Fix docker inspect network go template for network which doesn't have MTU

pkg/drivers/kic/oci/network_create.go

@@ -171,13 +171,18 @@ type networkInspect struct {
 	ContainerIPs []string
 }
 
+var dockerInsepctGetter = func(name string) (*RunResult, error) {
+	cmd := exec.Command(Docker, "network", "inspect", name, "--format", `{"Name": "{{.Name}}","Driver": "{{.Driver}}","Subnet": "{{range .IPAM.Config}}{{.Subnet}}{{end}}","Gateway": "{{range .IPAM.Config}}{{.Gateway}}{{end}}","MTU": {{if (index .Options "com.docker.network.driver.mtu")}}{{(index .Options "com.docker.network.driver.mtu")}}{{else}}0{{end}},{{$first := true}} "ContainerIPs": [{{range $k,$v := .Containers }}{{if $first}}{{$first = false}}{{else}}, {{end}}"{{$v.IPv4Address}}"{{end}}]}`)
+	rr, err := runCmd(cmd)
+	return rr, err
+}
+
 // if exists returns subnet, gateway and mtu
 func dockerNetworkInspect(name string) (netInfo, error) {
 	var vals networkInspect
 	var info = netInfo{name: name}
 
-	cmd := exec.Command(Docker, "network", "inspect", name, "--format", `{"Name": "{{.Name}}","Driver": "{{.Driver}}","Subnet": "{{range .IPAM.Config}}{{.Subnet}}{{end}}","Gateway": "{{range .IPAM.Config}}{{.Gateway}}{{end}}","MTU": {{(index .Options "com.docker.network.driver.mtu")}},{{$first := true}} "ContainerIPs": [{{range $k,$v := .Containers }}{{if $first}}{{$first = false}}{{else}}, {{end}}"{{$v.IPv4Address}}"{{end}}]}`)
-	rr, err := runCmd(cmd)
+	rr, err := dockerInsepctGetter(name)
 	if err != nil {
 		logDockerNetworkInspect(Docker, name)
 		if strings.Contains(rr.Output(), "No such network") {

pkg/drivers/kic/oci/network_create_test.go

@@ -0,0 +1,84 @@
+/*
+Copyright 2019 The Kubernetes Authors All rights reserved.
+
+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 oci
+
+import (
+	"bytes"
+	"net"
+	"testing"
+)
+
+var dockerResponse string
+var dockerInspectGetterMock = func(name string) (*RunResult, error) {
+	var responseInBytes bytes.Buffer
+	responseInBytes.WriteString(dockerResponse)
+	response := &RunResult{Stdout: responseInBytes}
+
+	return response, nil
+}
+
+func TestDockerInspectWithMTU(t *testing.T) {
+	var tests = []struct {
+		name                  string
+		dockerInspectResponse string
+		gateway               string
+		subnetIP              string
+		mtu                   int
+	}{
+		{
+			name:                  "withMTU",
+			dockerInspectResponse: `{"Name": "m2","Driver": "bridge","Subnet": "172.19.0.0/16","Gateway": "172.19.0.1","MTU": 9216, "ContainerIPs": []}`,
+			gateway:               "172.19.0.1",
+			subnetIP:              "172.19.0.0",
+			mtu:                   9216,
+		},
+		{
+			name:                  "withoutMTU",
+			dockerInspectResponse: `{"Name": "m2","Driver": "bridge","Subnet": "172.19.0.0/16","Gateway": "172.19.0.1","MTU": 0, "ContainerIPs": []}`,
+			gateway:               "172.19.0.1",
+			subnetIP:              "172.19.0.0",
+			mtu:                   0,
+		},
+	}
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			dockerInspectResponseWithMtu := tc.dockerInspectResponse
+
+			// setting up mock funcs
+			dockerResponse = dockerInspectResponseWithMtu
+			dockerInsepctGetter = dockerInspectGetterMock
+
+			netInfo, err := dockerNetworkInspect("m2")
+
+			if err != nil {
+				t.Errorf("Expected not to have error but got %v", err)
+			}
+
+			if netInfo.mtu != tc.mtu {
+				t.Errorf("Expected not to have MTU as %v but got %v", tc.mtu, netInfo.mtu)
+			}
+
+			if !netInfo.gateway.Equal(net.ParseIP(tc.gateway)) {
+				t.Errorf("Expected not to have gateway as %v but got %v", tc.gateway, netInfo.gateway)
+			}
+
+			if !netInfo.subnet.IP.Equal(net.ParseIP(tc.subnetIP)) {
+				t.Errorf("Expected not to have subnet as %v but got %v", tc.subnetIP, netInfo.gateway)
+			}
+		})
+	}
+}