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                 /* Create a range if not specified */
  99                 struct ifreq ifreq;
 100                 strncpy(ifreq.ifr_name, iface->ifname, sizeof(ifreq.ifr_name));
 101
 102                 struct sockaddr_in *saddr = (struct sockaddr_in*)&ifreq.ifr_addr;
 103                 struct sockaddr_in *smask = (struct sockaddr_in*)&ifreq.ifr_netmask;
 104                 if (!(iface->dhcpv4_start.s_addr & htonl(0xffff0000)) &&
 105                                 !(iface->dhcpv4_end.s_addr & htonl(0xffff0000)) &&
 106                                 !ioctl(sock, SIOCGIFADDR, &ifreq)) {
 107                         struct in_addr addr = saddr->sin_addr;
 108
 109                         ioctl(sock, SIOCGIFNETMASK, &ifreq);
 110                         struct in_addr mask = smask->sin_addr;
 111
 112                         uint32_t start = ntohl(iface->dhcpv4_start.s_addr);
 113                         uint32_t end = ntohl(iface->dhcpv4_end.s_addr);
 114
 115                         if (start && end && start < end &&
 116                                         start > ntohl(addr.s_addr & ~mask.s_addr) &&
 117                                         (start & ntohl(~mask.s_addr)) == start &&
 118                                         (end & ntohl(~mask.s_addr)) == end) {
 119                                 iface->dhcpv4_start.s_addr = htonl(start) |
 120                                                 (addr.s_addr & mask.s_addr);
 121                                 iface->dhcpv4_end.s_addr = htonl(end) |
 122                                                 (addr.s_addr & mask.s_addr);
 123                         } else if (ntohl(mask.s_addr) <= 0xfffffff0) {
 124                                 start = addr.s_addr & mask.s_addr;
 125                                 end = addr.s_addr & mask.s_addr;
 126
 127                                 if (ntohl(mask.s_addr) <= 0xffffff00) {
 128                                         iface->dhcpv4_start.s_addr = start | htonl(100);
 129                                         iface->dhcpv4_end.s_addr = end | htonl(250);
 130                                 } else if (ntohl(mask.s_addr) <= 0xffffffc0) {
 131                                         iface->dhcpv4_start.s_addr = start | htonl(10);
 132                                         iface->dhcpv4_end.s_addr = end | htonl(60);
 133                                 } else if (ntohl(mask.s_addr) <= 0xffffffe0) {
 134                                         iface->dhcpv4_start.s_addr = start | htonl(10);
 135                                         iface->dhcpv4_end.s_addr = end | htonl(30);
 136                                 } else {
 137                                         iface->dhcpv4_start.s_addr = start | htonl(3);
 138                                         iface->dhcpv4_end.s_addr = end | htonl(12);
 139                                 }
 140                         }
 141
 142
 143                 }
 144
 145                 /* Parse static entries */
 146                 struct lease *lease;
 147                 list_for_each_entry(lease, &leases, head) {
 148                         /* Construct entry */
 149                         struct dhcpv4_assignment *a = calloc(1, sizeof(*a));
 150                         if (!a) {
 151                                 syslog(LOG_ERR, "Calloc failed for static lease on interface %s",
 152                                         iface->ifname);
 153                                 return -1;
 154                         }
 155
 156                         a->leasetime = lease->dhcpv4_leasetime;
 157
 158                         a->addr = ntohl(lease->ipaddr.s_addr);
 159                         memcpy(a->hwaddr, lease->mac.ether_addr_octet, sizeof(a->hwaddr));
 160                         /* Static assignment */
 161                         a->flags |= OAF_STATIC;
 162                         /* Infinite valid */
 163                         a->valid_until = 0;
 164
 165                         /* Assign to all interfaces */
 166                         struct dhcpv4_assignment *c;
 167                         list_for_each_entry(c, &iface->dhcpv4_assignments, head) {
 168                                 if (c->addr > a->addr) {
 169                                         list_add_tail(&a->head, &c->head);
 170                                         break;
 171                                 } else if (c->addr == a->addr)
 172                                         /* Already an assignment with that number */
 173                                         break;
 174                         }
 175
 176                         if (&c->head == &iface->dhcpv4_assignments)
 177                                 list_add(&a->head, &iface->dhcpv4_assignments);
 178
 179                         if (a->head.next) {
 180                                 if (lease->hostname[0]) {
 181                                         free(a->hostname);
 182                                         a->hostname = strdup(lease->hostname);
 183                                 }
 184                         } else
 185                                 free_dhcpv4_assignment(a);
 186                 }
 187
 188                 // Clean invalid assignments
 189                 struct dhcpv4_assignment *a, *n;
 190                 list_for_each_entry_safe(a, n, &iface->dhcpv4_assignments, head) {
 191                         if ((htonl(a->addr) & smask->sin_addr.s_addr) !=
 192                                         (iface->dhcpv4_start.s_addr & smask->sin_addr.s_addr))
 193                                 free_dhcpv4_assignment(a);
 194                 }
 195
 196                 iface->dhcpv4_event.uloop.fd = sock;
 197                 iface->dhcpv4_event.handle_dgram = handle_dhcpv4;
 198                 odhcpd_register(&iface->dhcpv4_event);
 199         } else if (iface->dhcpv4_assignments.next) {
 200                 while (!list_empty(&iface->dhcpv4_assignments))
 201                         free_dhcpv4_assignment(list_first_entry(&iface->dhcpv4_assignments,
 202                                                         struct dhcpv4_assignment, head));
 203         }
 204         return 0;
 205 }
 206
 207 static char *dhcpv4_msg_to_string(uint8_t reqmsg)
 208 {
 209         switch (reqmsg) {
 210         case (DHCPV4_MSG_DISCOVER):
 211                 return "DHCPV4_MSG_DISCOVER";
 212         case (DHCPV4_MSG_OFFER):
 213                 return "DHCPV4_MSG_OFFER";
 214         case (DHCPV4_MSG_REQUEST):
 215                 return "DHCPV4_MSG_REQUEST";
 216         case (DHCPV4_MSG_DECLINE):
 217                 return "DHCPV4_MSG_DECLINE";
 218         case (DHCPV4_MSG_ACK):
 219                 return "DHCPV4_MSG_ACK";
 220         case (DHCPV4_MSG_NAK):
 221                 return "DHCPV4_MSG_NAK";
 222         case (DHCPV4_MSG_RELEASE):
 223                 return "DHCPV4_MSG_RELEASE";
 224         case (DHCPV4_MSG_INFORM):
 225                 return "DHCPV4_MSG_INFORM";
 226         default:
 227                 return "UNKNOWN";
 228         }
 229 }
 230
 231 static void free_dhcpv4_assignment(struct dhcpv4_assignment *a)
 232 {
 233         if (a->head.next)
 234                 list_del(&a->head);
 235
 236         free(a->hostname);
 237         free(a);
 238 }
 239
 240 static void dhcpv4_put(struct dhcpv4_message *msg, uint8_t **cookie,
 241                 uint8_t type, uint8_t len, const void *data)
 242 {
 243         uint8_t *c = *cookie;
 244         uint8_t *end = (uint8_t *)msg + sizeof(*msg);
 245
 246         if (*cookie + 2 + len > end)
 247                 return;
 248
 249         *c++ = type;
 250         *c++ = len;
 251         memcpy(c, data, len);
 252
 253         *cookie = c + len;
 254 }
 255
 256 // Handler for DHCPv4 messages
 257 static void handle_dhcpv4(void *addr, void *data, size_t len,
 258                 struct interface *iface, _unused void *dest_addr)
 259 {
 260         if (!iface->dhcpv4)
 261                 return;
 262
 263         struct dhcpv4_message *req = data;
 264         if (len < offsetof(struct dhcpv4_message, options) + 4 ||
 265                         req->op != DHCPV4_BOOTREQUEST || req->hlen != 6)
 266                 return;
 267
 268         int sock = iface->dhcpv4_event.uloop.fd;
 269         struct sockaddr_in ifaddr;
 270         struct sockaddr_in ifnetmask;
 271
 272         syslog(LOG_NOTICE, "Got DHCPv4 request");
 273
 274         struct ifreq ifreq;
 275         memcpy(ifreq.ifr_name, iface->ifname, sizeof(ifreq.ifr_name));
 276         if (ioctl(sock, SIOCGIFADDR, &ifreq)) {
 277                 syslog(LOG_WARNING, "DHCPv4 failed to detect address: %s", strerror(errno));
 278                 return;
 279         }
 280
 281         memcpy(&ifaddr, &ifreq.ifr_addr, sizeof(ifaddr));
 282         if (ioctl(sock, SIOCGIFNETMASK, &ifreq))
 283                 return;
 284
 285         memcpy(&ifnetmask, &ifreq.ifr_netmask, sizeof(ifnetmask));
 286         uint32_t network = ifaddr.sin_addr.s_addr & ifnetmask.sin_addr.s_addr;
 287
 288         if ((iface->dhcpv4_start.s_addr & ifnetmask.sin_addr.s_addr) != network ||
 289                         (iface->dhcpv4_end.s_addr & ifnetmask.sin_addr.s_addr) != network) {
 290                 syslog(LOG_WARNING, "DHCPv4 range out of assigned network");
 291                 return;
 292         }
 293
 294         struct ifreq ifr = {.ifr_name = ""};
 295         strncpy(ifr.ifr_name, iface->ifname, sizeof(ifr.ifr_name));
 296
 297         struct dhcpv4_message reply = {
 298                 .op = DHCPV4_BOOTREPLY,
 299                 .htype = 1,
 300                 .hlen = 6,
 301                 .hops = 0,
 302                 .xid = req->xid,
 303                 .secs = 0,
 304                 .flags = req->flags,
 305                 .ciaddr = {INADDR_ANY},
 306                 .giaddr = req->giaddr,
 307                 .siaddr = ifaddr.sin_addr,
 308         };
 309         memcpy(reply.chaddr, req->chaddr, sizeof(reply.chaddr));
 310
 311         reply.options[0] = 0x63;
 312         reply.options[1] = 0x82;
 313         reply.options[2] = 0x53;
 314         reply.options[3] = 0x63;
 315
 316         uint8_t *cookie = &reply.options[4];
 317         uint8_t reqmsg = DHCPV4_MSG_REQUEST;
 318         uint8_t msg = DHCPV4_MSG_ACK;
 319
 320         struct in_addr reqaddr = {INADDR_ANY};
 321         uint32_t leasetime = 0;
 322         size_t hostname_len = 0;
 323         char hostname[256];
 324
 325         uint8_t *start = &req->options[4];
 326         uint8_t *end = ((uint8_t*)data) + len;
 327         struct dhcpv4_option *opt;
 328         dhcpv4_for_each_option(start, end, opt) {
 329                 if (opt->type == DHCPV4_OPT_MESSAGE && opt->len == 1)
 330                         reqmsg = opt->data[0];
 331                 else if (opt->type == DHCPV4_OPT_HOSTNAME && opt->len > 0) {
 332                         hostname_len = opt->len;
 333                         memcpy(hostname, opt->data, hostname_len);
 334                         hostname[hostname_len] = 0;
 335                 } else if (opt->type == DHCPV4_OPT_IPADDRESS && opt->len == 4)
 336                         memcpy(&reqaddr, opt->data, 4);
 337                 else if (opt->type == DHCPV4_OPT_SERVERID && opt->len == 4) {
 338                         if (memcmp(opt->data, &ifaddr.sin_addr, 4))
 339                                 return;
 340                 } else if (iface->filter_class && opt->type == DHCPV4_OPT_USER_CLASS) {
 341                         uint8_t *c = opt->data, *cend = &opt->data[opt->len];
 342                         for (; c < cend && &c[*c] < cend; c = &c[1 + *c]) {
 343                                 size_t elen = strlen(iface->filter_class);
 344                                 if (*c == elen && !memcmp(&c[1], iface->filter_class, elen))
 345                                         return; // Ignore from homenet
 346                         }
 347                 } else if (opt->type == DHCPV4_OPT_LEASETIME && opt->len == 4)
 348                         memcpy(&leasetime, opt->data, 4);
 349         }
 350
 351         if (reqmsg != DHCPV4_MSG_DISCOVER && reqmsg != DHCPV4_MSG_REQUEST &&
 352                         reqmsg != DHCPV4_MSG_INFORM && reqmsg != DHCPV4_MSG_DECLINE &&
 353                         reqmsg != DHCPV4_MSG_RELEASE)
 354                 return;
 355
 356         struct dhcpv4_assignment *lease = NULL;
 357         if (reqmsg != DHCPV4_MSG_INFORM)
 358                 lease = dhcpv4_lease(iface, reqmsg, req->chaddr, reqaddr,
 359                                         &leasetime, hostname, hostname_len);
 360
 361         if (!lease) {
 362                 if (reqmsg == DHCPV4_MSG_REQUEST)
 363                         msg = DHCPV4_MSG_NAK;
 364                 else if (reqmsg == DHCPV4_MSG_DISCOVER)
 365                         return;
 366         } else if (reqmsg == DHCPV4_MSG_DISCOVER)
 367                 msg = DHCPV4_MSG_OFFER;
 368         else if (reqmsg == DHCPV4_MSG_REQUEST && reqaddr.s_addr &&
 369                         reqaddr.s_addr != htonl(lease->addr)) {
 370                 msg = DHCPV4_MSG_NAK;
 371                 /*
 372                  * DHCP client requested an IP which we can't offer to him. Probably the
 373                  * client changed the network. The reply type is set to DHCPV4_MSG_NAK,
 374                  * because the client should not use that IP.
 375                  *
 376                  * For modern devices we build an answer that includes a valid IP, like
 377                  * a DHCPV4_MSG_ACK. The client will use that IP and doesn't need to
 378                  * perform additional DHCP round trips.
 379                  *
 380                  */
 381         }
 382
 383         syslog(LOG_WARNING, "received %s from %x:%x:%x:%x:%x:%x",
 384                         dhcpv4_msg_to_string(reqmsg),
 385                         req->chaddr[0],req->chaddr[1],req->chaddr[2],
 386                         req->chaddr[3],req->chaddr[4],req->chaddr[5]);
 387
 388         if (reqmsg == DHCPV4_MSG_DECLINE || reqmsg == DHCPV4_MSG_RELEASE)
 389                 return;
 390
 391         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_MESSAGE, 1, &msg);
 392         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SERVERID, 4, &ifaddr.sin_addr);
 393
 394         if (lease) {
 395                 uint32_t val;
 396
 397                 reply.yiaddr.s_addr = htonl(lease->addr);
 398
 399                 val = htonl(leasetime);
 400                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_LEASETIME, 4, &val);
 401
 402                 if (leasetime != UINT32_MAX) {
 403                         val = htonl(500 * leasetime / 1000);
 404                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_RENEW, 4, &val);
 405
 406                         val = htonl(875 * leasetime / 1000);
 407                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_REBIND, 4, &val);
 408                 }
 409
 410                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_NETMASK, 4, &ifnetmask.sin_addr);
 411
 412                 if (lease->hostname)
 413                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_HOSTNAME,
 414                                         strlen(lease->hostname), lease->hostname);
 415
 416                 if (!ioctl(sock, SIOCGIFBRDADDR, &ifr)) {
 417                         struct sockaddr_in *ina = (struct sockaddr_in*)&ifr.ifr_broadaddr;
 418                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_BROADCAST, 4, &ina->sin_addr);
 419                 }
 420         }
 421
 422         if (!ioctl(sock, SIOCGIFMTU, &ifr)) {
 423                 uint16_t mtu = htons(ifr.ifr_mtu);
 424                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_MTU, 2, &mtu);
 425         }
 426
 427         if (iface->search && iface->search_len <= 255)
 428                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SEARCH_DOMAIN,
 429                                 iface->search_len, iface->search);
 430         else if (!res_init() && _res.dnsrch[0] && _res.dnsrch[0][0]) {
 431                 uint8_t search_buf[256];
 432                 int len = dn_comp(_res.dnsrch[0], search_buf,
 433                                                 sizeof(search_buf), NULL, NULL);
 434                 if (len > 0)
 435                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SEARCH_DOMAIN,
 436                                         len, search_buf);
 437         }
 438
 439         if (iface->dhcpv4_router_cnt == 0)
 440                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_ROUTER, 4, &ifaddr.sin_addr);
 441         else
 442                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_ROUTER,
 443                                 4 * iface->dhcpv4_router_cnt, iface->dhcpv4_router);
 444
 445
 446         if (iface->dhcpv4_dns_cnt == 0)
 447                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_DNSSERVER, 4, &ifaddr.sin_addr);
 448         else
 449                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_DNSSERVER,
 450                                 4 * iface->dhcpv4_dns_cnt, iface->dhcpv4_dns);
 451
 452
 453         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_END, 0, NULL);
 454
 455         struct sockaddr_in dest = *((struct sockaddr_in*)addr);
 456         if (req->giaddr.s_addr) {
 457                 /*
 458                  * relay agent is configured, send reply to the agent
 459                  */
 460                 dest.sin_addr = req->giaddr;
 461                 dest.sin_port = htons(DHCPV4_SERVER_PORT);
 462         } else if (req->ciaddr.s_addr && req->ciaddr.s_addr != dest.sin_addr.s_addr) {
 463                 /*
 464                  * client has existing configuration (ciaddr is set) AND this address is
 465                  * not the address it used for the dhcp message
 466                  */
 467                 dest.sin_addr = req->ciaddr;
 468                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 469         } else if ((ntohs(req->flags) & DHCPV4_FLAG_BROADCAST) ||
 470                         req->hlen != reply.hlen || !reply.yiaddr.s_addr) {
 471                 /*
 472                  * client requests a broadcast reply OR we can't offer an IP
 473                  */
 474                 dest.sin_addr.s_addr = INADDR_BROADCAST;
 475                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 476         } else if (!req->ciaddr.s_addr && msg == DHCPV4_MSG_NAK) {
 477                 /*
 478                  * client has no previous configuration -> no IP, so we need to reply
 479                  * with a broadcast packet
 480                  */
 481                 dest.sin_addr.s_addr = INADDR_BROADCAST;
 482                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 483         } else {
 484                 /*
 485                  * send reply to the newly (in this proccess) allocated IP
 486                  */
 487                 dest.sin_addr = reply.yiaddr;
 488                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 489
 490                 struct arpreq arp = {.arp_flags = ATF_COM};
 491                 memcpy(arp.arp_ha.sa_data, req->chaddr, 6);
 492                 memcpy(&arp.arp_pa, &dest, sizeof(arp.arp_pa));
 493                 memcpy(arp.arp_dev, iface->ifname, sizeof(arp.arp_dev));
 494                 ioctl(sock, SIOCSARP, &arp);
 495         }
 496
 497         if (dest.sin_addr.s_addr == INADDR_BROADCAST)
 498                 /* reply goes to IP broadcast -> MAC broadcast */
 499                 syslog(LOG_WARNING, "sending %s to ff:ff:ff:ff:ff:ff - %s",
 500                                 dhcpv4_msg_to_string(msg),
 501                                 inet_ntoa(dest.sin_addr));
 502         else
 503                 /*
 504                  * reply is send directly to IP,
 505                  * MAC is assumed to be the same as the request
 506                  */
 507                 syslog(LOG_WARNING, "sending %s to %x:%x:%x:%x:%x:%x - %s",
 508                                 dhcpv4_msg_to_string(msg),
 509                                 req->chaddr[0],req->chaddr[1],req->chaddr[2],
 510                                 req->chaddr[3],req->chaddr[4],req->chaddr[5],
 511                                 inet_ntoa(dest.sin_addr));
 512
 513         sendto(sock, &reply, sizeof(reply), MSG_DONTWAIT,
 514                         (struct sockaddr*)&dest, sizeof(dest));
 515 }
 516
 517 static bool dhcpv4_test(struct interface *iface, uint32_t try)
 518 {
 519         struct dhcpv4_assignment *c;
 520         list_for_each_entry(c, &iface->dhcpv4_assignments, head) {
 521                 if (c->addr == try)
 522                         return false;
 523
 524         }
 525
 526         return true;
 527 }
 528
 529 static bool dhcpv4_assign(struct interface *iface,
 530                 struct dhcpv4_assignment *assign, uint32_t raddr)
 531 {
 532         uint32_t start = ntohl(iface->dhcpv4_start.s_addr);
 533         uint32_t end = ntohl(iface->dhcpv4_end.s_addr);
 534         uint32_t count = end - start + 1;
 535
 536         // try to assign the IP the client asked for
 537         if (start <= raddr && raddr <= end && dhcpv4_test(iface, raddr)) {
 538                 assign->addr = raddr;
 539                 list_add(&assign->head, &iface->dhcpv4_assignments);
 540                 syslog(LOG_INFO, "assigning the IP the client asked for: %u.%u.%u.%u",
 541                                 (assign->addr & 0xff000000) >> 24,
 542                                 (assign->addr & 0x00ff0000) >> 16,
 543                                 (assign->addr & 0x0000ff00) >> 8,
 544                                 (assign->addr & 0x000000ff));
 545                 return true;
 546         }
 547
 548         // Seed RNG with checksum of hwaddress
 549         uint32_t seed = 0;
 550         for (size_t i = 0; i < sizeof(assign->hwaddr); ++i) {
 551                 // Knuth's multiplicative method
 552                 uint8_t o = assign->hwaddr[i];
 553                 seed += (o*2654435761) % UINT32_MAX;
 554         }
 555
 556         srand(seed);
 557
 558         uint32_t try = (((uint32_t)rand()) % count) + start;
 559
 560         if (list_empty(&iface->dhcpv4_assignments)) {
 561                 assign->addr = try;
 562                 list_add(&assign->head, &iface->dhcpv4_assignments);
 563                 syslog(LOG_INFO, "assigning mapped IP (empty list): %u.%u.%u.%u",
 564                                 (assign->addr & 0xff000000) >> 24,
 565                                 (assign->addr & 0x00ff0000) >> 16,
 566                                 (assign->addr & 0x0000ff00) >> 8,
 567                                 (assign->addr & 0x000000ff));
 568                 return true;
 569         }
 570
 571         for (uint32_t i = 0; i < count; ++i) {
 572                 if (dhcpv4_test(iface, try)) {
 573                         /* test was successful: IP address is not assigned, assign it */
 574                         assign->addr = try;
 575                         list_add(&assign->head, &iface->dhcpv4_assignments);
 576                         syslog(LOG_DEBUG, "assigning mapped IP: %u.%u.%u.%u (try %u of %u)",
 577                                         (assign->addr & 0xff000000) >> 24,
 578                                         (assign->addr & 0x00ff0000) >> 16,
 579                                         (assign->addr & 0x0000ff00) >> 8,
 580                                         (assign->addr & 0x000000ff), i, count);
 581                         return true;
 582                 }
 583                 try = (((try - start) + 1) % count) + start;
 584         }
 585
 586         syslog(LOG_WARNING, "can't assign any IP address -> address space is full");
 587         return false;
 588 }
 589
 590
 591 static struct dhcpv4_assignment* dhcpv4_lease(struct interface *iface,
 592                 enum dhcpv4_msg msg, const uint8_t *mac, struct in_addr reqaddr,
 593                 uint32_t *leasetime, const char *hostname, const size_t hostname_len)
 594 {
 595         struct dhcpv4_assignment *lease = NULL;
 596         uint32_t raddr = ntohl(reqaddr.s_addr);
 597         time_t now = odhcpd_time();
 598
 599         struct dhcpv4_assignment *c, *n, *a = NULL;
 600         list_for_each_entry_safe(c, n, &iface->dhcpv4_assignments, head) {
 601                 if (!memcmp(c->hwaddr, mac, 6)) {
 602                         a = c;
 603                         if (c->addr == raddr)
 604                                 break;
 605                 } else if (!INFINITE_VALID(c->valid_until) && c->valid_until < now)
 606                         free_dhcpv4_assignment(c);
 607         }
 608
 609         if (msg == DHCPV4_MSG_DISCOVER || msg == DHCPV4_MSG_REQUEST) {
 610                 bool assigned = !!a;
 611                 uint32_t my_leasetime;
 612
 613                 if (!a && !iface->no_dynamic_dhcp) {
 614                         /* Create new binding */
 615                         a = calloc(1, sizeof(*a));
 616                         if (!a) {
 617                                 syslog(LOG_ERR, "Failed to calloc binding on interface %s", iface->ifname);
 618                                 return NULL;
 619                         }
 620                         memcpy(a->hwaddr, mac, sizeof(a->hwaddr));
 621                         /* Don't consider new assignment as infinite */
 622                         a->valid_until = now;
 623
 624                         assigned = dhcpv4_assign(iface, a, raddr);
 625                 }
 626
 627                 if (a->leasetime)
 628                         my_leasetime = a->leasetime;
 629                 else
 630                         my_leasetime = iface->dhcpv4_leasetime;
 631
 632                 if ((*leasetime == 0) || (my_leasetime < *leasetime))
 633                         *leasetime = my_leasetime;
 634
 635                 if (assigned) {
 636                         if (msg == DHCPV4_MSG_DISCOVER) {
 637                                 a->flags &= ~OAF_BOUND;
 638
 639                                 if (!(a->flags & OAF_STATIC))
 640                                         a->valid_until = now;
 641                         } else {
 642                                 if (hostname_len > 0) {
 643                                         a->hostname = realloc(a->hostname, hostname_len + 1);
 644                                         if (a->hostname) {
 645                                                 memcpy(a->hostname, hostname, hostname_len);
 646                                                 a->hostname[hostname_len] = 0;
 647                                         }
 648                                 }
 649
 650                                 a->flags |= OAF_BOUND;
 651
 652                                 if (!(a->flags & OAF_STATIC))
 653                                         a->valid_until = ((*leasetime == UINT32_MAX) ? 0 : (time_t)(now + *leasetime));
 654                         }
 655                 } else if (!assigned && a) {
 656                         /* Cleanup failed assignment */
 657                         free_dhcpv4_assignment(a);
 658                         a = NULL;
 659                 }
 660
 661                 if (assigned && a)
 662                         lease = a;
 663         } else if (msg == DHCPV4_MSG_RELEASE && a) {
 664                 a->flags &= ~OAF_BOUND;
 665
 666                 if (!(a->flags & OAF_STATIC))
 667                         a->valid_until = now - 1;
 668
 669         } else if (msg == DHCPV4_MSG_DECLINE && a) {
 670                 a->flags &= ~OAF_BOUND;
 671
 672                 if (!(a->flags & OAF_STATIC)) {
 673                         memset(a->hwaddr, 0, sizeof(a->hwaddr));
 674                         a->valid_until = now + 3600; /* Block address for 1h */
 675                 }
 676         }
 677
 678         dhcpv6_write_statefile();
 679
 680         return lease;
 681 }