Add pods created by kube play to a default network

In order to allow pods to reach other pods (as in Kubernetes) they all
need to be added to the same network. A network is created (if it
doesn't exist) and pods created by play-kube are added to that network.
When network options are passed to kube command the pods are not
attached to the default kube network.

Signed-off-by: Andrei Natanael Cosma <andrei@intersect.ro>

docs/source/markdown/podman-kube-play.1.md.in

@@ -155,7 +155,7 @@ Note: When joining multiple networks you should use the **--network name:mac=\<m
 
 @@option network
 
-The *host* network mode should be configured in the YAML file.
+When no network option is specified and *host* network mode is not configured in the YAML file, a new network stack is created and pods are attached to it making possible pod to pod communication.
 
 @@option no-hosts
 

pkg/domain/infra/abi/play.go

@@ -40,6 +40,9 @@ import (
 // container-specific sd-notify modes.
 const sdNotifyAnnotation = "io.containers.sdnotify"
 
+// default network created/used by kube
+const kubeDefaultNetwork = "podman-default-kube-network"
+
 // createServiceContainer creates a container that can later on
 // be associated with the pods of a K8s yaml.  It will be started along with
 // the first pod.
@@ -114,6 +117,19 @@ func (ic *ContainerEngine) PlayKube(ctx context.Context, body io.Reader, options
 	report := &entities.PlayKubeReport{}
 	validKinds := 0
 
+	// when no network options are specified, create a common network for all the pods
+	if len(options.Networks) == 0 {
+		_, err := ic.NetworkCreate(
+			ctx, nettypes.Network{
+				Name:       kubeDefaultNetwork,
+				DNSEnabled: true,
+			},
+		)
+		if err != nil && !errors.Is(err, nettypes.ErrNetworkExists) {
+			return nil, err
+		}
+	}
+
 	// read yaml document
 	content, err := io.ReadAll(body)
 	if err != nil {
@@ -338,6 +354,11 @@ func (ic *ContainerEngine) playKubePod(ctx context.Context, podName string, podY
 		return nil, err
 	}
 
+	// add kube default network if no network is explicitly added
+	if podOpt.Net.Network.NSMode != "host" && len(options.Networks) == 0 {
+		options.Networks = []string{kubeDefaultNetwork}
+	}
+
 	if len(options.Networks) > 0 {
 		ns, networks, netOpts, err := specgen.ParseNetworkFlag(options.Networks)
 		if err != nil {

test/e2e/play_kube_test.go

@@ -3000,6 +3000,21 @@ MemoryReservation: {{ .HostConfig.MemoryReservation }}`})
 		Expect(logs.OutputToString()).To(Equal(netns))
 	})
 
+	It("podman play kube test with kube default network", func() {
+		pod := getPod()
+		err := generateKubeYaml("pod", pod, kubeYaml)
+		Expect(err).To(BeNil())
+
+		kube := podmanTest.Podman([]string{"play", "kube", kubeYaml})
+		kube.WaitWithDefaultTimeout()
+		Expect(kube).Should(Exit(0))
+
+		inspect := podmanTest.Podman([]string{"inspect", pod.Name, "--format", "{{ .InfraConfig.Networks }}"})
+		inspect.WaitWithDefaultTimeout()
+		Expect(inspect).Should(Exit(0))
+		Expect(inspect.OutputToString()).To(Equal("[podman-default-kube-network]"))
+	})
+
 	It("podman play kube persistentVolumeClaim", func() {
 		volName := "myvol"
 		volDevice := "tmpfs"