 }
188 if (opt == OPT_END) {
189 break;
190 }
191 optlen = *x++;
192 len -= 2;
193 if (optlen > len) {
194 break;
195 }
196 switch(opt) {
197 case OPT_SUBNET_MASK:
198 if (optlen >= 4) {
199 in_addr_t mask;
200 memcpy(&mask, x, 4);
201 info->prefixLength = ipv4NetmaskToPrefixLength(mask);
202 }
203 break;
204 case OPT_GATEWAY:
205 if (optlen >= 4) memcpy(&info->gateway, x, 4);
206 break;
207 case OPT_DNS:
208 if (optlen >= 4) memcpy(&info->dns1, x + 0, 4);
209 if (optlen >= 8) memcpy(&info->dns2, x + 4, 4);
210 break;
211 case OPT_LEASE_TIME:
212 if (optlen >= 4) {
213 memcpy(&info->lease, x, 4);
214 info->lease = ntohl(info->lease);
215 }
216 break;
217 case OPT_SERVER_ID:
218 if (optlen >= 4) memcpy(&info->serveraddr, x, 4);
219 break;
220 case OPT_MESSAGE_TYPE:
221 info->type = *x;
222 break;
223 default:
224 break;
225 }
226 x += optlen;
227 len -= optlen;
228 }
229
230 info->ipaddr = msg->yiaddr;
231
232 return 0;
233 }
234
235 #if VERBOSE
236
hex2str(char * buf,size_t buf_size,const unsigned char * array,int len)237 static void hex2str(char *buf, size_t buf_size, const unsigned char *array, int len)
238 {
239 int i;
240 char *cp = buf;
241 char *buf_end = buf + buf_size;
242 for (i = 0; i < len; i++) {
243 cp += snprintf(cp, buf_end - cp, " %02x ", array[i]);
244 }
245 }
246
dump_dhcp_msg(dhcp_msg * msg,int len)247 void dump_dhcp_msg(dhcp_msg *msg, int len)
248 {
249 unsigned char *x;
250 unsigned int n,c;
251 int optsz;
252 const char *name;
253 char buf[2048];
254
255 ALOGD("===== DHCP message:");
256 if (len < DHCP_MSG_FIXED_SIZE) {
257 ALOGD("Invalid length %d, should be %d", len, DHCP_MSG_FIXED_SIZE);
258 return;
259 }
260
261 len -= DHCP_MSG_FIXED_SIZE;
262
263 if (msg->op == OP_BOOTREQUEST)
264 name = "BOOTREQUEST";
265 else if (msg->op == OP_BOOTREPLY)
266 name = "BOOTREPLY";
267 else
268 name = "????";
269 ALOGD("op = %s (%d), htype = %d, hlen = %d, hops = %d",
270 name, msg->op, msg->htype, msg->hlen, msg->hops);
271 ALOGD("xid = 0x%08x secs = %d, flags = 0x%04x optlen = %d",
272 ntohl(msg->xid), ntohs(msg->secs), ntohs(msg->flags), len);
273 ALOGD("ciaddr = %s", ipaddr(msg->ciaddr));
274 ALOGD("yiaddr = %s", ipaddr(msg->yiaddr));
275 ALOGD("siaddr = %s", ipaddr(msg->siaddr));
276 ALOGD("giaddr = %s", ipaddr(msg->giaddr));
277
278 c = msg->hlen > 16 ? 16 : msg->hlen;
279 hex2str(buf, sizeof(buf), msg->chaddr, c);
280 ALOGD("chaddr = {%s}", buf);
281
282 for (n = 0; n < 64; n++) {
283 unsigned char x = msg->sname[n];
284 if ((x < ' ') || (x > 127)) {
285 if (x == 0) break;
286 msg->sname[n] = '.';
287 }
288 }
289 msg->sname[63] = 0;
290
291 for (n = 0; n < 128; n++) {
292 unsigned char x = msg->file[n];
293 if ((x < ' ') || (x > 127)) {
294 if (x == 0) break;
295 msg->file[n] = '.';
296 }
297 }
298 msg->file[127] = 0;
299
300 ALOGD("sname = '%s'", msg->sname);
301 ALOGD("file = '%s'", msg->file);
302
303 if (len < 4) return;
304 len -= 4;
305 x = msg->options + 4;
306
307 while (len > 2) {
308 if (*x == 0) {
309 x++;
310 len--;
311 continue;
312 }
313 if (*x == OPT_END) {
314 break;
315 }
316 len -= 2;
317 optsz = x[1];
318 if (optsz > len) break;
319 if (x[0] == OPT_DOMAIN_NAME || x[0] == OPT_MESSAGE) {
320 if ((unsigned int)optsz < sizeof(buf) - 1) {
321 n = optsz;
322 } else {
323 n = sizeof(buf) - 1;
324 }
325 memcpy(buf, &x[2], n);
326 buf[n] = '\0';
327 } else {
328 hex2str(buf, sizeof(buf), &x[2], optsz);
329 }
330 if (x[0] == OPT_MESSAGE_TYPE)
331 name = dhcp_type_to_name(x[2]);
332 else
333 name = NULL;
334 ALOGD("op %d len %d {%s} %s", x[0], optsz, buf, name == NULL ? "" : name);
335 len -= optsz;
336 x = x + optsz + 2;
337 }
338 }
339
340 #endif
341
send_message(int sock,int if_index,dhcp_msg * msg,int size)342 static int send_message(int sock, int if_index, dhcp_msg *msg, int size)
343 {
344 #if VERBOSE > 1
345 dump_dhcp_msg(msg, size);
346 #endif
347 return send_packet(sock, if_index, msg, size, INADDR_ANY, INADDR_BROADCAST,
348 PORT_BOOTP_CLIENT, PORT_BOOTP_SERVER);
349 }
350
is_valid_reply(dhcp_msg * msg,dhcp_msg * reply,int sz)351 static int is_valid_reply(dhcp_msg *msg, dhcp_msg *reply, int sz)
352 {
353 if (sz < DHCP_MSG_FIXED_SIZE) {
354 if (verbose) ALOGD("Wrong size %d != %d\n", sz, DHCP_MSG_FIXED_SIZE);
355 return 0;
356 }
357 if (reply->op != OP_BOOTREPLY) {
358 if (verbose) ALOGD("Wrong Op %d != %d\n", reply->op, OP_BOOTREPLY);
359 return 0;
360 }
361 if (reply->xid != msg->xid) {
362 if (verbose) ALOGD("Wrong Xid 0x%x != 0x%x\n", ntohl(reply->xid),
363 ntohl(msg->xid));
364 return 0;
365 }
366 if (reply->htype != msg->htype) {
367 if (verbose) ALOGD("Wrong Htype %d != %d\n", reply->htype, msg->htype);
368 return 0;
369 }
370 if (reply->hlen != msg->hlen) {
371 if (verbose) ALOGD("Wrong Hlen %d != %d\n", reply->hlen, msg->hlen);
372 return 0;
373 }
374 if (memcmp(msg->chaddr, reply->chaddr, msg->hlen)) {
375 if (verbose) ALOGD("Wrong chaddr %x != %x\n", *(reply->chaddr),*(msg->chaddr));
376 return 0;
377 }
378 return 1;
379 }
380
381 #define STATE_SELECTING 1
382 #define STATE_REQUESTING 2
383
384 #define TIMEOUT_INITIAL 4000
385 #define TIMEOUT_MAX 32000
386
dhcp_init_ifc(const char * ifname)387 int dhcp_init_ifc(const char *ifname)
388 {
389 dhcp_msg discover_msg;
390 dhcp_msg request_msg;
391 dhcp_msg reply;
392 dhcp_msg *msg;
393 dhcp_info info;
394 int s, r, size;
395 int valid_reply;
396 uint32_t xid;
397 unsigned char hwaddr[6];
398 struct pollfd pfd;
399 unsigned int state;
400 unsigned int timeout;
401 int if_index;
402
403 xid = (uint32_t) get_msecs();
404
405 if (ifc_get_hwaddr(ifname, hwaddr)) {
406 return fatal("cannot obtain interface address");
407 }
408 if (ifc_get_ifindex(ifname, &if_index)) {
409 return fatal("cannot obtain interface index");
410 }
411
412 s = open_raw_socket(ifname, hwaddr, if_index);
413
414 timeout = TIMEOUT_INITIAL;
415 state = STATE_SELECTING;
416 info.type = 0;
417 goto transmit;
418
419 for (;;) {
420 pfd.fd = s;
421 pfd.events = POLLIN;
422 pfd.revents = 0;
423 r = poll(&pfd, 1, timeout);
424
425 if (r == 0) {
426 #if VERBOSE
427 printerr("TIMEOUT\n");
428 #endif
429 if (timeout >= TIMEOUT_MAX) {
430 printerr("timed out\n");
431 if ( info.type == DHCPOFFER ) {
432 printerr("no acknowledgement from DHCP server\nconfiguring %s with offered parameters\n", ifname);
433 return dhcp_configure(ifname, &info);
434 }
435 errno = ETIME;
436 close(s);
437 return -1;
438 }
439 timeout = timeout * 2;
440
441 transmit:
442 size = 0;
443 msg = NULL;
444 switch(state) {
445 case STATE_SELECTING:
446 msg = &discover_msg;
447 size = init_dhcp_discover_msg(msg, hwaddr, xid);
448 break;
449 case STATE_REQUESTING:
450 msg = &request_msg;
451 size = init_dhcp_request_msg(msg, hwaddr, xid, info.ipaddr, info.serveraddr);
452 break;
453 default:
454 r = 0;
455 }
456 if (size != 0) {
457 r = send_message(s, if_index, msg, size);
458 if (r < 0) {
459 printerr("error sending dhcp msg: %s\n", strerror(errno));
460 }
461 }
462 continue;
463 }
464
465 if (r < 0) {
466 if ((errno == EAGAIN) || (errno == EINTR)) {
467 continue;
468 }
469 return fatal("poll failed");
470 }
471
472 errno = 0;
473 r = receive_packet(s, &reply);
474 if (r < 0) {
475 if (errno != 0) {
476 ALOGD("receive_packet failed (%d): %s", r, strerror(errno));
477 if (errno == ENETDOWN || errno == ENXIO) {
478 return -1;
479 }
480 }
481 continue;
482 }
483
484 #if VERBOSE > 1
485 dump_dhcp_msg(&reply, r);
486 #endif
487 decode_dhcp_msg(&reply, r, &info);
488
489 if (state == STATE_SELECTING) {
490 valid_reply = is_valid_reply(&discover_msg, &reply, r);
491 } else {
492 valid_reply = is_valid_reply(&request_msg, &reply, r);
493 }
494 if (!valid_reply) {
495 printerr("invalid reply\n");
496 continue;
497 }
498
499 if (verbose) dump_dhcp_info(&info);
500
501 switch(state) {
502 case STATE_SELECTING:
503 if (info.type == DHCPOFFER) {
504 state = STATE_REQUESTING;
505 timeout = TIMEOUT_INITIAL;
506 xid++;
507 goto transmit;
508 }
509 break;
510 case STATE_REQUESTING:
511 if (info.type == DHCPACK) {
512 printerr("configuring %s\n", ifname);
513 close(s);
514 return dhcp_configure(ifname, &info);
515 } else if (info.type == DHCPNAK) {
516 printerr("configuration request denied\n");
517 close(s);
518 return -1;
519 } else {
520 printerr("ignoring %s message in state %d\n",
521 dhcp_type_to_name(info.type), state);
522 }
523 break;
524 }
525 }
526 close(s);
527 return 0;
528 }
529
do_dhcp(char * iname)530 int do_dhcp(char *iname)
531 {
532 if (ifc_set_addr(iname, 0)) {
533 printerr("failed to set ip addr for %s to 0.0.0.0: %s\n", iname, strerror(errno));
534 return -1;
535 }
536
537 if (ifc_up(iname)) {
538 printerr("failed to bring up interface %s: %s\n", iname, strerror(errno));
539 return -1;
540 }
541
542 return dhcp_init_ifc(iname);
543 }
544