Add support for AllocateDefaultGateway Feature

add `allocateDefaultGateway` flag to cni-args that
activates the special behaviour.
When CNI is called with this flag, the plugin
will try to allocate IP address of the pool's
default gateway  as interface IP for the cotnainer.

api/grpc/proto/nvidia/ipam/node/v1/node.proto

@@ -71,10 +71,12 @@ message IPAMParameters {
   string cni_ifname = 3;
   // required, additional metadata to identify IP allocation
   IPAMMetadata metadata = 4;
-  // type of the pool which is refered by the name in the pools field
+  // optional, type of the pool which is refered by the name in the pools field
   PoolType pool_type = 5;
-  // conatins IP that were statically requested
+  // optional, conatins IP that were statically requested
   repeated string requested_ips = 6;
+  // optional, conatins extra features requested for the allocation
+  IPAMFeatures features = 7;
 }
 
 // IPAMMetadata contains metadata for IPAM calls
@@ -89,6 +91,12 @@ message IPAMMetadata {
   string device_id = 4;
 }
 
+// IPAMFeatures contains extra features requested for the IPAM call
+message IPAMFeatures {
+  // optional, request IP of the default gateway from the pool be allocated for container
+  bool allocate_default_gateway = 1;
+}
+
 // IsAllocatedRequest contains parameters for IsAllocated rpc call
 message IsAllocatedRequest {
   // required, IPAMParameters contains parameters IPAM parameters related to the request

pkg/cni/plugin/plugin.go

@@ -213,6 +213,9 @@ func cniConfToGRPCReq(conf *types.NetConf, args *skel.CmdArgs) *nodev1.IPAMParam
 			DeviceId:        conf.DeviceID,
 		},
 		RequestedIps: requestedIPs,
+		Features: &nodev1.IPAMFeatures{
+			AllocateDefaultGateway: conf.IPAM.Features.AllocateDefaultGateway,
+		},
 	}
 	if req.Metadata.K8SPodUid == "" {
 		log.Warningf("K8S_POD_UID is not provided by container runtime")

pkg/cni/plugin/plugin_test.go

@@ -100,6 +100,7 @@ var _ = Describe("plugin tests", func() {
 						K8SPodNamespace: "test",
 					},
 					RequestedIps: []string{},
+					Features:     &nodev1.IPAMFeatures{},
 				}}).Return(&nodev1.AllocateResponse{
 				Allocations: []*nodev1.AllocationInfo{{
 					Pool:     "my-pool",

pkg/cni/types/types.go

@@ -77,6 +77,12 @@ type IPAMConf struct {
 	} `json:"-"`
 	// requested IPs from CNI_ARGS, args and capabilities
 	RequestedIPs []net.IP `json:"-"`
+	// internal representation of the requested features
+	Features struct {
+		// request to allocate pool's default gateway as
+		// interface IP address for the container
+		AllocateDefaultGateway bool
+	} `json:"-"`
 }
 
 // NetConf is CNI network config
@@ -95,9 +101,10 @@ type NetConf struct {
 
 // IPAMArgs holds arguments from stdin args["cni"]
 type IPAMArgs struct {
-	IPs       []string `json:"ips"`
-	PoolNames []string `json:"poolNames"`
-	PoolType  string   `json:"poolType"`
+	IPs                    []string `json:"ips"`
+	PoolNames              []string `json:"poolNames"`
+	PoolType               string   `json:"poolType"`
+	AllocateDefaultGateway bool     `json:"allocateDefaultGateway"`
 }
 
 // IPAMEnvArgs holds arguments from CNI_ARGS env variable
@@ -173,6 +180,16 @@ func (cl *confLoader) LoadConf(args *skel.CmdArgs) (*NetConf, error) {
 		return nil, err
 	}
 
+	if n.Args != nil && n.Args.ArgsCNI != nil {
+		n.IPAM.Features.AllocateDefaultGateway = n.Args.ArgsCNI.AllocateDefaultGateway
+	}
+
+	if n.IPAM.Features.AllocateDefaultGateway {
+		if len(n.IPAM.RequestedIPs) > 0 {
+			return nil, fmt.Errorf("allocatedDefaultGateway can't be used together with static IP request")
+		}
+	}
+
 	n.IPAM.Pools, err = getPools(n)
 	if err != nil {
 		return nil, err

pkg/ipam-node/handlers/allocate.go

@@ -135,11 +135,12 @@ func (h *Handlers) allocateInPool(poolName string, reqLog logr.Logger,
 	if err != nil || subnet == nil || subnet.IP == nil || subnet.Mask == nil {
 		return PoolAlloc{}, poolCfgError(poolLog, poolName, poolType, "invalid subnet")
 	}
+	gateway := net.ParseIP(poolCfg.Gateway)
 	rangeSet := &allocator.RangeSet{allocator.Range{
 		RangeStart: rangeStart,
 		RangeEnd:   rangeEnd,
 		Subnet:     cniTypes.IPNet(*subnet),
-		Gateway:    net.ParseIP(poolCfg.Gateway),
+		Gateway:    gateway,
 	}}
 	if err := rangeSet.Canonicalize(); err != nil {
 		return PoolAlloc{}, poolCfgError(poolLog, poolName, poolType,
@@ -152,6 +153,16 @@ func (h *Handlers) allocateInPool(poolName string, reqLog logr.Logger,
 			break
 		}
 	}
+
+	if params.Features != nil && params.Features.AllocateDefaultGateway {
+		if gateway == nil {
+			return PoolAlloc{}, status.Errorf(codes.InvalidArgument,
+				"pool without gateway can't be used with allocate_default_gateway feature,"+
+					"pool \"%s\", poolType \"%s\"", poolName, poolType)
+		}
+		selectedStaticIP = gateway
+	}
+
 	exclusionRangeSet := make(allocator.RangeSet, 0, len(poolCfg.Exclusions))
 	for _, e := range poolCfg.Exclusions {
 		exclusionRangeSet = append(exclusionRangeSet, allocator.Range{
@@ -197,8 +208,13 @@ func (h *Handlers) allocateInPool(poolName string, reqLog logr.Logger,
 		return PoolAlloc{}, status.Errorf(codes.Internal,
 			"failed to allocate IP address in pool \"%s\", poolType \"%s\"", poolName, poolType)
 	}
-	poolLog.Info("IP address allocated", "allocation", result.String())
+	if params.Features != nil && params.Features.AllocateDefaultGateway {
+		// TODO (ykulazhenkov): do we want to keep gateway in this case?
+		// if we will return gateway here, the container will have same IP as interface address and as gateway
+		result.Gateway = nil
+	}
 
+	poolLog.Info("IP address allocated", "allocation", result.String())
 	return PoolAlloc{
 		Pool:     poolName,
 		IPConfig: result,

pkg/ipam-node/handlers/handlers.go

@@ -120,6 +120,10 @@ func validateReq(req paramsGetter) error {
 			return fieldsIsInvalidError(fmt.Sprintf("parameters.requested_ips[%d]", i))
 		}
 	}
+	if params.Features != nil && params.Features.AllocateDefaultGateway && len(params.RequestedIps) > 0 {
+		return status.Errorf(codes.InvalidArgument,
+			"parameters.features.allocate_default_gateway can't be used together with static IPs")
+	}
 	return nil
 }