281 lines
8.0 KiB
C
281 lines
8.0 KiB
C
/* $Id$ */
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/* Copyright 1998 by the Massachusetts Institute of Technology.
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*
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* Permission to use, copy, modify, and distribute this
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* software and its documentation for any purpose and without
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* fee is hereby granted, provided that the above copyright
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* notice appear in all copies and that both that copyright
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* notice and this permission notice appear in supporting
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* documentation, and that the name of M.I.T. not be used in
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* advertising or publicity pertaining to distribution of the
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* software without specific, written prior permission.
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* M.I.T. makes no representations about the suitability of
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* this software for any purpose. It is provided "as is"
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* without express or implied warranty.
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*/
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#include "setup.h"
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <ctype.h>
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#if defined(WIN32) && !defined(WATT32)
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#include "nameser.h"
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#endif
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#include "ares.h"
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#include "ares_private.h"
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struct search_query {
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/* Arguments passed to ares_search */
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ares_channel channel;
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char *name; /* copied into an allocated buffer */
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int dnsclass;
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int type;
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ares_callback callback;
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void *arg;
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int status_as_is; /* error status from trying as-is */
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int next_domain; /* next search domain to try */
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int trying_as_is; /* current query is for name as-is */
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};
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static void search_callback(void *arg, int status, unsigned char *abuf,
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int alen);
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static void end_squery(struct search_query *squery, int status,
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unsigned char *abuf, int alen);
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static int cat_domain(const char *name, const char *domain, char **s);
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static int single_domain(ares_channel channel, const char *name, char **s);
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void ares_search(ares_channel channel, const char *name, int dnsclass,
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int type, ares_callback callback, void *arg)
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{
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struct search_query *squery;
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char *s;
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const char *p;
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int status, ndots;
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/* If name only yields one domain to search, then we don't have
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* to keep extra state, so just do an ares_query().
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*/
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status = single_domain(channel, name, &s);
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if (status != ARES_SUCCESS)
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{
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callback(arg, status, NULL, 0);
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return;
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}
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if (s)
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{
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ares_query(channel, s, dnsclass, type, callback, arg);
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free(s);
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return;
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}
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/* Allocate a search_query structure to hold the state necessary for
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* doing multiple lookups.
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*/
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squery = malloc(sizeof(struct search_query));
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if (!squery)
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{
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callback(arg, ARES_ENOMEM, NULL, 0);
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return;
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}
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squery->channel = channel;
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squery->name = strdup(name);
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if (!squery->name)
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{
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free(squery);
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callback(arg, ARES_ENOMEM, NULL, 0);
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return;
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}
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squery->dnsclass = dnsclass;
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squery->type = type;
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squery->status_as_is = -1;
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squery->callback = callback;
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squery->arg = arg;
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/* Count the number of dots in name. */
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ndots = 0;
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for (p = name; *p; p++)
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{
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if (*p == '.')
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ndots++;
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}
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/* If ndots is at least the channel ndots threshold (usually 1),
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* then we try the name as-is first. Otherwise, we try the name
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* as-is last.
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*/
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if (ndots >= channel->ndots)
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{
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/* Try the name as-is first. */
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squery->next_domain = 0;
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squery->trying_as_is = 1;
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ares_query(channel, name, dnsclass, type, search_callback, squery);
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}
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else
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{
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/* Try the name as-is last; start with the first search domain. */
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squery->next_domain = 1;
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squery->trying_as_is = 0;
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status = cat_domain(name, channel->domains[0], &s);
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if (status == ARES_SUCCESS)
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{
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ares_query(channel, s, dnsclass, type, search_callback, squery);
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free(s);
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}
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else
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{
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/* failed, free the malloc()ed memory */
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free(squery->name);
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free(squery);
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callback(arg, status, NULL, 0);
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}
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}
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}
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static void search_callback(void *arg, int status, unsigned char *abuf,
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int alen)
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{
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struct search_query *squery = (struct search_query *) arg;
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ares_channel channel = squery->channel;
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char *s;
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/* Stop searching unless we got a non-fatal error. */
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if (status != ARES_ENODATA && status != ARES_ESERVFAIL
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&& status != ARES_ENOTFOUND)
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end_squery(squery, status, abuf, alen);
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else
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{
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/* Save the status if we were trying as-is. */
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if (squery->trying_as_is)
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squery->status_as_is = status;
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if (squery->next_domain < channel->ndomains)
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{
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/* Try the next domain. */
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status = cat_domain(squery->name,
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channel->domains[squery->next_domain], &s);
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if (status != ARES_SUCCESS)
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end_squery(squery, status, NULL, 0);
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else
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{
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squery->trying_as_is = 0;
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squery->next_domain++;
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ares_query(channel, s, squery->dnsclass, squery->type,
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search_callback, squery);
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free(s);
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}
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}
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else if (squery->status_as_is == -1)
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{
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/* Try the name as-is at the end. */
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squery->trying_as_is = 1;
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ares_query(channel, squery->name, squery->dnsclass, squery->type,
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search_callback, squery);
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}
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else
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end_squery(squery, squery->status_as_is, NULL, 0);
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}
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}
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static void end_squery(struct search_query *squery, int status,
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unsigned char *abuf, int alen)
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{
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squery->callback(squery->arg, status, abuf, alen);
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free(squery->name);
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free(squery);
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}
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/* Concatenate two domains. */
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static int cat_domain(const char *name, const char *domain, char **s)
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{
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size_t nlen = strlen(name);
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size_t dlen = strlen(domain);
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*s = malloc(nlen + 1 + dlen + 1);
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if (!*s)
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return ARES_ENOMEM;
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memcpy(*s, name, nlen);
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(*s)[nlen] = '.';
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memcpy(*s + nlen + 1, domain, dlen);
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(*s)[nlen + 1 + dlen] = 0;
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return ARES_SUCCESS;
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}
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/* Determine if this name only yields one query. If it does, set *s to
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* the string we should query, in an allocated buffer. If not, set *s
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* to NULL.
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*/
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static int single_domain(ares_channel channel, const char *name, char **s)
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{
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size_t len = strlen(name);
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const char *hostaliases;
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FILE *fp;
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char *line = NULL;
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int linesize, status;
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const char *p, *q;
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/* If the name contains a trailing dot, then the single query is the name
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* sans the trailing dot.
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*/
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if (name[len - 1] == '.')
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{
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*s = strdup(name);
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return (*s) ? ARES_SUCCESS : ARES_ENOMEM;
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}
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if (!(channel->flags & ARES_FLAG_NOALIASES) && !strchr(name, '.'))
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{
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/* The name might be a host alias. */
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hostaliases = getenv("HOSTALIASES");
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if (hostaliases)
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{
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fp = fopen(hostaliases, "r");
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if (fp)
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{
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while ((status = ares__read_line(fp, &line, &linesize))
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== ARES_SUCCESS)
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{
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if (strncasecmp(line, name, len) != 0 ||
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!ISSPACE(line[len]))
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continue;
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p = line + len;
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while (ISSPACE(*p))
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p++;
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if (*p)
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{
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q = p + 1;
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while (*q && !ISSPACE(*q))
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q++;
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*s = malloc(q - p + 1);
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if (*s)
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{
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memcpy(*s, p, q - p);
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(*s)[q - p] = 0;
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}
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free(line);
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fclose(fp);
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return (*s) ? ARES_SUCCESS : ARES_ENOMEM;
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}
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}
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free(line);
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fclose(fp);
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if (status != ARES_SUCCESS)
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return status;
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}
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}
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}
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if (channel->flags & ARES_FLAG_NOSEARCH || channel->ndomains == 0)
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{
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/* No domain search to do; just try the name as-is. */
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*s = strdup(name);
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return (*s) ? ARES_SUCCESS : ARES_ENOMEM;
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}
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*s = NULL;
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return ARES_SUCCESS;
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}
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