mounts: Deduce additional information about system mounts

We need to pass information about mounts that need special
handling inside the VM to the agent. Deduce all the information
before the container is started by the agent.

Signed-off-by: Archana Shinde <archana.m.shinde@intel.com>

container.go

@@ -99,6 +99,16 @@ func (c *ContainerConfig) valid() bool {
 	return true
 }
 
+// SystemMountsInfo describes additional information for system mounts that the agent
+// needs to handle
+type SystemMountsInfo struct {
+	// Indicates if /dev has been passed as a bind mount for the host /dev
+	BindMountDev bool
+
+	// Size of /dev/shm assigned on the host.
+	DevShmSize uint
+}
+
 // Container is composed of a set of containers and a runtime environment.
 // A Container can be created, deleted, started, stopped, listed, entered, paused and restored.
 type Container struct {
@@ -122,6 +132,8 @@ type Container struct {
 	mounts []Mount
 
 	devices []Device
+
+	systemMountsInfo SystemMountsInfo
 }
 
 // ID returns the container identifier string.
@@ -482,6 +494,19 @@ func (c *Container) fetchState(cmd string) (State, error) {
 	return state, nil
 }
 
+func (c *Container) getSystemMountInfo() {
+	// check if /dev needs to be bind mounted from host /dev
+	for _, m := range c.mounts {
+		if m.Source == "/dev" && m.Destination == "/dev" && m.Type == "bind" {
+			c.systemMountsInfo.BindMountDev = true
+		} else {
+			c.systemMountsInfo.BindMountDev = false
+		}
+	}
+
+	// TODO Deduce /dev/shm size. See https://github.com/clearcontainers/runtime/issues/138
+}
+
 func (c *Container) start() error {
 	state, err := c.fetchState("start")
 	if err != nil {
@@ -519,6 +544,10 @@ func (c *Container) start() error {
 		return err
 	}
 
+	// Deduce additional system mount info that should be handled by the agent
+	// inside the VM
+	c.getSystemMountInfo()
+
 	if err = c.pod.agent.startContainer(*(c.pod), *c); err != nil {
 		c.Logger().WithError(err).Error("Failed to start container")
 

container_test.go

@@ -25,6 +25,8 @@ import (
 	"strings"
 	"syscall"
 	"testing"
+
+	"github.com/stretchr/testify/assert"
 )
 
 func TestGetAnnotations(t *testing.T) {
@@ -49,6 +51,28 @@ func TestGetAnnotations(t *testing.T) {
 	}
 }
 
+func TestContainerSystemMountsInfo(t *testing.T) {
+	mounts := []Mount{
+		{
+			Source:      "/dev",
+			Destination: "/dev",
+			Type:        "bind",
+		},
+	}
+
+	c := Container{
+		mounts: mounts,
+	}
+
+	assert.False(t, c.systemMountsInfo.BindMountDev)
+	c.getSystemMountInfo()
+	assert.True(t, c.systemMountsInfo.BindMountDev)
+
+	c.mounts[0].Type = "tmpfs"
+	c.getSystemMountInfo()
+	assert.False(t, c.systemMountsInfo.BindMountDev)
+}
+
 func TestContainerPod(t *testing.T) {
 	expectedPod := &Pod{}