| 1 | #!/bin/sh -
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| 2 | #
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| 3 | # Shuffle nameservers listed based on the query times, if enabled in
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| 4 | # resolv.conf. Bare in mind the special syntax.
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| 5 | #
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| 6 | # Rick van der Zwet <rick@wirelessleiden.nl>
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| 7 | #
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| 8 |
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| 9 | # ``Random'' sleep to avoid ``slamming'' on the DNS door
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| 10 | verbose=true
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| 11 | if [ "$1" = "cron" ]; then
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| 12 | verbose=false
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| 13 | sleep `expr $$ % 30`
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| 14 | fi
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| 15 |
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| 16 | TAG='^# START DYNAMIC LIST - updated by /tools/nameserver-shuffle$'
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| 17 | $verbose && echo "# Searching in /etc/resolv.conf for tag '$TAG'"
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| 18 |
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| 19 | TDIR=`mktemp -d -t $(basename $0)`
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| 20 | # Cleanup before going home
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| 21 | trap "rm -Rf $TDIR; exit 1" 1 2 3 15
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| 22 | trap "rm -Rf $TDIR; exit 0" 0
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| 23 |
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| 24 | DYNLIST=$TDIR/dynlist
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| 25 | RESULTLIST=$TDIR/resultlist
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| 26 | NEWRESOLV=$TDIR/resolv.conf.new
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| 27 |
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| 28 | # Get enabled DYNAMIC LIST nameservers
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| 29 | sed "1,\+$TAG+d" /etc/resolv.conf > $DYNLIST || exit 1
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| 30 | NAMESERVERS=`awk '/^nameserver/ {print $2}' $DYNLIST` || exit 1
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| 31 |
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| 32 | # Only do something if we have dynamic nameservers
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| 33 | $verbose && echo "# Processing" `echo $NAMESERVERS | wc -w` nameservers
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| 34 | if [ -n "$NAMESERVERS" ]; then
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| 35 | # Find query times
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| 36 | for NAMESERVER in $NAMESERVERS; do
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| 37 | $verbose && printf "## Testing nameserver %-16s query time: " $NAMESERVER
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| 38 | # Strict checking to avoid buggy links to return decent results.
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| 39 | QUERY_TIME=`drill +time=1 +tries=1 SOA wleiden.net @$NAMESERVER | awk '/Query time:/ {print $4}'`
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| 40 | # Failed to complete succesfully
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| 41 | [ -z "$QUERY_TIME" ] && QUERY_TIME="9999"
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| 42 | $verbose && echo "$QUERY_TIME"
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| 43 | echo "$QUERY_TIME $NAMESERVER" >> $RESULTLIST
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| 44 | done
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| 45 |
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| 46 | # Get the header part
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| 47 | sed -n "1,\+$TAG+p" /etc/resolv.conf > $NEWRESOLV || exit 1
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| 48 |
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| 49 | # Output sorted list
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| 50 | NAMESERVERS=`sort -n $RESULTLIST | awk '{print $2}'`
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| 51 | for NAMESERVER in $NAMESERVERS; do
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| 52 | QUERY_TIME=`grep $NAMESERVER $RESULTLIST | cut -d' ' -f1`
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| 53 | [ $QUERY_TIME = "9999" ] && STATUS="Query time: down" || STATUS="Query time: $QUERY_TIME"
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| 54 | # awk magic to get maximum length of comment field (for display purposes).
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| 55 | ML=`awk '/^nameserver/ {l=length($4);if (l>ml){ml=l}}END{print ml}' $DYNLIST`
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| 56 | # awk magic allows adding or updating of status of nameserver
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| 57 | awk '/^nameserver[[:blank:]]+'"$NAMESERVER"'[[:blank:]]*/ {printf "nameserver %-16s # %-'$ML's (%s)\n", $2, $4,"'"$STATUS"'"}' $DYNLIST >> $NEWRESOLV || exit 1
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| 58 | done
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| 59 | $verbose && echo "################################"
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| 60 | $verbose && echo "## BEGIN new /etc/resolv.conf ##"
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| 61 | $verbose && echo "################################"
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| 62 | $verbose && cat $NEWRESOLV
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| 63 | $verbose && echo "################################"
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| 64 | $verbose && echo "## END new /etc/resolv.conf ##"
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| 65 | $verbose && echo "################################"
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| 66 | cat $NEWRESOLV > /etc/resolv.conf || exit 1
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| 67 | fi
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