Add Support for TUN-based Channels (kqueue/epoll)

example/pom.xml

@@ -175,6 +175,19 @@
       <groupId>com.sun.activation</groupId>
       <artifactId>javax.activation</artifactId>
     </dependency>
+
+    <dependency>
+      <groupId>${project.groupId}</groupId>
+      <artifactId>netty-transport-classes-epoll</artifactId>
+      <version>${project.version}</version>
+      <scope>compile</scope>
+    </dependency>
+    <dependency>
+      <groupId>${project.groupId}</groupId>
+      <artifactId>netty-transport-classes-kqueue</artifactId>
+      <version>${project.version}</version>
+      <scope>compile</scope>
+    </dependency>
   </dependencies>
 
   <build>
@@ -198,5 +211,65 @@
       </plugin>
     </plugins>
   </build>
+
+  <profiles>
+    <profile>
+      <id>native-dependencies</id>
+      <dependencies>
+        <dependency>
+          <groupId>${project.groupId}</groupId>
+          <artifactId>netty-transport-native-epoll</artifactId>
+          <version>${project.version}</version>
+          <classifier>linux-x86_64</classifier>
+          <scope>runtime</scope>
+        </dependency>
+        <dependency>
+          <groupId>${project.groupId}</groupId>
+          <artifactId>netty-transport-native-epoll</artifactId>
+          <version>${project.version}</version>
+          <classifier>linux-aarch_64</classifier>
+          <scope>runtime</scope>
+        </dependency>
+        <dependency>
+          <groupId>${project.groupId}</groupId>
+          <artifactId>netty-transport-native-kqueue</artifactId>
+          <version>${project.version}</version>
+          <classifier>osx-x86_64</classifier>
+          <scope>runtime</scope>
+        </dependency>
+        <dependency>
+          <groupId>${project.groupId}</groupId>
+          <artifactId>netty-transport-native-kqueue</artifactId>
+          <version>${project.version}</version>
+          <classifier>osx-aarch_64</classifier>
+          <scope>runtime</scope>
+        </dependency>
+      </dependencies>
+    </profile>
+    <profile>
+      <id>linux</id>
+      <dependencies>
+        <dependency>
+          <groupId>${project.groupId}</groupId>
+          <artifactId>netty-transport-native-epoll</artifactId>
+          <version>${project.version}</version>
+          <classifier>${jni.classifier}</classifier>
+          <scope>runtime</scope>
+        </dependency>
+      </dependencies>
+    </profile>
+    <profile>
+      <id>mac</id>
+      <dependencies>
+        <dependency>
+          <groupId>${project.groupId}</groupId>
+          <artifactId>netty-transport-native-kqueue</artifactId>
+          <version>${project.version}</version>
+          <classifier>${jni.classifier}</classifier>
+          <scope>runtime</scope>
+        </dependency>
+      </dependencies>
+    </profile>
+  </profiles>
 </project>
 

example/src/main/java/io/netty/example/tun/Echo4Handler.java

@@ -0,0 +1,54 @@
+/*
+ * Copyright 2022 The Netty Project
+ *
+ * The Netty Project licenses this file to you 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:
+ *
+ *   https://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.netty.example.tun;
+
+import io.netty.buffer.ByteBuf;
+import io.netty.channel.ChannelHandler.Sharable;
+import io.netty.channel.ChannelHandlerContext;
+import io.netty.channel.SimpleChannelInboundHandler;
+import io.netty.channel.socket.Tun4Packet;
+import io.netty.channel.socket.TunPacket;
+
+import static io.netty.channel.socket.Tun4Packet.INET4_DESTINATION_ADDRESS;
+import static io.netty.channel.socket.Tun4Packet.INET4_SOURCE_ADDRESS;
+
+/**
+ * Echoes received IPv4 packets by swapping source and destination addresses.
+ */
+@Sharable
+public class Echo4Handler extends SimpleChannelInboundHandler<Tun4Packet> {
+    @Override
+    protected void channelRead0(ChannelHandlerContext ctx,
+                                Tun4Packet packet) throws Exception {
+        // swap source and destination addresses. Depending on the layer 4 protocol used, this may
+        // require recalculation of existing checksums. However, UDP and TCP work without
+        // recalculation.
+        ByteBuf buf = packet.content();
+        int sourceAddress = buf.getInt(INET4_SOURCE_ADDRESS);
+        int destinationAddress = buf.getInt(INET4_DESTINATION_ADDRESS);
+        buf.setInt(INET4_SOURCE_ADDRESS, destinationAddress);
+        buf.setInt(INET4_DESTINATION_ADDRESS, sourceAddress);
+
+        TunPacket response = new Tun4Packet(buf.retain());
+        ctx.write(response);
+    }
+
+    @Override
+    public void channelReadComplete(ChannelHandlerContext ctx) {
+        ctx.fireChannelReadComplete();
+        ctx.flush();
+    }
+}

example/src/main/java/io/netty/example/tun/Echo6Handler.java

@@ -0,0 +1,56 @@
+/*
+ * Copyright 2022 The Netty Project
+ *
+ * The Netty Project licenses this file to you 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:
+ *
+ *   https://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.netty.example.tun;
+
+import io.netty.buffer.ByteBuf;
+import io.netty.channel.ChannelHandler.Sharable;
+import io.netty.channel.ChannelHandlerContext;
+import io.netty.channel.SimpleChannelInboundHandler;
+import io.netty.channel.socket.Tun6Packet;
+import io.netty.channel.socket.TunPacket;
+
+import static io.netty.channel.socket.Tun6Packet.INET6_DESTINATION_ADDRESS;
+import static io.netty.channel.socket.Tun6Packet.INET6_SOURCE_ADDRESS;
+
+/**
+ * Echoes received IPv6 packets by swapping source and destination addresses.
+ */
+@Sharable
+public class Echo6Handler extends SimpleChannelInboundHandler<Tun6Packet> {
+    @Override
+    protected void channelRead0(ChannelHandlerContext ctx,
+                                Tun6Packet packet) throws Exception {
+        // swap source and destination addresses. Depending on the layer 4 protocol used, this may
+        // require recalculation of existing checksums. However, UDP and TCP work without
+        // recalculation.
+        ByteBuf buf = packet.content();
+        byte[] sourceAddress = new byte[16];
+        buf.getBytes(INET6_SOURCE_ADDRESS, sourceAddress, 0, 16);
+        byte[] destinationAddress = new byte[16];
+        buf.getBytes(INET6_DESTINATION_ADDRESS, destinationAddress, 0, 16);
+        buf.setBytes(INET6_SOURCE_ADDRESS, destinationAddress);
+        buf.setBytes(INET6_DESTINATION_ADDRESS, sourceAddress);
+
+        TunPacket response = new Tun6Packet(buf.retain());
+        ctx.write(response);
+    }
+
+    @Override
+    public void channelReadComplete(ChannelHandlerContext ctx) {
+        ctx.fireChannelReadComplete();
+        ctx.flush();
+    }
+}

example/src/main/java/io/netty/example/tun/Ping4Handler.java

@@ -0,0 +1,65 @@
+/*
+ * Copyright 2022 The Netty Project
+ *
+ * The Netty Project licenses this file to you 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:
+ *
+ *   https://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.netty.example.tun;
+
+import io.netty.buffer.ByteBuf;
+import io.netty.channel.ChannelHandler.Sharable;
+import io.netty.channel.ChannelHandlerContext;
+import io.netty.channel.SimpleChannelInboundHandler;
+import io.netty.channel.socket.Tun4Packet;
+import io.netty.channel.socket.TunPacket;
+
+import java.net.InetAddress;
+
+import static io.netty.channel.socket.Tun4Packet.INET4_DESTINATION_ADDRESS;
+import static io.netty.channel.socket.Tun4Packet.INET4_SOURCE_ADDRESS;
+
+/**
+ * Replies to ICMP echo ping requests.
+ */
+@Sharable
+public class Ping4Handler extends SimpleChannelInboundHandler<Tun4Packet> {
+    // https://www.iana.org/assignments/protocol-numbers/protocol-numbers.xhtml
+    public static final int PROTOCOL = 1;
+    // https://datatracker.ietf.org/doc/html/rfc792
+    public static final int TYPE = 20;
+    public static final int CHECKSUM = 22;
+    public static final int ECHO = 8;
+    public static final int ECHO_REPLY = 0;
+
+    @Override
+    protected void channelRead0(ChannelHandlerContext ctx,
+                                Tun4Packet packet) {
+        if (packet.protocol() == PROTOCOL) {
+            short icmpType = packet.content().getUnsignedByte(TYPE);
+            if (icmpType == ECHO) {
+                InetAddress source = packet.sourceAddress();
+                InetAddress destination = packet.destinationAddress();
+                int checksum = packet.content().getUnsignedShort(CHECKSUM);
+
+                // create response
+                ByteBuf buf = packet.content();
+                buf.setBytes(INET4_SOURCE_ADDRESS, destination.getAddress());
+                buf.setBytes(INET4_DESTINATION_ADDRESS, source.getAddress());
+                buf.setByte(TYPE, ECHO_REPLY);
+                buf.setShort(CHECKSUM, (checksum + 0x0800) % 0xffff);
+
+                TunPacket response = new Tun4Packet(buf.retain());
+                ctx.writeAndFlush(response);
+            }
+        }
+    }
+}

example/src/main/java/io/netty/example/tun/Ping6Handler.java

@@ -0,0 +1,67 @@
+/*
+ * Copyright 2022 The Netty Project
+ *
+ * The Netty Project licenses this file to you 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:
+ *
+ *   https://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.netty.example.tun;
+
+import io.netty.buffer.ByteBuf;
+import io.netty.channel.ChannelHandler.Sharable;
+import io.netty.channel.ChannelHandlerContext;
+import io.netty.channel.SimpleChannelInboundHandler;
+import io.netty.channel.socket.Tun6Packet;
+import io.netty.channel.socket.TunPacket;
+
+import java.net.InetAddress;
+
+import static io.netty.channel.socket.Tun6Packet.INET6_DESTINATION_ADDRESS;
+import static io.netty.channel.socket.Tun6Packet.INET6_SOURCE_ADDRESS;
+
+/**
+ * Replies to IPv6-ICMP echo ping requests.
+ */
+@Sharable
+public class Ping6Handler extends SimpleChannelInboundHandler<Tun6Packet> {
+    // https://www.iana.org/assignments/protocol-numbers/protocol-numbers.xhtml
+    public static final int PROTOCOL = 58;
+    // https://datatracker.ietf.org/doc/html/rfc8200
+    public static final int NEXT_HEADER = 6;
+    public static final int TYPE = 40;
+    public static final int CHECKSUM = 42;
+    public static final int ECHO = 128;
+    public static final int ECHO_REPLY = 129;
+
+    @Override
+    protected void channelRead0(ChannelHandlerContext ctx,
+                                Tun6Packet packet) {
+        int nextHeader = packet.content().getUnsignedByte(NEXT_HEADER);
+        if (nextHeader == PROTOCOL) {
+            short icmpType = packet.content().getUnsignedByte(TYPE);
+            if (icmpType == ECHO) {
+                InetAddress source = packet.sourceAddress();
+                InetAddress destination = packet.destinationAddress();
+                int checksum = packet.content().getUnsignedShort(CHECKSUM);
+
+                // create response
+                ByteBuf buf = packet.content();
+                buf.setBytes(INET6_SOURCE_ADDRESS, destination.getAddress());
+                buf.setBytes(INET6_DESTINATION_ADDRESS, source.getAddress());
+                buf.setByte(TYPE, ECHO_REPLY);
+                buf.setShort(CHECKSUM, checksum - 0x100);
+
+                TunPacket response = new Tun6Packet(buf.retain());
+                ctx.writeAndFlush(response);
+            }
+        }
+    }
+}