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         if (init_ubus())
  87                 return 4;
  88
  89         odhcpd_run();
  90         return 0;
  91 }
  92
  93 int odhcpd_open_rtnl(void)
  94 {
  95         int sock = socket(AF_NETLINK, SOCK_RAW | SOCK_CLOEXEC, NETLINK_ROUTE);
  96
  97         // Connect to the kernel netlink interface
  98         struct sockaddr_nl nl = {.nl_family = AF_NETLINK};
  99         if (connect(sock, (struct sockaddr*)&nl, sizeof(nl))) {
 100                 syslog(LOG_ERR, "Failed to connect to kernel rtnetlink: %s",
 101                                 strerror(errno));
 102                 return -1;
 103         }
 104
 105         return sock;
 106 }
 107
 108
 109 // Read IPv6 MTU for interface
 110 int odhcpd_get_interface_mtu(const char *ifname)
 111 {
 112         char buf[64];
 113         const char *sysctl_pattern = "/proc/sys/net/ipv6/conf/%s/mtu";
 114         snprintf(buf, sizeof(buf), sysctl_pattern, ifname);
 115
 116         int fd = open(buf, O_RDONLY);
 117         ssize_t len = read(fd, buf, sizeof(buf) - 1);
 118         close(fd);
 119
 120         if (len < 0)
 121                 return -1;
 122
 123
 124         buf[len] = 0;
 125         return atoi(buf);
 126
 127 }
 128
 129
 130 // Read IPv6 MAC for interface
 131 int odhcpd_get_mac(const struct interface *iface, uint8_t mac[6])
 132 {
 133         struct ifreq ifr;
 134         strncpy(ifr.ifr_name, iface->ifname, sizeof(ifr.ifr_name));
 135         if (ioctl(ioctl_sock, SIOCGIFHWADDR, &ifr) < 0)
 136                 return -1;
 137         memcpy(mac, ifr.ifr_hwaddr.sa_data, 6);
 138         return 0;
 139 }
 140
 141
 142 // Forwards a packet on a specific interface
 143 ssize_t odhcpd_send(int socket, struct sockaddr_in6 *dest,
 144                 struct iovec *iov, size_t iov_len,
 145                 const struct interface *iface)
 146 {
 147         // Construct headers
 148         uint8_t cmsg_buf[CMSG_SPACE(sizeof(struct in6_pktinfo))] = {0};
 149         struct msghdr msg = {(void*)dest, sizeof(*dest), iov, iov_len,
 150                                 cmsg_buf, sizeof(cmsg_buf), 0};
 151
 152         // Set control data (define destination interface)
 153         struct cmsghdr *chdr = CMSG_FIRSTHDR(&msg);
 154         chdr->cmsg_level = IPPROTO_IPV6;
 155         chdr->cmsg_type = IPV6_PKTINFO;
 156         chdr->cmsg_len = CMSG_LEN(sizeof(struct in6_pktinfo));
 157         struct in6_pktinfo *pktinfo = (struct in6_pktinfo*)CMSG_DATA(chdr);
 158         pktinfo->ipi6_ifindex = iface->ifindex;
 159
 160         // Also set scope ID if link-local
 161         if (IN6_IS_ADDR_LINKLOCAL(&dest->sin6_addr)
 162                         || IN6_IS_ADDR_MC_LINKLOCAL(&dest->sin6_addr))
 163                 dest->sin6_scope_id = iface->ifindex;
 164
 165         // IPV6_PKTINFO doesn't really work for IPv6-raw sockets (bug?)
 166         if (dest->sin6_port == 0) {
 167                 msg.msg_control = NULL;
 168                 msg.msg_controllen = 0;
 169         }
 170
 171         char ipbuf[INET6_ADDRSTRLEN];
 172         inet_ntop(AF_INET6, &dest->sin6_addr, ipbuf, sizeof(ipbuf));
 173
 174         ssize_t sent = sendmsg(socket, &msg, MSG_DONTWAIT);
 175         if (sent < 0)
 176                 syslog(LOG_WARNING, "Failed to send to %s%%%s (%s)",
 177                                 ipbuf, iface->ifname, strerror(errno));
 178         else
 179                 syslog(LOG_NOTICE, "Sent %li bytes to %s%%%s",
 180                                 (long)sent, ipbuf, iface->ifname);
 181         return sent;
 182 }
 183
 184
 185 // Detect an IPV6-address currently assigned to the given interface
 186 ssize_t odhcpd_get_interface_addresses(int ifindex,
 187                 struct odhcpd_ipaddr *addrs, size_t cnt)
 188 {
 189         struct {
 190                 struct nlmsghdr nhm;
 191                 struct ifaddrmsg ifa;
 192         } req = {{sizeof(req), RTM_GETADDR, NLM_F_REQUEST | NLM_F_DUMP,
 193                         ++rtnl_seq, 0}, {AF_INET6, 0, 0, 0, ifindex}};
 194         if (send(rtnl_socket, &req, sizeof(req), 0) < (ssize_t)sizeof(req))
 195                 return 0;
 196
 197         uint8_t buf[8192];
 198         ssize_t len = 0, ret = 0;
 199
 200         for (struct nlmsghdr *nhm = NULL; ; nhm = NLMSG_NEXT(nhm, len)) {
 201                 while (len < 0 || !NLMSG_OK(nhm, (size_t)len)) {
 202                         len = recv(rtnl_socket, buf, sizeof(buf), 0);
 203                         nhm = (struct nlmsghdr*)buf;
 204                         if (len < 0 || !NLMSG_OK(nhm, (size_t)len)) {
 205                                 if (errno == EINTR)
 206                                         continue;
 207                                 else
 208                                         return ret;
 209                         }
 210                 }
 211
 212                 if (nhm->nlmsg_type != RTM_NEWADDR)
 213                         break;
 214
 215                 // Skip address but keep clearing socket buffer
 216                 if (ret >= (ssize_t)cnt)
 217                         continue;
 218
 219                 struct ifaddrmsg *ifa = NLMSG_DATA(nhm);
 220                 if (ifa->ifa_scope != RT_SCOPE_UNIVERSE ||
 221                                 ifa->ifa_index != (unsigned)ifindex)
 222                         continue;
 223
 224                 struct rtattr *rta = (struct rtattr*)&ifa[1];
 225                 size_t alen = NLMSG_PAYLOAD(nhm, sizeof(*ifa));
 226                 memset(&addrs[ret], 0, sizeof(addrs[ret]));
 227                 addrs[ret].prefix = ifa->ifa_prefixlen;
 228
 229                 while (RTA_OK(rta, alen)) {
 230                         if (rta->rta_type == IFA_ADDRESS) {
 231                                 memcpy(&addrs[ret].addr, RTA_DATA(rta),
 232                                                 sizeof(struct in6_addr));
 233                         } else if (rta->rta_type == IFA_CACHEINFO) {
 234                                 struct ifa_cacheinfo *ifc = RTA_DATA(rta);
 235                                 addrs[ret].preferred = ifc->ifa_prefered;
 236                                 addrs[ret].valid = ifc->ifa_valid;
 237                         }
 238
 239                         rta = RTA_NEXT(rta, alen);
 240                 }
 241
 242                 if (ifa->ifa_flags & IFA_F_DEPRECATED)
 243                         addrs[ret].preferred = 0;
 244
 245                 ++ret;
 246         }
 247
 248         return ret;
 249 }
 250
 251
 252 struct interface* odhcpd_get_interface_by_index(int ifindex)
 253 {
 254         struct interface *iface;
 255         list_for_each_entry(iface, &interfaces, head)
 256                 if (iface->ifindex == ifindex)
 257                         return iface;
 258
 259         return NULL;
 260 }
 261
 262
 263 struct interface* odhcpd_get_interface_by_name(const char *name)
 264 {
 265         struct interface *iface;
 266         list_for_each_entry(iface, &interfaces, head)
 267                 if (!strcmp(iface->ifname, name))
 268                         return iface;
 269
 270         return NULL;
 271 }
 272
 273
 274 struct interface* odhcpd_get_master_interface(void)
 275 {
 276         struct interface *iface;
 277         list_for_each_entry(iface, &interfaces, head)
 278                 if (iface->master)
 279                         return iface;
 280
 281         return NULL;
 282 }
 283
 284
 285 // Convenience function to receive and do basic validation of packets
 286 static void odhcpd_receive_packets(struct uloop_fd *u, _unused unsigned int events)
 287 {
 288         struct odhcpd_event *e = container_of(u, struct odhcpd_event, uloop);
 289
 290         uint8_t data_buf[RELAYD_BUFFER_SIZE], cmsg_buf[128];
 291         union {
 292                 struct sockaddr_in6 in6;
 293                 struct sockaddr_in in;
 294                 struct sockaddr_ll ll;
 295                 struct sockaddr_nl nl;
 296         } addr;
 297
 298         while (true) {
 299                 struct iovec iov = {data_buf, sizeof(data_buf)};
 300                 struct msghdr msg = {&addr, sizeof(addr), &iov, 1,
 301                                 cmsg_buf, sizeof(cmsg_buf), 0};
 302
 303                 ssize_t len = recvmsg(u->fd, &msg, MSG_DONTWAIT);
 304                 if (len < 0) {
 305                         if (errno == EAGAIN)
 306                                 break;
 307                         else
 308                                 continue;
 309                 }
 310
 311
 312                 // Extract destination interface
 313                 int destiface = 0;
 314                 int *hlim = NULL;
 315                 struct in6_pktinfo *pktinfo;
 316                 struct in_pktinfo *pkt4info;
 317                 for (struct cmsghdr *ch = CMSG_FIRSTHDR(&msg); ch != NULL &&
 318                                 destiface == 0; ch = CMSG_NXTHDR(&msg, ch)) {
 319                         if (ch->cmsg_level == IPPROTO_IPV6 &&
 320                                         ch->cmsg_type == IPV6_PKTINFO) {
 321                                 pktinfo = (struct in6_pktinfo*)CMSG_DATA(ch);
 322                                 destiface = pktinfo->ipi6_ifindex;
 323                         } else if (ch->cmsg_level == IPPROTO_IP &&
 324                                         ch->cmsg_type == IP_PKTINFO) {
 325                                 pkt4info = (struct in_pktinfo*)CMSG_DATA(ch);
 326                                 destiface = pkt4info->ipi_ifindex;
 327                         } else if (ch->cmsg_level == IPPROTO_IPV6 &&
 328                                         ch->cmsg_type == IPV6_HOPLIMIT) {
 329                                 hlim = (int*)CMSG_DATA(ch);
 330                         }
 331                 }
 332
 333                 // Check hoplimit if received
 334                 if (hlim && *hlim != 255)
 335                         continue;
 336
 337                 // Detect interface for packet sockets
 338                 if (addr.ll.sll_family == AF_PACKET)
 339                         destiface = addr.ll.sll_ifindex;
 340
 341                 struct interface *iface =
 342                                 odhcpd_get_interface_by_index(destiface);
 343
 344                 if (!iface && addr.nl.nl_family != AF_NETLINK)
 345                         continue;
 346
 347                 char ipbuf[INET6_ADDRSTRLEN] = "kernel";
 348                 if (addr.ll.sll_family == AF_PACKET &&
 349                                 len >= (ssize_t)sizeof(struct ip6_hdr))
 350                         inet_ntop(AF_INET6, &data_buf[8], ipbuf, sizeof(ipbuf));
 351                 else if (addr.in6.sin6_family == AF_INET6)
 352                         inet_ntop(AF_INET6, &addr.in6.sin6_addr, ipbuf, sizeof(ipbuf));
 353                 else if (addr.in.sin_family == AF_INET)
 354                         inet_ntop(AF_INET, &addr.in.sin_addr, ipbuf, sizeof(ipbuf));
 355
 356                 syslog(LOG_NOTICE, "--");
 357                 syslog(LOG_NOTICE, "Received %li Bytes from %s%%%s", (long)len,
 358                                 ipbuf, (iface) ? iface->ifname : "netlink");
 359
 360                 e->handle_dgram(&addr, data_buf, len, iface);
 361         }
 362 }
 363
 364 // Register events for the multiplexer
 365 int odhcpd_register(struct odhcpd_event *event)
 366 {
 367         event->uloop.cb = odhcpd_receive_packets;
 368         return uloop_fd_add(&event->uloop, ULOOP_READ);
 369 }
 370
 371 void odhcpd_urandom(void *data, size_t len)
 372 {
 373         read(urandom_fd, data, len);
 374 }
 375
 376
 377 time_t odhcpd_time(void)
 378 {
 379         struct timespec ts;
 380         syscall(SYS_clock_gettime, CLOCK_MONOTONIC, &ts);
 381         return ts.tv_sec;
 382 }
 383
 384
 385 static const char hexdigits[] = "0123456789abcdef";
 386 static const int8_t hexvals[] = {
 387     -1, -1, -1, -1, -1, -1, -1, -1, -1, -2, -2, -1, -1, -2, -1, -1,
 388     -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 389     -2, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 390      0,  1,  2,  3,  4,  5,  6,  7,  8,  9, -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     -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 394     -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 395 };
 396
 397 ssize_t odhcpd_unhexlify(uint8_t *dst, size_t len, const char *src)
 398 {
 399         size_t c;
 400         for (c = 0; c < len && src[0] && src[1]; ++c) {
 401                 int8_t x = (int8_t)*src++;
 402                 int8_t y = (int8_t)*src++;
 403                 if (x < 0 || (x = hexvals[x]) < 0
 404                                 || y < 0 || (y = hexvals[y]) < 0)
 405                         return -1;
 406                 dst[c] = x << 4 | y;
 407                 while (((int8_t)*src) < 0 ||
 408                                 (*src && hexvals[(uint8_t)*src] < 0))
 409                         src++;
 410         }
 411
 412         return c;
 413 }
 414
 415
 416 void odhcpd_hexlify(char *dst, const uint8_t *src, size_t len)
 417 {
 418         for (size_t i = 0; i < len; ++i) {
 419                 *dst++ = hexdigits[src[i] >> 4];
 420                 *dst++ = hexdigits[src[i] & 0x0f];
 421         }
 422         *dst = 0;
 423 }