The path validation status and anti-amplification limit status is actually
two different variables. It is possible that validating path should not
be limited (for example, when re-validating former path).
Previously, path was considered valid during arbitrary selected 10m timeout
since validation. This is quite not what RFC 9000 says; the relevant
part is:
An endpoint MAY skip validation of a peer address if that
address has been seen recently.
The patch considers a path to be 'recently seen' if packets were received
during idle timeout. If a packet is received from the path that was seen
not so recently, such path is considered new, and anti-amplification
restrictions apply.
After creation, a client stream is added to qc->streams.uninitialized queue.
After initialization it's removed from the queue. If a stream is never
initialized, it is freed in ngx_quic_close_streams(). Stream initializer
is now set as read event handler in stream connection.
Previously qc->streams.uninitialized was used only for delayed stream
initialization.
The change makes it possible not to handle separately the case of a new stream
in stream-related frame handlers. It makes these handlers simpler since new
streams and existing streams are now handled by the same code.
With sendfile() in threads ("aio threads; sendfile on;"), client connection
can block on writing, waiting for sendfile() to complete. In HTTP/2 this
might result in the request hang, since an attempt to continue processing
in thread event handler will call request's write event handler, which
is usually stopped by ngx_http_v2_send_chain(): it does nothing if there
are no additional data and stream->queued is set. Further, HTTP/2 resets
stream's c->write->ready to 0 if writing blocks, so just fixing
ngx_http_v2_send_chain() is not enough.
Can be reproduced with test suite on Linux with:
TEST_NGINX_GLOBALS_HTTP="aio threads; sendfile on;" prove h2*.t
The following tests currently fail: h2_keepalive.t, h2_priority.t,
h2_proxy_max_temp_file_size.t, h2.t, h2_trailers.t.
Similarly, sendfile() with AIO preloading on FreeBSD can block as well,
with similar results. This is, however, harder to reproduce, especially
on modern FreeBSD systems, since sendfile() usually does not return EBUSY.
Fix is to modify ngx_http_v2_send_chain() so it actually tries to send
data to the main connection when called, and to make sure that
c->write->ready is set by the relevant event handlers.
With sendfile in threads, "task already active" alerts might appear in logs
if a write event happens on the main HTTP/2 connection, triggering a sendfile
in threads while another thread operation is already running. Observed
with "aio threads; aio_write on; sendfile on;" and with thread event handlers
modified to post a write event to the main HTTP/2 connection (though can
happen without any modifications).
Similarly, sendfile() with AIO preloading on FreeBSD can trigger duplicate
aio operation, resulting in "second aio post" alerts. This is, however,
harder to reproduce, especially on modern FreeBSD systems, since sendfile()
usually does not return EBUSY.
Fix is to avoid starting a sendfile operation if other thread operation
is active by checking r->aio in the thread handler (and, similarly, in
aio preload handler). The added check also makes duplicate calls protection
redundant, so it is removed.
The SSL_OP_ENABLE_MIDDLEBOX_COMPAT option is provided by QuicTLS and enabled
by default in the newly created SSL contexts. SSL_set_quic_method() is used
to clear it, which is required for SSL handshake to work on QUIC connections.
Switching context in the ngx_http_ssl_servername() SNI callback overrides SSL
options from the new SSL context. This results in the option set again.
Fix is to explicitly clear it when switching to another SSL context.
Initially reported here (in Russian):
http://mailman.nginx.org/pipermail/nginx-ru/2021-November/063989.html
ngx_http_v3_tables.h and ngx_http_v3_tables.c are renamed to
ngx_http_v3_table.h and ngx_http_v3_table.c to better match HTTP/2 code.
ngx_http_v3_streams.h and ngx_http_v3_streams.c are renamed to
ngx_http_v3_uni.h and ngx_http_v3_uni.c to better match their content.
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.
A new variable $http3 is added. The variable equals to "h3" for HTTP/3
connections, "hq" for hq connections and is an empty string otherwise.
The variable $quic is eliminated.
The new variable is similar to $http2 variable.
RFC 9000 19.16
The sequence number specified in a RETIRE_CONNECTION_ID frame MUST NOT
refer to the Destination Connection ID field of the packet in which the
frame is contained.
Before the patch, the RETIRE_CONNECTION_ID frame was sent before switching
to the new client id. If retired client id was currently in use, this lead
to violation of the spec.
The c->udp->dgram may be NULL only if the quic connection was just
created: the ngx_event_udp_recvmsg() passes information about datagrams
to existing connections by providing information in c->udp.
If case of a new connection, c->udp is allocated by the QUIC code during
creation of quic connection (it uses c->sockaddr to initialize qsock->path).
Thus the check for qsock->path is excessive and can be read wrong, assuming
that other options possible, leading to warnings from clang static analyzer.
Removed sending CLOSE_CONNECTION directly to avoid duplicate frames,
since it is sent later again in SSL_do_handshake() error handling.
As such, removed redundant settings of error fields set elsewhere.
While here, improved debug message.
All open sockets are stored in a queue. There is no need to close some
of them separately. If it happens that active and backup point to same
socket, double close may happen (leading to possible segfault).
The RFC 9000 allows a packet from known CID arrive from unknown path:
These requirements regarding connection ID reuse apply only to the
sending of packets, as unintentional changes in path without a change
in connection ID are possible. For example, after a period of
network inactivity, NAT rebinding might cause packets to be sent on a
new path when the client resumes sending.
Before the patch, such packets were rejected with an error in the
ngx_quic_check_migration() function. Removing the check makes the
separate function excessive - remaining checks are early migration
check and "disable_active_migration" check. The latter is a transport
parameter sent to client and it should not be used by server.
The server should send "disable_active_migration" "if the endpoint does
not support active connection migration" (18.2). The support status depends
on nginx configuration: to have migration working with multiple workers,
you need bpf helper, available on recent Linux systems. The patch does
not set "disable_active_migration" automatically and leaves it for the
administrator. By default, active migration is enabled.
RFC 900 says that it is ok to migrate if the peer violates
"disable_active_migration" flag requirements:
If the peer violates this requirement,
the endpoint MUST either drop the incoming packets on that path without
generating a Stateless Reset
OR
proceed with path validation and allow the peer to migrate. Generating a
Stateless Reset or closing the connection would allow third parties in the
network to cause connections to close by spoofing or otherwise manipulating
observed traffic.
So, nginx adheres to the second option and proceeds to path validation.
Note:
The ngtcp2 may be used for testing both active migration and NAT rebinding:
ngtcp2/client --change-local-addr=200ms --delay-stream=500ms <ip> <port> <url>
ngtcp2/client --change-local-addr=200ms --delay-stream=500ms --nat-rebinding \
<ip> <port> <url>
Single UDP datagram may contain multiple QUIC datagrams. In order to
facilitate handling of such cases, 'first' flag in the ngx_quic_header_t
structure is introduced.
Previously, the retired socket was not closed if it didn't match
active or backup.
New sockets could not be created (due to count limit), since retired socket
was not closed before calling ngx_quic_create_sockets().
When replacing retired socket, new socket is only requested after closing
old one, to avoid hitting the limit on the number of active connection ids.
Together with added restrictions, this fixes an issue when a current socket
could be closed during migration, recreated and erroneously reused leading
to null pointer dereference.
Previously the frame was not handled and connection was closed with an error.
Now, after receiving this frame, global flow control is updated and new
flow control credit is sent to client.
Previously, after receiving STREAM_DATA_BLOCKED, current flow control limit
was sent to client. Now, if the limit can be updated to the full window size,
it is updated and the new value is sent to client, otherwise nothing is sent.
The change lets client update flow control credit on demand. Also, it saves
traffic by not sending MAX_STREAM_DATA with the same value twice.
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.
The variable contains a negotiated curve used for the handshake key
exchange process. Known curves are listed by their names, unknown
ones are shown in hex.
Note that for resumed sessions in TLSv1.2 and older protocols,
$ssl_curve contains the curve used during the initial handshake,
while in TLSv1.3 it contains the curve used during the session
resumption (see the SSL_get_negotiated_group manual page for
details).
The variable is only meaningful when using OpenSSL 3.0 and above.
With older versions the variable is empty.
Without this change, aio used with HTTP/2 can result in connection hang,
as observed with "aio threads; aio_write on;" and proxying (ticket #2248).
The problem is that HTTP/2 updates buffers outside of the output filters
(notably, marks them as sent), and then posts a write event to call
output filters. If a filter does not call the next one for some reason
(for example, because of an AIO operation in progress), this might
result in a state when the owner of a buffer already called
ngx_chain_update_chains() and can reuse the buffer, while the same buffer
is still sitting in the busy chain of some other filter.
In the particular case a buffer was sitting in output chain's ctx->busy,
and was reused by event pipe. Output chain's ctx->busy was permanently
blocked by it, and this resulted in connection hang.
Fix is to change ngx_chain_update_chains() to skip buffers from other
modules unconditionally, without trying to wait for these buffers to
become empty.
The "sendfile_max_chunk" directive is important to prevent worker
monopolization by fast connections. The 2m value implies maximum 200ms
delay with 100 Mbps links, 20ms delay with 1 Gbps links, and 2ms on
10 Gbps links. It also seems to be a good value for disks.
