RFR: 8315767: InetAddress: constructing objects from BSD literal addresses [v4]

[Daniel Fuchs]

On Thu, 11 Apr 2024 12:58:07 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:
> 
>   moved algorithm description from class spec to the method spec, updated code examples to reflect the network byte order

Thanks for taking on the feedback @sercher . I believe we're in a much better place now. I will let @AlekseiEfimov comment on the test and implementation.

src/java.base/share/classes/java/net/Inet4Address.java line 195:

> 193:      * Creates an {@code Inet4Address} based on the provided {@linkplain
> 194:      * Inet4Address##format textual representation} of an IPv4 address in
> 195:      * POSIX {@code inet_addr} compatible form.

Suggestion:

     * Creates an {@code Inet4Address} based on the provided {@linkplain
     * Inet4Address##format-posix textual representation of an IPv4 address in
     * POSIX {@code inet_addr} compatible form}.


Alternatively you could just remove the link, since the format description is just below.

src/java.base/share/classes/java/net/Inet4Address.java line 245:

> 243:      * {@code IllegalArgumentException}.
> 244:      *
> 245:      * @param posixIPAddressLiteral the textual representation of an IPv4 address.

Suggestion:

     * @param posixIPAddressLiteral a textual representation of an IPv4 address.

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PR Review: https://git.openjdk.org/jdk/pull/18493#pullrequestreview-1994510777
PR Review Comment: https://git.openjdk.org/jdk/pull/18493#discussion_r1561205498
PR Review Comment: https://git.openjdk.org/jdk/pull/18493#discussion_r1561210422