Re: [quicwg/base-drafts] Specify behavior for post-handshake CRYPTO messages (#2524)

[Jana Iyengar <[e-mail]>]

janaiyengar commented on this pull request.

A few comments

> @@ -1438,6 +1438,31 @@ New transport parameters can be registered according to the rules in
 {{iana-transport-parameters}}.
 
 
+## Cryptographic Message Buffering
+
+Implementations need to maintain a buffer of CRYPTO data received out of order.
+Because there is no flow control of CRYPTO frames, an endpoint could
+potentially force its peer to buffer an unbounded amount of data.
+
+Implementations MUST support buffering at least 4096 bytes of data received in
+CRYPTO frames out of order. Endpoints MAY choose to allow more data to be
+buffered during the handshake. A larger limit during the handshake could allow
+for larger keys or credentials to be exchanged. An endpoint's buffer size does
+not need to remain constant during the life of the connection.
+
+Being unable to buffer CRYPTO frames during the handshake leads to a connection

```suggestion
Being unable to buffer CRYPTO frames during the handshake can lead to a connection
```

> +potentially force its peer to buffer an unbounded amount of data.
+
+Implementations MUST support buffering at least 4096 bytes of data received in
+CRYPTO frames out of order. Endpoints MAY choose to allow more data to be
+buffered during the handshake. A larger limit during the handshake could allow
+for larger keys or credentials to be exchanged. An endpoint's buffer size does
+not need to remain constant during the life of the connection.
+
+Being unable to buffer CRYPTO frames during the handshake leads to a connection
+failure. If an endpoint's buffer is exceeded during the handshake, it can expand
+its buffer temporarily to complete the handshake. If an endpoint cannot expand
+its buffer, it MUST close the connection with a CRYPTO_BUFFER_EXCEEDED error
+code.
+
+Once the handshake completes, if an endpoint is unable to buffer all data in a
+CRYPTO frame, it MAY discard all subsequent CRYPTO frames, or it MAY close the

This isn't clear to me. If the endpoint is unable to buffer data in a CRYPTO frame, why does it need to drop _subsequent_ CRYPTO frames?

> +CRYPTO frames out of order. Endpoints MAY choose to allow more data to be
+buffered during the handshake. A larger limit during the handshake could allow
+for larger keys or credentials to be exchanged. An endpoint's buffer size does
+not need to remain constant during the life of the connection.
+
+Being unable to buffer CRYPTO frames during the handshake leads to a connection
+failure. If an endpoint's buffer is exceeded during the handshake, it can expand
+its buffer temporarily to complete the handshake. If an endpoint cannot expand
+its buffer, it MUST close the connection with a CRYPTO_BUFFER_EXCEEDED error
+code.
+
+Once the handshake completes, if an endpoint is unable to buffer all data in a
+CRYPTO frame, it MAY discard all subsequent CRYPTO frames, or it MAY close the
+connection with an CRYPTO_BUFFER_EXCEEDED error code. If an endpoint chooses to
+discard all subsequent CRYPTO frames, the packets containing these CRYPTO frames
+MUST be acknowledged.

The endpoint MUST ack frames that are dropped? I don't think I follow this.

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