src/network/networkd-dhcp-server.c

   1 /* SPDX-License-Identifier: LGPL-2.1-or-later */
   2
   3 #include <netinet/in.h>
   4 #include <linux/if_arp.h>
   5 #include <linux/if.h>
   6
   7 #include "sd-dhcp-server.h"
   8
   9 #include "fd-util.h"
  10 #include "fileio.h"
  11 #include "networkd-address.h"
  12 #include "networkd-dhcp-server-bus.h"
  13 #include "networkd-dhcp-server-static-lease.h"
  14 #include "networkd-dhcp-server.h"
  15 #include "networkd-link.h"
  16 #include "networkd-manager.h"
  17 #include "networkd-network.h"
  18 #include "networkd-queue.h"
  19 #include "networkd-route-util.h"
  20 #include "parse-util.h"
  21 #include "socket-netlink.h"
  22 #include "string-table.h"
  23 #include "string-util.h"
  24 #include "strv.h"
  25
  26 static bool link_dhcp4_server_enabled(Link *link) {
  27         assert(link);
  28
  29         if (link->flags & IFF_LOOPBACK)
  30                 return false;
  31
  32         if (!link->network)
  33                 return false;
  34
  35         if (link->iftype == ARPHRD_CAN)
  36                 return false;
  37
  38         return link->network->dhcp_server;
  39 }
  40
  41 void network_adjust_dhcp_server(Network *network) {
  42         assert(network);
  43
  44         if (!network->dhcp_server)
  45                 return;
  46
  47         if (network->bond) {
  48                 log_warning("%s: DHCPServer= is enabled for bond slave. Disabling DHCP server.",
  49                             network->filename);
  50                 network->dhcp_server = false;
  51                 return;
  52         }
  53
  54         if (!in4_addr_is_set(&network->dhcp_server_address)) {
  55                 Address *address;
  56                 bool have = false;
  57
  58                 ORDERED_HASHMAP_FOREACH(address, network->addresses_by_section) {
  59                         if (section_is_invalid(address->section))
  60                                 continue;
  61
  62                         if (address->family != AF_INET)
  63                                 continue;
  64
  65                         if (in4_addr_is_localhost(&address->in_addr.in))
  66                                 continue;
  67
  68                         if (in4_addr_is_link_local(&address->in_addr.in))
  69                                 continue;
  70
  71                         if (in4_addr_is_set(&address->in_addr_peer.in))
  72                                 continue;
  73
  74                         have = true;
  75                         break;
  76                 }
  77                 if (!have) {
  78                         log_warning("%s: DHCPServer= is enabled, but no static address configured. "
  79                                     "Disabling DHCP server.",
  80                                     network->filename);
  81                         network->dhcp_server = false;
  82                         return;
  83                 }
  84         }
  85 }
  86
  87 int link_request_dhcp_server_address(Link *link) {
  88         _cleanup_(address_freep) Address *address = NULL;
  89         Address *existing;
  90         int r;
  91
  92         assert(link);
  93         assert(link->network);
  94
  95         if (!link_dhcp4_server_enabled(link))
  96                 return 0;
  97
  98         if (!in4_addr_is_set(&link->network->dhcp_server_address))
  99                 return 0;
 100
 101         r = address_new(&address);
 102         if (r < 0)
 103                 return r;
 104
 105         address->source = NETWORK_CONFIG_SOURCE_STATIC;
 106         address->family = AF_INET;
 107         address->in_addr.in = link->network->dhcp_server_address;
 108         address->prefixlen = link->network->dhcp_server_address_prefixlen;
 109         address_set_broadcast(address, link);
 110
 111         if (address_get(link, address, &existing) >= 0 &&
 112             address_exists(existing) &&
 113             existing->source == NETWORK_CONFIG_SOURCE_STATIC)
 114                 /* The same address seems explicitly configured in [Address] or [Network] section.
 115                  * Configure the DHCP server address only when it is not. */
 116                 return 0;
 117
 118         return link_request_static_address(link, TAKE_PTR(address), true);
 119 }
 120
 121 static int link_find_dhcp_server_address(Link *link, Address **ret) {
 122         Address *address;
 123
 124         assert(link);
 125         assert(link->network);
 126
 127         /* If ServerAddress= is specified, then use the address. */
 128         if (in4_addr_is_set(&link->network->dhcp_server_address))
 129                 return link_get_ipv4_address(link, &link->network->dhcp_server_address,
 130                                              link->network->dhcp_server_address_prefixlen, ret);
 131
 132         /* If not, then select one from static addresses. */
 133         SET_FOREACH(address, link->addresses) {
 134                 if (address->source != NETWORK_CONFIG_SOURCE_STATIC)
 135                         continue;
 136                 if (!address_exists(address))
 137                         continue;
 138                 if (address->family != AF_INET)
 139                         continue;
 140                 if (in4_addr_is_localhost(&address->in_addr.in))
 141                         continue;
 142                 if (in4_addr_is_link_local(&address->in_addr.in))
 143                         continue;
 144                 if (in4_addr_is_set(&address->in_addr_peer.in))
 145                         continue;
 146
 147                 *ret = address;
 148                 return 0;
 149         }
 150
 151         return -ENOENT;
 152 }
 153
 154 static int dhcp_server_find_uplink(Link *link, Link **ret) {
 155         assert(link);
 156
 157         if (link->network->dhcp_server_uplink_name)
 158                 return link_get_by_name(link->manager, link->network->dhcp_server_uplink_name, ret);
 159
 160         if (link->network->dhcp_server_uplink_index > 0)
 161                 return link_get_by_index(link->manager, link->network->dhcp_server_uplink_index, ret);
 162
 163         if (link->network->dhcp_server_uplink_index == UPLINK_INDEX_AUTO) {
 164                 /* It is not necessary to propagate error in automatic selection. */
 165                 if (manager_find_uplink(link->manager, AF_INET, link, ret) < 0)
 166                         *ret = NULL;
 167                 return 0;
 168         }
 169
 170         *ret = NULL;
 171         return 0;
 172 }
 173
 174 static int link_push_uplink_to_dhcp_server(
 175                 Link *link,
 176                 sd_dhcp_lease_server_type_t what,
 177                 sd_dhcp_server *s) {
 178
 179         _cleanup_free_ struct in_addr *addresses = NULL;
 180         bool use_dhcp_lease_data = true;
 181         size_t n_addresses = 0;
 182
 183         assert(link);
 184
 185         if (!link->network)
 186                 return 0;
 187         assert(link->network);
 188
 189         log_link_debug(link, "Copying %s from link", dhcp_lease_server_type_to_string(what));
 190
 191         switch (what) {
 192
 193         case SD_DHCP_LEASE_DNS:
 194                 /* For DNS we have a special case. We the data configured explicitly locally along with the
 195                  * data from the DHCP lease. */
 196
 197                 for (unsigned i = 0; i < link->network->n_dns; i++) {
 198                         struct in_addr ia;
 199
 200                         /* Only look for IPv4 addresses */
 201                         if (link->network->dns[i]->family != AF_INET)
 202                                 continue;
 203
 204                         ia = link->network->dns[i]->address.in;
 205
 206                         /* Never propagate obviously borked data */
 207                         if (in4_addr_is_null(&ia) || in4_addr_is_localhost(&ia))
 208                                 continue;
 209
 210                         if (!GREEDY_REALLOC(addresses, n_addresses + 1))
 211                                 return log_oom();
 212
 213                         addresses[n_addresses++] = ia;
 214                 }
 215
 216                 use_dhcp_lease_data = link->network->dhcp_use_dns;
 217                 break;
 218
 219         case SD_DHCP_LEASE_NTP: {
 220                 char **i;
 221
 222                 /* For NTP things are similar, but for NTP hostnames can be configured too, which we cannot
 223                  * propagate via DHCP. Hence let's only propagate those which are IP addresses. */
 224
 225                 STRV_FOREACH(i, link->network->ntp) {
 226                         union in_addr_union ia;
 227
 228                         if (in_addr_from_string(AF_INET, *i, &ia) < 0)
 229                                 continue;
 230
 231                         /* Never propagate obviously borked data */
 232                         if (in4_addr_is_null(&ia.in) || in4_addr_is_localhost(&ia.in))
 233                                 continue;
 234
 235                         if (!GREEDY_REALLOC(addresses, n_addresses + 1))
 236                                 return log_oom();
 237
 238                         addresses[n_addresses++] = ia.in;
 239                 }
 240
 241                 use_dhcp_lease_data = link->network->dhcp_use_ntp;
 242                 break;
 243         }
 244
 245         case SD_DHCP_LEASE_SIP:
 246
 247                 /* For SIP we don't allow explicit, local configuration, but there's control whether to use the data */
 248                 use_dhcp_lease_data = link->network->dhcp_use_sip;
 249                 break;
 250
 251         case SD_DHCP_LEASE_POP3:
 252         case SD_DHCP_LEASE_SMTP:
 253         case SD_DHCP_LEASE_LPR:
 254                 /* For the other server types we currently do not allow local configuration of server data,
 255                  * since there are typically no local consumers of the data. */
 256                 break;
 257
 258         default:
 259                 assert_not_reached();
 260         }
 261
 262         if (use_dhcp_lease_data && link->dhcp_lease) {
 263                 const struct in_addr *da;
 264
 265                 int n = sd_dhcp_lease_get_servers(link->dhcp_lease, what, &da);
 266                 if (n > 0) {
 267                         if (!GREEDY_REALLOC(addresses, n_addresses + n))
 268                                 return log_oom();
 269
 270                         for (int j = 0; j < n; j++)
 271                                 if (in4_addr_is_non_local(&da[j]))
 272                                         addresses[n_addresses++] = da[j];
 273                 }
 274         }
 275
 276         if (n_addresses <= 0)
 277                 return 0;
 278
 279         return sd_dhcp_server_set_servers(s, what, addresses, n_addresses);
 280 }
 281
 282 static int dhcp4_server_parse_dns_server_string_and_warn(
 283                 const char *string,
 284                 struct in_addr **addresses,
 285                 size_t *n_addresses) {
 286
 287         for (;;) {
 288                 _cleanup_free_ char *word = NULL, *server_name = NULL;
 289                 union in_addr_union address;
 290                 int family, r, ifindex = 0;
 291
 292                 r = extract_first_word(&string, &word, NULL, 0);
 293                 if (r < 0)
 294                         return r;
 295                 if (r == 0)
 296                         break;
 297
 298                 r = in_addr_ifindex_name_from_string_auto(word, &family, &address, &ifindex, &server_name);
 299                 if (r < 0) {
 300                         log_warning_errno(r, "Failed to parse DNS server address '%s', ignoring: %m", word);
 301                         continue;
 302                 }
 303
 304                 /* Only look for IPv4 addresses */
 305                 if (family != AF_INET)
 306                         continue;
 307
 308                 /* Never propagate obviously borked data */
 309                 if (in4_addr_is_null(&address.in) || in4_addr_is_localhost(&address.in))
 310                         continue;
 311
 312                 if (!GREEDY_REALLOC(*addresses, *n_addresses + 1))
 313                         return log_oom();
 314
 315                 (*addresses)[(*n_addresses)++] = address.in;
 316         }
 317
 318         return 0;
 319 }
 320
 321 static int dhcp4_server_set_dns_from_resolve_conf(Link *link) {
 322         _cleanup_free_ struct in_addr *addresses = NULL;
 323         _cleanup_fclose_ FILE *f = NULL;
 324         size_t n_addresses = 0;
 325         int n = 0, r;
 326
 327         f = fopen(PRIVATE_UPLINK_RESOLV_CONF, "re");
 328         if (!f) {
 329                 if (errno == ENOENT)
 330                         return 0;
 331
 332                 return log_warning_errno(errno, "Failed to open " PRIVATE_UPLINK_RESOLV_CONF ": %m");
 333         }
 334
 335         for (;;) {
 336                 _cleanup_free_ char *line = NULL;
 337                 const char *a;
 338                 char *l;
 339
 340                 r = read_line(f, LONG_LINE_MAX, &line);
 341                 if (r < 0)
 342                         return log_error_errno(r, "Failed to read " PRIVATE_UPLINK_RESOLV_CONF ": %m");
 343                 if (r == 0)
 344                         break;
 345
 346                 n++;
 347
 348                 l = strstrip(line);
 349                 if (IN_SET(*l, '#', ';', 0))
 350                         continue;
 351
 352                 a = first_word(l, "nameserver");
 353                 if (!a)
 354                         continue;
 355
 356                 r = dhcp4_server_parse_dns_server_string_and_warn(a, &addresses, &n_addresses);
 357                 if (r < 0)
 358                         log_warning_errno(r, "Failed to parse DNS server address '%s', ignoring.", a);
 359         }
 360
 361         if (n_addresses <= 0)
 362                 return 0;
 363
 364         return sd_dhcp_server_set_dns(link->dhcp_server, addresses, n_addresses);
 365 }
 366
 367 static int dhcp4_server_configure(Link *link) {
 368         bool acquired_uplink = false;
 369         sd_dhcp_option *p;
 370         DHCPStaticLease *static_lease;
 371         Link *uplink = NULL;
 372         Address *address;
 373         bool bind_to_interface;
 374         int r;
 375
 376         assert(link);
 377
 378         log_link_debug(link, "Configuring DHCP Server.");
 379
 380         if (link->dhcp_server)
 381                 return -EBUSY;
 382
 383         r = sd_dhcp_server_new(&link->dhcp_server, link->ifindex);
 384         if (r < 0)
 385                 return r;
 386
 387         r = sd_dhcp_server_attach_event(link->dhcp_server, link->manager->event, 0);
 388         if (r < 0)
 389                 return r;
 390
 391         r = sd_dhcp_server_set_callback(link->dhcp_server, dhcp_server_callback, link);
 392         if (r < 0)
 393                 return log_link_warning_errno(link, r, "Failed to set callback for DHCPv4 server instance: %m");
 394
 395         r = link_find_dhcp_server_address(link, &address);
 396         if (r < 0)
 397                 return log_link_error_errno(link, r, "Failed to find suitable address for DHCPv4 server instance: %m");
 398
 399         /* use the server address' subnet as the pool */
 400         r = sd_dhcp_server_configure_pool(link->dhcp_server, &address->in_addr.in, address->prefixlen,
 401                                           link->network->dhcp_server_pool_offset, link->network->dhcp_server_pool_size);
 402         if (r < 0)
 403                 return log_link_error_errno(link, r, "Failed to configure address pool for DHCPv4 server instance: %m");
 404
 405         if (link->network->dhcp_server_max_lease_time_usec > 0) {
 406                 r = sd_dhcp_server_set_max_lease_time(link->dhcp_server,
 407                                                       DIV_ROUND_UP(link->network->dhcp_server_max_lease_time_usec, USEC_PER_SEC));
 408                 if (r < 0)
 409                         return log_link_error_errno(link, r, "Failed to set maximum lease time for DHCPv4 server instance: %m");
 410         }
 411
 412         if (link->network->dhcp_server_default_lease_time_usec > 0) {
 413                 r = sd_dhcp_server_set_default_lease_time(link->dhcp_server,
 414                                                           DIV_ROUND_UP(link->network->dhcp_server_default_lease_time_usec, USEC_PER_SEC));
 415                 if (r < 0)
 416                         return log_link_error_errno(link, r, "Failed to set default lease time for DHCPv4 server instance: %m");
 417         }
 418
 419         r = sd_dhcp_server_set_next_server(link->dhcp_server, &link->network->dhcp_server_next_server);
 420         if (r < 0)
 421                 return log_link_warning_errno(link, r, "Failed to set next server for DHCPv4 server instance: %m");
 422
 423         r = sd_dhcp_server_set_filename(link->dhcp_server, link->network->dhcp_server_filename);
 424         if (r < 0)
 425                 return log_link_warning_errno(link, r, "Failed to set filename for DHCPv4 server instance: %m");
 426
 427         for (sd_dhcp_lease_server_type_t type = 0; type < _SD_DHCP_LEASE_SERVER_TYPE_MAX; type ++) {
 428
 429                 if (!link->network->dhcp_server_emit[type].emit)
 430                         continue;
 431
 432                 if (link->network->dhcp_server_emit[type].n_addresses > 0)
 433                         /* Explicitly specified servers to emit */
 434                         r = sd_dhcp_server_set_servers(
 435                                         link->dhcp_server,
 436                                         type,
 437                                         link->network->dhcp_server_emit[type].addresses,
 438                                         link->network->dhcp_server_emit[type].n_addresses);
 439                 else {
 440                         /* Emission is requested, but nothing explicitly configured. Let's find a suitable upling */
 441                         if (!acquired_uplink) {
 442                                 (void) dhcp_server_find_uplink(link, &uplink);
 443                                 acquired_uplink = true;
 444                         }
 445
 446                         if (uplink && uplink->network)
 447                                 r = link_push_uplink_to_dhcp_server(uplink, type, link->dhcp_server);
 448                         else if (type == SD_DHCP_LEASE_DNS)
 449                                 r = dhcp4_server_set_dns_from_resolve_conf(link);
 450                         else {
 451                                 log_link_debug(link,
 452                                                "Not emitting %s on link, couldn't find suitable uplink.",
 453                                                dhcp_lease_server_type_to_string(type));
 454                                 continue;
 455                         }
 456                 }
 457
 458                 if (r < 0)
 459                         log_link_warning_errno(link, r,
 460                                                "Failed to set %s for DHCP server, ignoring: %m",
 461                                                dhcp_lease_server_type_to_string(type));
 462         }
 463
 464         if (link->network->dhcp_server_emit_router) {
 465                 r = sd_dhcp_server_set_router(link->dhcp_server, &link->network->dhcp_server_router);
 466                 if (r < 0)
 467                         return log_link_error_errno(link, r, "Failed to set router address for DHCP server: %m");
 468         }
 469
 470         r = sd_dhcp_server_set_relay_target(link->dhcp_server, &link->network->dhcp_server_relay_target);
 471         if (r < 0)
 472                 return log_link_error_errno(link, r, "Failed to set relay target for DHCP server: %m");
 473
 474         bind_to_interface = sd_dhcp_server_is_in_relay_mode(link->dhcp_server) ? false : link->network->dhcp_server_bind_to_interface;
 475         r = sd_dhcp_server_set_bind_to_interface(link->dhcp_server, bind_to_interface);
 476         if (r < 0)
 477                 return log_link_error_errno(link, r, "Failed to set interface binding for DHCP server: %m");
 478
 479         r = sd_dhcp_server_set_relay_agent_information(link->dhcp_server, link->network->dhcp_server_relay_agent_circuit_id, link->network->dhcp_server_relay_agent_remote_id);
 480         if (r < 0)
 481                 return log_link_error_errno(link, r, "Failed to set agent circuit/remote id for DHCP server: %m");
 482
 483         if (link->network->dhcp_server_emit_timezone) {
 484                 _cleanup_free_ char *buffer = NULL;
 485                 const char *tz = NULL;
 486
 487                 if (link->network->dhcp_server_timezone)
 488                         tz = link->network->dhcp_server_timezone;
 489                 else {
 490                         r = get_timezone(&buffer);
 491                         if (r < 0)
 492                                 log_link_warning_errno(link, r, "Failed to determine timezone, not sending timezone: %m");
 493                         else
 494                                 tz = buffer;
 495                 }
 496
 497                 if (tz) {
 498                         r = sd_dhcp_server_set_timezone(link->dhcp_server, tz);
 499                         if (r < 0)
 500                                 return log_link_error_errno(link, r, "Failed to set timezone for DHCP server: %m");
 501                 }
 502         }
 503
 504         ORDERED_HASHMAP_FOREACH(p, link->network->dhcp_server_send_options) {
 505                 r = sd_dhcp_server_add_option(link->dhcp_server, p);
 506                 if (r == -EEXIST)
 507                         continue;
 508                 if (r < 0)
 509                         return log_link_error_errno(link, r, "Failed to set DHCPv4 option: %m");
 510         }
 511
 512         ORDERED_HASHMAP_FOREACH(p, link->network->dhcp_server_send_vendor_options) {
 513                 r = sd_dhcp_server_add_vendor_option(link->dhcp_server, p);
 514                 if (r == -EEXIST)
 515                         continue;
 516                 if (r < 0)
 517                         return log_link_error_errno(link, r, "Failed to set DHCPv4 option: %m");
 518         }
 519
 520         HASHMAP_FOREACH(static_lease, link->network->dhcp_static_leases_by_section) {
 521                 r = sd_dhcp_server_set_static_lease(link->dhcp_server, &static_lease->address, static_lease->client_id, static_lease->client_id_size);
 522                 if (r < 0)
 523                         return log_link_error_errno(link, r, "Failed to set DHCPv4 static lease for DHCP server: %m");
 524         }
 525
 526         r = sd_dhcp_server_start(link->dhcp_server);
 527         if (r < 0)
 528                 return log_link_error_errno(link, r, "Could not start DHCPv4 server instance: %m");
 529
 530         log_link_debug(link, "Offering DHCPv4 leases");
 531
 532         return 1;
 533 }
 534
 535 int link_request_dhcp_server(Link *link) {
 536         assert(link);
 537
 538         if (!link_dhcp4_server_enabled(link))
 539                 return 0;
 540
 541         if (link->dhcp_server)
 542                 return 0;
 543
 544         log_link_debug(link, "Requesting DHCP server.");
 545         return link_queue_request(link, REQUEST_TYPE_DHCP_SERVER, NULL, false, NULL, NULL, NULL);
 546 }
 547
 548 static bool dhcp_server_is_ready_to_configure(Link *link) {
 549         Link *uplink = NULL;
 550         Address *a;
 551
 552         assert(link);
 553
 554         if (!link->network)
 555                 return false;
 556
 557         if (!IN_SET(link->state, LINK_STATE_CONFIGURING, LINK_STATE_CONFIGURED))
 558                 return false;
 559
 560         if (link->set_flags_messages > 0)
 561                 return false;
 562
 563         if (!link_has_carrier(link))
 564                 return false;
 565
 566         if (!link->static_addresses_configured)
 567                 return false;
 568
 569         if (link_find_dhcp_server_address(link, &a) < 0)
 570                 return false;
 571
 572         if (!address_is_ready(a))
 573                 return false;
 574
 575         if (dhcp_server_find_uplink(link, &uplink) < 0)
 576                 return false;
 577
 578         if (uplink && !uplink->network)
 579                 return false;
 580
 581         return true;
 582 }
 583
 584 int request_process_dhcp_server(Request *req) {
 585         assert(req);
 586         assert(req->link);
 587         assert(req->type == REQUEST_TYPE_DHCP_SERVER);
 588
 589         if (!dhcp_server_is_ready_to_configure(req->link))
 590                 return 0;
 591
 592         return dhcp4_server_configure(req->link);
 593 }
 594
 595 int config_parse_dhcp_server_relay_agent_suboption(
 596                 const char *unit,
 597                 const char *filename,
 598                 unsigned line,
 599                 const char *section,
 600                 unsigned section_line,
 601                 const char *lvalue,
 602                 int ltype,
 603                 const char *rvalue,
 604                 void *data,
 605                 void *userdata) {
 606
 607         char **suboption_value = data;
 608         char* p;
 609
 610         assert(filename);
 611         assert(lvalue);
 612         assert(rvalue);
 613
 614         if (isempty(rvalue)) {
 615                 *suboption_value = mfree(*suboption_value);
 616                 return 0;
 617         }
 618
 619         p = startswith(rvalue, "string:");
 620         if (!p) {
 621                 log_syntax(unit, LOG_WARNING, filename, line, 0,
 622                            "Failed to parse %s=%s'. Invalid format, ignoring.", lvalue, rvalue);
 623                 return 0;
 624         }
 625         return free_and_strdup(suboption_value, empty_to_null(p));
 626 }
 627
 628 int config_parse_dhcp_server_emit(
 629                 const char *unit,
 630                 const char *filename,
 631                 unsigned line,
 632                 const char *section,
 633                 unsigned section_line,
 634                 const char *lvalue,
 635                 int ltype,
 636                 const char *rvalue,
 637                 void *data,
 638                 void *userdata) {
 639
 640         NetworkDHCPServerEmitAddress *emit = data;
 641
 642         assert(emit);
 643         assert(rvalue);
 644
 645         if (isempty(rvalue)) {
 646                 emit->addresses = mfree(emit->addresses);
 647                 emit->n_addresses = 0;
 648                 return 0;
 649         }
 650
 651         for (const char *p = rvalue;;) {
 652                 _cleanup_free_ char *w = NULL;
 653                 union in_addr_union a;
 654                 int r;
 655
 656                 r = extract_first_word(&p, &w, NULL, 0);
 657                 if (r == -ENOMEM)
 658                         return log_oom();
 659                 if (r < 0) {
 660                         log_syntax(unit, LOG_WARNING, filename, line, r,
 661                                    "Failed to extract word, ignoring: %s", rvalue);
 662                         return 0;
 663                 }
 664                 if (r == 0)
 665                         return 0;
 666
 667                 if (streq(w, "_server_address"))
 668                         a = IN_ADDR_NULL; /* null address will be converted to the server address. */
 669                 else {
 670                         r = in_addr_from_string(AF_INET, w, &a);
 671                         if (r < 0) {
 672                                 log_syntax(unit, LOG_WARNING, filename, line, r,
 673                                            "Failed to parse %s= address '%s', ignoring: %m", lvalue, w);
 674                                 continue;
 675                         }
 676
 677                         if (in4_addr_is_null(&a.in)) {
 678                                 log_syntax(unit, LOG_WARNING, filename, line, 0,
 679                                            "Found a null address in %s=, ignoring.", lvalue);
 680                                 continue;
 681                         }
 682                 }
 683
 684                 if (!GREEDY_REALLOC(emit->addresses, emit->n_addresses + 1))
 685                         return log_oom();
 686
 687                 emit->addresses[emit->n_addresses++] = a.in;
 688         }
 689 }
 690
 691 int config_parse_dhcp_server_address(
 692                 const char *unit,
 693                 const char *filename,
 694                 unsigned line,
 695                 const char *section,
 696                 unsigned section_line,
 697                 const char *lvalue,
 698                 int ltype,
 699                 const char *rvalue,
 700                 void *data,
 701                 void *userdata) {
 702
 703         Network *network = userdata;
 704         union in_addr_union a;
 705         unsigned char prefixlen;
 706         int r;
 707
 708         assert(filename);
 709         assert(lvalue);
 710         assert(rvalue);
 711
 712         if (isempty(rvalue)) {
 713                 network->dhcp_server_address = (struct in_addr) {};
 714                 network->dhcp_server_address_prefixlen = 0;
 715                 return 0;
 716         }
 717
 718         r = in_addr_prefix_from_string(rvalue, AF_INET, &a, &prefixlen);
 719         if (r < 0) {
 720                 log_syntax(unit, LOG_WARNING, filename, line, r,
 721                            "Failed to parse %s=, ignoring assignment: %s", lvalue, rvalue);
 722                 return 0;
 723         }
 724         if (in4_addr_is_null(&a.in) || in4_addr_is_localhost(&a.in)) {
 725                 log_syntax(unit, LOG_WARNING, filename, line, 0,
 726                            "DHCP server address cannot be the ANY address or a localhost address, "
 727                            "ignoring assignment: %s", rvalue);
 728                 return 0;
 729         }
 730
 731         network->dhcp_server_address = a.in;
 732         network->dhcp_server_address_prefixlen = prefixlen;
 733         return 0;
 734 }