Re: [quicwg/base-drafts] Curtail CONNECTION_CLOSE for small Initial (#3292)

Kazuho Oku <notifications@github.com> Mon, 09 December 2019 15:41 UTC

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Subject: Re: [quicwg/base-drafts] Curtail CONNECTION_CLOSE for small Initial (#3292)
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kazuho commented on this pull request.



> @@ -3476,10 +3485,12 @@ Datagrams containing Initial packets MAY exceed 1200 bytes if the client
 believes that the Path Maximum Transmission Unit (PMTU) supports the size that
 it chooses.
 
-A server MAY send a CONNECTION_CLOSE frame with error code PROTOCOL_VIOLATION in
-response to an Initial packet it receives from a client if the UDP datagram is
-smaller than 1200 bytes. It MUST NOT send any other frame type in response, or
-otherwise behave as if any part of the offending packet was processed as valid.
+A server that has no existing state for a connection MUST discard an Initial
+packet that is carried in a UDP datagram that is smaller than 1200 bytes.  Other
+packets in the datagram SHOULD also be discarded.  A server MAY send a
+CONNECTION_CLOSE frame with error code PROTOCOL_VIOLATION in addition to
+discarding a packet if that does not affect a connection for which the server
+has established state; see {{immediate-close}}.

I am confused by the last sentence. Is it saying that when a server receives a small Initial packet for a connection for which it already has state, the server MAY send a PROTOCOL_VIOLATION, but it must retain the state for that connection? Assuming that is the case, I wonder if there is a value in having such a requirement. I am not sure if there is a case such a behavior helps us mitigate attacks.

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