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}]]
}