Create a plugin for up'ing a lo device

- Believe we need sudo to create netns
- Use syscall instead of relying on ip netns
- Add sudo to .travis.yml
- Needs more -E
- Revert Godeps GoVersion to 1.4.2
- in travis, test command is run with all necessary env vars
- Loopback plugin only works on 'lo' interface
- Update README, add loopback plugin config
- note script dependency on jq

Signed-off-by: Gabe Rosenhouse <grosenhouse@pivotal.io>

plugins/main/loopback/loopback_suite_test.go

@@ -0,0 +1,58 @@
+package main_test
+
+import (
+	"os"
+
+	"github.com/onsi/gomega/gexec"
+
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+
+	"testing"
+
+	"golang.org/x/sys/unix"
+)
+
+var pathToLoPlugin string
+
+func TestLoopback(t *testing.T) {
+	RegisterFailHandler(Fail)
+	RunSpecs(t, "Loopback Suite")
+}
+
+var _ = BeforeSuite(func() {
+	var err error
+	pathToLoPlugin, err = gexec.Build("github.com/appc/cni/plugins/main/loopback")
+	Expect(err).NotTo(HaveOccurred())
+})
+
+var _ = AfterSuite(func() {
+	gexec.CleanupBuildArtifacts()
+})
+
+func makeNetworkNS(containerID string) string {
+	namespace := "/var/run/netns/" + containerID
+
+	err := os.MkdirAll("/var/run/netns", 0600)
+	Expect(err).NotTo(HaveOccurred())
+
+	err = unix.Unshare(unix.CLONE_NEWNET)
+	Expect(err).NotTo(HaveOccurred())
+
+	fd, err := os.Create(namespace)
+	Expect(err).NotTo(HaveOccurred())
+	defer fd.Close()
+
+	err = unix.Mount("/proc/self/ns/net", namespace, "none", unix.MS_BIND, "")
+	Expect(err).NotTo(HaveOccurred())
+
+	Expect(namespace).To(BeAnExistingFile())
+	return namespace
+}
+
+func removeNetworkNS(networkNS string) error {
+	err := unix.Unmount(networkNS, unix.MNT_DETACH)
+
+	err = os.RemoveAll(networkNS)
+	return err
+}