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 char *dhcpv4_msg_to_string(uint8_t reqmsg)
  49 {
  50         switch (reqmsg) {
  51         case (DHCPV4_MSG_DISCOVER):
  52                 return "DHCPV4_MSG_DISCOVER";
  53         case (DHCPV4_MSG_OFFER):
  54                 return "DHCPV4_MSG_OFFER";
  55         case (DHCPV4_MSG_REQUEST):
  56                 return "DHCPV4_MSG_REQUEST";
  57         case (DHCPV4_MSG_DECLINE):
  58                 return "DHCPV4_MSG_DECLINE";
  59         case (DHCPV4_MSG_ACK):
  60                 return "DHCPV4_MSG_ACK";
  61         case (DHCPV4_MSG_NAK):
  62                 return "DHCPV4_MSG_NAK";
  63         case (DHCPV4_MSG_RELEASE):
  64                 return "DHCPV4_MSG_RELEASE";
  65         case (DHCPV4_MSG_INFORM):
  66                 return "DHCPV4_MSG_INFORM";
  67         default:
  68                 return "UNKNOWN";
  69         }
  70 }
  71
  72 int setup_dhcpv4_interface(struct interface *iface, bool enable)
  73 {
  74         if (iface->dhcpv4_event.uloop.fd > 0) {
  75                 uloop_fd_delete(&iface->dhcpv4_event.uloop);
  76                 close(iface->dhcpv4_event.uloop.fd);
  77                 iface->dhcpv4_event.uloop.fd = -1;
  78         }
  79
  80         if (iface->dhcpv4 && enable) {
  81                 if (!iface->dhcpv4_assignments.next)
  82                         INIT_LIST_HEAD(&iface->dhcpv4_assignments);
  83
  84                 int sock = socket(AF_INET, SOCK_DGRAM | SOCK_CLOEXEC, IPPROTO_UDP);
  85                 if (sock < 0) {
  86                         syslog(LOG_ERR, "Failed to create DHCPv4 server socket: %s",
  87                                         strerror(errno));
  88                         return -1;
  89                 }
  90
  91                 // Basic IPv6 configuration
  92                 int val = 1;
  93                 setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &val, sizeof(val));
  94                 setsockopt(sock, SOL_SOCKET, SO_BROADCAST, &val, sizeof(val));
  95                 setsockopt(sock, IPPROTO_IP, IP_PKTINFO, &val, sizeof(val));
  96
  97                 val = IPTOS_PREC_INTERNETCONTROL;
  98                 setsockopt(sock, IPPROTO_IP, IP_TOS, &val, sizeof(val));
  99
 100                 val = IP_PMTUDISC_DONT;
 101                 setsockopt(sock, IPPROTO_IP, IP_MTU_DISCOVER, &val, sizeof(val));
 102
 103                 setsockopt(sock, SOL_SOCKET, SO_BINDTODEVICE,
 104                                 iface->ifname, strlen(iface->ifname));
 105
 106                 struct sockaddr_in bind_addr = {AF_INET, htons(DHCPV4_SERVER_PORT),
 107                                         {INADDR_ANY}, {0}};
 108
 109                 if (bind(sock, (struct sockaddr*)&bind_addr, sizeof(bind_addr))) {
 110                         syslog(LOG_ERR, "Failed to open DHCPv4 server socket: %s",
 111                                         strerror(errno));
 112                         return -1;
 113                 }
 114
 115
 116                 if (ntohl(iface->dhcpv4_start.s_addr) > ntohl(iface->dhcpv4_end.s_addr)) {
 117                         syslog(LOG_ERR, "Invalid DHCP range");
 118                         return -1;
 119                 }
 120
 121                 // Create a range if not specified
 122                 if (!(iface->dhcpv4_start.s_addr & htonl(0xffff0000)) &&
 123                                 !(iface->dhcpv4_end.s_addr & htonl(0xffff0000))) {
 124                         struct in_addr addr = ubus_get_address4(iface->ifname);
 125
 126                         struct in_addr mask = ubus_get_mask4(iface->ifname);
 127
 128                         uint32_t start = ntohl(iface->dhcpv4_start.s_addr);
 129                         uint32_t end = ntohl(iface->dhcpv4_end.s_addr);
 130
 131                         if (start && end && start < end &&
 132                                         start > ntohl(addr.s_addr & ~mask.s_addr) &&
 133                                         (start & ntohl(~mask.s_addr)) == start &&
 134                                         (end & ntohl(~mask.s_addr)) == end) {
 135                                 iface->dhcpv4_start.s_addr = htonl(start) |
 136                                                 (addr.s_addr & mask.s_addr);
 137                                 iface->dhcpv4_end.s_addr = htonl(end) |
 138                                                 (addr.s_addr & mask.s_addr);
 139                         } else if (ntohl(mask.s_addr) <= 0xfffffff0) {
 140                                 start = addr.s_addr & mask.s_addr;
 141                                 end = addr.s_addr & mask.s_addr;
 142
 143                                 if (ntohl(mask.s_addr) <= 0xffffff00) {
 144                                         iface->dhcpv4_start.s_addr = start | htonl(100);
 145                                         iface->dhcpv4_end.s_addr = end | htonl(250);
 146                                 } else if (ntohl(mask.s_addr) <= 0xffffffc0) {
 147                                         iface->dhcpv4_start.s_addr = start | htonl(10);
 148                                         iface->dhcpv4_end.s_addr = end | htonl(60);
 149                                 } else if (ntohl(mask.s_addr) <= 0xffffffe0) {
 150                                         iface->dhcpv4_start.s_addr = start | htonl(10);
 151                                         iface->dhcpv4_end.s_addr = end | htonl(30);
 152                                 } else {
 153                                         iface->dhcpv4_start.s_addr = start | htonl(3);
 154                                         iface->dhcpv4_end.s_addr = end | htonl(12);
 155                                 }
 156                         }
 157
 158
 159                 }
 160
 161                 // Parse static entries
 162                 struct lease *lease;
 163                 list_for_each_entry(lease, &leases, head) {
 164                         // Construct entry
 165                         size_t hostlen = strlen(lease->hostname) + 1;
 166                         struct dhcpv4_assignment *a = calloc(1, sizeof(*a) + hostlen);
 167                         if (!a) {
 168                                 syslog(LOG_ERR, "Calloc failed for static lease on interface %s",
 169                                         iface->ifname);
 170                                 return -1;
 171                         }
 172                         a->addr = ntohl(lease->ipaddr.s_addr);
 173                         memcpy(a->hwaddr, lease->mac.ether_addr_octet, sizeof(a->hwaddr));
 174                         memcpy(a->hostname, lease->hostname, hostlen);
 175                         a->valid_until = LONG_MAX;
 176
 177                         // Assign to all interfaces
 178                         struct dhcpv4_assignment *c;
 179                         list_for_each_entry(c, &iface->dhcpv4_assignments, head) {
 180                                 if (c->addr > a->addr) {
 181                                         list_add_tail(&a->head, &c->head);
 182                                         break;
 183                                 } else if (c->addr == a->addr) {
 184                                         // Already an assignment with that number
 185                                         break;
 186                                 }
 187                         }
 188                         if (&c->head == &iface->dhcpv4_assignments) {
 189                                 list_add(&a->head, &iface->dhcpv4_assignments);
 190                         }
 191
 192                         if (!a->head.next)
 193                                 free(a);
 194                 }
 195
 196                 // Clean invalid assignments
 197                 struct dhcpv4_assignment *a, *n;
 198                 list_for_each_entry_safe(a, n, &iface->dhcpv4_assignments, head) {
 199                         if ((htonl(a->addr) & smask->sin_addr.s_addr) !=
 200                                         (iface->dhcpv4_start.s_addr & smask->sin_addr.s_addr)) {
 201                                 list_del(&a->head);
 202                                 free(a);
 203                         }
 204                 }
 205
 206
 207                 if (iface->dhcpv4_leasetime < 60)
 208                         iface->dhcpv4_leasetime = 43200;
 209
 210                 iface->dhcpv4_event.uloop.fd = sock;
 211                 iface->dhcpv4_event.handle_dgram = handle_dhcpv4;
 212                 odhcpd_register(&iface->dhcpv4_event);
 213         } else if (iface->dhcpv4_assignments.next) {
 214                 while (!list_empty(&iface->dhcpv4_assignments)) {
 215                         struct dhcpv4_assignment *a = list_first_entry(&iface->dhcpv4_assignments,
 216                                         struct dhcpv4_assignment, head);
 217                         list_del(&a->head);
 218                         free(a);
 219                 }
 220
 221         }
 222         return 0;
 223 }
 224
 225
 226 static void dhcpv4_put(struct dhcpv4_message *msg, uint8_t **cookie,
 227                 uint8_t type, uint8_t len, const void *data)
 228 {
 229         uint8_t *c = *cookie;
 230         if (*cookie + 2 + len > (uint8_t*)&msg[1])
 231                 return;
 232
 233         *c++ = type;
 234         *c++ = len;
 235         memcpy(c, data, len);
 236
 237         *cookie = c + len;
 238 }
 239
 240
 241 // Simple DHCPv6-server for information requests
 242 static void handle_dhcpv4(void *addr, void *data, size_t len,
 243                 struct interface *iface, _unused void *dest_addr)
 244 {
 245         if (!iface->dhcpv4)
 246                 return;
 247
 248         struct dhcpv4_message *req = data;
 249         if (len < offsetof(struct dhcpv4_message, options) + 4 ||
 250                         req->op != DHCPV4_BOOTREQUEST || req->hlen != 6)
 251                 return;
 252
 253         int sock = iface->dhcpv4_event.uloop.fd;
 254         struct sockaddr_in ifaddr;
 255         struct sockaddr_in ifnetmask;
 256
 257         syslog(LOG_NOTICE, "Got DHCPv4 request");
 258
 259         struct ifreq ifreq;
 260         memcpy(ifreq.ifr_name, iface->ifname, sizeof(ifreq.ifr_name));
 261         if (ioctl(sock, SIOCGIFADDR, &ifreq)) {
 262                 syslog(LOG_WARNING, "DHCPv4 failed to detect address: %s", strerror(errno));
 263                 return;
 264         }
 265
 266         memcpy(&ifaddr, &ifreq.ifr_addr, sizeof(ifaddr));
 267         if (ioctl(sock, SIOCGIFNETMASK, &ifreq))
 268                 return;
 269
 270         memcpy(&ifnetmask, &ifreq.ifr_netmask, sizeof(ifnetmask));
 271         uint32_t network = ifaddr.sin_addr.s_addr & ifnetmask.sin_addr.s_addr;
 272
 273         if ((iface->dhcpv4_start.s_addr & ifnetmask.sin_addr.s_addr) != network ||
 274                         (iface->dhcpv4_end.s_addr & ifnetmask.sin_addr.s_addr) != network) {
 275                 syslog(LOG_WARNING, "DHCPv4 range out of assigned network");
 276                 return;
 277         }
 278
 279         struct ifreq ifr = {.ifr_name = ""};
 280         strncpy(ifr.ifr_name, iface->ifname, sizeof(ifr.ifr_name));
 281
 282         struct dhcpv4_message reply = {
 283                 .op = DHCPV4_BOOTREPLY,
 284                 .htype = 1,
 285                 .hlen = 6,
 286                 .hops = 0,
 287                 .xid = req->xid,
 288                 .secs = 0,
 289                 .flags = req->flags,
 290                 .ciaddr = {INADDR_ANY},
 291                 .giaddr = req->giaddr,
 292                 .siaddr = ifaddr.sin_addr,
 293         };
 294         memcpy(reply.chaddr, req->chaddr, sizeof(reply.chaddr));
 295
 296         reply.options[0] = 0x63;
 297         reply.options[1] = 0x82;
 298         reply.options[2] = 0x53;
 299         reply.options[3] = 0x63;
 300
 301         uint8_t *cookie = &reply.options[4];
 302         uint8_t reqmsg = DHCPV4_MSG_REQUEST;
 303         uint8_t msg = DHCPV4_MSG_ACK;
 304
 305         struct in_addr reqaddr = {INADDR_ANY};
 306         char hostname[256];
 307         hostname[0] = 0;
 308
 309         uint8_t *start = &req->options[4];
 310         uint8_t *end = ((uint8_t*)data) + len;
 311         struct dhcpv4_option *opt;
 312         dhcpv4_for_each_option(start, end, opt) {
 313                 if (opt->type == DHCPV4_OPT_MESSAGE && opt->len == 1) {
 314                         reqmsg = opt->data[0];
 315                 } else if (opt->type == DHCPV4_OPT_HOSTNAME && opt->len > 0) {
 316                         memcpy(hostname, opt->data, opt->len);
 317                         hostname[opt->len] = 0;
 318                 } else if (opt->type == DHCPV4_OPT_IPADDRESS && opt->len == 4) {
 319                         memcpy(&reqaddr, opt->data, 4);
 320                 } else if (opt->type == DHCPV4_OPT_SERVERID && opt->len == 4) {
 321                         if (memcmp(opt->data, &ifaddr.sin_addr, 4))
 322                                 return;
 323                 } else if (iface->filter_class && opt->type == DHCPV4_OPT_USER_CLASS) {
 324                         uint8_t *c = opt->data, *cend = &opt->data[opt->len];
 325                         for (; c < cend && &c[*c] < cend; c = &c[1 + *c]) {
 326                                 size_t elen = strlen(iface->filter_class);
 327                                 if (*c == elen && !memcmp(&c[1], iface->filter_class, elen))
 328                                         return; // Ignore from homenet
 329                         }
 330                 }
 331         }
 332
 333         if (reqmsg != DHCPV4_MSG_DISCOVER && reqmsg != DHCPV4_MSG_REQUEST &&
 334                         reqmsg != DHCPV4_MSG_INFORM && reqmsg != DHCPV4_MSG_DECLINE &&
 335                         reqmsg != DHCPV4_MSG_RELEASE)
 336                 return;
 337
 338         struct dhcpv4_assignment *lease = NULL;
 339         if (reqmsg != DHCPV4_MSG_INFORM)
 340                 lease = dhcpv4_lease(iface, reqmsg, req->chaddr, reqaddr, hostname);
 341
 342         if (!lease) {
 343                 if (reqmsg == DHCPV4_MSG_REQUEST)
 344                         msg = DHCPV4_MSG_NAK;
 345                 else if (reqmsg == DHCPV4_MSG_DISCOVER)
 346                         return;
 347         } else if (reqmsg == DHCPV4_MSG_DISCOVER) {
 348                 msg = DHCPV4_MSG_OFFER;
 349         } else if (reqmsg == DHCPV4_MSG_REQUEST && reqaddr.s_addr &&
 350                         reqaddr.s_addr != htonl(lease->addr)) {
 351                 msg = DHCPV4_MSG_NAK;
 352                 /*
 353                  * DHCP client requested an IP which we can't offer to him. Probably the
 354                  * client changed the network. The reply type is set to DHCPV4_MSG_NAK,
 355                  * because the client should not use that IP.
 356                  *
 357                  * For modern devices we build an answer that includes a valid IP, like
 358                  * a DHCPV4_MSG_ACK. The client will use that IP and doesn't need to
 359                  * perform additional DHCP round trips.
 360                  *
 361                  */
 362         }
 363
 364         syslog(LOG_WARNING, "received %s from %x:%x:%x:%x:%x:%x",
 365                         dhcpv4_msg_to_string(reqmsg),
 366                         req->chaddr[0],req->chaddr[1],req->chaddr[2],
 367                         req->chaddr[3],req->chaddr[4],req->chaddr[5]);
 368
 369         if (reqmsg == DHCPV4_MSG_DECLINE || reqmsg == DHCPV4_MSG_RELEASE)
 370                 return;
 371
 372         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_MESSAGE, 1, &msg);
 373         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SERVERID, 4, &ifaddr.sin_addr);
 374
 375         if (lease) {
 376                 reply.yiaddr.s_addr = htonl(lease->addr);
 377
 378                 uint32_t val = htonl(iface->dhcpv4_leasetime);
 379                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_LEASETIME, 4, &val);
 380
 381                 val = htonl(500 * iface->dhcpv4_leasetime / 1000);
 382                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_RENEW, 4, &val);
 383
 384                 val = htonl(875 * iface->dhcpv4_leasetime / 1000);
 385                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_REBIND, 4, &val);
 386
 387                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_NETMASK, 4, &ifnetmask.sin_addr);
 388
 389                 if (lease->hostname[0])
 390                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_HOSTNAME,
 391                                         strlen(lease->hostname), lease->hostname);
 392
 393                 if (!ioctl(sock, SIOCGIFBRDADDR, &ifr)) {
 394                         struct sockaddr_in *ina = (struct sockaddr_in*)&ifr.ifr_broadaddr;
 395                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_BROADCAST, 4, &ina->sin_addr);
 396                 }
 397         }
 398
 399         if (!ioctl(sock, SIOCGIFMTU, &ifr)) {
 400                 uint16_t mtu = htons(ifr.ifr_mtu);
 401                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_MTU, 2, &mtu);
 402         }
 403
 404         if (iface->search && iface->search_len <= 255) {
 405                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SEARCH_DOMAIN,
 406                                 iface->search_len, iface->search);
 407         } else if (!res_init() && _res.dnsrch[0] && _res.dnsrch[0][0]) {
 408                 uint8_t search_buf[256];
 409                 int len = dn_comp(_res.dnsrch[0], search_buf,
 410                                                 sizeof(search_buf), NULL, NULL);
 411                 if (len > 0)
 412                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SEARCH_DOMAIN,
 413                                         len, search_buf);
 414         }
 415
 416         if (iface->dhcpv4_router_cnt == 0)
 417                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_ROUTER, 4, &ifaddr.sin_addr);
 418         else
 419                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_ROUTER,
 420                                 4 * iface->dhcpv4_router_cnt, iface->dhcpv4_router);
 421
 422
 423         if (iface->dhcpv4_dns_cnt == 0)
 424                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_DNSSERVER, 4, &ifaddr.sin_addr);
 425         else
 426                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_DNSSERVER,
 427                                 4 * iface->dhcpv4_dns_cnt, iface->dhcpv4_dns);
 428
 429
 430         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_END, 0, NULL);
 431
 432         struct sockaddr_in dest = *((struct sockaddr_in*)addr);
 433         if (req->giaddr.s_addr) {
 434                 /*
 435                  * relay agent is configured, send reply to the agent
 436                  */
 437                 dest.sin_addr = req->giaddr;
 438                 dest.sin_port = htons(DHCPV4_SERVER_PORT);
 439         } else if (req->ciaddr.s_addr && req->ciaddr.s_addr != dest.sin_addr.s_addr) {
 440                 /*
 441                  * client has existing configuration (ciaddr is set) AND this address is
 442                  * not the address it used for the dhcp message
 443                  */
 444                 dest.sin_addr = req->ciaddr;
 445                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 446         } else if ((ntohs(req->flags) & DHCPV4_FLAG_BROADCAST) ||
 447                         req->hlen != reply.hlen || !reply.yiaddr.s_addr) {
 448                 /*
 449                  * client requests a broadcast reply OR we can't offer an IP
 450                  */
 451                 dest.sin_addr.s_addr = INADDR_BROADCAST;
 452                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 453         } else if (!req->ciaddr.s_addr && msg == DHCPV4_MSG_NAK) {
 454                 /*
 455                  * client has no previous configuration -> no IP, so we need to reply
 456                  * with a broadcast packet
 457                  */
 458                 dest.sin_addr.s_addr = INADDR_BROADCAST;
 459                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 460         } else {
 461                 /*
 462                  * send reply to the newly (in this proccess) allocated IP
 463                  */
 464                 dest.sin_addr = reply.yiaddr;
 465                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 466
 467                 struct arpreq arp = {.arp_flags = ATF_COM};
 468                 memcpy(arp.arp_ha.sa_data, req->chaddr, 6);
 469                 memcpy(&arp.arp_pa, &dest, sizeof(arp.arp_pa));
 470                 memcpy(arp.arp_dev, iface->ifname, sizeof(arp.arp_dev));
 471                 ioctl(sock, SIOCSARP, &arp);
 472         }
 473
 474         if (dest.sin_addr.s_addr == INADDR_BROADCAST) {
 475                 /*
 476                  * reply goes to IP broadcast -> MAC broadcast
 477                  */
 478                 syslog(LOG_WARNING, "sending %s to ff:ff:ff:ff:ff:ff - %s",
 479                                 dhcpv4_msg_to_string(msg),
 480                                 inet_ntoa(dest.sin_addr));
 481         } else {
 482                 /*
 483                  * reply is send directly to IP,
 484                  * MAC is assumed to be the same as the request
 485                  */
 486                 syslog(LOG_WARNING, "sending %s to %x:%x:%x:%x:%x:%x - %s",
 487                                 dhcpv4_msg_to_string(msg),
 488                                 req->chaddr[0],req->chaddr[1],req->chaddr[2],
 489                                 req->chaddr[3],req->chaddr[4],req->chaddr[5],
 490                                 inet_ntoa(dest.sin_addr));
 491         }
 492
 493         sendto(sock, &reply, sizeof(reply), MSG_DONTWAIT,
 494                         (struct sockaddr*)&dest, sizeof(dest));
 495 }
 496
 497 static bool dhcpv4_test(struct interface *iface, uint32_t try)
 498 {
 499         struct dhcpv4_assignment *c;
 500         list_for_each_entry(c, &iface->dhcpv4_assignments, head) {
 501                 if (c->addr == try) {
 502                         return false;
 503                 }
 504         }
 505         return true;
 506 }
 507
 508 static bool dhcpv4_assign(struct interface *iface,
 509                 struct dhcpv4_assignment *assign, uint32_t raddr)
 510 {
 511         uint32_t start = ntohl(iface->dhcpv4_start.s_addr);
 512         uint32_t end = ntohl(iface->dhcpv4_end.s_addr);
 513         uint32_t count = end - start + 1;
 514
 515         // try to assign the IP the client asked for
 516         if (start <= raddr && raddr <= end && dhcpv4_test(iface, raddr)) {
 517                 assign->addr = raddr;
 518                 list_add(&assign->head, &iface->dhcpv4_assignments);
 519                 syslog(LOG_DEBUG, "assigning the IP the client asked for: %u.%u.%u.%u",
 520                                 (assign->addr & 0xff000000) >> 24,
 521                                 (assign->addr & 0x00ff0000) >> 16,
 522                                 (assign->addr & 0x0000ff00) >> 8,
 523                                 (assign->addr & 0x000000ff));
 524                 return true;
 525         }
 526
 527         // Seed RNG with checksum of hwaddress
 528         uint32_t seed = 0;
 529         for (size_t i = 0; i < sizeof(assign->hwaddr); ++i) {
 530                 // Knuth's multiplicative method
 531                 uint8_t o = assign->hwaddr[i];
 532                 seed += (o*2654435761) % UINT32_MAX;
 533         }
 534         srand(seed);
 535
 536         uint32_t try = (((uint32_t)rand()) % count) + start;
 537
 538         if (list_empty(&iface->dhcpv4_assignments)) {
 539                 assign->addr = try;
 540                 list_add(&assign->head, &iface->dhcpv4_assignments);
 541                 syslog(LOG_DEBUG, "assigning mapped IP (empty list): %u.%u.%u.%u",
 542                                 (assign->addr & 0xff000000) >> 24,
 543                                 (assign->addr & 0x00ff0000) >> 16,
 544                                 (assign->addr & 0x0000ff00) >> 8,
 545                                 (assign->addr & 0x000000ff));
 546                 return true;
 547         }
 548
 549         for (uint32_t i = 0; i < count; ++i) {
 550                 if (dhcpv4_test(iface, try)) {
 551                         /* test was successful: IP address is not assigned, assign it */
 552                         assign->addr = try;
 553                         list_add(&assign->head, &iface->dhcpv4_assignments);
 554                         syslog(LOG_DEBUG, "assigning mapped IP: %u.%u.%u.%u (try %u of %u)",
 555                                         (assign->addr & 0xff000000) >> 24,
 556                                         (assign->addr & 0x00ff0000) >> 16,
 557                                         (assign->addr & 0x0000ff00) >> 8,
 558                                         (assign->addr & 0x000000ff), i, count);
 559                         return true;
 560                 }
 561                 try = (((try - start) + 1) % count) + start;
 562         }
 563
 564         syslog(LOG_DEBUG, "can't assign any IP address -> address space is full");
 565         return false;
 566 }
 567
 568
 569 static struct dhcpv4_assignment* dhcpv4_lease(struct interface *iface,
 570                 enum dhcpv4_msg msg, const uint8_t *mac, struct in_addr reqaddr,
 571                 const char *hostname)
 572 {
 573         struct dhcpv4_assignment *lease = NULL;
 574         uint32_t raddr = ntohl(reqaddr.s_addr);
 575         time_t now = odhcpd_time();
 576
 577         struct dhcpv4_assignment *c, *n, *a = NULL;
 578         list_for_each_entry_safe(c, n, &iface->dhcpv4_assignments, head) {
 579                 if (!memcmp(c->hwaddr, mac, 6)) {
 580                         a = c;
 581                         if (c->addr == raddr)
 582                                 break;
 583                 } else if (c->valid_until < now) {
 584                         list_del(&c->head);
 585                         free(c);
 586                 }
 587         }
 588
 589         if (msg == DHCPV4_MSG_DISCOVER || msg == DHCPV4_MSG_REQUEST) {
 590                 bool assigned = !!a;
 591                 size_t hostlen = strlen(hostname) + 1;
 592
 593                 if (!a && !iface->no_dynamic_dhcp) { // Create new binding
 594                         a = calloc(1, sizeof(*a) + hostlen);
 595                         if (!a) {
 596                                 syslog(LOG_ERR, "Failed to calloc binding on interface %s", iface->ifname);
 597                                 return NULL;
 598                         }
 599                         memcpy(a->hwaddr, mac, sizeof(a->hwaddr));
 600                         memcpy(a->hostname, hostname, hostlen);
 601
 602                         assigned = dhcpv4_assign(iface, a, raddr);
 603                 }
 604
 605                 if (assigned && !a->hostname[0] && hostname) {
 606                         a = realloc(a, sizeof(*a) + hostlen);
 607                         if (!a) {
 608                                 syslog(LOG_ERR, "Failed to realloc binding on interface %s", iface->ifname);
 609                                 return NULL;
 610                         }
 611                         memcpy(a->hostname, hostname, hostlen);
 612
 613                         // Fixup list
 614                         a->head.next->prev = &a->head;
 615                         a->head.prev->next = &a->head;
 616                 }
 617
 618                 // Was only a solicitation: mark binding for removal
 619                 if (assigned && a->valid_until < now) {
 620                         a->valid_until = (msg == DHCPV4_MSG_DISCOVER) ? 0 :
 621                                         (now + iface->dhcpv4_leasetime);
 622                 } else if (!assigned && a) { // Cleanup failed assignment
 623                         free(a);
 624                         a = NULL;
 625                 }
 626
 627                 if (assigned && a)
 628                         lease = a;
 629         } else if (msg == DHCPV4_MSG_RELEASE) {
 630                 if (a && a->valid_until != LONG_MAX)
 631                         a->valid_until = 0;
 632         } else if (msg == DHCPV4_MSG_DECLINE && a && a->valid_until != LONG_MAX) {
 633                 memset(a->hwaddr, 0, sizeof(a->hwaddr));
 634                 a->valid_until = now + 3600; // Block address for 1h
 635         }
 636
 637         dhcpv6_write_statefile();
 638
 639         return lease;
 640 }
 641