runtime: Implement POSIX platform hooks

[r10r]

Implement and test POSIX platform hooks defined by the runtime spec.

https://github.com/opencontainers/runtime-spec/blob/master/config.md#posix-platform-hooks

Most of the OCI hooks could probably simply be mapped to the lxc CONTAINER HOOKS (man lxc.container.conf).

[r10r]

OCI hooks are implemented as of release v0.11.0

Prestart and CreateRuntime

Prestart and CreateRuntime hooks are executed in the liblxc hooklxc.hook.pre-mount using the lxcri-hook cmd.

lxcri/create.go

Line 366 in cbc79e1

if len(c.Spec.Hooks.Prestart) > 0 || len(c.Spec.Hooks.CreateRuntime) > 0 {

CreateContainer

CreateContainer hooks are executed in the liblxc hook lxc.hook.mount using the lxcri-hook cmd.

lxcri/create.go

Line 371 in cbc79e1

if len(c.Spec.Hooks.CreateContainer) > 0 {

StartContainer

StartContainer hooks run with the same process atrributes (permissions, uid, gid ...) as the container process in lxcri-init,
right before execing the container process:

lxcri/cmd/lxcri-init/main.go

Line 102 in cbc79e1

err = specki.RunHooks(ctx, state, spec.Hooks.StartContainer, false)

Poststart

Poststart hooks run at the end of Runtime.Start in lxcri start.

lxcri/runtime.go

Line 246 in cbc79e1

specki.RunHooks(ctx, &state.SpecState, c.Spec.Hooks.Poststart, true)

Poststop

Poststop hooks run at the end of Runtime.Delete in lxcri delete.

lxcri/runtime.go

Line 426 in cbc79e1

specki.RunHooks(ctx, &state.SpecState, c.Spec.Hooks.Poststop, true)