Assign specific client address to dhcp server

Bug: 141256482
Test: manual
      atest TetheringTests

Change-Id: Ief76c98c843ba5420224cbf0f34464f366c891b7

Tethering/common/TetheringLib/src/android/net/TetheringManager.java

@@ -520,9 +520,8 @@ public class TetheringManager {
             /**
              * Configure tethering with static IPv4 assignment.
              *
-             * The clientAddress must be in the localIPv4Address prefix. A DHCP server will be
+             * A DHCP server will be started, but will only be able to offer the client address.
-             * started, but will only be able to offer the client address. The two addresses must
+             * The two addresses must be in the same prefix.
-             * be in the same prefix.
              *
              * @param localIPv4Address The preferred local IPv4 link address to use.
              * @param clientAddress The static client address.
@@ -533,10 +532,7 @@ public class TetheringManager {
                     @NonNull final LinkAddress clientAddress) {
                 Objects.requireNonNull(localIPv4Address);
                 Objects.requireNonNull(clientAddress);
-                if (localIPv4Address.getPrefixLength() != clientAddress.getPrefixLength()
+                if (!checkStaticAddressConfiguration(localIPv4Address, clientAddress)) {
-                        || !localIPv4Address.isIpv4() || !clientAddress.isIpv4()
-                        || !new IpPrefix(localIPv4Address.toString()).equals(
-                        new IpPrefix(clientAddress.toString()))) {
                     throw new IllegalArgumentException("Invalid server or client addresses");
                 }
 
@@ -580,6 +576,19 @@ public class TetheringManager {
             }
         }
 
+        /**
+         * Check whether the two addresses are ipv4 and in the same prefix.
+         * @hide
+         */
+        public static boolean checkStaticAddressConfiguration(
+                @NonNull final LinkAddress localIPv4Address,
+                @NonNull final LinkAddress clientAddress) {
+            return localIPv4Address.getPrefixLength() == clientAddress.getPrefixLength()
+                    && localIPv4Address.isIpv4() && clientAddress.isIpv4()
+                    && new IpPrefix(localIPv4Address.toString()).equals(
+                    new IpPrefix(clientAddress.toString()));
+        }
+
         /**
          * Get a TetheringRequestParcel from the configuration
          * @hide

Tethering/src/android/net/dhcp/DhcpServingParamsParcelExt.java

@@ -18,10 +18,12 @@ package android.net.dhcp;
 
 import static android.net.shared.Inet4AddressUtils.inet4AddressToIntHTH;
 
-import android.annotation.NonNull;
 import android.net.LinkAddress;
 import android.util.ArraySet;
 
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+
 import java.net.Inet4Address;
 import java.util.Collection;
 import java.util.Collections;
@@ -160,6 +162,17 @@ public class DhcpServingParamsParcelExt extends DhcpServingParamsParcel {
         return this;
     }
 
+    /**
+     * Set the client address to tell DHCP server only offer this address.
+     * The client's prefix length is the same as server's.
+     *
+     * <p>If not set, the default value is null.
+     */
+    public DhcpServingParamsParcelExt setSingleClientAddr(@Nullable Inet4Address clientAddr) {
+        this.clientAddr = clientAddr == null ? 0 : inet4AddressToIntHTH(clientAddr);
+        return this;
+    }
+
     private static int[] toIntArray(@NonNull Collection<Inet4Address> addrs) {
         int[] res = new int[addrs.size()];
         int i = 0;

Tethering/src/android/net/ip/IpServer.java

@@ -18,6 +18,7 @@ package android.net.ip;
 
 import static android.net.InetAddresses.parseNumericAddress;
 import static android.net.RouteInfo.RTN_UNICAST;
+import static android.net.TetheringManager.TetheringRequest.checkStaticAddressConfiguration;
 import static android.net.dhcp.IDhcpServer.STATUS_SUCCESS;
 import static android.net.shared.Inet4AddressUtils.intToInet4AddressHTH;
 import static android.net.util.NetworkConstants.FF;
@@ -492,17 +493,24 @@ public class IpServer extends StateMachine {
         }
     }
 
-    private boolean startDhcp(Inet4Address addr, int prefixLen) {
+    private boolean startDhcp(final LinkAddress serverLinkAddr, final LinkAddress clientLinkAddr) {
         if (mUsingLegacyDhcp) {
             return true;
         }
+
+        final Inet4Address addr = (Inet4Address) serverLinkAddr.getAddress();
+        final int prefixLen = serverLinkAddr.getPrefixLength();
+        final Inet4Address clientAddr = clientLinkAddr == null ? null :
+                (Inet4Address) clientLinkAddr.getAddress();
+
         final DhcpServingParamsParcel params;
         params = new DhcpServingParamsParcelExt()
                 .setDefaultRouters(addr)
                 .setDhcpLeaseTimeSecs(DHCP_LEASE_TIME_SECS)
                 .setDnsServers(addr)
-                .setServerAddr(new LinkAddress(addr, prefixLen))
+                .setServerAddr(serverLinkAddr)
-                .setMetered(true);
+                .setMetered(true)
+                .setSingleClientAddr(clientAddr);
         // TODO: also advertise link MTU
 
         mDhcpServerStartIndex++;
@@ -537,9 +545,10 @@ public class IpServer extends StateMachine {
         }
     }
 
-    private boolean configureDhcp(boolean enable, Inet4Address addr, int prefixLen) {
+    private boolean configureDhcp(boolean enable, final LinkAddress serverAddr,
+            final LinkAddress clientAddr) {
         if (enable) {
-            return startDhcp(addr, prefixLen);
+            return startDhcp(serverAddr, clientAddr);
         } else {
             stopDhcp();
             return true;
@@ -587,7 +596,7 @@ public class IpServer extends StateMachine {
                 // code that calls into NetworkManagementService directly.
                 srvAddr = (Inet4Address) parseNumericAddress(BLUETOOTH_IFACE_ADDR);
                 mIpv4Address = new LinkAddress(srvAddr, BLUETOOTH_DHCP_PREFIX_LENGTH);
-                return configureDhcp(enabled, srvAddr, BLUETOOTH_DHCP_PREFIX_LENGTH);
+                return configureDhcp(enabled, mIpv4Address, null /* clientAddress */);
             }
             mIpv4Address = new LinkAddress(srvAddr, prefixLen);
         } catch (IllegalArgumentException e) {
@@ -624,7 +633,7 @@ public class IpServer extends StateMachine {
             mLinkProperties.removeRoute(route);
         }
 
-        return configureDhcp(enabled, srvAddr, prefixLen);
+        return configureDhcp(enabled, mIpv4Address, mStaticIpv4ClientAddr);
     }
 
     private String getRandomWifiIPv4Address() {
@@ -945,7 +954,14 @@ public class IpServer extends StateMachine {
     }
 
     private void maybeConfigureStaticIp(final TetheringRequestParcel request) {
-        if (request == null) return;
+        // Ignore static address configuration if they are invalid or null. In theory, static
+        // addresses should not be invalid here because TetheringManager do not allow caller to
+        // specify invalid static address configuration.
+        if (request == null || request.localIPv4Address == null
+                || request.staticClientAddress == null || !checkStaticAddressConfiguration(
+                request.localIPv4Address, request.staticClientAddress)) {
+            return;
+        }
 
         mStaticIpv4ServerAddr = request.localIPv4Address;
         mStaticIpv4ClientAddr = request.staticClientAddress;

Tethering/tests/unit/src/android/net/dhcp/DhcpServingParamsParcelExtTest.java

@@ -42,7 +42,9 @@ import java.util.stream.IntStream;
 @SmallTest
 public class DhcpServingParamsParcelExtTest {
     private static final Inet4Address TEST_ADDRESS = inet4Addr("192.168.0.123");
+    private static final Inet4Address TEST_CLIENT_ADDRESS = inet4Addr("192.168.0.42");
     private static final int TEST_ADDRESS_PARCELED = 0xc0a8007b;
+    private static final int TEST_CLIENT_ADDRESS_PARCELED = 0xc0a8002a;
     private static final int TEST_PREFIX_LENGTH = 17;
     private static final int TEST_LEASE_TIME_SECS = 120;
     private static final int TEST_MTU = 1000;
@@ -105,6 +107,12 @@ public class DhcpServingParamsParcelExtTest {
         assertFalse(mParcel.metered);
     }
 
+    @Test
+    public void testSetClientAddr() {
+        mParcel.setSingleClientAddr(TEST_CLIENT_ADDRESS);
+        assertEquals(TEST_CLIENT_ADDRESS_PARCELED, mParcel.clientAddr);
+    }
+
     private static Inet4Address inet4Addr(String addr) {
         return (Inet4Address) parseNumericAddress(addr);
     }

Tethering/tests/unit/src/com/android/server/connectivity/tethering/TetheringTest.java

@@ -38,6 +38,7 @@ import static android.net.TetheringManager.TETHER_HARDWARE_OFFLOAD_FAILED;
 import static android.net.TetheringManager.TETHER_HARDWARE_OFFLOAD_STARTED;
 import static android.net.TetheringManager.TETHER_HARDWARE_OFFLOAD_STOPPED;
 import static android.net.dhcp.IDhcpServer.STATUS_SUCCESS;
+import static android.net.shared.Inet4AddressUtils.intToInet4AddressHTH;
 import static android.net.wifi.WifiManager.EXTRA_WIFI_AP_INTERFACE_NAME;
 import static android.net.wifi.WifiManager.EXTRA_WIFI_AP_MODE;
 import static android.net.wifi.WifiManager.EXTRA_WIFI_AP_STATE;
@@ -1651,10 +1652,13 @@ public class TetheringTest {
     }
 
     @Test
-    public void testRequestStaticServerIp() throws Exception {
+    public void testRequestStaticIp() throws Exception {
-        final LinkAddress serverLinkAddr = new LinkAddress("192.168.20.1/24");
+        final LinkAddress serverLinkAddr = new LinkAddress("192.168.0.123/24");
-        final LinkAddress clientLinkAddr = new LinkAddress("192.168.20.42/24");
+        final LinkAddress clientLinkAddr = new LinkAddress("192.168.0.42/24");
-        final String serverAddr = "192.168.20.1";
+        final String serverAddr = "192.168.0.123";
+        final int clientAddrParceled = 0xc0a8002a;
+        final ArgumentCaptor<DhcpServingParamsParcel> dhcpParamsCaptor =
+                ArgumentCaptor.forClass(DhcpServingParamsParcel.class);
         mTethering.startTethering(createTetheringRequestParcel(TETHERING_USB,
                   serverLinkAddr, clientLinkAddr), null);
         mLooper.dispatchAll();
@@ -1663,8 +1667,12 @@ public class TetheringTest {
         sendUsbBroadcast(true, true, true, TETHERING_USB);
         mLooper.dispatchAll();
         verify(mNetd).interfaceSetCfg(argThat(cfg -> serverAddr.equals(cfg.ipv4Addr)));
-
+        verify(mIpServerDependencies, times(1)).makeDhcpServer(any(), dhcpParamsCaptor.capture(),
-        // TODO: test static client address.
+                any());
+        final DhcpServingParamsParcel params = dhcpParamsCaptor.getValue();
+        assertEquals(serverAddr, intToInet4AddressHTH(params.serverAddr).getHostAddress());
+        assertEquals(24, params.serverAddrPrefixLength);
+        assertEquals(clientAddrParceled, params.clientAddr);
     }
 
     // TODO: Test that a request for hotspot mode doesn't interfere with an