RFR: 8272215: Add InetAddress methods for parsing IP address literals [v2]

[Jaikiran Pai]

On Sat, 23 Sep 2023 17:28:55 GMT, Aleksei Efimov <aefimov at openjdk.org> wrote:

>> ### Summary 
>> 
>> The changes in this PR add new API to `java.net.InetAddress`, `java.net.Inet4Address`, and
>>  `java.net.Inet6Address` classes to parse IP address literals:
>>  ```
>> method public static java.net.InetAddress java.net.InetAddress.ofLiteral(java.lang.String)
>> method public static java.net.Inet4Address java.net.Inet4Address.ofLiteral(java.lang.String)
>> method public static java.net.InetAddress java.net.Inet6Address.ofLiteral(java.lang.String)
>> ``` 
>> 
>> ### How new methods differ from existing ones
>> 
>> These methods differ from `InetAddress.getByName` and `InetAddress.getAllByName` in the following ways:
>> 1. If a string supplied is not an address literal it is not forwarded to the system-wide resolver, but IllegalArgumentException is thrown instead. The system-wide resolver is never called from these new methods.
>> 2. No reverse lookup is performed to resolve a hostname for the supplied address literal - the `InetAddress[46 ]` instances returned by the new `ofLiteral` API has no hostname set.
>> 3. Each `ofLiteral` static method returns addresses of its class only. It gives the ability to check if an IP address literal is of a specific address type. 
>> 
>> ### The list of noteworthy changes
>> - `IPv4-mapped IPv6 address` and `IPv4-compatible IPv6 addresses` require some special handling in the new API to implement all supported IP address types.  
>> - All address literal parsing code has been moved from `InetAddress.getAllByName` to address type-specific `Inet4Address.parseAddressString` and `Inet6Address.parseAddressString` methods.
>> - The text with scoped IPv6 addresses architecture draft IETF file has been replaced from `[draft-ietf-ipngwg-scoping-arch-04.txt]` to reference `RFC 4007: IPv6 Scoped Address Architecture`. The "RFC 4007" has been also added as `@ spec` into Inet6Address class-level Javadoc.
>> 
>> ### Testing 
>> 
>> `jdk-tier1`, `jdk-tier2`, and `jdk-tier3` test sets show no failure with the changes.
>> 
>> `java/net` JCK tests are failing with new methods added failure (CSR is planned for this change):
>> 
>> Added Methods
>> -------------
>> 
>> java.net.Inet4Address:                  method public static java.net.Inet4Address java.net.Inet4Address.ofLiteral(java.lang.String)
>> java.net.Inet6Address:                  method public static java.net.InetAddress java.net.Inet6Address.ofLiteral(java.lang.String)
>> java.net.InetAddress:                   method public static java.net.InetAddress java.net.InetAddress.ofLiteral(java.lan...
>
> Aleksei Efimov has updated the pull request incrementally with two additional commits since the last revision:
> 
>  - updates for Inet6Address.ofLiteral return type, javadoc and the regression test
>  - add null checks and NPE to methods javadoc

Hello Aleksei, it's good to see the addition of these new APIs. On the naming front, I like the proposal of using either `ofLiteral` or `parseLiteral`.

The new APIs are proposing to throw an `IllegalArgumentException` if the passed literal is not an IP address literal. That seems logical. However, the existing `getByAddress(byte[] ...)` API which accepts a byte form of the raw IP address, currently throws `UnknownHostException` in the case where the IP address isn't of a valid length. Should we consider throwing `UnknownHostException` from these new APIs too? I prefer `IllegalArgumentException` in these new APIs, but `UnknownHostException` might be something that would need to be considered?

The proposed changes also have text which talks about "ambiguous" address literals. The term ambiguous seems new in the InetAddress (and sub-classes). The package-info.java too doesn't have previous references to it. Should we add some details on what addresses are considered ambiguous (and how/if such addresses are treated by existing APIs)?

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PR Comment: https://git.openjdk.org/jdk/pull/15775#issuecomment-1752441558