H2Upgraded::poll_write returns Ok(0) while tokio-rustls assumes Ok(0) is 'successful'

[hatoo]

Version
List the version(s) of hyper, and any relevant hyper dependency (such as h2 if this is related to HTTP/2).
hyper: commit 12717d1

Platform
The output of uname -a (UNIX), or version and 32 or 64-bit (Windows)

WSL2 Ubuntu on Windows 11

❯ uname -a
Linux WindowsNVMe 5.15.167.4-microsoft-standard-WSL2 #1 SMP Tue Nov 5 00:21:55 UTC 2024 x86_64 x86_64 x86_64 GNU/Linux

Description

When we wrap tokio-rustls around HTTP2 Upgraded stream, tokio-rustls will infinite loop because Upgraded stream returns Ok(0) on poll_write when shutdown. relevant issue rustls/tokio-rustls#92

hyper/src/proto/h2/mod.rs

Lines 329 to 337 in 12717d1

	let cnt = match ready!(self.send_stream.poll_capacity(cx)) {
	None => Some(0),
	Some(Ok(cnt)) => self
	.send_stream
	.write(&buf[..cnt], false)
	.ok()
	.map(|()| cnt),
	Some(Err(_)) => None,
	};

I've found that when I replace None => Some(0), to None => None, it works fine.

Honestly, I don't know the issue should be resolved in either hyper or tokio-rustls. But this issue is important when I implement HTTP2 proxy.

[seanmonstar]

tokio-rustls will infinite loop because Upgraded stream returns Ok(0) on poll_write when shutdown.

What do you mean? As opposed to what?

[hatoo]

https://github.com/rustls/tokio-rustls/blob/66fb0ae98fbc9e71d5aa855d45e88ca8d53f95f3/src/common/mod.rs#L330-L334

tokio-rustls writes the remaining data on poll_shutdown and because H2Upgraded::poll_write always returns Ok(0) on the write (perhaps because the stream is already closed by the other side), tokio-rustls goes an infinite loop.

[seanmonstar]

Oh OK. That's a bug in tokio-rustls, then. Returning Ok(0) is the normal way for IO resources to indicate no more bytes are allowed (see https://doc.rust-lang.org/std/io/trait.Write.html#tymethod.write).

[hatoo]

Fixed in tokio-rustls side rustls/tokio-rustls#93