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 int setup_dhcpv4_interface(struct interface *iface, bool enable)
  50 {
  51         if (iface->dhcpv4_event.uloop.fd > 0) {
  52                 uloop_fd_delete(&iface->dhcpv4_event.uloop);
  53                 close(iface->dhcpv4_event.uloop.fd);
  54                 iface->dhcpv4_event.uloop.fd = -1;
  55         }
  56
  57         if (iface->dhcpv4 && enable) {
  58                 if (!iface->dhcpv4_assignments.next)
  59                         INIT_LIST_HEAD(&iface->dhcpv4_assignments);
  60
  61                 int sock = socket(AF_INET, SOCK_DGRAM | SOCK_CLOEXEC, IPPROTO_UDP);
  62                 if (sock < 0) {
  63                         syslog(LOG_ERR, "Failed to create DHCPv4 server socket: %s",
  64                                         strerror(errno));
  65                         return -1;
  66                 }
  67
  68                 /* Basic IPv4 configuration */
  69                 int val = 1;
  70                 setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &val, sizeof(val));
  71                 setsockopt(sock, SOL_SOCKET, SO_BROADCAST, &val, sizeof(val));
  72                 setsockopt(sock, IPPROTO_IP, IP_PKTINFO, &val, sizeof(val));
  73
  74                 val = IPTOS_PREC_INTERNETCONTROL;
  75                 setsockopt(sock, IPPROTO_IP, IP_TOS, &val, sizeof(val));
  76
  77                 val = IP_PMTUDISC_DONT;
  78                 setsockopt(sock, IPPROTO_IP, IP_MTU_DISCOVER, &val, sizeof(val));
  79
  80                 setsockopt(sock, SOL_SOCKET, SO_BINDTODEVICE,
  81                                 iface->ifname, strlen(iface->ifname));
  82
  83                 struct sockaddr_in bind_addr = {AF_INET, htons(DHCPV4_SERVER_PORT),
  84                                         {INADDR_ANY}, {0}};
  85
  86                 if (bind(sock, (struct sockaddr*)&bind_addr, sizeof(bind_addr))) {
  87                         syslog(LOG_ERR, "Failed to open DHCPv4 server socket: %s",
  88                                         strerror(errno));
  89                         return -1;
  90                 }
  91
  92
  93                 if (ntohl(iface->dhcpv4_start.s_addr) > ntohl(iface->dhcpv4_end.s_addr)) {
  94                         syslog(LOG_ERR, "Invalid DHCP range");
  95                         return -1;
  96                 }
  97
  98                 uint32_t mask = iface->addr4 && iface->addr4[0].prefix ?
  99                         htonl(~((1 << (32 - iface->addr4[0].prefix)) - 1)) : 0xffffffff;
 100
 101                 /* Create a range if not specified */
 102                 if (!(iface->dhcpv4_start.s_addr & htonl(0xffff0000)) &&
 103                                 !(iface->dhcpv4_end.s_addr & htonl(0xffff0000)) &&
 104                                 iface->addr4_len) {
 105                         struct in_addr *addr = &iface->addr4[0].addr.in;
 106
 107                         uint32_t start = ntohl(iface->dhcpv4_start.s_addr);
 108                         uint32_t end = ntohl(iface->dhcpv4_end.s_addr);
 109
 110                         if (start && end && start < end &&
 111                                         start > ntohl(addr->s_addr & ~mask) &&
 112                                         (start & ntohl(~mask)) == start &&
 113                                         (end & ntohl(~mask)) == end) {
 114                                 iface->dhcpv4_start.s_addr = htonl(start) |
 115                                                 (addr->s_addr & mask);
 116                                 iface->dhcpv4_end.s_addr = htonl(end) |
 117                                                 (addr->s_addr & mask);
 118                         } else if (ntohl(mask) <= 0xfffffff0) {
 119                                 start = addr->s_addr & mask;
 120                                 end = addr->s_addr & mask;
 121
 122                                 if (ntohl(mask) <= 0xffffff00) {
 123                                         iface->dhcpv4_start.s_addr = start | htonl(100);
 124                                         iface->dhcpv4_end.s_addr = end | htonl(250);
 125                                 } else if (ntohl(mask) <= 0xffffffc0) {
 126                                         iface->dhcpv4_start.s_addr = start | htonl(10);
 127                                         iface->dhcpv4_end.s_addr = end | htonl(60);
 128                                 } else if (ntohl(mask) <= 0xffffffe0) {
 129                                         iface->dhcpv4_start.s_addr = start | htonl(10);
 130                                         iface->dhcpv4_end.s_addr = end | htonl(30);
 131                                 } else {
 132                                         iface->dhcpv4_start.s_addr = start | htonl(3);
 133                                         iface->dhcpv4_end.s_addr = end | htonl(12);
 134                                 }
 135                         }
 136                 }
 137
 138                 /* Parse static entries */
 139                 struct lease *lease;
 140                 list_for_each_entry(lease, &leases, head) {
 141                         /* Construct entry */
 142                         struct dhcpv4_assignment *a = calloc(1, sizeof(*a));
 143                         if (!a) {
 144                                 syslog(LOG_ERR, "Calloc failed for static lease on interface %s",
 145                                         iface->ifname);
 146                                 return -1;
 147                         }
 148
 149                         a->leasetime = lease->dhcpv4_leasetime;
 150
 151                         a->addr = ntohl(lease->ipaddr.s_addr);
 152                         memcpy(a->hwaddr, lease->mac.ether_addr_octet, sizeof(a->hwaddr));
 153                         /* Static assignment */
 154                         a->flags |= OAF_STATIC;
 155                         /* Infinite valid */
 156                         a->valid_until = 0;
 157
 158                         /* Assign to all interfaces */
 159                         struct dhcpv4_assignment *c;
 160                         list_for_each_entry(c, &iface->dhcpv4_assignments, head) {
 161                                 if (c->addr > a->addr) {
 162                                         list_add_tail(&a->head, &c->head);
 163                                         break;
 164                                 } else if (c->addr == a->addr)
 165                                         /* Already an assignment with that number */
 166                                         break;
 167                         }
 168
 169                         if (&c->head == &iface->dhcpv4_assignments)
 170                                 list_add(&a->head, &iface->dhcpv4_assignments);
 171
 172                         if (a->head.next) {
 173                                 if (lease->hostname[0]) {
 174                                         free(a->hostname);
 175                                         a->hostname = strdup(lease->hostname);
 176                                 }
 177                         } else
 178                                 free_dhcpv4_assignment(a);
 179                 }
 180
 181                 // Clean invalid assignments
 182                 struct dhcpv4_assignment *a, *n;
 183                 list_for_each_entry_safe(a, n, &iface->dhcpv4_assignments, head) {
 184                         if ((htonl(a->addr) & mask) !=
 185                                         (iface->dhcpv4_start.s_addr & mask))
 186                                 free_dhcpv4_assignment(a);
 187                 }
 188
 189                 iface->dhcpv4_event.uloop.fd = sock;
 190                 iface->dhcpv4_event.handle_dgram = handle_dhcpv4;
 191                 odhcpd_register(&iface->dhcpv4_event);
 192         } else if (iface->dhcpv4_assignments.next) {
 193                 while (!list_empty(&iface->dhcpv4_assignments))
 194                         free_dhcpv4_assignment(list_first_entry(&iface->dhcpv4_assignments,
 195                                                         struct dhcpv4_assignment, head));
 196         }
 197         return 0;
 198 }
 199
 200 static char *dhcpv4_msg_to_string(uint8_t reqmsg)
 201 {
 202         switch (reqmsg) {
 203         case (DHCPV4_MSG_DISCOVER):
 204                 return "DHCPV4_MSG_DISCOVER";
 205         case (DHCPV4_MSG_OFFER):
 206                 return "DHCPV4_MSG_OFFER";
 207         case (DHCPV4_MSG_REQUEST):
 208                 return "DHCPV4_MSG_REQUEST";
 209         case (DHCPV4_MSG_DECLINE):
 210                 return "DHCPV4_MSG_DECLINE";
 211         case (DHCPV4_MSG_ACK):
 212                 return "DHCPV4_MSG_ACK";
 213         case (DHCPV4_MSG_NAK):
 214                 return "DHCPV4_MSG_NAK";
 215         case (DHCPV4_MSG_RELEASE):
 216                 return "DHCPV4_MSG_RELEASE";
 217         case (DHCPV4_MSG_INFORM):
 218                 return "DHCPV4_MSG_INFORM";
 219         default:
 220                 return "UNKNOWN";
 221         }
 222 }
 223
 224 static void free_dhcpv4_assignment(struct dhcpv4_assignment *a)
 225 {
 226         if (a->head.next)
 227                 list_del(&a->head);
 228
 229         free(a->hostname);
 230         free(a);
 231 }
 232
 233 static void dhcpv4_put(struct dhcpv4_message *msg, uint8_t **cookie,
 234                 uint8_t type, uint8_t len, const void *data)
 235 {
 236         uint8_t *c = *cookie;
 237         if (*cookie + 2 + len > (uint8_t*)&msg[1])
 238                 return;
 239
 240         *c++ = type;
 241         *c++ = len;
 242         memcpy(c, data, len);
 243
 244         *cookie = c + len;
 245 }
 246
 247 // Handler for DHCPv4 messages
 248 static void handle_dhcpv4(void *addr, void *data, size_t len,
 249                 struct interface *iface, _unused void *dest_addr)
 250 {
 251         if (!iface->dhcpv4)
 252                 return;
 253
 254         struct dhcpv4_message *req = data;
 255         if (len < offsetof(struct dhcpv4_message, options) + 4 ||
 256                         req->op != DHCPV4_BOOTREQUEST || req->hlen != 6)
 257                 return;
 258
 259
 260         syslog(LOG_NOTICE, "Got DHCPv4 request");
 261
 262         if (!iface->addr4_len) {
 263                 syslog(LOG_WARNING, "DHCPv4 no address found on %s", iface->name);
 264                 return;
 265         }
 266
 267         struct in_addr *ifaddr = &iface->addr4[0].addr.in;
 268         struct in_addr *ifbroadcast = &iface->addr4[0].broadcast;
 269         uint32_t mask = iface->addr4[0].prefix ? htonl(~((1 << (32 - iface->addr4[0].prefix)) - 1)) : 0;
 270         uint32_t network = iface->addr4[0].addr.in.s_addr & mask;
 271         int sock = iface->dhcpv4_event.uloop.fd;
 272
 273         if ((iface->dhcpv4_start.s_addr & mask) != network ||
 274                         (iface->dhcpv4_end.s_addr & mask) != network) {
 275                 syslog(LOG_WARNING, "DHCPv4 range out of assigned network");
 276                 return;
 277         }
 278
 279         struct dhcpv4_message reply = {
 280                 .op = DHCPV4_BOOTREPLY,
 281                 .htype = 1,
 282                 .hlen = 6,
 283                 .hops = 0,
 284                 .xid = req->xid,
 285                 .secs = 0,
 286                 .flags = req->flags,
 287                 .ciaddr = {INADDR_ANY},
 288                 .giaddr = req->giaddr,
 289                 .siaddr = *ifaddr,
 290         };
 291         memcpy(reply.chaddr, req->chaddr, sizeof(reply.chaddr));
 292
 293         reply.options[0] = 0x63;
 294         reply.options[1] = 0x82;
 295         reply.options[2] = 0x53;
 296         reply.options[3] = 0x63;
 297
 298         uint8_t *cookie = &reply.options[4];
 299         uint8_t reqmsg = DHCPV4_MSG_REQUEST;
 300         uint8_t msg = DHCPV4_MSG_ACK;
 301
 302         struct in_addr reqaddr = {INADDR_ANY};
 303         uint32_t leasetime = 0;
 304         size_t hostname_len = 0;
 305         char hostname[256];
 306
 307         uint8_t *start = &req->options[4];
 308         uint8_t *end = ((uint8_t*)data) + len;
 309         struct dhcpv4_option *opt;
 310         dhcpv4_for_each_option(start, end, opt) {
 311                 if (opt->type == DHCPV4_OPT_MESSAGE && opt->len == 1)
 312                         reqmsg = opt->data[0];
 313                 else if (opt->type == DHCPV4_OPT_HOSTNAME && opt->len > 0) {
 314                         hostname_len = opt->len;
 315                         memcpy(hostname, opt->data, hostname_len);
 316                         hostname[hostname_len] = 0;
 317                 } else if (opt->type == DHCPV4_OPT_IPADDRESS && opt->len == 4)
 318                         memcpy(&reqaddr, opt->data, 4);
 319                 else if (opt->type == DHCPV4_OPT_SERVERID && opt->len == 4) {
 320                         if (memcmp(opt->data, ifaddr, 4))
 321                                 return;
 322                 } else if (iface->filter_class && opt->type == DHCPV4_OPT_USER_CLASS) {
 323                         uint8_t *c = opt->data, *cend = &opt->data[opt->len];
 324                         for (; c < cend && &c[*c] < cend; c = &c[1 + *c]) {
 325                                 size_t elen = strlen(iface->filter_class);
 326                                 if (*c == elen && !memcmp(&c[1], iface->filter_class, elen))
 327                                         return; // Ignore from homenet
 328                         }
 329                 } else if (opt->type == DHCPV4_OPT_LEASETIME && opt->len == 4)
 330                         memcpy(&leasetime, opt->data, 4);
 331         }
 332
 333         if (reqmsg != DHCPV4_MSG_DISCOVER && reqmsg != DHCPV4_MSG_REQUEST &&
 334                         reqmsg != DHCPV4_MSG_INFORM && reqmsg != DHCPV4_MSG_DECLINE &&
 335                         reqmsg != DHCPV4_MSG_RELEASE)
 336                 return;
 337
 338         struct dhcpv4_assignment *lease = NULL;
 339         if (reqmsg != DHCPV4_MSG_INFORM)
 340                 lease = dhcpv4_lease(iface, reqmsg, req->chaddr, reqaddr,
 341                                         &leasetime, hostname, hostname_len);
 342
 343         if (!lease) {
 344                 if (reqmsg == DHCPV4_MSG_REQUEST)
 345                         msg = DHCPV4_MSG_NAK;
 346                 else if (reqmsg == DHCPV4_MSG_DISCOVER)
 347                         return;
 348         } else if (reqmsg == DHCPV4_MSG_DISCOVER)
 349                 msg = DHCPV4_MSG_OFFER;
 350         else if (reqmsg == DHCPV4_MSG_REQUEST && reqaddr.s_addr &&
 351                         reqaddr.s_addr != htonl(lease->addr)) {
 352                 msg = DHCPV4_MSG_NAK;
 353                 /*
 354                  * DHCP client requested an IP which we can't offer to him. Probably the
 355                  * client changed the network. The reply type is set to DHCPV4_MSG_NAK,
 356                  * because the client should not use that IP.
 357                  *
 358                  * For modern devices we build an answer that includes a valid IP, like
 359                  * a DHCPV4_MSG_ACK. The client will use that IP and doesn't need to
 360                  * perform additional DHCP round trips.
 361                  *
 362                  */
 363         }
 364
 365         syslog(LOG_WARNING, "received %s from %02x:%02x:%02x:%02x:%02x:%02x",
 366                         dhcpv4_msg_to_string(reqmsg),
 367                         req->chaddr[0],req->chaddr[1],req->chaddr[2],
 368                         req->chaddr[3],req->chaddr[4],req->chaddr[5]);
 369
 370         if (reqmsg == DHCPV4_MSG_DECLINE || reqmsg == DHCPV4_MSG_RELEASE)
 371                 return;
 372
 373         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_MESSAGE, 1, &msg);
 374         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SERVERID, 4, ifaddr);
 375
 376         if (lease) {
 377                 uint32_t val;
 378
 379                 reply.yiaddr.s_addr = htonl(lease->addr);
 380
 381                 val = htonl(leasetime);
 382                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_LEASETIME, 4, &val);
 383
 384                 if (leasetime != UINT32_MAX) {
 385                         val = htonl(500 * leasetime / 1000);
 386                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_RENEW, 4, &val);
 387
 388                         val = htonl(875 * leasetime / 1000);
 389                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_REBIND, 4, &val);
 390                 }
 391
 392                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_NETMASK, 4, &mask);
 393
 394                 if (lease->hostname)
 395                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_HOSTNAME,
 396                                         strlen(lease->hostname), lease->hostname);
 397
 398                 if (ifbroadcast->s_addr != INADDR_ANY)
 399                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_BROADCAST, 4, ifbroadcast);
 400         }
 401
 402         struct ifreq ifr = {.ifr_name = ""};
 403         strncpy(ifr.ifr_name, iface->ifname, sizeof(ifr.ifr_name));
 404
 405         if (!ioctl(sock, SIOCGIFMTU, &ifr)) {
 406                 uint16_t mtu = htons(ifr.ifr_mtu);
 407                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_MTU, 2, &mtu);
 408         }
 409
 410         if (iface->search && iface->search_len <= 255)
 411                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SEARCH_DOMAIN,
 412                                 iface->search_len, iface->search);
 413         else if (!res_init() && _res.dnsrch[0] && _res.dnsrch[0][0]) {
 414                 uint8_t search_buf[256];
 415                 int len = dn_comp(_res.dnsrch[0], search_buf,
 416                                                 sizeof(search_buf), NULL, NULL);
 417                 if (len > 0)
 418                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SEARCH_DOMAIN,
 419                                         len, search_buf);
 420         }
 421
 422         if (iface->dhcpv4_router_cnt == 0)
 423                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_ROUTER, 4, ifaddr);
 424         else
 425                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_ROUTER,
 426                                 4 * iface->dhcpv4_router_cnt, iface->dhcpv4_router);
 427
 428
 429         if (iface->dhcpv4_dns_cnt == 0)
 430                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_DNSSERVER, 4, ifaddr);
 431         else
 432                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_DNSSERVER,
 433                                 4 * iface->dhcpv4_dns_cnt, iface->dhcpv4_dns);
 434
 435
 436         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_END, 0, NULL);
 437
 438         struct sockaddr_in dest = *((struct sockaddr_in*)addr);
 439         if (req->giaddr.s_addr) {
 440                 /*
 441                  * relay agent is configured, send reply to the agent
 442                  */
 443                 dest.sin_addr = req->giaddr;
 444                 dest.sin_port = htons(DHCPV4_SERVER_PORT);
 445         } else if (req->ciaddr.s_addr && req->ciaddr.s_addr != dest.sin_addr.s_addr) {
 446                 /*
 447                  * client has existing configuration (ciaddr is set) AND this address is
 448                  * not the address it used for the dhcp message
 449                  */
 450                 dest.sin_addr = req->ciaddr;
 451                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 452         } else if ((ntohs(req->flags) & DHCPV4_FLAG_BROADCAST) ||
 453                         req->hlen != reply.hlen || !reply.yiaddr.s_addr) {
 454                 /*
 455                  * client requests a broadcast reply OR we can't offer an IP
 456                  */
 457                 dest.sin_addr.s_addr = INADDR_BROADCAST;
 458                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 459         } else if (!req->ciaddr.s_addr && msg == DHCPV4_MSG_NAK) {
 460                 /*
 461                  * client has no previous configuration -> no IP, so we need to reply
 462                  * with a broadcast packet
 463                  */
 464                 dest.sin_addr.s_addr = INADDR_BROADCAST;
 465                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 466         } else {
 467                 /*
 468                  * send reply to the newly (in this proccess) allocated IP
 469                  */
 470                 dest.sin_addr = reply.yiaddr;
 471                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 472
 473                 struct arpreq arp = {.arp_flags = ATF_COM};
 474                 memcpy(arp.arp_ha.sa_data, req->chaddr, 6);
 475                 memcpy(&arp.arp_pa, &dest, sizeof(arp.arp_pa));
 476                 memcpy(arp.arp_dev, iface->ifname, sizeof(arp.arp_dev));
 477                 ioctl(sock, SIOCSARP, &arp);
 478         }
 479
 480         if (dest.sin_addr.s_addr == INADDR_BROADCAST)
 481                 /* reply goes to IP broadcast -> MAC broadcast */
 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 %02x:%02x:%02x:%02x:%02x:%02x - %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         sendto(sock, &reply, sizeof(reply), MSG_DONTWAIT,
 497                         (struct sockaddr*)&dest, sizeof(dest));
 498 }
 499
 500 static bool dhcpv4_test(struct interface *iface, uint32_t try)
 501 {
 502         struct dhcpv4_assignment *c;
 503         list_for_each_entry(c, &iface->dhcpv4_assignments, head) {
 504                 if (c->addr == try)
 505                         return false;
 506
 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                 syslog(LOG_INFO, "assigning the IP the client asked for: %u.%u.%u.%u",
 523                                 (assign->addr & 0xff000000) >> 24,
 524                                 (assign->addr & 0x00ff0000) >> 16,
 525                                 (assign->addr & 0x0000ff00) >> 8,
 526                                 (assign->addr & 0x000000ff));
 527                 return true;
 528         }
 529
 530         // Seed RNG with checksum of hwaddress
 531         uint32_t seed = 0;
 532         for (size_t i = 0; i < sizeof(assign->hwaddr); ++i) {
 533                 // Knuth's multiplicative method
 534                 uint8_t o = assign->hwaddr[i];
 535                 seed += (o*2654435761) % UINT32_MAX;
 536         }
 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                 syslog(LOG_INFO, "assigning mapped IP (empty list): %u.%u.%u.%u",
 545                                 (assign->addr & 0xff000000) >> 24,
 546                                 (assign->addr & 0x00ff0000) >> 16,
 547                                 (assign->addr & 0x0000ff00) >> 8,
 548                                 (assign->addr & 0x000000ff));
 549                 return true;
 550         }
 551
 552         for (uint32_t i = 0; i < count; ++i) {
 553                 if (dhcpv4_test(iface, try)) {
 554                         /* test was successful: IP address is not assigned, assign it */
 555                         assign->addr = try;
 556                         syslog(LOG_DEBUG, "assigning mapped IP: %u.%u.%u.%u (try %u of %u)",
 557                                         (assign->addr & 0xff000000) >> 24,
 558                                         (assign->addr & 0x00ff0000) >> 16,
 559                                         (assign->addr & 0x0000ff00) >> 8,
 560                                         (assign->addr & 0x000000ff), i, count);
 561                         return true;
 562                 }
 563                 try = (((try - start) + 1) % count) + start;
 564         }
 565
 566         syslog(LOG_WARNING, "can't assign any IP address -> address space is full");
 567         return false;
 568 }
 569
 570
 571 static struct dhcpv4_assignment* dhcpv4_lease(struct interface *iface,
 572                 enum dhcpv4_msg msg, const uint8_t *mac, struct in_addr reqaddr,
 573                 uint32_t *leasetime, const char *hostname, const size_t hostname_len)
 574 {
 575         struct dhcpv4_assignment *lease = NULL;
 576         uint32_t raddr = ntohl(reqaddr.s_addr);
 577         time_t now = odhcpd_time();
 578
 579         struct dhcpv4_assignment *c, *n, *a = NULL;
 580         list_for_each_entry_safe(c, n, &iface->dhcpv4_assignments, head) {
 581                 if (!memcmp(c->hwaddr, mac, 6)) {
 582                         a = c;
 583                         if (c->addr == raddr)
 584                                 break;
 585                 } else if (!INFINITE_VALID(c->valid_until) && c->valid_until < now)
 586                         free_dhcpv4_assignment(c);
 587         }
 588
 589         if (msg == DHCPV4_MSG_DISCOVER || msg == DHCPV4_MSG_REQUEST) {
 590                 bool assigned = !!a;
 591
 592                 if (!a && !iface->no_dynamic_dhcp) {
 593                         /* Create new binding */
 594                         a = calloc(1, sizeof(*a));
 595                         if (!a) {
 596                                 syslog(LOG_ERR, "Failed to calloc binding on interface %s", iface->ifname);
 597                                 return NULL;
 598                         }
 599                         memcpy(a->hwaddr, mac, sizeof(a->hwaddr));
 600                         /* Don't consider new assignment as infinite */
 601                         a->valid_until = now;
 602
 603                         assigned = dhcpv4_assign(iface, a, raddr);
 604                         if (assigned)
 605                                 list_add(&a->head, &iface->dhcpv4_assignments);
 606                 }
 607
 608                 if (assigned) {
 609                         uint32_t my_leasetime;
 610
 611                         if (a->leasetime)
 612                                 my_leasetime = a->leasetime;
 613                         else
 614                                 my_leasetime = iface->dhcpv4_leasetime;
 615
 616                         if ((*leasetime == 0) || (my_leasetime < *leasetime))
 617                                 *leasetime = my_leasetime;
 618
 619                         if (msg == DHCPV4_MSG_DISCOVER) {
 620                                 a->flags &= ~OAF_BOUND;
 621
 622                                 if (!(a->flags & OAF_STATIC))
 623                                         a->valid_until = now;
 624                         } else {
 625                                 if (hostname_len > 0) {
 626                                         a->hostname = realloc(a->hostname, hostname_len + 1);
 627                                         if (a->hostname) {
 628                                                 memcpy(a->hostname, hostname, hostname_len);
 629                                                 a->hostname[hostname_len] = 0;
 630                                         }
 631                                 }
 632
 633                                 a->flags |= OAF_BOUND;
 634
 635                                 if (!(a->flags & OAF_STATIC))
 636                                         a->valid_until = ((*leasetime == UINT32_MAX) ? 0 : (time_t)(now + *leasetime));
 637                         }
 638                 } else if (!assigned && a) {
 639                         /* Cleanup failed assignment */
 640                         free_dhcpv4_assignment(a);
 641                         a = NULL;
 642                 }
 643
 644                 if (assigned && a)
 645                         lease = a;
 646         } else if (msg == DHCPV4_MSG_RELEASE && a) {
 647                 a->flags &= ~OAF_BOUND;
 648
 649                 if (!(a->flags & OAF_STATIC))
 650                         a->valid_until = now - 1;
 651
 652         } else if (msg == DHCPV4_MSG_DECLINE && a) {
 653                 a->flags &= ~OAF_BOUND;
 654
 655                 if (!(a->flags & OAF_STATIC)) {
 656                         memset(a->hwaddr, 0, sizeof(a->hwaddr));
 657                         a->valid_until = now + 3600; /* Block address for 1h */
 658                 }
 659         }
 660
 661         dhcpv6_write_statefile();
 662
 663         return lease;
 664 }