grafana/k6 · error

failed to parse CIDR '%s': %w

Error message

failed to parse CIDR '%s': %w

What it means

Raised by IPNet.UnmarshalText while parsing a blocked hostnames/IP entry: the value is not valid CIDR notation, and the underlying parsing error is wrapped with %w. This feeds the hosts/blockHostnames options.

Source

Thrown at lib/options.go:205

		return nil, err
	}
	key = pem.EncodeToMemory(&pem.Block{
		Type:  blockType,
		Bytes: decryptedKey,
	})
	return key, nil
}

// IPNet is a wrapper around net.IPNet for JSON unmarshalling
type IPNet struct {
	net.IPNet
}

// UnmarshalText populates the IPNet from the given CIDR
func (ipnet *IPNet) UnmarshalText(b []byte) error {
	newIPNet, err := ParseCIDR(string(b))
	if err != nil {
		return fmt.Errorf("failed to parse CIDR '%s': %w", string(b), err)
	}

	*ipnet = *newIPNet
	return nil
}

// MarshalText encodes the IPNet representation using CIDR notation.
func (ipnet *IPNet) MarshalText() ([]byte, error) {
	return []byte(ipnet.String()), nil
}

// ParseCIDR creates an IPNet out of a CIDR string
func ParseCIDR(s string) (*IPNet, error) {
	_, ipnet, err := net.ParseCIDR(s)
	if err != nil {
		return nil, err
	}

View on GitHub (pinned to 01ffac6f24)

Solutions

1. Provide a valid CIDR such as 10.0.0.0/8
2. For single IPs, use the address with a /32 (IPv4) or /128 (IPv6) suffix or a plain IP form accepted by the parser

When it happens

Trigger: Thrown at lib/options.go:205 when the library encounters an invalid state.

Common situations: See trigger scenarios.

Understand the failure class

• Parsing and encoding errors: unexpected token, malformed input — why parsers reject input and how to find the real culprit.

AI-assisted analysis of grafana/k6@01ffac6f24 (2026-08-18). Data as JSON: /api/errors/e668d0f4fc9532ae. Report an issue: GitHub.