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 int odhcpd_get_flags(const struct interface *iface)
 175 {
 176         struct ifreq ifr;
 177
 178         memset(&ifr, 0, sizeof(ifr));
 179         strncpy(ifr.ifr_name, iface->ifname, sizeof(ifr.ifr_name) - 1);
 180         if (ioctl(ioctl_sock, SIOCGIFFLAGS, &ifr) < 0)
 181                 return -1;
 182
 183         return ifr.ifr_flags;
 184 }
 185
 186
 187 /* Forwards a packet on a specific interface */
 188 ssize_t odhcpd_send(int socket, struct sockaddr_in6 *dest,
 189                 struct iovec *iov, size_t iov_len,
 190                 const struct interface *iface)
 191 {
 192         /* Construct headers */
 193         uint8_t cmsg_buf[CMSG_SPACE(sizeof(struct in6_pktinfo))] = {0};
 194         struct msghdr msg = {
 195                 .msg_name = (void *) dest,
 196                 .msg_namelen = sizeof(*dest),
 197                 .msg_iov = iov,
 198                 .msg_iovlen = iov_len,
 199                 .msg_control = cmsg_buf,
 200                 .msg_controllen = sizeof(cmsg_buf),
 201                 .msg_flags = 0
 202         };
 203
 204         /* Set control data (define destination interface) */
 205         struct cmsghdr *chdr = CMSG_FIRSTHDR(&msg);
 206         chdr->cmsg_level = IPPROTO_IPV6;
 207         chdr->cmsg_type = IPV6_PKTINFO;
 208         chdr->cmsg_len = CMSG_LEN(sizeof(struct in6_pktinfo));
 209         struct in6_pktinfo *pktinfo = (struct in6_pktinfo*)CMSG_DATA(chdr);
 210         pktinfo->ipi6_ifindex = iface->ifindex;
 211
 212         /* Also set scope ID if link-local */
 213         if (IN6_IS_ADDR_LINKLOCAL(&dest->sin6_addr)
 214                         || IN6_IS_ADDR_MC_LINKLOCAL(&dest->sin6_addr))
 215                 dest->sin6_scope_id = iface->ifindex;
 216
 217         char ipbuf[INET6_ADDRSTRLEN];
 218         inet_ntop(AF_INET6, &dest->sin6_addr, ipbuf, sizeof(ipbuf));
 219
 220         ssize_t sent = sendmsg(socket, &msg, MSG_DONTWAIT);
 221         if (sent < 0)
 222                 syslog(LOG_ERR, "Failed to send to %s%%%s@%s (%m)",
 223                                 ipbuf, iface->name, iface->ifname);
 224         else
 225                 syslog(LOG_DEBUG, "Sent %zd bytes to %s%%%s@%s",
 226                                 sent, ipbuf, iface->name, iface->ifname);
 227         return sent;
 228 }
 229
 230
 231 static int odhcpd_get_linklocal_interface_address(int ifindex, struct in6_addr *lladdr)
 232 {
 233         int ret = -1;
 234         struct sockaddr_in6 addr;
 235         socklen_t alen = sizeof(addr);
 236         int sock = socket(AF_INET6, SOCK_RAW, IPPROTO_ICMPV6);
 237
 238         if (sock < 0)
 239                 return -1;
 240
 241         memset(&addr, 0, sizeof(addr));
 242         addr.sin6_family = AF_INET6;
 243         inet_pton(AF_INET6, ALL_IPV6_ROUTERS, &addr.sin6_addr);
 244         addr.sin6_scope_id = ifindex;
 245
 246         if (!connect(sock, (struct sockaddr*)&addr, sizeof(addr)) &&
 247                         !getsockname(sock, (struct sockaddr*)&addr, &alen)) {
 248                 *lladdr = addr.sin6_addr;
 249                 ret = 0;
 250         }
 251
 252         close(sock);
 253         return ret;
 254 }
 255
 256 /*
 257  * DNS address selection criteria order :
 258  * - use IPv6 address with valid lifetime if none is yet selected
 259  * - use IPv6 address with a preferred lifetime if the already selected IPv6 address is deprecated
 260  * - use an IPv6 ULA address if the already selected IPv6 address is not an ULA address
 261  * - use the IPv6 address with the longest preferred lifetime
 262  */
 263 int odhcpd_get_interface_dns_addr(const struct interface *iface, struct in6_addr *addr)
 264 {
 265         time_t now = odhcpd_time();
 266         ssize_t m = -1;
 267
 268         if (!iface->dns_service)
 269                 return -1;
 270
 271         for (size_t i = 0; i < iface->addr6_len; ++i) {
 272                 if (iface->addr6[i].valid_lt <= (uint32_t)now)
 273                         continue;
 274
 275                 if (m < 0) {
 276                         m = i;
 277                         continue;
 278                 }
 279
 280                 if (iface->addr6[m].preferred_lt >= (uint32_t)now &&
 281                                 iface->addr6[i].preferred_lt < (uint32_t)now)
 282                         continue;
 283
 284                 if (IN6_IS_ADDR_ULA(&iface->addr6[i].addr.in6)) {
 285                         if (!IN6_IS_ADDR_ULA(&iface->addr6[m].addr.in6)) {
 286                                 m = i;
 287                                 continue;
 288                         }
 289                 } else if (IN6_IS_ADDR_ULA(&iface->addr6[m].addr.in6))
 290                         continue;
 291
 292                 if (iface->addr6[i].preferred_lt > iface->addr6[m].preferred_lt)
 293                         m = i;
 294         }
 295
 296         if (m >= 0) {
 297                 *addr = iface->addr6[m].addr.in6;
 298                 return 0;
 299         }
 300
 301         return odhcpd_get_linklocal_interface_address(iface->ifindex, addr);
 302 }
 303
 304 struct interface* odhcpd_get_interface_by_index(int ifindex)
 305 {
 306         struct interface *iface;
 307
 308         avl_for_each_element(&interfaces, iface, avl) {
 309                 if (iface->ifindex == ifindex)
 310                         return iface;
 311         }
 312
 313         return NULL;
 314 }
 315
 316 /* Convenience function to receive and do basic validation of packets */
 317 static void odhcpd_receive_packets(struct uloop_fd *u, _unused unsigned int events)
 318 {
 319         struct odhcpd_event *e = container_of(u, struct odhcpd_event, uloop);
 320
 321         uint8_t data_buf[8192], cmsg_buf[128];
 322         union {
 323                 struct sockaddr_in6 in6;
 324                 struct sockaddr_in in;
 325                 struct sockaddr_ll ll;
 326                 struct sockaddr_nl nl;
 327         } addr;
 328
 329         if (u->error) {
 330                 int ret = -1;
 331                 socklen_t ret_len = sizeof(ret);
 332
 333                 u->error = false;
 334                 if (e->handle_error && getsockopt(u->fd, SOL_SOCKET, SO_ERROR, &ret, &ret_len) == 0)
 335                         e->handle_error(e, ret);
 336         }
 337
 338         if (e->recv_msgs) {
 339                 e->recv_msgs(e);
 340                 return;
 341         }
 342
 343         while (true) {
 344                 struct iovec iov = {data_buf, sizeof(data_buf)};
 345                 struct msghdr msg = {
 346                         .msg_name = (void *) &addr,
 347                         .msg_namelen = sizeof(addr),
 348                         .msg_iov = &iov,
 349                         .msg_iovlen = 1,
 350                         .msg_control = cmsg_buf,
 351                         .msg_controllen = sizeof(cmsg_buf),
 352                         .msg_flags = 0
 353                 };
 354
 355                 ssize_t len = recvmsg(u->fd, &msg, MSG_DONTWAIT);
 356                 if (len < 0) {
 357                         if (errno == EAGAIN)
 358                                 break;
 359                         else
 360                                 continue;
 361                 }
 362
 363
 364                 /* Extract destination interface */
 365                 int destiface = 0;
 366                 int *hlim = NULL;
 367                 void *dest = NULL;
 368                 struct in6_pktinfo *pktinfo;
 369                 struct in_pktinfo *pkt4info;
 370                 for (struct cmsghdr *ch = CMSG_FIRSTHDR(&msg); ch != NULL; ch = CMSG_NXTHDR(&msg, ch)) {
 371                         if (ch->cmsg_level == IPPROTO_IPV6 &&
 372                                         ch->cmsg_type == IPV6_PKTINFO) {
 373                                 pktinfo = (struct in6_pktinfo*)CMSG_DATA(ch);
 374                                 destiface = pktinfo->ipi6_ifindex;
 375                                 dest = &pktinfo->ipi6_addr;
 376                         } else if (ch->cmsg_level == IPPROTO_IP &&
 377                                         ch->cmsg_type == IP_PKTINFO) {
 378                                 pkt4info = (struct in_pktinfo*)CMSG_DATA(ch);
 379                                 destiface = pkt4info->ipi_ifindex;
 380                                 dest = &pkt4info->ipi_addr;
 381                         } else if (ch->cmsg_level == IPPROTO_IPV6 &&
 382                                         ch->cmsg_type == IPV6_HOPLIMIT) {
 383                                 hlim = (int*)CMSG_DATA(ch);
 384                         }
 385                 }
 386
 387                 /* Check hoplimit if received */
 388                 if (hlim && *hlim != 255)
 389                         continue;
 390
 391                 /* Detect interface for packet sockets */
 392                 if (addr.ll.sll_family == AF_PACKET)
 393                         destiface = addr.ll.sll_ifindex;
 394
 395                 char ipbuf[INET6_ADDRSTRLEN] = "kernel";
 396                 if (addr.ll.sll_family == AF_PACKET &&
 397                                 len >= (ssize_t)sizeof(struct ip6_hdr))
 398                         inet_ntop(AF_INET6, &data_buf[8], ipbuf, sizeof(ipbuf));
 399                 else if (addr.in6.sin6_family == AF_INET6)
 400                         inet_ntop(AF_INET6, &addr.in6.sin6_addr, ipbuf, sizeof(ipbuf));
 401                 else if (addr.in.sin_family == AF_INET)
 402                         inet_ntop(AF_INET, &addr.in.sin_addr, ipbuf, sizeof(ipbuf));
 403
 404                 /* From netlink */
 405                 if (addr.nl.nl_family == AF_NETLINK) {
 406                         syslog(LOG_DEBUG, "Received %zd Bytes from %s%%netlink", len,
 407                                         ipbuf);
 408                         e->handle_dgram(&addr, data_buf, len, NULL, dest);
 409                         return;
 410                 } else if (destiface != 0) {
 411                         struct interface *iface;
 412
 413                         avl_for_each_element(&interfaces, iface, avl) {
 414                                 if (iface->ifindex != destiface)
 415                                         continue;
 416
 417                                 syslog(LOG_DEBUG, "Received %zd Bytes from %s%%%s@%s", len,
 418                                                 ipbuf, iface->name, iface->ifname);
 419
 420                                 e->handle_dgram(&addr, data_buf, len, iface, dest);
 421                         }
 422                 }
 423
 424
 425         }
 426 }
 427
 428 /* Register events for the multiplexer */
 429 int odhcpd_register(struct odhcpd_event *event)
 430 {
 431         event->uloop.cb = odhcpd_receive_packets;
 432         return uloop_fd_add(&event->uloop, ULOOP_READ |
 433                         ((event->handle_error) ? ULOOP_ERROR_CB : 0));
 434 }
 435
 436 int odhcpd_deregister(struct odhcpd_event *event)
 437 {
 438         event->uloop.cb = NULL;
 439         return uloop_fd_delete(&event->uloop);
 440 }
 441
 442 void odhcpd_process(struct odhcpd_event *event)
 443 {
 444         odhcpd_receive_packets(&event->uloop, 0);
 445 }
 446
 447 int odhcpd_urandom(void *data, size_t len)
 448 {
 449         return read(urandom_fd, data, len);
 450 }
 451
 452
 453 time_t odhcpd_time(void)
 454 {
 455         struct timespec ts;
 456         clock_gettime(CLOCK_MONOTONIC, &ts);
 457         return ts.tv_sec;
 458 }
 459
 460
 461 static const char hexdigits[] = "0123456789abcdef";
 462 static const int8_t hexvals[] = {
 463     -1, -1, -1, -1, -1, -1, -1, -1, -1, -2, -2, -1, -1, -2, -1, -1,
 464     -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 465     -2, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 466      0,  1,  2,  3,  4,  5,  6,  7,  8,  9, -1, -1, -1, -1, -1, -1,
 467     -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 468     -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 469     -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 470     -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 471 };
 472
 473 ssize_t odhcpd_unhexlify(uint8_t *dst, size_t len, const char *src)
 474 {
 475         size_t c;
 476         for (c = 0; c < len && src[0] && src[1]; ++c) {
 477                 int8_t x = (int8_t)*src++;
 478                 int8_t y = (int8_t)*src++;
 479                 if (x < 0 || (x = hexvals[x]) < 0
 480                                 || y < 0 || (y = hexvals[y]) < 0)
 481                         return -1;
 482                 dst[c] = x << 4 | y;
 483                 while (((int8_t)*src) < 0 ||
 484                                 (*src && hexvals[(uint8_t)*src] < 0))
 485                         src++;
 486         }
 487
 488         return c;
 489 }
 490
 491
 492 void odhcpd_hexlify(char *dst, const uint8_t *src, size_t len)
 493 {
 494         for (size_t i = 0; i < len; ++i) {
 495                 *dst++ = hexdigits[src[i] >> 4];
 496                 *dst++ = hexdigits[src[i] & 0x0f];
 497         }
 498         *dst = 0;
 499 }
 500
 501 const char *odhcpd_print_mac(const uint8_t *mac, const size_t len)
 502 {
 503         static char buf[32];
 504
 505         snprintf(buf, sizeof(buf), "%02x", mac[0]);
 506         for (size_t i = 1, j = 2; i < len && j < sizeof(buf); i++, j += 3)
 507                 snprintf(buf + j, sizeof(buf) - j, ":%02x", mac[i]);
 508
 509         return buf;
 510 }
 511
 512 int odhcpd_bmemcmp(const void *av, const void *bv, size_t bits)
 513 {
 514         const uint8_t *a = av, *b = bv;
 515         size_t bytes = bits / 8;
 516         bits %= 8;
 517
 518         int res = memcmp(a, b, bytes);
 519         if (res == 0 && bits > 0)
 520                 res = (a[bytes] >> (8 - bits)) - (b[bytes] >> (8 - bits));
 521
 522         return res;
 523 }
 524
 525
 526 void odhcpd_bmemcpy(void *av, const void *bv, size_t bits)
 527 {
 528         uint8_t *a = av;
 529         const uint8_t *b = bv;
 530
 531         size_t bytes = bits / 8;
 532         bits %= 8;
 533         memcpy(a, b, bytes);
 534
 535         if (bits > 0) {
 536                 uint8_t mask = (1 << (8 - bits)) - 1;
 537                 a[bytes] = (a[bytes] & mask) | ((~mask) & b[bytes]);
 538         }
 539 }
 540
 541
 542 int odhcpd_netmask2bitlen(bool inet6, void *mask)
 543 {
 544         int bits;
 545         struct in_addr *v4;
 546         struct in6_addr *v6;
 547
 548         if (inet6)
 549                 for (bits = 0, v6 = mask;
 550                      bits < 128 && (v6->s6_addr[bits / 8] << (bits % 8)) & 128;
 551                      bits++);
 552         else
 553                 for (bits = 0, v4 = mask;
 554                      bits < 32 && (ntohl(v4->s_addr) << bits) & 0x80000000;
 555                      bits++);
 556
 557         return bits;
 558 }
 559
 560 bool odhcpd_bitlen2netmask(bool inet6, unsigned int bits, void *mask)
 561 {
 562         uint8_t b;
 563         struct in_addr *v4;
 564         struct in6_addr *v6;
 565
 566         if (inet6)
 567         {
 568                 if (bits > 128)
 569                         return false;
 570
 571                 v6 = mask;
 572
 573                 for (unsigned int i = 0; i < sizeof(v6->s6_addr); i++)
 574                 {
 575                         b = (bits > 8) ? 8 : bits;
 576                         v6->s6_addr[i] = (uint8_t)(0xFF << (8 - b));
 577                         bits -= b;
 578                 }
 579         }
 580         else
 581         {
 582                 if (bits > 32)
 583                         return false;
 584
 585                 v4 = mask;
 586                 v4->s_addr = bits ? htonl(~((1 << (32 - bits)) - 1)) : 0;
 587         }
 588
 589         return true;
 590 }
 591
 592 bool odhcpd_valid_hostname(const char *name)
 593 {
 594 #define MAX_LABEL       63
 595         const char *c, *label, *label_end;
 596         int label_sz = 0;
 597
 598         for (c = name, label_sz = 0, label = name, label_end = name + strcspn(name, ".") - 1;
 599                         *c && label_sz <= MAX_LABEL; c++) {
 600                 if ((*c >= '0' && *c <= '9') ||
 601                     (*c >= 'A' && *c <= 'Z') ||
 602                     (*c >= 'a' && *c <= 'z')) {
 603                         label_sz++;
 604                         continue;
 605                 }
 606
 607                 if ((*c == '_' || *c == '-') && c != label && c != label_end) {
 608                         label_sz++;
 609                         continue;
 610                 }
 611
 612                 if (*c == '.') {
 613                         if (*(c + 1)) {
 614                                 label = c + 1;
 615                                 label_end = label + strcspn(label, ".") - 1;
 616                                 label_sz = 0;
 617                         }
 618                         continue;
 619                 }
 620
 621                 return false;
 622         }
 623
 624         return (label_sz && label_sz <= MAX_LABEL ? true : false);
 625 }