ns: fix reading net namespace in multi-threaded processes

/proc/self/ns/net gives the main thread's namespace, not necessarily
the namespace of the thread that's running the testcases.  This causes
sporadic failures of the tests.

For example, with a testcase reading inodes after switching netns:

/proc/27686/task/27689/ns/net 4026532565
/proc/self/ns/net 4026531969
/proc/27686/task/27689/ns/net 4026532565

See also:
https://github.com/vishvananda/netns/commit/008d17ae001344769b031375bdb38a86219154c6

Running Suite: pkg/ns Suite
===========================
Random Seed: 1459953577
Will run 6 of 6 specs

• Failure [0.028 seconds]
Linux namespace operations
/cni/gopath/src/github.com/appc/cni/pkg/ns/ns_test.go:167
  WithNetNS
  /cni/gopath/src/github.com/appc/cni/pkg/ns/ns_test.go:166
    executes the callback within the target network namespace [It]
    /cni/gopath/src/github.com/appc/cni/pkg/ns/ns_test.go:97

    Expected
        <uint64>: 4026531969
    to equal
        <uint64>: 4026532565

    /cni/gopath/src/github.com/appc/cni/pkg/ns/ns_test.go:96
------------------------------
•••••

Summarizing 1 Failure:

[Fail] Linux namespace operations WithNetNS [It] executes the callback within the target network namespace
/cni/gopath/src/github.com/appc/cni/pkg/ns/ns_test.go:96

Ran 6 of 6 Specs in 0.564 seconds
FAIL! -- 5 Passed | 1 Failed | 0 Pending | 0 Skipped --- FAIL: TestNs (0.56s)
FAIL

diff --git a/ns/ns_test.go b/ns/ns_test.go
index 42fc632..7ad882f 100644 (file)
--- a/ns/ns_test.go
+++ b/ns/ns_test.go
@@ -28,13 +28,9 @@ import (
        . "github.com/onsi/gomega"
 )
 
-const CurrentNetNS = "/proc/self/ns/net"
-
 var _ = Describe("Linux namespace operations", func() {
        Describe("WithNetNS", func() {
                var (
-                       originalNetNS *os.File
-
                        targetNetNSName string
                        targetNetNSPath string
                        targetNetNS     *os.File
@@ -42,8 +38,6 @@ var _ = Describe("Linux namespace operations", func() {
 
                BeforeEach(func() {
                        var err error
-                       originalNetNS, err = os.Open(CurrentNetNS)
-                       Expect(err).NotTo(HaveOccurred())
 
                        targetNetNSName = fmt.Sprintf("test-netns-%d", rand.Int())
 
@@ -60,8 +54,6 @@ var _ = Describe("Linux namespace operations", func() {
 
                        err := exec.Command("ip", "netns", "del", targetNetNSName).Run()
                        Expect(err).NotTo(HaveOccurred())
-
-                       Expect(originalNetNS.Close()).To(Succeed())
                })
 
                It("executes the callback within the target network namespace", func() {
@@ -71,7 +63,7 @@ var _ = Describe("Linux namespace operations", func() {
                        var actualInode uint64
                        var innerErr error
                        err = ns.WithNetNS(targetNetNS, false, func(*os.File) error {
-                               actualInode, innerErr = testhelpers.GetInode(CurrentNetNS)
+                               actualInode, innerErr = testhelpers.GetInodeCurNetNS()
                                return nil
                        })
                        Expect(err).NotTo(HaveOccurred())
@@ -81,7 +73,7 @@ var _ = Describe("Linux namespace operations", func() {
                })
 
                It("provides the original namespace as the argument to the callback", func() {
-                       hostNSInode, err := testhelpers.GetInode(CurrentNetNS)
+                       hostNSInode, err := testhelpers.GetInodeCurNetNS()
                        Expect(err).NotTo(HaveOccurred())
 
                        var inputNSInode uint64
@@ -97,7 +89,7 @@ var _ = Describe("Linux namespace operations", func() {
                })
 
                It("restores the calling thread to the original network namespace", func() {
-                       preTestInode, err := testhelpers.GetInode(CurrentNetNS)
+                       preTestInode, err := testhelpers.GetInodeCurNetNS()
                        Expect(err).NotTo(HaveOccurred())
 
                        err = ns.WithNetNS(targetNetNS, false, func(*os.File) error {
@@ -105,7 +97,7 @@ var _ = Describe("Linux namespace operations", func() {
                        })
                        Expect(err).NotTo(HaveOccurred())
 
-                       postTestInode, err := testhelpers.GetInode(CurrentNetNS)
+                       postTestInode, err := testhelpers.GetInodeCurNetNS()
                        Expect(err).NotTo(HaveOccurred())
 
                        Expect(postTestInode).To(Equal(preTestInode))
@@ -113,14 +105,14 @@ var _ = Describe("Linux namespace operations", func() {
 
                Context("when the callback returns an error", func() {
                        It("restores the calling thread to the original namespace before returning", func() {
-                               preTestInode, err := testhelpers.GetInode(CurrentNetNS)
+                               preTestInode, err := testhelpers.GetInodeCurNetNS()
                                Expect(err).NotTo(HaveOccurred())
 
                                _ = ns.WithNetNS(targetNetNS, false, func(*os.File) error {
                                        return errors.New("potato")
                                })
 
-                               postTestInode, err := testhelpers.GetInode(CurrentNetNS)
+                               postTestInode, err := testhelpers.GetInodeCurNetNS()
                                Expect(err).NotTo(HaveOccurred())
 
                                Expect(postTestInode).To(Equal(preTestInode))
@@ -136,7 +128,7 @@ var _ = Describe("Linux namespace operations", func() {
 
                Describe("validating inode mapping to namespaces", func() {
                        It("checks that different namespaces have different inodes", func() {
-                               hostNSInode, err := testhelpers.GetInode(CurrentNetNS)
+                               hostNSInode, err := testhelpers.GetInodeCurNetNS()
                                Expect(err).NotTo(HaveOccurred())
 
                                testNsInode, err := testhelpers.GetInode(targetNetNSPath)

diff --git a/testhelpers/testhelpers.go b/testhelpers/testhelpers.go
index 0963121..004006a 100644 (file)
--- a/testhelpers/testhelpers.go
+++ b/testhelpers/testhelpers.go
@@ -27,6 +27,16 @@ import (
        . "github.com/onsi/gomega"
 )
 
+func getCurrentThreadNetNSPath() string {
+       pid := unix.Getpid()
+       tid := unix.Gettid()
+       return fmt.Sprintf("/proc/%d/task/%d/ns/net", pid, tid)
+}
+
+func GetInodeCurNetNS() (uint64, error) {
+       return GetInode(getCurrentThreadNetNSPath())
+}
+
 func GetInode(path string) (uint64, error) {
        file, err := os.Open(path)
        if err != nil {
@@ -68,9 +78,7 @@ func MakeNetworkNS(containerID string) string {
                defer GinkgoRecover()
 
                // capture current thread's original netns
-               pid := unix.Getpid()
-               tid := unix.Gettid()
-               currentThreadNetNSPath := fmt.Sprintf("/proc/%d/task/%d/ns/net", pid, tid)
+               currentThreadNetNSPath := getCurrentThreadNetNSPath()
                originalNetNS, err := unix.Open(currentThreadNetNSPath, unix.O_RDONLY, 0)
                Expect(err).NotTo(HaveOccurred())
                defer unix.Close(originalNetNS)