3 files changed, 42 insertions, 9 deletions
diff --git a/src/android/net/dhcp/DhcpLeaseRepository.java b/src/android/net/dhcp/DhcpLeaseRepository.java
index d0dc389..3639a2d 100644
--- a/src/android/net/dhcp/DhcpLeaseRepository.java
+++ b/src/android/net/dhcp/DhcpLeaseRepository.java
@@ -80,6 +80,8 @@ class DhcpLeaseRepository {
     private int mSubnetMask;
     private int mNumAddresses;
     private long mLeaseTimeMs;
+    @Nullable
+    private Inet4Address mClientAddr;
 
     /**
      * Next timestamp when committed or declined leases should be checked for expired ones. This
@@ -128,21 +130,24 @@ class DhcpLeaseRepository {
     private final LinkedHashMap<Inet4Address, Long> mDeclinedAddrs = new LinkedHashMap<>();
 
     DhcpLeaseRepository(@NonNull IpPrefix prefix, @NonNull Set<Inet4Address> reservedAddrs,
-            long leaseTimeMs, @NonNull SharedLog log, @NonNull Clock clock) {
-        updateParams(prefix, reservedAddrs, leaseTimeMs);
+            long leaseTimeMs, @Nullable Inet4Address clientAddr, @NonNull SharedLog log,
+            @NonNull Clock clock) {
         mLog = log;
         mClock = clock;
+        mClientAddr = clientAddr;
+        updateParams(prefix, reservedAddrs, leaseTimeMs, clientAddr);
     }
 
     public void updateParams(@NonNull IpPrefix prefix, @NonNull Set<Inet4Address> reservedAddrs,
-            long leaseTimeMs) {
+            long leaseTimeMs, @Nullable Inet4Address clientAddr) {
         mPrefix = prefix;
         mReservedAddrs = Collections.unmodifiableSet(new HashSet<>(reservedAddrs));
         mPrefixLength = prefix.getPrefixLength();
         mSubnetMask = prefixLengthToV4NetmaskIntHTH(mPrefixLength);
         mSubnetAddr = inet4AddressToIntHTH((Inet4Address) prefix.getAddress()) & mSubnetMask;
-        mNumAddresses = 1 << (IPV4_ADDR_BITS - prefix.getPrefixLength());
+        mNumAddresses = clientAddr != null ? 1 : 1 << (IPV4_ADDR_BITS - prefix.getPrefixLength());
         mLeaseTimeMs = leaseTimeMs;
+        mClientAddr = clientAddr;
 
         cleanMap(mDeclinedAddrs);
         if (cleanMap(mCommittedLeases)) {
@@ -514,6 +519,9 @@ class DhcpLeaseRepository {
      * address (with the ordering in {@link #getAddrIndex(int)}) is returned.
      */
     private int getValidAddress(int addr) {
+        // Only mClientAddr is valid if static client address is enforced.
+        if (mClientAddr != null) return inet4AddressToIntHTH(mClientAddr);
+
         final int lastByteMask = 0xff;
         int addrIndex = getAddrIndex(addr); // 0-based index of the address in the subnet
 
diff --git a/src/android/net/dhcp/DhcpServer.java b/src/android/net/dhcp/DhcpServer.java
index 064aa5d..429b10c 100644
--- a/src/android/net/dhcp/DhcpServer.java
+++ b/src/android/net/dhcp/DhcpServer.java
@@ -205,8 +205,8 @@ public class DhcpServer extends IDhcpServer.Stub {
                 @NonNull SharedLog log, @NonNull Clock clock) {
             return new DhcpLeaseRepository(
                     DhcpServingParams.makeIpPrefix(servingParams.serverAddr),
-                    servingParams.excludedAddrs,
-                    servingParams.dhcpLeaseTimeSecs * 1000, log.forSubComponent(REPO_TAG), clock);
+                    servingParams.excludedAddrs, servingParams.dhcpLeaseTimeSecs * 1000,
+                    servingParams.clientAddr, log.forSubComponent(REPO_TAG), clock);
         }
 
         @Override
@@ -351,7 +351,8 @@ public class DhcpServer extends IDhcpServer.Stub {
                     mLeaseRepo.updateParams(
                             DhcpServingParams.makeIpPrefix(mServingParams.serverAddr),
                             params.excludedAddrs,
-                            params.dhcpLeaseTimeSecs);
+                            params.dhcpLeaseTimeSecs,
+                            params.clientAddr);
 
                     cb = pair.second;
                     break;
diff --git a/src/android/net/dhcp/DhcpServingParams.java b/src/android/net/dhcp/DhcpServingParams.java
index eafe44e..63f847d 100644
--- a/src/android/net/dhcp/DhcpServingParams.java
+++ b/src/android/net/dhcp/DhcpServingParams.java
@@ -85,6 +85,12 @@ public class DhcpServingParams {
     public final boolean metered;
 
     /**
+     * Client inet address. This will be the only address offered by DhcpServer if set.
+     */
+    @Nullable
+    public final Inet4Address clientAddr;
+
+    /**
      * Checked exception thrown when some parameters used to build {@link DhcpServingParams} are
      * missing or invalid.
      */
@@ -97,7 +103,7 @@ 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) {
+            long dhcpLeaseTimeSecs, int linkMtu, boolean metered, Inet4Address clientAddr) {
         this.serverAddr = serverAddr;
         this.defaultRouters = defaultRouters;
         this.dnsServers = dnsServers;
@@ -105,6 +111,7 @@ public class DhcpServingParams {
         this.dhcpLeaseTimeSecs = dhcpLeaseTimeSecs;
         this.linkMtu = linkMtu;
         this.metered = metered;
+        this.clientAddr = clientAddr;
     }
 
     /**
@@ -119,6 +126,11 @@ public class DhcpServingParams {
         final LinkAddress serverAddr = new LinkAddress(
                 intToInet4AddressHTH(parcel.serverAddr),
                 parcel.serverAddrPrefixLength);
+        Inet4Address clientAddr = null;
+        if (parcel.clientAddr != 0) {
+            clientAddr = intToInet4AddressHTH(parcel.clientAddr);
+        }
+
         return new Builder()
                 .setServerAddr(serverAddr)
                 .setDefaultRouters(toInet4AddressSet(parcel.defaultRouters))
@@ -127,6 +139,7 @@ public class DhcpServingParams {
                 .setDhcpLeaseTimeSecs(parcel.dhcpLeaseTimeSecs)
                 .setLinkMtu(parcel.linkMtu)
                 .setMetered(parcel.metered)
+                .setClientAddr(clientAddr)
                 .build();
     }
 
@@ -181,6 +194,7 @@ public class DhcpServingParams {
         private long mDhcpLeaseTimeSecs;
         private int mLinkMtu = MTU_UNSET;
         private boolean mMetered;
+        private Inet4Address mClientAddr;
 
         /**
          * Set the server address and served prefix for the DHCP server.
@@ -305,6 +319,16 @@ public class DhcpServingParams {
         }
 
         /**
+         * Set the client address.
+         *
+         * <p>If not set, the default value is null.
+         */
+        public Builder setClientAddr(@Nullable Inet4Address clientAddr) {
+            this.mClientAddr = clientAddr;
+            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
@@ -358,7 +382,7 @@ public class DhcpServingParams {
                     Collections.unmodifiableSet(new HashSet<>(mDefaultRouters)),
                     Collections.unmodifiableSet(new HashSet<>(mDnsServers)),
                     Collections.unmodifiableSet(excl),
-                    mDhcpLeaseTimeSecs, mLinkMtu, mMetered);
+                    mDhcpLeaseTimeSecs, mLinkMtu, mMetered, mClientAddr);
         }
     }