Check imds version to confirm if imds changes are available

Author: NihaNallappagari

cns/fakes/imdsclientfake.go

@@ -8,6 +8,7 @@ package fakes
 
 import (
 	"context"
+	"net"
 
 	"github.com/Azure/azure-container-networking/cns/imds"
 	"github.com/Azure/azure-container-networking/cns/wireserver"
@@ -59,19 +60,38 @@ func (m *MockIMDSClient) GetVMUniqueID(ctx context.Context) (string, error) {
 }
 
 func (m *MockIMDSClient) GetNetworkInterfaces(ctx context.Context) ([]imds.NetworkInterface, error) {
-	if ctx.Value(SimulateError) != nil {
-		return nil, imds.ErrUnexpectedStatusCode
-	}
+    if ctx.Value(SimulateError) != nil {
+        return nil, imds.ErrUnexpectedStatusCode
+    }
 
-	// Return some mock network interfaces for testing
-	return []imds.NetworkInterface{
-		{
-			InterfaceCompartmentID:      "nc1",
-			InterfaceCompartmentVersion: "1",
-		},
-		{
-			InterfaceCompartmentID:      "nc2",
-			InterfaceCompartmentVersion: "2",
-		},
-	}, nil
+    // Parse MAC addresses for testing
+    macAddr1, _ := net.ParseMAC("00:15:5d:01:02:01")
+    macAddr2, _ := net.ParseMAC("00:15:5d:01:02:02")
+
+    // Return some mock network interfaces for testing
+    return []imds.NetworkInterface{
+        {
+            InterfaceCompartmentID: "nc1",
+            MacAddress:            imds.HardwareAddr(macAddr1),
+        },
+        {
+            InterfaceCompartmentID: "nc2",
+            MacAddress:            imds.HardwareAddr(macAddr2),
+        },
+    }, nil
 }
+
+func (m *MockIMDSClient) GetIMDSVersions(ctx context.Context) (*imds.APIVersionsResponse, error) {
+    if ctx.Value(SimulateError) != nil {
+        return nil, imds.ErrUnexpectedStatusCode
+    }
+
+    // Return supported API versions including the expected one
+    return &imds.APIVersionsResponse{
+        APIVersions: []string{
+            "2017-03-01",
+            "2021-01-01",
+            "2025-07-24",
+        },
+    }, nil
+}

cns/imds/client.go

@@ -6,6 +6,7 @@ package imds
 import (
 	"context"
 	"encoding/json"
+	"net"
 	"net/http"
 	"net/url"
 
@@ -44,15 +45,17 @@ func RetryAttempts(attempts uint) ClientOption {
 }
 
 const (
-	vmUniqueIDProperty   = "vmId"
-	imdsComputePath      = "/metadata/instance/compute"
-	imdsNetworkPath      = "/metadata/instance/network"
-	imdsAPIVersion       = "api-version=2025-07-24"
-	imdsFormatJSON       = "format=json"
-	metadataHeaderKey    = "Metadata"
-	metadataHeaderValue  = "true"
-	defaultRetryAttempts = 3
-	defaultIMDSEndpoint  = "http://169.254.169.254"
+	vmUniqueIDProperty   	= "vmId"
+	imdsComputePath      	= "/metadata/instance/compute"
+	imdsNetworkPath      	= "/metadata/instance/network"
+	imdsVersionsPath     	= "/metadata/versions"
+	imdsDefaultAPIVersion  	= "api-version=2021-01-01"
+	imdsNCDetailsVersion 	= "api-version=2025-07-24"
+	imdsFormatJSON      	= "format=json"
+	metadataHeaderKey   	= "Metadata"
+	metadataHeaderValue  	= "true"
+	defaultRetryAttempts 	= 3
+	defaultIMDSEndpoint  	= "http://169.254.169.254"
 )
 
 var (
@@ -80,7 +83,7 @@ func NewClient(opts ...ClientOption) *Client {
 func (c *Client) GetVMUniqueID(ctx context.Context) (string, error) {
 	var vmUniqueID string
 	err := retry.Do(func() error {
-		computeDoc, err := c.getInstanceMetadata(ctx, imdsComputePath)
+		computeDoc, err := c.getInstanceMetadata(ctx, imdsComputePath, imdsDefaultAPIVersion)
 		if err != nil {
 			return errors.Wrap(err, "error getting IMDS compute metadata")
 		}
@@ -106,7 +109,7 @@ func (c *Client) GetVMUniqueID(ctx context.Context) (string, error) {
 func (c *Client) GetNetworkInterfaces(ctx context.Context) ([]NetworkInterface, error) {
 	var networkData NetworkInterfaces
 	err := retry.Do(func() error {
-		networkInterfaces, err := c.getInstanceMetadata(ctx, imdsNetworkPath)
+		networkInterfaces, err := c.getInstanceMetadata(ctx, imdsNetworkPath, imdsNCDetailsVersion)
 		if err != nil {
 			return errors.Wrap(err, "error getting IMDS network metadata")
 		}
@@ -130,7 +133,7 @@ func (c *Client) GetNetworkInterfaces(ctx context.Context) ([]NetworkInterface,
 	return networkData.Interface, nil
 }
 
-func (c *Client) getInstanceMetadata(ctx context.Context, imdsMetadataPath string) (map[string]any, error) {
+func (c *Client) getInstanceMetadata(ctx context.Context, imdsMetadataPath string, imdsAPIVersion string) (map[string]any, error) {
 	imdsRequestURL, err := url.JoinPath(c.config.endpoint, imdsMetadataPath)
 	if err != nil {
 		return nil, errors.Wrap(err, "unable to build path to IMDS metadata for path"+imdsMetadataPath)
@@ -162,14 +165,83 @@ func (c *Client) getInstanceMetadata(ctx context.Context, imdsMetadataPath strin
 	return m, nil
 }
 
+func (c *Client) GetIMDSVersions(ctx context.Context) (*APIVersionsResponse, error) {
+    var versionsResp APIVersionsResponse
+    err := retry.Do(func() error {
+        // Build the URL for the versions endpoint
+        imdsRequestURL, err := url.JoinPath(c.config.endpoint, imdsVersionsPath)
+        if err != nil {
+            return errors.Wrap(err, "unable to build path to IMDS versions endpoint")
+        }
+
+        req, err := http.NewRequestWithContext(ctx, http.MethodGet, imdsRequestURL, http.NoBody)
+        if err != nil {
+            return errors.Wrap(err, "error building IMDS versions http request")
+        }
+
+        req.Header.Add(metadataHeaderKey, metadataHeaderValue)
+        resp, err := c.cli.Do(req)
+        if err != nil {
+            return errors.Wrap(err, "error querying IMDS versions API")
+        }
+        defer resp.Body.Close()
+
+        if resp.StatusCode != http.StatusOK {
+            return errors.Wrapf(ErrUnexpectedStatusCode, "unexpected status code %d", resp.StatusCode)
+        }
+
+        if err := json.NewDecoder(resp.Body).Decode(&versionsResp); err != nil {
+            return errors.Wrap(err, "error decoding IMDS versions response as json")
+        }
+
+        return nil
+    }, retry.Context(ctx), retry.Attempts(c.config.retryAttempts), retry.DelayType(retry.BackOffDelay))
+    
+    if err != nil {
+        return nil, errors.Wrap(err, "exhausted retries querying IMDS versions")
+    }
+
+    return &versionsResp, nil
+}
+
+// Required for  marshaling/unmarshaling of mac address
+type HardwareAddr net.HardwareAddr
+
+func (h HardwareAddr) MarshalJSON() ([]byte, error) {
+    return json.Marshal(net.HardwareAddr(h).String())
+}
+
+func (h *HardwareAddr) UnmarshalJSON(data []byte) error {
+    var s string
+    if err := json.Unmarshal(data, &s); err != nil {
+        return err
+    }
+    mac, err := net.ParseMAC(s)
+    if err != nil {
+        return err
+    }
+    *h = HardwareAddr(mac)
+    return nil
+}
+
+func (h HardwareAddr) String() string {
+    return net.HardwareAddr(h).String()
+}
+
 // NetworkInterface represents a network interface from IMDS
 type NetworkInterface struct {
 	// IMDS returns compartment fields - these are mapped to NC ID and NC version
-	InterfaceCompartmentID      string `json:"interfaceCompartmentID,omitempty"`
-	InterfaceCompartmentVersion string `json:"interfaceCompartmentVersion,omitempty"`
+	MacAddress               HardwareAddr      `json:"macAddress"`
+	InterfaceCompartmentID   string            `json:"interfaceCompartmentID,omitempty"`
 }
 
 // NetworkInterfaces represents the network interfaces from IMDS
 type NetworkInterfaces struct {
 	Interface []NetworkInterface `json:"interface"`
 }
+
+
+// APIVersionsResponse represents versions form IMDS
+type APIVersionsResponse struct {
+    APIVersions []string `json:"apiVersions"`
+}