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libcontainer/specconv/spec_linux: Support empty 'type' for bind mounts

From the "Creating a bind mount" section of mount(2) [1]:

> If mountflags includes MS_BIND (available since Linux 2.4), then
> perform a bind mount...
>
> The filesystemtype and data arguments are ignored.

This commit adds support for configurations that leave the OPTIONAL
type [2] unset for bind mounts.  There's a related spec-example change
in flight with [3], although my personal preference would be a more
explicit spec for the whole mount structure [4].

[1]: http://man7.org/linux/man-pages/man2/mount.2.html
[2]: https://github.com/opencontainers/runtime-spec/blame/v1.0.1/config.md#L102
[3]: opencontainers/runtime-spec#954
[4]: opencontainers/runtime-spec#771

Signed-off-by: W. Trevor King <wking@tremily.us>
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wking committed Mar 6, 2018
1 parent ce80fa0 commit 0aa6e4e5d35b409405077adfd1c7abf3d91992c8
Showing with 28 additions and 3 deletions.
  1. +6 −2 libcontainer/specconv/spec_linux.go
  2. +1 −1 notify_socket.go
  3. +21 −0 tests/integration/mounts.bats
@@ -269,13 +269,17 @@ func CreateLibcontainerConfig(opts *CreateOpts) (*configs.Config, error) {
func createLibcontainerMount(cwd string, m specs.Mount) *configs.Mount {
flags, pgflags, data, ext := parseMountOptions(m.Options)
source := m.Source
if m.Type == "bind" {
device := m.Type
if flags|unix.MS_BIND != 0 {
if device == "" {
device = "bind"
}
if !filepath.IsAbs(source) {
source = filepath.Join(cwd, m.Source)
}
}
return &configs.Mount{
Device: m.Type,
Device: device,
Source: source,
Destination: m.Destination,
Data: data,
View
@@ -44,7 +44,7 @@ func (ns *notifySocket) Close() error {
// If systemd is supporting sd_notify protocol, this function will add support
// for sd_notify protocol from within the container.
func (s *notifySocket) setupSpec(context *cli.Context, spec *specs.Spec) {
mount := specs.Mount{Destination: s.host, Type: "bind", Source: s.socketPath, Options: []string{"bind"}}
mount := specs.Mount{Destination: s.host, Source: s.socketPath, Options: []string{"bind"}}
spec.Mounts = append(spec.Mounts, mount)
spec.Process.Env = append(spec.Process.Env, fmt.Sprintf("NOTIFY_SOCKET=%s", s.host))
}
@@ -0,0 +1,21 @@
#!/usr/bin/env bats
load helpers
function setup() {
teardown_busybox
setup_busybox
}
function teardown() {
teardown_busybox
}
@test "runc run [bind mount]" {
CONFIG=$(jq '.mounts |= . + [{"source": ".", "destination": "/tmp/bind", "options": ["bind"]}] | .process.args = ["ls", "/tmp/bind/config.json"]' config.json)
echo "${CONFIG}" >config.json
runc run test_bind_mount
[ "$status" -eq 0 ]
[[ "${lines[0]}" =~ '/tmp/bind/config.json' ]]
}

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