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moby--moby/daemon/config/config_windows.go
Kir Kolyshkin 7120976d74 Implement none, private, and shareable ipc modes
Since the commit d88fe447df ("Add support for sharing /dev/shm/ and
/dev/mqueue between containers") container's /dev/shm is mounted on the
host first, then bind-mounted inside the container. This is done that
way in order to be able to share this container's IPC namespace
(and the /dev/shm mount point) with another container.

Unfortunately, this functionality breaks container checkpoint/restore
(even if IPC is not shared). Since /dev/shm is an external mount, its
contents is not saved by `criu checkpoint`, and so upon restore any
application that tries to access data under /dev/shm is severily
disappointed (which usually results in a fatal crash).

This commit solves the issue by introducing new IPC modes for containers
(in addition to 'host' and 'container:ID'). The new modes are:

 - 'shareable':	enables sharing this container's IPC with others
		(this used to be the implicit default);

 - 'private':	disables sharing this container's IPC.

In 'private' mode, container's /dev/shm is truly mounted inside the
container, without any bind-mounting from the host, which solves the
issue.

While at it, let's also implement 'none' mode. The motivation, as
eloquently put by Justin Cormack, is:

> I wondered a while back about having a none shm mode, as currently it is
> not possible to have a totally unwriteable container as there is always
> a /dev/shm writeable mount. It is a bit of a niche case (and clearly
> should never be allowed to be daemon default) but it would be trivial to
> add now so maybe we should...

...so here's yet yet another mode:

 - 'none':	no /dev/shm mount inside the container (though it still
		has its own private IPC namespace).

Now, to ultimately solve the abovementioned checkpoint/restore issue, we'd
need to make 'private' the default mode, but unfortunately it breaks the
backward compatibility. So, let's make the default container IPC mode
per-daemon configurable (with the built-in default set to 'shareable'
for now). The default can be changed either via a daemon CLI option
(--default-shm-mode) or a daemon.json configuration file parameter
of the same name.

Note one can only set either 'shareable' or 'private' IPC modes as a
daemon default (i.e. in this context 'host', 'container', or 'none'
do not make much sense).

Some other changes this patch introduces are:

1. A mount for /dev/shm is added to default OCI Linux spec.

2. IpcMode.Valid() is simplified to remove duplicated code that parsed
   'container:ID' form. Note the old version used to check that ID does
   not contain a semicolon -- this is no longer the case (tests are
   modified accordingly). The motivation is we should either do a
   proper check for container ID validity, or don't check it at all
   (since it is checked in other places anyway). I chose the latter.

3. IpcMode.Container() is modified to not return container ID if the
   mode value does not start with "container:", unifying the check to
   be the same as in IpcMode.IsContainer().

3. IPC mode unit tests (runconfig/hostconfig_test.go) are modified
   to add checks for newly added values.

[v2: addressed review at https://github.com/moby/moby/pull/34087#pullrequestreview-51345997]
[v3: addressed review at https://github.com/moby/moby/pull/34087#pullrequestreview-53902833]
[v4: addressed the case of upgrading from older daemon, in this case
     container.HostConfig.IpcMode is unset and this is valid]
[v5: document old and new IpcMode values in api/swagger.yaml]
[v6: add the 'none' mode, changelog entry to docs/api/version-history.md]

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
2017-08-14 10:50:39 +03:00

57 lines
1.4 KiB
Go

package config
import (
"github.com/docker/docker/api/types"
)
// BridgeConfig stores all the bridge driver specific
// configuration.
type BridgeConfig struct {
commonBridgeConfig
}
// Config defines the configuration of a docker daemon.
// These are the configuration settings that you pass
// to the docker daemon when you launch it with say: `dockerd -e windows`
type Config struct {
CommonConfig
// Fields below here are platform specific. (There are none presently
// for the Windows daemon.)
}
// GetRuntime returns the runtime path and arguments for a given
// runtime name
func (conf *Config) GetRuntime(name string) *types.Runtime {
return nil
}
// GetInitPath returns the configure docker-init path
func (conf *Config) GetInitPath() string {
return ""
}
// GetDefaultRuntimeName returns the current default runtime
func (conf *Config) GetDefaultRuntimeName() string {
return StockRuntimeName
}
// GetAllRuntimes returns a copy of the runtimes map
func (conf *Config) GetAllRuntimes() map[string]types.Runtime {
return map[string]types.Runtime{}
}
// GetExecRoot returns the user configured Exec-root
func (conf *Config) GetExecRoot() string {
return ""
}
// IsSwarmCompatible defines if swarm mode can be enabled in this config
func (conf *Config) IsSwarmCompatible() error {
return nil
}
// ValidatePlatformConfig checks if any platform-specific configuration settings are invalid.
func (conf *Config) ValidatePlatformConfig() error {
return nil
}