fix: Filter mechanism chain element works incorrectly in remote case (n…

…etworkservicemesh#575)

Signed-off-by: denis-tingajkin <denis.tingajkin@xored.com>

pkg/networkservice/common/filtermechanisms/README.md

@@ -0,0 +1,94 @@
+## Intro
+
+Package `filtermechanisms` filters out remote mechanisms if communicating by remote url 
+filters out local mechanisms otherwise. Can be used with eNSMGR.
+
+## Options
+
+Supported option `WithExternalThreshold` that sets max path segments count for eNSMgrs.
+
+## Examples
+Note: **Is local** true when path segment index less than localThreshold and nsmgr knows NSE url
+
+ 1. Local:
+ ```
+     Scheme: nsc-->NSMgr-->cross-nse-->NSMgr-->nse
+        NSMgr knows nse: true 
+        filterMechanismsServer.localThreshold: 5 
+        len(request.Connection.Path.PathSegments):  4
+        Is local: true
+```
+
+ 2. Local eNSM:
+ ```
+     Scheme: nsc-->eNSMgr-->nse
+         eNSMgr knows nse: true
+         filterMechanismsServer.localThreshold:  3
+         len(request.Connection.Path.PathSegments): 2
+         Is local: true
+```
+
+ 3. Remote eNSM:
+ ```
+     Scheme: nsc-->eNSMgr1-->eNSMgr2-->nse
+        eNSMgr1:
+            knows nse: false
+            filterMechanismsServer.localThreshold = 3
+            len(request.Connection.Path.PathSegments) = 2
+            Is local: false
+
+        eNSMgr2:
+            knows nse: true
+            filterMechanismsServer.localThreshold = 3
+            len(request.Connection.Path.PathSegments) = 3
+            Is local: false
+```
+
+ 4. Remote NSMgr + eNSMGR
+ ```
+     Scheme: nsc-->NSMgr1-->cross-nse1-->NSMgr1-->eNSMgr1-->nse
+        NSMgr1:
+            knows nse: false
+            filterMechanismsServer.localThreshold = 5
+            len(request.Connection.Path.PathSegments) = 4
+            Is local: false
+
+        eNSMgr1:
+            knows nse: true
+            filterMechanismsServer.localThreshold = 3
+            len(request.Connection.Path.PathSegments) = 5
+            Is local: false
+```
+
+ 5. Remote eNSMGR + NSMgr
+ ```
+     Scheme: nsc-->eNSMgr1-->NSMgr1-->cross-nse1-->NSMgr1-->eNSMgr2-->nse
+        eNSMgr1:
+            knows nse: false
+            filterMechanismsServer.localThreshold = 3
+            len(request.Connection.Path.PathSegments) = 2
+            Is local: false
+
+        NSMgr1:
+            knows nse: true
+            filterMechanismsServer.localThreshold = 5
+            len(request.Connection.Path.PathSegments) = 5
+            Is local: false
+```
+
+6. Remote
+
+```
+     Scheme: nsc-->NSMgr1-->cross-nse1-->NSMgr1-->NSMgr2-->cross-nse2-->NSMgr2-->nse
+        NSMgr2:
+            knows nse: false
+            filterMechanismsServer.localThreshold = 5
+            len(request.Connection.Path.PathSegments) = 4
+            Is local: false
+
+        NSMgr1:
+            knows nse: true
+            filterMechanismsServer.localThreshold = 5
+            len(request.Connection.Path.PathSegments) = 7
+            Is local: false
+```

pkg/networkservice/common/filtermechanisms/const.go

@@ -0,0 +1,23 @@
+// Copyright (c) 2020 Doc.ai and/or its affiliates.
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at:
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package filtermechanisms
+
+const (
+	// See at examples section in README.md
+	defaultThreshold  = 5
+	externalThreshold = 3
+)

pkg/networkservice/common/filtermechanisms/options.go

@@ -0,0 +1,27 @@
+// Copyright (c) 2020 Doc.ai and/or its affiliates.
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at:
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package filtermechanisms
+
+// Option is option applier for filterMechanismsServer
+type Option func(server *filterMechanismsServer)
+
+// WithExternalThreshold configures filterMechanismsServer to work with external NSMgr.
+func WithExternalThreshold() Option {
+	return Option(func(server *filterMechanismsServer) {
+		server.localThreshold = externalThreshold
+	})
+}

pkg/networkservice/common/filtermechanisms/server.go

@@ -33,21 +33,31 @@ import (
 )
 
 type filterMechanismsServer struct {
-	urls endpointurls.Set
+	urls           endpointurls.Set
+	localThreshold int
 }
 
 // NewServer - filters out remote mechanisms if connection is received from a unix file socket, otherwise filters
-// out local mechanisms
-func NewServer(registryServer *registry.NetworkServiceEndpointRegistryServer) networkservice.NetworkServiceServer {
-	result := &filterMechanismsServer{}
+// out local mechanisms.
+func NewServer(registryServer *registry.NetworkServiceEndpointRegistryServer, options ...Option) networkservice.NetworkServiceServer {
+	result := &filterMechanismsServer{
+		localThreshold: defaultThreshold,
+	}
+	for _, applyOption := range options {
+		applyOption(result)
+	}
 	*registryServer = endpointurls.NewNetworkServiceEndpointRegistryServer(&result.urls)
 	return result
 }
 
 func (f *filterMechanismsServer) Request(ctx context.Context, request *networkservice.NetworkServiceRequest) (*networkservice.Connection, error) {
 	u := clienturlctx.ClientURL(ctx)
+
 	if _, ok := f.urls.Load(*u); ok {
-		request.MechanismPreferences = filterMechanismsByCls(request.GetMechanismPreferences(), cls.LOCAL)
+		filteredMechanisms := filterMechanismsByCls(request.GetMechanismPreferences(), cls.LOCAL)
+		if len(filteredMechanisms) > 0 {
+			request.MechanismPreferences = filteredMechanisms
+		}
 	} else {
 		request.MechanismPreferences = filterMechanismsByCls(request.GetMechanismPreferences(), cls.REMOTE)
 	}

pkg/networkservice/common/filtermechanisms/server_test.go

@@ -21,6 +21,8 @@ import (
 	"net/url"
 	"testing"
 
+	"github.com/networkservicemesh/sdk/pkg/networkservice/core/next"
+
 	"github.com/networkservicemesh/api/pkg/api/networkservice"
 	"github.com/networkservicemesh/api/pkg/api/networkservice/mechanisms/cls"
 	"github.com/networkservicemesh/api/pkg/api/networkservice/mechanisms/kernel"
@@ -34,6 +36,72 @@ import (
 	"github.com/networkservicemesh/sdk/pkg/tools/clienturlctx"
 )
 
+func TestFilterMechanisms_RemoteExternal(t *testing.T) {
+	request := &networkservice.NetworkServiceRequest{
+		MechanismPreferences: []*networkservice.Mechanism{
+			{
+				Cls:  cls.REMOTE,
+				Type: vxlan.MECHANISM,
+			},
+			{
+				Cls:  cls.LOCAL,
+				Type: kernel.MECHANISM,
+			},
+		},
+		Connection: &networkservice.Connection{
+			Path: &networkservice.Path{
+				PathSegments: make([]*networkservice.PathSegment, 3),
+			},
+		},
+	}
+
+	var localRegistryServer registry.NetworkServiceEndpointRegistryServer
+	localServer := filtermechanisms.NewServer(&localRegistryServer)
+	var remoteRegistryServer registry.NetworkServiceEndpointRegistryServer
+	remoteServer := filtermechanisms.NewServer(&remoteRegistryServer, filtermechanisms.WithExternalThreshold())
+	u := &url.URL{Path: "test"}
+	_, _ = remoteRegistryServer.Register(context.Background(), &registry.NetworkServiceEndpoint{
+		Url: u.String(),
+	})
+	_, err := next.NewNetworkServiceServer(localServer, remoteServer).Request(clienturlctx.WithClientURL(context.Background(), u), request)
+	require.NoError(t, err)
+	require.Len(t, request.MechanismPreferences, 1)
+	require.Equal(t, cls.REMOTE, request.MechanismPreferences[0].Cls)
+}
+
+func TestFilterMechanisms_Remote(t *testing.T) {
+	request := &networkservice.NetworkServiceRequest{
+		MechanismPreferences: []*networkservice.Mechanism{
+			{
+				Cls:  cls.REMOTE,
+				Type: vxlan.MECHANISM,
+			},
+			{
+				Cls:  cls.LOCAL,
+				Type: kernel.MECHANISM,
+			},
+		},
+		Connection: &networkservice.Connection{
+			Path: &networkservice.Path{
+				PathSegments: make([]*networkservice.PathSegment, 5),
+			},
+		},
+	}
+
+	var localRegistryServer registry.NetworkServiceEndpointRegistryServer
+	localServer := filtermechanisms.NewServer(&localRegistryServer)
+	var remoteRegistryServer registry.NetworkServiceEndpointRegistryServer
+	remoteServer := filtermechanisms.NewServer(&remoteRegistryServer)
+	u := &url.URL{Path: "test"}
+	_, _ = remoteRegistryServer.Register(context.Background(), &registry.NetworkServiceEndpoint{
+		Url: u.String(),
+	})
+	_, err := next.NewNetworkServiceServer(localServer, remoteServer).Request(clienturlctx.WithClientURL(context.Background(), u), request)
+	require.NoError(t, err)
+	require.Len(t, request.MechanismPreferences, 1)
+	require.Equal(t, cls.REMOTE, request.MechanismPreferences[0].Cls)
+}
+
 func TestFilterMechanismsServer_Request(t *testing.T) {
 	request := func() *networkservice.NetworkServiceRequest {
 		return &networkservice.NetworkServiceRequest{