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