On 11/10/2023 12:25 PM, David Howells
wrote:
Jeffrey E Altman <jaltman@xxxxxxxxxxxx> wrote:I do ignore ack.serial == 0 for this purpose.Zero has the special meaning - this ACK is not explicitly in response to a received packet. However, as mentioned, the serial number counter wraps frequently and most RxRPC implementations do not transition from serial 0xffffffff -> 0x00000001 when wrapping.I don't skip zero serial numbers either. I'm not sure whether it would be better to do so.
If a DATA packet is sent with serial number zero and an ACK
packet is sent in response to it
with the ack.serial field set to the DATA packet serial number
(zero), then the receiver of the
ACK will be unable to compute an RTT from that DATA packet. It
will happen rarely but it
will happen.
Jeffrey
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