refactor: replace rand crate with fastrand

Replaces the `rand` crate with `fastrand` for improved performance in rate control and reflector selection.

src/ratecontroller.rs

@@ -1,8 +1,6 @@
 use crate::netlink::{Netlink, NetlinkError, Qdisc};
 use crate::{Config, ReflectorStats};
 use log::{debug, info, warn};
-use rand::seq::IndexedRandom;
-use rand::{RngExt, rng};
 use std::collections::HashMap;
 use std::fs::File;
 use std::io::Write;
@@ -51,7 +49,7 @@ fn generate_initial_speeds(base_speed: f64, size: u32) -> Vec<f64> {
     let mut rates = Vec::new();
 
     for _ in 0..size {
-        rates.push((rng().random_range(0.0..1.0) as f64 * 0.2 + 0.75) * base_speed);
+        rates.push((fastrand::f64() * 0.2 + 0.75) * base_speed);
     }
 
     rates
@@ -183,8 +181,7 @@ impl Ratecontroller {
                 }
 
                 if state.delta_stat > delay_ms {
-                    let mut rng = rng();
-                    match state.safe_rates.choose(&mut rng) {
+                    match state.safe_rates.get(fastrand::usize(..state.safe_rates.len())) {
                         Some(rnd_rate) => {
                             state.next_rate =
                                 rnd_rate.min(0.9 * state.current_rate * state.load);

src/reflector_selector.rs

@@ -1,7 +1,5 @@
 use crate::{Config, ReflectorStats};
 use log::{debug, info};
-use rand::seq::IndexedRandom;
-use rand::{RngExt, rng};
 use std::collections::HashMap;
 use std::net::IpAddr;
 use std::sync::mpsc::Receiver;
@@ -24,8 +22,6 @@ impl ReflectorSelector {
         let baseline_sleep_time =
             Duration::from_secs_f64(self.config.tick_interval * std::f64::consts::PI);
 
-        let mut rng = rng();
-
         // Initial wait of several seconds to allow some OWD data to build up
         sleep(baseline_sleep_time);
 
@@ -57,7 +53,7 @@ impl ReflectorSelector {
             }
 
             for _ in 0..20 {
-                let next_candidate = self.reflector_pool.choose(&mut rng).unwrap();
+                let next_candidate = &self.reflector_pool[fastrand::usize(..self.reflector_pool.len())];
                 if next_peers.contains(next_candidate) {
                     continue;
                 }
@@ -110,7 +106,7 @@ impl ReflectorSelector {
 
             // Shuffle the deck so we avoid overwhelming good reflectors (Fisher-Yates)
             for i in (1_usize..candidates.len()).rev() {
-                let j = rng.random_range(0..(i + 1));
+                let j = fastrand::usize(0..=i);
                 candidates.swap(i, j);
             }