shadow1ng/fscan · error

parser_ip_range_failed: %w

Error message

parser_ip_range_failed: %w

What it means

newHostSource fails when a host expression containing '-' and looking like an IP range cannot be parsed by newRangeHostSource, wrapping the parse error with an i18n message. It indicates a malformed IP range in the target specification.

Source

Thrown at common/parsers/host_iterator.go:313

func newHostSource(host string) (hostSource, error) {
	switch {
	case host == "192":
		return newCIDRHostSource("192.168.0.0/16")
	case host == "172":
		return newCIDRHostSource("172.16.0.0/12")
	case host == "10":
		return newCIDRHostSource("10.0.0.0/8")
	case strings.Contains(host, "/"):
		src, err := newCIDRHostSource(host)
		if err != nil {
			return nil, fmt.Errorf(i18n.Tr("parser_cidr_failed", host)+": %w", err)
		}
		return src, nil
	case strings.Contains(host, "-") && !strings.Contains(host, ":") && looksLikeIPRange(host):
		src, err := newRangeHostSource(host)
		if err != nil {
			return nil, fmt.Errorf(i18n.Tr("parser_ip_range_failed", host)+": %w", err)
		}
		return src, nil
	default:
		return &singleHostSource{host: host}, nil
	}
}

func newCIDRHostSource(cidr string) (hostSource, error) {
	_, ipNet, err := net.ParseCIDR(cidr)
	if err != nil {
		return nil, err
	}

	start, ok := ipToUint32(ipNet.IP)
	if !ok {
		return nil, fmt.Errorf("%s", i18n.GetText("parser_ipv4_only"))
	}
	ones, bits := ipNet.Mask.Size()

View on GitHub (pinned to 95cc12e753)

Solutions

1. Correct the range: valid IPs and start <= end, e.g. 192.168.1.1-192.168.1.254
2. Validate endpoints with net.ParseIP before passing
3. Check the wrapped error to see the exact parse failure

Example fix

// before
"192.168.1.10-192.168.1.2" // reversed
// after
"192.168.1.2-192.168.1.10"

if strings.Contains(target, "-") {
    parts := strings.SplitN(target, "-", 2)
    a, b := net.ParseIP(parts[0]), net.ParseIP(parts[1])
    if a == nil || b == nil || compareIP(a, b) > 0 {
        return fmt.Errorf("invalid IP range %q", target)
    }
}

srcs, err := newHostSources(targets)
if err != nil {
    if strings.Contains(err.Error(), "parser_ip_range_failed") {
        log.Fatalf("fix IP range: %v", err)
    }
}

When it happens

Trigger: Passing ranges like '192.168.1.5-192.168.1.2' (start > end), '192.168.1.5-999', or truncated tails where looksLikeIPRange passed but parsing failed.

Common situations: Typos in range endpoints; octet values above 255; reversed start/end; truncated copy-paste of a range.

Understand the failure class

Background: "Invalid ... format", "must be in format X", "does not look like a ..." — invalid argument format errors across CLI tools and libraries — this error's family across 17 libraries.

Related errors

• parser_invalid_ip_end_val
• parser_invalid_ip_range_val
• parser_cidr_failed: %w
• parser_start_gt_end
• parser_invalid_ip_fmt

AI-assisted analysis of shadow1ng/fscan@95cc12e753 (2026-09-06). Data as JSON: /api/errors/9d51d9e44a4b8dda. Report an issue: GitHub.