release/src/router/dnsmasq/debian/resolvconf

   1 #!/bin/bash
   2 #
   3 # Script to update the resolver list for dnsmasq
   4 #
   5 # N.B. Resolvconf may run us even if dnsmasq is not running.
   6 # If dnsmasq is installed then we go ahead and update
   7 # the resolver list in case dnsmasq is started later.
   8 #
   9 # Assumption: On entry, PWD contains the resolv.conf-type files
  10 #
  11 # Requires bash because it uses a non-POSIX printf extension.
  12 #
  13 # Licensed under the GNU GPL.  See /usr/share/common-licenses/GPL.
  14 #
  15
  16 set -e
  17
  18 RUN_DIR="/var/run/dnsmasq"
  19 RSLVRLIST_FILE="${RUN_DIR}/resolv.conf"
  20 TMP_FILE="${RSLVRLIST_FILE}_new.$$"
  21
  22 [ -x /usr/sbin/dnsmasq ] || exit 0
  23 [ -x /lib/resolvconf/list-records ] || exit 1
  24
  25 PATH=/bin:/sbin
  26
  27 report_err() { echo "$0: Error: $*" >&2 ; }
  28
  29 # Stores arguments (minus duplicates) in RSLT, separated by spaces
  30 # Doesn't work properly if an argument itself contain whitespace
  31 uniquify()
  32 {
  33         RSLT=""
  34         while [ "$1" ] ; do
  35                 for E in $RSLT ; do
  36                         [ "$1" = "$E" ] && { shift ; continue 2 ; }
  37                 done
  38                 RSLT="${RSLT:+$RSLT }$1"
  39                 shift
  40         done
  41 }
  42
  43 if [ ! -d "$RUN_DIR" ] && ! mkdir --parents --mode=0755 "$RUN_DIR" ; then
  44         report_err "Failed trying to create directory $RUN_DIR"
  45         exit 1
  46 fi
  47
  48 RSLVCNFFILES="$(/lib/resolvconf/list-records | sed -e '/^lo.dnsmasq$/d')"
  49
  50 NMSRVRS=""
  51 if [ "$RSLVCNFFILES" ] ; then
  52         uniquify $(sed -n -e 's/^[[:space:]]*nameserver[[:space:]]\+//p' $RSLVCNFFILES)
  53         NMSRVRS="$RSLT"
  54 fi
  55
  56 # Dnsmasq uses the mtime of $RSLVRLIST_FILE, with a resolution of one second,
  57 # to detect changes in the file. This means that if a resolvconf update occurs
  58 # within one second of the previous one then dnsmasq may fail to notice the
  59 # more recent change.  To work around this problem we sleep here to ensure
  60 # that the new mtime is different.
  61 if [ -f "$RSLVRLIST_FILE" ] && [ "$(ls -go --time-style='+%s' "$RSLVRLIST_FILE" | { read p h s t n ; echo "$t" ; })" = "$(date +%s)" ] ; then
  62         sleep 1
  63 fi
  64
  65 clean_up() { rm -f "$TMP_FILE" ; }
  66 trap clean_up EXIT
  67 : >| "$TMP_FILE"
  68 for N in $NMSRVRS ; do echo "nameserver $N" >> "$TMP_FILE" ; done
  69 mv -f "$TMP_FILE" "$RSLVRLIST_FILE"
  70