diff --git a/core/java/android/net/IpPrefix.java b/core/java/android/net/IpPrefix.java
index b4f3a28..416157c 100644
--- a/core/java/android/net/IpPrefix.java
+++ b/core/java/android/net/IpPrefix.java
@@ -16,6 +16,7 @@
 
 package android.net;
 
+import android.annotation.IntRange;
 import android.annotation.NonNull;
 import android.annotation.SystemApi;
 import android.annotation.TestApi;
@@ -71,7 +72,7 @@
      *
      * @hide
      */
-    public IpPrefix(@NonNull byte[] address, int prefixLength) {
+    public IpPrefix(@NonNull byte[] address, @IntRange(from = 0, to = 128) int prefixLength) {
         this.address = address.clone();
         this.prefixLength = prefixLength;
         checkAndMaskAddressAndPrefixLength();
@@ -88,7 +89,7 @@
      */
     @SystemApi
     @TestApi
-    public IpPrefix(@NonNull InetAddress address, int prefixLength) {
+    public IpPrefix(@NonNull InetAddress address, @IntRange(from = 0, to = 128) int prefixLength) {
         // We don't reuse the (byte[], int) constructor because it calls clone() on the byte array,
         // which is unnecessary because getAddress() already returns a clone.
         this.address = address.getAddress();
@@ -150,13 +151,13 @@
      *
      * @return the address in the form of a byte array.
      */
-    public InetAddress getAddress() {
+    public @NonNull InetAddress getAddress() {
         try {
             return InetAddress.getByAddress(address);
         } catch (UnknownHostException e) {
             // Cannot happen. InetAddress.getByAddress can only throw an exception if the byte
             // array is the wrong length, but we check that in the constructor.
-            return null;
+            throw new IllegalArgumentException("Address is invalid");
         }
     }
 
@@ -166,7 +167,7 @@
      *
      * @return the address in the form of a byte array.
      */
-    public byte[] getRawAddress() {
+    public @NonNull byte[] getRawAddress() {
         return address.clone();
     }
 
@@ -175,6 +176,7 @@
      *
      * @return the prefix length.
      */
+    @IntRange(from = 0, to = 128)
     public int getPrefixLength() {
         return prefixLength;
     }
@@ -183,10 +185,10 @@
      * Determines whether the prefix contains the specified address.
      *
      * @param address An {@link InetAddress} to test.
-     * @return {@code true} if the prefix covers the given address.
+     * @return {@code true} if the prefix covers the given address. {@code false} otherwise.
      */
-    public boolean contains(InetAddress address) {
-        byte[] addrBytes = (address == null) ? null : address.getAddress();
+    public boolean contains(@NonNull InetAddress address) {
+        byte[] addrBytes = address.getAddress();
         if (addrBytes == null || addrBytes.length != this.address.length) {
             return false;
         }
@@ -201,7 +203,7 @@
      * @param otherPrefix the prefix to test
      * @hide
      */
-    public boolean containsPrefix(IpPrefix otherPrefix) {
+    public boolean containsPrefix(@NonNull IpPrefix otherPrefix) {
         if (otherPrefix.getPrefixLength() < prefixLength) return false;
         final byte[] otherAddress = otherPrefix.getRawAddress();
         NetworkUtils.maskRawAddress(otherAddress, prefixLength);
diff --git a/core/java/android/net/LinkAddress.java b/core/java/android/net/LinkAddress.java
index 78b4665..f17adea 100644
--- a/core/java/android/net/LinkAddress.java
+++ b/core/java/android/net/LinkAddress.java
@@ -25,6 +25,7 @@
 import static android.system.OsConstants.RT_SCOPE_SITE;
 import static android.system.OsConstants.RT_SCOPE_UNIVERSE;
 
+import android.annotation.IntRange;
 import android.annotation.NonNull;
 import android.annotation.Nullable;
 import android.annotation.SystemApi;
@@ -170,7 +171,7 @@
      * Constructs a new {@code LinkAddress} from an {@code InetAddress} and prefix length, with
      * the specified flags and scope. Flags and scope are not checked for validity.
      * @param address The IP address.
-     * @param prefixLength The prefix length.
+     * @param prefixLength The prefix length. Must be &gt;= 0 and &lt;= (32 or 128) (IPv4 or IPv6).
      * @param flags A bitmask of {@code IFA_F_*} values representing properties of the address.
      * @param scope An integer defining the scope in which the address is unique (e.g.,
      *              {@link OsConstants#RT_SCOPE_LINK} or {@link OsConstants#RT_SCOPE_SITE}).
@@ -178,7 +179,8 @@
      */
     @SystemApi
     @TestApi
-    public LinkAddress(InetAddress address, int prefixLength, int flags, int scope) {
+    public LinkAddress(@NonNull InetAddress address, @IntRange(from = 0, to = 128) int prefixLength,
+            int flags, int scope) {
         init(address, prefixLength, flags, scope);
     }
 
@@ -186,12 +188,13 @@
      * Constructs a new {@code LinkAddress} from an {@code InetAddress} and a prefix length.
      * The flags are set to zero and the scope is determined from the address.
      * @param address The IP address.
-     * @param prefixLength The prefix length.
+     * @param prefixLength The prefix length. Must be &gt;= 0 and &lt;= (32 or 128) (IPv4 or IPv6).
      * @hide
      */
     @SystemApi
     @TestApi
-    public LinkAddress(@NonNull InetAddress address, int prefixLength) {
+    public LinkAddress(@NonNull InetAddress address,
+            @IntRange(from = 0, to = 128) int prefixLength) {
         this(address, prefixLength, 0, 0);
         this.scope = scopeForUnicastAddress(address);
     }
@@ -202,7 +205,7 @@
      * @param interfaceAddress The interface address.
      * @hide
      */
-    public LinkAddress(InterfaceAddress interfaceAddress) {
+    public LinkAddress(@NonNull InterfaceAddress interfaceAddress) {
         this(interfaceAddress.getAddress(),
              interfaceAddress.getNetworkPrefixLength());
     }
@@ -306,6 +309,7 @@
     /**
      * Returns the prefix length of this {@code LinkAddress}.
      */
+    @IntRange(from = 0, to = 128)
     public int getPrefixLength() {
         return prefixLength;
     }
@@ -316,6 +320,7 @@
      * @hide
      */
     @UnsupportedAppUsage
+    @IntRange(from = 0, to = 128)
     public int getNetworkPrefixLength() {
         return getPrefixLength();
     }
diff --git a/core/java/android/net/RouteInfo.java b/core/java/android/net/RouteInfo.java
index 24d9b8e..fdd904a 100644
--- a/core/java/android/net/RouteInfo.java
+++ b/core/java/android/net/RouteInfo.java
@@ -16,6 +16,8 @@
 
 package android.net;
 
+import android.annotation.IntDef;
+import android.annotation.NonNull;
 import android.annotation.Nullable;
 import android.annotation.SystemApi;
 import android.annotation.TestApi;
@@ -24,6 +26,8 @@
 import android.os.Parcel;
 import android.os.Parcelable;
 
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
 import java.net.Inet4Address;
 import java.net.Inet6Address;
 import java.net.InetAddress;
@@ -51,20 +55,32 @@
  * (IPv4 or IPv6).
  */
 public final class RouteInfo implements Parcelable {
+    /** @hide */
+    @IntDef(value = {
+            RTN_UNICAST,
+            RTN_UNREACHABLE,
+            RTN_THROW,
+    })
+    @Retention(RetentionPolicy.SOURCE)
+    public @interface RouteType {}
+
     /**
      * The IP destination address for this route.
      */
+    @NonNull
     private final IpPrefix mDestination;
 
     /**
      * The gateway address for this route.
      */
     @UnsupportedAppUsage
+    @Nullable
     private final InetAddress mGateway;
 
     /**
      * The interface for this route.
      */
+    @Nullable
     private final String mInterface;
 
 
@@ -108,13 +124,14 @@
      * @param destination the destination prefix
      * @param gateway the IP address to route packets through
      * @param iface the interface name to send packets on
+     * @param type the type of this route
      *
      * @hide
      */
     @SystemApi
     @TestApi
     public RouteInfo(@Nullable IpPrefix destination, @Nullable InetAddress gateway,
-            @Nullable String iface, int type) {
+            @Nullable String iface, @RouteType int type) {
         switch (type) {
             case RTN_UNICAST:
             case RTN_UNREACHABLE:
@@ -173,10 +190,24 @@
     }
 
     /**
-     *  @hide
+     * Constructs a {@code RouteInfo} object.
+     *
+     * If destination is null, then gateway must be specified and the
+     * constructed route is either the IPv4 default route <code>0.0.0.0</code>
+     * if the gateway is an instance of {@link Inet4Address}, or the IPv6 default
+     * route <code>::/0</code> if gateway is an instance of {@link Inet6Address}.
+     * <p>
+     * Destination and gateway may not both be null.
+     *
+     * @param destination the destination address and prefix in an {@link IpPrefix}
+     * @param gateway the {@link InetAddress} to route packets through
+     * @param iface the interface name to send packets on
+     *
+     * @hide
      */
     @UnsupportedAppUsage
-    public RouteInfo(IpPrefix destination, InetAddress gateway, String iface) {
+    public RouteInfo(@Nullable IpPrefix destination, @Nullable InetAddress gateway,
+            @Nullable String iface) {
         this(destination, gateway, iface, RTN_UNICAST);
     }
 
@@ -184,7 +215,8 @@
      * @hide
      */
     @UnsupportedAppUsage
-    public RouteInfo(LinkAddress destination, InetAddress gateway, String iface) {
+    public RouteInfo(@Nullable LinkAddress destination, @Nullable InetAddress gateway,
+            @Nullable String iface) {
         this(destination == null ? null :
                 new IpPrefix(destination.getAddress(), destination.getPrefixLength()),
                 gateway, iface);
@@ -205,7 +237,7 @@
      *
      * @hide
      */
-    public RouteInfo(IpPrefix destination, InetAddress gateway) {
+    public RouteInfo(@Nullable IpPrefix destination, @Nullable InetAddress gateway) {
         this(destination, gateway, null);
     }
 
@@ -215,7 +247,7 @@
      * TODO: Remove this.
      */
     @UnsupportedAppUsage
-    public RouteInfo(LinkAddress destination, InetAddress gateway) {
+    public RouteInfo(@Nullable LinkAddress destination, @Nullable InetAddress gateway) {
         this(destination, gateway, null);
     }
 
@@ -227,7 +259,7 @@
      * @hide
      */
     @UnsupportedAppUsage
-    public RouteInfo(InetAddress gateway) {
+    public RouteInfo(@NonNull InetAddress gateway) {
         this((IpPrefix) null, gateway, null);
     }
 
@@ -239,35 +271,36 @@
      *
      * @hide
      */
-    public RouteInfo(IpPrefix destination) {
+    public RouteInfo(@NonNull IpPrefix destination) {
         this(destination, null, null);
     }
 
     /**
      * @hide
      */
-    public RouteInfo(LinkAddress destination) {
+    public RouteInfo(@NonNull LinkAddress destination) {
         this(destination, null, null);
     }
 
     /**
      * @hide
      */
-    public RouteInfo(IpPrefix destination, int type) {
+    public RouteInfo(@NonNull IpPrefix destination, @RouteType int type) {
         this(destination, null, null, type);
     }
 
     /**
      * @hide
      */
-    public static RouteInfo makeHostRoute(InetAddress host, String iface) {
+    public static RouteInfo makeHostRoute(@NonNull InetAddress host, @Nullable String iface) {
         return makeHostRoute(host, null, iface);
     }
 
     /**
      * @hide
      */
-    public static RouteInfo makeHostRoute(InetAddress host, InetAddress gateway, String iface) {
+    public static RouteInfo makeHostRoute(@Nullable InetAddress host, @Nullable InetAddress gateway,
+            @Nullable String iface) {
         if (host == null) return null;
 
         if (host instanceof Inet4Address) {
@@ -290,6 +323,7 @@
      *
      * @return {@link IpPrefix} specifying the destination.  This is never {@code null}.
      */
+    @NonNull
     public IpPrefix getDestination() {
         return mDestination;
     }
@@ -298,6 +332,7 @@
      * TODO: Convert callers to use IpPrefix and then remove.
      * @hide
      */
+    @NonNull
     public LinkAddress getDestinationLinkAddress() {
         return new LinkAddress(mDestination.getAddress(), mDestination.getPrefixLength());
     }
@@ -308,6 +343,7 @@
      * @return {@link InetAddress} specifying the gateway or next hop.  This may be
      *                             {@code null} for a directly-connected route."
      */
+    @Nullable
     public InetAddress getGateway() {
         return mGateway;
     }
@@ -317,6 +353,7 @@
      *
      * @return The name of the interface used for this route.
      */
+    @Nullable
     public String getInterface() {
         return mInterface;
     }
@@ -330,6 +367,7 @@
      */
     @TestApi
     @SystemApi
+    @RouteType
     public int getType() {
         return mType;
     }
@@ -401,6 +439,7 @@
      * @hide
      */
     @UnsupportedAppUsage
+    @Nullable
     public static RouteInfo selectBestRoute(Collection<RouteInfo> routes, InetAddress dest) {
         if ((routes == null) || (dest == null)) return null;
 
diff --git a/core/java/android/net/apf/ApfCapabilities.java b/core/java/android/net/apf/ApfCapabilities.java
index 17a03c7..4dd2ace 100644
--- a/core/java/android/net/apf/ApfCapabilities.java
+++ b/core/java/android/net/apf/ApfCapabilities.java
@@ -19,14 +19,17 @@
 import android.annotation.NonNull;
 import android.annotation.SystemApi;
 import android.annotation.TestApi;
-import android.content.Context;
+import android.content.res.Resources;
 import android.os.Parcel;
 import android.os.Parcelable;
 
 import com.android.internal.R;
 
 /**
- * APF program support capabilities.
+ * APF program support capabilities. APF stands for Android Packet Filtering and it is a flexible
+ * way to drop unwanted network packets to save power.
+ *
+ * See documentation at hardware/google/apf/apf.h
  *
  * This class is immutable.
  * @hide
@@ -104,10 +107,11 @@
     }
 
     /**
-     * Returns true if the APF interpreter advertises support for the data buffer access opcodes
-     * LDDW and STDW.
+     * Determines whether the APF interpreter advertises support for the data buffer access opcodes
+     * LDDW (LoaD Data Word) and STDW (STore Data Word). Full LDDW (LoaD Data Word) and
+     * STDW (STore Data Word) support is present from APFv4 on.
      *
-     * Full LDDW and STDW support is present from APFv4 on.
+     * @return {@code true} if the IWifiStaIface#readApfPacketFilterData is supported.
      */
     public boolean hasDataAccess() {
         return apfVersionSupported >= 4;
@@ -116,14 +120,14 @@
     /**
      * @return Whether the APF Filter in the device should filter out IEEE 802.3 Frames.
      */
-    public static boolean getApfDrop8023Frames(@NonNull Context context) {
-        return context.getResources().getBoolean(R.bool.config_apfDrop802_3Frames);
+    public static boolean getApfDrop8023Frames() {
+        return Resources.getSystem().getBoolean(R.bool.config_apfDrop802_3Frames);
     }
 
     /**
      * @return An array of blacklisted EtherType, packets with EtherTypes within it will be dropped.
      */
-    public static @NonNull int[] getApfEthTypeBlackList(@NonNull Context context) {
-        return context.getResources().getIntArray(R.array.config_apfEthTypeBlackList);
+    public static @NonNull int[] getApfEtherTypeBlackList() {
+        return Resources.getSystem().getIntArray(R.array.config_apfEthTypeBlackList);
     }
 }