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The event-loop inside `Tunnel` processes input according to a certain priority. We only take input from lower priority sources when the higher priority sources are not ready. The current priorities are: - Flush all buffers - Read from UDP sockets - Read from TUN device - Read from DNS servers - Process recursive DNS queries - Check timeout The idea of this priority ordering is to keep all kinds of processing bounded and "finish" any kind of work that is on-going before taking on new work. Anything that sits in a buffer is basically done with processing and just needs to be written out to the network / device. Arriving UDP packets have already traversed the network and been encrypted on the other end, meaning they are higher priority than reading from the TUN device. Packets from the TUN device still need to be encrypted and sent to the remote. Whilst there is merit in this design, it also bears the potential of starving input sources further down if the top ones are extremely busy. To prevent this, we refactor `Io` to read from all input sources and present it to the event-loop as a batch, allowing all sources to make progress before looping around. Since this event-loop has first been conceived, we have refactored `Io` to use background threads for the UDP sockets and TUN device, meaning they will make progress by themselves anyway until the channels to the main-thread fill up. As such, there shouldn't be any latency increase in processing packets even though we are performing slightly more work per event-loop tick. This kind of batch-processing highlights a problem: Bailing out with an error midway through processing a batch leaves the remainder of the batch unprocessed, essentially dropping packets. To fix this, we introduce a new `TunnelError` type that presents a collection of errors that we encountered while processing the batch. This might actually also be a problem with what is currently in `main` because we are already batch-processing packets there but possibly are bailing out midway through the batch. --------- Signed-off-by: Thomas Eizinger <thomas@eizinger.io> Co-authored-by: Mariusz Klochowicz <mariusz@klochowicz.com>
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.