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 the above copyright notice and this paragraph are |
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7 | * duplicated in all such forms and that any documentation, |
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8 | * advertising materials, and other materials related to such |
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9 | * distribution and use acknowledge that the software was developed |
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10 | * by the University of California, Berkeley. The name of the |
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11 | * University may not be used to endorse or promote products derived |
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12 | * from this software without specific prior written permission. |
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13 | * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR |
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14 | * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED |
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15 | * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE. |
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16 | */ |
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17 | |
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18 | #if defined(LIBC_SCCS) && !defined(lint) |
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19 | static char sccsid[] = "@(#)res_query.c 5.5 (Berkeley) 9/21/88"; |
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20 | #endif /* LIBC_SCCS and not lint */ |
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21 | |
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22 | #ifdef _IBMR2 |
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23 | #define BIT_ZERO_ON_LEFT |
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24 | #endif |
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25 | |
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26 | #ifdef _AUX_SOURCE |
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27 | #include <sys/types.h> |
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28 | #endif |
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29 | |
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30 | #include <sys/param.h> |
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31 | #include <sys/socket.h> |
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32 | #include <netinet/in.h> |
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33 | #include <ctype.h> |
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34 | #include <netdb.h> |
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35 | #include <stdio.h> |
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36 | #include <errno.h> |
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37 | #include <strings.h> |
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38 | #include <arpa/inet.h> |
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39 | #include <arpa/nameser.h> |
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40 | #include <resolv.h> |
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41 | |
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42 | #if !defined NO_DATA |
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43 | #define NO_DATA NO_ADDRESS |
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44 | #endif |
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45 | |
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46 | #if PACKETSZ > 1024 |
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47 | #define MAXPACKET PACKETSZ |
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48 | #else |
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49 | #define MAXPACKET 1024 |
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50 | #endif |
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51 | |
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52 | extern int server_specified; |
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53 | extern struct in_addr server_addr; |
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54 | extern int errno; |
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55 | int h_errno; |
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56 | |
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57 | /* |
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58 | * Formulate a normal query, send, and await answer. |
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59 | * Returned answer is placed in supplied buffer "answer". |
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60 | * Perform preliminary check of answer, returning success only |
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61 | * if no error is indicated and the answer count is nonzero. |
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62 | * Return the size of the response on success, -1 on error. |
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63 | * Error number is left in h_errno. |
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64 | * Caller must parse answer and determine whether it answers the question. |
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65 | */ |
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66 | res_query(name, class, type, answer, anslen) |
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67 | char *name; /* domain name */ |
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68 | int class, type; /* class and type of query */ |
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69 | u_char *answer; /* buffer to put answer */ |
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70 | int anslen; /* size of answer buffer */ |
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71 | { |
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72 | char buf[MAXPACKET]; |
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73 | HEADER *hp; |
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74 | int n; |
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75 | |
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76 | if ((_res.options & RES_INIT) == 0 && res_init() == -1) |
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77 | return (-1); |
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78 | |
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79 | if(server_specified) |
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80 | _res.nsaddr.sin_addr = server_addr; |
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81 | |
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82 | #ifdef DEBUG |
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83 | if (_res.options & RES_DEBUG) |
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84 | printf("res_query(%s, %d, %d)\n", name, class, type); |
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85 | #endif |
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86 | n = res_mkquery(QUERY, name, class, type, (char *)NULL, 0, NULL, |
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87 | buf, sizeof(buf)); |
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88 | |
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89 | if (n <= 0) { |
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90 | #ifdef DEBUG |
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91 | if (_res.options & RES_DEBUG) |
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92 | printf("res_query: mkquery failed\n"); |
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93 | #endif |
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94 | h_errno = NO_RECOVERY; |
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95 | return (n); |
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96 | } |
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97 | n = res_send(buf, n, answer, anslen); |
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98 | if (n < 0) { |
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99 | #ifdef DEBUG |
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100 | if (_res.options & RES_DEBUG) |
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101 | printf("res_query: send error\n"); |
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102 | #endif |
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103 | h_errno = TRY_AGAIN; |
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104 | return(n); |
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105 | } |
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106 | |
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107 | hp = (HEADER *) answer; |
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108 | if (hp->rcode != NOERROR || ntohs(hp->ancount) == 0) { |
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109 | #ifdef DEBUG |
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110 | if (_res.options & RES_DEBUG) |
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111 | printf("rcode = %d, ancount=%d\n", hp->rcode, |
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112 | ntohs(hp->ancount)); |
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113 | #endif |
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114 | switch (hp->rcode) { |
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115 | case NXDOMAIN: |
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116 | h_errno = HOST_NOT_FOUND; |
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117 | break; |
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118 | case SERVFAIL: |
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119 | h_errno = TRY_AGAIN; |
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120 | break; |
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121 | case NOERROR: |
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122 | h_errno = NO_DATA; |
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123 | break; |
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124 | case FORMERR: |
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125 | case NOTIMP: |
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126 | case REFUSED: |
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127 | default: |
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128 | h_errno = NO_RECOVERY; |
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129 | break; |
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130 | } |
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131 | return (-1); |
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132 | } |
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133 | return(n); |
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134 | } |
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135 | |
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136 | /* |
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137 | * Formulate a normal query, send, and retrieve answer in supplied buffer. |
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138 | * Return the size of the response on success, -1 on error. |
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139 | * If enabled, implement search rules until answer or unrecoverable failure |
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140 | * is detected. Error number is left in h_errno. |
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141 | * Only useful for queries in the same name hierarchy as the local host |
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142 | * (not, for example, for host address-to-name lookups in domain in-addr.arpa). |
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143 | */ |
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144 | res_search(name, class, type, answer, anslen) |
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145 | char *name; /* domain name */ |
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146 | int class, type; /* class and type of query */ |
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147 | u_char *answer; /* buffer to put answer */ |
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148 | int anslen; /* size of answer */ |
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149 | { |
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150 | register char *cp, **domain; |
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151 | int n, ret, got_nodata = 0; |
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152 | char *hostalias(); |
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153 | |
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154 | if ((_res.options & RES_INIT) == 0 && res_init() == -1) |
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155 | return (-1); |
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156 | |
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157 | errno = 0; |
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158 | h_errno = HOST_NOT_FOUND; /* default, if we never query */ |
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159 | for (cp = name, n = 0; *cp; cp++) |
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160 | if (*cp == '.') |
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161 | n++; |
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162 | if (n == 0 && (cp = hostalias(name))) |
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163 | return (res_query(cp, class, type, answer, anslen)); |
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164 | |
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165 | /* |
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166 | * We do at least one level of search if |
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167 | * - there is no dot and RES_DEFNAME is set, or |
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168 | * - there is at least one dot, there is no trailing dot, |
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169 | * and RES_DNSRCH is set. |
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170 | */ |
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171 | if ((n == 0 && _res.options & RES_DEFNAMES) || |
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172 | (n != 0 && *--cp != '.' && _res.options & RES_DNSRCH)) |
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173 | for (domain = _res.dnsrch; *domain; domain++) { |
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174 | ret = res_querydomain(name, *domain, class, type, |
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175 | answer, anslen); |
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176 | if (ret > 0) |
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177 | return (ret); |
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178 | /* |
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179 | * If no server present, give up. |
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180 | * If name isn't found in this domain, |
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181 | * keep trying higher domains in the search list |
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182 | * (if that's enabled). |
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183 | * On a NO_DATA error, keep trying, otherwise |
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184 | * a wildcard entry of another type could keep us |
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185 | * from finding this entry higher in the domain. |
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186 | * If we get some other error (negative answer or |
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187 | * server failure), then stop searching up, |
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188 | * but try the input name below in case it's fully-qualified. |
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189 | */ |
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190 | if (errno == ECONNREFUSED) { |
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191 | h_errno = TRY_AGAIN; |
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192 | return (-1); |
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193 | } |
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194 | if (h_errno == NO_DATA) |
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195 | got_nodata++; |
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196 | if ((h_errno != HOST_NOT_FOUND && h_errno != NO_DATA) || |
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197 | (_res.options & RES_DNSRCH) == 0) |
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198 | break; |
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199 | } |
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200 | /* |
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201 | * If the search/default failed, try the name as fully-qualified, |
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202 | * but only if it contained at least one dot (even trailing). |
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203 | * This is purely a heuristic; we assume that any reasonable query |
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204 | * about a top-level domain (for servers, SOA, etc) will not use |
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205 | * res_search. |
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206 | */ |
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207 | if (n && (ret = res_querydomain(name, (char *)NULL, class, type, |
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208 | answer, anslen)) > 0) |
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209 | return (ret); |
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210 | if (got_nodata) |
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211 | h_errno = NO_DATA; |
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212 | return (-1); |
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213 | } |
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214 | |
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215 | /* |
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216 | * Perform a call on res_query on the concatenation of name and domain, |
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217 | * removing a trailing dot from name if domain is NULL. |
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218 | */ |
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219 | res_querydomain(name, domain, class, type, answer, anslen) |
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220 | char *name, *domain; |
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221 | int class, type; /* class and type of query */ |
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222 | u_char *answer; /* buffer to put answer */ |
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223 | int anslen; /* size of answer */ |
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224 | { |
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225 | char nbuf[2*MAXDNAME+2]; |
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226 | char *longname = nbuf; |
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227 | int n; |
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228 | |
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229 | #ifdef DEBUG |
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230 | if (_res.options & RES_DEBUG) |
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231 | printf("res_querydomain(%s, %s, %d, %d)\n", |
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232 | name, domain, class, type); |
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233 | #endif |
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234 | if (domain == NULL) { |
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235 | /* |
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236 | * Check for trailing '.'; |
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237 | * copy without '.' if present. |
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238 | */ |
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239 | n = strlen(name) - 1; |
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240 | if (name[n] == '.' && n < sizeof(nbuf) - 1) { |
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241 | bcopy(name, nbuf, n); |
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242 | nbuf[n] = '\0'; |
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243 | } else |
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244 | longname = name; |
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245 | } else |
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246 | (void)sprintf(nbuf, "%.*s.%.*s", |
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247 | MAXDNAME, name, MAXDNAME, domain); |
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248 | |
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249 | return (res_query(longname, class, type, answer, anslen)); |
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250 | } |
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251 | |
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252 | char * |
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253 | hostalias(name) |
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254 | register char *name; |
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255 | { |
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256 | register char *C1, *C2; |
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257 | FILE *fp; |
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258 | #ifndef _IBMR2 |
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259 | char *file, *getenv(), *strcpy(), *strncpy(); |
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260 | #else |
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261 | char *file; |
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262 | #endif |
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263 | char buf[BUFSIZ]; |
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264 | static char abuf[MAXDNAME]; |
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265 | |
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266 | file = getenv("HOSTALIASES"); |
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267 | if (file == NULL || (fp = fopen(file, "r")) == NULL) |
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268 | return (NULL); |
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269 | buf[sizeof(buf) - 1] = '\0'; |
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270 | while (fgets(buf, sizeof(buf), fp)) { |
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271 | for (C1 = buf; *C1 && !isspace(*C1); ++C1); |
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272 | if (!*C1) |
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273 | break; |
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274 | *C1 = '\0'; |
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275 | if (!strcasecmp(buf, name)) { |
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276 | while (isspace(*++C1)); |
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277 | if (!*C1) |
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278 | break; |
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279 | for (C2 = C1 + 1; *C2 && !isspace(*C2); ++C2); |
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280 | abuf[sizeof(abuf) - 1] = *C2 = '\0'; |
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281 | (void)strncpy(abuf, C1, sizeof(abuf) - 1); |
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282 | fclose(fp); |
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283 | return (abuf); |
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284 | } |
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285 | } |
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286 | fclose(fp); |
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287 | return (NULL); |
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288 | } |
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