You're right, I think we should be able to minimize the number of
window adjustements to decrease traffic.
On Thu, Dec 15, 2011 at 16:35, Simon Paradis <spara...@pgsolutions.com> wrote:
> Hi,
>
> I'm using SSHD 0.6.0 on Oracle JVM 1.6.0_23-b05 on Windows 7 x64. I have a
> custom server channel subclassing AbstractServerChannel. I'm wondering if my
> handling of SSH window adjustment message is correct. I'm sending a window
> adjustment everytime the window size decreases by half. Apparenly, some
> OpenSSH implementation works this way. This code is talking to another C++
> process built with libssh2 1.3.0.
>
> protected void doWriteData(byte[] p_Data, int p_Offset, int p_Length)
> throws IOException
> {
> // The localWindow.consumeAndCheck() send too much window adjustments.
> localWindow.consume(p_Length);
> int size = localWindow.getSize();
> int maxSize = localWindow.getMaxSize();
> if (size < maxSize/2) {
> localWindow.expand(maxSize - size);
> sendWindowAdjust(maxSize - size);
> }
>
> // Do stuff ...
> }
>
> Before that, I was calling localWindow.consumeAndCheck(p_Length) but I found
> out it sends quite a lot of these adjustment down the wire. In Window.java,
> we have this
>
> public void consumeAndCheck(int len) throws IOException {
> synchronized (lock) {
> size -= len;
> if (log.isTraceEnabled()) {
> log.trace("Consume " + name + " by " + len + " down to " + size);
> }
> check(maxSize);
> }
> }
>
> public void check(int maxFree) throws IOException {
> synchronized (lock) {
> if ((size < maxFree) && (maxFree - size > packetSize * 3 || size < maxFree
> / 2)) {
> if (log.isDebugEnabled()) {
> log.debug("Increase " + name + " by " + (maxFree - size) + " up to " +
> maxFree);
> }
> channel.sendWindowAdjust(maxFree - size);
> size = maxFree;
> }
> }
> }
>
> This is sending a window adjustment every 3 * packetSize, so every 96kb in my
> case since the packet size is 32kb. Is there a practical reason for doing
> this instead of sending it every half of the maximum size ?
>
> Thanks,
>
> Simon Paradis
--
------------------------
Guillaume Nodet
------------------------
Blog: http://gnodet.blogspot.com/
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