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         ssize_t len = read(fd, buf, sizeof(buf) - 1);
 132         close(fd);
 133
 134         if (len < 0)
 135                 return -1;
 136
 137         buf[len] = 0;
 138         return atoi(buf);
 139 }
 140
 141
 142 // Read IPv6 MAC for interface
 143 int odhcpd_get_mac(const struct interface *iface, uint8_t mac[6])
 144 {
 145         struct ifreq ifr;
 146
 147         memset(&ifr, 0, sizeof(ifr));
 148         strncpy(ifr.ifr_name, iface->ifname, sizeof(ifr.ifr_name) - 1);
 149         if (ioctl(ioctl_sock, SIOCGIFHWADDR, &ifr) < 0)
 150                 return -1;
 151
 152         memcpy(mac, ifr.ifr_hwaddr.sa_data, 6);
 153         return 0;
 154 }
 155
 156
 157 // Forwards a packet on a specific interface
 158 ssize_t odhcpd_send(int socket, struct sockaddr_in6 *dest,
 159                 struct iovec *iov, size_t iov_len,
 160                 const struct interface *iface)
 161 {
 162         // Construct headers
 163         uint8_t cmsg_buf[CMSG_SPACE(sizeof(struct in6_pktinfo))] = {0};
 164         struct msghdr msg = {
 165                 .msg_name = (void *) dest,
 166                 .msg_namelen = sizeof(*dest),
 167                 .msg_iov = iov,
 168                 .msg_iovlen = iov_len,
 169                 .msg_control = cmsg_buf,
 170                 .msg_controllen = sizeof(cmsg_buf),
 171                 .msg_flags = 0
 172         };
 173
 174         // Set control data (define destination interface)
 175         struct cmsghdr *chdr = CMSG_FIRSTHDR(&msg);
 176         chdr->cmsg_level = IPPROTO_IPV6;
 177         chdr->cmsg_type = IPV6_PKTINFO;
 178         chdr->cmsg_len = CMSG_LEN(sizeof(struct in6_pktinfo));
 179         struct in6_pktinfo *pktinfo = (struct in6_pktinfo*)CMSG_DATA(chdr);
 180         pktinfo->ipi6_ifindex = iface->ifindex;
 181
 182         // Also set scope ID if link-local
 183         if (IN6_IS_ADDR_LINKLOCAL(&dest->sin6_addr)
 184                         || IN6_IS_ADDR_MC_LINKLOCAL(&dest->sin6_addr))
 185                 dest->sin6_scope_id = iface->ifindex;
 186
 187         char ipbuf[INET6_ADDRSTRLEN];
 188         inet_ntop(AF_INET6, &dest->sin6_addr, ipbuf, sizeof(ipbuf));
 189
 190         ssize_t sent = sendmsg(socket, &msg, MSG_DONTWAIT);
 191         if (sent < 0)
 192                 syslog(LOG_NOTICE, "Failed to send to %s%%%s (%m)",
 193                                 ipbuf, iface->ifname);
 194         else
 195                 syslog(LOG_DEBUG, "Sent %li bytes to %s%%%s",
 196                                 (long)sent, ipbuf, iface->ifname);
 197         return sent;
 198 }
 199
 200
 201 static int odhcpd_get_linklocal_interface_address(int ifindex, struct in6_addr *lladdr)
 202 {
 203         int ret = -1;
 204         struct sockaddr_in6 addr;
 205         socklen_t alen = sizeof(addr);
 206         int sock = socket(AF_INET6, SOCK_RAW, IPPROTO_ICMPV6);
 207
 208         if (sock < 0)
 209                 return -1;
 210
 211         memset(&addr, 0, sizeof(addr));
 212         addr.sin6_family = AF_INET6;
 213         inet_pton(AF_INET6, ALL_IPV6_ROUTERS, &addr.sin6_addr);
 214         addr.sin6_scope_id = ifindex;
 215
 216         if (!connect(sock, (struct sockaddr*)&addr, sizeof(addr)) &&
 217                         !getsockname(sock, (struct sockaddr*)&addr, &alen)) {
 218                 *lladdr = addr.sin6_addr;
 219                 ret = 0;
 220         }
 221
 222         close(sock);
 223         return ret;
 224 }
 225
 226 /*
 227  * DNS address selection criteria order :
 228  * - use IPv6 address with valid lifetime if none is yet selected
 229  * - use IPv6 address with a preferred lifetime if the already selected IPv6 address is deprecated
 230  * - use an IPv6 ULA address if the already selected IPv6 address is not an ULA address
 231  * - use the IPv6 address with the longest preferred lifetime
 232  */
 233 int odhcpd_get_interface_dns_addr(const struct interface *iface, struct in6_addr *addr)
 234 {
 235         time_t now = odhcpd_time();
 236         ssize_t m = -1;
 237
 238         for (size_t i = 0; i < iface->addr6_len; ++i) {
 239                 if (iface->addr6[i].valid <= (uint32_t)now)
 240                         continue;
 241
 242                 if (m < 0) {
 243                         m = i;
 244                         continue;
 245                 }
 246
 247                 if (iface->addr6[m].preferred >= (uint32_t)now &&
 248                                 iface->addr6[i].preferred < (uint32_t)now)
 249                         continue;
 250
 251                 if (IN6_IS_ADDR_ULA(&iface->addr6[i].addr.in6)) {
 252                         if (!IN6_IS_ADDR_ULA(&iface->addr6[m].addr.in6)) {
 253                                 m = i;
 254                                 continue;
 255                         }
 256                 } else if (IN6_IS_ADDR_ULA(&iface->addr6[m].addr.in6))
 257                         continue;
 258
 259                 if (iface->addr6[i].preferred > iface->addr6[m].preferred)
 260                         m = i;
 261         }
 262
 263         if (m >= 0) {
 264                 *addr = iface->addr6[m].addr.in6;
 265                 return 0;
 266         }
 267
 268         return odhcpd_get_linklocal_interface_address(iface->ifindex, addr);
 269 }
 270
 271 struct interface* odhcpd_get_interface_by_index(int ifindex)
 272 {
 273         struct interface *iface;
 274         list_for_each_entry(iface, &interfaces, head)
 275                 if (iface->ifindex == ifindex)
 276                         return iface;
 277
 278         return NULL;
 279 }
 280
 281
 282 struct interface* odhcpd_get_interface_by_name(const char *name)
 283 {
 284         struct interface *iface;
 285         list_for_each_entry(iface, &interfaces, head)
 286                 if (!strcmp(iface->ifname, name))
 287                         return iface;
 288
 289         return NULL;
 290 }
 291
 292
 293 struct interface* odhcpd_get_master_interface(void)
 294 {
 295         struct interface *iface;
 296         list_for_each_entry(iface, &interfaces, head)
 297                 if (iface->master)
 298                         return iface;
 299
 300         return NULL;
 301 }
 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                 getsockopt(u->fd, SOL_SOCKET, SO_ERROR, &ret, &ret_len);
 321                 u->error = false;
 322                 if (e->handle_error)
 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 %li Bytes from %s%%%s", (long)len,
 395                                         ipbuf, "netlink");
 396                         e->handle_dgram(&addr, data_buf, len, NULL, dest);
 397                         return;
 398                 } else if (destiface != 0) {
 399                         struct interface *iface;
 400                         list_for_each_entry(iface, &interfaces, head) {
 401                                 if (iface->ifindex != destiface)
 402                                         continue;
 403
 404                                 syslog(LOG_DEBUG, "Received %li Bytes from %s%%%s", (long)len,
 405                                                 ipbuf, 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 }