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                 int bits = ubus_get_mask4(iface->name);
 125                 struct in_addr mask;
 126                 if (!(bits < -32 || bits > 32)) {
 127                         mask.s_addr = bits ? htonl(~((1 << (32 - abs(bits))) - 1)) : 0;
 128                         if (bits < 0)
 129                                 mask.s_addr = ~mask.s_addr;
 130                 }
 131
 132
 133                 // Create a range if not specified
 134                 if (!(iface->dhcpv4_start.s_addr & htonl(0xffff0000)) &&
 135                                 !(iface->dhcpv4_end.s_addr & htonl(0xffff0000))) {
 136
 137
 138                         uint32_t start = ntohl(iface->dhcpv4_start.s_addr);
 139                         uint32_t end = ntohl(iface->dhcpv4_end.s_addr);
 140
 141                         if (start && end && start < end &&
 142                                         start > ntohl(addr.s_addr & ~mask.s_addr) &&
 143                                         (start & ntohl(~mask.s_addr)) == start &&
 144                                         (end & ntohl(~mask.s_addr)) == end) {
 145                                 iface->dhcpv4_start.s_addr = htonl(start) |
 146                                                 (addr.s_addr & mask.s_addr);
 147                                 iface->dhcpv4_end.s_addr = htonl(end) |
 148                                                 (addr.s_addr & mask.s_addr);
 149                         } else if (ntohl(mask.s_addr) <= 0xfffffff0) {
 150                                 start = addr.s_addr & mask.s_addr;
 151                                 end = addr.s_addr & mask.s_addr;
 152
 153                                 if (ntohl(mask.s_addr) <= 0xffffff00) {
 154                                         iface->dhcpv4_start.s_addr = start | htonl(100);
 155                                         iface->dhcpv4_end.s_addr = end | htonl(250);
 156                                 } else if (ntohl(mask.s_addr) <= 0xffffffc0) {
 157                                         iface->dhcpv4_start.s_addr = start | htonl(10);
 158                                         iface->dhcpv4_end.s_addr = end | htonl(60);
 159                                 } else if (ntohl(mask.s_addr) <= 0xffffffe0) {
 160                                         iface->dhcpv4_start.s_addr = start | htonl(10);
 161                                         iface->dhcpv4_end.s_addr = end | htonl(30);
 162                                 } else {
 163                                         iface->dhcpv4_start.s_addr = start | htonl(3);
 164                                         iface->dhcpv4_end.s_addr = end | htonl(12);
 165                                 }
 166                         }
 167
 168
 169                 }
 170
 171                 // Parse static entries
 172                 struct lease *lease;
 173                 list_for_each_entry(lease, &leases, head) {
 174                         // Construct entry
 175                         size_t hostlen = strlen(lease->hostname) + 1;
 176                         struct dhcpv4_assignment *a = calloc(1, sizeof(*a) + hostlen);
 177                         if (!a) {
 178                                 syslog(LOG_ERR, "Calloc failed for static lease on interface %s",
 179                                         iface->ifname);
 180                                 return -1;
 181                         }
 182                         a->addr = ntohl(lease->ipaddr.s_addr);
 183                         memcpy(a->hwaddr, lease->mac.ether_addr_octet, sizeof(a->hwaddr));
 184                         memcpy(a->hostname, lease->hostname, hostlen);
 185                         a->valid_until = LONG_MAX;
 186
 187                         // Assign to all interfaces
 188                         struct dhcpv4_assignment *c;
 189                         list_for_each_entry(c, &iface->dhcpv4_assignments, head) {
 190                                 if (c->addr > a->addr) {
 191                                         list_add_tail(&a->head, &c->head);
 192                                         break;
 193                                 } else if (c->addr == a->addr) {
 194                                         // Already an assignment with that number
 195                                         break;
 196                                 }
 197                         }
 198                         if (&c->head == &iface->dhcpv4_assignments) {
 199                                 list_add(&a->head, &iface->dhcpv4_assignments);
 200                         }
 201
 202                         if (!a->head.next)
 203                                 free(a);
 204                 }
 205
 206                 // Clean invalid assignments
 207                 struct dhcpv4_assignment *a, *n;
 208                 list_for_each_entry_safe(a, n, &iface->dhcpv4_assignments, head) {
 209                         if ((htonl(a->addr) & mask.s_addr) !=
 210                                         (iface->dhcpv4_start.s_addr & mask.s_addr)) {
 211                                 list_del(&a->head);
 212                                 free(a);
 213                         }
 214                 }
 215
 216
 217                 if (iface->dhcpv4_leasetime < 60)
 218                         iface->dhcpv4_leasetime = 43200;
 219
 220                 iface->dhcpv4_event.uloop.fd = sock;
 221                 iface->dhcpv4_event.handle_dgram = handle_dhcpv4;
 222                 odhcpd_register(&iface->dhcpv4_event);
 223         } else if (iface->dhcpv4_assignments.next) {
 224                 while (!list_empty(&iface->dhcpv4_assignments)) {
 225                         struct dhcpv4_assignment *a = list_first_entry(&iface->dhcpv4_assignments,
 226                                         struct dhcpv4_assignment, head);
 227                         list_del(&a->head);
 228                         free(a);
 229                 }
 230
 231         }
 232         return 0;
 233 }
 234
 235
 236 static void dhcpv4_put(struct dhcpv4_message *msg, uint8_t **cookie,
 237                 uint8_t type, uint8_t len, const void *data)
 238 {
 239         uint8_t *c = *cookie;
 240         if (*cookie + 2 + len > (uint8_t*)&msg[1])
 241                 return;
 242
 243         *c++ = type;
 244         *c++ = len;
 245         memcpy(c, data, len);
 246
 247         *cookie = c + len;
 248 }
 249
 250
 251 // Simple DHCPv6-server for information requests
 252 static void handle_dhcpv4(void *addr, void *data, size_t len,
 253                 struct interface *iface, _unused void *dest_addr)
 254 {
 255         if (!iface->dhcpv4)
 256                 return;
 257
 258         struct dhcpv4_message *req = data;
 259         if (len < offsetof(struct dhcpv4_message, options) + 4 ||
 260                         req->op != DHCPV4_BOOTREQUEST || req->hlen != 6)
 261                 return;
 262
 263         int sock = iface->dhcpv4_event.uloop.fd;
 264         struct sockaddr_in ifaddr;
 265         struct sockaddr_in ifnetmask;
 266
 267         syslog(LOG_NOTICE, "Got DHCPv4 request");
 268
 269         struct ifreq ifreq;
 270         memcpy(ifreq.ifr_name, iface->ifname, sizeof(ifreq.ifr_name));
 271         if (ioctl(sock, SIOCGIFADDR, &ifreq)) {
 272                 syslog(LOG_WARNING, "DHCPv4 failed to detect address: %s", strerror(errno));
 273                 return;
 274         }
 275
 276         memcpy(&ifaddr, &ifreq.ifr_addr, sizeof(ifaddr));
 277         if (ioctl(sock, SIOCGIFNETMASK, &ifreq))
 278                 return;
 279
 280         memcpy(&ifnetmask, &ifreq.ifr_netmask, sizeof(ifnetmask));
 281         uint32_t network = ifaddr.sin_addr.s_addr & ifnetmask.sin_addr.s_addr;
 282
 283         if ((iface->dhcpv4_start.s_addr & ifnetmask.sin_addr.s_addr) != network ||
 284                         (iface->dhcpv4_end.s_addr & ifnetmask.sin_addr.s_addr) != network) {
 285                 syslog(LOG_WARNING, "DHCPv4 range out of assigned network");
 286                 return;
 287         }
 288
 289         struct ifreq ifr = {.ifr_name = ""};
 290         strncpy(ifr.ifr_name, iface->ifname, sizeof(ifr.ifr_name));
 291
 292         struct dhcpv4_message reply = {
 293                 .op = DHCPV4_BOOTREPLY,
 294                 .htype = 1,
 295                 .hlen = 6,
 296                 .hops = 0,
 297                 .xid = req->xid,
 298                 .secs = 0,
 299                 .flags = req->flags,
 300                 .ciaddr = {INADDR_ANY},
 301                 .giaddr = req->giaddr,
 302                 .siaddr = ifaddr.sin_addr,
 303         };
 304         memcpy(reply.chaddr, req->chaddr, sizeof(reply.chaddr));
 305
 306         reply.options[0] = 0x63;
 307         reply.options[1] = 0x82;
 308         reply.options[2] = 0x53;
 309         reply.options[3] = 0x63;
 310
 311         uint8_t *cookie = &reply.options[4];
 312         uint8_t reqmsg = DHCPV4_MSG_REQUEST;
 313         uint8_t msg = DHCPV4_MSG_ACK;
 314
 315         struct in_addr reqaddr = {INADDR_ANY};
 316         char hostname[256];
 317         hostname[0] = 0;
 318
 319         uint8_t *start = &req->options[4];
 320         uint8_t *end = ((uint8_t*)data) + len;
 321         struct dhcpv4_option *opt;
 322         dhcpv4_for_each_option(start, end, opt) {
 323                 if (opt->type == DHCPV4_OPT_MESSAGE && opt->len == 1) {
 324                         reqmsg = opt->data[0];
 325                 } else if (opt->type == DHCPV4_OPT_HOSTNAME && opt->len > 0) {
 326                         memcpy(hostname, opt->data, opt->len);
 327                         hostname[opt->len] = 0;
 328                 } else if (opt->type == DHCPV4_OPT_IPADDRESS && opt->len == 4) {
 329                         memcpy(&reqaddr, opt->data, 4);
 330                 } else if (opt->type == DHCPV4_OPT_SERVERID && opt->len == 4) {
 331                         if (memcmp(opt->data, &ifaddr.sin_addr, 4))
 332                                 return;
 333                 } else if (iface->filter_class && opt->type == DHCPV4_OPT_USER_CLASS) {
 334                         uint8_t *c = opt->data, *cend = &opt->data[opt->len];
 335                         for (; c < cend && &c[*c] < cend; c = &c[1 + *c]) {
 336                                 size_t elen = strlen(iface->filter_class);
 337                                 if (*c == elen && !memcmp(&c[1], iface->filter_class, elen))
 338                                         return; // Ignore from homenet
 339                         }
 340                 }
 341         }
 342
 343         if (reqmsg != DHCPV4_MSG_DISCOVER && reqmsg != DHCPV4_MSG_REQUEST &&
 344                         reqmsg != DHCPV4_MSG_INFORM && reqmsg != DHCPV4_MSG_DECLINE &&
 345                         reqmsg != DHCPV4_MSG_RELEASE)
 346                 return;
 347
 348         struct dhcpv4_assignment *lease = NULL;
 349         if (reqmsg != DHCPV4_MSG_INFORM)
 350                 lease = dhcpv4_lease(iface, reqmsg, req->chaddr, reqaddr, hostname);
 351
 352         if (!lease) {
 353                 if (reqmsg == DHCPV4_MSG_REQUEST)
 354                         msg = DHCPV4_MSG_NAK;
 355                 else if (reqmsg == DHCPV4_MSG_DISCOVER)
 356                         return;
 357         } else if (reqmsg == DHCPV4_MSG_DISCOVER) {
 358                 msg = DHCPV4_MSG_OFFER;
 359         } else if (reqmsg == DHCPV4_MSG_REQUEST && reqaddr.s_addr &&
 360                         reqaddr.s_addr != htonl(lease->addr)) {
 361                 msg = DHCPV4_MSG_NAK;
 362                 /*
 363                  * DHCP client requested an IP which we can't offer to him. Probably the
 364                  * client changed the network. The reply type is set to DHCPV4_MSG_NAK,
 365                  * because the client should not use that IP.
 366                  *
 367                  * For modern devices we build an answer that includes a valid IP, like
 368                  * a DHCPV4_MSG_ACK. The client will use that IP and doesn't need to
 369                  * perform additional DHCP round trips.
 370                  *
 371                  */
 372         }
 373
 374         syslog(LOG_WARNING, "received %s from %x:%x:%x:%x:%x:%x",
 375                         dhcpv4_msg_to_string(reqmsg),
 376                         req->chaddr[0],req->chaddr[1],req->chaddr[2],
 377                         req->chaddr[3],req->chaddr[4],req->chaddr[5]);
 378
 379         if (reqmsg == DHCPV4_MSG_DECLINE || reqmsg == DHCPV4_MSG_RELEASE)
 380                 return;
 381
 382         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_MESSAGE, 1, &msg);
 383         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SERVERID, 4, &ifaddr.sin_addr);
 384
 385         if (lease) {
 386                 reply.yiaddr.s_addr = htonl(lease->addr);
 387
 388                 uint32_t val = htonl(iface->dhcpv4_leasetime);
 389                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_LEASETIME, 4, &val);
 390
 391                 val = htonl(500 * iface->dhcpv4_leasetime / 1000);
 392                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_RENEW, 4, &val);
 393
 394                 val = htonl(875 * iface->dhcpv4_leasetime / 1000);
 395                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_REBIND, 4, &val);
 396
 397                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_NETMASK, 4, &ifnetmask.sin_addr);
 398
 399                 if (lease->hostname[0])
 400                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_HOSTNAME,
 401                                         strlen(lease->hostname), lease->hostname);
 402
 403                 if (!ioctl(sock, SIOCGIFBRDADDR, &ifr)) {
 404                         struct sockaddr_in *ina = (struct sockaddr_in*)&ifr.ifr_broadaddr;
 405                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_BROADCAST, 4, &ina->sin_addr);
 406                 }
 407         }
 408
 409         if (!ioctl(sock, SIOCGIFMTU, &ifr)) {
 410                 uint16_t mtu = htons(ifr.ifr_mtu);
 411                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_MTU, 2, &mtu);
 412         }
 413
 414         if (iface->search && iface->search_len <= 255) {
 415                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SEARCH_DOMAIN,
 416                                 iface->search_len, iface->search);
 417         } else if (!res_init() && _res.dnsrch[0] && _res.dnsrch[0][0]) {
 418                 uint8_t search_buf[256];
 419                 int len = dn_comp(_res.dnsrch[0], search_buf,
 420                                                 sizeof(search_buf), NULL, NULL);
 421                 if (len > 0)
 422                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SEARCH_DOMAIN,
 423                                         len, search_buf);
 424         }
 425
 426         if (iface->dhcpv4_router_cnt == 0)
 427                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_ROUTER, 4, &ifaddr.sin_addr);
 428         else
 429                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_ROUTER,
 430                                 4 * iface->dhcpv4_router_cnt, iface->dhcpv4_router);
 431
 432
 433         if (iface->dhcpv4_dns_cnt == 0)
 434                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_DNSSERVER, 4, &ifaddr.sin_addr);
 435         else
 436                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_DNSSERVER,
 437                                 4 * iface->dhcpv4_dns_cnt, iface->dhcpv4_dns);
 438
 439
 440         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_END, 0, NULL);
 441
 442         struct sockaddr_in dest = *((struct sockaddr_in*)addr);
 443         if (req->giaddr.s_addr) {
 444                 /*
 445                  * relay agent is configured, send reply to the agent
 446                  */
 447                 dest.sin_addr = req->giaddr;
 448                 dest.sin_port = htons(DHCPV4_SERVER_PORT);
 449         } else if (req->ciaddr.s_addr && req->ciaddr.s_addr != dest.sin_addr.s_addr) {
 450                 /*
 451                  * client has existing configuration (ciaddr is set) AND this address is
 452                  * not the address it used for the dhcp message
 453                  */
 454                 dest.sin_addr = req->ciaddr;
 455                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 456         } else if ((ntohs(req->flags) & DHCPV4_FLAG_BROADCAST) ||
 457                         req->hlen != reply.hlen || !reply.yiaddr.s_addr) {
 458                 /*
 459                  * client requests a broadcast reply OR we can't offer an IP
 460                  */
 461                 dest.sin_addr.s_addr = INADDR_BROADCAST;
 462                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 463         } else if (!req->ciaddr.s_addr && msg == DHCPV4_MSG_NAK) {
 464                 /*
 465                  * client has no previous configuration -> no IP, so we need to reply
 466                  * with a broadcast packet
 467                  */
 468                 dest.sin_addr.s_addr = INADDR_BROADCAST;
 469                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 470         } else {
 471                 /*
 472                  * send reply to the newly (in this proccess) allocated IP
 473                  */
 474                 dest.sin_addr = reply.yiaddr;
 475                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 476
 477                 struct arpreq arp = {.arp_flags = ATF_COM};
 478                 memcpy(arp.arp_ha.sa_data, req->chaddr, 6);
 479                 memcpy(&arp.arp_pa, &dest, sizeof(arp.arp_pa));
 480                 memcpy(arp.arp_dev, iface->ifname, sizeof(arp.arp_dev));
 481                 ioctl(sock, SIOCSARP, &arp);
 482         }
 483
 484         if (dest.sin_addr.s_addr == INADDR_BROADCAST) {
 485                 /*
 486                  * reply goes to IP broadcast -> MAC broadcast
 487                  */
 488                 syslog(LOG_WARNING, "sending %s to ff:ff:ff:ff:ff:ff - %s",
 489                                 dhcpv4_msg_to_string(msg),
 490                                 inet_ntoa(dest.sin_addr));
 491         } else {
 492                 /*
 493                  * reply is send directly to IP,
 494                  * MAC is assumed to be the same as the request
 495                  */
 496                 syslog(LOG_WARNING, "sending %s to %x:%x:%x:%x:%x:%x - %s",
 497                                 dhcpv4_msg_to_string(msg),
 498                                 req->chaddr[0],req->chaddr[1],req->chaddr[2],
 499                                 req->chaddr[3],req->chaddr[4],req->chaddr[5],
 500                                 inet_ntoa(dest.sin_addr));
 501         }
 502
 503         sendto(sock, &reply, sizeof(reply), MSG_DONTWAIT,
 504                         (struct sockaddr*)&dest, sizeof(dest));
 505 }
 506
 507 static bool dhcpv4_test(struct interface *iface, uint32_t try)
 508 {
 509         struct dhcpv4_assignment *c;
 510         list_for_each_entry(c, &iface->dhcpv4_assignments, head) {
 511                 if (c->addr == try) {
 512                         return false;
 513                 }
 514         }
 515         return true;
 516 }
 517
 518 static bool dhcpv4_assign(struct interface *iface,
 519                 struct dhcpv4_assignment *assign, uint32_t raddr)
 520 {
 521         uint32_t start = ntohl(iface->dhcpv4_start.s_addr);
 522         uint32_t end = ntohl(iface->dhcpv4_end.s_addr);
 523         uint32_t count = end - start + 1;
 524
 525         // try to assign the IP the client asked for
 526         if (start <= raddr && raddr <= end && dhcpv4_test(iface, raddr)) {
 527                 assign->addr = raddr;
 528                 list_add(&assign->head, &iface->dhcpv4_assignments);
 529                 syslog(LOG_DEBUG, "assigning the IP the client asked for: %u.%u.%u.%u",
 530                                 (assign->addr & 0xff000000) >> 24,
 531                                 (assign->addr & 0x00ff0000) >> 16,
 532                                 (assign->addr & 0x0000ff00) >> 8,
 533                                 (assign->addr & 0x000000ff));
 534                 return true;
 535         }
 536
 537         // Seed RNG with checksum of hwaddress
 538         uint32_t seed = 0;
 539         for (size_t i = 0; i < sizeof(assign->hwaddr); ++i) {
 540                 // Knuth's multiplicative method
 541                 uint8_t o = assign->hwaddr[i];
 542                 seed += (o*2654435761) % UINT32_MAX;
 543         }
 544         srand(seed);
 545
 546         uint32_t try = (((uint32_t)rand()) % count) + start;
 547
 548         if (list_empty(&iface->dhcpv4_assignments)) {
 549                 assign->addr = try;
 550                 list_add(&assign->head, &iface->dhcpv4_assignments);
 551                 syslog(LOG_DEBUG, "assigning mapped IP (empty list): %u.%u.%u.%u",
 552                                 (assign->addr & 0xff000000) >> 24,
 553                                 (assign->addr & 0x00ff0000) >> 16,
 554                                 (assign->addr & 0x0000ff00) >> 8,
 555                                 (assign->addr & 0x000000ff));
 556                 return true;
 557         }
 558
 559         for (uint32_t i = 0; i < count; ++i) {
 560                 if (dhcpv4_test(iface, try)) {
 561                         /* test was successful: IP address is not assigned, assign it */
 562                         assign->addr = try;
 563                         list_add(&assign->head, &iface->dhcpv4_assignments);
 564                         syslog(LOG_DEBUG, "assigning mapped IP: %u.%u.%u.%u (try %u of %u)",
 565                                         (assign->addr & 0xff000000) >> 24,
 566                                         (assign->addr & 0x00ff0000) >> 16,
 567                                         (assign->addr & 0x0000ff00) >> 8,
 568                                         (assign->addr & 0x000000ff), i, count);
 569                         return true;
 570                 }
 571                 try = (((try - start) + 1) % count) + start;
 572         }
 573
 574         syslog(LOG_DEBUG, "can't assign any IP address -> address space is full");
 575         return false;
 576 }
 577
 578
 579 static struct dhcpv4_assignment* dhcpv4_lease(struct interface *iface,
 580                 enum dhcpv4_msg msg, const uint8_t *mac, struct in_addr reqaddr,
 581                 const char *hostname)
 582 {
 583         struct dhcpv4_assignment *lease = NULL;
 584         uint32_t raddr = ntohl(reqaddr.s_addr);
 585         time_t now = odhcpd_time();
 586
 587         struct dhcpv4_assignment *c, *n, *a = NULL;
 588         list_for_each_entry_safe(c, n, &iface->dhcpv4_assignments, head) {
 589                 if (!memcmp(c->hwaddr, mac, 6)) {
 590                         a = c;
 591                         if (c->addr == raddr)
 592                                 break;
 593                 } else if (c->valid_until < now) {
 594                         list_del(&c->head);
 595                         free(c);
 596                 }
 597         }
 598
 599         if (msg == DHCPV4_MSG_DISCOVER || msg == DHCPV4_MSG_REQUEST) {
 600                 bool assigned = !!a;
 601                 size_t hostlen = strlen(hostname) + 1;
 602
 603                 if (!a && !iface->no_dynamic_dhcp) { // Create new binding
 604                         a = calloc(1, sizeof(*a) + hostlen);
 605                         if (!a) {
 606                                 syslog(LOG_ERR, "Failed to calloc binding on interface %s", iface->ifname);
 607                                 return NULL;
 608                         }
 609                         memcpy(a->hwaddr, mac, sizeof(a->hwaddr));
 610                         memcpy(a->hostname, hostname, hostlen);
 611
 612                         assigned = dhcpv4_assign(iface, a, raddr);
 613                 }
 614
 615                 if (assigned && !a->hostname[0] && hostname) {
 616                         a = realloc(a, sizeof(*a) + hostlen);
 617                         if (!a) {
 618                                 syslog(LOG_ERR, "Failed to realloc binding on interface %s", iface->ifname);
 619                                 return NULL;
 620                         }
 621                         memcpy(a->hostname, hostname, hostlen);
 622
 623                         // Fixup list
 624                         a->head.next->prev = &a->head;
 625                         a->head.prev->next = &a->head;
 626                 }
 627
 628                 // Was only a solicitation: mark binding for removal
 629                 if (assigned && a->valid_until < now) {
 630                         a->valid_until = (msg == DHCPV4_MSG_DISCOVER) ? 0 :
 631                                         (now + iface->dhcpv4_leasetime);
 632                 } else if (!assigned && a) { // Cleanup failed assignment
 633                         free(a);
 634                         a = NULL;
 635                 }
 636
 637                 if (assigned && a)
 638                         lease = a;
 639         } else if (msg == DHCPV4_MSG_RELEASE) {
 640                 if (a && a->valid_until != LONG_MAX)
 641                         a->valid_until = 0;
 642         } else if (msg == DHCPV4_MSG_DECLINE && a && a->valid_until != LONG_MAX) {
 643                 memset(a->hwaddr, 0, sizeof(a->hwaddr));
 644                 a->valid_until = now + 3600; // Block address for 1h
 645         }
 646
 647         dhcpv6_write_statefile();
 648
 649         return lease;
 650 }
 651