feat(sim): docs, more scaffolding

msg-sim/README.md

@@ -0,0 +1,25 @@
+# `msg-sim`
+
+## Overview
+This crate provides functionality to simulate real-world network conditions over an interface (e.g. `lo0`) for testing and benchmarking purposes.
+It only works on MacOS and Linux.
+
+## Implementation
+
+### MacOS
+* https://gist.github.com/tellyworth/2ce28add99fe743c702c090c8144355e
+
+* `dnctl` for creating a dummynet pipe
+
+Example:
+```bash
+dnctl pipe 1 config bw 10Kbit/s delay 300 plr 0.1 noerror`
+```
+
+* `pfctl` for creating a rule to match traffic and send it through the pipe
+
+Example:
+```bash
+echo "dummynet out proto tcp from any to any pipe 1" | sudo pfctl -f -
+pfctl -e
+```

msg-sim/src/cmd/macos.rs

@@ -0,0 +1,4 @@
+//! This module contains all the commands necessary to start and stop a simulation.
+//!
+//! ## Implementation
+//! Under the hood, this module uses the `pfctl` command.

msg-sim/src/cmd/mod.rs

@@ -0,0 +1,5 @@
+#[cfg(target_os = "linux")]
+pub mod linux;
+
+#[cfg(target_os = "macos")]
+pub mod macos;

msg-sim/src/lib.rs

@@ -1,5 +1,10 @@
 use std::{collections::HashMap, time::Duration};
 
+use protocol::Protocol;
+
+mod cmd;
+mod protocol;
+
 /// A type alias for a network device.
 pub type Device = String;
 
@@ -9,8 +14,10 @@ pub struct SimConfig {
     target_bw: u64,
     default_bw: u64,
     packet_loss: f64,
+    protocols: Vec<Protocol>,
 }
 
+#[derive(Default)]
 pub struct Simulator {
     /// A map of active simulations.
     active_sims: HashMap<Device, Simulation>,

msg-sim/src/protocol.rs

@@ -0,0 +1,18 @@
+#[derive(Debug, Clone, Copy)]
+#[allow(clippy::upper_case_acronyms)]
+pub enum Protocol {
+    TCP,
+    UDP,
+    ICMP,
+}
+
+impl From<&str> for Protocol {
+    fn from(s: &str) -> Self {
+        match s {
+            "tcp" => Self::TCP,
+            "udp" => Self::UDP,
+            "icmp" => Self::ICMP,
+            _ => panic!("invalid protocol"),
+        }
+    }
+}