Create containers with initial network attachments

[danegsta]

Initial container startup should not create on the default network and then wait for JIT attach just to reach the desired topology. This changes create-time networking so Docker and Podman receive the full initial network and alias set in the container create command once all requested networks are ready.

Summary

• Add CreateContainerOptions.Networks as the only create-time networking API and emit runtime-specific multi-network arguments for Docker and Podman.
• Resolve initial ContainerNetworks before creation, remove the startup-time JIT connection delay, and keep dynamic attach/detach reconciliation for later network changes.
• Update the test orchestrator and integration coverage, including preserving unmanaged runtime connections so the network controller does not disconnect create-time attachments before connection objects exist.

Validation

• go test -count 1 -parallel 32 ./internal/containers ./internal/docker ./internal/podman ./internal/testutil/ctrlutil ./controllers ./test/integration -run 'TestApplyCreateContainerOptionsNetworks|TestContainerNetworkKeepsUnmanagedConnections|TestContainerNetworkDoesNotStartUntilNetworkExists|TestContainerNetworkWithAliases|TestContainerFastExitingWithNetwork|TestResourceHarvesting' -timeout 180s
• Manual Docker smoke test with kubectl-created ContainerNetwork and Container resources.
• Manual Podman smoke test with DCP forced to --container-runtime podman.

[Copilot]

Pull request overview

This PR reworks container create-time networking so that Docker/Podman receive the full set of initial networks (and per-network aliases) directly in the create command, rather than the previous approach of creating on the default network and then relying on just-in-time (JIT) attach/detach to reach the desired topology. It defers container creation until all requested ContainerNetworks are ready, and adjusts the network controller so create-time ("unmanaged") connections are not disconnected before their ContainerNetworkConnection objects exist.

Changes:

• Replace CreateContainerOptions.Network/NetworkAliases with a single Networks []CreateContainerNetworkOptions API, and emit runtime-specific multi-network arguments (Docker: name=<net>,alias=<a>; Podman: <net>:alias=<a>).
• Resolve initial networks before creation (getInitialCreateContainerNetworks, retryable errInitialContainerNetworksNotReady), remove the startup-time JIT detach logic in finishCreatedContainerStartup, and count create-time attachments as valid connected networks.
• Simplify the network reconciler to only disconnect connections it previously managed (removing shouldKeepUnmanagedConnections), and update the test orchestrator plus integration/unit tests.

Reviewed changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
internal/containers/container_orchestrator.go	Introduces Networks/CreateContainerNetworkOptions, replacing the single-network create-time API.
internal/docker/cli_orchestrator.go	Emits per-network --network name=,alias= args for Docker.
internal/podman/cli_orchestrator.go	Emits per-network --network <net>:alias= args for Podman.
internal/docker/cli_orchestrator_test.go	Adds unit tests for Docker multi-network arg formatting.
internal/podman/cli_orchestrator_test.go	Adds unit tests for Podman multi-network arg formatting.
controllers/container_controller.go	Resolves initial networks pre-creation, removes JIT detach, adds retryable not-ready error, marks create-time networks valid.
controllers/network_controller.go	Only disconnects reconciler-managed connections; removes shouldKeepUnmanagedConnections.
controllers/container_network_tunnel_proxy_controller.go	Updates client proxy creation to the new Networks API.
internal/testutil/ctrlutil/test_container_orchestrator.go	Adds resolveCreateContainerNetworks to mirror multi-network create behavior.
test/integration/container_network_connection_test.go	Adds/updates tests for not-starting-until-ready and keeping unmanaged connections.
test/integration/resource_harvesting_test.go	Migrates test call sites to the new Networks field.

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[Copilot]

Pull request overview

Copilot reviewed 13 out of 13 changed files in this pull request and generated 1 comment.

[danegsta]

/backport to release/0.25

[github-actions]

Started backporting to release/0.25: https://github.com/microsoft/dcp/actions/runs/28552264712

[github-actions]

@danegsta backport PR couldn't be created automatically, please create the backport PR manually!

Open backport PR into release/0.25.