Async IO, Mio support

[koraa]

Thank you for building hermit; I hope this will become a conerstone of rust infrastructure soon!

At Rosenpass (post quantum security for WireGuard in Rust) we are currently exploring using broker based security sandboxing. As part of this project we are trying to add experimental support for running significant parts of the Rosenpass deployment inside Hermit OS.

The core rosenpass process uses mio to handle IO operations to enable the use of async io. We are considering eventually migrating to tokio.

Building hermit-rs-template with --target x86_64-unknown-hermit and a dependency on mio without non-default features yields a successful build. Adding the net feature yields a whole bunch of compile time errors (log).

Is using mio expected to work?

diff --git a/Cargo.toml b/Cargo.toml
index 452bbdc..240333f 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -4,4 +4,7 @@ version = "0.1.0"
 edition = "2021"

 [target.'cfg(target_os = "hermit")'.dependencies]
-hermit = "0.8"
+hermit = { version = "0.8", features = ["pci", "pci-ids", "acpi", "fsgsbase", "tcp", "rtl8139"]}
+
+[dependencies]
+mio = { version = "0.8.10", features = ["net"] }

Errors (excerpt)

   Compiling mio v0.8.10
error[E0425]: cannot find value `listener` in this scope
  --> /home/karo/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-0.8.10/src/net/tcp/listener.rs:74:24
   |
74 |         set_reuseaddr(&listener.inner, true)?;
   |                        ^^^^^^^^ help: a function with a similar name exists: `listen`
   |
  ::: /home/karo/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-0.8.10/src/sys/shell/tcp.rs:20:1
   |
20 | pub(crate) fn listen(_: &net::TcpListener, _: u32) -> io::Result<()> {
   | -------------------------------------------------------------------- similarly named function `listen` defined here

error[E0425]: cannot find value `listener` in this scope
  --> /home/karo/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-0.8.10/src/net/tcp/listener.rs:76:15
   |
76 |         bind(&listener.inner, addr)?;
   |               ^^^^^^^^ help: a function with a similar name exists: `listen`
   |
  ::: /home/karo/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-0.8.10/src/sys/shell/tcp.rs:20:1
   |
20 | pub(crate) fn listen(_: &net::TcpListener, _: u32) -> io::Result<()> {
   | -------------------------------------------------------------------- similarly named function `listen` defined here

[mkroening]

We are working on async support for userspace. :)

See also smol-rs/polling#177

[koraa]

We are working on async support for userspace. :)

See also smol-rs/polling#177

That is wonderful, thank you :)

So we'd probably have to mygrate to smol-rs/polling to make use of that?

[mkroening]

So we'd probably have to mygrate to smol-rs/polling to make use of that?

No, we want to support Mio too. We are currently at the stage of needing to implement the kernel primitives, but are happy to support multiple different user space crates for async I/O.

[koraa]

So we'd probably have to mygrate to smol-rs/polling to make use of that?

No, we want to support Mio too. We are currently at the stage of needing to implement the kernel primitives, but are happy to support multiple different user space crates for async I/O.

Sounds great, thank you for that work! Then we will try again once that lands.

[mkroening]

@stlankes just made a lot of progress towards async I/O on Hermit by adding poll support in #1046. 🥳