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                 const char* saddr = ubus_get_address4(iface->name);
 122                 struct in_addr addr;
 123                 inet_pton(AF_INET,saddr, &addr);
 124                 iface->dhcpv4_addr.s_addr = addr.s_addr;
 125                 int bits = ubus_get_mask4(iface->name);
 126                 struct in_addr mask;
 127                 if (bits < -32 || bits > 32)
 128                         bits = 0;
 129
 130                 mask.s_addr = bits ? htonl(~((1 << (32 - abs(bits))) - 1)) : 0;
 131                 if (bits < 0)
 132                         mask.s_addr = ~mask.s_addr;
 133
 134                 iface->dhcpv4_mask.s_addr = mask.s_addr;
 135
 136                 // Create a range if not specified
 137                 if (!(iface->dhcpv4_start.s_addr & htonl(0xffff0000)) &&
 138                                 !(iface->dhcpv4_end.s_addr & htonl(0xffff0000))) {
 139
 140
 141                         uint32_t start = ntohl(iface->dhcpv4_start.s_addr);
 142                         uint32_t end = ntohl(iface->dhcpv4_end.s_addr);
 143
 144                         if (start && end && start < end &&
 145                                         start > ntohl(addr.s_addr & ~mask.s_addr) &&
 146                                         (start & ntohl(~mask.s_addr)) == start &&
 147                                         (end & ntohl(~mask.s_addr)) == end) {
 148                                 iface->dhcpv4_start.s_addr = htonl(start) |
 149                                                 (addr.s_addr & mask.s_addr);
 150                                 iface->dhcpv4_end.s_addr = htonl(end) |
 151                                                 (addr.s_addr & mask.s_addr);
 152                         } else if (ntohl(mask.s_addr) <= 0xfffffff0) {
 153                                 start = addr.s_addr & mask.s_addr;
 154                                 end = addr.s_addr & mask.s_addr;
 155
 156                                 if (ntohl(mask.s_addr) <= 0xffffff00) {
 157                                         iface->dhcpv4_start.s_addr = start | htonl(100);
 158                                         iface->dhcpv4_end.s_addr = end | htonl(250);
 159                                 } else if (ntohl(mask.s_addr) <= 0xffffffc0) {
 160                                         iface->dhcpv4_start.s_addr = start | htonl(10);
 161                                         iface->dhcpv4_end.s_addr = end | htonl(60);
 162                                 } else if (ntohl(mask.s_addr) <= 0xffffffe0) {
 163                                         iface->dhcpv4_start.s_addr = start | htonl(10);
 164                                         iface->dhcpv4_end.s_addr = end | htonl(30);
 165                                 } else {
 166                                         iface->dhcpv4_start.s_addr = start | htonl(3);
 167                                         iface->dhcpv4_end.s_addr = end | htonl(12);
 168                                 }
 169                         }
 170
 171
 172                 }
 173                 syslog(LOG_WARNING, "DHCPv4 dhcp addr  %s", inet_ntoa(iface->dhcpv4_addr));
 174                 syslog(LOG_WARNING, "DHCPv4 dhcp mask  %s", inet_ntoa(iface->dhcpv4_mask));
 175                 syslog(LOG_WARNING, "DHCPv4 dhcp start %s", inet_ntoa(iface->dhcpv4_start));
 176                 syslog(LOG_WARNING, "DHCPv4 dhcp end   %s", inet_ntoa(iface->dhcpv4_end));
 177
 178
 179                 // Parse static entries
 180                 struct lease *lease;
 181                 list_for_each_entry(lease, &leases, head) {
 182                         // Construct entry
 183                         size_t hostlen = strlen(lease->hostname) + 1;
 184                         struct dhcpv4_assignment *a = calloc(1, sizeof(*a) + hostlen);
 185                         if (!a) {
 186                                 syslog(LOG_ERR, "Calloc failed for static lease on interface %s",
 187                                         iface->ifname);
 188                                 return -1;
 189                         }
 190                         a->addr = ntohl(lease->ipaddr.s_addr);
 191                         memcpy(a->hwaddr, lease->mac.ether_addr_octet, sizeof(a->hwaddr));
 192                         memcpy(a->hostname, lease->hostname, hostlen);
 193                         a->valid_until = LONG_MAX;
 194
 195                         // Assign to all interfaces
 196                         struct dhcpv4_assignment *c;
 197                         list_for_each_entry(c, &iface->dhcpv4_assignments, head) {
 198                                 if (c->addr > a->addr) {
 199                                         list_add_tail(&a->head, &c->head);
 200                                         break;
 201                                 } else if (c->addr == a->addr) {
 202                                         // Already an assignment with that number
 203                                         break;
 204                                 }
 205                         }
 206                         if (&c->head == &iface->dhcpv4_assignments) {
 207                                 list_add(&a->head, &iface->dhcpv4_assignments);
 208                         }
 209
 210                         if (!a->head.next)
 211                                 free(a);
 212                 }
 213
 214                 // Clean invalid assignments
 215                 struct dhcpv4_assignment *a, *n;
 216                 list_for_each_entry_safe(a, n, &iface->dhcpv4_assignments, head) {
 217                         if ((htonl(a->addr) & mask.s_addr) !=
 218                                         (iface->dhcpv4_start.s_addr & mask.s_addr)) {
 219                                 list_del(&a->head);
 220                                 free(a);
 221                         }
 222                 }
 223
 224
 225                 if (iface->dhcpv4_leasetime < 60)
 226                         iface->dhcpv4_leasetime = 43200;
 227
 228                 iface->dhcpv4_event.uloop.fd = sock;
 229                 iface->dhcpv4_event.handle_dgram = handle_dhcpv4;
 230                 odhcpd_register(&iface->dhcpv4_event);
 231         } else if (iface->dhcpv4_assignments.next) {
 232                 while (!list_empty(&iface->dhcpv4_assignments)) {
 233                         struct dhcpv4_assignment *a = list_first_entry(&iface->dhcpv4_assignments,
 234                                         struct dhcpv4_assignment, head);
 235                         list_del(&a->head);
 236                         free(a);
 237                 }
 238
 239         }
 240         return 0;
 241 }
 242
 243
 244 static void dhcpv4_put(struct dhcpv4_message *msg, uint8_t **cookie,
 245                 uint8_t type, uint8_t len, const void *data)
 246 {
 247         uint8_t *c = *cookie;
 248         if (*cookie + 2 + len > (uint8_t*)&msg[1])
 249                 return;
 250
 251         *c++ = type;
 252         *c++ = len;
 253         memcpy(c, data, len);
 254
 255         *cookie = c + len;
 256 }
 257
 258
 259 // Simple DHCPv6-server for information requests
 260 static void handle_dhcpv4(void *addr, void *data, size_t len,
 261                 struct interface *iface, _unused void *dest_addr)
 262 {
 263         if (!iface->dhcpv4)
 264                 return;
 265
 266         struct dhcpv4_message *req = data;
 267         if (len < offsetof(struct dhcpv4_message, options) + 4 ||
 268                         req->op != DHCPV4_BOOTREQUEST || req->hlen != 6)
 269                 return;
 270
 271         int sock = iface->dhcpv4_event.uloop.fd;
 272
 273         syslog(LOG_WARNING, "Got DHCPv4 request");
 274
 275         struct ifreq ifreq;
 276         memcpy(ifreq.ifr_name, iface->ifname, sizeof(ifreq.ifr_name));
 277         if (ioctl(sock, SIOCGIFADDR, &ifreq)) {
 278                 syslog(LOG_WARNING, "DHCPv4 failed to detect address: %s", strerror(errno));
 279                 return;
 280         }
 281
 282         uint32_t network = iface->dhcpv4_addr.s_addr & iface->dhcpv4_mask.s_addr;
 283
 284         if ((iface->dhcpv4_start.s_addr & iface->dhcpv4_mask.s_addr) != network ||
 285                         (iface->dhcpv4_end.s_addr & iface->dhcpv4_mask.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 = iface->dhcpv4_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         char hostname[256];
 318         hostname[0] = 0;
 319
 320         uint8_t *start = &req->options[4];
 321         uint8_t *end = ((uint8_t*)data) + len;
 322         struct dhcpv4_option *opt;
 323         dhcpv4_for_each_option(start, end, opt) {
 324                 if (opt->type == DHCPV4_OPT_MESSAGE && opt->len == 1) {
 325                         reqmsg = opt->data[0];
 326                 } else if (opt->type == DHCPV4_OPT_HOSTNAME && opt->len > 0) {
 327                         memcpy(hostname, opt->data, opt->len);
 328                         hostname[opt->len] = 0;
 329                 } else if (opt->type == DHCPV4_OPT_IPADDRESS && opt->len == 4) {
 330                         memcpy(&reqaddr, opt->data, 4);
 331                 } else if (opt->type == DHCPV4_OPT_SERVERID && opt->len == 4) {
 332                         if (memcmp(opt->data, &iface->dhcpv4_addr, 4))
 333                                 return;
 334                 } else if (iface->filter_class && opt->type == DHCPV4_OPT_USER_CLASS) {
 335                         uint8_t *c = opt->data, *cend = &opt->data[opt->len];
 336                         for (; c < cend && &c[*c] < cend; c = &c[1 + *c]) {
 337                                 size_t elen = strlen(iface->filter_class);
 338                                 if (*c == elen && !memcmp(&c[1], iface->filter_class, elen))
 339                                         return; // Ignore from homenet
 340                         }
 341                 }
 342         }
 343
 344         if (reqmsg != DHCPV4_MSG_DISCOVER && reqmsg != DHCPV4_MSG_REQUEST &&
 345                         reqmsg != DHCPV4_MSG_INFORM && reqmsg != DHCPV4_MSG_DECLINE &&
 346                         reqmsg != DHCPV4_MSG_RELEASE)
 347                 return;
 348
 349         struct dhcpv4_assignment *lease = NULL;
 350         if (reqmsg != DHCPV4_MSG_INFORM)
 351                 lease = dhcpv4_lease(iface, reqmsg, req->chaddr, reqaddr, hostname);
 352
 353         if (!lease) {
 354                 if (reqmsg == DHCPV4_MSG_REQUEST)
 355                         msg = DHCPV4_MSG_NAK;
 356                 else if (reqmsg == DHCPV4_MSG_DISCOVER)
 357                         return;
 358         } else if (reqmsg == DHCPV4_MSG_DISCOVER) {
 359                 msg = DHCPV4_MSG_OFFER;
 360         } else if (reqmsg == DHCPV4_MSG_REQUEST && reqaddr.s_addr &&
 361                         reqaddr.s_addr != htonl(lease->addr)) {
 362                 msg = DHCPV4_MSG_NAK;
 363                 /*
 364                  * DHCP client requested an IP which we can't offer to him. Probably the
 365                  * client changed the network. The reply type is set to DHCPV4_MSG_NAK,
 366                  * because the client should not use that IP.
 367                  *
 368                  * For modern devices we build an answer that includes a valid IP, like
 369                  * a DHCPV4_MSG_ACK. The client will use that IP and doesn't need to
 370                  * perform additional DHCP round trips.
 371                  *
 372                  */
 373         }
 374
 375         syslog(LOG_WARNING, "received %s from %x:%x:%x:%x:%x:%x",
 376                         dhcpv4_msg_to_string(reqmsg),
 377                         req->chaddr[0],req->chaddr[1],req->chaddr[2],
 378                         req->chaddr[3],req->chaddr[4],req->chaddr[5]);
 379
 380         if (reqmsg == DHCPV4_MSG_DECLINE || reqmsg == DHCPV4_MSG_RELEASE)
 381                 return;
 382
 383         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_MESSAGE, 1, &msg);
 384         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SERVERID, 4, &iface->dhcpv4_addr);
 385
 386         if (lease) {
 387                 reply.yiaddr.s_addr = htonl(lease->addr);
 388
 389                 uint32_t val = htonl(iface->dhcpv4_leasetime);
 390                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_LEASETIME, 4, &val);
 391
 392                 val = htonl(500 * iface->dhcpv4_leasetime / 1000);
 393                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_RENEW, 4, &val);
 394
 395                 val = htonl(875 * iface->dhcpv4_leasetime / 1000);
 396                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_REBIND, 4, &val);
 397
 398                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_NETMASK, 4, &iface->dhcpv4_mask);
 399
 400                 if (lease->hostname[0])
 401                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_HOSTNAME,
 402                                         strlen(lease->hostname), lease->hostname);
 403
 404                 if (!ioctl(sock, SIOCGIFBRDADDR, &ifr)) {
 405                         struct sockaddr_in *ina = (struct sockaddr_in*)&ifr.ifr_broadaddr;
 406                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_BROADCAST, 4, &ina->sin_addr);
 407                 }
 408         }
 409
 410         if (!ioctl(sock, SIOCGIFMTU, &ifr)) {
 411                 uint16_t mtu = htons(ifr.ifr_mtu);
 412                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_MTU, 2, &mtu);
 413         }
 414
 415         if (iface->search && iface->search_len <= 255) {
 416                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SEARCH_DOMAIN,
 417                                 iface->search_len, iface->search);
 418         } else if (!res_init() && _res.dnsrch[0] && _res.dnsrch[0][0]) {
 419                 uint8_t search_buf[256];
 420                 int len = dn_comp(_res.dnsrch[0], search_buf,
 421                                                 sizeof(search_buf), NULL, NULL);
 422                 if (len > 0)
 423                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SEARCH_DOMAIN,
 424                                         len, search_buf);
 425         }
 426
 427         if (iface->dhcpv4_router_cnt == 0)
 428                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_ROUTER, 4, &iface->dhcpv4_addr);
 429         else
 430                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_ROUTER,
 431                                 4 * iface->dhcpv4_router_cnt, iface->dhcpv4_router);
 432
 433
 434         if (iface->dhcpv4_dns_cnt == 0)
 435                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_DNSSERVER, 4, &iface->dhcpv4_addr);
 436         else
 437                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_DNSSERVER,
 438                                 4 * iface->dhcpv4_dns_cnt, iface->dhcpv4_dns);
 439
 440
 441         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_END, 0, NULL);
 442
 443         struct sockaddr_in dest = *((struct sockaddr_in*)addr);
 444         if (req->giaddr.s_addr) {
 445                 /*
 446                  * relay agent is configured, send reply to the agent
 447                  */
 448                 dest.sin_addr = req->giaddr;
 449                 dest.sin_port = htons(DHCPV4_SERVER_PORT);
 450         } else if (req->ciaddr.s_addr && req->ciaddr.s_addr != dest.sin_addr.s_addr) {
 451                 /*
 452                  * client has existing configuration (ciaddr is set) AND this address is
 453                  * not the address it used for the dhcp message
 454                  */
 455                 dest.sin_addr = req->ciaddr;
 456                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 457         } else if ((ntohs(req->flags) & DHCPV4_FLAG_BROADCAST) ||
 458                         req->hlen != reply.hlen || !reply.yiaddr.s_addr) {
 459                 /*
 460                  * client requests a broadcast reply OR we can't offer an IP
 461                  */
 462                 dest.sin_addr.s_addr = INADDR_BROADCAST;
 463                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 464         } else if (!req->ciaddr.s_addr && msg == DHCPV4_MSG_NAK) {
 465                 /*
 466                  * client has no previous configuration -> no IP, so we need to reply
 467                  * with a broadcast packet
 468                  */
 469                 dest.sin_addr.s_addr = INADDR_BROADCAST;
 470                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 471         } else {
 472                 /*
 473                  * send reply to the newly (in this proccess) allocated IP
 474                  */
 475                 dest.sin_addr = reply.yiaddr;
 476                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 477
 478                 struct arpreq arp = {.arp_flags = ATF_COM};
 479                 memcpy(arp.arp_ha.sa_data, req->chaddr, 6);
 480                 memcpy(&arp.arp_pa, &dest, sizeof(arp.arp_pa));
 481                 memcpy(arp.arp_dev, iface->ifname, sizeof(arp.arp_dev));
 482                 ioctl(sock, SIOCSARP, &arp);
 483         }
 484
 485         if (dest.sin_addr.s_addr == INADDR_BROADCAST) {
 486                 /*
 487                  * reply goes to IP broadcast -> MAC broadcast
 488                  */
 489                 syslog(LOG_WARNING, "sending %s to ff:ff:ff:ff:ff:ff - %s",
 490                                 dhcpv4_msg_to_string(msg),
 491                                 inet_ntoa(dest.sin_addr));
 492         } else {
 493                 /*
 494                  * reply is send directly to IP,
 495                  * MAC is assumed to be the same as the request
 496                  */
 497                 syslog(LOG_WARNING, "sending %s to %x:%x:%x:%x:%x:%x - %s",
 498                                 dhcpv4_msg_to_string(msg),
 499                                 req->chaddr[0],req->chaddr[1],req->chaddr[2],
 500                                 req->chaddr[3],req->chaddr[4],req->chaddr[5],
 501                                 inet_ntoa(dest.sin_addr));
 502         }
 503
 504         sendto(sock, &reply, sizeof(reply), MSG_DONTWAIT,
 505                         (struct sockaddr*)&dest, sizeof(dest));
 506 }
 507
 508 static bool dhcpv4_test(struct interface *iface, uint32_t try)
 509 {
 510         struct dhcpv4_assignment *c;
 511         list_for_each_entry(c, &iface->dhcpv4_assignments, head) {
 512                 if (c->addr == try) {
 513                         return false;
 514                 }
 515         }
 516         return true;
 517 }
 518
 519 static bool dhcpv4_assign(struct interface *iface,
 520                 struct dhcpv4_assignment *assign, uint32_t raddr)
 521 {
 522         uint32_t start = ntohl(iface->dhcpv4_start.s_addr);
 523         uint32_t end = ntohl(iface->dhcpv4_end.s_addr);
 524         uint32_t count = end - start + 1;
 525
 526         // try to assign the IP the client asked for
 527         if (start <= raddr && raddr <= end && dhcpv4_test(iface, raddr)) {
 528                 assign->addr = raddr;
 529                 list_add(&assign->head, &iface->dhcpv4_assignments);
 530                 syslog(LOG_DEBUG, "assigning the IP the client asked for: %u.%u.%u.%u",
 531                                 (assign->addr & 0xff000000) >> 24,
 532                                 (assign->addr & 0x00ff0000) >> 16,
 533                                 (assign->addr & 0x0000ff00) >> 8,
 534                                 (assign->addr & 0x000000ff));
 535                 return true;
 536         }
 537
 538         // Seed RNG with checksum of hwaddress
 539         uint32_t seed = 0;
 540         for (size_t i = 0; i < sizeof(assign->hwaddr); ++i) {
 541                 // Knuth's multiplicative method
 542                 uint8_t o = assign->hwaddr[i];
 543                 seed += (o*2654435761) % UINT32_MAX;
 544         }
 545         srand(seed);
 546
 547         uint32_t try = (((uint32_t)rand()) % count) + start;
 548
 549         if (list_empty(&iface->dhcpv4_assignments)) {
 550                 assign->addr = try;
 551                 list_add(&assign->head, &iface->dhcpv4_assignments);
 552                 syslog(LOG_DEBUG, "assigning mapped IP (empty list): %u.%u.%u.%u",
 553                                 (assign->addr & 0xff000000) >> 24,
 554                                 (assign->addr & 0x00ff0000) >> 16,
 555                                 (assign->addr & 0x0000ff00) >> 8,
 556                                 (assign->addr & 0x000000ff));
 557                 return true;
 558         }
 559
 560         for (uint32_t i = 0; i < count; ++i) {
 561                 if (dhcpv4_test(iface, try)) {
 562                         /* test was successful: IP address is not assigned, assign it */
 563                         assign->addr = try;
 564                         list_add(&assign->head, &iface->dhcpv4_assignments);
 565                         syslog(LOG_DEBUG, "assigning mapped IP: %u.%u.%u.%u (try %u of %u)",
 566                                         (assign->addr & 0xff000000) >> 24,
 567                                         (assign->addr & 0x00ff0000) >> 16,
 568                                         (assign->addr & 0x0000ff00) >> 8,
 569                                         (assign->addr & 0x000000ff), i, count);
 570                         return true;
 571                 }
 572                 try = (((try - start) + 1) % count) + start;
 573         }
 574
 575         syslog(LOG_DEBUG, "can't assign any IP address -> address space is full");
 576         return false;
 577 }
 578
 579
 580 static struct dhcpv4_assignment* dhcpv4_lease(struct interface *iface,
 581                 enum dhcpv4_msg msg, const uint8_t *mac, struct in_addr reqaddr,
 582                 const char *hostname)
 583 {
 584         struct dhcpv4_assignment *lease = NULL;
 585         uint32_t raddr = ntohl(reqaddr.s_addr);
 586         time_t now = odhcpd_time();
 587
 588         struct dhcpv4_assignment *c, *n, *a = NULL;
 589         list_for_each_entry_safe(c, n, &iface->dhcpv4_assignments, head) {
 590                 if (!memcmp(c->hwaddr, mac, 6)) {
 591                         a = c;
 592                         if (c->addr == raddr)
 593                                 break;
 594                 } else if (c->valid_until < now) {
 595                         list_del(&c->head);
 596                         free(c);
 597                 }
 598         }
 599
 600         if (msg == DHCPV4_MSG_DISCOVER || msg == DHCPV4_MSG_REQUEST) {
 601                 bool assigned = !!a;
 602                 size_t hostlen = strlen(hostname) + 1;
 603
 604                 if (!a && !iface->no_dynamic_dhcp) { // Create new binding
 605                         a = calloc(1, sizeof(*a) + hostlen);
 606                         if (!a) {
 607                                 syslog(LOG_ERR, "Failed to calloc binding on interface %s", iface->ifname);
 608                                 return NULL;
 609                         }
 610                         memcpy(a->hwaddr, mac, sizeof(a->hwaddr));
 611                         memcpy(a->hostname, hostname, hostlen);
 612
 613                         assigned = dhcpv4_assign(iface, a, raddr);
 614                 }
 615
 616                 if (assigned && !a->hostname[0] && hostname) {
 617                         a = realloc(a, sizeof(*a) + hostlen);
 618                         if (!a) {
 619                                 syslog(LOG_ERR, "Failed to realloc binding on interface %s", iface->ifname);
 620                                 return NULL;
 621                         }
 622                         memcpy(a->hostname, hostname, hostlen);
 623
 624                         // Fixup list
 625                         a->head.next->prev = &a->head;
 626                         a->head.prev->next = &a->head;
 627                 }
 628
 629                 // Was only a solicitation: mark binding for removal
 630                 if (assigned && a->valid_until < now) {
 631                         a->valid_until = (msg == DHCPV4_MSG_DISCOVER) ? 0 :
 632                                         (now + iface->dhcpv4_leasetime);
 633                 } else if (!assigned && a) { // Cleanup failed assignment
 634                         free(a);
 635                         a = NULL;
 636                 }
 637
 638                 if (assigned && a)
 639                         lease = a;
 640         } else if (msg == DHCPV4_MSG_RELEASE) {
 641                 if (a && a->valid_until != LONG_MAX)
 642                         a->valid_until = 0;
 643         } else if (msg == DHCPV4_MSG_DECLINE && a && a->valid_until != LONG_MAX) {
 644                 memset(a->hwaddr, 0, sizeof(a->hwaddr));
 645                 a->valid_until = now + 3600; // Block address for 1h
 646         }
 647
 648         dhcpv6_write_statefile();
 649
 650         return lease;
 651 }
 652