cidr_complement.sh

cidr_complement.sh

#!/bin/sh

cidr_complement() {
  awk -f - $* <<EOF
    function ip2int(ip) {
      ret=0
      n=split(ip,a,".")
      for (x=1;x<=n;x++) {
        ret=or(lshift(ret,8),a[x])
      }
      return ret
    }

    function int2ip(ip,ret,x) {
      ret=and(ip,255)
      ip=rshift(ip,8)
      for(;x<3;x++) {
        ret=and(ip,255)"."ret
        ip=rshift(ip,8)
      }
      return ret
    }

    function compl32(v) {
      ret=xor(v, 0xffffffff)
      return ret
    }

    function range2cidr(ipStart, ipEnd, bits, mask, newip) {
        bits = 1
        mask = 1
        result = ""
        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 = result int2ip(ipStart) "/" bits
        if (newip < ipEnd) result = result "\n" range2cidr(newip + 1, ipEnd)
        return result
    }

    BEGIN {
      start=0
      while ((getline cidr<"/tmp/test.list")>0) {
        slpos=index(cidr,"/")
        ipaddr=ip2int(substr(cidr,0,slpos-1))
        netmask=compl32(2**(32-int(substr(cidr,slpos+1)))-1)
        num=compl32(netmask)+1

        end=ipaddr - 1
        if (end>=start) {
          print range2cidr(start, end)
        }

        start=ipaddr + num
      }
      if (start<=4294967295) {
        print range2cidr(start, 4294967295)
      }
    }
EOF
}

cat /path/to/yourcidr.list | sort -n -t . -k 1,1 -k 2,2 -k 3,3 -k 4,4 >/tmp/test.list

cidr_complement