dhcpclient.c revision 58b64acef07e6426914a8cb2d972778fbe138655 
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#include <stdio.h>
18#include <stdarg.h>
19#include <stdlib.h>
20#include <unistd.h>
21#include <errno.h>
22#include <string.h>
23
24#include <time.h>
25#include <sys/time.h>
26#include <poll.h>
27
28#include <sys/socket.h>
29#include <sys/select.h>
30#include <sys/types.h>
31#include <netinet/in.h>
32
33#include <cutils/properties.h>
34#define LOG_TAG "DHCP"
35#include <cutils/log.h>
36
37#include <dirent.h>
38
39#include "dhcpmsg.h"
40#include "ifc_utils.h"
41#include "packet.h"
42
43#define VERBOSE 2
44
45static int verbose = 1;
46static char errmsg[2048];
47
48typedef unsigned long long msecs_t;
49#if VERBOSE
50void dump_dhcp_msg();
51#endif
52
53msecs_t get_msecs(void)
54{
55    struct timespec ts;
56
57    if (clock_gettime(CLOCK_MONOTONIC, &ts)) {
58        return 0;
59    } else {
60        return (((msecs_t) ts.tv_sec) * ((msecs_t) 1000)) +
61            (((msecs_t) ts.tv_nsec) / ((msecs_t) 1000000));
62    }
63}
64
65void printerr(char *fmt, ...)
66{
67    va_list ap;
68
69    va_start(ap, fmt);
70    vsnprintf(errmsg, sizeof(errmsg), fmt, ap);
71    va_end(ap);
72
73    LOGD("%s", errmsg);
74}
75
76const char *dhcp_lasterror()
77{
78    return errmsg;
79}
80
81int fatal(const char *reason)
82{
83    printerr("%s: %s\n", reason, strerror(errno));
84    return -1;
85//    exit(1);
86}
87
88const char *ipaddr(uint32_t addr)
89{
90    static char buf[32];
91
92    sprintf(buf,"%d.%d.%d.%d",
93            addr & 255,
94            ((addr >> 8) & 255),
95            ((addr >> 16) & 255),
96            (addr >> 24));
97    return buf;
98}
99
100typedef struct dhcp_info dhcp_info;
101
102struct dhcp_info {
103    uint32_t type;
104
105    uint32_t ipaddr;
106    uint32_t gateway;
107    uint32_t netmask;
108
109    uint32_t dns1;
110    uint32_t dns2;
111
112    uint32_t serveraddr;
113    uint32_t lease;
114};
115
116dhcp_info last_good_info;
117
118void get_dhcp_info(uint32_t *ipaddr, uint32_t *gateway, uint32_t *mask,
119                   uint32_t *dns1, uint32_t *dns2, uint32_t *server,
120                   uint32_t *lease)
121{
122    *ipaddr = last_good_info.ipaddr;
123    *gateway = last_good_info.gateway;
124    *mask = last_good_info.netmask;
125    *dns1 = last_good_info.dns1;
126    *dns2 = last_good_info.dns2;
127    *server = last_good_info.serveraddr;
128    *lease = last_good_info.lease;
129}
130
131static int ifc_configure(const char *ifname, dhcp_info *info)
132{
133    char dns_prop_name[PROPERTY_KEY_MAX];
134
135    if (ifc_set_addr(ifname, info->ipaddr)) {
136        printerr("failed to set ipaddr %s: %s\n", ipaddr(info->ipaddr), strerror(errno));
137        return -1;
138    }
139    if (ifc_set_mask(ifname, info->netmask)) {
140        printerr("failed to set netmask %s: %s\n", ipaddr(info->netmask), strerror(errno));
141        return -1;
142    }
143    if (ifc_create_default_route(ifname, info->gateway)) {
144        printerr("failed to set default route %s: %s\n", ipaddr(info->gateway), strerror(errno));
145        return -1;
146    }
147
148    snprintf(dns_prop_name, sizeof(dns_prop_name), "net.%s.dns1", ifname);
149    property_set(dns_prop_name, info->dns1 ? ipaddr(info->dns1) : "");
150    snprintf(dns_prop_name, sizeof(dns_prop_name), "net.%s.dns2", ifname);
151    property_set(dns_prop_name, info->dns2 ? ipaddr(info->dns2) : "");
152
153    last_good_info = *info;
154
155    return 0;
156}
157
158static const char *dhcp_type_to_name(uint32_t type)
159{
160    switch(type) {
161    case DHCPDISCOVER: return "discover";
162    case DHCPOFFER:    return "offer";
163    case DHCPREQUEST:  return "request";
164    case DHCPDECLINE:  return "decline";
165    case DHCPACK:      return "ack";
166    case DHCPNAK:      return "nak";
167    case DHCPRELEASE:  return "release";
168    case DHCPINFORM:   return "inform";
169    default:           return "???";
170    }
171}
172
173void dump_dhcp_info(dhcp_info *info)
174{
175    char addr[20], gway[20], mask[20];
176    LOGD("--- dhcp %s (%d) ---",
177            dhcp_type_to_name(info->type), info->type);
178    strcpy(addr, ipaddr(info->ipaddr));
179    strcpy(gway, ipaddr(info->gateway));
180    strcpy(mask, ipaddr(info->netmask));
181    LOGD("ip %s gw %s mask %s", addr, gway, mask);
182    if (info->dns1) LOGD("dns1: %s", ipaddr(info->dns1));
183    if (info->dns2) LOGD("dns2: %s", ipaddr(info->dns2));
184    LOGD("server %s, lease %d seconds",
185            ipaddr(info->serveraddr), info->lease);
186}
187
188
189int decode_dhcp_msg(dhcp_msg *msg, int len, dhcp_info *info)
190{
191    uint8_t *x;
192    unsigned int opt;
193    int optlen;
194
195    memset(info, 0, sizeof(dhcp_info));
196    if (len < (DHCP_MSG_FIXED_SIZE + 4)) return -1;
197
198    len -= (DHCP_MSG_FIXED_SIZE + 4);
199
200    if (msg->options[0] != OPT_COOKIE1) return -1;
201    if (msg->options[1] != OPT_COOKIE2) return -1;
202    if (msg->options[2] != OPT_COOKIE3) return -1;
203    if (msg->options[3] != OPT_COOKIE4) return -1;
204
205    x = msg->options + 4;
206
207    while (len > 2) {
208        opt = *x++;
209        if (opt == OPT_PAD) {
210            len--;
211            continue;
212        }
213        if (opt == OPT_END) {
214            break;
215        }
216        optlen = *x++;
217        len -= 2;
218        if (optlen > len) {
219            break;
220        }
221        switch(opt) {
222        case OPT_SUBNET_MASK:
223            if (optlen >= 4) memcpy(&info->netmask, x, 4);
224            break;
225        case OPT_GATEWAY:
226            if (optlen >= 4) memcpy(&info->gateway, x, 4);
227            break;
228        case OPT_DNS:
229            if (optlen >= 4) memcpy(&info->dns1, x + 0, 4);
230            if (optlen >= 8) memcpy(&info->dns2, x + 4, 4);
231            break;
232        case OPT_LEASE_TIME:
233            if (optlen >= 4) {
234                memcpy(&info->lease, x, 4);
235                info->lease = ntohl(info->lease);
236            }
237            break;
238        case OPT_SERVER_ID:
239            if (optlen >= 4) memcpy(&info->serveraddr, x, 4);
240            break;
241        case OPT_MESSAGE_TYPE:
242            info->type = *x;
243            break;
244        default:
245            break;
246        }
247        x += optlen;
248        len -= optlen;
249    }
250
251    info->ipaddr = msg->yiaddr;
252
253    return 0;
254}
255
256#if VERBOSE
257
258static void hex2str(char *buf, const unsigned char *array, int len)
259{
260    int i;
261    char *cp = buf;
262
263    for (i = 0; i < len; i++) {
264        cp += sprintf(cp, " %02x ", array[i]);
265    }
266}
267
268void dump_dhcp_msg(dhcp_msg *msg, int len)
269{
270    unsigned char *x;
271    unsigned int n,c;
272    int optsz;
273    const char *name;
274    char buf[2048];
275
276    LOGD("===== DHCP message:");
277    if (len < DHCP_MSG_FIXED_SIZE) {
278        LOGD("Invalid length %d, should be %d", len, DHCP_MSG_FIXED_SIZE);
279        return;
280    }
281
282    len -= DHCP_MSG_FIXED_SIZE;
283
284    if (msg->op == OP_BOOTREQUEST)
285        name = "BOOTREQUEST";
286    else if (msg->op == OP_BOOTREPLY)
287        name = "BOOTREPLY";
288    else
289        name = "????";
290    LOGD("op = %s (%d), htype = %d, hlen = %d, hops = %d",
291           name, msg->op, msg->htype, msg->hlen, msg->hops);
292    LOGD("xid = 0x%08x secs = %d, flags = 0x%04x optlen = %d",
293           ntohl(msg->xid), ntohs(msg->secs), ntohs(msg->flags), len);
294    LOGD("ciaddr = %s", ipaddr(msg->ciaddr));
295    LOGD("yiaddr = %s", ipaddr(msg->yiaddr));
296    LOGD("siaddr = %s", ipaddr(msg->siaddr));
297    LOGD("giaddr = %s", ipaddr(msg->giaddr));
298
299    c = msg->hlen > 16 ? 16 : msg->hlen;
300    hex2str(buf, msg->chaddr, c);
301    LOGD("chaddr = {%s}", buf);
302
303    for (n = 0; n < 64; n++) {
304        if ((msg->sname[n] < ' ') || (msg->sname[n] > 127)) {
305            if (msg->sname[n] == 0) break;
306            msg->sname[n] = '.';
307        }
308    }
309    msg->sname[63] = 0;
310
311    for (n = 0; n < 128; n++) {
312        if ((msg->file[n] < ' ') || (msg->file[n] > 127)) {
313            if (msg->file[n] == 0) break;
314            msg->file[n] = '.';
315        }
316    }
317    msg->file[127] = 0;
318
319    LOGD("sname = '%s'", msg->sname);
320    LOGD("file = '%s'", msg->file);
321
322    if (len < 4) return;
323    len -= 4;
324    x = msg->options + 4;
325
326    while (len > 2) {
327        if (*x == 0) {
328            x++;
329            len--;
330            continue;
331        }
332        if (*x == OPT_END) {
333            break;
334        }
335        len -= 2;
336        optsz = x[1];
337        if (optsz > len) break;
338        if (x[0] == OPT_DOMAIN_NAME || x[0] == OPT_MESSAGE) {
339            if ((unsigned int)optsz < sizeof(buf) - 1) {
340                n = optsz;
341            } else {
342                n = sizeof(buf) - 1;
343            }
344            memcpy(buf, &x[2], n);
345            buf[n] = '\0';
346        } else {
347            hex2str(buf, &x[2], optsz);
348        }
349        if (x[0] == OPT_MESSAGE_TYPE)
350            name = dhcp_type_to_name(x[2]);
351        else
352            name = NULL;
353        LOGD("op %d len %d {%s} %s", x[0], optsz, buf, name == NULL ? "" : name);
354        len -= optsz;
355        x = x + optsz + 2;
356    }
357}
358
359#endif
360
361static int send_message(int sock, int if_index, dhcp_msg  *msg, int size)
362{
363#if VERBOSE > 1
364    dump_dhcp_msg(msg, size);
365#endif
366    return send_packet(sock, if_index, msg, size, INADDR_ANY, INADDR_BROADCAST,
367                       PORT_BOOTP_CLIENT, PORT_BOOTP_SERVER);
368}
369
370static int is_valid_reply(dhcp_msg *msg, dhcp_msg *reply, int sz)
371{
372    if (sz < DHCP_MSG_FIXED_SIZE) {
373        if (verbose) LOGD("netcfg: Wrong size %d != %d\n", sz, DHCP_MSG_FIXED_SIZE);
374        return 0;
375    }
376    if (reply->op != OP_BOOTREPLY) {
377        if (verbose) LOGD("netcfg: Wrong Op %d != %d\n", reply->op, OP_BOOTREPLY);
378        return 0;
379    }
380    if (reply->xid != msg->xid) {
381        if (verbose) LOGD("netcfg: Wrong Xid 0x%x != 0x%x\n", ntohl(reply->xid),
382                          ntohl(msg->xid));
383        return 0;
384    }
385    if (reply->htype != msg->htype) {
386        if (verbose) LOGD("netcfg: Wrong Htype %d != %d\n", reply->htype, msg->htype);
387        return 0;
388    }
389    if (reply->hlen != msg->hlen) {
390        if (verbose) LOGD("netcfg: Wrong Hlen %d != %d\n", reply->hlen, msg->hlen);
391        return 0;
392    }
393    if (memcmp(msg->chaddr, reply->chaddr, msg->hlen)) {
394        if (verbose) LOGD("netcfg: Wrong chaddr %x != %x\n", *(reply->chaddr),*(msg->chaddr));
395        return 0;
396    }
397    return 1;
398}
399
400#define STATE_SELECTING  1
401#define STATE_REQUESTING 2
402
403#define TIMEOUT_INITIAL   4000
404#define TIMEOUT_MAX      32000
405
406int dhcp_init_ifc(const char *ifname)
407{
408    dhcp_msg discover_msg;
409    dhcp_msg request_msg;
410    dhcp_msg reply;
411    dhcp_msg *msg;
412    dhcp_info info;
413    int s, r, size;
414    int valid_reply;
415    uint32_t xid;
416    unsigned char hwaddr[6];
417    struct pollfd pfd;
418    unsigned int state;
419    unsigned int timeout;
420    int if_index;
421
422    xid = (uint32_t) get_msecs();
423
424    if (ifc_get_hwaddr(ifname, hwaddr)) {
425        return fatal("cannot obtain interface address");
426    }
427    if (ifc_get_ifindex(ifname, &if_index)) {
428        return fatal("cannot obtain interface index");
429    }
430
431    s = open_raw_socket(ifname, hwaddr, if_index);
432
433    timeout = TIMEOUT_INITIAL;
434    state = STATE_SELECTING;
435    info.type = 0;
436    goto transmit;
437
438    for (;;) {
439        pfd.fd = s;
440        pfd.events = POLLIN;
441        pfd.revents = 0;
442        r = poll(&pfd, 1, timeout);
443
444        if (r == 0) {
445#if VERBOSE
446            printerr("TIMEOUT\n");
447#endif
448            if (timeout >= TIMEOUT_MAX) {
449                printerr("timed out\n");
450                if ( info.type == DHCPOFFER ) {
451                    printerr("no acknowledgement from DHCP server\nconfiguring %s with offered parameters\n", ifname);
452                    return ifc_configure(ifname, &info);
453                }
454                errno = ETIME;
455                close(s);
456                return -1;
457            }
458            timeout = timeout * 2;
459
460        transmit:
461            size = 0;
462            msg = NULL;
463            switch(state) {
464            case STATE_SELECTING:
465                msg = &discover_msg;
466                size = init_dhcp_discover_msg(msg, hwaddr, xid);
467                break;
468            case STATE_REQUESTING:
469                msg = &request_msg;
470                size = init_dhcp_request_msg(msg, hwaddr, xid, info.ipaddr, info.serveraddr);
471                break;
472            default:
473                r = 0;
474            }
475            if (size != 0) {
476                r = send_message(s, if_index, msg, size);
477                if (r < 0) {
478                    printerr("error sending dhcp msg: %s\n", strerror(errno));
479                }
480            }
481            continue;
482        }
483
484        if (r < 0) {
485            if ((errno == EAGAIN) || (errno == EINTR)) {
486                continue;
487            }
488            return fatal("poll failed");
489        }
490
491        errno = 0;
492        r = receive_packet(s, &reply);
493        if (r < 0) {
494            if (errno != 0) {
495                LOGD("receive_packet failed (%d): %s", r, strerror(errno));
496                if (errno == ENETDOWN || errno == ENXIO) {
497                    return -1;
498                }
499            }
500            continue;
501        }
502
503#if VERBOSE > 1
504        dump_dhcp_msg(&reply, r);
505#endif
506        decode_dhcp_msg(&reply, r, &info);
507
508        if (state == STATE_SELECTING) {
509            valid_reply = is_valid_reply(&discover_msg, &reply, r);
510        } else {
511            valid_reply = is_valid_reply(&request_msg, &reply, r);
512        }
513        if (!valid_reply) {
514            printerr("invalid reply\n");
515            continue;
516        }
517
518        if (verbose) dump_dhcp_info(&info);
519
520        switch(state) {
521        case STATE_SELECTING:
522            if (info.type == DHCPOFFER) {
523                state = STATE_REQUESTING;
524                timeout = TIMEOUT_INITIAL;
525                xid++;
526                goto transmit;
527            }
528            break;
529        case STATE_REQUESTING:
530            if (info.type == DHCPACK) {
531                printerr("configuring %s\n", ifname);
532                close(s);
533                return ifc_configure(ifname, &info);
534            } else if (info.type == DHCPNAK) {
535                printerr("configuration request denied\n");
536                close(s);
537                return -1;
538            } else {
539                printerr("ignoring %s message in state %d\n",
540                         dhcp_type_to_name(info.type), state);
541            }
542            break;
543        }
544    }
545    close(s);
546    return 0;
547}
548
549int do_dhcp(char *iname)
550{
551    if (ifc_set_addr(iname, 0)) {
552        printerr("failed to set ip addr for %s to 0.0.0.0: %s\n", iname, strerror(errno));
553        return -1;
554    }
555
556    if (ifc_up(iname)) {
557        printerr("failed to bring up interface %s: %s\n", iname, strerror(errno));
558        return -1;
559    }
560
561    return dhcp_init_ifc(iname);
562}
563