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Sources/odhcpd/src/odhcpd.c

  1 /**
  2  * Copyright (C) 2012-2013 Steven Barth <steven@midlink.org>
  3  *
  4  * This program is free software; you can redistribute it and/or modify
  5  * it under the terms of the GNU General Public License v2 as published by
  6  * the Free Software Foundation.
  7  *
  8  * This program is distributed in the hope that it will be useful,
  9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
 10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 11  * GNU General Public License for more details.
 12  *
 13  */
 14 
 15 #include <time.h>
 16 #include <errno.h>
 17 #include <fcntl.h>
 18 #include <stdio.h>
 19 #include <resolv.h>
 20 #include <getopt.h>
 21 #include <stddef.h>
 22 #include <stdlib.h>
 23 #include <string.h>
 24 #include <unistd.h>
 25 #include <signal.h>
 26 #include <stdbool.h>
 27 #include <syslog.h>
 28 #include <alloca.h>
 29 #include <inttypes.h>
 30 
 31 #include <arpa/inet.h>
 32 #include <net/if.h>
 33 #include <netinet/ip6.h>
 34 #include <netpacket/packet.h>
 35 #include <linux/netlink.h>
 36 
 37 #include <sys/socket.h>
 38 #include <sys/ioctl.h>
 39 #include <sys/epoll.h>
 40 #include <sys/types.h>
 41 #include <sys/wait.h>
 42 #include <sys/syscall.h>
 43 
 44 #include <libubox/uloop.h>
 45 #include "odhcpd.h"
 46 
 47 static int ioctl_sock = -1;
 48 static int urandom_fd = -1;
 49 
 50 static void sighandler(_unused int signal)
 51 {
 52         uloop_end();
 53 }
 54 
 55 static void print_usage(const char *app)
 56 {
 57         printf(
 58         "== %s Usage ==\n\n"
 59         "  -h, --help   Print this help\n"
 60         "  -l level     Specify log level 0..7 (default %d)\n",
 61                 app, config.log_level
 62         );
 63 }
 64 
 65 static bool ipv6_enabled(void)
 66 {
 67         int fd = socket(AF_INET6, SOCK_DGRAM, 0);
 68 
 69         if (fd < 0)
 70                 return false;
 71 
 72         close(fd);
 73 
 74         return true;
 75 }
 76 
 77 int main(int argc, char **argv)
 78 {
 79         openlog("odhcpd", LOG_PERROR | LOG_PID, LOG_DAEMON);
 80         int opt;
 81 
 82         while ((opt = getopt(argc, argv, "hl:")) != -1) {
 83                 switch (opt) {
 84                 case 'h':
 85                         print_usage(argv[0]);
 86                         return 0;
 87                 case 'l':
 88                         config.log_level = (atoi(optarg) & LOG_PRIMASK);
 89                         fprintf(stderr, "Log level set to %d\n", config.log_level);
 90                         break;
 91                 }
 92         }
 93         setlogmask(LOG_UPTO(config.log_level));
 94         uloop_init();
 95 
 96         if (getuid() != 0) {
 97                 syslog(LOG_ERR, "Must be run as root!");
 98                 return 2;
 99         }
100 
101         ioctl_sock = socket(AF_INET, SOCK_DGRAM | SOCK_CLOEXEC, 0);
102 
103         if (ioctl_sock < 0)
104                 return 4;
105 
106         if ((urandom_fd = open("/dev/urandom", O_RDONLY | O_CLOEXEC)) < 0)
107                 return 4;
108 
109         signal(SIGUSR1, SIG_IGN);
110         signal(SIGINT, sighandler);
111         signal(SIGTERM, sighandler);
112 
113         if (netlink_init())
114                 return 4;
115 
116         if (ipv6_enabled()) {
117                 if (router_init())
118                         return 4;
119 
120                 if (dhcpv6_init())
121                         return 4;
122 
123                 if (ndp_init())
124                         return 4;
125         }
126 #ifndef DHCPV4_SUPPORT
127         else
128                 return 4;
129 #else
130         if (dhcpv4_init())
131                 return 4;
132 #endif
133 
134         odhcpd_run();
135         return 0;
136 }
137 
138 
139 /* Read IPv6 MTU for interface */
140 int odhcpd_get_interface_config(const char *ifname, const char *what)
141 {
142         char buf[64];
143         
144         snprintf(buf, sizeof(buf), "/proc/sys/net/ipv6/conf/%s/%s", ifname, what);
145 
146         int fd = open(buf, O_RDONLY);
147         if (fd < 0)
148                 return -1;
149 
150         ssize_t len = read(fd, buf, sizeof(buf) - 1);
151         close(fd);
152 
153         if (len < 0)
154                 return -1;
155 
156         buf[len] = 0;
157         return atoi(buf);
158 }
159 
160 
161 /* Read IPv6 MAC for interface */
162 int odhcpd_get_mac(const struct interface *iface, uint8_t mac[6])
163 {
164         struct ifreq ifr;
165 
166         memset(&ifr, 0, sizeof(ifr));
167         strncpy(ifr.ifr_name, iface->ifname, sizeof(ifr.ifr_name) - 1);
168         if (ioctl(ioctl_sock, SIOCGIFHWADDR, &ifr) < 0)
169                 return -1;
170 
171         memcpy(mac, ifr.ifr_hwaddr.sa_data, 6);
172         return 0;
173 }
174 
175 int odhcpd_get_flags(const struct interface *iface)
176 {
177         struct ifreq ifr;
178 
179         memset(&ifr, 0, sizeof(ifr));
180         strncpy(ifr.ifr_name, iface->ifname, sizeof(ifr.ifr_name) - 1);
181         if (ioctl(ioctl_sock, SIOCGIFFLAGS, &ifr) < 0)
182                 return -1;
183 
184         return ifr.ifr_flags;
185 }
186 
187 
188 /* Forwards a packet on a specific interface */
189 ssize_t odhcpd_send(int socket, struct sockaddr_in6 *dest,
190                 struct iovec *iov, size_t iov_len,
191                 const struct interface *iface)
192 {
193         /* Construct headers */
194         uint8_t cmsg_buf[CMSG_SPACE(sizeof(struct in6_pktinfo))] = {0};
195         struct msghdr msg = {
196                 .msg_name = (void *) dest,
197                 .msg_namelen = sizeof(*dest),
198                 .msg_iov = iov,
199                 .msg_iovlen = iov_len,
200                 .msg_control = cmsg_buf,
201                 .msg_controllen = sizeof(cmsg_buf),
202                 .msg_flags = 0
203         };
204 
205         /* Set control data (define destination interface) */
206         struct cmsghdr *chdr = CMSG_FIRSTHDR(&msg);
207         chdr->cmsg_level = IPPROTO_IPV6;
208         chdr->cmsg_type = IPV6_PKTINFO;
209         chdr->cmsg_len = CMSG_LEN(sizeof(struct in6_pktinfo));
210         struct in6_pktinfo *pktinfo = (struct in6_pktinfo*)CMSG_DATA(chdr);
211         pktinfo->ipi6_ifindex = iface->ifindex;
212 
213         /* Also set scope ID if link-local */
214         if (IN6_IS_ADDR_LINKLOCAL(&dest->sin6_addr)
215                         || IN6_IS_ADDR_MC_LINKLOCAL(&dest->sin6_addr))
216                 dest->sin6_scope_id = iface->ifindex;
217 
218         char ipbuf[INET6_ADDRSTRLEN];
219         inet_ntop(AF_INET6, &dest->sin6_addr, ipbuf, sizeof(ipbuf));
220 
221         ssize_t sent = sendmsg(socket, &msg, MSG_DONTWAIT);
222         if (sent < 0)
223                 syslog(LOG_ERR, "Failed to send to %s%%%s@%s (%m)",
224                                 ipbuf, iface->name, iface->ifname);
225         else
226                 syslog(LOG_DEBUG, "Sent %zd bytes to %s%%%s@%s",
227                                 sent, ipbuf, iface->name, iface->ifname);
228         return sent;
229 }
230 
231 
232 static int odhcpd_get_linklocal_interface_address(int ifindex, struct in6_addr *lladdr)
233 {
234         int ret = -1;
235         struct sockaddr_in6 addr;
236         socklen_t alen = sizeof(addr);
237         int sock = socket(AF_INET6, SOCK_RAW, IPPROTO_ICMPV6);
238 
239         if (sock < 0)
240                 return -1;
241 
242         memset(&addr, 0, sizeof(addr));
243         addr.sin6_family = AF_INET6;
244         inet_pton(AF_INET6, ALL_IPV6_ROUTERS, &addr.sin6_addr);
245         addr.sin6_scope_id = ifindex;
246 
247         if (!connect(sock, (struct sockaddr*)&addr, sizeof(addr)) &&
248                         !getsockname(sock, (struct sockaddr*)&addr, &alen)) {
249                 *lladdr = addr.sin6_addr;
250                 ret = 0;
251         }
252 
253         close(sock);
254         return ret;
255 }
256 
257 /*
258  * DNS address selection criteria order :
259  * - use IPv6 address with valid lifetime if none is yet selected
260  * - use IPv6 address with a preferred lifetime if the already selected IPv6 address is deprecated
261  * - use an IPv6 ULA address if the already selected IPv6 address is not an ULA address
262  * - use the IPv6 address with the longest preferred lifetime
263  */
264 int odhcpd_get_interface_dns_addr(const struct interface *iface, struct in6_addr *addr)
265 {
266         time_t now = odhcpd_time();
267         ssize_t m = -1;
268 
269         if (!iface->dns_service)
270                 return -1;
271 
272         for (size_t i = 0; i < iface->addr6_len; ++i) {
273                 if (iface->addr6[i].valid_lt <= (uint32_t)now)
274                         continue;
275 
276                 if (m < 0) {
277                         m = i;
278                         continue;
279                 }
280 
281                 if (iface->addr6[m].preferred_lt >= (uint32_t)now &&
282                                 iface->addr6[i].preferred_lt < (uint32_t)now)
283                         continue;
284 
285                 if (IN6_IS_ADDR_ULA(&iface->addr6[i].addr.in6)) {
286                         if (!IN6_IS_ADDR_ULA(&iface->addr6[m].addr.in6)) {
287                                 m = i;
288                                 continue;
289                         }
290                 } else if (IN6_IS_ADDR_ULA(&iface->addr6[m].addr.in6))
291                         continue;
292 
293                 if (iface->addr6[i].preferred_lt > iface->addr6[m].preferred_lt)
294                         m = i;
295         }
296 
297         if (m >= 0) {
298                 *addr = iface->addr6[m].addr.in6;
299                 return 0;
300         }
301 
302         return odhcpd_get_linklocal_interface_address(iface->ifindex, addr);
303 }
304 
305 struct interface* odhcpd_get_interface_by_index(int ifindex)
306 {
307         struct interface *iface;
308 
309         avl_for_each_element(&interfaces, iface, avl) {
310                 if (iface->ifindex == ifindex)
311                         return iface;
312         }
313 
314         return NULL;
315 }
316 
317 /* Convenience function to receive and do basic validation of packets */
318 static void odhcpd_receive_packets(struct uloop_fd *u, _unused unsigned int events)
319 {
320         struct odhcpd_event *e = container_of(u, struct odhcpd_event, uloop);
321 
322         uint8_t data_buf[8192], cmsg_buf[128];
323         union {
324                 struct sockaddr_in6 in6;
325                 struct sockaddr_in in;
326                 struct sockaddr_ll ll;
327                 struct sockaddr_nl nl;
328         } addr;
329 
330         if (u->error) {
331                 int ret = -1;
332                 socklen_t ret_len = sizeof(ret);
333 
334                 u->error = false;
335                 if (e->handle_error && getsockopt(u->fd, SOL_SOCKET, SO_ERROR, &ret, &ret_len) == 0)
336                         e->handle_error(e, ret);
337         }
338 
339         if (e->recv_msgs) {
340                 e->recv_msgs(e);
341                 return;
342         }
343 
344         while (true) {
345                 struct iovec iov = {data_buf, sizeof(data_buf)};
346                 struct msghdr msg = {
347                         .msg_name = (void *) &addr,
348                         .msg_namelen = sizeof(addr),
349                         .msg_iov = &iov,
350                         .msg_iovlen = 1,
351                         .msg_control = cmsg_buf,
352                         .msg_controllen = sizeof(cmsg_buf),
353                         .msg_flags = 0
354                 };
355 
356                 ssize_t len = recvmsg(u->fd, &msg, MSG_DONTWAIT);
357                 if (len < 0) {
358                         if (errno == EAGAIN)
359                                 break;
360                         else
361                                 continue;
362                 }
363 
364 
365                 /* Extract destination interface */
366                 int destiface = 0;
367                 int *hlim = NULL;
368                 void *dest = NULL;
369                 struct in6_pktinfo *pktinfo;
370                 struct in_pktinfo *pkt4info;
371                 for (struct cmsghdr *ch = CMSG_FIRSTHDR(&msg); ch != NULL; ch = CMSG_NXTHDR(&msg, ch)) {
372                         if (ch->cmsg_level == IPPROTO_IPV6 &&
373                                         ch->cmsg_type == IPV6_PKTINFO) {
374                                 pktinfo = (struct in6_pktinfo*)CMSG_DATA(ch);
375                                 destiface = pktinfo->ipi6_ifindex;
376                                 dest = &pktinfo->ipi6_addr;
377                         } else if (ch->cmsg_level == IPPROTO_IP &&
378                                         ch->cmsg_type == IP_PKTINFO) {
379                                 pkt4info = (struct in_pktinfo*)CMSG_DATA(ch);
380                                 destiface = pkt4info->ipi_ifindex;
381                                 dest = &pkt4info->ipi_addr;
382                         } else if (ch->cmsg_level == IPPROTO_IPV6 &&
383                                         ch->cmsg_type == IPV6_HOPLIMIT) {
384                                 hlim = (int*)CMSG_DATA(ch);
385                         }
386                 }
387 
388                 /* Check hoplimit if received */
389                 if (hlim && *hlim != 255)
390                         continue;
391 
392                 /* Detect interface for packet sockets */
393                 if (addr.ll.sll_family == AF_PACKET)
394                         destiface = addr.ll.sll_ifindex;
395 
396                 char ipbuf[INET6_ADDRSTRLEN] = "kernel";
397                 if (addr.ll.sll_family == AF_PACKET &&
398                                 len >= (ssize_t)sizeof(struct ip6_hdr))
399                         inet_ntop(AF_INET6, &data_buf[8], ipbuf, sizeof(ipbuf));
400                 else if (addr.in6.sin6_family == AF_INET6)
401                         inet_ntop(AF_INET6, &addr.in6.sin6_addr, ipbuf, sizeof(ipbuf));
402                 else if (addr.in.sin_family == AF_INET)
403                         inet_ntop(AF_INET, &addr.in.sin_addr, ipbuf, sizeof(ipbuf));
404 
405                 /* From netlink */
406                 if (addr.nl.nl_family == AF_NETLINK) {
407                         syslog(LOG_DEBUG, "Received %zd Bytes from %s%%netlink", len,
408                                         ipbuf);
409                         e->handle_dgram(&addr, data_buf, len, NULL, dest);
410                         return;
411                 } else if (destiface != 0) {
412                         struct interface *iface;
413 
414                         avl_for_each_element(&interfaces, iface, avl) {
415                                 if (iface->ifindex != destiface)
416                                         continue;
417 
418                                 syslog(LOG_DEBUG, "Received %zd Bytes from %s%%%s@%s", len,
419                                                 ipbuf, iface->name, iface->ifname);
420 
421                                 e->handle_dgram(&addr, data_buf, len, iface, dest);
422                         }
423                 }
424 
425 
426         }
427 }
428 
429 /* Register events for the multiplexer */
430 int odhcpd_register(struct odhcpd_event *event)
431 {
432         event->uloop.cb = odhcpd_receive_packets;
433         return uloop_fd_add(&event->uloop, ULOOP_READ |
434                         ((event->handle_error) ? ULOOP_ERROR_CB : 0));
435 }
436 
437 int odhcpd_deregister(struct odhcpd_event *event)
438 {
439         event->uloop.cb = NULL;
440         return uloop_fd_delete(&event->uloop);
441 }
442 
443 void odhcpd_process(struct odhcpd_event *event)
444 {
445         odhcpd_receive_packets(&event->uloop, 0);
446 }
447 
448 int odhcpd_urandom(void *data, size_t len)
449 {
450         return read(urandom_fd, data, len);
451 }
452 
453 
454 time_t odhcpd_time(void)
455 {
456         struct timespec ts;
457         clock_gettime(CLOCK_MONOTONIC, &ts);
458         return ts.tv_sec;
459 }
460 
461 
462 static const char hexdigits[] = "0123456789abcdef";
463 static const int8_t hexvals[] = {
464     -1, -1, -1, -1, -1, -1, -1, -1, -1, -2, -2, -1, -1, -2, -1, -1,
465     -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
466     -2, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
467      0,  1,  2,  3,  4,  5,  6,  7,  8,  9, -1, -1, -1, -1, -1, -1,
468     -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
469     -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
470     -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
471     -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
472 };
473 
474 ssize_t odhcpd_unhexlify(uint8_t *dst, size_t len, const char *src)
475 {
476         size_t c;
477         for (c = 0; c < len && src[0] && src[1]; ++c) {
478                 int8_t x = (int8_t)*src++;
479                 int8_t y = (int8_t)*src++;
480                 if (x < 0 || (x = hexvals[x]) < 0
481                                 || y < 0 || (y = hexvals[y]) < 0)
482                         return -1;
483                 dst[c] = x << 4 | y;
484                 while (((int8_t)*src) < 0 ||
485                                 (*src && hexvals[(uint8_t)*src] < 0))
486                         src++;
487         }
488 
489         return c;
490 }
491 
492 
493 void odhcpd_hexlify(char *dst, const uint8_t *src, size_t len)
494 {
495         for (size_t i = 0; i < len; ++i) {
496                 *dst++ = hexdigits[src[i] >> 4];
497                 *dst++ = hexdigits[src[i] & 0x0f];
498         }
499         *dst = 0;
500 }
501 
502 const char *odhcpd_print_mac(const uint8_t *mac, const size_t len)
503 {
504         static char buf[32];
505 
506         snprintf(buf, sizeof(buf), "%02x", mac[0]);
507         for (size_t i = 1, j = 2; i < len && j < sizeof(buf); i++, j += 3)
508                 snprintf(buf + j, sizeof(buf) - j, ":%02x", mac[i]);
509 
510         return buf;
511 }
512 
513 int odhcpd_bmemcmp(const void *av, const void *bv, size_t bits)
514 {
515         const uint8_t *a = av, *b = bv;
516         size_t bytes = bits / 8;
517         bits %= 8;
518 
519         int res = memcmp(a, b, bytes);
520         if (res == 0 && bits > 0)
521                 res = (a[bytes] >> (8 - bits)) - (b[bytes] >> (8 - bits));
522 
523         return res;
524 }
525 
526 
527 void odhcpd_bmemcpy(void *av, const void *bv, size_t bits)
528 {
529         uint8_t *a = av;
530         const uint8_t *b = bv;
531 
532         size_t bytes = bits / 8;
533         bits %= 8;
534         memcpy(a, b, bytes);
535 
536         if (bits > 0) {
537                 uint8_t mask = (1 << (8 - bits)) - 1;
538                 a[bytes] = (a[bytes] & mask) | ((~mask) & b[bytes]);
539         }
540 }
541 
542 
543 int odhcpd_parse_addr6_prefix(const char *str, struct in6_addr *addr, uint8_t *prefix)
544 {
545         size_t len;
546         char *delim;
547 
548         *prefix = 0;
549         if (!str)
550                 return -1;
551 
552         len = strlen(str);
553 
554         char buf[len + 1];
555         memcpy(buf, str, len);
556         buf[len] = '\0';
557 
558         delim = memchr(buf, '/', len);
559         if (!delim)
560                 return -1;
561 
562         *(delim++) = '\0';
563 
564         if (inet_pton(AF_INET6, buf, addr) != 1)
565                 return -1;
566 
567         if (sscanf(delim, "%" SCNu8, prefix) != 1 || *prefix > 128) {
568                 *prefix = 0;
569                 return -1;
570         }
571 
572         return 0;
573 }
574 
575 
576 int odhcpd_netmask2bitlen(bool inet6, void *mask)
577 {
578         int bits;
579         struct in_addr *v4;
580         struct in6_addr *v6;
581 
582         if (inet6)
583                 for (bits = 0, v6 = mask;
584                      bits < 128 && (v6->s6_addr[bits / 8] << (bits % 8)) & 128;
585                      bits++);
586         else
587                 for (bits = 0, v4 = mask;
588                      bits < 32 && (ntohl(v4->s_addr) << bits) & 0x80000000;
589                      bits++);
590 
591         return bits;
592 }
593 
594 bool odhcpd_bitlen2netmask(bool inet6, unsigned int bits, void *mask)
595 {
596         uint8_t b;
597         struct in_addr *v4;
598         struct in6_addr *v6;
599 
600         if (inet6)
601         {
602                 if (bits > 128)
603                         return false;
604 
605                 v6 = mask;
606 
607                 for (unsigned int i = 0; i < sizeof(v6->s6_addr); i++)
608                 {
609                         b = (bits > 8) ? 8 : bits;
610                         v6->s6_addr[i] = (uint8_t)(0xFF << (8 - b));
611                         bits -= b;
612                 }
613         }
614         else
615         {
616                 if (bits > 32)
617                         return false;
618 
619                 v4 = mask;
620                 v4->s_addr = bits ? htonl(~((1 << (32 - bits)) - 1)) : 0;
621         }
622 
623         return true;
624 }
625 
626 bool odhcpd_valid_hostname(const char *name)
627 {
628 #define MAX_LABEL       63
629         const char *c, *label, *label_end;
630         int label_sz = 0;
631 
632         for (c = name, label_sz = 0, label = name, label_end = name + strcspn(name, ".") - 1;
633                         *c && label_sz <= MAX_LABEL; c++) {
634                 if ((*c >= '' && *c <= '9') ||
635                     (*c >= 'A' && *c <= 'Z') ||
636                     (*c >= 'a' && *c <= 'z')) {
637                         label_sz++;
638                         continue;
639                 }
640 
641                 if ((*c == '_' || *c == '-') && c != label && c != label_end) {
642                         label_sz++;
643                         continue;
644                 }
645 
646                 if (*c == '.') {
647                         if (*(c + 1)) {
648                                 label = c + 1;
649                                 label_end = label + strcspn(label, ".") - 1;
650                                 label_sz = 0;
651                         }
652                         continue;
653                 }
654 
655                 return false;
656         }
657 
658         return (label_sz && label_sz <= MAX_LABEL ? true : false);
659 }
660 

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