RFR: 8315767: InetAddress: constructing objects from BSD literal addresses

[Daniel Fuchs]

On Tue, 26 Mar 2024 17:25:54 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#parseBsdLiteralV4()` method is e...

src/java.base/share/classes/java/net/Inet4Address.java line 124:

> 122:  *  // the constructed address bytes without any rearrangement
> 123:  *  Inet4Address.ofPosixLiteral("017700000001"); // ==> /127.0.0.1
> 124:  * }

Please move this part into the normative part of the `ofPosixLiteral` method description

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

PR Review Comment: https://git.openjdk.org/jdk/pull/18493#discussion_r1557767839