Convert ip ranges to CIDR netblocks Post: 302846763

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Top Forums Shell Programming and Scripting Convert ip ranges to CIDR netblocks Post 302846763 by Chubler_XL on Sunday 25th of August 2013 08:24:03 PM

08-25-2013

Moderator

How about this for range2cidr (Then call it like this range2cidr(ip2dec($1), ip2dec($2)):

Code:

function range2cidr(ipStart, ipEnd,  bits, mask, newip) {
    bits = 1
    mask = 1
    while (bits < 32) {
        newip = or(ipStart, mask)
        if ((newip>ipEnd) || ((lshift(rshift(ipStart,bits),bits)) != ipStart)) {
           bits--
           mask = rshift(mask,1)
           break
        }
        bits++
        mask = lshift(mask,1)+1
    }
    newip = or(ipStart, mask)
    bits = 32 - bits
    result = dec2ip(ipStart) "/" bits
    if (newip < ipEnd) result = result "\n" range2cidr(newip + 1, ipEnd)
    return result
}

---------- Post updated at 10:24 AM ---------- Previous update was at 08:31 AM ----------

Of course this does require the following gawk bitwise functions: or() lshift() and rshift()

We could be replace these with local (bit_) variants for more portability.

Code:

# Bitwise OR of var1 and var2
function bit_or(a, b, r, i, c) {
    for (r=i=0;i<32;i++) {
        c = 2 ^ i
        if ((int(a/c) % 2) || (int(b/c) % 2)) r += c
    }
    return r
}


# Rotate bytevalue left x times
function bit_lshift(var, x) {
  while(x--) var*=2;
  return var;
}

# Rotate bytevalue right x times
function bit_rshift(var, x) {
  while(x--) var=int(var/2);
  return var;
}

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