release/src/router/dnsmasq/debian/resolvconf

   1 #!/bin/sh
   2 #
   3 # Script to update the resolver list for dnsmasq
   4 #
   5 # N.B. Resolvconf may run us even if dnsmasq is not (yet) running.
   6 # If dnsmasq is installed then we go ahead and update the resolver list
   7 # in case dnsmasq is started later.
   8 #
   9 # Assumption: On entry, PWD contains the resolv.conf-type files.
  10 #
  11 # This file is part of the dnsmasq package.
  12 #
  13
  14 set -e
  15
  16 RUN_DIR="/var/run/dnsmasq"
  17 RSLVRLIST_FILE="${RUN_DIR}/resolv.conf"
  18 TMP_FILE="${RSLVRLIST_FILE}_new.$$"
  19 MY_NAME_FOR_RESOLVCONF="dnsmasq"
  20
  21 [ -x /usr/sbin/dnsmasq ] || exit 0
  22 [ -x /lib/resolvconf/list-records ] || exit 1
  23
  24 PATH=/bin:/sbin
  25
  26 report_err() { echo "$0: Error: $*" >&2 ; }
  27
  28 # Stores arguments (minus duplicates) in RSLT, separated by spaces
  29 # Doesn't work properly if an argument itself contains whitespace
  30 uniquify()
  31 {
  32         RSLT=""
  33         while [ "$1" ] ; do
  34                 for E in $RSLT ; do
  35                         [ "$1" = "$E" ] && { shift ; continue 2 ; }
  36                 done
  37                 RSLT="${RSLT:+$RSLT }$1"
  38                 shift
  39         done
  40 }
  41
  42 if [ ! -d "$RUN_DIR" ] && ! mkdir --parents --mode=0755 "$RUN_DIR" ; then
  43         report_err "Failed trying to create directory $RUN_DIR"
  44         exit 1
  45 fi
  46
  47 RSLVCNFFILES=""
  48 for F in $(/lib/resolvconf/list-records --after "lo.$MY_NAME_FOR_RESOLVCONF") ; do
  49         case "$F" in
  50             "lo.$MY_NAME_FOR_RESOLVCONF")
  51                 # Omit own record
  52                 ;;
  53             lo.*)
  54                 # Include no more records after one for a local nameserver
  55                 RSLVCNFFILES="${RSLVCNFFILES:+$RSLVCNFFILES }$F"
  56                 break
  57                 ;;
  58           *)
  59                 RSLVCNFFILES="${RSLVCNFFILES:+$RSLVCNFFILES }$F"
  60                 ;;
  61         esac
  62 done
  63
  64 NMSRVRS=""
  65 if [ "$RSLVCNFFILES" ] ; then
  66         uniquify $(sed -n -e 's/^[[:space:]]*nameserver[[:space:]]\+//p' $RSLVCNFFILES)
  67         NMSRVRS="$RSLT"
  68 fi
  69
  70 # Dnsmasq uses the mtime of $RSLVRLIST_FILE, with a resolution of one second,
  71 # to detect changes in the file. This means that if a resolvconf update occurs
  72 # within one second of the previous one then dnsmasq may fail to notice the
  73 # more recent change. To work around this problem we sleep one second here
  74 # if necessary in order to ensure that the new mtime is different.
  75 if [ -f "$RSLVRLIST_FILE" ] && [ "$(ls -go --time-style='+%s' "$RSLVRLIST_FILE" | { read p h s t n ; echo "$t" ; })" = "$(date +%s)" ] ; then
  76         sleep 1
  77 fi
  78
  79 clean_up() { rm -f "$TMP_FILE" ; }
  80 trap clean_up EXIT
  81 : >| "$TMP_FILE"
  82 for N in $NMSRVRS ; do echo "nameserver $N" >> "$TMP_FILE" ; done
  83 mv -f "$TMP_FILE" "$RSLVRLIST_FILE"
  84