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 int main()
  53 {
  54         openlog("odhcpd", LOG_PERROR | LOG_PID, LOG_DAEMON);
  55         uloop_init();
  56
  57         if (getuid() != 0) {
  58                 syslog(LOG_ERR, "Must be run as root!");
  59                 return 2;
  60         }
  61
  62         ioctl_sock = socket(AF_INET, SOCK_DGRAM | SOCK_CLOEXEC, 0);
  63
  64         if ((rtnl_socket = odhcpd_open_rtnl()) < 0) {
  65                 syslog(LOG_ERR, "Unable to open socket: %s", strerror(errno));
  66                 return 2;
  67         }
  68
  69         if ((urandom_fd = open("/dev/urandom", O_RDONLY | O_CLOEXEC)) < 0)
  70                 return 4;
  71
  72         signal(SIGUSR1, SIG_IGN);
  73
  74         if (init_router())
  75                 return 4;
  76
  77         if (init_dhcpv6())
  78                 return 4;
  79
  80         if (init_ndp())
  81                 return 4;
  82
  83         if (init_dhcpv4())
  84                 return 4;
  85
  86         odhcpd_run();
  87         return 0;
  88 }
  89
  90 int odhcpd_open_rtnl(void)
  91 {
  92         int sock = socket(AF_NETLINK, SOCK_RAW | SOCK_CLOEXEC, NETLINK_ROUTE);
  93
  94         // Connect to the kernel netlink interface
  95         struct sockaddr_nl nl = {.nl_family = AF_NETLINK};
  96         if (connect(sock, (struct sockaddr*)&nl, sizeof(nl))) {
  97                 syslog(LOG_ERR, "Failed to connect to kernel rtnetlink: %s",
  98                                 strerror(errno));
  99                 return -1;
 100         }
 101
 102         return sock;
 103 }
 104
 105
 106 // Read IPv6 MTU for interface
 107 int odhcpd_get_interface_mtu(const char *ifname)
 108 {
 109         char buf[64];
 110         const char *sysctl_pattern = "/proc/sys/net/ipv6/conf/%s/mtu";
 111         snprintf(buf, sizeof(buf), sysctl_pattern, ifname);
 112
 113         int fd = open(buf, O_RDONLY);
 114         ssize_t len = read(fd, buf, sizeof(buf) - 1);
 115         close(fd);
 116
 117         if (len < 0)
 118                 return -1;
 119
 120
 121         buf[len] = 0;
 122         return atoi(buf);
 123
 124 }
 125
 126
 127 // Read IPv6 MAC for interface
 128 int odhcpd_get_mac(const struct interface *iface, uint8_t mac[6])
 129 {
 130         struct ifreq ifr;
 131         memset(&ifr, 0, sizeof(ifr));
 132         strncpy(ifr.ifr_name, iface->ifname, sizeof(ifr.ifr_name));
 133         if (ioctl(ioctl_sock, SIOCGIFHWADDR, &ifr) < 0)
 134                 return -1;
 135         memcpy(mac, ifr.ifr_hwaddr.sa_data, 6);
 136         return 0;
 137 }
 138
 139
 140 // Forwards a packet on a specific interface
 141 ssize_t odhcpd_send(int socket, struct sockaddr_in6 *dest,
 142                 struct iovec *iov, size_t iov_len,
 143                 const struct interface *iface)
 144 {
 145         // Construct headers
 146         uint8_t cmsg_buf[CMSG_SPACE(sizeof(struct in6_pktinfo))] = {0};
 147         struct msghdr msg = {(void*)dest, sizeof(*dest), iov, iov_len,
 148                                 cmsg_buf, sizeof(cmsg_buf), 0};
 149
 150         // Set control data (define destination interface)
 151         struct cmsghdr *chdr = CMSG_FIRSTHDR(&msg);
 152         chdr->cmsg_level = IPPROTO_IPV6;
 153         chdr->cmsg_type = IPV6_PKTINFO;
 154         chdr->cmsg_len = CMSG_LEN(sizeof(struct in6_pktinfo));
 155         struct in6_pktinfo *pktinfo = (struct in6_pktinfo*)CMSG_DATA(chdr);
 156         pktinfo->ipi6_ifindex = iface->ifindex;
 157
 158         // Also set scope ID if link-local
 159         if (IN6_IS_ADDR_LINKLOCAL(&dest->sin6_addr)
 160                         || IN6_IS_ADDR_MC_LINKLOCAL(&dest->sin6_addr))
 161                 dest->sin6_scope_id = iface->ifindex;
 162
 163         // IPV6_PKTINFO doesn't really work for IPv6-raw sockets (bug?)
 164         if (dest->sin6_port == 0) {
 165                 msg.msg_control = NULL;
 166                 msg.msg_controllen = 0;
 167         }
 168
 169         char ipbuf[INET6_ADDRSTRLEN];
 170         inet_ntop(AF_INET6, &dest->sin6_addr, ipbuf, sizeof(ipbuf));
 171
 172         ssize_t sent = sendmsg(socket, &msg, MSG_DONTWAIT);
 173         if (sent < 0)
 174                 syslog(LOG_WARNING, "Failed to send to %s%%%s (%s)",
 175                                 ipbuf, iface->ifname, strerror(errno));
 176         else
 177                 syslog(LOG_NOTICE, "Sent %li bytes to %s%%%s",
 178                                 (long)sent, ipbuf, iface->ifname);
 179         return sent;
 180 }
 181
 182
 183 // Detect an IPV6-address currently assigned to the given interface
 184 ssize_t odhcpd_get_interface_addresses(int ifindex,
 185                 struct odhcpd_ipaddr *addrs, size_t cnt)
 186 {
 187         struct {
 188                 struct nlmsghdr nhm;
 189                 struct ifaddrmsg ifa;
 190         } req = {{sizeof(req), RTM_GETADDR, NLM_F_REQUEST | NLM_F_DUMP,
 191                         ++rtnl_seq, 0}, {AF_INET6, 0, 0, 0, ifindex}};
 192         if (send(rtnl_socket, &req, sizeof(req), 0) < (ssize_t)sizeof(req))
 193                 return 0;
 194
 195         uint8_t buf[8192];
 196         ssize_t len = 0, ret = 0;
 197
 198         for (struct nlmsghdr *nhm = NULL; ; nhm = NLMSG_NEXT(nhm, len)) {
 199                 while (len < 0 || !NLMSG_OK(nhm, (size_t)len)) {
 200                         len = recv(rtnl_socket, buf, sizeof(buf), 0);
 201                         nhm = (struct nlmsghdr*)buf;
 202                         if (len < 0 || !NLMSG_OK(nhm, (size_t)len)) {
 203                                 if (errno == EINTR)
 204                                         continue;
 205                                 else
 206                                         return ret;
 207                         }
 208                 }
 209
 210                 if (nhm->nlmsg_type != RTM_NEWADDR)
 211                         break;
 212
 213                 // Skip address but keep clearing socket buffer
 214                 if (ret >= (ssize_t)cnt)
 215                         continue;
 216
 217                 struct ifaddrmsg *ifa = NLMSG_DATA(nhm);
 218                 if (ifa->ifa_scope != RT_SCOPE_UNIVERSE ||
 219                                 ifa->ifa_index != (unsigned)ifindex)
 220                         continue;
 221
 222                 struct rtattr *rta = (struct rtattr*)&ifa[1];
 223                 size_t alen = NLMSG_PAYLOAD(nhm, sizeof(*ifa));
 224                 memset(&addrs[ret], 0, sizeof(addrs[ret]));
 225                 addrs[ret].prefix = ifa->ifa_prefixlen;
 226
 227                 while (RTA_OK(rta, alen)) {
 228                         if (rta->rta_type == IFA_ADDRESS) {
 229                                 memcpy(&addrs[ret].addr, RTA_DATA(rta),
 230                                                 sizeof(struct in6_addr));
 231                         } else if (rta->rta_type == IFA_CACHEINFO) {
 232                                 struct ifa_cacheinfo *ifc = RTA_DATA(rta);
 233                                 addrs[ret].preferred = ifc->ifa_prefered;
 234                                 addrs[ret].valid = ifc->ifa_valid;
 235                         }
 236
 237                         rta = RTA_NEXT(rta, alen);
 238                 }
 239
 240                 if (ifa->ifa_flags & IFA_F_DEPRECATED)
 241                         addrs[ret].preferred = 0;
 242
 243                 ++ret;
 244         }
 245
 246         return ret;
 247 }
 248
 249
 250 struct interface* odhcpd_get_interface_by_index(int ifindex)
 251 {
 252         struct interface *iface;
 253         list_for_each_entry(iface, &interfaces, head)
 254                 if (iface->ifindex == ifindex)
 255                         return iface;
 256
 257         return NULL;
 258 }
 259
 260
 261 struct interface* odhcpd_get_interface_by_name(const char *name)
 262 {
 263         struct interface *iface;
 264         list_for_each_entry(iface, &interfaces, head)
 265                 if (!strcmp(iface->ifname, name))
 266                         return iface;
 267
 268         return NULL;
 269 }
 270
 271
 272 struct interface* odhcpd_get_master_interface(void)
 273 {
 274         struct interface *iface;
 275         list_for_each_entry(iface, &interfaces, head)
 276                 if (iface->master)
 277                         return iface;
 278
 279         return NULL;
 280 }
 281
 282
 283 // Convenience function to receive and do basic validation of packets
 284 static void odhcpd_receive_packets(struct uloop_fd *u, _unused unsigned int events)
 285 {
 286         struct odhcpd_event *e = container_of(u, struct odhcpd_event, uloop);
 287
 288         uint8_t data_buf[RELAYD_BUFFER_SIZE], cmsg_buf[128];
 289         union {
 290                 struct sockaddr_in6 in6;
 291                 struct sockaddr_in in;
 292                 struct sockaddr_ll ll;
 293                 struct sockaddr_nl nl;
 294         } addr;
 295
 296         while (true) {
 297                 struct iovec iov = {data_buf, sizeof(data_buf)};
 298                 struct msghdr msg = {&addr, sizeof(addr), &iov, 1,
 299                                 cmsg_buf, sizeof(cmsg_buf), 0};
 300
 301                 ssize_t len = recvmsg(u->fd, &msg, MSG_DONTWAIT);
 302                 if (len < 0) {
 303                         if (errno == EAGAIN)
 304                                 break;
 305                         else
 306                                 continue;
 307                 }
 308
 309
 310                 // Extract destination interface
 311                 int destiface = 0;
 312                 int *hlim = NULL;
 313                 struct in6_pktinfo *pktinfo;
 314                 struct in_pktinfo *pkt4info;
 315                 for (struct cmsghdr *ch = CMSG_FIRSTHDR(&msg); ch != NULL &&
 316                                 destiface == 0; ch = CMSG_NXTHDR(&msg, ch)) {
 317                         if (ch->cmsg_level == IPPROTO_IPV6 &&
 318                                         ch->cmsg_type == IPV6_PKTINFO) {
 319                                 pktinfo = (struct in6_pktinfo*)CMSG_DATA(ch);
 320                                 destiface = pktinfo->ipi6_ifindex;
 321                         } else if (ch->cmsg_level == IPPROTO_IP &&
 322                                         ch->cmsg_type == IP_PKTINFO) {
 323                                 pkt4info = (struct in_pktinfo*)CMSG_DATA(ch);
 324                                 destiface = pkt4info->ipi_ifindex;
 325                         } else if (ch->cmsg_level == IPPROTO_IPV6 &&
 326                                         ch->cmsg_type == IPV6_HOPLIMIT) {
 327                                 hlim = (int*)CMSG_DATA(ch);
 328                         }
 329                 }
 330
 331                 // Check hoplimit if received
 332                 if (hlim && *hlim != 255)
 333                         continue;
 334
 335                 // Detect interface for packet sockets
 336                 if (addr.ll.sll_family == AF_PACKET)
 337                         destiface = addr.ll.sll_ifindex;
 338
 339                 struct interface *iface =
 340                                 odhcpd_get_interface_by_index(destiface);
 341
 342                 if (!iface && addr.nl.nl_family != AF_NETLINK)
 343                         continue;
 344
 345                 char ipbuf[INET6_ADDRSTRLEN] = "kernel";
 346                 if (addr.ll.sll_family == AF_PACKET &&
 347                                 len >= (ssize_t)sizeof(struct ip6_hdr))
 348                         inet_ntop(AF_INET6, &data_buf[8], ipbuf, sizeof(ipbuf));
 349                 else if (addr.in6.sin6_family == AF_INET6)
 350                         inet_ntop(AF_INET6, &addr.in6.sin6_addr, ipbuf, sizeof(ipbuf));
 351                 else if (addr.in.sin_family == AF_INET)
 352                         inet_ntop(AF_INET, &addr.in.sin_addr, ipbuf, sizeof(ipbuf));
 353
 354                 syslog(LOG_NOTICE, "--");
 355                 syslog(LOG_NOTICE, "Received %li Bytes from %s%%%s", (long)len,
 356                                 ipbuf, (iface) ? iface->ifname : "netlink");
 357
 358                 e->handle_dgram(&addr, data_buf, len, iface);
 359         }
 360 }
 361
 362 // Register events for the multiplexer
 363 int odhcpd_register(struct odhcpd_event *event)
 364 {
 365         event->uloop.cb = odhcpd_receive_packets;
 366         return uloop_fd_add(&event->uloop, ULOOP_READ);
 367 }
 368
 369 void odhcpd_urandom(void *data, size_t len)
 370 {
 371         read(urandom_fd, data, len);
 372 }
 373
 374
 375 time_t odhcpd_time(void)
 376 {
 377         struct timespec ts;
 378         syscall(SYS_clock_gettime, CLOCK_MONOTONIC, &ts);
 379         return ts.tv_sec;
 380 }
 381
 382
 383 static const char hexdigits[] = "0123456789abcdef";
 384 static const int8_t hexvals[] = {
 385     -1, -1, -1, -1, -1, -1, -1, -1, -1, -2, -2, -1, -1, -2, -1, -1,
 386     -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 387     -2, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 388      0,  1,  2,  3,  4,  5,  6,  7,  8,  9, -1, -1, -1, -1, -1, -1,
 389     -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 390     -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 391     -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 392     -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 393 };
 394
 395 ssize_t odhcpd_unhexlify(uint8_t *dst, size_t len, const char *src)
 396 {
 397         size_t c;
 398         for (c = 0; c < len && src[0] && src[1]; ++c) {
 399                 int8_t x = (int8_t)*src++;
 400                 int8_t y = (int8_t)*src++;
 401                 if (x < 0 || (x = hexvals[x]) < 0
 402                                 || y < 0 || (y = hexvals[y]) < 0)
 403                         return -1;
 404                 dst[c] = x << 4 | y;
 405                 while (((int8_t)*src) < 0 ||
 406                                 (*src && hexvals[(uint8_t)*src] < 0))
 407                         src++;
 408         }
 409
 410         return c;
 411 }
 412
 413
 414 void odhcpd_hexlify(char *dst, const uint8_t *src, size_t len)
 415 {
 416         for (size_t i = 0; i < len; ++i) {
 417                 *dst++ = hexdigits[src[i] >> 4];
 418                 *dst++ = hexdigits[src[i] & 0x0f];
 419         }
 420         *dst = 0;
 421 }