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