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: %m");
  90                         return -1;
  91                 }
  92
  93                 /* Basic IPv4 configuration */
  94                 int val = 1;
  95                 setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &val, sizeof(val));
  96                 setsockopt(sock, SOL_SOCKET, SO_BROADCAST, &val, sizeof(val));
  97                 setsockopt(sock, IPPROTO_IP, IP_PKTINFO, &val, sizeof(val));
  98
  99                 val = IPTOS_PREC_INTERNETCONTROL;
 100                 setsockopt(sock, IPPROTO_IP, IP_TOS, &val, sizeof(val));
 101
 102                 val = IP_PMTUDISC_DONT;
 103                 setsockopt(sock, IPPROTO_IP, IP_MTU_DISCOVER, &val, sizeof(val));
 104
 105                 setsockopt(sock, SOL_SOCKET, SO_BINDTODEVICE,
 106                                 iface->ifname, strlen(iface->ifname));
 107
 108                 struct sockaddr_in bind_addr = {AF_INET, htons(DHCPV4_SERVER_PORT),
 109                                         {INADDR_ANY}, {0}};
 110
 111                 if (bind(sock, (struct sockaddr*)&bind_addr, sizeof(bind_addr))) {
 112                         syslog(LOG_ERR, "Failed to open DHCPv4 server socket: %m");
 113                         return -1;
 114                 }
 115
 116                 iface->dhcpv4_event.uloop.fd = sock;
 117                 iface->dhcpv4_event.handle_dgram = handle_dhcpv4;
 118                 odhcpd_register(&iface->dhcpv4_event);
 119
 120                 if (setup_dhcpv4_addresses(iface) < 0)
 121                         return -1;
 122
 123                 update_static_assignments(iface);
 124         } else if (iface->dhcpv4_assignments.next) {
 125                 while (!list_empty(&iface->dhcpv4_assignments))
 126                         free_dhcpv4_assignment(list_first_entry(&iface->dhcpv4_assignments,
 127                                                         struct dhcpv4_assignment, head));
 128         }
 129         return 0;
 130 }
 131
 132
 133 static void dhcpv4_netevent_cb(unsigned long event, struct netevent_handler_info *info)
 134 {
 135         struct interface *iface = info->iface;
 136
 137         if (!iface || iface->dhcpv4 == MODE_DISABLED)
 138                 return;
 139
 140         switch (event) {
 141         case NETEV_IFINDEX_CHANGE:
 142                 dhcpv4_setup_interface(iface, true);
 143                 break;
 144         case NETEV_ADDRLIST_CHANGE:
 145                 handle_addrlist_change(iface);
 146                 break;
 147         default:
 148                 break;
 149         }
 150 }
 151
 152 static struct dhcpv4_assignment *find_assignment_by_hwaddr(struct interface *iface, const uint8_t *hwaddr)
 153 {
 154         struct dhcpv4_assignment *a;
 155
 156         list_for_each_entry(a, &iface->dhcpv4_assignments, head)
 157                 if (!memcmp(a->hwaddr, hwaddr, 6))
 158                         return a;
 159
 160         return NULL;
 161 }
 162
 163 static struct dhcpv4_assignment *find_assignment_by_addr(struct interface *iface, const uint32_t addr)
 164 {
 165         struct dhcpv4_assignment *a;
 166
 167         list_for_each_entry(a, &iface->dhcpv4_assignments, head)
 168                 if (a->addr == addr)
 169                         return a;
 170
 171         return NULL;
 172 }
 173
 174 static int setup_dhcpv4_addresses(struct interface *iface)
 175 {
 176         iface->dhcpv4_start_ip.s_addr = INADDR_ANY;
 177         iface->dhcpv4_end_ip.s_addr = INADDR_ANY;
 178         iface->dhcpv4_local.s_addr = INADDR_ANY;
 179         iface->dhcpv4_bcast.s_addr = INADDR_ANY;
 180         iface->dhcpv4_mask.s_addr = INADDR_ANY;
 181
 182         /* Sanity checks */
 183         if (iface->dhcpv4_start.s_addr & htonl(0xffff0000) ||
 184             iface->dhcpv4_end.s_addr & htonl(0xffff0000) ||
 185             ntohl(iface->dhcpv4_start.s_addr) > ntohl(iface->dhcpv4_end.s_addr)) {
 186                 syslog(LOG_ERR, "invalid DHCP range for %s", iface->name);
 187                 return -1;
 188         }
 189
 190         if (!iface->addr4_len) {
 191                 syslog(LOG_WARNING, "no network(s) available on %s", iface->name);
 192                 return -1;
 193         }
 194
 195         uint32_t start = ntohl(iface->dhcpv4_start.s_addr);
 196         uint32_t end = ntohl(iface->dhcpv4_end.s_addr);
 197
 198         for (size_t i = 0; i < iface->addr4_len && start && end; i++) {
 199                 struct in_addr *addr = &iface->addr4[i].addr.in;
 200                 struct in_addr mask;
 201
 202                 odhcpd_bitlen2netmask(false, iface->addr4[i].prefix, &mask);
 203                 if ((start & ntohl(~mask.s_addr)) == start &&
 204                             (end & ntohl(~mask.s_addr)) == end) {
 205                         iface->dhcpv4_start_ip.s_addr = htonl(start) |
 206                                                         (addr->s_addr & mask.s_addr);
 207                         iface->dhcpv4_end_ip.s_addr = htonl(end) |
 208                                                         (addr->s_addr & mask.s_addr);
 209                         iface->dhcpv4_local = *addr;
 210                         iface->dhcpv4_bcast = iface->addr4[i].broadcast;
 211                         iface->dhcpv4_mask = mask;
 212                         return 0;
 213                 }
 214         }
 215
 216         /* Don't allocate IP range for subnets bigger than 28 */
 217         if (iface->addr4[0].prefix > 28) {
 218                 syslog(LOG_WARNING, "auto allocation of DHCP range fails on %s", iface->name);
 219                 return -1;
 220         }
 221
 222         iface->dhcpv4_local = iface->addr4[0].addr.in;
 223         iface->dhcpv4_bcast = iface->addr4[0].broadcast;
 224         odhcpd_bitlen2netmask(false, iface->addr4[0].prefix, &iface->dhcpv4_mask);
 225         end = start = iface->dhcpv4_local.s_addr & iface->dhcpv4_mask.s_addr;
 226
 227         /* Auto allocate ranges */
 228         if (ntohl(iface->dhcpv4_mask.s_addr) <= 0xffffff00) {
 229                 iface->dhcpv4_start_ip.s_addr = start | htonl(100);
 230                 iface->dhcpv4_end_ip.s_addr = end | htonl(250);
 231         } else if (ntohl(iface->dhcpv4_mask.s_addr) <= 0xffffffc0) {
 232                 iface->dhcpv4_start_ip.s_addr = start | htonl(10);
 233                 iface->dhcpv4_end_ip.s_addr = end | htonl(60);
 234         } else if (ntohl(iface->dhcpv4_mask.s_addr) <= 0xffffffe0) {
 235                 iface->dhcpv4_start_ip.s_addr = start | htonl(10);
 236                 iface->dhcpv4_end_ip.s_addr = end | htonl(30);
 237         } else {
 238                 iface->dhcpv4_start_ip.s_addr = start | htonl(3);
 239                 iface->dhcpv4_end_ip.s_addr = end | htonl(12);
 240         }
 241
 242         return 0;
 243 }
 244
 245 static void update_static_assignments(struct interface *iface)
 246 {
 247         struct dhcpv4_assignment *a, *c;
 248
 249         /* Cleanup static entries not belonging to the network */
 250         list_for_each_entry_safe(a, c, &iface->dhcpv4_assignments, head) {
 251                 if ((a->flags & OAF_STATIC) &&
 252                                 ((a->addr & iface->dhcpv4_mask.s_addr) !=
 253                                  (iface->dhcpv4_start.s_addr & iface->dhcpv4_mask.s_addr)))
 254                         free_dhcpv4_assignment(a);
 255         }
 256
 257         /* Parse static entries */
 258         struct lease *lease;
 259         list_for_each_entry(lease, &leases, head) {
 260                 if ((iface->dhcpv4_start_ip.s_addr & iface->dhcpv4_mask.s_addr) !=
 261                                 (lease->ipaddr.s_addr & iface->dhcpv4_mask.s_addr)) {
 262                         continue;
 263                 }
 264
 265                 a = find_assignment_by_hwaddr(iface, lease->mac.ether_addr_octet);
 266
 267                 if (!a) {
 268                         /* Check if there's an assignment with the specified IP address */
 269                         if (find_assignment_by_addr(iface, lease->ipaddr.s_addr))
 270                                 continue;
 271
 272                         /* Construct entry */
 273                         a = calloc(1, sizeof(*a));
 274                         if (!a) {
 275                                 syslog(LOG_ERR, "Calloc failed for static lease on interface %s",
 276                                         iface->ifname);
 277                                 continue;
 278                         }
 279                         memcpy(a->hwaddr, lease->mac.ether_addr_octet, sizeof(a->hwaddr));
 280                 }
 281
 282                 a->leasetime = lease->dhcpv4_leasetime;
 283
 284                 a->addr = lease->ipaddr.s_addr;
 285                 /* Static assignment */
 286                 a->flags |= OAF_STATIC;
 287                 /* Infinite valid */
 288                 a->valid_until = 0;
 289                 a->iface = iface;
 290                 if (lease->hostname[0]) {
 291                         free(a->hostname);
 292                         a->hostname = strdup(lease->hostname);
 293                 }
 294
 295                 /* Assign to all interfaces */
 296                 list_for_each_entry(c, &iface->dhcpv4_assignments, head) {
 297                         if (ntohl(c->addr) > ntohl(a->addr)) {
 298                                 list_add_tail(&a->head, &c->head);
 299                                 break;
 300                         }
 301                 }
 302
 303                 if (&c->head == &iface->dhcpv4_assignments)
 304                         list_add(&a->head, &iface->dhcpv4_assignments);
 305         }
 306 }
 307
 308 static void inc_ref_cnt_ip(struct odhcpd_ref_ip **ptr, struct odhcpd_ref_ip *ip)
 309 {
 310         *ptr = ip;
 311         ip->ref_cnt++;
 312 }
 313
 314 static void decr_ref_cnt_ip(struct odhcpd_ref_ip **ptr, struct interface *iface)
 315 {
 316         struct odhcpd_ref_ip *ip = *ptr;
 317
 318         if (--ip->ref_cnt == 0) {
 319                 netlink_setup_addr(&ip->addr, iface->ifindex, false, false);
 320
 321                 list_del(&ip->head);
 322                 free(ip);
 323         }
 324
 325         *ptr = NULL;
 326 }
 327
 328 static bool leases_require_fr(struct interface *iface, struct odhcpd_ipaddr *addr,
 329                                 uint32_t mask)
 330 {
 331         struct dhcpv4_assignment *a = NULL;
 332         struct odhcpd_ref_ip *fr_ip = NULL;
 333
 334         list_for_each_entry(a, &iface->dhcpv4_assignments, head) {
 335                 if ((a->accept_fr_nonce || iface->dhcpv4_forcereconf) &&
 336                     !a->fr_ip &&
 337                     ((a->addr & mask) == (addr->addr.in.s_addr & mask))) {
 338                         if (!fr_ip) {
 339                                 fr_ip = calloc(1, sizeof(*fr_ip));
 340                                 if (!fr_ip)
 341                                         break;
 342
 343                                 list_add(&fr_ip->head, &iface->dhcpv4_fr_ips);
 344                                 fr_ip->addr = *addr;
 345                         }
 346                         inc_ref_cnt_ip(&a->fr_ip, fr_ip);
 347                 }
 348         }
 349
 350         return fr_ip ? true : false;
 351 }
 352
 353 static void valid_until_cb(struct uloop_timeout *event)
 354 {
 355         time_t now = odhcpd_time();
 356         struct interface *iface;
 357         list_for_each_entry(iface, &interfaces, head) {
 358                 if (iface->dhcpv4 != MODE_SERVER || iface->dhcpv4_assignments.next == NULL)
 359                         continue;
 360
 361                 struct dhcpv4_assignment *a, *n;
 362                 list_for_each_entry_safe(a, n, &iface->dhcpv4_assignments, head) {
 363                         if (!INFINITE_VALID(a->valid_until) && a->valid_until < now)
 364                                 free_dhcpv4_assignment(a);
 365                 }
 366         }
 367         uloop_timeout_set(event, 1000);
 368 }
 369
 370 static void handle_addrlist_change(struct interface *iface)
 371 {
 372         struct odhcpd_ipaddr ip;
 373         struct odhcpd_ref_ip *a;
 374         struct dhcpv4_assignment *c;
 375         uint32_t mask = iface->dhcpv4_mask.s_addr;
 376
 377         memset(&ip, 0, sizeof(ip));
 378         ip.addr.in = iface->dhcpv4_local;
 379         ip.prefix = odhcpd_netmask2bitlen(false, &iface->dhcpv4_mask);
 380         ip.broadcast = iface->dhcpv4_bcast;
 381
 382         setup_dhcpv4_addresses(iface);
 383
 384         if ((ip.addr.in.s_addr & mask) ==
 385             (iface->dhcpv4_local.s_addr & iface->dhcpv4_mask.s_addr))
 386                 return;
 387
 388         if (ip.addr.in.s_addr && !leases_require_fr(iface, &ip, mask))
 389                 return;
 390
 391         if (iface->dhcpv4_local.s_addr == INADDR_ANY || list_empty(&iface->dhcpv4_fr_ips))
 392                 return;
 393
 394         a = list_first_entry(&iface->dhcpv4_fr_ips, struct odhcpd_ref_ip, head);
 395
 396         if (netlink_setup_addr(&a->addr, iface->ifindex, false, true)) {
 397                 syslog(LOG_ERR, "Failed to add ip address");
 398                 return;
 399         }
 400
 401         list_for_each_entry(c, &iface->dhcpv4_assignments, head) {
 402                 if ((c->flags & OAF_BOUND) && c->fr_ip && !c->fr_cnt) {
 403                         if (c->accept_fr_nonce || iface->dhcpv4_forcereconf)
 404                                 dhcpv4_fr_start(c);
 405                         else
 406                                 dhcpv4_fr_stop(c);
 407                 }
 408         }
 409 }
 410
 411 static char *dhcpv4_msg_to_string(uint8_t reqmsg)
 412 {
 413         switch (reqmsg) {
 414         case (DHCPV4_MSG_DISCOVER):
 415                 return "DHCPV4_MSG_DISCOVER";
 416         case (DHCPV4_MSG_OFFER):
 417                 return "DHCPV4_MSG_OFFER";
 418         case (DHCPV4_MSG_REQUEST):
 419                 return "DHCPV4_MSG_REQUEST";
 420         case (DHCPV4_MSG_DECLINE):
 421                 return "DHCPV4_MSG_DECLINE";
 422         case (DHCPV4_MSG_ACK):
 423                 return "DHCPV4_MSG_ACK";
 424         case (DHCPV4_MSG_NAK):
 425                 return "DHCPV4_MSG_NAK";
 426         case (DHCPV4_MSG_RELEASE):
 427                 return "DHCPV4_MSG_RELEASE";
 428         case (DHCPV4_MSG_INFORM):
 429                 return "DHCPV4_MSG_INFORM";
 430         case (DHCPV4_MSG_FORCERENEW):
 431                 return "DHCPV4_MSG_FORCERENEW";
 432         default:
 433                 return "UNKNOWN";
 434         }
 435 }
 436
 437 static void free_dhcpv4_assignment(struct dhcpv4_assignment *a)
 438 {
 439         if (a->head.next)
 440                 list_del(&a->head);
 441
 442         if (a->fr_ip)
 443                 dhcpv4_fr_stop(a);
 444
 445         free(a->hostname);
 446         free(a);
 447 }
 448
 449 static void dhcpv4_put(struct dhcpv4_message *msg, uint8_t **cookie,
 450                 uint8_t type, uint8_t len, const void *data)
 451 {
 452         uint8_t *c = *cookie;
 453         if (*cookie + 2 + len > (uint8_t*)&msg[1])
 454                 return;
 455
 456         *c++ = type;
 457         *c++ = len;
 458         memcpy(c, data, len);
 459
 460         *cookie = c + len;
 461 }
 462
 463 static void dhcpv4_fr_send(struct dhcpv4_assignment *a)
 464 {
 465         struct dhcpv4_message fr_msg = {
 466                 .op = DHCPV4_BOOTREPLY,
 467                 .htype = 1,
 468                 .hlen = 6,
 469                 .hops = 0,
 470                 .secs = 0,
 471                 .flags = 0,
 472                 .ciaddr = {INADDR_ANY},
 473                 .yiaddr = {INADDR_ANY},
 474                 .siaddr = {INADDR_ANY},
 475                 .giaddr = {INADDR_ANY},
 476                 .chaddr = {0},
 477                 .sname = {0},
 478                 .file = {0},
 479         };
 480         struct dhcpv4_auth_forcerenew *auth_o, auth = {
 481                 .protocol = 3,
 482                 .algorithm = 1,
 483                 .rdm = 0,
 484                 .replay = {htonl(time(NULL)), htonl(++serial)},
 485                 .type = 2,
 486                 .key = {0},
 487         };
 488         struct interface *iface = a->iface;
 489
 490         odhcpd_urandom(&fr_msg.xid, sizeof(fr_msg.xid));
 491         memcpy(fr_msg.chaddr, a->hwaddr, fr_msg.hlen);
 492
 493         fr_msg.options[0] = 0x63;
 494         fr_msg.options[1] = 0x82;
 495         fr_msg.options[2] = 0x53;
 496         fr_msg.options[3] = 0x63;
 497
 498         uint8_t *cookie = &fr_msg.options[4];
 499         uint8_t msg = DHCPV4_MSG_FORCERENEW;
 500
 501         dhcpv4_put(&fr_msg, &cookie, DHCPV4_OPT_MESSAGE, 1, &msg);
 502         if (a->accept_fr_nonce) {
 503                 dhcpv4_put(&fr_msg, &cookie, DHCPV4_OPT_AUTHENTICATION, sizeof(auth), &auth);
 504                 auth_o = (struct dhcpv4_auth_forcerenew *)(cookie - sizeof(auth));
 505                 dhcpv4_put(&fr_msg, &cookie, DHCPV4_OPT_END, 0, NULL);
 506
 507                 md5_ctx_t md5;
 508                 uint8_t secretbytes[64];
 509                 memset(secretbytes, 0, sizeof(secretbytes));
 510                 memcpy(secretbytes, a->key, sizeof(a->key));
 511
 512                 for (size_t i = 0; i < sizeof(secretbytes); ++i)
 513                         secretbytes[i] ^= 0x36;
 514
 515                 md5_begin(&md5);
 516                 md5_hash(secretbytes, sizeof(secretbytes), &md5);
 517                 md5_hash(&fr_msg, sizeof(fr_msg), &md5);
 518                 md5_end(auth_o->key, &md5);
 519
 520                 for (size_t i = 0; i < sizeof(secretbytes); ++i) {
 521                         secretbytes[i] ^= 0x36;
 522                         secretbytes[i] ^= 0x5c;
 523                 }
 524
 525                 md5_begin(&md5);
 526                 md5_hash(secretbytes, sizeof(secretbytes), &md5);
 527                 md5_hash(auth_o->key, sizeof(auth_o->key), &md5);
 528                 md5_end(auth_o->key, &md5);
 529         } else {
 530                 dhcpv4_put(&fr_msg, &cookie, DHCPV4_OPT_SERVERID, 4,
 531                                 &a->fr_ip->addr.addr.in.s_addr);
 532                 dhcpv4_put(&fr_msg, &cookie, DHCPV4_OPT_END, 0, NULL);
 533         }
 534
 535         struct sockaddr_in dest;
 536         memset(&dest, 0, sizeof(dest));
 537         dest.sin_family = AF_INET;
 538         dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 539         dest.sin_addr.s_addr = a->addr;
 540
 541         syslog(LOG_WARNING, "sending %s to %02x:%02x:%02x:%02x:%02x:%02x - %s",
 542                         dhcpv4_msg_to_string(msg),
 543                         a->hwaddr[0], a->hwaddr[1], a->hwaddr[2],
 544                         a->hwaddr[3], a->hwaddr[4], a->hwaddr[5],
 545                         inet_ntoa(dest.sin_addr));
 546
 547         sendto(iface->dhcpv4_event.uloop.fd, &fr_msg, sizeof(fr_msg),
 548                         MSG_DONTWAIT, (struct sockaddr*)&dest, sizeof(dest));
 549 }
 550
 551 static void dhcpv4_fr_timer(struct uloop_timeout *event)
 552 {
 553         struct dhcpv4_assignment *a = container_of(event, struct dhcpv4_assignment, fr_timer);
 554
 555         if (a->fr_cnt > 0 && a->fr_cnt < 8) {
 556                 dhcpv4_fr_send(a);
 557                 uloop_timeout_set(&a->fr_timer, 1000 << a->fr_cnt);
 558                 a->fr_cnt++;
 559         } else
 560                 dhcpv4_fr_stop(a);
 561 }
 562
 563 static void dhcpv4_fr_start(struct dhcpv4_assignment *a)
 564 {
 565         uloop_timeout_set(&a->fr_timer, 1000 << a->fr_cnt);
 566         a->fr_timer.cb = dhcpv4_fr_timer;
 567         a->fr_cnt++;
 568
 569         dhcpv4_fr_send(a);
 570 }
 571
 572 static void dhcpv4_fr_stop(struct dhcpv4_assignment *a)
 573 {
 574         uloop_timeout_cancel(&a->fr_timer);
 575         decr_ref_cnt_ip(&a->fr_ip, a->iface);
 576         a->fr_cnt = 0;
 577         a->fr_timer.cb = NULL;
 578 }
 579
 580 // Handler for DHCPv4 messages
 581 static void handle_dhcpv4(void *addr, void *data, size_t len,
 582                 struct interface *iface, _unused void *dest_addr)
 583 {
 584         if (!iface->dhcpv4)
 585                 return;
 586
 587         struct dhcpv4_message *req = data;
 588         if (len < offsetof(struct dhcpv4_message, options) + 4 ||
 589                         req->op != DHCPV4_BOOTREQUEST || req->hlen != 6)
 590                 return;
 591
 592
 593         syslog(LOG_NOTICE, "Got DHCPv4 request");
 594
 595         if (!iface->dhcpv4_start_ip.s_addr && !iface->dhcpv4_end_ip.s_addr) {
 596                 syslog(LOG_WARNING, "No DHCP range available on %s", iface->name);
 597                 return;
 598         }
 599
 600         int sock = iface->dhcpv4_event.uloop.fd;
 601
 602         struct dhcpv4_message reply = {
 603                 .op = DHCPV4_BOOTREPLY,
 604                 .htype = req->htype,
 605                 .hlen = req->hlen,
 606                 .hops = 0,
 607                 .xid = req->xid,
 608                 .secs = 0,
 609                 .flags = req->flags,
 610                 .ciaddr = {INADDR_ANY},
 611                 .giaddr = req->giaddr,
 612                 .siaddr = iface->dhcpv4_local,
 613         };
 614         memcpy(reply.chaddr, req->chaddr, sizeof(reply.chaddr));
 615
 616         reply.options[0] = 0x63;
 617         reply.options[1] = 0x82;
 618         reply.options[2] = 0x53;
 619         reply.options[3] = 0x63;
 620
 621         uint8_t *cookie = &reply.options[4];
 622         uint8_t reqmsg = DHCPV4_MSG_REQUEST;
 623         uint8_t msg = DHCPV4_MSG_ACK;
 624
 625         uint32_t reqaddr = INADDR_ANY;
 626         uint32_t leasetime = 0;
 627         size_t hostname_len = 0;
 628         char hostname[256];
 629         bool accept_fr_nonce = false;
 630         bool incl_fr_opt = false;
 631
 632         uint8_t *start = &req->options[4];
 633         uint8_t *end = ((uint8_t*)data) + len;
 634         struct dhcpv4_option *opt;
 635         dhcpv4_for_each_option(start, end, opt) {
 636                 if (opt->type == DHCPV4_OPT_MESSAGE && opt->len == 1)
 637                         reqmsg = opt->data[0];
 638                 else if (opt->type == DHCPV4_OPT_HOSTNAME && opt->len > 0) {
 639                         hostname_len = opt->len;
 640                         memcpy(hostname, opt->data, hostname_len);
 641                         hostname[hostname_len] = 0;
 642                 } else if (opt->type == DHCPV4_OPT_IPADDRESS && opt->len == 4)
 643                         memcpy(&reqaddr, opt->data, 4);
 644                 else if (opt->type == DHCPV4_OPT_SERVERID && opt->len == 4) {
 645                         if (memcmp(opt->data, &iface->dhcpv4_local, 4))
 646                                 return;
 647                 } else if (iface->filter_class && opt->type == DHCPV4_OPT_USER_CLASS) {
 648                         uint8_t *c = opt->data, *cend = &opt->data[opt->len];
 649                         for (; c < cend && &c[*c] < cend; c = &c[1 + *c]) {
 650                                 size_t elen = strlen(iface->filter_class);
 651                                 if (*c == elen && !memcmp(&c[1], iface->filter_class, elen))
 652                                         return; // Ignore from homenet
 653                         }
 654                 } else if (opt->type == DHCPV4_OPT_LEASETIME && opt->len == 4)
 655                         memcpy(&leasetime, opt->data, 4);
 656                 else if (opt->type == DHCPV4_OPT_FORCERENEW_NONCE_CAPABLE && opt->len > 0) {
 657                         for (uint8_t i = 0; i < opt->len; i++) {
 658                                 if (opt->data[i] == 1) {
 659                                         accept_fr_nonce = true;
 660                                         break;
 661                                 }
 662                         }
 663
 664                 }
 665         }
 666
 667         if (reqmsg != DHCPV4_MSG_DISCOVER && reqmsg != DHCPV4_MSG_REQUEST &&
 668                         reqmsg != DHCPV4_MSG_INFORM && reqmsg != DHCPV4_MSG_DECLINE &&
 669                         reqmsg != DHCPV4_MSG_RELEASE)
 670                 return;
 671
 672         struct dhcpv4_assignment *lease = NULL;
 673         uint32_t serverid = iface->dhcpv4_local.s_addr;
 674         uint32_t fr_serverid = INADDR_ANY;
 675
 676         if (reqmsg != DHCPV4_MSG_INFORM)
 677                 lease = dhcpv4_lease(iface, reqmsg, req->chaddr, reqaddr,
 678                                         &leasetime, hostname, hostname_len,
 679                                         accept_fr_nonce, &incl_fr_opt, &fr_serverid);
 680
 681         if (!lease) {
 682                 if (reqmsg == DHCPV4_MSG_REQUEST)
 683                         msg = DHCPV4_MSG_NAK;
 684                 else if (reqmsg == DHCPV4_MSG_DISCOVER)
 685                         return;
 686         } else if (reqmsg == DHCPV4_MSG_DISCOVER)
 687                 msg = DHCPV4_MSG_OFFER;
 688         else if (reqmsg == DHCPV4_MSG_REQUEST &&
 689                         ((reqaddr && reqaddr != lease->addr) ||
 690                          (req->ciaddr.s_addr && req->ciaddr.s_addr != lease->addr))) {
 691                 msg = DHCPV4_MSG_NAK;
 692                 /*
 693                  * DHCP client requested an IP which we can't offer to him. Probably the
 694                  * client changed the network or the network has been changed. The reply
 695                  * type is set to DHCPV4_MSG_NAK, because the client should not use that IP.
 696                  *
 697                  * For modern devices we build an answer that includes a valid IP, like
 698                  * a DHCPV4_MSG_ACK. The client will use that IP and doesn't need to
 699                  * perform additional DHCP round trips.
 700                  *
 701                  */
 702
 703                 /*
 704                  *
 705                  * Buggy clients do serverid checking in nack messages; therefore set the
 706                  * serverid in nack messages triggered by a previous force renew equal to
 707                  * the server id in use at that time by the server
 708                  *
 709                  */
 710                 if (fr_serverid)
 711                         serverid = fr_serverid;
 712
 713                 if (req->ciaddr.s_addr &&
 714                                 ((iface->dhcpv4_start_ip.s_addr & iface->dhcpv4_mask.s_addr) !=
 715                                  (req->ciaddr.s_addr & iface->dhcpv4_mask.s_addr)))
 716                         req->ciaddr.s_addr = INADDR_ANY;
 717         }
 718
 719         syslog(LOG_WARNING, "received %s from %02x:%02x:%02x:%02x:%02x:%02x",
 720                         dhcpv4_msg_to_string(reqmsg),
 721                         req->chaddr[0],req->chaddr[1],req->chaddr[2],
 722                         req->chaddr[3],req->chaddr[4],req->chaddr[5]);
 723
 724 #ifdef WITH_UBUS
 725         if (reqmsg == DHCPV4_MSG_RELEASE)
 726                 ubus_bcast_dhcp_event("dhcp.release", req->chaddr, req->hlen,
 727                                         &req->ciaddr, hostname, iface->ifname);
 728 #endif
 729         if (reqmsg == DHCPV4_MSG_DECLINE || reqmsg == DHCPV4_MSG_RELEASE)
 730                 return;
 731
 732         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_MESSAGE, 1, &msg);
 733         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SERVERID, 4, &serverid);
 734
 735         if (lease) {
 736                 uint32_t val;
 737
 738                 reply.yiaddr.s_addr = lease->addr;
 739
 740                 val = htonl(leasetime);
 741                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_LEASETIME, 4, &val);
 742
 743                 if (leasetime != UINT32_MAX) {
 744                         val = htonl(500 * leasetime / 1000);
 745                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_RENEW, 4, &val);
 746
 747                         val = htonl(875 * leasetime / 1000);
 748                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_REBIND, 4, &val);
 749                 }
 750
 751                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_NETMASK, 4,
 752                                 &iface->dhcpv4_mask.s_addr);
 753
 754                 if (lease->hostname)
 755                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_HOSTNAME,
 756                                         strlen(lease->hostname), lease->hostname);
 757
 758                 if (iface->dhcpv4_bcast.s_addr != INADDR_ANY)
 759                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_BROADCAST, 4, &iface->dhcpv4_bcast);
 760
 761                 if (incl_fr_opt) {
 762                         if (reqmsg == DHCPV4_MSG_REQUEST) {
 763                                 struct dhcpv4_auth_forcerenew auth = {
 764                                         .protocol = 3,
 765                                         .algorithm = 1,
 766                                         .rdm = 0,
 767                                         .replay = {htonl(time(NULL)), htonl(++serial)},
 768                                         .type = 1,
 769                                         .key = {0},
 770                                 };
 771
 772                                 memcpy(auth.key, lease->key, sizeof(auth.key));
 773                                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_AUTHENTICATION, sizeof(auth), &auth);
 774                         } else {
 775                                 uint8_t one = 1;
 776                                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_FORCERENEW_NONCE_CAPABLE,
 777                                         sizeof(one), &one);
 778                         }
 779                 }
 780         }
 781
 782         struct ifreq ifr = {.ifr_name = ""};
 783         strncpy(ifr.ifr_name, iface->ifname, sizeof(ifr.ifr_name));
 784
 785         if (!ioctl(sock, SIOCGIFMTU, &ifr)) {
 786                 uint16_t mtu = htons(ifr.ifr_mtu);
 787                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_MTU, 2, &mtu);
 788         }
 789
 790         if (iface->search && iface->search_len <= 255)
 791                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SEARCH_DOMAIN,
 792                                 iface->search_len, iface->search);
 793         else if (!res_init() && _res.dnsrch[0] && _res.dnsrch[0][0]) {
 794                 uint8_t search_buf[256];
 795                 int len = dn_comp(_res.dnsrch[0], search_buf,
 796                                                 sizeof(search_buf), NULL, NULL);
 797                 if (len > 0)
 798                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SEARCH_DOMAIN,
 799                                         len, search_buf);
 800         }
 801
 802         if (iface->dhcpv4_router_cnt == 0)
 803                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_ROUTER, 4, &iface->dhcpv4_local);
 804         else
 805                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_ROUTER,
 806                                 4 * iface->dhcpv4_router_cnt, iface->dhcpv4_router);
 807
 808
 809         if (iface->dhcpv4_dns_cnt == 0)
 810                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_DNSSERVER, 4, &iface->dhcpv4_local);
 811         else
 812                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_DNSSERVER,
 813                                 4 * iface->dhcpv4_dns_cnt, iface->dhcpv4_dns);
 814
 815
 816         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_END, 0, NULL);
 817
 818         struct sockaddr_in dest = *((struct sockaddr_in*)addr);
 819         if (req->giaddr.s_addr) {
 820                 /*
 821                  * relay agent is configured, send reply to the agent
 822                  */
 823                 dest.sin_addr = req->giaddr;
 824                 dest.sin_port = htons(DHCPV4_SERVER_PORT);
 825         } else if (req->ciaddr.s_addr && req->ciaddr.s_addr != dest.sin_addr.s_addr) {
 826                 /*
 827                  * client has existing configuration (ciaddr is set) AND this address is
 828                  * not the address it used for the dhcp message
 829                  */
 830                 dest.sin_addr = req->ciaddr;
 831                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 832         } else if ((ntohs(req->flags) & DHCPV4_FLAG_BROADCAST) ||
 833                         req->hlen != reply.hlen || !reply.yiaddr.s_addr) {
 834                 /*
 835                  * client requests a broadcast reply OR we can't offer an IP
 836                  */
 837                 dest.sin_addr.s_addr = INADDR_BROADCAST;
 838                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 839         } else if (!req->ciaddr.s_addr && msg == DHCPV4_MSG_NAK) {
 840                 /*
 841                  * client has no previous configuration -> no IP, so we need to reply
 842                  * with a broadcast packet
 843                  */
 844                 dest.sin_addr.s_addr = INADDR_BROADCAST;
 845                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 846         } else {
 847                 /*
 848                  * send reply to the newly (in this proccess) allocated IP
 849                  */
 850                 dest.sin_addr = reply.yiaddr;
 851                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 852
 853                 struct arpreq arp = {.arp_flags = ATF_COM};
 854                 memcpy(arp.arp_ha.sa_data, req->chaddr, 6);
 855                 memcpy(&arp.arp_pa, &dest, sizeof(arp.arp_pa));
 856                 memcpy(arp.arp_dev, iface->ifname, sizeof(arp.arp_dev));
 857                 ioctl(sock, SIOCSARP, &arp);
 858         }
 859
 860         if (dest.sin_addr.s_addr == INADDR_BROADCAST)
 861                 /* reply goes to IP broadcast -> MAC broadcast */
 862                 syslog(LOG_WARNING, "sending %s to ff:ff:ff:ff:ff:ff - %s",
 863                                 dhcpv4_msg_to_string(msg),
 864                                 inet_ntoa(dest.sin_addr));
 865         else
 866                 /*
 867                  * reply is send directly to IP,
 868                  * MAC is assumed to be the same as the request
 869                  */
 870                 syslog(LOG_WARNING, "sending %s to %02x:%02x:%02x:%02x:%02x:%02x - %s",
 871                                 dhcpv4_msg_to_string(msg),
 872                                 req->chaddr[0],req->chaddr[1],req->chaddr[2],
 873                                 req->chaddr[3],req->chaddr[4],req->chaddr[5],
 874                                 inet_ntoa(dest.sin_addr));
 875
 876         sendto(sock, &reply, sizeof(reply), MSG_DONTWAIT,
 877                         (struct sockaddr*)&dest, sizeof(dest));
 878
 879 #ifdef WITH_UBUS
 880         if (msg == DHCPV4_MSG_ACK)
 881                 ubus_bcast_dhcp_event("dhcp.ack", req->chaddr, req->hlen, &reply.yiaddr,
 882                                         hostname, iface->ifname);
 883 #endif
 884 }
 885
 886 static bool dhcpv4_assign(struct interface *iface,
 887                 struct dhcpv4_assignment *assign, uint32_t raddr)
 888 {
 889         uint32_t start = ntohl(iface->dhcpv4_start_ip.s_addr);
 890         uint32_t end = ntohl(iface->dhcpv4_end_ip.s_addr);
 891         uint32_t count = end - start + 1;
 892
 893         // try to assign the IP the client asked for
 894         if (start <= ntohl(raddr) && ntohl(raddr) <= end &&
 895                         !find_assignment_by_addr(iface, raddr)) {
 896                 assign->addr = raddr;
 897                 syslog(LOG_INFO, "assigning the IP the client asked for: %u.%u.%u.%u",
 898                                 ((uint8_t *)&assign->addr)[0],
 899                                 ((uint8_t *)&assign->addr)[1],
 900                                 ((uint8_t *)&assign->addr)[2],
 901                                 ((uint8_t *)&assign->addr)[3]);
 902                 return true;
 903         }
 904
 905         // Seed RNG with checksum of hwaddress
 906         uint32_t seed = 0;
 907         for (size_t i = 0; i < sizeof(assign->hwaddr); ++i) {
 908                 // Knuth's multiplicative method
 909                 uint8_t o = assign->hwaddr[i];
 910                 seed += (o*2654435761) % UINT32_MAX;
 911         }
 912
 913         srand(seed);
 914
 915         uint32_t try = (((uint32_t)rand()) % count) + start;
 916
 917         if (list_empty(&iface->dhcpv4_assignments)) {
 918                 assign->addr = htonl(try);
 919                 syslog(LOG_INFO, "assigning mapped IP (empty list): %u.%u.%u.%u",
 920                                 ((uint8_t *)&assign->addr)[0],
 921                                 ((uint8_t *)&assign->addr)[1],
 922                                 ((uint8_t *)&assign->addr)[2],
 923                                 ((uint8_t *)&assign->addr)[3]);
 924                 return true;
 925         }
 926
 927         for (uint32_t i = 0; i < count; ++i) {
 928                 if (!find_assignment_by_addr(iface, htonl(try))) {
 929                         /* test was successful: IP address is not assigned, assign it */
 930                         assign->addr = htonl(try);
 931                         syslog(LOG_DEBUG, "assigning mapped IP: %u.%u.%u.%u (try %u of %u)",
 932                                         ((uint8_t *)&assign->addr)[0],
 933                                         ((uint8_t *)&assign->addr)[1],
 934                                         ((uint8_t *)&assign->addr)[2],
 935                                         ((uint8_t *)&assign->addr)[3],
 936                                         i, count);
 937                         return true;
 938                 }
 939                 try = (((try - start) + 1) % count) + start;
 940         }
 941
 942         syslog(LOG_WARNING, "can't assign any IP address -> address space is full");
 943         return false;
 944 }
 945
 946
 947 static struct dhcpv4_assignment* dhcpv4_lease(struct interface *iface,
 948                 enum dhcpv4_msg msg, const uint8_t *mac, const uint32_t reqaddr,
 949                 uint32_t *leasetime, const char *hostname, const size_t hostname_len,
 950                 const bool accept_fr_nonce, bool *incl_fr_opt, uint32_t *fr_serverid)
 951 {
 952         struct dhcpv4_assignment *a = find_assignment_by_hwaddr(iface, mac);
 953         struct dhcpv4_assignment *lease = NULL;
 954         time_t now = odhcpd_time();
 955
 956         if (a && (a->flags & OAF_BOUND) && a->fr_ip) {
 957                 *fr_serverid = a->fr_ip->addr.addr.in.s_addr;
 958                 dhcpv4_fr_stop(a);
 959         }
 960
 961         if (msg == DHCPV4_MSG_DISCOVER || msg == DHCPV4_MSG_REQUEST) {
 962                 bool assigned = !!a;
 963
 964                 if (!a) {
 965                         if (!iface->no_dynamic_dhcp) {
 966                                 /* Create new binding */
 967                                 a = calloc(1, sizeof(*a));
 968                                 if (!a) {
 969                                         syslog(LOG_ERR, "Failed to calloc binding on interface %s",
 970                                                         iface->ifname);
 971                                         return NULL;
 972                                 }
 973                                 memcpy(a->hwaddr, mac, sizeof(a->hwaddr));
 974                                 /* Don't consider new assignment as infinite */
 975                                 a->valid_until = now;
 976
 977                                 assigned = dhcpv4_assign(iface, a, reqaddr);
 978                                 if (assigned) {
 979                                         a->iface = iface;
 980                                         list_add(&a->head, &iface->dhcpv4_assignments);
 981                                 }
 982                         }
 983                 } else if ((a->addr & iface->dhcpv4_mask.s_addr) !=
 984                                 (iface->dhcpv4_start_ip.s_addr & iface->dhcpv4_mask.s_addr)) {
 985                         list_del(&a->head);
 986
 987                         assigned = dhcpv4_assign(iface, a, reqaddr);
 988                         if (assigned)
 989                                 list_add(&a->head, &iface->dhcpv4_assignments);
 990                 }
 991
 992                 if (assigned) {
 993                         uint32_t my_leasetime;
 994
 995                         if (a->leasetime)
 996                                 my_leasetime = a->leasetime;
 997                         else
 998                                 my_leasetime = iface->dhcpv4_leasetime;
 999
1000                         if ((*leasetime == 0) || (my_leasetime < *leasetime))
1001                                 *leasetime = my_leasetime;
1002
1003                         if (msg == DHCPV4_MSG_DISCOVER) {
1004                                 a->flags &= ~OAF_BOUND;
1005
1006                                 *incl_fr_opt = accept_fr_nonce;
1007                                 if (!(a->flags & OAF_STATIC))
1008                                         a->valid_until = now;
1009                         } else {
1010                                 if (hostname_len > 0) {
1011                                         a->hostname = realloc(a->hostname, hostname_len + 1);
1012                                         if (a->hostname) {
1013                                                 memcpy(a->hostname, hostname, hostname_len);
1014                                                 a->hostname[hostname_len] = 0;
1015                                         }
1016                                 }
1017
1018                                 if (!(a->flags & OAF_BOUND)) {
1019                                         a->accept_fr_nonce = accept_fr_nonce;
1020                                         *incl_fr_opt = accept_fr_nonce;
1021                                         odhcpd_urandom(a->key, sizeof(a->key));
1022                                         a->flags |= OAF_BOUND;
1023                                 } else
1024                                         *incl_fr_opt = false;
1025
1026                                 if (!(a->flags & OAF_STATIC))
1027                                         a->valid_until = ((*leasetime == UINT32_MAX) ? 0 : (time_t)(now + *leasetime));
1028                         }
1029                 } else if (!assigned && a) {
1030                         /* Cleanup failed assignment */
1031                         free_dhcpv4_assignment(a);
1032                         a = NULL;
1033                 }
1034
1035                 if (assigned && a)
1036                         lease = a;
1037         } else if (msg == DHCPV4_MSG_RELEASE && a) {
1038                 a->flags &= ~OAF_BOUND;
1039
1040                 if (!(a->flags & OAF_STATIC))
1041                         a->valid_until = now - 1;
1042
1043         } else if (msg == DHCPV4_MSG_DECLINE && a) {
1044                 a->flags &= ~OAF_BOUND;
1045
1046                 if (!(a->flags & OAF_STATIC)) {
1047                         memset(a->hwaddr, 0, sizeof(a->hwaddr));
1048                         a->valid_until = now + 3600; /* Block address for 1h */
1049                 }
1050         }
1051
1052         dhcpv6_write_statefile();
1053
1054         return lease;
1055 }