Directives that set transport parameters are removed from the configuration.
Corresponding values are derived from the quic configuration or initialized
to default. Whenever possible, quic configuration parameters are taken from
higher-level protocol settings, i.e. HTTP/3.
The reasons why a stream may not be created by server currently include hitting
worker_connections limit and memory allocation error. Previously in these
cases the entire QUIC connection was closed and all its streams were shut down.
Now the new stream is rejected and existing streams continue working.
To reject an HTTP/3 request stream, RESET_STREAM and STOP_SENDING with
H3_REQUEST_REJECTED error code are sent to client. HTTP/3 uni streams and
Stream streams are not rejected.
Previously, it was not enforced in the stream module.
Now, since b9e02e9b2f1d it is possible to specify protocols.
Since ALPN is always required, the 'require_alpn' setting is now obsolete.
The directive enables usage of UDP segmentation offloading by quic.
By default, gso is disabled since it is not always operational when
detected (depends on interface configuration).
Stop including QUIC headers with no user-serviceable parts inside.
This allows to provide a much cleaner QUIC interface. To cope with that,
ngx_quic_derive_key() is now explicitly exported for v3 and quic modules.
Additionally, this completely hides the ngx_quic_keys_t internal type.
The token generation in QUIC is reworked. Single host key is used to generate
all required keys of needed sizes using HKDF.
The "quic_stateless_reset_token_key" directive is removed. Instead, the
"quic_host_key" directive is used, which reads key from file, or sets it
to random bytes if not specified.
Previously, quic connection object was created when Retry packet was sent.
This is neither necessary nor convenient, and contradicts the idea of retry:
protecting from bad clients and saving server resources.
Now, the connection is not created, token is verified cryptographically
instead of holding it in connection.
Previously, if quic_stateless_reset_token_key was empty or unspecified,
initial stateless reset token was not generated. However subsequent tokens
were generated with empty key, which resulted in error with certain SSL
libraries, for example OpenSSL.
Now a random 32-byte stateless reset token key is generated if none is
specified in the configuration. As a result, stateless reset tokens are now
generated for all server ids.
