Add DhcpServingParams

Those parameters will be used to start DhcpServer or update its
configuration.

Test: runtest DhcpServingParamsTest.java
Bug: b/109584964
Change-Id: Id8d3dcf62d66dcb02accffa8d8500e30f07af452

core/java/android/net/NetworkUtils.java

@@ -161,7 +161,7 @@ public class NetworkUtils {
      * @param hostAddress an int coding for an IPv4 address, where higher-order int byte is
      *                    lower-order IPv4 address byte
      */
-    public static InetAddress intToInet4AddressHTL(int hostAddress) {
+    public static Inet4Address intToInet4AddressHTL(int hostAddress) {
         return intToInet4AddressHTH(Integer.reverseBytes(hostAddress));
     }
 
@@ -169,14 +169,14 @@ public class NetworkUtils {
      * Convert a IPv4 address from an integer to an InetAddress (0x01020304 -> 1.2.3.4)
      * @param hostAddress an int coding for an IPv4 address
      */
-    public static InetAddress intToInet4AddressHTH(int hostAddress) {
+    public static Inet4Address intToInet4AddressHTH(int hostAddress) {
         byte[] addressBytes = { (byte) (0xff & (hostAddress >> 24)),
                 (byte) (0xff & (hostAddress >> 16)),
                 (byte) (0xff & (hostAddress >> 8)),
                 (byte) (0xff & hostAddress) };
 
         try {
-            return InetAddress.getByAddress(addressBytes);
+            return (Inet4Address) InetAddress.getByAddress(addressBytes);
         } catch (UnknownHostException e) {
             throw new AssertionError();
         }
@@ -408,6 +408,28 @@ public class NetworkUtils {
         return new Pair<InetAddress, Integer>(address, prefixLength);
     }
 
+    /**
+     * Get a prefix mask as Inet4Address for a given prefix length.
+     *
+     * <p>For example 20 -> 255.255.240.0
+     */
+    public static Inet4Address getPrefixMaskAsInet4Address(int prefixLength)
+            throws IllegalArgumentException {
+        return intToInet4AddressHTH(prefixLengthToV4NetmaskIntHTH(prefixLength));
+    }
+
+    /**
+     * Get the broadcast address for a given prefix.
+     *
+     * <p>For example 192.168.0.1/24 -> 192.168.0.255
+     */
+    public static Inet4Address getBroadcastAddress(Inet4Address addr, int prefixLength)
+            throws IllegalArgumentException {
+        final int intBroadcastAddr = inet4AddressToIntHTH(addr)
+                | ~prefixLengthToV4NetmaskIntHTH(prefixLength);
+        return intToInet4AddressHTH(intBroadcastAddr);
+    }
+
     /**
      * Check if IP address type is consistent between two InetAddress.
      * @return true if both are the same type.  False otherwise.

tests/net/java/android/net/NetworkUtilsTest.java

@@ -24,6 +24,8 @@ import static android.net.NetworkUtils.intToInet4AddressHTL;
 import static android.net.NetworkUtils.netmaskToPrefixLength;
 import static android.net.NetworkUtils.prefixLengthToV4NetmaskIntHTH;
 import static android.net.NetworkUtils.prefixLengthToV4NetmaskIntHTL;
+import static android.net.NetworkUtils.getBroadcastAddress;
+import static android.net.NetworkUtils.getPrefixMaskAsInet4Address;
 
 import static junit.framework.Assert.assertEquals;
 
@@ -125,7 +127,6 @@ public class NetworkUtilsTest {
         assertInvalidNetworkMask(IPv4Address("255.255.0.255"));
     }
 
-
     @Test
     public void testPrefixLengthToV4NetmaskIntHTL() {
         assertEquals(0, prefixLengthToV4NetmaskIntHTL(0));
@@ -266,4 +267,44 @@ public class NetworkUtilsTest {
         assertEquals(BigInteger.valueOf(7l - 4 + 4 + 16 + 65536),
                 NetworkUtils.routedIPv6AddressCount(set));
     }
+
+    @Test
+    public void testGetPrefixMaskAsAddress() {
+        assertEquals("255.255.240.0", getPrefixMaskAsInet4Address(20).getHostAddress());
+        assertEquals("255.0.0.0", getPrefixMaskAsInet4Address(8).getHostAddress());
+        assertEquals("0.0.0.0", getPrefixMaskAsInet4Address(0).getHostAddress());
+        assertEquals("255.255.255.255", getPrefixMaskAsInet4Address(32).getHostAddress());
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void testGetPrefixMaskAsAddress_PrefixTooLarge() {
+        getPrefixMaskAsInet4Address(33);
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void testGetPrefixMaskAsAddress_NegativePrefix() {
+        getPrefixMaskAsInet4Address(-1);
+    }
+
+    @Test
+    public void testGetBroadcastAddress() {
+        assertEquals("192.168.15.255",
+                getBroadcastAddress(IPv4Address("192.168.0.123"), 20).getHostAddress());
+        assertEquals("192.255.255.255",
+                getBroadcastAddress(IPv4Address("192.168.0.123"), 8).getHostAddress());
+        assertEquals("192.168.0.123",
+                getBroadcastAddress(IPv4Address("192.168.0.123"), 32).getHostAddress());
+        assertEquals("255.255.255.255",
+                getBroadcastAddress(IPv4Address("192.168.0.123"), 0).getHostAddress());
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void testGetBroadcastAddress_PrefixTooLarge() {
+        getBroadcastAddress(IPv4Address("192.168.0.123"), 33);
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void testGetBroadcastAddress_NegativePrefix() {
+        getBroadcastAddress(IPv4Address("192.168.0.123"), -1);
+    }
 }