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      1 /*	$NetBSD: res_state.c,v 1.8 2024/12/15 11:34:14 riastradh 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 1.8 2024/12/15 11:34:14 riastradh Exp $");
     35 #endif
     36 
     37 /* Need to use libc-private names for atomic operations. */
     38 #include "../../common/lib/libc/atomic/atomic_op_namespace.h"
     39 
     40 #include <sys/types.h>
     41 #include <sys/queue.h>
     42 #include <arpa/inet.h>
     43 #include <arpa/nameser.h>
     44 #include <stdlib.h>
     45 #include <unistd.h>
     46 #include <resolv.h>
     47 #include <netdb.h>
     48 
     49 #include "pthread.h"
     50 #include "pthread_int.h"
     51 
     52 static SLIST_HEAD(, _res_st) res_list = LIST_HEAD_INITIALIZER(&res_list);
     53 
     54 struct _res_st {
     55 	/* __res_put_state() assumes st_res is the first member. */
     56 	struct __res_state	st_res;
     57 
     58 	SLIST_ENTRY(_res_st)	st_list;
     59 };
     60 
     61 static pthread_mutex_t res_mtx = PTHREAD_MUTEX_INITIALIZER;
     62 
     63 res_state __res_state(void);
     64 res_state __res_get_state(void);
     65 void __res_put_state(res_state);
     66 
     67 #ifdef RES_STATE_DEBUG
     68 static void
     69 res_state_debug(const char *msg, void *p)
     70 {
     71 	char buf[512];
     72 	pthread_t self = pthread__self();
     73 	int len = snprintf(buf, sizeof(buf), "%p: %s %p\n", self, msg, p);
     74 
     75 	(void)write(STDOUT_FILENO, buf, (size_t)len);
     76 }
     77 #else
     78 #define res_state_debug(a, b)
     79 #endif
     80 
     81 
     82 res_state
     83 __res_get_state(void)
     84 {
     85 	res_state res;
     86 	struct _res_st *st;
     87 	pthread_mutex_lock(&res_mtx);
     88 	st = SLIST_FIRST(&res_list);
     89 	if (st != NULL) {
     90 		SLIST_REMOVE_HEAD(&res_list, st_list);
     91 		pthread_mutex_unlock(&res_mtx);
     92 		res = &st->st_res;
     93 		res_state_debug("checkout from list", st);
     94 	} else {
     95 		pthread_mutex_unlock(&res_mtx);
     96 		st = calloc(1, sizeof(*st));
     97 		if (st == NULL) {
     98 			h_errno = NETDB_INTERNAL;
     99 			return NULL;
    100 		}
    101 		res = &st->st_res;
    102 		res->options = 0;
    103 		res_state_debug("alloc new", res);
    104 	}
    105 	if ((res->options & RES_INIT) == 0) {
    106 		if (res_ninit(res) == -1) {
    107 			h_errno = NETDB_INTERNAL;
    108 			free(st);
    109 			return NULL;
    110 		}
    111 	}
    112 	return res;
    113 }
    114 
    115 void
    116 /*ARGSUSED*/
    117 __res_put_state(res_state res)
    118 {
    119 	struct _res_st *st = (struct _res_st *)(void *)res;
    120 
    121 	res_state_debug("free", res);
    122 	pthread_mutex_lock(&res_mtx);
    123 	SLIST_INSERT_HEAD(&res_list, st, st_list);
    124 	pthread_mutex_unlock(&res_mtx);
    125 }
    126 
    127 /*
    128  * This is aliased via a macro to _res; don't allow multi-threaded programs
    129  * to use it.
    130  */
    131 res_state
    132 __res_state(void)
    133 {
    134 	static const char res[] = "_res is not supported for multi-threaded"
    135 	    " programs.\n";
    136 	(void)write(STDERR_FILENO, res, sizeof(res) - 1);
    137 	abort();
    138 	return NULL;
    139 }
    140