System.Net.Http: Closure causing excessive memory consumption

[filipnavara]

Description

We analyzed memory dump from one of our testers which was showing excessive memory usage. The memory profiler showed us this:

Apparently the certificate validation callback in System.Net.Http request captures the HttpRequestMessage in a closure when establishing SSL connections:

runtime/src/libraries/System.Net.Http/src/System/Net/Http/SocketsHttpHandler/ConnectHelper.cs

Lines 135 to 139 in d0e2281

	sslOptions = sslOptions.ShallowClone(); // Clone as we're about to mutate it and don't want to affect the cached copy
	Func<HttpRequestMessage, X509Certificate2?, X509Chain?, SslPolicyErrors, bool> localFromHttpClientHandler = mapper.FromHttpClientHandler;
	HttpRequestMessage localRequest = request;
	sslOptions.RemoteCertificateValidationCallback = (object sender, X509Certificate? certificate, X509Chain? chain, SslPolicyErrors sslPolicyErrors) =>
	localFromHttpClientHandler(localRequest, certificate as X509Certificate2, chain, sslPolicyErrors);

In our case that happened to hold close to 70Mb of data from that particular request.

Configuration

.NET 3.1.200 (but the same code is present in master as of d0e2281)
Windows x64

Regression?

It likely is regression with SocketsHttpHandler when compared to the older WinHTTP handler.

[ghost]

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