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.

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])
+}

utils/utils_suite_test.go

@@ -0,0 +1,13 @@
+package utils_test
+
+import (
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+
+	"testing"
+)
+
+func TestUtils(t *testing.T) {
+	RegisterFailHandler(Fail)
+	RunSpecs(t, "Utils Suite")
+}

utils/utils_test.go

@@ -0,0 +1,18 @@
+package utils
+
+import (
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+)
+
+var _ = Describe("Utils", func() {
+	It("should format a short name", func() {
+		chain := FormatChainName("test", "1234")
+		Expect(chain).To(Equal("CNI-test-d404559f602eab6f"))
+	})
+
+	It("should truncate a long name", func() {
+		chain := FormatChainName("testalongnamethatdoesnotmakesense", "1234")
+		Expect(chain).To(Equal("CNI-testalongnamethat-d404559f602eab6f"))
+	})
+})