virtcontainers: update context id of vsock to uint64

The CID of VSock needs to be change to uint64. Otherwise that leads to
an endianess issue. For more details see
kata-containers#947

Fixes: kata-containers#958

Signed-off-by: Alice Frosi <afrosi@de.ibm.com>

virtcontainers/kata_agent.go

@@ -73,7 +73,7 @@ type KataAgentConfig struct {
 }
 
 type kataVSOCK struct {
-	contextID uint32
+	contextID uint64
 	port      uint32
 	vhostFd   *os.File
 }

virtcontainers/qemu_test.go

@@ -249,7 +249,7 @@ func TestQemuAddDeviceSerialPortDev(t *testing.T) {
 }
 
 func TestQemuAddDeviceKataVSOCK(t *testing.T) {
-	contextID := uint32(3)
+	contextID := uint64(3)
 	port := uint32(1024)
 	vHostFD := os.NewFile(1, "vsock")
 

virtcontainers/utils/utils_linux.go

@@ -22,7 +22,10 @@ const ioctlVhostVsockSetGuestCid = 0x4008AF60
 
 var ioctlFunc = ioctl
 
-var maxUInt uint32 = 1<<32 - 1
+// maxUInt represents the maximum valid value for the context ID.
+// The upper 32 bits of the CID are reserved and zeroed.
+// See http://stefanha.github.io/virtio/
+var maxUInt uint64 = 1<<32 - 1
 
 func ioctl(fd uintptr, request int, arg1 uint64) error {
 	if _, _, errno := unix.Syscall(
@@ -51,15 +54,15 @@ func ioctl(fd uintptr, request int, arg1 uint64) error {
 // - Reduce the probability of a *DoS attack*, since other processes don't know whatis the initial context ID
 //   used by findContextID to find a context ID available
 //
-func FindContextID() (*os.File, uint32, error) {
+func FindContextID() (*os.File, uint64, error) {
 	// context IDs 0x0, 0x1 and 0x2 are reserved, 0x3 is the first context ID usable.
-	var firstContextID uint32 = 0x3
+	var firstContextID uint64 = 0x3
 	var contextID = firstContextID
 
 	// Generate a random number
 	n, err := rand.Int(rand.Reader, big.NewInt(int64(maxUInt)))
 	if err == nil && n.Int64() >= int64(firstContextID) {
-		contextID = uint32(n.Int64())
+		contextID = uint64(n.Int64())
 	}
 
 	// Open vhost-vsock device to check what context ID is available.
@@ -72,14 +75,14 @@ func FindContextID() (*os.File, uint32, error) {
 
 	// Looking for the first available context ID.
 	for cid := contextID; cid <= maxUInt; cid++ {
-		if err := ioctlFunc(vsockFd.Fd(), ioctlVhostVsockSetGuestCid, uint64(cid)); err == nil {
+		if err := ioctlFunc(vsockFd.Fd(), ioctlVhostVsockSetGuestCid, cid); err == nil {
 			return vsockFd, cid, nil
 		}
 	}
 
 	// Last chance to get a free context ID.
 	for cid := contextID - 1; cid >= firstContextID; cid-- {
-		if err := ioctlFunc(vsockFd.Fd(), ioctlVhostVsockSetGuestCid, uint64(cid)); err == nil {
+		if err := ioctlFunc(vsockFd.Fd(), ioctlVhostVsockSetGuestCid, cid); err == nil {
 			return vsockFd, cid, nil
 		}
 	}

virtcontainers/utils/utils_linux_test.go

@@ -26,7 +26,7 @@ func TestFindContextID(t *testing.T) {
 		maxUInt = orgMaxUInt
 	}()
 	VHostVSockDevicePath = "/dev/null"
-	maxUInt = uint32(1000000)
+	maxUInt = uint64(1000000)
 
 	f, cid, err := FindContextID()
 	assert.Nil(f)