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         // IPV6_PKTINFO doesn't really work for IPv6-raw sockets (bug?)
 178         if (dest->sin6_port == 0) {
 179                 msg.msg_control = NULL;
 180                 msg.msg_controllen = 0;
 181         }
 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 int odhcpd_iterate_interface_neighbors(const struct interface *iface,
 198                 void(*cb_neigh)(const struct in6_addr *addr,
 199                                 const struct interface *iface, void *data), void *data)
 200 {
 201         struct {
 202                 struct nlmsghdr nhm;
 203                 struct ndmsg ndm;
 204         } req = {{sizeof(req), RTM_GETNEIGH, NLM_F_REQUEST | NLM_F_DUMP,
 205                         ++rtnl_seq, 0}, {AF_INET6, 0, 0, iface->ifindex, 0, 0, 0}};
 206
 207         if (send(rtnl_socket, &req, sizeof(req), 0) < (ssize_t)sizeof(req))
 208                 return -1;
 209
 210         uint8_t buf[8192];
 211         ssize_t len = 0;
 212
 213         for (struct nlmsghdr *nhm = NULL; ; nhm = NLMSG_NEXT(nhm, len)) {
 214                 while (len < 0 || !NLMSG_OK(nhm, (size_t)len)) {
 215                         len = recv(rtnl_socket, buf, sizeof(buf), 0);
 216                         nhm = (struct nlmsghdr*)buf;
 217                         if (len < 0 || !NLMSG_OK(nhm, (size_t)len)) {
 218                                 if (errno == EINTR)
 219                                         continue;
 220                                 else
 221                                         return -1;
 222                         }
 223                 }
 224
 225                 if (nhm->nlmsg_type != RTM_NEWNEIGH)
 226                         break;
 227
 228                 struct ndmsg *ndm = NLMSG_DATA(nhm);
 229                 if (ndm->ndm_ifindex != iface->ifindex ||
 230                                 (ndm->ndm_state & NUD_FAILED))
 231                         continue;
 232
 233                 struct rtattr *rta = (struct rtattr*)&ndm[1];
 234                 size_t alen = NLMSG_PAYLOAD(nhm, sizeof(*ndm));
 235
 236                 while (RTA_OK(rta, alen)) {
 237                         if (rta->rta_type == NDA_DST &&
 238                                         RTA_PAYLOAD(rta) == sizeof(struct in6_addr)) {
 239                                 cb_neigh(RTA_DATA(rta), iface, data);
 240                                 break;
 241                         } else {
 242                                 rta = RTA_NEXT(rta, alen);
 243                         }
 244                 }
 245
 246         }
 247
 248         return 0;
 249 }
 250
 251
 252 // Detect an IPV6-address currently assigned to the given interface
 253 ssize_t odhcpd_get_interface_addresses(int ifindex,
 254                 struct odhcpd_ipaddr *addrs, size_t cnt)
 255 {
 256         struct {
 257                 struct nlmsghdr nhm;
 258                 struct ifaddrmsg ifa;
 259         } req = {{sizeof(req), RTM_GETADDR, NLM_F_REQUEST | NLM_F_DUMP,
 260                         ++rtnl_seq, 0}, {AF_INET6, 0, 0, 0, ifindex}};
 261         if (send(rtnl_socket, &req, sizeof(req), 0) < (ssize_t)sizeof(req))
 262                 return 0;
 263
 264         uint8_t buf[8192];
 265         ssize_t len = 0, ret = 0;
 266
 267         for (struct nlmsghdr *nhm = NULL; ; nhm = NLMSG_NEXT(nhm, len)) {
 268                 while (len < 0 || !NLMSG_OK(nhm, (size_t)len)) {
 269                         len = recv(rtnl_socket, buf, sizeof(buf), 0);
 270                         nhm = (struct nlmsghdr*)buf;
 271                         if (len < 0 || !NLMSG_OK(nhm, (size_t)len)) {
 272                                 if (errno == EINTR)
 273                                         continue;
 274                                 else
 275                                         return ret;
 276                         }
 277                 }
 278
 279                 if (nhm->nlmsg_type != RTM_NEWADDR)
 280                         break;
 281
 282                 // Skip address but keep clearing socket buffer
 283                 if (ret >= (ssize_t)cnt)
 284                         continue;
 285
 286                 struct ifaddrmsg *ifa = NLMSG_DATA(nhm);
 287                 if (ifa->ifa_scope != RT_SCOPE_UNIVERSE ||
 288                                 (ifindex && ifa->ifa_index != (unsigned)ifindex))
 289                         continue;
 290
 291                 struct rtattr *rta = (struct rtattr*)&ifa[1];
 292                 size_t alen = NLMSG_PAYLOAD(nhm, sizeof(*ifa));
 293                 memset(&addrs[ret], 0, sizeof(addrs[ret]));
 294                 addrs[ret].prefix = ifa->ifa_prefixlen;
 295
 296                 while (RTA_OK(rta, alen)) {
 297                         if (rta->rta_type == IFA_ADDRESS) {
 298                                 memcpy(&addrs[ret].addr, RTA_DATA(rta),
 299                                                 sizeof(struct in6_addr));
 300                         } else if (rta->rta_type == IFA_CACHEINFO) {
 301                                 struct ifa_cacheinfo *ifc = RTA_DATA(rta);
 302                                 addrs[ret].preferred = ifc->ifa_prefered;
 303                                 addrs[ret].valid = ifc->ifa_valid;
 304                         }
 305
 306                         rta = RTA_NEXT(rta, alen);
 307                 }
 308
 309                 if (ifa->ifa_flags & IFA_F_DEPRECATED)
 310                         addrs[ret].preferred = 0;
 311
 312                 ++ret;
 313         }
 314
 315         return ret;
 316 }
 317
 318 int odhcpd_get_preferred_interface_address(int ifindex, struct in6_addr *addr)
 319 {
 320         struct odhcpd_ipaddr ipaddrs[8];
 321         ssize_t ip_cnt = odhcpd_get_interface_addresses(ifindex, ipaddrs, ARRAY_SIZE(ipaddrs));
 322         uint32_t preferred = 0;
 323         int ret = 0;
 324
 325         for (ssize_t i = 0; i < ip_cnt; i++) {
 326                 struct odhcpd_ipaddr *ipaddr = &ipaddrs[i];
 327
 328                 if (ipaddr->preferred > preferred || !preferred) {
 329                         preferred = ipaddr->preferred;
 330                         *addr = ipaddr->addr;
 331                         ret = 1;
 332                 }
 333         }
 334
 335         return ret;
 336 }
 337
 338 struct interface* odhcpd_get_interface_by_index(int ifindex)
 339 {
 340         struct interface *iface;
 341         list_for_each_entry(iface, &interfaces, head)
 342                 if (iface->ifindex == ifindex)
 343                         return iface;
 344
 345         return NULL;
 346 }
 347
 348
 349 struct interface* odhcpd_get_interface_by_name(const char *name)
 350 {
 351         struct interface *iface;
 352         list_for_each_entry(iface, &interfaces, head)
 353                 if (!strcmp(iface->ifname, name))
 354                         return iface;
 355
 356         return NULL;
 357 }
 358
 359
 360 struct interface* odhcpd_get_master_interface(void)
 361 {
 362         struct interface *iface;
 363         list_for_each_entry(iface, &interfaces, head)
 364                 if (iface->master)
 365                         return iface;
 366
 367         return NULL;
 368 }
 369
 370
 371 // Convenience function to receive and do basic validation of packets
 372 static void odhcpd_receive_packets(struct uloop_fd *u, _unused unsigned int events)
 373 {
 374         struct odhcpd_event *e = container_of(u, struct odhcpd_event, uloop);
 375
 376         uint8_t data_buf[RELAYD_BUFFER_SIZE], cmsg_buf[128];
 377         union {
 378                 struct sockaddr_in6 in6;
 379                 struct sockaddr_in in;
 380                 struct sockaddr_ll ll;
 381                 struct sockaddr_nl nl;
 382         } addr;
 383
 384         while (true) {
 385                 struct iovec iov = {data_buf, sizeof(data_buf)};
 386                 struct msghdr msg = {
 387                         .msg_name = (void *) &addr,
 388                         .msg_namelen = sizeof(addr),
 389                         .msg_iov = &iov,
 390                         .msg_iovlen = 1,
 391                         .msg_control = cmsg_buf,
 392                         .msg_controllen = sizeof(cmsg_buf),
 393                         .msg_flags = 0
 394                 };
 395
 396                 ssize_t len = recvmsg(u->fd, &msg, MSG_DONTWAIT);
 397                 if (len < 0) {
 398                         if (errno == EAGAIN)
 399                                 break;
 400                         else
 401                                 continue;
 402                 }
 403
 404
 405                 // Extract destination interface
 406                 int destiface = 0;
 407                 int *hlim = NULL;
 408                 void *dest = NULL;
 409                 struct in6_pktinfo *pktinfo;
 410                 struct in_pktinfo *pkt4info;
 411                 for (struct cmsghdr *ch = CMSG_FIRSTHDR(&msg); ch != NULL; ch = CMSG_NXTHDR(&msg, ch)) {
 412                         if (ch->cmsg_level == IPPROTO_IPV6 &&
 413                                         ch->cmsg_type == IPV6_PKTINFO) {
 414                                 pktinfo = (struct in6_pktinfo*)CMSG_DATA(ch);
 415                                 destiface = pktinfo->ipi6_ifindex;
 416                                 dest = &pktinfo->ipi6_addr;
 417                         } else if (ch->cmsg_level == IPPROTO_IP &&
 418                                         ch->cmsg_type == IP_PKTINFO) {
 419                                 pkt4info = (struct in_pktinfo*)CMSG_DATA(ch);
 420                                 destiface = pkt4info->ipi_ifindex;
 421                                 dest = &pkt4info->ipi_addr;
 422                         } else if (ch->cmsg_level == IPPROTO_IPV6 &&
 423                                         ch->cmsg_type == IPV6_HOPLIMIT) {
 424                                 hlim = (int*)CMSG_DATA(ch);
 425                         }
 426                 }
 427
 428                 // Check hoplimit if received
 429                 if (hlim && *hlim != 255)
 430                         continue;
 431
 432                 // Detect interface for packet sockets
 433                 if (addr.ll.sll_family == AF_PACKET)
 434                         destiface = addr.ll.sll_ifindex;
 435
 436                 struct interface *iface =
 437                                 odhcpd_get_interface_by_index(destiface);
 438
 439                 if (!iface && addr.nl.nl_family != AF_NETLINK)
 440                         continue;
 441
 442                 char ipbuf[INET6_ADDRSTRLEN] = "kernel";
 443                 if (addr.ll.sll_family == AF_PACKET &&
 444                                 len >= (ssize_t)sizeof(struct ip6_hdr))
 445                         inet_ntop(AF_INET6, &data_buf[8], ipbuf, sizeof(ipbuf));
 446                 else if (addr.in6.sin6_family == AF_INET6)
 447                         inet_ntop(AF_INET6, &addr.in6.sin6_addr, ipbuf, sizeof(ipbuf));
 448                 else if (addr.in.sin_family == AF_INET)
 449                         inet_ntop(AF_INET, &addr.in.sin_addr, ipbuf, sizeof(ipbuf));
 450
 451                 syslog(LOG_DEBUG, "--");
 452                 syslog(LOG_DEBUG, "Received %li Bytes from %s%%%s", (long)len,
 453                                 ipbuf, (iface) ? iface->ifname : "netlink");
 454
 455                 e->handle_dgram(&addr, data_buf, len, iface, dest);
 456         }
 457 }
 458
 459 // Register events for the multiplexer
 460 int odhcpd_register(struct odhcpd_event *event)
 461 {
 462         event->uloop.cb = odhcpd_receive_packets;
 463         return uloop_fd_add(&event->uloop, ULOOP_READ);
 464 }
 465
 466 void odhcpd_process(struct odhcpd_event *event)
 467 {
 468         odhcpd_receive_packets(&event->uloop, 0);
 469 }
 470
 471 int odhcpd_urandom(void *data, size_t len)
 472 {
 473         return read(urandom_fd, data, len);
 474 }
 475
 476
 477 time_t odhcpd_time(void)
 478 {
 479         struct timespec ts;
 480         syscall(SYS_clock_gettime, CLOCK_MONOTONIC, &ts);
 481         return ts.tv_sec;
 482 }
 483
 484
 485 static const char hexdigits[] = "0123456789abcdef";
 486 static const int8_t hexvals[] = {
 487     -1, -1, -1, -1, -1, -1, -1, -1, -1, -2, -2, -1, -1, -2, -1, -1,
 488     -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 489     -2, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 490      0,  1,  2,  3,  4,  5,  6,  7,  8,  9, -1, -1, -1, -1, -1, -1,
 491     -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 492     -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 493     -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 494     -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 495 };
 496
 497 ssize_t odhcpd_unhexlify(uint8_t *dst, size_t len, const char *src)
 498 {
 499         size_t c;
 500         for (c = 0; c < len && src[0] && src[1]; ++c) {
 501                 int8_t x = (int8_t)*src++;
 502                 int8_t y = (int8_t)*src++;
 503                 if (x < 0 || (x = hexvals[x]) < 0
 504                                 || y < 0 || (y = hexvals[y]) < 0)
 505                         return -1;
 506                 dst[c] = x << 4 | y;
 507                 while (((int8_t)*src) < 0 ||
 508                                 (*src && hexvals[(uint8_t)*src] < 0))
 509                         src++;
 510         }
 511
 512         return c;
 513 }
 514
 515
 516 void odhcpd_hexlify(char *dst, const uint8_t *src, size_t len)
 517 {
 518         for (size_t i = 0; i < len; ++i) {
 519                 *dst++ = hexdigits[src[i] >> 4];
 520                 *dst++ = hexdigits[src[i] & 0x0f];
 521         }
 522         *dst = 0;
 523 }
 524
 525
 526 int odhcpd_bmemcmp(const void *av, const void *bv, size_t bits)
 527 {
 528         const uint8_t *a = av, *b = bv;
 529         size_t bytes = bits / 8;
 530         bits %= 8;
 531
 532         int res = memcmp(a, b, bytes);
 533         if (res == 0 && bits > 0)
 534                 res = (a[bytes] >> (8 - bits)) - (b[bytes] >> (8 - bits));
 535
 536         return res;
 537 }
 538
 539
 540 void odhcpd_bmemcpy(void *av, const void *bv, size_t bits)
 541 {
 542         uint8_t *a = av;
 543         const uint8_t *b = bv;
 544
 545         size_t bytes = bits / 8;
 546         bits %= 8;
 547         memcpy(a, b, bytes);
 548
 549         if (bits > 0) {
 550                 uint8_t mask = (1 << (8 - bits)) - 1;
 551                 a[bytes] = (a[bytes] & mask) | ((~mask) & b[bytes]);
 552         }
 553 }