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res_state.c revision 1.4.18.1 
      1 /*	$NetBSD: res_state.c,v 1.4.18.1 2008/01/09 01:36:40 matt Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 2004 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * This code is derived from software contributed to The NetBSD Foundation
      8  * by Christos Zoulas.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  * 3. All advertising materials mentioning features or use of this software
     19  *    must display the following acknowledgement:
     20  *        This product includes software developed by the NetBSD
     21  *        Foundation, Inc. and its contributors.
     22  * 4. Neither the name of The NetBSD Foundation nor the names of its
     23  *    contributors may be used to endorse or promote products derived
     24  *    from this software without specific prior written permission.
     25  *
     26  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     27  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     28  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     29  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     30  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     31  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     32  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     33  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     34  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     35  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     36  * POSSIBILITY OF SUCH DAMAGE.
     37  */
     38 
     39 #include <sys/cdefs.h>
     40 #if defined(LIBC_SCCS) && !defined(lint)
     41 __RCSID("$NetBSD: res_state.c,v 1.4.18.1 2008/01/09 01:36:40 matt Exp $");
     42 #endif
     43 
     44 #include <sys/types.h>
     45 #include <sys/queue.h>
     46 #include <arpa/inet.h>
     47 #include <arpa/nameser.h>
     48 #include <stdlib.h>
     49 #include <unistd.h>
     50 #include <resolv.h>
     51 #include <netdb.h>
     52 
     53 #include "pthread.h"
     54 #include "pthread_int.h"
     55 
     56 static SLIST_HEAD(, _res_st) res_list = LIST_HEAD_INITIALIZER(&res_list);
     57 
     58 struct _res_st {
     59 	/* __res_put_state() assumes st_res is the first member. */
     60 	struct __res_state	st_res;
     61 
     62 	SLIST_ENTRY(_res_st)	st_list;
     63 };
     64 
     65 static pthread_mutex_t res_mtx = PTHREAD_MUTEX_INITIALIZER;
     66 
     67 res_state __res_state(void);
     68 res_state __res_get_state(void);
     69 void __res_put_state(res_state);
     70 
     71 #ifdef RES_STATE_DEBUG
     72 static void
     73 res_state_debug(const char *msg, void *p)
     74 {
     75 	char buf[512];
     76 	pthread_t self = pthread__self();
     77 	int len = snprintf(buf, sizeof(buf), "%p: %s %p\n", self, msg, p);
     78 
     79 	(void)write(STDOUT_FILENO, buf, (size_t)len);
     80 }
     81 #else
     82 #define res_state_debug(a, b)
     83 #endif
     84 
     85 
     86 res_state
     87 __res_get_state(void)
     88 {
     89 	res_state res;
     90 	struct _res_st *st;
     91 	pthread_mutex_lock(&res_mtx);
     92 	st = SLIST_FIRST(&res_list);
     93 	if (st != NULL) {
     94 		SLIST_REMOVE_HEAD(&res_list, st_list);
     95 		pthread_mutex_unlock(&res_mtx);
     96 		res = &st->st_res;
     97 		res_state_debug("checkout from list", st);
     98 	} else {
     99 		pthread_mutex_unlock(&res_mtx);
    100 		st = malloc(sizeof(*st));
    101 		if (st == NULL) {
    102 			h_errno = NETDB_INTERNAL;
    103 			return NULL;
    104 		}
    105 		res = &st->st_res;
    106 		res->options = 0;
    107 		res_state_debug("alloc new", res);
    108 	}
    109 	if ((res->options & RES_INIT) == 0) {
    110 		if (res_ninit(res) == -1) {
    111 			h_errno = NETDB_INTERNAL;
    112 			free(st);
    113 			return NULL;
    114 		}
    115 	}
    116 	return res;
    117 }
    118 
    119 void
    120 /*ARGSUSED*/
    121 __res_put_state(res_state res)
    122 {
    123 	struct _res_st *st = (struct _res_st *)(void *)res;
    124 
    125 	res_state_debug("free", res);
    126 	pthread_mutex_lock(&res_mtx);
    127 	SLIST_INSERT_HEAD(&res_list, st, st_list);
    128 	pthread_mutex_unlock(&res_mtx);
    129 }
    130 
    131 /*
    132  * This is aliased via a macro to _res; don't allow multi-threaded programs
    133  * to use it.
    134  */
    135 res_state
    136 __res_state(void)
    137 {
    138 	static const char res[] = "_res is not supported for multi-threaded"
    139 	    " programs.\n";
    140 	(void)write(STDERR_FILENO, res, sizeof(res) - 1);
    141 	abort();
    142 	return NULL;
    143 }
    144