Unexpected result with IPv4Address.toSequentialRange method

[martinhansen]

The following ip: 127.0.0.158 (2130706590 in Integer form), with a subnet mask of 24.

When i create a range of ips with toSequentialRange() i don't get a complete range of ips. I get a IPv4AddressSeqRange with 1 IP inside it. (127.0.0.158 -> 127.0.0.158), when i expect it to be (127.0.0.0 -> 127.0.0.250), calculated with: http://jodies.de/ipcalc?host=130.225.157.76&mask1=24&mask2=

When i create the ip-range with toZeroHost and toMaxHost the range comes out as expected.

Using scala, jdk11, and v5.1.0 or 5.0.2 of this lib.

Code to reproduce:

    val ip = 2130706590
    val mask = 24
    val ipAdd = new IPv4Address(ip, mask)

    println(ipAdd)

    val ipRange = ipAdd.toSequentialRange
    val ipRange2 = ipAdd.toZeroHost.toSequentialRange(ipAdd.toMaxHost)

    if (ipRange != ipRange2) {
      println(s"$ipRange not the same as $ipRange2")
    }

same thing happens with 194.105.145.69/31 where the range is still just 1 IP, but i expect it to be 194.105.145.68 -> 194.105.145.69. (Again, using toZeroHost and toMaxHost works)

Is this a bug, or is my expectation of toSequentialRange wrong?

[seancfoley]

Hello,
In this library, when parsing a string with a prefix length, or when constructing an address with a prefix length directly like in your example, you will get a subnet if the host is zero, otherwise it will be a single address. In this example, 127.0.0.158/24 is not a subnet, it is just a single address, because the last segment is the host, and that last segment is 158, not 0. When you convert to IPSequentialRange, it will remain just a single address.

To get the subnet is not difficult, just call toPrefixBlock on your address object.

val ip = 2130706590
val mask = 24
val ipAdd = new IPv4Address(ip, mask).toPrefixBlock
val ipAdd2 = new IPv4Address(Array(127, 0, 0, 158).map(_.toByte), mask).toPrefixBlock
val ipAdd3 = new IPv4Address(Array(127, 0, 0, 0).map(_.toByte), mask)

println(ipAdd)
println(ipAdd2)
println(ipAdd3)

println(ipAdd.getCount) // subnet size
println(ipAdd2.getCount)
println(ipAdd3.getCount)

val ipRange = ipAdd.toSequentialRange
val ipRange2 = ipAdd.toZeroHost.toSequentialRange(ipAdd.toMaxHost)

if (ipRange != ipRange2) {
  println(s"$ipRange not the same as $ipRange2")
} else {
  println(s"$ipRange is the same as $ipRange2")
}

More details here: https://github.com/seancfoley/IPAddress/wiki/Code-Examples#parse-prefixed-as-subnet-or-ip-address

[martinhansen]

That makes sense. Thank you for your explanation. I was confused about it, because the toString method writes out the IP Address like i was a ip/cidr: 127.0.0.158/24, and so i assumed it would be the subnet.