external/bsd/dhcp/dist/contrib/dhclient-tz-exithook.sh

   1 #!/bin/bash
   2 #
   3 # dhclient-tz-exithook.sh
   4 # Version 1.01 elear
   5 #
   6 # Copyright (c) 2007, Cisco Systems, Inc.
   7 # All rights reserved.
   8 #
   9 # Redistribution and use in source and binary forms, with or without
  10 # modification, are permitted provided that the following conditions
  11 # are met:
  12 #
  13 #    - Redistributions of source code must retain the above copyright
  14 #      notice, this list of conditions and the following disclaimer.
  15 #
  16 #    - Redistributions in binary form must reproduce the above copyright
  17 #      notice, this list of conditions and the following disclaimer in
  18 #      the documentation and/or other materials provided with the
  19 #      distribution.
  20 #
  21 #    - Neither the name of Cisco Systems, Inc. nor the names of its
  22 #      contributors may be used to endorse or promote products derived
  23 #      from this software without specific prior written permission.
  24 #
  25 #    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  26 #    "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  27 #    LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  28 #    FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
  29 #    COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
  30 #    INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  31 #    DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
  32 #    GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  33 #    INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
  34 #    WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
  35 #    NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  36 #    THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  37 #
  38 # the following script is used to set the timezone based on the new
  39 # dhcp timezone option defined currently in the IETF document
  40 # draft-ietf-dhc-timezone-option-04.txt.
  41
  42 # this code is intended for use with ISC's dhclient.  it is to be called
  43 # either as, or by, dhclient-exit-hooks
  44 #
  45 # As this is test code, in order for it to be called two changes
  46 # must be made to /etc/dhclient.conf.  First, dhclient.conf must be
  47 # aware of the tzName option.  The IANA has assigned tzName option
  48 # code 101.  You may need to add this to your configuration file.
  49 #
  50 #  option tzName code 101 = text;
  51 #
  52 # Next, add tzName to the list of options in the "request" statement.
  53 # For example:
  54 #
  55 # request subnet-mask, broadcast-address, time-offset, routers,
  56 #         domain-name, domain-name-servers, host-name, tzName;
  57 #
  58 #
  59 # And of course make sure that your dhcp server is transmitting timezone
  60 # information for option 101.  For IOS this can be done as follows:
  61 #
  62 #    option 101 ascii "Europe/Berlin"
  63 #
  64
  65 timefile=/etc/localtime
  66 oldfile=$timefile.old
  67 tmpfile=$timefile.$$
  68
  69 # function to clean up just in case we are interrupted or something
  70 # bad happens.
  71 restore_file () {
  72
  73   if [ ! -f $timefile ]; then
  74      $DEBUG mv $tmpfile $timefile
  75   fi
  76   $DEBUG rm $tmpfile
  77   exit
  78 }
  79
  80
  81 #set DEBUG to "echo" to see what would happen.
  82 if [ x$DEBUG = x ]; then
  83    DEBUG=
  84 fi
  85
  86 # if something has already gone wrong we're not doing a thing.
  87 if [ x$exit_status != x0 ]; then
  88    exit $exit_status
  89 fi
  90
  91
  92 # if we don't have a new timezone, then we have nothing to change, so
  93 # goodbye.
  94 if [ x$new_tzName = x ]; then
  95    exit 0
  96 fi
  97
  98 # if the timezone doesn't exist, goodbye.
  99 if [ ! -e $timefile ]; then
 100    exit 0
 101 fi
 102
 103 # find zoneinfo. use the first one.
 104 ftz=0
 105 for a in /usr/share/zoneinfo /usr/lib/zoneinfo /var/share/zoneinfo /var/zoneinfo; do
 106   if [ -d $a -a $ftz = 0 ]; then
 107     zoneinfo=$a
 108     ftz=1
 109   fi
 110 done
 111
 112 # no zoneinfo found.  goodbye.
 113 if [ x$zoneinfo = x ]; then
 114    exit 0
 115 fi
 116
 117 # timezone not found.  goodbye.
 118 if [ ! -f $zoneinfo/$new_tzName ]; then
 119    exit 0
 120 fi
 121
 122 # if we're here we can actually do something useful.
 123 # first, link a copy of the existing timefile.
 124
 125 $DEBUG ln $timefile $tmpfile
 126
 127 if [ $? != 0 ]; then
 128   echo "unable to create temporary file"
 129   exit -1
 130 fi
 131
 132 # in case of interrupt, cleanup.
 133 trap restore_file SIGINT SIGSEGV SIGQUIT SIGTERM
 134
 135 # we destroy old backup files in this process.  if we cannot and the
 136 # file exists then something went wrong.
 137 if [ -e $oldfile ]; then
 138   $DEBUG rm $oldfile
 139   if [ $? != 0 ]; then
 140      echo "$0: failed to remove $oldfile"
 141      rm -f $tmpfile
 142      exit -1
 143   fi
 144 fi
 145
 146 # sensitive part happens here:
 147 #
 148 $DEBUG mv $timefile $oldfile
 149
 150   if [ $? != 0 ]; then
 151      echo "$0: failed to move old $timefile file out of the way"
 152      rm $tmpfile
 153      exit -1
 154   fi
 155
 156 $DEBUG ln $zoneinfo/$new_tzName $timefile
 157
 158 # we don't complain just yet- a hard link could fail because
 159 # we're on two different file systems.  Go for a soft link.
 160 #
 161
 162 if [ $? != 0 ]; then
 163   $DEBUG ln -s $zoneinfo/$new_tzName $timefile
 164 fi
 165
 166 if [ $? != 0 ]; then       # failed to softlink.  now we're getting nervous.
 167   echo "$0: unable to establish new timezone.  Attempting to revert."
 168   $DEBUG ln $tmpfile $timefile
 169 fi
 170
 171
 172 if [ $? != 0 ]; then       # we're absolutely hosed
 173   echo "$0: unable to link or softlink timezone file, and unable to restore old file - giving up!"
 174   exit -1
 175 fi
 176
 177 $DEBUG rm $tmpfile
 178
 179 exit $?