src/params.rs: Add data_network_ip (#22)

For ease of finding the data network IP address.

Author: ackintosh

CHANGELOG.md

@@ -5,10 +5,15 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [0.3.0] unreleased
+### Added
+
+- Add `RunParameters::data_network_ip` for ease of finding the IP within the data network assigned to the instance. See [PR 22].
+
 ### Change
 - Change `RunParameters::test_instance_params` from `String` to `HashMap` which contains key-value pairs from parsing the parameter string. See [PR 19].
 
 [PR 19]: https://github.com/testground/sdk-rust/pull/19
+[PR 22]: https://github.com/testground/sdk-rust/pull/22
 
 ## [0.2.0]
 ### Added

Cargo.toml

@@ -13,6 +13,7 @@ version = "0.3.0"
 [dependencies]
 clap = { version = "3", default-features = false, features = ["std", "derive", "env"] }
 futures = { version = "0.3", default-features = false, features = [] }
+if-addrs = "0.7.0"
 influxdb = { version = "0.5", default-features = false, features = ["reqwest", "serde", "serde_json", "derive"] }
 ipnetwork = { version = "0.19.0", default-features = false, features = ["serde"] }
 log = "0.4"

src/params.rs

@@ -1,5 +1,6 @@
 use clap::Parser;
 use std::collections::HashMap;
+use std::net::{IpAddr, Ipv4Addr};
 
 use std::path::PathBuf;
 
@@ -61,6 +62,26 @@ pub struct RunParameters {
                             // HOME: /
 }
 
+impl RunParameters {
+    /// Examines the local network interfaces, and tries to find our assigned IP
+    /// within the data network.
+    ///
+    /// If running in a sidecar-less environment, the loopback address is
+    /// returned.
+    pub fn data_network_ip(&self) -> std::io::Result<Option<IpAddr>> {
+        if !self.test_sidecar {
+            // This must be a local:exec runner and we currently don't support
+            // traffic shaping on it for now, just return the loopback address.
+            return Ok(Some(IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1))));
+        }
+
+        Ok(if_addrs::get_if_addrs()?
+            .into_iter()
+            .map(|i| i.addr.ip())
+            .find(|ip| self.test_subnet.contains(*ip)))
+    }
+}
+
 fn parse_key_val(s: &str) -> Result<HashMap<String, String>, String> {
     let mut hashmap = HashMap::new();