[#2644] Correctly release buffer when exception happens during send DatagramPacket or SctpMessage

Motivation:

When an exception is thrown during try to send DatagramPacket or SctpMessage a buffer may leak.

Modification:

Correctly handle allocated buffers in case of exception

Result:

No more leaks

transport-sctp/src/main/java/io/netty/channel/sctp/nio/NioSctpChannel.java

@@ -316,14 +316,18 @@ public class NioSctpChannel extends AbstractNioMessageChannel implements io.nett
             data = alloc.directBuffer(dataLen).writeBytes(data);
             nioData = data.nioBuffer();
         }
-
         final MessageInfo mi = MessageInfo.createOutgoing(association(), null, packet.streamIdentifier());
         mi.payloadProtocolID(packet.protocolIdentifier());
         mi.streamNumber(packet.streamIdentifier());
 
+        boolean done = false;
+        try {
             final int writtenBytes = javaChannel().send(nioData, mi);
-
+            done = writtenBytes > 0;
-        boolean done = writtenBytes > 0;
+            return done;
+        } finally {
+            // Handle this in the finally block to make sure we release the old buffer in all cases
+            // See https://github.com/netty/netty/issues/2644
             if (needsCopy) {
                 if (!done) {
                     in.current(new SctpMessage(mi, data));
@@ -331,7 +335,7 @@ public class NioSctpChannel extends AbstractNioMessageChannel implements io.nett
                     in.current(data);
                 }
             }
-        return done;
+        }
     }
 
     @Override

transport/src/main/java/io/netty/channel/socket/nio/NioDatagramChannel.java

@@ -300,17 +300,22 @@ public final class NioDatagramChannel
             nioData = data.nioBuffer();
         }
 
+        boolean done = false;
+        try {
             final int writtenBytes;
             if (remoteAddress != null) {
                 writtenBytes = javaChannel().send(nioData, remoteAddress);
             } else {
                 writtenBytes = javaChannel().write(nioData);
             }
-
+            done =  writtenBytes > 0;
-        boolean done =  writtenBytes > 0;
+            return done;
+        } finally {
+            // Handle this in the finally block to make sure we release the old buffer in all cases
+            // See https://github.com/netty/netty/issues/2644
             if (needsCopy) {
-            // This means we have allocated a new buffer and need to store it back so we not need to allocate it again
+                // This means we have allocated a new buffer and need to store it back so we not need to allocate it
-            // later
+                // later again
                 if (remoteAddress == null) {
                     // remoteAddress is null which means we can handle it as ByteBuf directly
                     in.current(data);
@@ -319,12 +324,12 @@ public final class NioDatagramChannel
                         // store it back with all the needed informations
                         in.current(new DefaultAddressedEnvelope<ByteBuf, SocketAddress>(data, remoteAddress));
                     } else {
-                    // Just store back the new create buffer so it is cleaned up once in.remove() is called.
+                        // Just store back the new created buffer so it is cleaned up once in.remove() is called.
                         in.current(data);
                     }
                 }
             }
-        return done;
+        }
     }
 
     @Override