caddyserver/caddy · error

parsing CIDR expression: %v

Error message

parsing CIDR expression: %v

What it means

Error "parsing CIDR expression: %v" thrown in caddyserver/caddy.

Source

Thrown at modules/caddytls/matchers.go:376

		ipStr = remoteAddr // weird; maybe no port?
	}
	ipAddr, err := netip.ParseAddr(ipStr)
	if err != nil {
		if c := m.logger.Check(zapcore.ErrorLevel, "invalid client IP address"); c != nil {
			c.Write(zap.String("ip", ipStr))
		}
		return false
	}
	return (len(m.cidrs) == 0 || m.matches(ipAddr, m.cidrs)) &&
		(len(m.notCidrs) == 0 || !m.matches(ipAddr, m.notCidrs))
}

func (MatchRemoteIP) parseIPRange(str string) ([]netip.Prefix, error) {
	var cidrs []netip.Prefix
	if strings.Contains(str, "/") {
		ipNet, err := netip.ParsePrefix(str)
		if err != nil {
			return nil, fmt.Errorf("parsing CIDR expression: %v", err)
		}
		cidrs = append(cidrs, ipNet)
	} else {
		ipAddr, err := netip.ParseAddr(str)
		if err != nil {
			return nil, fmt.Errorf("invalid IP address: '%s': %v", str, err)
		}
		ip := netip.PrefixFrom(ipAddr, ipAddr.BitLen())
		cidrs = append(cidrs, ip)
	}
	return cidrs, nil
}

func (MatchRemoteIP) matches(ip netip.Addr, ranges []netip.Prefix) bool {
	return slices.ContainsFunc(ranges, func(prefix netip.Prefix) bool {
		return prefix.Contains(ip)
	})
}

View on GitHub (pinned to 50e54ee279)

Solutions

1. Fix the CIDR expression, e.g. '192.168.0.0/16'; the wrapped error explains the parse failure.

When it happens

Trigger: Thrown at modules/caddytls/matchers.go:376 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of caddyserver/caddy@50e54ee279 (2026-08-15). Data as JSON: /api/errors/5941f76ca2b9c6d4. Report an issue: GitHub.