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
  28 #include <arpa/inet.h>
  29 #include <net/if.h>
  30 #include <netinet/ip6.h>
  31 #include <netpacket/packet.h>
  32 #include <linux/rtnetlink.h>
  33
  34 #include <sys/socket.h>
  35 #include <sys/ioctl.h>
  36 #include <sys/epoll.h>
  37 #include <sys/types.h>
  38 #include <sys/wait.h>
  39 #include <sys/syscall.h>
  40
  41 #include <libubox/uloop.h>
  42 #include "odhcpd.h"
  43
  44
  45
  46 static int ioctl_sock;
  47 static int rtnl_socket = -1;
  48 static int rtnl_seq = 0;
  49 static int urandom_fd = -1;
  50
  51
  52 static void sighandler(_unused int signal)
  53 {
  54         uloop_end();
  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, LOG_WARNING
  64         );
  65 }
  66
  67 int main(int argc, char **argv)
  68 {
  69         openlog("odhcpd", LOG_PERROR | LOG_PID, LOG_DAEMON);
  70         int opt;
  71         int log_level = LOG_WARNING;
  72         while ((opt = getopt(argc, argv, "hl:")) != -1) {
  73                 switch (opt) {
  74                 case 'h':
  75                         print_usage(argv[0]);
  76                         return 0;
  77                 case 'l':
  78                         log_level = atoi(optarg);
  79                         fprintf(stderr, "Log level set to %d\n", log_level);
  80                         break;
  81                 }
  82         }
  83         setlogmask(LOG_UPTO(log_level));
  84         uloop_init();
  85
  86         if (getuid() != 0) {
  87                 syslog(LOG_ERR, "Must be run as root!");
  88                 return 2;
  89         }
  90
  91         ioctl_sock = socket(AF_INET, SOCK_DGRAM | SOCK_CLOEXEC, 0);
  92
  93         if ((rtnl_socket = odhcpd_open_rtnl()) < 0) {
  94                 syslog(LOG_ERR, "Unable to open socket: %s", strerror(errno));
  95                 return 2;
  96         }
  97
  98         if ((urandom_fd = open("/dev/urandom", O_RDONLY | O_CLOEXEC)) < 0)
  99                 return 4;
 100
 101         signal(SIGUSR1, SIG_IGN);
 102         signal(SIGINT, sighandler);
 103         signal(SIGTERM, sighandler);
 104
 105         if (init_router())
 106                 return 4;
 107
 108         if (init_dhcpv6())
 109                 return 4;
 110
 111         if (init_ndp())
 112                 return 4;
 113
 114         if (init_dhcpv4())
 115                 return 4;
 116
 117         odhcpd_run();
 118         return 0;
 119 }
 120
 121 int odhcpd_open_rtnl(void)
 122 {
 123         int sock = socket(AF_NETLINK, SOCK_RAW | SOCK_CLOEXEC, NETLINK_ROUTE);
 124
 125         // Connect to the kernel netlink interface
 126         struct sockaddr_nl nl = {.nl_family = AF_NETLINK};
 127         if (connect(sock, (struct sockaddr*)&nl, sizeof(nl))) {
 128                 syslog(LOG_ERR, "Failed to connect to kernel rtnetlink: %s",
 129                                 strerror(errno));
 130                 return -1;
 131         }
 132
 133         return sock;
 134 }
 135
 136
 137 // Read IPv6 MTU for interface
 138 int odhcpd_get_interface_config(const char *ifname, const char *what)
 139 {
 140         char buf[64];
 141         const char *sysctl_pattern = "/proc/sys/net/ipv6/conf/%s/%s";
 142         snprintf(buf, sizeof(buf), sysctl_pattern, ifname, what);
 143
 144         int fd = open(buf, O_RDONLY);
 145         ssize_t len = read(fd, buf, sizeof(buf) - 1);
 146         close(fd);
 147
 148         if (len < 0)
 149                 return -1;
 150
 151         buf[len] = 0;
 152         return atoi(buf);
 153 }
 154
 155
 156 // Read IPv6 MAC for interface
 157 int odhcpd_get_mac(const struct interface *iface, uint8_t mac[6])
 158 {
 159         struct ifreq ifr;
 160         memset(&ifr, 0, sizeof(ifr));
 161         strncpy(ifr.ifr_name, iface->ifname, sizeof(ifr.ifr_name));
 162         if (ioctl(ioctl_sock, SIOCGIFHWADDR, &ifr) < 0)
 163                 return -1;
 164         memcpy(mac, ifr.ifr_hwaddr.sa_data, 6);
 165         return 0;
 166 }
 167
 168
 169 // Forwards a packet on a specific interface
 170 ssize_t odhcpd_send(int socket, struct sockaddr_in6 *dest,
 171                 struct iovec *iov, size_t iov_len,
 172                 const struct interface *iface)
 173 {
 174         // Construct headers
 175         uint8_t cmsg_buf[CMSG_SPACE(sizeof(struct in6_pktinfo))] = {0};
 176         struct msghdr msg = {
 177                 .msg_name = (void *) dest,
 178                 .msg_namelen = sizeof(*dest),
 179                 .msg_iov = iov,
 180                 .msg_iovlen = iov_len,
 181                 .msg_control = cmsg_buf,
 182                 .msg_controllen = sizeof(cmsg_buf),
 183                 .msg_flags = 0
 184         };
 185
 186         // Set control data (define destination interface)
 187         struct cmsghdr *chdr = CMSG_FIRSTHDR(&msg);
 188         chdr->cmsg_level = IPPROTO_IPV6;
 189         chdr->cmsg_type = IPV6_PKTINFO;
 190         chdr->cmsg_len = CMSG_LEN(sizeof(struct in6_pktinfo));
 191         struct in6_pktinfo *pktinfo = (struct in6_pktinfo*)CMSG_DATA(chdr);
 192         pktinfo->ipi6_ifindex = iface->ifindex;
 193
 194         // Also set scope ID if link-local
 195         if (IN6_IS_ADDR_LINKLOCAL(&dest->sin6_addr)
 196                         || IN6_IS_ADDR_MC_LINKLOCAL(&dest->sin6_addr))
 197                 dest->sin6_scope_id = iface->ifindex;
 198
 199         char ipbuf[INET6_ADDRSTRLEN];
 200         inet_ntop(AF_INET6, &dest->sin6_addr, ipbuf, sizeof(ipbuf));
 201
 202         ssize_t sent = sendmsg(socket, &msg, MSG_DONTWAIT);
 203         if (sent < 0)
 204                 syslog(LOG_NOTICE, "Failed to send to %s%%%s (%s)",
 205                                 ipbuf, iface->ifname, strerror(errno));
 206         else
 207                 syslog(LOG_DEBUG, "Sent %li bytes to %s%%%s",
 208                                 (long)sent, ipbuf, iface->ifname);
 209         return sent;
 210 }
 211
 212
 213 // Detect an IPV6-address currently assigned to the given interface
 214 ssize_t odhcpd_get_interface_addresses(int ifindex,
 215                 struct odhcpd_ipaddr *addrs, size_t cnt)
 216 {
 217         struct {
 218                 struct nlmsghdr nhm;
 219                 struct ifaddrmsg ifa;
 220         } req = {{sizeof(req), RTM_GETADDR, NLM_F_REQUEST | NLM_F_DUMP,
 221                         ++rtnl_seq, 0}, {AF_INET6, 0, 0, 0, ifindex}};
 222         if (send(rtnl_socket, &req, sizeof(req), 0) < (ssize_t)sizeof(req))
 223                 return 0;
 224
 225         uint8_t buf[8192];
 226         ssize_t len = 0, ret = 0;
 227
 228         for (struct nlmsghdr *nhm = NULL; ; nhm = NLMSG_NEXT(nhm, len)) {
 229                 while (len < 0 || !NLMSG_OK(nhm, (size_t)len)) {
 230                         len = recv(rtnl_socket, buf, sizeof(buf), 0);
 231                         nhm = (struct nlmsghdr*)buf;
 232                         if (len < 0 || !NLMSG_OK(nhm, (size_t)len)) {
 233                                 if (errno == EINTR)
 234                                         continue;
 235                                 else
 236                                         return ret;
 237                         }
 238                 }
 239
 240                 if (nhm->nlmsg_type != RTM_NEWADDR)
 241                         break;
 242
 243                 // Skip address but keep clearing socket buffer
 244                 if (ret >= (ssize_t)cnt)
 245                         continue;
 246
 247                 struct ifaddrmsg *ifa = NLMSG_DATA(nhm);
 248                 if (ifa->ifa_scope != RT_SCOPE_UNIVERSE ||
 249                                 (ifindex && ifa->ifa_index != (unsigned)ifindex))
 250                         continue;
 251
 252                 struct rtattr *rta = (struct rtattr*)&ifa[1];
 253                 size_t alen = NLMSG_PAYLOAD(nhm, sizeof(*ifa));
 254                 memset(&addrs[ret], 0, sizeof(addrs[ret]));
 255                 addrs[ret].prefix = ifa->ifa_prefixlen;
 256
 257                 while (RTA_OK(rta, alen)) {
 258                         if (rta->rta_type == IFA_ADDRESS) {
 259                                 memcpy(&addrs[ret].addr, RTA_DATA(rta),
 260                                                 sizeof(struct in6_addr));
 261                         } else if (rta->rta_type == IFA_CACHEINFO) {
 262                                 struct ifa_cacheinfo *ifc = RTA_DATA(rta);
 263                                 addrs[ret].preferred = ifc->ifa_prefered;
 264                                 addrs[ret].valid = ifc->ifa_valid;
 265                         }
 266
 267                         rta = RTA_NEXT(rta, alen);
 268                 }
 269
 270                 if (ifa->ifa_flags & IFA_F_DEPRECATED)
 271                         addrs[ret].preferred = 0;
 272
 273                 ++ret;
 274         }
 275
 276         return ret;
 277 }
 278
 279 int odhcpd_get_linklocal_interface_address(int ifindex, struct in6_addr *lladdr)
 280 {
 281                 int status = -1;
 282                 struct sockaddr_in6 addr = {AF_INET6, 0, 0, ALL_IPV6_ROUTERS, ifindex};
 283                 socklen_t alen = sizeof(addr);
 284                 int sock = socket(AF_INET6, SOCK_RAW, IPPROTO_ICMPV6);
 285
 286                 if (!connect(sock, (struct sockaddr*)&addr, sizeof(addr)) &&
 287                                 !getsockname(sock, (struct sockaddr*)&addr, &alen)) {
 288                         *lladdr = addr.sin6_addr;
 289                         status = 0;
 290                 }
 291
 292                 close(sock);
 293                 return status;
 294 }
 295
 296 void odhcpd_setup_route(const struct in6_addr *addr, int prefixlen,
 297                 const struct interface *iface, const struct in6_addr *gw,
 298                 int metric, bool add)
 299 {
 300         struct req {
 301                 struct nlmsghdr nh;
 302                 struct rtmsg rtm;
 303                 struct rtattr rta_dst;
 304                 struct in6_addr dst_addr;
 305                 struct rtattr rta_oif;
 306                 uint32_t ifindex;
 307                 struct rtattr rta_table;
 308                 uint32_t table;
 309                 struct rtattr rta_prio;
 310                 uint32_t prio;
 311                 struct rtattr rta_gw;
 312                 struct in6_addr gw;
 313         } req = {
 314                 {sizeof(req), 0, NLM_F_REQUEST, ++rtnl_seq, 0},
 315                 {AF_INET6, prefixlen, 0, 0, 0, 0, 0, 0, 0},
 316                 {sizeof(struct rtattr) + sizeof(struct in6_addr), RTA_DST},
 317                 *addr,
 318                 {sizeof(struct rtattr) + sizeof(uint32_t), RTA_OIF},
 319                 iface->ifindex,
 320                 {sizeof(struct rtattr) + sizeof(uint32_t), RTA_TABLE},
 321                 RT_TABLE_MAIN,
 322                 {sizeof(struct rtattr) + sizeof(uint32_t), RTA_PRIORITY},
 323                 metric,
 324                 {sizeof(struct rtattr) + sizeof(struct in6_addr), RTA_GATEWAY},
 325                 IN6ADDR_ANY_INIT,
 326         };
 327
 328         if (gw)
 329                 req.gw = *gw;
 330
 331         if (add) {
 332                 req.nh.nlmsg_type = RTM_NEWROUTE;
 333                 req.nh.nlmsg_flags |= (NLM_F_CREATE | NLM_F_REPLACE);
 334                 req.rtm.rtm_protocol = RTPROT_STATIC;
 335                 req.rtm.rtm_scope = (gw) ? RT_SCOPE_UNIVERSE : RT_SCOPE_LINK;
 336                 req.rtm.rtm_type = RTN_UNICAST;
 337         } else {
 338                 req.nh.nlmsg_type = RTM_DELROUTE;
 339                 req.rtm.rtm_scope = RT_SCOPE_NOWHERE;
 340         }
 341
 342         req.nh.nlmsg_len = (gw) ? sizeof(req) : offsetof(struct req, rta_gw);
 343         send(rtnl_socket, &req, req.nh.nlmsg_len, MSG_DONTWAIT);
 344 }
 345
 346 struct interface* odhcpd_get_interface_by_index(int ifindex)
 347 {
 348         struct interface *iface;
 349         list_for_each_entry(iface, &interfaces, head)
 350                 if (iface->ifindex == ifindex)
 351                         return iface;
 352
 353         return NULL;
 354 }
 355
 356
 357 struct interface* odhcpd_get_interface_by_name(const char *name)
 358 {
 359         struct interface *iface;
 360         list_for_each_entry(iface, &interfaces, head)
 361                 if (!strcmp(iface->ifname, name))
 362                         return iface;
 363
 364         return NULL;
 365 }
 366
 367
 368 struct interface* odhcpd_get_master_interface(void)
 369 {
 370         struct interface *iface;
 371         list_for_each_entry(iface, &interfaces, head)
 372                 if (iface->master)
 373                         return iface;
 374
 375         return NULL;
 376 }
 377
 378
 379 // Convenience function to receive and do basic validation of packets
 380 static void odhcpd_receive_packets(struct uloop_fd *u, _unused unsigned int events)
 381 {
 382         struct odhcpd_event *e = container_of(u, struct odhcpd_event, uloop);
 383
 384         uint8_t data_buf[RELAYD_BUFFER_SIZE], cmsg_buf[128];
 385         union {
 386                 struct sockaddr_in6 in6;
 387                 struct sockaddr_in in;
 388                 struct sockaddr_ll ll;
 389                 struct sockaddr_nl nl;
 390         } addr;
 391
 392         if (u->error) {
 393                 int ret = -1;
 394                 socklen_t ret_len = sizeof(ret);
 395                 getsockopt(u->fd, SOL_SOCKET, SO_ERROR, &ret, &ret_len);
 396                 u->error = false;
 397                 if (e->handle_error)
 398                         e->handle_error(ret);
 399         }
 400
 401         while (true) {
 402                 struct iovec iov = {data_buf, sizeof(data_buf)};
 403                 struct msghdr msg = {
 404                         .msg_name = (void *) &addr,
 405                         .msg_namelen = sizeof(addr),
 406                         .msg_iov = &iov,
 407                         .msg_iovlen = 1,
 408                         .msg_control = cmsg_buf,
 409                         .msg_controllen = sizeof(cmsg_buf),
 410                         .msg_flags = 0
 411                 };
 412
 413                 ssize_t len = recvmsg(u->fd, &msg, MSG_DONTWAIT);
 414                 if (len < 0) {
 415                         if (errno == EAGAIN)
 416                                 break;
 417                         else
 418                                 continue;
 419                 }
 420
 421
 422                 // Extract destination interface
 423                 int destiface = 0;
 424                 int *hlim = NULL;
 425                 void *dest = NULL;
 426                 struct in6_pktinfo *pktinfo;
 427                 struct in_pktinfo *pkt4info;
 428                 for (struct cmsghdr *ch = CMSG_FIRSTHDR(&msg); ch != NULL; ch = CMSG_NXTHDR(&msg, ch)) {
 429                         if (ch->cmsg_level == IPPROTO_IPV6 &&
 430                                         ch->cmsg_type == IPV6_PKTINFO) {
 431                                 pktinfo = (struct in6_pktinfo*)CMSG_DATA(ch);
 432                                 destiface = pktinfo->ipi6_ifindex;
 433                                 dest = &pktinfo->ipi6_addr;
 434                         } else if (ch->cmsg_level == IPPROTO_IP &&
 435                                         ch->cmsg_type == IP_PKTINFO) {
 436                                 pkt4info = (struct in_pktinfo*)CMSG_DATA(ch);
 437                                 destiface = pkt4info->ipi_ifindex;
 438                                 dest = &pkt4info->ipi_addr;
 439                         } else if (ch->cmsg_level == IPPROTO_IPV6 &&
 440                                         ch->cmsg_type == IPV6_HOPLIMIT) {
 441                                 hlim = (int*)CMSG_DATA(ch);
 442                         }
 443                 }
 444
 445                 // Check hoplimit if received
 446                 if (hlim && *hlim != 255)
 447                         continue;
 448
 449                 // Detect interface for packet sockets
 450                 if (addr.ll.sll_family == AF_PACKET)
 451                         destiface = addr.ll.sll_ifindex;
 452
 453                 struct interface *iface =
 454                                 odhcpd_get_interface_by_index(destiface);
 455
 456                 if (!iface && addr.nl.nl_family != AF_NETLINK)
 457                         continue;
 458
 459                 char ipbuf[INET6_ADDRSTRLEN] = "kernel";
 460                 if (addr.ll.sll_family == AF_PACKET &&
 461                                 len >= (ssize_t)sizeof(struct ip6_hdr))
 462                         inet_ntop(AF_INET6, &data_buf[8], ipbuf, sizeof(ipbuf));
 463                 else if (addr.in6.sin6_family == AF_INET6)
 464                         inet_ntop(AF_INET6, &addr.in6.sin6_addr, ipbuf, sizeof(ipbuf));
 465                 else if (addr.in.sin_family == AF_INET)
 466                         inet_ntop(AF_INET, &addr.in.sin_addr, ipbuf, sizeof(ipbuf));
 467
 468                 syslog(LOG_DEBUG, "Received %li Bytes from %s%%%s", (long)len,
 469                                 ipbuf, (iface) ? iface->ifname : "netlink");
 470
 471                 e->handle_dgram(&addr, data_buf, len, iface, dest);
 472         }
 473 }
 474
 475 // Register events for the multiplexer
 476 int odhcpd_register(struct odhcpd_event *event)
 477 {
 478         event->uloop.cb = odhcpd_receive_packets;
 479         return uloop_fd_add(&event->uloop, ULOOP_READ |
 480                         ((event->handle_error) ? ULOOP_ERROR_CB : 0));
 481 }
 482
 483 void odhcpd_process(struct odhcpd_event *event)
 484 {
 485         odhcpd_receive_packets(&event->uloop, 0);
 486 }
 487
 488 int odhcpd_urandom(void *data, size_t len)
 489 {
 490         return read(urandom_fd, data, len);
 491 }
 492
 493
 494 time_t odhcpd_time(void)
 495 {
 496         struct timespec ts;
 497         syscall(SYS_clock_gettime, CLOCK_MONOTONIC, &ts);
 498         return ts.tv_sec;
 499 }
 500
 501
 502 static const char hexdigits[] = "0123456789abcdef";
 503 static const int8_t hexvals[] = {
 504     -1, -1, -1, -1, -1, -1, -1, -1, -1, -2, -2, -1, -1, -2, -1, -1,
 505     -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 506     -2, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 507      0,  1,  2,  3,  4,  5,  6,  7,  8,  9, -1, -1, -1, -1, -1, -1,
 508     -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 509     -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 510     -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 511     -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 512 };
 513
 514 ssize_t odhcpd_unhexlify(uint8_t *dst, size_t len, const char *src)
 515 {
 516         size_t c;
 517         for (c = 0; c < len && src[0] && src[1]; ++c) {
 518                 int8_t x = (int8_t)*src++;
 519                 int8_t y = (int8_t)*src++;
 520                 if (x < 0 || (x = hexvals[x]) < 0
 521                                 || y < 0 || (y = hexvals[y]) < 0)
 522                         return -1;
 523                 dst[c] = x << 4 | y;
 524                 while (((int8_t)*src) < 0 ||
 525                                 (*src && hexvals[(uint8_t)*src] < 0))
 526                         src++;
 527         }
 528
 529         return c;
 530 }
 531
 532
 533 void odhcpd_hexlify(char *dst, const uint8_t *src, size_t len)
 534 {
 535         for (size_t i = 0; i < len; ++i) {
 536                 *dst++ = hexdigits[src[i] >> 4];
 537                 *dst++ = hexdigits[src[i] & 0x0f];
 538         }
 539         *dst = 0;
 540 }
 541
 542
 543 int odhcpd_bmemcmp(const void *av, const void *bv, size_t bits)
 544 {
 545         const uint8_t *a = av, *b = bv;
 546         size_t bytes = bits / 8;
 547         bits %= 8;
 548
 549         int res = memcmp(a, b, bytes);
 550         if (res == 0 && bits > 0)
 551                 res = (a[bytes] >> (8 - bits)) - (b[bytes] >> (8 - bits));
 552
 553         return res;
 554 }
 555
 556
 557 void odhcpd_bmemcpy(void *av, const void *bv, size_t bits)
 558 {
 559         uint8_t *a = av;
 560         const uint8_t *b = bv;
 561
 562         size_t bytes = bits / 8;
 563         bits %= 8;
 564         memcpy(a, b, bytes);
 565
 566         if (bits > 0) {
 567                 uint8_t mask = (1 << (8 - bits)) - 1;
 568                 a[bytes] = (a[bytes] & mask) | ((~mask) & b[bytes]);
 569         }
 570 }