Handle namespaces with care

- After creating new netns, switch back to main netns
- Lock thread during test and test setup

plugins/main/loopback/loopback_suite_test.go

@@ -1,7 +1,9 @@
 package main_test
 
 import (
+	"fmt"
 	"os"
+	"runtime"
 
 	"github.com/onsi/gomega/gexec"
 
@@ -32,21 +34,38 @@ var _ = AfterSuite(func() {
 
 func makeNetworkNS(containerID string) string {
 	namespace := "/var/run/netns/" + containerID
+	pid := unix.Getpid()
+	tid := unix.Gettid()
 
 	err := os.MkdirAll("/var/run/netns", 0600)
 	Expect(err).NotTo(HaveOccurred())
 
-	err = unix.Unshare(unix.CLONE_NEWNET)
-	Expect(err).NotTo(HaveOccurred())
+	runtime.LockOSThread()
+	defer runtime.UnlockOSThread()
+	go (func() {
+		defer GinkgoRecover()
 
-	fd, err := os.Create(namespace)
-	Expect(err).NotTo(HaveOccurred())
-	defer fd.Close()
+		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())
+	})()
 
-	err = unix.Mount("/proc/self/ns/net", namespace, "none", unix.MS_BIND, "")
+	Eventually(namespace).Should(BeAnExistingFile())
+
+	fd, err := unix.Open(fmt.Sprintf("/proc/%d/task/%d/ns/net", pid, tid), unix.O_RDONLY, 0)
 	Expect(err).NotTo(HaveOccurred())
 
-	Expect(namespace).To(BeAnExistingFile())
+	defer unix.Close(fd)
+
+	_, _, e1 := unix.Syscall(unix.SYS_SETNS, uintptr(fd), uintptr(unix.CLONE_NEWNET), 0)
+	Expect(e1).To(BeZero())
+
 	return namespace
 }
 

plugins/main/loopback/loopback_test.go

@@ -57,7 +57,7 @@ var _ = Describe("Loopback", func() {
 			Eventually(session).Should(gexec.Exit(0))
 
 			var lo *net.Interface
-			err = ns.WithNetNSPath(networkNS, false, func(hostNS *os.File) error {
+			err = ns.WithNetNSPath(networkNS, true, func(hostNS *os.File) error {
 				var err error
 				lo, err = net.InterfaceByName("lo")
 				return err