Avoid treating stale self pidfiles as active

Author: cursoragent

cmd/nssh/status.go

@@ -90,6 +90,7 @@ func activeSessions() []sessionInfo {
 	if err != nil {
 		return nil
 	}
+	currentPID := os.Getpid()
 	var out []sessionInfo
 	for _, e := range entries {
 		if e.IsDir() || !strings.HasSuffix(e.Name(), ".json") {
@@ -104,6 +105,11 @@ func activeSessions() []sessionInfo {
 		if err := json.Unmarshal(data, &info); err != nil {
 			continue
 		}
+		// A pidfile for our own PID is stale PID reuse; don't let replace kill us.
+		if info.PID == currentPID {
+			_ = os.Remove(path)
+			continue
+		}
 		// Signal 0 is a permission/existence probe on POSIX.
 		if err := syscall.Kill(info.PID, 0); err != nil {
 			_ = os.Remove(path)

cmd/nssh/status_test.go

@@ -0,0 +1,42 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"path/filepath"
+	"testing"
+	"time"
+)
+
+func TestActiveSessionsDropsStaleSelfPID(t *testing.T) {
+	t.Setenv("XDG_STATE_HOME", t.TempDir())
+
+	dir := sessionsDir()
+	if err := os.MkdirAll(dir, 0o755); err != nil {
+		t.Fatal(err)
+	}
+
+	path := filepath.Join(dir, fmt.Sprintf("%d.json", os.Getpid()))
+	data, err := json.Marshal(sessionInfo{
+		PID:     os.Getpid(),
+		Target:  "devbox",
+		Host:    "devbox",
+		Topic:   "nssh_stale",
+		Server:  defaultServer,
+		Started: time.Now().Add(-time.Hour),
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(path, data, 0o644); err != nil {
+		t.Fatal(err)
+	}
+
+	if sessions := activeSessions(); len(sessions) != 0 {
+		t.Fatalf("activeSessions() = %d sessions, want 0", len(sessions))
+	}
+	if _, err := os.Stat(path); !os.IsNotExist(err) {
+		t.Fatalf("stale self pidfile still exists: %v", err)
+	}
+}