1/* 2 NICTA Public Software Licence 3 Version 1.0 4 5 Copyright © 2004 National ICT Australia Ltd 6 7 All rights reserved. 8 9 By this licence, National ICT Australia Ltd (NICTA) grants permission, 10 free of charge, to any person who obtains a copy of this software 11 and any associated documentation files ("the Software") to use and 12 deal with the Software in source code and binary forms without 13 restriction, with or without modification, and to permit persons 14 to whom the Software is furnished to do so, provided that the 15 following conditions are met: 16 17 - Redistributions of source code must retain the above copyright 18 notice, this list of conditions and the following disclaimers. 19 - Redistributions in binary form must reproduce the above copyright 20 notice, this list of conditions and the following disclaimers in 21 the documentation and/or other materials provided with the 22 distribution. 23 - The name of NICTA may not be used to endorse or promote products 24 derived from this Software without specific prior written permission. 25 26 EXCEPT AS EXPRESSLY STATED IN THIS LICENCE AND TO THE FULL EXTENT 27 PERMITTED BY APPLICABLE LAW, THE SOFTWARE IS PROVIDED "AS-IS" AND 28 NICTA MAKES NO REPRESENTATIONS, WARRANTIES OR CONDITIONS OF ANY 29 KIND, EXPRESS OR IMPLIED, INCLUDING, WITHOUT LIMITATION, ANY 30 REPRESENTATIONS, WARRANTIES OR CONDITIONS REGARDING THE CONTENTS 31 OR ACCURACY OF THE SOFTWARE, OR OF TITLE, MERCHANTABILITY, FITNESS 32 FOR A PARTICULAR PURPOSE, NONINFRINGEMENT, THE ABSENCE OF LATENT 33 OR OTHER DEFECTS, OR THE PRESENCE OR ABSENCE OF ERRORS, WHETHER OR 34 NOT DISCOVERABLE. 35 36 TO THE FULL EXTENT PERMITTED BY APPLICABLE LAW, IN NO EVENT WILL 37 NICTA BE LIABLE ON ANY LEGAL THEORY (INCLUDING, WITHOUT LIMITATION, 38 NEGLIGENCE) FOR ANY LOSS OR DAMAGE WHATSOEVER, INCLUDING (WITHOUT 39 LIMITATION) LOSS OF PRODUCTION OR OPERATION TIME, LOSS, DAMAGE OR 40 CORRUPTION OF DATA OR RECORDS; OR LOSS OF ANTICIPATED SAVINGS, 41 OPPORTUNITY, REVENUE, PROFIT OR GOODWILL, OR OTHER ECONOMIC LOSS; 42 OR ANY SPECIAL, INCIDENTAL, INDIRECT, CONSEQUENTIAL, PUNITIVE OR 43 EXEMPLARY DAMAGES ARISING OUT OF OR IN CONNECTION WITH THIS LICENCE, 44 THE SOFTWARE OR THE USE OF THE SOFTWARE, EVEN IF NICTA HAS BEEN 45 ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. 46 47 If applicable legislation implies warranties or conditions, or 48 imposes obligations or liability on NICTA in respect of the Software 49 that cannot be wholly or partly excluded, restricted or modified, 50 NICTA's liability is limited, to the full extent permitted by the 51 applicable legislation, at its option, to: 52 53 a. in the case of goods, any one or more of the following: 54 i. the replacement of the goods or the supply of equivalent goods; 55 ii. the repair of the goods; 56 iii. the payment of the cost of replacing the goods or of acquiring 57 equivalent goods; 58 iv. the payment of the cost of having the goods repaired; or 59 b. in the case of services: 60 i. the supplying of the services again; or 61 ii. the payment of the cost of having the services supplied 62 again. 63 */ 64 65/* 66 NSSwitch Implementation of mDNS interface. 67 68 Andrew White (Andrew.White@nicta.com.au) 69 May 2004 70 */ 71 72#include <stdlib.h> 73#include <stdio.h> 74#include <string.h> 75#include <errno.h> 76#include <syslog.h> 77#include <pthread.h> 78#include <ctype.h> 79 80#include <sys/types.h> 81#include <sys/time.h> 82#include <sys/socket.h> 83 84#include <netinet/in.h> 85 86#include <arpa/inet.h> 87#define BIND_8_COMPAT 1 88#include <arpa/nameser.h> 89 90#include <dns_sd.h> 91 92 93//---------- 94// Public functions 95 96/* 97 Count the number of dots in a name string. 98 */ 99int 100count_dots (const char * name); 101 102 103/* 104 Test whether a domain name is local. 105 106 Returns 107 1 if name ends with ".local" or ".local." 108 0 otherwise 109 */ 110int 111islocal (const char * name); 112 113 114/* 115 Format an address structure as a string appropriate for DNS reverse (PTR) 116 lookup, based on address type. 117 118 Parameters 119 prefixlen 120 Prefix length, in bits. When formatting, this will be rounded up 121 to the nearest appropriate size. If -1, assume maximum. 122 buf 123 Output buffer. Must be long enough to hold largest possible 124 output. 125 Returns 126 Pointer to (first character of) output buffer, 127 or NULL on error. 128 */ 129char * 130format_reverse_addr (int af, const void * addr, int prefixlen, char * buf); 131 132 133/* 134 Format an address structure as a string appropriate for DNS reverse (PTR) 135 lookup for AF_INET. Output is in .in-addr.arpa domain. 136 137 Parameters 138 prefixlen 139 Prefix length, in bits. When formatting, this will be rounded up 140 to the nearest byte (8). If -1, assume 32. 141 buf 142 Output buffer. Must be long enough to hold largest possible 143 output. For AF_INET, this is 29 characters (including null). 144 Returns 145 Pointer to (first character of) output buffer, 146 or NULL on error. 147 */ 148char * 149format_reverse_addr_in ( 150 const struct in_addr * addr, 151 int prefixlen, 152 char * buf 153 ); 154#define DNS_PTR_AF_INET_SIZE 29 155 156/* 157 Format an address structure as a string appropriate for DNS reverse (PTR) 158 lookup for AF_INET6. Output is in .ip6.arpa domain. 159 160 Parameters 161 prefixlen 162 Prefix length, in bits. When formatting, this will be rounded up 163 to the nearest nibble (4). If -1, assume 128. 164 buf 165 Output buffer. Must be long enough to hold largest possible 166 output. For AF_INET6, this is 72 characters (including null). 167 Returns 168 Pointer to (first character of) output buffer, 169 or NULL on error. 170 */ 171char * 172format_reverse_addr_in6 ( 173 const struct in6_addr * addr, 174 int prefixlen, 175 char * buf 176 ); 177#define DNS_PTR_AF_INET6_SIZE 72 178 179 180/* 181 Compare whether the given dns name has the given domain suffix. 182 A single leading '.' on the name or leading or trailing '.' on the 183 domain is ignored for the purposes of the comparison. 184 Multiple leading or trailing '.'s are an error. Other DNS syntax 185 errors are not checked for. The comparison is case insensitive. 186 187 Returns 188 1 on success (match) 189 0 on failure (no match) 190 < 0 on error 191 */ 192int 193cmp_dns_suffix (const char * name, const char * domain); 194enum 195{ 196 CMP_DNS_SUFFIX_SUCCESS = 1, 197 CMP_DNS_SUFFIX_FAILURE = 0, 198 CMP_DNS_SUFFIX_BAD_NAME = 1, 199 CMP_DNS_SUFFIX_BAD_DOMAIN = -2 200}; 201 202typedef int ns_type_t; 203typedef int ns_class_t; 204 205/* 206 Convert a DNS resource record (RR) code to an address family (AF) code. 207 208 Parameters 209 rrtype 210 resource record type (from nameser.h) 211 212 Returns 213 Appropriate AF code (from socket.h), or AF_UNSPEC if an appropriate 214 mapping couldn't be determined 215 */ 216int 217rr_to_af (ns_type_t rrtype); 218 219 220/* 221 Convert an address family (AF) code to a DNS resource record (RR) code. 222 223 Parameters 224 int 225 address family code (from socket.h) 226 Returns 227 Appropriate RR code (from nameser.h), or ns_t_invalid if an appropriate 228 mapping couldn't be determined 229 */ 230ns_type_t 231af_to_rr (int af); 232 233 234/* 235 Convert a string to an address family (case insensitive). 236 237 Returns 238 Matching AF code, or AF_UNSPEC if no match found. 239 */ 240int 241str_to_af (const char * str); 242 243 244/* 245 Convert a string to an ns_class_t (case insensitive). 246 247 Returns 248 Matching ns_class_t, or ns_c_invalid if no match found. 249 */ 250ns_class_t 251str_to_ns_class (const char * str); 252 253 254/* 255 Convert a string to an ns_type_t (case insensitive). 256 257 Returns 258 Matching ns_type_t, or ns_t_invalid if no match found. 259 */ 260ns_type_t 261str_to_ns_type (const char * str); 262 263 264/* 265 Convert an address family code to a string. 266 267 Returns 268 String representation of AF, 269 or NULL if address family unrecognised or invalid. 270 */ 271const char * 272af_to_str (int in); 273 274 275/* 276 Convert an ns_class_t code to a string. 277 278 Returns 279 String representation of ns_class_t, 280 or NULL if ns_class_t unrecognised or invalid. 281 */ 282const char * 283ns_class_to_str (ns_class_t in); 284 285 286/* 287 Convert an ns_type_t code to a string. 288 289 Returns 290 String representation of ns_type_t, 291 or NULL if ns_type_t unrecognised or invalid. 292 */ 293const char * 294ns_type_to_str (ns_type_t in); 295 296 297/* 298 Convert DNS rdata in label format (RFC1034, RFC1035) to a name. 299 300 On error, partial data is written to name (as much as was successfully 301 processed) and an error code is returned. Errors include a name too 302 long for the buffer and a pointer in the label (which cannot be 303 resolved). 304 305 Parameters 306 rdata 307 Rdata formatted as series of labels. 308 rdlen 309 Length of rdata buffer. 310 name 311 Buffer to store fully qualified result in. 312 By RFC1034 section 3.1, a 255 character buffer (256 characters 313 including null) is long enough for any legal name. 314 name_len 315 Number of characters available in name buffer, not including 316 trailing null. 317 318 Returns 319 Length of name buffer (not including trailing null). 320 < 0 on error. 321 A return of 0 implies the empty domain. 322 */ 323static int 324dns_rdata_to_name (const unsigned char * rdata, int rdlen, char * name, unsigned int name_len); 325enum 326{ 327 DNS_RDATA_TO_NAME_BAD_FORMAT = -1, 328 // Format is broken. Usually because we ran out of data 329 // (according to rdata) before the labels said we should. 330 DNS_RDATA_TO_NAME_TOO_LONG = -2, 331 // The converted rdata is longer than the name buffer. 332 DNS_RDATA_TO_NAME_PTR = -3, 333 // The rdata contains a pointer. 334}; 335 336#define DNS_LABEL_MAXLEN 63 337// Maximum length of a single DNS label 338#define DNS_NAME_MAXLEN 256 339// Maximum length of a DNS name 340 341//---------- 342// Public types 343 344typedef int errcode_t; 345// Used for 0 = success, non-zero = error code functions 346 347 348//---------- 349// Public functions 350 351/* 352 Test whether a domain name is in a domain covered by nss_mdns. 353 The name is assumed to be fully qualified (trailing dot optional); 354 unqualified names will be processed but may return unusual results 355 if the unqualified prefix happens to match a domain suffix. 356 357 Returns 358 1 success 359 0 failure 360 -1 error, check errno 361 */ 362int 363config_is_mdns_suffix (const char * name); 364 365 366/* 367 Loads all relevant data from configuration file. Other code should 368 rarely need to call this function, since all other public configuration 369 functions do so implicitly. Once loaded, configuration info doesn't 370 change. 371 372 Returns 373 0 configuration ready 374 non-zero configuration error code 375 */ 376errcode_t 377init_config (); 378 379#define ENTNAME hostent 380#define DATABASE "hosts" 381 382#include <nss.h> 383// For nss_status 384#include <netdb.h> 385// For hostent 386#include <sys/types.h> 387// For size_t 388 389typedef enum nss_status nss_status; 390typedef struct hostent hostent; 391 392/* 393 gethostbyname implementation 394 395 name: 396 name to look up 397 result_buf: 398 resulting entry 399 buf: 400 auxillary buffer 401 buflen: 402 length of auxillary buffer 403 errnop: 404 pointer to errno 405 h_errnop: 406 pointer to h_errno 407 */ 408nss_status 409_nss_mdns_gethostbyname_r ( 410 const char *name, 411 hostent * result_buf, 412 char *buf, 413 size_t buflen, 414 int *errnop, 415 int *h_errnop 416 ); 417 418 419/* 420 gethostbyname2 implementation 421 422 name: 423 name to look up 424 af: 425 address family 426 result_buf: 427 resulting entry 428 buf: 429 auxillary buffer 430 buflen: 431 length of auxillary buffer 432 errnop: 433 pointer to errno 434 h_errnop: 435 pointer to h_errno 436 */ 437nss_status 438_nss_mdns_gethostbyname2_r ( 439 const char *name, 440 int af, 441 hostent * result_buf, 442 char *buf, 443 size_t buflen, 444 int *errnop, 445 int *h_errnop 446 ); 447 448 449/* 450 gethostbyaddr implementation 451 452 addr: 453 address structure to look up 454 len: 455 length of address structure 456 af: 457 address family 458 result_buf: 459 resulting entry 460 buf: 461 auxillary buffer 462 buflen: 463 length of auxillary buffer 464 errnop: 465 pointer to errno 466 h_errnop: 467 pointer to h_errno 468 */ 469nss_status 470_nss_mdns_gethostbyaddr_r ( 471 const void *addr, 472 socklen_t len, 473 int af, 474 hostent * result_buf, 475 char *buf, 476 size_t buflen, 477 int *errnop, 478 int *h_errnop 479 ); 480 481 482//---------- 483// Types and Constants 484 485const int MDNS_VERBOSE = 0; 486// This enables verbose syslog messages 487// If zero, only "imporant" messages will appear in syslog 488 489#define k_hostname_maxlen 256 490// As per RFC1034 and RFC1035 491#define k_aliases_max 15 492#define k_addrs_max 15 493 494typedef struct buf_header 495{ 496 char hostname [k_hostname_maxlen + 1]; 497 char * aliases [k_aliases_max + 1]; 498 char * addrs [k_addrs_max + 1]; 499} buf_header_t; 500 501typedef struct result_map 502{ 503 int done; 504 nss_status status; 505 hostent * hostent; 506 buf_header_t * header; 507 int aliases_count; 508 int addrs_count; 509 char * buffer; 510 int addr_idx; 511 // Index for addresses - grow from low end 512 // Index points to first empty space 513 int alias_idx; 514 // Index for aliases - grow from high end 515 // Index points to lowest entry 516 int r_errno; 517 int r_h_errno; 518} result_map_t; 519 520static const struct timeval 521k_select_time = { 0, 500000 }; 522// 0 seconds, 500 milliseconds 523 524//---------- 525// Local prototypes 526 527static nss_status 528mdns_gethostbyname2 ( 529 const char *name, 530 int af, 531 hostent * result_buf, 532 char *buf, 533 size_t buflen, 534 int *errnop, 535 int *h_errnop 536 ); 537 538 539/* 540 Lookup name using mDNS server 541 */ 542static nss_status 543mdns_lookup_name ( 544 const char * fullname, 545 int af, 546 result_map_t * result 547 ); 548 549/* 550 Lookup address using mDNS server 551 */ 552static nss_status 553mdns_lookup_addr ( 554 const void * addr, 555 socklen_t len, 556 int af, 557 const char * addr_str, 558 result_map_t * result 559 ); 560 561 562/* 563 Handle incoming MDNS events 564 */ 565static nss_status 566handle_events (DNSServiceRef sdref, result_map_t * result, const char * str); 567 568 569// Callback for mdns_lookup operations 570//DNSServiceQueryRecordReply mdns_lookup_callback; 571typedef void 572mdns_lookup_callback_t 573( 574 DNSServiceRef sdref, 575 DNSServiceFlags flags, 576 uint32_t interface_index, 577 DNSServiceErrorType error_code, 578 const char *fullname, 579 uint16_t rrtype, 580 uint16_t rrclass, 581 uint16_t rdlen, 582 const void *rdata, 583 uint32_t ttl, 584 void *context 585); 586 587mdns_lookup_callback_t mdns_lookup_callback; 588 589 590static int 591init_result ( 592 result_map_t * result, 593 hostent * result_buf, 594 char * buf, 595 size_t buflen 596 ); 597 598static int 599callback_body_ptr ( 600 const char * fullname, 601 result_map_t * result, 602 int rdlen, 603 const void * rdata 604 ); 605 606static void * 607add_address_to_buffer (result_map_t * result, const void * data, int len); 608static char * 609add_alias_to_buffer (result_map_t * result, const char * data, int len); 610static char * 611add_hostname_len (result_map_t * result, const char * fullname, int len); 612static char * 613add_hostname_or_alias (result_map_t * result, const char * data, int len); 614 615static void * 616contains_address (result_map_t * result, const void * data, int len); 617static char * 618contains_alias (result_map_t * result, const char * data); 619 620 621static const char * 622is_applicable_name ( 623 result_map_t * result, 624 const char * name, 625 char * lookup_name 626 ); 627 628static const char * 629is_applicable_addr ( 630 result_map_t * result, 631 const void * addr, 632 int af, 633 char * addr_str 634 ); 635 636 637// Error code functions 638 639static nss_status 640set_err (result_map_t * result, nss_status status, int err, int herr); 641 642static nss_status set_err_notfound (result_map_t * result); 643static nss_status set_err_bad_hostname (result_map_t * result); 644static nss_status set_err_buf_too_small (result_map_t * result); 645static nss_status set_err_internal_resource_full (result_map_t * result); 646static nss_status set_err_system (result_map_t * result); 647static nss_status set_err_mdns_failed (result_map_t * result); 648static nss_status set_err_success (result_map_t * result); 649 650 651//---------- 652// Global variables 653 654 655//---------- 656// NSS functions 657 658nss_status 659_nss_mdns_gethostbyname_r ( 660 const char *name, 661 hostent * result_buf, 662 char *buf, 663 size_t buflen, 664 int *errnop, 665 int *h_errnop 666 ) 667{ 668 if (MDNS_VERBOSE) 669 syslog (LOG_DEBUG, 670 "mdns: Called nss_mdns_gethostbyname with %s", 671 name 672 ); 673 674 return 675 mdns_gethostbyname2 ( 676 name, AF_INET, result_buf, buf, buflen, errnop, h_errnop 677 ); 678} 679 680 681nss_status 682_nss_mdns_gethostbyname2_r ( 683 const char *name, 684 int af, 685 hostent * result_buf, 686 char *buf, 687 size_t buflen, 688 int *errnop, 689 int *h_errnop 690 ) 691{ 692 if (MDNS_VERBOSE) 693 syslog (LOG_DEBUG, 694 "mdns: Called nss_mdns_gethostbyname2 with %s", 695 name 696 ); 697 698 return 699 mdns_gethostbyname2 ( 700 name, af, result_buf, buf, buflen, errnop, h_errnop 701 ); 702} 703 704 705nss_status 706_nss_mdns_gethostbyaddr_r ( 707 const void *addr, 708 socklen_t len, 709 int af, 710 hostent * result_buf, 711 char *buf, 712 size_t buflen, 713 int *errnop, 714 int *h_errnop 715 ) 716{ 717 char addr_str [NI_MAXHOST + 1]; 718 result_map_t result; 719 int err_status; 720 721 if (inet_ntop (af, addr, addr_str, NI_MAXHOST) == NULL) 722 { 723 const char * family = af_to_str (af); 724 if (family == NULL) 725 { 726 family = "Unknown"; 727 } 728 729 syslog (LOG_WARNING, 730 "mdns: Couldn't covert address, family %d (%s) in nss_mdns_gethostbyaddr: %s", 731 af, 732 family, 733 strerror (errno) 734 ); 735 736 // This address family never applicable to us, so return NOT_FOUND 737 738 *errnop = ENOENT; 739 *h_errnop = HOST_NOT_FOUND; 740 return NSS_STATUS_NOTFOUND; 741 } 742 if (MDNS_VERBOSE) 743 { 744 syslog (LOG_DEBUG, 745 "mdns: Called nss_mdns_gethostbyaddr with %s", 746 addr_str 747 ); 748 } 749 750 // Initialise result 751 err_status = init_result (&result, result_buf, buf, buflen); 752 if (err_status) 753 { 754 *errnop = err_status; 755 *h_errnop = NETDB_INTERNAL; 756 return NSS_STATUS_TRYAGAIN; 757 } 758 759 if (is_applicable_addr (&result, addr, af, addr_str)) 760 { 761 nss_status rv; 762 763 rv = mdns_lookup_addr (addr, len, af, addr_str, &result); 764 if (rv == NSS_STATUS_SUCCESS) 765 { 766 return rv; 767 } 768 } 769 770 // Return current error status (defaults to NOT_FOUND) 771 772 *errnop = result.r_errno; 773 *h_errnop = result.r_h_errno; 774 return result.status; 775} 776 777 778//---------- 779// Local functions 780 781nss_status 782mdns_gethostbyname2 ( 783 const char *name, 784 int af, 785 hostent * result_buf, 786 char *buf, 787 size_t buflen, 788 int *errnop, 789 int *h_errnop 790 ) 791{ 792 char lookup_name [k_hostname_maxlen + 1]; 793 result_map_t result; 794 int err_status; 795 796 // Initialise result 797 err_status = init_result (&result, result_buf, buf, buflen); 798 if (err_status) 799 { 800 *errnop = err_status; 801 *h_errnop = NETDB_INTERNAL; 802 return NSS_STATUS_TRYAGAIN; 803 } 804 805 if (is_applicable_name (&result, name, lookup_name)) 806 { 807 // Try using mdns 808 nss_status rv; 809 810 if (MDNS_VERBOSE) 811 syslog (LOG_DEBUG, 812 "mdns: Local name: %s", 813 name 814 ); 815 816 rv = mdns_lookup_name (name, af, &result); 817 if (rv == NSS_STATUS_SUCCESS) 818 { 819 return rv; 820 } 821 } 822 823 // Return current error status (defaults to NOT_FOUND) 824 825 *errnop = result.r_errno; 826 *h_errnop = result.r_h_errno; 827 return result.status; 828} 829 830 831/* 832 Lookup a fully qualified hostname using the default record type 833 for the specified address family. 834 835 Parameters 836 fullname 837 Fully qualified hostname. If not fully qualified the code will 838 still 'work', but the lookup is unlikely to succeed. 839 af 840 Either AF_INET or AF_INET6. Other families are not supported. 841 result 842 Initialised 'result' data structure. 843 */ 844static nss_status 845mdns_lookup_name ( 846 const char * fullname, 847 int af, 848 result_map_t * result 849 ) 850{ 851 // Lookup using mDNS. 852 DNSServiceErrorType errcode; 853 DNSServiceRef sdref; 854 ns_type_t rrtype; 855 nss_status status; 856 857 if (MDNS_VERBOSE) 858 syslog (LOG_DEBUG, 859 "mdns: Attempting lookup of %s", 860 fullname 861 ); 862 863 switch (af) 864 { 865 case AF_INET: 866 rrtype = kDNSServiceType_A; 867 result->hostent->h_length = 4; 868 // Length of an A record 869 break; 870 871 case AF_INET6: 872 rrtype = kDNSServiceType_AAAA; 873 result->hostent->h_length = 16; 874 // Length of an AAAA record 875 break; 876 877 default: 878 syslog (LOG_WARNING, 879 "mdns: Unsupported address family %d", 880 af 881 ); 882 return set_err_bad_hostname (result); 883 } 884 result->hostent->h_addrtype = af; 885 886 errcode = 887 DNSServiceQueryRecord ( 888 &sdref, 889 kDNSServiceFlagsForceMulticast, // force multicast query 890 kDNSServiceInterfaceIndexAny, // all interfaces 891 fullname, // full name to query for 892 rrtype, // resource record type 893 kDNSServiceClass_IN, // internet class records 894 mdns_lookup_callback, // callback 895 result // Context - result buffer 896 ); 897 898 if (errcode) 899 { 900 syslog (LOG_WARNING, 901 "mdns: Failed to initialise lookup, error %d", 902 errcode 903 ); 904 return set_err_mdns_failed (result); 905 } 906 907 status = handle_events (sdref, result, fullname); 908 DNSServiceRefDeallocate (sdref); 909 return status; 910} 911 912 913/* 914 Reverse (PTR) lookup for the specified address. 915 916 Parameters 917 addr 918 Either a struct in_addr or a struct in6_addr 919 addr_len 920 size of the address 921 af 922 Either AF_INET or AF_INET6. Other families are not supported. 923 Must match addr 924 addr_str 925 Address in format suitable for PTR lookup. 926 AF_INET: a.b.c.d -> d.c.b.a.in-addr.arpa 927 AF_INET6: reverse nibble format, x.x.x...x.ip6.arpa 928 result 929 Initialised 'result' data structure. 930 */ 931static nss_status 932mdns_lookup_addr ( 933 const void * addr, 934 socklen_t addr_len, 935 int af, 936 const char * addr_str, 937 result_map_t * result 938 ) 939{ 940 DNSServiceErrorType errcode; 941 DNSServiceRef sdref; 942 nss_status status; 943 944 if (MDNS_VERBOSE) 945 syslog (LOG_DEBUG, 946 "mdns: Attempting lookup of %s", 947 addr_str 948 ); 949 950 result->hostent->h_addrtype = af; 951 result->hostent->h_length = addr_len; 952 953 // Query address becomes "address" in result. 954 if (!add_address_to_buffer (result, addr, addr_len)) 955 { 956 return result->status; 957 } 958 959 result->hostent->h_name [0] = 0; 960 961 errcode = 962 DNSServiceQueryRecord ( 963 &sdref, 964 kDNSServiceFlagsForceMulticast, // force multicast query 965 kDNSServiceInterfaceIndexAny, // all interfaces 966 addr_str, // address string to query for 967 kDNSServiceType_PTR, // pointer RRs 968 kDNSServiceClass_IN, // internet class records 969 mdns_lookup_callback, // callback 970 result // Context - result buffer 971 ); 972 973 if (errcode) 974 { 975 syslog (LOG_WARNING, 976 "mdns: Failed to initialise mdns lookup, error %d", 977 errcode 978 ); 979 return set_err_mdns_failed (result); 980 } 981 982 status = handle_events (sdref, result, addr_str); 983 DNSServiceRefDeallocate (sdref); 984 return status; 985} 986 987 988/* 989 Wait on result of callback, and process it when it arrives. 990 991 Parameters 992 sdref 993 dns-sd reference 994 result 995 Initialised 'result' data structure. 996 str 997 lookup string, used for status/error reporting. 998 */ 999static nss_status 1000handle_events (DNSServiceRef sdref, result_map_t * result, const char * str) 1001{ 1002 int dns_sd_fd = DNSServiceRefSockFD(sdref); 1003 int nfds = dns_sd_fd + 1; 1004 fd_set readfds; 1005 struct timeval tv; 1006 int select_result; 1007 1008 while (!result->done) 1009 { 1010 FD_ZERO(&readfds); 1011 FD_SET(dns_sd_fd, &readfds); 1012 1013 tv = k_select_time; 1014 1015 select_result = 1016 select (nfds, &readfds, (fd_set*)NULL, (fd_set*)NULL, &tv); 1017 if (select_result > 0) 1018 { 1019 if (FD_ISSET(dns_sd_fd, &readfds)) 1020 { 1021 if (MDNS_VERBOSE) 1022 syslog (LOG_DEBUG, 1023 "mdns: Reply received for %s", 1024 str 1025 ); 1026 DNSServiceProcessResult(sdref); 1027 } 1028 else 1029 { 1030 syslog (LOG_WARNING, 1031 "mdns: Unexpected return from select on lookup of %s", 1032 str 1033 ); 1034 } 1035 } 1036 else 1037 { 1038 // Terminate loop due to timer expiry 1039 if (MDNS_VERBOSE) 1040 syslog (LOG_DEBUG, 1041 "mdns: %s not found - timer expired", 1042 str 1043 ); 1044 set_err_notfound (result); 1045 break; 1046 } 1047 } 1048 1049 return result->status; 1050} 1051 1052 1053/* 1054 Examine incoming data and add to relevant fields in result structure. 1055 This routine is called from DNSServiceProcessResult where appropriate. 1056 */ 1057void 1058mdns_lookup_callback 1059( 1060 DNSServiceRef sdref, 1061 DNSServiceFlags flags, 1062 uint32_t interface_index, 1063 DNSServiceErrorType error_code, 1064 const char *fullname, 1065 uint16_t rrtype, 1066 uint16_t rrclass, 1067 uint16_t rdlen, 1068 const void *rdata, 1069 uint32_t ttl, 1070 void *context 1071) 1072{ 1073 // A single record is received 1074 1075 result_map_t * result = (result_map_t *) context; 1076 1077 (void)sdref; // Unused 1078 (void)interface_index; // Unused 1079 (void)ttl; // Unused 1080 1081 if (!(flags & kDNSServiceFlagsMoreComing) ) 1082 { 1083 result->done = 1; 1084 } 1085 1086 if (error_code == kDNSServiceErr_NoError) 1087 { 1088 ns_type_t expected_rr_type = 1089 af_to_rr (result->hostent->h_addrtype); 1090 1091 // Idiot check class 1092 if (rrclass != C_IN) 1093 { 1094 syslog (LOG_WARNING, 1095 "mdns: Received bad RR class: expected %d (%s)," 1096 " got %d (%s), RR type %d (%s)", 1097 C_IN, 1098 ns_class_to_str (C_IN), 1099 rrclass, 1100 ns_class_to_str (rrclass), 1101 rrtype, 1102 ns_type_to_str (rrtype) 1103 ); 1104 return; 1105 } 1106 1107 // If a PTR 1108 if (rrtype == kDNSServiceType_PTR) 1109 { 1110 if (callback_body_ptr (fullname, result, rdlen, rdata) < 0) 1111 return; 1112 } 1113 else if (rrtype == expected_rr_type) 1114 { 1115 if (! 1116 add_hostname_or_alias ( 1117 result, 1118 fullname, 1119 strlen (fullname) 1120 ) 1121 ) 1122 { 1123 result->done = 1; 1124 return; 1125 // Abort on error 1126 } 1127 1128 if (!add_address_to_buffer (result, rdata, rdlen) ) 1129 { 1130 result->done = 1; 1131 return; 1132 // Abort on error 1133 } 1134 } 1135 else 1136 { 1137 syslog (LOG_WARNING, 1138 "mdns: Received bad RR type: expected %d (%s)," 1139 " got %d (%s)", 1140 expected_rr_type, 1141 ns_type_to_str (expected_rr_type), 1142 rrtype, 1143 ns_type_to_str (rrtype) 1144 ); 1145 return; 1146 } 1147 1148 if (result->status != NSS_STATUS_SUCCESS) 1149 set_err_success (result); 1150 } 1151 else 1152 { 1153 // For now, dump message to syslog and continue 1154 syslog (LOG_WARNING, 1155 "mdns: callback returned error %d", 1156 error_code 1157 ); 1158 } 1159} 1160 1161static int 1162callback_body_ptr ( 1163 const char * fullname, 1164 result_map_t * result, 1165 int rdlen, 1166 const void * rdata 1167 ) 1168{ 1169 char result_name [k_hostname_maxlen + 1]; 1170 int rv; 1171 1172 // Fullname should be .in-addr.arpa or equivalent, which we're 1173 // not interested in. Ignore it. 1174 1175 rv = dns_rdata_to_name (rdata, rdlen, result_name, k_hostname_maxlen); 1176 if (rv < 0) 1177 { 1178 const char * errmsg; 1179 1180 switch (rv) 1181 { 1182 case DNS_RDATA_TO_NAME_BAD_FORMAT: 1183 errmsg = "mdns: PTR '%s' result badly formatted ('%s...')"; 1184 break; 1185 1186 case DNS_RDATA_TO_NAME_TOO_LONG: 1187 errmsg = "mdns: PTR '%s' result too long ('%s...')"; 1188 break; 1189 1190 case DNS_RDATA_TO_NAME_PTR: 1191 errmsg = "mdns: PTR '%s' result contained pointer ('%s...')"; 1192 break; 1193 1194 default: 1195 errmsg = "mdns: PTR '%s' result conversion failed ('%s...')"; 1196 } 1197 1198 syslog (LOG_WARNING, 1199 errmsg, 1200 fullname, 1201 result_name 1202 ); 1203 1204 return -1; 1205 } 1206 1207 if (MDNS_VERBOSE) 1208 { 1209 syslog (LOG_DEBUG, 1210 "mdns: PTR '%s' resolved to '%s'", 1211 fullname, 1212 result_name 1213 ); 1214 } 1215 1216 // Data should be a hostname 1217 if (! 1218 add_hostname_or_alias ( 1219 result, 1220 result_name, 1221 rv 1222 ) 1223 ) 1224 { 1225 result->done = 1; 1226 return -1; 1227 } 1228 1229 return 0; 1230} 1231 1232 1233/* 1234 Add an address to the buffer. 1235 1236 Parameter 1237 result 1238 Result structure to write to 1239 data 1240 Incoming address data buffer 1241 Must be 'int' aligned 1242 len 1243 Length of data buffer (in bytes) 1244 Must match data alignment 1245 1246 Result 1247 Pointer to start of newly written data, 1248 or NULL on error. 1249 If address already exists in buffer, returns pointer to that instead. 1250 */ 1251static void * 1252add_address_to_buffer (result_map_t * result, const void * data, int len) 1253{ 1254 int new_addr; 1255 void * start; 1256 void * temp; 1257 1258 if ((temp = contains_address (result, data, len))) 1259 { 1260 return temp; 1261 } 1262 1263 if (result->addrs_count >= k_addrs_max) 1264 { 1265 // Not enough addr slots 1266 set_err_internal_resource_full (result); 1267 syslog (LOG_ERR, 1268 "mdns: Internal address buffer full; increase size" 1269 ); 1270 return NULL; 1271 } 1272 1273 // Idiot check 1274 if (len != result->hostent->h_length) 1275 { 1276 syslog (LOG_WARNING, 1277 "mdns: Unexpected rdata length for address. Expected %d, got %d", 1278 result->hostent->h_length, 1279 len 1280 ); 1281 // XXX And continue for now. 1282 } 1283 1284 new_addr = result->addr_idx + len; 1285 1286 if (new_addr > result->alias_idx) 1287 { 1288 // Not enough room 1289 set_err_buf_too_small (result); 1290 if (MDNS_VERBOSE) 1291 syslog (LOG_DEBUG, 1292 "mdns: Ran out of buffer when adding address %d", 1293 result->addrs_count + 1 1294 ); 1295 return NULL; 1296 } 1297 1298 start = result->buffer + result->addr_idx; 1299 memcpy (start, data, len); 1300 result->addr_idx = new_addr; 1301 result->header->addrs [result->addrs_count] = start; 1302 result->addrs_count++; 1303 result->header->addrs [result->addrs_count] = NULL; 1304 1305 return start; 1306} 1307 1308 1309static void * 1310contains_address (result_map_t * result, const void * data, int len) 1311{ 1312 int i; 1313 1314 // Idiot check 1315 if (len != result->hostent->h_length) 1316 { 1317 syslog (LOG_WARNING, 1318 "mdns: Unexpected rdata length for address. Expected %d, got %d", 1319 result->hostent->h_length, 1320 len 1321 ); 1322 // XXX And continue for now. 1323 } 1324 1325 for (i = 0; result->header->addrs [i]; i++) 1326 { 1327 if (memcmp (result->header->addrs [i], data, len) == 0) 1328 { 1329 return result->header->addrs [i]; 1330 } 1331 } 1332 1333 return NULL; 1334} 1335 1336 1337/* 1338 Add an alias to the buffer. 1339 1340 Parameter 1341 result 1342 Result structure to write to 1343 data 1344 Incoming alias (null terminated) 1345 len 1346 Length of data buffer (in bytes), including trailing null 1347 1348 Result 1349 Pointer to start of newly written data, 1350 or NULL on error 1351 If alias already exists in buffer, returns pointer to that instead. 1352 */ 1353static char * 1354add_alias_to_buffer (result_map_t * result, const char * data, int len) 1355{ 1356 int new_alias; 1357 char * start; 1358 char * temp; 1359 1360 if ((temp = contains_alias (result, data))) 1361 { 1362 return temp; 1363 } 1364 1365 if (result->aliases_count >= k_aliases_max) 1366 { 1367 // Not enough alias slots 1368 set_err_internal_resource_full (result); 1369 syslog (LOG_ERR, 1370 "mdns: Internal alias buffer full; increase size" 1371 ); 1372 return NULL; 1373 } 1374 1375 new_alias = result->alias_idx - len; 1376 1377 if (new_alias < result->addr_idx) 1378 { 1379 // Not enough room 1380 set_err_buf_too_small (result); 1381 if (MDNS_VERBOSE) 1382 syslog (LOG_DEBUG, 1383 "mdns: Ran out of buffer when adding alias %d", 1384 result->aliases_count + 1 1385 ); 1386 return NULL; 1387 } 1388 1389 start = result->buffer + new_alias; 1390 memcpy (start, data, len); 1391 result->alias_idx = new_alias; 1392 result->header->aliases [result->aliases_count] = start; 1393 result->aliases_count++; 1394 result->header->aliases [result->aliases_count] = NULL; 1395 1396 return start; 1397} 1398 1399 1400static char * 1401contains_alias (result_map_t * result, const char * alias) 1402{ 1403 int i; 1404 1405 for (i = 0; result->header->aliases [i]; i++) 1406 { 1407 if (strcmp (result->header->aliases [i], alias) == 0) 1408 { 1409 return result->header->aliases [i]; 1410 } 1411 } 1412 1413 return NULL; 1414} 1415 1416 1417/* 1418 Add fully qualified hostname to result. 1419 1420 Parameter 1421 result 1422 Result structure to write to 1423 fullname 1424 Fully qualified hostname 1425 1426 Result 1427 Pointer to start of hostname buffer, 1428 or NULL on error (usually hostname too long) 1429 */ 1430 1431static char * 1432add_hostname_len (result_map_t * result, const char * fullname, int len) 1433{ 1434 if (len >= k_hostname_maxlen) 1435 { 1436 set_err_bad_hostname (result); 1437 syslog (LOG_WARNING, 1438 "mdns: Hostname too long '%.*s': len %d, max %d", 1439 len, 1440 fullname, 1441 len, 1442 k_hostname_maxlen 1443 ); 1444 return NULL; 1445 } 1446 1447 result->hostent->h_name = 1448 strcpy (result->header->hostname, fullname); 1449 1450 return result->header->hostname; 1451} 1452 1453 1454/* 1455 Add fully qualified name as hostname or alias. 1456 1457 If hostname is not fully qualified this is not an error, but the data 1458 returned may be not what the application wanted. 1459 1460 Parameter 1461 result 1462 Result structure to write to 1463 data 1464 Incoming alias (null terminated) 1465 len 1466 Length of data buffer (in bytes), including trailing null 1467 1468 Result 1469 Pointer to start of newly written data, 1470 or NULL on error 1471 If alias or hostname already exists, returns pointer to that instead. 1472 */ 1473static char * 1474add_hostname_or_alias (result_map_t * result, const char * data, int len) 1475{ 1476 char * hostname = result->hostent->h_name; 1477 1478 if (*hostname) 1479 { 1480 if (strcmp (hostname, data) == 0) 1481 { 1482 return hostname; 1483 } 1484 else 1485 { 1486 return add_alias_to_buffer (result, data, len); 1487 } 1488 } 1489 else 1490 { 1491 return add_hostname_len (result, data, len); 1492 } 1493} 1494 1495 1496static int 1497init_result ( 1498 result_map_t * result, 1499 hostent * result_buf, 1500 char * buf, 1501 size_t buflen 1502 ) 1503{ 1504 if (buflen < sizeof (buf_header_t)) 1505 { 1506 return ERANGE; 1507 } 1508 1509 result->hostent = result_buf; 1510 result->header = (buf_header_t *) buf; 1511 result->header->hostname[0] = 0; 1512 result->aliases_count = 0; 1513 result->header->aliases[0] = NULL; 1514 result->addrs_count = 0; 1515 result->header->addrs[0] = NULL; 1516 result->buffer = buf + sizeof (buf_header_t); 1517 result->addr_idx = 0; 1518 result->alias_idx = buflen - sizeof (buf_header_t); 1519 result->done = 0; 1520 set_err_notfound (result); 1521 1522 // Point hostent to the right buffers 1523 result->hostent->h_name = result->header->hostname; 1524 result->hostent->h_aliases = result->header->aliases; 1525 result->hostent->h_addr_list = result->header->addrs; 1526 1527 return 0; 1528} 1529 1530/* 1531 Set the status in the result. 1532 1533 Parameters 1534 result 1535 Result structure to update 1536 status 1537 New nss_status value 1538 err 1539 New errno value 1540 herr 1541 New h_errno value 1542 1543 Returns 1544 New status value 1545 */ 1546static nss_status 1547set_err (result_map_t * result, nss_status status, int err, int herr) 1548{ 1549 result->status = status; 1550 result->r_errno = err; 1551 result->r_h_errno = herr; 1552 1553 return status; 1554} 1555 1556static nss_status 1557set_err_notfound (result_map_t * result) 1558{ 1559 return set_err (result, NSS_STATUS_NOTFOUND, ENOENT, HOST_NOT_FOUND); 1560} 1561 1562static nss_status 1563set_err_bad_hostname (result_map_t * result) 1564{ 1565 return set_err (result, NSS_STATUS_TRYAGAIN, ENOENT, NO_RECOVERY); 1566} 1567 1568static nss_status 1569set_err_buf_too_small (result_map_t * result) 1570{ 1571 return set_err (result, NSS_STATUS_TRYAGAIN, ERANGE, NETDB_INTERNAL); 1572} 1573 1574static nss_status 1575set_err_internal_resource_full (result_map_t * result) 1576{ 1577 return set_err (result, NSS_STATUS_RETURN, ERANGE, NO_RECOVERY); 1578} 1579 1580static nss_status 1581set_err_system (result_map_t * result) 1582{ 1583 return set_err (result, NSS_STATUS_UNAVAIL, errno, NETDB_INTERNAL); 1584} 1585 1586static nss_status 1587set_err_mdns_failed (result_map_t * result) 1588{ 1589 return set_err (result, NSS_STATUS_TRYAGAIN, EAGAIN, TRY_AGAIN); 1590} 1591 1592static nss_status 1593set_err_success (result_map_t * result) 1594{ 1595 result->status = NSS_STATUS_SUCCESS; 1596 return result->status; 1597} 1598 1599 1600/* 1601 Test whether name is applicable for mdns to process, and if so copy into 1602 lookup_name buffer (if non-NULL). 1603 1604 Returns 1605 Pointer to name to lookup up, if applicable, or NULL otherwise. 1606 */ 1607static const char * 1608is_applicable_name ( 1609 result_map_t * result, 1610 const char * name, 1611 char * lookup_name 1612 ) 1613{ 1614 int match = config_is_mdns_suffix (name); 1615 if (match > 0) 1616 { 1617 if (lookup_name) 1618 { 1619 strncpy (lookup_name, name, k_hostname_maxlen + 1); 1620 return lookup_name; 1621 } 1622 else 1623 { 1624 return name; 1625 } 1626 } 1627 else 1628 { 1629 if (match < 0) 1630 { 1631 set_err_system (result); 1632 } 1633 return NULL; 1634 } 1635} 1636 1637/* 1638 Test whether address is applicable for mdns to process, and if so copy into 1639 addr_str buffer as an address suitable for ptr lookup. 1640 1641 Returns 1642 Pointer to name to lookup up, if applicable, or NULL otherwise. 1643 */ 1644static const char * 1645is_applicable_addr ( 1646 result_map_t * result, 1647 const void * addr, 1648 int af, 1649 char * addr_str 1650 ) 1651{ 1652 int match; 1653 1654 if (!format_reverse_addr (af, addr, -1, addr_str)) 1655 { 1656 if (MDNS_VERBOSE) 1657 syslog (LOG_DEBUG, 1658 "mdns: Failed to create reverse address" 1659 ); 1660 return NULL; 1661 } 1662 1663 if (MDNS_VERBOSE) 1664 syslog (LOG_DEBUG, 1665 "mdns: Reverse address: %s", 1666 addr_str 1667 ); 1668 1669 match = config_is_mdns_suffix (addr_str); 1670 if (match > 0) 1671 { 1672 return addr_str; 1673 } 1674 else 1675 { 1676 if (match < 0) 1677 { 1678 set_err_system (result); 1679 } 1680 return NULL; 1681 } 1682} 1683 1684//---------- 1685// Types and Constants 1686 1687const char * k_conf_file = "/etc/nss_mdns.conf"; 1688#define CONF_LINE_SIZE 1024 1689 1690const char k_comment_char = '#'; 1691 1692const char * k_keyword_domain = "domain"; 1693 1694const char * k_default_domains [] = 1695{ 1696 "local", 1697 "254.169.in-addr.arpa", 1698 "8.e.f.ip6.int", 1699 "8.e.f.ip6.arpa", 1700 "9.e.f.ip6.int", 1701 "9.e.f.ip6.arpa", 1702 "a.e.f.ip6.int", 1703 "a.e.f.ip6.arpa", 1704 "b.e.f.ip6.int", 1705 "b.e.f.ip6.arpa", 1706 NULL 1707 // Always null terminated 1708}; 1709 1710// Linked list of domains 1711typedef struct domain_entry 1712{ 1713 char * domain; 1714 struct domain_entry * next; 1715} domain_entry_t; 1716 1717 1718// Config 1719typedef struct 1720{ 1721 domain_entry_t * domains; 1722} config_t; 1723 1724const config_t k_empty_config = 1725{ 1726 NULL 1727}; 1728 1729 1730// Context - tracks position in config file, used for error reporting 1731typedef struct 1732{ 1733 const char * filename; 1734 int linenum; 1735} config_file_context_t; 1736 1737 1738//---------- 1739// Local prototypes 1740 1741static errcode_t 1742load_config (config_t * conf); 1743 1744static errcode_t 1745process_config_line ( 1746 config_t * conf, 1747 char * line, 1748 config_file_context_t * context 1749 ); 1750 1751static char * 1752get_next_word (char * input, char **next); 1753 1754static errcode_t 1755default_config (config_t * conf); 1756 1757static errcode_t 1758add_domain (config_t * conf, const char * domain); 1759 1760static int 1761contains_domain (const config_t * conf, const char * domain); 1762 1763static int 1764contains_domain_suffix (const config_t * conf, const char * addr); 1765 1766 1767//---------- 1768// Global variables 1769 1770static config_t * g_config = NULL; 1771// Configuration info 1772 1773pthread_mutex_t g_config_mutex = 1774#ifdef PTHREAD_ERRORCHECK_MUTEX_INITIALIZER_NP 1775 PTHREAD_ERRORCHECK_MUTEX_INITIALIZER_NP; 1776#else 1777 PTHREAD_MUTEX_INITIALIZER; 1778#endif 1779 1780 1781//---------- 1782// Configuration functions 1783 1784 1785/* 1786 Initialise the configuration from the config file. 1787 1788 Returns 1789 0 success 1790 non-zero error code on failure 1791 */ 1792errcode_t 1793init_config () 1794{ 1795 if (g_config) 1796 { 1797 /* 1798 Safe to test outside mutex. 1799 If non-zero, initialisation is complete and g_config can be 1800 safely used read-only. If zero, then we do proper mutex 1801 testing before initialisation. 1802 */ 1803 return 0; 1804 } 1805 else 1806 { 1807 int errcode = -1; 1808 int presult; 1809 config_t * temp_config; 1810 1811 // Acquire mutex 1812 presult = pthread_mutex_lock (&g_config_mutex); 1813 if (presult) 1814 { 1815 syslog (LOG_ERR, 1816 "mdns: Fatal mutex lock error in nss_mdns:init_config, %s:%d: %d: %s", 1817 __FILE__, __LINE__, presult, strerror (presult) 1818 ); 1819 return presult; 1820 } 1821 1822 // Test again now we have mutex, in case initialisation occurred while 1823 // we were waiting 1824 if (!g_config) 1825 { 1826 temp_config = (config_t *) malloc (sizeof (config_t)); 1827 if (temp_config) 1828 { 1829 // Note: This code will leak memory if initialisation fails 1830 // repeatedly. This should only happen in the case of a memory 1831 // error, so I'm not sure if it's a meaningful problem. - AW 1832 *temp_config = k_empty_config; 1833 errcode = load_config (temp_config); 1834 1835 if (!errcode) 1836 { 1837 g_config = temp_config; 1838 } 1839 } 1840 else 1841 { 1842 syslog (LOG_ERR, 1843 "mdns: Can't allocate memory in nss_mdns:init_config, %s:%d", 1844 __FILE__, __LINE__ 1845 ); 1846 errcode = errno; 1847 } 1848 } 1849 1850 presult = pthread_mutex_unlock (&g_config_mutex); 1851 if (presult) 1852 { 1853 syslog (LOG_ERR, 1854 "mdns: Fatal mutex unlock error in nss_mdns:init_config, %s:%d: %d: %s", 1855 __FILE__, __LINE__, presult, strerror (presult) 1856 ); 1857 errcode = presult; 1858 } 1859 1860 return errcode; 1861 } 1862} 1863 1864 1865int 1866config_is_mdns_suffix (const char * name) 1867{ 1868 int errcode = init_config (); 1869 if (!errcode) 1870 { 1871 return contains_domain_suffix (g_config, name); 1872 } 1873 else 1874 { 1875 errno = errcode; 1876 return -1; 1877 } 1878} 1879 1880 1881//---------- 1882// Local functions 1883 1884static errcode_t 1885load_config (config_t * conf) 1886{ 1887 FILE * cf; 1888 char line [CONF_LINE_SIZE]; 1889 config_file_context_t context; 1890 1891 context.filename = k_conf_file; 1892 context.linenum = 0; 1893 1894 1895 cf = fopen (context.filename, "r"); 1896 if (!cf) 1897 { 1898 syslog (LOG_INFO, 1899 "mdns: Couldn't open nss_mdns configuration file %s, using default.", 1900 context.filename 1901 ); 1902 return default_config (conf); 1903 } 1904 1905 while (fgets (line, CONF_LINE_SIZE, cf)) 1906 { 1907 int errcode; 1908 context.linenum++; 1909 errcode = process_config_line (conf, line, &context); 1910 if (errcode) 1911 { 1912 // Critical error, give up 1913 fclose(cf); 1914 return errcode; 1915 } 1916 } 1917 1918 fclose (cf); 1919 1920 return 0; 1921} 1922 1923 1924/* 1925 Parse a line of the configuration file. 1926 For each keyword recognised, perform appropriate handling. 1927 If the keyword is not recognised, print a message to syslog 1928 and continue. 1929 1930 Returns 1931 0 success, or recoverable config file error 1932 non-zero serious system error, processing aborted 1933 */ 1934static errcode_t 1935process_config_line ( 1936 config_t * conf, 1937 char * line, 1938 config_file_context_t * context 1939 ) 1940{ 1941 char * curr = line; 1942 char * word; 1943 1944 word = get_next_word (curr, &curr); 1945 if (!word || word [0] == k_comment_char) 1946 { 1947 // Nothing interesting on this line 1948 return 0; 1949 } 1950 1951 if (strcmp (word, k_keyword_domain) == 0) 1952 { 1953 word = get_next_word (curr, &curr); 1954 if (word) 1955 { 1956 int errcode = add_domain (conf, word); 1957 if (errcode) 1958 { 1959 // something badly wrong, bail 1960 return errcode; 1961 } 1962 1963 if (get_next_word (curr, NULL)) 1964 { 1965 syslog (LOG_WARNING, 1966 "%s, line %d: ignored extra text found after domain", 1967 context->filename, 1968 context->linenum 1969 ); 1970 } 1971 } 1972 else 1973 { 1974 syslog (LOG_WARNING, 1975 "%s, line %d: no domain specified", 1976 context->filename, 1977 context->linenum 1978 ); 1979 } 1980 } 1981 else 1982 { 1983 syslog (LOG_WARNING, 1984 "%s, line %d: unknown keyword %s - skipping", 1985 context->filename, 1986 context->linenum, 1987 word 1988 ); 1989 } 1990 1991 return 0; 1992} 1993 1994 1995/* 1996 Get next word (whitespace separated) from input string. 1997 A null character is written into the first whitespace character following 1998 the word. 1999 2000 Parameters 2001 input 2002 Input string. This string is modified by get_next_word. 2003 next 2004 If non-NULL and the result is non-NULL, a pointer to the 2005 character following the end of the word (after the null) 2006 is written to 'next'. 2007 If no word is found, the original value is unchanged. 2008 If the word extended to the end of the string, 'next' points 2009 to the trailling NULL. 2010 It is safe to pass 'str' as 'input' and '&str' as 'next'. 2011 Returns 2012 Pointer to the first non-whitespace character (and thus word) found. 2013 if no word is found, returns NULL. 2014 */ 2015static char * 2016get_next_word (char * input, char **next) 2017{ 2018 char * curr = input; 2019 char * result; 2020 2021 while (isspace (*curr)) 2022 { 2023 curr++; 2024 } 2025 2026 if (*curr == 0) 2027 { 2028 return NULL; 2029 } 2030 2031 result = curr; 2032 while (*curr && !isspace (*curr)) 2033 { 2034 curr++; 2035 } 2036 if (*curr) 2037 { 2038 *curr = 0; 2039 if (next) 2040 { 2041 *next = curr+1; 2042 } 2043 } 2044 else 2045 { 2046 if (next) 2047 { 2048 *next = curr; 2049 } 2050 } 2051 2052 return result; 2053} 2054 2055 2056static errcode_t 2057default_config (config_t * conf) 2058{ 2059 int i; 2060 for (i = 0; k_default_domains [i]; i++) 2061 { 2062 int errcode = 2063 add_domain (conf, k_default_domains [i]); 2064 if (errcode) 2065 { 2066 // Something has gone (badly) wrong - let's bail 2067 return errcode; 2068 } 2069 } 2070 2071 return 0; 2072} 2073 2074 2075static errcode_t 2076add_domain (config_t * conf, const char * domain) 2077{ 2078 if (!contains_domain (conf, domain)) 2079 { 2080 domain_entry_t * d = 2081 (domain_entry_t *) malloc (sizeof (domain_entry_t)); 2082 if (!d) 2083 { 2084 syslog (LOG_ERR, 2085 "mdns: Can't allocate memory in nss_mdns:init_config, %s:%d", 2086 __FILE__, __LINE__ 2087 ); 2088 return ENOMEM; 2089 } 2090 2091 d->domain = strdup (domain); 2092 if (!d->domain) 2093 { 2094 syslog (LOG_ERR, 2095 "mdns: Can't allocate memory in nss_mdns:init_config, %s:%d", 2096 __FILE__, __LINE__ 2097 ); 2098 free (d); 2099 return ENOMEM; 2100 } 2101 d->next = conf->domains; 2102 conf->domains = d; 2103 } 2104 2105 return 0; 2106} 2107 2108 2109static int 2110contains_domain (const config_t * conf, const char * domain) 2111{ 2112 const domain_entry_t * curr = conf->domains; 2113 2114 while (curr != NULL) 2115 { 2116 if (strcasecmp (curr->domain, domain) == 0) 2117 { 2118 return 1; 2119 } 2120 2121 curr = curr->next; 2122 } 2123 2124 return 0; 2125} 2126 2127 2128static int 2129contains_domain_suffix (const config_t * conf, const char * addr) 2130{ 2131 const domain_entry_t * curr = conf->domains; 2132 2133 while (curr != NULL) 2134 { 2135 if (cmp_dns_suffix (addr, curr->domain) > 0) 2136 { 2137 return 1; 2138 } 2139 2140 curr = curr->next; 2141 } 2142 2143 return 0; 2144} 2145 2146//---------- 2147// Types and Constants 2148 2149static const char * k_local_suffix = "local"; 2150static const char k_dns_separator = '.'; 2151 2152static const unsigned int k_label_maxlen = DNS_LABEL_MAXLEN; 2153// Label entries longer than this are actually pointers. 2154 2155typedef struct 2156{ 2157 int value; 2158 const char * name; 2159 const char * comment; 2160} table_entry_t; 2161 2162static const table_entry_t k_table_af [] = 2163{ 2164 { AF_UNSPEC, NULL, NULL }, 2165 { AF_LOCAL, "LOCAL", NULL }, 2166 { AF_UNIX, "UNIX", NULL }, 2167 { AF_INET, "INET", NULL }, 2168 { AF_INET6, "INET6", NULL } 2169}; 2170static const int k_table_af_size = 2171 sizeof (k_table_af) / sizeof (*k_table_af); 2172 2173static const char * k_table_ns_class [] = 2174{ 2175 NULL, 2176 "IN" 2177}; 2178static const int k_table_ns_class_size = 2179 sizeof (k_table_ns_class) / sizeof (*k_table_ns_class); 2180 2181static const char * k_table_ns_type [] = 2182{ 2183 NULL, 2184 "A", 2185 "NS", 2186 "MD", 2187 "MF", 2188 "CNAME", 2189 "SOA", 2190 "MB", 2191 "MG", 2192 "MR", 2193 "NULL", 2194 "WKS", 2195 "PTR", 2196 "HINFO", 2197 "MINFO", 2198 "MX", 2199 "TXT", 2200 "RP", 2201 "AFSDB", 2202 "X25", 2203 "ISDN", 2204 "RT", 2205 "NSAP", 2206 NULL, 2207 "SIG", 2208 "KEY", 2209 "PX", 2210 "GPOS", 2211 "AAAA", 2212 "LOC", 2213 "NXT", 2214 "EID", 2215 "NIMLOC", 2216 "SRV", 2217 "ATMA", 2218 "NAPTR", 2219 "KX", 2220 "CERT", 2221 "A6", 2222 "DNAME", 2223 "SINK", 2224 "OPT" 2225}; 2226static const int k_table_ns_type_size = 2227 sizeof (k_table_ns_type) / sizeof (*k_table_ns_type); 2228 2229 2230//---------- 2231// Local prototypes 2232 2233static int 2234simple_table_index (const char * table [], int size, const char * str); 2235 2236static int 2237table_index_name (const table_entry_t table [], int size, const char * str); 2238 2239static int 2240table_index_value (const table_entry_t table [], int size, int n); 2241 2242 2243//---------- 2244// Global variables 2245 2246 2247//---------- 2248// Util functions 2249 2250int 2251count_dots (const char * name) 2252{ 2253 int count = 0; 2254 int i; 2255 for (i = 0; name[i]; i++) 2256 { 2257 if (name [i] == k_dns_separator) 2258 count++; 2259 } 2260 2261 return count; 2262} 2263 2264 2265int 2266islocal (const char * name) 2267{ 2268 return cmp_dns_suffix (name, k_local_suffix) > 0; 2269} 2270 2271 2272int 2273rr_to_af (ns_type_t rrtype) 2274{ 2275 switch (rrtype) 2276 { 2277 case kDNSServiceType_A: 2278 return AF_INET; 2279 2280 case kDNSServiceType_AAAA: 2281 return AF_INET6; 2282 2283 default: 2284 return AF_UNSPEC; 2285 } 2286} 2287 2288 2289ns_type_t 2290af_to_rr (int af) 2291{ 2292 switch (af) 2293 { 2294 case AF_INET: 2295 return kDNSServiceType_A; 2296 2297 case AF_INET6: 2298 return kDNSServiceType_AAAA; 2299 2300 default: 2301 //return ns_t_invalid; 2302 return 0; 2303 } 2304} 2305 2306 2307int 2308str_to_af (const char * str) 2309{ 2310 int result = 2311 table_index_name (k_table_af, k_table_af_size, str); 2312 if (result < 0) 2313 result = 0; 2314 2315 return k_table_af [result].value; 2316} 2317 2318 2319ns_class_t 2320str_to_ns_class (const char * str) 2321{ 2322 return (ns_class_t) 2323 simple_table_index (k_table_ns_class, k_table_ns_class_size, str); 2324} 2325 2326 2327ns_type_t 2328str_to_ns_type (const char * str) 2329{ 2330 return (ns_type_t) 2331 simple_table_index (k_table_ns_type, k_table_ns_type_size, str); 2332} 2333 2334 2335const char * 2336af_to_str (int in) 2337{ 2338 int result = 2339 table_index_value (k_table_af, k_table_af_size, in); 2340 if (result < 0) 2341 result = 0; 2342 2343 return k_table_af [result].name; 2344} 2345 2346 2347const char * 2348ns_class_to_str (ns_class_t in) 2349{ 2350 if (in < k_table_ns_class_size) 2351 return k_table_ns_class [in]; 2352 else 2353 return NULL; 2354} 2355 2356 2357const char * 2358ns_type_to_str (ns_type_t in) 2359{ 2360 if (in < k_table_ns_type_size) 2361 return k_table_ns_type [in]; 2362 else 2363 return NULL; 2364} 2365 2366 2367char * 2368format_reverse_addr_in ( 2369 const struct in_addr * addr, 2370 int prefixlen, 2371 char * buf 2372 ) 2373{ 2374 char * curr = buf; 2375 int i; 2376 2377 const uint8_t * in_addr_a = (uint8_t *) addr; 2378 2379 if (prefixlen > 32) 2380 return NULL; 2381 if (prefixlen < 0) 2382 prefixlen = 32; 2383 2384 i = (prefixlen + 7) / 8; 2385 // divide prefixlen into bytes, rounding up 2386 2387 while (i > 0) 2388 { 2389 i--; 2390 curr += sprintf (curr, "%d.", in_addr_a [i]); 2391 } 2392 sprintf (curr, "in-addr.arpa"); 2393 2394 return buf; 2395} 2396 2397 2398char * 2399format_reverse_addr_in6 ( 2400 const struct in6_addr * addr, 2401 int prefixlen, 2402 char * buf 2403 ) 2404{ 2405 char * curr = buf; 2406 int i; 2407 2408 const uint8_t * in_addr_a = (uint8_t *) addr; 2409 2410 if (prefixlen > 128) 2411 return NULL; 2412 if (prefixlen < 0) 2413 prefixlen = 128; 2414 2415 i = (prefixlen + 3) / 4; 2416 // divide prefixlen into nibbles, rounding up 2417 2418 // Special handling for first 2419 if (i % 2) 2420 { 2421 curr += sprintf (curr, "%d.", (in_addr_a [i/2] >> 4) & 0x0F); 2422 } 2423 i >>= 1; 2424 // Convert i to bytes (divide by 2) 2425 2426 while (i > 0) 2427 { 2428 uint8_t val; 2429 2430 i--; 2431 val = in_addr_a [i]; 2432 curr += sprintf (curr, "%x.%x.", val & 0x0F, (val >> 4) & 0x0F); 2433 } 2434 sprintf (curr, "ip6.arpa"); 2435 2436 return buf; 2437} 2438 2439 2440char * 2441format_reverse_addr ( 2442 int af, 2443 const void * addr, 2444 int prefixlen, 2445 char * buf 2446 ) 2447{ 2448 switch (af) 2449 { 2450 case AF_INET: 2451 return 2452 format_reverse_addr_in ( 2453 (struct in_addr *) addr, prefixlen, buf 2454 ); 2455 break; 2456 2457 case AF_INET6: 2458 return 2459 format_reverse_addr_in6 ( 2460 (struct in6_addr *) addr, prefixlen, buf 2461 ); 2462 break; 2463 2464 default: 2465 return NULL; 2466 } 2467} 2468 2469 2470int 2471cmp_dns_suffix (const char * name, const char * domain) 2472{ 2473 const char * nametail; 2474 const char * domaintail; 2475 2476 // Idiot checks 2477 if (*name == 0 || *name == k_dns_separator) 2478 { 2479 // Name can't be empty or start with separator 2480 return CMP_DNS_SUFFIX_BAD_NAME; 2481 } 2482 2483 if (*domain == 0) 2484 { 2485 return CMP_DNS_SUFFIX_SUCCESS; 2486 // trivially true 2487 } 2488 2489 if (*domain == k_dns_separator) 2490 { 2491 // drop leading separator from domain 2492 domain++; 2493 if (*domain == k_dns_separator) 2494 { 2495 return CMP_DNS_SUFFIX_BAD_DOMAIN; 2496 } 2497 } 2498 2499 // Find ends of strings 2500 for (nametail = name; *nametail; nametail++) 2501 ; 2502 for (domaintail = domain; *domaintail; domaintail++) 2503 ; 2504 2505 // Shuffle back to last real character, and drop any trailing '.' 2506 // while we're at it. 2507 nametail--; 2508 if (*nametail == k_dns_separator) 2509 { 2510 nametail--; 2511 if (*nametail == k_dns_separator) 2512 { 2513 return CMP_DNS_SUFFIX_BAD_NAME; 2514 } 2515 } 2516 domaintail--; 2517 if (*domaintail == k_dns_separator) 2518 { 2519 domaintail--; 2520 if (*domaintail == k_dns_separator) 2521 { 2522 return CMP_DNS_SUFFIX_BAD_DOMAIN; 2523 } 2524 } 2525 2526 // Compare. 2527 while ( 2528 nametail >= name 2529 && domaintail >= domain 2530 && tolower(*nametail) == tolower(*domaintail)) 2531 { 2532 nametail--; 2533 domaintail--; 2534 } 2535 2536 /* A successful finish will be one of the following: 2537 (leading and trailing . ignored) 2538 2539 name : domain2.domain1 2540 domain: domain2.domain1 2541 ^ 2542 2543 name : domain3.domain2.domain1 2544 domain: domain2.domain1 2545 ^ 2546 */ 2547 if ( 2548 domaintail < domain 2549 && (nametail < name || *nametail == k_dns_separator) 2550 ) 2551 { 2552 return CMP_DNS_SUFFIX_SUCCESS; 2553 } 2554 else 2555 { 2556 return CMP_DNS_SUFFIX_FAILURE; 2557 } 2558} 2559 2560 2561static int 2562dns_rdata_to_name (const unsigned char * rdata, int rdlen, char * name, unsigned int name_len) 2563{ 2564 int i = 0; 2565 // Index into 'name' 2566 const unsigned char * rdata_curr = rdata; 2567 2568 if (rdlen == 0) return DNS_RDATA_TO_NAME_BAD_FORMAT; 2569 2570 /* 2571 In RDATA, a DNS name is stored as a series of labels. 2572 Each label consists of a length octet (max value 63) 2573 followed by the data for that label. 2574 The series is terminated with a length 0 octet. 2575 A length octet beginning with bits 11 is a pointer to 2576 somewhere else in the payload, but we don't support these 2577 since we don't have access to the entire payload. 2578 2579 See RFC1034 section 3.1 and RFC1035 section 3.1. 2580 */ 2581 while (1) 2582 { 2583 unsigned int term_len = *rdata_curr; 2584 rdata_curr++; 2585 2586 if (term_len == 0) 2587 { 2588 break; 2589 // 0 length record terminates label 2590 } 2591 else if (term_len > k_label_maxlen) 2592 { 2593 name [i] = 0; 2594 return DNS_RDATA_TO_NAME_PTR; 2595 } 2596 else if (rdata_curr + term_len > rdata + rdlen) 2597 { 2598 name [i] = 0; 2599 return DNS_RDATA_TO_NAME_BAD_FORMAT; 2600 } 2601 2602 if (name_len < i + term_len + 1) 2603 // +1 is separator 2604 { 2605 name [i] = 0; 2606 return DNS_RDATA_TO_NAME_TOO_LONG; 2607 } 2608 2609 memcpy (name + i, rdata_curr, term_len); 2610 2611 i += term_len; 2612 rdata_curr += term_len; 2613 2614 name [i] = k_dns_separator; 2615 i++; 2616 } 2617 2618 name [i] = 0; 2619 return i; 2620} 2621 2622 2623//---------- 2624// Local functions 2625 2626/* 2627 Find the index of an string entry in a table. A case insenitive match 2628 is performed. If no entry is found, 0 is returned. 2629 2630 Parameters 2631 table 2632 Lookup table 2633 Table entries may be NULL. NULL entries will never match. 2634 size 2635 number of entries in table 2636 str 2637 lookup string 2638 2639 Result 2640 index of first matching entry, or 0 if no matches 2641 */ 2642static int 2643simple_table_index (const char * table [], int size, const char * str) 2644{ 2645 int i; 2646 for (i = 0; i < size; i++) 2647 { 2648 if ( 2649 table [i] 2650 && (strcasecmp (table [i], str) == 0) 2651 ) 2652 { 2653 return i; 2654 } 2655 } 2656 2657 return 0; 2658} 2659 2660 2661/* 2662 Find the index of a name in a table. 2663 2664 Parameters 2665 table 2666 array of table_entry_t records. The name field is compared 2667 (ignoring case) to the input string. 2668 size 2669 number of entries in table 2670 str 2671 lookup string 2672 2673 Result 2674 index of first matching entry, or -1 if no matches 2675 */ 2676static int 2677table_index_name (const table_entry_t table [], int size, const char * str) 2678{ 2679 int i; 2680 for (i = 0; i < size; i++) 2681 { 2682 if ( 2683 table [i].name 2684 && (strcasecmp (table [i].name, str) == 0) 2685 ) 2686 { 2687 return i; 2688 } 2689 } 2690 2691 return -1; 2692} 2693 2694 2695/* 2696 Find the index of a value a table. 2697 2698 Parameters 2699 table 2700 array of table_entry_t records. The value field is compared to 2701 the input value 2702 size 2703 number of entries in table 2704 n 2705 lookup value 2706 2707 Result 2708 index of first matching entry, or -1 if no matches 2709 */ 2710static int 2711table_index_value (const table_entry_t table [], int size, int n) 2712{ 2713 int i; 2714 for (i = 0; i < size; i++) 2715 { 2716 if (table [i].value == n) 2717 { 2718 return i; 2719 } 2720 } 2721 2722 return -1; 2723} 2724