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_mtu(const char *ifname)
 117 {
 118         char buf[64];
 119         const char *sysctl_pattern = "/proc/sys/net/ipv6/conf/%s/mtu";
 120         snprintf(buf, sizeof(buf), sysctl_pattern, ifname);
 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
 130         buf[len] = 0;
 131         return atoi(buf);
 132
 133 }
 134
 135
 136 // Read IPv6 MAC for interface
 137 int odhcpd_get_mac(const struct interface *iface, uint8_t mac[6])
 138 {
 139         struct ifreq ifr;
 140         memset(&ifr, 0, sizeof(ifr));
 141         strncpy(ifr.ifr_name, iface->ifname, sizeof(ifr.ifr_name));
 142         if (ioctl(ioctl_sock, SIOCGIFHWADDR, &ifr) < 0)
 143                 return -1;
 144         memcpy(mac, ifr.ifr_hwaddr.sa_data, 6);
 145         return 0;
 146 }
 147
 148
 149 // Forwards a packet on a specific interface
 150 ssize_t odhcpd_send(int socket, struct sockaddr_in6 *dest,
 151                 struct iovec *iov, size_t iov_len,
 152                 const struct interface *iface)
 153 {
 154         // Construct headers
 155         uint8_t cmsg_buf[CMSG_SPACE(sizeof(struct in6_pktinfo))] = {0};
 156         struct msghdr msg = {(void*)dest, sizeof(*dest), iov, iov_len,
 157                                 cmsg_buf, sizeof(cmsg_buf), 0};
 158
 159         // Set control data (define destination interface)
 160         struct cmsghdr *chdr = CMSG_FIRSTHDR(&msg);
 161         chdr->cmsg_level = IPPROTO_IPV6;
 162         chdr->cmsg_type = IPV6_PKTINFO;
 163         chdr->cmsg_len = CMSG_LEN(sizeof(struct in6_pktinfo));
 164         struct in6_pktinfo *pktinfo = (struct in6_pktinfo*)CMSG_DATA(chdr);
 165         pktinfo->ipi6_ifindex = iface->ifindex;
 166
 167         // Also set scope ID if link-local
 168         if (IN6_IS_ADDR_LINKLOCAL(&dest->sin6_addr)
 169                         || IN6_IS_ADDR_MC_LINKLOCAL(&dest->sin6_addr))
 170                 dest->sin6_scope_id = iface->ifindex;
 171
 172         // IPV6_PKTINFO doesn't really work for IPv6-raw sockets (bug?)
 173         if (dest->sin6_port == 0) {
 174                 msg.msg_control = NULL;
 175                 msg.msg_controllen = 0;
 176         }
 177
 178         char ipbuf[INET6_ADDRSTRLEN];
 179         inet_ntop(AF_INET6, &dest->sin6_addr, ipbuf, sizeof(ipbuf));
 180
 181         ssize_t sent = sendmsg(socket, &msg, MSG_DONTWAIT);
 182         if (sent < 0)
 183                 syslog(LOG_NOTICE, "Failed to send to %s%%%s (%s)",
 184                                 ipbuf, iface->ifname, strerror(errno));
 185         else
 186                 syslog(LOG_DEBUG, "Sent %li bytes to %s%%%s",
 187                                 (long)sent, ipbuf, iface->ifname);
 188         return sent;
 189 }
 190
 191
 192 // Detect an IPV6-address currently assigned to the given interface
 193 ssize_t odhcpd_get_interface_addresses(int ifindex,
 194                 struct odhcpd_ipaddr *addrs, size_t cnt)
 195 {
 196         struct {
 197                 struct nlmsghdr nhm;
 198                 struct ifaddrmsg ifa;
 199         } req = {{sizeof(req), RTM_GETADDR, NLM_F_REQUEST | NLM_F_DUMP,
 200                         ++rtnl_seq, 0}, {AF_INET6, 0, 0, 0, ifindex}};
 201         if (send(rtnl_socket, &req, sizeof(req), 0) < (ssize_t)sizeof(req))
 202                 return 0;
 203
 204         uint8_t buf[8192];
 205         ssize_t len = 0, ret = 0;
 206
 207         for (struct nlmsghdr *nhm = NULL; ; nhm = NLMSG_NEXT(nhm, len)) {
 208                 while (len < 0 || !NLMSG_OK(nhm, (size_t)len)) {
 209                         len = recv(rtnl_socket, buf, sizeof(buf), 0);
 210                         nhm = (struct nlmsghdr*)buf;
 211                         if (len < 0 || !NLMSG_OK(nhm, (size_t)len)) {
 212                                 if (errno == EINTR)
 213                                         continue;
 214                                 else
 215                                         return ret;
 216                         }
 217                 }
 218
 219                 if (nhm->nlmsg_type != RTM_NEWADDR)
 220                         break;
 221
 222                 // Skip address but keep clearing socket buffer
 223                 if (ret >= (ssize_t)cnt)
 224                         continue;
 225
 226                 struct ifaddrmsg *ifa = NLMSG_DATA(nhm);
 227                 if (ifa->ifa_scope != RT_SCOPE_UNIVERSE ||
 228                                 (ifindex && ifa->ifa_index != (unsigned)ifindex))
 229                         continue;
 230
 231                 struct rtattr *rta = (struct rtattr*)&ifa[1];
 232                 size_t alen = NLMSG_PAYLOAD(nhm, sizeof(*ifa));
 233                 memset(&addrs[ret], 0, sizeof(addrs[ret]));
 234                 addrs[ret].prefix = ifa->ifa_prefixlen;
 235
 236                 while (RTA_OK(rta, alen)) {
 237                         if (rta->rta_type == IFA_ADDRESS) {
 238                                 memcpy(&addrs[ret].addr, RTA_DATA(rta),
 239                                                 sizeof(struct in6_addr));
 240                         } else if (rta->rta_type == IFA_CACHEINFO) {
 241                                 struct ifa_cacheinfo *ifc = RTA_DATA(rta);
 242                                 addrs[ret].preferred = ifc->ifa_prefered;
 243                                 addrs[ret].valid = ifc->ifa_valid;
 244                         }
 245
 246                         rta = RTA_NEXT(rta, alen);
 247                 }
 248
 249                 if (ifa->ifa_flags & IFA_F_DEPRECATED)
 250                         addrs[ret].preferred = 0;
 251
 252                 addrs[ret].has_class = false;
 253                 addrs[ret].class = 0;
 254 #ifdef WITH_UBUS
 255                 struct interface *iface = odhcpd_get_interface_by_index(ifindex);
 256                 if (iface)
 257                         addrs[ret].has_class = ubus_get_class(iface->ifname,
 258                                         &addrs[ret].addr, &addrs[ret].class);
 259 #endif
 260                 ++ret;
 261         }
 262
 263         return ret;
 264 }
 265
 266 int odhcpd_get_preferred_interface_address(int ifindex, struct in6_addr *addr)
 267 {
 268         struct odhcpd_ipaddr ipaddrs[8];
 269         ssize_t ip_cnt = odhcpd_get_interface_addresses(ifindex, ipaddrs, ARRAY_SIZE(ipaddrs));
 270         uint32_t preferred = 0;
 271         int ret = 0;
 272
 273         for (ssize_t i = 0; i < ip_cnt; i++) {
 274                 struct odhcpd_ipaddr *ipaddr = &ipaddrs[i];
 275
 276                 if (ipaddr->preferred > preferred || !preferred) {
 277                         preferred = ipaddr->preferred;
 278                         *addr = ipaddr->addr;
 279                         ret = 1;
 280                 }
 281         }
 282
 283         return ret;
 284 }
 285
 286 struct interface* odhcpd_get_interface_by_index(int ifindex)
 287 {
 288         struct interface *iface;
 289         list_for_each_entry(iface, &interfaces, head)
 290                 if (iface->ifindex == ifindex)
 291                         return iface;
 292
 293         return NULL;
 294 }
 295
 296
 297 struct interface* odhcpd_get_interface_by_name(const char *name)
 298 {
 299         struct interface *iface;
 300         list_for_each_entry(iface, &interfaces, head)
 301                 if (!strcmp(iface->ifname, name))
 302                         return iface;
 303
 304         return NULL;
 305 }
 306
 307
 308 struct interface* odhcpd_get_master_interface(void)
 309 {
 310         struct interface *iface;
 311         list_for_each_entry(iface, &interfaces, head)
 312                 if (iface->master)
 313                         return iface;
 314
 315         return NULL;
 316 }
 317
 318
 319 // Convenience function to receive and do basic validation of packets
 320 static void odhcpd_receive_packets(struct uloop_fd *u, _unused unsigned int events)
 321 {
 322         struct odhcpd_event *e = container_of(u, struct odhcpd_event, uloop);
 323
 324         uint8_t data_buf[RELAYD_BUFFER_SIZE], cmsg_buf[128];
 325         union {
 326                 struct sockaddr_in6 in6;
 327                 struct sockaddr_in in;
 328                 struct sockaddr_ll ll;
 329                 struct sockaddr_nl nl;
 330         } addr;
 331
 332         while (true) {
 333                 struct iovec iov = {data_buf, sizeof(data_buf)};
 334                 struct msghdr msg = {&addr, sizeof(addr), &iov, 1,
 335                                 cmsg_buf, sizeof(cmsg_buf), 0};
 336
 337                 ssize_t len = recvmsg(u->fd, &msg, MSG_DONTWAIT);
 338                 if (len < 0) {
 339                         if (errno == EAGAIN)
 340                                 break;
 341                         else
 342                                 continue;
 343                 }
 344
 345
 346                 // Extract destination interface
 347                 int destiface = 0;
 348                 int *hlim = NULL;
 349                 void *dest = NULL;
 350                 struct in6_pktinfo *pktinfo;
 351                 struct in_pktinfo *pkt4info;
 352                 for (struct cmsghdr *ch = CMSG_FIRSTHDR(&msg); ch != NULL; ch = CMSG_NXTHDR(&msg, ch)) {
 353                         if (ch->cmsg_level == IPPROTO_IPV6 &&
 354                                         ch->cmsg_type == IPV6_PKTINFO) {
 355                                 pktinfo = (struct in6_pktinfo*)CMSG_DATA(ch);
 356                                 destiface = pktinfo->ipi6_ifindex;
 357                                 dest = &pktinfo->ipi6_addr;
 358                         } else if (ch->cmsg_level == IPPROTO_IP &&
 359                                         ch->cmsg_type == IP_PKTINFO) {
 360                                 pkt4info = (struct in_pktinfo*)CMSG_DATA(ch);
 361                                 destiface = pkt4info->ipi_ifindex;
 362                                 dest = &pkt4info->ipi_addr;
 363                         } else if (ch->cmsg_level == IPPROTO_IPV6 &&
 364                                         ch->cmsg_type == IPV6_HOPLIMIT) {
 365                                 hlim = (int*)CMSG_DATA(ch);
 366                         }
 367                 }
 368
 369                 // Check hoplimit if received
 370                 if (hlim && *hlim != 255)
 371                         continue;
 372
 373                 // Detect interface for packet sockets
 374                 if (addr.ll.sll_family == AF_PACKET)
 375                         destiface = addr.ll.sll_ifindex;
 376
 377                 struct interface *iface =
 378                                 odhcpd_get_interface_by_index(destiface);
 379
 380                 if (!iface && addr.nl.nl_family != AF_NETLINK)
 381                         continue;
 382
 383                 char ipbuf[INET6_ADDRSTRLEN] = "kernel";
 384                 if (addr.ll.sll_family == AF_PACKET &&
 385                                 len >= (ssize_t)sizeof(struct ip6_hdr))
 386                         inet_ntop(AF_INET6, &data_buf[8], ipbuf, sizeof(ipbuf));
 387                 else if (addr.in6.sin6_family == AF_INET6)
 388                         inet_ntop(AF_INET6, &addr.in6.sin6_addr, ipbuf, sizeof(ipbuf));
 389                 else if (addr.in.sin_family == AF_INET)
 390                         inet_ntop(AF_INET, &addr.in.sin_addr, ipbuf, sizeof(ipbuf));
 391
 392                 syslog(LOG_DEBUG, "--");
 393                 syslog(LOG_DEBUG, "Received %li Bytes from %s%%%s", (long)len,
 394                                 ipbuf, (iface) ? iface->ifname : "netlink");
 395
 396                 e->handle_dgram(&addr, data_buf, len, iface, dest);
 397         }
 398 }
 399
 400 // Register events for the multiplexer
 401 int odhcpd_register(struct odhcpd_event *event)
 402 {
 403         event->uloop.cb = odhcpd_receive_packets;
 404         return uloop_fd_add(&event->uloop, ULOOP_READ);
 405 }
 406
 407 void odhcpd_process(struct odhcpd_event *event)
 408 {
 409         odhcpd_receive_packets(&event->uloop, 0);
 410 }
 411
 412 void odhcpd_urandom(void *data, size_t len)
 413 {
 414         read(urandom_fd, data, len);
 415 }
 416
 417
 418 time_t odhcpd_time(void)
 419 {
 420         struct timespec ts;
 421         syscall(SYS_clock_gettime, CLOCK_MONOTONIC, &ts);
 422         return ts.tv_sec;
 423 }
 424
 425
 426 static const char hexdigits[] = "0123456789abcdef";
 427 static const int8_t hexvals[] = {
 428     -1, -1, -1, -1, -1, -1, -1, -1, -1, -2, -2, -1, -1, -2, -1, -1,
 429     -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 430     -2, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 431      0,  1,  2,  3,  4,  5,  6,  7,  8,  9, -1, -1, -1, -1, -1, -1,
 432     -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 433     -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 434     -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 435     -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 436 };
 437
 438 ssize_t odhcpd_unhexlify(uint8_t *dst, size_t len, const char *src)
 439 {
 440         size_t c;
 441         for (c = 0; c < len && src[0] && src[1]; ++c) {
 442                 int8_t x = (int8_t)*src++;
 443                 int8_t y = (int8_t)*src++;
 444                 if (x < 0 || (x = hexvals[x]) < 0
 445                                 || y < 0 || (y = hexvals[y]) < 0)
 446                         return -1;
 447                 dst[c] = x << 4 | y;
 448                 while (((int8_t)*src) < 0 ||
 449                                 (*src && hexvals[(uint8_t)*src] < 0))
 450                         src++;
 451         }
 452
 453         return c;
 454 }
 455
 456
 457 void odhcpd_hexlify(char *dst, const uint8_t *src, size_t len)
 458 {
 459         for (size_t i = 0; i < len; ++i) {
 460                 *dst++ = hexdigits[src[i] >> 4];
 461                 *dst++ = hexdigits[src[i] & 0x0f];
 462         }
 463         *dst = 0;
 464 }
 465
 466
 467 int odhcpd_bmemcmp(const void *av, const void *bv, size_t bits)
 468 {
 469         const uint8_t *a = av, *b = bv;
 470         size_t bytes = bits / 8;
 471         bits %= 8;
 472
 473         int res = memcmp(a, b, bytes);
 474         if (res == 0 && bits > 0)
 475                 res = (a[bytes] >> (8 - bits)) - (b[bytes] >> (8 - bits));
 476
 477         return res;
 478 }
 479
 480
 481 void odhcpd_bmemcpy(void *av, const void *bv, size_t bits)
 482 {
 483         uint8_t *a = av;
 484         const uint8_t *b = bv;
 485
 486         size_t bytes = bits / 8;
 487         bits %= 8;
 488         memcpy(a, b, bytes);
 489
 490         if (bits > 0) {
 491                 uint8_t mask = (1 << (8 - bits)) - 1;
 492                 a[bytes] = (a[bytes] & mask) | ((~mask) & b[bytes]);
 493         }
 494 }