[openib-general] RFC: mthca: implement timewait by tracking QPNs (was Fwd: Re: [PATCH ] RFC IB/cm do not track remote QPN in timewait state)

[Michael S. Tsirkin]

Roland, all, we plan to implement the timewait handling in mthca
in time for 2.6.19:

For all connected QPs:
- upon QP destroy or move from RTS to reset/error,
  start timer for the duration of packet lifetime
- until packet expires, do not reuse this QPN

This must be done to prevent stale packets from corruptiing the new connection
(see 9.7.1).

Could you pls let me know if this approach looks sane to you?

This approach has a number of advantages over attempting to implement
same in CM on top of verbs by not destroying the QP:

- Reduce resource usage by freeing the QP (only track QPN+timer)
- Applies to all verbs users even if they bypass CM
- Solves problem for userspace CM where we can't rely on CM
  to enforce timewait

More detail can be found in thread I'm replying to.

Please comment.
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MST