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/if_addr.h>
  34 #include <linux/rtnetlink.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 <netlink/msg.h>
  44 #include <netlink/socket.h>
  45 #include <netlink/attr.h>
  46 #include <libubox/uloop.h>
  47 #include "odhcpd.h"
  48
  49
  50
  51 static int ioctl_sock;
  52 static struct nl_sock *rtnl_socket = NULL;
  53 static int urandom_fd = -1;
  54
  55
  56 static void sighandler(_unused int signal)
  57 {
  58         uloop_end();
  59 }
  60
  61 static void print_usage(const char *app)
  62 {
  63         printf(
  64         "== %s Usage ==\n\n"
  65         "  -h, --help   Print this help\n"
  66         "  -l level     Specify log level 0..7 (default %d)\n",
  67                 app, LOG_WARNING
  68         );
  69 }
  70
  71 int main(int argc, char **argv)
  72 {
  73         openlog("odhcpd", LOG_PERROR | LOG_PID, LOG_DAEMON);
  74         int opt;
  75         int log_level = LOG_INFO;
  76         while ((opt = getopt(argc, argv, "hl:")) != -1) {
  77                 switch (opt) {
  78                 case 'h':
  79                         print_usage(argv[0]);
  80                         return 0;
  81                 case 'l':
  82                         log_level = atoi(optarg);
  83                         fprintf(stderr, "Log level set to %d\n", log_level);
  84                         break;
  85                 }
  86         }
  87         setlogmask(LOG_UPTO(log_level));
  88         uloop_init();
  89
  90         if (getuid() != 0) {
  91                 syslog(LOG_ERR, "Must be run as root!");
  92                 return 2;
  93         }
  94
  95         ioctl_sock = socket(AF_INET, SOCK_DGRAM | SOCK_CLOEXEC, 0);
  96
  97         if (!(rtnl_socket = odhcpd_create_nl_socket(NETLINK_ROUTE, 0))) {
  98                 syslog(LOG_ERR, "Unable to open nl socket: %s", strerror(errno));
  99                 return 2;
 100         }
 101
 102         if ((urandom_fd = open("/dev/urandom", O_RDONLY | O_CLOEXEC)) < 0)
 103                 return 4;
 104
 105         signal(SIGUSR1, SIG_IGN);
 106         signal(SIGINT, sighandler);
 107         signal(SIGTERM, sighandler);
 108
 109         if (init_router())
 110                 return 4;
 111
 112         if (init_dhcpv6())
 113                 return 4;
 114
 115         if (init_ndp())
 116                 return 4;
 117
 118         if (init_dhcpv4())
 119                 return 4;
 120
 121         odhcpd_run();
 122         return 0;
 123 }
 124
 125 struct nl_sock *odhcpd_create_nl_socket(int protocol, int groups)
 126 {
 127         struct nl_sock *nl_sock;
 128
 129         nl_sock = nl_socket_alloc();
 130         if (!nl_sock)
 131                 goto err;
 132
 133         if (groups)
 134                 nl_join_groups(nl_sock, groups);
 135
 136         if (nl_connect(nl_sock, protocol) < 0)
 137                 goto err;
 138
 139         return nl_sock;
 140
 141 err:
 142         if (nl_sock)
 143                 nl_socket_free(nl_sock);
 144
 145         return NULL;
 146 }
 147
 148
 149 // Read IPv6 MTU for interface
 150 int odhcpd_get_interface_config(const char *ifname, const char *what)
 151 {
 152         char buf[64];
 153         const char *sysctl_pattern = "/proc/sys/net/ipv6/conf/%s/%s";
 154         snprintf(buf, sizeof(buf), sysctl_pattern, ifname, what);
 155
 156         int fd = open(buf, O_RDONLY);
 157         ssize_t len = read(fd, buf, sizeof(buf) - 1);
 158         close(fd);
 159
 160         if (len < 0)
 161                 return -1;
 162
 163         buf[len] = 0;
 164         return atoi(buf);
 165 }
 166
 167
 168 // Read IPv6 MAC for interface
 169 int odhcpd_get_mac(const struct interface *iface, uint8_t mac[6])
 170 {
 171         struct ifreq ifr;
 172         memset(&ifr, 0, sizeof(ifr));
 173         strncpy(ifr.ifr_name, iface->ifname, sizeof(ifr.ifr_name));
 174         if (ioctl(ioctl_sock, SIOCGIFHWADDR, &ifr) < 0)
 175                 return -1;
 176         memcpy(mac, ifr.ifr_hwaddr.sa_data, 6);
 177         return 0;
 178 }
 179
 180
 181 // Forwards a packet on a specific interface
 182 ssize_t odhcpd_send(int socket, struct sockaddr_in6 *dest,
 183                 struct iovec *iov, size_t iov_len,
 184                 const struct interface *iface)
 185 {
 186         // Construct headers
 187         uint8_t cmsg_buf[CMSG_SPACE(sizeof(struct in6_pktinfo))] = {0};
 188         struct msghdr msg = {
 189                 .msg_name = (void *) dest,
 190                 .msg_namelen = sizeof(*dest),
 191                 .msg_iov = iov,
 192                 .msg_iovlen = iov_len,
 193                 .msg_control = cmsg_buf,
 194                 .msg_controllen = sizeof(cmsg_buf),
 195                 .msg_flags = 0
 196         };
 197
 198         // Set control data (define destination interface)
 199         struct cmsghdr *chdr = CMSG_FIRSTHDR(&msg);
 200         chdr->cmsg_level = IPPROTO_IPV6;
 201         chdr->cmsg_type = IPV6_PKTINFO;
 202         chdr->cmsg_len = CMSG_LEN(sizeof(struct in6_pktinfo));
 203         struct in6_pktinfo *pktinfo = (struct in6_pktinfo*)CMSG_DATA(chdr);
 204         pktinfo->ipi6_ifindex = iface->ifindex;
 205
 206         // Also set scope ID if link-local
 207         if (IN6_IS_ADDR_LINKLOCAL(&dest->sin6_addr)
 208                         || IN6_IS_ADDR_MC_LINKLOCAL(&dest->sin6_addr))
 209                 dest->sin6_scope_id = iface->ifindex;
 210
 211         char ipbuf[INET6_ADDRSTRLEN];
 212         inet_ntop(AF_INET6, &dest->sin6_addr, ipbuf, sizeof(ipbuf));
 213
 214         ssize_t sent = sendmsg(socket, &msg, MSG_DONTWAIT);
 215         if (sent < 0)
 216                 syslog(LOG_NOTICE, "Failed to send to %s%%%s (%s)",
 217                                 ipbuf, iface->ifname, strerror(errno));
 218         else
 219                 syslog(LOG_DEBUG, "Sent %li bytes to %s%%%s",
 220                                 (long)sent, ipbuf, iface->ifname);
 221         return sent;
 222 }
 223
 224 struct addr_info {
 225         int ifindex;
 226         struct odhcpd_ipaddr *addrs;
 227         size_t addrs_sz;
 228         int pending;
 229         ssize_t ret;
 230 };
 231
 232 static int cb_valid_handler(struct nl_msg *msg, void *arg)
 233 {
 234         struct addr_info *ctxt = (struct addr_info *)arg;
 235         struct nlmsghdr *hdr = nlmsg_hdr(msg);
 236         struct ifaddrmsg *ifa;
 237         struct nlattr *nla[__IFA_MAX];
 238
 239         if (hdr->nlmsg_type != RTM_NEWADDR || ctxt->ret >= (ssize_t)ctxt->addrs_sz)
 240                 return NL_SKIP;
 241
 242         ifa = NLMSG_DATA(hdr);
 243         if (ifa->ifa_scope != RT_SCOPE_UNIVERSE ||
 244                         (ctxt->ifindex && ifa->ifa_index != (unsigned)ctxt->ifindex))
 245                 return NL_SKIP;
 246
 247         nlmsg_parse(hdr, sizeof(*ifa), nla, __IFA_MAX - 1, NULL);
 248         if (!nla[IFA_ADDRESS])
 249                 return NL_SKIP;
 250
 251         memset(&ctxt->addrs[ctxt->ret], 0, sizeof(ctxt->addrs[ctxt->ret]));
 252         ctxt->addrs[ctxt->ret].prefix = ifa->ifa_prefixlen;
 253
 254         nla_memcpy(&ctxt->addrs[ctxt->ret].addr, nla[IFA_ADDRESS],
 255                         sizeof(ctxt->addrs[ctxt->ret].addr));
 256
 257         if (nla[IFA_CACHEINFO]) {
 258                 struct ifa_cacheinfo *ifc = nla_data(nla[IFA_CACHEINFO]);
 259
 260                 ctxt->addrs[ctxt->ret].preferred = ifc->ifa_prefered;
 261                 ctxt->addrs[ctxt->ret].valid = ifc->ifa_valid;
 262         }
 263
 264         if (ifa->ifa_flags & IFA_F_DEPRECATED)
 265                 ctxt->addrs[ctxt->ret].preferred = 0;
 266
 267         ctxt->ret++;
 268
 269         return NL_OK;
 270 }
 271
 272 static int cb_finish_handler(_unused struct nl_msg *msg, void *arg)
 273 {
 274         struct addr_info *ctxt = (struct addr_info *)arg;
 275
 276         ctxt->pending = 0;
 277
 278         return NL_STOP;
 279 }
 280
 281 static int cb_error_handler(_unused struct sockaddr_nl *nla, struct nlmsgerr *err,
 282                 void *arg)
 283 {
 284         struct addr_info *ctxt = (struct addr_info *)arg;
 285
 286         ctxt->pending = 0;
 287         ctxt->ret = err->error;
 288
 289         return NL_STOP;
 290 }
 291
 292 // Detect an IPV6-address currently assigned to the given interface
 293 ssize_t odhcpd_get_interface_addresses(int ifindex,
 294                 struct odhcpd_ipaddr *addrs, size_t cnt)
 295 {
 296         struct nl_msg *msg;
 297         struct ifaddrmsg ifa = {
 298                 .ifa_family = AF_INET6,
 299                 .ifa_prefixlen = 0,
 300                 .ifa_flags = 0,
 301                 .ifa_scope = 0,
 302                 .ifa_index = ifindex, };
 303         struct nl_cb *cb = nl_cb_alloc(NL_CB_DEFAULT);
 304         struct addr_info ctxt = {
 305                 .ifindex = ifindex,
 306                 .addrs = addrs,
 307                 .addrs_sz = cnt,
 308                 .ret = 0,
 309                 .pending = 1,
 310         };
 311
 312         if (!cb) {
 313                 ctxt.ret = -1;
 314                 goto out;
 315         }
 316
 317         msg = nlmsg_alloc_simple(RTM_GETADDR, NLM_F_REQUEST | NLM_F_DUMP);
 318
 319         if (!msg) {
 320                 ctxt.ret = - 1;
 321                 goto out;
 322         }
 323
 324         nlmsg_append(msg, &ifa, sizeof(ifa), 0);
 325
 326         nl_cb_set(cb, NL_CB_VALID, NL_CB_CUSTOM, cb_valid_handler, &ctxt);
 327         nl_cb_set(cb, NL_CB_FINISH, NL_CB_CUSTOM, cb_finish_handler, &ctxt);
 328         nl_cb_err(cb, NL_CB_CUSTOM, cb_error_handler, &ctxt);
 329
 330         nl_send_auto_complete(rtnl_socket, msg);
 331         while (ctxt.pending > 0)
 332                 nl_recvmsgs(rtnl_socket, cb);
 333
 334         nlmsg_free(msg);
 335 out:
 336         nl_cb_put(cb);
 337
 338         return ctxt.ret;
 339 }
 340
 341 int odhcpd_get_linklocal_interface_address(int ifindex, struct in6_addr *lladdr)
 342 {
 343         int status = -1;
 344         struct sockaddr_in6 addr = {AF_INET6, 0, 0, ALL_IPV6_ROUTERS, ifindex};
 345         socklen_t alen = sizeof(addr);
 346         int sock = socket(AF_INET6, SOCK_RAW, IPPROTO_ICMPV6);
 347
 348         if (!connect(sock, (struct sockaddr*)&addr, sizeof(addr)) &&
 349                         !getsockname(sock, (struct sockaddr*)&addr, &alen)) {
 350                 *lladdr = addr.sin6_addr;
 351                 status = 0;
 352         }
 353
 354         close(sock);
 355
 356         return status;
 357 }
 358
 359 int odhcpd_setup_route(const struct in6_addr *addr, int prefixlen,
 360                 const struct interface *iface, const struct in6_addr *gw,
 361                 uint32_t metric, bool add)
 362 {
 363         struct nl_msg *msg;
 364         struct rtmsg rtm = {
 365                 .rtm_family = AF_INET6,
 366                 .rtm_dst_len = prefixlen,
 367                 .rtm_src_len = 0,
 368                 .rtm_table = RT_TABLE_MAIN,
 369                 .rtm_protocol = (add ? RTPROT_STATIC : RTPROT_UNSPEC),
 370                 .rtm_scope = (add ? (gw ? RT_SCOPE_UNIVERSE : RT_SCOPE_LINK) : RT_SCOPE_NOWHERE),
 371                 .rtm_type = (add ? RTN_UNICAST : RTN_UNSPEC),
 372         };
 373         int ret = 0;
 374
 375         msg = nlmsg_alloc_simple(add ? RTM_NEWROUTE : RTM_DELROUTE,
 376                                         add ? NLM_F_CREATE | NLM_F_REPLACE : 0);
 377         if (!msg)
 378                 return -1;
 379
 380         nlmsg_append(msg, &rtm, sizeof(rtm), 0);
 381
 382         nla_put(msg, RTA_DST, sizeof(*addr), addr);
 383         nla_put_u32(msg, RTA_OIF, iface->ifindex);
 384         nla_put_u32(msg, RTA_PRIORITY, metric);
 385
 386         if (gw)
 387                 nla_put(msg, RTA_GATEWAY, sizeof(*gw), gw);
 388
 389         ret = nl_send_auto_complete(rtnl_socket, msg);
 390         nlmsg_free(msg);
 391
 392         if (ret < 0)
 393                 return ret;
 394
 395         return nl_wait_for_ack(rtnl_socket);
 396 }
 397
 398 struct interface* odhcpd_get_interface_by_index(int ifindex)
 399 {
 400         struct interface *iface;
 401         list_for_each_entry(iface, &interfaces, head)
 402                 if (iface->ifindex == ifindex)
 403                         return iface;
 404
 405         return NULL;
 406 }
 407
 408
 409 struct interface* odhcpd_get_interface_by_name(const char *name)
 410 {
 411         struct interface *iface;
 412         list_for_each_entry(iface, &interfaces, head)
 413                 if (!strcmp(iface->ifname, name))
 414                         return iface;
 415
 416         return NULL;
 417 }
 418
 419
 420 struct interface* odhcpd_get_master_interface(void)
 421 {
 422         struct interface *iface;
 423         list_for_each_entry(iface, &interfaces, head)
 424                 if (iface->master)
 425                         return iface;
 426
 427         return NULL;
 428 }
 429
 430
 431 // Convenience function to receive and do basic validation of packets
 432 static void odhcpd_receive_packets(struct uloop_fd *u, _unused unsigned int events)
 433 {
 434         struct odhcpd_event *e = container_of(u, struct odhcpd_event, uloop);
 435
 436         uint8_t data_buf[RELAYD_BUFFER_SIZE], cmsg_buf[128];
 437         union {
 438                 struct sockaddr_in6 in6;
 439                 struct sockaddr_in in;
 440                 struct sockaddr_ll ll;
 441                 struct sockaddr_nl nl;
 442         } addr;
 443
 444         if (u->error) {
 445                 int ret = -1;
 446                 socklen_t ret_len = sizeof(ret);
 447                 getsockopt(u->fd, SOL_SOCKET, SO_ERROR, &ret, &ret_len);
 448                 u->error = false;
 449                 if (e->handle_error)
 450                         e->handle_error(ret);
 451         }
 452
 453         while (true) {
 454                 struct iovec iov = {data_buf, sizeof(data_buf)};
 455                 struct msghdr msg = {
 456                         .msg_name = (void *) &addr,
 457                         .msg_namelen = sizeof(addr),
 458                         .msg_iov = &iov,
 459                         .msg_iovlen = 1,
 460                         .msg_control = cmsg_buf,
 461                         .msg_controllen = sizeof(cmsg_buf),
 462                         .msg_flags = 0
 463                 };
 464
 465                 ssize_t len = recvmsg(u->fd, &msg, MSG_DONTWAIT);
 466                 if (len < 0) {
 467                         if (errno == EAGAIN)
 468                                 break;
 469                         else
 470                                 continue;
 471                 }
 472
 473
 474                 // Extract destination interface
 475                 int destiface = 0;
 476                 int *hlim = NULL;
 477                 void *dest = NULL;
 478                 struct in6_pktinfo *pktinfo;
 479                 struct in_pktinfo *pkt4info;
 480                 for (struct cmsghdr *ch = CMSG_FIRSTHDR(&msg); ch != NULL; ch = CMSG_NXTHDR(&msg, ch)) {
 481                         if (ch->cmsg_level == IPPROTO_IPV6 &&
 482                                         ch->cmsg_type == IPV6_PKTINFO) {
 483                                 pktinfo = (struct in6_pktinfo*)CMSG_DATA(ch);
 484                                 destiface = pktinfo->ipi6_ifindex;
 485                                 dest = &pktinfo->ipi6_addr;
 486                         } else if (ch->cmsg_level == IPPROTO_IP &&
 487                                         ch->cmsg_type == IP_PKTINFO) {
 488                                 pkt4info = (struct in_pktinfo*)CMSG_DATA(ch);
 489                                 destiface = pkt4info->ipi_ifindex;
 490                                 dest = &pkt4info->ipi_addr;
 491                         } else if (ch->cmsg_level == IPPROTO_IPV6 &&
 492                                         ch->cmsg_type == IPV6_HOPLIMIT) {
 493                                 hlim = (int*)CMSG_DATA(ch);
 494                         }
 495                 }
 496
 497                 // Check hoplimit if received
 498                 if (hlim && *hlim != 255)
 499                         continue;
 500
 501                 // Detect interface for packet sockets
 502                 if (addr.ll.sll_family == AF_PACKET)
 503                         destiface = addr.ll.sll_ifindex;
 504
 505                 struct interface *iface =
 506                                 odhcpd_get_interface_by_index(destiface);
 507
 508                 if (!iface && addr.nl.nl_family != AF_NETLINK)
 509                         continue;
 510
 511                 char ipbuf[INET6_ADDRSTRLEN] = "kernel";
 512                 if (addr.ll.sll_family == AF_PACKET &&
 513                                 len >= (ssize_t)sizeof(struct ip6_hdr))
 514                         inet_ntop(AF_INET6, &data_buf[8], ipbuf, sizeof(ipbuf));
 515                 else if (addr.in6.sin6_family == AF_INET6)
 516                         inet_ntop(AF_INET6, &addr.in6.sin6_addr, ipbuf, sizeof(ipbuf));
 517                 else if (addr.in.sin_family == AF_INET)
 518                         inet_ntop(AF_INET, &addr.in.sin_addr, ipbuf, sizeof(ipbuf));
 519
 520                 syslog(LOG_DEBUG, "Received %li Bytes from %s%%%s", (long)len,
 521                                 ipbuf, (iface) ? iface->ifname : "netlink");
 522
 523                 e->handle_dgram(&addr, data_buf, len, iface, dest);
 524         }
 525 }
 526
 527 // Register events for the multiplexer
 528 int odhcpd_register(struct odhcpd_event *event)
 529 {
 530         event->uloop.cb = odhcpd_receive_packets;
 531         return uloop_fd_add(&event->uloop, ULOOP_READ |
 532                         ((event->handle_error) ? ULOOP_ERROR_CB : 0));
 533 }
 534
 535 void odhcpd_process(struct odhcpd_event *event)
 536 {
 537         odhcpd_receive_packets(&event->uloop, 0);
 538 }
 539
 540 int odhcpd_urandom(void *data, size_t len)
 541 {
 542         return read(urandom_fd, data, len);
 543 }
 544
 545
 546 time_t odhcpd_time(void)
 547 {
 548         struct timespec ts;
 549         syscall(SYS_clock_gettime, CLOCK_MONOTONIC, &ts);
 550         return ts.tv_sec;
 551 }
 552
 553
 554 static const char hexdigits[] = "0123456789abcdef";
 555 static const int8_t hexvals[] = {
 556     -1, -1, -1, -1, -1, -1, -1, -1, -1, -2, -2, -1, -1, -2, -1, -1,
 557     -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 558     -2, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 559      0,  1,  2,  3,  4,  5,  6,  7,  8,  9, -1, -1, -1, -1, -1, -1,
 560     -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 561     -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 562     -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 563     -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 564 };
 565
 566 ssize_t odhcpd_unhexlify(uint8_t *dst, size_t len, const char *src)
 567 {
 568         size_t c;
 569         for (c = 0; c < len && src[0] && src[1]; ++c) {
 570                 int8_t x = (int8_t)*src++;
 571                 int8_t y = (int8_t)*src++;
 572                 if (x < 0 || (x = hexvals[x]) < 0
 573                                 || y < 0 || (y = hexvals[y]) < 0)
 574                         return -1;
 575                 dst[c] = x << 4 | y;
 576                 while (((int8_t)*src) < 0 ||
 577                                 (*src && hexvals[(uint8_t)*src] < 0))
 578                         src++;
 579         }
 580
 581         return c;
 582 }
 583
 584
 585 void odhcpd_hexlify(char *dst, const uint8_t *src, size_t len)
 586 {
 587         for (size_t i = 0; i < len; ++i) {
 588                 *dst++ = hexdigits[src[i] >> 4];
 589                 *dst++ = hexdigits[src[i] & 0x0f];
 590         }
 591         *dst = 0;
 592 }
 593
 594
 595 int odhcpd_bmemcmp(const void *av, const void *bv, size_t bits)
 596 {
 597         const uint8_t *a = av, *b = bv;
 598         size_t bytes = bits / 8;
 599         bits %= 8;
 600
 601         int res = memcmp(a, b, bytes);
 602         if (res == 0 && bits > 0)
 603                 res = (a[bytes] >> (8 - bits)) - (b[bytes] >> (8 - bits));
 604
 605         return res;
 606 }
 607
 608
 609 void odhcpd_bmemcpy(void *av, const void *bv, size_t bits)
 610 {
 611         uint8_t *a = av;
 612         const uint8_t *b = bv;
 613
 614         size_t bytes = bits / 8;
 615         bits %= 8;
 616         memcpy(a, b, bytes);
 617
 618         if (bits > 0) {
 619                 uint8_t mask = (1 << (8 - bits)) - 1;
 620                 a[bytes] = (a[bytes] & mask) | ((~mask) & b[bytes]);
 621         }
 622 }