Fixed segfault in stats where container had netNS none or from container

Signed-off-by: haircommander <pehunt@redhat.com>

Closes: #1306
Approved by: rhatdan

libpod/networking_linux.go

@@ -249,9 +249,35 @@ func (r *Runtime) teardownNetNS(ctr *Container) error {
 	return nil
 }
 
+func getContainerNetNS(ctr *Container) (string, error) {
+	if ctr.state.NetNS != nil {
+		return ctr.state.NetNS.Path(), nil
+	}
+	if ctr.config.NetNsCtr != "" {
+		c, err := ctr.runtime.GetContainer(ctr.config.NetNsCtr)
+		if err != nil {
+			return "", err
+		}
+		if err = c.syncContainer(); err != nil {
+			return "", err
+		}
+		return c.state.NetNS.Path(), nil
+	}
+	return "", nil
+}
+
 func getContainerNetIO(ctr *Container) (*netlink.LinkStatistics, error) {
 	var netStats *netlink.LinkStatistics
-	err := ns.WithNetNSPath(ctr.state.NetNS.Path(), func(_ ns.NetNS) error {
+	netNSPath, netPathErr := getContainerNetNS(ctr)
+	if netPathErr != nil {
+		return nil, netPathErr
+	}
+	if netNSPath == "" {
+		// If netNSPath is empty, it was set as none, and no netNS was set up
+		// this is a valid state and thus return no error, nor any statistics
+		return nil, nil
+	}
+	err := ns.WithNetNSPath(netNSPath, func(_ ns.NetNS) error {
 		link, err := netlink.LinkByName(ocicni.DefaultInterfaceName)
 		if err != nil {
 			return err

libpod/stats.go

@@ -66,8 +66,14 @@ func (c *Container) GetContainerStats(previousStats *ContainerStats) (*Container
 	stats.BlockInput, stats.BlockOutput = calculateBlockIO(cgroupStats)
 	stats.CPUNano = cgroupStats.CPU.Usage.Total
 	stats.SystemNano = cgroupStats.CPU.Usage.Kernel
+	// Handle case where the container is not in a network namespace
+	if netStats != nil {
 		stats.NetInput = netStats.TxBytes
 		stats.NetOutput = netStats.RxBytes
+	} else {
+		stats.NetInput = 0
+		stats.NetOutput = 0
+	}
 
 	return stats, nil
 }

test/e2e/stats_test.go

@@ -90,4 +90,27 @@ var _ = Describe("Podman stats", func() {
 		Expect(session.IsJSONOutputValid()).To(BeTrue())
 	})
 
+	It("podman stats on a container with no net ns", func() {
+		session := podmanTest.Podman([]string{"run", "-d", "--net", "none", ALPINE, "top"})
+		session.WaitWithDefaultTimeout()
+		Expect(session.ExitCode()).To(Equal(0))
+		session = podmanTest.Podman([]string{"stats", "--no-stream", "-a"})
+		session.WaitWithDefaultTimeout()
+		Expect(session.ExitCode()).To(Equal(0))
+	})
+
+	It("podman stats on a container that joined another's net ns", func() {
+		session := podmanTest.RunTopContainer("")
+		session.WaitWithDefaultTimeout()
+		Expect(session.ExitCode()).To(Equal(0))
+		cid := session.OutputToString()
+
+		session = podmanTest.Podman([]string{"run", "-d", "--net", fmt.Sprintf("container:%s", cid), ALPINE, "top"})
+		session.WaitWithDefaultTimeout()
+		Expect(session.ExitCode()).To(Equal(0))
+
+		session = podmanTest.Podman([]string{"stats", "--no-stream", "-a"})
+		session.WaitWithDefaultTimeout()
+		Expect(session.ExitCode()).To(Equal(0))
+	})
 })