Fix data corruption in FileRegion transfer with epoll transport

Related issue: #2764

Motivation:

EpollSocketChannel.writeFileRegion() does not handle the case where the
position of a FileRegion is non-zero properly.

Modifications:

- Improve SocketFileRegionTest so that it tests the cases where the file
  transfer begins from the middle of the file
- Add another jlong parameter named 'base_off' so that we can take the
  position of a FileRegion into account

Result:

Improved test passes. Corruption is gone.

testsuite/src/test/java/io/netty/testsuite/transport/socket/SocketFileRegionTest.java

@@ -24,6 +24,7 @@ import io.netty.channel.ChannelInboundHandler;
 import io.netty.channel.DefaultFileRegion;
 import io.netty.channel.FileRegion;
 import io.netty.channel.SimpleChannelInboundHandler;
+import io.netty.util.internal.ThreadLocalRandom;
 import org.junit.Test;
 
 import java.io.File;
@@ -33,15 +34,15 @@ import java.io.IOException;
 import java.util.Random;
 import java.util.concurrent.atomic.AtomicReference;
 
+import static org.hamcrest.CoreMatchers.is;
 import static org.junit.Assert.*;
 
 public class SocketFileRegionTest extends AbstractSocketTest {
 
-    private static final Random random = new Random();
     static final byte[] data = new byte[1048576 * 10];
 
     static {
-        random.nextBytes(data);
+        ThreadLocalRandom.current().nextBytes(data);
     }
 
     @Test
@@ -82,11 +83,26 @@ public class SocketFileRegionTest extends AbstractSocketTest {
 
     private static void testFileRegion0(
             ServerBootstrap sb, Bootstrap cb, boolean voidPromise, final boolean autoRead) throws Throwable {
-        File file = File.createTempFile("netty-", ".tmp");
+        final File file = File.createTempFile("netty-", ".tmp");
         file.deleteOnExit();
 
-        FileOutputStream out = new FileOutputStream(file);
+        final FileOutputStream out = new FileOutputStream(file);
+        final Random random = ThreadLocalRandom.current();
+
+        // Prepend random data which will not be transferred, so that we can test non-zero start offset
+        final int startOffset = random.nextInt(8192);
+        for (int i = 0; i < startOffset; i ++) {
+            out.write(random.nextInt());
+        }
+
+        // .. and here comes the real data to transfer.
         out.write(data);
+
+        // .. and then some extra data which is not supposed to be transferred.
+        for (int i = random.nextInt(8192); i > 0; i --) {
+            out.write(random.nextInt());
+        }
+
         out.close();
 
         ChannelInboundHandler ch = new SimpleChannelInboundHandler<Object>() {
@@ -114,7 +130,7 @@ public class SocketFileRegionTest extends AbstractSocketTest {
         Channel sc = sb.bind().sync().channel();
 
         Channel cc = cb.connect().sync().channel();
-        FileRegion region = new DefaultFileRegion(new FileInputStream(file).getChannel(), 0L, file.length());
+        FileRegion region = new DefaultFileRegion(new FileInputStream(file).getChannel(), startOffset, data.length);
         if (voidPromise) {
             assertEquals(cc.voidPromise(), cc.writeAndFlush(region, cc.voidPromise()));
         } else {
@@ -143,6 +159,9 @@ public class SocketFileRegionTest extends AbstractSocketTest {
         if (sh.exception.get() != null) {
             throw sh.exception.get();
         }
+
+        // Make sure we did not receive more than we expected.
+        assertThat(sh.counter, is(data.length));
     }
 
     private static class TestHandler extends SimpleChannelInboundHandler<ByteBuf> {

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

@@ -933,7 +933,7 @@ JNIEXPORT jint JNICALL Java_io_netty_channel_epoll_Native_accept(JNIEnv * env, j
     return socketFd;
 }
 
-JNIEXPORT jlong JNICALL Java_io_netty_channel_epoll_Native_sendfile(JNIEnv *env, jclass clazz, jint fd, jobject fileRegion, jlong off, jlong len) {
+JNIEXPORT jlong JNICALL Java_io_netty_channel_epoll_Native_sendfile(JNIEnv *env, jclass clazz, jint fd, jobject fileRegion, jlong base_off, jlong off, jlong len) {
     jobject fileChannel = (*env)->GetObjectField(env, fileRegion, fileChannelFieldId);
     if (fileChannel == NULL) {
         throwRuntimeException(env, "Unable to obtain FileChannel from FileRegion");
@@ -950,7 +950,7 @@ JNIEXPORT jlong JNICALL Java_io_netty_channel_epoll_Native_sendfile(JNIEnv *env,
         return -1;
     }
     ssize_t res;
-    off_t offset = off;
+    off_t offset = base_off + off;
     int err;
     do {
       res = sendfile(fd, srcFd, &offset, (size_t) len);

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

@@ -62,7 +62,7 @@ void Java_io_netty_channel_epoll_Native_listen(JNIEnv * env, jclass clazz, jint
 jboolean Java_io_netty_channel_epoll_Native_connect(JNIEnv * env, jclass clazz, jint fd, jbyteArray address, jint scopeId, jint port);
 jboolean Java_io_netty_channel_epoll_Native_finishConnect(JNIEnv * env, jclass clazz, jint fd);
 jint Java_io_netty_channel_epoll_Native_accept(JNIEnv * env, jclass clazz, jint fd);
-jlong Java_io_netty_channel_epoll_Native_sendfile(JNIEnv *env, jclass clazz, jint fd, jobject fileRegion, jlong off, jlong len);
+jlong Java_io_netty_channel_epoll_Native_sendfile(JNIEnv *env, jclass clazz, jint fd, jobject fileRegion, jlong base_off, jlong off, jlong len);
 jobject Java_io_netty_channel_epoll_Native_remoteAddress(JNIEnv * env, jclass clazz, jint fd);
 jobject Java_io_netty_channel_epoll_Native_localAddress(JNIEnv * env, jclass clazz, jint fd);
 void Java_io_netty_channel_epoll_Native_setReuseAddress(JNIEnv * env, jclass clazz, jint fd, jint optval);

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

@@ -265,17 +265,19 @@ public final class EpollSocketChannel extends AbstractEpollChannel implements So
      * @return amount       the amount of written bytes
      */
     private boolean writeFileRegion(ChannelOutboundBuffer in, DefaultFileRegion region) throws Exception {
-        if (region.transfered() >= region.count()) {
+        final long regionCount = region.count();
+        if (region.transfered() >= regionCount) {
             in.remove();
             return true;
         }
 
+        final long baseOffset = region.position();
         boolean done = false;
         long flushedAmount = 0;
 
         for (int i = config().getWriteSpinCount() - 1; i >= 0; i --) {
-            long expected = region.count() - region.position();
+            final long offset = region.transfered();
-            long localFlushedAmount = Native.sendfile(fd, region, region.transfered(), expected);
+            final long localFlushedAmount = Native.sendfile(fd, region, baseOffset, offset, regionCount - offset);
             if (localFlushedAmount == 0) {
                 // Returned EAGAIN need to set EPOLLOUT
                 setEpollOut();
@@ -283,13 +285,15 @@ public final class EpollSocketChannel extends AbstractEpollChannel implements So
             }
 
             flushedAmount += localFlushedAmount;
-            if (region.transfered() >= region.count()) {
+            if (region.transfered() >= regionCount) {
                 done = true;
                 break;
             }
         }
 
-        in.progress(flushedAmount);
+        if (flushedAmount > 0) {
+            in.progress(flushedAmount);
+        }
 
         if (done) {
             in.remove();

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

@@ -75,7 +75,8 @@ final class Native {
     public static native int read(int fd, ByteBuffer buf, int pos, int limit) throws IOException;
     public static native int readAddress(int fd, long address, int pos, int limit) throws IOException;
 
-    public static native long sendfile(int dest, DefaultFileRegion src, long offset, long length) throws IOException;
+    public static native long sendfile(
+            int dest, DefaultFileRegion src, long baseOffset, long offset, long length) throws IOException;
 
     public static int sendTo(
             int fd, ByteBuffer buf, int pos, int limit, InetAddress addr, int port) throws IOException {