IP Calculator Final Version

Bob Sneidar bobsneidar at iotecdigital.com
Tue Jan 27 18:38:31 EST 2015


Hi Alex. 

Thanks for testing this for me and your input. Here is an updated function that accounts for any non-numerical octets and expands the limits of the CIDR to 0-32. Also, if the IP or the CIDR ends in any number of periods it returns an error. I have made the same check for subnet masks. 

This reminds me of when I originally started programming. I would proudly show off my new creation to a friend of mine who was a school principle, and he would set about breaking it. :-) It was a good lesson. 

function IPCalc theIPAddress, theSubnetMask
   /* IPCalc yyy
      Syntax:
      IPCalc theIPAddress, [theSubnetMask]
      Examples:
      
      Description:
      Derive Internet values from either CIDR notation in the IPAddress
      or a standard IP and subnet mask
   
      Input: 
      .    theIPAddress -  the IP address in CIDR notation
       or
      .    theIPAddress - a standard IP address and
     .     theSubNetMask - a standard subNetMask
   
      Returns an array of the following values:
      .   bcastaddr
      .   cidraddr
      .   cidrdepth
      .   firstaddr
      .   ipaddress
      .   lastaddr
      .   subnetaddr
      .   subnetmask
      .   usablecount
      Returns a string beginning with ERROR: if the parameters are out of range
      Check that the returned value is an array to see if there was an error
   
   Source:
       Bob Sneidar,  slylabs13 at icloud.com
   IPCalc */
   
   set the itemdelimiter to "."
   
   -- check parameters
   -- the IP address must be 4 octets of numbers
   if the number of items of theIPAddress <>4 \
         or the last char of theIPAddress is "." \
         or ".." is in theIPAddress then
      return "ERROR: The IP Address must be in the form:" & cr & \
            "'nnn.nnn.nnn.nnn' or 'nnn.nnn.nnn.nnn/nn'. (ipaddress = '" & theIPAddress & "')"
   end if
   
   -- initial setup
   set the numberFormat to "00000000"
   
   -- detemine format
   if theIPAddress contains "/" then
      put offset("/", theIPAddress) into theCIDRDelim
      put char theCIDRDelim +1 to -1 of theIPAddress into theCIDRDepth
      
      -- CIDR depth must be a WHOLE number
      put cleanString(theCIDRDepth) into theCIDRDepth
      
      if theCIDRDepth is not a number then
         return "ERROR: The CIDR Depth must be a number between 0 and 32. " & \
               "(CIDRDepth = '" & theCIDRDepth & "')"
      end if
      
      put charx("1", theCIDRDepth) & charx("0", 32-theCIDRDepth) into theBinSubnetMask
      put baseconvert(char 1 to 8 of theBinSubnetMask, 2, 10) into item 1 of theSubnetMask
      put baseconvert(char 9 to 16 of theBinSubnetMask, 2, 10) into item 2 of theSubnetMask
      put baseconvert(char 17 to 24 of theBinSubnetMask, 2, 10) into item 3 of theSubnetMask
      put baseconvert(char 25 to 32 of theBinSubnetMask, 2, 10) into item 4 of theSubnetMask
      put char 1 to theCIDRDelim -1 of theIPAddress into theIPAddress
   else
      -- subnet mask octets must be 4 numbers between 0 and 255
      -- and all octets after the first octet less than 255 must be 0
      
      if the number of items of theSubnetMask <>4 \
            or the last char of theSubnetMask is "." \
            or ".." is in theSubnetMask then
         return "ERROR: The Subnet Mask must be in the form:" & cr & \
               "'nnn.nnn.nnn.nnn' (subnetmask = '" & theSubnetMask & "')"
      end if
      
      put false into mustBeZero
      repeat for each item theOctet in theSubnetMask
         
         if theOctet <0 or theOctet >255 then
            return "Each octet in the subnet mask must be a number between 0 and 255. " & \
                  "(subnetmask = '" & theSubnetMask & "')"
         end if
         
         if mustBeZero and theOctet >0 then
            return "ERROR: All octets after an octet less than 255 must be 0. " & \
                  "(subnetmask = '" & theSubnetMask & "')"
         end if
         
         if theOctet <255 then
            put true into mustBeZero
         end if
      end repeat
      
      -- convert the subnet mask to binary
      put 0 into whichOctet
      repeat for each item theOctet in theSubnetMask
         add 1 to whichOctet
         
         -- subnet mask must contain only 4 octets
         if whichOctet >4 then
            return "ERROR: The Subnet Mask must contain 4 numbers between 0 and 255 " & \
                  "separated by periods. (subnetmask = '" & theSubnetMask & "')"
         end if
         
         put value(baseConvert(theOctet, 10, 2)) after theBinSubnetMask
      end repeat
      put offset("0", theBinSubnetMask) -1 into theCIDRDepth
   end if
   
   -- CIDR depth must be between 0 and 32
   if theCIDRDepth <0 or theCIDRDepth >32 then
      return "ERROR: The CIDR Depth must be between 0 and 32. " & \
            "(CIDRDepth = '" & theCIDRDepth & "')"
   end if
   
   -- All octets of the IP address must be between 0 and 255
   repeat for each item theOctet in theIPAddress
      if theOctet is empty or theOctet < 0 or theOctet > 255 then
         return "ERROR: Each IP Address octet must be a number between 0 and 255. " & \
               "(ipaddress = '" & theIPAddress & "')"
      end if
   end repeat
   
   -- convert the ip address to binary
   put 0 into whichOctet
   repeat for each item theOctet in theIPAddress
      add 1 to whichOctet
      put baseConvert(theOctet, 10, 2) into theBinValue
      add 0 to theBinValue
      put theBinValue after theBinIPAddress
   end repeat
   
   -- calculate the binary subnet address
   put char 1 to theCIDRDepth of theBinIPAddress into theBinNetworkAddr
   put char theCIDRDepth +1 to -1 of theBinIPAddress into theBinNodeAddr
   put theBinNodeAddr into theBinSubnetNodeAddr
   set the numberFormat to "0"
   replace "1" with "0" in theBinSubnetNodeAddr
   put theBinNetworkAddr & theBinSubnetNodeAddr into theBinSubnetAddr
   
   -- convert the binary subnet address to decimal
   put baseconvert(char 1 to 8 of theBinSubnetAddr, 2, 10)  into item 1 of theSubnetAddr
   put baseconvert(char 9 to 16 of theBinSubnetAddr, 2, 10)  into item 2 of theSubnetAddr
   put baseconvert(char 17 to 24 of theBinSubnetAddr, 2, 10)  into item 3 of theSubnetAddr
   put baseconvert(char 25 to 32 of theBinSubnetAddr, 2, 10)  into item 4 of theSubnetAddr
   
   -- calculate the first usable IP address
   put theSubnetAddr into theFirstAddr
   add 1 to item 4 of theFirstAddr
   
   -- calculate the binary broadcast address
   put theBinNodeAddr into theBinBcastNodeAddr
   replace "0" with "1" in theBinBcastNodeAddr
   put theBinNetworkAddr & theBinBcastNodeAddr into theBinBcastAddr
   
   -- convert the binary broadcast address to decimal
   put baseconvert(char 1 to 8 of theBinBcastAddr, 2, 10) into item 1 of theBcastAddr
   put baseconvert(char 9 to 16 of theBinBcastAddr, 2, 10) into item 2 of theBcastAddr
   put baseconvert(char 17 to 24 of theBinBcastAddr, 2, 10) into item 3 of theBcastAddr
   put baseconvert(char 25 to 32 of theBinBcastAddr, 2, 10) into item 4 of theBcastAddr
   
   -- calculate the last usable IP address
   put theBcastAddr into theLastAddr
   subtract 1 from item 4 of theLastAddr
   
   -- calculate the number of usable addresses
   -- put item 4 of theLastAddr - item 4 of theFirstAddr +1 into theAddrCount
   put baseconvert(theBinBcastNodeAddr, 2, 10) -1 into theAddrCount
   
   -- calculate the CIDR notation
   put theIPAddress & "/" & theCIDRDepth into theCIDRAddr
   
   -- create array
   put theIPAddress into ipdata ["ipaddress"]
   put theSubnetMask into ipdata ["subnetmask"]
   put theSubnetAddr into ipdata ["subnetaddr"]
   put theFirstAddr into ipdata ["firstaddr"]
   put theBcastAddr into ipdata["bcastaddr"]
   put theLastAddr into ipdata ["lastaddr"]
   put theCIDRDepth into ipdata ["cidrdepth"]
   put theAddrCount into ipdata ["usablecount"]
   put theCIDRAddr into ipdata ["cidraddr"]
   return ipdata
end IPCalc

Bob S


> On Jan 26, 2015, at 16:22 , Bob Sneidar <bobsneidar at iotecdigital.com> wrote:
> 
>> On Jan 26, 2015, at 12:14 , Alex Tweedly <alex at tweedly.net> wrote:
>> 
>> A couple of error cases that aren't caught gracefully
>> 
>> 192.168.1/24.1
>> 192.168..1/24
>> 
>> One that is accepted and shouldn't be
>> 192.168.1.1/24.    (note the trailing ".")
>> 
>> Also, not sure why you limit CIDRDepth to between 1 and 30. RFC 4632 specifically says between 0 and 3 - and indeed host routes (/32s) are common enough, as is default route.
>> 
>> Thanks again for contributing this Bob.
>> 
>> -- Alex.





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