False positives for InetAddresses.isInetAddress

[devikasondhi]

InetAddresses.isInetAddress method returns true for invalid IPv6 address containing two or more consecutive 0s in the last hextet.
Failing test case:
InetAddresses.isInetAddress("804c:404c::0:cc:c0:00c1c") //returns true

Expected to return false, as also verified with an online service here- https://www.helpsystems.com/intermapper/ipv6-test-address-validation

The issue seems to be due to the compression over zeroes involved.

[pmarks-net]

You're suggesting that parseHextet(String ipPart) should fail when ipPart.length() > 4.

I don't have a strong preference either way, but by what definition is this invalid? Guava isn't the only parser that works like this:

$ ping6 ::00000001
PING ::00000001(::1) 56 data bytes
64 bytes from ::1: icmp_seq=1 ttl=64 time=0.049 ms

[swankjesse]

The RFC suggests both Guava and ping6 have it wrong here:

   1. The preferred form is x:x:x:x:x:x:x:x, where the 'x's are one to
      four hexadecimal digits of the eight 16-bit pieces of the address.

[pmarks-net]

Looking at the history of the document:

• RFC1884 (1995): "where the 'x's are the hexadecimal values of the eight 16-bit pieces of the address."
• RFC2373 (1998): same
• RFC3513 (2003): same
• RFC4291 (2006): "where the 'x's are one to four hexadecimal digits of the eight 16-bit pieces of the address."

So the current behavior was standard for more than a decade, and is consistent with OpenJDK:

System.err.println("ip=" + InetAddress.getByName("::00000001"));
...
ip=/0:0:0:0:0:0:0:1

In other words, I don't see a compelling reason to change it.

[sandhu5]

Internally in the private method parseHextet() of InetAddresses.isInetAddress we are using this Integer.parsrInt() method to change hex to integer.
Actually Here in the Integer.parseInt() method When we pass "ipPart" and 16 it returns us an integer,
because internally Integer.parseInt() function does not change the value of "result" Variable by Leading Zeros(Look java docs or Its code)
i.e leading zeroes does not contribute in changing/creating the integer value
So we have to check the length of the String :- if > 4 throw exception

Assignment_IPV6.java.zip
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