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