XTLS/Xray-core · warning

failed to find the default "name" config

Error message

failed to find the default "name" config

What it means

In the trojan fallback path, after selecting a fallback 'name' from the SNI/header sniffing, napfb[name] is nil and even the unnamed default napfb[""] is nil — so no fallback group exists for this traffic at all. It is a configuration-shape error: fallbacks were configured, but none qualifies as the default.

Source

Thrown at proxy/trojan/server.go:405

	if len(napfb) > 1 || napfb[""] == nil {
		if name != "" && napfb[name] == nil {
			match := ""
			for n := range napfb {
				if n != "" && strings.Contains(name, n) && len(n) > len(match) {
					match = n
				}
			}
			name = match
		}
	}

	if napfb[name] == nil {
		name = ""
	}
	apfb := napfb[name]
	if apfb == nil {
		return errors.New(`failed to find the default "name" config`).AtWarning()
	}

	if apfb[alpn] == nil {
		alpn = ""
	}
	pfb := apfb[alpn]
	if pfb == nil {
		return errors.New(`failed to find the default "alpn" config`).AtWarning()
	}

	path := ""
	if len(pfb) > 1 || pfb[""] == nil {
		if firstLen >= 18 && first.Byte(4) != '*' { // not h2c
			firstBytes := first.Bytes()
			for i := 4; i <= 8; i++ { // 5 -> 9
				if firstBytes[i] == '/' && firstBytes[i-1] == ' ' {
					search := len(firstBytes)
					if search > 64 {

View on GitHub (pinned to 7d214f8b09)

Solutions

1. Add a fallback entry without 'name' (empty name) to serve as the default catch-all
2. Verify each fallback object's fields parse as expected (name/alpn/path/dest/type/xver) in the config
3. Check the sniffed SNI actually matches the names you configured (case sensitivity)

Example fix

// json: last entry with no name/alpn/path is the required default
"fallbacks": [
  {"name": "a.example.com", "dest": 8001},
  {"name": "b.example.com", "dest": 8002},
  {"dest": 8080}
]

// config validation before starting the trojan inbound
func validateFallbacks(fbs []Fallback) error {
    hasDefault := false
    for _, f := range fbs {
        if f.Name == "" { hasDefault = true }
    }
    if !hasDefault {
        return errors.New("fallbacks need at least one entry without 'name'")
    }
    return nil
}

When it happens

Trigger: All configured fallback entries carry a 'name' that does not match the sniffed name, and no entry with an empty name was provided (the required catch-all).

Common situations: Admin adds only named fallbacks (e.g. for specific SNI domains) and forgets the default; YAML/JSON indentation puts fallbacks under the wrong key so the map builds empty.

Related errors

• Trojan fallbacks: "path" must be empty or start with "/"
• Trojan fallbacks: please fill in a valid value for every "de
• Trojan fallbacks: invalid PROXY protocol version, "xver" onl
• failed to find the default "alpn" config
• failed to find the default "path" config

AI-assisted analysis of XTLS/Xray-core@7d214f8b09 (2026-08-15). Data as JSON: /api/errors/cc1eaf56613dea7e. Report an issue: GitHub.