diff --git a/core/java/android/net/IpPrefix.java b/core/java/android/net/IpPrefix.java
index 6e2654e..4631c56 100644
--- a/core/java/android/net/IpPrefix.java
+++ b/core/java/android/net/IpPrefix.java
@@ -25,6 +25,7 @@
 import java.net.InetAddress;
 import java.net.UnknownHostException;
 import java.util.Arrays;
+import java.util.Comparator;
 
 /**
  * This class represents an IP prefix, i.e., a contiguous block of IP addresses aligned on a
@@ -187,6 +188,20 @@
     }
 
     /**
+     * Returns whether the specified prefix is entirely contained in this prefix.
+     *
+     * Note this is mathematical inclusion, so a prefix is always contained within itself.
+     * @param otherPrefix the prefix to test
+     * @hide
+     */
+    public boolean containsPrefix(IpPrefix otherPrefix) {
+        if (otherPrefix.getPrefixLength() < prefixLength) return false;
+        final byte[] otherAddress = otherPrefix.getRawAddress();
+        NetworkUtils.maskRawAddress(otherAddress, prefixLength);
+        return Arrays.equals(otherAddress, address);
+    }
+
+    /**
      * @hide
      */
     public boolean isIPv6() {
@@ -230,6 +245,38 @@
     }
 
     /**
+     * Returns a comparator ordering IpPrefixes by length, shorter to longer.
+     * Contents of the address will break ties.
+     * @hide
+     */
+    public static Comparator<IpPrefix> lengthComparator() {
+        return new Comparator<IpPrefix>() {
+            @Override
+            public int compare(IpPrefix prefix1, IpPrefix prefix2) {
+                if (prefix1.isIPv4()) {
+                    if (prefix2.isIPv6()) return -1;
+                } else {
+                    if (prefix2.isIPv4()) return 1;
+                }
+                final int p1len = prefix1.getPrefixLength();
+                final int p2len = prefix2.getPrefixLength();
+                if (p1len < p2len) return -1;
+                if (p2len < p1len) return 1;
+                final byte[] a1 = prefix1.address;
+                final byte[] a2 = prefix2.address;
+                final int len = a1.length < a2.length ? a1.length : a2.length;
+                for (int i = 0; i < len; ++i) {
+                    if (a1[i] < a2[i]) return -1;
+                    if (a1[i] > a2[i]) return 1;
+                }
+                if (a2.length < len) return 1;
+                if (a1.length < len) return -1;
+                return 0;
+            }
+        };
+    }
+
+    /**
      * Implement the Parcelable interface.
      */
     public static final Creator<IpPrefix> CREATOR =
diff --git a/core/java/android/net/NetworkUtils.java b/core/java/android/net/NetworkUtils.java
index fe9563d..9a5d502 100644
--- a/core/java/android/net/NetworkUtils.java
+++ b/core/java/android/net/NetworkUtils.java
@@ -16,19 +16,20 @@
 
 package android.net;
 
-import java.io.FileDescriptor;
-import java.net.InetAddress;
-import java.net.Inet4Address;
-import java.net.Inet6Address;
-import java.net.SocketException;
-import java.net.UnknownHostException;
-import java.util.Collection;
-import java.util.Locale;
-
 import android.os.Parcel;
 import android.util.Log;
 import android.util.Pair;
 
+import java.io.FileDescriptor;
+import java.math.BigInteger;
+import java.net.Inet4Address;
+import java.net.Inet6Address;
+import java.net.InetAddress;
+import java.net.SocketException;
+import java.net.UnknownHostException;
+import java.util.Collection;
+import java.util.Locale;
+import java.util.TreeSet;
 
 /**
  * Native methods for managing network interfaces.
@@ -385,4 +386,72 @@
         result = builder.toString();
         return result;
     }
+
+    /**
+     * Returns a prefix set without overlaps.
+     *
+     * This expects the src set to be sorted from shorter to longer. Results are undefined
+     * failing this condition. The returned prefix set is sorted in the same order as the
+     * passed set, with the same comparator.
+     */
+    private static TreeSet<IpPrefix> deduplicatePrefixSet(final TreeSet<IpPrefix> src) {
+        final TreeSet<IpPrefix> dst = new TreeSet<>(src.comparator());
+        // Prefixes match addresses that share their upper part up to their length, therefore
+        // the only kind of possible overlap in two prefixes is strict inclusion of the longer
+        // (more restrictive) in the shorter (including equivalence if they have the same
+        // length).
+        // Because prefixes in the src set are sorted from shorter to longer, deduplicating
+        // is done by simply iterating in order, and not adding any longer prefix that is
+        // already covered by a shorter one.
+        newPrefixes:
+        for (IpPrefix newPrefix : src) {
+            for (IpPrefix existingPrefix : dst) {
+                if (existingPrefix.containsPrefix(newPrefix)) {
+                    continue newPrefixes;
+                }
+            }
+            dst.add(newPrefix);
+        }
+        return dst;
+    }
+
+    /**
+     * Returns how many IPv4 addresses match any of the prefixes in the passed ordered set.
+     *
+     * Obviously this returns an integral value between 0 and 2**32.
+     * The behavior is undefined if any of the prefixes is not an IPv4 prefix or if the
+     * set is not ordered smallest prefix to longer prefix.
+     *
+     * @param prefixes the set of prefixes, ordered by length
+     */
+    public static long routedIPv4AddressCount(final TreeSet<IpPrefix> prefixes) {
+        long routedIPCount = 0;
+        for (final IpPrefix prefix : deduplicatePrefixSet(prefixes)) {
+            if (!prefix.isIPv4()) {
+                Log.wtf(TAG, "Non-IPv4 prefix in routedIPv4AddressCount");
+            }
+            int rank = 32 - prefix.getPrefixLength();
+            routedIPCount += 1L << rank;
+        }
+        return routedIPCount;
+    }
+
+    /**
+     * Returns how many IPv6 addresses match any of the prefixes in the passed ordered set.
+     *
+     * This returns a BigInteger between 0 and 2**128.
+     * The behavior is undefined if any of the prefixes is not an IPv6 prefix or if the
+     * set is not ordered smallest prefix to longer prefix.
+     */
+    public static BigInteger routedIPv6AddressCount(final TreeSet<IpPrefix> prefixes) {
+        BigInteger routedIPCount = BigInteger.ZERO;
+        for (final IpPrefix prefix : deduplicatePrefixSet(prefixes)) {
+            if (!prefix.isIPv6()) {
+                Log.wtf(TAG, "Non-IPv6 prefix in routedIPv6AddressCount");
+            }
+            int rank = 128 - prefix.getPrefixLength();
+            routedIPCount = routedIPCount.add(BigInteger.ONE.shiftLeft(rank));
+        }
+        return routedIPCount;
+    }
 }
diff --git a/tests/net/java/android/net/IpPrefixTest.java b/tests/net/java/android/net/IpPrefixTest.java
index b5b2c07..1f1ba2e 100644
--- a/tests/net/java/android/net/IpPrefixTest.java
+++ b/tests/net/java/android/net/IpPrefixTest.java
@@ -223,14 +223,14 @@
     }
 
     @Test
-    public void testContains() {
+    public void testContainsInetAddress() {
         IpPrefix p = new IpPrefix("2001:db8:f00::ace:d00d/127");
         assertTrue(p.contains(Address("2001:db8:f00::ace:d00c")));
         assertTrue(p.contains(Address("2001:db8:f00::ace:d00d")));
         assertFalse(p.contains(Address("2001:db8:f00::ace:d00e")));
         assertFalse(p.contains(Address("2001:db8:f00::bad:d00d")));
         assertFalse(p.contains(Address("2001:4868:4860::8888")));
-        assertFalse(p.contains(null));
+        assertFalse(p.contains((InetAddress)null));
         assertFalse(p.contains(Address("8.8.8.8")));
 
         p = new IpPrefix("192.0.2.0/23");
@@ -251,6 +251,53 @@
     }
 
     @Test
+    public void testContainsIpPrefix() {
+        assertTrue(new IpPrefix("0.0.0.0/0").containsPrefix(new IpPrefix("0.0.0.0/0")));
+        assertTrue(new IpPrefix("0.0.0.0/0").containsPrefix(new IpPrefix("1.2.3.4/0")));
+        assertTrue(new IpPrefix("0.0.0.0/0").containsPrefix(new IpPrefix("1.2.3.4/8")));
+        assertTrue(new IpPrefix("0.0.0.0/0").containsPrefix(new IpPrefix("1.2.3.4/24")));
+        assertTrue(new IpPrefix("0.0.0.0/0").containsPrefix(new IpPrefix("1.2.3.4/23")));
+
+        assertTrue(new IpPrefix("1.2.3.4/8").containsPrefix(new IpPrefix("1.2.3.4/8")));
+        assertTrue(new IpPrefix("1.2.3.4/8").containsPrefix(new IpPrefix("1.254.12.9/8")));
+        assertTrue(new IpPrefix("1.2.3.4/21").containsPrefix(new IpPrefix("1.2.3.4/21")));
+        assertTrue(new IpPrefix("1.2.3.4/32").containsPrefix(new IpPrefix("1.2.3.4/32")));
+
+        assertTrue(new IpPrefix("1.2.3.4/20").containsPrefix(new IpPrefix("1.2.3.0/24")));
+
+        assertFalse(new IpPrefix("1.2.3.4/32").containsPrefix(new IpPrefix("1.2.3.5/32")));
+        assertFalse(new IpPrefix("1.2.3.4/8").containsPrefix(new IpPrefix("2.2.3.4/8")));
+        assertFalse(new IpPrefix("0.0.0.0/16").containsPrefix(new IpPrefix("0.0.0.0/15")));
+        assertFalse(new IpPrefix("100.0.0.0/8").containsPrefix(new IpPrefix("99.0.0.0/8")));
+
+        assertTrue(new IpPrefix("::/0").containsPrefix(new IpPrefix("::/0")));
+        assertTrue(new IpPrefix("::/0").containsPrefix(new IpPrefix("2001:db8::f00/1")));
+        assertTrue(new IpPrefix("::/0").containsPrefix(new IpPrefix("3d8a:661:a0::770/8")));
+        assertTrue(new IpPrefix("::/0").containsPrefix(new IpPrefix("2001:db8::f00/8")));
+        assertTrue(new IpPrefix("::/0").containsPrefix(new IpPrefix("2001:db8::f00/64")));
+        assertTrue(new IpPrefix("::/0").containsPrefix(new IpPrefix("2001:db8::f00/113")));
+        assertTrue(new IpPrefix("::/0").containsPrefix(new IpPrefix("2001:db8::f00/128")));
+
+        assertTrue(new IpPrefix("2001:db8:f00::ace:d00d/64").containsPrefix(
+                new IpPrefix("2001:db8:f00::ace:d00d/64")));
+        assertTrue(new IpPrefix("2001:db8:f00::ace:d00d/64").containsPrefix(
+                new IpPrefix("2001:db8:f00::ace:d00d/120")));
+        assertFalse(new IpPrefix("2001:db8:f00::ace:d00d/64").containsPrefix(
+                new IpPrefix("2001:db8:f00::ace:d00d/32")));
+        assertFalse(new IpPrefix("2001:db8:f00::ace:d00d/64").containsPrefix(
+                new IpPrefix("2006:db8:f00::ace:d00d/96")));
+
+        assertTrue(new IpPrefix("2001:db8:f00::ace:d00d/128").containsPrefix(
+                new IpPrefix("2001:db8:f00::ace:d00d/128")));
+        assertTrue(new IpPrefix("2001:db8:f00::ace:d00d/100").containsPrefix(
+                new IpPrefix("2001:db8:f00::ace:ccaf/110")));
+
+        assertFalse(new IpPrefix("2001:db8:f00::ace:d00d/128").containsPrefix(
+                new IpPrefix("2001:db8:f00::ace:d00e/128")));
+        assertFalse(new IpPrefix("::/30").containsPrefix(new IpPrefix("::/29")));
+    }
+
+    @Test
     public void testHashCode() {
         IpPrefix p = new IpPrefix(new byte[4], 0);
         Random random = new Random();
diff --git a/tests/net/java/android/net/NetworkUtilsTest.java b/tests/net/java/android/net/NetworkUtilsTest.java
index 8d51c3b..a5ee8e3 100644
--- a/tests/net/java/android/net/NetworkUtilsTest.java
+++ b/tests/net/java/android/net/NetworkUtilsTest.java
@@ -19,8 +19,10 @@
 import android.net.NetworkUtils;
 import android.test.suitebuilder.annotation.SmallTest;
 
+import java.math.BigInteger;
 import java.net.Inet4Address;
 import java.net.InetAddress;
+import java.util.TreeSet;
 
 import junit.framework.TestCase;
 
@@ -67,4 +69,101 @@
         assertInvalidNetworkMask(IPv4Address("255.255.255.253"));
         assertInvalidNetworkMask(IPv4Address("255.255.0.255"));
     }
+
+    @SmallTest
+    public void testRoutedIPv4AddressCount() {
+        final TreeSet<IpPrefix> set = new TreeSet<>(IpPrefix.lengthComparator());
+        // No routes routes to no addresses.
+        assertEquals(0, NetworkUtils.routedIPv4AddressCount(set));
+
+        set.add(new IpPrefix("0.0.0.0/0"));
+        assertEquals(1l << 32, NetworkUtils.routedIPv4AddressCount(set));
+
+        set.add(new IpPrefix("20.18.0.0/16"));
+        set.add(new IpPrefix("20.18.0.0/24"));
+        set.add(new IpPrefix("20.18.0.0/8"));
+        // There is a default route, still covers everything
+        assertEquals(1l << 32, NetworkUtils.routedIPv4AddressCount(set));
+
+        set.clear();
+        set.add(new IpPrefix("20.18.0.0/24"));
+        set.add(new IpPrefix("20.18.0.0/8"));
+        // The 8-length includes the 24-length prefix
+        assertEquals(1l << 24, NetworkUtils.routedIPv4AddressCount(set));
+
+        set.add(new IpPrefix("10.10.10.126/25"));
+        // The 8-length does not include this 25-length prefix
+        assertEquals((1l << 24) + (1 << 7), NetworkUtils.routedIPv4AddressCount(set));
+
+        set.clear();
+        set.add(new IpPrefix("1.2.3.4/32"));
+        set.add(new IpPrefix("1.2.3.4/32"));
+        set.add(new IpPrefix("1.2.3.4/32"));
+        set.add(new IpPrefix("1.2.3.4/32"));
+        assertEquals(1l, NetworkUtils.routedIPv4AddressCount(set));
+
+        set.add(new IpPrefix("1.2.3.5/32"));
+        set.add(new IpPrefix("1.2.3.6/32"));
+
+        set.add(new IpPrefix("1.2.3.7/32"));
+        set.add(new IpPrefix("1.2.3.8/32"));
+        set.add(new IpPrefix("1.2.3.9/32"));
+        set.add(new IpPrefix("1.2.3.0/32"));
+        assertEquals(7l, NetworkUtils.routedIPv4AddressCount(set));
+
+        // 1.2.3.4/30 eats 1.2.3.{4-7}/32
+        set.add(new IpPrefix("1.2.3.4/30"));
+        set.add(new IpPrefix("6.2.3.4/28"));
+        set.add(new IpPrefix("120.2.3.4/16"));
+        assertEquals(7l - 4 + 4 + 16 + 65536, NetworkUtils.routedIPv4AddressCount(set));
+    }
+
+    @SmallTest
+    public void testRoutedIPv6AddressCount() {
+        final TreeSet<IpPrefix> set = new TreeSet<>(IpPrefix.lengthComparator());
+        // No routes routes to no addresses.
+        assertEquals(BigInteger.ZERO, NetworkUtils.routedIPv6AddressCount(set));
+
+        set.add(new IpPrefix("::/0"));
+        assertEquals(BigInteger.ONE.shiftLeft(128), NetworkUtils.routedIPv6AddressCount(set));
+
+        set.add(new IpPrefix("1234:622a::18/64"));
+        set.add(new IpPrefix("add4:f00:80:f7:1111::6adb/96"));
+        set.add(new IpPrefix("add4:f00:80:f7:1111::6adb/8"));
+        // There is a default route, still covers everything
+        assertEquals(BigInteger.ONE.shiftLeft(128), NetworkUtils.routedIPv6AddressCount(set));
+
+        set.clear();
+        set.add(new IpPrefix("add4:f00:80:f7:1111::6adb/96"));
+        set.add(new IpPrefix("add4:f00:80:f7:1111::6adb/8"));
+        // The 8-length includes the 96-length prefix
+        assertEquals(BigInteger.ONE.shiftLeft(120), NetworkUtils.routedIPv6AddressCount(set));
+
+        set.add(new IpPrefix("10::26/64"));
+        // The 8-length does not include this 64-length prefix
+        assertEquals(BigInteger.ONE.shiftLeft(120).add(BigInteger.ONE.shiftLeft(64)),
+                NetworkUtils.routedIPv6AddressCount(set));
+
+        set.clear();
+        set.add(new IpPrefix("add4:f00:80:f7:1111::6ad4/128"));
+        set.add(new IpPrefix("add4:f00:80:f7:1111::6ad4/128"));
+        set.add(new IpPrefix("add4:f00:80:f7:1111::6ad4/128"));
+        set.add(new IpPrefix("add4:f00:80:f7:1111::6ad4/128"));
+        assertEquals(BigInteger.ONE, NetworkUtils.routedIPv6AddressCount(set));
+
+        set.add(new IpPrefix("add4:f00:80:f7:1111::6ad5/128"));
+        set.add(new IpPrefix("add4:f00:80:f7:1111::6ad6/128"));
+        set.add(new IpPrefix("add4:f00:80:f7:1111::6ad7/128"));
+        set.add(new IpPrefix("add4:f00:80:f7:1111::6ad8/128"));
+        set.add(new IpPrefix("add4:f00:80:f7:1111::6ad9/128"));
+        set.add(new IpPrefix("add4:f00:80:f7:1111::6ad0/128"));
+        assertEquals(BigInteger.valueOf(7), NetworkUtils.routedIPv6AddressCount(set));
+
+        // add4:f00:80:f7:1111::6ad4/126 eats add4:f00:8[:f7:1111::6ad{4-7}/128
+        set.add(new IpPrefix("add4:f00:80:f7:1111::6ad4/126"));
+        set.add(new IpPrefix("d00d:f00:80:f7:1111::6ade/124"));
+        set.add(new IpPrefix("f00b:a33::/112"));
+        assertEquals(BigInteger.valueOf(7l - 4 + 4 + 16 + 65536),
+                NetworkUtils.routedIPv6AddressCount(set));
+    }
 }
diff --git a/tests/net/java/com/android/server/connectivity/VpnTest.java b/tests/net/java/com/android/server/connectivity/VpnTest.java
index 1dbf9b2..f59850d 100644
--- a/tests/net/java/com/android/server/connectivity/VpnTest.java
+++ b/tests/net/java/com/android/server/connectivity/VpnTest.java
@@ -57,9 +57,13 @@
 import android.content.pm.UserInfo;
 import android.content.res.Resources;
 import android.net.ConnectivityManager;
+import android.net.IConnectivityManager;
+import android.net.IpPrefix;
+import android.net.LinkProperties;
 import android.net.Network;
 import android.net.NetworkCapabilities;
 import android.net.NetworkInfo.DetailedState;
+import android.net.RouteInfo;
 import android.net.UidRange;
 import android.net.VpnService;
 import android.os.Build.VERSION_CODES;
@@ -90,7 +94,8 @@
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Set;
-
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
 
 /**
  * Tests for {@link Vpn}.
@@ -563,4 +568,75 @@
             return networks.get(network);
         }).when(mConnectivityManager).getNetworkCapabilities(any());
     }
+
+    // Need multiple copies of this, but Java's Stream objects can't be reused or
+    // duplicated.
+    private Stream<String> publicIpV4Routes() {
+        return Stream.of(
+                "0.0.0.0/5", "8.0.0.0/7", "11.0.0.0/8", "12.0.0.0/6", "16.0.0.0/4",
+                "32.0.0.0/3", "64.0.0.0/2", "128.0.0.0/3", "160.0.0.0/5", "168.0.0.0/6",
+                "172.0.0.0/12", "172.32.0.0/11", "172.64.0.0/10", "172.128.0.0/9",
+                "173.0.0.0/8", "174.0.0.0/7", "176.0.0.0/4", "192.0.0.0/9", "192.128.0.0/11",
+                "192.160.0.0/13", "192.169.0.0/16", "192.170.0.0/15", "192.172.0.0/14",
+                "192.176.0.0/12", "192.192.0.0/10", "193.0.0.0/8", "194.0.0.0/7",
+                "196.0.0.0/6", "200.0.0.0/5", "208.0.0.0/4");
+    }
+
+    private Stream<String> publicIpV6Routes() {
+        return Stream.of(
+                "::/1", "8000::/2", "c000::/3", "e000::/4", "f000::/5", "f800::/6",
+                "fe00::/8", "2605:ef80:e:af1d::/64");
+    }
+
+    @Test
+    public void testProvidesRoutesToMostDestinations() {
+        final LinkProperties lp = new LinkProperties();
+
+        // Default route provides routes to all IPv4 destinations.
+        lp.addRoute(new RouteInfo(new IpPrefix("0.0.0.0/0")));
+        assertTrue(Vpn.providesRoutesToMostDestinations(lp));
+
+        // Empty LP provides routes to no destination
+        lp.clear();
+        assertFalse(Vpn.providesRoutesToMostDestinations(lp));
+
+        // All IPv4 routes except for local networks. This is the case most relevant
+        // to this function. It provides routes to almost the entire space.
+        // (clone the stream so that we can reuse it later)
+        publicIpV4Routes().forEach(s -> lp.addRoute(new RouteInfo(new IpPrefix(s))));
+        assertTrue(Vpn.providesRoutesToMostDestinations(lp));
+
+        // Removing a 16-bit prefix, which is 65536 addresses. This is still enough to
+        // provide routes to "most" destinations.
+        lp.removeRoute(new RouteInfo(new IpPrefix("192.169.0.0/16")));
+        assertTrue(Vpn.providesRoutesToMostDestinations(lp));
+
+        // Remove the /2 route, which represent a quarter of the available routing space.
+        // This LP does not provides routes to "most" destinations any more.
+        lp.removeRoute(new RouteInfo(new IpPrefix("64.0.0.0/2")));
+        assertFalse(Vpn.providesRoutesToMostDestinations(lp));
+
+        lp.clear();
+        publicIpV6Routes().forEach(s -> lp.addRoute(new RouteInfo(new IpPrefix(s))));
+        assertTrue(Vpn.providesRoutesToMostDestinations(lp));
+
+        lp.removeRoute(new RouteInfo(new IpPrefix("::/1")));
+        assertFalse(Vpn.providesRoutesToMostDestinations(lp));
+
+        // V6 does not provide sufficient coverage but v4 does
+        publicIpV4Routes().forEach(s -> lp.addRoute(new RouteInfo(new IpPrefix(s))));
+        assertTrue(Vpn.providesRoutesToMostDestinations(lp));
+
+        // V4 still does
+        lp.removeRoute(new RouteInfo(new IpPrefix("192.169.0.0/16")));
+        assertTrue(Vpn.providesRoutesToMostDestinations(lp));
+
+        // V4 does not any more
+        lp.removeRoute(new RouteInfo(new IpPrefix("64.0.0.0/2")));
+        assertFalse(Vpn.providesRoutesToMostDestinations(lp));
+
+        // V4 does not, but V6 has sufficient coverage again
+        lp.addRoute(new RouteInfo(new IpPrefix("::/1")));
+        assertTrue(Vpn.providesRoutesToMostDestinations(lp));
+    }
 }