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 <libubox/md5.h>
  33
  34 #include "odhcpd.h"
  35 #include "dhcpv4.h"
  36 #include "dhcpv6.h"
  37
  38 static int setup_dhcpv4_addresses(struct interface *iface);
  39 static void update_static_assignments(struct interface *iface);
  40 static void valid_until_cb(struct uloop_timeout *event);
  41 static void free_dhcpv4_assignment(struct dhcpv4_assignment *a);
  42 static void dhcpv4_fr_start(struct dhcpv4_assignment *a);
  43 static void dhcpv4_fr_stop(struct dhcpv4_assignment *a);
  44 static void handle_dhcpv4(void *addr, void *data, size_t len,
  45                 struct interface *iface, void *dest_addr);
  46 static struct dhcpv4_assignment* dhcpv4_lease(struct interface *iface,
  47                 enum dhcpv4_msg msg, const uint8_t *mac, struct in_addr reqaddr,
  48                 uint32_t *leasetime, const char *hostname, const size_t hostname_len,
  49                 const bool accept_fr_nonce, bool *incl_fr_opt, uint32_t *fr_serverid);
  50
  51 static struct uloop_timeout valid_until_timeout = {.cb = valid_until_cb};
  52 static uint32_t serial = 0;
  53
  54 struct odhcpd_ref_ip {
  55         struct list_head head;
  56         int ref_cnt;
  57         struct odhcpd_ipaddr addr;
  58 };
  59
  60 /* Create socket and register events */
  61 int init_dhcpv4(void)
  62 {
  63         uloop_timeout_set(&valid_until_timeout, 1000);
  64         return 0;
  65 }
  66
  67 int setup_dhcpv4_interface(struct interface *iface, bool enable)
  68 {
  69         if (iface->dhcpv4_event.uloop.fd > 0) {
  70                 uloop_fd_delete(&iface->dhcpv4_event.uloop);
  71                 close(iface->dhcpv4_event.uloop.fd);
  72                 iface->dhcpv4_event.uloop.fd = -1;
  73         }
  74
  75         if (iface->dhcpv4 && enable) {
  76                 if (!iface->dhcpv4_assignments.next)
  77                         INIT_LIST_HEAD(&iface->dhcpv4_assignments);
  78
  79                 if (!iface->dhcpv4_fr_ips.next)
  80                         INIT_LIST_HEAD(&iface->dhcpv4_fr_ips);
  81
  82                 int sock = socket(AF_INET, SOCK_DGRAM | SOCK_CLOEXEC, IPPROTO_UDP);
  83                 if (sock < 0) {
  84                         syslog(LOG_ERR, "Failed to create DHCPv4 server socket: %s",
  85                                         strerror(errno));
  86                         return -1;
  87                 }
  88
  89                 /* Basic IPv4 configuration */
  90                 int val = 1;
  91                 setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &val, sizeof(val));
  92                 setsockopt(sock, SOL_SOCKET, SO_BROADCAST, &val, sizeof(val));
  93                 setsockopt(sock, IPPROTO_IP, IP_PKTINFO, &val, sizeof(val));
  94
  95                 val = IPTOS_PREC_INTERNETCONTROL;
  96                 setsockopt(sock, IPPROTO_IP, IP_TOS, &val, sizeof(val));
  97
  98                 val = IP_PMTUDISC_DONT;
  99                 setsockopt(sock, IPPROTO_IP, IP_MTU_DISCOVER, &val, sizeof(val));
 100
 101                 setsockopt(sock, SOL_SOCKET, SO_BINDTODEVICE,
 102                                 iface->ifname, strlen(iface->ifname));
 103
 104                 struct sockaddr_in bind_addr = {AF_INET, htons(DHCPV4_SERVER_PORT),
 105                                         {INADDR_ANY}, {0}};
 106
 107                 if (bind(sock, (struct sockaddr*)&bind_addr, sizeof(bind_addr))) {
 108                         syslog(LOG_ERR, "Failed to open DHCPv4 server socket: %s",
 109                                         strerror(errno));
 110                         return -1;
 111                 }
 112
 113                 iface->dhcpv4_event.uloop.fd = sock;
 114                 iface->dhcpv4_event.handle_dgram = handle_dhcpv4;
 115                 odhcpd_register(&iface->dhcpv4_event);
 116
 117                 if (setup_dhcpv4_addresses(iface) < 0)
 118                         return -1;
 119
 120                 update_static_assignments(iface);
 121         } else if (iface->dhcpv4_assignments.next) {
 122                 while (!list_empty(&iface->dhcpv4_assignments))
 123                         free_dhcpv4_assignment(list_first_entry(&iface->dhcpv4_assignments,
 124                                                         struct dhcpv4_assignment, head));
 125         }
 126         return 0;
 127 }
 128
 129 static struct dhcpv4_assignment *find_assignment_by_hwaddr(struct interface *iface, const uint8_t *hwaddr)
 130 {
 131         struct dhcpv4_assignment *a;
 132
 133         list_for_each_entry(a, &iface->dhcpv4_assignments, head)
 134                 if (!memcmp(a->hwaddr, hwaddr, 6))
 135                         return a;
 136
 137         return NULL;
 138 }
 139
 140 static struct dhcpv4_assignment *find_assignment_by_addr(struct interface *iface, const uint32_t addr)
 141 {
 142         struct dhcpv4_assignment *a;
 143
 144         list_for_each_entry(a, &iface->dhcpv4_assignments, head)
 145                 if (a->addr == addr)
 146                         return a;
 147
 148         return NULL;
 149 }
 150
 151 static int setup_dhcpv4_addresses(struct interface *iface)
 152 {
 153         iface->dhcpv4_start_ip.s_addr = INADDR_ANY;
 154         iface->dhcpv4_end_ip.s_addr = INADDR_ANY;
 155         iface->dhcpv4_local.s_addr = INADDR_ANY;
 156         iface->dhcpv4_bcast.s_addr = INADDR_ANY;
 157         iface->dhcpv4_mask.s_addr = INADDR_ANY;
 158
 159         /* Sanity checks */
 160         if (iface->dhcpv4_start.s_addr & htonl(0xffff0000) ||
 161             iface->dhcpv4_end.s_addr & htonl(0xffff0000) ||
 162             ntohl(iface->dhcpv4_start.s_addr) > ntohl(iface->dhcpv4_end.s_addr)) {
 163                 syslog(LOG_ERR, "invalid DHCP range for %s", iface->name);
 164                 return -1;
 165         }
 166
 167         if (!iface->addr4_len) {
 168                 syslog(LOG_WARNING, "no network(s) available on %s", iface->name);
 169                 return -1;
 170         }
 171
 172         uint32_t start = ntohl(iface->dhcpv4_start.s_addr);
 173         uint32_t end = ntohl(iface->dhcpv4_end.s_addr);
 174
 175         for (size_t i = 0; i < iface->addr4_len && start && end; i++) {
 176                 struct in_addr *addr = &iface->addr4[i].addr.in;
 177                 struct in_addr mask;
 178
 179                 odhcpd_bitlen2netmask(false, iface->addr4[i].prefix, &mask);
 180                 if ((start & ntohl(~mask.s_addr)) == start &&
 181                             (end & ntohl(~mask.s_addr)) == end) {
 182                         iface->dhcpv4_start_ip.s_addr = htonl(start) |
 183                                                         (addr->s_addr & mask.s_addr);
 184                         iface->dhcpv4_end_ip.s_addr = htonl(end) |
 185                                                         (addr->s_addr & mask.s_addr);
 186                         iface->dhcpv4_local = *addr;
 187                         iface->dhcpv4_bcast = iface->addr4[i].broadcast;
 188                         iface->dhcpv4_mask = mask;
 189                         return 0;
 190                 }
 191         }
 192
 193         /* Don't allocate IP range for subnets bigger than 28 */
 194         if (iface->addr4[0].prefix > 28) {
 195                 syslog(LOG_WARNING, "auto allocation of DHCP range fails on %s", iface->name);
 196                 return -1;
 197         }
 198
 199         iface->dhcpv4_local = iface->addr4[0].addr.in;
 200         iface->dhcpv4_bcast = iface->addr4[0].broadcast;
 201         odhcpd_bitlen2netmask(false, iface->addr4[0].prefix, &iface->dhcpv4_mask);
 202         end = start = iface->dhcpv4_local.s_addr & iface->dhcpv4_mask.s_addr;
 203
 204         /* Auto allocate ranges */
 205         if (ntohl(iface->dhcpv4_mask.s_addr) <= 0xffffff00) {
 206                 iface->dhcpv4_start_ip.s_addr = start | htonl(100);
 207                 iface->dhcpv4_end_ip.s_addr = end | htonl(250);
 208         } else if (ntohl(iface->dhcpv4_mask.s_addr) <= 0xffffffc0) {
 209                 iface->dhcpv4_start_ip.s_addr = start | htonl(10);
 210                 iface->dhcpv4_end_ip.s_addr = end | htonl(60);
 211         } else if (ntohl(iface->dhcpv4_mask.s_addr) <= 0xffffffe0) {
 212                 iface->dhcpv4_start_ip.s_addr = start | htonl(10);
 213                 iface->dhcpv4_end_ip.s_addr = end | htonl(30);
 214         } else {
 215                 iface->dhcpv4_start_ip.s_addr = start | htonl(3);
 216                 iface->dhcpv4_end_ip.s_addr = end | htonl(12);
 217         }
 218
 219         return 0;
 220 }
 221
 222 static void update_static_assignments(struct interface *iface)
 223 {
 224         struct dhcpv4_assignment *a, *c;
 225
 226         /* Cleanup static entries not belonging to the network */
 227         list_for_each_entry_safe(a, c, &iface->dhcpv4_assignments, head) {
 228                 if ((a->flags & OAF_STATIC) &&
 229                                 ((a->addr & iface->dhcpv4_mask.s_addr) !=
 230                                  (iface->dhcpv4_start.s_addr & iface->dhcpv4_mask.s_addr)))
 231                         free_dhcpv4_assignment(a);
 232         }
 233
 234         /* Parse static entries */
 235         struct lease *lease;
 236         list_for_each_entry(lease, &leases, head) {
 237                 if ((iface->dhcpv4_start_ip.s_addr & iface->dhcpv4_mask.s_addr) !=
 238                                 (lease->ipaddr.s_addr & iface->dhcpv4_mask.s_addr)) {
 239                         continue;
 240                 }
 241
 242                 a = find_assignment_by_hwaddr(iface, lease->mac.ether_addr_octet);
 243
 244                 if (!a) {
 245                         /* Check if there's an assignment with the specified IP address */
 246                         if (find_assignment_by_addr(iface, lease->ipaddr.s_addr))
 247                                 continue;
 248
 249                         /* Construct entry */
 250                         a = calloc(1, sizeof(*a));
 251                         if (!a) {
 252                                 syslog(LOG_ERR, "Calloc failed for static lease on interface %s",
 253                                         iface->ifname);
 254                                 continue;
 255                         }
 256                         memcpy(a->hwaddr, lease->mac.ether_addr_octet, sizeof(a->hwaddr));
 257                 }
 258
 259                 a->leasetime = lease->dhcpv4_leasetime;
 260
 261                 a->addr = lease->ipaddr.s_addr;
 262                 /* Static assignment */
 263                 a->flags |= OAF_STATIC;
 264                 /* Infinite valid */
 265                 a->valid_until = 0;
 266                 a->iface = iface;
 267                 if (lease->hostname[0]) {
 268                         free(a->hostname);
 269                         a->hostname = strdup(lease->hostname);
 270                 }
 271
 272                 /* Assign to all interfaces */
 273                 list_for_each_entry(c, &iface->dhcpv4_assignments, head) {
 274                         if (ntohl(c->addr) > ntohl(a->addr)) {
 275                                 list_add_tail(&a->head, &c->head);
 276                                 break;
 277                         }
 278                 }
 279
 280                 if (&c->head == &iface->dhcpv4_assignments)
 281                         list_add(&a->head, &iface->dhcpv4_assignments);
 282         }
 283 }
 284
 285 static void inc_ref_cnt_ip(struct odhcpd_ref_ip **ptr, struct odhcpd_ref_ip *ip)
 286 {
 287         *ptr = ip;
 288         ip->ref_cnt++;
 289 }
 290
 291 static void decr_ref_cnt_ip(struct odhcpd_ref_ip **ptr, struct interface *iface)
 292 {
 293         struct odhcpd_ref_ip *ip = *ptr;
 294
 295         if (--ip->ref_cnt == 0) {
 296                 odhcpd_setup_addr(&ip->addr, iface, false, false);
 297
 298                 list_del(&ip->head);
 299                 free(ip);
 300         }
 301
 302         *ptr = NULL;
 303 }
 304
 305 static bool leases_require_fr(struct interface *iface, struct odhcpd_ipaddr *addr,
 306                                 uint32_t mask)
 307 {
 308         struct dhcpv4_assignment *a = NULL;
 309         struct odhcpd_ref_ip *fr_ip = NULL;
 310
 311         list_for_each_entry(a, &iface->dhcpv4_assignments, head) {
 312                 if ((a->accept_fr_nonce || iface->dhcpv4_forcereconf) &&
 313                     !a->fr_ip &&
 314                     ((a->addr & mask) == (addr->addr.in.s_addr & mask))) {
 315                         if (!fr_ip) {
 316                                 fr_ip = calloc(1, sizeof(*fr_ip));
 317                                 if (!fr_ip)
 318                                         break;
 319
 320                                 list_add(&fr_ip->head, &iface->dhcpv4_fr_ips);
 321                                 fr_ip->addr = *addr;
 322                         }
 323                         inc_ref_cnt_ip(&a->fr_ip, fr_ip);
 324                 }
 325         }
 326
 327         return fr_ip ? true : false;
 328 }
 329
 330 static void valid_until_cb(struct uloop_timeout *event)
 331 {
 332         time_t now = odhcpd_time();
 333         struct interface *iface;
 334         list_for_each_entry(iface, &interfaces, head) {
 335                 if (iface->dhcpv4 != MODE_SERVER || iface->dhcpv4_assignments.next == NULL)
 336                         continue;
 337
 338                 struct dhcpv4_assignment *a, *n;
 339                 list_for_each_entry_safe(a, n, &iface->dhcpv4_assignments, head) {
 340                         if (!INFINITE_VALID(a->valid_until) && a->valid_until < now)
 341                                 free_dhcpv4_assignment(a);
 342                 }
 343         }
 344         uloop_timeout_set(event, 1000);
 345 }
 346
 347 void dhcpv4_addr_update(struct interface *iface)
 348 {
 349         if (iface->dhcpv4 == MODE_DISABLED)
 350                 return;
 351
 352         struct odhcpd_ipaddr ip;
 353         struct odhcpd_ref_ip *a;
 354         struct dhcpv4_assignment *c;
 355         uint32_t mask = iface->dhcpv4_mask.s_addr;
 356
 357         memset(&ip, sizeof(ip), 0);
 358         ip.addr.in = iface->dhcpv4_local;
 359         ip.prefix = odhcpd_netmask2bitlen(false, &iface->dhcpv4_mask);
 360         ip.broadcast = iface->dhcpv4_bcast;
 361
 362         setup_dhcpv4_addresses(iface);
 363
 364         if ((ip.addr.in.s_addr & mask) ==
 365             (iface->dhcpv4_local.s_addr & iface->dhcpv4_mask.s_addr))
 366                 return;
 367
 368         if (ip.addr.in.s_addr && !leases_require_fr(iface, &ip, mask))
 369                 return;
 370
 371         if (iface->dhcpv4_local.s_addr == INADDR_ANY || list_empty(&iface->dhcpv4_fr_ips))
 372                 return;
 373
 374         a = list_first_entry(&iface->dhcpv4_fr_ips, struct odhcpd_ref_ip, head);
 375
 376         if (odhcpd_setup_addr(&a->addr, iface, false, true)) {
 377                 syslog(LOG_ERR, "Failed to add ip address");
 378                 return;
 379         }
 380
 381         list_for_each_entry(c, &iface->dhcpv4_assignments, head) {
 382                 if ((c->flags & OAF_BOUND) && c->fr_ip && !c->fr_cnt) {
 383                         if (c->accept_fr_nonce || iface->dhcpv4_forcereconf)
 384                                 dhcpv4_fr_start(c);
 385                         else
 386                                 dhcpv4_fr_stop(c);
 387                 }
 388         }
 389 }
 390
 391 static char *dhcpv4_msg_to_string(uint8_t reqmsg)
 392 {
 393         switch (reqmsg) {
 394         case (DHCPV4_MSG_DISCOVER):
 395                 return "DHCPV4_MSG_DISCOVER";
 396         case (DHCPV4_MSG_OFFER):
 397                 return "DHCPV4_MSG_OFFER";
 398         case (DHCPV4_MSG_REQUEST):
 399                 return "DHCPV4_MSG_REQUEST";
 400         case (DHCPV4_MSG_DECLINE):
 401                 return "DHCPV4_MSG_DECLINE";
 402         case (DHCPV4_MSG_ACK):
 403                 return "DHCPV4_MSG_ACK";
 404         case (DHCPV4_MSG_NAK):
 405                 return "DHCPV4_MSG_NAK";
 406         case (DHCPV4_MSG_RELEASE):
 407                 return "DHCPV4_MSG_RELEASE";
 408         case (DHCPV4_MSG_INFORM):
 409                 return "DHCPV4_MSG_INFORM";
 410         case (DHCPV4_MSG_FORCERENEW):
 411                 return "DHCPV4_MSG_FORCERENEW";
 412         default:
 413                 return "UNKNOWN";
 414         }
 415 }
 416
 417 static void free_dhcpv4_assignment(struct dhcpv4_assignment *a)
 418 {
 419         if (a->head.next)
 420                 list_del(&a->head);
 421
 422         if (a->fr_ip)
 423                 dhcpv4_fr_stop(a);
 424
 425         free(a->hostname);
 426         free(a);
 427 }
 428
 429 static void dhcpv4_put(struct dhcpv4_message *msg, uint8_t **cookie,
 430                 uint8_t type, uint8_t len, const void *data)
 431 {
 432         uint8_t *c = *cookie;
 433         if (*cookie + 2 + len > (uint8_t*)&msg[1])
 434                 return;
 435
 436         *c++ = type;
 437         *c++ = len;
 438         memcpy(c, data, len);
 439
 440         *cookie = c + len;
 441 }
 442
 443 static void dhcpv4_fr_send(struct dhcpv4_assignment *a)
 444 {
 445         struct dhcpv4_message fr_msg = {
 446                 .op = DHCPV4_BOOTREPLY,
 447                 .htype = 1,
 448                 .hlen = 6,
 449                 .hops = 0,
 450                 .secs = 0,
 451                 .flags = 0,
 452                 .ciaddr = {INADDR_ANY},
 453                 .yiaddr = {INADDR_ANY},
 454                 .siaddr = {INADDR_ANY},
 455                 .giaddr = {INADDR_ANY},
 456                 .chaddr = {0},
 457                 .sname = {0},
 458                 .file = {0},
 459         };
 460         struct dhcpv4_auth_forcerenew *auth_o, auth = {
 461                 .protocol = 3,
 462                 .algorithm = 1,
 463                 .rdm = 0,
 464                 .replay = {htonl(time(NULL)), htonl(++serial)},
 465                 .type = 2,
 466                 .key = {0},
 467         };
 468         struct interface *iface = a->iface;
 469
 470         odhcpd_urandom(&fr_msg.xid, sizeof(fr_msg.xid));
 471         memcpy(fr_msg.chaddr, a->hwaddr, fr_msg.hlen);
 472
 473         fr_msg.options[0] = 0x63;
 474         fr_msg.options[1] = 0x82;
 475         fr_msg.options[2] = 0x53;
 476         fr_msg.options[3] = 0x63;
 477
 478         uint8_t *cookie = &fr_msg.options[4];
 479         uint8_t msg = DHCPV4_MSG_FORCERENEW;
 480
 481         dhcpv4_put(&fr_msg, &cookie, DHCPV4_OPT_MESSAGE, 1, &msg);
 482         if (a->accept_fr_nonce) {
 483                 dhcpv4_put(&fr_msg, &cookie, DHCPV4_OPT_AUTHENTICATION, sizeof(auth), &auth);
 484                 auth_o = (struct dhcpv4_auth_forcerenew *)(cookie - sizeof(auth));
 485                 dhcpv4_put(&fr_msg, &cookie, DHCPV4_OPT_END, 0, NULL);
 486
 487                 md5_ctx_t md5;
 488                 uint8_t secretbytes[64];
 489                 memset(secretbytes, 0, sizeof(secretbytes));
 490                 memcpy(secretbytes, a->key, sizeof(a->key));
 491
 492                 for (size_t i = 0; i < sizeof(secretbytes); ++i)
 493                         secretbytes[i] ^= 0x36;
 494
 495                 md5_begin(&md5);
 496                 md5_hash(secretbytes, sizeof(secretbytes), &md5);
 497                 md5_hash(&fr_msg, sizeof(fr_msg), &md5);
 498                 md5_end(auth_o->key, &md5);
 499
 500                 for (size_t i = 0; i < sizeof(secretbytes); ++i) {
 501                         secretbytes[i] ^= 0x36;
 502                         secretbytes[i] ^= 0x5c;
 503                 }
 504
 505                 md5_begin(&md5);
 506                 md5_hash(secretbytes, sizeof(secretbytes), &md5);
 507                 md5_hash(auth_o->key, sizeof(auth_o->key), &md5);
 508                 md5_end(auth_o->key, &md5);
 509         } else {
 510                 dhcpv4_put(&fr_msg, &cookie, DHCPV4_OPT_SERVERID, 4,
 511                                 &a->fr_ip->addr.addr.in.s_addr);
 512                 dhcpv4_put(&fr_msg, &cookie, DHCPV4_OPT_END, 0, NULL);
 513         }
 514
 515         struct sockaddr_in dest;
 516         memset(&dest, 0, sizeof(dest));
 517         dest.sin_family = AF_INET;
 518         dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 519         dest.sin_addr.s_addr = a->addr;
 520
 521         syslog(LOG_WARNING, "sending %s to %02x:%02x:%02x:%02x:%02x:%02x - %s",
 522                         dhcpv4_msg_to_string(msg),
 523                         a->hwaddr[0], a->hwaddr[1], a->hwaddr[2],
 524                         a->hwaddr[3], a->hwaddr[4], a->hwaddr[5],
 525                         inet_ntoa(dest.sin_addr));
 526
 527         sendto(iface->dhcpv4_event.uloop.fd, &fr_msg, sizeof(fr_msg),
 528                         MSG_DONTWAIT, (struct sockaddr*)&dest, sizeof(dest));
 529 }
 530
 531 static void dhcpv4_fr_timer(struct uloop_timeout *event)
 532 {
 533         struct dhcpv4_assignment *a = container_of(event, struct dhcpv4_assignment, fr_timer);
 534
 535         if (a->fr_cnt > 0 && a->fr_cnt < 8) {
 536                 dhcpv4_fr_send(a);
 537                 uloop_timeout_set(&a->fr_timer, 1000 << a->fr_cnt);
 538                 a->fr_cnt++;
 539         } else
 540                 dhcpv4_fr_stop(a);
 541 }
 542
 543 static void dhcpv4_fr_start(struct dhcpv4_assignment *a)
 544 {
 545         uloop_timeout_set(&a->fr_timer, 1000 << a->fr_cnt);
 546         a->fr_timer.cb = dhcpv4_fr_timer;
 547         a->fr_cnt++;
 548
 549         dhcpv4_fr_send(a);
 550 }
 551
 552 static void dhcpv4_fr_stop(struct dhcpv4_assignment *a)
 553 {
 554         uloop_timeout_cancel(&a->fr_timer);
 555         decr_ref_cnt_ip(&a->fr_ip, a->iface);
 556         a->fr_cnt = 0;
 557         a->fr_timer.cb = NULL;
 558 }
 559
 560 // Handler for DHCPv4 messages
 561 static void handle_dhcpv4(void *addr, void *data, size_t len,
 562                 struct interface *iface, _unused void *dest_addr)
 563 {
 564         if (!iface->dhcpv4)
 565                 return;
 566
 567         struct dhcpv4_message *req = data;
 568         if (len < offsetof(struct dhcpv4_message, options) + 4 ||
 569                         req->op != DHCPV4_BOOTREQUEST || req->hlen != 6)
 570                 return;
 571
 572
 573         syslog(LOG_NOTICE, "Got DHCPv4 request");
 574
 575         if (!iface->dhcpv4_start_ip.s_addr && !iface->dhcpv4_end_ip.s_addr) {
 576                 syslog(LOG_WARNING, "No DHCP range available on %s", iface->name);
 577                 return;
 578         }
 579
 580         int sock = iface->dhcpv4_event.uloop.fd;
 581
 582         struct dhcpv4_message reply = {
 583                 .op = DHCPV4_BOOTREPLY,
 584                 .htype = req->htype,
 585                 .hlen = req->hlen,
 586                 .hops = 0,
 587                 .xid = req->xid,
 588                 .secs = 0,
 589                 .flags = req->flags,
 590                 .ciaddr = {INADDR_ANY},
 591                 .giaddr = req->giaddr,
 592                 .siaddr = iface->dhcpv4_local,
 593         };
 594         memcpy(reply.chaddr, req->chaddr, sizeof(reply.chaddr));
 595
 596         reply.options[0] = 0x63;
 597         reply.options[1] = 0x82;
 598         reply.options[2] = 0x53;
 599         reply.options[3] = 0x63;
 600
 601         uint8_t *cookie = &reply.options[4];
 602         uint8_t reqmsg = DHCPV4_MSG_REQUEST;
 603         uint8_t msg = DHCPV4_MSG_ACK;
 604
 605         struct in_addr reqaddr = {INADDR_ANY};
 606         uint32_t leasetime = 0;
 607         size_t hostname_len = 0;
 608         char hostname[256];
 609         bool accept_fr_nonce = false;
 610         bool incl_fr_opt = false;
 611
 612         uint8_t *start = &req->options[4];
 613         uint8_t *end = ((uint8_t*)data) + len;
 614         struct dhcpv4_option *opt;
 615         dhcpv4_for_each_option(start, end, opt) {
 616                 if (opt->type == DHCPV4_OPT_MESSAGE && opt->len == 1)
 617                         reqmsg = opt->data[0];
 618                 else if (opt->type == DHCPV4_OPT_HOSTNAME && opt->len > 0) {
 619                         hostname_len = opt->len;
 620                         memcpy(hostname, opt->data, hostname_len);
 621                         hostname[hostname_len] = 0;
 622                 } else if (opt->type == DHCPV4_OPT_IPADDRESS && opt->len == 4)
 623                         memcpy(&reqaddr, opt->data, 4);
 624                 else if (opt->type == DHCPV4_OPT_SERVERID && opt->len == 4) {
 625                         if (memcmp(opt->data, &iface->dhcpv4_local, 4))
 626                                 return;
 627                 } else if (iface->filter_class && opt->type == DHCPV4_OPT_USER_CLASS) {
 628                         uint8_t *c = opt->data, *cend = &opt->data[opt->len];
 629                         for (; c < cend && &c[*c] < cend; c = &c[1 + *c]) {
 630                                 size_t elen = strlen(iface->filter_class);
 631                                 if (*c == elen && !memcmp(&c[1], iface->filter_class, elen))
 632                                         return; // Ignore from homenet
 633                         }
 634                 } else if (opt->type == DHCPV4_OPT_LEASETIME && opt->len == 4)
 635                         memcpy(&leasetime, opt->data, 4);
 636                 else if (opt->type == DHCPV4_OPT_FORCERENEW_NONCE_CAPABLE && opt->len > 0) {
 637                         for (uint8_t i = 0; i < opt->len; i++) {
 638                                 if (opt->data[i] == 1) {
 639                                         accept_fr_nonce = true;
 640                                         break;
 641                                 }
 642                         }
 643
 644                 }
 645         }
 646
 647         if (reqmsg != DHCPV4_MSG_DISCOVER && reqmsg != DHCPV4_MSG_REQUEST &&
 648                         reqmsg != DHCPV4_MSG_INFORM && reqmsg != DHCPV4_MSG_DECLINE &&
 649                         reqmsg != DHCPV4_MSG_RELEASE)
 650                 return;
 651
 652         struct dhcpv4_assignment *lease = NULL;
 653         uint32_t serverid = iface->dhcpv4_local.s_addr;
 654         uint32_t fr_serverid = INADDR_ANY;
 655
 656         if (reqmsg != DHCPV4_MSG_INFORM)
 657                 lease = dhcpv4_lease(iface, reqmsg, req->chaddr, reqaddr,
 658                                         &leasetime, hostname, hostname_len,
 659                                         accept_fr_nonce, &incl_fr_opt, &fr_serverid);
 660
 661         if (!lease) {
 662                 if (reqmsg == DHCPV4_MSG_REQUEST)
 663                         msg = DHCPV4_MSG_NAK;
 664                 else if (reqmsg == DHCPV4_MSG_DISCOVER)
 665                         return;
 666         } else if (reqmsg == DHCPV4_MSG_DISCOVER)
 667                 msg = DHCPV4_MSG_OFFER;
 668         else if (reqmsg == DHCPV4_MSG_REQUEST &&
 669                         ((reqaddr.s_addr && reqaddr.s_addr != lease->addr) ||
 670                          (req->ciaddr.s_addr && req->ciaddr.s_addr != lease->addr))) {
 671                 msg = DHCPV4_MSG_NAK;
 672                 /*
 673                  * DHCP client requested an IP which we can't offer to him. Probably the
 674                  * client changed the network or the network has been changed. The reply
 675                  * type is set to DHCPV4_MSG_NAK, because the client should not use that IP.
 676                  *
 677                  * For modern devices we build an answer that includes a valid IP, like
 678                  * a DHCPV4_MSG_ACK. The client will use that IP and doesn't need to
 679                  * perform additional DHCP round trips.
 680                  *
 681                  */
 682
 683                 /*
 684                  *
 685                  * Buggy clients do serverid checking in nack messages; therefore set the
 686                  * serverid in nack messages triggered by a previous force renew equal to
 687                  * the server id in use at that time by the server
 688                  *
 689                  */
 690                 if (fr_serverid)
 691                         serverid = fr_serverid;
 692
 693                 if (req->ciaddr.s_addr &&
 694                                 ((iface->dhcpv4_start_ip.s_addr & iface->dhcpv4_mask.s_addr) !=
 695                                  (req->ciaddr.s_addr & iface->dhcpv4_mask.s_addr)))
 696                         req->ciaddr.s_addr = INADDR_ANY;
 697         }
 698
 699         syslog(LOG_WARNING, "received %s from %02x:%02x:%02x:%02x:%02x:%02x",
 700                         dhcpv4_msg_to_string(reqmsg),
 701                         req->chaddr[0],req->chaddr[1],req->chaddr[2],
 702                         req->chaddr[3],req->chaddr[4],req->chaddr[5]);
 703
 704         if (reqmsg == DHCPV4_MSG_DECLINE || reqmsg == DHCPV4_MSG_RELEASE)
 705                 return;
 706
 707         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_MESSAGE, 1, &msg);
 708         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SERVERID, 4, &serverid);
 709
 710         if (lease) {
 711                 uint32_t val;
 712
 713                 reply.yiaddr.s_addr = lease->addr;
 714
 715                 val = htonl(leasetime);
 716                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_LEASETIME, 4, &val);
 717
 718                 if (leasetime != UINT32_MAX) {
 719                         val = htonl(500 * leasetime / 1000);
 720                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_RENEW, 4, &val);
 721
 722                         val = htonl(875 * leasetime / 1000);
 723                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_REBIND, 4, &val);
 724                 }
 725
 726                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_NETMASK, 4,
 727                                 &iface->dhcpv4_mask.s_addr);
 728
 729                 if (lease->hostname)
 730                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_HOSTNAME,
 731                                         strlen(lease->hostname), lease->hostname);
 732
 733                 if (iface->dhcpv4_bcast.s_addr != INADDR_ANY)
 734                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_BROADCAST, 4, &iface->dhcpv4_bcast);
 735
 736                 if (incl_fr_opt) {
 737                         if (reqmsg == DHCPV4_MSG_REQUEST) {
 738                                 struct dhcpv4_auth_forcerenew auth = {
 739                                         .protocol = 3,
 740                                         .algorithm = 1,
 741                                         .rdm = 0,
 742                                         .replay = {htonl(time(NULL)), htonl(++serial)},
 743                                         .type = 1,
 744                                         .key = {0},
 745                                 };
 746
 747                                 memcpy(auth.key, lease->key, sizeof(auth.key));
 748                                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_AUTHENTICATION, sizeof(auth), &auth);
 749                         } else {
 750                                 uint8_t one = 1;
 751                                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_FORCERENEW_NONCE_CAPABLE,
 752                                         sizeof(one), &one);
 753                         }
 754                 }
 755         }
 756
 757         struct ifreq ifr = {.ifr_name = ""};
 758         strncpy(ifr.ifr_name, iface->ifname, sizeof(ifr.ifr_name));
 759
 760         if (!ioctl(sock, SIOCGIFMTU, &ifr)) {
 761                 uint16_t mtu = htons(ifr.ifr_mtu);
 762                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_MTU, 2, &mtu);
 763         }
 764
 765         if (iface->search && iface->search_len <= 255)
 766                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SEARCH_DOMAIN,
 767                                 iface->search_len, iface->search);
 768         else if (!res_init() && _res.dnsrch[0] && _res.dnsrch[0][0]) {
 769                 uint8_t search_buf[256];
 770                 int len = dn_comp(_res.dnsrch[0], search_buf,
 771                                                 sizeof(search_buf), NULL, NULL);
 772                 if (len > 0)
 773                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SEARCH_DOMAIN,
 774                                         len, search_buf);
 775         }
 776
 777         if (iface->dhcpv4_router_cnt == 0)
 778                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_ROUTER, 4, &iface->dhcpv4_local);
 779         else
 780                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_ROUTER,
 781                                 4 * iface->dhcpv4_router_cnt, iface->dhcpv4_router);
 782
 783
 784         if (iface->dhcpv4_dns_cnt == 0)
 785                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_DNSSERVER, 4, &iface->dhcpv4_local);
 786         else
 787                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_DNSSERVER,
 788                                 4 * iface->dhcpv4_dns_cnt, iface->dhcpv4_dns);
 789
 790
 791         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_END, 0, NULL);
 792
 793         struct sockaddr_in dest = *((struct sockaddr_in*)addr);
 794         if (req->giaddr.s_addr) {
 795                 /*
 796                  * relay agent is configured, send reply to the agent
 797                  */
 798                 dest.sin_addr = req->giaddr;
 799                 dest.sin_port = htons(DHCPV4_SERVER_PORT);
 800         } else if (req->ciaddr.s_addr && req->ciaddr.s_addr != dest.sin_addr.s_addr) {
 801                 /*
 802                  * client has existing configuration (ciaddr is set) AND this address is
 803                  * not the address it used for the dhcp message
 804                  */
 805                 dest.sin_addr = req->ciaddr;
 806                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 807         } else if ((ntohs(req->flags) & DHCPV4_FLAG_BROADCAST) ||
 808                         req->hlen != reply.hlen || !reply.yiaddr.s_addr) {
 809                 /*
 810                  * client requests a broadcast reply OR we can't offer an IP
 811                  */
 812                 dest.sin_addr.s_addr = INADDR_BROADCAST;
 813                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 814         } else if (!req->ciaddr.s_addr && msg == DHCPV4_MSG_NAK) {
 815                 /*
 816                  * client has no previous configuration -> no IP, so we need to reply
 817                  * with a broadcast packet
 818                  */
 819                 dest.sin_addr.s_addr = INADDR_BROADCAST;
 820                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 821         } else {
 822                 /*
 823                  * send reply to the newly (in this proccess) allocated IP
 824                  */
 825                 dest.sin_addr = reply.yiaddr;
 826                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 827
 828                 struct arpreq arp = {.arp_flags = ATF_COM};
 829                 memcpy(arp.arp_ha.sa_data, req->chaddr, 6);
 830                 memcpy(&arp.arp_pa, &dest, sizeof(arp.arp_pa));
 831                 memcpy(arp.arp_dev, iface->ifname, sizeof(arp.arp_dev));
 832                 ioctl(sock, SIOCSARP, &arp);
 833         }
 834
 835         if (dest.sin_addr.s_addr == INADDR_BROADCAST)
 836                 /* reply goes to IP broadcast -> MAC broadcast */
 837                 syslog(LOG_WARNING, "sending %s to ff:ff:ff:ff:ff:ff - %s",
 838                                 dhcpv4_msg_to_string(msg),
 839                                 inet_ntoa(dest.sin_addr));
 840         else
 841                 /*
 842                  * reply is send directly to IP,
 843                  * MAC is assumed to be the same as the request
 844                  */
 845                 syslog(LOG_WARNING, "sending %s to %02x:%02x:%02x:%02x:%02x:%02x - %s",
 846                                 dhcpv4_msg_to_string(msg),
 847                                 req->chaddr[0],req->chaddr[1],req->chaddr[2],
 848                                 req->chaddr[3],req->chaddr[4],req->chaddr[5],
 849                                 inet_ntoa(dest.sin_addr));
 850
 851         sendto(sock, &reply, sizeof(reply), MSG_DONTWAIT,
 852                         (struct sockaddr*)&dest, sizeof(dest));
 853 }
 854
 855 static bool dhcpv4_test(struct interface *iface, uint32_t try)
 856 {
 857         struct dhcpv4_assignment *c;
 858         list_for_each_entry(c, &iface->dhcpv4_assignments, head) {
 859                 if (c->addr == try)
 860                         return false;
 861         }
 862
 863         return true;
 864 }
 865
 866 static bool dhcpv4_assign(struct interface *iface,
 867                 struct dhcpv4_assignment *assign, uint32_t raddr)
 868 {
 869         uint32_t start = ntohl(iface->dhcpv4_start_ip.s_addr);
 870         uint32_t end = ntohl(iface->dhcpv4_end_ip.s_addr);
 871         uint32_t count = end - start + 1;
 872
 873         // try to assign the IP the client asked for
 874         if (start <= ntohl(raddr) && ntohl(raddr) <= end && dhcpv4_test(iface, raddr)) {
 875                 assign->addr = raddr;
 876                 syslog(LOG_INFO, "assigning the IP the client asked for: %u.%u.%u.%u",
 877                                 ((uint8_t *)&assign->addr)[0],
 878                                 ((uint8_t *)&assign->addr)[1],
 879                                 ((uint8_t *)&assign->addr)[2],
 880                                 ((uint8_t *)&assign->addr)[3]);
 881                 return true;
 882         }
 883
 884         // Seed RNG with checksum of hwaddress
 885         uint32_t seed = 0;
 886         for (size_t i = 0; i < sizeof(assign->hwaddr); ++i) {
 887                 // Knuth's multiplicative method
 888                 uint8_t o = assign->hwaddr[i];
 889                 seed += (o*2654435761) % UINT32_MAX;
 890         }
 891
 892         srand(seed);
 893
 894         uint32_t try = (((uint32_t)rand()) % count) + start;
 895
 896         if (list_empty(&iface->dhcpv4_assignments)) {
 897                 assign->addr = htonl(try);
 898                 syslog(LOG_INFO, "assigning mapped IP (empty list): %u.%u.%u.%u",
 899                                 ((uint8_t *)&assign->addr)[0],
 900                                 ((uint8_t *)&assign->addr)[1],
 901                                 ((uint8_t *)&assign->addr)[2],
 902                                 ((uint8_t *)&assign->addr)[3]);
 903                 return true;
 904         }
 905
 906         for (uint32_t i = 0; i < count; ++i) {
 907                 if (dhcpv4_test(iface, htonl(try))) {
 908                         /* test was successful: IP address is not assigned, assign it */
 909                         assign->addr = htonl(try);
 910                         syslog(LOG_DEBUG, "assigning mapped IP: %u.%u.%u.%u (try %u of %u)",
 911                                         ((uint8_t *)&assign->addr)[0],
 912                                         ((uint8_t *)&assign->addr)[1],
 913                                         ((uint8_t *)&assign->addr)[2],
 914                                         ((uint8_t *)&assign->addr)[3],
 915                                         i, count);
 916                         return true;
 917                 }
 918                 try = (((try - start) + 1) % count) + start;
 919         }
 920
 921         syslog(LOG_WARNING, "can't assign any IP address -> address space is full");
 922         return false;
 923 }
 924
 925
 926 static struct dhcpv4_assignment* dhcpv4_lease(struct interface *iface,
 927                 enum dhcpv4_msg msg, const uint8_t *mac, struct in_addr reqaddr,
 928                 uint32_t *leasetime, const char *hostname, const size_t hostname_len,
 929                 const bool accept_fr_nonce, bool *incl_fr_opt, uint32_t *fr_serverid)
 930 {
 931         struct dhcpv4_assignment *lease = NULL;
 932         time_t now = odhcpd_time();
 933
 934         struct dhcpv4_assignment *c, *a = NULL;
 935         list_for_each_entry(c, &iface->dhcpv4_assignments, head) {
 936                 if (!memcmp(c->hwaddr, mac, 6)) {
 937                         a = c;
 938                         if (c->addr == reqaddr.s_addr)
 939                                 break;
 940                 }
 941         }
 942
 943         if (a && (a->flags & OAF_BOUND) && a->fr_ip) {
 944                 *fr_serverid = a->fr_ip->addr.addr.in.s_addr;
 945                 dhcpv4_fr_stop(a);
 946         }
 947
 948         if (msg == DHCPV4_MSG_DISCOVER || msg == DHCPV4_MSG_REQUEST) {
 949                 bool assigned = !!a;
 950
 951                 if (!a) {
 952                         if (!iface->no_dynamic_dhcp) {
 953                                 /* Create new binding */
 954                                 a = calloc(1, sizeof(*a));
 955                                 if (!a) {
 956                                         syslog(LOG_ERR, "Failed to calloc binding on interface %s",
 957                                                         iface->ifname);
 958                                         return NULL;
 959                                 }
 960                                 memcpy(a->hwaddr, mac, sizeof(a->hwaddr));
 961                                 /* Don't consider new assignment as infinite */
 962                                 a->valid_until = now;
 963
 964                                 assigned = dhcpv4_assign(iface, a, reqaddr.s_addr);
 965                                 if (assigned) {
 966                                         a->iface = iface;
 967                                         list_add(&a->head, &iface->dhcpv4_assignments);
 968                                 }
 969                         }
 970                 } else if ((a->addr & iface->dhcpv4_mask.s_addr) !=
 971                                 (iface->dhcpv4_start_ip.s_addr & iface->dhcpv4_mask.s_addr)) {
 972                         list_del(&a->head);
 973
 974                         assigned = dhcpv4_assign(iface, a, reqaddr.s_addr);
 975                         if (assigned)
 976                                 list_add(&a->head, &iface->dhcpv4_assignments);
 977                 }
 978
 979                 if (assigned) {
 980                         uint32_t my_leasetime;
 981
 982                         if (a->leasetime)
 983                                 my_leasetime = a->leasetime;
 984                         else
 985                                 my_leasetime = iface->dhcpv4_leasetime;
 986
 987                         if ((*leasetime == 0) || (my_leasetime < *leasetime))
 988                                 *leasetime = my_leasetime;
 989
 990                         if (msg == DHCPV4_MSG_DISCOVER) {
 991                                 a->flags &= ~OAF_BOUND;
 992
 993                                 *incl_fr_opt = accept_fr_nonce;
 994                                 if (!(a->flags & OAF_STATIC))
 995                                         a->valid_until = now;
 996                         } else {
 997                                 if (hostname_len > 0) {
 998                                         a->hostname = realloc(a->hostname, hostname_len + 1);
 999                                         if (a->hostname) {
1000                                                 memcpy(a->hostname, hostname, hostname_len);
1001                                                 a->hostname[hostname_len] = 0;
1002                                         }
1003                                 }
1004
1005                                 if (!(a->flags & OAF_BOUND)) {
1006                                         a->accept_fr_nonce = accept_fr_nonce;
1007                                         *incl_fr_opt = accept_fr_nonce;
1008                                         odhcpd_urandom(a->key, sizeof(a->key));
1009                                         a->flags |= OAF_BOUND;
1010                                 } else
1011                                         *incl_fr_opt = false;
1012
1013                                 if (!(a->flags & OAF_STATIC))
1014                                         a->valid_until = ((*leasetime == UINT32_MAX) ? 0 : (time_t)(now + *leasetime));
1015                         }
1016                 } else if (!assigned && a) {
1017                         /* Cleanup failed assignment */
1018                         free_dhcpv4_assignment(a);
1019                         a = NULL;
1020                 }
1021
1022                 if (assigned && a)
1023                         lease = a;
1024         } else if (msg == DHCPV4_MSG_RELEASE && a) {
1025                 a->flags &= ~OAF_BOUND;
1026
1027                 if (!(a->flags & OAF_STATIC))
1028                         a->valid_until = now - 1;
1029
1030         } else if (msg == DHCPV4_MSG_DECLINE && a) {
1031                 a->flags &= ~OAF_BOUND;
1032
1033                 if (!(a->flags & OAF_STATIC)) {
1034                         memset(a->hwaddr, 0, sizeof(a->hwaddr));
1035                         a->valid_until = now + 3600; /* Block address for 1h */
1036                 }
1037         }
1038
1039         dhcpv6_write_statefile();
1040
1041         return lease;
1042 }