Directly receive remote address when call accept(...)

Motivation:

There is a small race in the native transport where an accept(...) may success but a later try to obtain the remote address from the fd may fail is the fd is already closed.

Modifications:

Let accept(...) directly set the remote address.

Result:

No more race possible.

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

@@ -173,7 +173,24 @@ jobject createInetSocketAddress(JNIEnv* env, struct sockaddr_storage addr) {
     return socketAddr;
 }
 
-static jbyteArray createInetSocketAddressArray(JNIEnv* env, struct sockaddr_storage addr) {
+
+static inline int addressLength(struct sockaddr_storage addr) {
+    if (addr.ss_family == AF_INET) {
+        return 8;
+    } else {
+        struct sockaddr_in6* s = (struct sockaddr_in6*) &addr;
+        if (s->sin6_addr.s6_addr[0] == 0x00 && s->sin6_addr.s6_addr[1] == 0x00 && s->sin6_addr.s6_addr[2] == 0x00 && s->sin6_addr.s6_addr[3] == 0x00 && s->sin6_addr.s6_addr[4] == 0x00
+                && s->sin6_addr.s6_addr[5] == 0x00 && s->sin6_addr.s6_addr[6] == 0x00 && s->sin6_addr.s6_addr[7] == 0x00 && s->sin6_addr.s6_addr[8] == 0x00 && s->sin6_addr.s6_addr[9] == 0x00
+                 && s->sin6_addr.s6_addr[10] == 0xff && s->sin6_addr.s6_addr[11] == 0xff) {
+            // IPv4-mapped-on-IPv6
+            return 8;
+        } else {
+            return 24;
+        }
+    }
+}
+
+static inline void initInetSocketAddressArray(JNIEnv* env, struct sockaddr_storage addr, jbyteArray bArray, int offset, int len) {
     int port;
     if (addr.ss_family == AF_INET) {
         struct sockaddr_in* s = (struct sockaddr_in*) &addr;
@@ -190,17 +207,12 @@ static jbyteArray createInetSocketAddressArray(JNIEnv* env, struct sockaddr_stor
         a[6] = port >> 8;
         a[7] = port;
 
-        jbyteArray bArray = (*env)->NewByteArray(env, 8);
+        (*env)->SetByteArrayRegion(env, bArray, offset, 8, (jbyte*) &a);
-        (*env)->SetByteArrayRegion(env, bArray, 0, 8, (jbyte*) &a);
-
-        return bArray;
     } else {
         struct sockaddr_in6* s = (struct sockaddr_in6*) &addr;
         port = ntohs(s->sin6_port);
 
-        if (s->sin6_addr.s6_addr[0] == 0x00 && s->sin6_addr.s6_addr[1] == 0x00 && s->sin6_addr.s6_addr[2] == 0x00 && s->sin6_addr.s6_addr[3] == 0x00 && s->sin6_addr.s6_addr[4] == 0x00
+        if (len == 8) {
-                && s->sin6_addr.s6_addr[5] == 0x00 && s->sin6_addr.s6_addr[6] == 0x00 && s->sin6_addr.s6_addr[7] == 0x00 && s->sin6_addr.s6_addr[8] == 0x00 && s->sin6_addr.s6_addr[9] == 0x00
-                 && s->sin6_addr.s6_addr[10] == 0xff && s->sin6_addr.s6_addr[11] == 0xff) {
             // IPv4-mapped-on-IPv6
             // Encode port into the array and write it into the jbyteArray
             unsigned char a[4];
@@ -209,12 +221,9 @@ static jbyteArray createInetSocketAddressArray(JNIEnv* env, struct sockaddr_stor
             a[2] = port >> 8;
             a[3] = port;
 
-            jbyteArray bArray = (*env)->NewByteArray(env, 8);
             // we only need the last 4 bytes for mapped address
-            (*env)->SetByteArrayRegion(env, bArray, 0, 4, (jbyte*) &(s->sin6_addr.s6_addr[12]));
+            (*env)->SetByteArrayRegion(env, bArray, offset, 4, (jbyte*) &(s->sin6_addr.s6_addr[12]));
-            (*env)->SetByteArrayRegion(env, bArray, 4, 4, (jbyte*) &a);
+            (*env)->SetByteArrayRegion(env, bArray, offset + 4, 4, (jbyte*) &a);
-
-            return bArray;
         } else {
             // Encode scopeid and port into the array
             unsigned char a[8];
@@ -227,14 +236,20 @@ static jbyteArray createInetSocketAddressArray(JNIEnv* env, struct sockaddr_stor
             a[6] = port >> 8;
             a[7] = port;
 
-            jbyteArray bArray = (*env)->NewByteArray(env, 24);
+            (*env)->SetByteArrayRegion(env, bArray, offset, 16, (jbyte*) &(s->sin6_addr.s6_addr));
-            (*env)->SetByteArrayRegion(env, bArray, 0, 16, (jbyte*) &(s->sin6_addr.s6_addr));
+            (*env)->SetByteArrayRegion(env, bArray, offset + 16, 8, (jbyte*) &a);
-            (*env)->SetByteArrayRegion(env, bArray, 16, 8, (jbyte*) &a);
-            return bArray;
         }
     }
 }
 
+static jbyteArray createInetSocketAddressArray(JNIEnv* env, struct sockaddr_storage addr) {
+    int len = addressLength(addr);
+    jbyteArray bArray = (*env)->NewByteArray(env, len);
+
+    initInetSocketAddressArray(env, addr, bArray, 0, len);
+    return bArray;
+}
+
 static jobject createDatagramSocketAddress(JNIEnv* env, struct sockaddr_storage addr, int len) {
     char ipstr[INET6_ADDRSTRLEN];
     int port;
@@ -537,6 +552,7 @@ jint JNI_OnLoad(JavaVM* vm, void* reserved) {
             throwRuntimeException(env, "failed to get field ID: NativeDatagramPacket.count");
             return JNI_ERR;
         }
+
         return JNI_VERSION_1_6;
     }
 }
@@ -1018,21 +1034,30 @@ JNIEXPORT jint JNICALL Java_io_netty_channel_epoll_Native_finishConnect0(JNIEnv*
     return -optval;
 }
 
-JNIEXPORT jint JNICALL Java_io_netty_channel_epoll_Native_accept0(JNIEnv* env, jclass clazz, jint fd) {
+JNIEXPORT jint JNICALL Java_io_netty_channel_epoll_Native_accept0(JNIEnv* env, jclass clazz, jint fd, jbyteArray acceptedAddress) {
     jint socketFd;
     int err;
+    struct sockaddr_storage addr;
+    socklen_t address_len = sizeof(addr);
 
     do {
         if (accept4) {
-            socketFd = accept4(fd, NULL, 0, SOCK_NONBLOCK | SOCK_CLOEXEC);
+            socketFd = accept4(fd, (struct sockaddr*) &addr, &address_len, SOCK_NONBLOCK | SOCK_CLOEXEC);
         } else  {
-            socketFd = accept(fd, NULL, 0);
+            socketFd = accept(fd, (struct sockaddr*) &addr, &address_len);
         }
     } while (socketFd == -1 && ((err = errno) == EINTR));
 
     if (socketFd == -1) {
         return -err;
     }
+
+    int len = addressLength(addr);
+
+    // Fill in remote address details
+    (*env)->SetByteArrayRegion(env, acceptedAddress, 0, 4, (jbyte*) &len);
+    initInetSocketAddressArray(env, addr, acceptedAddress, 1, len);
+
     if (accept4)  {
         return socketFd;
     } else  {

transport-native-epoll/src/main/c/io_netty_channel_epoll_Native.h

@@ -69,7 +69,7 @@ jint Java_io_netty_channel_epoll_Native_listen0(JNIEnv* env, jclass clazz, jint
 jint Java_io_netty_channel_epoll_Native_connect(JNIEnv* env, jclass clazz, jint fd, jbyteArray address, jint scopeId, jint port);
 jint Java_io_netty_channel_epoll_Native_connectDomainSocket(JNIEnv* env, jclass clazz, jint fd, jstring address);
 jint Java_io_netty_channel_epoll_Native_finishConnect0(JNIEnv* env, jclass clazz, jint fd);
-jint Java_io_netty_channel_epoll_Native_accept0(JNIEnv* env, jclass clazz, jint fd);
+jint Java_io_netty_channel_epoll_Native_accept0(JNIEnv* env, jclass clazz, jint fd, jbyteArray acceptedAddress);
 jlong Java_io_netty_channel_epoll_Native_sendfile0(JNIEnv* env, jclass clazz, jint fd, jobject fileRegion, jlong base_off, jlong off, jlong len);
 jbyteArray Java_io_netty_channel_epoll_Native_remoteAddress0(JNIEnv* env, jclass clazz, jint fd);
 jbyteArray Java_io_netty_channel_epoll_Native_localAddress0(JNIEnv* env, jclass clazz, jint fd);

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

@@ -63,9 +63,13 @@ public abstract class AbstractEpollServerChannel extends AbstractEpollChannel im
         throw new UnsupportedOperationException();
     }
 
-    protected abstract Channel newChildChannel(int fd) throws Exception;
+    abstract Channel newChildChannel(int fd, byte[] remote, int offset, int len) throws Exception;
 
     final class EpollServerSocketUnsafe extends AbstractEpollUnsafe {
+        // Will hold the remote address after accept(...) was sucesssful.
+        // We need 24 bytes for the address as maximum + 1 byte for storing the length.
+        // So use 26 bytes as it's a power of two.
+        private final byte[] acceptedAddress = new byte[26];
 
         @Override
         public void connect(SocketAddress socketAddress, SocketAddress socketAddress2, ChannelPromise channelPromise) {
@@ -94,7 +98,7 @@ public abstract class AbstractEpollServerChannel extends AbstractEpollChannel im
                             ? Integer.MAX_VALUE : config.getMaxMessagesPerRead();
                     int messages = 0;
                     do {
-                        int socketFd = Native.accept(fd().intValue());
+                        int socketFd = Native.accept(fd().intValue(), acceptedAddress);
                         if (socketFd == -1) {
                             // this means everything was handled for now
                             break;
@@ -102,7 +106,8 @@ public abstract class AbstractEpollServerChannel extends AbstractEpollChannel im
                         readPending = false;
 
                         try {
-                            pipeline.fireChannelRead(newChildChannel(socketFd));
+                            int len = acceptedAddress[0];
+                            pipeline.fireChannelRead(newChildChannel(socketFd, acceptedAddress, 1, len));
                         } catch (Throwable t) {
                             // keep on reading as we use epoll ET and need to consume everything from the socket
                             pipeline.fireChannelReadComplete();

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

@@ -46,7 +46,7 @@ public final class EpollServerDomainSocketChannel extends AbstractEpollServerCha
     }
 
     @Override
-    protected Channel newChildChannel(int fd) throws Exception {
+    protected Channel newChildChannel(int fd, byte[] addr, int offset, int len) throws Exception {
         return new EpollDomainSocketChannel(this, fd);
     }
 

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

@@ -86,7 +86,7 @@ public final class EpollServerSocketChannel extends AbstractEpollServerChannel i
     }
 
     @Override
-    protected Channel newChildChannel(int fd) throws Exception {
+    protected Channel newChildChannel(int fd, byte[] address, int offset, int len) throws Exception {
-        return new EpollSocketChannel(this, fd);
+        return new EpollSocketChannel(this, fd, Native.address(address, offset, len));
     }
 }

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

@@ -40,12 +40,12 @@ public final class EpollSocketChannel extends AbstractEpollStreamChannel impleme
     private volatile InetSocketAddress local;
     private volatile InetSocketAddress remote;
 
-    EpollSocketChannel(Channel parent, int fd) {
+    EpollSocketChannel(Channel parent, int fd, InetSocketAddress remote) {
         super(parent, fd);
         config = new EpollSocketChannelConfig(this);
         // Directly cache the remote and local addresses
         // See https://github.com/netty/netty/issues/2359
-        remote = Native.remoteAddress(fd);
+        this.remote = remote;
         local = Native.localAddress(fd);
     }
 
@@ -184,7 +184,7 @@ public final class EpollSocketChannel extends AbstractEpollStreamChannel impleme
         if (super.doConnect(remoteAddress, localAddress)) {
             int fd = fd().intValue();
             local = Native.localAddress(fd);
-            remote = Native.remoteAddress(fd);
+            remote = (InetSocketAddress) remoteAddress;
             return true;
         }
         return false;

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

@@ -458,7 +458,7 @@ final class Native {
         if (addr == null) {
             return null;
         }
-        return address(addr);
+        return address(addr, 0, addr.length);
     }
 
     public static InetSocketAddress localAddress(int fd) {
@@ -468,11 +468,10 @@ final class Native {
         if (addr == null) {
             return null;
         }
-        return address(addr);
+        return address(addr, 0, addr.length);
     }
 
-    static InetSocketAddress address(byte[] addr) {
+    static InetSocketAddress address(byte[] addr, int offset, int len) {
-        int len = addr.length;
         // The last 4 bytes are always the port
         final int port = decodeInt(addr, len - 4);
         final InetAddress address;
@@ -484,7 +483,7 @@ final class Native {
                 // - 4  == port
                 case 8:
                     byte[] ipv4 = new byte[4];
-                    System.arraycopy(addr, 0, ipv4, 0, 4);
+                    System.arraycopy(addr, offset, ipv4, 0, 4);
                     address = InetAddress.getByAddress(ipv4);
                     break;
 
@@ -494,7 +493,7 @@ final class Native {
                 // - 4   == port
                 case 24:
                     byte[] ipv6 = new byte[16];
-                    System.arraycopy(addr, 0, ipv6, 0, 16);
+                    System.arraycopy(addr, offset, ipv6, 0, 16);
                     int scopeId = decodeInt(addr, len  - 8);
                     address = Inet6Address.getByAddress(null, ipv6, scopeId);
                     break;
@@ -507,7 +506,7 @@ final class Native {
         }
     }
 
-    private static int decodeInt(byte[] addr, int index) {
+    static int decodeInt(byte[] addr, int index) {
         return  (addr[index]     & 0xff) << 24 |
                 (addr[index + 1] & 0xff) << 16 |
                 (addr[index + 2] & 0xff) <<  8 |
@@ -517,8 +516,8 @@ final class Native {
     private static native byte[] remoteAddress0(int fd);
     private static native byte[] localAddress0(int fd);
 
-    public static int accept(int fd) throws IOException {
+    public static int accept(int fd, byte[] addr) throws IOException {
-        int res = accept0(fd);
+        int res = accept0(fd, addr);
         if (res >= 0) {
             return res;
         }
@@ -529,7 +528,7 @@ final class Native {
         throw newIOException("accept", res);
     }
 
-    private static native int accept0(int fd);
+    private static native int accept0(int fd, byte[] addr);
 
     public static int recvFd(int fd) throws IOException {
         int res = recvFd0(fd);

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

@@ -32,7 +32,7 @@ public class NativeTest {
         ByteBuffer buffer = ByteBuffer.wrap(bytes);
         buffer.put(inetAddress.getAddress().getAddress());
         buffer.putInt(inetAddress.getPort());
-        Assert.assertEquals(inetAddress, Native.address(buffer.array()));
+        Assert.assertEquals(inetAddress, Native.address(buffer.array(), 0, bytes.length));
     }
 
     @Test
@@ -44,6 +44,6 @@ public class NativeTest {
         buffer.put(address.getAddress());
         buffer.putInt(address.getScopeId());
         buffer.putInt(inetAddress.getPort());
-        Assert.assertEquals(inetAddress, Native.address(buffer.array()));
+        Assert.assertEquals(inetAddress, Native.address(buffer.array(), 0, bytes.length));
     }
 }