RFR: 8315767: InetAddress: constructing objects from BSD literal addresses [v10]

[Michael McMahon]

On Fri, 17 May 2024 11:23:34 GMT, Sergey Chernyshev <schernyshev at openjdk.org> wrote:

>> There are two distinct approaches to parsing IPv4 literal addresses. One is the Java baseline "strict" syntax (all-decimal d.d.d.d form family), another one is the "loose" syntax of RFC 6943 section 3.1.1 [1] (POSIX `inet_addr` allowing octal and hexadecimal forms [2]). The goal of this PR is to provide interface to construct InetAddress objects from literal addresses in POSIX form, to applications that need to mimic the behavior of `inet_addr` used by standard network utilities such as netcat/curl/wget and the majority of web browsers. At present time, there's no way to construct `InetAddress` object from such literal addresses because the existing APIs such as `InetAddress.getByName()`, `InetAddress#ofLiteral()` and `Inet4Address#ofLiteral()` will consume an address and successfully parse it as decimal, regardless of the octal prefix. Hence, the resulting object will point to a different IP address.
>> 
>> Historically `InetAddress.getByName()/.getAllByName()` were the only way to convert a literal address into an InetAddress object. `getAllByName()` API relies on POSIX `getaddrinfo` / `inet_addr` which parses IP address segments with `strtoul` (accepts octal and hexadecimal bases).
>> 
>> The fallback to `getaddrinfo` is undesirable as it may end up with network queries (blocking mode), if `inet_addr` rejects the input literal address. The Java standard explicitly says that
>> 
>> "If a literal IP address is supplied, only the validity of the address format is checked."
>> 
>> @AlekseiEfimov contributed JDK-8272215 [3] that adds new factory methods `.ofLiteral()` to `InetAddress` classes. Although the new API is not affected by the `getaddrinfo` fallback issue, it is not sufficient for an application that needs to interoperate with external tooling that follows POSIX standard. In the current state, `InetAddress#ofLiteral()` and `Inet4Address#ofLiteral()` will consume the input literal address and (regardless of the octal prefix) parse it as decimal numbers. Hence, it's not possible to reliably construct an `InetAddress` object from a literal address in POSIX form that would point to the desired host.
>> 
>> It is proposed to extend the factory methods with `Inet4Address#ofPosixLiteral()` that allows parsing literal IP(v4) addresses in "loose" syntax, compatible with `inet_addr` POSIX api. The implementation is based on `.isBsdParsableV4()` method added along with JDK-8277608 [4]. The changes in the original algorithm are as follows:
>> 
>> - `IPAddressUtil#parseB...
>
> Sergey Chernyshev has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Apply suggestions from code review
>   
>   Co-authored-by: Michael McMahon <70538289+Michael-Mc-Mahon at users.noreply.github.com>

Marked as reviewed by michaelm (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/18493#pullrequestreview-2063099323