Merge pull request #1552 from quicwg/retry-0rtt

Allow Retry in response to 0-RTT packets

draft-ietf-quic-transport.md

@@ -598,7 +598,10 @@ of subsequent packets that it sends.
 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.
+A server MUST NOT send a Retry in response to packets other than Initial
+or 0-RTT packets.  A server MAY choose to only send Retry in response to Initial
+packets and discard or buffer 0-RTT packets corresponding to unvalidated client
+addresses.
 
 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