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         setlogmask(LOG_UPTO(LOG_INFO));
  56         uloop_init();
  57
  58         if (getuid() != 0) {
  59                 syslog(LOG_ERR, "Must be run as root!");
  60                 return 2;
  61         }
  62
  63         ioctl_sock = socket(AF_INET, SOCK_DGRAM | SOCK_CLOEXEC, 0);
  64
  65         if ((rtnl_socket = odhcpd_open_rtnl()) < 0) {
  66                 syslog(LOG_ERR, "Unable to open socket: %s", strerror(errno));
  67                 return 2;
  68         }
  69
  70         if ((urandom_fd = open("/dev/urandom", O_RDONLY | O_CLOEXEC)) < 0)
  71                 return 4;
  72
  73         signal(SIGUSR1, SIG_IGN);
  74
  75         if (init_router())
  76                 return 4;
  77
  78         if (init_dhcpv6())
  79                 return 4;
  80
  81         if (init_ndp())
  82                 return 4;
  83
  84         if (init_dhcpv4())
  85                 return 4;
  86
  87         odhcpd_run();
  88         return 0;
  89 }
  90
  91 int odhcpd_open_rtnl(void)
  92 {
  93         int sock = socket(AF_NETLINK, SOCK_RAW | SOCK_CLOEXEC, NETLINK_ROUTE);
  94
  95         // Connect to the kernel netlink interface
  96         struct sockaddr_nl nl = {.nl_family = AF_NETLINK};
  97         if (connect(sock, (struct sockaddr*)&nl, sizeof(nl))) {
  98                 syslog(LOG_ERR, "Failed to connect to kernel rtnetlink: %s",
  99                                 strerror(errno));
 100                 return -1;
 101         }
 102
 103         return sock;
 104 }
 105
 106
 107 // Read IPv6 MTU for interface
 108 int odhcpd_get_interface_mtu(const char *ifname)
 109 {
 110         char buf[64];
 111         const char *sysctl_pattern = "/proc/sys/net/ipv6/conf/%s/mtu";
 112         snprintf(buf, sizeof(buf), sysctl_pattern, ifname);
 113
 114         int fd = open(buf, O_RDONLY);
 115         ssize_t len = read(fd, buf, sizeof(buf) - 1);
 116         close(fd);
 117
 118         if (len < 0)
 119                 return -1;
 120
 121
 122         buf[len] = 0;
 123         return atoi(buf);
 124
 125 }
 126
 127
 128 // Read IPv6 MAC for interface
 129 int odhcpd_get_mac(const struct interface *iface, uint8_t mac[6])
 130 {
 131         struct ifreq ifr;
 132         memset(&ifr, 0, sizeof(ifr));
 133         strncpy(ifr.ifr_name, iface->ifname, sizeof(ifr.ifr_name));
 134         if (ioctl(ioctl_sock, SIOCGIFHWADDR, &ifr) < 0)
 135                 return -1;
 136         memcpy(mac, ifr.ifr_hwaddr.sa_data, 6);
 137         return 0;
 138 }
 139
 140
 141 // Forwards a packet on a specific interface
 142 ssize_t odhcpd_send(int socket, struct sockaddr_in6 *dest,
 143                 struct iovec *iov, size_t iov_len,
 144                 const struct interface *iface)
 145 {
 146         // Construct headers
 147         uint8_t cmsg_buf[CMSG_SPACE(sizeof(struct in6_pktinfo))] = {0};
 148         struct msghdr msg = {(void*)dest, sizeof(*dest), iov, iov_len,
 149                                 cmsg_buf, sizeof(cmsg_buf), 0};
 150
 151         // Set control data (define destination interface)
 152         struct cmsghdr *chdr = CMSG_FIRSTHDR(&msg);
 153         chdr->cmsg_level = IPPROTO_IPV6;
 154         chdr->cmsg_type = IPV6_PKTINFO;
 155         chdr->cmsg_len = CMSG_LEN(sizeof(struct in6_pktinfo));
 156         struct in6_pktinfo *pktinfo = (struct in6_pktinfo*)CMSG_DATA(chdr);
 157         pktinfo->ipi6_ifindex = iface->ifindex;
 158
 159         // Also set scope ID if link-local
 160         if (IN6_IS_ADDR_LINKLOCAL(&dest->sin6_addr)
 161                         || IN6_IS_ADDR_MC_LINKLOCAL(&dest->sin6_addr))
 162                 dest->sin6_scope_id = iface->ifindex;
 163
 164         // IPV6_PKTINFO doesn't really work for IPv6-raw sockets (bug?)
 165         if (dest->sin6_port == 0) {
 166                 msg.msg_control = NULL;
 167                 msg.msg_controllen = 0;
 168         }
 169
 170         char ipbuf[INET6_ADDRSTRLEN];
 171         inet_ntop(AF_INET6, &dest->sin6_addr, ipbuf, sizeof(ipbuf));
 172
 173         ssize_t sent = sendmsg(socket, &msg, MSG_DONTWAIT);
 174         if (sent < 0)
 175                 syslog(LOG_WARNING, "Failed to send to %s%%%s (%s)",
 176                                 ipbuf, iface->ifname, strerror(errno));
 177         else
 178                 syslog(LOG_DEBUG, "Sent %li bytes to %s%%%s",
 179                                 (long)sent, ipbuf, iface->ifname);
 180         return sent;
 181 }
 182
 183
 184 // Detect an IPV6-address currently assigned to the given interface
 185 ssize_t odhcpd_get_interface_addresses(int ifindex,
 186                 struct odhcpd_ipaddr *addrs, size_t cnt)
 187 {
 188         struct {
 189                 struct nlmsghdr nhm;
 190                 struct ifaddrmsg ifa;
 191         } req = {{sizeof(req), RTM_GETADDR, NLM_F_REQUEST | NLM_F_DUMP,
 192                         ++rtnl_seq, 0}, {AF_INET6, 0, 0, 0, ifindex}};
 193         if (send(rtnl_socket, &req, sizeof(req), 0) < (ssize_t)sizeof(req))
 194                 return 0;
 195
 196         uint8_t buf[8192];
 197         ssize_t len = 0, ret = 0;
 198
 199         for (struct nlmsghdr *nhm = NULL; ; nhm = NLMSG_NEXT(nhm, len)) {
 200                 while (len < 0 || !NLMSG_OK(nhm, (size_t)len)) {
 201                         len = recv(rtnl_socket, buf, sizeof(buf), 0);
 202                         nhm = (struct nlmsghdr*)buf;
 203                         if (len < 0 || !NLMSG_OK(nhm, (size_t)len)) {
 204                                 if (errno == EINTR)
 205                                         continue;
 206                                 else
 207                                         return ret;
 208                         }
 209                 }
 210
 211                 if (nhm->nlmsg_type != RTM_NEWADDR)
 212                         break;
 213
 214                 // Skip address but keep clearing socket buffer
 215                 if (ret >= (ssize_t)cnt)
 216                         continue;
 217
 218                 struct ifaddrmsg *ifa = NLMSG_DATA(nhm);
 219                 if (ifa->ifa_scope != RT_SCOPE_UNIVERSE ||
 220                                 ifa->ifa_index != (unsigned)ifindex)
 221                         continue;
 222
 223                 struct rtattr *rta = (struct rtattr*)&ifa[1];
 224                 size_t alen = NLMSG_PAYLOAD(nhm, sizeof(*ifa));
 225                 memset(&addrs[ret], 0, sizeof(addrs[ret]));
 226                 addrs[ret].prefix = ifa->ifa_prefixlen;
 227
 228                 while (RTA_OK(rta, alen)) {
 229                         if (rta->rta_type == IFA_ADDRESS) {
 230                                 memcpy(&addrs[ret].addr, RTA_DATA(rta),
 231                                                 sizeof(struct in6_addr));
 232                         } else if (rta->rta_type == IFA_CACHEINFO) {
 233                                 struct ifa_cacheinfo *ifc = RTA_DATA(rta);
 234                                 addrs[ret].preferred = ifc->ifa_prefered;
 235                                 addrs[ret].valid = ifc->ifa_valid;
 236                         }
 237
 238                         rta = RTA_NEXT(rta, alen);
 239                 }
 240
 241                 if (ifa->ifa_flags & IFA_F_DEPRECATED)
 242                         addrs[ret].preferred = 0;
 243
 244                 addrs[ret].has_class = false;
 245                 addrs[ret].class = 0;
 246 #ifdef WITH_UBUS
 247                 struct interface *iface = odhcpd_get_interface_by_index(ifindex);
 248                 if (iface)
 249                         addrs[ret].has_class = ubus_get_class(iface->ifname,
 250                                         &addrs[ret].addr, &addrs[ret].class);
 251 #endif
 252                 ++ret;
 253         }
 254
 255         return ret;
 256 }
 257
 258
 259 struct interface* odhcpd_get_interface_by_index(int ifindex)
 260 {
 261         struct interface *iface;
 262         list_for_each_entry(iface, &interfaces, head)
 263                 if (iface->ifindex == ifindex)
 264                         return iface;
 265
 266         return NULL;
 267 }
 268
 269
 270 struct interface* odhcpd_get_interface_by_name(const char *name)
 271 {
 272         struct interface *iface;
 273         list_for_each_entry(iface, &interfaces, head)
 274                 if (!strcmp(iface->ifname, name))
 275                         return iface;
 276
 277         return NULL;
 278 }
 279
 280
 281 struct interface* odhcpd_get_master_interface(void)
 282 {
 283         struct interface *iface;
 284         list_for_each_entry(iface, &interfaces, head)
 285                 if (iface->master)
 286                         return iface;
 287
 288         return NULL;
 289 }
 290
 291
 292 // Convenience function to receive and do basic validation of packets
 293 static void odhcpd_receive_packets(struct uloop_fd *u, _unused unsigned int events)
 294 {
 295         struct odhcpd_event *e = container_of(u, struct odhcpd_event, uloop);
 296
 297         uint8_t data_buf[RELAYD_BUFFER_SIZE], cmsg_buf[128];
 298         union {
 299                 struct sockaddr_in6 in6;
 300                 struct sockaddr_in in;
 301                 struct sockaddr_ll ll;
 302                 struct sockaddr_nl nl;
 303         } addr;
 304
 305         while (true) {
 306                 struct iovec iov = {data_buf, sizeof(data_buf)};
 307                 struct msghdr msg = {&addr, sizeof(addr), &iov, 1,
 308                                 cmsg_buf, sizeof(cmsg_buf), 0};
 309
 310                 ssize_t len = recvmsg(u->fd, &msg, MSG_DONTWAIT);
 311                 if (len < 0) {
 312                         if (errno == EAGAIN)
 313                                 break;
 314                         else
 315                                 continue;
 316                 }
 317
 318
 319                 // Extract destination interface
 320                 int destiface = 0;
 321                 int *hlim = NULL;
 322                 struct in6_pktinfo *pktinfo;
 323                 struct in_pktinfo *pkt4info;
 324                 for (struct cmsghdr *ch = CMSG_FIRSTHDR(&msg); ch != NULL; ch = CMSG_NXTHDR(&msg, ch)) {
 325                         if (ch->cmsg_level == IPPROTO_IPV6 &&
 326                                         ch->cmsg_type == IPV6_PKTINFO) {
 327                                 pktinfo = (struct in6_pktinfo*)CMSG_DATA(ch);
 328                                 destiface = pktinfo->ipi6_ifindex;
 329                         } else if (ch->cmsg_level == IPPROTO_IP &&
 330                                         ch->cmsg_type == IP_PKTINFO) {
 331                                 pkt4info = (struct in_pktinfo*)CMSG_DATA(ch);
 332                                 destiface = pkt4info->ipi_ifindex;
 333                         } else if (ch->cmsg_level == IPPROTO_IPV6 &&
 334                                         ch->cmsg_type == IPV6_HOPLIMIT) {
 335                                 hlim = (int*)CMSG_DATA(ch);
 336                         }
 337                 }
 338
 339                 // Check hoplimit if received
 340                 if (hlim && *hlim != 255)
 341                         continue;
 342
 343                 // Detect interface for packet sockets
 344                 if (addr.ll.sll_family == AF_PACKET)
 345                         destiface = addr.ll.sll_ifindex;
 346
 347                 struct interface *iface =
 348                                 odhcpd_get_interface_by_index(destiface);
 349
 350                 if (!iface && addr.nl.nl_family != AF_NETLINK)
 351                         continue;
 352
 353                 char ipbuf[INET6_ADDRSTRLEN] = "kernel";
 354                 if (addr.ll.sll_family == AF_PACKET &&
 355                                 len >= (ssize_t)sizeof(struct ip6_hdr))
 356                         inet_ntop(AF_INET6, &data_buf[8], ipbuf, sizeof(ipbuf));
 357                 else if (addr.in6.sin6_family == AF_INET6)
 358                         inet_ntop(AF_INET6, &addr.in6.sin6_addr, ipbuf, sizeof(ipbuf));
 359                 else if (addr.in.sin_family == AF_INET)
 360                         inet_ntop(AF_INET, &addr.in.sin_addr, ipbuf, sizeof(ipbuf));
 361
 362                 syslog(LOG_DEBUG, "--");
 363                 syslog(LOG_DEBUG, "Received %li Bytes from %s%%%s", (long)len,
 364                                 ipbuf, (iface) ? iface->ifname : "netlink");
 365
 366                 e->handle_dgram(&addr, data_buf, len, iface);
 367         }
 368 }
 369
 370 // Register events for the multiplexer
 371 int odhcpd_register(struct odhcpd_event *event)
 372 {
 373         event->uloop.cb = odhcpd_receive_packets;
 374         return uloop_fd_add(&event->uloop, ULOOP_READ);
 375 }
 376
 377 void odhcpd_urandom(void *data, size_t len)
 378 {
 379         read(urandom_fd, data, len);
 380 }
 381
 382
 383 time_t odhcpd_time(void)
 384 {
 385         struct timespec ts;
 386         syscall(SYS_clock_gettime, CLOCK_MONOTONIC, &ts);
 387         return ts.tv_sec;
 388 }
 389
 390
 391 static const char hexdigits[] = "0123456789abcdef";
 392 static const int8_t hexvals[] = {
 393     -1, -1, -1, -1, -1, -1, -1, -1, -1, -2, -2, -1, -1, -2, -1, -1,
 394     -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 395     -2, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 396      0,  1,  2,  3,  4,  5,  6,  7,  8,  9, -1, -1, -1, -1, -1, -1,
 397     -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 398     -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 399     -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 400     -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 401 };
 402
 403 ssize_t odhcpd_unhexlify(uint8_t *dst, size_t len, const char *src)
 404 {
 405         size_t c;
 406         for (c = 0; c < len && src[0] && src[1]; ++c) {
 407                 int8_t x = (int8_t)*src++;
 408                 int8_t y = (int8_t)*src++;
 409                 if (x < 0 || (x = hexvals[x]) < 0
 410                                 || y < 0 || (y = hexvals[y]) < 0)
 411                         return -1;
 412                 dst[c] = x << 4 | y;
 413                 while (((int8_t)*src) < 0 ||
 414                                 (*src && hexvals[(uint8_t)*src] < 0))
 415                         src++;
 416         }
 417
 418         return c;
 419 }
 420
 421
 422 void odhcpd_hexlify(char *dst, const uint8_t *src, size_t len)
 423 {
 424         for (size_t i = 0; i < len; ++i) {
 425                 *dst++ = hexdigits[src[i] >> 4];
 426                 *dst++ = hexdigits[src[i] & 0x0f];
 427         }
 428         *dst = 0;
 429 }