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If client stream does not have any data to sink and neither received EOF, a dummy packet is sent to the daemon signalising client is ready to sink some data. However, after we added event loop to client a race may occur: Thread 1 calls virNetClientStreamRecvPacket and since no data are cached nor stream has EOF, it decides to send dummy packet to server which will sent some data in turn. However, during this decision and actual message exchange with server - Thread 2 receives last stream data from server. Therefore an EOF is set on stream and if there is a call waiting (which is not yet) it is woken up. However, Thread 1 haven't sent anything so far, so there is no call to be woken up. So this thread sent dummy packet to daemon, which ignores that as no stream is associated with such packet and therefore no reply will ever come. This race causes client to hang indefinitely.
79 lines
3.0 KiB
C
79 lines
3.0 KiB
C
/*
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* virnetclientstream.h: generic network RPC client stream
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*
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* Copyright (C) 2006-2011 Red Hat, Inc.
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*
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* Author: Daniel P. Berrange <berrange@redhat.com>
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*/
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#ifndef __VIR_NET_CLIENT_STREAM_H__
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# define __VIR_NET_CLIENT_STREAM_H__
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# include "virnetclientprogram.h"
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typedef struct _virNetClientStream virNetClientStream;
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typedef virNetClientStream *virNetClientStreamPtr;
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typedef void (*virNetClientStreamEventCallback)(virNetClientStreamPtr stream,
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int events, void *opaque);
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virNetClientStreamPtr virNetClientStreamNew(virNetClientProgramPtr prog,
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int proc,
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unsigned serial);
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void virNetClientStreamRef(virNetClientStreamPtr st);
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void virNetClientStreamFree(virNetClientStreamPtr st);
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bool virNetClientStreamRaiseError(virNetClientStreamPtr st);
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int virNetClientStreamSetError(virNetClientStreamPtr st,
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virNetMessagePtr msg);
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bool virNetClientStreamMatches(virNetClientStreamPtr st,
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virNetMessagePtr msg);
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int virNetClientStreamQueuePacket(virNetClientStreamPtr st,
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virNetMessagePtr msg);
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int virNetClientStreamSendPacket(virNetClientStreamPtr st,
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virNetClientPtr client,
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int status,
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const char *data,
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size_t nbytes);
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int virNetClientStreamRecvPacket(virNetClientStreamPtr st,
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virNetClientPtr client,
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char *data,
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size_t nbytes,
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bool nonblock);
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int virNetClientStreamEventAddCallback(virNetClientStreamPtr st,
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int events,
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virNetClientStreamEventCallback cb,
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void *opaque,
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virFreeCallback ff);
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int virNetClientStreamEventUpdateCallback(virNetClientStreamPtr st,
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int events);
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int virNetClientStreamEventRemoveCallback(virNetClientStreamPtr st);
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bool virNetClientStreamEOF(virNetClientStreamPtr st)
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ATTRIBUTE_NONNULL(1);
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#endif /* __VIR_NET_CLIENT_STREAM_H__ */
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