routemon.sh

   1 #!/bin/bash
   2 #
   3 # vi: set softtabstop=4 shiftwidth=4 tabstop=8 expandtab:
   4 #
   5 # Creates logfiles to track the nexthop for a list of dynamic routes.
   6
   7 usage()
   8 {
   9     echo "usage: $0 -d logdir -r routelist -s snmpconffile" 1>&2
  10     exit 1
  11 }
  12
  13 # routines for converting a prefix to a netmask
  14 dooctet()
  15 {
  16     local prefix=$1
  17     local bytenum=$2
  18     prefix=$((prefix - 8*bytenum))
  19     [ $prefix -ge 8 ] && echo 255 && return
  20     echo $((256 - 2**(8-$prefix)))
  21 }
  22
  23 dooctets()
  24 {
  25     local prefix=$1
  26     shift
  27     for i in $*
  28     do
  29         dooctet $prefix $i
  30     done | tr '\012' . | sed 's,.$,\n,'
  31 }
  32
  33 prefix2octets()
  34 {
  35     dooctets $1 0 1 2 3
  36 }
  37 prefix2octets_reversed()
  38 {
  39     dooctets $1 3 2 1 0
  40 }
  41
  42
  43 routelist=
  44 outdir=
  45 snmpconf=
  46
  47 while getopts "d:r:s:" option
  48 do
  49     case "$option" in
  50         d) outdir=$OPTARG ;;
  51         r) routelist=$OPTARG ;;
  52         s) snmpconf=$OPTARG ;;
  53         *) usage ;;
  54     esac
  55 done
  56
  57 if [ -n "$routelist" ] && [ -n "$outdir" ] && [ -n "$snmpconf" ]
  58 then
  59     :
  60 else
  61     echo "Missing parameters." 1>&2
  62     usage
  63 fi
  64
  65 if [ ! -r "$routelist" ]
  66 then
  67     echo "Can't read route list '$routelist'." 1>&2
  68     exit 1
  69 fi
  70
  71 snmpargs=$(cat "$snmpconf") || {
  72     echo "Can't read SNMP argument file '$snmpconf'." 1>&2
  73     exit 1
  74 }
  75
  76 if [ ! -d "$outdir" ]
  77 then
  78     echo "Output directory '$outdir' does not exist." 1>&2
  79     exit 1
  80 fi
  81
  82 stamp="$(date +%Y-%m-%d/%H:%M:%S/%s)"
  83
  84 while read name router route nexthops
  85 do
  86     case "$name" in
  87         ""|"#"*) continue ;;
  88     esac
  89
  90     # 10.11.7.0/26 -> 10.11.7.0.192.255.255.255
  91     ip=${route%/*}
  92     prefix=${route#*/}
  93     revmask=$(prefix2octets_reversed "$prefix")
  94     target="$ip.$revmask"
  95
  96     # -Ov: display value only, not OID name
  97     # -Oq: display value only, not type
  98     nexthop=$(snmpwalk -Ov -Oq $snmpargs "$router"    \
  99         "IP-FORWARD-MIB::ipCidrRouteNextHop.$target")
 100
 101     # Now figure out which nexthop it's using.
 102     # 0 for none, 1 for first nexthop, 2 for second, -1 for unexpected nexthop
 103     if [ -z "$nexthop" ]
 104     then
 105         hopcode=-1
 106         hopdescription=snmp-failure
 107     elif echo "$nexthop" | grep -q -i "no such instance"
 108     then
 109         # We treat this as the route not existing, but it could also
 110         # mean the SNMP instance doesn't have IP-FORWARD-MIB.
 111         hopcode=0
 112         hopdescription=route-not-found
 113     else
 114         hopcode=-1
 115         hopdescription=$nexthop
 116
 117         index=1
 118         for candidate in $nexthops
 119         do
 120             if [ "$candidate" = "$nexthop" ]
 121             then
 122                 hopcode=$index
 123                 break
 124             fi
 125             index=$((index + 1))
 126         done
 127     fi
 128
 129     if ! echo "$stamp $hopcode $hopdescription" >> "$outdir/$name"
 130     then
 131         echo "Can't write to $outdir/$name." 1>&2
 132         exit 1
 133     fi
 134 done < "$routelist"