Allow HttpSys zero-byte reads

[Tratcher]

Allow HttpSys zero-byte reads

Allow zero length reads from the Http.Sys request body stream

Description

AspNetCore and YARP have started to take advantage of the zero-byte-read pattern, where zero length buffers are passed to read operations to be notified when data is available. This allows the caller to avoid allocations and pinning on slow/idle streams like gRPC and WebSockets.

The Http.Sys server request body stream does not currently allow this. First, it performs argument checks that disallow a zero length buffer. Also, when the native read completes it returns ERROR_MORE_DATA rather than SUCCESS. This needs to be handled by the stream or it will throw an IOException.

Fixes #41305

Customer Impact

Since YARP 1.1 adopted the zero-byte-read pattern for performance reasons customers can no longer use it with our Http.Sys server.

Regression?

• Yes
• No

Risk

• High
• Medium
• Low

Verification

• Manual (required)
• Automated

Packaging changes reviewed?

• Yes
• No
• N/A

[ghost]

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[ghost]

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[halter73]

Backport of #41332.