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 "odhcpd.h"
  33 #include "dhcpv4.h"
  34 #include "dhcpv6.h"
  35
  36 static void free_dhcpv4_assignment(struct dhcpv4_assignment *a);
  37 static void handle_dhcpv4(void *addr, void *data, size_t len,
  38                 struct interface *iface, void *dest_addr);
  39 static struct dhcpv4_assignment* dhcpv4_lease(struct interface *iface,
  40                 enum dhcpv4_msg msg, const uint8_t *mac, struct in_addr reqaddr,
  41                 uint32_t *leasetime, const char *hostname, const size_t hostname_len);
  42
  43 /* Create socket and register events */
  44 int init_dhcpv4(void)
  45 {
  46         return 0;
  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 IPv4 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                 /* Parse static entries */
 144                 struct lease *lease;
 145                 list_for_each_entry(lease, &leases, head) {
 146                         /* Construct entry */
 147                         struct dhcpv4_assignment *a = calloc(1, sizeof(*a));
 148                         if (!a) {
 149                                 syslog(LOG_ERR, "Calloc failed for static lease on interface %s",
 150                                         iface->ifname);
 151                                 return -1;
 152                         }
 153
 154                         a->leasetime = lease->dhcpv4_leasetime;
 155
 156                         a->addr = ntohl(lease->ipaddr.s_addr);
 157                         memcpy(a->hwaddr, lease->mac.ether_addr_octet, sizeof(a->hwaddr));
 158                         /* Static assignment */
 159                         a->flags |= OAF_STATIC;
 160                         /* Infinite valid */
 161                         a->valid_until = 0;
 162
 163                         /* Assign to all interfaces */
 164                         struct dhcpv4_assignment *c;
 165                         list_for_each_entry(c, &iface->dhcpv4_assignments, head) {
 166                                 if (c->addr > a->addr) {
 167                                         list_add_tail(&a->head, &c->head);
 168                                         break;
 169                                 } else if (c->addr == a->addr)
 170                                         /* Already an assignment with that number */
 171                                         break;
 172                         }
 173
 174                         if (&c->head == &iface->dhcpv4_assignments)
 175                                 list_add(&a->head, &iface->dhcpv4_assignments);
 176
 177                         if (a->head.next) {
 178                                 if (lease->hostname[0]) {
 179                                         free(a->hostname);
 180                                         a->hostname = strdup(lease->hostname);
 181                                 }
 182                         } else
 183                                 free_dhcpv4_assignment(a);
 184                 }
 185
 186                 // Clean invalid assignments
 187                 struct dhcpv4_assignment *a, *n;
 188                 list_for_each_entry_safe(a, n, &iface->dhcpv4_assignments, head) {
 189                         if ((htonl(a->addr) & smask->sin_addr.s_addr) !=
 190                                         (iface->dhcpv4_start.s_addr & smask->sin_addr.s_addr))
 191                                 free_dhcpv4_assignment(a);
 192                 }
 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                         free_dhcpv4_assignment(list_first_entry(&iface->dhcpv4_assignments,
 200                                                         struct dhcpv4_assignment, head));
 201         }
 202         return 0;
 203 }
 204
 205 static char *dhcpv4_msg_to_string(uint8_t reqmsg)
 206 {
 207         switch (reqmsg) {
 208         case (DHCPV4_MSG_DISCOVER):
 209                 return "DHCPV4_MSG_DISCOVER";
 210         case (DHCPV4_MSG_OFFER):
 211                 return "DHCPV4_MSG_OFFER";
 212         case (DHCPV4_MSG_REQUEST):
 213                 return "DHCPV4_MSG_REQUEST";
 214         case (DHCPV4_MSG_DECLINE):
 215                 return "DHCPV4_MSG_DECLINE";
 216         case (DHCPV4_MSG_ACK):
 217                 return "DHCPV4_MSG_ACK";
 218         case (DHCPV4_MSG_NAK):
 219                 return "DHCPV4_MSG_NAK";
 220         case (DHCPV4_MSG_RELEASE):
 221                 return "DHCPV4_MSG_RELEASE";
 222         case (DHCPV4_MSG_INFORM):
 223                 return "DHCPV4_MSG_INFORM";
 224         default:
 225                 return "UNKNOWN";
 226         }
 227 }
 228
 229 static void free_dhcpv4_assignment(struct dhcpv4_assignment *a)
 230 {
 231         if (a->head.next)
 232                 list_del(&a->head);
 233
 234         free(a->hostname);
 235         free(a);
 236 }
 237
 238 static void dhcpv4_put(struct dhcpv4_message *msg, uint8_t **cookie,
 239                 uint8_t type, uint8_t len, const void *data)
 240 {
 241         uint8_t *c = *cookie;
 242         if (*cookie + 2 + len > (uint8_t*)&msg[1])
 243                 return;
 244
 245         *c++ = type;
 246         *c++ = len;
 247         memcpy(c, data, len);
 248
 249         *cookie = c + len;
 250 }
 251
 252 // Handler for DHCPv4 messages
 253 static void handle_dhcpv4(void *addr, void *data, size_t len,
 254                 struct interface *iface, _unused void *dest_addr)
 255 {
 256         if (!iface->dhcpv4)
 257                 return;
 258
 259         struct dhcpv4_message *req = data;
 260         if (len < offsetof(struct dhcpv4_message, options) + 4 ||
 261                         req->op != DHCPV4_BOOTREQUEST || req->hlen != 6)
 262                 return;
 263
 264         int sock = iface->dhcpv4_event.uloop.fd;
 265         struct sockaddr_in ifaddr;
 266         struct sockaddr_in ifnetmask;
 267
 268         syslog(LOG_NOTICE, "Got DHCPv4 request");
 269
 270         struct ifreq ifreq;
 271         memcpy(ifreq.ifr_name, iface->ifname, sizeof(ifreq.ifr_name));
 272         if (ioctl(sock, SIOCGIFADDR, &ifreq)) {
 273                 syslog(LOG_WARNING, "DHCPv4 failed to detect address: %s", strerror(errno));
 274                 return;
 275         }
 276
 277         memcpy(&ifaddr, &ifreq.ifr_addr, sizeof(ifaddr));
 278         if (ioctl(sock, SIOCGIFNETMASK, &ifreq))
 279                 return;
 280
 281         memcpy(&ifnetmask, &ifreq.ifr_netmask, sizeof(ifnetmask));
 282         uint32_t network = ifaddr.sin_addr.s_addr & ifnetmask.sin_addr.s_addr;
 283
 284         if ((iface->dhcpv4_start.s_addr & ifnetmask.sin_addr.s_addr) != network ||
 285                         (iface->dhcpv4_end.s_addr & ifnetmask.sin_addr.s_addr) != network) {
 286                 syslog(LOG_WARNING, "DHCPv4 range out of assigned network");
 287                 return;
 288         }
 289
 290         struct ifreq ifr = {.ifr_name = ""};
 291         strncpy(ifr.ifr_name, iface->ifname, sizeof(ifr.ifr_name));
 292
 293         struct dhcpv4_message reply = {
 294                 .op = DHCPV4_BOOTREPLY,
 295                 .htype = 1,
 296                 .hlen = 6,
 297                 .hops = 0,
 298                 .xid = req->xid,
 299                 .secs = 0,
 300                 .flags = req->flags,
 301                 .ciaddr = {INADDR_ANY},
 302                 .giaddr = req->giaddr,
 303                 .siaddr = ifaddr.sin_addr,
 304         };
 305         memcpy(reply.chaddr, req->chaddr, sizeof(reply.chaddr));
 306
 307         reply.options[0] = 0x63;
 308         reply.options[1] = 0x82;
 309         reply.options[2] = 0x53;
 310         reply.options[3] = 0x63;
 311
 312         uint8_t *cookie = &reply.options[4];
 313         uint8_t reqmsg = DHCPV4_MSG_REQUEST;
 314         uint8_t msg = DHCPV4_MSG_ACK;
 315
 316         struct in_addr reqaddr = {INADDR_ANY};
 317         uint32_t leasetime = 0;
 318         size_t hostname_len = 0;
 319         char hostname[256];
 320
 321         uint8_t *start = &req->options[4];
 322         uint8_t *end = ((uint8_t*)data) + len;
 323         struct dhcpv4_option *opt;
 324         dhcpv4_for_each_option(start, end, opt) {
 325                 if (opt->type == DHCPV4_OPT_MESSAGE && opt->len == 1)
 326                         reqmsg = opt->data[0];
 327                 else if (opt->type == DHCPV4_OPT_HOSTNAME && opt->len > 0) {
 328                         hostname_len = opt->len;
 329                         memcpy(hostname, opt->data, hostname_len);
 330                         hostname[hostname_len] = 0;
 331                 } else if (opt->type == DHCPV4_OPT_IPADDRESS && opt->len == 4)
 332                         memcpy(&reqaddr, opt->data, 4);
 333                 else if (opt->type == DHCPV4_OPT_SERVERID && opt->len == 4) {
 334                         if (memcmp(opt->data, &ifaddr.sin_addr, 4))
 335                                 return;
 336                 } else if (iface->filter_class && opt->type == DHCPV4_OPT_USER_CLASS) {
 337                         uint8_t *c = opt->data, *cend = &opt->data[opt->len];
 338                         for (; c < cend && &c[*c] < cend; c = &c[1 + *c]) {
 339                                 size_t elen = strlen(iface->filter_class);
 340                                 if (*c == elen && !memcmp(&c[1], iface->filter_class, elen))
 341                                         return; // Ignore from homenet
 342                         }
 343                 } else if (opt->type == DHCPV4_OPT_LEASETIME && opt->len == 4)
 344                         memcpy(&leasetime, opt->data, 4);
 345         }
 346
 347         if (reqmsg != DHCPV4_MSG_DISCOVER && reqmsg != DHCPV4_MSG_REQUEST &&
 348                         reqmsg != DHCPV4_MSG_INFORM && reqmsg != DHCPV4_MSG_DECLINE &&
 349                         reqmsg != DHCPV4_MSG_RELEASE)
 350                 return;
 351
 352         struct dhcpv4_assignment *lease = NULL;
 353         if (reqmsg != DHCPV4_MSG_INFORM)
 354                 lease = dhcpv4_lease(iface, reqmsg, req->chaddr, reqaddr,
 355                                         &leasetime, hostname, hostname_len);
 356
 357         if (!lease) {
 358                 if (reqmsg == DHCPV4_MSG_REQUEST)
 359                         msg = DHCPV4_MSG_NAK;
 360                 else if (reqmsg == DHCPV4_MSG_DISCOVER)
 361                         return;
 362         } else if (reqmsg == DHCPV4_MSG_DISCOVER)
 363                 msg = DHCPV4_MSG_OFFER;
 364         else if (reqmsg == DHCPV4_MSG_REQUEST && reqaddr.s_addr &&
 365                         reqaddr.s_addr != htonl(lease->addr)) {
 366                 msg = DHCPV4_MSG_NAK;
 367                 /*
 368                  * DHCP client requested an IP which we can't offer to him. Probably the
 369                  * client changed the network. The reply type is set to DHCPV4_MSG_NAK,
 370                  * because the client should not use that IP.
 371                  *
 372                  * For modern devices we build an answer that includes a valid IP, like
 373                  * a DHCPV4_MSG_ACK. The client will use that IP and doesn't need to
 374                  * perform additional DHCP round trips.
 375                  *
 376                  */
 377         }
 378
 379         syslog(LOG_WARNING, "received %s from %02x:%02x:%02x:%02x:%02x:%02x",
 380                         dhcpv4_msg_to_string(reqmsg),
 381                         req->chaddr[0],req->chaddr[1],req->chaddr[2],
 382                         req->chaddr[3],req->chaddr[4],req->chaddr[5]);
 383
 384         if (reqmsg == DHCPV4_MSG_DECLINE || reqmsg == DHCPV4_MSG_RELEASE)
 385                 return;
 386
 387         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_MESSAGE, 1, &msg);
 388         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SERVERID, 4, &ifaddr.sin_addr);
 389
 390         if (lease) {
 391                 uint32_t val;
 392
 393                 reply.yiaddr.s_addr = htonl(lease->addr);
 394
 395                 val = htonl(leasetime);
 396                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_LEASETIME, 4, &val);
 397
 398                 if (leasetime != UINT32_MAX) {
 399                         val = htonl(500 * leasetime / 1000);
 400                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_RENEW, 4, &val);
 401
 402                         val = htonl(875 * leasetime / 1000);
 403                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_REBIND, 4, &val);
 404                 }
 405
 406                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_NETMASK, 4, &ifnetmask.sin_addr);
 407
 408                 if (lease->hostname)
 409                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_HOSTNAME,
 410                                         strlen(lease->hostname), lease->hostname);
 411
 412                 if (!ioctl(sock, SIOCGIFBRDADDR, &ifr)) {
 413                         struct sockaddr_in *ina = (struct sockaddr_in*)&ifr.ifr_broadaddr;
 414                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_BROADCAST, 4, &ina->sin_addr);
 415                 }
 416         }
 417
 418         if (!ioctl(sock, SIOCGIFMTU, &ifr)) {
 419                 uint16_t mtu = htons(ifr.ifr_mtu);
 420                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_MTU, 2, &mtu);
 421         }
 422
 423         if (iface->search && iface->search_len <= 255)
 424                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SEARCH_DOMAIN,
 425                                 iface->search_len, iface->search);
 426         else if (!res_init() && _res.dnsrch[0] && _res.dnsrch[0][0]) {
 427                 uint8_t search_buf[256];
 428                 int len = dn_comp(_res.dnsrch[0], search_buf,
 429                                                 sizeof(search_buf), NULL, NULL);
 430                 if (len > 0)
 431                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SEARCH_DOMAIN,
 432                                         len, search_buf);
 433         }
 434
 435         if (iface->dhcpv4_router_cnt == 0)
 436                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_ROUTER, 4, &ifaddr.sin_addr);
 437         else
 438                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_ROUTER,
 439                                 4 * iface->dhcpv4_router_cnt, iface->dhcpv4_router);
 440
 441
 442         if (iface->dhcpv4_dns_cnt == 0)
 443                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_DNSSERVER, 4, &ifaddr.sin_addr);
 444         else
 445                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_DNSSERVER,
 446                                 4 * iface->dhcpv4_dns_cnt, iface->dhcpv4_dns);
 447
 448
 449         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_END, 0, NULL);
 450
 451         struct sockaddr_in dest = *((struct sockaddr_in*)addr);
 452         if (req->giaddr.s_addr) {
 453                 /*
 454                  * relay agent is configured, send reply to the agent
 455                  */
 456                 dest.sin_addr = req->giaddr;
 457                 dest.sin_port = htons(DHCPV4_SERVER_PORT);
 458         } else if (req->ciaddr.s_addr && req->ciaddr.s_addr != dest.sin_addr.s_addr) {
 459                 /*
 460                  * client has existing configuration (ciaddr is set) AND this address is
 461                  * not the address it used for the dhcp message
 462                  */
 463                 dest.sin_addr = req->ciaddr;
 464                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 465         } else if ((ntohs(req->flags) & DHCPV4_FLAG_BROADCAST) ||
 466                         req->hlen != reply.hlen || !reply.yiaddr.s_addr) {
 467                 /*
 468                  * client requests a broadcast reply OR we can't offer an IP
 469                  */
 470                 dest.sin_addr.s_addr = INADDR_BROADCAST;
 471                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 472         } else if (!req->ciaddr.s_addr && msg == DHCPV4_MSG_NAK) {
 473                 /*
 474                  * client has no previous configuration -> no IP, so we need to reply
 475                  * with a broadcast packet
 476                  */
 477                 dest.sin_addr.s_addr = INADDR_BROADCAST;
 478                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 479         } else {
 480                 /*
 481                  * send reply to the newly (in this proccess) allocated IP
 482                  */
 483                 dest.sin_addr = reply.yiaddr;
 484                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 485
 486                 struct arpreq arp = {.arp_flags = ATF_COM};
 487                 memcpy(arp.arp_ha.sa_data, req->chaddr, 6);
 488                 memcpy(&arp.arp_pa, &dest, sizeof(arp.arp_pa));
 489                 memcpy(arp.arp_dev, iface->ifname, sizeof(arp.arp_dev));
 490                 ioctl(sock, SIOCSARP, &arp);
 491         }
 492
 493         if (dest.sin_addr.s_addr == INADDR_BROADCAST)
 494                 /* reply goes to IP broadcast -> MAC broadcast */
 495                 syslog(LOG_WARNING, "sending %s to ff:ff:ff:ff:ff:ff - %s",
 496                                 dhcpv4_msg_to_string(msg),
 497                                 inet_ntoa(dest.sin_addr));
 498         else
 499                 /*
 500                  * reply is send directly to IP,
 501                  * MAC is assumed to be the same as the request
 502                  */
 503                 syslog(LOG_WARNING, "sending %s to %02x:%02x:%02x:%02x:%02x:%02x - %s",
 504                                 dhcpv4_msg_to_string(msg),
 505                                 req->chaddr[0],req->chaddr[1],req->chaddr[2],
 506                                 req->chaddr[3],req->chaddr[4],req->chaddr[5],
 507                                 inet_ntoa(dest.sin_addr));
 508
 509         sendto(sock, &reply, sizeof(reply), MSG_DONTWAIT,
 510                         (struct sockaddr*)&dest, sizeof(dest));
 511 }
 512
 513 static bool dhcpv4_test(struct interface *iface, uint32_t try)
 514 {
 515         struct dhcpv4_assignment *c;
 516         list_for_each_entry(c, &iface->dhcpv4_assignments, head) {
 517                 if (c->addr == try)
 518                         return false;
 519
 520         }
 521
 522         return true;
 523 }
 524
 525 static bool dhcpv4_assign(struct interface *iface,
 526                 struct dhcpv4_assignment *assign, uint32_t raddr)
 527 {
 528         uint32_t start = ntohl(iface->dhcpv4_start.s_addr);
 529         uint32_t end = ntohl(iface->dhcpv4_end.s_addr);
 530         uint32_t count = end - start + 1;
 531
 532         // try to assign the IP the client asked for
 533         if (start <= raddr && raddr <= end && dhcpv4_test(iface, raddr)) {
 534                 assign->addr = raddr;
 535                 list_add(&assign->head, &iface->dhcpv4_assignments);
 536                 syslog(LOG_INFO, "assigning the IP the client asked for: %u.%u.%u.%u",
 537                                 (assign->addr & 0xff000000) >> 24,
 538                                 (assign->addr & 0x00ff0000) >> 16,
 539                                 (assign->addr & 0x0000ff00) >> 8,
 540                                 (assign->addr & 0x000000ff));
 541                 return true;
 542         }
 543
 544         // Seed RNG with checksum of hwaddress
 545         uint32_t seed = 0;
 546         for (size_t i = 0; i < sizeof(assign->hwaddr); ++i) {
 547                 // Knuth's multiplicative method
 548                 uint8_t o = assign->hwaddr[i];
 549                 seed += (o*2654435761) % UINT32_MAX;
 550         }
 551
 552         srand(seed);
 553
 554         uint32_t try = (((uint32_t)rand()) % count) + start;
 555
 556         if (list_empty(&iface->dhcpv4_assignments)) {
 557                 assign->addr = try;
 558                 list_add(&assign->head, &iface->dhcpv4_assignments);
 559                 syslog(LOG_INFO, "assigning mapped IP (empty list): %u.%u.%u.%u",
 560                                 (assign->addr & 0xff000000) >> 24,
 561                                 (assign->addr & 0x00ff0000) >> 16,
 562                                 (assign->addr & 0x0000ff00) >> 8,
 563                                 (assign->addr & 0x000000ff));
 564                 return true;
 565         }
 566
 567         for (uint32_t i = 0; i < count; ++i) {
 568                 if (dhcpv4_test(iface, try)) {
 569                         /* test was successful: IP address is not assigned, assign it */
 570                         assign->addr = try;
 571                         list_add(&assign->head, &iface->dhcpv4_assignments);
 572                         syslog(LOG_DEBUG, "assigning mapped IP: %u.%u.%u.%u (try %u of %u)",
 573                                         (assign->addr & 0xff000000) >> 24,
 574                                         (assign->addr & 0x00ff0000) >> 16,
 575                                         (assign->addr & 0x0000ff00) >> 8,
 576                                         (assign->addr & 0x000000ff), i, count);
 577                         return true;
 578                 }
 579                 try = (((try - start) + 1) % count) + start;
 580         }
 581
 582         syslog(LOG_WARNING, "can't assign any IP address -> address space is full");
 583         return false;
 584 }
 585
 586
 587 static struct dhcpv4_assignment* dhcpv4_lease(struct interface *iface,
 588                 enum dhcpv4_msg msg, const uint8_t *mac, struct in_addr reqaddr,
 589                 uint32_t *leasetime, const char *hostname, const size_t hostname_len)
 590 {
 591         struct dhcpv4_assignment *lease = NULL;
 592         uint32_t raddr = ntohl(reqaddr.s_addr);
 593         time_t now = odhcpd_time();
 594
 595         struct dhcpv4_assignment *c, *n, *a = NULL;
 596         list_for_each_entry_safe(c, n, &iface->dhcpv4_assignments, head) {
 597                 if (!memcmp(c->hwaddr, mac, 6)) {
 598                         a = c;
 599                         if (c->addr == raddr)
 600                                 break;
 601                 } else if (!INFINITE_VALID(c->valid_until) && c->valid_until < now)
 602                         free_dhcpv4_assignment(c);
 603         }
 604
 605         if (msg == DHCPV4_MSG_DISCOVER || msg == DHCPV4_MSG_REQUEST) {
 606                 bool assigned = !!a;
 607                 uint32_t my_leasetime;
 608
 609                 if (!a && !iface->no_dynamic_dhcp) {
 610                         /* Create new binding */
 611                         a = calloc(1, sizeof(*a));
 612                         if (!a) {
 613                                 syslog(LOG_ERR, "Failed to calloc binding on interface %s", iface->ifname);
 614                                 return NULL;
 615                         }
 616                         memcpy(a->hwaddr, mac, sizeof(a->hwaddr));
 617                         /* Don't consider new assignment as infinite */
 618                         a->valid_until = now;
 619
 620                         assigned = dhcpv4_assign(iface, a, raddr);
 621                 }
 622
 623                 if (a->leasetime)
 624                         my_leasetime = a->leasetime;
 625                 else
 626                         my_leasetime = iface->dhcpv4_leasetime;
 627
 628                 if ((*leasetime == 0) || (my_leasetime < *leasetime))
 629                         *leasetime = my_leasetime;
 630
 631                 if (assigned) {
 632                         if (msg == DHCPV4_MSG_DISCOVER) {
 633                                 a->flags &= ~OAF_BOUND;
 634
 635                                 if (!(a->flags & OAF_STATIC))
 636                                         a->valid_until = now;
 637                         } else {
 638                                 if (hostname_len > 0) {
 639                                         a->hostname = realloc(a->hostname, hostname_len + 1);
 640                                         if (a->hostname) {
 641                                                 memcpy(a->hostname, hostname, hostname_len);
 642                                                 a->hostname[hostname_len] = 0;
 643                                         }
 644                                 }
 645
 646                                 a->flags |= OAF_BOUND;
 647
 648                                 if (!(a->flags & OAF_STATIC))
 649                                         a->valid_until = ((*leasetime == UINT32_MAX) ? 0 : (time_t)(now + *leasetime));
 650                         }
 651                 } else if (!assigned && a) {
 652                         /* Cleanup failed assignment */
 653                         free_dhcpv4_assignment(a);
 654                         a = NULL;
 655                 }
 656
 657                 if (assigned && a)
 658                         lease = a;
 659         } else if (msg == DHCPV4_MSG_RELEASE && a) {
 660                 a->flags &= ~OAF_BOUND;
 661
 662                 if (!(a->flags & OAF_STATIC))
 663                         a->valid_until = now - 1;
 664
 665         } else if (msg == DHCPV4_MSG_DECLINE && a) {
 666                 a->flags &= ~OAF_BOUND;
 667
 668                 if (!(a->flags & OAF_STATIC)) {
 669                         memset(a->hwaddr, 0, sizeof(a->hwaddr));
 670                         a->valid_until = now + 3600; /* Block address for 1h */
 671                 }
 672         }
 673
 674         dhcpv6_write_statefile();
 675
 676         return lease;
 677 }