13.2.4. Limiting Ranges by Tracking ACK Frames
When a packet containing an ACK frame is sent, the largest
acknowledged in that frame may be saved. When a packet containing an
ACK frame is acknowledged, the receiver can stop acknowledging
packets less than or equal to the largest acknowledged in the sent
ACK frame.
The history of acknowledged packet is kept in send context as ranges.
Up to NGX_QUIC_MAX_RANGES ranges is stored.
As a result, instead of separate ack frames, single frame with ranges
is sent.
Per draft-ietf-quic-transport-32 on the topic:
: Similarly, a server MUST expand the payload of all UDP datagrams carrying
: ack-eliciting Initial packets to at least the smallest allowed maximum
: datagram size of 1200 bytes.
The history of acknowledged packet is kept in send context as ranges.
Up to NGX_QUIC_MAX_RANGES ranges is stored.
As a result, instead of separate ack frames, single frame with ranges
is sent.
Previously, this field was not set while creating a QUIC stream connection.
As a result, calling ngx_connection_local_sockaddr() led to getsockname()
bad descriptor error.
If client acknowledged an Initial packet with CRYPTO frame and then
sent another Initial packet containing duplicate CRYPTO again, this
could result in resending frames off the empty send queue.
The new "quic_stateless_reset_token_key" directive is added. It sets the
endpoint key used to generate stateless reset tokens and enables feature.
If the endpoint receives short-header packet that can't be matched to
existing connection, a stateless reset packet is generated with
a proper token.
If a valid stateless reset token is found in the incoming packet,
the connection is closed.
Example configuration:
http {
quic_stateless_reset_token_key "foo";
...
}
The flag is tied to the initial secret creation. The presence of c->quic
pointer is sufficient to enable execution of ngx_quic_close_quic().
The ngx_quic_new_connection() function now returns the allocated quic
connection object and the c->quic pointer is set by the caller.
If an early error occurs before secrets initialization (i.e. in cases
of invalid retry token or nginx exiting), it is still possible to
generate an error response by trying to initialize secrets directly
in the ngx_quic_send_cc() function.
Before the change such early errors failed to send proper connection close
message and logged an error.
An auxilliary ngx_quic_init_secrets() function is introduced to avoid
verbose call to ngx_quic_set_initial_secret() requiring local variable.
All packet header parsing is now performed by ngx_quic_parse_packet()
function, located in the ngx_quic_transport.c file.
The packet processing is centralized in the ngx_quic_process_packet()
function which decides if the packet should be accepted, ignored or
connection should be closed, depending on the connection state.
As a result of refactoring, behavior has changed in some places:
- minimal size of Initial packet is now always tested
- connection IDs are always tested in existing connections
- old keys are discarded on encryption level switch
In 7717:e3e8b8234f05, the 1st bit was incorrectly used. It shouldn't
be used for bitmask values, as it is used by NGX_CONF_BITMASK_SET.
Additionally, special value "off" added to make it possible to clear
inherited userid_flags value.
