Fix AWS DHCP option set domain names causing garbled InternalDNS or Hostname addresses on Node

pkg/cloudprovider/providers/aws/aws.go

@@ -1351,14 +1351,17 @@ func (c *Cloud) NodeAddresses(ctx context.Context, name types.NodeName) ([]v1.No
 			addresses = append(addresses, v1.NodeAddress{Type: v1.NodeExternalIP, Address: externalIP})
 		}
 
-		internalDNS, err := c.metadata.GetMetadata("local-hostname")
-		if err != nil || len(internalDNS) == 0 {
+		localHostname, err := c.metadata.GetMetadata("local-hostname")
+		if err != nil || len(localHostname) == 0 {
 			//TODO: It would be nice to be able to determine the reason for the failure,
 			// but the AWS client masks all failures with the same error description.
 			klog.V(4).Info("Could not determine private DNS from AWS metadata.")
 		} else {
-			addresses = append(addresses, v1.NodeAddress{Type: v1.NodeInternalDNS, Address: internalDNS})
-			addresses = append(addresses, v1.NodeAddress{Type: v1.NodeHostName, Address: internalDNS})
+			hostname, internalDNS := parseMetadataLocalHostname(localHostname)
+			addresses = append(addresses, v1.NodeAddress{Type: v1.NodeHostName, Address: hostname})
+			for _, d := range internalDNS {
+				addresses = append(addresses, v1.NodeAddress{Type: v1.NodeInternalDNS, Address: d})
+			}
 		}
 
 		externalDNS, err := c.metadata.GetMetadata("public-hostname")
@@ -1380,6 +1383,26 @@ func (c *Cloud) NodeAddresses(ctx context.Context, name types.NodeName) ([]v1.No
 	return extractNodeAddresses(instance)
 }
 
+// parseMetadataLocalHostname parses the output of "local-hostname" metadata.
+// If a DHCP option set is configured for a VPC and it has multiple domain names, GetMetadata
+// returns a string containing first the hostname followed by additional domain names,
+// space-separated. For example, if the DHCP option set has:
+// domain-name = us-west-2.compute.internal a.a b.b c.c d.d;
+// $ curl http://169.254.169.254/latest/meta-data/local-hostname
+// ip-192-168-111-51.us-west-2.compute.internal a.a b.b c.c d.d
+func parseMetadataLocalHostname(metadata string) (string, []string) {
+	localHostnames := strings.Fields(metadata)
+	hostname := localHostnames[0]
+	internalDNS := []string{hostname}
+
+	privateAddress := strings.Split(hostname, ".")[0]
+	for _, h := range localHostnames[1:] {
+		internalDNSAddress := privateAddress + "." + h
+		internalDNS = append(internalDNS, internalDNSAddress)
+	}
+	return hostname, internalDNS
+}
+
 // extractNodeAddresses maps the instance information from EC2 to an array of NodeAddresses
 func extractNodeAddresses(instance *ec2.Instance) ([]v1.NodeAddress, error) {
 	// Not clear if the order matters here, but we might as well indicate a sensible preference order

pkg/cloudprovider/providers/aws/aws_test.go

@@ -681,6 +681,41 @@ func TestNodeAddressesWithMetadata(t *testing.T) {
 	testHasNodeAddress(t, addrs, v1.NodeExternalIP, "2.3.4.5")
 }
 
+func TestParseMetadataLocalHostname(t *testing.T) {
+	tests := []struct {
+		name        string
+		metadata    string
+		hostname    string
+		internalDNS []string
+	}{
+		{
+			"single hostname",
+			"ip-172-31-16-168.us-west-2.compute.internal",
+			"ip-172-31-16-168.us-west-2.compute.internal",
+			[]string{"ip-172-31-16-168.us-west-2.compute.internal"},
+		},
+		{
+			"dhcp options set with three additional domain names",
+			"ip-172-31-16-168.us-west-2.compute.internal example.com example.ca example.org",
+			"ip-172-31-16-168.us-west-2.compute.internal",
+			[]string{"ip-172-31-16-168.us-west-2.compute.internal", "ip-172-31-16-168.example.com", "ip-172-31-16-168.example.ca", "ip-172-31-16-168.example.org"},
+		},
+	}
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			hostname, internalDNS := parseMetadataLocalHostname(test.metadata)
+			if hostname != test.hostname {
+				t.Errorf("got hostname %v, expected %v", hostname, test.hostname)
+			}
+			for i, v := range internalDNS {
+				if v != test.internalDNS[i] {
+					t.Errorf("got an internalDNS %v, expected %v", v, test.internalDNS[i])
+				}
+			}
+		})
+	}
+}
+
 func TestGetRegion(t *testing.T) {
 	aws := mockAvailabilityZone("us-west-2e")
 	zones, ok := aws.Zones()