fact: handle errors from Close() explicitely

pkg/controllers/proxy/network_services_controller.go

@@ -958,20 +958,20 @@ func (ln *linuxNetworking) prepareEndpointForDsr(containerID string, endpointIP
 	if err != nil {
 		return errors.New("Failed to get namespace due to " + err.Error())
 	}
-	defer hostNetworkNamespaceHandle.Close()
+	defer utils.CloseCloserDisregardError(&hostNetworkNamespaceHandle)
 
 	activeNetworkNamespaceHandle, err = netns.Get()
 	if err != nil {
 		return errors.New("Failed to get namespace due to " + err.Error())
 	}
 	klog.V(1).Infof("Current network namespace before netns.Set: " + activeNetworkNamespaceHandle.String())
-	activeNetworkNamespaceHandle.Close()
+	defer utils.CloseCloserDisregardError(&activeNetworkNamespaceHandle)
 
 	dockerClient, err := client.NewClientWithOpts(client.FromEnv)
 	if err != nil {
 		return errors.New("Failed to get docker client due to " + err.Error())
 	}
-	defer dockerClient.Close()
+	defer utils.CloseCloserDisregardError(dockerClient)
 
 	containerSpec, err := dockerClient.ContainerInspect(context.Background(), containerID)
 	if err != nil {
@@ -983,7 +983,7 @@ func (ln *linuxNetworking) prepareEndpointForDsr(containerID string, endpointIP
 	if err != nil {
 		return errors.New("Failed to get endpoint namespace due to " + err.Error())
 	}
-	defer endpointNamespaceHandle.Close()
+	defer utils.CloseCloserDisregardError(&endpointNamespaceHandle)
 
 	err = netns.Set(endpointNamespaceHandle)
 	if err != nil {
@@ -995,7 +995,7 @@ func (ln *linuxNetworking) prepareEndpointForDsr(containerID string, endpointIP
 		return errors.New("Failed to get activeNetworkNamespace due to " + err.Error())
 	}
 	klog.V(2).Infof("Current network namespace after netns. Set to container network namespace: " + activeNetworkNamespaceHandle.String())
-	activeNetworkNamespaceHandle.Close()
+	_ = activeNetworkNamespaceHandle.Close()
 
 	// create a ipip tunnel interface inside the endpoint container
 	tunIf, err := netlink.LinkByName(KubeTunnelIf)
@@ -1085,7 +1085,7 @@ func (ln *linuxNetworking) prepareEndpointForDsr(containerID string, endpointIP
 		return errors.New("Failed to get activeNetworkNamespace handle due to " + err.Error())
 	}
 	klog.Infof("Current network namespace after revert namespace to host network namespace: " + activeNetworkNamespaceHandle.String())
-	activeNetworkNamespaceHandle.Close()
+	_ = activeNetworkNamespaceHandle.Close()
 	return nil
 }
 
@@ -1110,7 +1110,7 @@ func (ln *linuxNetworking) prepareEndpointForDsrWithCRI(runtimeEndpoint, contain
 		return errors.New("failed to get host namespace due to " + err.Error())
 	}
 	klog.V(1).Infof("current network namespace before netns.Set: " + hostNetworkNamespaceHandle.String())
-	defer hostNetworkNamespaceHandle.Close()
+	defer utils.CloseCloserDisregardError(&hostNetworkNamespaceHandle)
 
 	rs, err := cri.NewRemoteRuntimeService(runtimeEndpoint, cri.DefaultConnectionTimeout)
 	if err != nil {
@@ -1130,7 +1130,7 @@ func (ln *linuxNetworking) prepareEndpointForDsrWithCRI(runtimeEndpoint, contain
 	if err != nil {
 		return fmt.Errorf("failed to get endpoint namespace (containerID=%s, pid=%d, error=%s)", containerID, pid, err)
 	}
-	defer endpointNamespaceHandle.Close()
+	defer utils.CloseCloserDisregardError(&endpointNamespaceHandle)
 
 	err = netns.Set(endpointNamespaceHandle)
 	if err != nil {
@@ -1142,7 +1142,7 @@ func (ln *linuxNetworking) prepareEndpointForDsrWithCRI(runtimeEndpoint, contain
 		return errors.New("failed to get activeNetworkNamespace due to " + err.Error())
 	}
 	klog.V(2).Infof("Current network namespace after netns. Set to container network namespace: " + activeNetworkNamespaceHandle.String())
-	activeNetworkNamespaceHandle.Close()
+	_ = activeNetworkNamespaceHandle.Close()
 
 	// TODO: fix boilerplate `netns.Set(hostNetworkNamespaceHandle)` code. Need a robust
 	// way to switch back to old namespace, pretty much all things will go wrong if we dont switch back
@@ -1235,7 +1235,7 @@ func (ln *linuxNetworking) prepareEndpointForDsrWithCRI(runtimeEndpoint, contain
 		return errors.New("Failed to get activeNetworkNamespace handle due to " + err.Error())
 	}
 	klog.Infof("Current network namespace after revert namespace to host network namespace: " + activeNetworkNamespaceHandle.String())
-	activeNetworkNamespaceHandle.Close()
+	_ = activeNetworkNamespaceHandle.Close()
 	return nil
 }
 
@@ -2063,7 +2063,7 @@ func (ln *linuxNetworking) setupPolicyRoutingForDSR() error {
 		if err != nil {
 			return errors.New("Failed to setup policy routing required for DSR due to " + err.Error())
 		}
-		defer f.Close()
+		defer utils.CloseCloserDisregardError(f)
 		if _, err = f.WriteString(customDSRRouteTableID + " " + customDSRRouteTableName + "\n"); err != nil {
 			return errors.New("Failed to setup policy routing required for DSR due to " + err.Error())
 		}
@@ -2094,7 +2094,7 @@ func (ln *linuxNetworking) setupRoutesForExternalIPForDSR(serviceInfoMap service
 		if err != nil {
 			return errors.New("Failed setup external ip routing table required for DSR due to " + err.Error())
 		}
-		defer f.Close()
+		defer utils.CloseCloserDisregardError(f)
 		if _, err = f.WriteString(externalIPRouteTableID + " " + externalIPRouteTableName + "\n"); err != nil {
 			return errors.New("Failed setup external ip routing table required for DSR due to " + err.Error())
 		}

pkg/controllers/routing/pbr.go

@@ -6,6 +6,8 @@ import (
 	"os"
 	"os/exec"
 	"strings"
+
+	"github.com/cloudnativelabs/kube-router/pkg/utils"
 )
 
 // setup a custom routing table that will be used for policy based routing to ensure traffic originating
@@ -64,7 +66,7 @@ func rtTablesAdd(tableNumber, tableName string) error {
 		if err != nil {
 			return fmt.Errorf("failed to open: %s", err.Error())
 		}
-		defer f.Close()
+		defer utils.CloseCloserDisregardError(f)
 		if _, err = f.WriteString(tableNumber + " " + tableName + "\n"); err != nil {
 			return fmt.Errorf("failed to write: %s", err.Error())
 		}

pkg/controllers/routing/utils.go

@@ -65,7 +65,7 @@ func ipv4IsEnabled() bool {
 	if err != nil {
 		return false
 	}
-	l.Close()
+	_ = l.Close()
 
 	return true
 }
@@ -82,7 +82,7 @@ func ipv6IsEnabled() bool {
 	if err != nil {
 		return false
 	}
-	l.Close()
+	_ = l.Close()
 
 	return true
 }

pkg/utils/utils.go

@@ -1,6 +1,7 @@
 package utils
 
 import (
+	"io"
 	"sync"
 )
 
@@ -41,3 +42,9 @@ func (b *Broadcaster) Notify(instance interface{}) {
 		go listener.OnUpdate(instance)
 	}
 }
+
+// CloseCloserDisregardError it is a common need throughout kube-router's code base to need close a closer in defer
+// statements, this allows an action like that to pass a linter as well as describe its intention well
+func CloseCloserDisregardError(handler io.Closer) {
+	_ = handler.Close()
+}