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[NET] IPNetwork clears the lower bits instead of throwing. #117367

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Merged
merged 3 commits into from
Jul 8, 2025
Merged

[NET] IPNetwork clears the lower bits instead of throwing. #117367

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7d11140
IPNetwork clears the lower bits instead of throwing.
ManickaP Jul 7, 2025
82c32ba
Update src/libraries/System.Net.Primitives/src/System/Net/IPNetwork.cs
ManickaP Jul 7, 2025
774cd77
Update src/libraries/System.Net.Primitives/src/System/Net/IPNetwork.cs
ManickaP Jul 7, 2025
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3 changes: 0 additions & 3 deletions src/libraries/System.Net.Primitives/src/Resources/Strings.resx
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Original file line number Diff line number Diff line change
Expand Up @@ -81,9 +81,6 @@
<data name="net_bad_ip_network" xml:space="preserve">
<value>An invalid IP network was specified.</value>
</data>
<data name="net_bad_ip_network_invalid_baseaddress" xml:space="preserve">
<value>The specified baseAddress has non-zero bits after the network prefix.</value>
</data>
<data name="net_container_add_cookie" xml:space="preserve">
<value>An error occurred when adding a cookie to the container.</value>
</data>
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49 changes: 27 additions & 22 deletions src/libraries/System.Net.Primitives/src/System/Net/IPNetwork.cs
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Expand Up @@ -52,19 +52,11 @@ public IPNetwork(IPAddress baseAddress, int prefixLength)
ThrowArgumentOutOfRangeException();
}

if (HasNonZeroBitsAfterNetworkPrefix(baseAddress, prefixLength))
{
ThrowInvalidBaseAddressException();
}

_baseAddress = baseAddress;
_baseAddress = ClearNonZeroBitsAfterNetworkPrefix(baseAddress, prefixLength);
PrefixLength = prefixLength;

[DoesNotReturn]
static void ThrowArgumentOutOfRangeException() => throw new ArgumentOutOfRangeException(nameof(prefixLength));

[DoesNotReturn]
static void ThrowInvalidBaseAddressException() => throw new ArgumentException(SR.net_bad_ip_network_invalid_baseaddress, nameof(baseAddress));
}

// Non-validating ctor
Expand Down Expand Up @@ -203,8 +195,7 @@ public static bool TryParse(ReadOnlySpan<char> s, out IPNetwork result)

if (IPAddress.TryParse(ipAddressSpan, out IPAddress? address) &&
int.TryParse(prefixLengthSpan, NumberStyles.None, CultureInfo.InvariantCulture, out int prefixLength) &&
prefixLength <= GetMaxPrefixLength(address) &&
!HasNonZeroBitsAfterNetworkPrefix(address, prefixLength))
prefixLength <= GetMaxPrefixLength(address))
{
Debug.Assert(prefixLength >= 0); // Parsing with NumberStyles.None should ensure that prefixLength is always non-negative.
result = new IPNetwork(address, prefixLength, false);
Expand Down Expand Up @@ -232,8 +223,7 @@ public static bool TryParse(ReadOnlySpan<byte> utf8Text, out IPNetwork result)

if (IPAddress.TryParse(ipAddressSpan, out IPAddress? address) &&
int.TryParse(prefixLengthSpan, NumberStyles.None, CultureInfo.InvariantCulture, out int prefixLength) &&
prefixLength <= GetMaxPrefixLength(address) &&
!HasNonZeroBitsAfterNetworkPrefix(address, prefixLength))
prefixLength <= GetMaxPrefixLength(address))
{
Debug.Assert(prefixLength >= 0); // Parsing with NumberStyles.None should ensure that prefixLength is always non-negative.
result = new IPNetwork(address, prefixLength, false);
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The baseAddress is the original non-mask address. Is it intended?

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Fudge, good catch. It also means we don't have a good test coverage for this. I'll put up a PR asap.

Expand All @@ -247,36 +237,51 @@ public static bool TryParse(ReadOnlySpan<byte> utf8Text, out IPNetwork result)

private static int GetMaxPrefixLength(IPAddress baseAddress) => baseAddress.AddressFamily == AddressFamily.InterNetwork ? 32 : 128;

private static bool HasNonZeroBitsAfterNetworkPrefix(IPAddress baseAddress, int prefixLength)
private static IPAddress ClearNonZeroBitsAfterNetworkPrefix(IPAddress baseAddress, int prefixLength)
{
if (baseAddress.AddressFamily == AddressFamily.InterNetwork)
{
// The cast to long ensures that the mask becomes 0 for the case where 'prefixLength == 0'.
uint mask = (uint)((long)uint.MaxValue << (32 - prefixLength));
// Bitwise shift works only for lower 5-bits count operands.
if (prefixLength == 0)
{
// Corresponds to 0.0.0.0
return IPAddress.Any;
}

uint mask = uint.MaxValue << (32 - prefixLength);
if (BitConverter.IsLittleEndian)
{
mask = BinaryPrimitives.ReverseEndianness(mask);
}

return (baseAddress.PrivateAddress & mask) != baseAddress.PrivateAddress;
uint newAddress = baseAddress.PrivateAddress & mask;
return newAddress == baseAddress.PrivateAddress
? baseAddress
: new IPAddress(newAddress);
}
else
{
UInt128 value = default;
baseAddress.TryWriteBytes(MemoryMarshal.AsBytes(new Span<UInt128>(ref value)), out int bytesWritten);
Debug.Assert(bytesWritten == IPAddressParserStatics.IPv6AddressBytes);
// Bitwise shift works only for lower 7-bits count operands.
if (prefixLength == 0)
{
return value != UInt128.Zero;
// Corresponds to [::]
return IPAddress.IPv6Any;
}

UInt128 value = default;
baseAddress.TryWriteBytes(MemoryMarshal.AsBytes(new Span<UInt128>(ref value)), out int bytesWritten);
Debug.Assert(bytesWritten == IPAddressParserStatics.IPv6AddressBytes);

UInt128 mask = UInt128.MaxValue << (128 - prefixLength);
if (BitConverter.IsLittleEndian)
{
mask = BinaryPrimitives.ReverseEndianness(mask);
}

return (value & mask) != value;
UInt128 newAddress = value & mask;
return newAddress == value
? baseAddress
: new IPAddress(MemoryMarshal.AsBytes(new Span<UInt128>(ref newAddress)));
}
}

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57 changes: 38 additions & 19 deletions src/libraries/System.Net.Primitives/tests/FunctionalTests/IPNetworkTest.cs
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Original file line number Diff line number Diff line change
@@ -1,9 +1,13 @@
// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

using System.Buffers.Binary;
using System.Collections;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Net.Sockets;
using System.Runtime.InteropServices;
using System.Text;
using Xunit;

Expand All @@ -26,38 +30,64 @@ public class IPNetworkTest
{
{ "127.0.0.1/33" }, // PrefixLength max is 32 for IPv4
{ "ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff/129" }, // PrefixLength max is 128 for IPv6
{ "127.0.0.1/31" }, // Bits exceed the prefix length of 31 (32nd bit is on)
{ "198.51.255.0/23" }, // Bits exceed the prefix length of 23
{ "ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff/127" }, // Bits exceed the prefix length of 31
{ "2a01:110:8012::/45" }, // Bits exceed the prefix length of 45 (47th bit is on)
};

public static TheoryData<string> ValidIPNetworkData = new TheoryData<string>()
{
{ "0.0.0.0/32" }, // the whole IPv4 space
{ "0.0.0.0/0" },
{ "192.168.0.10/0" },
{ "128.0.0.0/1" },
{ "127.0.0.1/8" },
{ "127.0.0.1/31" },
{ "198.51.255.0/23" },
{ "::/128" }, // the whole IPv6 space
{ "255.255.255.255/32" },
{ "198.51.254.0/23" },
{ "42.42.128.0/17" },
{ "ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff/128" },
{ "2a01:110:8012::/47" },
{ "2a01:110:8012::/100" },
{ "ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff/127" },
{ "2a01:110:8012::/45" },
};

private uint GetMask32(int prefix)
{
Debug.Assert(prefix != 0);

uint mask = uint.MaxValue << (32 - prefix);
return BitConverter.IsLittleEndian ? BinaryPrimitives.ReverseEndianness(mask) : mask;
}
private UInt128 GetMask128(int prefix)
{
Debug.Assert(prefix != 0);

UInt128 mask = UInt128.MaxValue << (128 - prefix);
return BitConverter.IsLittleEndian ? BinaryPrimitives.ReverseEndianness(mask) : mask;
}
private IPAddress GetBaseAddress(IPAddress address, int prefix)
=> (address.AddressFamily, prefix) switch
{
(AddressFamily.InterNetwork, 0) => new IPAddress([0, 0, 0, 0]),
(AddressFamily.InterNetwork, _) => new IPAddress(MemoryMarshal.Read<uint>(address.GetAddressBytes()) & GetMask32(prefix)),
(AddressFamily.InterNetworkV6, 0) => new IPAddress([0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]),
(AddressFamily.InterNetworkV6, _) => new IPAddress(MemoryMarshal.AsBytes([MemoryMarshal.Read<UInt128>(address.GetAddressBytes()) & GetMask128(prefix)])),
_ => throw new ArgumentOutOfRangeException($"Unexpected address family {address.AddressFamily} of {address}.")
};

[Theory]
[MemberData(nameof(ValidIPNetworkData))]
public void Constructor_Valid_Succeeds(string input)
{
string[] splitInput = input.Split('/');
IPAddress address = IPAddress.Parse(splitInput[0]);
int prefixLegth = int.Parse(splitInput[1]);
int prefixLength = int.Parse(splitInput[1]);

IPNetwork network = new IPNetwork(address, prefixLegth);
IPNetwork network = new IPNetwork(address, prefixLength);

Assert.Equal(address, network.BaseAddress);
Assert.Equal(prefixLegth, network.PrefixLength);
Assert.Equal(GetBaseAddress(address, prefixLength), network.BaseAddress);
Assert.Equal(prefixLength, network.PrefixLength);
}

[Fact]
Expand All @@ -77,17 +107,6 @@ public void Constructor_PrefixLenghtOutOfRange_ThrowsArgumentOutOfRangeException
Assert.Throws<ArgumentOutOfRangeException>(() => new IPNetwork(address, prefixLength));
}

[Theory]
[InlineData("192.168.0.1", 31)]
[InlineData("42.42.192.0", 17)]
[InlineData("128.0.0.0", 0)]
[InlineData("2a01:110:8012::", 46)]
public void Constructor_NonZeroBitsAfterNetworkPrefix_ThrowsArgumentException(string ipStr, int prefixLength)
{
IPAddress address = IPAddress.Parse(ipStr);
Assert.Throws<ArgumentException>(() => new IPNetwork(address, prefixLength));
}

[Theory]
[MemberData(nameof(IncorrectFormatData))]
public void Parse_IncorrectFormat_ThrowsFormatException(string input)
Expand Down
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