Update Windows CNI implementation to free resources in case of HNS failures (#223)

Update Windows CNI implementation to free resources in case of HNS failures

Author: tamilmani1989

cni/network/network_windows.go

@@ -1,6 +1,7 @@
 package network
 
 import (
+	"fmt"
 	"net"
 
 	"github.com/Azure/azure-container-networking/cni"
@@ -19,7 +20,7 @@ import (
  * Issue link: https://github.com/kubernetes/kubernetes/issues/57253
  */
 func handleConsecutiveAdd(containerId, endpointId string, nwInfo *network.NetworkInfo, nwCfg *cni.NetworkConfig) (*cniTypesCurr.Result, error) {
-	hnsEndpoint, _ := hcsshim.GetHNSEndpointByName(endpointId)
+	hnsEndpoint, err := hcsshim.GetHNSEndpointByName(endpointId)
 	if hnsEndpoint != nil {
 		log.Printf("[net] Found existing endpoint through hcsshim: %+v", hnsEndpoint)
 		log.Printf("[net] Attaching ep %v to container %v", hnsEndpoint.Id, containerId)
@@ -55,7 +56,8 @@ func handleConsecutiveAdd(containerId, endpointId string, nwInfo *network.Networ
 		return result, nil
 	}
 
-	return nil, nil
+	err = fmt.Errorf("GetHNSEndpointByName for %v returned nil with err %v", endpointId, err)
+	return nil, err
 }
 
 func addDefaultRoute(gwIPString string, epInfo *network.EndpointInfo, result *cniTypesCurr.Result) {

network/endpoint_windows.go

@@ -47,6 +47,7 @@ func ConstructEndpointID(containerID string, netNsPath string, ifName string) (s
 // newEndpointImpl creates a new endpoint in the network.
 func (nw *network) newEndpointImpl(epInfo *EndpointInfo) (*endpoint, error) {
 	// Get Infrastructure containerID. Handle ADD calls for workload container.
+	var err error
 	infraEpName, _ := ConstructEndpointID(epInfo.ContainerID, epInfo.NetNsPath, epInfo.IfName)
 
 	hnsEndpoint := &hcsshim.HNSEndpoint{
@@ -79,11 +80,20 @@ func (nw *network) newEndpointImpl(epInfo *EndpointInfo) (*endpoint, error) {
 		return nil, err
 	}
 
+	defer func() {
+		if err != nil {
+			log.Printf("[net] HNSEndpointRequest DELETE id:%v", hnsResponse.Id)
+			hnsResponse, err := hcsshim.HNSEndpointRequest("DELETE", hnsResponse.Id, "")
+			log.Printf("[net] HNSEndpointRequest DELETE response:%+v err:%v.", hnsResponse, err)
+		}
+	}()
+
 	// Attach the endpoint.
 	log.Printf("[net] Attaching endpoint %v to container %v.", hnsResponse.Id, epInfo.ContainerID)
 	err = hcsshim.HotAttachEndpoint(epInfo.ContainerID, hnsResponse.Id)
 	if err != nil {
 		log.Printf("[net] Failed to attach endpoint: %v.", err)
+		return nil, err
 	}
 
 	// Create the endpoint object.