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 = {
 157                 .msg_name = (void *) dest,
 158                 .msg_namelen = sizeof(*dest),
 159                 .msg_iov = iov,
 160                 .msg_iovlen = iov_len,
 161                 .msg_control = cmsg_buf,
 162                 .msg_controllen = sizeof(cmsg_buf),
 163                 .msg_flags = 0
 164         };
 165
 166         // Set control data (define destination interface)
 167         struct cmsghdr *chdr = CMSG_FIRSTHDR(&msg);
 168         chdr->cmsg_level = IPPROTO_IPV6;
 169         chdr->cmsg_type = IPV6_PKTINFO;
 170         chdr->cmsg_len = CMSG_LEN(sizeof(struct in6_pktinfo));
 171         struct in6_pktinfo *pktinfo = (struct in6_pktinfo*)CMSG_DATA(chdr);
 172         pktinfo->ipi6_ifindex = iface->ifindex;
 173
 174         // Also set scope ID if link-local
 175         if (IN6_IS_ADDR_LINKLOCAL(&dest->sin6_addr)
 176                         || IN6_IS_ADDR_MC_LINKLOCAL(&dest->sin6_addr))
 177                 dest->sin6_scope_id = iface->ifindex;
 178
 179         // IPV6_PKTINFO doesn't really work for IPv6-raw sockets (bug?)
 180         if (dest->sin6_port == 0) {
 181                 msg.msg_control = NULL;
 182                 msg.msg_controllen = 0;
 183         }
 184
 185         char ipbuf[INET6_ADDRSTRLEN];
 186         inet_ntop(AF_INET6, &dest->sin6_addr, ipbuf, sizeof(ipbuf));
 187
 188         ssize_t sent = sendmsg(socket, &msg, MSG_DONTWAIT);
 189         if (sent < 0)
 190                 syslog(LOG_NOTICE, "Failed to send to %s%%%s (%s)",
 191                                 ipbuf, iface->ifname, strerror(errno));
 192         else
 193                 syslog(LOG_DEBUG, "Sent %li bytes to %s%%%s",
 194                                 (long)sent, ipbuf, iface->ifname);
 195         return sent;
 196 }
 197
 198
 199 // Detect an IPV6-address currently assigned to the given interface
 200 ssize_t odhcpd_get_interface_addresses(int ifindex,
 201                 struct odhcpd_ipaddr *addrs, size_t cnt)
 202 {
 203         struct {
 204                 struct nlmsghdr nhm;
 205                 struct ifaddrmsg ifa;
 206         } req = {{sizeof(req), RTM_GETADDR, NLM_F_REQUEST | NLM_F_DUMP,
 207                         ++rtnl_seq, 0}, {AF_INET6, 0, 0, 0, ifindex}};
 208         if (send(rtnl_socket, &req, sizeof(req), 0) < (ssize_t)sizeof(req))
 209                 return 0;
 210
 211         uint8_t buf[8192];
 212         ssize_t len = 0, ret = 0;
 213
 214         for (struct nlmsghdr *nhm = NULL; ; nhm = NLMSG_NEXT(nhm, len)) {
 215                 while (len < 0 || !NLMSG_OK(nhm, (size_t)len)) {
 216                         len = recv(rtnl_socket, buf, sizeof(buf), 0);
 217                         nhm = (struct nlmsghdr*)buf;
 218                         if (len < 0 || !NLMSG_OK(nhm, (size_t)len)) {
 219                                 if (errno == EINTR)
 220                                         continue;
 221                                 else
 222                                         return ret;
 223                         }
 224                 }
 225
 226                 if (nhm->nlmsg_type != RTM_NEWADDR)
 227                         break;
 228
 229                 // Skip address but keep clearing socket buffer
 230                 if (ret >= (ssize_t)cnt)
 231                         continue;
 232
 233                 struct ifaddrmsg *ifa = NLMSG_DATA(nhm);
 234                 if (ifa->ifa_scope != RT_SCOPE_UNIVERSE ||
 235                                 (ifindex && ifa->ifa_index != (unsigned)ifindex))
 236                         continue;
 237
 238                 struct rtattr *rta = (struct rtattr*)&ifa[1];
 239                 size_t alen = NLMSG_PAYLOAD(nhm, sizeof(*ifa));
 240                 memset(&addrs[ret], 0, sizeof(addrs[ret]));
 241                 addrs[ret].prefix = ifa->ifa_prefixlen;
 242
 243                 while (RTA_OK(rta, alen)) {
 244                         if (rta->rta_type == IFA_ADDRESS) {
 245                                 memcpy(&addrs[ret].addr, RTA_DATA(rta),
 246                                                 sizeof(struct in6_addr));
 247                         } else if (rta->rta_type == IFA_CACHEINFO) {
 248                                 struct ifa_cacheinfo *ifc = RTA_DATA(rta);
 249                                 addrs[ret].preferred = ifc->ifa_prefered;
 250                                 addrs[ret].valid = ifc->ifa_valid;
 251                         }
 252
 253                         rta = RTA_NEXT(rta, alen);
 254                 }
 255
 256                 if (ifa->ifa_flags & IFA_F_DEPRECATED)
 257                         addrs[ret].preferred = 0;
 258
 259                 ++ret;
 260         }
 261
 262         return ret;
 263 }
 264
 265 int odhcpd_get_preferred_interface_address(int ifindex, struct in6_addr *addr)
 266 {
 267         struct odhcpd_ipaddr ipaddrs[8];
 268         ssize_t ip_cnt = odhcpd_get_interface_addresses(ifindex, ipaddrs, ARRAY_SIZE(ipaddrs));
 269         uint32_t preferred = 0;
 270         int ret = 0;
 271
 272         for (ssize_t i = 0; i < ip_cnt; i++) {
 273                 struct odhcpd_ipaddr *ipaddr = &ipaddrs[i];
 274
 275                 if (ipaddr->preferred > preferred || !preferred) {
 276                         preferred = ipaddr->preferred;
 277                         *addr = ipaddr->addr;
 278                         ret = 1;
 279                 }
 280         }
 281
 282         return ret;
 283 }
 284
 285 struct interface* odhcpd_get_interface_by_index(int ifindex)
 286 {
 287         struct interface *iface;
 288         list_for_each_entry(iface, &interfaces, head)
 289                 if (iface->ifindex == ifindex)
 290                         return iface;
 291
 292         return NULL;
 293 }
 294
 295
 296 struct interface* odhcpd_get_interface_by_name(const char *name)
 297 {
 298         struct interface *iface;
 299         list_for_each_entry(iface, &interfaces, head)
 300                 if (!strcmp(iface->ifname, name))
 301                         return iface;
 302
 303         return NULL;
 304 }
 305
 306
 307 struct interface* odhcpd_get_master_interface(void)
 308 {
 309         struct interface *iface;
 310         list_for_each_entry(iface, &interfaces, head)
 311                 if (iface->master)
 312                         return iface;
 313
 314         return NULL;
 315 }
 316
 317
 318 // Convenience function to receive and do basic validation of packets
 319 static void odhcpd_receive_packets(struct uloop_fd *u, _unused unsigned int events)
 320 {
 321         struct odhcpd_event *e = container_of(u, struct odhcpd_event, uloop);
 322
 323         uint8_t data_buf[RELAYD_BUFFER_SIZE], cmsg_buf[128];
 324         union {
 325                 struct sockaddr_in6 in6;
 326                 struct sockaddr_in in;
 327                 struct sockaddr_ll ll;
 328                 struct sockaddr_nl nl;
 329         } addr;
 330
 331         while (true) {
 332                 struct iovec iov = {data_buf, sizeof(data_buf)};
 333                 struct msghdr msg = {
 334                         .msg_name = (void *) &addr,
 335                         .msg_namelen = sizeof(addr),
 336                         .msg_iov = &iov,
 337                         .msg_iovlen = 1,
 338                         .msg_control = cmsg_buf,
 339                         .msg_controllen = sizeof(cmsg_buf),
 340                         .msg_flags = 0
 341                 };
 342
 343                 ssize_t len = recvmsg(u->fd, &msg, MSG_DONTWAIT);
 344                 if (len < 0) {
 345                         if (errno == EAGAIN)
 346                                 break;
 347                         else
 348                                 continue;
 349                 }
 350
 351
 352                 // Extract destination interface
 353                 int destiface = 0;
 354                 int *hlim = NULL;
 355                 void *dest = NULL;
 356                 struct in6_pktinfo *pktinfo;
 357                 struct in_pktinfo *pkt4info;
 358                 for (struct cmsghdr *ch = CMSG_FIRSTHDR(&msg); ch != NULL; ch = CMSG_NXTHDR(&msg, ch)) {
 359                         if (ch->cmsg_level == IPPROTO_IPV6 &&
 360                                         ch->cmsg_type == IPV6_PKTINFO) {
 361                                 pktinfo = (struct in6_pktinfo*)CMSG_DATA(ch);
 362                                 destiface = pktinfo->ipi6_ifindex;
 363                                 dest = &pktinfo->ipi6_addr;
 364                         } else if (ch->cmsg_level == IPPROTO_IP &&
 365                                         ch->cmsg_type == IP_PKTINFO) {
 366                                 pkt4info = (struct in_pktinfo*)CMSG_DATA(ch);
 367                                 destiface = pkt4info->ipi_ifindex;
 368                                 dest = &pkt4info->ipi_addr;
 369                         } else if (ch->cmsg_level == IPPROTO_IPV6 &&
 370                                         ch->cmsg_type == IPV6_HOPLIMIT) {
 371                                 hlim = (int*)CMSG_DATA(ch);
 372                         }
 373                 }
 374
 375                 // Check hoplimit if received
 376                 if (hlim && *hlim != 255)
 377                         continue;
 378
 379                 // Detect interface for packet sockets
 380                 if (addr.ll.sll_family == AF_PACKET)
 381                         destiface = addr.ll.sll_ifindex;
 382
 383                 struct interface *iface =
 384                                 odhcpd_get_interface_by_index(destiface);
 385
 386                 if (!iface && addr.nl.nl_family != AF_NETLINK)
 387                         continue;
 388
 389                 char ipbuf[INET6_ADDRSTRLEN] = "kernel";
 390                 if (addr.ll.sll_family == AF_PACKET &&
 391                                 len >= (ssize_t)sizeof(struct ip6_hdr))
 392                         inet_ntop(AF_INET6, &data_buf[8], ipbuf, sizeof(ipbuf));
 393                 else if (addr.in6.sin6_family == AF_INET6)
 394                         inet_ntop(AF_INET6, &addr.in6.sin6_addr, ipbuf, sizeof(ipbuf));
 395                 else if (addr.in.sin_family == AF_INET)
 396                         inet_ntop(AF_INET, &addr.in.sin_addr, ipbuf, sizeof(ipbuf));
 397
 398                 syslog(LOG_DEBUG, "--");
 399                 syslog(LOG_DEBUG, "Received %li Bytes from %s%%%s", (long)len,
 400                                 ipbuf, (iface) ? iface->ifname : "netlink");
 401
 402                 e->handle_dgram(&addr, data_buf, len, iface, dest);
 403         }
 404 }
 405
 406 // Register events for the multiplexer
 407 int odhcpd_register(struct odhcpd_event *event)
 408 {
 409         event->uloop.cb = odhcpd_receive_packets;
 410         return uloop_fd_add(&event->uloop, ULOOP_READ);
 411 }
 412
 413 void odhcpd_process(struct odhcpd_event *event)
 414 {
 415         odhcpd_receive_packets(&event->uloop, 0);
 416 }
 417
 418 int odhcpd_urandom(void *data, size_t len)
 419 {
 420         return read(urandom_fd, data, len);
 421 }
 422
 423
 424 time_t odhcpd_time(void)
 425 {
 426         struct timespec ts;
 427         syscall(SYS_clock_gettime, CLOCK_MONOTONIC, &ts);
 428         return ts.tv_sec;
 429 }
 430
 431
 432 static const char hexdigits[] = "0123456789abcdef";
 433 static const int8_t hexvals[] = {
 434     -1, -1, -1, -1, -1, -1, -1, -1, -1, -2, -2, -1, -1, -2, -1, -1,
 435     -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 436     -2, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 437      0,  1,  2,  3,  4,  5,  6,  7,  8,  9, -1, -1, -1, -1, -1, -1,
 438     -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 439     -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 440     -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 441     -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 442 };
 443
 444 ssize_t odhcpd_unhexlify(uint8_t *dst, size_t len, const char *src)
 445 {
 446         size_t c;
 447         for (c = 0; c < len && src[0] && src[1]; ++c) {
 448                 int8_t x = (int8_t)*src++;
 449                 int8_t y = (int8_t)*src++;
 450                 if (x < 0 || (x = hexvals[x]) < 0
 451                                 || y < 0 || (y = hexvals[y]) < 0)
 452                         return -1;
 453                 dst[c] = x << 4 | y;
 454                 while (((int8_t)*src) < 0 ||
 455                                 (*src && hexvals[(uint8_t)*src] < 0))
 456                         src++;
 457         }
 458
 459         return c;
 460 }
 461
 462
 463 void odhcpd_hexlify(char *dst, const uint8_t *src, size_t len)
 464 {
 465         for (size_t i = 0; i < len; ++i) {
 466                 *dst++ = hexdigits[src[i] >> 4];
 467                 *dst++ = hexdigits[src[i] & 0x0f];
 468         }
 469         *dst = 0;
 470 }
 471
 472
 473 int odhcpd_bmemcmp(const void *av, const void *bv, size_t bits)
 474 {
 475         const uint8_t *a = av, *b = bv;
 476         size_t bytes = bits / 8;
 477         bits %= 8;
 478
 479         int res = memcmp(a, b, bytes);
 480         if (res == 0 && bits > 0)
 481                 res = (a[bytes] >> (8 - bits)) - (b[bytes] >> (8 - bits));
 482
 483         return res;
 484 }
 485
 486
 487 void odhcpd_bmemcpy(void *av, const void *bv, size_t bits)
 488 {
 489         uint8_t *a = av;
 490         const uint8_t *b = bv;
 491
 492         size_t bytes = bits / 8;
 493         bits %= 8;
 494         memcpy(a, b, bytes);
 495
 496         if (bits > 0) {
 497                 uint8_t mask = (1 << (8 - bits)) - 1;
 498                 a[bytes] = (a[bytes] & mask) | ((~mask) & b[bytes]);
 499         }
 500 }