🐛 Fix DockerMachine panic

[makhov]

What this PR does / why we need it:

The PR fixes panic in the DockerMachineReconciler in case cluster.Spec.InfrastructureRef doesn't yet exist.
When using ClusterClass, the Cluster can contain just spec.topology at the beginning, other fields will be added later by the controller manager.

(the trace below is from the v1.5.3, but the bug still exists in the main branch)

panic: runtime error: invalid memory address or nil pointer dereference [recovered]
        panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x20 pc=0x11a40ec]

goroutine 229 [running]:
sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).Reconcile.func1()
        sigs.k8s.io/controller-runtime@v0.15.1/pkg/internal/controller/controller.go:115 +0x1a4
panic({0x13564e0, 0x25cf020})
        runtime/panic.go:884 +0x1f4
sigs.k8s.io/cluster-api/test/infrastructure/docker/internal/controllers.(*DockerMachineReconciler).Reconcile(0x400003a700, {0x183a980, 0x4000946570}, {{{0x4000aa6976?, 0x30?}, {0x4000801b80?, 0xffff71389001?}}})
        sigs.k8s.io/cluster-api/test/infrastructure/docker/internal/controllers/dockermachine_controller.go:124 +0x55c
sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).Reconcile(0x183a980?, {0x183a980?, 0x4000946570?}, {{{0x4000aa6976?, 0x12caea0?}, {0x4000801b80?, 0x4000b91e08?}}})
        sigs.k8s.io/controller-runtime@v0.15.1/pkg/internal/controller/controller.go:118 +0x8c
sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).reconcileHandler(0x4000466460, {0x183a8d8, 0x40000eb5e0}, {0x13e79a0?, 0x4000370360?})
        sigs.k8s.io/controller-runtime@v0.15.1/pkg/internal/controller/controller.go:314 +0x2cc
sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).processNextWorkItem(0x4000466460, {0x183a8d8, 0x40000eb5e0})
        sigs.k8s.io/controller-runtime@v0.15.1/pkg/internal/controller/controller.go:265 +0x1a0
sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).Start.func2.2()
        sigs.k8s.io/controller-runtime@v0.15.1/pkg/internal/controller/controller.go:226 +0x74
created by sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).Start.func2
        sigs.k8s.io/controller-runtime@v0.15.1/pkg/internal/controller/controller.go:222 +0x43c

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[k8s-ci-robot]

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[killianmuldoon]

/ok-to-test
/area provider/infrastructure-docker

Q: Can a dockermachine possibly be created in a topology managed cluster where the infrastructureRef isn't set? That's surprising to me.

[killianmuldoon]

Change looks good to me - just one Q

/lgtm

[k8s-ci-robot]

LGTM label has been added.

Git tree hash: 5f2b1b16974fa454851ce33dd8ffd445c2ad8990

[killianmuldoon]

/cherry-pick release-1.4

[killianmuldoon]

/cherry-pick release-1.5

[makhov]

Q: Can a dockermachine possibly be created in a topology managed cluster where the infrastructureRef isn't set? That's surprising to me.

Yes. I bumped into this when I was working on adding ClusterClass support to the k0smotron Cluster API provider, and had some of the resources misconfigured. CAPI controller manager wasn't able to add infrastructureRef to the Cluster object, which caused panic.

[killianmuldoon]

Yes. I bumped into this when I was working on k0sproject/k0smotron#325 to the k0smotron Cluster API provider, and had some of the resources misconfigured. CAPI controller manager wasn't able to add infrastructureRef to the Cluster object, which caused panic.

Hmm - I guess the topology controller does go ahead and create the MDs etc. even if the Cluster doesn't have an infrastructureRef. Surprising to me, but not necessarily a bug IMO.

[makhov]

Hmm - I guess the topology controller does go ahead and create the MDs etc. even if the Cluster doesn't have an infrastructureRef. Surprising to me, but not necessarily a bug IMO.

That's fine, I think, the problem here is the panic.

[vincepri]

/approve

[k8s-ci-robot]

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[killianmuldoon]

/cherry-pick release-1.5

[killianmuldoon]

/cherry-pick release-1.4

[k8s-infra-cherrypick-robot]

@killianmuldoon: new pull request created: #9689

In response to this:

/cherry-pick release-1.5

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[k8s-infra-cherrypick-robot]

@killianmuldoon: new pull request created: #9690

In response to this:

/cherry-pick release-1.4

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.