get rid of over-zealous sending of channel EOF & close messages which was implemented with questionable synchronization

fixes #105

also relevant to #126 since AbstractChannel does not synchronize on
'this' anymore

src/main/java/net/schmizz/sshj/connection/channel/AbstractChannel.java

@@ -86,10 +86,7 @@ public abstract class AbstractChannel
     protected final Event<ConnectionException> openEvent;
     /** Channel close event */
     protected final Event<ConnectionException> closeEvent;
-
-    /* Access to these fields should be synchronized using this object */
-    private boolean eofSent;
-    private boolean eofGot;
+    /** Whether we have already sent a CHANNEL_CLOSE request to the server */
     private boolean closeRequested;
 
     /** Local window */
@@ -282,8 +279,9 @@ public abstract class AbstractChannel
         closeEvent.await(timeout, unit);
     }
 
-    protected synchronized void sendClose()
+    protected void sendClose()
             throws TransportException {
+        openCloseLock.lock();
         try {
             if (!closeRequested) {
                 log.debug("Sending close");
@@ -291,11 +289,12 @@ public abstract class AbstractChannel
             }
         } finally {
             closeRequested = true;
+            openCloseLock.unlock();
         }
     }
 
     @Override
-    public synchronized boolean isOpen() {
+    public boolean isOpen() {
         openCloseLock.lock();
         try {
             return openEvent.isSet() && !closeEvent.isSet() && !closeRequested;
@@ -405,13 +404,10 @@ public abstract class AbstractChannel
         }
     }
 
-    private synchronized void gotEOF()
+    private void gotEOF()
             throws TransportException {
         log.debug("Got EOF");
-        eofGot = true;
         eofInputStreams();
-        if (eofSent)
-            sendClose();
     }
 
     /** Called when EOF has been received. Subclasses can override but must call super. */
@@ -419,22 +415,6 @@ public abstract class AbstractChannel
         in.eof();
     }
 
-    @Override
-    public synchronized void sendEOF()
-            throws TransportException {
-        try {
-            if (!closeRequested && !eofSent) {
-                log.debug("Sending EOF");
-                trans.write(newBuffer(Message.CHANNEL_EOF));
-                if (eofGot)
-                    sendClose();
-            }
-        } finally {
-            eofSent = true;
-            out.setClosed();
-        }
-    }
-
     @Override
     public String toString() {
         return "< " + type + " channel: id=" + id + ", recipient=" + recipient + ", localWin=" + lwin + ", remoteWin="

src/main/java/net/schmizz/sshj/connection/channel/Channel.java

@@ -119,15 +119,6 @@ public interface Channel
     /** @return whether the channel is open. */
     boolean isOpen();
 
-    /**
-     * Sends an EOF message to the server for this channel; indicating that no more data will be sent by us. The {@code
-     * OutputStream} for this channel will be closed and no longer usable.
-     *
-     * @throws TransportException if there is an error sending the EOF message
-     */
-    void sendEOF()
-            throws TransportException;
-
     /**
      * Set whether local window should automatically expand when data is received, irrespective of whether data has been
      * read from that stream. This is useful e.g. when a remote command produces a lot of output that would fill the

src/main/java/net/schmizz/sshj/connection/channel/ChannelOutputStream.java

@@ -84,7 +84,7 @@ public final class ChannelOutputStream
                 throws TransportException, ConnectionException {
             final int bufferSize = packet.wpos() - dataOffset;
             if (bufferSize >= win.getMaxPacketSize()) {
-                flush(bufferSize);
+                flush(bufferSize, true);
                 return 0;
             } else {
                 final int n = Math.min(len, win.getMaxPacketSize() - bufferSize);
@@ -93,18 +93,23 @@ public final class ChannelOutputStream
             }
         }
 
-        void flush()
+        boolean flush(boolean canAwaitExpansion)
                 throws TransportException, ConnectionException {
-            flush(packet.wpos() - dataOffset);
+            return flush(packet.wpos() - dataOffset, canAwaitExpansion);
         }
-        
-        void flush(int bufferSize)
+
+        boolean flush(int bufferSize, boolean canAwaitExpansion)
                 throws TransportException, ConnectionException {
             while (bufferSize > 0) {
 
                 long remoteWindowSize = win.getSize();
-                if (remoteWindowSize == 0)
-                    remoteWindowSize = win.awaitExpansion(remoteWindowSize);
+                if (remoteWindowSize == 0) {
+                    if (canAwaitExpansion) {
+                        remoteWindowSize = win.awaitExpansion(remoteWindowSize);
+                    } else {
+                        return false;
+                    }
+                }
 
                 // We can only write the min. of
                 // a) how much data we have
@@ -136,6 +141,8 @@ public final class ChannelOutputStream
 
                 bufferSize = leftOverBytes;
             }
+
+            return true;
         }
 
     }
@@ -184,18 +191,14 @@ public final class ChannelOutputStream
             throws IOException {
         if (!closed) {
             try {
-                buffer.flush();
-                chan.sendEOF();
+                buffer.flush(false);
+                trans.write(new SSHPacket(Message.CHANNEL_EOF).putUInt32(chan.getRecipient()));
             } finally {
-                setClosed();
+                closed = true;
             }
         }
     }
 
-    public synchronized void setClosed() {
-        closed = true;
-    }
-
     /**
      * Send all data currently buffered. If window space is exhausted in the process, this will block
      * until it is expanded by the server.
@@ -206,7 +209,7 @@ public final class ChannelOutputStream
     public synchronized void flush()
             throws IOException {
         checkClose();
-        buffer.flush();
+        buffer.flush(true);
     }
 
     @Override