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

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