f01fd4ddf6
Our DNS over TCP implementation uses `smoltcp` which requires us to manage sockets individually, i.e. there is no such thing as a listening socket. Instead, we have to create multiple sockets and rotate through them. Whenever we receive new DNS servers from the host app, we throw away all of those sockets and create new ones. The way we refer to these sockets internally is via `smoltcp`'s `SocketHandle`. These are just indices into a `Vec` and this access can panic when it is out of range. Normally that doesn't happen because such a `SocketHandle` is only created when the socket is created and therefore, each `SocketHandle` in existence should be valid. What we overlooked is that these sockets get destroyed and re-created when we call `set_listen_addresses` which happens when the host app tells us about new DNS servers. In that case, sockets that we had just received a query on and are waiting for a response have their handles stored in a temporary `HashMap`. Attempting to send back a response for one of those queries will then either fail with an error that the socket is not in the right state or - worse - panic with an out of bounds error if the previously had more listen addresses than we have now. To fix this, we need to clear this map of pending queries every time we call `set_listen_addresses`.
Rust development guide
Firezone uses Rust for all data plane components. This directory contains the Linux and Windows clients, and low-level networking implementations related to STUN/TURN.
We target the last stable release of Rust using rust-toolchain.toml.
If you are using rustup, that is automatically handled for you.
Otherwise, ensure you have the latest stable version of Rust installed.
Reading Client logs
The Client logs are written as JSONL for machine-readability.
To make them more human-friendly, pipe them through jq like this:
cd path/to/logs # e.g. `$HOME/.cache/dev.firezone.client/data/logs` on Linux
cat *.log | jq -r '"\(.time) \(.severity) \(.message)"'
Resulting in, e.g.
2024-04-01T18:25:47.237661392Z INFO started log
2024-04-01T18:25:47.238193266Z INFO GIT_VERSION = 1.0.0-pre.11-35-gcc0d43531
2024-04-01T18:25:48.295243016Z INFO No token / actor_name on disk, starting in signed-out state
2024-04-01T18:25:48.295360641Z INFO null
Benchmarking on Linux
The recommended way for benchmarking any of the Rust components is Linux' perf utility.
For example, to attach to a running application, do:
- Ensure the binary you are profiling is compiled with the
releaseprofile. sudo perf record -g --freq 10000 --pid $(pgrep <your-binary>).- Run the speed test or whatever load-inducing task you want to measure.
sudo perf script > profile.perf- Open profiler.firefox.com and load
profile.perf
Instead of attaching to a process with --pid, you can also specify the path to executable directly.
That is useful if you want to capture perf data for a test or a micro-benchmark.