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                 }
 144
 145                 /* Parse static entries */
 146                 struct lease *lease;
 147                 list_for_each_entry(lease, &leases, head) {
 148                         /* Construct entry */
 149                         struct dhcpv4_assignment *a = calloc(1, sizeof(*a));
 150                         if (!a) {
 151                                 syslog(LOG_ERR, "Calloc failed for static lease on interface %s",
 152                                         iface->ifname);
 153                                 return -1;
 154                         }
 155
 156                         a->leasetime = lease->dhcpv4_leasetime;
 157
 158                         a->addr = ntohl(lease->ipaddr.s_addr);
 159                         memcpy(a->hwaddr, lease->mac.ether_addr_octet, sizeof(a->hwaddr));
 160                         /* Static assignment */
 161                         a->flags |= OAF_STATIC;
 162                         /* Infinite valid */
 163                         a->valid_until = 0;
 164
 165                         /* Assign to all interfaces */
 166                         struct dhcpv4_assignment *c;
 167                         list_for_each_entry(c, &iface->dhcpv4_assignments, head) {
 168                                 if (c->addr > a->addr) {
 169                                         list_add_tail(&a->head, &c->head);
 170                                         break;
 171                                 } else if (c->addr == a->addr)
 172                                         /* Already an assignment with that number */
 173                                         break;
 174                         }
 175
 176                         if (&c->head == &iface->dhcpv4_assignments)
 177                                 list_add(&a->head, &iface->dhcpv4_assignments);
 178
 179                         if (a->head.next) {
 180                                 if (lease->hostname[0]) {
 181                                         free(a->hostname);
 182                                         a->hostname = strdup(lease->hostname);
 183                                 }
 184                         } else
 185                                 free_dhcpv4_assignment(a);
 186                 }
 187
 188                 // Clean invalid assignments
 189                 struct dhcpv4_assignment *a, *n;
 190                 list_for_each_entry_safe(a, n, &iface->dhcpv4_assignments, head) {
 191                         if ((htonl(a->addr) & smask->sin_addr.s_addr) !=
 192                                         (iface->dhcpv4_start.s_addr & smask->sin_addr.s_addr))
 193                                 free_dhcpv4_assignment(a);
 194                 }
 195
 196                 iface->dhcpv4_event.uloop.fd = sock;
 197                 iface->dhcpv4_event.handle_dgram = handle_dhcpv4;
 198                 odhcpd_register(&iface->dhcpv4_event);
 199         } else if (iface->dhcpv4_assignments.next) {
 200                 while (!list_empty(&iface->dhcpv4_assignments))
 201                         free_dhcpv4_assignment(list_first_entry(&iface->dhcpv4_assignments,
 202                                                         struct dhcpv4_assignment, head));
 203         }
 204         return 0;
 205 }
 206
 207 static char *dhcpv4_msg_to_string(uint8_t reqmsg)
 208 {
 209         switch (reqmsg) {
 210         case (DHCPV4_MSG_DISCOVER):
 211                 return "DHCPV4_MSG_DISCOVER";
 212         case (DHCPV4_MSG_OFFER):
 213                 return "DHCPV4_MSG_OFFER";
 214         case (DHCPV4_MSG_REQUEST):
 215                 return "DHCPV4_MSG_REQUEST";
 216         case (DHCPV4_MSG_DECLINE):
 217                 return "DHCPV4_MSG_DECLINE";
 218         case (DHCPV4_MSG_ACK):
 219                 return "DHCPV4_MSG_ACK";
 220         case (DHCPV4_MSG_NAK):
 221                 return "DHCPV4_MSG_NAK";
 222         case (DHCPV4_MSG_RELEASE):
 223                 return "DHCPV4_MSG_RELEASE";
 224         case (DHCPV4_MSG_INFORM):
 225                 return "DHCPV4_MSG_INFORM";
 226         default:
 227                 return "UNKNOWN";
 228         }
 229 }
 230
 231 static void free_dhcpv4_assignment(struct dhcpv4_assignment *a)
 232 {
 233         if (a->head.next)
 234                 list_del(&a->head);
 235
 236         free(a->hostname);
 237         free(a);
 238 }
 239
 240 static void dhcpv4_put(struct dhcpv4_message *msg, uint8_t **cookie,
 241                 uint8_t type, uint8_t len, const void *data)
 242 {
 243         uint8_t *c = *cookie;
 244         if (*cookie + 2 + len > (uint8_t*)&msg[1])
 245                 return;
 246
 247         *c++ = type;
 248         *c++ = len;
 249         memcpy(c, data, len);
 250
 251         *cookie = c + len;
 252 }
 253
 254 // Handler for DHCPv4 messages
 255 static void handle_dhcpv4(void *addr, void *data, size_t len,
 256                 struct interface *iface, _unused void *dest_addr)
 257 {
 258         if (!iface->dhcpv4)
 259                 return;
 260
 261         struct dhcpv4_message *req = data;
 262         if (len < offsetof(struct dhcpv4_message, options) + 4 ||
 263                         req->op != DHCPV4_BOOTREQUEST || req->hlen != 6)
 264                 return;
 265
 266         int sock = iface->dhcpv4_event.uloop.fd;
 267         struct sockaddr_in ifaddr;
 268         struct sockaddr_in ifnetmask;
 269
 270         syslog(LOG_NOTICE, "Got DHCPv4 request");
 271
 272         struct ifreq ifreq;
 273         memcpy(ifreq.ifr_name, iface->ifname, sizeof(ifreq.ifr_name));
 274         if (ioctl(sock, SIOCGIFADDR, &ifreq)) {
 275                 syslog(LOG_WARNING, "DHCPv4 failed to detect address: %s", strerror(errno));
 276                 return;
 277         }
 278
 279         memcpy(&ifaddr, &ifreq.ifr_addr, sizeof(ifaddr));
 280         if (ioctl(sock, SIOCGIFNETMASK, &ifreq))
 281                 return;
 282
 283         memcpy(&ifnetmask, &ifreq.ifr_netmask, sizeof(ifnetmask));
 284         uint32_t network = ifaddr.sin_addr.s_addr & ifnetmask.sin_addr.s_addr;
 285
 286         if ((iface->dhcpv4_start.s_addr & ifnetmask.sin_addr.s_addr) != network ||
 287                         (iface->dhcpv4_end.s_addr & ifnetmask.sin_addr.s_addr) != network) {
 288                 syslog(LOG_WARNING, "DHCPv4 range out of assigned network");
 289                 return;
 290         }
 291
 292         struct ifreq ifr = {.ifr_name = ""};
 293         strncpy(ifr.ifr_name, iface->ifname, sizeof(ifr.ifr_name));
 294
 295         struct dhcpv4_message reply = {
 296                 .op = DHCPV4_BOOTREPLY,
 297                 .htype = 1,
 298                 .hlen = 6,
 299                 .hops = 0,
 300                 .xid = req->xid,
 301                 .secs = 0,
 302                 .flags = req->flags,
 303                 .ciaddr = {INADDR_ANY},
 304                 .giaddr = req->giaddr,
 305                 .siaddr = ifaddr.sin_addr,
 306         };
 307         memcpy(reply.chaddr, req->chaddr, sizeof(reply.chaddr));
 308
 309         reply.options[0] = 0x63;
 310         reply.options[1] = 0x82;
 311         reply.options[2] = 0x53;
 312         reply.options[3] = 0x63;
 313
 314         uint8_t *cookie = &reply.options[4];
 315         uint8_t reqmsg = DHCPV4_MSG_REQUEST;
 316         uint8_t msg = DHCPV4_MSG_ACK;
 317
 318         struct in_addr reqaddr = {INADDR_ANY};
 319         uint32_t leasetime = 0;
 320         size_t hostname_len = 0;
 321         char hostname[256];
 322
 323         uint8_t *start = &req->options[4];
 324         uint8_t *end = ((uint8_t*)data) + len;
 325         struct dhcpv4_option *opt;
 326         dhcpv4_for_each_option(start, end, opt) {
 327                 if (opt->type == DHCPV4_OPT_MESSAGE && opt->len == 1)
 328                         reqmsg = opt->data[0];
 329                 else if (opt->type == DHCPV4_OPT_HOSTNAME && opt->len > 0) {
 330                         hostname_len = opt->len;
 331                         memcpy(hostname, opt->data, hostname_len);
 332                         hostname[hostname_len] = 0;
 333                 } else if (opt->type == DHCPV4_OPT_IPADDRESS && opt->len == 4)
 334                         memcpy(&reqaddr, opt->data, 4);
 335                 else if (opt->type == DHCPV4_OPT_SERVERID && opt->len == 4) {
 336                         if (memcmp(opt->data, &ifaddr.sin_addr, 4))
 337                                 return;
 338                 } else if (iface->filter_class && opt->type == DHCPV4_OPT_USER_CLASS) {
 339                         uint8_t *c = opt->data, *cend = &opt->data[opt->len];
 340                         for (; c < cend && &c[*c] < cend; c = &c[1 + *c]) {
 341                                 size_t elen = strlen(iface->filter_class);
 342                                 if (*c == elen && !memcmp(&c[1], iface->filter_class, elen))
 343                                         return; // Ignore from homenet
 344                         }
 345                 } else if (opt->type == DHCPV4_OPT_LEASETIME && opt->len == 4)
 346                         memcpy(&leasetime, opt->data, 4);
 347         }
 348
 349         if (reqmsg != DHCPV4_MSG_DISCOVER && reqmsg != DHCPV4_MSG_REQUEST &&
 350                         reqmsg != DHCPV4_MSG_INFORM && reqmsg != DHCPV4_MSG_DECLINE &&
 351                         reqmsg != DHCPV4_MSG_RELEASE)
 352                 return;
 353
 354         struct dhcpv4_assignment *lease = NULL;
 355         if (reqmsg != DHCPV4_MSG_INFORM)
 356                 lease = dhcpv4_lease(iface, reqmsg, req->chaddr, reqaddr,
 357                                         &leasetime, hostname, hostname_len);
 358
 359         if (!lease) {
 360                 if (reqmsg == DHCPV4_MSG_REQUEST)
 361                         msg = DHCPV4_MSG_NAK;
 362                 else if (reqmsg == DHCPV4_MSG_DISCOVER)
 363                         return;
 364         } else if (reqmsg == DHCPV4_MSG_DISCOVER)
 365                 msg = DHCPV4_MSG_OFFER;
 366         else if (reqmsg == DHCPV4_MSG_REQUEST && reqaddr.s_addr &&
 367                         reqaddr.s_addr != htonl(lease->addr)) {
 368                 msg = DHCPV4_MSG_NAK;
 369                 /*
 370                  * DHCP client requested an IP which we can't offer to him. Probably the
 371                  * client changed the network. The reply type is set to DHCPV4_MSG_NAK,
 372                  * because the client should not use that IP.
 373                  *
 374                  * For modern devices we build an answer that includes a valid IP, like
 375                  * a DHCPV4_MSG_ACK. The client will use that IP and doesn't need to
 376                  * perform additional DHCP round trips.
 377                  *
 378                  */
 379         }
 380
 381         syslog(LOG_WARNING, "received %s from %02x:%02x:%02x:%02x:%02x:%02x",
 382                         dhcpv4_msg_to_string(reqmsg),
 383                         req->chaddr[0],req->chaddr[1],req->chaddr[2],
 384                         req->chaddr[3],req->chaddr[4],req->chaddr[5]);
 385
 386         if (reqmsg == DHCPV4_MSG_DECLINE || reqmsg == DHCPV4_MSG_RELEASE)
 387                 return;
 388
 389         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_MESSAGE, 1, &msg);
 390         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SERVERID, 4, &ifaddr.sin_addr);
 391
 392         if (lease) {
 393                 uint32_t val;
 394
 395                 reply.yiaddr.s_addr = htonl(lease->addr);
 396
 397                 val = htonl(leasetime);
 398                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_LEASETIME, 4, &val);
 399
 400                 if (leasetime != UINT32_MAX) {
 401                         val = htonl(500 * leasetime / 1000);
 402                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_RENEW, 4, &val);
 403
 404                         val = htonl(875 * leasetime / 1000);
 405                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_REBIND, 4, &val);
 406                 }
 407
 408                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_NETMASK, 4, &ifnetmask.sin_addr);
 409
 410                 if (lease->hostname)
 411                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_HOSTNAME,
 412                                         strlen(lease->hostname), lease->hostname);
 413
 414                 if (!ioctl(sock, SIOCGIFBRDADDR, &ifr)) {
 415                         struct sockaddr_in *ina = (struct sockaddr_in*)&ifr.ifr_broadaddr;
 416                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_BROADCAST, 4, &ina->sin_addr);
 417                 }
 418         }
 419
 420         if (!ioctl(sock, SIOCGIFMTU, &ifr)) {
 421                 uint16_t mtu = htons(ifr.ifr_mtu);
 422                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_MTU, 2, &mtu);
 423         }
 424
 425         if (iface->search && iface->search_len <= 255)
 426                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SEARCH_DOMAIN,
 427                                 iface->search_len, iface->search);
 428         else if (!res_init() && _res.dnsrch[0] && _res.dnsrch[0][0]) {
 429                 uint8_t search_buf[256];
 430                 int len = dn_comp(_res.dnsrch[0], search_buf,
 431                                                 sizeof(search_buf), NULL, NULL);
 432                 if (len > 0)
 433                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SEARCH_DOMAIN,
 434                                         len, search_buf);
 435         }
 436
 437         if (iface->dhcpv4_router_cnt == 0)
 438                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_ROUTER, 4, &ifaddr.sin_addr);
 439         else
 440                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_ROUTER,
 441                                 4 * iface->dhcpv4_router_cnt, iface->dhcpv4_router);
 442
 443
 444         if (iface->dhcpv4_dns_cnt == 0)
 445                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_DNSSERVER, 4, &ifaddr.sin_addr);
 446         else
 447                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_DNSSERVER,
 448                                 4 * iface->dhcpv4_dns_cnt, iface->dhcpv4_dns);
 449
 450
 451         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_END, 0, NULL);
 452
 453         struct sockaddr_in dest = *((struct sockaddr_in*)addr);
 454         if (req->giaddr.s_addr) {
 455                 /*
 456                  * relay agent is configured, send reply to the agent
 457                  */
 458                 dest.sin_addr = req->giaddr;
 459                 dest.sin_port = htons(DHCPV4_SERVER_PORT);
 460         } else if (req->ciaddr.s_addr && req->ciaddr.s_addr != dest.sin_addr.s_addr) {
 461                 /*
 462                  * client has existing configuration (ciaddr is set) AND this address is
 463                  * not the address it used for the dhcp message
 464                  */
 465                 dest.sin_addr = req->ciaddr;
 466                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 467         } else if ((ntohs(req->flags) & DHCPV4_FLAG_BROADCAST) ||
 468                         req->hlen != reply.hlen || !reply.yiaddr.s_addr) {
 469                 /*
 470                  * client requests a broadcast reply OR we can't offer an IP
 471                  */
 472                 dest.sin_addr.s_addr = INADDR_BROADCAST;
 473                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 474         } else if (!req->ciaddr.s_addr && msg == DHCPV4_MSG_NAK) {
 475                 /*
 476                  * client has no previous configuration -> no IP, so we need to reply
 477                  * with a broadcast packet
 478                  */
 479                 dest.sin_addr.s_addr = INADDR_BROADCAST;
 480                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 481         } else {
 482                 /*
 483                  * send reply to the newly (in this proccess) allocated IP
 484                  */
 485                 dest.sin_addr = reply.yiaddr;
 486                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 487
 488                 struct arpreq arp = {.arp_flags = ATF_COM};
 489                 memcpy(arp.arp_ha.sa_data, req->chaddr, 6);
 490                 memcpy(&arp.arp_pa, &dest, sizeof(arp.arp_pa));
 491                 memcpy(arp.arp_dev, iface->ifname, sizeof(arp.arp_dev));
 492                 ioctl(sock, SIOCSARP, &arp);
 493         }
 494
 495         if (dest.sin_addr.s_addr == INADDR_BROADCAST)
 496                 /* reply goes to IP broadcast -> MAC broadcast */
 497                 syslog(LOG_WARNING, "sending %s to ff:ff:ff:ff:ff:ff - %s",
 498                                 dhcpv4_msg_to_string(msg),
 499                                 inet_ntoa(dest.sin_addr));
 500         else
 501                 /*
 502                  * reply is send directly to IP,
 503                  * MAC is assumed to be the same as the request
 504                  */
 505                 syslog(LOG_WARNING, "sending %s to %02x:%02x:%02x:%02x:%02x:%02x - %s",
 506                                 dhcpv4_msg_to_string(msg),
 507                                 req->chaddr[0],req->chaddr[1],req->chaddr[2],
 508                                 req->chaddr[3],req->chaddr[4],req->chaddr[5],
 509                                 inet_ntoa(dest.sin_addr));
 510
 511         sendto(sock, &reply, sizeof(reply), MSG_DONTWAIT,
 512                         (struct sockaddr*)&dest, sizeof(dest));
 513 }
 514
 515 static bool dhcpv4_test(struct interface *iface, uint32_t try)
 516 {
 517         struct dhcpv4_assignment *c;
 518         list_for_each_entry(c, &iface->dhcpv4_assignments, head) {
 519                 if (c->addr == try)
 520                         return false;
 521
 522         }
 523
 524         return true;
 525 }
 526
 527 static bool dhcpv4_assign(struct interface *iface,
 528                 struct dhcpv4_assignment *assign, uint32_t raddr)
 529 {
 530         uint32_t start = ntohl(iface->dhcpv4_start.s_addr);
 531         uint32_t end = ntohl(iface->dhcpv4_end.s_addr);
 532         uint32_t count = end - start + 1;
 533
 534         // try to assign the IP the client asked for
 535         if (start <= raddr && raddr <= end && dhcpv4_test(iface, raddr)) {
 536                 assign->addr = raddr;
 537                 list_add(&assign->head, &iface->dhcpv4_assignments);
 538                 syslog(LOG_INFO, "assigning the IP the client asked for: %u.%u.%u.%u",
 539                                 (assign->addr & 0xff000000) >> 24,
 540                                 (assign->addr & 0x00ff0000) >> 16,
 541                                 (assign->addr & 0x0000ff00) >> 8,
 542                                 (assign->addr & 0x000000ff));
 543                 return true;
 544         }
 545
 546         // Seed RNG with checksum of hwaddress
 547         uint32_t seed = 0;
 548         for (size_t i = 0; i < sizeof(assign->hwaddr); ++i) {
 549                 // Knuth's multiplicative method
 550                 uint8_t o = assign->hwaddr[i];
 551                 seed += (o*2654435761) % UINT32_MAX;
 552         }
 553
 554         srand(seed);
 555
 556         uint32_t try = (((uint32_t)rand()) % count) + start;
 557
 558         if (list_empty(&iface->dhcpv4_assignments)) {
 559                 assign->addr = try;
 560                 list_add(&assign->head, &iface->dhcpv4_assignments);
 561                 syslog(LOG_INFO, "assigning mapped IP (empty list): %u.%u.%u.%u",
 562                                 (assign->addr & 0xff000000) >> 24,
 563                                 (assign->addr & 0x00ff0000) >> 16,
 564                                 (assign->addr & 0x0000ff00) >> 8,
 565                                 (assign->addr & 0x000000ff));
 566                 return true;
 567         }
 568
 569         for (uint32_t i = 0; i < count; ++i) {
 570                 if (dhcpv4_test(iface, try)) {
 571                         /* test was successful: IP address is not assigned, assign it */
 572                         assign->addr = try;
 573                         list_add(&assign->head, &iface->dhcpv4_assignments);
 574                         syslog(LOG_DEBUG, "assigning mapped IP: %u.%u.%u.%u (try %u of %u)",
 575                                         (assign->addr & 0xff000000) >> 24,
 576                                         (assign->addr & 0x00ff0000) >> 16,
 577                                         (assign->addr & 0x0000ff00) >> 8,
 578                                         (assign->addr & 0x000000ff), i, count);
 579                         return true;
 580                 }
 581                 try = (((try - start) + 1) % count) + start;
 582         }
 583
 584         syslog(LOG_WARNING, "can't assign any IP address -> address space is full");
 585         return false;
 586 }
 587
 588
 589 static struct dhcpv4_assignment* dhcpv4_lease(struct interface *iface,
 590                 enum dhcpv4_msg msg, const uint8_t *mac, struct in_addr reqaddr,
 591                 uint32_t *leasetime, const char *hostname, const size_t hostname_len)
 592 {
 593         struct dhcpv4_assignment *lease = NULL;
 594         uint32_t raddr = ntohl(reqaddr.s_addr);
 595         time_t now = odhcpd_time();
 596
 597         struct dhcpv4_assignment *c, *n, *a = NULL;
 598         list_for_each_entry_safe(c, n, &iface->dhcpv4_assignments, head) {
 599                 if (!memcmp(c->hwaddr, mac, 6)) {
 600                         a = c;
 601                         if (c->addr == raddr)
 602                                 break;
 603                 } else if (!INFINITE_VALID(c->valid_until) && c->valid_until < now)
 604                         free_dhcpv4_assignment(c);
 605         }
 606
 607         if (msg == DHCPV4_MSG_DISCOVER || msg == DHCPV4_MSG_REQUEST) {
 608                 bool assigned = !!a;
 609                 uint32_t my_leasetime;
 610
 611                 if (!a && !iface->no_dynamic_dhcp) {
 612                         /* Create new binding */
 613                         a = calloc(1, sizeof(*a));
 614                         if (!a) {
 615                                 syslog(LOG_ERR, "Failed to calloc binding on interface %s", iface->ifname);
 616                                 return NULL;
 617                         }
 618                         memcpy(a->hwaddr, mac, sizeof(a->hwaddr));
 619                         /* Don't consider new assignment as infinite */
 620                         a->valid_until = now;
 621
 622                         assigned = dhcpv4_assign(iface, a, raddr);
 623                 }
 624
 625                 if (a->leasetime)
 626                         my_leasetime = a->leasetime;
 627                 else
 628                         my_leasetime = iface->dhcpv4_leasetime;
 629
 630                 if ((*leasetime == 0) || (my_leasetime < *leasetime))
 631                         *leasetime = my_leasetime;
 632
 633                 if (assigned) {
 634                         if (msg == DHCPV4_MSG_DISCOVER) {
 635                                 a->flags &= ~OAF_BOUND;
 636
 637                                 if (!(a->flags & OAF_STATIC))
 638                                         a->valid_until = now;
 639                         } else {
 640                                 if (hostname_len > 0) {
 641                                         a->hostname = realloc(a->hostname, hostname_len + 1);
 642                                         if (a->hostname) {
 643                                                 memcpy(a->hostname, hostname, hostname_len);
 644                                                 a->hostname[hostname_len] = 0;
 645                                         }
 646                                 }
 647
 648                                 a->flags |= OAF_BOUND;
 649
 650                                 if (!(a->flags & OAF_STATIC))
 651                                         a->valid_until = ((*leasetime == UINT32_MAX) ? 0 : (time_t)(now + *leasetime));
 652                         }
 653                 } else if (!assigned && a) {
 654                         /* Cleanup failed assignment */
 655                         free_dhcpv4_assignment(a);
 656                         a = NULL;
 657                 }
 658
 659                 if (assigned && a)
 660                         lease = a;
 661         } else if (msg == DHCPV4_MSG_RELEASE && a) {
 662                 a->flags &= ~OAF_BOUND;
 663
 664                 if (!(a->flags & OAF_STATIC))
 665                         a->valid_until = now - 1;
 666
 667         } else if (msg == DHCPV4_MSG_DECLINE && a) {
 668                 a->flags &= ~OAF_BOUND;
 669
 670                 if (!(a->flags & OAF_STATIC)) {
 671                         memset(a->hwaddr, 0, sizeof(a->hwaddr));
 672                         a->valid_until = now + 3600; /* Block address for 1h */
 673                 }
 674         }
 675
 676         dhcpv6_write_statefile();
 677
 678         return lease;
 679 }