Add bus method to spawn an external client

sidebus-broker/src/bus.rs

@@ -1,6 +1,6 @@
 use std::sync::Arc;
 use tokio_stream::StreamExt as _;
-use tracing::trace;
+use tracing::{debug, trace};
 
 pub struct HostedBus {
     peers: Arc<busd::peers::Peers>,
@@ -78,6 +78,10 @@ impl HostedBus {
 
 pub trait SharedHostedBus {
     async fn run_unix_listener(self, listener: tokio::net::UnixListener);
+    async fn spawn_external_client(
+        self,
+        command: &mut tokio::process::Command,
+    ) -> eyre::Result<tokio::process::Child>;
 }
 
 impl SharedHostedBus for Arc<tokio::sync::Mutex<HostedBus>> {
@@ -86,6 +90,24 @@ impl SharedHostedBus for Arc<tokio::sync::Mutex<HostedBus>> {
             self.lock().await.connect_unix(socket).await.unwrap()
         }
     }
+
+    async fn spawn_external_client(
+        self,
+        command: &mut tokio::process::Command,
+    ) -> eyre::Result<tokio::process::Child> {
+        // NOTE: abstract sockets belong to the *network* namespace
+        // Possibly better to only accept once and let go of the listener / use socketpair & /dev/fd? (Uncommon to reconnect?)
+        let abstract_path = format!("/run/sidebus-broker/{}", zbus::Guid::generate());
+        let listener = tokio::net::UnixListener::bind(format!("\0{abstract_path}"))?;
+        debug!(%abstract_path, "opened listener for external client");
+        tokio::spawn(self.run_unix_listener(listener));
+        Ok(command
+            .env(
+                "DBUS_SESSION_BUS_ADDRESS",
+                format!("unix:abstract={abstract_path}"),
+            )
+            .spawn()?)
+    }
 }
 
 pub struct NameOwnerStream {