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