diff --git a/services/core/java/com/android/server/ConnectivityService.java b/services/core/java/com/android/server/ConnectivityService.java
index bb3b9f7..14503f9 100644
--- a/services/core/java/com/android/server/ConnectivityService.java
+++ b/services/core/java/com/android/server/ConnectivityService.java
@@ -274,7 +274,8 @@
     private int mDefaultInetConditionPublished = 0;
 
     private INetworkManagementService mNMS;
-    private INetd mNetd;
+    @VisibleForTesting
+    protected INetd mNetd;
     private INetworkStatsService mStatsService;
     private INetworkPolicyManager mPolicyManager;
     private NetworkPolicyManagerInternal mPolicyManagerInternal;
@@ -2090,7 +2091,8 @@
         }
     }
 
-    private static final String DEFAULT_TCP_BUFFER_SIZES = "4096,87380,110208,4096,16384,110208";
+    @VisibleForTesting
+    protected static final String DEFAULT_TCP_BUFFER_SIZES = "4096,87380,110208,4096,16384,110208";
     private static final String DEFAULT_TCP_RWND_KEY = "net.tcp.default_init_rwnd";
 
     // Overridden for testing purposes to avoid writing to SystemProperties.
@@ -2116,15 +2118,11 @@
         try {
             if (VDBG || DDBG) Slog.d(TAG, "Setting tx/rx TCP buffers to " + tcpBufferSizes);
 
-            final String prefix = "/sys/kernel/ipv4/tcp_";
-            FileUtils.stringToFile(prefix + "rmem_min", values[0]);
-            FileUtils.stringToFile(prefix + "rmem_def", values[1]);
-            FileUtils.stringToFile(prefix + "rmem_max", values[2]);
-            FileUtils.stringToFile(prefix + "wmem_min", values[3]);
-            FileUtils.stringToFile(prefix + "wmem_def", values[4]);
-            FileUtils.stringToFile(prefix + "wmem_max", values[5]);
+            String rmemValues = String.join(" ", values[0], values[1], values[2]);
+            String wmemValues = String.join(" ", values[3], values[4], values[5]);
+            mNetd.setTcpRWmemorySize(rmemValues, wmemValues);
             mCurrentTcpBufferSizes = tcpBufferSizes;
-        } catch (IOException e) {
+        } catch (RemoteException | ServiceSpecificException e) {
             loge("Can't set TCP buffer sizes:" + e);
         }
 
diff --git a/tests/net/java/com/android/server/ConnectivityServiceTest.java b/tests/net/java/com/android/server/ConnectivityServiceTest.java
index 17bcea0..71529fd 100644
--- a/tests/net/java/com/android/server/ConnectivityServiceTest.java
+++ b/tests/net/java/com/android/server/ConnectivityServiceTest.java
@@ -96,6 +96,7 @@
 import android.net.ConnectivityManager.PacketKeepaliveCallback;
 import android.net.ConnectivityManager.TooManyRequestsException;
 import android.net.ConnectivityThread;
+import android.net.INetd;
 import android.net.INetworkPolicyListener;
 import android.net.INetworkPolicyManager;
 import android.net.INetworkStatsService;
@@ -228,6 +229,7 @@
     @Mock INetworkManagementService mNetworkManagementService;
     @Mock INetworkStatsService mStatsService;
     @Mock INetworkPolicyManager mNpm;
+    @Mock INetd mMockNetd;
 
     private ArgumentCaptor<String[]> mStringArrayCaptor = ArgumentCaptor.forClass(String[].class);
 
@@ -926,8 +928,9 @@
 
         public WrappedConnectivityService(Context context, INetworkManagementService netManager,
                 INetworkStatsService statsService, INetworkPolicyManager policyManager,
-                IpConnectivityLog log) {
+                IpConnectivityLog log, INetd netd) {
             super(context, netManager, statsService, policyManager, log);
+            mNetd = netd;
             mLingerDelayMs = TEST_LINGER_DELAY_MS;
         }
 
@@ -1087,7 +1090,8 @@
                 mNetworkManagementService,
                 mStatsService,
                 mNpm,
-                mock(IpConnectivityLog.class));
+                mock(IpConnectivityLog.class),
+                mMockNetd);
 
         final ArgumentCaptor<INetworkPolicyListener> policyListenerCaptor =
                 ArgumentCaptor.forClass(INetworkPolicyListener.class);
@@ -4766,4 +4770,30 @@
         // Clean up
         mCm.unregisterNetworkCallback(networkCallback);
     }
+
+    private static final String TEST_TCP_BUFFER_SIZES = "1,2,3,4,5,6";
+
+    private void verifyTcpBufferSizeChange(String tcpBufferSizes) throws Exception {
+        String[] values = tcpBufferSizes.split(",");
+        String rmemValues = String.join(" ", values[0], values[1], values[2]);
+        String wmemValues = String.join(" ", values[3], values[4], values[5]);
+        waitForIdle();
+        verify(mMockNetd, atLeastOnce()).setTcpRWmemorySize(rmemValues, wmemValues);
+        reset(mMockNetd);
+    }
+
+    @Test
+    public void testTcpBufferReset() throws Exception {
+        mCellNetworkAgent = new MockNetworkAgent(TRANSPORT_CELLULAR);
+        reset(mMockNetd);
+        // Simple connection should have updated tcp buffer size.
+        mCellNetworkAgent.connect(false);
+        verifyTcpBufferSizeChange(ConnectivityService.DEFAULT_TCP_BUFFER_SIZES);
+
+        // Change link Properties should have updated tcp buffer size.
+        LinkProperties lp = new LinkProperties();
+        lp.setTcpBufferSizes(TEST_TCP_BUFFER_SIZES);
+        mCellNetworkAgent.sendLinkProperties(lp);
+        verifyTcpBufferSizeChange(TEST_TCP_BUFFER_SIZES);
+    }
 }
diff --git a/tests/net/java/com/android/server/IpSecServiceParameterizedTest.java b/tests/net/java/com/android/server/IpSecServiceParameterizedTest.java
index 4dc0341..d8f9618 100644
--- a/tests/net/java/com/android/server/IpSecServiceParameterizedTest.java
+++ b/tests/net/java/com/android/server/IpSecServiceParameterizedTest.java
@@ -542,7 +542,7 @@
 
         verify(mMockNetd)
                 .ipSecApplyTransportModeTransform(
-                        eq(pfd.getFileDescriptor()),
+                        eq(pfd),
                         eq(mUid),
                         eq(IpSecManager.DIRECTION_OUT),
                         anyString(),
@@ -555,7 +555,7 @@
         ParcelFileDescriptor pfd = ParcelFileDescriptor.fromSocket(new Socket());
         mIpSecService.removeTransportModeTransforms(pfd);
 
-        verify(mMockNetd).ipSecRemoveTransportModeTransform(pfd.getFileDescriptor());
+        verify(mMockNetd).ipSecRemoveTransportModeTransform(pfd);
     }
 
     private IpSecTunnelInterfaceResponse createAndValidateTunnel(
diff --git a/tests/net/java/com/android/server/IpSecServiceTest.java b/tests/net/java/com/android/server/IpSecServiceTest.java
index 2c94a60..724446e 100644
--- a/tests/net/java/com/android/server/IpSecServiceTest.java
+++ b/tests/net/java/com/android/server/IpSecServiceTest.java
@@ -425,7 +425,7 @@
         ParcelFileDescriptor pfd = ParcelFileDescriptor.fromSocket(new Socket());
         mIpSecService.removeTransportModeTransforms(pfd);
 
-        verify(mMockNetd).ipSecRemoveTransportModeTransform(pfd.getFileDescriptor());
+        verify(mMockNetd).ipSecRemoveTransportModeTransform(pfd);
     }
 
     @Test
@@ -620,10 +620,10 @@
                 mIpSecService.openUdpEncapsulationSocket(0, new Binder());
 
         FileDescriptor sockFd = udpEncapResp.fileDescriptor.getFileDescriptor();
-        ArgumentMatcher<FileDescriptor> fdMatcher = (arg) -> {
+        ArgumentMatcher<ParcelFileDescriptor> fdMatcher = (arg) -> {
                     try {
                         StructStat sockStat = Os.fstat(sockFd);
-                        StructStat argStat = Os.fstat(arg);
+                        StructStat argStat = Os.fstat(arg.getFileDescriptor());
 
                         return sockStat.st_ino == argStat.st_ino
                                 && sockStat.st_dev == argStat.st_dev;