SystemConfiguration.fproj/SCPLock.c

   1 /*
   2  * Copyright(c) 2000 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * The contents of this file constitute Original Code as defined in and
   7  * are subject to the Apple Public Source License Version 1.1(the
   8  * "License").  You may not use this file except in compliance with the
   9  * License.  Please obtain a copy of the License at
  10  * http://www.apple.com/publicsource and read it before using this file.
  11  *
  12  * This Original Code and all software distributed under the License are
  13  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  14  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  15  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  16  * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
  17  * License for the specific language governing rights and limitations
  18  * under the License.
  19  *
  20  * @APPLE_LICENSE_HEADER_END@
  21  */
  22
  23 #include <SystemConfiguration/SCP.h>
  24 #include "SCPPrivate.h"
  25
  26 #include <SystemConfiguration/SCD.h>
  27
  28 #include <fcntl.h>
  29 #include <unistd.h>
  30 #include <sys/errno.h>
  31
  32
  33 SCPStatus
  34 SCPLock(SCPSessionRef session, boolean_t wait)
  35 {
  36         SCPStatus               scp_status;
  37         SCDStatus               scd_status;
  38         SCPSessionPrivateRef    sessionPrivate;
  39         SCDHandleRef            handle = NULL;
  40         CFDateRef               value;
  41         CFArrayRef              changes;
  42         struct stat             statBuf;
  43         CFDataRef               currentSignature;
  44
  45         if (session == NULL) {
  46                 return SCP_FAILED;           /* you can't do anything with a closed session */
  47         }
  48         sessionPrivate = (SCPSessionPrivateRef)session;
  49
  50         if (!sessionPrivate->isRoot) {
  51                 /* CONFIGD REALLY NEEDS NON-ROOT WRITE ACCESS */
  52                 goto notRoot;
  53         }
  54
  55         if (sessionPrivate->session == NULL) {
  56                 /* open a session */
  57                 scd_status = SCDOpen(&sessionPrivate->session, sessionPrivate->name);
  58                 if (scd_status != SCD_OK) {
  59                         SCDLog(LOG_INFO, CFSTR("SCDOpen() failed: %s"), SCDError(scd_status));
  60                         return SCP_FAILED;
  61                 }
  62         }
  63
  64         if (sessionPrivate->sessionKeyLock == NULL) {
  65                 /* create the session "lock" key */
  66                 sessionPrivate->sessionKeyLock = _SCPNotificationKey(sessionPrivate->prefsID,
  67                                                                      sessionPrivate->perUser,
  68                                                                      sessionPrivate->user,
  69                                                                      kSCPKeyLock);
  70         }
  71
  72         scd_status = SCDNotifierAdd(sessionPrivate->session,
  73                                     sessionPrivate->sessionKeyLock,
  74                                     0);
  75         if (scd_status != SCD_OK) {
  76                 SCDLog(LOG_INFO, CFSTR("SCDNotifierAdd() failed: %s"), SCDError(scd_status));
  77                 scp_status = SCP_FAILED;
  78                 goto error;
  79         }
  80
  81         handle = SCDHandleInit();
  82         value  = CFDateCreate(NULL, CFAbsoluteTimeGetCurrent());
  83         SCDHandleSetData(handle, value);
  84         CFRelease(value);
  85
  86         while (TRUE) {
  87                 /*
  88                  * Attempt to acquire the lock
  89                  */
  90                 scd_status = SCDAddSession(sessionPrivate->session,
  91                                            sessionPrivate->sessionKeyLock,
  92                                            handle);
  93                 switch (scd_status) {
  94                         case SCD_OK :
  95                                 scp_status = SCP_OK;
  96                                 goto done;
  97                         case SCD_EXISTS :
  98                                 if (!wait) {
  99                                         scp_status = SCP_BUSY;
 100                                         goto error;
 101                                 }
 102                                 break;
 103                         default :
 104                                 SCDLog(LOG_INFO, CFSTR("SCDAddSession() failed: %s"), SCDError(scd_status));
 105                                 scp_status = SCP_FAILED;
 106                                 goto error;
 107                 }
 108
 109                 /*
 110                  * Wait for the lock to be released
 111                  */
 112                 scd_status = SCDNotifierWait(sessionPrivate->session);
 113                 if (scd_status != SCD_OK) {
 114                         SCDLog(LOG_INFO, CFSTR("SCDAddSession() failed: %s"), SCDError(scd_status));
 115                         scp_status = SCP_FAILED;
 116                         goto error;
 117                 }
 118         }
 119
 120     done :
 121
 122         SCDHandleRelease(handle);
 123         handle = NULL;
 124
 125         scd_status = SCDNotifierRemove(sessionPrivate->session,
 126                                        sessionPrivate->sessionKeyLock,
 127                                        0);
 128         if (scd_status != SCD_OK) {
 129                 SCDLog(LOG_INFO, CFSTR("SCDNotifierRemove() failed: %s"), SCDError(scd_status));
 130                 scp_status = SCP_FAILED;
 131                 goto error;
 132         }
 133
 134         scd_status = SCDNotifierGetChanges(sessionPrivate->session, &changes);
 135         if (scd_status != SCD_OK) {
 136                 SCDLog(LOG_INFO, CFSTR("SCDNotifierGetChanges() failed: %s"), SCDError(scd_status));
 137                 scp_status = SCP_FAILED;
 138                 goto error;
 139         }
 140         CFRelease(changes);
 141
 142     notRoot:
 143
 144         /*
 145          * Check the signature
 146          */
 147         if (stat(sessionPrivate->path, &statBuf) == -1) {
 148                 if (errno == ENOENT) {
 149                         bzero(&statBuf, sizeof(statBuf));
 150                 } else {
 151                         SCDLog(LOG_DEBUG, CFSTR("stat() failed: %s"), strerror(errno));
 152                         scp_status = SCP_STALE;
 153                         goto error;
 154                 }
 155         }
 156
 157         currentSignature = _SCPSignatureFromStatbuf(&statBuf);
 158         if (!CFEqual(sessionPrivate->signature, currentSignature)) {
 159                 CFRelease(currentSignature);
 160                 scp_status = SCP_STALE;
 161                 goto error;
 162         }
 163         CFRelease(currentSignature);
 164
 165         sessionPrivate->locked = TRUE;
 166         return SCD_OK;
 167
 168     error :
 169
 170         if (handle)     SCDHandleRelease(handle);
 171         return scp_status;
 172 }