runtime: SslStream.WriteAsync hangs after updating to CoreFx 4.4

We’ve recently updated package references in Kestrel to CoreFx 4.4 https://github.com/aspnet/KestrelHttpServer/commit/5b8f7c2b2be5744edac8ce3c5a2dea86ed65b8ee.

After this update, Kestrel can’t serve HTTPS anymore. We have a stream that wraps an SslStream, and it’s hanging when writing here:

https://github.com/aspnet/KestrelHttpServer/blob/5b8f7c2b2be5744edac8ce3c5a2dea86ed65b8ee/src/Microsoft.AspNetCore.Server.Kestrel/Filter/Internal/StreamSocketOutput.cs#L59

Reproing is straightforward: just run the Kestrel sample app (under samples/SampleApp in the repo) and hit it with any client, and you will see the hang.

This only happens on .NET Core. Desktop .NET works fine.

About this issue

Original URL
State: closed
Created 8 years ago
Comments: 40 (30 by maintainers)

Most upvoted comments

.NET Full Framework 1.1+ had async methods Stream.BeginWrite/Stream.EndWrite and Stream.BeginRead/Stream.EndRead on the base class. This approach to async was depreciated when Tasks became a thing and the new Task based methods Stream.WriteAsync and Stream.ReadAsync became the preferred method of doing async.

The base classes implementation of BeginX/EndX are sync methods to support Streams that don’t actually have async methods. A lot of the conversions for the historic Streams newer XXXAsync methods have wrapped these BeginX/EndX methods to achieve the newer async paths; using helpers that do the conversion.

As these methods were deprecated they were not brought to .NET Core. To reuse the same code that expected BeginX/EndX without doing lots of rewriting to directly implement WriteAsync/ReadAsync; which would be additional replumbing and testing to end up with the same result (although it would be cleaner); extension methods were created to behave as the BeginX/EndX methods. So all was fine…

However, as part of returning the apis for .NET Standard 2.0; this has meant the base class implementations for BeginX/EndX have reappeared. The virtual base class methods take precedence over extension methods; so the behaviour has moved back to sync-blocking on the async methods; rather than actually being async.

Hence this issue has arisen… 😢

The fastest way to fix it is likely to copy paste the extension methods code into SslStream/NetworkStream etc. The best way to fix it would be to actually implement the WriteAsync/ReadAsync methods - though likely that would also be more risky.

benaadams on Dec 30, 2016