[Live-devel] RTSP proxy not noticing server restart

[Ross Finlayson]

> It is possible to restart an origin server quickly enough that a live 555 proxy server does not notice.
> 
> As a test this can be done by modifying one of the live 555 test programs (I was using testH264VideoStreamer) to enable SO_REUSEADDR/SO_REUSEPORT, then the process could be quickly killed and restarted without waiting for the socket to timeout.

And that's precisely why you shouldn't make such a change to the server's code :-)

But anyway, the proxy server sends periodic RTSP "OPTIONS" commands to the 'back-end' server, to test whether its still alive.  If any of these "OPTIONS" commands fails (or if the RTSP (TCP) connection to the back-end server fails), then the proxy server will notice this, and establish a new connection (with a new "DESCRIBE" command) to the back-end server.

You should be able to see this by running the proxy server with the -V (uppercase "V") option.

But (getting back to the first point) if your server is able to restart in such a way that a previously-set-up TCP connection can get misinterpreted as still being valid, then that's a serious security flaw in your server OS; that's the real bug that you should be fixing.


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

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