fix(agent): fall back to install record for sing-box core version (item 12)

Locally built sing-box v1.13.21 carries no version stamp and reports
'unknown', leaving the panel core-version column empty. The agent probe
now falls back to /etc/nexusgate/sing-box/version when the binary
reports no version; agent-singbox.sh writes that record (version
without the v prefix) on every successful install path, including the
already-installed early exit. Agent version stays 0.6.8.

agent-go/health.go

@@ -211,11 +211,12 @@ type engineReport struct {
 
 var singBoxVersionMu sync.Mutex
 var singBoxVersionCache struct {
-	path    string
-	mtimeNs int64
-	size    int64
-	version string
-	probed  bool
+	path      string
+	mtimeNs   int64
+	size      int64
+	vfMtimeNs int64 // install-record file mtime (part of the cache key)
+	version   string
+	probed    bool
 }
 
 // parseSingBoxVersion extracts the version token from the first line of
@@ -233,22 +234,50 @@ func parseSingBoxVersion(out string) string {
 	return ""
 }
 
+var singBoxVersionRe = regexp.MustCompile(`^\d+\.\d+\.\d+(?:[-+][0-9A-Za-z.-]+)?$`)
+
+// installedSingBoxVersion reads the install record written by
+// agent-singbox.sh (/etc/nexusgate/sing-box/version, content like
+// "1.13.21"). It is the fallback for the locally built sing-box, whose
+// binary carries no version stamp and reports "unknown" (round-3 item
+// 12). A leading "v" is tolerated and stripped; anything that does not
+// look like a version is ignored.
+func installedSingBoxVersion() string {
+	data, err := os.ReadFile(cfg.SingBoxVersionFile)
+	if err != nil {
+		return ""
+	}
+	v := strings.TrimSpace(string(data))
+	v = strings.TrimPrefix(v, "v")
+	if !singBoxVersionRe.MatchString(v) {
+		return ""
+	}
+	return v
+}
+
 func singBoxVersion() string {
 	info, err := os.Stat(cfg.SingBoxBin)
 	if err != nil {
 		return ""
 	}
+	var vfMtimeNs int64 = -1
+	if vfInfo, err := os.Stat(cfg.SingBoxVersionFile); err == nil {
+		vfMtimeNs = vfInfo.ModTime().UnixNano()
+	}
 	singBoxVersionMu.Lock()
 	defer singBoxVersionMu.Unlock()
 	c := &singBoxVersionCache
-	if c.probed && c.path == cfg.SingBoxBin && c.mtimeNs == info.ModTime().UnixNano() && c.size == info.Size() {
+	if c.probed && c.path == cfg.SingBoxBin && c.mtimeNs == info.ModTime().UnixNano() && c.size == info.Size() && c.vfMtimeNs == vfMtimeNs {
 		return c.version
 	}
 	version := ""
 	if out, _, code := runCapture(5*time.Second, cfg.SingBoxBin, "version"); code == 0 {
 		version = parseSingBoxVersion(out)
 	}
-	c.path, c.mtimeNs, c.size, c.version, c.probed = cfg.SingBoxBin, info.ModTime().UnixNano(), info.Size(), version, true
+	if version == "" {
+		version = installedSingBoxVersion()
+	}
+	c.path, c.mtimeNs, c.size, c.vfMtimeNs, c.version, c.probed = cfg.SingBoxBin, info.ModTime().UnixNano(), info.Size(), vfMtimeNs, version, true
 	return version
 }
 

agent-go/main.go

@@ -35,6 +35,7 @@ type config struct {
 	Root            string // NG_CONFIG_DIR
 	ResourceDir     string // Root + "/resources"
 	SingBoxConfig   string
+	SingBoxVersionFile string
 	SingBoxLog      string
 	SingBoxCursor   string
 	KeyFile         string
@@ -74,6 +75,7 @@ func loadConfig() config {
 		Root:            root,
 		ResourceDir:     root + "/resources",
 		SingBoxConfig:   envOr("NG_SINGBOX_CONFIG", "/etc/nexusgate/sing-box/config.json"),
+		SingBoxVersionFile: envOr("NG_SINGBOX_VERSION_FILE", "/etc/nexusgate/sing-box/version"),
 		SingBoxLog:      envOr("NG_SINGBOX_LOG", "/var/log/nexusgate/sing-box-access.log"),
 		SingBoxCursor:   envOr("NG_SINGBOX_CURSOR", "/etc/nexusgate/sing-box-cursor.json"),
 		KeyFile:         envOr("NG_KEY_FILE", "/etc/nexusgate/keys.json"),

agent-go/singboxversion_test.go

@@ -71,6 +71,49 @@ func TestSingBoxVersionProbeCachesByMtime(t *testing.T) {
 	}
 }
 
+// Round-3 item 12: when the binary reports "unknown" (the locally built
+// sing-box has no version stamp), the probe falls back to the install
+// record written by agent-singbox.sh.
+func TestSingBoxVersionFallsBackToInstallRecord(t *testing.T) {
+	dir := t.TempDir()
+	binPath, _ := writeFakeSingBox(t, dir, "unknown")
+	recordPath := filepath.Join(dir, "version")
+	if err := os.WriteFile(recordPath, []byte("1.13.21\n"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	oldBin, oldRecord := cfg.SingBoxBin, cfg.SingBoxVersionFile
+	cfg.SingBoxBin, cfg.SingBoxVersionFile = binPath, recordPath
+	defer func() { cfg.SingBoxBin, cfg.SingBoxVersionFile = oldBin, oldRecord }()
+	singBoxVersionCache.probed = false
+	defer func() { singBoxVersionCache.probed = false }()
+
+	if got := singBoxVersion(); got != "1.13.21" {
+		t.Fatalf("fallback probe = %q, want 1.13.21", got)
+	}
+	// A stamped binary wins over the record.
+	writeFakeSingBox(t, dir, "1.13.22")
+	if got := singBoxVersion(); got != "1.13.22" {
+		t.Fatalf("stamped probe = %q, want 1.13.22 (record must not shadow it)", got)
+	}
+	// A garbage record is ignored.
+	if err := os.WriteFile(recordPath, []byte("not-a-version\n"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	writeFakeSingBox(t, dir, "unknown")
+	if got := singBoxVersion(); got != "" {
+		t.Fatalf("garbage record: got %q, want empty", got)
+	}
+	if got := installedSingBoxVersion(); got != "" {
+		t.Fatalf("installedSingBoxVersion(garbage) = %q, want empty", got)
+	}
+	if err := os.WriteFile(recordPath, []byte("v1.13.21\n"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	if got := installedSingBoxVersion(); got != "1.13.21" {
+		t.Fatalf("installedSingBoxVersion(v-prefixed) = %q, want 1.13.21", got)
+	}
+}
+
 func TestSingBoxVersionMissingBinary(t *testing.T) {
 	oldBin := cfg.SingBoxBin
 	cfg.SingBoxBin = filepath.Join(t.TempDir(), "does-not-exist")