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         memset(&ifr, 0, sizeof(ifr));
 147         strncpy(ifr.ifr_name, iface->ifname, sizeof(ifr.ifr_name));
 148         if (ioctl(ioctl_sock, SIOCGIFHWADDR, &ifr) < 0)
 149                 return -1;
 150         memcpy(mac, ifr.ifr_hwaddr.sa_data, 6);
 151         return 0;
 152 }
 153
 154
 155 // Forwards a packet on a specific interface
 156 ssize_t odhcpd_send(int socket, struct sockaddr_in6 *dest,
 157                 struct iovec *iov, size_t iov_len,
 158                 const struct interface *iface)
 159 {
 160         // Construct headers
 161         uint8_t cmsg_buf[CMSG_SPACE(sizeof(struct in6_pktinfo))] = {0};
 162         struct msghdr msg = {
 163                 .msg_name = (void *) dest,
 164                 .msg_namelen = sizeof(*dest),
 165                 .msg_iov = iov,
 166                 .msg_iovlen = iov_len,
 167                 .msg_control = cmsg_buf,
 168                 .msg_controllen = sizeof(cmsg_buf),
 169                 .msg_flags = 0
 170         };
 171
 172         // Set control data (define destination interface)
 173         struct cmsghdr *chdr = CMSG_FIRSTHDR(&msg);
 174         chdr->cmsg_level = IPPROTO_IPV6;
 175         chdr->cmsg_type = IPV6_PKTINFO;
 176         chdr->cmsg_len = CMSG_LEN(sizeof(struct in6_pktinfo));
 177         struct in6_pktinfo *pktinfo = (struct in6_pktinfo*)CMSG_DATA(chdr);
 178         pktinfo->ipi6_ifindex = iface->ifindex;
 179
 180         // Also set scope ID if link-local
 181         if (IN6_IS_ADDR_LINKLOCAL(&dest->sin6_addr)
 182                         || IN6_IS_ADDR_MC_LINKLOCAL(&dest->sin6_addr))
 183                 dest->sin6_scope_id = iface->ifindex;
 184
 185         char ipbuf[INET6_ADDRSTRLEN];
 186         inet_ntop(AF_INET6, &dest->sin6_addr, ipbuf, sizeof(ipbuf));
 187
 188         ssize_t sent = sendmsg(socket, &msg, MSG_DONTWAIT);
 189         if (sent < 0)
 190                 syslog(LOG_NOTICE, "Failed to send to %s%%%s (%s)",
 191                                 ipbuf, iface->ifname, strerror(errno));
 192         else
 193                 syslog(LOG_DEBUG, "Sent %li bytes to %s%%%s",
 194                                 (long)sent, ipbuf, iface->ifname);
 195         return sent;
 196 }
 197
 198
 199 static int odhcpd_get_linklocal_interface_address(int ifindex, struct in6_addr *lladdr)
 200 {
 201         int status = -1;
 202         struct sockaddr_in6 addr = {AF_INET6, 0, 0, ALL_IPV6_ROUTERS, ifindex};
 203         socklen_t alen = sizeof(addr);
 204         int sock = socket(AF_INET6, SOCK_RAW, IPPROTO_ICMPV6);
 205
 206         if (!connect(sock, (struct sockaddr*)&addr, sizeof(addr)) &&
 207                         !getsockname(sock, (struct sockaddr*)&addr, &alen)) {
 208                 *lladdr = addr.sin6_addr;
 209                 status = 0;
 210         }
 211
 212         close(sock);
 213
 214         return status;
 215 }
 216
 217 /*
 218  * DNS address selection criteria order :
 219  * - use IPv6 address with valid lifetime if none is yet selected
 220  * - use IPv6 address with a preferred lifetime if the already selected IPv6 address is deprecated
 221  * - use an IPv6 ULA address if the already selected IPv6 address is not an ULA address
 222  * - use the IPv6 address with the longest preferred lifetime
 223  */
 224 int odhcpd_get_interface_dns_addr(const struct interface *iface, struct in6_addr *addr)
 225 {
 226         time_t now = odhcpd_time();
 227         ssize_t m = -1;
 228
 229         for (size_t i = 0; i < iface->addr6_len; ++i) {
 230                 if (iface->addr6[i].valid <= (uint32_t)now)
 231                         continue;
 232
 233                 if (m < 0) {
 234                         m = i;
 235                         continue;
 236                 }
 237
 238                 if (iface->addr6[m].preferred >= (uint32_t)now &&
 239                                 iface->addr6[i].preferred < (uint32_t)now)
 240                         continue;
 241
 242                 if (IN6_IS_ADDR_ULA(&iface->addr6[i].addr.in6)) {
 243                         if (!IN6_IS_ADDR_ULA(&iface->addr6[m].addr.in6)) {
 244                                 m = i;
 245                                 continue;
 246                         }
 247                 } else if (IN6_IS_ADDR_ULA(&iface->addr6[m].addr.in6))
 248                         continue;
 249
 250                 if (iface->addr6[i].preferred > iface->addr6[m].preferred)
 251                         m = i;
 252         }
 253
 254         if (m >= 0) {
 255                 *addr = iface->addr6[m].addr.in6;
 256                 return 0;
 257         }
 258
 259         return odhcpd_get_linklocal_interface_address(iface->ifindex, addr);
 260 }
 261
 262 struct interface* odhcpd_get_interface_by_index(int ifindex)
 263 {
 264         struct interface *iface;
 265         list_for_each_entry(iface, &interfaces, head)
 266                 if (iface->ifindex == ifindex)
 267                         return iface;
 268
 269         return NULL;
 270 }
 271
 272
 273 struct interface* odhcpd_get_interface_by_name(const char *name)
 274 {
 275         struct interface *iface;
 276         list_for_each_entry(iface, &interfaces, head)
 277                 if (!strcmp(iface->ifname, name))
 278                         return iface;
 279
 280         return NULL;
 281 }
 282
 283
 284 struct interface* odhcpd_get_master_interface(void)
 285 {
 286         struct interface *iface;
 287         list_for_each_entry(iface, &interfaces, head)
 288                 if (iface->master)
 289                         return iface;
 290
 291         return NULL;
 292 }
 293
 294
 295 // Convenience function to receive and do basic validation of packets
 296 static void odhcpd_receive_packets(struct uloop_fd *u, _unused unsigned int events)
 297 {
 298         struct odhcpd_event *e = container_of(u, struct odhcpd_event, uloop);
 299
 300         uint8_t data_buf[8192], cmsg_buf[128];
 301         union {
 302                 struct sockaddr_in6 in6;
 303                 struct sockaddr_in in;
 304                 struct sockaddr_ll ll;
 305                 struct sockaddr_nl nl;
 306         } addr;
 307
 308         if (u->error) {
 309                 int ret = -1;
 310                 socklen_t ret_len = sizeof(ret);
 311                 getsockopt(u->fd, SOL_SOCKET, SO_ERROR, &ret, &ret_len);
 312                 u->error = false;
 313                 if (e->handle_error)
 314                         e->handle_error(e, ret);
 315         }
 316
 317         if (e->recv_msgs) {
 318                 e->recv_msgs(e);
 319                 return;
 320         }
 321
 322         while (true) {
 323                 struct iovec iov = {data_buf, sizeof(data_buf)};
 324                 struct msghdr msg = {
 325                         .msg_name = (void *) &addr,
 326                         .msg_namelen = sizeof(addr),
 327                         .msg_iov = &iov,
 328                         .msg_iovlen = 1,
 329                         .msg_control = cmsg_buf,
 330                         .msg_controllen = sizeof(cmsg_buf),
 331                         .msg_flags = 0
 332                 };
 333
 334                 ssize_t len = recvmsg(u->fd, &msg, MSG_DONTWAIT);
 335                 if (len < 0) {
 336                         if (errno == EAGAIN)
 337                                 break;
 338                         else
 339                                 continue;
 340                 }
 341
 342
 343                 // Extract destination interface
 344                 int destiface = 0;
 345                 int *hlim = NULL;
 346                 void *dest = NULL;
 347                 struct in6_pktinfo *pktinfo;
 348                 struct in_pktinfo *pkt4info;
 349                 for (struct cmsghdr *ch = CMSG_FIRSTHDR(&msg); ch != NULL; ch = CMSG_NXTHDR(&msg, ch)) {
 350                         if (ch->cmsg_level == IPPROTO_IPV6 &&
 351                                         ch->cmsg_type == IPV6_PKTINFO) {
 352                                 pktinfo = (struct in6_pktinfo*)CMSG_DATA(ch);
 353                                 destiface = pktinfo->ipi6_ifindex;
 354                                 dest = &pktinfo->ipi6_addr;
 355                         } else if (ch->cmsg_level == IPPROTO_IP &&
 356                                         ch->cmsg_type == IP_PKTINFO) {
 357                                 pkt4info = (struct in_pktinfo*)CMSG_DATA(ch);
 358                                 destiface = pkt4info->ipi_ifindex;
 359                                 dest = &pkt4info->ipi_addr;
 360                         } else if (ch->cmsg_level == IPPROTO_IPV6 &&
 361                                         ch->cmsg_type == IPV6_HOPLIMIT) {
 362                                 hlim = (int*)CMSG_DATA(ch);
 363                         }
 364                 }
 365
 366                 // Check hoplimit if received
 367                 if (hlim && *hlim != 255)
 368                         continue;
 369
 370                 // Detect interface for packet sockets
 371                 if (addr.ll.sll_family == AF_PACKET)
 372                         destiface = addr.ll.sll_ifindex;
 373
 374                 struct interface *iface =
 375                                 odhcpd_get_interface_by_index(destiface);
 376
 377                 if (!iface && addr.nl.nl_family != AF_NETLINK)
 378                         continue;
 379
 380                 char ipbuf[INET6_ADDRSTRLEN] = "kernel";
 381                 if (addr.ll.sll_family == AF_PACKET &&
 382                                 len >= (ssize_t)sizeof(struct ip6_hdr))
 383                         inet_ntop(AF_INET6, &data_buf[8], ipbuf, sizeof(ipbuf));
 384                 else if (addr.in6.sin6_family == AF_INET6)
 385                         inet_ntop(AF_INET6, &addr.in6.sin6_addr, ipbuf, sizeof(ipbuf));
 386                 else if (addr.in.sin_family == AF_INET)
 387                         inet_ntop(AF_INET, &addr.in.sin_addr, ipbuf, sizeof(ipbuf));
 388
 389                 syslog(LOG_DEBUG, "Received %li Bytes from %s%%%s", (long)len,
 390                                 ipbuf, (iface) ? iface->ifname : "netlink");
 391
 392                 e->handle_dgram(&addr, data_buf, len, iface, dest);
 393         }
 394 }
 395
 396 // Register events for the multiplexer
 397 int odhcpd_register(struct odhcpd_event *event)
 398 {
 399         event->uloop.cb = odhcpd_receive_packets;
 400         return uloop_fd_add(&event->uloop, ULOOP_READ |
 401                         ((event->handle_error) ? ULOOP_ERROR_CB : 0));
 402 }
 403
 404 int odhcpd_deregister(struct odhcpd_event *event)
 405 {
 406         event->uloop.cb = NULL;
 407         return uloop_fd_delete(&event->uloop);
 408 }
 409
 410 void odhcpd_process(struct odhcpd_event *event)
 411 {
 412         odhcpd_receive_packets(&event->uloop, 0);
 413 }
 414
 415 int odhcpd_urandom(void *data, size_t len)
 416 {
 417         return read(urandom_fd, data, len);
 418 }
 419
 420
 421 time_t odhcpd_time(void)
 422 {
 423         struct timespec ts;
 424         syscall(SYS_clock_gettime, CLOCK_MONOTONIC, &ts);
 425         return ts.tv_sec;
 426 }
 427
 428
 429 static const char hexdigits[] = "0123456789abcdef";
 430 static const int8_t hexvals[] = {
 431     -1, -1, -1, -1, -1, -1, -1, -1, -1, -2, -2, -1, -1, -2, -1, -1,
 432     -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 433     -2, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 434      0,  1,  2,  3,  4,  5,  6,  7,  8,  9, -1, -1, -1, -1, -1, -1,
 435     -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 436     -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 437     -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 438     -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 439 };
 440
 441 ssize_t odhcpd_unhexlify(uint8_t *dst, size_t len, const char *src)
 442 {
 443         size_t c;
 444         for (c = 0; c < len && src[0] && src[1]; ++c) {
 445                 int8_t x = (int8_t)*src++;
 446                 int8_t y = (int8_t)*src++;
 447                 if (x < 0 || (x = hexvals[x]) < 0
 448                                 || y < 0 || (y = hexvals[y]) < 0)
 449                         return -1;
 450                 dst[c] = x << 4 | y;
 451                 while (((int8_t)*src) < 0 ||
 452                                 (*src && hexvals[(uint8_t)*src] < 0))
 453                         src++;
 454         }
 455
 456         return c;
 457 }
 458
 459
 460 void odhcpd_hexlify(char *dst, const uint8_t *src, size_t len)
 461 {
 462         for (size_t i = 0; i < len; ++i) {
 463                 *dst++ = hexdigits[src[i] >> 4];
 464                 *dst++ = hexdigits[src[i] & 0x0f];
 465         }
 466         *dst = 0;
 467 }
 468
 469 const char *odhcpd_print_mac(const uint8_t *mac, const size_t len)
 470 {
 471         static char buf[32];
 472
 473         snprintf(buf, sizeof(buf), "%02x", mac[0]);
 474         for (size_t i = 1, j = 2; i < len && j < sizeof(buf); i++, j += 3)
 475                 snprintf(buf + j, sizeof(buf) - j, ":%02x", mac[i]);
 476
 477         return buf;
 478 }
 479
 480 int odhcpd_bmemcmp(const void *av, const void *bv, size_t bits)
 481 {
 482         const uint8_t *a = av, *b = bv;
 483         size_t bytes = bits / 8;
 484         bits %= 8;
 485
 486         int res = memcmp(a, b, bytes);
 487         if (res == 0 && bits > 0)
 488                 res = (a[bytes] >> (8 - bits)) - (b[bytes] >> (8 - bits));
 489
 490         return res;
 491 }
 492
 493
 494 void odhcpd_bmemcpy(void *av, const void *bv, size_t bits)
 495 {
 496         uint8_t *a = av;
 497         const uint8_t *b = bv;
 498
 499         size_t bytes = bits / 8;
 500         bits %= 8;
 501         memcpy(a, b, bytes);
 502
 503         if (bits > 0) {
 504                 uint8_t mask = (1 << (8 - bits)) - 1;
 505                 a[bytes] = (a[bytes] & mask) | ((~mask) & b[bytes]);
 506         }
 507 }
 508
 509
 510 int odhcpd_netmask2bitlen(bool inet6, void *mask)
 511 {
 512         int bits;
 513         struct in_addr *v4;
 514         struct in6_addr *v6;
 515
 516         if (inet6)
 517                 for (bits = 0, v6 = mask;
 518                      bits < 128 && (v6->s6_addr[bits / 8] << (bits % 8)) & 128;
 519                      bits++);
 520         else
 521                 for (bits = 0, v4 = mask;
 522                      bits < 32 && (ntohl(v4->s_addr) << bits) & 0x80000000;
 523                      bits++);
 524
 525         return bits;
 526 }
 527
 528 bool odhcpd_bitlen2netmask(bool inet6, unsigned int bits, void *mask)
 529 {
 530         uint8_t b;
 531         struct in_addr *v4;
 532         struct in6_addr *v6;
 533
 534         if (inet6)
 535         {
 536                 if (bits > 128)
 537                         return false;
 538
 539                 v6 = mask;
 540
 541                 for (unsigned int i = 0; i < sizeof(v6->s6_addr); i++)
 542                 {
 543                         b = (bits > 8) ? 8 : bits;
 544                         v6->s6_addr[i] = (uint8_t)(0xFF << (8 - b));
 545                         bits -= b;
 546                 }
 547         }
 548         else
 549         {
 550                 if (bits > 32)
 551                         return false;
 552
 553                 v4 = mask;
 554                 v4->s_addr = bits ? htonl(~((1 << (32 - bits)) - 1)) : 0;
 555         }
 556
 557         return true;
 558 }