embedded-nal(-async) for embassy-net

[olanod]

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Starting to dig into the embedded networking story of Rust I find embassy-net as a very interesting option as I prefer the async nature of the embassy stack. However I initially started prototyping something using embedded-nal-async abstractions to then realize there are no implementations. Found smoltcp-nal that seems like a nice and simple alternative but it doesn't yet implement the async versions of the embedded-nal traits. Is it something that would make sense to implement here?

[Dirbaio]

The embedded-nal (nb-based) traits will not be implemented. nb is broken by design, async is superior to it in every way, the Embassy project will not invest effort in nb.

The current embedded-nal-async has a big design mistake: all methods requiring &mut self on the stack means you can't read/write/connect on several sockets concurrently from different tasks. I believe this makes the traits unusable in the real world, embassy-net won't implement them until this is fixed.

There's a WIP TcpClient trait that would fix it, we will have an impl for it when it's merged: https://github.com/rust-embedded-community/embedded-nal/pull/69

Also note embassy-net already impls the embedded-io traits, which is enough abstraction for many things in practice. You create the socket with embassy-net directly (not through a trait) then pass it to whatever lib which takes an embedded-io reader/writer.

[lulf]

Embedded-nal-async has been redesigned and implemented in embassy-net in #895