Correctly handle ipv6 mapped ipv4 addresses when using recvmmsg (#9541)

Motivation:

394a1b3485 introduced the possibility to use recvmmsg(...) but did not correctly handle ipv6 mapped ip4 addresses to make it consistent with other transports.

Modifications:

- Correctly handle ipv6 mapped ipv4 addresses by only copy over the relevant bytes
- Small improvement on how to detect ipv6 mapped ipv4 addresses by using memcmp and not byte by byte compare
- Adjust test to cover this bug

Result:

Correctly handle ipv6 mapped ipv4 addresses

testsuite/src/main/java/io/netty/testsuite/transport/socket/DatagramUnicastTest.java

@@ -30,6 +30,7 @@ import io.netty.channel.socket.DatagramPacket;
 import org.junit.Test;
 
 import java.net.InetSocketAddress;
+import java.net.SocketAddress;
 import java.nio.channels.NotYetConnectedException;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.TimeUnit;
@@ -157,14 +158,19 @@ public class DatagramUnicastTest extends AbstractDatagramTest {
                 }
             });
 
-            final CountDownLatch latch = new CountDownLatch(count);
+            final SocketAddress sender;
-            sc = setupServerChannel(sb, bytes, latch, false);
             if (bindClient) {
                 cc = cb.bind(newSocketAddress()).sync().channel();
+                sender = cc.localAddress();
             } else {
                 cb.option(ChannelOption.DATAGRAM_CHANNEL_ACTIVE_ON_REGISTRATION, true);
                 cc = cb.register().sync().channel();
+                sender = null;
             }
+
+            final CountDownLatch latch = new CountDownLatch(count);
+            sc = setupServerChannel(sb, bytes, sender, latch, false);
+
             InetSocketAddress addr = (InetSocketAddress) sc.localAddress();
             for (int i = 0; i < count; i++) {
                 switch (wrapType) {
@@ -231,8 +237,10 @@ public class DatagramUnicastTest extends AbstractDatagramTest {
         DatagramChannel cc = null;
         try {
             final CountDownLatch latch = new CountDownLatch(count);
-            sc = setupServerChannel(sb, bytes, latch, true);
+            cc = (DatagramChannel) cb.bind(newSocketAddress()).sync().channel();
-            cc = (DatagramChannel) cb.connect(sc.localAddress()).sync().channel();
+            sc = setupServerChannel(sb, bytes, cc.localAddress(), latch, true);
+
+            cc.connect(sc.localAddress()).syncUninterruptibly();
 
             for (int i = 0; i < count; i++) {
                 switch (wrapType) {
@@ -275,7 +283,8 @@ public class DatagramUnicastTest extends AbstractDatagramTest {
     }
 
     @SuppressWarnings("deprecation")
-    private Channel setupServerChannel(Bootstrap sb, final byte[] bytes, final CountDownLatch latch, final boolean echo)
+    private Channel setupServerChannel(Bootstrap sb, final byte[] bytes, final SocketAddress sender,
+                                       final CountDownLatch latch, final boolean echo)
             throws Throwable {
         sb.handler(new ChannelInitializer<Channel>() {
             @Override
@@ -283,6 +292,12 @@ public class DatagramUnicastTest extends AbstractDatagramTest {
                 ch.pipeline().addLast(new SimpleChannelInboundHandler<DatagramPacket>() {
                     @Override
                     public void channelRead0(ChannelHandlerContext ctx, DatagramPacket msg) throws Exception {
+                        if (sender == null) {
+                            assertNotNull(msg.sender());
+                        } else {
+                            assertEquals(sender, msg.sender());
+                        }
+
                         ByteBuf buf = msg.content();
                         assertEquals(bytes.length, buf.readableBytes());
                         for (int i = 0; i < bytes.length; i++) {

transport-native-epoll/src/main/c/netty_epoll_native.c

@@ -67,6 +67,7 @@ struct mmsghdr {
 
 // Those are initialized in the init(...) method and cached for performance reasons
 static jfieldID packetAddrFieldId = NULL;
+static jfieldID packetAddrLenFieldId = NULL;
 static jfieldID packetScopeIdFieldId = NULL;
 static jfieldID packetPortFieldId = NULL;
 static jfieldID packetMemoryAddressFieldId = NULL;
@@ -362,12 +363,20 @@ static jint netty_epoll_native_recvmmsg0(JNIEnv* env, jclass clazz, jint fd, jbo
             struct sockaddr_in* ipaddr = (struct sockaddr_in*) addr;
 
             (*env)->SetByteArrayRegion(env, address, 0, 4, (jbyte*) &ipaddr->sin_addr.s_addr);
+            (*env)->SetIntField(env, packet, packetAddrLenFieldId, 4);
             (*env)->SetIntField(env, packet, packetScopeIdFieldId, 0);
             (*env)->SetIntField(env, packet, packetPortFieldId, ntohs(ipaddr->sin_port));
         } else {
+              int addrLen = netty_unix_socket_ipAddressLength(addr);
               struct sockaddr_in6* ip6addr = (struct sockaddr_in6*) addr;
 
-              (*env)->SetByteArrayRegion(env, address, 0, 16, (jbyte*) &ip6addr->sin6_addr.s6_addr);
+              if (addrLen == 4) {
+                  // IPV4 mapped IPV6 address
+                  (*env)->SetByteArrayRegion(env, address, 12, 4, (jbyte*) &ip6addr->sin6_addr.s6_addr);
+              } else {
+                  (*env)->SetByteArrayRegion(env, address, 0, 16, (jbyte*) &ip6addr->sin6_addr.s6_addr);
+              }
+              (*env)->SetIntField(env, packet, packetAddrLenFieldId, addrLen);
               (*env)->SetIntField(env, packet, packetScopeIdFieldId, ip6addr->sin6_scope_id);
               (*env)->SetIntField(env, packet, packetPortFieldId, ntohs(ip6addr->sin6_port));
         }
@@ -605,6 +614,11 @@ static jint netty_epoll_native_JNI_OnLoad(JNIEnv* env, const char* packagePrefix
         netty_unix_errors_throwRuntimeException(env, "failed to get field ID: NativeDatagramPacket.addr");
         goto error;
     }
+    packetAddrLenFieldId = (*env)->GetFieldID(env, nativeDatagramPacketCls, "addrLen", "I");
+    if (packetAddrLenFieldId == NULL) {
+        netty_unix_errors_throwRuntimeException(env, "failed to get field ID: NativeDatagramPacket.addrLen");
+        goto error;
+    }
     packetScopeIdFieldId = (*env)->GetFieldID(env, nativeDatagramPacketCls, "scopeId", "I");
     if (packetScopeIdFieldId == NULL) {
         netty_unix_errors_throwRuntimeException(env, "failed to get field ID: NativeDatagramPacket.scopeId");
@@ -649,6 +663,7 @@ error:
        netty_epoll_linuxsocket_JNI_OnUnLoad(env);
    }
    packetAddrFieldId = NULL;
+   packetAddrLenFieldId = NULL;
    packetScopeIdFieldId = NULL;
    packetPortFieldId = NULL;
    packetMemoryAddressFieldId = NULL;
@@ -666,6 +681,7 @@ static void netty_epoll_native_JNI_OnUnLoad(JNIEnv* env) {
     netty_epoll_linuxsocket_JNI_OnUnLoad(env);
 
     packetAddrFieldId = NULL;
+    packetAddrLenFieldId = NULL;
     packetScopeIdFieldId = NULL;
     packetPortFieldId = NULL;
     packetMemoryAddressFieldId = NULL;

transport-native-epoll/src/main/java/io/netty/channel/epoll/NativeDatagramPacketArray.java

@@ -40,6 +40,10 @@ final class NativeDatagramPacketArray implements ChannelOutboundBuffer.MessagePr
     // We share one IovArray for all NativeDatagramPackets to reduce memory overhead. This will allow us to write
     // up to IOV_MAX iovec across all messages in one sendmmsg(...) call.
     private final IovArray iovArray = new IovArray();
+
+    // temporary array to copy the ipv4 part of ipv6-mapped-ipv4 addresses and then create a Inet4Address out of it.
+    private final byte[] ipv4Bytes = new byte[4];
+
     private int count;
 
     NativeDatagramPacketArray() {
@@ -110,13 +114,14 @@ final class NativeDatagramPacketArray implements ChannelOutboundBuffer.MessagePr
      * Used to pass needed data to JNI.
      */
     @SuppressWarnings("unused")
-    static final class NativeDatagramPacket {
+    final class NativeDatagramPacket {
 
         // This is the actual struct iovec*
         private long memoryAddress;
         private int count;
 
         private final byte[] addr = new byte[16];
+
         private int addrLen;
         private int scopeId;
         private int port;
@@ -145,10 +150,11 @@ final class NativeDatagramPacketArray implements ChannelOutboundBuffer.MessagePr
 
         DatagramPacket newDatagramPacket(ByteBuf buffer, InetSocketAddress localAddress) throws UnknownHostException {
             final InetAddress address;
-            if (scopeId != 0) {
+            if (addrLen == ipv4Bytes.length) {
-                address = Inet6Address.getByAddress(null, addr, scopeId);
+                System.arraycopy(addr, 0, ipv4Bytes, 0, addrLen);
+                address = InetAddress.getByAddress(ipv4Bytes);
             } else {
-                address = InetAddress.getByAddress(addr);
+                address = Inet6Address.getByAddress(null, addr, scopeId);
             }
             return new DatagramPacket(buffer.writerIndex(count),
                     localAddress, new InetSocketAddress(address, port));

transport-native-epoll/src/test/java/io/netty/channel/epoll/EpollDatagramScatteringReadTest.java

@@ -28,6 +28,7 @@ import io.netty.testsuite.transport.socket.AbstractDatagramTest;
 import org.junit.Test;
 
 import java.net.InetSocketAddress;
+import java.net.SocketAddress;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.concurrent.CountDownLatch;
@@ -82,6 +83,9 @@ public class EpollDatagramScatteringReadTest extends AbstractDatagramTest  {
                     // Nothing will be sent.
                 }
             });
+            cc = cb.bind(newSocketAddress()).sync().channel();
+            final SocketAddress ccAddress = cc.localAddress();
+
             final AtomicReference<Throwable> errorRef = new AtomicReference<Throwable>();
             final byte[] bytes = new byte[packetSize];
             ThreadLocalRandom.current().nextBytes(bytes);
@@ -98,6 +102,8 @@ public class EpollDatagramScatteringReadTest extends AbstractDatagramTest  {
 
                 @Override
                 protected void channelRead0(ChannelHandlerContext ctx, DatagramPacket msg) {
+                    assertEquals(ccAddress, msg.sender());
+
                     assertEquals(bytes.length, msg.content().readableBytes());
                     byte[] receivedBytes = new byte[bytes.length];
                     msg.content().readBytes(receivedBytes);
@@ -115,7 +121,6 @@ public class EpollDatagramScatteringReadTest extends AbstractDatagramTest  {
 
             sb.option(ChannelOption.AUTO_READ, false);
             sc = sb.bind(newSocketAddress()).sync().channel();
-            cc = cb.bind(newSocketAddress()).sync().channel();
 
             InetSocketAddress addr = (InetSocketAddress) sc.localAddress();
 

transport-native-unix-common/src/main/c/netty_unix_socket.c

@@ -43,6 +43,7 @@ static jclass inetSocketAddressClass = NULL;
 static int socketType = AF_INET;
 static const unsigned char wildcardAddress[] = { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 };
 static const unsigned char ipv4MappedWildcardAddress[] = { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xff, 0xff, 0x00, 0x00, 0x00, 0x00 };
+static const unsigned char ipv4MappedAddress[] = { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xff, 0xff };
 
 // Optional external methods
 extern int accept4(int sockFd, struct sockaddr* addr, socklen_t* addrlen, int flags) __attribute__((weak)) __attribute__((weak_import));
@@ -67,15 +68,13 @@ static int nettyNonBlockingSocket(int domain, int type, int protocol) {
 #endif
 }
 
-static int ipAddressLength(const struct sockaddr_storage* addr) {
+int netty_unix_socket_ipAddressLength(const struct sockaddr_storage* addr) {
     if (addr->ss_family == AF_INET) {
         return 4;
     }
     struct sockaddr_in6* s = (struct sockaddr_in6*) addr;
-    if (s->sin6_addr.s6_addr[11] == 0xff && s->sin6_addr.s6_addr[10] == 0xff &&
+    if (memcmp(s->sin6_addr.s6_addr, ipv4MappedAddress, 12) == 0) {
-            s->sin6_addr.s6_addr[9] == 0x00 && s->sin6_addr.s6_addr[8] == 0x00 && s->sin6_addr.s6_addr[7] == 0x00 && s->sin6_addr.s6_addr[6] == 0x00 && s->sin6_addr.s6_addr[5] == 0x00 &&
+         // IPv4-mapped-on-IPv6
-            s->sin6_addr.s6_addr[4] == 0x00 && s->sin6_addr.s6_addr[3] == 0x00 && s->sin6_addr.s6_addr[2] == 0x00 && s->sin6_addr.s6_addr[1] == 0x00 && s->sin6_addr.s6_addr[0] == 0x00) {
-            // IPv4-mapped-on-IPv6
          return 4;
     }
     return 16;
@@ -84,7 +83,7 @@ static int ipAddressLength(const struct sockaddr_storage* addr) {
 static jobject createDatagramSocketAddress(JNIEnv* env, const struct sockaddr_storage* addr, int len, jobject local) {
     int port;
     int scopeId;
-    int ipLength = ipAddressLength(addr);
+    int ipLength = netty_unix_socket_ipAddressLength(addr);
     jbyteArray addressBytes = (*env)->NewByteArray(env, ipLength);
 
     if (addr->ss_family == AF_INET) {
@@ -114,7 +113,7 @@ static jobject createDatagramSocketAddress(JNIEnv* env, const struct sockaddr_st
 }
 
 static jsize addressLength(const struct sockaddr_storage* addr) {
-    int len = ipAddressLength(addr);
+    int len = netty_unix_socket_ipAddressLength(addr);
     if (len == 4) {
         // Only encode port into it
         return len + 4;

transport-native-unix-common/src/main/c/netty_unix_socket.h

@@ -23,6 +23,7 @@
 int netty_unix_socket_initSockaddr(JNIEnv* env, jboolean ipv6, jbyteArray address, jint scopeId, jint jport, const struct sockaddr_storage* addr, socklen_t* addrSize);
 int netty_unix_socket_getOption(JNIEnv* env, jint fd, int level, int optname, void* optval, socklen_t optlen);
 int netty_unix_socket_setOption(JNIEnv* env, jint fd, int level, int optname, const void* optval, socklen_t len);
+int netty_unix_socket_ipAddressLength(const struct sockaddr_storage* addr);
 
 // These method is sometimes needed if you want to special handle some errno value before throwing an exception.
 int netty_unix_socket_getOption0(jint fd, int level, int optname, void* optval, socklen_t optlen);