Add a new field changePrefixOnDecline in DhcpServingParamsParcel.

A new boolean flag (changePrefixOnDecline) to be added in
the DhcpServingParamsParcel, indicating whether or not the DHCP
server should request a new prefix (e.g. a different subnet
prefix) from IpServer when receiving DHCPDECLINE message.

Bug: 130741856
Test: atest NetworkStackTests NetworkStackNextTests
Merged-In: I8cb0f844ef98a5f17d4e07e1812a1abf73aa4c07
Change-Id: I8cb0f844ef98a5f17d4e07e1812a1abf73aa4c07

4 files changed, 33 insertions, 5 deletions

diff --git a/common/networkstackclient/aidl_api/networkstack-aidl-interfaces/current/android/net/dhcp/DhcpServingParamsParcel.aidl b/common/networkstackclient/aidl_api/networkstack-aidl-interfaces/current/android/net/dhcp/DhcpServingParamsParcel.aidl
index eb780a2..657b83c 100644
--- a/common/networkstackclient/aidl_api/networkstack-aidl-interfaces/current/android/net/dhcp/DhcpServingParamsParcel.aidl
+++ b/common/networkstackclient/aidl_api/networkstack-aidl-interfaces/current/android/net/dhcp/DhcpServingParamsParcel.aidl
@@ -26,4 +26,5 @@ parcelable DhcpServingParamsParcel {
   int linkMtu;
   boolean metered;
   int clientAddr;
+  boolean changePrefixOnDecline;
 }
diff --git a/common/networkstackclient/src/android/net/dhcp/DhcpServingParamsParcel.aidl b/common/networkstackclient/src/android/net/dhcp/DhcpServingParamsParcel.aidl
index 5e19374..1ba0195 100644
--- a/common/networkstackclient/src/android/net/dhcp/DhcpServingParamsParcel.aidl
+++ b/common/networkstackclient/src/android/net/dhcp/DhcpServingParamsParcel.aidl
@@ -27,5 +27,5 @@ parcelable DhcpServingParamsParcel {
     int linkMtu;
     boolean metered;
     int clientAddr;
+    boolean changePrefixOnDecline;
 }
-
diff --git a/src/android/net/dhcp/DhcpServingParams.java b/src/android/net/dhcp/DhcpServingParams.java
index 63f847d..c52cae9 100644
--- a/src/android/net/dhcp/DhcpServingParams.java
+++ b/src/android/net/dhcp/DhcpServingParams.java
@@ -91,6 +91,13 @@ public class DhcpServingParams {
     public final Inet4Address clientAddr;
 
     /**
+     * Indicates whether the DHCP server should request a new prefix from IpServer when receiving
+     * DHCPDECLINE message in certain particular link (e.g. there is only one downstream USB
+     * tethering client). If it's false, process DHCPDECLINE message as RFC2131#4.3.3 suggests.
+     */
+    public final boolean changePrefixOnDecline;
+
+    /**
      * Checked exception thrown when some parameters used to build {@link DhcpServingParams} are
      * missing or invalid.
      */
@@ -103,7 +110,8 @@ public class DhcpServingParams {
     private DhcpServingParams(@NonNull LinkAddress serverAddr,
             @NonNull Set<Inet4Address> defaultRouters,
             @NonNull Set<Inet4Address> dnsServers, @NonNull Set<Inet4Address> excludedAddrs,
-            long dhcpLeaseTimeSecs, int linkMtu, boolean metered, Inet4Address clientAddr) {
+            long dhcpLeaseTimeSecs, int linkMtu, boolean metered, Inet4Address clientAddr,
+            boolean changePrefixOnDecline) {
         this.serverAddr = serverAddr;
         this.defaultRouters = defaultRouters;
         this.dnsServers = dnsServers;
@@ -112,6 +120,7 @@ public class DhcpServingParams {
         this.linkMtu = linkMtu;
         this.metered = metered;
         this.clientAddr = clientAddr;
+        this.changePrefixOnDecline = changePrefixOnDecline;
     }
 
     /**
@@ -140,6 +149,7 @@ public class DhcpServingParams {
                 .setLinkMtu(parcel.linkMtu)
                 .setMetered(parcel.metered)
                 .setClientAddr(clientAddr)
+                .setChangePrefixOnDecline(parcel.changePrefixOnDecline)
                 .build();
     }
 
@@ -195,6 +205,7 @@ public class DhcpServingParams {
         private int mLinkMtu = MTU_UNSET;
         private boolean mMetered;
         private Inet4Address mClientAddr;
+        private boolean mChangePrefixOnDecline;
 
         /**
          * Set the server address and served prefix for the DHCP server.
@@ -329,6 +340,17 @@ public class DhcpServingParams {
         }
 
         /**
+         * Set whether the DHCP server should request a new prefix from IpServer when receiving
+         * DHCPDECLINE message in certain particular link.
+         *
+         * <p>If not set, the default value is false.
+         */
+        public Builder setChangePrefixOnDecline(boolean changePrefixOnDecline) {
+            this.mChangePrefixOnDecline = changePrefixOnDecline;
+            return this;
+        }
+
+        /**
          * Create a new {@link DhcpServingParams} instance based on parameters set in the builder.
          *
          * <p>This method has no side-effects. If it does not throw, a valid
@@ -382,7 +404,7 @@ public class DhcpServingParams {
                     Collections.unmodifiableSet(new HashSet<>(mDefaultRouters)),
                     Collections.unmodifiableSet(new HashSet<>(mDnsServers)),
                     Collections.unmodifiableSet(excl),
-                    mDhcpLeaseTimeSecs, mLinkMtu, mMetered, mClientAddr);
+                    mDhcpLeaseTimeSecs, mLinkMtu, mMetered, mClientAddr, mChangePrefixOnDecline);
         }
     }
 
diff --git a/tests/unit/src/android/net/dhcp/DhcpServingParamsTest.java b/tests/unit/src/android/net/dhcp/DhcpServingParamsTest.java
index 9948fe3..5962696 100644
--- a/tests/unit/src/android/net/dhcp/DhcpServingParamsTest.java
+++ b/tests/unit/src/android/net/dhcp/DhcpServingParamsTest.java
@@ -63,6 +63,7 @@ public class DhcpServingParamsTest {
     private static final Set<Inet4Address> TEST_EXCLUDED_ADDRS = new HashSet<>(
             Arrays.asList(parseAddr("192.168.0.200"), parseAddr("192.168.0.201")));
     private static final boolean TEST_METERED = true;
+    private static final boolean TEST_CHANGE_PREFIX_ON_DECLINE = true;
 
     @Before
     public void setUp() {
@@ -74,7 +75,8 @@ public class DhcpServingParamsTest {
                 .setLinkMtu(TEST_MTU)
                 .setExcludedAddrs(TEST_EXCLUDED_ADDRS)
                 .setMetered(TEST_METERED)
-                .setClientAddr(TEST_CLIENT_ADDR);
+                .setClientAddr(TEST_CLIENT_ADDR)
+                .setChangePrefixOnDecline(TEST_CHANGE_PREFIX_ON_DECLINE);
     }
 
     @Test
@@ -101,6 +103,7 @@ public class DhcpServingParamsTest {
         assertEquals(TEST_LINKADDR, params.serverAddr);
         assertEquals(TEST_MTU, params.linkMtu);
         assertEquals(TEST_METERED, params.metered);
+        assertEquals(TEST_CHANGE_PREFIX_ON_DECLINE, params.changePrefixOnDecline);
 
         assertContains(params.excludedAddrs, TEST_EXCLUDED_ADDRS);
         assertContains(params.excludedAddrs, TEST_DEFAULT_ROUTERS);
@@ -182,6 +185,7 @@ public class DhcpServingParamsTest {
         parcel.excludedAddrs = toIntArray(TEST_EXCLUDED_ADDRS);
         parcel.metered = TEST_METERED;
         parcel.clientAddr = inet4AddressToIntHTH(TEST_CLIENT_ADDR);
+        parcel.changePrefixOnDecline = TEST_CHANGE_PREFIX_ON_DECLINE;
         final DhcpServingParams parceled = DhcpServingParams.fromParcelableObject(parcel);
 
         assertEquals(params.defaultRouters, parceled.defaultRouters);
@@ -192,8 +196,9 @@ public class DhcpServingParamsTest {
         assertEquals(params.excludedAddrs, parceled.excludedAddrs);
         assertEquals(params.metered, parceled.metered);
         assertEquals(params.clientAddr, parceled.clientAddr);
+        assertEquals(params.changePrefixOnDecline, parceled.changePrefixOnDecline);
 
-        MiscAssertsKt.assertFieldCountEquals(9, DhcpServingParamsParcel.class);
+        MiscAssertsKt.assertFieldCountEquals(10, DhcpServingParamsParcel.class);
     }
 
     @Test(expected = InvalidParameterException.class)