PT 2004-Jun-07 I think it would be useful to have a module in tcllib to do some manipulations of internet addresses. If we can think up a sensible API then we can provide something to help cope with both IPv4 and IPv6 addresses. For instance, how do I check that an address is within a certain range? Is 192.168.0.4 within 192.168.0.0./24 or within 192.16./16 or even within 192.168.0.0./255.255.255.0?
Here are a few helper functions I've used elsewhere. It's likely there are faster/neater implementations :) Assume at some point we have done
namespace eval ip4 {}Please feel free to comment and edit. I could especially use some equivalent functions to deal with IPv6 addresses.
There are some similar functions on A Little CIDR Calculator - I shall attempt to collect the fastest versions together here. PT
ip2x Convert an IPv4 address in dotted quad notation into a hexadecimal representation. This will extend truncated ip4 addresses with zeros. eg: ip2x 192.168.0.4 -> 0xc0a80004 or ip2x 127 -> 0x7f000000 This is a little faster using [binary] than using [format]
proc ::ip4::ip2x {ip {validate 0}} {
set octets [split $ip .]
if {[llength $octets] != 4} {
set octets [lrange [concat $octets 0 0 0] 0 3]
}
if {$validate} {
foreach oct $octets {
if {$oct < 0 || $oct > 255} {
return -code error "invalid ip address"
}
}
}
binary scan [binary format c4 $octets] H8 x
return 0x$x
}x2ip Turn the hex representation of an IPv4 address into dotted quad notation.
proc ::ip4::x2ip {hex} {
set r {}
set bin [binary format I [expr {$hex}]]
binary scan $bin c4 octets
foreach octet $octets {
lappend r [expr {$octet & 0xFF}]
}
return [join $r .]
}ipmask Returns an IPv4 address masked with subnet bits as a hexadecimal representation. For instance: [ipmask 192.168.0.4 24] -> 0xc0a80000 This makes it easy to compare addresses as described in the introduction. Is 192.168.0.4 within 192.168/16? [expr {[ipmask 192.168.0.4 16] == [ipmask 192.168 16]}]
proc ::ip4::ipmask {ip {bits {}}} {
if {[string length $bits] < 1} { set bits 32 }
set ipx [ip2x $ip]
if {[string is integer $bits]} {
set mask [expr {(0xFFFFFFFF << (32 - $bits)) & 0xFFFFFFFF}]
} else {
set mask [ip2x $bits]
}
return [format 0x%08x [expr {$ipx & $mask}]]
}is_ip4_addr Use the ip4x conversion proc to check that the given address is really an IPv4 address.
proc ::ip4::is_ip4_addr {ip} {
if {[catch {ip2x $ip true}]} {
return 0
}
return 1
}splitspec Split an address specification into a ipadd and mask part. This doesn't validate the address portion. If a spec with no mask is provided then the mask will be 32 (all bits significant).
proc ::ip4::splitspec {spec} {
set bits 32
set domain $spec
set slash [string last / $spec]
if {$slash != -1} {
incr slash -1
set domain [string range $spec 0 $slash]
incr slash 2
set bits [string range $spec $slash end]
}
return [list $domain $bits]
}Examples
proc IpaddrInDomain {addr domainspec} {
foreach {network bits} [ip4::splitspec $domainspec] {}
set net [ip4::ipmask $network $bits]
set ipx [ip4::ipmask $addr $bits]
if {$ipx == $net} {
return 1
}
return 0
}escargo 7 Jun 2004 - From my networking experience, I can think of some functions that would be useful in handling IP addresses.
These would all be appropriate predicates to provide in such a library.
For a widget that allows validation of dotted decimal IP addresses take a look at mentry.