Bug 39315 - Mono.Security.Protocol.Tls.SslStreamBase blocks on asynchronous operations
Summary: Mono.Security.Protocol.Tls.SslStreamBase blocks on asynchronous operations
Status: RESOLVED FEATURE
Alias: None
Product: Class Libraries
Classification: Mono
Component: Mono.Security ()
Version: 4.2.0 (C6)
Hardware: PC Linux
: --- normal
Target Milestone: Untriaged
Assignee: Martin Baulig
URL:
Depends on:
Blocks:
 
Reported: 2016-03-03 09:42 UTC by Dr. John Wason
Modified: 2017-09-13 19:29 UTC (History)
2 users (show)

Tags:
Is this bug a regression?: ---
Last known good build:

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Status:
RESOLVED FEATURE

Description Dr. John Wason 2016-03-03 09:42:36 UTC
The class Mono.Security.Tls.SslStreamBase provides asynchronous stream functions including BeginRead, EndRead, BeginWrite, and EndWrite. Unfortunately these asynchronous functions are blocking in situations where both BeginRead and BeginWrite are called at the same time, as is very common in threaded networking design.  An example of the offending code in BeginRead is:

                        if (this.MightNeedHandshake)
			{
				if (! BeginNegotiateHandshake(asyncResult))
				{
					//we made it down here so the handshake was not started.
					//another thread must have started it in the mean time.
					//wait for it to complete and then perform our original operation
					this.negotiationComplete.WaitOne();

					InternalBeginRead(asyncResult);
				}
			}
			else
			{
				InternalBeginRead(asyncResult);
			}

The "this.negotiationComplete.WaitOne();" causes a deadlock that is very difficult if not impossible to avoid.  The class needs to either expose the handshaking as a separate function like SslStream does, or it needs to not have a hard block in the asynchronous functions.