Handle nilgateway scenario

Author: NihaNallappagari

azure-ipam/ipam.go

@@ -136,7 +136,14 @@ func (p *IPAMPlugin) CmdAdd(args *cniSkel.CmdArgs) error {
 				Mask: net.CIDRMask(ipNet.Bits(), 128), // nolint
 			}
 		}
-		ipConfig.Gateway = (*gatewayIP)[i]
+
+		if gatewayIP != nil && len(*gatewayIP) > i {
+			ipConfig.Gateway = (*gatewayIP)[i]
+		} else {
+			p.logger.Warn("No gateway IP returned from CNS, setting to nil", zap.Any("gatewayIP", gatewayIP), zap.Int("index", i))
+			ipConfig.Gateway = nil
+		}
+
 		cniResult.IPs[i] = ipConfig
 	}
 

azure-ipam/ipam_test.go

@@ -85,6 +85,33 @@ func (c *MockCNSClient) RequestIPAddress(ctx context.Context, ipconfig cns.IPCon
 			},
 		}
 		return result, nil
+	case "invalidGateway":
+		result := &cns.IPConfigResponse{
+			PodIpInfo: cns.PodIpInfo{
+				PodIPConfig: cns.IPSubnet{
+					IPAddress:    "10.0.1.10",
+					PrefixLength: 24,
+				},
+				NetworkContainerPrimaryIPConfig: cns.IPConfiguration{
+					IPSubnet: cns.IPSubnet{
+						IPAddress:    "10.0.1.0",
+						PrefixLength: 24,
+					},
+					DNSServers:       nil,
+					GatewayIPAddress: "invalidgatewayip",
+				},
+				HostPrimaryIPInfo: cns.HostIPInfo{
+					Gateway:   "invalidgatewayip",
+					PrimaryIP: "10.0.0.1",
+					Subnet:    "10.0.0.0/24",
+				},
+			},
+			Response: cns.Response{
+				ReturnCode: 0,
+				Message:    "",
+			},
+		}
+		return result, nil
 	default:
 		result := &cns.IPConfigResponse{
 			PodIpInfo: cns.PodIpInfo{
@@ -120,7 +147,7 @@ func (c *MockCNSClient) RequestIPs(ctx context.Context, ipconfig cns.IPConfigsRe
 	switch ipconfig.InfraContainerID {
 	case "failRequestCNSArgs":
 		return nil, errFoo
-	case "happyArgsSingle", "failProcessCNSRespSingleIP", "failRequestCNSArgsSingleIP", "nilGateway":
+	case "happyArgsSingle", "failProcessCNSRespSingleIP", "failRequestCNSArgsSingleIP", "nilGateway", "invalidGateway":
 		e := &client.CNSClientError{}
 		e.Code = types.UnsupportedAPI
 		e.Err = errUnsupportedAPI
@@ -407,8 +434,27 @@ func TestCmdAdd(t *testing.T) {
 			wantErr: false,
 		},
 		{
-			name:    "CNI add with nil gateway IP",
-			args:    buildArgs("nilGateway", happyPodArgs, happyNetConfByteArr),
+			name: "CNI add with nil gateway IP",
+			args: buildArgs("nilGateway", happyPodArgs, happyNetConfByteArr),
+			want: &types100.Result{
+				CNIVersion: "1.0.0",
+				Interfaces: nil,
+				IPs: []*types100.IPConfig{
+					{
+						Address: net.IPNet{
+							IP:   net.IPv4(10, 0, 1, 10),
+							Mask: net.CIDRMask(24, 32),
+						},
+						Gateway: nil, // No gateway
+					},
+				},
+				DNS: cniTypes.DNS{},
+			},
+			wantErr: false,
+		},
+		{
+			name:    "CNI add with invalid gateway IP",
+			args:    buildArgs("invalidGateway", happyPodArgs, happyNetConfByteArr),
 			wantErr: true,
 		},
 		{

azure-ipam/ipconfig/ipconfig.go

@@ -13,7 +13,7 @@ import (
 )
 
 const (
-	defaultV6Gateway   = "fe80::1234:5678:9abc"
+	defaultV6Gateway = "fe80::1234:5678:9abc"
 )
 
 func CreateOrchestratorContext(args *cniSkel.CmdArgs) ([]byte, error) {
@@ -93,9 +93,13 @@ func ProcessIPConfigsResp(resp *cns.IPConfigsResponse) (*[]netip.Prefix, *[]net.
 			gatewayStr = defaultV6Gateway
 		}
 
-		gatewayIP = net.ParseIP(gatewayStr)
-		if gatewayIP == nil {
-			return nil, nil, errors.Errorf("failed to parse gateway IP %q for pod ip %s", gatewayStr, resp.PodIPInfo[i].PodIPConfig.IPAddress)
+		if gatewayStr != "" {
+			gatewayIP = net.ParseIP(gatewayStr)
+			if gatewayIP == nil {
+				return nil, nil, errors.Errorf("failed to parse gateway IP %q for pod ip %s", gatewayStr, resp.PodIPInfo[i].PodIPConfig.IPAddress)
+			}
+		} else {
+			gatewayIP = nil
 		}
 		gatewaysIPs[i] = gatewayIP
 	}