[openib-general] [PATCH ] RFC IB/cm do not track remote QPN in timewait state

[Sean Hefty]

Michael S. Tsirkin wrote:
> IB spec, section 12.4, says:
> 
> 	CMs shall maintain enough connection state information to detect an attempt
> 	to initiate a connection on a remote QP/EEC that has not been released
> 	from a connection with a local QP/EEC, or that is in the TimeWait
> 	state. Such an event could occur if the remote CM had dropped the connection
> 	and sent DREQ, but the DREQ was not received by the local CM.
> 	If the local CM receives a REQ that includes a QPN (or EECN if
> 	REQ:RDC Exists is not set), that it believes to be connected to a local
> 	QP/EEC, the local CM shall act as defined in section 12.9.8.3.
> 
> Note here, that while CM must maintain QPs in TimeWait state (to enable
> detection of TimeWait packets, as explained in 9.7.1 PACKET SEQUENCE NUMBERS),
> such QPs are not connected (they are normally in reset state).
> Thus even if a local QP was connected to a specific remote QPN, once the
> connection enters the timewait state CM must not reject the connection request
> even if it includes the specific remote QPN.

My interpretation of 12.4 is:

The CM should track remote QPs that are either:

1. Part of an active connection, or
2. A connection that has been placed into timewait.

The CM should detect attempts to connect such remote QPs, and reject them.  The 
entire paragraph is referring to stale connection handling, and I believe the 
reference to timewait is included as part of that general discussion.

- Sean