src/dhcpv4.c

   1 /**
   2  * Copyright (C) 2012-2013 Steven Barth <steven@midlink.org>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License v2 as published by
   6  * the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11  * GNU General Public License for more details.
  12  *
  13  *
  14  */
  15
  16 #include <time.h>
  17 #include <errno.h>
  18 #include <fcntl.h>
  19 #include <unistd.h>
  20 #include <stddef.h>
  21 #include <stdlib.h>
  22 #include <resolv.h>
  23 #include <limits.h>
  24 #include <net/if.h>
  25 #include <net/if_arp.h>
  26 #include <netinet/ip.h>
  27 #include <sys/ioctl.h>
  28 #include <sys/timerfd.h>
  29 #include <arpa/inet.h>
  30
  31 #include "odhcpd.h"
  32 #include "dhcpv4.h"
  33 #include "dhcpv6.h"
  34
  35
  36 static void handle_dhcpv4(void *addr, void *data, size_t len,
  37                 struct interface *iface, void *dest_addr);
  38 static struct dhcpv4_assignment* dhcpv4_lease(struct interface *iface,
  39                 enum dhcpv4_msg msg, const uint8_t *mac, struct in_addr reqaddr,
  40                 const char *hostname);
  41
  42 // Create socket and register events
  43 int init_dhcpv4(void)
  44 {
  45         return 0;
  46 }
  47
  48 char *dhcpv4_msg_to_string(uint8_t reqmsg)
  49 {
  50         switch (reqmsg) {
  51         case (DHCPV4_MSG_DISCOVER):
  52                 return "DHCPV4_MSG_DISCOVER";
  53         case (DHCPV4_MSG_OFFER):
  54                 return "DHCPV4_MSG_OFFER";
  55         case (DHCPV4_MSG_REQUEST):
  56                 return "DHCPV4_MSG_REQUEST";
  57         case (DHCPV4_MSG_DECLINE):
  58                 return "DHCPV4_MSG_DECLINE";
  59         case (DHCPV4_MSG_ACK):
  60                 return "DHCPV4_MSG_ACK";
  61         case (DHCPV4_MSG_NAK):
  62                 return "DHCPV4_MSG_NAK";
  63         case (DHCPV4_MSG_RELEASE):
  64                 return "DHCPV4_MSG_RELEASE";
  65         case (DHCPV4_MSG_INFORM):
  66                 return "DHCPV4_MSG_INFORM";
  67         default:
  68                 return "UNKNOWN";
  69         }
  70 }
  71
  72 int setup_dhcpv4_interface(struct interface *iface, bool enable)
  73 {
  74         if (iface->dhcpv4_event.uloop.fd > 0) {
  75                 uloop_fd_delete(&iface->dhcpv4_event.uloop);
  76                 close(iface->dhcpv4_event.uloop.fd);
  77                 iface->dhcpv4_event.uloop.fd = -1;
  78         }
  79
  80         if (iface->dhcpv4 && enable) {
  81                 if (!iface->dhcpv4_assignments.next)
  82                         INIT_LIST_HEAD(&iface->dhcpv4_assignments);
  83
  84                 int sock = socket(AF_INET, SOCK_DGRAM | SOCK_CLOEXEC, IPPROTO_UDP);
  85                 if (sock < 0) {
  86                         syslog(LOG_ERR, "Failed to create DHCPv4 server socket: %s",
  87                                         strerror(errno));
  88                         return -1;
  89                 }
  90
  91                 // Basic IPv6 configuration
  92                 int val = 1;
  93                 setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &val, sizeof(val));
  94                 setsockopt(sock, SOL_SOCKET, SO_BROADCAST, &val, sizeof(val));
  95                 setsockopt(sock, IPPROTO_IP, IP_PKTINFO, &val, sizeof(val));
  96
  97                 val = IPTOS_PREC_INTERNETCONTROL;
  98                 setsockopt(sock, IPPROTO_IP, IP_TOS, &val, sizeof(val));
  99
 100                 val = IP_PMTUDISC_DONT;
 101                 setsockopt(sock, IPPROTO_IP, IP_MTU_DISCOVER, &val, sizeof(val));
 102
 103                 setsockopt(sock, SOL_SOCKET, SO_BINDTODEVICE,
 104                                 iface->ifname, strlen(iface->ifname));
 105
 106                 struct sockaddr_in bind_addr = {AF_INET, htons(DHCPV4_SERVER_PORT),
 107                                         {INADDR_ANY}, {0}};
 108
 109                 if (bind(sock, (struct sockaddr*)&bind_addr, sizeof(bind_addr))) {
 110                         syslog(LOG_ERR, "Failed to open DHCPv4 server socket: %s",
 111                                         strerror(errno));
 112                         return -1;
 113                 }
 114
 115
 116                 if (ntohl(iface->dhcpv4_start.s_addr) > ntohl(iface->dhcpv4_end.s_addr)) {
 117                         syslog(LOG_ERR, "Invalid DHCP range");
 118                         return -1;
 119                 }
 120
 121 #ifndef WITH_UBUS
 122                 struct ifreq ifreq;
 123                 strncpy(ifreq.ifr_name, iface->ifname, sizeof(ifreq.ifr_name));
 124
 125                 struct sockaddr_in *saddr = (struct sockaddr_in*)&ifreq.ifr_addr;
 126                 struct sockaddr_in *smask = (struct sockaddr_in*)&ifreq.ifr_netmask;
 127
 128                 if (!ioctl(sock, SIOCGIFADDR, &ifreq)) {
 129                         struct in_addr addr = saddr->sin_addr;
 130                         iface->dhcpv4_addr.s_addr = addr.s_addr;
 131                         ioctl(sock, SIOCGIFNETMASK, &ifreq);
 132                         struct in_addr mask = smask->sin_addr;
 133                         iface->dhcpv4_mask.s_addr = mask.s_addr;
 134                 }
 135 #else
 136                 const char* saddr = ubus_get_address4(iface->name);
 137                 struct in_addr addr;
 138                 inet_pton(AF_INET,saddr, &addr);
 139                 iface->dhcpv4_addr.s_addr = addr.s_addr;
 140                 int bits = ubus_get_mask4(iface->name);
 141                 struct in_addr mask;
 142                 if (bits < -32 || bits > 32)
 143                         bits = 0;
 144
 145                 mask.s_addr = bits ? htonl(~((1 << (32 - abs(bits))) - 1)) : 0;
 146                 if (bits < 0)
 147                         mask.s_addr = ~mask.s_addr;
 148
 149                 iface->dhcpv4_mask.s_addr = mask.s_addr;
 150 #endif
 151
 152                 // Create a range if not specified
 153                 if (!(iface->dhcpv4_start.s_addr & htonl(0xffff0000)) &&
 154                                 !(iface->dhcpv4_end.s_addr & htonl(0xffff0000)) &&
 155                                 iface->dhcpv4_addr.s_addr) {
 156
 157                         uint32_t start = ntohl(iface->dhcpv4_start.s_addr);
 158                         uint32_t end = ntohl(iface->dhcpv4_end.s_addr);
 159
 160                         if (start && end && start < end &&
 161                                         start > ntohl(addr.s_addr & ~mask.s_addr) &&
 162                                         (start & ntohl(~mask.s_addr)) == start &&
 163                                         (end & ntohl(~mask.s_addr)) == end) {
 164                                 iface->dhcpv4_start.s_addr = htonl(start) |
 165                                                 (addr.s_addr & mask.s_addr);
 166                                 iface->dhcpv4_end.s_addr = htonl(end) |
 167                                                 (addr.s_addr & mask.s_addr);
 168                         } else if (ntohl(mask.s_addr) <= 0xfffffff0) {
 169                                 start = addr.s_addr & mask.s_addr;
 170                                 end = addr.s_addr & mask.s_addr;
 171
 172                                 if (ntohl(mask.s_addr) <= 0xffffff00) {
 173                                         iface->dhcpv4_start.s_addr = start | htonl(100);
 174                                         iface->dhcpv4_end.s_addr = end | htonl(250);
 175                                 } else if (ntohl(mask.s_addr) <= 0xffffffc0) {
 176                                         iface->dhcpv4_start.s_addr = start | htonl(10);
 177                                         iface->dhcpv4_end.s_addr = end | htonl(60);
 178                                 } else if (ntohl(mask.s_addr) <= 0xffffffe0) {
 179                                         iface->dhcpv4_start.s_addr = start | htonl(10);
 180                                         iface->dhcpv4_end.s_addr = end | htonl(30);
 181                                 } else {
 182                                         iface->dhcpv4_start.s_addr = start | htonl(3);
 183                                         iface->dhcpv4_end.s_addr = end | htonl(12);
 184                                 }
 185                         }
 186
 187
 188                 }
 189                 syslog(LOG_WARNING, "DHCPv4 dhcp addr  %s", inet_ntoa(iface->dhcpv4_addr));
 190                 syslog(LOG_WARNING, "DHCPv4 dhcp mask  %s", inet_ntoa(iface->dhcpv4_mask));
 191                 syslog(LOG_WARNING, "DHCPv4 dhcp start %s", inet_ntoa(iface->dhcpv4_start));
 192                 syslog(LOG_WARNING, "DHCPv4 dhcp end   %s", inet_ntoa(iface->dhcpv4_end));
 193
 194
 195                 // Parse static entries
 196                 struct lease *lease;
 197                 list_for_each_entry(lease, &leases, head) {
 198                         // Construct entry
 199                         size_t hostlen = strlen(lease->hostname) + 1;
 200                         struct dhcpv4_assignment *a = calloc(1, sizeof(*a) + hostlen);
 201                         if (!a) {
 202                                 syslog(LOG_ERR, "Calloc failed for static lease on interface %s",
 203                                         iface->ifname);
 204                                 return -1;
 205                         }
 206                         a->addr = ntohl(lease->ipaddr.s_addr);
 207                         memcpy(a->hwaddr, lease->mac.ether_addr_octet, sizeof(a->hwaddr));
 208                         memcpy(a->hostname, lease->hostname, hostlen);
 209                         a->valid_until = LONG_MAX;
 210
 211                         // Assign to all interfaces
 212                         struct dhcpv4_assignment *c;
 213                         list_for_each_entry(c, &iface->dhcpv4_assignments, head) {
 214                                 if (c->addr > a->addr) {
 215                                         list_add_tail(&a->head, &c->head);
 216                                         break;
 217                                 } else if (c->addr == a->addr) {
 218                                         // Already an assignment with that number
 219                                         break;
 220                                 }
 221                         }
 222                         if (&c->head == &iface->dhcpv4_assignments) {
 223                                 list_add(&a->head, &iface->dhcpv4_assignments);
 224                         }
 225
 226                         if (!a->head.next)
 227                                 free(a);
 228                 }
 229
 230                 // Clean invalid assignments
 231                 struct dhcpv4_assignment *a, *n;
 232                 list_for_each_entry_safe(a, n, &iface->dhcpv4_assignments, head) {
 233                         if ((htonl(a->addr) & mask.s_addr) !=
 234                                         (iface->dhcpv4_start.s_addr & mask.s_addr)) {
 235                                 list_del(&a->head);
 236                                 free(a);
 237                         }
 238                 }
 239
 240
 241                 if (iface->dhcpv4_leasetime < 60)
 242                         iface->dhcpv4_leasetime = 43200;
 243
 244                 iface->dhcpv4_event.uloop.fd = sock;
 245                 iface->dhcpv4_event.handle_dgram = handle_dhcpv4;
 246                 odhcpd_register(&iface->dhcpv4_event);
 247         } else if (iface->dhcpv4_assignments.next) {
 248                 while (!list_empty(&iface->dhcpv4_assignments)) {
 249                         struct dhcpv4_assignment *a = list_first_entry(&iface->dhcpv4_assignments,
 250                                         struct dhcpv4_assignment, head);
 251                         list_del(&a->head);
 252                         free(a);
 253                 }
 254
 255         }
 256         return 0;
 257 }
 258
 259
 260 static void dhcpv4_put(struct dhcpv4_message *msg, uint8_t **cookie,
 261                 uint8_t type, uint8_t len, const void *data)
 262 {
 263         uint8_t *c = *cookie;
 264         if (*cookie + 2 + len > (uint8_t*)&msg[1])
 265                 return;
 266
 267         *c++ = type;
 268         *c++ = len;
 269         memcpy(c, data, len);
 270
 271         *cookie = c + len;
 272 }
 273
 274
 275 // Simple DHCPv6-server for information requests
 276 static void handle_dhcpv4(void *addr, void *data, size_t len,
 277                 struct interface *iface, _unused void *dest_addr)
 278 {
 279         if (!iface->dhcpv4)
 280                 return;
 281
 282         struct dhcpv4_message *req = data;
 283         if (len < offsetof(struct dhcpv4_message, options) + 4 ||
 284                         req->op != DHCPV4_BOOTREQUEST || req->hlen != 6)
 285                 return;
 286
 287         int sock = iface->dhcpv4_event.uloop.fd;
 288
 289         syslog(LOG_NOTICE, "Got DHCPv4 request");
 290
 291         struct ifreq ifreq;
 292         memcpy(ifreq.ifr_name, iface->ifname, sizeof(ifreq.ifr_name));
 293         if (ioctl(sock, SIOCGIFADDR, &ifreq)) {
 294                 syslog(LOG_WARNING, "DHCPv4 failed to detect address: %s", strerror(errno));
 295                 return;
 296         }
 297
 298         uint32_t network = iface->dhcpv4_addr.s_addr & iface->dhcpv4_mask.s_addr;
 299
 300         if ((iface->dhcpv4_start.s_addr & iface->dhcpv4_mask.s_addr) != network ||
 301                         (iface->dhcpv4_end.s_addr & iface->dhcpv4_mask.s_addr) != network) {
 302                 syslog(LOG_WARNING, "DHCPv4 range out of assigned network");
 303                 return;
 304         }
 305
 306         struct ifreq ifr = {.ifr_name = ""};
 307         strncpy(ifr.ifr_name, iface->ifname, sizeof(ifr.ifr_name));
 308
 309         struct dhcpv4_message reply = {
 310                 .op = DHCPV4_BOOTREPLY,
 311                 .htype = 1,
 312                 .hlen = 6,
 313                 .hops = 0,
 314                 .xid = req->xid,
 315                 .secs = 0,
 316                 .flags = req->flags,
 317                 .ciaddr = {INADDR_ANY},
 318                 .giaddr = req->giaddr,
 319                 .siaddr = iface->dhcpv4_addr,
 320         };
 321         memcpy(reply.chaddr, req->chaddr, sizeof(reply.chaddr));
 322
 323         reply.options[0] = 0x63;
 324         reply.options[1] = 0x82;
 325         reply.options[2] = 0x53;
 326         reply.options[3] = 0x63;
 327
 328         uint8_t *cookie = &reply.options[4];
 329         uint8_t reqmsg = DHCPV4_MSG_REQUEST;
 330         uint8_t msg = DHCPV4_MSG_ACK;
 331
 332         struct in_addr reqaddr = {INADDR_ANY};
 333         char hostname[256];
 334         hostname[0] = 0;
 335
 336         uint8_t *start = &req->options[4];
 337         uint8_t *end = ((uint8_t*)data) + len;
 338         struct dhcpv4_option *opt;
 339         dhcpv4_for_each_option(start, end, opt) {
 340                 if (opt->type == DHCPV4_OPT_MESSAGE && opt->len == 1) {
 341                         reqmsg = opt->data[0];
 342                 } else if (opt->type == DHCPV4_OPT_HOSTNAME && opt->len > 0) {
 343                         memcpy(hostname, opt->data, opt->len);
 344                         hostname[opt->len] = 0;
 345                 } else if (opt->type == DHCPV4_OPT_IPADDRESS && opt->len == 4) {
 346                         memcpy(&reqaddr, opt->data, 4);
 347                 } else if (opt->type == DHCPV4_OPT_SERVERID && opt->len == 4) {
 348                         if (memcmp(opt->data, &iface->dhcpv4_addr, 4))
 349                                 return;
 350                 } else if (iface->filter_class && opt->type == DHCPV4_OPT_USER_CLASS) {
 351                         uint8_t *c = opt->data, *cend = &opt->data[opt->len];
 352                         for (; c < cend && &c[*c] < cend; c = &c[1 + *c]) {
 353                                 size_t elen = strlen(iface->filter_class);
 354                                 if (*c == elen && !memcmp(&c[1], iface->filter_class, elen))
 355                                         return; // Ignore from homenet
 356                         }
 357                 }
 358         }
 359
 360         if (reqmsg != DHCPV4_MSG_DISCOVER && reqmsg != DHCPV4_MSG_REQUEST &&
 361                         reqmsg != DHCPV4_MSG_INFORM && reqmsg != DHCPV4_MSG_DECLINE &&
 362                         reqmsg != DHCPV4_MSG_RELEASE)
 363                 return;
 364
 365         struct dhcpv4_assignment *lease = NULL;
 366         if (reqmsg != DHCPV4_MSG_INFORM)
 367                 lease = dhcpv4_lease(iface, reqmsg, req->chaddr, reqaddr, hostname);
 368
 369         if (!lease) {
 370                 if (reqmsg == DHCPV4_MSG_REQUEST)
 371                         msg = DHCPV4_MSG_NAK;
 372                 else if (reqmsg == DHCPV4_MSG_DISCOVER)
 373                         return;
 374         } else if (reqmsg == DHCPV4_MSG_DISCOVER) {
 375                 msg = DHCPV4_MSG_OFFER;
 376         } else if (reqmsg == DHCPV4_MSG_REQUEST && reqaddr.s_addr &&
 377                         reqaddr.s_addr != htonl(lease->addr)) {
 378                 msg = DHCPV4_MSG_NAK;
 379                 /*
 380                  * DHCP client requested an IP which we can't offer to him. Probably the
 381                  * client changed the network. The reply type is set to DHCPV4_MSG_NAK,
 382                  * because the client should not use that IP.
 383                  *
 384                  * For modern devices we build an answer that includes a valid IP, like
 385                  * a DHCPV4_MSG_ACK. The client will use that IP and doesn't need to
 386                  * perform additional DHCP round trips.
 387                  *
 388                  */
 389         }
 390
 391         syslog(LOG_WARNING, "received %s from %x:%x:%x:%x:%x:%x",
 392                         dhcpv4_msg_to_string(reqmsg),
 393                         req->chaddr[0],req->chaddr[1],req->chaddr[2],
 394                         req->chaddr[3],req->chaddr[4],req->chaddr[5]);
 395
 396         if (reqmsg == DHCPV4_MSG_DECLINE || reqmsg == DHCPV4_MSG_RELEASE)
 397                 return;
 398
 399         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_MESSAGE, 1, &msg);
 400         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SERVERID, 4, &iface->dhcpv4_addr);
 401
 402         if (lease) {
 403                 reply.yiaddr.s_addr = htonl(lease->addr);
 404
 405                 uint32_t val = htonl(iface->dhcpv4_leasetime);
 406                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_LEASETIME, 4, &val);
 407
 408                 val = htonl(500 * iface->dhcpv4_leasetime / 1000);
 409                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_RENEW, 4, &val);
 410
 411                 val = htonl(875 * iface->dhcpv4_leasetime / 1000);
 412                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_REBIND, 4, &val);
 413
 414                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_NETMASK, 4, &iface->dhcpv4_mask);
 415
 416                 if (lease->hostname[0])
 417                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_HOSTNAME,
 418                                         strlen(lease->hostname), lease->hostname);
 419
 420                 if (!ioctl(sock, SIOCGIFBRDADDR, &ifr)) {
 421                         struct sockaddr_in *ina = (struct sockaddr_in*)&ifr.ifr_broadaddr;
 422                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_BROADCAST, 4, &ina->sin_addr);
 423                 }
 424         }
 425
 426         if (!ioctl(sock, SIOCGIFMTU, &ifr)) {
 427                 uint16_t mtu = htons(ifr.ifr_mtu);
 428                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_MTU, 2, &mtu);
 429         }
 430
 431         if (iface->search && iface->search_len <= 255) {
 432                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SEARCH_DOMAIN,
 433                                 iface->search_len, iface->search);
 434         } else if (!res_init() && _res.dnsrch[0] && _res.dnsrch[0][0]) {
 435                 uint8_t search_buf[256];
 436                 int len = dn_comp(_res.dnsrch[0], search_buf,
 437                                                 sizeof(search_buf), NULL, NULL);
 438                 if (len > 0)
 439                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SEARCH_DOMAIN,
 440                                         len, search_buf);
 441         }
 442
 443         if (iface->dhcpv4_router_cnt == 0)
 444                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_ROUTER, 4, &iface->dhcpv4_addr);
 445         else
 446                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_ROUTER,
 447                                 4 * iface->dhcpv4_router_cnt, iface->dhcpv4_router);
 448
 449
 450         if (iface->dhcpv4_dns_cnt == 0)
 451                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_DNSSERVER, 4, &iface->dhcpv4_addr);
 452         else
 453                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_DNSSERVER,
 454                                 4 * iface->dhcpv4_dns_cnt, iface->dhcpv4_dns);
 455
 456
 457         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_END, 0, NULL);
 458
 459         struct sockaddr_in dest = *((struct sockaddr_in*)addr);
 460         if (req->giaddr.s_addr) {
 461                 /*
 462                  * relay agent is configured, send reply to the agent
 463                  */
 464                 dest.sin_addr = req->giaddr;
 465                 dest.sin_port = htons(DHCPV4_SERVER_PORT);
 466         } else if (req->ciaddr.s_addr && req->ciaddr.s_addr != dest.sin_addr.s_addr) {
 467                 /*
 468                  * client has existing configuration (ciaddr is set) AND this address is
 469                  * not the address it used for the dhcp message
 470                  */
 471                 dest.sin_addr = req->ciaddr;
 472                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 473         } else if ((ntohs(req->flags) & DHCPV4_FLAG_BROADCAST) ||
 474                         req->hlen != reply.hlen || !reply.yiaddr.s_addr) {
 475                 /*
 476                  * client requests a broadcast reply OR we can't offer an IP
 477                  */
 478                 dest.sin_addr.s_addr = INADDR_BROADCAST;
 479                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 480         } else if (!req->ciaddr.s_addr && msg == DHCPV4_MSG_NAK) {
 481                 /*
 482                  * client has no previous configuration -> no IP, so we need to reply
 483                  * with a broadcast packet
 484                  */
 485                 dest.sin_addr.s_addr = INADDR_BROADCAST;
 486                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 487         } else {
 488                 /*
 489                  * send reply to the newly (in this proccess) allocated IP
 490                  */
 491                 dest.sin_addr = reply.yiaddr;
 492                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 493
 494                 struct arpreq arp = {.arp_flags = ATF_COM};
 495                 memcpy(arp.arp_ha.sa_data, req->chaddr, 6);
 496                 memcpy(&arp.arp_pa, &dest, sizeof(arp.arp_pa));
 497                 memcpy(arp.arp_dev, iface->ifname, sizeof(arp.arp_dev));
 498                 ioctl(sock, SIOCSARP, &arp);
 499         }
 500
 501         if (dest.sin_addr.s_addr == INADDR_BROADCAST) {
 502                 /*
 503                  * reply goes to IP broadcast -> MAC broadcast
 504                  */
 505                 syslog(LOG_WARNING, "sending %s to ff:ff:ff:ff:ff:ff - %s",
 506                                 dhcpv4_msg_to_string(msg),
 507                                 inet_ntoa(dest.sin_addr));
 508         } else {
 509                 /*
 510                  * reply is send directly to IP,
 511                  * MAC is assumed to be the same as the request
 512                  */
 513                 syslog(LOG_WARNING, "sending %s to %x:%x:%x:%x:%x:%x - %s",
 514                                 dhcpv4_msg_to_string(msg),
 515                                 req->chaddr[0],req->chaddr[1],req->chaddr[2],
 516                                 req->chaddr[3],req->chaddr[4],req->chaddr[5],
 517                                 inet_ntoa(dest.sin_addr));
 518         }
 519
 520         sendto(sock, &reply, sizeof(reply), MSG_DONTWAIT,
 521                         (struct sockaddr*)&dest, sizeof(dest));
 522 }
 523
 524 static bool dhcpv4_test(struct interface *iface, uint32_t try)
 525 {
 526         struct dhcpv4_assignment *c;
 527         list_for_each_entry(c, &iface->dhcpv4_assignments, head) {
 528                 if (c->addr == try) {
 529                         return false;
 530                 }
 531         }
 532         return true;
 533 }
 534
 535 static bool dhcpv4_assign(struct interface *iface,
 536                 struct dhcpv4_assignment *assign, uint32_t raddr)
 537 {
 538         uint32_t start = ntohl(iface->dhcpv4_start.s_addr);
 539         uint32_t end = ntohl(iface->dhcpv4_end.s_addr);
 540         uint32_t count = end - start + 1;
 541
 542         // try to assign the IP the client asked for
 543         if (start <= raddr && raddr <= end && dhcpv4_test(iface, raddr)) {
 544                 assign->addr = raddr;
 545                 list_add(&assign->head, &iface->dhcpv4_assignments);
 546                 syslog(LOG_DEBUG, "assigning the IP the client asked for: %u.%u.%u.%u",
 547                                 (assign->addr & 0xff000000) >> 24,
 548                                 (assign->addr & 0x00ff0000) >> 16,
 549                                 (assign->addr & 0x0000ff00) >> 8,
 550                                 (assign->addr & 0x000000ff));
 551                 return true;
 552         }
 553
 554         // Seed RNG with checksum of hwaddress
 555         uint32_t seed = 0;
 556         for (size_t i = 0; i < sizeof(assign->hwaddr); ++i) {
 557                 // Knuth's multiplicative method
 558                 uint8_t o = assign->hwaddr[i];
 559                 seed += (o*2654435761) % UINT32_MAX;
 560         }
 561         srand(seed);
 562
 563         uint32_t try = (((uint32_t)rand()) % count) + start;
 564
 565         if (list_empty(&iface->dhcpv4_assignments)) {
 566                 assign->addr = try;
 567                 list_add(&assign->head, &iface->dhcpv4_assignments);
 568                 syslog(LOG_DEBUG, "assigning mapped IP (empty list): %u.%u.%u.%u",
 569                                 (assign->addr & 0xff000000) >> 24,
 570                                 (assign->addr & 0x00ff0000) >> 16,
 571                                 (assign->addr & 0x0000ff00) >> 8,
 572                                 (assign->addr & 0x000000ff));
 573                 return true;
 574         }
 575
 576         for (uint32_t i = 0; i < count; ++i) {
 577                 if (dhcpv4_test(iface, try)) {
 578                         /* test was successful: IP address is not assigned, assign it */
 579                         assign->addr = try;
 580                         list_add(&assign->head, &iface->dhcpv4_assignments);
 581                         syslog(LOG_DEBUG, "assigning mapped IP: %u.%u.%u.%u (try %u of %u)",
 582                                         (assign->addr & 0xff000000) >> 24,
 583                                         (assign->addr & 0x00ff0000) >> 16,
 584                                         (assign->addr & 0x0000ff00) >> 8,
 585                                         (assign->addr & 0x000000ff), i, count);
 586                         return true;
 587                 }
 588                 try = (((try - start) + 1) % count) + start;
 589         }
 590
 591         syslog(LOG_DEBUG, "can't assign any IP address -> address space is full");
 592         return false;
 593 }
 594
 595
 596 static struct dhcpv4_assignment* dhcpv4_lease(struct interface *iface,
 597                 enum dhcpv4_msg msg, const uint8_t *mac, struct in_addr reqaddr,
 598                 const char *hostname)
 599 {
 600         struct dhcpv4_assignment *lease = NULL;
 601         uint32_t raddr = ntohl(reqaddr.s_addr);
 602         time_t now = odhcpd_time();
 603
 604         struct dhcpv4_assignment *c, *n, *a = NULL;
 605         list_for_each_entry_safe(c, n, &iface->dhcpv4_assignments, head) {
 606                 if (!memcmp(c->hwaddr, mac, 6)) {
 607                         a = c;
 608                         if (c->addr == raddr)
 609                                 break;
 610                 } else if (c->valid_until < now) {
 611                         list_del(&c->head);
 612                         free(c);
 613                 }
 614         }
 615
 616         if (msg == DHCPV4_MSG_DISCOVER || msg == DHCPV4_MSG_REQUEST) {
 617                 bool assigned = !!a;
 618                 size_t hostlen = strlen(hostname) + 1;
 619
 620                 if (!a && !iface->no_dynamic_dhcp) { // Create new binding
 621                         a = calloc(1, sizeof(*a) + hostlen);
 622                         if (!a) {
 623                                 syslog(LOG_ERR, "Failed to calloc binding on interface %s", iface->ifname);
 624                                 return NULL;
 625                         }
 626                         memcpy(a->hwaddr, mac, sizeof(a->hwaddr));
 627                         memcpy(a->hostname, hostname, hostlen);
 628
 629                         assigned = dhcpv4_assign(iface, a, raddr);
 630                 }
 631
 632                 if (assigned && !a->hostname[0] && hostname) {
 633                         a = realloc(a, sizeof(*a) + hostlen);
 634                         if (!a) {
 635                                 syslog(LOG_ERR, "Failed to realloc binding on interface %s", iface->ifname);
 636                                 return NULL;
 637                         }
 638                         memcpy(a->hostname, hostname, hostlen);
 639
 640                         // Fixup list
 641                         a->head.next->prev = &a->head;
 642                         a->head.prev->next = &a->head;
 643                 }
 644
 645                 // Was only a solicitation: mark binding for removal
 646                 if (assigned && a->valid_until < now) {
 647                         a->valid_until = (msg == DHCPV4_MSG_DISCOVER) ? 0 :
 648                                         (now + iface->dhcpv4_leasetime);
 649                 } else if (!assigned && a) { // Cleanup failed assignment
 650                         free(a);
 651                         a = NULL;
 652                 }
 653
 654                 if (assigned && a)
 655                         lease = a;
 656         } else if (msg == DHCPV4_MSG_RELEASE) {
 657                 if (a && a->valid_until != LONG_MAX)
 658                         a->valid_until = 0;
 659         } else if (msg == DHCPV4_MSG_DECLINE && a && a->valid_until != LONG_MAX) {
 660                 memset(a->hwaddr, 0, sizeof(a->hwaddr));
 661                 a->valid_until = now + 3600; // Block address for 1h
 662         }
 663
 664         dhcpv6_write_statefile();
 665
 666         return lease;
 667 }
 668