Re: [quicwg/base-drafts] Rework Retry packet (#1498)

Nick Banks <notifications@github.com> Thu, 19 July 2018 15:11 UTC

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Date: Thu, 19 Jul 2018 15:10:53 +0000
From: Nick Banks <notifications@github.com>
Reply-To: quicwg/base-drafts <reply+0166e4ab33c9360aefc17aabc9163b43bdd412218538b4d192cf0000000117686bfd92a169ce14138c09@reply.github.com>
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Subject: Re: [quicwg/base-drafts] Rework Retry packet (#1498)
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nibanks commented on this pull request.



> +A Retry packet does not include a packet number and cannot be explictly
+acknowledged by a client.
+
+A server MUST only send a Retry in response to a client Initial packet.
+
+If the Original Destination Connection ID field does not match the Destination
+Connection ID from the most recent Initial packet it sent, clients MUST discard
+the packet.  This prevents an off-path attacker from injecting a Retry packet.
+
+The client responds to a Retry packet with an Initial packet that includes the
+provided Retry Token to continue connection establishment.
+
+A server that might send another Retry packet in response to a subsequent
+Initial packet MUST set the Source Connection ID to a new value of at least 8
+octets in length.  This allows clients to distinguish between Retry packets when
+the server sends multiple rounds of Retry packets.  Consequently, a valid Retry

The client's DCID is essentially the nonce, and it will always be random 8 bytes for each Retry. I am still unclear why you think that's not enough.

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