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refactor: minor tweak to sans-io intro to be more conservative (#5709)

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Signed-off-by: Thomas Eizinger <thomas@eizinger.io>
Co-authored-by: Thomas Eizinger <thomas@eizinger.io>
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Jamil
2024-07-03 19:50:54 -07:00
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parent 086c730aaf
commit d84c4f0713
2 changed files with 20 additions and 10 deletions
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24
website/src/app/blog/sans-io/readme.mdx
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@@ -1,14 +1,14 @@
import Image from "next/image";
import Alert from "@/components/DocsAlert";
At Firezone, we build secure remote access that scales, be it from your Android
phone, MacOS computer or Linux server. At the core of each app sits a
connectivity library &mdash; aptly named
At Firezone, we use Rust[^1] to build secure remote access that scales, be it
from your Android phone, MacOS computer or Linux server. At the core of each app
sits a connectivity library &mdash; aptly named
[`connlib`](https://www.github.com/firezone/firezone/tree/main/rust/connlib)
&mdash; that manages network connections and WireGuard tunnels to secure your
traffic. After several iterations, we’ve landed on a design that we are
extremely happy with. It gives us blazingly fast and exhaustive tests, deep
customisation and overall high assurance that it does what we want it to do.
extremely happy with. It gives us fast and exhaustive tests, deep customisation
and overall high assurance that it does what we want it to do.
`connlib` is built in Rust and the design we are talking about is known as
sans-IO. Rust's premise of speed and memory-safety makes it a great choice for
@@ -453,7 +453,7 @@ event loop are: `handle_timeout`, `handle_input`, `poll_transmit` and
protocols can be implemented with these or some variation of them. As a result,
it is very easy to compose these state machines together: want to query 5 STUN
servers for your public IP? No problem. Just make 5 `StunBinding`s and call them
in order[^3].
in order[^4].
In the case of Firezone, you can see this in the example of
[`snownet`](https://github.com/firezone/firezone/tree/main/rust/connlib/snownet),
@@ -461,7 +461,7 @@ a library that combines ICE and WireGuard and thereby exposes "magic" IP tunnels
that work in any network setup to the rest of the application.
`snownet` builds on top of `str0m`, a sans-IO WebRTC library and `boringtun`, an
(almost[^2]) sans-IO WireGuard implementation. We don’t need the majority of the
(almost[^3]) sans-IO WireGuard implementation. We don’t need the majority of the
WebRTC stack though. The only thing we are interested in is the `IceAgent` which
implements [RFC 8445](https://datatracker.ietf.org/doc/html/rfc8445). ICE uses a
clever algorithm that ensures two agents, deployed into arbitrary network
@@ -572,7 +572,7 @@ is sound. In comparison, `async` Rust and `&mut` almost feel somewhat at odds
with each other.
In Rust, `async` functions are just syntax sugar for a data structure that
implements `Future`. Spawning a `Future` into a runtime[^1] like `tokio`
implements `Future`. Spawning a `Future` into a runtime[^2] like `tokio`
requires this data structure to be `'static` and therefore, it cannot contain
any references, including `&mut`. To mutate state that isn't local to the
`Future`, you basically have two options:
@@ -644,12 +644,16 @@ Many thanks to [@algesten](https://github.com/algesten) for providing feedback
on drafts of this post.
[^1]:
Technically, a thread-per-core runtime could allow non-`'static` `Future`s.
For more details on Firezone's tech stack, see
[this article](/kb/architecture/tech-stack) in our architecture docs.
[^2]:
Technically, a thread-per-core runtime could allow non-`'static` `Future`s.
[^3]:
`boringtun` does call `Instant::now` internally and is thus unfortunately
partly impure, see https://github.com/cloudflare/boringtun/issues/391.
[^3]:
[^4]:
Be sure to implement proper multiplexing of STUN messages at this point.
Hint: Use the `TransactionId` and/or the server's address.

6
website/src/app/kb/architecture/tech-stack/readme.mdx
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@@ -57,6 +57,12 @@ These manage the control path and hot paths of the Client, respectively. They
interact through a thin software layer to exchange WireGuard keys and STUN
information between the control plane API and the TUN interface.
<Alert color="warning">
For a deep dive into Firezone's data plane architecture and its sans-IO
design, we recommend reading [sans-IO: The secret to effective Rust for
network services](/blog/sans-io).
</Alert>
Here's a high-level diagram of the various software components used in the
Client applications: