Ipv6 Increment issue with segment-2

[himanshu-goyal-cloudsmartz]

Hi SeancFoley,
Maven jar Version : 5.3.1
i was trying to get two subnets of mask 25 from IPv6 CIDR "7c40:​100::/24".
which will result this ("7c40:​100::/25", "7c40:180::/25")

I am able to get the first subnet of 25 using addr.getNetworkSection(25)
And for second subnet of same mask i.e 25 using addr.getNetworkSection(25).getUpper().increment(1) which is throwing Below mentioned exception

Exception in thread "main" inet.ipaddr.AddressValueException: 1, IP Address error: exceeds address size
at inet.ipaddr.format.standard.AddressDivisionGrouping.checkOverflow(AddressDivisionGrouping.java:1209)
at inet.ipaddr.ipv6.IPv6AddressSection.increment(IPv6AddressSection.java:1333)
at inet.ipaddr.ipv6.IPv6AddressSection.increment(IPv6AddressSection.java:99)
at com.ipam.mgmt.util.IpBlockUtils.getSubnet(IpBlockUtils.java:157)
at com.ipam.mgmt.util.IpBlockUtils.main(Unknown Source)

Doing some debugging i do found the root cause of the problem and solution for it too.

ROOT Cause: in IPv6AddressSection.java while checking the checkOverflow condition exception is thrown and reason why it throws exception is it get MAX_VALUES_BY_SEGMENT for segment 2 as -1

Solution : The IPv6AddressSection.java contains a BigInteger Array as pasted below
private static final BigInteger MAX_VALUES_BY_SEGMENT[] = {
BigInteger.ZERO,
BigInteger.valueOf(IPv6Address.MAX_VALUE_PER_SEGMENT),
BigInteger.valueOf(0xffffffff),
BigInteger.valueOf(0xffffffffffffL),
BigInteger.valueOf(1).shiftLeft(16 * 4).subtract(BigInteger.ONE),
BigInteger.valueOf(1).shiftLeft(16 * 5).subtract(BigInteger.ONE),
BigInteger.valueOf(1).shiftLeft(16 * 6).subtract(BigInteger.ONE),
BigInteger.valueOf(1).shiftLeft(16 * 7).subtract(BigInteger.ONE),
BigInteger.valueOf(1).shiftLeft(16 * 8).subtract(BigInteger.ONE),
};

The implementation of "BigInteger.valueOf(0xffffffff)" at index 3 is returning -1 whereas it was supposed to return "4294967295".
which can be fixed by correcting the Value at 3rd Index by adding L as shown below
"BigInteger.valueOf(0xffffffff)" -> BigInteger.valueOf(0xffffffffL)

"BigInteger.valueOf(0xffffffff)" gives -1
"BigInteger.valueOf(0xffffffffL)" gives 4294967295

Please fix it and provide new Hotfix for it.

[seancfoley]

Thanks for the analysis, the analysis looks correct at first glance. I can add this to the next release which is coming soon.

[seancfoley]

BTW, your code does not do exactly what you think, although it is not far off.

You could do this:

IPAddressString addressString = new IPAddressString("7c40:100::/24");
IPAddress addr = addressString.getAddress();
IPAddress adjusted = addr.adjustPrefixLength(1, false);
Iterator<? extends IPAddress> iter = adjusted.prefixBlockIterator();
while(iter.hasNext()) {
	IPAddress next = iter.next();
	System.out.println(next);
}	

which gives
7c40:​100::/25
7c40:180::/25

You could also do this, which is more similar to your code.
The lower and the upper give you the two sections you want, you can just zero out the bits with the upper:

IPAddressString addressString = new IPAddressString("7c40:100::/24");
IPAddress addr = addressString.getAddress();
IPAddressSection sect = addr.getNetworkSection(25);
IPAddressSection n1 = sect.getLower();
IPAddressSection n2 = sect.getUpper().toZeroHost();
System.out.println(sect  + " " + n1 + " " + n2);

which gives
7c40:100-180/25 7c40:100/25 7c40:180/25

[himanshu-goyal-cloudsmartz]

Thanks.. i am following the second option.

[seancfoley]

Fixed in version 5.3.2