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Merging main into darc-main-b3d99129-0da1-44dd-9167-5a0ff9ee9993
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‎src/Servers/Kestrel/Core/src/HttpsConnectionAdapterOptions.cs‎

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// Licensed to the .NET Foundation under one or more agreements.
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// The .NET Foundation licenses this file to you under the MIT license.
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using System.Buffers;
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using System.Net.Security;
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using System.Security.Authentication;
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using System.Security.Cryptography.X509Certificates;
@@ -96,6 +97,14 @@ public void AllowAnyClientCertificate()
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/// </summary>
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public Action<ConnectionContext, SslServerAuthenticationOptions>? OnAuthenticate { get; set; }
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/// <summary>
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/// A callback to be invoked to get the TLS client hello bytes.
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/// Null by default.
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/// If you want to store the bytes from the <see cref="System.Buffers.ReadOnlySequence{T}"/>,
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/// copy them into a buffer that you control rather than keeping a reference to the <see cref="ReadOnlySequence{T}"/> or <see cref="ReadOnlyMemory{T}"/> instances.
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/// </summary>
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public Action<ConnectionContext, ReadOnlySequence<byte>>? TlsClientHelloBytesCallback { get; set; }
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/// <summary>
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/// Specifies the maximum amount of time allowed for the TLS/SSL handshake. This must be positive
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/// or <see cref="Timeout.InfiniteTimeSpan"/>. Defaults to 10 seconds.

‎src/Servers/Kestrel/Core/src/ListenOptionsHttpsExtensions.cs‎

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using System.Security.Cryptography.X509Certificates;
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using Microsoft.AspNetCore.Server.Kestrel.Core;
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using Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Infrastructure;
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using Microsoft.AspNetCore.Server.Kestrel.Core.Middleware;
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using Microsoft.AspNetCore.Server.Kestrel.Https;
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using Microsoft.AspNetCore.Server.Kestrel.Https.Internal;
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using Microsoft.Extensions.DependencyInjection;
@@ -197,6 +198,15 @@ public static ListenOptions UseHttps(this ListenOptions listenOptions, HttpsConn
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listenOptions.IsTls = true;
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listenOptions.HttpsOptions = httpsOptions;
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if (httpsOptions.TlsClientHelloBytesCallback is not null)
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{
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listenOptions.Use(next =>
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{
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var middleware = new TlsListenerMiddleware(next, httpsOptions.TlsClientHelloBytesCallback);
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return middleware.OnTlsClientHelloAsync;
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});
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}
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listenOptions.Use(next =>
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{
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var middleware = new HttpsConnectionMiddleware(next, httpsOptions, listenOptions.Protocols, loggerFactory, metrics);

‎src/Servers/Kestrel/Core/src/Middleware/TlsListenerMiddleware.cs‎

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// Licensed to the .NET Foundation under one or more agreements.
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// The .NET Foundation licenses this file to you under the MIT license.
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using System.Buffers;
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using System.Diagnostics;
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using Microsoft.AspNetCore.Connections;
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namespace Microsoft.AspNetCore.Server.Kestrel.Core.Middleware;
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internal sealed class TlsListenerMiddleware
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{
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private readonly ConnectionDelegate _next;
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private readonly Action<ConnectionContext, ReadOnlySequence<byte>> _tlsClientHelloBytesCallback;
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public TlsListenerMiddleware(ConnectionDelegate next, Action<ConnectionContext, ReadOnlySequence<byte>> tlsClientHelloBytesCallback)
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{
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_next = next;
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_tlsClientHelloBytesCallback = tlsClientHelloBytesCallback;
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}
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/// <summary>
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/// Sniffs the TLS Client Hello message, and invokes a callback if found.
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/// </summary>
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internal async Task OnTlsClientHelloAsync(ConnectionContext connection)
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{
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var input = connection.Transport.Input;
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ClientHelloParseState parseState = ClientHelloParseState.NotEnoughData;
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while (true)
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{
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var result = await input.ReadAsync();
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var buffer = result.Buffer;
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try
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{
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// If the buffer length is less than 6 bytes (handshake + version + length + client-hello byte)
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// and no more data is coming, we can't block in a loop here because we will not get more data
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if (result.IsCompleted && buffer.Length < 6)
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{
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break;
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}
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parseState = TryParseClientHello(buffer, out var clientHelloBytes);
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if (parseState == ClientHelloParseState.NotEnoughData)
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{
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// if no data will be added, and we still lack enough bytes
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// we can't block in a loop, so just exit
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if (result.IsCompleted)
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{
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break;
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}
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continue;
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}
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if (parseState == ClientHelloParseState.ValidTlsClientHello)
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{
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_tlsClientHelloBytesCallback(connection, clientHelloBytes);
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}
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Debug.Assert(parseState is ClientHelloParseState.ValidTlsClientHello or ClientHelloParseState.NotTlsClientHello);
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break; // We can continue with the middleware pipeline
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}
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finally
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{
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if (parseState is ClientHelloParseState.NotEnoughData)
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{
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input.AdvanceTo(buffer.Start, buffer.End);
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}
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else
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{
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// ready to continue middleware pipeline, reset the buffer to initial state
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input.AdvanceTo(buffer.Start);
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}
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}
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}
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await _next(connection);
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}
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/// <summary>
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/// RFCs
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/// ----
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/// TLS 1.1: https://datatracker.ietf.org/doc/html/rfc4346#section-6.2
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/// TLS 1.2: https://datatracker.ietf.org/doc/html/rfc5246#section-6.2
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/// TLS 1.3: https://datatracker.ietf.org/doc/html/rfc8446#section-5.1
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/// </summary>
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private static ClientHelloParseState TryParseClientHello(ReadOnlySequence<byte> buffer, out ReadOnlySequence<byte> clientHelloBytes)
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{
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clientHelloBytes = default;
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if (buffer.Length < 6)
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{
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return ClientHelloParseState.NotEnoughData;
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}
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var reader = new SequenceReader<byte>(buffer);
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// Content type must be 0x16 for TLS Handshake
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if (!reader.TryRead(out byte contentType) || contentType != 0x16)
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{
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return ClientHelloParseState.NotTlsClientHello;
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}
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// Protocol version
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if (!reader.TryReadBigEndian(out short version) || !IsValidProtocolVersion(version))
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{
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return ClientHelloParseState.NotTlsClientHello;
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}
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// Record length
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if (!reader.TryReadBigEndian(out short recordLength))
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{
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return ClientHelloParseState.NotTlsClientHello;
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}
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// byte 6: handshake message type (must be 0x01 for ClientHello)
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if (!reader.TryRead(out byte handshakeType) || handshakeType != 0x01)
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{
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return ClientHelloParseState.NotTlsClientHello;
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}
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// 5 bytes are
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// 1) Handshake (1 byte)
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// 2) Protocol version (2 bytes)
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// 3) Record length (2 bytes)
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if (buffer.Length < 5 + recordLength)
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{
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return ClientHelloParseState.NotEnoughData;
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}
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clientHelloBytes = buffer.Slice(0, 5 + recordLength);
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return ClientHelloParseState.ValidTlsClientHello;
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}
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private static bool IsValidProtocolVersion(short version)
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=> version is 0x0300 // SSL 3.0 (0x0300)
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or 0x0301 // TLS 1.0 (0x0301)
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or 0x0302 // TLS 1.1 (0x0302)
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or 0x0303 // TLS 1.2 (0x0303)
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or 0x0304; // TLS 1.3 (0x0304)
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private enum ClientHelloParseState : byte
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{
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NotEnoughData,
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NotTlsClientHello,
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ValidTlsClientHello
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}
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}

‎src/Servers/Kestrel/Core/src/PublicAPI.Unshipped.txt‎

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#nullable enable
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Microsoft.AspNetCore.Server.Kestrel.Https.HttpsConnectionAdapterOptions.TlsClientHelloBytesCallback.get -> System.Action<Microsoft.AspNetCore.Connections.ConnectionContext!, System.Buffers.ReadOnlySequence<byte>>?
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Microsoft.AspNetCore.Server.Kestrel.Https.HttpsConnectionAdapterOptions.TlsClientHelloBytesCallback.set -> void

‎src/Servers/Kestrel/Core/test/TestHelpers/ObservablePipeReader.cs‎

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// Licensed to the .NET Foundation under one or more agreements.
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// The .NET Foundation licenses this file to you under the MIT license.
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using System;
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using System.Collections.Generic;
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using System.IO.Pipelines;
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using System.Text;
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namespace Microsoft.AspNetCore.Server.Kestrel.Core.Tests.TestHelpers;
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internal class ObservablePipeReader : PipeReader
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{
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private readonly PipeReader _inner;
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public ObservablePipeReader(PipeReader reader)
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{
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_inner = reader;
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}
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/// <summary>
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/// Number of times <see cref="ReadAsync(CancellationToken)"/> was called.
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/// </summary>
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public int ReadAsyncCounter { get; private set; }
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public override void AdvanceTo(SequencePosition consumed)
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=> _inner.AdvanceTo(consumed);
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public override void AdvanceTo(SequencePosition consumed, SequencePosition examined)
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=> _inner.AdvanceTo(consumed, examined);
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public override void CancelPendingRead()
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=> _inner.CancelPendingRead();
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public override void Complete(Exception exception = null)
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=> _inner.Complete(exception);
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public override ValueTask<ReadResult> ReadAsync(CancellationToken cancellationToken = default)
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{
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ReadAsyncCounter++;
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return _inner.ReadAsync(cancellationToken);
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}
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public override bool TryRead(out ReadResult result)
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{
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return _inner.TryRead(out result);
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}
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}

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