1 files changed, 28 insertions, 0 deletions
diff --git a/pkg/resolvconf/dns/resolvconf.go b/pkg/resolvconf/dns/resolvconf.go
new file mode 100644
index 000000000..cb4bd1033
--- /dev/null
+++ b/pkg/resolvconf/dns/resolvconf.go
@@ -0,0 +1,28 @@
+// Originally from github.com/docker/libnetwork/resolvconf/dns
+
+package dns
+
+import (
+	"regexp"
+)
+
+// IPLocalhost is a regex pattern for IPv4 or IPv6 loopback range.
+const IPLocalhost = `((127\.([0-9]{1,3}\.){2}[0-9]{1,3})|(::1)$)`
+
+// IPv4Localhost is a regex pattern for IPv4 localhost address range.
+const IPv4Localhost = `(127\.([0-9]{1,3}\.){2}[0-9]{1,3})`
+
+var localhostIPRegexp = regexp.MustCompile(IPLocalhost)
+var localhostIPv4Regexp = regexp.MustCompile(IPv4Localhost)
+
+// 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)
+}
+
+// IsIPv4Localhost returns true if ip matches the IPv4 localhost regular expression.
+func IsIPv4Localhost(ip string) bool {
+	return localhostIPv4Regexp.MatchString(ip)
+}