daemon: make all components optional

In addition to having routing protocols as optional features, make
the base components optional as well for extra modularity.

The optional feature dependency graph is as follows:
* keychain
* interface <- routing <- policy
                          protocols

By default, all features remain enabled.

This change allows users to customize the daemon according to their
specific requirements, reducing binary size on systems where certain
components are unnecessary (e.g., keychains and routing policies).

NOTE: some #[allow(...)] annotations were added to silence build
warnings when --no-default-features is passed.

Suggested-by: Frederic LOUI <[email protected]>
Signed-off-by: Renato Westphal <[email protected]>

holo-daemon/Cargo.toml

@@ -30,17 +30,17 @@ tracing.workspace = true
 tracing-subscriber.workspace = true
 yang2.workspace = true
 
-holo-interface = { path = "../holo-interface" }
+holo-interface = { path = "../holo-interface", optional = true  }
 holo-bfd = { path = "../holo-bfd", optional = true }
 holo-bgp = { path = "../holo-bgp", optional = true }
-holo-keychain = { path = "../holo-keychain" }
+holo-keychain = { path = "../holo-keychain", optional = true }
 holo-ldp = { path = "../holo-ldp", optional = true }
 holo-northbound = { path = "../holo-northbound" }
 holo-ospf = { path = "../holo-ospf", optional = true }
-holo-policy = { path = "../holo-policy" }
+holo-policy = { path = "../holo-policy", optional = true }
 holo-protocol = { path = "../holo-protocol" }
 holo-rip = { path = "../holo-rip", optional = true }
-holo-routing = { path = "../holo-routing" }
+holo-routing = { path = "../holo-routing", optional = true  }
 holo-utils = { path = "../holo-utils" }
 holo-yang = { path = "../holo-yang" }
 
@@ -55,10 +55,32 @@ name = "holod"
 path = "src/main.rs"
 
 [features]
-default = ["bfd", "bgp", "ldp", "ospf", "rip"]
-bfd = ["holo-bfd"]
-bgp = ["holo-bgp"]
-ldp = ["holo-ldp"]
-ospf = ["holo-ospf"]
-rip = ["holo-rip"]
+default = [
+  # Base components
+  "interface",
+  "keychain",
+  "policy",
+  "routing",
+  # Protocols
+  "bfd",
+  "bgp",
+  "ldp",
+  "ospf",
+  "rip",
+]
+
+# Base components
+interface = ["holo-interface"]
+keychain = ["holo-keychain"]
+policy = ["holo-policy", "holo-routing"]
+routing = ["holo-routing", "holo-interface"]
+
+# Protocols
+bfd = ["holo-bfd", "holo-routing"]
+bgp = ["holo-bgp", "holo-routing"]
+ldp = ["holo-ldp", "holo-routing"]
+ospf = ["holo-ospf", "holo-routing"]
+rip = ["holo-rip", "holo-routing"]
+
+# Other features
 io_uring = ["tokio-uring"]

holo-daemon/src/northbound/core.rs

@@ -16,6 +16,7 @@ use holo_northbound::state::NodeAttributes;
 use holo_northbound::{
     api as papi, CallbackKey, CallbackOp, NbDaemonSender, NbProviderReceiver,
 };
+use holo_utils::ibus::{IbusReceiver, IbusSender};
 use holo_utils::task::TimeoutTask;
 use holo_utils::{Database, Receiver, Sender, UnboundedReceiver};
 use holo_yang::YANG_CTX;
@@ -623,43 +624,57 @@ impl Default for ConfirmedCommit {
 // ===== helper functions =====
 
 // Starts base data providers.
+#[allow(unused_mut, unused_variables)]
 fn start_providers(
     config: &Config,
     db: Database,
 ) -> (NbProviderReceiver, Vec<NbDaemonSender>) {
     let mut providers = Vec::new();
     let (provider_tx, provider_rx) = mpsc::unbounded_channel();
-    let (ibus_tx, ibus_rx) = broadcast::channel(1024);
+    let (ibus_tx, ibus_rx): (IbusSender, IbusReceiver) =
+        broadcast::channel(1024);
 
     // Start holo-routing.
-    let daemon_tx = holo_routing::start(
-        provider_tx.clone(),
-        ibus_tx.clone(),
-        ibus_tx.subscribe(),
-        db,
-        config.event_recorder.clone(),
-    );
-    providers.push(daemon_tx);
+    #[cfg(feature = "routing")]
+    {
+        let daemon_tx = holo_routing::start(
+            provider_tx.clone(),
+            ibus_tx.clone(),
+            ibus_tx.subscribe(),
+            db,
+            config.event_recorder.clone(),
+        );
+        providers.push(daemon_tx);
+    }
 
     // Start holo-interface.
-    let daemon_tx = holo_interface::start(
-        provider_tx.clone(),
-        ibus_tx.clone(),
-        ibus_tx.subscribe(),
-    );
-    providers.push(daemon_tx);
+    #[cfg(feature = "interface")]
+    {
+        let daemon_tx = holo_interface::start(
+            provider_tx.clone(),
+            ibus_tx.clone(),
+            ibus_tx.subscribe(),
+        );
+        providers.push(daemon_tx);
+    }
 
     // Start holo-keychain.
-    let daemon_tx = holo_keychain::start(
-        provider_tx.clone(),
-        ibus_tx.clone(),
-        ibus_tx.subscribe(),
-    );
-    providers.push(daemon_tx);
+    #[cfg(feature = "keychain")]
+    {
+        let daemon_tx = holo_keychain::start(
+            provider_tx.clone(),
+            ibus_tx.clone(),
+            ibus_tx.subscribe(),
+        );
+        providers.push(daemon_tx);
+    }
 
     // Start holo-policy.
-    let daemon_tx = holo_policy::start(provider_tx, ibus_tx, ibus_rx);
-    providers.push(daemon_tx);
+    #[cfg(feature = "policy")]
+    {
+        let daemon_tx = holo_policy::start(provider_tx, ibus_tx, ibus_rx);
+        providers.push(daemon_tx);
+    }
 
     (provider_rx, providers)
 }

holo-daemon/src/northbound/yang.rs

@@ -10,6 +10,7 @@ use holo_northbound::ProviderBase;
 use holo_yang as yang;
 use holo_yang::YANG_CTX;
 
+#[allow(dead_code)]
 fn modules_add<P: ProviderBase>(modules: &mut Vec<&'static str>) {
     modules.extend(P::yang_modules().iter());
 }
@@ -30,9 +31,16 @@ pub(crate) fn create_context() {
     }
 
     // Add core modules.
+    #[cfg(feature = "interface")]
     modules_add::<holo_interface::Master>(&mut modules);
+
+    #[cfg(feature = "routing")]
     modules_add::<holo_routing::Master>(&mut modules);
+
+    #[cfg(feature = "keychain")]
     modules_add::<holo_keychain::Master>(&mut modules);
+
+    #[cfg(feature = "policy")]
     modules_add::<holo_policy::Master>(&mut modules);
 
     // Add protocol modules based on enabled features.