| 1 | /*
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| 2 | * Copyright (c) 1988 Regents of the University of California.
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| 3 | * All rights reserved.
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| 4 | *
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| 5 | * Redistribution and use in source and binary forms are permitted
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| 6 | * provided that: (1) source distributions retain this entire copyright
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| 7 | * notice and comment, and (2) distributions including binaries display
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| 8 | * the following acknowledgement: ``This product includes software
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| 9 | * developed by the University of California, Berkeley and its contributors''
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| 10 | * in the documentation or other materials provided with the distribution
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| 11 | * and in all advertising materials mentioning features or use of this
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| 12 | * software. Neither the name of the University nor the names of its
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| 13 | * contributors may be used to endorse or promote products derived
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| 14 | * from this software without specific prior written permission.
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| 15 | * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
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| 16 | * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
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| 17 | * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
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| 18 | */
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| 19 |
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| 20 | #if defined(LIBC_SCCS) && !defined(lint)
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| 21 | static char sccsid[] = "@(#)res_query.c 5.7 (Berkeley) 6/1/90";
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| 22 | #endif /* LIBC_SCCS and not lint */
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| 23 |
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| 24 | #if _MINIX
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| 25 | #include <sys/types.h>
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| 26 | #include <ctype.h>
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| 27 | #include <errno.h>
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| 28 | #include <stdio.h>
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| 29 | #include <stdlib.h>
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| 30 | #include <string.h>
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| 31 |
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| 32 | #include <net/hton.h>
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| 33 | #include <net/gen/in.h>
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| 34 | #include <net/gen/nameser.h>
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| 35 | #include <net/gen/netdb.h>
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| 36 | #include <net/gen/resolv.h>
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| 37 |
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| 38 | #define bcopy(s,d,l) memcpy(d,s,l)
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| 39 |
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| 40 | #define hostalias __hostalias
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| 41 | #else
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| 42 | #include <sys/param.h>
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| 43 | #include <sys/socket.h>
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| 44 | #include <netinet/in.h>
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| 45 | #include <ctype.h>
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| 46 | #include <netdb.h>
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| 47 | #include <stdio.h>
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| 48 | #include <errno.h>
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| 49 | #include <string.h>
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| 50 | #include <arpa/inet.h>
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| 51 | #include <arpa/nameser.h>
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| 52 | #include <resolv.h>
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| 53 |
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| 54 | extern int errno;
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| 55 | #endif
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| 56 |
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| 57 | #if __STDC__
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| 58 | #define CONST const
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| 59 | #else
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| 60 | #define CONST
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| 61 | #endif
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| 62 |
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| 63 | #if PACKETSZ > 1024
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| 64 | #define MAXPACKET PACKETSZ
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| 65 | #else
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| 66 | #define MAXPACKET 1024
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| 67 | #endif
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| 68 |
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| 69 | int h_errno;
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| 70 |
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| 71 | /*
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| 72 | * Formulate a normal query, send, and await answer.
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| 73 | * Returned answer is placed in supplied buffer "answer".
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| 74 | * Perform preliminary check of answer, returning success only
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| 75 | * if no error is indicated and the answer count is nonzero.
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| 76 | * Return the size of the response on success, -1 on error.
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| 77 | * Error number is left in h_errno.
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| 78 | * Caller must parse answer and determine whether it answers the question.
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| 79 | */
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| 80 | int
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| 81 | res_query(name, class, type, answer, anslen)
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| 82 | char *name; /* domain name */
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| 83 | int class, type; /* class and type of query */
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| 84 | u_char *answer; /* buffer to put answer */
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| 85 | int anslen; /* size of answer buffer */
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| 86 | {
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| 87 | char buf[MAXPACKET];
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| 88 | dns_hdr_t *hp;
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| 89 | int n;
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| 90 |
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| 91 | if ((_res.options & RES_INIT) == 0 && res_init() == -1)
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| 92 | return (-1);
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| 93 | #ifdef DEBUG
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| 94 | if (_res.options & RES_DEBUG)
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| 95 | printf("res_query(%s, %d, %d)\n", name, class, type);
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| 96 | #endif
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| 97 | n = res_mkquery(QUERY, name, class, type, (char *)NULL, 0, NULL,
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| 98 | buf, sizeof(buf));
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| 99 |
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| 100 | if (n <= 0) {
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| 101 | #ifdef DEBUG
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| 102 | if (_res.options & RES_DEBUG)
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| 103 | printf("res_query: mkquery failed\n");
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| 104 | #endif
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| 105 | h_errno = NO_RECOVERY;
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| 106 | return (n);
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| 107 | }
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| 108 | n = res_send(buf, n, (char *)answer, anslen);
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| 109 | if (n < 0) {
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| 110 | #ifdef DEBUG
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| 111 | if (_res.options & RES_DEBUG)
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| 112 | printf("res_query: send error(%d)\n", errno);
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| 113 | #endif
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| 114 | h_errno = TRY_AGAIN;
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| 115 | return(n);
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| 116 | }
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| 117 |
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| 118 | hp = (dns_hdr_t *) answer;
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| 119 | if ((hp->dh_flag2 & DHF_RCODE) != NOERROR ||
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| 120 | ntohs(hp->dh_ancount) == 0) {
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| 121 | #ifdef DEBUG
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| 122 | if (_res.options & RES_DEBUG)
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| 123 | printf("rcode = %d, ancount=%d\n",
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| 124 | hp->dh_flag2 & DHF_RCODE,
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| 125 | ntohs(hp->dh_ancount));
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| 126 | #endif
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| 127 | switch (hp->dh_flag2 & DHF_RCODE) {
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| 128 | case NXDOMAIN:
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| 129 | h_errno = HOST_NOT_FOUND;
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| 130 | break;
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| 131 | case SERVFAIL:
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| 132 | h_errno = TRY_AGAIN;
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| 133 | break;
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| 134 | case NOERROR:
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| 135 | h_errno = NO_DATA;
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| 136 | break;
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| 137 | case FORMERR:
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| 138 | case NOTIMP:
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| 139 | case REFUSED:
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| 140 | default:
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| 141 | h_errno = NO_RECOVERY;
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| 142 | break;
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| 143 | }
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| 144 | return (-1);
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| 145 | }
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| 146 | return(n);
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| 147 | }
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| 148 |
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| 149 | /*
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| 150 | * Formulate a normal query, send, and retrieve answer in supplied buffer.
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| 151 | * Return the size of the response on success, -1 on error.
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| 152 | * If enabled, implement search rules until answer or unrecoverable failure
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| 153 | * is detected. Error number is left in h_errno.
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| 154 | * Only useful for queries in the same name hierarchy as the local host
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| 155 | * (not, for example, for host address-to-name lookups in domain in-addr.arpa).
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| 156 | */
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| 157 | res_search(name, class, type, answer, anslen)
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| 158 | char *name; /* domain name */
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| 159 | int class, type; /* class and type of query */
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| 160 | u_char *answer; /* buffer to put answer */
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| 161 | int anslen; /* size of answer */
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| 162 | {
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| 163 | register char *cp, **domain;
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| 164 | int n, ret, got_nodata = 0;
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| 165 |
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| 166 | if ((_res.options & RES_INIT) == 0 && res_init() == -1)
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| 167 | return (-1);
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| 168 |
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| 169 | errno = 0;
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| 170 | h_errno = HOST_NOT_FOUND; /* default, if we never query */
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| 171 | for (cp = name, n = 0; *cp; cp++)
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| 172 | if (*cp == '.')
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| 173 | n++;
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| 174 | if (n == 0 && (cp = hostalias(name)))
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| 175 | return (res_query(cp, class, type, answer, anslen));
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| 176 |
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| 177 | /*
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| 178 | * We do at least one level of search if
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| 179 | * - there is no dot and RES_DEFNAME is set, or
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| 180 | * - there is at least one dot, there is no trailing dot,
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| 181 | * and RES_DNSRCH is set.
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| 182 | */
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| 183 | if ((n == 0 && _res.options & RES_DEFNAMES) ||
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| 184 | (n != 0 && *--cp != '.' && _res.options & RES_DNSRCH))
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| 185 | for (domain = _res.dnsrch; *domain; domain++) {
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| 186 | ret = res_querydomain(name, *domain, class, type,
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| 187 | answer, anslen);
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| 188 | if (ret > 0)
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| 189 | return (ret);
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| 190 | /*
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| 191 | * If no server present, give up.
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| 192 | * If name isn't found in this domain,
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| 193 | * keep trying higher domains in the search list
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| 194 | * (if that's enabled).
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| 195 | * On a NO_DATA error, keep trying, otherwise
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| 196 | * a wildcard entry of another type could keep us
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| 197 | * from finding this entry higher in the domain.
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| 198 | * If we get some other error (negative answer or
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| 199 | * server failure), then stop searching up,
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| 200 | * but try the input name below in case it's fully-qualified.
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| 201 | */
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| 202 | if (errno == ECONNREFUSED) {
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| 203 | h_errno = TRY_AGAIN;
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| 204 | return (-1);
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| 205 | }
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| 206 | if (h_errno == NO_DATA)
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| 207 | got_nodata++;
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| 208 | if ((h_errno != HOST_NOT_FOUND && h_errno != NO_DATA) ||
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| 209 | (_res.options & RES_DNSRCH) == 0)
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| 210 | break;
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| 211 | }
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| 212 | /*
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| 213 | * If the search/default failed, try the name as fully-qualified,
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| 214 | * but only if it contained at least one dot (even trailing).
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| 215 | * This is purely a heuristic; we assume that any reasonable query
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| 216 | * about a top-level domain (for servers, SOA, etc) will not use
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| 217 | * res_search.
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| 218 | */
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| 219 | if (n && (ret = res_querydomain(name, (char *)NULL, class, type,
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| 220 | answer, anslen)) > 0)
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| 221 | return (ret);
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| 222 | if (got_nodata)
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| 223 | h_errno = NO_DATA;
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| 224 | return (-1);
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| 225 | }
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| 226 |
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| 227 | /*
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| 228 | * Perform a call on res_query on the concatenation of name and domain,
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| 229 | * removing a trailing dot from name if domain is NULL.
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| 230 | */
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| 231 | int
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| 232 | res_querydomain(name, domain, class, type, answer, anslen)
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| 233 | char *name, *domain;
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| 234 | int class, type; /* class and type of query */
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| 235 | u_char *answer; /* buffer to put answer */
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| 236 | int anslen; /* size of answer */
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| 237 | {
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| 238 | char nbuf[2*MAXDNAME+2];
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| 239 | char *longname = nbuf;
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| 240 | int n;
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| 241 |
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| 242 | #ifdef DEBUG
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| 243 | if (_res.options & RES_DEBUG)
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| 244 | printf("res_querydomain(%s, %s, %d, %d)\n",
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| 245 | name, domain, class, type);
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| 246 | #endif
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| 247 | if (domain == NULL) {
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| 248 | /*
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| 249 | * Check for trailing '.';
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| 250 | * copy without '.' if present.
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| 251 | */
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| 252 | n = strlen(name) - 1;
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| 253 | if (name[n] == '.' && n < sizeof(nbuf) - 1) {
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| 254 | bcopy(name, nbuf, n);
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| 255 | nbuf[n] = '\0';
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| 256 | } else
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| 257 | longname = name;
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| 258 | } else
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| 259 | (void)sprintf(nbuf, "%.*s.%.*s",
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| 260 | MAXDNAME, name, MAXDNAME, domain);
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| 261 |
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| 262 | return (res_query(longname, class, type, answer, anslen));
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| 263 | }
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| 264 |
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| 265 | char *
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| 266 | hostalias(name)
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| 267 | register CONST char *name;
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| 268 | {
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| 269 | register char *C1, *C2;
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| 270 | FILE *fp;
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| 271 | char *file;
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| 272 | char buf[BUFSIZ];
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| 273 | static char abuf[MAXDNAME];
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| 274 |
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| 275 | file = getenv("HOSTALIASES");
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| 276 | if (file == NULL || (fp = fopen(file, "r")) == NULL)
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| 277 | return (NULL);
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| 278 | buf[sizeof(buf) - 1] = '\0';
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| 279 | while (fgets(buf, sizeof(buf), fp)) {
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| 280 | for (C1 = buf; *C1 && !isspace(*C1); ++C1);
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| 281 | if (!*C1)
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| 282 | break;
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| 283 | *C1 = '\0';
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| 284 | if (!strcasecmp(buf, name)) {
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| 285 | while (isspace(*++C1));
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| 286 | if (!*C1)
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| 287 | break;
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| 288 | for (C2 = C1 + 1; *C2 && !isspace(*C2); ++C2);
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| 289 | abuf[sizeof(abuf) - 1] = *C2 = '\0';
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| 290 | (void)strncpy(abuf, C1, sizeof(abuf) - 1);
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| 291 | fclose(fp);
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| 292 | return (abuf);
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| 293 | }
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| 294 | }
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| 295 | fclose(fp);
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| 296 | return (NULL);
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| 297 | }
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