[Live-devel] Two possible problems in RTSPServer class

[Ross Finlayson]

>>> 2. Also I have seen possible ServerMediaSession object relations bug
>>> in RTSPServer::addServerMediaSession/RTSPServer::removeServerMediaSession
>>> methods.
>>> Method addServerMediaSession adds a ServerMediaSession object to
>>> hashmap fServerMediaSessions and call removeServerMediaSession on
>>> ServerMediaSession object previously set in the hashmap (if both
>>> objects have same stream name). Method removeServerMediaSession
>>> removes from the hashmap new ServerMediaSession object just added by
>>> addServerMediaSession.
>> 
>> Yes, this is a bug. It will get fixed in a future release.
> 
> I'm sorry, but I fail to see how this was a bug. Seems to me that RTSPServer::addServerMediaSession was removing an existing ServerMediaSession with the same name as the one being created, if any. 

No, the old code was doing (when implementing "RTSPServer::addServerMediaSession()"):

	ServerMediaSession* existingSession
		= (ServerMediaSession*)(fServerMediaSessions->Add(sessionName, (void*)serverMediaSession));
	removeServerMediaSession(existingSession); // if any

which was a bug, because - if "existingSession" was not NULL, then the call to

	removeServerMediaSession(existingSession); // if any

happened to remove - from the hash table - the *new* "serverMediaSession" that had just been added - because of the way that

	RTSPServer::removeServerMediaSession(ServerMediaSession* existingSession)

is implemented by calling

	Remove(existingSession->streamName());

on the internal hash table.


The new code does:

	removeServerMediaSession(sessionName); // in case an existing "ServerMediaSession" with this name already exists
	fServerMediaSessions->Add(sessionName, (void*)serverMediaSession);

which is correct, except for the fact that

	void RTSPServer::removeServerMediaSession(char const* sessionName)

is implemented by calling

	removeServerMediaSession(lookupServerMediaSession(sessionName));

i.e., by calling the "lookupServerMediaSession()" *virtual function*.  That's a bug.  The code should just be doing a hash table lookup here; not calling the "lookupServerMediaSession()" virtual function.

I've now installed a new version (2012.05.17) of the code that fixes this.

Ross Finlayson
Live Networks, Inc.
http://www.live555.com/

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