tokio_tcp::TcpStream::poll_read_ready fails to detect HUP

[vi]

Version

• tokio-tcp 0.1.3
• tokio 0.1.21
• mio 0.6.19

Platform

x86_64-unknown-linux-gnu

Description

TcpStream::poll_read_ready claims to always include HUP on supported platform. I assume Linux (and Unix in genereal) is a supported platform. Yet arrival of FIN on the socket does not cause it to return Ok(Async::Ready).

Sample code

extern crate tokio;
extern crate tokio_tcp;
extern crate mio;

use tokio::prelude::*;

// Wait for TCP socket reset without reading or writing to it
struct WaitForJustHup(tokio_tcp::TcpStream);

impl Future for WaitForJustHup {
    type Item=();
    type Error=();
    fn poll(&mut self) -> Poll<(), ()> {
        let mut m = mio::Ready::empty();
        #[cfg(unix)] {
            m = mio::unix::UnixReady::hup().into();
        }
        let ret = self.0.poll_read_ready(m);
        println!("{:?}", ret);
        match ret {
            Ok(Async::NotReady) => Ok(Async::NotReady),
            _ => Ok(Async::Ready(())),
        }
    }
}

fn main() {
    let sa = "127.0.0.1:1234".parse().unwrap();
    let job = tokio_tcp::TcpStream::connect(&sa).map_err(drop).and_then(|tcp| {
        WaitForJustHup(tcp)
    });
    tokio::runtime::run(job);
}

When I run it against nc -nvlp 1234, I get:

Ok(NotReady)   # it connected
Ok(NotReady)   # I typed something into netcat
Ok(NotReady)   # I terminated netcat. I expect it to be Ok(Ready(_)) instead.

[vi]

With mio = "=0.6.16" it works:

Ok(NotReady)
Ok(NotReady)
Ok(Ready(Hup))

With mio = "=0.6.17" it fails:

Ok(NotReady)
Ok(NotReady)
Ok(NotReady)
^C

[vi]

tokio-rs/mio@b89e3bd

[carllerche]

@vi yes, that was a bug. Reporting RDHUP as HUP was incorrect. I'm going to close this specific issue. I plan to revisit what events are exposed as part of 0.2.

[vi]

Will it be possible to:

• monitor for TCP's FIN or RSTs
• while having the socket already shut down for writing
• without reading from it (backpressure)

after the revisit? Ideally also portably.

[carllerche]

Yes, I would like to. It will most likely require platform specific code in Tokio to do so.

[carllerche]

I added a note here: #1209.