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