TCL procedures to compress/expand a IPv6 address notation

Hi Kai,

good job.

for the compress procedure, I suggest to use this code which is more performant (around 5 clicks):

proc compress_ipv6_addr { addr } {
     Enumerate and store IPv6 ZoneID / Route Domain suffix
    if { [set id [getfield $addr "%" 2]] ne "" } then {
        set id "%$id"
        set addr [getfield $addr "%" 1]
    }

    return "[IP::addr $addr mask ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff]$id"
}

and the following procedure (50% clicks more) to prevent the shared variables requirements

proc expand_ipv6_addr_sp { addr } {
    if { [catch {
         Enumerating and storing IPv6 ZoneID / Route Domain suffix
        if { [set id [getfield $addr "%" 2]] ne "" } then {
            set id "%$id"
            set addr [getfield $addr "%" 1]
        }
         Parsing the first IPv6 address block of a possible :: notation by splitting the block into : separated IPv6 address groups
        set blk1 ""
        foreach val [split [getfield $addr "::" 1] ":"] {
            if { $val contains "." } then {
                     The current group contains a IPv4 address notation. Trying to extract the four IPv4 address octets
                    scan $val {%d.%d.%d.%d} oct1 oct2 oct3 oct4
                     Convert the four IPv4 address octets into two IPv6 address groups
                    append blk1 [format "%02x%02x %02x%02x " $oct1 $oct2 $oct3 $oct4]
                    unset -nocomplain oct1 oct2 oct3 oct4
                } else {
                    append blk1 "[format %04x 0x$val] "
                }
        }                           
        set blk2 ""
        foreach val [split [getfield $addr "::" 2] ":"] {
            if { $val contains "." } then {
                     The current group contains a IPv4 address notation. Trying to extract the four IPv4 address octets
                    scan $val {%d.%d.%d.%d} oct1 oct2 oct3 oct4
                     Convert the four IPv4 address octets into two IPv6 address groups
                    append blk2 [format "%02x%02x %02x%02x " $oct1 $oct2 $oct3 $oct4]
                    unset -nocomplain oct1 oct2 oct3 oct4
                } else {
                    append blk2 "[format %04x 0x$val] "
                }
        }
        set addr "[join "$blk1[string repeat "0000 " [expr {8 - [string length "$blk1$blk2"]/5}]] $blk2" ":"]"
    }] } then {
         log local0.debug "errorInfo: [subst \$::errorInfo]"
         return "errorInfo: [subst \$::errorInfo]"
        return ""
    }
     Append the previously extracted IPv6 ZoneID / Route Domain suffix and return the expanded IPv6 address notation
    return "$addr$id"
}