src/dhcpv4.c

   1 /**
   2  * Copyright (C) 2012-2013 Steven Barth <steven@midlink.org>
   3  * Copyright (C) 2016 Hans Dedecker <dedeckeh@gmail.com>
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License v2 as published by
   7  * the Free Software Foundation.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  *
  15  */
  16
  17 #include <time.h>
  18 #include <errno.h>
  19 #include <fcntl.h>
  20 #include <unistd.h>
  21 #include <stddef.h>
  22 #include <stdlib.h>
  23 #include <resolv.h>
  24 #include <limits.h>
  25 #include <net/if.h>
  26 #include <net/if_arp.h>
  27 #include <netinet/ip.h>
  28 #include <sys/ioctl.h>
  29 #include <sys/timerfd.h>
  30 #include <arpa/inet.h>
  31
  32 #include <libubox/md5.h>
  33
  34 #include "odhcpd.h"
  35 #include "dhcpv4.h"
  36 #include "dhcpv6.h"
  37
  38 static void dhcpv4_netevent_cb(unsigned long event, struct netevent_handler_info *info);
  39 static int setup_dhcpv4_addresses(struct interface *iface);
  40 static void update_static_assignments(struct interface *iface);
  41 static void valid_until_cb(struct uloop_timeout *event);
  42 static void handle_addrlist_change(struct interface *iface);
  43 static void free_dhcpv4_assignment(struct dhcpv4_assignment *a);
  44 static void dhcpv4_fr_start(struct dhcpv4_assignment *a);
  45 static void dhcpv4_fr_stop(struct dhcpv4_assignment *a);
  46 static void handle_dhcpv4(void *addr, void *data, size_t len,
  47                 struct interface *iface, void *dest_addr);
  48 static struct dhcpv4_assignment* dhcpv4_lease(struct interface *iface,
  49                 enum dhcpv4_msg msg, const uint8_t *mac, const uint32_t reqaddr,
  50                 uint32_t *leasetime, const char *hostname, const size_t hostname_len,
  51                 const bool accept_fr_nonce, bool *incl_fr_opt, uint32_t *fr_serverid);
  52
  53 static struct netevent_handler dhcpv4_netevent_handler = { .cb = dhcpv4_netevent_cb, };
  54 static struct uloop_timeout valid_until_timeout = {.cb = valid_until_cb};
  55 static uint32_t serial = 0;
  56
  57 struct odhcpd_ref_ip {
  58         struct list_head head;
  59         int ref_cnt;
  60         struct odhcpd_ipaddr addr;
  61 };
  62
  63 /* Create socket and register events */
  64 int dhcpv4_init(void)
  65 {
  66         uloop_timeout_set(&valid_until_timeout, 1000);
  67         netlink_add_netevent_handler(&dhcpv4_netevent_handler);
  68
  69         return 0;
  70 }
  71
  72 int dhcpv4_setup_interface(struct interface *iface, bool enable)
  73 {
  74         if (iface->dhcpv4_event.uloop.fd > 0) {
  75                 uloop_fd_delete(&iface->dhcpv4_event.uloop);
  76                 close(iface->dhcpv4_event.uloop.fd);
  77                 iface->dhcpv4_event.uloop.fd = -1;
  78         }
  79
  80         if (iface->dhcpv4 && enable) {
  81                 if (!iface->dhcpv4_assignments.next)
  82                         INIT_LIST_HEAD(&iface->dhcpv4_assignments);
  83
  84                 if (!iface->dhcpv4_fr_ips.next)
  85                         INIT_LIST_HEAD(&iface->dhcpv4_fr_ips);
  86
  87                 int sock = socket(AF_INET, SOCK_DGRAM | SOCK_CLOEXEC, IPPROTO_UDP);
  88                 if (sock < 0) {
  89                         syslog(LOG_ERR, "Failed to create DHCPv4 server socket: %s",
  90                                         strerror(errno));
  91                         return -1;
  92                 }
  93
  94                 /* Basic IPv4 configuration */
  95                 int val = 1;
  96                 setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &val, sizeof(val));
  97                 setsockopt(sock, SOL_SOCKET, SO_BROADCAST, &val, sizeof(val));
  98                 setsockopt(sock, IPPROTO_IP, IP_PKTINFO, &val, sizeof(val));
  99
 100                 val = IPTOS_PREC_INTERNETCONTROL;
 101                 setsockopt(sock, IPPROTO_IP, IP_TOS, &val, sizeof(val));
 102
 103                 val = IP_PMTUDISC_DONT;
 104                 setsockopt(sock, IPPROTO_IP, IP_MTU_DISCOVER, &val, sizeof(val));
 105
 106                 setsockopt(sock, SOL_SOCKET, SO_BINDTODEVICE,
 107                                 iface->ifname, strlen(iface->ifname));
 108
 109                 struct sockaddr_in bind_addr = {AF_INET, htons(DHCPV4_SERVER_PORT),
 110                                         {INADDR_ANY}, {0}};
 111
 112                 if (bind(sock, (struct sockaddr*)&bind_addr, sizeof(bind_addr))) {
 113                         syslog(LOG_ERR, "Failed to open DHCPv4 server socket: %s",
 114                                         strerror(errno));
 115                         return -1;
 116                 }
 117
 118                 iface->dhcpv4_event.uloop.fd = sock;
 119                 iface->dhcpv4_event.handle_dgram = handle_dhcpv4;
 120                 odhcpd_register(&iface->dhcpv4_event);
 121
 122                 if (setup_dhcpv4_addresses(iface) < 0)
 123                         return -1;
 124
 125                 update_static_assignments(iface);
 126         } else if (iface->dhcpv4_assignments.next) {
 127                 while (!list_empty(&iface->dhcpv4_assignments))
 128                         free_dhcpv4_assignment(list_first_entry(&iface->dhcpv4_assignments,
 129                                                         struct dhcpv4_assignment, head));
 130         }
 131         return 0;
 132 }
 133
 134
 135 static void dhcpv4_netevent_cb(unsigned long event, struct netevent_handler_info *info)
 136 {
 137         struct interface *iface = info->iface;
 138
 139         if (!iface || iface->dhcpv4 == MODE_DISABLED)
 140                 return;
 141
 142         switch (event) {
 143         case NETEV_IFINDEX_CHANGE:
 144                 dhcpv4_setup_interface(iface, true);
 145                 break;
 146         case NETEV_ADDRLIST_CHANGE:
 147                 handle_addrlist_change(iface);
 148                 break;
 149         default:
 150                 break;
 151         }
 152 }
 153
 154 static struct dhcpv4_assignment *find_assignment_by_hwaddr(struct interface *iface, const uint8_t *hwaddr)
 155 {
 156         struct dhcpv4_assignment *a;
 157
 158         list_for_each_entry(a, &iface->dhcpv4_assignments, head)
 159                 if (!memcmp(a->hwaddr, hwaddr, 6))
 160                         return a;
 161
 162         return NULL;
 163 }
 164
 165 static struct dhcpv4_assignment *find_assignment_by_addr(struct interface *iface, const uint32_t addr)
 166 {
 167         struct dhcpv4_assignment *a;
 168
 169         list_for_each_entry(a, &iface->dhcpv4_assignments, head)
 170                 if (a->addr == addr)
 171                         return a;
 172
 173         return NULL;
 174 }
 175
 176 static int setup_dhcpv4_addresses(struct interface *iface)
 177 {
 178         iface->dhcpv4_start_ip.s_addr = INADDR_ANY;
 179         iface->dhcpv4_end_ip.s_addr = INADDR_ANY;
 180         iface->dhcpv4_local.s_addr = INADDR_ANY;
 181         iface->dhcpv4_bcast.s_addr = INADDR_ANY;
 182         iface->dhcpv4_mask.s_addr = INADDR_ANY;
 183
 184         /* Sanity checks */
 185         if (iface->dhcpv4_start.s_addr & htonl(0xffff0000) ||
 186             iface->dhcpv4_end.s_addr & htonl(0xffff0000) ||
 187             ntohl(iface->dhcpv4_start.s_addr) > ntohl(iface->dhcpv4_end.s_addr)) {
 188                 syslog(LOG_ERR, "invalid DHCP range for %s", iface->name);
 189                 return -1;
 190         }
 191
 192         if (!iface->addr4_len) {
 193                 syslog(LOG_WARNING, "no network(s) available on %s", iface->name);
 194                 return -1;
 195         }
 196
 197         uint32_t start = ntohl(iface->dhcpv4_start.s_addr);
 198         uint32_t end = ntohl(iface->dhcpv4_end.s_addr);
 199
 200         for (size_t i = 0; i < iface->addr4_len && start && end; i++) {
 201                 struct in_addr *addr = &iface->addr4[i].addr.in;
 202                 struct in_addr mask;
 203
 204                 odhcpd_bitlen2netmask(false, iface->addr4[i].prefix, &mask);
 205                 if ((start & ntohl(~mask.s_addr)) == start &&
 206                             (end & ntohl(~mask.s_addr)) == end) {
 207                         iface->dhcpv4_start_ip.s_addr = htonl(start) |
 208                                                         (addr->s_addr & mask.s_addr);
 209                         iface->dhcpv4_end_ip.s_addr = htonl(end) |
 210                                                         (addr->s_addr & mask.s_addr);
 211                         iface->dhcpv4_local = *addr;
 212                         iface->dhcpv4_bcast = iface->addr4[i].broadcast;
 213                         iface->dhcpv4_mask = mask;
 214                         return 0;
 215                 }
 216         }
 217
 218         /* Don't allocate IP range for subnets bigger than 28 */
 219         if (iface->addr4[0].prefix > 28) {
 220                 syslog(LOG_WARNING, "auto allocation of DHCP range fails on %s", iface->name);
 221                 return -1;
 222         }
 223
 224         iface->dhcpv4_local = iface->addr4[0].addr.in;
 225         iface->dhcpv4_bcast = iface->addr4[0].broadcast;
 226         odhcpd_bitlen2netmask(false, iface->addr4[0].prefix, &iface->dhcpv4_mask);
 227         end = start = iface->dhcpv4_local.s_addr & iface->dhcpv4_mask.s_addr;
 228
 229         /* Auto allocate ranges */
 230         if (ntohl(iface->dhcpv4_mask.s_addr) <= 0xffffff00) {
 231                 iface->dhcpv4_start_ip.s_addr = start | htonl(100);
 232                 iface->dhcpv4_end_ip.s_addr = end | htonl(250);
 233         } else if (ntohl(iface->dhcpv4_mask.s_addr) <= 0xffffffc0) {
 234                 iface->dhcpv4_start_ip.s_addr = start | htonl(10);
 235                 iface->dhcpv4_end_ip.s_addr = end | htonl(60);
 236         } else if (ntohl(iface->dhcpv4_mask.s_addr) <= 0xffffffe0) {
 237                 iface->dhcpv4_start_ip.s_addr = start | htonl(10);
 238                 iface->dhcpv4_end_ip.s_addr = end | htonl(30);
 239         } else {
 240                 iface->dhcpv4_start_ip.s_addr = start | htonl(3);
 241                 iface->dhcpv4_end_ip.s_addr = end | htonl(12);
 242         }
 243
 244         return 0;
 245 }
 246
 247 static void update_static_assignments(struct interface *iface)
 248 {
 249         struct dhcpv4_assignment *a, *c;
 250
 251         /* Cleanup static entries not belonging to the network */
 252         list_for_each_entry_safe(a, c, &iface->dhcpv4_assignments, head) {
 253                 if ((a->flags & OAF_STATIC) &&
 254                                 ((a->addr & iface->dhcpv4_mask.s_addr) !=
 255                                  (iface->dhcpv4_start.s_addr & iface->dhcpv4_mask.s_addr)))
 256                         free_dhcpv4_assignment(a);
 257         }
 258
 259         /* Parse static entries */
 260         struct lease *lease;
 261         list_for_each_entry(lease, &leases, head) {
 262                 if ((iface->dhcpv4_start_ip.s_addr & iface->dhcpv4_mask.s_addr) !=
 263                                 (lease->ipaddr.s_addr & iface->dhcpv4_mask.s_addr)) {
 264                         continue;
 265                 }
 266
 267                 a = find_assignment_by_hwaddr(iface, lease->mac.ether_addr_octet);
 268
 269                 if (!a) {
 270                         /* Check if there's an assignment with the specified IP address */
 271                         if (find_assignment_by_addr(iface, lease->ipaddr.s_addr))
 272                                 continue;
 273
 274                         /* Construct entry */
 275                         a = calloc(1, sizeof(*a));
 276                         if (!a) {
 277                                 syslog(LOG_ERR, "Calloc failed for static lease on interface %s",
 278                                         iface->ifname);
 279                                 continue;
 280                         }
 281                         memcpy(a->hwaddr, lease->mac.ether_addr_octet, sizeof(a->hwaddr));
 282                 }
 283
 284                 a->leasetime = lease->dhcpv4_leasetime;
 285
 286                 a->addr = lease->ipaddr.s_addr;
 287                 /* Static assignment */
 288                 a->flags |= OAF_STATIC;
 289                 /* Infinite valid */
 290                 a->valid_until = 0;
 291                 a->iface = iface;
 292                 if (lease->hostname[0]) {
 293                         free(a->hostname);
 294                         a->hostname = strdup(lease->hostname);
 295                 }
 296
 297                 /* Assign to all interfaces */
 298                 list_for_each_entry(c, &iface->dhcpv4_assignments, head) {
 299                         if (ntohl(c->addr) > ntohl(a->addr)) {
 300                                 list_add_tail(&a->head, &c->head);
 301                                 break;
 302                         }
 303                 }
 304
 305                 if (&c->head == &iface->dhcpv4_assignments)
 306                         list_add(&a->head, &iface->dhcpv4_assignments);
 307         }
 308 }
 309
 310 static void inc_ref_cnt_ip(struct odhcpd_ref_ip **ptr, struct odhcpd_ref_ip *ip)
 311 {
 312         *ptr = ip;
 313         ip->ref_cnt++;
 314 }
 315
 316 static void decr_ref_cnt_ip(struct odhcpd_ref_ip **ptr, struct interface *iface)
 317 {
 318         struct odhcpd_ref_ip *ip = *ptr;
 319
 320         if (--ip->ref_cnt == 0) {
 321                 netlink_setup_addr(&ip->addr, iface->ifindex, false, false);
 322
 323                 list_del(&ip->head);
 324                 free(ip);
 325         }
 326
 327         *ptr = NULL;
 328 }
 329
 330 static bool leases_require_fr(struct interface *iface, struct odhcpd_ipaddr *addr,
 331                                 uint32_t mask)
 332 {
 333         struct dhcpv4_assignment *a = NULL;
 334         struct odhcpd_ref_ip *fr_ip = NULL;
 335
 336         list_for_each_entry(a, &iface->dhcpv4_assignments, head) {
 337                 if ((a->accept_fr_nonce || iface->dhcpv4_forcereconf) &&
 338                     !a->fr_ip &&
 339                     ((a->addr & mask) == (addr->addr.in.s_addr & mask))) {
 340                         if (!fr_ip) {
 341                                 fr_ip = calloc(1, sizeof(*fr_ip));
 342                                 if (!fr_ip)
 343                                         break;
 344
 345                                 list_add(&fr_ip->head, &iface->dhcpv4_fr_ips);
 346                                 fr_ip->addr = *addr;
 347                         }
 348                         inc_ref_cnt_ip(&a->fr_ip, fr_ip);
 349                 }
 350         }
 351
 352         return fr_ip ? true : false;
 353 }
 354
 355 static void valid_until_cb(struct uloop_timeout *event)
 356 {
 357         time_t now = odhcpd_time();
 358         struct interface *iface;
 359         list_for_each_entry(iface, &interfaces, head) {
 360                 if (iface->dhcpv4 != MODE_SERVER || iface->dhcpv4_assignments.next == NULL)
 361                         continue;
 362
 363                 struct dhcpv4_assignment *a, *n;
 364                 list_for_each_entry_safe(a, n, &iface->dhcpv4_assignments, head) {
 365                         if (!INFINITE_VALID(a->valid_until) && a->valid_until < now)
 366                                 free_dhcpv4_assignment(a);
 367                 }
 368         }
 369         uloop_timeout_set(event, 1000);
 370 }
 371
 372 static void handle_addrlist_change(struct interface *iface)
 373 {
 374         struct odhcpd_ipaddr ip;
 375         struct odhcpd_ref_ip *a;
 376         struct dhcpv4_assignment *c;
 377         uint32_t mask = iface->dhcpv4_mask.s_addr;
 378
 379         memset(&ip, 0, sizeof(ip));
 380         ip.addr.in = iface->dhcpv4_local;
 381         ip.prefix = odhcpd_netmask2bitlen(false, &iface->dhcpv4_mask);
 382         ip.broadcast = iface->dhcpv4_bcast;
 383
 384         setup_dhcpv4_addresses(iface);
 385
 386         if ((ip.addr.in.s_addr & mask) ==
 387             (iface->dhcpv4_local.s_addr & iface->dhcpv4_mask.s_addr))
 388                 return;
 389
 390         if (ip.addr.in.s_addr && !leases_require_fr(iface, &ip, mask))
 391                 return;
 392
 393         if (iface->dhcpv4_local.s_addr == INADDR_ANY || list_empty(&iface->dhcpv4_fr_ips))
 394                 return;
 395
 396         a = list_first_entry(&iface->dhcpv4_fr_ips, struct odhcpd_ref_ip, head);
 397
 398         if (netlink_setup_addr(&a->addr, iface->ifindex, false, true)) {
 399                 syslog(LOG_ERR, "Failed to add ip address");
 400                 return;
 401         }
 402
 403         list_for_each_entry(c, &iface->dhcpv4_assignments, head) {
 404                 if ((c->flags & OAF_BOUND) && c->fr_ip && !c->fr_cnt) {
 405                         if (c->accept_fr_nonce || iface->dhcpv4_forcereconf)
 406                                 dhcpv4_fr_start(c);
 407                         else
 408                                 dhcpv4_fr_stop(c);
 409                 }
 410         }
 411 }
 412
 413 static char *dhcpv4_msg_to_string(uint8_t reqmsg)
 414 {
 415         switch (reqmsg) {
 416         case (DHCPV4_MSG_DISCOVER):
 417                 return "DHCPV4_MSG_DISCOVER";
 418         case (DHCPV4_MSG_OFFER):
 419                 return "DHCPV4_MSG_OFFER";
 420         case (DHCPV4_MSG_REQUEST):
 421                 return "DHCPV4_MSG_REQUEST";
 422         case (DHCPV4_MSG_DECLINE):
 423                 return "DHCPV4_MSG_DECLINE";
 424         case (DHCPV4_MSG_ACK):
 425                 return "DHCPV4_MSG_ACK";
 426         case (DHCPV4_MSG_NAK):
 427                 return "DHCPV4_MSG_NAK";
 428         case (DHCPV4_MSG_RELEASE):
 429                 return "DHCPV4_MSG_RELEASE";
 430         case (DHCPV4_MSG_INFORM):
 431                 return "DHCPV4_MSG_INFORM";
 432         case (DHCPV4_MSG_FORCERENEW):
 433                 return "DHCPV4_MSG_FORCERENEW";
 434         default:
 435                 return "UNKNOWN";
 436         }
 437 }
 438
 439 static void free_dhcpv4_assignment(struct dhcpv4_assignment *a)
 440 {
 441         if (a->head.next)
 442                 list_del(&a->head);
 443
 444         if (a->fr_ip)
 445                 dhcpv4_fr_stop(a);
 446
 447         free(a->hostname);
 448         free(a);
 449 }
 450
 451 static void dhcpv4_put(struct dhcpv4_message *msg, uint8_t **cookie,
 452                 uint8_t type, uint8_t len, const void *data)
 453 {
 454         uint8_t *c = *cookie;
 455         if (*cookie + 2 + len > (uint8_t*)&msg[1])
 456                 return;
 457
 458         *c++ = type;
 459         *c++ = len;
 460         memcpy(c, data, len);
 461
 462         *cookie = c + len;
 463 }
 464
 465 static void dhcpv4_fr_send(struct dhcpv4_assignment *a)
 466 {
 467         struct dhcpv4_message fr_msg = {
 468                 .op = DHCPV4_BOOTREPLY,
 469                 .htype = 1,
 470                 .hlen = 6,
 471                 .hops = 0,
 472                 .secs = 0,
 473                 .flags = 0,
 474                 .ciaddr = {INADDR_ANY},
 475                 .yiaddr = {INADDR_ANY},
 476                 .siaddr = {INADDR_ANY},
 477                 .giaddr = {INADDR_ANY},
 478                 .chaddr = {0},
 479                 .sname = {0},
 480                 .file = {0},
 481         };
 482         struct dhcpv4_auth_forcerenew *auth_o, auth = {
 483                 .protocol = 3,
 484                 .algorithm = 1,
 485                 .rdm = 0,
 486                 .replay = {htonl(time(NULL)), htonl(++serial)},
 487                 .type = 2,
 488                 .key = {0},
 489         };
 490         struct interface *iface = a->iface;
 491
 492         odhcpd_urandom(&fr_msg.xid, sizeof(fr_msg.xid));
 493         memcpy(fr_msg.chaddr, a->hwaddr, fr_msg.hlen);
 494
 495         fr_msg.options[0] = 0x63;
 496         fr_msg.options[1] = 0x82;
 497         fr_msg.options[2] = 0x53;
 498         fr_msg.options[3] = 0x63;
 499
 500         uint8_t *cookie = &fr_msg.options[4];
 501         uint8_t msg = DHCPV4_MSG_FORCERENEW;
 502
 503         dhcpv4_put(&fr_msg, &cookie, DHCPV4_OPT_MESSAGE, 1, &msg);
 504         if (a->accept_fr_nonce) {
 505                 dhcpv4_put(&fr_msg, &cookie, DHCPV4_OPT_AUTHENTICATION, sizeof(auth), &auth);
 506                 auth_o = (struct dhcpv4_auth_forcerenew *)(cookie - sizeof(auth));
 507                 dhcpv4_put(&fr_msg, &cookie, DHCPV4_OPT_END, 0, NULL);
 508
 509                 md5_ctx_t md5;
 510                 uint8_t secretbytes[64];
 511                 memset(secretbytes, 0, sizeof(secretbytes));
 512                 memcpy(secretbytes, a->key, sizeof(a->key));
 513
 514                 for (size_t i = 0; i < sizeof(secretbytes); ++i)
 515                         secretbytes[i] ^= 0x36;
 516
 517                 md5_begin(&md5);
 518                 md5_hash(secretbytes, sizeof(secretbytes), &md5);
 519                 md5_hash(&fr_msg, sizeof(fr_msg), &md5);
 520                 md5_end(auth_o->key, &md5);
 521
 522                 for (size_t i = 0; i < sizeof(secretbytes); ++i) {
 523                         secretbytes[i] ^= 0x36;
 524                         secretbytes[i] ^= 0x5c;
 525                 }
 526
 527                 md5_begin(&md5);
 528                 md5_hash(secretbytes, sizeof(secretbytes), &md5);
 529                 md5_hash(auth_o->key, sizeof(auth_o->key), &md5);
 530                 md5_end(auth_o->key, &md5);
 531         } else {
 532                 dhcpv4_put(&fr_msg, &cookie, DHCPV4_OPT_SERVERID, 4,
 533                                 &a->fr_ip->addr.addr.in.s_addr);
 534                 dhcpv4_put(&fr_msg, &cookie, DHCPV4_OPT_END, 0, NULL);
 535         }
 536
 537         struct sockaddr_in dest;
 538         memset(&dest, 0, sizeof(dest));
 539         dest.sin_family = AF_INET;
 540         dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 541         dest.sin_addr.s_addr = a->addr;
 542
 543         syslog(LOG_WARNING, "sending %s to %02x:%02x:%02x:%02x:%02x:%02x - %s",
 544                         dhcpv4_msg_to_string(msg),
 545                         a->hwaddr[0], a->hwaddr[1], a->hwaddr[2],
 546                         a->hwaddr[3], a->hwaddr[4], a->hwaddr[5],
 547                         inet_ntoa(dest.sin_addr));
 548
 549         sendto(iface->dhcpv4_event.uloop.fd, &fr_msg, sizeof(fr_msg),
 550                         MSG_DONTWAIT, (struct sockaddr*)&dest, sizeof(dest));
 551 }
 552
 553 static void dhcpv4_fr_timer(struct uloop_timeout *event)
 554 {
 555         struct dhcpv4_assignment *a = container_of(event, struct dhcpv4_assignment, fr_timer);
 556
 557         if (a->fr_cnt > 0 && a->fr_cnt < 8) {
 558                 dhcpv4_fr_send(a);
 559                 uloop_timeout_set(&a->fr_timer, 1000 << a->fr_cnt);
 560                 a->fr_cnt++;
 561         } else
 562                 dhcpv4_fr_stop(a);
 563 }
 564
 565 static void dhcpv4_fr_start(struct dhcpv4_assignment *a)
 566 {
 567         uloop_timeout_set(&a->fr_timer, 1000 << a->fr_cnt);
 568         a->fr_timer.cb = dhcpv4_fr_timer;
 569         a->fr_cnt++;
 570
 571         dhcpv4_fr_send(a);
 572 }
 573
 574 static void dhcpv4_fr_stop(struct dhcpv4_assignment *a)
 575 {
 576         uloop_timeout_cancel(&a->fr_timer);
 577         decr_ref_cnt_ip(&a->fr_ip, a->iface);
 578         a->fr_cnt = 0;
 579         a->fr_timer.cb = NULL;
 580 }
 581
 582 // Handler for DHCPv4 messages
 583 static void handle_dhcpv4(void *addr, void *data, size_t len,
 584                 struct interface *iface, _unused void *dest_addr)
 585 {
 586         if (!iface->dhcpv4)
 587                 return;
 588
 589         struct dhcpv4_message *req = data;
 590         if (len < offsetof(struct dhcpv4_message, options) + 4 ||
 591                         req->op != DHCPV4_BOOTREQUEST || req->hlen != 6)
 592                 return;
 593
 594
 595         syslog(LOG_NOTICE, "Got DHCPv4 request");
 596
 597         if (!iface->dhcpv4_start_ip.s_addr && !iface->dhcpv4_end_ip.s_addr) {
 598                 syslog(LOG_WARNING, "No DHCP range available on %s", iface->name);
 599                 return;
 600         }
 601
 602         int sock = iface->dhcpv4_event.uloop.fd;
 603
 604         struct dhcpv4_message reply = {
 605                 .op = DHCPV4_BOOTREPLY,
 606                 .htype = req->htype,
 607                 .hlen = req->hlen,
 608                 .hops = 0,
 609                 .xid = req->xid,
 610                 .secs = 0,
 611                 .flags = req->flags,
 612                 .ciaddr = {INADDR_ANY},
 613                 .giaddr = req->giaddr,
 614                 .siaddr = iface->dhcpv4_local,
 615         };
 616         memcpy(reply.chaddr, req->chaddr, sizeof(reply.chaddr));
 617
 618         reply.options[0] = 0x63;
 619         reply.options[1] = 0x82;
 620         reply.options[2] = 0x53;
 621         reply.options[3] = 0x63;
 622
 623         uint8_t *cookie = &reply.options[4];
 624         uint8_t reqmsg = DHCPV4_MSG_REQUEST;
 625         uint8_t msg = DHCPV4_MSG_ACK;
 626
 627         uint32_t reqaddr = INADDR_ANY;
 628         uint32_t leasetime = 0;
 629         size_t hostname_len = 0;
 630         char hostname[256];
 631         bool accept_fr_nonce = false;
 632         bool incl_fr_opt = false;
 633
 634         uint8_t *start = &req->options[4];
 635         uint8_t *end = ((uint8_t*)data) + len;
 636         struct dhcpv4_option *opt;
 637         dhcpv4_for_each_option(start, end, opt) {
 638                 if (opt->type == DHCPV4_OPT_MESSAGE && opt->len == 1)
 639                         reqmsg = opt->data[0];
 640                 else if (opt->type == DHCPV4_OPT_HOSTNAME && opt->len > 0) {
 641                         hostname_len = opt->len;
 642                         memcpy(hostname, opt->data, hostname_len);
 643                         hostname[hostname_len] = 0;
 644                 } else if (opt->type == DHCPV4_OPT_IPADDRESS && opt->len == 4)
 645                         memcpy(&reqaddr, opt->data, 4);
 646                 else if (opt->type == DHCPV4_OPT_SERVERID && opt->len == 4) {
 647                         if (memcmp(opt->data, &iface->dhcpv4_local, 4))
 648                                 return;
 649                 } else if (iface->filter_class && opt->type == DHCPV4_OPT_USER_CLASS) {
 650                         uint8_t *c = opt->data, *cend = &opt->data[opt->len];
 651                         for (; c < cend && &c[*c] < cend; c = &c[1 + *c]) {
 652                                 size_t elen = strlen(iface->filter_class);
 653                                 if (*c == elen && !memcmp(&c[1], iface->filter_class, elen))
 654                                         return; // Ignore from homenet
 655                         }
 656                 } else if (opt->type == DHCPV4_OPT_LEASETIME && opt->len == 4)
 657                         memcpy(&leasetime, opt->data, 4);
 658                 else if (opt->type == DHCPV4_OPT_FORCERENEW_NONCE_CAPABLE && opt->len > 0) {
 659                         for (uint8_t i = 0; i < opt->len; i++) {
 660                                 if (opt->data[i] == 1) {
 661                                         accept_fr_nonce = true;
 662                                         break;
 663                                 }
 664                         }
 665
 666                 }
 667         }
 668
 669         if (reqmsg != DHCPV4_MSG_DISCOVER && reqmsg != DHCPV4_MSG_REQUEST &&
 670                         reqmsg != DHCPV4_MSG_INFORM && reqmsg != DHCPV4_MSG_DECLINE &&
 671                         reqmsg != DHCPV4_MSG_RELEASE)
 672                 return;
 673
 674         struct dhcpv4_assignment *lease = NULL;
 675         uint32_t serverid = iface->dhcpv4_local.s_addr;
 676         uint32_t fr_serverid = INADDR_ANY;
 677
 678         if (reqmsg != DHCPV4_MSG_INFORM)
 679                 lease = dhcpv4_lease(iface, reqmsg, req->chaddr, reqaddr,
 680                                         &leasetime, hostname, hostname_len,
 681                                         accept_fr_nonce, &incl_fr_opt, &fr_serverid);
 682
 683         if (!lease) {
 684                 if (reqmsg == DHCPV4_MSG_REQUEST)
 685                         msg = DHCPV4_MSG_NAK;
 686                 else if (reqmsg == DHCPV4_MSG_DISCOVER)
 687                         return;
 688         } else if (reqmsg == DHCPV4_MSG_DISCOVER)
 689                 msg = DHCPV4_MSG_OFFER;
 690         else if (reqmsg == DHCPV4_MSG_REQUEST &&
 691                         ((reqaddr && reqaddr != lease->addr) ||
 692                          (req->ciaddr.s_addr && req->ciaddr.s_addr != lease->addr))) {
 693                 msg = DHCPV4_MSG_NAK;
 694                 /*
 695                  * DHCP client requested an IP which we can't offer to him. Probably the
 696                  * client changed the network or the network has been changed. The reply
 697                  * type is set to DHCPV4_MSG_NAK, because the client should not use that IP.
 698                  *
 699                  * For modern devices we build an answer that includes a valid IP, like
 700                  * a DHCPV4_MSG_ACK. The client will use that IP and doesn't need to
 701                  * perform additional DHCP round trips.
 702                  *
 703                  */
 704
 705                 /*
 706                  *
 707                  * Buggy clients do serverid checking in nack messages; therefore set the
 708                  * serverid in nack messages triggered by a previous force renew equal to
 709                  * the server id in use at that time by the server
 710                  *
 711                  */
 712                 if (fr_serverid)
 713                         serverid = fr_serverid;
 714
 715                 if (req->ciaddr.s_addr &&
 716                                 ((iface->dhcpv4_start_ip.s_addr & iface->dhcpv4_mask.s_addr) !=
 717                                  (req->ciaddr.s_addr & iface->dhcpv4_mask.s_addr)))
 718                         req->ciaddr.s_addr = INADDR_ANY;
 719         }
 720
 721         syslog(LOG_WARNING, "received %s from %02x:%02x:%02x:%02x:%02x:%02x",
 722                         dhcpv4_msg_to_string(reqmsg),
 723                         req->chaddr[0],req->chaddr[1],req->chaddr[2],
 724                         req->chaddr[3],req->chaddr[4],req->chaddr[5]);
 725
 726         if (reqmsg == DHCPV4_MSG_DECLINE || reqmsg == DHCPV4_MSG_RELEASE)
 727                 return;
 728
 729         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_MESSAGE, 1, &msg);
 730         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SERVERID, 4, &serverid);
 731
 732         if (lease) {
 733                 uint32_t val;
 734
 735                 reply.yiaddr.s_addr = lease->addr;
 736
 737                 val = htonl(leasetime);
 738                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_LEASETIME, 4, &val);
 739
 740                 if (leasetime != UINT32_MAX) {
 741                         val = htonl(500 * leasetime / 1000);
 742                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_RENEW, 4, &val);
 743
 744                         val = htonl(875 * leasetime / 1000);
 745                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_REBIND, 4, &val);
 746                 }
 747
 748                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_NETMASK, 4,
 749                                 &iface->dhcpv4_mask.s_addr);
 750
 751                 if (lease->hostname)
 752                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_HOSTNAME,
 753                                         strlen(lease->hostname), lease->hostname);
 754
 755                 if (iface->dhcpv4_bcast.s_addr != INADDR_ANY)
 756                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_BROADCAST, 4, &iface->dhcpv4_bcast);
 757
 758                 if (incl_fr_opt) {
 759                         if (reqmsg == DHCPV4_MSG_REQUEST) {
 760                                 struct dhcpv4_auth_forcerenew auth = {
 761                                         .protocol = 3,
 762                                         .algorithm = 1,
 763                                         .rdm = 0,
 764                                         .replay = {htonl(time(NULL)), htonl(++serial)},
 765                                         .type = 1,
 766                                         .key = {0},
 767                                 };
 768
 769                                 memcpy(auth.key, lease->key, sizeof(auth.key));
 770                                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_AUTHENTICATION, sizeof(auth), &auth);
 771                         } else {
 772                                 uint8_t one = 1;
 773                                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_FORCERENEW_NONCE_CAPABLE,
 774                                         sizeof(one), &one);
 775                         }
 776                 }
 777         }
 778
 779         struct ifreq ifr = {.ifr_name = ""};
 780         strncpy(ifr.ifr_name, iface->ifname, sizeof(ifr.ifr_name));
 781
 782         if (!ioctl(sock, SIOCGIFMTU, &ifr)) {
 783                 uint16_t mtu = htons(ifr.ifr_mtu);
 784                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_MTU, 2, &mtu);
 785         }
 786
 787         if (iface->search && iface->search_len <= 255)
 788                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SEARCH_DOMAIN,
 789                                 iface->search_len, iface->search);
 790         else if (!res_init() && _res.dnsrch[0] && _res.dnsrch[0][0]) {
 791                 uint8_t search_buf[256];
 792                 int len = dn_comp(_res.dnsrch[0], search_buf,
 793                                                 sizeof(search_buf), NULL, NULL);
 794                 if (len > 0)
 795                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SEARCH_DOMAIN,
 796                                         len, search_buf);
 797         }
 798
 799         if (iface->dhcpv4_router_cnt == 0)
 800                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_ROUTER, 4, &iface->dhcpv4_local);
 801         else
 802                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_ROUTER,
 803                                 4 * iface->dhcpv4_router_cnt, iface->dhcpv4_router);
 804
 805
 806         if (iface->dhcpv4_dns_cnt == 0)
 807                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_DNSSERVER, 4, &iface->dhcpv4_local);
 808         else
 809                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_DNSSERVER,
 810                                 4 * iface->dhcpv4_dns_cnt, iface->dhcpv4_dns);
 811
 812
 813         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_END, 0, NULL);
 814
 815         struct sockaddr_in dest = *((struct sockaddr_in*)addr);
 816         if (req->giaddr.s_addr) {
 817                 /*
 818                  * relay agent is configured, send reply to the agent
 819                  */
 820                 dest.sin_addr = req->giaddr;
 821                 dest.sin_port = htons(DHCPV4_SERVER_PORT);
 822         } else if (req->ciaddr.s_addr && req->ciaddr.s_addr != dest.sin_addr.s_addr) {
 823                 /*
 824                  * client has existing configuration (ciaddr is set) AND this address is
 825                  * not the address it used for the dhcp message
 826                  */
 827                 dest.sin_addr = req->ciaddr;
 828                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 829         } else if ((ntohs(req->flags) & DHCPV4_FLAG_BROADCAST) ||
 830                         req->hlen != reply.hlen || !reply.yiaddr.s_addr) {
 831                 /*
 832                  * client requests a broadcast reply OR we can't offer an IP
 833                  */
 834                 dest.sin_addr.s_addr = INADDR_BROADCAST;
 835                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 836         } else if (!req->ciaddr.s_addr && msg == DHCPV4_MSG_NAK) {
 837                 /*
 838                  * client has no previous configuration -> no IP, so we need to reply
 839                  * with a broadcast packet
 840                  */
 841                 dest.sin_addr.s_addr = INADDR_BROADCAST;
 842                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 843         } else {
 844                 /*
 845                  * send reply to the newly (in this proccess) allocated IP
 846                  */
 847                 dest.sin_addr = reply.yiaddr;
 848                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 849
 850                 struct arpreq arp = {.arp_flags = ATF_COM};
 851                 memcpy(arp.arp_ha.sa_data, req->chaddr, 6);
 852                 memcpy(&arp.arp_pa, &dest, sizeof(arp.arp_pa));
 853                 memcpy(arp.arp_dev, iface->ifname, sizeof(arp.arp_dev));
 854                 ioctl(sock, SIOCSARP, &arp);
 855         }
 856
 857         if (dest.sin_addr.s_addr == INADDR_BROADCAST)
 858                 /* reply goes to IP broadcast -> MAC broadcast */
 859                 syslog(LOG_WARNING, "sending %s to ff:ff:ff:ff:ff:ff - %s",
 860                                 dhcpv4_msg_to_string(msg),
 861                                 inet_ntoa(dest.sin_addr));
 862         else
 863                 /*
 864                  * reply is send directly to IP,
 865                  * MAC is assumed to be the same as the request
 866                  */
 867                 syslog(LOG_WARNING, "sending %s to %02x:%02x:%02x:%02x:%02x:%02x - %s",
 868                                 dhcpv4_msg_to_string(msg),
 869                                 req->chaddr[0],req->chaddr[1],req->chaddr[2],
 870                                 req->chaddr[3],req->chaddr[4],req->chaddr[5],
 871                                 inet_ntoa(dest.sin_addr));
 872
 873         sendto(sock, &reply, sizeof(reply), MSG_DONTWAIT,
 874                         (struct sockaddr*)&dest, sizeof(dest));
 875 }
 876
 877 static bool dhcpv4_assign(struct interface *iface,
 878                 struct dhcpv4_assignment *assign, uint32_t raddr)
 879 {
 880         uint32_t start = ntohl(iface->dhcpv4_start_ip.s_addr);
 881         uint32_t end = ntohl(iface->dhcpv4_end_ip.s_addr);
 882         uint32_t count = end - start + 1;
 883
 884         // try to assign the IP the client asked for
 885         if (start <= ntohl(raddr) && ntohl(raddr) <= end &&
 886                         !find_assignment_by_addr(iface, raddr)) {
 887                 assign->addr = raddr;
 888                 syslog(LOG_INFO, "assigning the IP the client asked for: %u.%u.%u.%u",
 889                                 ((uint8_t *)&assign->addr)[0],
 890                                 ((uint8_t *)&assign->addr)[1],
 891                                 ((uint8_t *)&assign->addr)[2],
 892                                 ((uint8_t *)&assign->addr)[3]);
 893                 return true;
 894         }
 895
 896         // Seed RNG with checksum of hwaddress
 897         uint32_t seed = 0;
 898         for (size_t i = 0; i < sizeof(assign->hwaddr); ++i) {
 899                 // Knuth's multiplicative method
 900                 uint8_t o = assign->hwaddr[i];
 901                 seed += (o*2654435761) % UINT32_MAX;
 902         }
 903
 904         srand(seed);
 905
 906         uint32_t try = (((uint32_t)rand()) % count) + start;
 907
 908         if (list_empty(&iface->dhcpv4_assignments)) {
 909                 assign->addr = htonl(try);
 910                 syslog(LOG_INFO, "assigning mapped IP (empty list): %u.%u.%u.%u",
 911                                 ((uint8_t *)&assign->addr)[0],
 912                                 ((uint8_t *)&assign->addr)[1],
 913                                 ((uint8_t *)&assign->addr)[2],
 914                                 ((uint8_t *)&assign->addr)[3]);
 915                 return true;
 916         }
 917
 918         for (uint32_t i = 0; i < count; ++i) {
 919                 if (!find_assignment_by_addr(iface, htonl(try))) {
 920                         /* test was successful: IP address is not assigned, assign it */
 921                         assign->addr = htonl(try);
 922                         syslog(LOG_DEBUG, "assigning mapped IP: %u.%u.%u.%u (try %u of %u)",
 923                                         ((uint8_t *)&assign->addr)[0],
 924                                         ((uint8_t *)&assign->addr)[1],
 925                                         ((uint8_t *)&assign->addr)[2],
 926                                         ((uint8_t *)&assign->addr)[3],
 927                                         i, count);
 928                         return true;
 929                 }
 930                 try = (((try - start) + 1) % count) + start;
 931         }
 932
 933         syslog(LOG_WARNING, "can't assign any IP address -> address space is full");
 934         return false;
 935 }
 936
 937
 938 static struct dhcpv4_assignment* dhcpv4_lease(struct interface *iface,
 939                 enum dhcpv4_msg msg, const uint8_t *mac, const uint32_t reqaddr,
 940                 uint32_t *leasetime, const char *hostname, const size_t hostname_len,
 941                 const bool accept_fr_nonce, bool *incl_fr_opt, uint32_t *fr_serverid)
 942 {
 943         struct dhcpv4_assignment *a = find_assignment_by_hwaddr(iface, mac);
 944         struct dhcpv4_assignment *lease = NULL;
 945         time_t now = odhcpd_time();
 946
 947         if (a && (a->flags & OAF_BOUND) && a->fr_ip) {
 948                 *fr_serverid = a->fr_ip->addr.addr.in.s_addr;
 949                 dhcpv4_fr_stop(a);
 950         }
 951
 952         if (msg == DHCPV4_MSG_DISCOVER || msg == DHCPV4_MSG_REQUEST) {
 953                 bool assigned = !!a;
 954
 955                 if (!a) {
 956                         if (!iface->no_dynamic_dhcp) {
 957                                 /* Create new binding */
 958                                 a = calloc(1, sizeof(*a));
 959                                 if (!a) {
 960                                         syslog(LOG_ERR, "Failed to calloc binding on interface %s",
 961                                                         iface->ifname);
 962                                         return NULL;
 963                                 }
 964                                 memcpy(a->hwaddr, mac, sizeof(a->hwaddr));
 965                                 /* Don't consider new assignment as infinite */
 966                                 a->valid_until = now;
 967
 968                                 assigned = dhcpv4_assign(iface, a, reqaddr);
 969                                 if (assigned) {
 970                                         a->iface = iface;
 971                                         list_add(&a->head, &iface->dhcpv4_assignments);
 972                                 }
 973                         }
 974                 } else if ((a->addr & iface->dhcpv4_mask.s_addr) !=
 975                                 (iface->dhcpv4_start_ip.s_addr & iface->dhcpv4_mask.s_addr)) {
 976                         list_del(&a->head);
 977
 978                         assigned = dhcpv4_assign(iface, a, reqaddr);
 979                         if (assigned)
 980                                 list_add(&a->head, &iface->dhcpv4_assignments);
 981                 }
 982
 983                 if (assigned) {
 984                         uint32_t my_leasetime;
 985
 986                         if (a->leasetime)
 987                                 my_leasetime = a->leasetime;
 988                         else
 989                                 my_leasetime = iface->dhcpv4_leasetime;
 990
 991                         if ((*leasetime == 0) || (my_leasetime < *leasetime))
 992                                 *leasetime = my_leasetime;
 993
 994                         if (msg == DHCPV4_MSG_DISCOVER) {
 995                                 a->flags &= ~OAF_BOUND;
 996
 997                                 *incl_fr_opt = accept_fr_nonce;
 998                                 if (!(a->flags & OAF_STATIC))
 999                                         a->valid_until = now;
1000                         } else {
1001                                 if (hostname_len > 0) {
1002                                         a->hostname = realloc(a->hostname, hostname_len + 1);
1003                                         if (a->hostname) {
1004                                                 memcpy(a->hostname, hostname, hostname_len);
1005                                                 a->hostname[hostname_len] = 0;
1006                                         }
1007                                 }
1008
1009                                 if (!(a->flags & OAF_BOUND)) {
1010                                         a->accept_fr_nonce = accept_fr_nonce;
1011                                         *incl_fr_opt = accept_fr_nonce;
1012                                         odhcpd_urandom(a->key, sizeof(a->key));
1013                                         a->flags |= OAF_BOUND;
1014                                 } else
1015                                         *incl_fr_opt = false;
1016
1017                                 if (!(a->flags & OAF_STATIC))
1018                                         a->valid_until = ((*leasetime == UINT32_MAX) ? 0 : (time_t)(now + *leasetime));
1019                         }
1020                 } else if (!assigned && a) {
1021                         /* Cleanup failed assignment */
1022                         free_dhcpv4_assignment(a);
1023                         a = NULL;
1024                 }
1025
1026                 if (assigned && a)
1027                         lease = a;
1028         } else if (msg == DHCPV4_MSG_RELEASE && a) {
1029                 a->flags &= ~OAF_BOUND;
1030
1031                 if (!(a->flags & OAF_STATIC))
1032                         a->valid_until = now - 1;
1033
1034         } else if (msg == DHCPV4_MSG_DECLINE && a) {
1035                 a->flags &= ~OAF_BOUND;
1036
1037                 if (!(a->flags & OAF_STATIC)) {
1038                         memset(a->hwaddr, 0, sizeof(a->hwaddr));
1039                         a->valid_until = now + 3600; /* Block address for 1h */
1040                 }
1041         }
1042
1043         dhcpv6_write_statefile();
1044
1045         return lease;
1046 }