This was a small project I set myself to learn a bit about the use of the binary command in Tcl which allows the manipulation and conversion to different bases/formats of binary data.
It takes an IP address and CIDR [L1 ] number (e.g. 192.168.100.1/24) and shows the network and broadcast addresses, number of usable IP addresses and first and last usable IP addresses in the block.
#!/bin/sh
# Emacs: please open this file in -*-Tcl-*- mode
#
# Author: Mark Oakden http://wiki.tcl.tk/MNO
# Version: 1.1
#
# Note: this is almost certainly riddled with byte order
# and 32-bit assumptions.
#
# Changes since 1.0:-
# changed usage of regsub to accomodate earlier tcl/tk versions than 8.4.1
# changed layout to accomodate PocketPC better
#
# the next but one line restarts with tclsh...
# DO NOT REMOVE THIS BACKSLASH -> \
exec tclsh "$0" ${1+"$@"}
#
package require Tk
#
# a couple of defaults
#
set IP 192.168.100.1
set CIDR 24
# IPtoHex assumes IP has already been validated
proc IPtoHex { IP } {
binary scan [binary format c4 [split $IP .]] H8 Hex
return $Hex
}
proc hexToIP { Hex } {
binary scan [binary format H8 $Hex] c4 IPtmp
foreach num $IPtmp {
# binary scan "c" format gives signed int - the following
# [expr]-ology converts to unsigned (from [binary] manpage)
lappend IP [expr ($num + 0x100) % 0x100]
}
set IP [join $IP .]
return $IP
}
proc CIDRtoHexNetmask { CIDR } {
set zeros [expr 32 - $CIDR]
set ones $CIDR
set binaryCIDR [string repeat 1 $ones]
append binaryCIDR [string repeat 0 $zeros]
binary scan [binary format B32 $binaryCIDR] H8 HexNetmask
return $HexNetmask
}
proc IPisValid { IP } {
# must contain only dots and digits
# this originally read:-
#if { [regsub -all {[.0-9]} $IP {}] != "" } {
# return 0
#}
regsub -all {[.0-9]} $IP {} tmpStr
if { $tmpStr != "" } {
return 0
}
# however this appears to be a 8.4.1-ism which doesn't work with
# earlier versions (e.g. the 8.4a2 version that the PocketPC tcltk
# version is based on.
#
# exactly three dots
regsub -all {[0-9]} $IP {} tmpStr
if { $tmpStr != "..." } {
return 0
}
# each numerical component is between 0 and 255
foreach b [split $IP .] {
if { [string length $b] == 0 } {
return 0
}
set ob $b
scan $b %d b ;# allow for leading zeros which tcl thinks are octal
if { $b < 0 | $b > 255 } {
return 0
}
}
return 1
}
proc CIDRisValid { CIDR } {
if { [string length $CIDR] == 0 } {
return 0
}
regsub -all {[0-9]} $CIDR {} tmpStr
if { [string length $tmpStr] != 0 } {
return 0
}
scan $CIDR %d $CIDR
# 4 is arbitrary restriction on my part, but no-one uses CIDR to
# amalgamate multiple class A addresses! CIDR of 31 and 32 are
# non-useful also (/31 would leave just two IP addresses in the
# subnet, one of which would be the network address, the other
# the broadcast address - i.e. no usable IPs)
if { $CIDR < 4 | $CIDR > 30 } {
return 0
}
return 1
}
# IP and netmask in Hex, returns hex
proc networkAddress { hexIP hexNetmask } {
set compNetmask [expr 0x$hexNetmask ^ 0xffffffff]
set tmpNetAddr [expr ( 0x$hexIP | $compNetmask ) ^ $compNetmask]
binary scan [binary format I $tmpNetAddr] H8 networkAddress
return $networkAddress
}
# IP and netmask in Hex, returns hex
proc broadcastAddress { hexIP hexNetmask } {
set tmpBrdAddr [expr 0x$hexIP | ( 0x$hexNetmask ^ 0xffffffff )]
binary scan [binary format I $tmpBrdAddr] H8 broadcastAddress
return $broadcastAddress
}
#
proc buildGUI {} {
pack [frame .f] -expand 1 -fill x
label .f.l1 -text "IP Address/CIDR:"
label .f.l2 -text "/"
entry .f.ip -textvariable ::IP -width 15
entry .f.cidr -textvariable ::CIDR -width 2
bind .f.ip <Return> {calculate $::IP $::CIDR}
bind .f.cidr <Return> {calculate $::IP $::CIDR}
button .f.go -text "Go" -command {calculate $::IP $::CIDR}
pack .f.l1 .f.ip .f.l2 .f.cidr -side left
pack .f.go -side left -fill x -expand true
pack [frame .g] -expand 1 -fill x
text .g.t -width 32 -height 7 -font {Courier 8}
pack .g.t -expand 1 -fill x
}
proc calculate { IP CIDR } {
if { ! [IPisValid $IP] } {
error "IP is not valid"
}
if { ! [CIDRisValid $CIDR] } {
error "CIDR is not valid"
}
set hexIP [IPtoHex $IP]
set hexNetmask [CIDRtoHexNetmask $CIDR]
set netmask [hexToIP $hexNetmask]
set hexNetworkAddress [networkAddress $hexIP $hexNetmask]
set networkAddress [hexToIP $hexNetworkAddress]
set hexBroadcastAddress [broadcastAddress $hexIP $hexNetmask]
set broadcastAddress [hexToIP $hexBroadcastAddress]
set numIPs [expr 0x$hexBroadcastAddress - 0x$hexNetworkAddress - 1]
binary scan [binary format I [expr 0x$hexNetworkAddress + 1]] \
H8 firstIP
set firstIP [hexToIP $firstIP]
binary scan [binary format I [expr 0x$hexBroadcastAddress - 1]]\
H8 lastIP
set lastIP [hexToIP $lastIP]
.g.t delete 1.0 end
.g.t insert end "netmask: $netmask\n"
.g.t insert end " (hex): (0x$hexNetmask)\n"
.g.t insert end "network: $networkAddress\n"
.g.t insert end " b'cast: $broadcastAddress\n"
.g.t insert end " # IPs: $numIPs\n"
.g.t insert end " 1st IP: $firstIP\nlast IP: $lastIP\n"
}
buildGUI
# That's all, folks.