Add relay_id configuration option.

This makes it possible to override the relay_id instead of
(automatically) using the 4 least significant bytes of the Gateway ID.

Author: brocaar

src/backend.rs

@@ -174,7 +174,16 @@ async fn setup_mesh_conncentratord(conf: &Configuration) -> Result<()> {
     info!("Retrieved Gateway ID: {}", resp.gateway_id);
 
     let mut relay_id: [u8; 4] = [0; 4];
-    relay_id.copy_from_slice(&hex::decode(&resp.gateway_id)?[4..]);
+    if conf.mesh.relay_id.is_empty() {
+        relay_id.copy_from_slice(&hex::decode(&resp.gateway_id)?[4..]);
+    } else {
+        info!("Using relay_id from configuration file");
+        let b = hex::decode(&conf.mesh.relay_id)?;
+        if b.len() != 4 {
+            return Err(anyhow!("relay_id must be exactly 4 bytes!"));
+        }
+        relay_id.copy_from_slice(&b);
+    }
     RELAY_ID
         .set(Mutex::new(relay_id))
         .map_err(|e| anyhow!("OnceLock error: {:?}", e))?;

src/cmd/configfile.rs

@@ -39,6 +39,13 @@ pub fn run() {
   # above root_key, but this key will be used.
   signing_key="{{ mesh.signing_key }}"
 
+  # Relay ID.
+  #
+  # If set, this will override the Relay ID that is derived from the
+  # Gateway ID provided by the Concentratord backend (using the 4 least
+  # significant bytes). Example: "01020304".
+  relay_id="{{ mesh.relay_id }}"
+
   # Border Gateway.
   #
   # If this is set to true, then the ChirpStack Gateway Mesh will consider

src/config.rs

@@ -58,6 +58,7 @@ impl Default for Logging {
 #[derive(Serialize, Deserialize)]
 #[serde(default)]
 pub struct Mesh {
+    pub relay_id: String,
     pub root_key: Aes128Key,
     pub signing_key: Aes128Key,
     pub frequencies: Vec<u32>,
@@ -73,6 +74,7 @@ pub struct Mesh {
 impl Default for Mesh {
     fn default() -> Self {
         Mesh {
+            relay_id: "".into(),
             root_key: Aes128Key::null(),
             signing_key: Aes128Key::null(),
             frequencies: vec![868100000, 868300000, 868500000],