RFR: 8272215: Add InetAddress methods for parsing IP address literals

[Daniel Fuchs]

On Sun, 17 Sep 2023 13:38:08 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.Inet6Address 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. Address literal strings are not forwarded to the system-wide resolver - they are only parsed and validated by the internal 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.Inet6Address java.net.Inet6Address.ofLiteral(java.lang.String)
> java.net.InetAddress:                   method public static java.net.InetAddress java.net.InetAddress.ofLiteral(java.lang.String)

Good work Aleksei, certainly enough to get the discussion going :-) 
I'm not entirely sure of some aspects of this proposal though. See my other comments inline.

src/java.base/share/classes/java/net/Inet4Address.java line 148:

> 146:      *   <blockquote><ul style="list-style-type:none">
> 147:      *   <li>{@code 1.2.3.4}</li>
> 148:      *   <li>{@code 06.07.08.09}</li>

It might be clearer to transform this in a kind of JShell like snippet, showing the Inet4Adress call and what is returned? I would also expect to see an example of IPv4-compatible IPv6 address literal here.

Something like:

     * {@snippet:
     *     Inet4Address.ofLiteral("1.2.3.4")            ==>    /1.2.3.4
     *     Inet4Address.ofLiteral("06.07.08.09")        ==>    /6.7.8.9
     *     Inet4Address.ofLiteral(""::ffff:1020:3040")  ==>    /16.32.48.64
     * }


As a side note, I suspect that Inet4Adress.ofLiteral() accepting IPv4-compatible IPv6 addresses will be surprising for most users. I wonder if we should change that, and have Inet6Address.ofLiteral() return InetAddress instead of Inet6Address, and take care of that edge case.

As a user of the API I could very well see myself trying to do something like:

if (addr.startsWith("[") && addr.endsWith("]")) {
    var ipv6 = addr.substring(1, addr.length() - 1);
    try {
         Inet6Address.ofLiteral(ipv6);
    }  catch (...) {
         throw new IllegalArgumentException("Invalid IPv6 literal between "[ ]"");
    }
}

I'm not saying we shouldn't do what you're suggesting here, but I believe we should get more feedback.

src/java.base/share/classes/java/net/Inet6Address.java line 490:

> 488:      * java.net.spi.InetAddressResolver resolver} is not queried to resolve
> 489:      * the provided literal, and no reverse lookup is performed.
> 490:      * @implNote <a href="Inet6Address.html#special-ipv6-address-heading">

`@implNote` is not appropriate here. This should be part of the spec (if we keep it). See my other comment above in `Inet4Address`.

-------------

PR Review: https://git.openjdk.org/jdk/pull/15775#pullrequestreview-1631177877
PR Review Comment: https://git.openjdk.org/jdk/pull/15775#discussion_r1328799014
PR Review Comment: https://git.openjdk.org/jdk/pull/15775#discussion_r1328804396