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https://codeberg.org/Mercury-IM/Smack
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Fix a race on graceful disconnect
A sequence of connect(), disconnect(), and connect() could cause the connection to get disconnected again by the old reader thread, which was blocking on disconnect because a closing stream tag was read. If the second connect() was processed before the disconnect(), then the connectin would get disconnected right after the second connect(). This showed up as a "strange" sequence of stanzas in the XMPP servers log. Note that the stanza ID of the unavailable presence has a lower number then the previous stanzas: Jun 11 23:11:11 c2s18c2370 debug Resource bound: smack-inttest-two-93t70@geekplace.eu/two-93t70 Jun 11 23:11:11 c2s18c2370 debug Received[c2s]: <iq id='qn03S-26' type='get'> Jun 11 23:11:11 c2s18c2370 debug Received[c2s]: <presence id='qn03S-27'> Jun 11 23:11:11 c2s18c2370 debug Received[c2s]: <presence id='qn03S-23' type='unavailable'> Jun 11 23:11:11 c2s18c2370 debug Received </stream:stream> This is because the disconnect() of the first reader thread could generate the unavailable presence, but was blocked afterwards when entering the synchronized disconnect(Presence unavailablePresence). SMACK-633.
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989076a166
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1 changed files with 22 additions and 20 deletions
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@ -465,6 +465,16 @@ public class XMPPTCPConnection extends AbstractXMPPConnection {
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packetWriter.shutdown(instant);
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}
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try {
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// After we send the closing stream element, check if there was already a
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// closing stream element sent by the server or wait with a timeout for a
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// closing stream element to be received from the server.
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Exception res = closingStreamReceived.checkIfSuccessOrWait();
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LOGGER.info("closingstream " + res);
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} catch (InterruptedException | NoResponseException e) {
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LOGGER.log(Level.INFO, "Exception while waiting for closing stream element from the server " + this, e);
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}
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if (packetReader != null) {
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packetReader.shutdown();
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}
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@ -1101,8 +1111,15 @@ public class XMPPTCPConnection extends AbstractXMPPConnection {
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LOGGER.warning(XMPPTCPConnection.this + " </stream> but different namespace " + parser.getNamespace());
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break;
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}
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// Check if the queue was already shut down before reporting success on closing stream tag
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// received. This avoids a race if there is a disconnect(), followed by a connect(), which
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// did re-start the queue again, causing this writer to assume that the queue is not
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// shutdown, which results in a call to disconnect().
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final boolean queueWasShutdown = packetWriter.queue.isShutdown();
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closingStreamReceived.reportSuccess();
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if (packetWriter.queue.isShutdown()) {
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if (queueWasShutdown) {
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// We received a closing stream element *after* we initiated the
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// termination of the session by sending a closing stream element to
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// the server first
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@ -1382,17 +1399,6 @@ public class XMPPTCPConnection extends AbstractXMPPConnection {
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LOGGER.log(Level.WARNING, "Exception writing closing stream element", e);
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}
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try {
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// After we send the closing stream element, check if there was already a
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// closing stream element sent by the server or wait with a timeout for a
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// closing stream element to be received from the server.
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closingStreamReceived.checkIfSuccessOrWait();
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} catch (NoResponseException e) {
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LOGGER.log(Level.INFO, "No response while waiting for closing stream element from the server (" + getConnectionCounter() + ")", e);
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} catch (InterruptedException e) {
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LOGGER.log(Level.INFO, "Waiting for closing stream element from the server was interrupted (" + getConnectionCounter() + ")", e);
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}
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// Delete the queue contents (hopefully nothing is left).
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queue.clear();
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} else if (instantShutdown && isSmEnabled()) {
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@ -1400,14 +1406,10 @@ public class XMPPTCPConnection extends AbstractXMPPConnection {
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// into the unacknowledgedStanzas queue
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drainWriterQueueToUnacknowledgedStanzas();
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}
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try {
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writer.close();
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}
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catch (Exception e) {
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// Do nothing
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}
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// Do *not* close the writer here, as it will cause the socket
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// to get closed. But we may want to receive further stanzas
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// until the closing stream tag is received. The socket will be
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// closed in shutdown().
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}
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catch (Exception e) {
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// The exception can be ignored if the the connection is 'done'
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