Re: Some RDDP attacks

At 02:50 PM 7/5/2004, [email protected] wrote:
>I think that's actually indicative of a DDP problem, in that the current
>DDP draft is too quick to close a connection when receiving anything it
>doesn't expect.  Mandating "silent drop" rather than "tear down the
>connection" would make this attack significantly harder to pull off.

Silent drop would be a disastrous choice for DDP errors, especially
bad MSN or invalid STag! This would be like TCP ack'ing a hole in
sequence space or bad checksum. It would give the upper layers
on both sides of the connection an indication that messages had
been received when they had not.

Consider an RDMA Write with bad STag that was dropped at the
receiver. The subsequent Send, signalling the receipt, would then
pass upwards. Oops. Or consider a sender exceeding its credits
and losing a string messages in the middle, but not the end, of a
sequence.

Because it's an ack-less protocol, the only valid response DDP can
make is to send a Terminate and close the connection. Which it must.

Tom.

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