1 files changed, 32 insertions, 0 deletions
diff --git a/internal/utils/ip.go b/internal/utils/ip.go
new file mode 100644
index 000000000..c5547fda5
--- /dev/null
+++ b/internal/utils/ip.go
@@ -0,0 +1,32 @@
+package utils
+
+import (
+	"net"
+	"strings"
+)
+
+// ParseHostCIDR parses a raw string as a *net.IPNet similar to net.ParseCIDR, in fact it leverages it. The only
+// differences between the functions is if the input does not contain a single '/' it first parses it with net.ParseIP
+// to determine if it's a IPv4 or IPv6 and then adds the relevant CIDR suffix for a single host, and it only returns the
+// *net.IPNet and error, discarding the net.IP.
+func ParseHostCIDR(s string) (cidr *net.IPNet, err error) {
+	switch strings.Count(s, "/") {
+	case 1:
+		_, cidr, err = net.ParseCIDR(s)
+
+		return
+	case 0:
+		switch n := net.ParseIP(s); {
+		case n == nil:
+			return nil, &net.ParseError{Type: "CIDR address", Text: s}
+		case n.To4() == nil:
+			_, cidr, err = net.ParseCIDR(s + "/128")
+		default:
+			_, cidr, err = net.ParseCIDR(s + "/32")
+		}
+
+		return
+	default:
+		return nil, &net.ParseError{Type: "CIDR address", Text: s}
+	}
+}