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7120976d74
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>
53 lines
3.3 KiB
Go
53 lines
3.3 KiB
Go
// +build linux,!solaris freebsd,!solaris
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package main
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import (
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"github.com/docker/docker/daemon/config"
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"github.com/docker/docker/opts"
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units "github.com/docker/go-units"
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"github.com/spf13/pflag"
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)
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// installConfigFlags adds flags to the pflag.FlagSet to configure the daemon
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func installConfigFlags(conf *config.Config, flags *pflag.FlagSet) {
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// First handle install flags which are consistent cross-platform
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installCommonConfigFlags(conf, flags)
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// Then install flags common to unix platforms
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installUnixConfigFlags(conf, flags)
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conf.Ulimits = make(map[string]*units.Ulimit)
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// Set default value for `--default-shm-size`
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conf.ShmSize = opts.MemBytes(config.DefaultShmSize)
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// Then platform-specific install flags
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flags.BoolVar(&conf.EnableSelinuxSupport, "selinux-enabled", false, "Enable selinux support")
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flags.Var(opts.NewNamedUlimitOpt("default-ulimits", &conf.Ulimits), "default-ulimit", "Default ulimits for containers")
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flags.BoolVar(&conf.BridgeConfig.EnableIPTables, "iptables", true, "Enable addition of iptables rules")
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flags.BoolVar(&conf.BridgeConfig.EnableIPForward, "ip-forward", true, "Enable net.ipv4.ip_forward")
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flags.BoolVar(&conf.BridgeConfig.EnableIPMasq, "ip-masq", true, "Enable IP masquerading")
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flags.BoolVar(&conf.BridgeConfig.EnableIPv6, "ipv6", false, "Enable IPv6 networking")
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flags.StringVar(&conf.ExecRoot, "exec-root", defaultExecRoot, "Root directory for execution state files")
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flags.StringVar(&conf.BridgeConfig.FixedCIDRv6, "fixed-cidr-v6", "", "IPv6 subnet for fixed IPs")
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flags.BoolVar(&conf.BridgeConfig.EnableUserlandProxy, "userland-proxy", true, "Use userland proxy for loopback traffic")
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flags.StringVar(&conf.BridgeConfig.UserlandProxyPath, "userland-proxy-path", "", "Path to the userland proxy binary")
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flags.BoolVar(&conf.EnableCors, "api-enable-cors", false, "Enable CORS headers in the Engine API, this is deprecated by --api-cors-header")
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flags.MarkDeprecated("api-enable-cors", "Please use --api-cors-header")
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flags.StringVar(&conf.CgroupParent, "cgroup-parent", "", "Set parent cgroup for all containers")
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flags.StringVar(&conf.RemappedRoot, "userns-remap", "", "User/Group setting for user namespaces")
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flags.StringVar(&conf.ContainerdAddr, "containerd", "", "Path to containerd socket")
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flags.BoolVar(&conf.LiveRestoreEnabled, "live-restore", false, "Enable live restore of docker when containers are still running")
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flags.IntVar(&conf.OOMScoreAdjust, "oom-score-adjust", -500, "Set the oom_score_adj for the daemon")
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flags.BoolVar(&conf.Init, "init", false, "Run an init in the container to forward signals and reap processes")
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flags.StringVar(&conf.InitPath, "init-path", "", "Path to the docker-init binary")
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flags.Int64Var(&conf.CPURealtimePeriod, "cpu-rt-period", 0, "Limit the CPU real-time period in microseconds")
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flags.Int64Var(&conf.CPURealtimeRuntime, "cpu-rt-runtime", 0, "Limit the CPU real-time runtime in microseconds")
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flags.StringVar(&conf.SeccompProfile, "seccomp-profile", "", "Path to seccomp profile")
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flags.Var(&conf.ShmSize, "default-shm-size", "Default shm size for containers")
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flags.BoolVar(&conf.NoNewPrivileges, "no-new-privileges", false, "Set no-new-privileges by default for new containers")
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flags.StringVar(&conf.IpcMode, "default-ipc-mode", config.DefaultIpcMode, `Default mode for containers ipc ("shareable" | "private")`)
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attachExperimentalFlags(conf, flags)
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}
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