Create default EndpointSettings if no --network provided

[akerouanton]

Depends on:

• daemon: Improve NetworkingConfig & EndpointSettings validation moby/moby#46183

- What I did

Following flags are silently ignored when they're passed with no --network specified (ie. when the default network is used):

• --network-alias
• --ip
• --ip6
• --link-local-ip

This is not really an issue right now since the first 3 parameters are not allowed on the default bridge network. However, with moby/moby#45905, the container-wide MacAddress parameter will be deprecated and dismissed. Because of that, with docker/cli#4419, it's currently not possible to use the --mac-address flag with no default network specified.

Morever, docker network connect --link-local-ip ... works properly, so it should also work on docker container create. This also lay the ground for making the default bridge network just a "normal" network.

Since the 3 parameters in the list above aren't ignored anymore, if users provide them, moby's ContainerStart endpoint will complain about those. To provide better UX, moby/moby#46183 make sure these invalid parameters lead to a proper error message on docker container create / docker run.

- How to verify it

# Before:
$ docker container create --link-local-ip 169.254.169.254 --name test busybox
$ docker inspect -f "{{ json .NetworkSettings.Networks.bridge.IPAMConfig }}" test
null

# After:
$ docker container create --link-local-ip 169.254.169.254 --name test busybox
$ docker inspect -f "{{ json .NetworkSettings.Networks.bridge.IPAMConfig }}" test
{"LinkLocalIPs":["169.254.169.254"]}

- Description for the changelog

• --link-local-ip is now supported by docker container create and docker run when no --network parameter is specified

- A picture of a cute animal (not mandatory but encouraged)

[codecov-commenter]

Codecov Report

Merging #4493 (f1048e1) into master (d4aca90) will decrease coverage by 0.01%.
The diff coverage is 53.84%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4493      +/-   ##
==========================================
- Coverage   59.66%   59.66%   -0.01%     
==========================================
  Files         288      288              
  Lines       24785    24797      +12     
==========================================
+ Hits        14789    14795       +6     
- Misses       9111     9115       +4     
- Partials      885      887       +2     

[thaJeztah]

I had to double-check if this was only a thing on Windows, but I think we use the magic default on both. It reminded me of;

• Networking: find better solution for the magic "default" value moby/moby#19421

And we should look at having a const for this (makes it easier to discover where its used), but that's a change to make in the daemon code, so not for this PR.

[akerouanton]

See:

• api: Add consts for predefined networks moby/moby#46447

[thaJeztah]

I dug up my original PR / commit that changed this code; 5bc0963

A couple of things there that I was curious about (but it's a long time); on this line, there's an error that treats container.links and ep.links as separate things; 5bc0963#diff-e546b85d27f9dbea4fd41e83a58e36bb540bcda3e304355d56c92a119cd5aa2aR721

if len(n.Links) > 0 && copts.links.Len() > 0 {
	return errdefs.InvalidParameter(errors.New("conflicting options: cannot specify both --link and per-network links"))
}

It's valid to use --link on the default ("bridge") network, but for that network (currently) only with the legacy link implementation (hard-wired links).

Do you know if the daemon-side code makes this distinction as well when using the network-config make / slice? (i.e. does it look "if its the default (bridge) network, then use legacy links, and otherwise the DNS-based links?) or would the daemon only look at container.links to create legacy links?

[thaJeztah]

note that the above validation is only performed on the first network in the list (which holds data of the "default" network)

[akerouanton]

You're right:

• copts.links will be put into HostConfig.Links, which is the way to use legacy links;
• n.Links is used for DNS-based links.

I removed the first commit (ie. the one removing this check) and instead I changed the condition under which copts.links is copied into n.Links (ie. to not do that on "default" network).

[thaJeztah]

LGTM