diff --git a/services/core/java/com/android/server/ConnectivityService.java b/services/core/java/com/android/server/ConnectivityService.java
index 45b0384..d5adf48 100644
--- a/services/core/java/com/android/server/ConnectivityService.java
+++ b/services/core/java/com/android/server/ConnectivityService.java
@@ -90,7 +90,6 @@
 import android.os.RemoteException;
 import android.os.ResultReceiver;
 import android.os.SystemClock;
-import android.os.SystemProperties;
 import android.os.UserHandle;
 import android.os.UserManager;
 import android.provider.Settings;
@@ -204,6 +203,8 @@
     // See Settings.Secure.CONNECTIVITY_RELEASE_PENDING_INTENT_DELAY_MS
     private final int mReleasePendingIntentDelayMs;
 
+    private MockableSystemProperties mSystemProperties;
+
     private Tethering mTethering;
 
     private final PermissionMonitor mPermissionMonitor;
@@ -676,6 +677,8 @@
             IpConnectivityLog logger) {
         if (DBG) log("ConnectivityService starting up");
 
+        mSystemProperties = getSystemProperties();
+
         mMetricsLog = logger;
         mDefaultRequest = createInternetRequestForTransport(-1, NetworkRequest.Type.REQUEST);
         NetworkRequestInfo defaultNRI = new NetworkRequestInfo(null, mDefaultRequest, new Binder());
@@ -693,7 +696,7 @@
         mReleasePendingIntentDelayMs = Settings.Secure.getInt(context.getContentResolver(),
                 Settings.Secure.CONNECTIVITY_RELEASE_PENDING_INTENT_DELAY_MS, 5_000);
 
-        mLingerDelayMs = SystemProperties.getInt(LINGER_DELAY_PROPERTY, DEFAULT_LINGER_DELAY_MS);
+        mLingerDelayMs = mSystemProperties.getInt(LINGER_DELAY_PROPERTY, DEFAULT_LINGER_DELAY_MS);
 
         mContext = checkNotNull(context, "missing Context");
         mNetd = checkNotNull(netManager, "missing INetworkManagementService");
@@ -723,7 +726,7 @@
         mNetConfigs = new NetworkConfig[ConnectivityManager.MAX_NETWORK_TYPE+1];
 
         // TODO: What is the "correct" way to do determine if this is a wifi only device?
-        boolean wifiOnly = SystemProperties.getBoolean("ro.radio.noril", false);
+        boolean wifiOnly = mSystemProperties.getBoolean("ro.radio.noril", false);
         log("wifiOnly=" + wifiOnly);
         String[] naStrings = context.getResources().getStringArray(
                 com.android.internal.R.array.networkAttributes);
@@ -776,8 +779,8 @@
             }
         }
 
-        mTestMode = SystemProperties.get("cm.test.mode").equals("true")
-                && SystemProperties.get("ro.build.type").equals("eng");
+        mTestMode = mSystemProperties.get("cm.test.mode").equals("true")
+                && mSystemProperties.get("ro.build.type").equals("eng");
 
         mTethering = new Tethering(mContext, mNetd, statsService, mPolicyManager,
                                    IoThread.get().getLooper(), new MockableSystemProperties());
@@ -1733,8 +1736,8 @@
 
     // Overridden for testing purposes to avoid writing to SystemProperties.
     @VisibleForTesting
-    protected int getDefaultTcpRwnd() {
-        return SystemProperties.getInt(DEFAULT_TCP_RWND_KEY, 0);
+    protected MockableSystemProperties getSystemProperties() {
+        return new MockableSystemProperties();
     }
 
     private void updateTcpBufferSizes(NetworkAgentInfo nai) {
@@ -1772,10 +1775,11 @@
         }
 
         Integer rwndValue = Settings.Global.getInt(mContext.getContentResolver(),
-            Settings.Global.TCP_DEFAULT_INIT_RWND, getDefaultTcpRwnd());
+            Settings.Global.TCP_DEFAULT_INIT_RWND,
+                    mSystemProperties.getInt("net.tcp.default_init_rwnd", 0));
         final String sysctlKey = "sys.sysctl.tcp_def_init_rwnd";
         if (rwndValue != 0) {
-            SystemProperties.set(sysctlKey, rwndValue.toString());
+            mSystemProperties.set(sysctlKey, rwndValue.toString());
         }
     }
 
@@ -1799,7 +1803,7 @@
 
     @Override
     public int getRestoreDefaultNetworkDelay(int networkType) {
-        String restoreDefaultNetworkDelayStr = SystemProperties.get(
+        String restoreDefaultNetworkDelayStr = mSystemProperties.get(
                 NETWORK_RESTORE_DELAY_PROP_NAME);
         if(restoreDefaultNetworkDelayStr != null &&
                 restoreDefaultNetworkDelayStr.length() != 0) {
@@ -2966,7 +2970,7 @@
     @Override
     public boolean isTetheringSupported() {
         enforceTetherAccessPermission();
-        int defaultVal = (SystemProperties.get("ro.tether.denied").equals("true") ? 0 : 1);
+        int defaultVal = (mSystemProperties.get("ro.tether.denied").equals("true") ? 0 : 1);
         boolean tetherEnabledInSettings = (Settings.Global.getInt(mContext.getContentResolver(),
                 Settings.Global.TETHER_SUPPORTED, defaultVal) != 0)
                 && !mUserManager.hasUserRestriction(UserManager.DISALLOW_CONFIG_TETHERING);
@@ -4473,17 +4477,24 @@
         int last = 0;
         for (InetAddress dns : dnses) {
             ++last;
-            String key = "net.dns" + last;
-            String value = dns.getHostAddress();
-            SystemProperties.set(key, value);
+            setNetDnsProperty(last, dns.getHostAddress());
         }
         for (int i = last + 1; i <= mNumDnsEntries; ++i) {
-            String key = "net.dns" + i;
-            SystemProperties.set(key, "");
+            setNetDnsProperty(i, "");
         }
         mNumDnsEntries = last;
     }
 
+    private void setNetDnsProperty(int which, String value) {
+        final String key = "net.dns" + which;
+        // Log and forget errors setting unsupported properties.
+        try {
+            mSystemProperties.set(key, value);
+        } catch (Exception e) {
+            Log.e(TAG, "Error setting unsupported net.dns property: ", e);
+        }
+    }
+
     private String getNetworkPermission(NetworkCapabilities nc) {
         // TODO: make these permission strings AIDL constants instead.
         if (!nc.hasCapability(NET_CAPABILITY_NOT_RESTRICTED)) {
diff --git a/tests/net/java/com/android/server/ConnectivityServiceTest.java b/tests/net/java/com/android/server/ConnectivityServiceTest.java
index 7c7a3f8..6140a89 100644
--- a/tests/net/java/com/android/server/ConnectivityServiceTest.java
+++ b/tests/net/java/com/android/server/ConnectivityServiceTest.java
@@ -23,7 +23,12 @@
 import static android.net.ConnectivityManager.getNetworkTypeName;
 import static android.net.NetworkCapabilities.*;
 
+import static org.mockito.Mockito.anyBoolean;
+import static org.mockito.Mockito.anyInt;
+import static org.mockito.Mockito.eq;
 import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.spy;
+import static org.mockito.Mockito.when;
 
 import android.app.NotificationManager;
 import android.app.PendingIntent;
@@ -33,6 +38,7 @@
 import android.content.ContextWrapper;
 import android.content.Intent;
 import android.content.IntentFilter;
+import android.content.res.Resources;
 import android.net.ConnectivityManager;
 import android.net.ConnectivityManager.NetworkCallback;
 import android.net.ConnectivityManager.PacketKeepalive;
@@ -82,12 +88,17 @@
 import com.android.internal.util.WakeupMessage;
 import com.android.internal.util.test.BroadcastInterceptingContext;
 import com.android.internal.util.test.FakeSettingsProvider;
+import com.android.server.connectivity.MockableSystemProperties;
 import com.android.server.connectivity.NetworkAgentInfo;
 import com.android.server.connectivity.NetworkMonitor;
 import com.android.server.connectivity.NetworkMonitor.CaptivePortalProbeResult;
 import com.android.server.net.NetworkPinner;
 import com.android.server.net.NetworkPolicyManagerInternal;
 
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
+import org.mockito.Spy;
+
 import java.net.InetAddress;
 import java.util.ArrayList;
 import java.util.Arrays;
@@ -140,8 +151,19 @@
     private class MockContext extends BroadcastInterceptingContext {
         private final MockContentResolver mContentResolver;
 
+        @Spy private Resources mResources;
+
         MockContext(Context base) {
             super(base);
+
+            mResources = spy(base.getResources());
+            when(mResources.getStringArray(com.android.internal.R.array.networkAttributes)).
+                    thenReturn(new String[] {
+                            "wifi,1,1,1,-1,true",
+                            "mobile,0,0,0,-1,true",
+                            "mobile_mms,2,0,2,60000,true",
+                    });
+
             mContentResolver = new MockContentResolver();
             mContentResolver.addProvider(Settings.AUTHORITY, new FakeSettingsProvider());
         }
@@ -157,6 +179,11 @@
         public ContentResolver getContentResolver() {
             return mContentResolver;
         }
+
+        @Override
+        public Resources getResources() {
+            return mResources;
+        }
     }
 
     /**
@@ -632,6 +659,7 @@
     private class WrappedConnectivityService extends ConnectivityService {
         public WrappedMultinetworkPolicyTracker wrappedMultinetworkPolicyTracker;
         private WrappedNetworkMonitor mLastCreatedNetworkMonitor;
+        private MockableSystemProperties mSystemProperties;
 
         public WrappedConnectivityService(Context context, INetworkManagementService netManager,
                 INetworkStatsService statsService, INetworkPolicyManager policyManager,
@@ -641,9 +669,13 @@
         }
 
         @Override
-        protected int getDefaultTcpRwnd() {
-            // Prevent wrapped ConnectivityService from trying to write to SystemProperties.
-            return 0;
+        protected MockableSystemProperties getSystemProperties() {
+            // Minimal approach to overriding system properties: let most calls fall through to real
+            // device values, and only override ones values that are important to this test.
+            mSystemProperties = spy(new MockableSystemProperties());
+            when(mSystemProperties.getInt("net.tcp.default_init_rwnd", 0)).thenReturn(0);
+            when(mSystemProperties.getBoolean("ro.radio.noril", false)).thenReturn(false);
+            return mSystemProperties;
         }
 
         @Override
@@ -816,6 +848,14 @@
         return cv;
     }
 
+    public void testNetworkTypes() {
+        // Ensure that our mocks for the networkAttributes config variable work as expected. If they
+        // don't, then tests that depend on CONNECTIVITY_ACTION broadcasts for these network types
+        // will fail. Failing here is much easier to debug.
+        assertTrue(mCm.isNetworkSupported(TYPE_WIFI));
+        assertTrue(mCm.isNetworkSupported(TYPE_MOBILE));
+    }
+
     @SmallTest
     public void testLingering() throws Exception {
         verifyNoNetwork();