Make c.networks() list include the default network

This makes things a lot more clear - if we are actually joining a
CNI network, we are guaranteed to get a non-zero length list of
networks.

We do, however, need to know if the network we are joining is the
default network for inspecting containers as it determines how we
populate the response struct. To handle this, add a bool to
indicate that the network listed was the default network, and
only the default network.

Signed-off-by: Matthew Heon <mheon@redhat.com>

libpod/container.go

@@ -13,6 +13,7 @@ import (
 	"github.com/containers/image/v5/manifest"
 	"github.com/containers/podman/v2/libpod/define"
 	"github.com/containers/podman/v2/libpod/lock"
+	"github.com/containers/podman/v2/pkg/rootless"
 	"github.com/containers/storage"
 	"github.com/cri-o/ocicni/pkg/ocicni"
 	spec "github.com/opencontainers/runtime-spec/specs-go"
@@ -1095,13 +1096,17 @@ func (c *Container) Umask() string {
 // values at runtime via network connect and disconnect.
 // If the container is configured to use CNI and this function returns an empty
 // array, the container will still be connected to the default network.
-func (c *Container) Networks() ([]string, error) {
+// The second return parameter, a bool, indicates that the container container
+// is joining the default CNI network - the network name will be included in the
+// returned array of network names, but the container did not explicitly join
+// this network.
+func (c *Container) Networks() ([]string, bool, error) {
 	if !c.batched {
 		c.lock.Lock()
 		defer c.lock.Unlock()
 
 		if err := c.syncContainer(); err != nil {
-			return nil, err
+			return nil, false, err
 		}
 	}
 
@@ -1109,19 +1114,22 @@ func (c *Container) Networks() ([]string, error) {
 }
 
 // Unlocked accessor for networks
-func (c *Container) networks() ([]string, error) {
+func (c *Container) networks() ([]string, bool, error) {
 	networks, err := c.runtime.state.GetNetworks(c)
 	if err != nil && errors.Cause(err) == define.ErrNoSuchNetwork {
-		return c.config.Networks, nil
+		if len(c.config.Networks) == 0 && !rootless.IsRootless() {
+			return []string{c.runtime.netPlugin.GetDefaultNetworkName()}, true, nil
+		}
+		return c.config.Networks, false, nil
 	}
 
-	return networks, err
+	return networks, false, err
 }
 
 // networksByNameIndex provides us with a map of container networks where key
 // is network name and value is the index position
 func (c *Container) networksByNameIndex() (map[string]int, error) {
-	networks, err := c.networks()
+	networks, _, err := c.networks()
 	if err != nil {
 		return nil, err
 	}