rancherOS/vendor/github.com/docker/libnetwork/resolvconf/dns/resolvconf.go

package dns

import (
	"regexp"
)

// IPLocalhost is a regex patter for localhost IP address range.
const IPLocalhost = `((127\.([0-9]{1,3}\.){2}[0-9]{1,3})|(::1)$)`

var localhostIPRegexp = regexp.MustCompile(IPLocalhost)

// IsLocalhost returns true if ip matches the localhost IP regular expression.
// Used for determining if nameserver settings are being passed which are
// localhost addresses
func IsLocalhost(ip string) bool {
	return localhostIPRegexp.MatchString(ip)
}