api: allow NW name that is the prefix of a swarm NW ID

api/server/router/network/network_routes.go

@@ -80,7 +80,7 @@ func (n *networkRouter) postNetworkCreate(ctx context.Context, w http.ResponseWr
 		return err
 	}
 
-	if _, err := n.clusterProvider.GetNetwork(create.Name); err == nil {
+	if nws, err := n.clusterProvider.GetNetworksByName(create.Name); err == nil && len(nws) > 0 {
 		return libnetwork.NetworkNameError(create.Name)
 	}
 

daemon/cluster/cluster.go

@@ -1375,8 +1375,7 @@ func (c *Cluster) GetNetwork(input string) (apitypes.NetworkResource, error) {
 	return convert.BasicNetworkFromGRPC(*network), nil
 }
 
-// GetNetworks returns all current cluster managed networks.
-func (c *Cluster) GetNetworks() ([]apitypes.NetworkResource, error) {
+func (c *Cluster) getNetworks(filters *swarmapi.ListNetworksRequest_Filters) ([]apitypes.NetworkResource, error) {
 	c.mu.RLock()
 	defer c.mu.RUnlock()
 
@@ -1388,7 +1387,7 @@ func (c *Cluster) GetNetworks() ([]apitypes.NetworkResource, error) {
 	ctx, cancel := c.getRequestContext()
 	defer cancel()
 
-	r, err := state.controlClient.ListNetworks(ctx, &swarmapi.ListNetworksRequest{})
+	r, err := state.controlClient.ListNetworks(ctx, &swarmapi.ListNetworksRequest{Filters: filters})
 	if err != nil {
 		return nil, err
 	}
@@ -1402,6 +1401,21 @@ func (c *Cluster) GetNetworks() ([]apitypes.NetworkResource, error) {
 	return networks, nil
 }
 
+// GetNetworks returns all current cluster managed networks.
+func (c *Cluster) GetNetworks() ([]apitypes.NetworkResource, error) {
+	return c.getNetworks(nil)
+}
+
+// GetNetworksByName returns cluster managed networks by name.
+// It is ok to have multiple networks here. #18864
+func (c *Cluster) GetNetworksByName(name string) ([]apitypes.NetworkResource, error) {
+	// Note that swarmapi.GetNetworkRequest.Name is not functional.
+	// So we cannot just use that with c.GetNetwork.
+	return c.getNetworks(&swarmapi.ListNetworksRequest_Filters{
+		Names: []string{name},
+	})
+}
+
 func attacherKey(target, containerID string) string {
 	return containerID + ":" + target
 }

integration-cli/docker_cli_swarm_test.go

@@ -1508,3 +1508,50 @@ func (s *DockerTrustedSwarmSuite) TestTrustedServiceUpdate(c *check.C) {
 	c.Assert(err, check.NotNil, check.Commentf(out))
 	c.Assert(string(out), checker.Contains, "Error: remote trust data does not exist", check.Commentf(out))
 }
+
+// Test case for issue #27866, which did not allow NW name that is the prefix of a swarm NW ID.
+// e.g. if the ingress ID starts with "n1", it was impossible to create a NW named "n1".
+func (s *DockerSwarmSuite) TestSwarmNetworkCreateIssue27866(c *check.C) {
+	d := s.AddDaemon(c, true, true)
+	out, err := d.Cmd("network", "inspect", "-f", "{{.Id}}", "ingress")
+	c.Assert(err, checker.IsNil, check.Commentf("out: %v", out))
+	ingressID := strings.TrimSpace(out)
+	c.Assert(ingressID, checker.Not(checker.Equals), "")
+
+	// create a network of which name is the prefix of the ID of an overlay network
+	// (ingressID in this case)
+	newNetName := ingressID[0:2]
+	out, err = d.Cmd("network", "create", "--driver", "overlay", newNetName)
+	// In #27866, it was failing because of "network with name %s already exists"
+	c.Assert(err, checker.IsNil, check.Commentf("out: %v", out))
+	out, err = d.Cmd("network", "rm", newNetName)
+	c.Assert(err, checker.IsNil, check.Commentf("out: %v", out))
+}
+
+// Test case for https://github.com/docker/docker/pull/27938#issuecomment-265768303
+// This test creates two networks with the same name sequentially, with various drivers.
+// Since the operations in this test are done sequentially, the 2nd call should fail with
+// "network with name FOO already exists".
+// Note that it is to ok have multiple networks with the same name if the operations are done
+// in parallel. (#18864)
+func (s *DockerSwarmSuite) TestSwarmNetworkCreateDup(c *check.C) {
+	d := s.AddDaemon(c, true, true)
+	drivers := []string{"bridge", "overlay"}
+	for i, driver1 := range drivers {
+		nwName := fmt.Sprintf("network-test-%d", i)
+		for _, driver2 := range drivers {
+			c.Logf("Creating a network named %q with %q, then %q",
+				nwName, driver1, driver2)
+			out, err := d.Cmd("network", "create", "--driver", driver1, nwName)
+			c.Assert(err, checker.IsNil, check.Commentf("out: %v", out))
+			out, err = d.Cmd("network", "create", "--driver", driver2, nwName)
+			c.Assert(out, checker.Contains,
+				fmt.Sprintf("network with name %s already exists", nwName))
+			c.Assert(err, checker.NotNil)
+			c.Logf("As expected, the attempt to network %q with %q failed: %s",
+				nwName, driver2, out)
+			out, err = d.Cmd("network", "rm", nwName)
+			c.Assert(err, checker.IsNil, check.Commentf("out: %v", out))
+		}
+	}
+}