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
  58 int main()
  59 {
  60         openlog("odhcpd", LOG_PERROR | LOG_PID, LOG_DAEMON);
  61         setlogmask(LOG_UPTO(LOG_WARNING));
  62         uloop_init();
  63
  64         if (getuid() != 0) {
  65                 syslog(LOG_ERR, "Must be run as root!");
  66                 return 2;
  67         }
  68
  69         ioctl_sock = socket(AF_INET, SOCK_DGRAM | SOCK_CLOEXEC, 0);
  70
  71         if ((rtnl_socket = odhcpd_open_rtnl()) < 0) {
  72                 syslog(LOG_ERR, "Unable to open socket: %s", strerror(errno));
  73                 return 2;
  74         }
  75
  76         if ((urandom_fd = open("/dev/urandom", O_RDONLY | O_CLOEXEC)) < 0)
  77                 return 4;
  78
  79         signal(SIGUSR1, SIG_IGN);
  80         signal(SIGINT, sighandler);
  81         signal(SIGTERM, sighandler);
  82
  83         if (init_router())
  84                 return 4;
  85
  86         if (init_dhcpv6())
  87                 return 4;
  88
  89         if (init_ndp())
  90                 return 4;
  91
  92         if (init_dhcpv4())
  93                 return 4;
  94
  95         odhcpd_run();
  96         return 0;
  97 }
  98
  99 int odhcpd_open_rtnl(void)
 100 {
 101         int sock = socket(AF_NETLINK, SOCK_RAW | SOCK_CLOEXEC, NETLINK_ROUTE);
 102
 103         // Connect to the kernel netlink interface
 104         struct sockaddr_nl nl = {.nl_family = AF_NETLINK};
 105         if (connect(sock, (struct sockaddr*)&nl, sizeof(nl))) {
 106                 syslog(LOG_ERR, "Failed to connect to kernel rtnetlink: %s",
 107                                 strerror(errno));
 108                 return -1;
 109         }
 110
 111         return sock;
 112 }
 113
 114
 115 // Read IPv6 MTU for interface
 116 int odhcpd_get_interface_config(const char *ifname, const char *what)
 117 {
 118         char buf[64];
 119         const char *sysctl_pattern = "/proc/sys/net/ipv6/conf/%s/%s";
 120         snprintf(buf, sizeof(buf), sysctl_pattern, ifname, what);
 121
 122         int fd = open(buf, O_RDONLY);
 123         ssize_t len = read(fd, buf, sizeof(buf) - 1);
 124         close(fd);
 125
 126         if (len < 0)
 127                 return -1;
 128
 129         buf[len] = 0;
 130         return atoi(buf);
 131 }
 132
 133
 134 // Read IPv6 MAC for interface
 135 int odhcpd_get_mac(const struct interface *iface, uint8_t mac[6])
 136 {
 137         struct ifreq ifr;
 138         memset(&ifr, 0, sizeof(ifr));
 139         strncpy(ifr.ifr_name, iface->ifname, sizeof(ifr.ifr_name));
 140         if (ioctl(ioctl_sock, SIOCGIFHWADDR, &ifr) < 0)
 141                 return -1;
 142         memcpy(mac, ifr.ifr_hwaddr.sa_data, 6);
 143         return 0;
 144 }
 145
 146
 147 // Forwards a packet on a specific interface
 148 ssize_t odhcpd_send(int socket, struct sockaddr_in6 *dest,
 149                 struct iovec *iov, size_t iov_len,
 150                 const struct interface *iface)
 151 {
 152         // Construct headers
 153         uint8_t cmsg_buf[CMSG_SPACE(sizeof(struct in6_pktinfo))] = {0};
 154         struct msghdr msg = {
 155                 .msg_name = (void *) dest,
 156                 .msg_namelen = sizeof(*dest),
 157                 .msg_iov = iov,
 158                 .msg_iovlen = iov_len,
 159                 .msg_control = cmsg_buf,
 160                 .msg_controllen = sizeof(cmsg_buf),
 161                 .msg_flags = 0
 162         };
 163
 164         // Set control data (define destination interface)
 165         struct cmsghdr *chdr = CMSG_FIRSTHDR(&msg);
 166         chdr->cmsg_level = IPPROTO_IPV6;
 167         chdr->cmsg_type = IPV6_PKTINFO;
 168         chdr->cmsg_len = CMSG_LEN(sizeof(struct in6_pktinfo));
 169         struct in6_pktinfo *pktinfo = (struct in6_pktinfo*)CMSG_DATA(chdr);
 170         pktinfo->ipi6_ifindex = iface->ifindex;
 171
 172         // Also set scope ID if link-local
 173         if (IN6_IS_ADDR_LINKLOCAL(&dest->sin6_addr)
 174                         || IN6_IS_ADDR_MC_LINKLOCAL(&dest->sin6_addr))
 175                 dest->sin6_scope_id = iface->ifindex;
 176
 177         char ipbuf[INET6_ADDRSTRLEN];
 178         inet_ntop(AF_INET6, &dest->sin6_addr, ipbuf, sizeof(ipbuf));
 179
 180         ssize_t sent = sendmsg(socket, &msg, MSG_DONTWAIT);
 181         if (sent < 0)
 182                 syslog(LOG_NOTICE, "Failed to send to %s%%%s (%s)",
 183                                 ipbuf, iface->ifname, strerror(errno));
 184         else
 185                 syslog(LOG_DEBUG, "Sent %li bytes to %s%%%s",
 186                                 (long)sent, ipbuf, iface->ifname);
 187         return sent;
 188 }
 189
 190
 191 // Detect an IPV6-address currently assigned to the given interface
 192 ssize_t odhcpd_get_interface_addresses(int ifindex,
 193                 struct odhcpd_ipaddr *addrs, size_t cnt)
 194 {
 195         struct {
 196                 struct nlmsghdr nhm;
 197                 struct ifaddrmsg ifa;
 198         } req = {{sizeof(req), RTM_GETADDR, NLM_F_REQUEST | NLM_F_DUMP,
 199                         ++rtnl_seq, 0}, {AF_INET6, 0, 0, 0, ifindex}};
 200         if (send(rtnl_socket, &req, sizeof(req), 0) < (ssize_t)sizeof(req))
 201                 return 0;
 202
 203         uint8_t buf[8192];
 204         ssize_t len = 0, ret = 0;
 205
 206         for (struct nlmsghdr *nhm = NULL; ; nhm = NLMSG_NEXT(nhm, len)) {
 207                 while (len < 0 || !NLMSG_OK(nhm, (size_t)len)) {
 208                         len = recv(rtnl_socket, buf, sizeof(buf), 0);
 209                         nhm = (struct nlmsghdr*)buf;
 210                         if (len < 0 || !NLMSG_OK(nhm, (size_t)len)) {
 211                                 if (errno == EINTR)
 212                                         continue;
 213                                 else
 214                                         return ret;
 215                         }
 216                 }
 217
 218                 if (nhm->nlmsg_type != RTM_NEWADDR)
 219                         break;
 220
 221                 // Skip address but keep clearing socket buffer
 222                 if (ret >= (ssize_t)cnt)
 223                         continue;
 224
 225                 struct ifaddrmsg *ifa = NLMSG_DATA(nhm);
 226                 if (ifa->ifa_scope != RT_SCOPE_UNIVERSE ||
 227                                 (ifindex && ifa->ifa_index != (unsigned)ifindex))
 228                         continue;
 229
 230                 struct rtattr *rta = (struct rtattr*)&ifa[1];
 231                 size_t alen = NLMSG_PAYLOAD(nhm, sizeof(*ifa));
 232                 memset(&addrs[ret], 0, sizeof(addrs[ret]));
 233                 addrs[ret].prefix = ifa->ifa_prefixlen;
 234
 235                 while (RTA_OK(rta, alen)) {
 236                         if (rta->rta_type == IFA_ADDRESS) {
 237                                 memcpy(&addrs[ret].addr, RTA_DATA(rta),
 238                                                 sizeof(struct in6_addr));
 239                         } else if (rta->rta_type == IFA_CACHEINFO) {
 240                                 struct ifa_cacheinfo *ifc = RTA_DATA(rta);
 241                                 addrs[ret].preferred = ifc->ifa_prefered;
 242                                 addrs[ret].valid = ifc->ifa_valid;
 243                         }
 244
 245                         rta = RTA_NEXT(rta, alen);
 246                 }
 247
 248                 if (ifa->ifa_flags & IFA_F_DEPRECATED)
 249                         addrs[ret].preferred = 0;
 250
 251                 ++ret;
 252         }
 253
 254         return ret;
 255 }
 256
 257 int odhcpd_get_linklocal_interface_address(int ifindex, struct in6_addr *lladdr)
 258 {
 259                 int status = -1;
 260                 struct sockaddr_in6 addr = {AF_INET6, 0, 0, ALL_IPV6_ROUTERS, ifindex};
 261                 socklen_t alen = sizeof(addr);
 262                 int sock = socket(AF_INET6, SOCK_RAW, IPPROTO_ICMPV6);
 263
 264                 if (!connect(sock, (struct sockaddr*)&addr, sizeof(addr)) &&
 265                                 !getsockname(sock, (struct sockaddr*)&addr, &alen)) {
 266                         *lladdr = addr.sin6_addr;
 267                         status = 0;
 268                 }
 269
 270                 close(sock);
 271                 return status;
 272 }
 273
 274 void odhcpd_setup_route(const struct in6_addr *addr, int prefixlen,
 275                 const struct interface *iface, const struct in6_addr *gw,
 276                 int metric, bool add)
 277 {
 278         struct req {
 279                 struct nlmsghdr nh;
 280                 struct rtmsg rtm;
 281                 struct rtattr rta_dst;
 282                 struct in6_addr dst_addr;
 283                 struct rtattr rta_oif;
 284                 uint32_t ifindex;
 285                 struct rtattr rta_table;
 286                 uint32_t table;
 287                 struct rtattr rta_prio;
 288                 uint32_t prio;
 289                 struct rtattr rta_gw;
 290                 struct in6_addr gw;
 291         } req = {
 292                 {sizeof(req), 0, NLM_F_REQUEST, ++rtnl_seq, 0},
 293                 {AF_INET6, prefixlen, 0, 0, 0, 0, 0, 0, 0},
 294                 {sizeof(struct rtattr) + sizeof(struct in6_addr), RTA_DST},
 295                 *addr,
 296                 {sizeof(struct rtattr) + sizeof(uint32_t), RTA_OIF},
 297                 iface->ifindex,
 298                 {sizeof(struct rtattr) + sizeof(uint32_t), RTA_TABLE},
 299                 RT_TABLE_MAIN,
 300                 {sizeof(struct rtattr) + sizeof(uint32_t), RTA_PRIORITY},
 301                 metric,
 302                 {sizeof(struct rtattr) + sizeof(struct in6_addr), RTA_GATEWAY},
 303                 IN6ADDR_ANY_INIT,
 304         };
 305
 306         if (gw)
 307                 req.gw = *gw;
 308
 309         if (add) {
 310                 req.nh.nlmsg_type = RTM_NEWROUTE;
 311                 req.nh.nlmsg_flags |= (NLM_F_CREATE | NLM_F_REPLACE);
 312                 req.rtm.rtm_protocol = RTPROT_STATIC;
 313                 req.rtm.rtm_scope = (gw) ? RT_SCOPE_UNIVERSE : RT_SCOPE_LINK;
 314                 req.rtm.rtm_type = RTN_UNICAST;
 315         } else {
 316                 req.nh.nlmsg_type = RTM_DELROUTE;
 317                 req.rtm.rtm_scope = RT_SCOPE_NOWHERE;
 318         }
 319
 320         req.nh.nlmsg_len = (gw) ? sizeof(req) : offsetof(struct req, rta_gw);
 321         send(rtnl_socket, &req, req.nh.nlmsg_len, MSG_DONTWAIT);
 322 }
 323
 324 struct interface* odhcpd_get_interface_by_index(int ifindex)
 325 {
 326         struct interface *iface;
 327         list_for_each_entry(iface, &interfaces, head)
 328                 if (iface->ifindex == ifindex)
 329                         return iface;
 330
 331         return NULL;
 332 }
 333
 334
 335 struct interface* odhcpd_get_interface_by_name(const char *name)
 336 {
 337         struct interface *iface;
 338         list_for_each_entry(iface, &interfaces, head)
 339                 if (!strcmp(iface->ifname, name))
 340                         return iface;
 341
 342         return NULL;
 343 }
 344
 345
 346 struct interface* odhcpd_get_master_interface(void)
 347 {
 348         struct interface *iface;
 349         list_for_each_entry(iface, &interfaces, head)
 350                 if (iface->master)
 351                         return iface;
 352
 353         return NULL;
 354 }
 355
 356
 357 // Convenience function to receive and do basic validation of packets
 358 static void odhcpd_receive_packets(struct uloop_fd *u, _unused unsigned int events)
 359 {
 360         struct odhcpd_event *e = container_of(u, struct odhcpd_event, uloop);
 361
 362         uint8_t data_buf[RELAYD_BUFFER_SIZE], cmsg_buf[128];
 363         union {
 364                 struct sockaddr_in6 in6;
 365                 struct sockaddr_in in;
 366                 struct sockaddr_ll ll;
 367                 struct sockaddr_nl nl;
 368         } addr;
 369
 370         if (u->error) {
 371                 int ret = -1;
 372                 socklen_t ret_len = sizeof(ret);
 373                 getsockopt(u->fd, SOL_SOCKET, SO_ERROR, &ret, &ret_len);
 374                 u->error = false;
 375                 if (e->handle_error)
 376                         e->handle_error(ret);
 377         }
 378
 379         while (true) {
 380                 struct iovec iov = {data_buf, sizeof(data_buf)};
 381                 struct msghdr msg = {
 382                         .msg_name = (void *) &addr,
 383                         .msg_namelen = sizeof(addr),
 384                         .msg_iov = &iov,
 385                         .msg_iovlen = 1,
 386                         .msg_control = cmsg_buf,
 387                         .msg_controllen = sizeof(cmsg_buf),
 388                         .msg_flags = 0
 389                 };
 390
 391                 ssize_t len = recvmsg(u->fd, &msg, MSG_DONTWAIT);
 392                 if (len < 0) {
 393                         if (errno == EAGAIN)
 394                                 break;
 395                         else
 396                                 continue;
 397                 }
 398
 399
 400                 // Extract destination interface
 401                 int destiface = 0;
 402                 int *hlim = NULL;
 403                 void *dest = NULL;
 404                 struct in6_pktinfo *pktinfo;
 405                 struct in_pktinfo *pkt4info;
 406                 for (struct cmsghdr *ch = CMSG_FIRSTHDR(&msg); ch != NULL; ch = CMSG_NXTHDR(&msg, ch)) {
 407                         if (ch->cmsg_level == IPPROTO_IPV6 &&
 408                                         ch->cmsg_type == IPV6_PKTINFO) {
 409                                 pktinfo = (struct in6_pktinfo*)CMSG_DATA(ch);
 410                                 destiface = pktinfo->ipi6_ifindex;
 411                                 dest = &pktinfo->ipi6_addr;
 412                         } else if (ch->cmsg_level == IPPROTO_IP &&
 413                                         ch->cmsg_type == IP_PKTINFO) {
 414                                 pkt4info = (struct in_pktinfo*)CMSG_DATA(ch);
 415                                 destiface = pkt4info->ipi_ifindex;
 416                                 dest = &pkt4info->ipi_addr;
 417                         } else if (ch->cmsg_level == IPPROTO_IPV6 &&
 418                                         ch->cmsg_type == IPV6_HOPLIMIT) {
 419                                 hlim = (int*)CMSG_DATA(ch);
 420                         }
 421                 }
 422
 423                 // Check hoplimit if received
 424                 if (hlim && *hlim != 255)
 425                         continue;
 426
 427                 // Detect interface for packet sockets
 428                 if (addr.ll.sll_family == AF_PACKET)
 429                         destiface = addr.ll.sll_ifindex;
 430
 431                 struct interface *iface =
 432                                 odhcpd_get_interface_by_index(destiface);
 433
 434                 if (!iface && addr.nl.nl_family != AF_NETLINK)
 435                         continue;
 436
 437                 char ipbuf[INET6_ADDRSTRLEN] = "kernel";
 438                 if (addr.ll.sll_family == AF_PACKET &&
 439                                 len >= (ssize_t)sizeof(struct ip6_hdr))
 440                         inet_ntop(AF_INET6, &data_buf[8], ipbuf, sizeof(ipbuf));
 441                 else if (addr.in6.sin6_family == AF_INET6)
 442                         inet_ntop(AF_INET6, &addr.in6.sin6_addr, ipbuf, sizeof(ipbuf));
 443                 else if (addr.in.sin_family == AF_INET)
 444                         inet_ntop(AF_INET, &addr.in.sin_addr, ipbuf, sizeof(ipbuf));
 445
 446                 syslog(LOG_DEBUG, "Received %li Bytes from %s%%%s", (long)len,
 447                                 ipbuf, (iface) ? iface->ifname : "netlink");
 448
 449                 e->handle_dgram(&addr, data_buf, len, iface, dest);
 450         }
 451 }
 452
 453 // Register events for the multiplexer
 454 int odhcpd_register(struct odhcpd_event *event)
 455 {
 456         event->uloop.cb = odhcpd_receive_packets;
 457         return uloop_fd_add(&event->uloop, ULOOP_READ |
 458                         ((event->handle_error) ? ULOOP_ERROR_CB : 0));
 459 }
 460
 461 void odhcpd_process(struct odhcpd_event *event)
 462 {
 463         odhcpd_receive_packets(&event->uloop, 0);
 464 }
 465
 466 int odhcpd_urandom(void *data, size_t len)
 467 {
 468         return read(urandom_fd, data, len);
 469 }
 470
 471
 472 time_t odhcpd_time(void)
 473 {
 474         struct timespec ts;
 475         syscall(SYS_clock_gettime, CLOCK_MONOTONIC, &ts);
 476         return ts.tv_sec;
 477 }
 478
 479
 480 static const char hexdigits[] = "0123456789abcdef";
 481 static const int8_t hexvals[] = {
 482     -1, -1, -1, -1, -1, -1, -1, -1, -1, -2, -2, -1, -1, -2, -1, -1,
 483     -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 484     -2, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 485      0,  1,  2,  3,  4,  5,  6,  7,  8,  9, -1, -1, -1, -1, -1, -1,
 486     -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 487     -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 488     -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 489     -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 490 };
 491
 492 ssize_t odhcpd_unhexlify(uint8_t *dst, size_t len, const char *src)
 493 {
 494         size_t c;
 495         for (c = 0; c < len && src[0] && src[1]; ++c) {
 496                 int8_t x = (int8_t)*src++;
 497                 int8_t y = (int8_t)*src++;
 498                 if (x < 0 || (x = hexvals[x]) < 0
 499                                 || y < 0 || (y = hexvals[y]) < 0)
 500                         return -1;
 501                 dst[c] = x << 4 | y;
 502                 while (((int8_t)*src) < 0 ||
 503                                 (*src && hexvals[(uint8_t)*src] < 0))
 504                         src++;
 505         }
 506
 507         return c;
 508 }
 509
 510
 511 void odhcpd_hexlify(char *dst, const uint8_t *src, size_t len)
 512 {
 513         for (size_t i = 0; i < len; ++i) {
 514                 *dst++ = hexdigits[src[i] >> 4];
 515                 *dst++ = hexdigits[src[i] & 0x0f];
 516         }
 517         *dst = 0;
 518 }
 519
 520
 521 int odhcpd_bmemcmp(const void *av, const void *bv, size_t bits)
 522 {
 523         const uint8_t *a = av, *b = bv;
 524         size_t bytes = bits / 8;
 525         bits %= 8;
 526
 527         int res = memcmp(a, b, bytes);
 528         if (res == 0 && bits > 0)
 529                 res = (a[bytes] >> (8 - bits)) - (b[bytes] >> (8 - bits));
 530
 531         return res;
 532 }
 533
 534
 535 void odhcpd_bmemcpy(void *av, const void *bv, size_t bits)
 536 {
 537         uint8_t *a = av;
 538         const uint8_t *b = bv;
 539
 540         size_t bytes = bits / 8;
 541         bits %= 8;
 542         memcpy(a, b, bytes);
 543
 544         if (bits > 0) {
 545                 uint8_t mask = (1 << (8 - bits)) - 1;
 546                 a[bytes] = (a[bytes] & mask) | ((~mask) & b[bytes]);
 547         }
 548 }