feat: expose max allocatable IPs thru grpc server

Author: mselim00

pkg/ipamd/ipamd.go

@@ -2347,6 +2347,23 @@ func (c *IPAMContext) getPrefixesNeeded() int {
 	return toAllocate
 }
 
+// getMaxIPs returns the maximum number of ipv4 addresses allocatable given the context
+func (c *IPAMContext) getMaxIPs() (int, error) {
+	enisForPods, err := c.getMaxENI()
+	if err != nil {
+		return 0, err
+	}
+	if c.useCustomNetworking {
+		enisForPods = enisForPods - 1
+	}
+
+	ipv4Limit, _, err := c.GetIPv4Limit()
+	if err != nil {
+		return 0, err
+	}
+	return enisForPods * ipv4Limit, nil
+}
+
 func (c *IPAMContext) initENIAndIPLimits() (err error) {
 	if c.enableIPv4 {
 		nodeMaxENI, err := c.getMaxENI()

pkg/ipamd/ipamd_test.go

@@ -1265,6 +1265,56 @@ func TestGetWarmIPTargetStateWithPDenabled(t *testing.T) {
 	assert.Equal(t, 0, over)
 }
 
+func TestGetMaxIPs(t *testing.T) {
+	m := setup(t)
+	defer m.ctrl.Finish()
+
+	for _, testCase := range []struct {
+		enablePrefixDelegation bool
+		useCustomNetworking    bool
+		eniLimit               int
+		eniIpv4Limit           int
+		expectedMaxIps         int
+	}{
+		{
+			// modeled for a t3.medium
+			eniLimit:       3,
+			eniIpv4Limit:   5,
+			expectedMaxIps: 15,
+		},
+		{
+			// modeled for a t3.medium
+			eniLimit:               3,
+			eniIpv4Limit:           5,
+			enablePrefixDelegation: true,
+			expectedMaxIps:         240,
+		},
+		{
+			// modeled for a t3.medium
+			eniLimit:            3,
+			eniIpv4Limit:        5,
+			useCustomNetworking: true,
+			expectedMaxIps:      10,
+		},
+	} {
+		mockContext := &IPAMContext{
+			awsClient:              m.awsutils,
+			networkClient:          m.network,
+			primaryIP:              make(map[string]string),
+			terminating:            int32(0),
+			enablePrefixDelegation: testCase.enablePrefixDelegation,
+			useCustomNetworking:    testCase.useCustomNetworking,
+		}
+		m.awsutils.EXPECT().GetENILimit().Return(testCase.eniLimit)
+		m.awsutils.EXPECT().GetENIIPv4Limit().Return(testCase.eniIpv4Limit)
+
+		maxIps, err := mockContext.getMaxIPs()
+
+		assert.NoError(t, err)
+		assert.Equal(t, testCase.expectedMaxIps, maxIps)
+	}
+}
+
 func TestIPAMContext_nodeIPPoolTooLow(t *testing.T) {
 	m := setup(t)
 	defer m.ctrl.Finish()

pkg/ipamd/rpc_handler.go

@@ -334,6 +334,18 @@ func (s *server) GetNetworkPolicyConfigs(ctx context.Context, e *emptypb.Empty)
 	return resp, nil
 }
 
+func (s *server) GetAllocatableValues(ctx context.Context, e *emptypb.Empty) (*rpc.GetAllocatableValuesReply, error) {
+	log.Infof("Received GetAllocatableValues request")
+
+	maxIPs, err := s.ipamContext.getMaxIPs()
+	resp := &rpc.GetAllocatableValuesReply{
+		MaxAllocatableIPs: int32(maxIPs),
+	}
+
+	log.Infof("Send GetAllocatableValues: MaxAllocatableIPs: %d, err: %v", resp.MaxAllocatableIPs, err)
+	return resp, err
+}
+
 // RunRPCHandler handles request from gRPC
 func (c *IPAMContext) RunRPCHandler(version string) error {
 	log.Infof("Serving RPC Handler version %s on %s", version, ipamdgRPCaddress)