slackhq/nebula · error

config `%s.interfaces` has invalid value (type %T): %v

Error message

config `%s.interfaces` has invalid value (type %T): %v

What it means

Validation error from getAllowListInterfaces: a value inside the `<key>.interfaces` map (the per-interface allow/deny rule) could not be coerced to a boolean by config.AsBool. The offending entry is rawAllow, whose dynamic Go type is shown in the message — e.g. a list or nested map where true/false (or a string form of them) was expected.

Source

Thrown at allow_list.go:184

	}

	return &AllowList{cidrTree: tree}, nil
}

func getAllowListInterfaces(k string, v any) ([]AllowListNameRule, error) {
	var nameRules []AllowListNameRule

	rawRules, ok := v.(map[string]any)
	if !ok {
		return nil, fmt.Errorf("config `%s.interfaces` is invalid (type %T): %v", k, v, v)
	}

	firstEntry := true
	var allValues bool
	for name, rawAllow := range rawRules {
		allow, ok := config.AsBool(rawAllow)
		if !ok {
			return nil, fmt.Errorf("config `%s.interfaces` has invalid value (type %T): %v", k, rawAllow, rawAllow)
		}

		nameRE, err := regexp.Compile("^" + name + "$")
		if err != nil {
			return nil, fmt.Errorf("config `%s.interfaces` has invalid key: %s: %v", k, name, err)
		}

		nameRules = append(nameRules, AllowListNameRule{
			Name:  nameRE,
			Allow: allow,
		})

		if firstEntry {
			allValues = allow
			firstEntry = false
		} else {
			if allow != allValues {
				return nil, fmt.Errorf("config `%s.interfaces` values must all be the same true/false value", k)

View on GitHub (pinned to dd8f660c0a)

Solutions

  1. Change every interface value to literal true or false
  2. Unquote values so YAML/JSON parses them as booleans
  3. Check the type %T in the message to see what the value parsed as

Example fix

// before
interfaces:
  eth0: "yes"
// after
interfaces:
  eth0: true
Defensive patterns

Strategy: validation

Validate before calling

func interfaceValuesAreBool(m map[string]any) bool {
	for _, v := range m {
		if _, ok := v.(bool); !ok {
			return false
		}
	}
	return true
}

Type guard

func isBool(v any) bool { _, ok := v.(bool); return ok }

Prevention

When it happens

Trigger: getAllowListInterfaces encountering an entry like eth0: "yes", eth0: 1, or a nested map under an interface name.

Common situations: Unquoted yes/no strings, numeric flags, or pasting rules from other tools that use accept/deny semantics.

Understand the failure class

Background: "Invalid value" and "allowed values are" config errors: what your library rejected and how to fix it — this error's family across 41 libraries.

Related errors

AI-assisted analysis of slackhq/nebula@dd8f660c0a (2026-09-03). Data as JSON: /api/errors/32749efea9aede2d. Report an issue: GitHub.