fix: restore post-connect fallback for multi-network stacks on API < 1.44

[jotka]

Problem

Docker Compose 5.1.0 broke multi-network stacks on Docker daemons older than API 1.44 (Docker Engine < 23.0), including Synology DSM 7.1 (API 1.41) and DSM 7.2 (API 1.43). The error is:

Container cannot be connected to network endpoints

This is a regression from 5.0.2 which worked correctly on these daemons.

Closes #13628

Context

I maintain Dockhand, a Docker management application. Many of our users run Dockhand on Synology NAS devices (DSM 7.1/7.2), which ship with Docker 20.10 (API 1.41). This regression broke multi-network stack deployments for all of them when we updated docker-compose to 5.1.0. We had to cap docker-compose at 5.0.2 as a workaround while investigating the root cause.

Root Cause

Both regressions were introduced in commit bfb5511 (go.mod: bump github.com/moby/moby/api v1.53.0, moby/client v0.2.2):

1. defaultNetworkSettings() in create.go

The versions.GreaterThanOrEqualTo(version, APIVersion144) guard was removed during the moby API bump, making defaultNetworkSettings unconditionally include ALL networks in EndpointsConfig for ContainerCreate. Old daemons (< API 1.44) only accept a single entry and reject the request with the error above.

2. The post-connect fallback was removed from convergence.go

The same commit removed the NetworkConnect fallback loop from createMobyContainer(). Previously (since aaa7ef6), after ContainerCreate, the code checked versions.LessThan(apiVersion, "1.44") and connected extra networks one-by-one via NetworkConnect(). This entire block was dropped during the API migration.

Fix

First commit (4f14ab8): Restore backward compat

Restores the two behaviors from 5.0.2:

1. create.go — defaultNetworkSettings(): Only include extra networks in EndpointsConfig when apiVersion >= 1.44 (guarded by !versions.LessThan(version, apiVersion144)).

2. convergence.go — createMobyContainer(): Restore the post-connect fallback. After container creation, when apiVersion < 1.44, iterate the service's extra networks and call NetworkConnect() for each, skipping the primary network (already configured via NetworkMode in ContainerCreate).

Second commit (7895a5a)

1. Pass APIVersion through createConfigs: Added APIVersion field to the createConfigs struct, populated from the existing apiVersion local in getCreateConfigs(). This eliminates the redundant s.RuntimeVersion(ctx) call in createMobyContainer.

2. Reorder ContainerInspect after NetworkConnect: Moved the inspect call after the NetworkConnect loop so the returned container.Summary includes all attached networks.

3. Unit tests for the < 1.44 code path:

   • TestDefaultNetworkSettings sub-test with version "1.43" — asserts EndpointsConfig contains only the primary network.
   • TestCreateMobyContainerLegacyAPI — asserts ContainerCreate gets only the primary network, NetworkConnect is called for the secondary, and ContainerInspect runs after NetworkConnect.

Testing

• Unit tests pass (the TestRunHook_ConsoleSize failure is a pre-existing PTY crash on macOS/arm64, unrelated to this change and present on main before this fix)
• Tested manually against Docker 20.10 (API 1.41) — multi-network stacks now deploy correctly
• No regression expected on modern daemons (API >= 1.44): they continue to use the multi-endpoint ContainerCreate path