feat(settings): parse reflector lists with CSV

Add CSV-based reflector list parsing with Serde reflector records.
The load_reflectors method reads a CSV file with reflector_ip,
ip_version, and description columns, validating IP version
consistency for each entry.

Cargo.lock

@@ -106,6 +106,27 @@ dependencies = [
  "winnow",
 ]
 
+[[package]]
+name = "csv"
+version = "1.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "52cd9d68cf7efc6ddfaaee42e7288d3a99d613d4b50f76ce9827ae0c6e14f938"
+dependencies = [
+ "csv-core",
+ "itoa",
+ "ryu",
+ "serde_core",
+]
+
+[[package]]
+name = "csv-core"
+version = "0.1.13"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "704a3c26996a80471189265814dbc2c257598b96b8a7feae2d31ace646bb9782"
+dependencies = [
+ "memchr",
+]
+
 [[package]]
 name = "either"
 version = "1.16.0"
@@ -184,6 +205,12 @@ dependencies = [
  "either",
 ]
 
+[[package]]
+name = "itoa"
+version = "1.0.18"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8f42a60cbdf9a97f5d2305f08a87dc4e09308d1276d28c869c684d7777685682"
+
 [[package]]
 name = "js-sys"
 version = "0.3.103"
@@ -402,6 +429,12 @@ version = "1.0.23"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "cf54715a573b99ac80df0bc206da022bcd442c974952c7b9720069370852e21f"
 
+[[package]]
+name = "ryu"
+version = "1.0.23"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9774ba4a74de5f7b1c1451ed6cd5285a32eddb5cccb8cc655a4e50009e06477f"
+
 [[package]]
 name = "scopeguard"
 version = "1.2.0"
@@ -484,6 +517,7 @@ version = "0.4.1"
 dependencies = [
  "anyhow",
  "config",
+ "csv",
  "fastrand",
  "flume",
  "icmp-socket2",

Cargo.toml

@@ -27,6 +27,7 @@ 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 }
+csv = "1.4.0"
 serde = { version = "1", features = ["derive"] }
 
 [dependencies.log]

src/settings/mod.rs

@@ -7,6 +7,7 @@ use config::{Config, ConfigError, Environment};
 use log::Level;
 use serde::{Deserialize, Deserializer, de};
 use std::fmt::{self, Display};
+use std::net::IpAddr;
 use std::str::FromStr;
 
 #[cfg(all(feature = "uci", unix))]
@@ -61,6 +62,14 @@ impl FromStr for ObservabilityProtocol {
     }
 }
 
+#[derive(Debug, Deserialize)]
+struct ReflectorRecord {
+    reflector_ip: IpAddr,
+    ip_version: u8,
+    #[allow(dead_code)]
+    description: String,
+}
+
 #[derive(Clone, Debug, Deserialize)]
 pub(crate) struct Settings {
     pub(crate) network: NetworkSettings,
@@ -92,6 +101,41 @@ impl Settings {
 
         built_config.try_deserialize()
     }
+
+    pub fn load_reflectors(&self) -> anyhow::Result<Vec<IpAddr>> {
+        let mut reader = csv::ReaderBuilder::new()
+            .has_headers(true)
+            .trim(csv::Trim::All)
+            .from_path(&self.advanced_settings.reflector_list_file)
+            .with_context(|| {
+                format!(
+                    "failed to open reflector list: {}",
+                    self.advanced_settings.reflector_list_file
+                )
+            })?;
+
+        let mut reflectors = Vec::with_capacity(50);
+
+        for record in reader.deserialize::<ReflectorRecord>() {
+            let record = record.with_context(|| {
+                format!(
+                    "failed to parse reflector list: {}",
+                    self.advanced_settings.reflector_list_file
+                )
+            })?;
+
+            match (record.ip_version, record.reflector_ip) {
+                (4, IpAddr::V4(_)) | (6, IpAddr::V6(_)) => {}
+                (version, address) => {
+                    bail!("reflector {address} has inconsistent IP version {version}");
+                }
+            }
+
+            reflectors.push(record.reflector_ip);
+        }
+
+        Ok(reflectors)
+    }
 }
 
 #[derive(Clone, Debug, Deserialize)]