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;
  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_NOTICE, "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         syscall(SYS_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 >= '0' && *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 }