Changing the get network request to return swarm scope predefined networks

Starting 17.06 swarm service create supports service creates with predefined
networks like host and bridge. Due to the nature of the feature, swarm manager
has a swarm scope predefined networks in addition to local scoped
predefined networks on all nodes. However network inspects for swarm scoped
predefined networks was not possible. The fix adds support for network inspect
for swarm scoped predefined networks.

Signed-off-by: Abhinandan Prativadi <abhi@docker.com>

api/server/router/network/network_routes.go

@@ -16,6 +16,7 @@ import (
 	"github.com/docker/docker/api/types/network"
 	"github.com/docker/docker/api/types/versions"
 	"github.com/docker/libnetwork"
+	netconst "github.com/docker/libnetwork/datastore"
 	"github.com/docker/libnetwork/networkdb"
 )
 
@@ -135,6 +136,17 @@ func (n *networkRouter) getNetwork(ctx context.Context, w http.ResponseWriter, r
 		}
 	}
 
+	nwk, err := n.cluster.GetNetwork(term)
+	if err == nil {
+		// If the get network is passed with a specific network ID / partial network ID
+		// or if the get network was passed with a network name and scope as swarm
+		// return the network. Skipped using isMatchingScope because it is true if the scope
+		// is not set which would be case if the client API v1.30
+		if strings.HasPrefix(nwk.ID, term) || (netconst.SwarmScope == scope) {
+			return httputils.WriteJSON(w, http.StatusOK, nwk)
+		}
+	}
+
 	nr, _ := n.cluster.GetNetworks()
 	for _, network := range nr {
 		if network.ID == term && isMatchingScope(network.Scope, scope) {