Function isCIDRMatch

internal/registry/config.go:188–222

isCIDRMatch returns true if urlHost matches an element of cidrs. urlHost is a URL.Host ("host:port" or "host") where the `host` part can be either a domain name or an IP address. If it is a domain name, then it will be resolved to IP addresses for matching. If resolution fails, false is returned.

(cidrs []*net.IPNet, urlHost string)

// where the `host` part can be either a domain name or an IP address. If it is a domain name, then it will be
// resolved to IP addresses for matching. If resolution fails, false is returned.
func isCIDRMatch(cidrs []*net.IPNet, urlHost string) bool {
	if len(cidrs) == 0 {
		return false
	}

	host, _, err := net.SplitHostPort(urlHost)
	if err != nil {
		// Assume urlHost is a host without port and go on.
		host = urlHost
	}

	var addresses []net.IP
	if ip := net.ParseIP(host); ip != nil {
		// Host is an IP-address.
		addresses = append(addresses, ip)
	} else {
		// Try to resolve the host's IP-address.
		addresses, err = lookupIP(host)
		if err != nil {
			// We failed to resolve the host; assume there's no match.
			return false
		}
	}

	for _, addr := range addresses {
		for _, ipnet := range cidrs {
			// check if the addr falls in the subnet
			if ipnet.Contains(addr) {
				return true
			}
		}
	}

	return false
}

func normalizeIndexName(val string) string {
	if val == "index.docker.io" {