What if the packet number of a retry packet is not zero? #1448
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-transport
design
An issue that affects the design of the protocol; resolution requires consensus.
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The draft-12 spec says:
I understand the requirement on the sender side, but what about receivers? Does it mean that the number is ignored by receivers, or that packets with non-zero numbers are just dropped on the floor, or that this is treated like a protocol error and a connection close is sent? Oh, wait, this is a retry packet, the sender side connection is already closed!
Of course, if the receivers do not somehow enforce the requirement, broken senders will have no incentive to fix their code. But then, if receivers do enforce the requirement by dropping the packet, they will end up repeating the Client Hello 4 times, receive an incorrect retry each time, ignore it, and finally release the connection after the last timer elapsed. Not ideal either.
My proposal would be to add text. "Clients who receive an otherwise valid Retry packet with a non-zero PN value should treat this as a protocol error and immediately terminate the connection."
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