Add an echo client to be used instead of nc.

nc behaviour depends on the implementation version of what's on the current host.
Here we use our own client with stable behaviour.

Signed-off-by: Federico Paolinelli <fpaoline@redhat.com>

pkg/testutils/echo/echo_test.go

@@ -0,0 +1,98 @@
+package main_test
+
+import (
+	"fmt"
+	"io/ioutil"
+	"net"
+	"os/exec"
+	"strings"
+
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+	"github.com/onsi/gomega/gbytes"
+	"github.com/onsi/gomega/gexec"
+)
+
+var serverBinaryPath, clientBinaryPath string
+
+var _ = SynchronizedBeforeSuite(func() []byte {
+	serverBinaryPath, err := gexec.Build("github.com/containernetworking/plugins/pkg/testutils/echo/server")
+	Expect(err).NotTo(HaveOccurred())
+	clientBinaryPath, err := gexec.Build("github.com/containernetworking/plugins/pkg/testutils/echo/client")
+	Expect(err).NotTo(HaveOccurred())
+	return []byte(fmt.Sprintf("%s,%s", serverBinaryPath, clientBinaryPath))
+}, func(data []byte) {
+	binaries := strings.Split(string(data), ",")
+	serverBinaryPath = binaries[0]
+	clientBinaryPath = binaries[1]
+})
+
+var _ = SynchronizedAfterSuite(func() {}, func() {
+	gexec.CleanupBuildArtifacts()
+})
+
+var _ = Describe("Echosvr", func() {
+	var session *gexec.Session
+	BeforeEach(func() {
+		var err error
+		cmd := exec.Command(serverBinaryPath)
+		session, err = gexec.Start(cmd, GinkgoWriter, GinkgoWriter)
+		Expect(err).NotTo(HaveOccurred())
+	})
+
+	AfterEach(func() {
+		session.Kill().Wait()
+	})
+
+	Context("Server test", func() {
+		It("starts and doesn't terminate immediately", func() {
+			Consistently(session).ShouldNot(gexec.Exit())
+		})
+
+		tryConnect := func() (net.Conn, error) {
+			programOutput := session.Out.Contents()
+			addr := strings.TrimSpace(string(programOutput))
+
+			conn, err := net.Dial("tcp", addr)
+			if err != nil {
+				return nil, err
+			}
+			return conn, err
+		}
+
+		It("prints its listening address to stdout", func() {
+			Eventually(session.Out).Should(gbytes.Say("\n"))
+			conn, err := tryConnect()
+			Expect(err).NotTo(HaveOccurred())
+			conn.Close()
+		})
+
+		It("will echo data back to us", func() {
+			Eventually(session.Out).Should(gbytes.Say("\n"))
+			conn, err := tryConnect()
+			Expect(err).NotTo(HaveOccurred())
+			defer conn.Close()
+
+			fmt.Fprintf(conn, "hello\n")
+			Expect(ioutil.ReadAll(conn)).To(Equal([]byte("hello")))
+		})
+	})
+
+	Context("Client Server Test", func() {
+		It("starts and doesn't terminate immediately", func() {
+			Consistently(session).ShouldNot(gexec.Exit())
+		})
+
+		It("connects successfully using echo client", func() {
+			Eventually(session.Out).Should(gbytes.Say("\n"))
+			serverAddress := strings.TrimSpace(string(session.Out.Contents()))
+			fmt.Println("Server address", string(serverAddress))
+
+			cmd := exec.Command(clientBinaryPath, "-target", serverAddress, "-message", "hello")
+			clientSession, err := gexec.Start(cmd, GinkgoWriter, GinkgoWriter)
+			Expect(err).NotTo(HaveOccurred())
+			Eventually(clientSession.Out).Should(gbytes.Say("hello"))
+			Eventually(clientSession).Should(gexec.Exit())
+		})
+	})
+})