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 :)


'''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''
 proc ::ip4::ip2x {ip} {
    set octets [lrange [concat [split $ip .] 0 0 0] 0 3]
    foreach oct $octets {
        if {$oct < 0 || $oct > 255} {
            return -code error "invalid ip address"
        }
    }
    eval [linsert $octets 0 format 0x%02x%02x%02x%02x]
 }

'''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]
    set mask [expr {(0xFFFFFFFF << (32 - $bits)) & 0xFFFFFFFF}]
    return [format 0x%08x [expr {$ipx & $mask}]]
 }
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[[[Category Internet]]]