1*0Sstevel@tonic-gate /* 2*0Sstevel@tonic-gate * CDDL HEADER START 3*0Sstevel@tonic-gate * 4*0Sstevel@tonic-gate * The contents of this file are subject to the terms of the 5*0Sstevel@tonic-gate * Common Development and Distribution License, Version 1.0 only 6*0Sstevel@tonic-gate * (the "License"). You may not use this file except in compliance 7*0Sstevel@tonic-gate * with the License. 8*0Sstevel@tonic-gate * 9*0Sstevel@tonic-gate * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE 10*0Sstevel@tonic-gate * or http://www.opensolaris.org/os/licensing. 11*0Sstevel@tonic-gate * See the License for the specific language governing permissions 12*0Sstevel@tonic-gate * and limitations under the License. 13*0Sstevel@tonic-gate * 14*0Sstevel@tonic-gate * When distributing Covered Code, include this CDDL HEADER in each 15*0Sstevel@tonic-gate * file and include the License file at usr/src/OPENSOLARIS.LICENSE. 16*0Sstevel@tonic-gate * If applicable, add the following below this CDDL HEADER, with the 17*0Sstevel@tonic-gate * fields enclosed by brackets "[]" replaced with your own identifying 18*0Sstevel@tonic-gate * information: Portions Copyright [yyyy] [name of copyright owner] 19*0Sstevel@tonic-gate * 20*0Sstevel@tonic-gate * CDDL HEADER END 21*0Sstevel@tonic-gate */ 22*0Sstevel@tonic-gate /* 23*0Sstevel@tonic-gate * Copyright (c) 1993, 1998-2001 by Sun Microsystems, Inc. 24*0Sstevel@tonic-gate * All rights reserved. 25*0Sstevel@tonic-gate */ 26*0Sstevel@tonic-gate 27*0Sstevel@tonic-gate #pragma ident "%Z%%M% %I% %E% SMI" 28*0Sstevel@tonic-gate 29*0Sstevel@tonic-gate /* 30*0Sstevel@tonic-gate * dns_mt.c 31*0Sstevel@tonic-gate * 32*0Sstevel@tonic-gate * This file contains all the MT related routines for the DNS backend. 33*0Sstevel@tonic-gate */ 34*0Sstevel@tonic-gate 35*0Sstevel@tonic-gate #include "dns_common.h" 36*0Sstevel@tonic-gate #include <dlfcn.h> 37*0Sstevel@tonic-gate 38*0Sstevel@tonic-gate /* 39*0Sstevel@tonic-gate * If the DNS name service switch routines are used in a binary that depends 40*0Sstevel@tonic-gate * on an older libresolv (libresolv.so.1, say), then having nss_dns.so.1 or 41*0Sstevel@tonic-gate * libnss_dns.a depend on a newer libresolv (libresolv.so.2) will cause 42*0Sstevel@tonic-gate * relocation problems. In particular, copy relocation of the _res structure 43*0Sstevel@tonic-gate * (which changes in size from libresolv.so.1 to libresolv.so.2) could 44*0Sstevel@tonic-gate * cause corruption, and result in a number of strange problems, including 45*0Sstevel@tonic-gate * core dumps. Hence, we check if a libresolv is already loaded. 46*0Sstevel@tonic-gate */ 47*0Sstevel@tonic-gate 48*0Sstevel@tonic-gate #pragma init(_nss_dns_init) 49*0Sstevel@tonic-gate static void _nss_dns_init(void); 50*0Sstevel@tonic-gate 51*0Sstevel@tonic-gate extern struct hostent *res_gethostbyname(const char *); 52*0Sstevel@tonic-gate #pragma weak res_gethostbyname 53*0Sstevel@tonic-gate 54*0Sstevel@tonic-gate #define RES_SET_NO_HOSTS_FALLBACK "__res_set_no_hosts_fallback" 55*0Sstevel@tonic-gate extern void __res_set_no_hosts_fallback(void); 56*0Sstevel@tonic-gate #pragma weak __res_set_no_hosts_fallback 57*0Sstevel@tonic-gate 58*0Sstevel@tonic-gate #define RES_UNSET_NO_HOSTS_FALLBACK "__res_unset_no_hosts_fallback" 59*0Sstevel@tonic-gate extern void __res_unset_no_hosts_fallback(void); 60*0Sstevel@tonic-gate #pragma weak __res_unset_no_hosts_fallback 61*0Sstevel@tonic-gate 62*0Sstevel@tonic-gate #define RES_GET_RES "__res_get_res" 63*0Sstevel@tonic-gate extern struct __res_state *__res_get_res(void); 64*0Sstevel@tonic-gate #pragma weak __res_get_res 65*0Sstevel@tonic-gate 66*0Sstevel@tonic-gate #define RES_ENABLE_MT "__res_enable_mt" 67*0Sstevel@tonic-gate extern int __res_enable_mt(void); 68*0Sstevel@tonic-gate #pragma weak __res_enable_mt 69*0Sstevel@tonic-gate 70*0Sstevel@tonic-gate #define RES_DISABLE_MT "__res_disable_mt" 71*0Sstevel@tonic-gate extern int __res_disable_mt(void); 72*0Sstevel@tonic-gate #pragma weak __res_disable_mt 73*0Sstevel@tonic-gate 74*0Sstevel@tonic-gate #define RES_GET_H_ERRNO "__res_get_h_errno" 75*0Sstevel@tonic-gate extern int *__res_get_h_errno(); 76*0Sstevel@tonic-gate #pragma weak __res_get_h_errno 77*0Sstevel@tonic-gate 78*0Sstevel@tonic-gate #define __H_ERRNO "__h_errno" 79*0Sstevel@tonic-gate extern int *__h_errno(void); 80*0Sstevel@tonic-gate #pragma weak __h_errno 81*0Sstevel@tonic-gate 82*0Sstevel@tonic-gate #define RES_OVERRIDE_RETRY "__res_override_retry" 83*0Sstevel@tonic-gate extern int __res_override_retry(int); 84*0Sstevel@tonic-gate #pragma weak __res_override_retry 85*0Sstevel@tonic-gate 86*0Sstevel@tonic-gate static void __fallback_set_no_hosts(void); 87*0Sstevel@tonic-gate static int *__fallback_h_errno(void); 88*0Sstevel@tonic-gate static int __fallback_override_retry(int); 89*0Sstevel@tonic-gate static int __is_mt_safe(void); 90*0Sstevel@tonic-gate 91*0Sstevel@tonic-gate void (*set_no_hosts_fallback)(void) = __fallback_set_no_hosts; 92*0Sstevel@tonic-gate void (*unset_no_hosts_fallback)(void) = __fallback_set_no_hosts; 93*0Sstevel@tonic-gate struct __res_state *(*set_res_retry)() = 0; 94*0Sstevel@tonic-gate int (*enable_mt)() = 0; 95*0Sstevel@tonic-gate int (*disable_mt)() = 0; 96*0Sstevel@tonic-gate int *(*get_h_errno)(void) = 0; 97*0Sstevel@tonic-gate int (*override_retry)(int) = 0; 98*0Sstevel@tonic-gate 99*0Sstevel@tonic-gate /* Usually set from the Makefile */ 100*0Sstevel@tonic-gate #ifndef NSS_DNS_LIBRESOLV 101*0Sstevel@tonic-gate #define NSS_DNS_LIBRESOLV "libresolv.so.2" 102*0Sstevel@tonic-gate #endif 103*0Sstevel@tonic-gate 104*0Sstevel@tonic-gate /* From libresolv */ 105*0Sstevel@tonic-gate extern int h_errno; 106*0Sstevel@tonic-gate 107*0Sstevel@tonic-gate mutex_t one_lane = DEFAULTMUTEX; 108*0Sstevel@tonic-gate 109*0Sstevel@tonic-gate void 110*0Sstevel@tonic-gate _nss_dns_init(void) 111*0Sstevel@tonic-gate { 112*0Sstevel@tonic-gate struct hostent *(*f_hostent_ptr)(); 113*0Sstevel@tonic-gate void *reslib, (*f_void_ptr)(); 114*0Sstevel@tonic-gate 115*0Sstevel@tonic-gate /* If no libresolv library, then load one */ 116*0Sstevel@tonic-gate if ((f_hostent_ptr = res_gethostbyname) == 0) { 117*0Sstevel@tonic-gate if ((reslib = 118*0Sstevel@tonic-gate dlopen(NSS_DNS_LIBRESOLV, RTLD_LAZY|RTLD_GLOBAL)) != 0) { 119*0Sstevel@tonic-gate /* Turn off /etc/hosts fall back in libresolv */ 120*0Sstevel@tonic-gate if ((f_void_ptr = (void (*)(void))dlsym(reslib, 121*0Sstevel@tonic-gate RES_SET_NO_HOSTS_FALLBACK)) != 0) { 122*0Sstevel@tonic-gate set_no_hosts_fallback = f_void_ptr; 123*0Sstevel@tonic-gate } 124*0Sstevel@tonic-gate if ((f_void_ptr = (void (*)(void))dlsym(reslib, 125*0Sstevel@tonic-gate RES_SET_NO_HOSTS_FALLBACK)) != 0) { 126*0Sstevel@tonic-gate unset_no_hosts_fallback = f_void_ptr; 127*0Sstevel@tonic-gate } 128*0Sstevel@tonic-gate /* Set number of resolver retries */ 129*0Sstevel@tonic-gate if ((override_retry = (int (*)(int))dlsym(reslib, 130*0Sstevel@tonic-gate RES_OVERRIDE_RETRY)) == 0) { 131*0Sstevel@tonic-gate set_res_retry = 132*0Sstevel@tonic-gate (struct __res_state *(*)(void))dlsym(reslib, 133*0Sstevel@tonic-gate RES_GET_RES); 134*0Sstevel@tonic-gate override_retry = __fallback_override_retry; 135*0Sstevel@tonic-gate } 136*0Sstevel@tonic-gate /* 137*0Sstevel@tonic-gate * Select h_errno retrieval function. A BIND 8.2.2 138*0Sstevel@tonic-gate * libresolv.so.2 will have __h_errno, a BIND 8.1.2 139*0Sstevel@tonic-gate * one will have __res_get_h_errno, and other 140*0Sstevel@tonic-gate * versions may have nothing at all. 141*0Sstevel@tonic-gate * 142*0Sstevel@tonic-gate * Also try to bind to the relevant MT enable/disable 143*0Sstevel@tonic-gate * functions which are also dependent on the version 144*0Sstevel@tonic-gate * of the BIND libresolv.so.2 being used. 145*0Sstevel@tonic-gate */ 146*0Sstevel@tonic-gate if ((get_h_errno = (int *(*)(void))dlsym(reslib, 147*0Sstevel@tonic-gate __H_ERRNO)) != 0) { 148*0Sstevel@tonic-gate /* BIND 8.2.2 libresolv.so.2 is MT safe. */ 149*0Sstevel@tonic-gate enable_mt = __is_mt_safe; 150*0Sstevel@tonic-gate disable_mt = __is_mt_safe; 151*0Sstevel@tonic-gate } else { 152*0Sstevel@tonic-gate if ((get_h_errno = 153*0Sstevel@tonic-gate (int *(*)(void))dlsym(reslib, 154*0Sstevel@tonic-gate RES_GET_H_ERRNO)) == 0) { 155*0Sstevel@tonic-gate get_h_errno = __fallback_h_errno; 156*0Sstevel@tonic-gate } 157*0Sstevel@tonic-gate /* 158*0Sstevel@tonic-gate * Pre-BIND 8.2.2 was not MT safe. Try to 159*0Sstevel@tonic-gate * bind the MT enable/disable functions. 160*0Sstevel@tonic-gate */ 161*0Sstevel@tonic-gate if ((enable_mt = (int (*)(void))dlsym(reslib, 162*0Sstevel@tonic-gate RES_ENABLE_MT)) != 0 && 163*0Sstevel@tonic-gate (disable_mt = (int (*)(void))dlsym(reslib, 164*0Sstevel@tonic-gate RES_DISABLE_MT)) == 0) { 165*0Sstevel@tonic-gate enable_mt = 0; 166*0Sstevel@tonic-gate } 167*0Sstevel@tonic-gate } 168*0Sstevel@tonic-gate } 169*0Sstevel@tonic-gate } else { 170*0Sstevel@tonic-gate /* Libresolv already loaded */ 171*0Sstevel@tonic-gate if ((f_void_ptr = __res_set_no_hosts_fallback) != 0) { 172*0Sstevel@tonic-gate set_no_hosts_fallback = f_void_ptr; 173*0Sstevel@tonic-gate } 174*0Sstevel@tonic-gate if ((f_void_ptr = __res_unset_no_hosts_fallback) != 0) { 175*0Sstevel@tonic-gate unset_no_hosts_fallback = f_void_ptr; 176*0Sstevel@tonic-gate } 177*0Sstevel@tonic-gate if ((override_retry = __res_override_retry) == 0) { 178*0Sstevel@tonic-gate set_res_retry = __res_get_res; 179*0Sstevel@tonic-gate override_retry = __fallback_override_retry; 180*0Sstevel@tonic-gate } 181*0Sstevel@tonic-gate if ((get_h_errno = __h_errno) == 0 && 182*0Sstevel@tonic-gate (get_h_errno = __res_get_h_errno) == 0) { 183*0Sstevel@tonic-gate get_h_errno = __fallback_h_errno; 184*0Sstevel@tonic-gate } 185*0Sstevel@tonic-gate if (get_h_errno == __h_errno) { 186*0Sstevel@tonic-gate enable_mt = __is_mt_safe; 187*0Sstevel@tonic-gate disable_mt = __is_mt_safe; 188*0Sstevel@tonic-gate } else { 189*0Sstevel@tonic-gate if ((enable_mt = __res_enable_mt) != 0 && 190*0Sstevel@tonic-gate (disable_mt = __res_disable_mt) == 0) { 191*0Sstevel@tonic-gate enable_mt = 0; 192*0Sstevel@tonic-gate } 193*0Sstevel@tonic-gate } 194*0Sstevel@tonic-gate } 195*0Sstevel@tonic-gate } 196*0Sstevel@tonic-gate 197*0Sstevel@tonic-gate 198*0Sstevel@tonic-gate /* 199*0Sstevel@tonic-gate * 200*0Sstevel@tonic-gate * Integration of BIND 8.1.2 introduced two new Sun private functions, 201*0Sstevel@tonic-gate * __res_enable_mt() and __res_disable_mt(), that enabled and disabled 202*0Sstevel@tonic-gate * MT mode per-thread. These functions are in the private libresolv.so.2 203*0Sstevel@tonic-gate * interface, and intended for use by nss_dns.so.1. 204*0Sstevel@tonic-gate * 205*0Sstevel@tonic-gate * BIND 8.2.2 removed the need for those two functions. As similar 206*0Sstevel@tonic-gate * functionality was provided in BIND further up the stack. However the 207*0Sstevel@tonic-gate * functions remain to satisfy any application that directly called upon 208*0Sstevel@tonic-gate * them. Only, __res_enable_mt() was modified to return failure. 209*0Sstevel@tonic-gate * Indicated by a non-zero return value. So that those unconventional 210*0Sstevel@tonic-gate * applications would not then presume that res_send() and friends are 211*0Sstevel@tonic-gate * MT-safe, when in fact they are not. 212*0Sstevel@tonic-gate * 213*0Sstevel@tonic-gate * To prevent nss_dns from locking inappropriately __is_mt_safe() is 214*0Sstevel@tonic-gate * called in place of __res_enable_mt() and __res_disable_mt() if BIND 215*0Sstevel@tonic-gate * 8.2.2 libresolv.so.2 being used. __is_mt_safe() returns success 216*0Sstevel@tonic-gate * indicated by a return code of zero. Signifying that no locking is 217*0Sstevel@tonic-gate * necessary. 218*0Sstevel@tonic-gate * 219*0Sstevel@tonic-gate * MT applications making calls to gethostby*_r() or getipnodeby*() 220*0Sstevel@tonic-gate * linked to libresolv.so.1 or linked statically with pre-BIND 8.2.2 221*0Sstevel@tonic-gate * libresolv.a, doubtful as we don't ship a static version, would require 222*0Sstevel@tonic-gate * locking within the nsswitch back-end. Hence the mechanism can not 223*0Sstevel@tonic-gate * simply be removed. 224*0Sstevel@tonic-gate * 225*0Sstevel@tonic-gate */ 226*0Sstevel@tonic-gate static int 227*0Sstevel@tonic-gate __is_mt_safe(void) { 228*0Sstevel@tonic-gate return (0); 229*0Sstevel@tonic-gate } 230*0Sstevel@tonic-gate 231*0Sstevel@tonic-gate 232*0Sstevel@tonic-gate /* 233*0Sstevel@tonic-gate * Return pointer to the global h_errno variable 234*0Sstevel@tonic-gate */ 235*0Sstevel@tonic-gate static int * 236*0Sstevel@tonic-gate __fallback_h_errno(void) { 237*0Sstevel@tonic-gate return (&h_errno); 238*0Sstevel@tonic-gate } 239*0Sstevel@tonic-gate 240*0Sstevel@tonic-gate 241*0Sstevel@tonic-gate /* 242*0Sstevel@tonic-gate * This function is called when the resolver library doesn't provide its 243*0Sstevel@tonic-gate * own function to establish an override retry. If we can get a pointer 244*0Sstevel@tonic-gate * to the per-thread _res (i.e., set_res_retry != 0), we set the retries 245*0Sstevel@tonic-gate * directly, and return the previous number of retries. Otherwise, there's 246*0Sstevel@tonic-gate * nothing to do. 247*0Sstevel@tonic-gate */ 248*0Sstevel@tonic-gate static int 249*0Sstevel@tonic-gate __fallback_override_retry(int retry) { 250*0Sstevel@tonic-gate struct __res_state *res; 251*0Sstevel@tonic-gate int old_retry = 0; 252*0Sstevel@tonic-gate 253*0Sstevel@tonic-gate if (set_res_retry != 0) { 254*0Sstevel@tonic-gate res = set_res_retry(); 255*0Sstevel@tonic-gate old_retry = res->retry; 256*0Sstevel@tonic-gate res->retry = retry; 257*0Sstevel@tonic-gate } 258*0Sstevel@tonic-gate return (old_retry); 259*0Sstevel@tonic-gate } 260*0Sstevel@tonic-gate 261*0Sstevel@tonic-gate 262*0Sstevel@tonic-gate static void 263*0Sstevel@tonic-gate __fallback_set_no_hosts(void) { 264*0Sstevel@tonic-gate } 265*0Sstevel@tonic-gate 266*0Sstevel@tonic-gate 267*0Sstevel@tonic-gate /* 268*0Sstevel@tonic-gate * Common code to enable/disable MT mode, set/unset no-/etc/hosts fallback, 269*0Sstevel@tonic-gate * and to set the number of retries. 270*0Sstevel@tonic-gate */ 271*0Sstevel@tonic-gate void 272*0Sstevel@tonic-gate switch_resolver_setup(int *mt_disabled, sigset_t *oldmask, int *old_retry) { 273*0Sstevel@tonic-gate 274*0Sstevel@tonic-gate /* 275*0Sstevel@tonic-gate * Try to enable MT mode. If that isn't possible, mask signals, 276*0Sstevel@tonic-gate * and mutex_lock. 277*0Sstevel@tonic-gate */ 278*0Sstevel@tonic-gate *mt_disabled = 1; 279*0Sstevel@tonic-gate if (enable_mt == 0 || (*mt_disabled = (*enable_mt)()) != 0) { 280*0Sstevel@tonic-gate sigset_t newmask; 281*0Sstevel@tonic-gate (void) sigfillset(&newmask); 282*0Sstevel@tonic-gate _thr_sigsetmask(SIG_SETMASK, &newmask, oldmask); 283*0Sstevel@tonic-gate _mutex_lock(&one_lane); 284*0Sstevel@tonic-gate } 285*0Sstevel@tonic-gate 286*0Sstevel@tonic-gate /* 287*0Sstevel@tonic-gate * Disable any fallback to /etc/hosts (or /etc/inet/ipnodes, when 288*0Sstevel@tonic-gate * libresolv knows about that file). 289*0Sstevel@tonic-gate */ 290*0Sstevel@tonic-gate (*set_no_hosts_fallback)(); 291*0Sstevel@tonic-gate 292*0Sstevel@tonic-gate /* 293*0Sstevel@tonic-gate * The NS switch wants to handle retries on its own. 294*0Sstevel@tonic-gate */ 295*0Sstevel@tonic-gate *old_retry = (*override_retry)(1); 296*0Sstevel@tonic-gate } 297*0Sstevel@tonic-gate 298*0Sstevel@tonic-gate 299*0Sstevel@tonic-gate void 300*0Sstevel@tonic-gate switch_resolver_reset(int mt_disabled, sigset_t oldmask, int old_retry) { 301*0Sstevel@tonic-gate 302*0Sstevel@tonic-gate if (mt_disabled) { 303*0Sstevel@tonic-gate _mutex_unlock(&one_lane); 304*0Sstevel@tonic-gate _thr_sigsetmask(SIG_SETMASK, &oldmask, NULL); 305*0Sstevel@tonic-gate } else { 306*0Sstevel@tonic-gate (void) (*disable_mt)(); 307*0Sstevel@tonic-gate } 308*0Sstevel@tonic-gate 309*0Sstevel@tonic-gate (*unset_no_hosts_fallback)(); 310*0Sstevel@tonic-gate 311*0Sstevel@tonic-gate (void) (*override_retry)(old_retry); 312*0Sstevel@tonic-gate } 313