From 2cd14f06ae15c6b92f7e1d2a3e482bd89ab2026e Mon Sep 17 00:00:00 2001
From: syoul <syoul@librezo.fr>
Date: Sat, 25 Apr 2026 23:51:35 +0200
Subject: [PATCH] fix(sidecar): use ephemeral ports for tcp/quic listen too

mycelium defaults --tcp-listen-port and --quic-listen-port to 9651
when not provided. If anything else holds 9651 (a previous test
instance, a Docker container from the level-1 procedure, another
mycelium running on the host), the daemon comes up far enough to
serve the loopback API for a few seconds before tearing itself
down on the listen failure.

Pick three distinct ephemeral ports (api, tcp, quic) per spawn.
Trade-off: inbound peers need the actual port number, which we
already log; the user can pin via a future SidecarConfig field.
---
 src-tauri/src/sidecar.rs | 40 +++++++++++++++++++++++++++++++++++-----
 1 file changed, 35 insertions(+), 5 deletions(-)

diff --git a/src-tauri/src/sidecar.rs b/src-tauri/src/sidecar.rs
index 45b14fd..89704a9 100644
--- a/src-tauri/src/sidecar.rs
+++ b/src-tauri/src/sidecar.rs
@@ -102,8 +102,14 @@ impl SidecarHandle {
         }
 
         let bin = locate_sidecar(app)?;
-        let port = portpicker::pick_unused_port()
-            .ok_or_else(|| AppError::Other("no free port available".into()))?;
+        // Three ports: HTTP API (loopback), TCP listen, QUIC (UDP) listen.
+        // mycelium defaults to 9651 for both peer-listen ports, which
+        // collides if another instance (or a leftover from a previous test)
+        // is already up. Always picking ephemeral ports avoids that at the
+        // cost of inbound peers needing the actual port number.
+        let api_port = pick_port()?;
+        let tcp_port = pick_port_skip(&[api_port])?;
+        let quic_port = pick_port_skip(&[api_port, tcp_port])?;
 
         let data_dir = app
             .path()
@@ -115,7 +121,11 @@ impl SidecarHandle {
 
         let mut args = vec![
             "--api-addr".to_string(),
-            format!("127.0.0.1:{port}"),
+            format!("127.0.0.1:{api_port}"),
+            "--tcp-listen-port".to_string(),
+            tcp_port.to_string(),
+            "--quic-listen-port".to_string(),
+            quic_port.to_string(),
             "--key-file".to_string(),
             key_path.display().to_string(),
         ];
@@ -137,7 +147,11 @@ impl SidecarHandle {
             }
         }
 
-        info!(?bin, port, "spawning mycelium sidecar via pkexec");
+        info!(
+            ?bin,
+            api_port, tcp_port, quic_port,
+            "spawning mycelium sidecar via pkexec"
+        );
 
         let mut cmd = elevation::elevated(&bin, &args);
         cmd.stdout(Stdio::piped())
@@ -150,7 +164,7 @@ impl SidecarHandle {
 
         // Stash before we await the health check, so a slow daemon
         // doesn't leave us with a zombie process if anything panics.
-        let api_url = format!("http://127.0.0.1:{port}");
+        let api_url = format!("http://127.0.0.1:{api_port}");
         *self.child.lock() = Some(child);
         *self.api_url.lock() = Some(api_url.clone());
         *self.config_path.lock() = Some(config_path);
@@ -257,6 +271,22 @@ impl SidecarHandle {
     }
 }
 
+fn pick_port() -> AppResult<u16> {
+    portpicker::pick_unused_port().ok_or_else(|| AppError::Other("no free port available".into()))
+}
+
+fn pick_port_skip(taken: &[u16]) -> AppResult<u16> {
+    for _ in 0..16 {
+        let p = pick_port()?;
+        if !taken.contains(&p) {
+            return Ok(p);
+        }
+    }
+    Err(AppError::Other(
+        "could not find a unique free port".into(),
+    ))
+}
+
 /// Resolve the bundled `mycelium-<triple>` binary in both `tauri dev`
 /// (cargo manifest) and bundled (resource_dir) modes.
 fn locate_sidecar(app: &AppHandle) -> AppResult<PathBuf> {