core,netty: add NettySocketSupport to populate TcpInfo (#4306)

NettySocketSupport is responsible for making the low level calls to
get and populate the TcpInfo structure.

2 files changed, 69 insertions, 0 deletions

diff --git a/netty/src/main/java/io/grpc/netty/NettySocketSupport.java b/netty/src/main/java/io/grpc/netty/NettySocketSupport.java
new file mode 100644
index 000000000..597927b6f
--- /dev/null
+++ b/netty/src/main/java/io/grpc/netty/NettySocketSupport.java
@@ -0,0 +1,60 @@
+/*
+ * Copyright 2018, gRPC Authors All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.grpc.netty;
+
+import com.google.common.base.Preconditions;
+import com.google.common.collect.ImmutableMap;
+import io.grpc.internal.Channelz.TcpInfo;
+import io.netty.channel.Channel;
+import java.util.HashMap;
+import java.util.Map;
+import javax.annotation.Nullable;
+
+/**
+ * An class for getting low level socket info.
+ */
+final class NettySocketSupport {
+
+  /**
+   * Returns the info on the socket if possible. Returns null if the info can not be discovered.
+   */
+  @Nullable
+  public static NativeSocketOptions getNativeSocketOptions(Channel ch) {
+    // TODO(zpencer): if netty-epoll, use reflection to call EpollSocketChannel.tcpInfo()
+    // And/or if some other low level socket support library is available, call it now.
+    return null;
+  }
+
+  /**
+   * A TcpInfo and additional other info that will be turned into channelz socket options.
+   */
+  public static final class NativeSocketOptions {
+    @Nullable public final TcpInfo tcpInfo;
+    public final ImmutableMap<String, String> otherInfo;
+
+    /** Creates an instance. */
+    public NativeSocketOptions(
+        TcpInfo tcpInfo,
+        Map<String, String> otherInfo) {
+      Preconditions.checkNotNull(otherInfo);
+      this.tcpInfo = tcpInfo;
+      this.otherInfo = ImmutableMap.copyOf(new HashMap<String, String>(otherInfo));
+    }
+  }
+
+  private NettySocketSupport() {}
+}
diff --git a/netty/src/main/java/io/grpc/netty/Utils.java b/netty/src/main/java/io/grpc/netty/Utils.java
index 473a4c8ef..fc2203c9c 100644
--- a/netty/src/main/java/io/grpc/netty/Utils.java
+++ b/netty/src/main/java/io/grpc/netty/Utils.java
@@ -32,6 +32,7 @@ import io.grpc.internal.Channelz;
 import io.grpc.internal.GrpcUtil;
 import io.grpc.internal.SharedResourceHolder.Resource;
 import io.grpc.netty.GrpcHttp2HeadersUtils.GrpcHttp2InboundHeaders;
+import io.grpc.netty.NettySocketSupport.NativeSocketOptions;
 import io.netty.channel.Channel;
 import io.netty.channel.ChannelConfig;
 import io.netty.channel.ChannelOption;
@@ -235,6 +236,14 @@ class Utils {
       // zpencer: Can a netty option be null?
       b.addOption(key.name(), String.valueOf(value));
     }
+
+    NativeSocketOptions nativeOptions = NettySocketSupport.getNativeSocketOptions(channel);
+    if (nativeOptions != null) {
+      b.setTcpInfo(nativeOptions.tcpInfo); // may be null
+      for (Entry<String, String> entry : nativeOptions.otherInfo.entrySet()) {
+        b.addOption(entry.getKey(), entry.getValue());
+      }
+    }
     return b.build();
   }