On Jan 26, 2016, at 9:43 PM, Victor Orlikowski <[email protected]> wrote:
> 
> One could say that the Datapath is "assured" upon reaching MAIN_DISPATCHER 
> state - but what happens when the Datapath is disconnected without a FIN or 
> RST being sent?
> 
> Unless the application is keeping track (by itself, or via dpset or 
> topology), the Ryu core has no other way of shutting down the Datapath; it's 
> just stuck.

Let me correct myself - there is only one way that the Ryu core could know to 
shut down the Datapath.
The Ryu core would need to send echo requests to the switch, just as the switch 
sends them to Ryu, as a default behavior, with a configurable interval.

We already automatically respond to echo requests in ofp_handler.
We would need to set up a thread in the Datapath that sent echo requests on a 
regular (user-configurable) basis, handle echo replies in ofp_handler, and 
close() the datapath after a (user-configurable) number of missed replies.
Furthermore - the user could disable the default behavior (sending echos) by 
setting an echo request interval of zero.

That’s the only way we end up hiding this from the users, that I can imagine.
But - that also encodes a new default behavior into Ryu, that might be 
unexpected by users doing their own regular echo requests.

If the above behavior is preferred, I’ll see what I can do to implement it 
before the 3.30 window closes.

Best,
Victor
--
Victor J. Orlikowski <> vjo@[cs.]duke.edu

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