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 <limits.h>
  24 #include <net/if.h>
  25 #include <net/if_arp.h>
  26 #include <netinet/ip.h>
  27 #include <sys/ioctl.h>
  28 #include <sys/timerfd.h>
  29 #include <arpa/inet.h>
  30
  31 #include "odhcpd.h"
  32 #include "dhcpv4.h"
  33 #include "dhcpv6.h"
  34
  35
  36 static void handle_dhcpv4(void *addr, void *data, size_t len,
  37                 struct interface *iface, void *dest_addr);
  38 static struct dhcpv4_assignment* dhcpv4_lease(struct interface *iface,
  39                 enum dhcpv4_msg msg, const uint8_t *mac, struct in_addr reqaddr,
  40                 const char *hostname);
  41
  42 // Create socket and register events
  43 int init_dhcpv4(void)
  44 {
  45         return 0;
  46 }
  47
  48
  49 int setup_dhcpv4_interface(struct interface *iface, bool enable)
  50 {
  51         if (iface->dhcpv4_event.uloop.fd > 0) {
  52                 uloop_fd_delete(&iface->dhcpv4_event.uloop);
  53                 close(iface->dhcpv4_event.uloop.fd);
  54                 iface->dhcpv4_event.uloop.fd = -1;
  55         }
  56
  57         if (iface->dhcpv4 && enable) {
  58                 if (!iface->dhcpv4_assignments.next)
  59                         INIT_LIST_HEAD(&iface->dhcpv4_assignments);
  60
  61                 int sock = socket(AF_INET, SOCK_DGRAM | SOCK_CLOEXEC, IPPROTO_UDP);
  62                 if (sock < 0) {
  63                         syslog(LOG_ERR, "Failed to create DHCPv4 server socket: %s",
  64                                         strerror(errno));
  65                         return -1;
  66                 }
  67
  68                 // Basic IPv6 configuration
  69                 int val = 1;
  70                 setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &val, sizeof(val));
  71                 setsockopt(sock, SOL_SOCKET, SO_BROADCAST, &val, sizeof(val));
  72                 setsockopt(sock, IPPROTO_IP, IP_PKTINFO, &val, sizeof(val));
  73
  74                 val = IPTOS_PREC_INTERNETCONTROL;
  75                 setsockopt(sock, IPPROTO_IP, IP_TOS, &val, sizeof(val));
  76
  77                 val = IP_PMTUDISC_DONT;
  78                 setsockopt(sock, IPPROTO_IP, IP_MTU_DISCOVER, &val, sizeof(val));
  79
  80                 setsockopt(sock, SOL_SOCKET, SO_BINDTODEVICE,
  81                                 iface->ifname, strlen(iface->ifname));
  82
  83                 struct sockaddr_in bind_addr = {AF_INET, htons(DHCPV4_SERVER_PORT),
  84                                         {INADDR_ANY}, {0}};
  85
  86                 if (bind(sock, (struct sockaddr*)&bind_addr, sizeof(bind_addr))) {
  87                         syslog(LOG_ERR, "Failed to open DHCPv4 server socket: %s",
  88                                         strerror(errno));
  89                         return -1;
  90                 }
  91
  92
  93                 if (ntohl(iface->dhcpv4_start.s_addr) > ntohl(iface->dhcpv4_end.s_addr)) {
  94                         syslog(LOG_ERR, "Invalid DHCP range");
  95                         return -1;
  96                 }
  97
  98                 // Create a range if not specified
  99                 struct ifreq ifreq;
 100                 strncpy(ifreq.ifr_name, iface->ifname, sizeof(ifreq.ifr_name));
 101
 102                 struct sockaddr_in *saddr = (struct sockaddr_in*)&ifreq.ifr_addr;
 103                 struct sockaddr_in *smask = (struct sockaddr_in*)&ifreq.ifr_netmask;
 104                 if (!(iface->dhcpv4_start.s_addr & htonl(0xffff0000)) &&
 105                                 !(iface->dhcpv4_end.s_addr & htonl(0xffff0000)) &&
 106                                 !ioctl(sock, SIOCGIFADDR, &ifreq)) {
 107                         struct in_addr addr = saddr->sin_addr;
 108
 109                         ioctl(sock, SIOCGIFNETMASK, &ifreq);
 110                         struct in_addr mask = smask->sin_addr;
 111
 112                         uint32_t start = ntohl(iface->dhcpv4_start.s_addr);
 113                         uint32_t end = ntohl(iface->dhcpv4_end.s_addr);
 114
 115                         if (start && end && start < end &&
 116                                         start > ntohl(addr.s_addr & ~mask.s_addr) &&
 117                                         (start & ntohl(mask.s_addr)) == start &&
 118                                         (end & ntohl(mask.s_addr)) == end) {
 119                                 iface->dhcpv4_start.s_addr = htonl(start) |
 120                                                 (addr.s_addr & mask.s_addr);
 121                                 iface->dhcpv4_end.s_addr = htonl(end) |
 122                                                 (addr.s_addr & mask.s_addr);
 123                         } else if (ntohl(mask.s_addr) <= 0xfffffff0) {
 124                                 start = addr.s_addr & mask.s_addr;
 125                                 end = addr.s_addr & mask.s_addr;
 126
 127                                 if (ntohl(mask.s_addr) <= 0xffffff00) {
 128                                         iface->dhcpv4_start.s_addr = start | htonl(100);
 129                                         iface->dhcpv4_end.s_addr = end | htonl(250);
 130                                 } else if (ntohl(mask.s_addr) <= 0xffffffc0) {
 131                                         iface->dhcpv4_start.s_addr = start | htonl(10);
 132                                         iface->dhcpv4_end.s_addr = end | htonl(60);
 133                                 } else if (ntohl(mask.s_addr) <= 0xffffffe0) {
 134                                         iface->dhcpv4_start.s_addr = start | htonl(10);
 135                                         iface->dhcpv4_end.s_addr = end | htonl(30);
 136                                 } else {
 137                                         iface->dhcpv4_start.s_addr = start | htonl(3);
 138                                         iface->dhcpv4_end.s_addr = end | htonl(12);
 139                                 }
 140                         }
 141
 142
 143                 }
 144
 145                 // Parse static entries
 146                 struct lease *lease;
 147                 list_for_each_entry(lease, &leases, head) {
 148                         // Construct entry
 149                         size_t hostlen = strlen(lease->hostname) + 1;
 150                         struct dhcpv4_assignment *a = calloc(1, sizeof(*a) + hostlen);
 151                         if (!a) {
 152                                 syslog(LOG_ERR, "Calloc failed for static lease on interface %s",
 153                                         iface->ifname);
 154                                 return -1;
 155                         }
 156                         a->addr = ntohl(lease->ipaddr.s_addr);
 157                         memcpy(a->hwaddr, lease->mac.ether_addr_octet, sizeof(a->hwaddr));
 158                         memcpy(a->hostname, lease->hostname, hostlen);
 159                         a->valid_until = LONG_MAX;
 160
 161                         // Assign to all interfaces
 162                         struct dhcpv4_assignment *c;
 163                         list_for_each_entry(c, &iface->dhcpv4_assignments, head) {
 164                                 if (c->addr > a->addr) {
 165                                         list_add_tail(&a->head, &c->head);
 166                                         break;
 167                                 } else if (c->addr == a->addr) {
 168                                         // Already an assignment with that number
 169                                         break;
 170                                 }
 171                         }
 172                         if (&c->head == &iface->dhcpv4_assignments) {
 173                                 list_add(&a->head, &iface->dhcpv4_assignments);
 174                         }
 175
 176                         if (!a->head.next)
 177                                 free(a);
 178                 }
 179
 180                 // Clean invalid assignments
 181                 struct dhcpv4_assignment *a, *n;
 182                 list_for_each_entry_safe(a, n, &iface->dhcpv4_assignments, head) {
 183                         if ((htonl(a->addr) & smask->sin_addr.s_addr) !=
 184                                         (iface->dhcpv4_start.s_addr & smask->sin_addr.s_addr)) {
 185                                 list_del(&a->head);
 186                                 free(a);
 187                         }
 188                 }
 189
 190
 191                 if (iface->dhcpv4_leasetime < 60)
 192                         iface->dhcpv4_leasetime = 43200;
 193
 194                 iface->dhcpv4_event.uloop.fd = sock;
 195                 iface->dhcpv4_event.handle_dgram = handle_dhcpv4;
 196                 odhcpd_register(&iface->dhcpv4_event);
 197         } else if (iface->dhcpv4_assignments.next) {
 198                 while (!list_empty(&iface->dhcpv4_assignments)) {
 199                         struct dhcpv4_assignment *a = list_first_entry(&iface->dhcpv4_assignments,
 200                                         struct dhcpv4_assignment, head);
 201                         list_del(&a->head);
 202                         free(a->hostname);
 203                         free(a);
 204                 }
 205
 206         }
 207         return 0;
 208 }
 209
 210
 211 static void dhcpv4_put(struct dhcpv4_message *msg, uint8_t **cookie,
 212                 uint8_t type, uint8_t len, const void *data)
 213 {
 214         uint8_t *c = *cookie;
 215         if (*cookie + 2 + len > (uint8_t*)&msg[1])
 216                 return;
 217
 218         *c++ = type;
 219         *c++ = len;
 220         memcpy(c, data, len);
 221
 222         *cookie = c + len;
 223 }
 224
 225
 226 // Simple DHCPv6-server for information requests
 227 static void handle_dhcpv4(void *addr, void *data, size_t len,
 228                 struct interface *iface, _unused void *dest_addr)
 229 {
 230         if (!iface->dhcpv4)
 231                 return;
 232
 233         struct dhcpv4_message *req = data;
 234         if (len < offsetof(struct dhcpv4_message, options) + 4 ||
 235                         req->op != DHCPV4_BOOTREQUEST || req->hlen != 6)
 236                 return;
 237
 238         int sock = iface->dhcpv4_event.uloop.fd;
 239         struct sockaddr_in ifaddr;
 240         struct sockaddr_in ifnetmask;
 241
 242         syslog(LOG_NOTICE, "Got DHCPv4 request");
 243
 244         struct ifreq ifreq;
 245         memcpy(ifreq.ifr_name, iface->ifname, sizeof(ifreq.ifr_name));
 246         if (ioctl(sock, SIOCGIFADDR, &ifreq)) {
 247                 syslog(LOG_WARNING, "DHCPv4 failed to detect address: %s", strerror(errno));
 248                 return;
 249         }
 250
 251         memcpy(&ifaddr, &ifreq.ifr_addr, sizeof(ifaddr));
 252         if (ioctl(sock, SIOCGIFNETMASK, &ifreq))
 253                 return;
 254
 255         memcpy(&ifnetmask, &ifreq.ifr_netmask, sizeof(ifnetmask));
 256         uint32_t network = ifaddr.sin_addr.s_addr & ifnetmask.sin_addr.s_addr;
 257
 258         if ((iface->dhcpv4_start.s_addr & ifnetmask.sin_addr.s_addr) != network ||
 259                         (iface->dhcpv4_end.s_addr & ifnetmask.sin_addr.s_addr) != network) {
 260                 syslog(LOG_WARNING, "DHCPv4 range out of assigned network");
 261                 return;
 262         }
 263
 264         struct ifreq ifr = {.ifr_name = ""};
 265         strncpy(ifr.ifr_name, iface->ifname, sizeof(ifr.ifr_name));
 266
 267         struct dhcpv4_message reply = {
 268                 .op = DHCPV4_BOOTREPLY,
 269                 .htype = 1,
 270                 .hlen = 6,
 271                 .hops = 0,
 272                 .xid = req->xid,
 273                 .secs = 0,
 274                 .flags = req->flags,
 275                 .ciaddr = {INADDR_ANY},
 276                 .giaddr = req->giaddr,
 277                 .siaddr = ifaddr.sin_addr,
 278         };
 279         memcpy(reply.chaddr, req->chaddr, sizeof(reply.chaddr));
 280
 281         reply.options[0] = 0x63;
 282         reply.options[1] = 0x82;
 283         reply.options[2] = 0x53;
 284         reply.options[3] = 0x63;
 285
 286         uint8_t *cookie = &reply.options[4];
 287         uint8_t reqmsg = DHCPV4_MSG_REQUEST;
 288         uint8_t msg = DHCPV4_MSG_ACK;
 289
 290         struct in_addr reqaddr = {INADDR_ANY};
 291         char hostname[256];
 292         hostname[0] = 0;
 293
 294         uint8_t *start = &req->options[4];
 295         uint8_t *end = ((uint8_t*)data) + len;
 296         struct dhcpv4_option *opt;
 297         dhcpv4_for_each_option(start, end, opt) {
 298                 if (opt->type == DHCPV4_OPT_MESSAGE && opt->len == 1) {
 299                         reqmsg = opt->data[0];
 300                 } else if (opt->type == DHCPV4_OPT_HOSTNAME && opt->len > 0) {
 301                         memcpy(hostname, opt->data, opt->len);
 302                         hostname[opt->len] = 0;
 303                 } else if (opt->type == DHCPV4_OPT_IPADDRESS && opt->len == 4) {
 304                         memcpy(&reqaddr, opt->data, 4);
 305                 } else if (opt->type == DHCPV4_OPT_SERVERID && opt->len == 4) {
 306                         if (memcmp(opt->data, &ifaddr.sin_addr, 4))
 307                                 return;
 308                 } else if (iface->filter_class && opt->type == DHCPV4_OPT_USER_CLASS) {
 309                         uint8_t *c = opt->data, *cend = &opt->data[opt->len];
 310                         for (; c < cend && &c[*c] < cend; c = &c[1 + *c]) {
 311                                 size_t elen = strlen(iface->filter_class);
 312                                 if (*c == elen && !memcmp(&c[1], iface->filter_class, elen))
 313                                         return; // Ignore from homenet
 314                         }
 315                 }
 316         }
 317
 318         if (reqmsg != DHCPV4_MSG_DISCOVER && reqmsg != DHCPV4_MSG_REQUEST &&
 319                         reqmsg != DHCPV4_MSG_INFORM && reqmsg != DHCPV4_MSG_DECLINE &&
 320                         reqmsg != DHCPV4_MSG_RELEASE)
 321                 return;
 322
 323         struct dhcpv4_assignment *lease = NULL;
 324         if (reqmsg != DHCPV4_MSG_INFORM)
 325                 lease = dhcpv4_lease(iface, reqmsg, req->chaddr, reqaddr, hostname);
 326
 327         if (!lease) {
 328                 if (reqmsg == DHCPV4_MSG_REQUEST)
 329                         msg = DHCPV4_MSG_NAK;
 330                 else if (reqmsg == DHCPV4_MSG_DISCOVER)
 331                         return;
 332         } else if (reqmsg == DHCPV4_MSG_DISCOVER) {
 333                 msg = DHCPV4_MSG_OFFER;
 334         } else if (reqmsg == DHCPV4_MSG_REQUEST && reqaddr.s_addr &&
 335                         reqaddr.s_addr != htonl(lease->addr)) {
 336                 msg = DHCPV4_MSG_NAK;
 337                 /*
 338                  * DHCP client requested an IP which we can't offer to him. Probably the
 339                  * client changed the network. The reply type is set to DHCPV4_MSG_NAK,
 340                  * because the client should not use that IP.
 341                  *
 342                  * For modern devices we build an answer that includes a valid IP, like
 343                  * a DHCPV4_MSG_ACK. The client will use that IP and doesn't need to
 344                  * perform additional DHCP round trips.
 345                  *
 346                  */
 347         }
 348
 349         if (reqmsg == DHCPV4_MSG_DECLINE || reqmsg == DHCPV4_MSG_RELEASE)
 350                 return;
 351
 352         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_MESSAGE, 1, &msg);
 353         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SERVERID, 4, &ifaddr.sin_addr);
 354
 355         if (lease) {
 356                 reply.yiaddr.s_addr = htonl(lease->addr);
 357
 358                 uint32_t val = htonl(iface->dhcpv4_leasetime);
 359                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_LEASETIME, 4, &val);
 360
 361                 val = htonl(500 * iface->dhcpv4_leasetime / 1000);
 362                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_RENEW, 4, &val);
 363
 364                 val = htonl(875 * iface->dhcpv4_leasetime / 1000);
 365                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_REBIND, 4, &val);
 366
 367                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_NETMASK, 4, &ifnetmask.sin_addr);
 368
 369                 if (lease->hostname[0])
 370                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_HOSTNAME,
 371                                         strlen(lease->hostname), lease->hostname);
 372
 373                 if (!ioctl(sock, SIOCGIFBRDADDR, &ifr)) {
 374                         struct sockaddr_in *ina = (struct sockaddr_in*)&ifr.ifr_broadaddr;
 375                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_BROADCAST, 4, &ina->sin_addr);
 376                 }
 377         }
 378
 379         if (!ioctl(sock, SIOCGIFMTU, &ifr)) {
 380                 uint16_t mtu = htons(ifr.ifr_mtu);
 381                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_MTU, 2, &mtu);
 382         }
 383
 384         if (iface->search && iface->search_len <= 255) {
 385                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SEARCH_DOMAIN,
 386                                 iface->search_len, iface->search);
 387         } else if (!res_init() && _res.dnsrch[0] && _res.dnsrch[0][0]) {
 388                 uint8_t search_buf[256];
 389                 int len = dn_comp(_res.dnsrch[0], search_buf,
 390                                                 sizeof(search_buf), NULL, NULL);
 391                 if (len > 0)
 392                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SEARCH_DOMAIN,
 393                                         len, search_buf);
 394         }
 395
 396         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_ROUTER, 4, &ifaddr.sin_addr);
 397
 398
 399
 400         if (iface->dhcpv4_dns_cnt == 0)
 401                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_DNSSERVER, 4, &ifaddr.sin_addr);
 402         else
 403                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_DNSSERVER,
 404                                 4 * iface->dhcpv4_dns_cnt, iface->dhcpv4_dns);
 405
 406
 407         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_END, 0, NULL);
 408
 409         struct sockaddr_in dest = *((struct sockaddr_in*)addr);
 410         if (req->giaddr.s_addr) {
 411                 dest.sin_addr = req->giaddr;
 412                 dest.sin_port = htons(DHCPV4_SERVER_PORT);
 413         } else if (req->ciaddr.s_addr && req->ciaddr.s_addr != dest.sin_addr.s_addr) {
 414                 dest.sin_addr = req->ciaddr;
 415                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 416         } else if ((ntohs(req->flags) & DHCPV4_FLAG_BROADCAST) ||
 417                         req->hlen != reply.hlen || !reply.yiaddr.s_addr) {
 418                 dest.sin_addr.s_addr = INADDR_BROADCAST;
 419                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 420         } else {
 421                 dest.sin_addr = reply.yiaddr;
 422                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 423
 424                 struct arpreq arp = {.arp_flags = ATF_COM};
 425                 memcpy(arp.arp_ha.sa_data, req->chaddr, 6);
 426                 memcpy(&arp.arp_pa, &dest, sizeof(arp.arp_pa));
 427                 memcpy(arp.arp_dev, iface->ifname, sizeof(arp.arp_dev));
 428                 ioctl(sock, SIOCSARP, &arp);
 429         }
 430
 431         sendto(sock, &reply, sizeof(reply), MSG_DONTWAIT,
 432                         (struct sockaddr*)&dest, sizeof(dest));
 433 }
 434
 435
 436 static bool dhcpv4_assign(struct interface *iface,
 437                 struct dhcpv4_assignment *assign, uint32_t raddr)
 438 {
 439         const unsigned tries = 10;
 440         uint32_t start = ntohl(iface->dhcpv4_start.s_addr);
 441         uint32_t end = ntohl(iface->dhcpv4_end.s_addr);
 442         uint32_t count = end - start + 1;
 443
 444         // Seed RNG with checksum of DUID
 445         uint32_t seed = 0;
 446         for (size_t i = 0; i < sizeof(assign->hwaddr); ++i)
 447                 seed += assign->hwaddr[i];
 448         srand(seed);
 449
 450         // Try to assign up to 100x
 451         for (unsigned i = 0; i < tries; ++i) {
 452                 uint32_t try = (((uint32_t)rand()) % count) + start;
 453                 if (i == 0 && raddr >= start && raddr <= end)
 454                         try = raddr;
 455                 else if (i == tries - 1)
 456                         try = start;
 457
 458                 if (list_empty(&iface->dhcpv4_assignments)) {
 459                         assign->addr = try;
 460                         list_add(&assign->head, &iface->dhcpv4_assignments);
 461                         return true;
 462                 }
 463
 464                 struct dhcpv4_assignment *c;
 465                 list_for_each_entry(c, &iface->dhcpv4_assignments, head) {
 466                         if (c->addr > try) {
 467                                 assign->addr = try;
 468                                 list_add_tail(&assign->head, &c->head);
 469                                 return true;
 470                         } else if (c->addr == try) {
 471                                 if (i < tries - 1)
 472                                         break;
 473                                 else
 474                                         ++try;
 475                         }
 476                 }
 477         }
 478
 479         return false;
 480 }
 481
 482
 483 static struct dhcpv4_assignment* dhcpv4_lease(struct interface *iface,
 484                 enum dhcpv4_msg msg, const uint8_t *mac, struct in_addr reqaddr,
 485                 const char *hostname)
 486 {
 487         struct dhcpv4_assignment *lease = NULL;
 488         uint32_t raddr = ntohl(reqaddr.s_addr);
 489         time_t now = odhcpd_time();
 490
 491         struct dhcpv4_assignment *c, *n, *a = NULL;
 492         list_for_each_entry_safe(c, n, &iface->dhcpv4_assignments, head) {
 493                 if (!memcmp(c->hwaddr, mac, 6)) {
 494                         a = c;
 495                         if (c->addr == raddr)
 496                                 break;
 497                 } else if (c->valid_until < now) {
 498                         list_del(&c->head);
 499                         free(c);
 500                 }
 501         }
 502
 503         if (msg == DHCPV4_MSG_DISCOVER || msg == DHCPV4_MSG_REQUEST) {
 504                 bool assigned = !!a;
 505                 size_t hostlen = strlen(hostname) + 1;
 506
 507                 if (!a && !iface->no_dynamic_dhcp) { // Create new binding
 508                         a = calloc(1, sizeof(*a) + hostlen);
 509                         if (!a) {
 510                                 syslog(LOG_ERR, "Failed to calloc binding on interface %s", iface->ifname);
 511                                 return NULL;
 512                         }
 513                         memcpy(a->hwaddr, mac, sizeof(a->hwaddr));
 514                         memcpy(a->hostname, hostname, hostlen);
 515
 516                         assigned = dhcpv4_assign(iface, a, raddr);
 517                 }
 518
 519                 if (assigned && !a->hostname[0] && hostname) {
 520                         a = realloc(a, sizeof(*a) + hostlen);
 521                         if (!a) {
 522                                 syslog(LOG_ERR, "Failed to realloc binding on interface %s", iface->ifname);
 523                                 return NULL;
 524                         }
 525                         memcpy(a->hostname, hostname, hostlen);
 526
 527                         // Fixup list
 528                         a->head.next->prev = &a->head;
 529                         a->head.prev->next = &a->head;
 530                 }
 531
 532                 // Was only a solicitation: mark binding for removal
 533                 if (assigned && a->valid_until < now) {
 534                         a->valid_until = (msg == DHCPV4_MSG_DISCOVER) ? 0 :
 535                                         (now + iface->dhcpv4_leasetime);
 536                 } else if (!assigned && a) { // Cleanup failed assignment
 537                         free(a);
 538                         a = NULL;
 539                 }
 540
 541                 if (assigned && a)
 542                         lease = a;
 543         } else if (msg == DHCPV4_MSG_RELEASE) {
 544                 if (a) {
 545                         a->valid_until = 0;
 546                 }
 547         } else if (msg == DHCPV4_MSG_DECLINE) {
 548                 memset(a->hwaddr, 0, sizeof(a->hwaddr));
 549                 a->valid_until = now + 3600; // Block address for 1h
 550         }
 551
 552         dhcpv6_write_statefile();
 553
 554         return lease;
 555 }
 556