#!/bin/sh
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#
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# Script to update the resolver list for dnsmasq
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#
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# N.B. Resolvconf may run us even if dnsmasq is not (yet) running.
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# If dnsmasq is installed then we go ahead and update the resolver list
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# in case dnsmasq is started later.
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#
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# Assumption: On entry, PWD contains the resolv.conf-type files.
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#
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# This file is part of the dnsmasq package.
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#
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set -e
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RUN_DIR="/run/dnsmasq"
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RSLVRLIST_FILE="${RUN_DIR}/resolv.conf"
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TMP_FILE="${RSLVRLIST_FILE}_new.$$"
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MY_NAME_FOR_RESOLVCONF="dnsmasq"
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[ -x /usr/bin/dnsmasq ] || exit 0
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[ -x /lib/resolvconf/list-records ] || exit 1
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PATH=/bin:/sbin
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report_err() { echo "$0: Error: $*" >&2 ; }
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# Stores arguments (minus duplicates) in RSLT, separated by spaces
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# Doesn't work properly if an argument itself contains whitespace
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uniquify()
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{
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RSLT=""
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while [ "$1" ] ; do
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for E in $RSLT ; do
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[ "$1" = "$E" ] && { shift ; continue 2 ; }
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done
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RSLT="${RSLT:+$RSLT }$1"
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shift
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done
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}
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if [ ! -d "$RUN_DIR" ] && ! mkdir --parents --mode=0755 "$RUN_DIR" ; then
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report_err "Failed trying to create directory $RUN_DIR"
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exit 1
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fi
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RSLVCNFFILES=""
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for F in $(/lib/resolvconf/list-records --after "lo.$MY_NAME_FOR_RESOLVCONF") ; do
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case "$F" in
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"lo.$MY_NAME_FOR_RESOLVCONF")
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# Omit own record
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;;
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lo.*)
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# Include no more records after one for a local nameserver
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RSLVCNFFILES="${RSLVCNFFILES:+$RSLVCNFFILES }$F"
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break
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;;
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*)
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RSLVCNFFILES="${RSLVCNFFILES:+$RSLVCNFFILES }$F"
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;;
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esac
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done
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NMSRVRS=""
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if [ "$RSLVCNFFILES" ] ; then
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uniquify $(sed -n -e 's/^[[:space:]]*nameserver[[:space:]]\+//p' $RSLVCNFFILES)
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NMSRVRS="$RSLT"
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fi
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# Dnsmasq uses the mtime of $RSLVRLIST_FILE, with a resolution of one second,
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# to detect changes in the file. This means that if a resolvconf update occurs
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# within one second of the previous one then dnsmasq may fail to notice the
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# more recent change. To work around this problem we sleep one second here
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# if necessary in order to ensure that the new mtime is different.
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if [ -f "$RSLVRLIST_FILE" ] && [ "$(stat -c %X "$RSLVRLIST_FILE")" = "$(date +%s)" ] ; then
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sleep 1
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fi
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clean_up() { rm -f "$TMP_FILE" ; }
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trap clean_up EXIT
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: >| "$TMP_FILE"
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for N in $NMSRVRS ; do echo "nameserver $N" >> "$TMP_FILE" ; done
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mv -f "$TMP_FILE" "$RSLVRLIST_FILE"
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