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[System.Net] Fix IPNetwork.Contains for mapped IPv4 addresses #131862

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Merged
MihaZupan merged 1 commit into from
Aug 6, 2026
Merged

[System.Net] Fix IPNetwork.Contains for mapped IPv4 addresses #131862

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2 changes: 1 addition & 1 deletion src/libraries/System.Net.Primitives/src/System/Net/IPNetwork.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -78,7 +78,7 @@ public bool Contains(IPAddress address)
return true;
}

if (address.AddressFamily == AddressFamily.InterNetwork || address.IsIPv4MappedToIPv6)
if (BaseAddress.AddressFamily == AddressFamily.InterNetwork)
{
uint mask = uint.MaxValue << (32 - PrefixLength);
if (BitConverter.IsLittleEndian)
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10 changes: 10 additions & 0 deletions src/libraries/System.Net.Primitives/tests/FunctionalTests/IPNetworkTest.cs
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Expand Up @@ -210,6 +210,16 @@ public void Contains_DifferentAddressFamily_ReturnsFalse()
Assert.False(network.Contains(IPAddress.Loopback));
}

[Theory]
[InlineData("2000::/3", "::ffff:1.2.3.4", false)]
[InlineData("::ffff:0:0/96", "::ffff:192.0.2.1", true)]
public void Contains_IPv4MappedAddressInIPv6Network_ReturnsExpected(string networkString, string addressString, bool expected)
{
IPNetwork network = IPNetwork.Parse(networkString);

Assert.Equal(expected, network.Contains(IPAddress.Parse(addressString)));
}

[Theory]
[InlineData("0.0.0.0/0", "0.0.0.0", "127.127.127.127", "255.255.255.255")] // the whole IPv4 space
[InlineData("0.0.0.0/0", "0.0.0.0", "::ffff:127.127.127.127", "::ffff:255.255.255.255")] // the whole IPv4 space
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