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/netlink.h>
  33 #include <linux/rtnetlink.h>
  34
  35 #include <sys/socket.h>
  36 #include <sys/ioctl.h>
  37 #include <sys/epoll.h>
  38 #include <sys/types.h>
  39 #include <sys/wait.h>
  40 #include <sys/syscall.h>
  41
  42 #include <libubox/uloop.h>
  43 #include "odhcpd.h"
  44
  45
  46
  47 static int ioctl_sock;
  48 static int rtnl_socket = -1;
  49 static int rtnl_seq = 0;
  50 static int urandom_fd = -1;
  51
  52
  53 static void sighandler(_unused int signal)
  54 {
  55         uloop_end();
  56 }
  57
  58 static void print_usage(const char *app)
  59 {
  60         printf(
  61         "== %s Usage ==\n\n"
  62         "  -h, --help   Print this help\n"
  63         "  -l level     Specify log level 0..7 (default %d)\n",
  64                 app, LOG_WARNING
  65         );
  66 }
  67
  68 int main(int argc, char **argv)
  69 {
  70         openlog("odhcpd", LOG_PERROR | LOG_PID, LOG_DAEMON);
  71         int opt;
  72         int log_level = LOG_INFO;
  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                         log_level = atoi(optarg);
  80                         fprintf(stderr, "Log level set to %d\n", log_level);
  81                         break;
  82                 }
  83         }
  84         setlogmask(LOG_UPTO(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 ((rtnl_socket = odhcpd_open_rtnl()) < 0) {
  95                 syslog(LOG_ERR, "Unable to open socket: %s", strerror(errno));
  96                 return 2;
  97         }
  98
  99         if ((urandom_fd = open("/dev/urandom", O_RDONLY | O_CLOEXEC)) < 0)
 100                 return 4;
 101
 102         signal(SIGUSR1, SIG_IGN);
 103         signal(SIGINT, sighandler);
 104         signal(SIGTERM, sighandler);
 105
 106         if (init_router())
 107                 return 4;
 108
 109         if (init_dhcpv6())
 110                 return 4;
 111
 112         if (init_ndp())
 113                 return 4;
 114
 115         if (init_dhcpv4())
 116                 return 4;
 117
 118         odhcpd_run();
 119         return 0;
 120 }
 121
 122 int odhcpd_open_rtnl(void)
 123 {
 124         int sock = socket(AF_NETLINK, SOCK_RAW | SOCK_CLOEXEC, NETLINK_ROUTE);
 125
 126         // Connect to the kernel netlink interface
 127         struct sockaddr_nl nl = {.nl_family = AF_NETLINK};
 128         if (connect(sock, (struct sockaddr*)&nl, sizeof(nl))) {
 129                 syslog(LOG_ERR, "Failed to connect to kernel rtnetlink: %s",
 130                                 strerror(errno));
 131                 return -1;
 132         }
 133
 134         return sock;
 135 }
 136
 137
 138 // Read IPv6 MTU for interface
 139 int odhcpd_get_interface_config(const char *ifname, const char *what)
 140 {
 141         char buf[64];
 142         const char *sysctl_pattern = "/proc/sys/net/ipv6/conf/%s/%s";
 143         snprintf(buf, sizeof(buf), sysctl_pattern, ifname, what);
 144
 145         int fd = open(buf, O_RDONLY);
 146         ssize_t len = read(fd, buf, sizeof(buf) - 1);
 147         close(fd);
 148
 149         if (len < 0)
 150                 return -1;
 151
 152         buf[len] = 0;
 153         return atoi(buf);
 154 }
 155
 156
 157 // Read IPv6 MAC for interface
 158 int odhcpd_get_mac(const struct interface *iface, uint8_t mac[6])
 159 {
 160         struct ifreq ifr;
 161         memset(&ifr, 0, sizeof(ifr));
 162         strncpy(ifr.ifr_name, iface->ifname, sizeof(ifr.ifr_name));
 163         if (ioctl(ioctl_sock, SIOCGIFHWADDR, &ifr) < 0)
 164                 return -1;
 165         memcpy(mac, ifr.ifr_hwaddr.sa_data, 6);
 166         return 0;
 167 }
 168
 169
 170 // Forwards a packet on a specific interface
 171 ssize_t odhcpd_send(int socket, struct sockaddr_in6 *dest,
 172                 struct iovec *iov, size_t iov_len,
 173                 const struct interface *iface)
 174 {
 175         // Construct headers
 176         uint8_t cmsg_buf[CMSG_SPACE(sizeof(struct in6_pktinfo))] = {0};
 177         struct msghdr msg = {
 178                 .msg_name = (void *) dest,
 179                 .msg_namelen = sizeof(*dest),
 180                 .msg_iov = iov,
 181                 .msg_iovlen = iov_len,
 182                 .msg_control = cmsg_buf,
 183                 .msg_controllen = sizeof(cmsg_buf),
 184                 .msg_flags = 0
 185         };
 186
 187         // Set control data (define destination interface)
 188         struct cmsghdr *chdr = CMSG_FIRSTHDR(&msg);
 189         chdr->cmsg_level = IPPROTO_IPV6;
 190         chdr->cmsg_type = IPV6_PKTINFO;
 191         chdr->cmsg_len = CMSG_LEN(sizeof(struct in6_pktinfo));
 192         struct in6_pktinfo *pktinfo = (struct in6_pktinfo*)CMSG_DATA(chdr);
 193         pktinfo->ipi6_ifindex = iface->ifindex;
 194
 195         // Also set scope ID if link-local
 196         if (IN6_IS_ADDR_LINKLOCAL(&dest->sin6_addr)
 197                         || IN6_IS_ADDR_MC_LINKLOCAL(&dest->sin6_addr))
 198                 dest->sin6_scope_id = iface->ifindex;
 199
 200         char ipbuf[INET6_ADDRSTRLEN];
 201         inet_ntop(AF_INET6, &dest->sin6_addr, ipbuf, sizeof(ipbuf));
 202
 203         ssize_t sent = sendmsg(socket, &msg, MSG_DONTWAIT);
 204         if (sent < 0)
 205                 syslog(LOG_NOTICE, "Failed to send to %s%%%s (%s)",
 206                                 ipbuf, iface->ifname, strerror(errno));
 207         else
 208                 syslog(LOG_DEBUG, "Sent %li bytes to %s%%%s",
 209                                 (long)sent, ipbuf, iface->ifname);
 210         return sent;
 211 }
 212
 213
 214 // Detect an IPV6-address currently assigned to the given interface
 215 ssize_t odhcpd_get_interface_addresses(int ifindex,
 216                 struct odhcpd_ipaddr *addrs, size_t cnt)
 217 {
 218         struct {
 219                 struct nlmsghdr nhm;
 220                 struct ifaddrmsg ifa;
 221         } req = {{sizeof(req), RTM_GETADDR, NLM_F_REQUEST | NLM_F_DUMP,
 222                         ++rtnl_seq, 0}, {AF_INET6, 0, 0, 0, ifindex}};
 223         if (send(rtnl_socket, &req, sizeof(req), 0) < (ssize_t)sizeof(req)) {
 224                 syslog(LOG_WARNING, "Request failed to dump IPv6 addresses (%s)", strerror(errno));
 225                 return 0;
 226         }
 227
 228         uint8_t buf[8192];
 229         ssize_t len = 0, ret = 0;
 230
 231         for (struct nlmsghdr *nhm = NULL; ; nhm = NLMSG_NEXT(nhm, len)) {
 232                 while (len < 0 || !NLMSG_OK(nhm, (size_t)len)) {
 233                         len = recv(rtnl_socket, buf, sizeof(buf), 0);
 234                         nhm = (struct nlmsghdr*)buf;
 235                         if (len < 0 || !NLMSG_OK(nhm, (size_t)len)) {
 236                                 if (errno == EINTR)
 237                                         continue;
 238
 239                                 syslog(LOG_WARNING, "Failed to receive IPv6 address rtnetlink message (%s)", strerror(errno));
 240                                 ret = -1;
 241                                 goto out;
 242                         }
 243                 }
 244
 245                 switch (nhm->nlmsg_type) {
 246                 case RTM_NEWADDR: {
 247                         // Skip address but keep clearing socket buffer
 248                         if (ret >= (ssize_t)cnt)
 249                                 continue;
 250
 251                         struct ifaddrmsg *ifa = NLMSG_DATA(nhm);
 252                         if (ifa->ifa_scope != RT_SCOPE_UNIVERSE ||
 253                                         (ifindex && ifa->ifa_index != (unsigned)ifindex))
 254                                 continue;
 255
 256                         struct rtattr *rta = (struct rtattr*)&ifa[1];
 257                         size_t alen = NLMSG_PAYLOAD(nhm, sizeof(*ifa));
 258                         memset(&addrs[ret], 0, sizeof(addrs[ret]));
 259                         addrs[ret].prefix = ifa->ifa_prefixlen;
 260
 261                         while (RTA_OK(rta, alen)) {
 262                                 if (rta->rta_type == IFA_ADDRESS) {
 263                                         memcpy(&addrs[ret].addr, RTA_DATA(rta),
 264                                                         sizeof(struct in6_addr));
 265                                 } else if (rta->rta_type == IFA_CACHEINFO) {
 266                                         struct ifa_cacheinfo *ifc = RTA_DATA(rta);
 267                                         addrs[ret].preferred = ifc->ifa_prefered;
 268                                         addrs[ret].valid = ifc->ifa_valid;
 269                                 }
 270
 271                                 rta = RTA_NEXT(rta, alen);
 272                         }
 273
 274                         if (ifa->ifa_flags & IFA_F_DEPRECATED)
 275                                 addrs[ret].preferred = 0;
 276
 277                         ++ret;
 278                         break;
 279                 }
 280                 case NLMSG_DONE:
 281                         goto out;
 282                 default:
 283                         syslog(LOG_WARNING, "Unexpected rtnetlink message (%d) in response to IPv6 address dump", nhm->nlmsg_type);
 284                         ret = -1;
 285                         goto out;
 286                 }
 287
 288         }
 289 out:
 290         return ret;
 291 }
 292
 293 int odhcpd_get_linklocal_interface_address(int ifindex, struct in6_addr *lladdr)
 294 {
 295                 int status = -1;
 296                 struct sockaddr_in6 addr = {AF_INET6, 0, 0, ALL_IPV6_ROUTERS, ifindex};
 297                 socklen_t alen = sizeof(addr);
 298                 int sock = socket(AF_INET6, SOCK_RAW, IPPROTO_ICMPV6);
 299
 300                 if (!connect(sock, (struct sockaddr*)&addr, sizeof(addr)) &&
 301                                 !getsockname(sock, (struct sockaddr*)&addr, &alen)) {
 302                         *lladdr = addr.sin6_addr;
 303                         status = 0;
 304                 }
 305
 306                 close(sock);
 307                 return status;
 308 }
 309
 310 void odhcpd_setup_route(const struct in6_addr *addr, int prefixlen,
 311                 const struct interface *iface, const struct in6_addr *gw,
 312                 int metric, bool add)
 313 {
 314         struct req {
 315                 struct nlmsghdr nh;
 316                 struct rtmsg rtm;
 317                 struct rtattr rta_dst;
 318                 struct in6_addr dst_addr;
 319                 struct rtattr rta_oif;
 320                 uint32_t ifindex;
 321                 struct rtattr rta_table;
 322                 uint32_t table;
 323                 struct rtattr rta_prio;
 324                 uint32_t prio;
 325                 struct rtattr rta_gw;
 326                 struct in6_addr gw;
 327         } req = {
 328                 {sizeof(req), 0, NLM_F_REQUEST, ++rtnl_seq, 0},
 329                 {AF_INET6, prefixlen, 0, 0, 0, 0, 0, 0, 0},
 330                 {sizeof(struct rtattr) + sizeof(struct in6_addr), RTA_DST},
 331                 *addr,
 332                 {sizeof(struct rtattr) + sizeof(uint32_t), RTA_OIF},
 333                 iface->ifindex,
 334                 {sizeof(struct rtattr) + sizeof(uint32_t), RTA_TABLE},
 335                 RT_TABLE_MAIN,
 336                 {sizeof(struct rtattr) + sizeof(uint32_t), RTA_PRIORITY},
 337                 metric,
 338                 {sizeof(struct rtattr) + sizeof(struct in6_addr), RTA_GATEWAY},
 339                 IN6ADDR_ANY_INIT,
 340         };
 341
 342         if (gw)
 343                 req.gw = *gw;
 344
 345         if (add) {
 346                 req.nh.nlmsg_type = RTM_NEWROUTE;
 347                 req.nh.nlmsg_flags |= (NLM_F_CREATE | NLM_F_REPLACE);
 348                 req.rtm.rtm_protocol = RTPROT_STATIC;
 349                 req.rtm.rtm_scope = (gw) ? RT_SCOPE_UNIVERSE : RT_SCOPE_LINK;
 350                 req.rtm.rtm_type = RTN_UNICAST;
 351         } else {
 352                 req.nh.nlmsg_type = RTM_DELROUTE;
 353                 req.rtm.rtm_scope = RT_SCOPE_NOWHERE;
 354         }
 355
 356         req.nh.nlmsg_len = (gw) ? sizeof(req) : offsetof(struct req, rta_gw);
 357         send(rtnl_socket, &req, req.nh.nlmsg_len, MSG_DONTWAIT);
 358 }
 359
 360 struct interface* odhcpd_get_interface_by_index(int ifindex)
 361 {
 362         struct interface *iface;
 363         list_for_each_entry(iface, &interfaces, head)
 364                 if (iface->ifindex == ifindex)
 365                         return iface;
 366
 367         return NULL;
 368 }
 369
 370
 371 struct interface* odhcpd_get_interface_by_name(const char *name)
 372 {
 373         struct interface *iface;
 374         list_for_each_entry(iface, &interfaces, head)
 375                 if (!strcmp(iface->ifname, name))
 376                         return iface;
 377
 378         return NULL;
 379 }
 380
 381
 382 struct interface* odhcpd_get_master_interface(void)
 383 {
 384         struct interface *iface;
 385         list_for_each_entry(iface, &interfaces, head)
 386                 if (iface->master)
 387                         return iface;
 388
 389         return NULL;
 390 }
 391
 392
 393 // Convenience function to receive and do basic validation of packets
 394 static void odhcpd_receive_packets(struct uloop_fd *u, _unused unsigned int events)
 395 {
 396         struct odhcpd_event *e = container_of(u, struct odhcpd_event, uloop);
 397
 398         uint8_t data_buf[RELAYD_BUFFER_SIZE], cmsg_buf[128];
 399         union {
 400                 struct sockaddr_in6 in6;
 401                 struct sockaddr_in in;
 402                 struct sockaddr_ll ll;
 403                 struct sockaddr_nl nl;
 404         } addr;
 405
 406         if (u->error) {
 407                 int ret = -1;
 408                 socklen_t ret_len = sizeof(ret);
 409                 getsockopt(u->fd, SOL_SOCKET, SO_ERROR, &ret, &ret_len);
 410                 u->error = false;
 411                 if (e->handle_error)
 412                         e->handle_error(ret);
 413         }
 414
 415         while (true) {
 416                 struct iovec iov = {data_buf, sizeof(data_buf)};
 417                 struct msghdr msg = {
 418                         .msg_name = (void *) &addr,
 419                         .msg_namelen = sizeof(addr),
 420                         .msg_iov = &iov,
 421                         .msg_iovlen = 1,
 422                         .msg_control = cmsg_buf,
 423                         .msg_controllen = sizeof(cmsg_buf),
 424                         .msg_flags = 0
 425                 };
 426
 427                 ssize_t len = recvmsg(u->fd, &msg, MSG_DONTWAIT);
 428                 if (len < 0) {
 429                         if (errno == EAGAIN)
 430                                 break;
 431                         else
 432                                 continue;
 433                 }
 434
 435
 436                 // Extract destination interface
 437                 int destiface = 0;
 438                 int *hlim = NULL;
 439                 void *dest = NULL;
 440                 struct in6_pktinfo *pktinfo;
 441                 struct in_pktinfo *pkt4info;
 442                 for (struct cmsghdr *ch = CMSG_FIRSTHDR(&msg); ch != NULL; ch = CMSG_NXTHDR(&msg, ch)) {
 443                         if (ch->cmsg_level == IPPROTO_IPV6 &&
 444                                         ch->cmsg_type == IPV6_PKTINFO) {
 445                                 pktinfo = (struct in6_pktinfo*)CMSG_DATA(ch);
 446                                 destiface = pktinfo->ipi6_ifindex;
 447                                 dest = &pktinfo->ipi6_addr;
 448                         } else if (ch->cmsg_level == IPPROTO_IP &&
 449                                         ch->cmsg_type == IP_PKTINFO) {
 450                                 pkt4info = (struct in_pktinfo*)CMSG_DATA(ch);
 451                                 destiface = pkt4info->ipi_ifindex;
 452                                 dest = &pkt4info->ipi_addr;
 453                         } else if (ch->cmsg_level == IPPROTO_IPV6 &&
 454                                         ch->cmsg_type == IPV6_HOPLIMIT) {
 455                                 hlim = (int*)CMSG_DATA(ch);
 456                         }
 457                 }
 458
 459                 // Check hoplimit if received
 460                 if (hlim && *hlim != 255)
 461                         continue;
 462
 463                 // Detect interface for packet sockets
 464                 if (addr.ll.sll_family == AF_PACKET)
 465                         destiface = addr.ll.sll_ifindex;
 466
 467                 struct interface *iface =
 468                                 odhcpd_get_interface_by_index(destiface);
 469
 470                 if (!iface && addr.nl.nl_family != AF_NETLINK)
 471                         continue;
 472
 473                 char ipbuf[INET6_ADDRSTRLEN] = "kernel";
 474                 if (addr.ll.sll_family == AF_PACKET &&
 475                                 len >= (ssize_t)sizeof(struct ip6_hdr))
 476                         inet_ntop(AF_INET6, &data_buf[8], ipbuf, sizeof(ipbuf));
 477                 else if (addr.in6.sin6_family == AF_INET6)
 478                         inet_ntop(AF_INET6, &addr.in6.sin6_addr, ipbuf, sizeof(ipbuf));
 479                 else if (addr.in.sin_family == AF_INET)
 480                         inet_ntop(AF_INET, &addr.in.sin_addr, ipbuf, sizeof(ipbuf));
 481
 482                 syslog(LOG_DEBUG, "Received %li Bytes from %s%%%s", (long)len,
 483                                 ipbuf, (iface) ? iface->ifname : "netlink");
 484
 485                 e->handle_dgram(&addr, data_buf, len, iface, dest);
 486         }
 487 }
 488
 489 // Register events for the multiplexer
 490 int odhcpd_register(struct odhcpd_event *event)
 491 {
 492         event->uloop.cb = odhcpd_receive_packets;
 493         return uloop_fd_add(&event->uloop, ULOOP_READ |
 494                         ((event->handle_error) ? ULOOP_ERROR_CB : 0));
 495 }
 496
 497 void odhcpd_process(struct odhcpd_event *event)
 498 {
 499         odhcpd_receive_packets(&event->uloop, 0);
 500 }
 501
 502 int odhcpd_urandom(void *data, size_t len)
 503 {
 504         return read(urandom_fd, data, len);
 505 }
 506
 507
 508 time_t odhcpd_time(void)
 509 {
 510         struct timespec ts;
 511         syscall(SYS_clock_gettime, CLOCK_MONOTONIC, &ts);
 512         return ts.tv_sec;
 513 }
 514
 515
 516 static const char hexdigits[] = "0123456789abcdef";
 517 static const int8_t hexvals[] = {
 518     -1, -1, -1, -1, -1, -1, -1, -1, -1, -2, -2, -1, -1, -2, -1, -1,
 519     -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 520     -2, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 521      0,  1,  2,  3,  4,  5,  6,  7,  8,  9, -1, -1, -1, -1, -1, -1,
 522     -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 523     -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 524     -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 525     -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 526 };
 527
 528 ssize_t odhcpd_unhexlify(uint8_t *dst, size_t len, const char *src)
 529 {
 530         size_t c;
 531         for (c = 0; c < len && src[0] && src[1]; ++c) {
 532                 int8_t x = (int8_t)*src++;
 533                 int8_t y = (int8_t)*src++;
 534                 if (x < 0 || (x = hexvals[x]) < 0
 535                                 || y < 0 || (y = hexvals[y]) < 0)
 536                         return -1;
 537                 dst[c] = x << 4 | y;
 538                 while (((int8_t)*src) < 0 ||
 539                                 (*src && hexvals[(uint8_t)*src] < 0))
 540                         src++;
 541         }
 542
 543         return c;
 544 }
 545
 546
 547 void odhcpd_hexlify(char *dst, const uint8_t *src, size_t len)
 548 {
 549         for (size_t i = 0; i < len; ++i) {
 550                 *dst++ = hexdigits[src[i] >> 4];
 551                 *dst++ = hexdigits[src[i] & 0x0f];
 552         }
 553         *dst = 0;
 554 }
 555
 556
 557 int odhcpd_bmemcmp(const void *av, const void *bv, size_t bits)
 558 {
 559         const uint8_t *a = av, *b = bv;
 560         size_t bytes = bits / 8;
 561         bits %= 8;
 562
 563         int res = memcmp(a, b, bytes);
 564         if (res == 0 && bits > 0)
 565                 res = (a[bytes] >> (8 - bits)) - (b[bytes] >> (8 - bits));
 566
 567         return res;
 568 }
 569
 570
 571 void odhcpd_bmemcpy(void *av, const void *bv, size_t bits)
 572 {
 573         uint8_t *a = av;
 574         const uint8_t *b = bv;
 575
 576         size_t bytes = bits / 8;
 577         bits %= 8;
 578         memcpy(a, b, bytes);
 579
 580         if (bits > 0) {
 581                 uint8_t mask = (1 << (8 - bits)) - 1;
 582                 a[bytes] = (a[bytes] & mask) | ((~mask) & b[bytes]);
 583         }
 584 }