1 /* 2 * CDDL HEADER START 3 * 4 * The contents of this file are subject to the terms of the 5 * Common Development and Distribution License (the "License"). 6 * You may not use this file except in compliance with the License. 7 * 8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE 9 * or http://www.opensolaris.org/os/licensing. 10 * See the License for the specific language governing permissions 11 * and limitations under the License. 12 * 13 * When distributing Covered Code, include this CDDL HEADER in each 14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE. 15 * If applicable, add the following below this CDDL HEADER, with the 16 * fields enclosed by brackets "[]" replaced with your own identifying 17 * information: Portions Copyright [yyyy] [name of copyright owner] 18 * 19 * CDDL HEADER END 20 */ 21 22 /* 23 * Copyright 2007 Sun Microsystems, Inc. All rights reserved. 24 * Use is subject to license terms. 25 */ 26 27 #pragma ident "%Z%%M% %I% %E% SMI" 28 29 #include <sys/types.h> 30 #include <netinet/in.h> 31 #include <arpa/nameser.h> 32 #include <resolv.h> 33 #include <netdb.h> 34 #include <limits.h> 35 #include <stdlib.h> 36 #include <string.h> 37 #include <unistd.h> 38 #include <ctype.h> 39 40 int 41 /* ARGSUSED */ 42 main(int argc, char **argv) 43 { 44 unsigned char answer[NS_MAXMSG], *ansp = NULL, *end; 45 int len = 0, anslen, hostlen, nq, na, type, class; 46 char hostname[MAXHOSTNAMELEN], *cp; 47 struct __res_state stat; 48 int found = 0; 49 HEADER *h; 50 51 if (argc != 1) 52 exit(1); 53 54 if (gethostname(hostname, MAXHOSTNAMELEN) != 0) 55 exit(1); 56 57 (void) memset(&stat, 0, sizeof (stat)); 58 59 if (res_ninit(&stat) == -1) 60 exit(1); 61 62 anslen = sizeof (answer); 63 len = res_nsearch(&stat, hostname, C_IN, T_A, answer, anslen); 64 65 if (len < sizeof (HEADER)) 66 exit(1); 67 68 ansp = answer; 69 end = ansp + anslen; 70 71 /* LINTED */ 72 h = (HEADER *)answer; 73 nq = ntohs(h->qdcount); 74 na = ntohs(h->ancount); 75 ansp += HFIXEDSZ; 76 77 if (nq != 1 || na < 1) 78 exit(1); 79 80 hostlen = sizeof (hostname); 81 len = dn_expand(answer, end, ansp, hostname, hostlen); 82 if (len < 0) 83 exit(1); 84 85 ansp += len + QFIXEDSZ; 86 87 if (ansp > end) 88 exit(1); 89 90 while (na-- > 0 && ansp < end) { 91 len = dn_expand(answer, end, ansp, hostname, hostlen); 92 93 if (len < 0) 94 continue; 95 ansp += len; /* hostname */ 96 type = ns_get16(ansp); 97 ansp += INT16SZ; /* type */ 98 class = ns_get16(ansp); 99 ansp += INT16SZ; /* class */ 100 ansp += INT32SZ; /* ttl */ 101 len = ns_get16(ansp); 102 ansp += INT16SZ; /* size */ 103 ansp += len; 104 if (type == T_A && class == C_IN) { 105 found = 1; 106 break; 107 } 108 } 109 110 if (found != 1) 111 exit(1); 112 113 for (cp = hostname; *cp; cp++) { 114 *cp = tolower(*cp); 115 } 116 117 (void) printf("%s\n", hostname); 118 119 return (0); 120 } 121