src/dhcpv4.c

   1 /**
   2  * Copyright (C) 2012-2013 Steven Barth <steven@midlink.org>
   3  * Copyright (C) 2016 Hans Dedecker <dedeckeh@gmail.com>
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License v2 as published by
   7  * the Free Software Foundation.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  *
  15  */
  16
  17 #include <time.h>
  18 #include <errno.h>
  19 #include <fcntl.h>
  20 #include <unistd.h>
  21 #include <stddef.h>
  22 #include <stdlib.h>
  23 #include <resolv.h>
  24 #include <limits.h>
  25 #include <net/if.h>
  26 #include <net/if_arp.h>
  27 #include <netinet/ip.h>
  28 #include <sys/ioctl.h>
  29 #include <sys/timerfd.h>
  30 #include <arpa/inet.h>
  31
  32 #include "odhcpd.h"
  33 #include "dhcpv4.h"
  34 #include "dhcpv6.h"
  35
  36 static void free_dhcpv4_assignment(struct dhcpv4_assignment *a);
  37 static void handle_dhcpv4(void *addr, void *data, size_t len,
  38                 struct interface *iface, void *dest_addr);
  39 static struct dhcpv4_assignment* dhcpv4_lease(struct interface *iface,
  40                 enum dhcpv4_msg msg, const uint8_t *mac, struct in_addr reqaddr,
  41                 uint32_t *leasetime, const char *hostname, const size_t hostname_len);
  42
  43 // Create socket and register events
  44 int init_dhcpv4(void)
  45 {
  46         return 0;
  47 }
  48
  49 char *dhcpv4_msg_to_string(uint8_t reqmsg)
  50 {
  51         switch (reqmsg) {
  52         case (DHCPV4_MSG_DISCOVER):
  53                 return "DHCPV4_MSG_DISCOVER";
  54         case (DHCPV4_MSG_OFFER):
  55                 return "DHCPV4_MSG_OFFER";
  56         case (DHCPV4_MSG_REQUEST):
  57                 return "DHCPV4_MSG_REQUEST";
  58         case (DHCPV4_MSG_DECLINE):
  59                 return "DHCPV4_MSG_DECLINE";
  60         case (DHCPV4_MSG_ACK):
  61                 return "DHCPV4_MSG_ACK";
  62         case (DHCPV4_MSG_NAK):
  63                 return "DHCPV4_MSG_NAK";
  64         case (DHCPV4_MSG_RELEASE):
  65                 return "DHCPV4_MSG_RELEASE";
  66         case (DHCPV4_MSG_INFORM):
  67                 return "DHCPV4_MSG_INFORM";
  68         default:
  69                 return "UNKNOWN";
  70         }
  71 }
  72
  73 int setup_dhcpv4_interface(struct interface *iface, bool enable)
  74 {
  75         if (iface->dhcpv4_event.uloop.fd > 0) {
  76                 uloop_fd_delete(&iface->dhcpv4_event.uloop);
  77                 close(iface->dhcpv4_event.uloop.fd);
  78                 iface->dhcpv4_event.uloop.fd = -1;
  79         }
  80
  81         if (iface->dhcpv4 && enable) {
  82                 if (!iface->dhcpv4_assignments.next)
  83                         INIT_LIST_HEAD(&iface->dhcpv4_assignments);
  84
  85                 int sock = socket(AF_INET, SOCK_DGRAM | SOCK_CLOEXEC, IPPROTO_UDP);
  86                 if (sock < 0) {
  87                         syslog(LOG_ERR, "Failed to create DHCPv4 server socket: %s",
  88                                         strerror(errno));
  89                         return -1;
  90                 }
  91
  92                 // Basic IPv6 configuration
  93                 int val = 1;
  94                 setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &val, sizeof(val));
  95                 setsockopt(sock, SOL_SOCKET, SO_BROADCAST, &val, sizeof(val));
  96                 setsockopt(sock, IPPROTO_IP, IP_PKTINFO, &val, sizeof(val));
  97
  98                 val = IPTOS_PREC_INTERNETCONTROL;
  99                 setsockopt(sock, IPPROTO_IP, IP_TOS, &val, sizeof(val));
 100
 101                 val = IP_PMTUDISC_DONT;
 102                 setsockopt(sock, IPPROTO_IP, IP_MTU_DISCOVER, &val, sizeof(val));
 103
 104                 setsockopt(sock, SOL_SOCKET, SO_BINDTODEVICE,
 105                                 iface->ifname, strlen(iface->ifname));
 106
 107                 struct sockaddr_in bind_addr = {AF_INET, htons(DHCPV4_SERVER_PORT),
 108                                         {INADDR_ANY}, {0}};
 109
 110                 if (bind(sock, (struct sockaddr*)&bind_addr, sizeof(bind_addr))) {
 111                         syslog(LOG_ERR, "Failed to open DHCPv4 server socket: %s",
 112                                         strerror(errno));
 113                         return -1;
 114                 }
 115
 116
 117                 if (ntohl(iface->dhcpv4_start.s_addr) > ntohl(iface->dhcpv4_end.s_addr)) {
 118                         syslog(LOG_ERR, "Invalid DHCP range");
 119                         return -1;
 120                 }
 121
 122                 // Create a range if not specified
 123                 struct ifreq ifreq;
 124                 strncpy(ifreq.ifr_name, iface->ifname, sizeof(ifreq.ifr_name));
 125
 126                 struct sockaddr_in *saddr = (struct sockaddr_in*)&ifreq.ifr_addr;
 127                 struct sockaddr_in *smask = (struct sockaddr_in*)&ifreq.ifr_netmask;
 128                 if (!(iface->dhcpv4_start.s_addr & htonl(0xffff0000)) &&
 129                                 !(iface->dhcpv4_end.s_addr & htonl(0xffff0000)) &&
 130                                 !ioctl(sock, SIOCGIFADDR, &ifreq)) {
 131                         struct in_addr addr = saddr->sin_addr;
 132
 133                         ioctl(sock, SIOCGIFNETMASK, &ifreq);
 134                         struct in_addr mask = smask->sin_addr;
 135
 136                         uint32_t start = ntohl(iface->dhcpv4_start.s_addr);
 137                         uint32_t end = ntohl(iface->dhcpv4_end.s_addr);
 138
 139                         if (start && end && start < end &&
 140                                         start > ntohl(addr.s_addr & ~mask.s_addr) &&
 141                                         (start & ntohl(~mask.s_addr)) == start &&
 142                                         (end & ntohl(~mask.s_addr)) == end) {
 143                                 iface->dhcpv4_start.s_addr = htonl(start) |
 144                                                 (addr.s_addr & mask.s_addr);
 145                                 iface->dhcpv4_end.s_addr = htonl(end) |
 146                                                 (addr.s_addr & mask.s_addr);
 147                         } else if (ntohl(mask.s_addr) <= 0xfffffff0) {
 148                                 start = addr.s_addr & mask.s_addr;
 149                                 end = addr.s_addr & mask.s_addr;
 150
 151                                 if (ntohl(mask.s_addr) <= 0xffffff00) {
 152                                         iface->dhcpv4_start.s_addr = start | htonl(100);
 153                                         iface->dhcpv4_end.s_addr = end | htonl(250);
 154                                 } else if (ntohl(mask.s_addr) <= 0xffffffc0) {
 155                                         iface->dhcpv4_start.s_addr = start | htonl(10);
 156                                         iface->dhcpv4_end.s_addr = end | htonl(60);
 157                                 } else if (ntohl(mask.s_addr) <= 0xffffffe0) {
 158                                         iface->dhcpv4_start.s_addr = start | htonl(10);
 159                                         iface->dhcpv4_end.s_addr = end | htonl(30);
 160                                 } else {
 161                                         iface->dhcpv4_start.s_addr = start | htonl(3);
 162                                         iface->dhcpv4_end.s_addr = end | htonl(12);
 163                                 }
 164                         }
 165
 166
 167                 }
 168
 169                 // Parse static entries
 170                 struct lease *lease;
 171                 list_for_each_entry(lease, &leases, head) {
 172                         // Construct entry
 173                         struct dhcpv4_assignment *a = calloc(1, sizeof(*a));
 174                         if (!a) {
 175                                 syslog(LOG_ERR, "Calloc failed for static lease on interface %s",
 176                                         iface->ifname);
 177                                 return -1;
 178                         }
 179                         if (lease->dhcpv4_leasetime >= 60)
 180                                 a->leasetime = lease->dhcpv4_leasetime;
 181
 182                         a->addr = ntohl(lease->ipaddr.s_addr);
 183                         memcpy(a->hwaddr, lease->mac.ether_addr_octet, sizeof(a->hwaddr));
 184                         /* Static assignment */
 185                         a->flags |= OAF_STATIC;
 186                         /* Infinite valid */
 187                         a->valid_until = 0;
 188
 189                         // Assign to all interfaces
 190                         struct dhcpv4_assignment *c;
 191                         list_for_each_entry(c, &iface->dhcpv4_assignments, head) {
 192                                 if (c->addr > a->addr) {
 193                                         list_add_tail(&a->head, &c->head);
 194                                         break;
 195                                 } else if (c->addr == a->addr) {
 196                                         // Already an assignment with that number
 197                                         break;
 198                                 }
 199                         }
 200                         if (&c->head == &iface->dhcpv4_assignments) {
 201                                 list_add(&a->head, &iface->dhcpv4_assignments);
 202                         }
 203
 204                         if (a->head.next) {
 205                                 if (lease->hostname[0]) {
 206                                         free(a->hostname);
 207                                         a->hostname = strdup(lease->hostname);
 208                                 }
 209                         } else
 210                                 free_dhcpv4_assignment(a);
 211                 }
 212
 213                 // Clean invalid assignments
 214                 struct dhcpv4_assignment *a, *n;
 215                 list_for_each_entry_safe(a, n, &iface->dhcpv4_assignments, head) {
 216                         if ((htonl(a->addr) & smask->sin_addr.s_addr) !=
 217                                         (iface->dhcpv4_start.s_addr & smask->sin_addr.s_addr))
 218                                 free_dhcpv4_assignment(a);
 219                 }
 220
 221
 222                 if (iface->dhcpv4_leasetime < 60)
 223                         iface->dhcpv4_leasetime = 43200;
 224
 225                 iface->dhcpv4_event.uloop.fd = sock;
 226                 iface->dhcpv4_event.handle_dgram = handle_dhcpv4;
 227                 odhcpd_register(&iface->dhcpv4_event);
 228         } else if (iface->dhcpv4_assignments.next) {
 229                 while (!list_empty(&iface->dhcpv4_assignments))
 230                         free_dhcpv4_assignment(list_first_entry(&iface->dhcpv4_assignments,
 231                                                         struct dhcpv4_assignment, head));
 232         }
 233         return 0;
 234 }
 235
 236 static void free_dhcpv4_assignment(struct dhcpv4_assignment *a)
 237 {
 238         if (a->head.next)
 239                 list_del(&a->head);
 240
 241         free(a->hostname);
 242         free(a);
 243 }
 244
 245 static void dhcpv4_put(struct dhcpv4_message *msg, uint8_t **cookie,
 246                 uint8_t type, uint8_t len, const void *data)
 247 {
 248         uint8_t *c = *cookie;
 249         if (*cookie + 2 + len > (uint8_t*)&msg[1])
 250                 return;
 251
 252         *c++ = type;
 253         *c++ = len;
 254         memcpy(c, data, len);
 255
 256         *cookie = c + len;
 257 }
 258
 259 // Handler for DHCPv4 messages
 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         struct sockaddr_in ifaddr;
 273         struct sockaddr_in ifnetmask;
 274
 275         syslog(LOG_NOTICE, "Got DHCPv4 request");
 276
 277         struct ifreq ifreq;
 278         memcpy(ifreq.ifr_name, iface->ifname, sizeof(ifreq.ifr_name));
 279         if (ioctl(sock, SIOCGIFADDR, &ifreq)) {
 280                 syslog(LOG_WARNING, "DHCPv4 failed to detect address: %s", strerror(errno));
 281                 return;
 282         }
 283
 284         memcpy(&ifaddr, &ifreq.ifr_addr, sizeof(ifaddr));
 285         if (ioctl(sock, SIOCGIFNETMASK, &ifreq))
 286                 return;
 287
 288         memcpy(&ifnetmask, &ifreq.ifr_netmask, sizeof(ifnetmask));
 289         uint32_t network = ifaddr.sin_addr.s_addr & ifnetmask.sin_addr.s_addr;
 290
 291         if ((iface->dhcpv4_start.s_addr & ifnetmask.sin_addr.s_addr) != network ||
 292                         (iface->dhcpv4_end.s_addr & ifnetmask.sin_addr.s_addr) != network) {
 293                 syslog(LOG_WARNING, "DHCPv4 range out of assigned network");
 294                 return;
 295         }
 296
 297         struct ifreq ifr = {.ifr_name = ""};
 298         strncpy(ifr.ifr_name, iface->ifname, sizeof(ifr.ifr_name));
 299
 300         struct dhcpv4_message reply = {
 301                 .op = DHCPV4_BOOTREPLY,
 302                 .htype = 1,
 303                 .hlen = 6,
 304                 .hops = 0,
 305                 .xid = req->xid,
 306                 .secs = 0,
 307                 .flags = req->flags,
 308                 .ciaddr = {INADDR_ANY},
 309                 .giaddr = req->giaddr,
 310                 .siaddr = ifaddr.sin_addr,
 311         };
 312         memcpy(reply.chaddr, req->chaddr, sizeof(reply.chaddr));
 313
 314         reply.options[0] = 0x63;
 315         reply.options[1] = 0x82;
 316         reply.options[2] = 0x53;
 317         reply.options[3] = 0x63;
 318
 319         uint8_t *cookie = &reply.options[4];
 320         uint8_t reqmsg = DHCPV4_MSG_REQUEST;
 321         uint8_t msg = DHCPV4_MSG_ACK;
 322
 323         struct in_addr reqaddr = {INADDR_ANY};
 324         uint32_t leasetime = 0;
 325         size_t hostname_len = 0;
 326         char hostname[256];
 327
 328         uint8_t *start = &req->options[4];
 329         uint8_t *end = ((uint8_t*)data) + len;
 330         struct dhcpv4_option *opt;
 331         dhcpv4_for_each_option(start, end, opt) {
 332                 if (opt->type == DHCPV4_OPT_MESSAGE && opt->len == 1) {
 333                         reqmsg = opt->data[0];
 334                 } else if (opt->type == DHCPV4_OPT_HOSTNAME && opt->len > 0) {
 335                         hostname_len = opt->len;
 336                         memcpy(hostname, opt->data, hostname_len);
 337                         hostname[hostname_len] = 0;
 338                 } else if (opt->type == DHCPV4_OPT_IPADDRESS && opt->len == 4) {
 339                         memcpy(&reqaddr, opt->data, 4);
 340                 } else if (opt->type == DHCPV4_OPT_SERVERID && opt->len == 4) {
 341                         if (memcmp(opt->data, &ifaddr.sin_addr, 4))
 342                                 return;
 343                 } else if (iface->filter_class && opt->type == DHCPV4_OPT_USER_CLASS) {
 344                         uint8_t *c = opt->data, *cend = &opt->data[opt->len];
 345                         for (; c < cend && &c[*c] < cend; c = &c[1 + *c]) {
 346                                 size_t elen = strlen(iface->filter_class);
 347                                 if (*c == elen && !memcmp(&c[1], iface->filter_class, elen))
 348                                         return; // Ignore from homenet
 349                         }
 350                 } else if (opt->type == DHCPV4_OPT_LEASETIME && opt->len == 4)
 351                         memcpy(&leasetime, opt->data, 4);
 352         }
 353
 354         if (reqmsg != DHCPV4_MSG_DISCOVER && reqmsg != DHCPV4_MSG_REQUEST &&
 355                         reqmsg != DHCPV4_MSG_INFORM && reqmsg != DHCPV4_MSG_DECLINE &&
 356                         reqmsg != DHCPV4_MSG_RELEASE)
 357                 return;
 358
 359         struct dhcpv4_assignment *lease = NULL;
 360         if (reqmsg != DHCPV4_MSG_INFORM)
 361                 lease = dhcpv4_lease(iface, reqmsg, req->chaddr, reqaddr,
 362                                         &leasetime, hostname, hostname_len);
 363
 364         if (!lease) {
 365                 if (reqmsg == DHCPV4_MSG_REQUEST)
 366                         msg = DHCPV4_MSG_NAK;
 367                 else if (reqmsg == DHCPV4_MSG_DISCOVER)
 368                         return;
 369         } else if (reqmsg == DHCPV4_MSG_DISCOVER) {
 370                 msg = DHCPV4_MSG_OFFER;
 371         } else if (reqmsg == DHCPV4_MSG_REQUEST && reqaddr.s_addr &&
 372                         reqaddr.s_addr != htonl(lease->addr)) {
 373                 msg = DHCPV4_MSG_NAK;
 374                 /*
 375                  * DHCP client requested an IP which we can't offer to him. Probably the
 376                  * client changed the network. The reply type is set to DHCPV4_MSG_NAK,
 377                  * because the client should not use that IP.
 378                  *
 379                  * For modern devices we build an answer that includes a valid IP, like
 380                  * a DHCPV4_MSG_ACK. The client will use that IP and doesn't need to
 381                  * perform additional DHCP round trips.
 382                  *
 383                  */
 384         }
 385
 386         syslog(LOG_WARNING, "received %s from %x:%x:%x:%x:%x:%x",
 387                         dhcpv4_msg_to_string(reqmsg),
 388                         req->chaddr[0],req->chaddr[1],req->chaddr[2],
 389                         req->chaddr[3],req->chaddr[4],req->chaddr[5]);
 390
 391         if (reqmsg == DHCPV4_MSG_DECLINE || reqmsg == DHCPV4_MSG_RELEASE)
 392                 return;
 393
 394         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_MESSAGE, 1, &msg);
 395         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SERVERID, 4, &ifaddr.sin_addr);
 396
 397         if (lease) {
 398                 uint32_t val;
 399
 400                 reply.yiaddr.s_addr = htonl(lease->addr);
 401
 402                 val = htonl(leasetime);
 403                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_LEASETIME, 4, &val);
 404
 405                 if (leasetime != UINT32_MAX) {
 406                         val = htonl(500 * leasetime / 1000);
 407                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_RENEW, 4, &val);
 408
 409                         val = htonl(875 * leasetime / 1000);
 410                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_REBIND, 4, &val);
 411                 }
 412
 413                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_NETMASK, 4, &ifnetmask.sin_addr);
 414
 415                 if (lease->hostname)
 416                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_HOSTNAME,
 417                                         strlen(lease->hostname), lease->hostname);
 418
 419                 if (!ioctl(sock, SIOCGIFBRDADDR, &ifr)) {
 420                         struct sockaddr_in *ina = (struct sockaddr_in*)&ifr.ifr_broadaddr;
 421                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_BROADCAST, 4, &ina->sin_addr);
 422                 }
 423         }
 424
 425         if (!ioctl(sock, SIOCGIFMTU, &ifr)) {
 426                 uint16_t mtu = htons(ifr.ifr_mtu);
 427                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_MTU, 2, &mtu);
 428         }
 429
 430         if (iface->search && iface->search_len <= 255) {
 431                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SEARCH_DOMAIN,
 432                                 iface->search_len, iface->search);
 433         } else if (!res_init() && _res.dnsrch[0] && _res.dnsrch[0][0]) {
 434                 uint8_t search_buf[256];
 435                 int len = dn_comp(_res.dnsrch[0], search_buf,
 436                                                 sizeof(search_buf), NULL, NULL);
 437                 if (len > 0)
 438                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SEARCH_DOMAIN,
 439                                         len, search_buf);
 440         }
 441
 442         if (iface->dhcpv4_router_cnt == 0)
 443                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_ROUTER, 4, &ifaddr.sin_addr);
 444         else
 445                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_ROUTER,
 446                                 4 * iface->dhcpv4_router_cnt, iface->dhcpv4_router);
 447
 448
 449         if (iface->dhcpv4_dns_cnt == 0)
 450                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_DNSSERVER, 4, &ifaddr.sin_addr);
 451         else
 452                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_DNSSERVER,
 453                                 4 * iface->dhcpv4_dns_cnt, iface->dhcpv4_dns);
 454
 455
 456         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_END, 0, NULL);
 457
 458         struct sockaddr_in dest = *((struct sockaddr_in*)addr);
 459         if (req->giaddr.s_addr) {
 460                 /*
 461                  * relay agent is configured, send reply to the agent
 462                  */
 463                 dest.sin_addr = req->giaddr;
 464                 dest.sin_port = htons(DHCPV4_SERVER_PORT);
 465         } else if (req->ciaddr.s_addr && req->ciaddr.s_addr != dest.sin_addr.s_addr) {
 466                 /*
 467                  * client has existing configuration (ciaddr is set) AND this address is
 468                  * not the address it used for the dhcp message
 469                  */
 470                 dest.sin_addr = req->ciaddr;
 471                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 472         } else if ((ntohs(req->flags) & DHCPV4_FLAG_BROADCAST) ||
 473                         req->hlen != reply.hlen || !reply.yiaddr.s_addr) {
 474                 /*
 475                  * client requests a broadcast reply OR we can't offer an IP
 476                  */
 477                 dest.sin_addr.s_addr = INADDR_BROADCAST;
 478                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 479         } else if (!req->ciaddr.s_addr && msg == DHCPV4_MSG_NAK) {
 480                 /*
 481                  * client has no previous configuration -> no IP, so we need to reply
 482                  * with a broadcast packet
 483                  */
 484                 dest.sin_addr.s_addr = INADDR_BROADCAST;
 485                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 486         } else {
 487                 /*
 488                  * send reply to the newly (in this proccess) allocated IP
 489                  */
 490                 dest.sin_addr = reply.yiaddr;
 491                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 492
 493                 struct arpreq arp = {.arp_flags = ATF_COM};
 494                 memcpy(arp.arp_ha.sa_data, req->chaddr, 6);
 495                 memcpy(&arp.arp_pa, &dest, sizeof(arp.arp_pa));
 496                 memcpy(arp.arp_dev, iface->ifname, sizeof(arp.arp_dev));
 497                 ioctl(sock, SIOCSARP, &arp);
 498         }
 499
 500         if (dest.sin_addr.s_addr == INADDR_BROADCAST) {
 501                 /*
 502                  * reply goes to IP broadcast -> MAC broadcast
 503                  */
 504                 syslog(LOG_WARNING, "sending %s to ff:ff:ff:ff:ff:ff - %s",
 505                                 dhcpv4_msg_to_string(msg),
 506                                 inet_ntoa(dest.sin_addr));
 507         } else {
 508                 /*
 509                  * reply is send directly to IP,
 510                  * MAC is assumed to be the same as the request
 511                  */
 512                 syslog(LOG_WARNING, "sending %s to %x:%x:%x:%x:%x:%x - %s",
 513                                 dhcpv4_msg_to_string(msg),
 514                                 req->chaddr[0],req->chaddr[1],req->chaddr[2],
 515                                 req->chaddr[3],req->chaddr[4],req->chaddr[5],
 516                                 inet_ntoa(dest.sin_addr));
 517         }
 518
 519         sendto(sock, &reply, sizeof(reply), MSG_DONTWAIT,
 520                         (struct sockaddr*)&dest, sizeof(dest));
 521 }
 522
 523 static bool dhcpv4_test(struct interface *iface, uint32_t try)
 524 {
 525         struct dhcpv4_assignment *c;
 526         list_for_each_entry(c, &iface->dhcpv4_assignments, head) {
 527                 if (c->addr == try) {
 528                         return false;
 529                 }
 530         }
 531         return true;
 532 }
 533
 534 static bool dhcpv4_assign(struct interface *iface,
 535                 struct dhcpv4_assignment *assign, uint32_t raddr)
 536 {
 537         uint32_t start = ntohl(iface->dhcpv4_start.s_addr);
 538         uint32_t end = ntohl(iface->dhcpv4_end.s_addr);
 539         uint32_t count = end - start + 1;
 540
 541         // try to assign the IP the client asked for
 542         if (start <= raddr && raddr <= end && dhcpv4_test(iface, raddr)) {
 543                 assign->addr = raddr;
 544                 list_add(&assign->head, &iface->dhcpv4_assignments);
 545                 syslog(LOG_DEBUG, "assigning the IP the client asked for: %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         // Seed RNG with checksum of hwaddress
 554         uint32_t seed = 0;
 555         for (size_t i = 0; i < sizeof(assign->hwaddr); ++i) {
 556                 // Knuth's multiplicative method
 557                 uint8_t o = assign->hwaddr[i];
 558                 seed += (o*2654435761) % UINT32_MAX;
 559         }
 560         srand(seed);
 561
 562         uint32_t try = (((uint32_t)rand()) % count) + start;
 563
 564         if (list_empty(&iface->dhcpv4_assignments)) {
 565                 assign->addr = try;
 566                 list_add(&assign->head, &iface->dhcpv4_assignments);
 567                 syslog(LOG_DEBUG, "assigning mapped IP (empty list): %u.%u.%u.%u",
 568                                 (assign->addr & 0xff000000) >> 24,
 569                                 (assign->addr & 0x00ff0000) >> 16,
 570                                 (assign->addr & 0x0000ff00) >> 8,
 571                                 (assign->addr & 0x000000ff));
 572                 return true;
 573         }
 574
 575         for (uint32_t i = 0; i < count; ++i) {
 576                 if (dhcpv4_test(iface, try)) {
 577                         /* test was successful: IP address is not assigned, assign it */
 578                         assign->addr = try;
 579                         list_add(&assign->head, &iface->dhcpv4_assignments);
 580                         syslog(LOG_DEBUG, "assigning mapped IP: %u.%u.%u.%u (try %u of %u)",
 581                                         (assign->addr & 0xff000000) >> 24,
 582                                         (assign->addr & 0x00ff0000) >> 16,
 583                                         (assign->addr & 0x0000ff00) >> 8,
 584                                         (assign->addr & 0x000000ff), i, count);
 585                         return true;
 586                 }
 587                 try = (((try - start) + 1) % count) + start;
 588         }
 589
 590         syslog(LOG_DEBUG, "can't assign any IP address -> address space is full");
 591         return false;
 592 }
 593
 594
 595 static struct dhcpv4_assignment* dhcpv4_lease(struct interface *iface,
 596                 enum dhcpv4_msg msg, const uint8_t *mac, struct in_addr reqaddr,
 597                 uint32_t *leasetime, const char *hostname, const size_t hostname_len)
 598 {
 599         struct dhcpv4_assignment *lease = NULL;
 600         uint32_t raddr = ntohl(reqaddr.s_addr);
 601         time_t now = odhcpd_time();
 602
 603         struct dhcpv4_assignment *c, *n, *a = NULL;
 604         list_for_each_entry_safe(c, n, &iface->dhcpv4_assignments, head) {
 605                 if (!memcmp(c->hwaddr, mac, 6)) {
 606                         a = c;
 607                         if (c->addr == raddr)
 608                                 break;
 609                 } else if (!INFINITE_VALID(c->valid_until) && c->valid_until < now)
 610                         free_dhcpv4_assignment(c);
 611         }
 612
 613         if (msg == DHCPV4_MSG_DISCOVER || msg == DHCPV4_MSG_REQUEST) {
 614                 bool assigned = !!a;
 615                 uint32_t my_leasetime;
 616
 617                 if (!a && !iface->no_dynamic_dhcp) { // Create new binding
 618                         a = calloc(1, sizeof(*a));
 619                         if (!a) {
 620                                 syslog(LOG_ERR, "Failed to calloc binding on interface %s", iface->ifname);
 621                                 return NULL;
 622                         }
 623                         memcpy(a->hwaddr, mac, sizeof(a->hwaddr));
 624                         // Don't consider new assignment as infinite
 625                         a->valid_until = now;
 626
 627                         assigned = dhcpv4_assign(iface, a, raddr);
 628                 }
 629
 630                 if (a->leasetime >= 60) {
 631                         my_leasetime = a->leasetime;
 632                 } else {
 633                         my_leasetime = iface->dhcpv4_leasetime;
 634                 }
 635
 636                 if ((*leasetime == 0) || (my_leasetime < *leasetime))
 637                         *leasetime = my_leasetime;
 638
 639                 if (assigned) {
 640                         if (msg == DHCPV4_MSG_DISCOVER) {
 641                                 a->flags &= ~OAF_BOUND;
 642
 643                                 if (!(a->flags & OAF_STATIC))
 644                                         a->valid_until = now;
 645                         } else {
 646                                 if (hostname_len > 0) {
 647                                         a->hostname = realloc(a->hostname, hostname_len + 1);
 648                                         if (a->hostname) {
 649                                                 memcpy(a->hostname, hostname, hostname_len);
 650                                                 a->hostname[hostname_len] = 0;
 651                                         }
 652                                 }
 653
 654                                 a->flags |= OAF_BOUND;
 655
 656                                 if (!(a->flags & OAF_STATIC))
 657                                         a->valid_until = ((*leasetime == UINT32_MAX) ? 0 : (time_t)(now + *leasetime));
 658                         }
 659                 } else if (!assigned && a) { // Cleanup failed assignment
 660                         free_dhcpv4_assignment(a);
 661                         a = NULL;
 662                 }
 663
 664                 if (assigned && a)
 665                         lease = a;
 666         } else if (msg == DHCPV4_MSG_RELEASE && a) {
 667                 a->flags &= ~OAF_BOUND;
 668
 669                 if (!(a->flags & OAF_STATIC))
 670                         a->valid_until = now - 1;
 671
 672         } else if (msg == DHCPV4_MSG_DECLINE && a) {
 673                 a->flags &= ~OAF_BOUND;
 674
 675                 if (!(a->flags & OAF_STATIC)) {
 676                         memset(a->hwaddr, 0, sizeof(a->hwaddr));
 677                         a->valid_until = now + 3600; // Block address for 1h
 678                 }
 679         }
 680
 681         dhcpv6_write_statefile();
 682
 683         return lease;
 684 }
 685