src/dhcpv4.c

   1 /**
   2  * Copyright (C) 2012-2013 Steven Barth <steven@midlink.org>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License v2 as published by
   6  * the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11  * GNU General Public License for more details.
  12  *
  13  *
  14  */
  15
  16 #include <time.h>
  17 #include <errno.h>
  18 #include <fcntl.h>
  19 #include <unistd.h>
  20 #include <stddef.h>
  21 #include <stdlib.h>
  22 #include <resolv.h>
  23 #include <net/if.h>
  24 #include <net/if_arp.h>
  25 #include <netinet/ip.h>
  26 #include <sys/ioctl.h>
  27 #include <sys/timerfd.h>
  28 #include <arpa/inet.h>
  29
  30 #include "odhcpd.h"
  31 #include "dhcpv4.h"
  32 #include "dhcpv6.h"
  33
  34
  35 static void handle_dhcpv4(void *addr, void *data, size_t len,
  36                 struct interface *iface);
  37 static struct dhcpv4_assignment* dhcpv4_lease(struct interface *iface,
  38                 enum dhcpv4_msg msg, const uint8_t *mac, struct in_addr reqaddr,
  39                 const char *hostname);
  40
  41 // Create socket and register events
  42 int init_dhcpv4(void)
  43 {
  44         return 0;
  45 }
  46
  47
  48 int setup_dhcpv4_interface(struct interface *iface, bool enable)
  49 {
  50         if (iface->dhcpv4_event.uloop.fd > 0) {
  51                 uloop_fd_delete(&iface->dhcpv4_event.uloop);
  52                 close(iface->dhcpv4_event.uloop.fd);
  53                 iface->dhcpv4_event.uloop.fd = -1;
  54         }
  55
  56         if (iface->dhcpv4 && enable) {
  57                 if (!iface->dhcpv4_assignments.next)
  58                         INIT_LIST_HEAD(&iface->dhcpv4_assignments);
  59
  60                 int sock = socket(AF_INET, SOCK_DGRAM | SOCK_CLOEXEC, IPPROTO_UDP);
  61                 if (sock < 0) {
  62                         syslog(LOG_ERR, "Failed to create DHCPv4 server socket: %s",
  63                                         strerror(errno));
  64                         return -1;
  65                 }
  66
  67                 // Basic IPv6 configuration
  68                 int val = 1;
  69                 setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &val, sizeof(val));
  70                 setsockopt(sock, SOL_SOCKET, SO_BROADCAST, &val, sizeof(val));
  71                 setsockopt(sock, IPPROTO_IP, IP_PKTINFO, &val, sizeof(val));
  72
  73                 val = IPTOS_PREC_INTERNETCONTROL;
  74                 setsockopt(sock, IPPROTO_IP, IP_TOS, &val, sizeof(val));
  75
  76                 val = IP_PMTUDISC_DONT;
  77                 setsockopt(sock, IPPROTO_IP, IP_MTU_DISCOVER, &val, sizeof(val));
  78
  79                 setsockopt(sock, SOL_SOCKET, SO_BINDTODEVICE,
  80                                 iface->ifname, strlen(iface->ifname));
  81
  82                 struct sockaddr_in bind_addr = {AF_INET, htons(DHCPV4_SERVER_PORT),
  83                                         {INADDR_ANY}, {0}};
  84
  85                 if (bind(sock, (struct sockaddr*)&bind_addr, sizeof(bind_addr))) {
  86                         syslog(LOG_ERR, "Failed to open DHCPv4 server socket: %s",
  87                                         strerror(errno));
  88                         return -1;
  89                 }
  90
  91
  92                 if (ntohl(iface->dhcpv4_start.s_addr) > ntohl(iface->dhcpv4_end.s_addr)) {
  93                         syslog(LOG_ERR, "Invalid DHCP range");
  94                         return -1;
  95                 }
  96
  97                 // Create a range if not specified
  98                 struct ifreq ifreq;
  99                 strncpy(ifreq.ifr_name, iface->ifname, sizeof(ifreq.ifr_name));
 100
 101                 struct sockaddr_in *saddr = (struct sockaddr_in*)&ifreq.ifr_addr;
 102                 struct sockaddr_in *smask = (struct sockaddr_in*)&ifreq.ifr_netmask;
 103                 if (!(iface->dhcpv4_start.s_addr & htonl(0xffff0000)) &&
 104                                 !(iface->dhcpv4_end.s_addr & htonl(0xffff0000)) &&
 105                                 !ioctl(sock, SIOCGIFADDR, &ifreq)) {
 106                         struct in_addr addr = saddr->sin_addr;
 107
 108                         ioctl(sock, SIOCGIFNETMASK, &ifreq);
 109                         struct in_addr mask = smask->sin_addr;
 110
 111                         uint32_t start = ntohl(iface->dhcpv4_start.s_addr);
 112                         uint32_t end = ntohl(iface->dhcpv4_end.s_addr);
 113
 114                         if (start && end && start < end &&
 115                                         start > ntohl(addr.s_addr & ~mask.s_addr) &&
 116                                         (start & ntohl(mask.s_addr)) == start &&
 117                                         (end & ntohl(mask.s_addr)) == end) {
 118                                 iface->dhcpv4_start.s_addr = htonl(start) |
 119                                                 (addr.s_addr & mask.s_addr);
 120                                 iface->dhcpv4_end.s_addr = htonl(end) |
 121                                                 (addr.s_addr & mask.s_addr);
 122                         } else if (ntohl(mask.s_addr) <= 0xfffffff0) {
 123                                 start = addr.s_addr & mask.s_addr;
 124                                 end = addr.s_addr & mask.s_addr;
 125
 126                                 if (ntohl(mask.s_addr) <= 0xffffff00) {
 127                                         iface->dhcpv4_start.s_addr = start | htonl(100);
 128                                         iface->dhcpv4_end.s_addr = end | htonl(250);
 129                                 } else if (ntohl(mask.s_addr) <= 0xffffffc0) {
 130                                         iface->dhcpv4_start.s_addr = start | htonl(10);
 131                                         iface->dhcpv4_end.s_addr = end | htonl(60);
 132                                 } else if (ntohl(mask.s_addr) <= 0xffffffe0) {
 133                                         iface->dhcpv4_start.s_addr = start | htonl(10);
 134                                         iface->dhcpv4_end.s_addr = end | htonl(30);
 135                                 } else {
 136                                         iface->dhcpv4_start.s_addr = start | htonl(3);
 137                                         iface->dhcpv4_end.s_addr = end | htonl(12);
 138                                 }
 139                         }
 140
 141
 142                 }
 143
 144                 // Parse static entries
 145                 struct lease *lease;
 146                 list_for_each_entry(lease, &leases, head) {
 147                         // Construct entry
 148                         size_t hostlen = strlen(lease->hostname) + 1;
 149                         struct dhcpv4_assignment *a = calloc(1, sizeof(*a) + hostlen);
 150                         if (!a) {
 151                                 syslog(LOG_ERR, "Calloc failed for static lease on interface %s",
 152                                         iface->ifname);
 153                                 return -1;
 154                         }
 155                         a->addr = ntohl(lease->ipaddr.s_addr);
 156                         memcpy(a->hwaddr, lease->mac.ether_addr_octet, sizeof(a->hwaddr));
 157                         memcpy(a->hostname, lease->hostname, hostlen);
 158
 159                         // Assign to all interfaces
 160                         struct dhcpv4_assignment *c;
 161                         list_for_each_entry(c, &iface->dhcpv4_assignments, head) {
 162                                 if (c->addr > a->addr) {
 163                                         list_add_tail(&a->head, &c->head);
 164                                 } else if (c->addr == a->addr) {
 165                                         // Already an assignment with that number
 166                                         break;
 167                                 }
 168                         }
 169
 170                         if (!a->head.next)
 171                                 free(a);
 172                 }
 173
 174                 // Clean invalid assignments
 175                 struct dhcpv4_assignment *a, *n;
 176                 list_for_each_entry_safe(a, n, &iface->dhcpv4_assignments, head) {
 177                         if ((htonl(a->addr) & smask->sin_addr.s_addr) !=
 178                                         (saddr->sin_addr.s_addr & smask->sin_addr.s_addr)) {
 179                                 list_del(&a->head);
 180                                 free(a);
 181                         }
 182                 }
 183
 184
 185                 if (iface->dhcpv4_leasetime < 60)
 186                         iface->dhcpv4_leasetime = 43200;
 187
 188                 iface->dhcpv4_event.uloop.fd = sock;
 189                 iface->dhcpv4_event.handle_dgram = handle_dhcpv4;
 190                 odhcpd_register(&iface->dhcpv4_event);
 191         } else if (iface->dhcpv4_assignments.next) {
 192                 while (!list_empty(&iface->dhcpv4_assignments)) {
 193                         struct dhcpv4_assignment *a = list_first_entry(&iface->dhcpv4_assignments,
 194                                         struct dhcpv4_assignment, head);
 195                         list_del(&a->head);
 196                         free(a->hostname);
 197                         free(a);
 198                 }
 199
 200         }
 201         return 0;
 202 }
 203
 204
 205 static void dhcpv4_put(struct dhcpv4_message *msg, uint8_t **cookie,
 206                 uint8_t type, uint8_t len, const void *data)
 207 {
 208         uint8_t *c = *cookie;
 209         if (*cookie + 2 + len > (uint8_t*)&msg[1])
 210                 return;
 211
 212         *c++ = type;
 213         *c++ = len;
 214         memcpy(c, data, len);
 215
 216         *cookie = c + len;
 217 }
 218
 219
 220 // Simple DHCPv6-server for information requests
 221 static void handle_dhcpv4(void *addr, void *data, size_t len,
 222                 struct interface *iface)
 223 {
 224         if (!iface->dhcpv4)
 225                 return;
 226
 227         struct dhcpv4_message *req = data;
 228         if (len < offsetof(struct dhcpv4_message, options) + 4 ||
 229                         req->op != DHCPV4_BOOTREQUEST || req->hlen != 6)
 230                 return;
 231
 232         int sock = iface->dhcpv4_event.uloop.fd;
 233         struct sockaddr_in ifaddr;
 234         struct sockaddr_in ifnetmask;
 235
 236         syslog(LOG_NOTICE, "Got DHCPv4 request");
 237
 238         struct ifreq ifreq;
 239         memcpy(ifreq.ifr_name, iface->ifname, sizeof(ifreq.ifr_name));
 240         if (ioctl(sock, SIOCGIFADDR, &ifreq)) {
 241                 syslog(LOG_WARNING, "DHCPv4 failed to detect address: %s", strerror(errno));
 242                 return;
 243         }
 244
 245         memcpy(&ifaddr, &ifreq.ifr_addr, sizeof(ifaddr));
 246         if (ioctl(sock, SIOCGIFNETMASK, &ifreq))
 247                 return;
 248
 249         memcpy(&ifnetmask, &ifreq.ifr_netmask, sizeof(ifnetmask));
 250         uint32_t network = ifaddr.sin_addr.s_addr & ifnetmask.sin_addr.s_addr;
 251
 252         if ((iface->dhcpv4_start.s_addr & ifnetmask.sin_addr.s_addr) != network ||
 253                         (iface->dhcpv4_end.s_addr & ifnetmask.sin_addr.s_addr) != network) {
 254                 syslog(LOG_WARNING, "DHCPv4 range out of assigned network");
 255                 return;
 256         }
 257
 258         struct ifreq ifr = {.ifr_name = ""};
 259         strncpy(ifr.ifr_name, iface->ifname, sizeof(ifr.ifr_name));
 260
 261         struct dhcpv4_message reply = {
 262                 .op = DHCPV4_BOOTREPLY,
 263                 .htype = 1,
 264                 .hlen = 6,
 265                 .hops = 0,
 266                 .xid = req->xid,
 267                 .secs = 0,
 268                 .flags = req->flags,
 269                 .ciaddr = {INADDR_ANY},
 270                 .giaddr = req->giaddr,
 271                 .siaddr = ifaddr.sin_addr,
 272         };
 273         memcpy(reply.chaddr, req->chaddr, sizeof(reply.chaddr));
 274
 275         reply.options[0] = 0x63;
 276         reply.options[1] = 0x82;
 277         reply.options[2] = 0x53;
 278         reply.options[3] = 0x63;
 279
 280         uint8_t *cookie = &reply.options[4];
 281         uint8_t reqmsg = DHCPV4_MSG_REQUEST;
 282         uint8_t msg = DHCPV4_MSG_ACK;
 283
 284         struct in_addr reqaddr = {INADDR_ANY};
 285         char hostname[256];
 286         hostname[0] = 0;
 287
 288         uint8_t *start = &req->options[4];
 289         uint8_t *end = ((uint8_t*)data) + len;
 290         struct dhcpv4_option *opt;
 291         dhcpv4_for_each_option(start, end, opt) {
 292                 if (opt->type == DHCPV4_OPT_MESSAGE && opt->len == 1) {
 293                         reqmsg = opt->data[0];
 294                 } else if (opt->type == DHCPV4_OPT_HOSTNAME && opt->len > 0) {
 295                         memcpy(hostname, opt->data, opt->len);
 296                         hostname[opt->len] = 0;
 297                 } else if (opt->type == DHCPV4_OPT_IPADDRESS && opt->len == 4) {
 298                         memcpy(&reqaddr, opt->data, 4);
 299                 } else if (opt->type == DHCPV4_OPT_SERVERID && opt->len == 4) {
 300                         if (memcmp(opt->data, &ifaddr.sin_addr, 4))
 301                                 return;
 302                 } else if (iface->filter_class && opt->type == DHCPV4_OPT_USER_CLASS) {
 303                         uint8_t *c = opt->data, *cend = &opt->data[opt->len];
 304                         for (; c < cend && &c[*c] < cend; c = &c[1 + *c]) {
 305                                 size_t elen = strlen(iface->filter_class);
 306                                 if (*c == elen && !memcmp(&c[1], iface->filter_class, elen))
 307                                         return; // Ignore from homenet
 308                         }
 309                 }
 310         }
 311
 312         if (reqmsg != DHCPV4_MSG_DISCOVER && reqmsg != DHCPV4_MSG_REQUEST &&
 313                         reqmsg != DHCPV4_MSG_INFORM && reqmsg != DHCPV4_MSG_DECLINE &&
 314                         reqmsg != DHCPV4_MSG_RELEASE)
 315                 return;
 316
 317         struct dhcpv4_assignment *lease = NULL;
 318         if (reqmsg != DHCPV4_MSG_INFORM)
 319                 lease = dhcpv4_lease(iface, reqmsg, req->chaddr, reqaddr, hostname);
 320
 321         if (!lease) {
 322                 if (reqmsg == DHCPV4_MSG_REQUEST)
 323                         msg = DHCPV4_MSG_NAK;
 324                 else if (reqmsg == DHCPV4_MSG_DISCOVER)
 325                         return;
 326         } else if (reqmsg == DHCPV4_MSG_DISCOVER) {
 327                 msg = DHCPV4_MSG_OFFER;
 328         }
 329
 330         if (reqmsg == DHCPV4_MSG_DECLINE || reqmsg == DHCPV4_MSG_RELEASE)
 331                 return;
 332
 333         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_MESSAGE, 1, &msg);
 334         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SERVERID, 4, &ifaddr.sin_addr);
 335
 336         if (lease) {
 337                 reply.yiaddr.s_addr = htonl(lease->addr);
 338
 339                 uint32_t val = htonl(iface->dhcpv4_leasetime);
 340                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_LEASETIME, 4, &val);
 341
 342                 val = htonl(500 * iface->dhcpv4_leasetime / 1000);
 343                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_RENEW, 4, &val);
 344
 345                 val = htonl(875 * iface->dhcpv4_leasetime / 1000);
 346                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_REBIND, 4, &val);
 347
 348                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_NETMASK, 4, &ifnetmask.sin_addr);
 349
 350                 if (lease->hostname[0])
 351                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_HOSTNAME,
 352                                         strlen(lease->hostname), lease->hostname);
 353
 354                 if (!ioctl(sock, SIOCGIFBRDADDR, &ifr)) {
 355                         struct sockaddr_in *ina = (struct sockaddr_in*)&ifr.ifr_broadaddr;
 356                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_BROADCAST, 4, &ina->sin_addr);
 357                 }
 358         }
 359
 360         if (!ioctl(sock, SIOCGIFMTU, &ifr)) {
 361                 uint16_t mtu = htons(ifr.ifr_mtu);
 362                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_MTU, 2, &mtu);
 363         }
 364
 365         if (iface->search && iface->search_len <= 255) {
 366                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SEARCH_DOMAIN,
 367                                 iface->search_len, iface->search);
 368         } else if (!res_init() && _res.dnsrch[0] && _res.dnsrch[0][0]) {
 369                 uint8_t search_buf[256];
 370                 int len = dn_comp(_res.dnsrch[0], search_buf,
 371                                                 sizeof(search_buf), NULL, NULL);
 372                 if (len > 0)
 373                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SEARCH_DOMAIN,
 374                                         len, search_buf);
 375         }
 376
 377         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_ROUTER, 4, &ifaddr.sin_addr);
 378
 379
 380
 381         if (iface->dhcpv4_dns_cnt == 0)
 382                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_DNSSERVER, 4, &ifaddr.sin_addr);
 383         else
 384                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_DNSSERVER,
 385                                 4 * iface->dhcpv4_dns_cnt, iface->dhcpv4_dns);
 386
 387
 388         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_END, 0, NULL);
 389
 390         struct sockaddr_in dest = *((struct sockaddr_in*)addr);
 391         if (req->giaddr.s_addr) {
 392                 dest.sin_addr = req->giaddr;
 393                 dest.sin_port = htons(DHCPV4_SERVER_PORT);
 394         } else if (req->ciaddr.s_addr && req->ciaddr.s_addr != dest.sin_addr.s_addr) {
 395                 dest.sin_addr = req->ciaddr;
 396                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 397         } else if ((ntohs(req->flags) & DHCPV4_FLAG_BROADCAST) ||
 398                         req->hlen != reply.hlen) {
 399                 dest.sin_addr.s_addr = INADDR_BROADCAST;
 400                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 401         } else {
 402                 dest.sin_addr = reply.yiaddr;
 403                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 404
 405                 struct arpreq arp = {.arp_flags = ATF_COM};
 406                 memcpy(arp.arp_ha.sa_data, req->chaddr, 6);
 407                 memcpy(&arp.arp_pa, &dest, sizeof(arp.arp_pa));
 408                 memcpy(arp.arp_dev, iface->ifname, sizeof(arp.arp_dev));
 409                 ioctl(sock, SIOCSARP, &arp);
 410         }
 411
 412         sendto(sock, &reply, sizeof(reply), MSG_DONTWAIT,
 413                         (struct sockaddr*)&dest, sizeof(dest));
 414 }
 415
 416
 417 static bool dhcpv4_assign(struct interface *iface,
 418                 struct dhcpv4_assignment *assign, uint32_t raddr)
 419 {
 420         const unsigned tries = 10;
 421         uint32_t start = ntohl(iface->dhcpv4_start.s_addr);
 422         uint32_t end = ntohl(iface->dhcpv4_end.s_addr);
 423         uint32_t count = end - start + 1;
 424
 425         // Seed RNG with checksum of DUID
 426         uint32_t seed = 0;
 427         for (size_t i = 0; i < sizeof(assign->hwaddr); ++i)
 428                 seed += assign->hwaddr[i];
 429         srand(seed);
 430
 431         // Try to assign up to 100x
 432         for (unsigned i = 0; i < tries; ++i) {
 433                 uint32_t try = (((uint32_t)rand()) % count) + start;
 434                 if (i == 0 && raddr >= start && raddr <= end)
 435                         try = raddr;
 436                 else if (i == tries - 1)
 437                         try = start;
 438
 439                 if (list_empty(&iface->dhcpv4_assignments)) {
 440                         assign->addr = try;
 441                         list_add(&assign->head, &iface->dhcpv4_assignments);
 442                         return true;
 443                 }
 444
 445                 struct dhcpv4_assignment *c;
 446                 list_for_each_entry(c, &iface->dhcpv4_assignments, head) {
 447                         if (c->addr > try) {
 448                                 assign->addr = try;
 449                                 list_add_tail(&assign->head, &c->head);
 450                                 return true;
 451                         } else if (c->addr == try) {
 452                                 if (i < tries - 1)
 453                                         break;
 454                                 else
 455                                         ++try;
 456                         }
 457                 }
 458         }
 459
 460         return false;
 461 }
 462
 463
 464 static struct dhcpv4_assignment* dhcpv4_lease(struct interface *iface,
 465                 enum dhcpv4_msg msg, const uint8_t *mac, struct in_addr reqaddr,
 466                 const char *hostname)
 467 {
 468         struct dhcpv4_assignment *lease = NULL;
 469         uint32_t raddr = ntohl(reqaddr.s_addr);
 470         time_t now = odhcpd_time();
 471
 472         struct dhcpv4_assignment *c, *n, *a = NULL;
 473         list_for_each_entry_safe(c, n, &iface->dhcpv4_assignments, head) {
 474                 if (c->addr == raddr && !memcmp(c->hwaddr, mac, 6)) {
 475                         a = c;
 476                         break;
 477                 } else if (c->valid_until < now) {
 478                         list_del(&c->head);
 479                         free(c);
 480                 }
 481         }
 482
 483         bool update_state = false;
 484         if (msg == DHCPV4_MSG_DISCOVER || msg == DHCPV4_MSG_REQUEST) {
 485                 bool assigned = !!a;
 486                 size_t hostlen = strlen(hostname) + 1;
 487
 488                 if (!a && !iface->no_dynamic_dhcp) { // Create new binding
 489                         a = calloc(1, sizeof(*a) + hostlen);
 490                         if (!a) {
 491                                 syslog(LOG_ERR, "Failed to calloc binding on interface %s", iface->ifname);
 492                                 return NULL;
 493                         }
 494                         memcpy(a->hwaddr, mac, sizeof(a->hwaddr));
 495                         memcpy(a->hostname, hostname, hostlen);
 496
 497                         assigned = dhcpv4_assign(iface, a, raddr);
 498                 }
 499
 500                 if (assigned && !a->hostname[0] && hostname) {
 501                         a = realloc(a, sizeof(*a) + hostlen);
 502                         if (!a) {
 503                                 syslog(LOG_ERR, "Failed to realloc binding on interface %s", iface->ifname);
 504                                 return NULL;
 505                         }
 506                         memcpy(a->hostname, hostname, hostlen);
 507
 508                         // Fixup list
 509                         a->head.next->prev = &a->head;
 510                         a->head.prev->next = &a->head;
 511                 }
 512
 513                 // Was only a solicitation: mark binding for removal
 514                 if (assigned && a->valid_until < now) {
 515                         a->valid_until = (msg == DHCPV4_MSG_DISCOVER) ? 0 :
 516                                         (now + iface->dhcpv4_leasetime);
 517                 } else if (!assigned && a) { // Cleanup failed assignment
 518                         free(a);
 519                         a = NULL;
 520                 } else {
 521                         update_state = true;
 522                 }
 523
 524                 if (assigned && a)
 525                         lease = a;
 526         } else if (msg == DHCPV4_MSG_RELEASE) {
 527                 if (a) {
 528                         a->valid_until = 0;
 529                         update_state = true;
 530                 }
 531         } else if (msg == DHCPV4_MSG_DECLINE) {
 532                 memset(a->hwaddr, 0, sizeof(a->hwaddr));
 533                 a->valid_until = now + 3600; // Block address for 1h
 534                 update_state = true;
 535         }
 536
 537         if (update_state)
 538                 dhcpv6_write_statefile();
 539
 540         return lease;
 541 }
 542