[ENet-discuss] Bug in enet_protocol_handle_disconnect?

[Lee Salzman]

This was actually fixed in a roughly similar way in ENet CVS not too 
long ago. I need to put together a new stable release probably. :)

Lee

Blair Holloway wrote:
> G'day,
>
> During development we found an issue with the way ENet handles the 
> disconnect command. We generally service our host 30 times per second 
> (in step with our framerate), however, during a level load there's an 
> unavoidable second or two where the game finalises some data - we 
> found that, if the host disconnected the client during this time, the 
> client would never be notified of the disconnect - the peer 
> representing the host on the client machine would simply become reset.
>
> After some investigation, we found that this was happening:
>
> - Client goes into its 1-2 second deadstate;
> - Host issues a ENET_PROTOCOL_COMMAND_DISCONNECT command to the client;
> - Host times out the command, having not received an acknowledgement, 
> and resends it (this can happen easily in a LAN environment where ping 
> is low);
> - Client wakes up from its deadstate and starts to call enet_host_service;
> - Client receives the initial disconnect command, and 
> enet_protocol_handle_disconnect transitions to 
> state ENET_PEER_STATE_ACKNOWLEDGING_DISCONNECT;
> - Client immediately receives the second disconnect command, and 
> enet_protocol_handle_disconnect calls enet_peer_reset -- the client is 
> then not notified of the disconnection.
>
> Our solution was to not reset the peer if the peer is in 
> the acknowledging disconnect state -- changing:
>
>     if (peer -> state != ENET_PEER_STATE_CONNECTED && peer -> state != 
> ENET_PEER_STATE_DISCONNECT_LATER)
>
> to:
>
>     if (peer -> state != ENET_PEER_STATE_CONNECTED && peer -> state != 
> ENET_PEER_STATE_DISCONNECT_LATER
>       && peer -> state != ENET_PEER_STATE_ACKNOWLEDGING_DISCONNECT)
>
> solved our issue.
>
> I thought I would share this, as it was tricky to track down, and 
> there's also the possibility that I'm Doin' It Wrong and there's 
> another solution that I have overlooked... J
>
> Regards,
>
> - Blair
>