Use the JDK's built-in support for Unix Domain Sockets on Java 16+

Author: mcculls

utils/socket-utils/build.gradle

@@ -1,8 +1,37 @@
 apply from: "$rootDir/gradle/java.gradle"
+apply plugin: "idea"
+
+sourceSets {
+  main_java17 {
+    java.srcDirs "${project.projectDir}/src/main/java17"
+  }
+}
+
+compileMain_java17Java.configure {
+  setJavaVersion(it, 17)
+  sourceCompatibility = JavaVersion.VERSION_1_8
+  targetCompatibility = JavaVersion.VERSION_1_8
+}
 
 dependencies {
+  compileOnly sourceSets.main_java17.output
+
   implementation libs.slf4j
   implementation project(':internal-api')
 
   implementation group: 'com.github.jnr', name: 'jnr-unixsocket', version: libs.versions.jnr.unixsocket.get()
 }
+
+jar {
+  from sourceSets.main_java17.output
+}
+
+forbiddenApisMain_java17 {
+  failOnMissingClasses = false
+}
+
+idea {
+  module {
+    jdkName = '17'
+  }
+}

utils/socket-utils/src/main/java/datadog/common/socket/UnixDomainSocketFactory.java

@@ -3,6 +3,7 @@
 import static java.util.concurrent.TimeUnit.MINUTES;
 
 import datadog.trace.api.Config;
+import datadog.trace.api.Platform;
 import datadog.trace.relocate.api.RatelimitedLogger;
 import java.io.File;
 import java.io.IOException;
@@ -24,6 +25,8 @@
 public final class UnixDomainSocketFactory extends SocketFactory {
   private static final Logger log = LoggerFactory.getLogger(UnixDomainSocketFactory.class);
 
+  private static final boolean JDK_HAS_UDS = Platform.isJavaVersionAtLeast(16);
+
   private final RatelimitedLogger rlLog = new RatelimitedLogger(log, 5, MINUTES);
 
   private final File path;
@@ -35,8 +38,14 @@ public UnixDomainSocketFactory(final File path) {
   @Override
   public Socket createSocket() throws IOException {
     try {
-      final UnixSocketChannel channel = UnixSocketChannel.open();
-      return new TunnelingUnixSocket(path, channel);
+      if (JDK_HAS_UDS) {
+        try {
+          return new TunnelingJdkSocket(path.toPath());
+        } catch (Throwable ignore) {
+          // fall back to jnr-unixsocket library
+        }
+      }
+      return new TunnelingUnixSocket(path, UnixSocketChannel.open());
     } catch (Throwable e) {
       if (Config.get().isAgentConfiguredUsingDefault()) {
         // fall back to port if we previously auto-discovered this socket file

utils/socket-utils/src/main/java17/datadog/common/socket/TunnelingJdkSocket.java

@@ -0,0 +1,185 @@
+package datadog.common.socket;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.net.InetAddress;
+import java.net.InetSocketAddress;
+import java.net.Socket;
+import java.net.SocketAddress;
+import java.net.SocketException;
+import java.net.UnixDomainSocketAddress;
+import java.nio.channels.Channels;
+import java.nio.channels.SocketChannel;
+import java.nio.file.Path;
+
+/**
+ * Subtype UNIX socket for a higher-fidelity impersonation of TCP sockets. This is named "tunneling"
+ * because it assumes the ultimate destination has a hostname and port.
+ *
+ * <p>Copied from <a
+ * href="https://github.com/square/okhttp/blob/master/samples/unixdomainsockets/src/main/java/okhttp3/unixdomainsockets/UnixDomainServerSocketFactory.java">okHttp
+ * examples</a>.
+ */
+final class TunnelingJdkSocket extends Socket {
+  private final SocketAddress unixSocketAddress;
+  private InetSocketAddress inetSocketAddress;
+
+  private SocketChannel unixSocketChannel;
+
+  private int timeout;
+  private boolean shutIn;
+  private boolean shutOut;
+  private boolean closed;
+
+  TunnelingJdkSocket(final Path path) {
+    this.unixSocketAddress = UnixDomainSocketAddress.of(path);
+  }
+
+  TunnelingJdkSocket(final Path path, final InetSocketAddress address) {
+    this(path);
+    inetSocketAddress = address;
+  }
+
+  @Override
+  public boolean isConnected() {
+    return null != unixSocketChannel;
+  }
+
+  @Override
+  public boolean isInputShutdown() {
+    return shutIn;
+  }
+
+  @Override
+  public boolean isOutputShutdown() {
+    return shutOut;
+  }
+
+  @Override
+  public boolean isClosed() {
+    return closed;
+  }
+
+  @Override
+  public synchronized void setSoTimeout(int timeout) throws SocketException {
+    if (isClosed()) {
+      throw new SocketException("Socket is closed");
+    }
+    if (timeout < 0) {
+      throw new IllegalArgumentException("Socket timeout can't be negative");
+    }
+    this.timeout = timeout;
+  }
+
+  @Override
+  public synchronized int getSoTimeout() throws SocketException {
+    if (isClosed()) {
+      throw new SocketException("Socket is closed");
+    }
+    return timeout;
+  }
+
+  @Override
+  public void connect(final SocketAddress endpoint) throws IOException {
+    if (isClosed()) {
+      throw new SocketException("Socket is closed");
+    }
+    if (isConnected()) {
+      throw new SocketException("Socket is already connected");
+    }
+    inetSocketAddress = (InetSocketAddress) endpoint;
+    unixSocketChannel = SocketChannel.open(unixSocketAddress);
+  }
+
+  @Override
+  public void connect(final SocketAddress endpoint, final int timeout) throws IOException {
+    if (isClosed()) {
+      throw new SocketException("Socket is closed");
+    }
+    if (isConnected()) {
+      throw new SocketException("Socket is already connected");
+    }
+    inetSocketAddress = (InetSocketAddress) endpoint;
+    unixSocketChannel = SocketChannel.open(unixSocketAddress);
+  }
+
+  @Override
+  public SocketChannel getChannel() {
+    return unixSocketChannel;
+  }
+
+  @Override
+  public InputStream getInputStream() throws IOException {
+    if (isClosed()) {
+      throw new SocketException("Socket is closed");
+    }
+    if (!isConnected()) {
+      throw new SocketException("Socket is not connected");
+    }
+    if (isInputShutdown()) {
+      throw new SocketException("Socket input is shutdown");
+    }
+    return Channels.newInputStream(unixSocketChannel);
+  }
+
+  @Override
+  public OutputStream getOutputStream() throws IOException {
+    if (isClosed()) {
+      throw new SocketException("Socket is closed");
+    }
+    if (!isConnected()) {
+      throw new SocketException("Socket is not connected");
+    }
+    if (isInputShutdown()) {
+      throw new SocketException("Socket output is shutdown");
+    }
+    return Channels.newOutputStream(unixSocketChannel);
+  }
+
+  @Override
+  public void shutdownInput() throws IOException {
+    if (isClosed()) {
+      throw new SocketException("Socket is closed");
+    }
+    if (!isConnected()) {
+      throw new SocketException("Socket is not connected");
+    }
+    if (isInputShutdown()) {
+      throw new SocketException("Socket input is already shutdown");
+    }
+    unixSocketChannel.shutdownInput();
+    shutIn = true;
+  }
+
+  @Override
+  public void shutdownOutput() throws IOException {
+    if (isClosed()) {
+      throw new SocketException("Socket is closed");
+    }
+    if (!isConnected()) {
+      throw new SocketException("Socket is not connected");
+    }
+    if (isOutputShutdown()) {
+      throw new SocketException("Socket output is already shutdown");
+    }
+    unixSocketChannel.shutdownOutput();
+    shutOut = true;
+  }
+
+  @Override
+  public InetAddress getInetAddress() {
+    return inetSocketAddress.getAddress();
+  }
+
+  @Override
+  public void close() throws IOException {
+    if (isClosed()) {
+      return;
+    }
+    if (null != unixSocketChannel) {
+      unixSocketChannel.close();
+    }
+    closed = true;
+  }
+}