Add IPNetwork.Parse and TryParse

[david-acker]

Add Parse and TryParse methods for IPNetwork

Adds Parse and TryParse methods for creating an IPNetwork using an input string in CIDR notation or 'slash notation'

Description

Adds the following Parse and TryParse static methods to IPNetwork:

public static IPNetwork Parse(ReadOnlySpan<char> networkSpan);
public static bool TryParse(ReadOnlySpan<char> networkSpan, out IPNetwork? network);

Examples

IPv4

// Using Parse
var network = IPNetwork.Parse("192.168.0.1/32");

// Using TryParse
bool success = IPNetwork.TryParse("192.168.0.1/32", out var network);

// Ctor equivalent
var network = new IPNetwork(IPAddress.Parse("192.168.0.1"), 32);

IPv6

// Using Parse
var network = IPNetwork.Parse("2001:db8:3c4d::1/128");

// Using TryParse
bool success = IPNetwork.TryParse("2001:db8:3c4d::1/128", out var network);

// Ctor equivalent
var network = new IPNetwork(IPAddress.Parse("2001:db8:3c4d::1"), 128);

Fixes #8606

[ghost]

Thanks for your PR, @david-acker. Someone from the team will get assigned to your PR shortly and we'll get it reviewed.

[gfoidl]

Left some nits / hints.

[gfoidl]

Unrleated to your change: but these should be if-else if-else to avoid double-checks, or actually I'd write it as

static bool IsValidPrefixLengthRange1(IPAddress prefix, int prefixLength)
{
    return prefix.AddressFamily switch
    {
        AddressFamily.InterNetwork => prefixLength <= 32,
        AddressFamily.InterNetworkV6 => prefixLength <= 128,
        _ => prefixLength >= 0
    };
}

and let Roslyn and JIT optimize it.

[david-acker]

Ah, that's a good point. Although with your example, the prefixLength >= 0 check isn't be enforced for the non-default cases so negative prefixLength values would slip through. How about this instead?

static bool IsValidPrefixLengthRange(IPAddress prefix, int prefixLength)
{
+   if (prefixLength < 0)
+   {
+       return false;
+   }

    return prefix.AddressFamily switch
    {
        AddressFamily.InterNetwork => prefixLength <= 32,
        AddressFamily.InterNetworkV6 => prefixLength <= 128,
-       _ => prefixLength >= 0
+      _ => true
    };
}

[gfoidl]

Yep, you're right 👍🏻

[danmoseley]

@MihaZupan this type seems like something you'd expect in System.Net. I wonder whether there is missing API there.

[MihaZupan]

We've had a few issues about CIDR support in System.Net: dotnet/runtime#36428, dotnet/runtime#64033, dotnet/runtime#42845
So far they've all been rejected/gone quiet due to lack of demand/being a bit niche.

It looks like users are satisfied with the NuGet package that offers all sorts of these helpers https://github.com/jsakamoto/ipaddressrange and haven't been pushing on the runtime team.

[slang25]

There's no package out there that I'm completely happy with. I'd like something in System.Net that has good performance (a struct implementation would be ideal).

I rolled my own version of this last week to avoid adding a dependency to my library.

[danmoseley]

I'd like something in System.Net that has good performance (a struct implementation would be ideal).

If you want to pursue that, you'll want to create an API proposal there of course. Edit: oh, I misread, sounds like we already have discussion there.

[ghost]

@david-acker, this change will be considered for inclusion in the blog post for the release it'll ship in. Nice work!

Please ensure that the original comment in this thread contains a clear explanation of what the change does, why it's important (what problem does it solve?), and, if relevant, include things like code samples and/or performance numbers.

This content may not be exactly what goes into the blog post, but it will help the team putting together the announcement.

Thanks!

[Tratcher]

Thanks