mount_linux.go

package main

import (
	"fmt"
	"os"
	"path/filepath"
	"strings"

	"github.com/opencontainers/runtime-spec/specs-go"
	"golang.org/x/sys/unix"
)

func prepareMount(src, dest string) error {
	srcStat, err := os.Stat(src)
	if err != nil {
		return err
	}

	if _, err := os.Stat(dest); err != nil {
		if os.IsNotExist(err) {
			if srcStat.IsDir() {
				return os.MkdirAll(dest, 0755)
			}
			if err := os.MkdirAll(filepath.Dir(dest), 0755); err != nil {
				return err
			}
			f, err := os.OpenFile(dest, os.O_CREATE, 0755)
			if err != nil {
				return err
			}
			f.Close()
		}
	}
	return nil
}

func doMount(src, dest string, flags uintptr) error {

	if err := unix.Mount(src, dest, "bind", flags, ""); err != nil {
		return fmt.Errorf("mount %s on %s failed", src, dest)
	}
	if err := unix.Mount("", dest, "bind", unix.MS_REC|unix.MS_PRIVATE, ""); err != nil {
		return fmt.Errorf("mount private on %s failed", dest)
	}
	if flags&unix.MS_RDONLY != 0 {
		if err := unix.Mount(src, dest, "bind", flags|unix.MS_REMOUNT, ""); err != nil {
			return fmt.Errorf("remount %s on %s failed", src, dest)
		}
	}
	return nil
}

func doMounts(spec *specs.Spec) (bool, error) {
	rootfs := spec.Root.Path
	volumeMounted := false
	_, hasRootFs, err := checkFsFlags(spec)
	if err != nil {
		return false, err
	}

	for _, m := range spec.Mounts {
		var (
			dest          = m.Destination
			flags uintptr = unix.MS_REC
		)
		if !strings.HasPrefix(dest, rootfs) {
			dest = filepath.Join(rootfs, dest)
		}

		for _, f := range m.Options {
			switch f {
			case "rbind":
				flags = flags | unix.MS_BIND
			case "ro":
				flags = flags | unix.MS_RDONLY
			}
		}

		switch m.Type {
		case "bind":
			doBreak := false
			for _, d := range []string{"/etc/hosts", "/etc/hostname", "/etc/resolv.conf", "/dev/shm"} {
				if m.Destination == d {
					doBreak = true
					break
				}
			}
			if doBreak {
				break
			}

			if hasRootFs {
				return false, fmt.Errorf("LKL_ROOTFS cannot be used with -v options")
			}
			if err := prepareMount(m.Source, dest); err != nil {
				return false, err
			}
			if err := doMount(m.Source, dest, flags); err != nil {
				return false, err
			}
			volumeMounted = true
		}
	}

	return volumeMounted, nil
}