contrib/reverse-dns/reverse_replace.sh

   1 #!/bin/ash
   2 # $Id: reverse_replace.sh 18 2015-03-01 16:12:35Z jo $
   3 #
   4 # Usage e.g.: netstat -n -4 | reverse_replace.sh
   5 # Parses stdin for IP4 addresses and replaces them
   6 # with names retrieved by parsing the dnsmasq log.
   7 # This currently only gives CNAMEs. But these
   8 # usually tell ou more than the mones from reverse
   9 # lookups.
  10 #
  11 # This has been tested on debian and asuswrt. Plese
  12 # report successful tests on other platforms.
  13 #
  14 # Author: Joachim Zobel <jz-2014@heute-morgen.de>
  15 # License: Consider this MIT style licensed. You can
  16 #   do as you ike, but you must not remove my name.
  17 #
  18
  19 LOG=/var/log/dnsmasq.log
  20 MAX_LINES=15000
  21
  22 # sed regex do match IPs
  23 IP_regex='[0-9]\{1,3\}\.[0-9]\{1,3\}\.[0-9]\{1,3\}\.[0-9]\{1,3\}'
  24 # private IP ranges
  25 IP_private='\(^127\.\)\|\(^192\.168\.\)\|\(^10\.\)\|\(^172\.1[6-9]\.\)\|\(^172\.2[0-9]\.\)\|\(^172\.3[0-1]\.\)'
  26
  27 #######################################################################
  28 # Find Commands
  29
  30 HOST=nslookup
  31 if type host > /dev/null 2>&1; then
  32   # echo "No need for nslookup, host is there"
  33   HOST=host
  34 fi
  35
  36 #######################################################################
  37 # Functions
  38
  39 # Use shell variables for an (IP) lookup table
  40 create_lookup_table()
  41 {
  42   # Parse log into lookup table
  43   local CMDS="$( tail -"$MAX_LINES" "$LOG" | \
  44     grep " is $IP_regex" | \
  45     sed "s#.* \([^ ]*\) is \($IP_regex\).*#set_val \2 \1;#" )"
  46
  47   local IFS='
  48 '
  49   for CMD in $CMDS
  50   do
  51     eval $CMD
  52   done
  53 }
  54
  55 set_val()
  56 {
  57   local _IP=$(echo $1 | tr . _)
  58   local KEY="__IP__$_IP"
  59   eval "$KEY"=$2
  60 }
  61
  62 get_val()
  63 {
  64   local _IP=$(echo $1 | tr . _)
  65   local KEY="__IP__$_IP"
  66   eval echo -n '${'"$KEY"'}'
  67 }
  68
  69 dns_lookup()
  70 {
  71   local IP=$1
  72
  73   local RTN="$($HOST $IP | \
  74         sed 's#\s\+#\n#g' | \
  75         grep -v '^$' | \
  76         tail -1 | tr -d '\n' | \
  77         sed 's#\.$##')"
  78   if echo $RTN | grep -q NXDOMAIN; then
  79     echo -n $IP
  80   else
  81     echo -n "$RTN"
  82   fi
  83 }
  84
  85 reverse_dns()
  86 {
  87   local IP=$1
  88
  89   # Skip if it is not an IP
  90   if ! echo $IP | grep -q "^$IP_regex$"; then
  91     echo -n $IP
  92     return
  93   fi
  94
  95   # Do a dns lookup, if it is a local IP
  96   if echo $IP | grep -q $IP_private; then
  97     dns_lookup $IP
  98     return
  99   fi
 100
 101   local NAME="$(get_val $IP)"
 102
 103   if [ -z "$NAME" ]; then
 104     echo -n $IP
 105   else
 106     echo -n $NAME
 107   fi
 108 }
 109
 110 #######################################################################
 111 # Main
 112 create_lookup_table
 113
 114 while read LINE; do
 115   for IP in $(echo "$LINE" | \
 116               sed "s#\b\($IP_regex\)\b#\n\1\n#g" | \
 117               grep $IP_regex)
 118   do
 119     NAME=`reverse_dns $IP `
 120     # echo "$NAME $IP"
 121     LINE=`echo "$LINE" | sed "s#$IP#$NAME#" `
 122   done
 123   echo $LINE
 124 done
 125