What causes "must specify at least one port" in ginuerzh/gost?

Provide a non-empty comma-separated port list, e.g. "80,443" or "8000-9000"

must specify at least one port

Error message

must specify at least one port

What it means

ParsePortSet rejects an empty string because a PortSet with no ports would never match anything and is almost certainly a configuration mistake. Permissions strings are comma-separated, and an empty segment means no port was specified at all.

Source

Thrown at permissions.go:76

		return nil, fmt.Errorf("invalid range: %s", s)
	}
}

// Contains checks whether the value is within this range.
func (ir *PortRange) Contains(value int) bool {
	return value >= ir.Min && value <= ir.Max
}

// PortSet is a set of PortRange
type PortSet []PortRange

// ParsePortSet parses the s to a PortSet.
// The s shoud be a comma separated string.
func ParsePortSet(s string) (*PortSet, error) {
	ps := &PortSet{}

	if s == "" {
		return nil, errors.New("must specify at least one port")
	}

	ranges := strings.Split(s, ",")

	for _, r := range ranges {
		portRange, err := ParsePortRange(r)

		if err != nil {
			return nil, err
		}

		*ps = append(*ps, *portRange)
	}

	return ps, nil
}

// Contains checks whether the value is within this port set.

View on GitHub (pinned to a33fdbf4c9)

Solutions

Provide a non-empty comma-separated port list, e.g. "80,443" or "8000-9000"
Check the config file/env var that feeds the permissions string for missing or blank values
If an empty set is legitimate in your app, skip calling ParsePortSet when the input is empty

Example fix

// before
ps, err := permissions.ParsePortSet(portStr) // portStr == ""
// after
var ps *permissions.PortSet
if portStr != "" {
    ps, err = permissions.ParsePortSet(portStr)
}

Defensive patterns

Strategy: validation

Validate before calling

if strings.TrimSpace(portStr) == "" {
    return errors.New("ports must be a non-empty comma-separated list")
}
ps, err := permissions.ParsePortSet(portStr)

Try / catch

if err != nil {
    return fmt.Errorf("invalid port permissions %q: %w", portStr, err)
}

Prevention

Validate config files at startup with required non-empty fields
Avoid defaulting env vars to empty strings for required lists
Use a linter/schema validator for permission configs

When it happens

Trigger: Calling ParsePortSet("") directly, or ParsePermissions with a port field that is the empty string (e.g. missing or blank in a config file).

Common situations: Blank 'ports' entry in a YAML/JSON config, an environment variable that is unset and defaults to empty string, or template rendering producing an empty value.

Related errors

AI-assisted analysis of ginuerzh/gost@a33fdbf4c9 (2026-09-02). Data as JSON: /api/errors/70670e90d00a4e42. Report an issue: GitHub.