Fix network alias issue

This fix tries to address the issue raised in 33661 where
network alias does not work when connect to a network the second time.

This fix address the issue.

This fix fixes 33661.

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

api/server/router/network/network_routes.go

@@ -275,12 +275,11 @@ func (n *networkRouter) postNetworkConnect(ctx context.Context, w http.ResponseW
 		return err
 	}
 
-	// Always make sure there is no ambiguity with respect to the network ID/name
-	nw, err := n.backend.FindNetwork(vars["id"])
-	if err != nil {
-		return err
-	}
-	return n.backend.ConnectContainerToNetwork(connect.Container, nw.ID(), connect.EndpointConfig)
+	// Unlike other operations, we does not check ambiguity of the name/ID here.
+	// The reason is that, In case of attachable network in swarm scope, the actual local network
+	// may not be available at the time. At the same time, inside daemon `ConnectContainerToNetwork`
+	// does the ambiguity check anyway. Therefore, passing the name to daemon would be enough.
+	return n.backend.ConnectContainerToNetwork(connect.Container, vars["id"], connect.EndpointConfig)
 }
 
 func (n *networkRouter) postNetworkDisconnect(ctx context.Context, w http.ResponseWriter, r *http.Request, vars map[string]string) error {

daemon/container_operations.go

@@ -20,6 +20,7 @@ import (
 	"github.com/docker/docker/runconfig"
 	"github.com/docker/go-connections/nat"
 	"github.com/docker/libnetwork"
+	netconst "github.com/docker/libnetwork/datastore"
 	"github.com/docker/libnetwork/netlabel"
 	"github.com/docker/libnetwork/options"
 	"github.com/docker/libnetwork/types"
@@ -259,6 +260,13 @@ func (daemon *Daemon) updateNetworkSettings(container *container.Container, n li
 		}
 
 		if sn.Name() == n.Name() {
+			// If the network scope is swarm, then this
+			// is an attachable network, which may not
+			// be locally available previously.
+			// So always update.
+			if n.Info().Scope() == netconst.SwarmScope {
+				continue
+			}
 			// Avoid duplicate config
 			return nil
 		}
@@ -272,10 +280,8 @@ func (daemon *Daemon) updateNetworkSettings(container *container.Container, n li
 		}
 	}
 
-	if _, ok := container.NetworkSettings.Networks[n.Name()]; !ok {
-		container.NetworkSettings.Networks[n.Name()] = &network.EndpointSettings{
-			EndpointSettings: endpointConfig,
-		}
+	container.NetworkSettings.Networks[n.Name()] = &network.EndpointSettings{
+		EndpointSettings: endpointConfig,
 	}
 
 	return nil