pkg: add a function to generate chain names

Adds a function to generate chain names for use in iptables and
ports all drivers to use that function. Also adds tests for the
said function.

pkg/utils/utils.go

@@ -0,0 +1,20 @@
+package utils
+
+import (
+	"crypto/sha512"
+	"fmt"
+)
+
+// 29 - len('CNI') - 2*len('-')
+const maxNameLen = 16
+
+// Generates a chain name to be used with iptables.
+// Ensures that the generated name is less than
+// 29 chars in length
+func FormatChainName(name string, id string) string {
+	h := sha512.Sum512([]byte(id))
+	if len(name) > maxNameLen {
+		return fmt.Sprintf("CNI-%s-%x", name[:len(name)-maxNameLen], h[:8])
+	}
+	return fmt.Sprintf("CNI-%s-%x", name, h[:8])
+}