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res_state.c revision 1.6.66.1 
      1 /*	$NetBSD: res_state.c,v 1.6.66.1 2024/12/15 15:04:53 martin 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  *
     19  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     20  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     21  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     23  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     24  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     25  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     26  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     27  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     28  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     29  * POSSIBILITY OF SUCH DAMAGE.
     30  */
     31 
     32 #include <sys/cdefs.h>
     33 #if defined(LIBC_SCCS) && !defined(lint)
     34 __RCSID("$NetBSD: res_state.c,v 1.6.66.1 2024/12/15 15:04:53 martin Exp $");
     35 #endif
     36 
     37 #include <sys/types.h>
     38 #include <sys/queue.h>
     39 #include <arpa/inet.h>
     40 #include <arpa/nameser.h>
     41 #include <stdlib.h>
     42 #include <unistd.h>
     43 #include <resolv.h>
     44 #include <netdb.h>
     45 
     46 #include "pthread.h"
     47 #include "pthread_int.h"
     48 
     49 static SLIST_HEAD(, _res_st) res_list = LIST_HEAD_INITIALIZER(&res_list);
     50 
     51 struct _res_st {
     52 	/* __res_put_state() assumes st_res is the first member. */
     53 	struct __res_state	st_res;
     54 
     55 	SLIST_ENTRY(_res_st)	st_list;
     56 };
     57 
     58 static pthread_mutex_t res_mtx = PTHREAD_MUTEX_INITIALIZER;
     59 
     60 res_state __res_state(void);
     61 res_state __res_get_state(void);
     62 void __res_put_state(res_state);
     63 
     64 #ifdef RES_STATE_DEBUG
     65 static void
     66 res_state_debug(const char *msg, void *p)
     67 {
     68 	char buf[512];
     69 	pthread_t self = pthread__self();
     70 	int len = snprintf(buf, sizeof(buf), "%p: %s %p\n", self, msg, p);
     71 
     72 	(void)write(STDOUT_FILENO, buf, (size_t)len);
     73 }
     74 #else
     75 #define res_state_debug(a, b)
     76 #endif
     77 
     78 
     79 res_state
     80 __res_get_state(void)
     81 {
     82 	res_state res;
     83 	struct _res_st *st;
     84 	pthread_mutex_lock(&res_mtx);
     85 	st = SLIST_FIRST(&res_list);
     86 	if (st != NULL) {
     87 		SLIST_REMOVE_HEAD(&res_list, st_list);
     88 		pthread_mutex_unlock(&res_mtx);
     89 		res = &st->st_res;
     90 		res_state_debug("checkout from list", st);
     91 	} else {
     92 		pthread_mutex_unlock(&res_mtx);
     93 		st = calloc(1, sizeof(*st));
     94 		if (st == NULL) {
     95 			h_errno = NETDB_INTERNAL;
     96 			return NULL;
     97 		}
     98 		res = &st->st_res;
     99 		res->options = 0;
    100 		res_state_debug("alloc new", res);
    101 	}
    102 	if ((res->options & RES_INIT) == 0) {
    103 		if (res_ninit(res) == -1) {
    104 			h_errno = NETDB_INTERNAL;
    105 			free(st);
    106 			return NULL;
    107 		}
    108 	}
    109 	return res;
    110 }
    111 
    112 void
    113 /*ARGSUSED*/
    114 __res_put_state(res_state res)
    115 {
    116 	struct _res_st *st = (struct _res_st *)(void *)res;
    117 
    118 	res_state_debug("free", res);
    119 	pthread_mutex_lock(&res_mtx);
    120 	SLIST_INSERT_HEAD(&res_list, st, st_list);
    121 	pthread_mutex_unlock(&res_mtx);
    122 }
    123 
    124 /*
    125  * This is aliased via a macro to _res; don't allow multi-threaded programs
    126  * to use it.
    127  */
    128 res_state
    129 __res_state(void)
    130 {
    131 	static const char res[] = "_res is not supported for multi-threaded"
    132 	    " programs.\n";
    133 	(void)write(STDERR_FILENO, res, sizeof(res) - 1);
    134 	abort();
    135 	return NULL;
    136 }
    137