netty: bump to 4.1.32 and tcnative 2.0.20

diff --git a/SECURITY.md b/SECURITY.md
index 4be72ca..0b1c8f0 100644
--- a/SECURITY.md
+++ b/SECURITY.md
@@ -90,7 +90,7 @@
     <dependency>
       <groupId>io.netty</groupId>
       <artifactId>netty-tcnative-boringssl-static</artifactId>
-      <version>2.0.17.Final</version>
+      <version>2.0.20.Final</version>
     </dependency>
   </dependencies>
 </project>
@@ -108,7 +108,7 @@
 }
 
 dependencies {
-    compile 'io.netty:netty-tcnative-boringssl-static:2.0.17.Final'
+    compile 'io.netty:netty-tcnative-boringssl-static:2.0.20.Final'
 }
 ```
 
@@ -143,7 +143,7 @@
     <dependency>
       <groupId>io.netty</groupId>
       <artifactId>netty-tcnative</artifactId>
-      <version>2.0.17.Final</version>
+      <version>2.0.20.Final</version>
       <classifier>${tcnative.classifier}</classifier>
     </dependency>
   </dependencies>
@@ -211,7 +211,7 @@
 }
 
 dependencies {
-    compile 'io.netty:netty-tcnative:2.0.17.Final:' + tcnative_classifier
+    compile 'io.netty:netty-tcnative:2.0.20.Final:' + tcnative_classifier
 }
 ```
 
@@ -374,7 +374,8 @@
 1.11.x-1.12.x      | 4.1.22.Final          | 2.0.7.Final
 1.13.x             | 4.1.25.Final          | 2.0.8.Final
 1.14.x-1.15.x      | 4.1.27.Final          | 2.0.12.Final
-1.16.x-            | 4.1.30.Final          | 2.0.17.Final
+1.16.x-1.17.x      | 4.1.30.Final          | 2.0.17.Final
+1.18.x-            | 4.1.32.Final          | 2.0.20.Final
 
 _(grpc-netty-shaded avoids issues with keeping these versions in sync.)_
 
diff --git a/build.gradle b/build.gradle
index afc95d2..c4cc052 100644
--- a/build.gradle
+++ b/build.gradle
@@ -105,7 +105,7 @@
         protocPluginBaseName = 'protoc-gen-grpc-java'
         javaPluginPath = "$rootDir/compiler/build/exe/java_plugin/$protocPluginBaseName$exeSuffix"
 
-        nettyVersion = '4.1.30.Final'
+        nettyVersion = '4.1.32.Final'
         guavaVersion = '26.0-android'
         protobufVersion = '3.5.1'
         protocVersion = '3.5.1-1'
@@ -223,7 +223,7 @@
             // Keep the following references of tcnative version in sync whenever it's updated
             // SECURITY.md (multiple occurrences)
             // examples/build.gradle
-            netty_tcnative: 'io.netty:netty-tcnative-boringssl-static:2.0.17.Final',
+            netty_tcnative: 'io.netty:netty-tcnative-boringssl-static:2.0.20.Final',
 
             conscrypt: 'org.conscrypt:conscrypt-openjdk-uber:1.0.1',
             re2j: 'com.google.re2j:re2j:1.2',
diff --git a/examples/build.gradle b/examples/build.gradle
index 5dc5912..9061994 100644
--- a/examples/build.gradle
+++ b/examples/build.gradle
@@ -23,7 +23,7 @@
 // Feel free to delete the comment at the next line. It is just for safely
 // updating the version in our release process.
 def grpcVersion = '1.18.0-SNAPSHOT' // CURRENT_GRPC_VERSION
-def nettyTcNativeVersion = '2.0.17.Final'
+def nettyTcNativeVersion = '2.0.20.Final'
 def protobufVersion = '3.5.1'
 def protocVersion = '3.5.1-1'
 
diff --git a/netty/src/test/java/io/grpc/netty/UtilsTest.java b/netty/src/test/java/io/grpc/netty/UtilsTest.java
index d2febab..9575d05 100644
--- a/netty/src/test/java/io/grpc/netty/UtilsTest.java
+++ b/netty/src/test/java/io/grpc/netty/UtilsTest.java
@@ -33,7 +33,6 @@
 import io.netty.channel.WriteBufferWaterMark;
 import io.netty.channel.embedded.EmbeddedChannel;
 import io.netty.channel.socket.nio.NioSocketChannel;
-import io.netty.channel.socket.oio.OioSocketChannel;
 import io.netty.handler.codec.http2.DefaultHttp2Headers;
 import io.netty.handler.codec.http2.Http2Error;
 import io.netty.handler.codec.http2.Http2Exception;
@@ -137,8 +136,9 @@
   }
 
   @Test
+  @SuppressWarnings("deprecation")
   public void channelOptionsTest_oio() {
-    Channel channel = new OioSocketChannel();
+    Channel channel = new io.netty.channel.socket.oio.OioSocketChannel();
     SocketOptions socketOptions = setAndValidateGeneric(channel);
     assertEquals(250, (int) socketOptions.soTimeoutMillis);
   }
diff --git a/repositories.bzl b/repositories.bzl
index 2a96969..d8f3bbf 100644
--- a/repositories.bzl
+++ b/repositories.bzl
@@ -227,78 +227,78 @@
 def io_netty_buffer():
     native.maven_jar(
         name = "io_netty_netty_buffer",
-        artifact = "io.netty:netty-buffer:4.1.30.Final",
-        sha1 = "597adb653306470fb3ec1af3c0f3f30a37b1310a",
+        artifact = "io.netty:netty-buffer:4.1.32.Final",
+        sha1 = "046ede57693788181b2cafddc3a5967ed2f621c8",
     )
 
 def io_netty_codec():
     native.maven_jar(
         name = "io_netty_netty_codec",
-        artifact = "io.netty:netty-codec:4.1.30.Final",
-        sha1 = "515c8f609aaca28a94f984d89a9667dd3359c1b1",
+        artifact = "io.netty:netty-codec:4.1.32.Final",
+        sha1 = "8f32bd79c5a16f014a4372ed979dc62b39ede33a",
     )
 
 def io_netty_codec_http():
     native.maven_jar(
         name = "io_netty_netty_codec_http",
-        artifact = "io.netty:netty-codec-http:4.1.30.Final",
-        sha1 = "1384c630e8a0eeef33ad12a28791dce6e1d8767c",
+        artifact = "io.netty:netty-codec-http:4.1.32.Final",
+        sha1 = "0b9218adba7353ad5a75fcb639e4755d64bd6ddf",
     )
 
 def io_netty_codec_http2():
     native.maven_jar(
         name = "io_netty_netty_codec_http2",
-        artifact = "io.netty:netty-codec-http2:4.1.30.Final",
-        sha1 = "2da92f518409904954d3e8dcc42eb6a562a70302",
+        artifact = "io.netty:netty-codec-http2:4.1.32.Final",
+        sha1 = "d14eb053a1f96d3330ec48e77d489118d547557a",
     )
 
 def io_netty_codec_socks():
     native.maven_jar(
         name = "io_netty_netty_codec_socks",
-        artifact = "io.netty:netty-codec-socks:4.1.30.Final",
-        sha1 = "ea272e3bb281d3a91d27278f47e61b4de285cc27",
+        artifact = "io.netty:netty-codec-socks:4.1.32.Final",
+        sha1 = "b1e83cb772f842839dbeebd9a1f053da98bf56d2",
     )
 
 def io_netty_common():
     native.maven_jar(
         name = "io_netty_netty_common",
-        artifact = "io.netty:netty-common:4.1.30.Final",
-        sha1 = "5dca0c34d8f38af51a2398614e81888f51cf811a",
+        artifact = "io.netty:netty-common:4.1.32.Final",
+        sha1 = "e95de4f762606f492328e180c8ad5438565a5e3b",
     )
 
 def io_netty_handler():
     native.maven_jar(
         name = "io_netty_netty_handler",
-        artifact = "io.netty:netty-handler:4.1.30.Final",
-        sha1 = "ecc076332ed103411347f4806a44ee32d9d9cb5f",
+        artifact = "io.netty:netty-handler:4.1.32.Final",
+        sha1 = "b4e3fa13f219df14a9455cc2111f133374428be0",
     )
 
 def io_netty_handler_proxy():
     native.maven_jar(
         name = "io_netty_netty_handler_proxy",
-        artifact = "io.netty:netty-handler-proxy:4.1.30.Final",
-        sha1 = "1baa1568fa936caddca0fae96fdf127fd5cbad16",
+        artifact = "io.netty:netty-handler-proxy:4.1.32.Final",
+        sha1 = "58b621246262127b97a871b88c09374c8c324cb7",
     )
 
 def io_netty_resolver():
     native.maven_jar(
         name = "io_netty_netty_resolver",
-        artifact = "io.netty:netty-resolver:4.1.30.Final",
-        sha1 = "5106fd687066ffd712e5295d32af4e2ac6482613",
+        artifact = "io.netty:netty-resolver:4.1.32.Final",
+        sha1 = "3e0114715cb125a12db8d982b2208e552a91256d",
     )
 
 def io_netty_tcnative_boringssl_static():
     native.maven_jar(
         name = "io_netty_netty_tcnative_boringssl_static",
-        artifact = "io.netty:netty-tcnative-boringssl-static:2.0.17.Final",
-        sha1 = "b1e5acbde8c444c656131238ac6ab9e73f694300",
+        artifact = "io.netty:netty-tcnative-boringssl-static:2.0.20.Final",
+        sha1 = "071141fca3e805d9d248cb43e1909cf6a50ad92c",
     )
 
 def io_netty_transport():
     native.maven_jar(
         name = "io_netty_netty_transport",
-        artifact = "io.netty:netty-transport:4.1.30.Final",
-        sha1 = "3d27bb432a3b125167ac161b26415ad29ec17f02",
+        artifact = "io.netty:netty-transport:4.1.32.Final",
+        sha1 = "d5e5a8ff9c2bc7d91ddccc536a5aca1a4355bd8b",
     )
 
 def io_opencensus_api():