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
 125                         struct in_addr *saddr = ubus_get_address4(iface->name);
 126                         struct in_addr addr = { .s_addr = saddr->s_addr } ;
 127                         struct in_addr *smask = ubus_get_mask4(iface->name);
 128                         struct in_addr mask = { .s_addr = smask->s_addr } ;
 129
 130                         uint32_t start = ntohl(iface->dhcpv4_start.s_addr);
 131                         uint32_t end = ntohl(iface->dhcpv4_end.s_addr);
 132
 133                         if (start && end && start < end &&
 134                                         start > ntohl(addr.s_addr & ~mask.s_addr) &&
 135                                         (start & ntohl(~mask.s_addr)) == start &&
 136                                         (end & ntohl(~mask.s_addr)) == end) {
 137                                 iface->dhcpv4_start.s_addr = htonl(start) |
 138                                                 (addr.s_addr & mask.s_addr);
 139                                 iface->dhcpv4_end.s_addr = htonl(end) |
 140                                                 (addr.s_addr & mask.s_addr);
 141                         } else if (ntohl(mask.s_addr) <= 0xfffffff0) {
 142                                 start = addr.s_addr & mask.s_addr;
 143                                 end = addr.s_addr & mask.s_addr;
 144
 145                                 if (ntohl(mask.s_addr) <= 0xffffff00) {
 146                                         iface->dhcpv4_start.s_addr = start | htonl(100);
 147                                         iface->dhcpv4_end.s_addr = end | htonl(250);
 148                                 } else if (ntohl(mask.s_addr) <= 0xffffffc0) {
 149                                         iface->dhcpv4_start.s_addr = start | htonl(10);
 150                                         iface->dhcpv4_end.s_addr = end | htonl(60);
 151                                 } else if (ntohl(mask.s_addr) <= 0xffffffe0) {
 152                                         iface->dhcpv4_start.s_addr = start | htonl(10);
 153                                         iface->dhcpv4_end.s_addr = end | htonl(30);
 154                                 } else {
 155                                         iface->dhcpv4_start.s_addr = start | htonl(3);
 156                                         iface->dhcpv4_end.s_addr = end | htonl(12);
 157                                 }
 158                         }
 159
 160
 161                 }
 162
 163                 // Parse static entries
 164                 struct lease *lease;
 165                 list_for_each_entry(lease, &leases, head) {
 166                         // Construct entry
 167                         size_t hostlen = strlen(lease->hostname) + 1;
 168                         struct dhcpv4_assignment *a = calloc(1, sizeof(*a) + hostlen);
 169                         if (!a) {
 170                                 syslog(LOG_ERR, "Calloc failed for static lease on interface %s",
 171                                         iface->ifname);
 172                                 return -1;
 173                         }
 174                         a->addr = ntohl(lease->ipaddr.s_addr);
 175                         memcpy(a->hwaddr, lease->mac.ether_addr_octet, sizeof(a->hwaddr));
 176                         memcpy(a->hostname, lease->hostname, hostlen);
 177                         a->valid_until = LONG_MAX;
 178
 179                         // Assign to all interfaces
 180                         struct dhcpv4_assignment *c;
 181                         list_for_each_entry(c, &iface->dhcpv4_assignments, head) {
 182                                 if (c->addr > a->addr) {
 183                                         list_add_tail(&a->head, &c->head);
 184                                         break;
 185                                 } else if (c->addr == a->addr) {
 186                                         // Already an assignment with that number
 187                                         break;
 188                                 }
 189                         }
 190                         if (&c->head == &iface->dhcpv4_assignments) {
 191                                 list_add(&a->head, &iface->dhcpv4_assignments);
 192                         }
 193
 194                         if (!a->head.next)
 195                                 free(a);
 196                 }
 197
 198                 // Clean invalid assignments
 199                 struct dhcpv4_assignment *a, *n;
 200                 struct in_addr *smask = ubus_get_mask4(iface->name);
 201                 struct in_addr mask = { .s_addr = smask->s_addr } ;
 202                 list_for_each_entry_safe(a, n, &iface->dhcpv4_assignments, head) {
 203                         if ((htonl(a->addr) & mask.s_addr) !=
 204                                         (iface->dhcpv4_start.s_addr & mask.s_addr)) {
 205                                 list_del(&a->head);
 206                                 free(a);
 207                         }
 208                 }
 209
 210
 211                 if (iface->dhcpv4_leasetime < 60)
 212                         iface->dhcpv4_leasetime = 43200;
 213
 214                 iface->dhcpv4_event.uloop.fd = sock;
 215                 iface->dhcpv4_event.handle_dgram = handle_dhcpv4;
 216                 odhcpd_register(&iface->dhcpv4_event);
 217         } else if (iface->dhcpv4_assignments.next) {
 218                 while (!list_empty(&iface->dhcpv4_assignments)) {
 219                         struct dhcpv4_assignment *a = list_first_entry(&iface->dhcpv4_assignments,
 220                                         struct dhcpv4_assignment, head);
 221                         list_del(&a->head);
 222                         free(a);
 223                 }
 224
 225         }
 226         return 0;
 227 }
 228
 229
 230 static void dhcpv4_put(struct dhcpv4_message *msg, uint8_t **cookie,
 231                 uint8_t type, uint8_t len, const void *data)
 232 {
 233         uint8_t *c = *cookie;
 234         if (*cookie + 2 + len > (uint8_t*)&msg[1])
 235                 return;
 236
 237         *c++ = type;
 238         *c++ = len;
 239         memcpy(c, data, len);
 240
 241         *cookie = c + len;
 242 }
 243
 244
 245 // Simple DHCPv6-server for information requests
 246 static void handle_dhcpv4(void *addr, void *data, size_t len,
 247                 struct interface *iface, _unused void *dest_addr)
 248 {
 249         if (!iface->dhcpv4)
 250                 return;
 251
 252         struct dhcpv4_message *req = data;
 253         if (len < offsetof(struct dhcpv4_message, options) + 4 ||
 254                         req->op != DHCPV4_BOOTREQUEST || req->hlen != 6)
 255                 return;
 256
 257         int sock = iface->dhcpv4_event.uloop.fd;
 258         struct sockaddr_in ifaddr;
 259         struct sockaddr_in ifnetmask;
 260
 261         syslog(LOG_NOTICE, "Got DHCPv4 request");
 262
 263         struct ifreq ifreq;
 264         memcpy(ifreq.ifr_name, iface->ifname, sizeof(ifreq.ifr_name));
 265         if (ioctl(sock, SIOCGIFADDR, &ifreq)) {
 266                 syslog(LOG_WARNING, "DHCPv4 failed to detect address: %s", strerror(errno));
 267                 return;
 268         }
 269
 270         memcpy(&ifaddr, &ifreq.ifr_addr, sizeof(ifaddr));
 271         if (ioctl(sock, SIOCGIFNETMASK, &ifreq))
 272                 return;
 273
 274         memcpy(&ifnetmask, &ifreq.ifr_netmask, sizeof(ifnetmask));
 275         uint32_t network = ifaddr.sin_addr.s_addr & ifnetmask.sin_addr.s_addr;
 276
 277         if ((iface->dhcpv4_start.s_addr & ifnetmask.sin_addr.s_addr) != network ||
 278                         (iface->dhcpv4_end.s_addr & ifnetmask.sin_addr.s_addr) != network) {
 279                 syslog(LOG_WARNING, "DHCPv4 range out of assigned network");
 280                 return;
 281         }
 282
 283         struct ifreq ifr = {.ifr_name = ""};
 284         strncpy(ifr.ifr_name, iface->ifname, sizeof(ifr.ifr_name));
 285
 286         struct dhcpv4_message reply = {
 287                 .op = DHCPV4_BOOTREPLY,
 288                 .htype = 1,
 289                 .hlen = 6,
 290                 .hops = 0,
 291                 .xid = req->xid,
 292                 .secs = 0,
 293                 .flags = req->flags,
 294                 .ciaddr = {INADDR_ANY},
 295                 .giaddr = req->giaddr,
 296                 .siaddr = ifaddr.sin_addr,
 297         };
 298         memcpy(reply.chaddr, req->chaddr, sizeof(reply.chaddr));
 299
 300         reply.options[0] = 0x63;
 301         reply.options[1] = 0x82;
 302         reply.options[2] = 0x53;
 303         reply.options[3] = 0x63;
 304
 305         uint8_t *cookie = &reply.options[4];
 306         uint8_t reqmsg = DHCPV4_MSG_REQUEST;
 307         uint8_t msg = DHCPV4_MSG_ACK;
 308
 309         struct in_addr reqaddr = {INADDR_ANY};
 310         char hostname[256];
 311         hostname[0] = 0;
 312
 313         uint8_t *start = &req->options[4];
 314         uint8_t *end = ((uint8_t*)data) + len;
 315         struct dhcpv4_option *opt;
 316         dhcpv4_for_each_option(start, end, opt) {
 317                 if (opt->type == DHCPV4_OPT_MESSAGE && opt->len == 1) {
 318                         reqmsg = opt->data[0];
 319                 } else if (opt->type == DHCPV4_OPT_HOSTNAME && opt->len > 0) {
 320                         memcpy(hostname, opt->data, opt->len);
 321                         hostname[opt->len] = 0;
 322                 } else if (opt->type == DHCPV4_OPT_IPADDRESS && opt->len == 4) {
 323                         memcpy(&reqaddr, opt->data, 4);
 324                 } else if (opt->type == DHCPV4_OPT_SERVERID && opt->len == 4) {
 325                         if (memcmp(opt->data, &ifaddr.sin_addr, 4))
 326                                 return;
 327                 } else if (iface->filter_class && opt->type == DHCPV4_OPT_USER_CLASS) {
 328                         uint8_t *c = opt->data, *cend = &opt->data[opt->len];
 329                         for (; c < cend && &c[*c] < cend; c = &c[1 + *c]) {
 330                                 size_t elen = strlen(iface->filter_class);
 331                                 if (*c == elen && !memcmp(&c[1], iface->filter_class, elen))
 332                                         return; // Ignore from homenet
 333                         }
 334                 }
 335         }
 336
 337         if (reqmsg != DHCPV4_MSG_DISCOVER && reqmsg != DHCPV4_MSG_REQUEST &&
 338                         reqmsg != DHCPV4_MSG_INFORM && reqmsg != DHCPV4_MSG_DECLINE &&
 339                         reqmsg != DHCPV4_MSG_RELEASE)
 340                 return;
 341
 342         struct dhcpv4_assignment *lease = NULL;
 343         if (reqmsg != DHCPV4_MSG_INFORM)
 344                 lease = dhcpv4_lease(iface, reqmsg, req->chaddr, reqaddr, hostname);
 345
 346         if (!lease) {
 347                 if (reqmsg == DHCPV4_MSG_REQUEST)
 348                         msg = DHCPV4_MSG_NAK;
 349                 else if (reqmsg == DHCPV4_MSG_DISCOVER)
 350                         return;
 351         } else if (reqmsg == DHCPV4_MSG_DISCOVER) {
 352                 msg = DHCPV4_MSG_OFFER;
 353         } else if (reqmsg == DHCPV4_MSG_REQUEST && reqaddr.s_addr &&
 354                         reqaddr.s_addr != htonl(lease->addr)) {
 355                 msg = DHCPV4_MSG_NAK;
 356                 /*
 357                  * DHCP client requested an IP which we can't offer to him. Probably the
 358                  * client changed the network. The reply type is set to DHCPV4_MSG_NAK,
 359                  * because the client should not use that IP.
 360                  *
 361                  * For modern devices we build an answer that includes a valid IP, like
 362                  * a DHCPV4_MSG_ACK. The client will use that IP and doesn't need to
 363                  * perform additional DHCP round trips.
 364                  *
 365                  */
 366         }
 367
 368         syslog(LOG_WARNING, "received %s from %x:%x:%x:%x:%x:%x",
 369                         dhcpv4_msg_to_string(reqmsg),
 370                         req->chaddr[0],req->chaddr[1],req->chaddr[2],
 371                         req->chaddr[3],req->chaddr[4],req->chaddr[5]);
 372
 373         if (reqmsg == DHCPV4_MSG_DECLINE || reqmsg == DHCPV4_MSG_RELEASE)
 374                 return;
 375
 376         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_MESSAGE, 1, &msg);
 377         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SERVERID, 4, &ifaddr.sin_addr);
 378
 379         if (lease) {
 380                 reply.yiaddr.s_addr = htonl(lease->addr);
 381
 382                 uint32_t val = htonl(iface->dhcpv4_leasetime);
 383                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_LEASETIME, 4, &val);
 384
 385                 val = htonl(500 * iface->dhcpv4_leasetime / 1000);
 386                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_RENEW, 4, &val);
 387
 388                 val = htonl(875 * iface->dhcpv4_leasetime / 1000);
 389                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_REBIND, 4, &val);
 390
 391                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_NETMASK, 4, &ifnetmask.sin_addr);
 392
 393                 if (lease->hostname[0])
 394                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_HOSTNAME,
 395                                         strlen(lease->hostname), lease->hostname);
 396
 397                 if (!ioctl(sock, SIOCGIFBRDADDR, &ifr)) {
 398                         struct sockaddr_in *ina = (struct sockaddr_in*)&ifr.ifr_broadaddr;
 399                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_BROADCAST, 4, &ina->sin_addr);
 400                 }
 401         }
 402
 403         if (!ioctl(sock, SIOCGIFMTU, &ifr)) {
 404                 uint16_t mtu = htons(ifr.ifr_mtu);
 405                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_MTU, 2, &mtu);
 406         }
 407
 408         if (iface->search && iface->search_len <= 255) {
 409                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SEARCH_DOMAIN,
 410                                 iface->search_len, iface->search);
 411         } else if (!res_init() && _res.dnsrch[0] && _res.dnsrch[0][0]) {
 412                 uint8_t search_buf[256];
 413                 int len = dn_comp(_res.dnsrch[0], search_buf,
 414                                                 sizeof(search_buf), NULL, NULL);
 415                 if (len > 0)
 416                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SEARCH_DOMAIN,
 417                                         len, search_buf);
 418         }
 419
 420         if (iface->dhcpv4_router_cnt == 0)
 421                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_ROUTER, 4, &ifaddr.sin_addr);
 422         else
 423                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_ROUTER,
 424                                 4 * iface->dhcpv4_router_cnt, iface->dhcpv4_router);
 425
 426
 427         if (iface->dhcpv4_dns_cnt == 0)
 428                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_DNSSERVER, 4, &ifaddr.sin_addr);
 429         else
 430                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_DNSSERVER,
 431                                 4 * iface->dhcpv4_dns_cnt, iface->dhcpv4_dns);
 432
 433
 434         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_END, 0, NULL);
 435
 436         struct sockaddr_in dest = *((struct sockaddr_in*)addr);
 437         if (req->giaddr.s_addr) {
 438                 /*
 439                  * relay agent is configured, send reply to the agent
 440                  */
 441                 dest.sin_addr = req->giaddr;
 442                 dest.sin_port = htons(DHCPV4_SERVER_PORT);
 443         } else if (req->ciaddr.s_addr && req->ciaddr.s_addr != dest.sin_addr.s_addr) {
 444                 /*
 445                  * client has existing configuration (ciaddr is set) AND this address is
 446                  * not the address it used for the dhcp message
 447                  */
 448                 dest.sin_addr = req->ciaddr;
 449                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 450         } else if ((ntohs(req->flags) & DHCPV4_FLAG_BROADCAST) ||
 451                         req->hlen != reply.hlen || !reply.yiaddr.s_addr) {
 452                 /*
 453                  * client requests a broadcast reply OR we can't offer an IP
 454                  */
 455                 dest.sin_addr.s_addr = INADDR_BROADCAST;
 456                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 457         } else if (!req->ciaddr.s_addr && msg == DHCPV4_MSG_NAK) {
 458                 /*
 459                  * client has no previous configuration -> no IP, so we need to reply
 460                  * with a broadcast packet
 461                  */
 462                 dest.sin_addr.s_addr = INADDR_BROADCAST;
 463                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 464         } else {
 465                 /*
 466                  * send reply to the newly (in this proccess) allocated IP
 467                  */
 468                 dest.sin_addr = reply.yiaddr;
 469                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 470
 471                 struct arpreq arp = {.arp_flags = ATF_COM};
 472                 memcpy(arp.arp_ha.sa_data, req->chaddr, 6);
 473                 memcpy(&arp.arp_pa, &dest, sizeof(arp.arp_pa));
 474                 memcpy(arp.arp_dev, iface->ifname, sizeof(arp.arp_dev));
 475                 ioctl(sock, SIOCSARP, &arp);
 476         }
 477
 478         if (dest.sin_addr.s_addr == INADDR_BROADCAST) {
 479                 /*
 480                  * reply goes to IP broadcast -> MAC broadcast
 481                  */
 482                 syslog(LOG_WARNING, "sending %s to ff:ff:ff:ff:ff:ff - %s",
 483                                 dhcpv4_msg_to_string(msg),
 484                                 inet_ntoa(dest.sin_addr));
 485         } else {
 486                 /*
 487                  * reply is send directly to IP,
 488                  * MAC is assumed to be the same as the request
 489                  */
 490                 syslog(LOG_WARNING, "sending %s to %x:%x:%x:%x:%x:%x - %s",
 491                                 dhcpv4_msg_to_string(msg),
 492                                 req->chaddr[0],req->chaddr[1],req->chaddr[2],
 493                                 req->chaddr[3],req->chaddr[4],req->chaddr[5],
 494                                 inet_ntoa(dest.sin_addr));
 495         }
 496
 497         sendto(sock, &reply, sizeof(reply), MSG_DONTWAIT,
 498                         (struct sockaddr*)&dest, sizeof(dest));
 499 }
 500
 501 static bool dhcpv4_test(struct interface *iface, uint32_t try)
 502 {
 503         struct dhcpv4_assignment *c;
 504         list_for_each_entry(c, &iface->dhcpv4_assignments, head) {
 505                 if (c->addr == try) {
 506                         return false;
 507                 }
 508         }
 509         return true;
 510 }
 511
 512 static bool dhcpv4_assign(struct interface *iface,
 513                 struct dhcpv4_assignment *assign, uint32_t raddr)
 514 {
 515         uint32_t start = ntohl(iface->dhcpv4_start.s_addr);
 516         uint32_t end = ntohl(iface->dhcpv4_end.s_addr);
 517         uint32_t count = end - start + 1;
 518
 519         // try to assign the IP the client asked for
 520         if (start <= raddr && raddr <= end && dhcpv4_test(iface, raddr)) {
 521                 assign->addr = raddr;
 522                 list_add(&assign->head, &iface->dhcpv4_assignments);
 523                 syslog(LOG_DEBUG, "assigning the IP the client asked for: %u.%u.%u.%u",
 524                                 (assign->addr & 0xff000000) >> 24,
 525                                 (assign->addr & 0x00ff0000) >> 16,
 526                                 (assign->addr & 0x0000ff00) >> 8,
 527                                 (assign->addr & 0x000000ff));
 528                 return true;
 529         }
 530
 531         // Seed RNG with checksum of hwaddress
 532         uint32_t seed = 0;
 533         for (size_t i = 0; i < sizeof(assign->hwaddr); ++i) {
 534                 // Knuth's multiplicative method
 535                 uint8_t o = assign->hwaddr[i];
 536                 seed += (o*2654435761) % UINT32_MAX;
 537         }
 538         srand(seed);
 539
 540         uint32_t try = (((uint32_t)rand()) % count) + start;
 541
 542         if (list_empty(&iface->dhcpv4_assignments)) {
 543                 assign->addr = try;
 544                 list_add(&assign->head, &iface->dhcpv4_assignments);
 545                 syslog(LOG_DEBUG, "assigning mapped IP (empty list): %u.%u.%u.%u",
 546                                 (assign->addr & 0xff000000) >> 24,
 547                                 (assign->addr & 0x00ff0000) >> 16,
 548                                 (assign->addr & 0x0000ff00) >> 8,
 549                                 (assign->addr & 0x000000ff));
 550                 return true;
 551         }
 552
 553         for (uint32_t i = 0; i < count; ++i) {
 554                 if (dhcpv4_test(iface, try)) {
 555                         /* test was successful: IP address is not assigned, assign it */
 556                         assign->addr = try;
 557                         list_add(&assign->head, &iface->dhcpv4_assignments);
 558                         syslog(LOG_DEBUG, "assigning mapped IP: %u.%u.%u.%u (try %u of %u)",
 559                                         (assign->addr & 0xff000000) >> 24,
 560                                         (assign->addr & 0x00ff0000) >> 16,
 561                                         (assign->addr & 0x0000ff00) >> 8,
 562                                         (assign->addr & 0x000000ff), i, count);
 563                         return true;
 564                 }
 565                 try = (((try - start) + 1) % count) + start;
 566         }
 567
 568         syslog(LOG_DEBUG, "can't assign any IP address -> address space is full");
 569         return false;
 570 }
 571
 572
 573 static struct dhcpv4_assignment* dhcpv4_lease(struct interface *iface,
 574                 enum dhcpv4_msg msg, const uint8_t *mac, struct in_addr reqaddr,
 575                 const char *hostname)
 576 {
 577         struct dhcpv4_assignment *lease = NULL;
 578         uint32_t raddr = ntohl(reqaddr.s_addr);
 579         time_t now = odhcpd_time();
 580
 581         struct dhcpv4_assignment *c, *n, *a = NULL;
 582         list_for_each_entry_safe(c, n, &iface->dhcpv4_assignments, head) {
 583                 if (!memcmp(c->hwaddr, mac, 6)) {
 584                         a = c;
 585                         if (c->addr == raddr)
 586                                 break;
 587                 } else if (c->valid_until < now) {
 588                         list_del(&c->head);
 589                         free(c);
 590                 }
 591         }
 592
 593         if (msg == DHCPV4_MSG_DISCOVER || msg == DHCPV4_MSG_REQUEST) {
 594                 bool assigned = !!a;
 595                 size_t hostlen = strlen(hostname) + 1;
 596
 597                 if (!a && !iface->no_dynamic_dhcp) { // Create new binding
 598                         a = calloc(1, sizeof(*a) + hostlen);
 599                         if (!a) {
 600                                 syslog(LOG_ERR, "Failed to calloc binding on interface %s", iface->ifname);
 601                                 return NULL;
 602                         }
 603                         memcpy(a->hwaddr, mac, sizeof(a->hwaddr));
 604                         memcpy(a->hostname, hostname, hostlen);
 605
 606                         assigned = dhcpv4_assign(iface, a, raddr);
 607                 }
 608
 609                 if (assigned && !a->hostname[0] && hostname) {
 610                         a = realloc(a, sizeof(*a) + hostlen);
 611                         if (!a) {
 612                                 syslog(LOG_ERR, "Failed to realloc binding on interface %s", iface->ifname);
 613                                 return NULL;
 614                         }
 615                         memcpy(a->hostname, hostname, hostlen);
 616
 617                         // Fixup list
 618                         a->head.next->prev = &a->head;
 619                         a->head.prev->next = &a->head;
 620                 }
 621
 622                 // Was only a solicitation: mark binding for removal
 623                 if (assigned && a->valid_until < now) {
 624                         a->valid_until = (msg == DHCPV4_MSG_DISCOVER) ? 0 :
 625                                         (now + iface->dhcpv4_leasetime);
 626                 } else if (!assigned && a) { // Cleanup failed assignment
 627                         free(a);
 628                         a = NULL;
 629                 }
 630
 631                 if (assigned && a)
 632                         lease = a;
 633         } else if (msg == DHCPV4_MSG_RELEASE) {
 634                 if (a && a->valid_until != LONG_MAX)
 635                         a->valid_until = 0;
 636         } else if (msg == DHCPV4_MSG_DECLINE && a && a->valid_until != LONG_MAX) {
 637                 memset(a->hwaddr, 0, sizeof(a->hwaddr));
 638                 a->valid_until = now + 3600; // Block address for 1h
 639         }
 640
 641         dhcpv6_write_statefile();
 642
 643         return lease;
 644 }
 645