feat(config): add config-rs settings support

Introduce config-rs and Serde support with a nested Settings model.
Add config and serde dependencies with toml feature for file-based
configuration loading. The Settings struct provides typed configuration
with sensible defaults for network, output, observability, and advanced
settings sections. Environment variable override via SQMA__ prefix is
supported. The legacy Config remains in use; migration follows later.

Cargo.lock

@@ -94,6 +94,18 @@ dependencies = [
  "cc",
 ]
 
+[[package]]
+name = "config"
+version = "0.15.25"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b85f248a4de22d204ceabc6299d89d2c70fbd7f09fea53c06c852369652d8139"
+dependencies = [
+ "pathdiff",
+ "serde_core",
+ "toml",
+ "winnow",
+]
+
 [[package]]
 name = "either"
 version = "1.16.0"
@@ -284,6 +296,12 @@ version = "1.21.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9f7c3e4beb33f85d45ae3e3a1792185706c8e16d043238c593331cc7cd313b50"
 
+[[package]]
+name = "pathdiff"
+version = "0.2.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "df94ce210e5bc13cb6651479fa48d14f601d9858cfe0467f43ae157023b938d3"
+
 [[package]]
 name = "prettyplease"
 version = "0.2.37"
@@ -389,6 +407,45 @@ version = "1.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "94143f37725109f92c262ed2cf5e59bce7498c01bcc1502d7b9afe439a4e9f49"
 
+[[package]]
+name = "serde"
+version = "1.0.229"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4148590afebada386688f18773da617792bf2ef03ffc1e4cbd2b1d45b023e0ba"
+dependencies = [
+ "serde_core",
+ "serde_derive",
+]
+
+[[package]]
+name = "serde_core"
+version = "1.0.229"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "67dca2c9c51e58a4791a4b1ed58308b39c64224d349a935ab5039aa360942a48"
+dependencies = [
+ "serde_derive",
+]
+
+[[package]]
+name = "serde_derive"
+version = "1.0.229"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e7a5d71263a5a7d47b41f6b3f06ba276f10cc18b0931f1799f710578e2309348"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn 3.0.2",
+]
+
+[[package]]
+name = "serde_spanned"
+version = "1.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6662b5879511e06e8999a8a235d848113e942c9124f211511b16466ee2995f26"
+dependencies = [
+ "serde_core",
+]
+
 [[package]]
 name = "shlex"
 version = "1.3.0"
@@ -425,6 +482,7 @@ name = "sqm-autorate-rust"
 version = "0.4.1"
 dependencies = [
  "anyhow",
+ "config",
  "fastrand",
  "flume",
  "icmp-socket2",
@@ -434,6 +492,7 @@ dependencies = [
  "netlink-socket2",
  "rust-uci",
  "rustix",
+ "serde",
  "thiserror",
 ]
 
@@ -479,6 +538,37 @@ dependencies = [
  "syn 3.0.2",
 ]
 
+[[package]]
+name = "toml"
+version = "1.1.4+spec-1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3aace63f4bbcdfc2c965b059de67119c89c4017a70d633be6c104910f67056f5"
+dependencies = [
+ "serde_core",
+ "serde_spanned",
+ "toml_datetime",
+ "toml_parser",
+ "winnow",
+]
+
+[[package]]
+name = "toml_datetime"
+version = "1.1.1+spec-1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3165f65f62e28e0115a00b2ebdd37eb6f3b641855f9d636d3cd4103767159ad7"
+dependencies = [
+ "serde_core",
+]
+
+[[package]]
+name = "toml_parser"
+version = "1.1.3+spec-1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1d38ac1cf9b95face32296c0a3ede1fdc270627c9d9c02a7274dd6d960dc4d56"
+dependencies = [
+ "winnow",
+]
+
 [[package]]
 name = "unicode-ident"
 version = "1.0.24"
@@ -544,3 +634,12 @@ checksum = "ae137229bcbd6cdf0f7b80a31df61766145077ddf49416a728b02cb3921ff3fc"
 dependencies = [
  "windows-link",
 ]
+
+[[package]]
+name = "winnow"
+version = "1.0.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "23b97319f7b8343df12cc98938e5c3eb436064524c8d2b4e30a1d3a36eecdf81"
+dependencies = [
+ "memchr",
+]

Cargo.toml

@@ -26,6 +26,8 @@ rustix = { version = "1.1", features = ["fs", "system", "thread", "time"] }
 thiserror = "2.0"
 libc = "0.2"
 flume = { version = "0.12.0",  default-features = false, features = ["eventual-fairness", "select"] }
+config = { version = "0.15.25", default-features = false }
+serde = { version = "1", features = ["derive"] }
 
 [dependencies.log]
 features = ["std"]
@@ -37,4 +39,6 @@ netlink-socket2 = { version = "0.3.3" }
 rust-uci = { git = "https://github.com/namib-project/rust-uci.git", rev = "3e7b6153b6df92b45428c32bb6461756563deecb", optional = true }
 
 [features]
+default = ["toml"]
+toml = ["config/toml"]
 uci = ["dep:rust-uci"]

src/main.rs

@@ -17,6 +17,7 @@ mod pinger_icmp_ts;
 mod platform;
 mod ratecontroller;
 mod reflector_selector;
+mod settings;
 mod time;
 mod util;
 

src/settings/mod.rs

@@ -0,0 +1,223 @@
+// SPDX-FileCopyrightText: 2026-Present Nils Andreas Svee mailto:contact@lochnair.net (github @Lochnair)
+//
+// SPDX-License-Identifier: MPL-2.0
+
+use anyhow::{Context, bail};
+use config::{Config, ConfigError, Environment};
+use log::Level;
+use serde::{Deserialize, Deserializer, de};
+use std::fmt::{self, Display};
+use std::str::FromStr;
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
+pub enum MeasurementType {
+    Icmp = 1,
+    IcmpTimestamps,
+}
+
+impl Display for MeasurementType {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            MeasurementType::Icmp => write!(f, "icmp"),
+            MeasurementType::IcmpTimestamps => write!(f, "icmp-timestamps"),
+        }
+    }
+}
+
+impl FromStr for MeasurementType {
+    type Err = ConfigError;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        match s.to_lowercase().as_str() {
+            "icmp" => Ok(MeasurementType::Icmp),
+            "icmp-timestamps" | "icmp_timestamps" => Ok(MeasurementType::IcmpTimestamps),
+            _ => Err(ConfigError::Message(format!(
+                "invalid measurement type: {s}"
+            ))),
+        }
+    }
+}
+
+#[derive(Clone, Copy, Debug)]
+pub enum ObservabilityProtocol {
+    Udp,
+    Tcp,
+}
+
+impl FromStr for ObservabilityProtocol {
+    type Err = ConfigError;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        match s.to_lowercase().as_str() {
+            "udp" => Ok(ObservabilityProtocol::Udp),
+            "tcp" => Ok(ObservabilityProtocol::Tcp),
+            _ => Err(ConfigError::Message(format!(
+                "invalid observability protocol: {s}",
+            ))),
+        }
+    }
+}
+
+#[derive(Clone, Debug, Deserialize)]
+pub(crate) struct Settings {
+    pub(crate) network: NetworkSettings,
+
+    #[serde(default)]
+    pub(crate) output: OutputSettings,
+
+    #[serde(default)]
+    pub(crate) observability: ObservabilitySettings,
+
+    #[serde(default)]
+    pub(crate) advanced_settings: AdvancedSettings,
+}
+
+impl Settings {
+    pub(crate) fn load() -> Result<Self, ConfigError> {
+        let builder = Config::builder();
+
+        #[cfg(feature = "toml")]
+        let builder = builder.add_source(
+            config::File::with_name("/etc/sqm-autorate-rust/config.toml").required(false),
+        );
+
+        let builder = builder.add_source(Environment::with_prefix("SQMA").separator("__"));
+        let built_config = builder.build()?;
+
+        built_config.try_deserialize()
+    }
+}
+
+#[derive(Clone, Debug, Deserialize)]
+pub(crate) struct NetworkSettings {
+    pub(crate) download_interface: String,
+    pub(crate) upload_interface: String,
+    pub(crate) download_base_kbits: f64,
+    #[serde(default = "default_min_percent")]
+    pub(crate) download_min_percent: f64,
+    pub(crate) upload_base_kbits: f64,
+    #[serde(default = "default_min_percent")]
+    pub(crate) upload_min_percent: f64,
+}
+
+impl NetworkSettings {
+    pub(crate) fn download_min_kbits(&self) -> f64 {
+        (self.download_base_kbits * self.download_min_percent / 100.0).floor()
+    }
+
+    pub(crate) fn upload_min_kbits(&self) -> f64 {
+        (self.upload_base_kbits * self.upload_min_percent / 100.0).floor()
+    }
+}
+
+#[derive(Clone, Debug, Deserialize)]
+#[serde(default)]
+pub(crate) struct OutputSettings {
+    #[serde(deserialize_with = "deserialize_from_str")]
+    pub(crate) log_level: Level,
+    pub(crate) speed_hist_file: String,
+    pub(crate) stats_file: String,
+    pub(crate) suppress_statistics: bool,
+}
+
+impl Default for OutputSettings {
+    fn default() -> Self {
+        Self {
+            log_level: Level::Error,
+            speed_hist_file: "/tmp/sqm-speedhist.csv".to_owned(),
+            stats_file: "/tmp/sqm-autorate-rust.csv".to_owned(),
+            suppress_statistics: false,
+        }
+    }
+}
+
+#[derive(Clone, Debug, Deserialize)]
+#[serde(default)]
+pub(crate) struct ObservabilitySettings {
+    pub(crate) enabled: bool,
+    #[serde(deserialize_with = "deserialize_from_str")]
+    pub(crate) protocol: ObservabilityProtocol,
+    pub(crate) host: Option<String>,
+    pub(crate) port: u16,
+    pub(crate) batch_size: usize,
+    pub(crate) batch_timeout_ms: u64,
+    pub(crate) export_ping_metrics: bool,
+    pub(crate) export_rate_metrics: bool,
+    pub(crate) export_baseline_metrics: bool,
+    pub(crate) export_events: bool,
+    pub(crate) host_tag: String,
+}
+
+impl Default for ObservabilitySettings {
+    fn default() -> Self {
+        Self {
+            enabled: false,
+            protocol: ObservabilityProtocol::Udp,
+            host: None,
+            port: 8089,
+            batch_size: 25,
+            batch_timeout_ms: 100,
+            export_ping_metrics: false,
+            export_rate_metrics: true,
+            export_baseline_metrics: false,
+            export_events: true,
+            host_tag: default_host_tag(),
+        }
+    }
+}
+
+#[derive(Clone, Debug, Deserialize)]
+#[serde(default)]
+pub(crate) struct AdvancedSettings {
+    pub(crate) download_delay_ms: f64,
+    pub(crate) high_load_level: f64,
+    pub(crate) min_change_interval: f64,
+    #[serde(deserialize_with = "deserialize_from_str")]
+    pub(crate) measurement_type: MeasurementType,
+    pub(crate) num_reflectors: u8,
+    pub(crate) peer_reselection_time: u64,
+    pub(crate) reflector_list_file: String,
+    pub(crate) speed_hist_size: u32,
+    pub(crate) tick_interval: f64,
+    pub(crate) upload_delay_ms: f64,
+    pub(crate) dry_run: bool,
+}
+
+impl Default for AdvancedSettings {
+    fn default() -> Self {
+        Self {
+            download_delay_ms: 15.0,
+            high_load_level: 0.8,
+            min_change_interval: 0.5,
+            measurement_type: MeasurementType::IcmpTimestamps,
+            num_reflectors: 5,
+            peer_reselection_time: 15,
+            reflector_list_file: "/etc/sqm-autorate/reflectors-icmp.csv".to_owned(),
+            speed_hist_size: 100,
+            tick_interval: 0.5,
+            upload_delay_ms: 15.0,
+            dry_run: false,
+        }
+    }
+}
+
+fn default_min_percent() -> f64 {
+    20.0
+}
+
+fn default_host_tag() -> String {
+    rustix::system::uname()
+        .nodename()
+        .to_string_lossy()
+        .into_owned()
+}
+
+fn deserialize_from_str<'de, D, T>(deserializer: D) -> Result<T, D::Error>
+where
+    D: Deserializer<'de>,
+    T: FromStr,
+    T::Err: Display,
+{
+    let value = String::deserialize(deserializer)?;
+    value.parse().map_err(de::Error::custom)
+}