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[0].prefix ? htonl(~((1 << (32 - iface->addr4[0].prefix)) - 1)) : 0;
  99
 100                 /* Create a range if not specified */
 101                 if (!(iface->dhcpv4_start.s_addr & htonl(0xffff0000)) &&
 102                                 !(iface->dhcpv4_end.s_addr & htonl(0xffff0000)) &&
 103                                 iface->addr4_len) {
 104                         struct in_addr *addr = &iface->addr4[0].addr.in;
 105
 106                         uint32_t start = ntohl(iface->dhcpv4_start.s_addr);
 107                         uint32_t end = ntohl(iface->dhcpv4_end.s_addr);
 108
 109                         if (start && end && start < end &&
 110                                         start > ntohl(addr->s_addr & ~mask) &&
 111                                         (start & ntohl(~mask)) == start &&
 112                                         (end & ntohl(~mask)) == end) {
 113                                 iface->dhcpv4_start.s_addr = htonl(start) |
 114                                                 (addr->s_addr & mask);
 115                                 iface->dhcpv4_end.s_addr = htonl(end) |
 116                                                 (addr->s_addr & mask);
 117                         } else if (ntohl(mask) <= 0xfffffff0) {
 118                                 start = addr->s_addr & mask;
 119                                 end = addr->s_addr & mask;
 120
 121                                 if (ntohl(mask) <= 0xffffff00) {
 122                                         iface->dhcpv4_start.s_addr = start | htonl(100);
 123                                         iface->dhcpv4_end.s_addr = end | htonl(250);
 124                                 } else if (ntohl(mask) <= 0xffffffc0) {
 125                                         iface->dhcpv4_start.s_addr = start | htonl(10);
 126                                         iface->dhcpv4_end.s_addr = end | htonl(60);
 127                                 } else if (ntohl(mask) <= 0xffffffe0) {
 128                                         iface->dhcpv4_start.s_addr = start | htonl(10);
 129                                         iface->dhcpv4_end.s_addr = end | htonl(30);
 130                                 } else {
 131                                         iface->dhcpv4_start.s_addr = start | htonl(3);
 132                                         iface->dhcpv4_end.s_addr = end | htonl(12);
 133                                 }
 134                         }
 135                 }
 136
 137                 /* Parse static entries */
 138                 struct lease *lease;
 139                 list_for_each_entry(lease, &leases, head) {
 140                         /* Construct entry */
 141                         struct dhcpv4_assignment *a = calloc(1, sizeof(*a));
 142                         if (!a) {
 143                                 syslog(LOG_ERR, "Calloc failed for static lease on interface %s",
 144                                         iface->ifname);
 145                                 return -1;
 146                         }
 147
 148                         a->leasetime = lease->dhcpv4_leasetime;
 149
 150                         a->addr = ntohl(lease->ipaddr.s_addr);
 151                         memcpy(a->hwaddr, lease->mac.ether_addr_octet, sizeof(a->hwaddr));
 152                         /* Static assignment */
 153                         a->flags |= OAF_STATIC;
 154                         /* Infinite valid */
 155                         a->valid_until = 0;
 156
 157                         /* Assign to all interfaces */
 158                         struct dhcpv4_assignment *c;
 159                         list_for_each_entry(c, &iface->dhcpv4_assignments, head) {
 160                                 if (c->addr > a->addr) {
 161                                         list_add_tail(&a->head, &c->head);
 162                                         break;
 163                                 } else if (c->addr == a->addr)
 164                                         /* Already an assignment with that number */
 165                                         break;
 166                         }
 167
 168                         if (&c->head == &iface->dhcpv4_assignments)
 169                                 list_add(&a->head, &iface->dhcpv4_assignments);
 170
 171                         if (a->head.next) {
 172                                 if (lease->hostname[0]) {
 173                                         free(a->hostname);
 174                                         a->hostname = strdup(lease->hostname);
 175                                 }
 176                         } else
 177                                 free_dhcpv4_assignment(a);
 178                 }
 179
 180                 // Clean invalid assignments
 181                 struct dhcpv4_assignment *a, *n;
 182                 list_for_each_entry_safe(a, n, &iface->dhcpv4_assignments, head) {
 183                         if ((htonl(a->addr) & mask) !=
 184                                         (iface->dhcpv4_start.s_addr & mask))
 185                                 free_dhcpv4_assignment(a);
 186                 }
 187
 188                 iface->dhcpv4_event.uloop.fd = sock;
 189                 iface->dhcpv4_event.handle_dgram = handle_dhcpv4;
 190                 odhcpd_register(&iface->dhcpv4_event);
 191         } else if (iface->dhcpv4_assignments.next) {
 192                 while (!list_empty(&iface->dhcpv4_assignments))
 193                         free_dhcpv4_assignment(list_first_entry(&iface->dhcpv4_assignments,
 194                                                         struct dhcpv4_assignment, head));
 195         }
 196         return 0;
 197 }
 198
 199 static char *dhcpv4_msg_to_string(uint8_t reqmsg)
 200 {
 201         switch (reqmsg) {
 202         case (DHCPV4_MSG_DISCOVER):
 203                 return "DHCPV4_MSG_DISCOVER";
 204         case (DHCPV4_MSG_OFFER):
 205                 return "DHCPV4_MSG_OFFER";
 206         case (DHCPV4_MSG_REQUEST):
 207                 return "DHCPV4_MSG_REQUEST";
 208         case (DHCPV4_MSG_DECLINE):
 209                 return "DHCPV4_MSG_DECLINE";
 210         case (DHCPV4_MSG_ACK):
 211                 return "DHCPV4_MSG_ACK";
 212         case (DHCPV4_MSG_NAK):
 213                 return "DHCPV4_MSG_NAK";
 214         case (DHCPV4_MSG_RELEASE):
 215                 return "DHCPV4_MSG_RELEASE";
 216         case (DHCPV4_MSG_INFORM):
 217                 return "DHCPV4_MSG_INFORM";
 218         default:
 219                 return "UNKNOWN";
 220         }
 221 }
 222
 223 static void free_dhcpv4_assignment(struct dhcpv4_assignment *a)
 224 {
 225         if (a->head.next)
 226                 list_del(&a->head);
 227
 228         free(a->hostname);
 229         free(a);
 230 }
 231
 232 static void dhcpv4_put(struct dhcpv4_message *msg, uint8_t **cookie,
 233                 uint8_t type, uint8_t len, const void *data)
 234 {
 235         uint8_t *c = *cookie;
 236         if (*cookie + 2 + len > (uint8_t*)&msg[1])
 237                 return;
 238
 239         *c++ = type;
 240         *c++ = len;
 241         memcpy(c, data, len);
 242
 243         *cookie = c + len;
 244 }
 245
 246 // Handler for DHCPv4 messages
 247 static void handle_dhcpv4(void *addr, void *data, size_t len,
 248                 struct interface *iface, _unused void *dest_addr)
 249 {
 250         if (!iface->dhcpv4)
 251                 return;
 252
 253         struct dhcpv4_message *req = data;
 254         if (len < offsetof(struct dhcpv4_message, options) + 4 ||
 255                         req->op != DHCPV4_BOOTREQUEST || req->hlen != 6)
 256                 return;
 257
 258
 259         syslog(LOG_NOTICE, "Got DHCPv4 request");
 260
 261         if (!iface->addr4_len) {
 262                 syslog(LOG_WARNING, "DHCPv4 no address found on %s", iface->name);
 263                 return;
 264         }
 265
 266         struct in_addr *ifaddr = &iface->addr4[0].addr.in;
 267         struct in_addr *ifbroadcast = &iface->addr4[0].broadcast;
 268         uint32_t mask = iface->addr4[0].prefix ? htonl(~((1 << (32 - iface->addr4[0].prefix)) - 1)) : 0;
 269         uint32_t network = iface->addr4[0].addr.in.s_addr & mask;
 270         int sock = iface->dhcpv4_event.uloop.fd;
 271
 272         if ((iface->dhcpv4_start.s_addr & mask) != network ||
 273                         (iface->dhcpv4_end.s_addr & mask) != network) {
 274                 syslog(LOG_WARNING, "DHCPv4 range out of assigned network");
 275                 return;
 276         }
 277
 278         struct dhcpv4_message reply = {
 279                 .op = DHCPV4_BOOTREPLY,
 280                 .htype = 1,
 281                 .hlen = 6,
 282                 .hops = 0,
 283                 .xid = req->xid,
 284                 .secs = 0,
 285                 .flags = req->flags,
 286                 .ciaddr = {INADDR_ANY},
 287                 .giaddr = req->giaddr,
 288                 .siaddr = *ifaddr,
 289         };
 290         memcpy(reply.chaddr, req->chaddr, sizeof(reply.chaddr));
 291
 292         reply.options[0] = 0x63;
 293         reply.options[1] = 0x82;
 294         reply.options[2] = 0x53;
 295         reply.options[3] = 0x63;
 296
 297         uint8_t *cookie = &reply.options[4];
 298         uint8_t reqmsg = DHCPV4_MSG_REQUEST;
 299         uint8_t msg = DHCPV4_MSG_ACK;
 300
 301         struct in_addr reqaddr = {INADDR_ANY};
 302         uint32_t leasetime = 0;
 303         size_t hostname_len = 0;
 304         char hostname[256];
 305
 306         uint8_t *start = &req->options[4];
 307         uint8_t *end = ((uint8_t*)data) + len;
 308         struct dhcpv4_option *opt;
 309         dhcpv4_for_each_option(start, end, opt) {
 310                 if (opt->type == DHCPV4_OPT_MESSAGE && opt->len == 1)
 311                         reqmsg = opt->data[0];
 312                 else if (opt->type == DHCPV4_OPT_HOSTNAME && opt->len > 0) {
 313                         hostname_len = opt->len;
 314                         memcpy(hostname, opt->data, hostname_len);
 315                         hostname[hostname_len] = 0;
 316                 } else if (opt->type == DHCPV4_OPT_IPADDRESS && opt->len == 4)
 317                         memcpy(&reqaddr, opt->data, 4);
 318                 else if (opt->type == DHCPV4_OPT_SERVERID && opt->len == 4) {
 319                         if (memcmp(opt->data, ifaddr, 4))
 320                                 return;
 321                 } else if (iface->filter_class && opt->type == DHCPV4_OPT_USER_CLASS) {
 322                         uint8_t *c = opt->data, *cend = &opt->data[opt->len];
 323                         for (; c < cend && &c[*c] < cend; c = &c[1 + *c]) {
 324                                 size_t elen = strlen(iface->filter_class);
 325                                 if (*c == elen && !memcmp(&c[1], iface->filter_class, elen))
 326                                         return; // Ignore from homenet
 327                         }
 328                 } else if (opt->type == DHCPV4_OPT_LEASETIME && opt->len == 4)
 329                         memcpy(&leasetime, opt->data, 4);
 330         }
 331
 332         if (reqmsg != DHCPV4_MSG_DISCOVER && reqmsg != DHCPV4_MSG_REQUEST &&
 333                         reqmsg != DHCPV4_MSG_INFORM && reqmsg != DHCPV4_MSG_DECLINE &&
 334                         reqmsg != DHCPV4_MSG_RELEASE)
 335                 return;
 336
 337         struct dhcpv4_assignment *lease = NULL;
 338         if (reqmsg != DHCPV4_MSG_INFORM)
 339                 lease = dhcpv4_lease(iface, reqmsg, req->chaddr, reqaddr,
 340                                         &leasetime, hostname, hostname_len);
 341
 342         if (!lease) {
 343                 if (reqmsg == DHCPV4_MSG_REQUEST)
 344                         msg = DHCPV4_MSG_NAK;
 345                 else if (reqmsg == DHCPV4_MSG_DISCOVER)
 346                         return;
 347         } else if (reqmsg == DHCPV4_MSG_DISCOVER)
 348                 msg = DHCPV4_MSG_OFFER;
 349         else if (reqmsg == DHCPV4_MSG_REQUEST && reqaddr.s_addr &&
 350                         reqaddr.s_addr != htonl(lease->addr)) {
 351                 msg = DHCPV4_MSG_NAK;
 352                 /*
 353                  * DHCP client requested an IP which we can't offer to him. Probably the
 354                  * client changed the network. The reply type is set to DHCPV4_MSG_NAK,
 355                  * because the client should not use that IP.
 356                  *
 357                  * For modern devices we build an answer that includes a valid IP, like
 358                  * a DHCPV4_MSG_ACK. The client will use that IP and doesn't need to
 359                  * perform additional DHCP round trips.
 360                  *
 361                  */
 362         }
 363
 364         syslog(LOG_WARNING, "received %s from %02x:%02x:%02x:%02x:%02x:%02x",
 365                         dhcpv4_msg_to_string(reqmsg),
 366                         req->chaddr[0],req->chaddr[1],req->chaddr[2],
 367                         req->chaddr[3],req->chaddr[4],req->chaddr[5]);
 368
 369         if (reqmsg == DHCPV4_MSG_DECLINE || reqmsg == DHCPV4_MSG_RELEASE)
 370                 return;
 371
 372         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_MESSAGE, 1, &msg);
 373         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SERVERID, 4, ifaddr);
 374
 375         if (lease) {
 376                 uint32_t val;
 377
 378                 reply.yiaddr.s_addr = htonl(lease->addr);
 379
 380                 val = htonl(leasetime);
 381                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_LEASETIME, 4, &val);
 382
 383                 if (leasetime != UINT32_MAX) {
 384                         val = htonl(500 * leasetime / 1000);
 385                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_RENEW, 4, &val);
 386
 387                         val = htonl(875 * leasetime / 1000);
 388                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_REBIND, 4, &val);
 389                 }
 390
 391                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_NETMASK, 4, &mask);
 392
 393                 if (lease->hostname)
 394                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_HOSTNAME,
 395                                         strlen(lease->hostname), lease->hostname);
 396
 397                 if (ifbroadcast->s_addr != INADDR_ANY)
 398                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_BROADCAST, 4, ifbroadcast);
 399         }
 400
 401         struct ifreq ifr = {.ifr_name = ""};
 402         strncpy(ifr.ifr_name, iface->ifname, sizeof(ifr.ifr_name));
 403
 404         if (!ioctl(sock, SIOCGIFMTU, &ifr)) {
 405                 uint16_t mtu = htons(ifr.ifr_mtu);
 406                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_MTU, 2, &mtu);
 407         }
 408
 409         if (iface->search && iface->search_len <= 255)
 410                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SEARCH_DOMAIN,
 411                                 iface->search_len, iface->search);
 412         else if (!res_init() && _res.dnsrch[0] && _res.dnsrch[0][0]) {
 413                 uint8_t search_buf[256];
 414                 int len = dn_comp(_res.dnsrch[0], search_buf,
 415                                                 sizeof(search_buf), NULL, NULL);
 416                 if (len > 0)
 417                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SEARCH_DOMAIN,
 418                                         len, search_buf);
 419         }
 420
 421         if (iface->dhcpv4_router_cnt == 0)
 422                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_ROUTER, 4, ifaddr);
 423         else
 424                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_ROUTER,
 425                                 4 * iface->dhcpv4_router_cnt, iface->dhcpv4_router);
 426
 427
 428         if (iface->dhcpv4_dns_cnt == 0)
 429                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_DNSSERVER, 4, ifaddr);
 430         else
 431                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_DNSSERVER,
 432                                 4 * iface->dhcpv4_dns_cnt, iface->dhcpv4_dns);
 433
 434
 435         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_END, 0, NULL);
 436
 437         struct sockaddr_in dest = *((struct sockaddr_in*)addr);
 438         if (req->giaddr.s_addr) {
 439                 /*
 440                  * relay agent is configured, send reply to the agent
 441                  */
 442                 dest.sin_addr = req->giaddr;
 443                 dest.sin_port = htons(DHCPV4_SERVER_PORT);
 444         } else if (req->ciaddr.s_addr && req->ciaddr.s_addr != dest.sin_addr.s_addr) {
 445                 /*
 446                  * client has existing configuration (ciaddr is set) AND this address is
 447                  * not the address it used for the dhcp message
 448                  */
 449                 dest.sin_addr = req->ciaddr;
 450                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 451         } else if ((ntohs(req->flags) & DHCPV4_FLAG_BROADCAST) ||
 452                         req->hlen != reply.hlen || !reply.yiaddr.s_addr) {
 453                 /*
 454                  * client requests a broadcast reply OR we can't offer an IP
 455                  */
 456                 dest.sin_addr.s_addr = INADDR_BROADCAST;
 457                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 458         } else if (!req->ciaddr.s_addr && msg == DHCPV4_MSG_NAK) {
 459                 /*
 460                  * client has no previous configuration -> no IP, so we need to reply
 461                  * with a broadcast packet
 462                  */
 463                 dest.sin_addr.s_addr = INADDR_BROADCAST;
 464                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 465         } else {
 466                 /*
 467                  * send reply to the newly (in this proccess) allocated IP
 468                  */
 469                 dest.sin_addr = reply.yiaddr;
 470                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 471
 472                 struct arpreq arp = {.arp_flags = ATF_COM};
 473                 memcpy(arp.arp_ha.sa_data, req->chaddr, 6);
 474                 memcpy(&arp.arp_pa, &dest, sizeof(arp.arp_pa));
 475                 memcpy(arp.arp_dev, iface->ifname, sizeof(arp.arp_dev));
 476                 ioctl(sock, SIOCSARP, &arp);
 477         }
 478
 479         if (dest.sin_addr.s_addr == INADDR_BROADCAST)
 480                 /* reply goes to IP broadcast -> MAC broadcast */
 481                 syslog(LOG_WARNING, "sending %s to ff:ff:ff:ff:ff:ff - %s",
 482                                 dhcpv4_msg_to_string(msg),
 483                                 inet_ntoa(dest.sin_addr));
 484         else
 485                 /*
 486                  * reply is send directly to IP,
 487                  * MAC is assumed to be the same as the request
 488                  */
 489                 syslog(LOG_WARNING, "sending %s to %02x:%02x:%02x:%02x:%02x:%02x - %s",
 490                                 dhcpv4_msg_to_string(msg),
 491                                 req->chaddr[0],req->chaddr[1],req->chaddr[2],
 492                                 req->chaddr[3],req->chaddr[4],req->chaddr[5],
 493                                 inet_ntoa(dest.sin_addr));
 494
 495         sendto(sock, &reply, sizeof(reply), MSG_DONTWAIT,
 496                         (struct sockaddr*)&dest, sizeof(dest));
 497 }
 498
 499 static bool dhcpv4_test(struct interface *iface, uint32_t try)
 500 {
 501         struct dhcpv4_assignment *c;
 502         list_for_each_entry(c, &iface->dhcpv4_assignments, head) {
 503                 if (c->addr == try)
 504                         return false;
 505
 506         }
 507
 508         return true;
 509 }
 510
 511 static bool dhcpv4_assign(struct interface *iface,
 512                 struct dhcpv4_assignment *assign, uint32_t raddr)
 513 {
 514         uint32_t start = ntohl(iface->dhcpv4_start.s_addr);
 515         uint32_t end = ntohl(iface->dhcpv4_end.s_addr);
 516         uint32_t count = end - start + 1;
 517
 518         // try to assign the IP the client asked for
 519         if (start <= raddr && raddr <= end && dhcpv4_test(iface, raddr)) {
 520                 assign->addr = raddr;
 521                 syslog(LOG_INFO, "assigning the IP the client asked for: %u.%u.%u.%u",
 522                                 (assign->addr & 0xff000000) >> 24,
 523                                 (assign->addr & 0x00ff0000) >> 16,
 524                                 (assign->addr & 0x0000ff00) >> 8,
 525                                 (assign->addr & 0x000000ff));
 526                 return true;
 527         }
 528
 529         // Seed RNG with checksum of hwaddress
 530         uint32_t seed = 0;
 531         for (size_t i = 0; i < sizeof(assign->hwaddr); ++i) {
 532                 // Knuth's multiplicative method
 533                 uint8_t o = assign->hwaddr[i];
 534                 seed += (o*2654435761) % UINT32_MAX;
 535         }
 536
 537         srand(seed);
 538
 539         uint32_t try = (((uint32_t)rand()) % count) + start;
 540
 541         if (list_empty(&iface->dhcpv4_assignments)) {
 542                 assign->addr = try;
 543                 syslog(LOG_INFO, "assigning mapped IP (empty list): %u.%u.%u.%u",
 544                                 (assign->addr & 0xff000000) >> 24,
 545                                 (assign->addr & 0x00ff0000) >> 16,
 546                                 (assign->addr & 0x0000ff00) >> 8,
 547                                 (assign->addr & 0x000000ff));
 548                 return true;
 549         }
 550
 551         for (uint32_t i = 0; i < count; ++i) {
 552                 if (dhcpv4_test(iface, try)) {
 553                         /* test was successful: IP address is not assigned, assign it */
 554                         assign->addr = try;
 555                         syslog(LOG_DEBUG, "assigning mapped IP: %u.%u.%u.%u (try %u of %u)",
 556                                         (assign->addr & 0xff000000) >> 24,
 557                                         (assign->addr & 0x00ff0000) >> 16,
 558                                         (assign->addr & 0x0000ff00) >> 8,
 559                                         (assign->addr & 0x000000ff), i, count);
 560                         return true;
 561                 }
 562                 try = (((try - start) + 1) % count) + start;
 563         }
 564
 565         syslog(LOG_WARNING, "can't assign any IP address -> address space is full");
 566         return false;
 567 }
 568
 569
 570 static struct dhcpv4_assignment* dhcpv4_lease(struct interface *iface,
 571                 enum dhcpv4_msg msg, const uint8_t *mac, struct in_addr reqaddr,
 572                 uint32_t *leasetime, const char *hostname, const size_t hostname_len)
 573 {
 574         struct dhcpv4_assignment *lease = NULL;
 575         uint32_t raddr = ntohl(reqaddr.s_addr);
 576         time_t now = odhcpd_time();
 577
 578         struct dhcpv4_assignment *c, *n, *a = NULL;
 579         list_for_each_entry_safe(c, n, &iface->dhcpv4_assignments, head) {
 580                 if (!memcmp(c->hwaddr, mac, 6)) {
 581                         a = c;
 582                         if (c->addr == raddr)
 583                                 break;
 584                 } else if (!INFINITE_VALID(c->valid_until) && c->valid_until < now)
 585                         free_dhcpv4_assignment(c);
 586         }
 587
 588         if (msg == DHCPV4_MSG_DISCOVER || msg == DHCPV4_MSG_REQUEST) {
 589                 bool assigned = !!a;
 590
 591                 if (!a && !iface->no_dynamic_dhcp) {
 592                         /* Create new binding */
 593                         a = calloc(1, sizeof(*a));
 594                         if (!a) {
 595                                 syslog(LOG_ERR, "Failed to calloc binding on interface %s", iface->ifname);
 596                                 return NULL;
 597                         }
 598                         memcpy(a->hwaddr, mac, sizeof(a->hwaddr));
 599                         /* Don't consider new assignment as infinite */
 600                         a->valid_until = now;
 601
 602                         assigned = dhcpv4_assign(iface, a, raddr);
 603                         if (assigned)
 604                                 list_add(&a->head, &iface->dhcpv4_assignments);
 605                 }
 606
 607                 if (assigned) {
 608                         uint32_t my_leasetime;
 609
 610                         if (a->leasetime)
 611                                 my_leasetime = a->leasetime;
 612                         else
 613                                 my_leasetime = iface->dhcpv4_leasetime;
 614
 615                         if ((*leasetime == 0) || (my_leasetime < *leasetime))
 616                                 *leasetime = my_leasetime;
 617
 618                         if (msg == DHCPV4_MSG_DISCOVER) {
 619                                 a->flags &= ~OAF_BOUND;
 620
 621                                 if (!(a->flags & OAF_STATIC))
 622                                         a->valid_until = now;
 623                         } else {
 624                                 if (hostname_len > 0) {
 625                                         a->hostname = realloc(a->hostname, hostname_len + 1);
 626                                         if (a->hostname) {
 627                                                 memcpy(a->hostname, hostname, hostname_len);
 628                                                 a->hostname[hostname_len] = 0;
 629                                         }
 630                                 }
 631
 632                                 a->flags |= OAF_BOUND;
 633
 634                                 if (!(a->flags & OAF_STATIC))
 635                                         a->valid_until = ((*leasetime == UINT32_MAX) ? 0 : (time_t)(now + *leasetime));
 636                         }
 637                 } else if (!assigned && a) {
 638                         /* Cleanup failed assignment */
 639                         free_dhcpv4_assignment(a);
 640                         a = NULL;
 641                 }
 642
 643                 if (assigned && a)
 644                         lease = a;
 645         } else if (msg == DHCPV4_MSG_RELEASE && a) {
 646                 a->flags &= ~OAF_BOUND;
 647
 648                 if (!(a->flags & OAF_STATIC))
 649                         a->valid_until = now - 1;
 650
 651         } else if (msg == DHCPV4_MSG_DECLINE && a) {
 652                 a->flags &= ~OAF_BOUND;
 653
 654                 if (!(a->flags & OAF_STATIC)) {
 655                         memset(a->hwaddr, 0, sizeof(a->hwaddr));
 656                         a->valid_until = now + 3600; /* Block address for 1h */
 657                 }
 658         }
 659
 660         dhcpv6_write_statefile();
 661
 662         return lease;
 663 }