runtime: move all code to src/runtime

To prepare for merging into kata-containers repository.

Signed-off-by: Peng Tao <bergwolf@hyper.sh>

src/runtime/virtcontainers/utils/utils_linux.go

@@ -0,0 +1,143 @@
+// Copyright (c) 2018 Intel Corporation
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+
+package utils
+
+import (
+	"bufio"
+	"crypto/rand"
+	"fmt"
+	"io"
+	"math/big"
+	"os"
+	"strings"
+	"syscall"
+	"unsafe"
+
+	"golang.org/x/sys/unix"
+)
+
+var ioctlFunc = Ioctl
+
+// 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, data uintptr) error {
+	if _, _, errno := unix.Syscall(unix.SYS_IOCTL, fd, request, data); errno != 0 {
+		//uintptr(request)
+		//uintptr(unsafe.Pointer(&arg1)),
+		//); errno != 0 {
+		return os.NewSyscallError("ioctl", fmt.Errorf("%d", int(errno)))
+	}
+
+	return nil
+}
+
+// FindContextID finds a unique context ID by generating a random number between 3 and max unsigned int (maxUint).
+// Using the ioctl VHOST_VSOCK_SET_GUEST_CID, findContextID asks to the kernel if the given
+// context ID (N) is available, when the context ID is not available, incrementing by 1 findContextID
+// iterates from N to maxUint until an available context ID is found, otherwise decrementing by 1
+// findContextID iterates from N to 3 until an available context ID is found, this is the last chance
+// to find a context ID available.
+// On success vhost file and a context ID greater or equal than 3 are returned, otherwise 0 and an error are returned.
+// vhost file can be used to send vhost file decriptor to QEMU. It's the caller's responsibility to
+// close vhost file descriptor.
+//
+// Benefits of using random context IDs:
+// - 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, uint64, error) {
+	// context IDs 0x0, 0x1 and 0x2 are reserved, 0x3 is the first context ID usable.
+	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 = uint64(n.Int64())
+	}
+
+	// Open vhost-vsock device to check what context ID is available.
+	// This file descriptor holds/locks the context ID and it should be
+	// inherited by QEMU process.
+	vsockFd, err := os.OpenFile(VHostVSockDevicePath, syscall.O_RDWR, 0666)
+	if err != nil {
+		return nil, 0, err
+	}
+
+	// Looking for the first available context ID.
+	for cid := contextID; cid <= maxUInt; cid++ {
+		if err = ioctlFunc(vsockFd.Fd(), ioctlVhostVsockSetGuestCid, uintptr(unsafe.Pointer(&cid))); err == nil {
+			return vsockFd, cid, nil
+		}
+	}
+
+	ioctlVhostVsockSetGuestCid := getIoctlVhostVsockGuestCid()
+	// Last chance to get a free context ID.
+	for cid := contextID - 1; cid >= firstContextID; cid-- {
+		if err = ioctlFunc(vsockFd.Fd(), ioctlVhostVsockSetGuestCid, uintptr(unsafe.Pointer(&cid))); err == nil {
+			return vsockFd, cid, nil
+		}
+	}
+
+	vsockFd.Close()
+	return nil, 0, fmt.Errorf("Could not get a unique context ID for the vsock : %s", err)
+}
+
+const (
+	procMountsFile = "/proc/mounts"
+
+	fieldsPerLine = 6
+)
+
+const (
+	procDeviceIndex = iota
+	procPathIndex
+	procTypeIndex
+)
+
+// GetDevicePathAndFsType gets the device for the mount point and the file system type
+// of the mount.
+func GetDevicePathAndFsType(mountPoint string) (devicePath, fsType string, err error) {
+	if mountPoint == "" {
+		err = fmt.Errorf("Mount point cannot be empty")
+		return
+	}
+
+	var file *os.File
+
+	file, err = os.Open(procMountsFile)
+	if err != nil {
+		return
+	}
+
+	defer file.Close()
+
+	reader := bufio.NewReader(file)
+	for {
+		var line string
+
+		line, err = reader.ReadString('\n')
+		if err == io.EOF {
+			err = fmt.Errorf("Mount %s not found", mountPoint)
+			return
+		}
+
+		fields := strings.Fields(line)
+		if len(fields) != fieldsPerLine {
+			err = fmt.Errorf("Incorrect no of fields (expected %d, got %d)) :%s", fieldsPerLine, len(fields), line)
+			return
+		}
+
+		if mountPoint == fields[procPathIndex] {
+			devicePath = fields[procDeviceIndex]
+			fsType = fields[procTypeIndex]
+			return
+		}
+	}
+}