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Similar to lingering_time, it limits total connection lifetime before
keepalive is switched off. The default is 1 hour, which is close to
the total maximum connection lifetime possible with default
keepalive_requests and keepalive_timeout.
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Firefox uses several idle streams for PRIORITY frames[1], and
"http2_max_concurrent_streams 1;" results in "client sent too many
PRIORITY frames" errors when a connection is established by Firefox.
Fix is to relax the PRIORITY frames limit to use at least 100 as
the initial value (which is the recommended by the HTTP/2 protocol
minimum limit on the number of concurrent streams, so it is not
unreasonable for clients to assume that similar number of idle streams
can be used for prioritization).
[1] https://hg.mozilla.org/mozilla-central/file/32a9e6e145d6e3071c3993a20bb603a2f388722b/netwerk/protocol/http/Http2Stream.cpp#l1270
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Without explicit handling, a zero timer was actually added, leading to
multiple unneeded syscalls. Further, sending GOAWAY frame early might
be beneficial for clients.
Reported by Sergey Kandaurov.
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With this change, behaviour of HTTP/2 becomes even closer to HTTP/1.x,
and client_header_timeout instead of keepalive_timeout is used before
the first request is received.
This fixes HTTP/2 connections being closed even before the first request
if "keepalive_timeout 0;" was used in the configuration; the problem
appeared in f790816a0e87 (1.19.7).
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Instead, size of one large_client_header_buffers buffer and all large
client header buffers are used.
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Previously, PINGs and other frames extended possible keepalive time,
making it possible to keep an open HTTP/2 connection for a long time.
Now the connection is always closed as long as keepalive_timeout expires,
similarly to how it happens in HTTP/1.x.
Note that as a part of this change, incomplete frames are no longer
trigger a separate timeout, so http2_recv_timeout (replaced by
client_header_timeout in previous patches) is essentially cancelled.
The client_header_timeout is, however, used for SSL handshake and
while reading HEADERS frames.
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Instead, keepalive_timeout and keepalive_requests are now used. This
is expected to simplify HTTP/2 code and usage. This also matches
directives used by upstream module for all protocols.
In case of default settings, this effectively changes maximum number
of requests per connection from 1000 to 100. This looks acceptable,
especially given that HTTP/2 code now properly supports lingering close.
Further, this changes default keepalive timeout in HTTP/2 from 300 seconds
to 75 seconds. This also looks acceptable, and larger than PING interval
used by Firefox (network.http.spdy.ping-threshold defaults to 58s),
the only browser to use PINGs.
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Instead, the client_header_timeout is now used for HTTP/2 reading.
Further, the timeout is changed to be set once till no further data
left to read, similarly to how client_header_timeout is used in other
places.
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The spdy_* directives are not available since introduction of HTTP/2 module
in nginx 1.9.5 more than five years ago.
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New connections are marked reusable by ngx_http_init_connection() if there
are no data available for reading. As a result, if SSL is not used,
ngx_http_v2_init() might be called when the connection is marked reusable.
If a HEADERS frame is immediately available for reading, this resulted
in connection being preserved in reusable state with an active request,
and possibly closed later as if during worker shutdown (that is, after
all active requests were finalized).
Fix is to explicitly mark connections non-reusable in ngx_http_v2_init()
instead of (incorrectly) assuming they are already non-reusable.
Found by Sergey Kandaurov.
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Prodded by Taewoo Kim.
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This is particularly important in HTTP/2, where keepalive connections
are closed with lingering. Before the patch, reusing a keepalive HTTP/2
connection resulted in the connection waiting for lingering close to
remain in the reusable connections queue, preventing ngx_drain_connections()
from closing additional connections.
The patch fixes it by marking the connection reusable again, and so
moving it in the reusable connections queue. Further, it makes actually
possible to reuse such connections if needed.
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This part somehow slipped away from c5840ca2063d.
While it is not expected to be needed in case of lingering close,
it is good to keep it for correctness (see 2b5528023f6b).
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Ensure c->recv is properly reset to ngx_recv if SSL_shutdown()
blocks on writing.
The bug had appeared in 554c6ae25ffc.
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When doing lingering close, the socket was first shut down for writing,
so SSL shutdown initiated after lingering close was not able to send
the close_notify alerts (ticket #2056).
The fix is to call ngx_ssl_shutdown() before shutting down the socket.
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HTTP/2 code failed to run posted requests after calling the request body
handler, and this resulted in connection hang if a subrequest was created
in the body handler and no other actions were made.
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If 400 errors were redirected to an upstream server using the error_page
directive, DATA frames from the client might cause segmentation fault
due to null pointer dereference. The bug had appeared in 6989:2c4dbcd6f2e4
(1.13.0).
Fix is to skip such frames in ngx_http_v2_state_read_data() (similarly
to 7561:9f1f9d6e056a). With the fix, behaviour of 400 errors in HTTP/2
is now similar to one in HTTP/1.x, that is, nginx doesn't try to read the
request body.
Note that proxying 400 errors, as well as other early stage errors, to
upstream servers might not be a good idea anyway. These errors imply
that reading and processing of the request (and the request headers)
wasn't complete, and proxying of such incomplete request might lead to
various errors.
Reported by Chenglong Zhang.
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Prodded by Xu Yang.
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Without the flag, SSL shutdown is attempted on such connections,
resulting in useless work and/or bogus "SSL_shutdown() failed
(SSL: ... bad write retry)" critical log messages if there are
blocked writes.
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After sending the GOAWAY frame, a connection is now closed using
the lingering close mechanism.
This allows for the reliable delivery of the GOAWAY frames, while
also fixing connection resets observed when http2_max_requests is
reached (ticket #1250), or with graceful shutdown (ticket #1544),
when some additional data from the client is received on a fully
closed connection.
For HTTP/2, the settings lingering_close, lingering_timeout, and
lingering_time are taken from the "server" level.
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Previously, invalid connection preface errors were only logged at debug
level, providing no visible feedback, in particular, when a plain text
HTTP/2 listening socket is erroneously used for HTTP/1.x connections.
Now these are explicitly logged at the info level, much like other
client-related errors.
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A connection could get stuck without timers if a client has partially sent
the HEADERS frame such that it was split on the individual header boundary.
In this case, it cannot be processed without the rest of the HEADERS frame.
The fix is to call ngx_http_v2_state_headers_save() in this case. Normally,
it would be called from the ngx_http_v2_state_header_block() handler on the
next iteration, when there is not enough data to continue processing. This
isn't the case if recv_buffer became empty and there's no more data to read.
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With the recent change to prevent frames flood in d4448892a294,
nginx will finalize the connection with NGX_HTTP_V2_INTERNAL_ERROR
whenever flood is detected, causing nginx aborting or stopping if
the debug_points directive is used in nginx config.
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When ngx_http_v2_close_stream_handler() is used to retry stream close
after queued frames are sent, client timeouts on the stream can be
logged multiple times and/or in addition to already happened errors.
To resolve this, separate ngx_http_v2_retry_close_stream_handler()
was introduced, which does not try to log timeouts.
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If a stream is closed with queued frames, it is possible that no further
write events will occur on the stream, leading to the socket leak.
To fix this, the stream's fake connection read handler is set to
ngx_http_v2_close_stream_handler(), to make sure that finalizing the
connection with ngx_http_v2_finalize_connection() will be able to
close the stream regardless of the current number of queued frames.
Additionally, the stream's fake connection fc->error flag is explicitly
set, so ngx_http_v2_handle_stream() will post a write event when queued
frames are finally sent even if stream flow control window is exhausted.
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This could happen when graceful shutdown configured by worker_shutdown_timeout
times out and is then followed by another timeout such as proxy_read_timeout.
In this case, the HEADERS frame is added to the output queue, but attempt to
send it fails (due to c->error forcibly set during graceful shutdown timeout).
This triggers request finalization which attempts to close the stream. But the
stream cannot be closed because there is a frame in the output queue, and the
connection cannot be finalized. This leaves the connection open without any
timer events leading to alert.
The fix is to post write event when sending output queue fails on c->error.
That will finalize the connection.
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With this patch, all traffic over an HTTP/2 connection is counted in
the h2c->total_bytes field, and payload traffic is counted in
the h2c->payload_bytes field. As long as total traffic is many times
larger than payload traffic, we consider this to be a flood.
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In 8df664ebe037, we've switched to maximizing stream window instead
of sending RST_STREAM. Since then handling of RST_STREAM with NO_ERROR
was fixed at least in Chrome, hence we switch back to using RST_STREAM.
This allows more effective rejecting of large bodies, and also minimizes
non-payload traffic to be accounted in the next patch.
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Don't waste server resources by sending RST_STREAM frames. Instead,
reject WINDOW_UPDATE frames with invalid zero increment by closing
connection with PROTOCOL_ERROR.
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Don't waste server resources by sending RST_STREAM frames. Instead,
reject HEADERS and PRIORITY frames with self-dependency by closing
connection with PROTOCOL_ERROR.
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Previously, if unbuffered request body reading wasn't finished before
the request was redirected to a different location using error_page
or X-Accel-Redirect, and the request body is read again, this could
lead to disastrous effects, such as a duplicate post_handler call or
"http request count is zero" alert followed by a segmentation fault.
This happened in the following configuration (ticket #1819):
location / {
proxy_request_buffering off;
proxy_pass http://bad;
proxy_intercept_errors on;
error_page 502 = /error;
}
location /error {
proxy_pass http://backend;
}
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Fixed excessive CPU usage caused by a peer that continuously shuffles
priority of streams. Fix is to limit the number of PRIORITY frames.
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Fixed excessive memory growth and CPU usage if stream windows are
manipulated in a way that results in generating many small DATA frames.
Fix is to limit the number of simultaneously allocated DATA frames.
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Fixed uncontrolled memory growth if peer sends a stream of
headers with a 0-length header name and 0-length header value.
Fix is to reject headers with zero name length.
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Without this, an (incorrect) output on a closed stream could result in
a socket leak.
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An attack that continuously switches HTTP/2 connection between
idle and active states can result in excessive CPU usage.
This is because when a connection switches to the idle state,
all of its memory pool caches are freed.
This change limits the maximum allowed number of idle state
switches to 10 * http2_max_requests (i.e., 10000 by default).
This limits possible CPU usage in one connection, and also
imposes a limit on the maximum lifetime of a connection.
Initially reported by Gal Goldshtein from F5 Networks.
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Fixed uncontrolled memory growth in case peer is flooding us with
some frames (e.g., SETTINGS and PING) and doesn't read data. Fix
is to limit the number of allocated control frames.
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Socket leak was observed in the following configuration:
error_page 400 = /close;
location = /close {
return 444;
}
The problem is that "return 444" triggers termination of the request,
and due to error_page termination thinks that it needs to use a posted
request to clear stack. But at the early request processing where 400
errors are generated there are no ngx_http_run_posted_requests() calls,
so the request is only terminated after an external event.
Variants of the problem include "error_page 497" instead (ticket #695)
and various other errors generated during early request processing
(405, 414, 421, 494, 495, 496, 501, 505).
The same problem can be also triggered with "return 499" and "return 408"
as both codes trigger ngx_http_terminate_request(), much like "return 444".
To fix this, the patch adds ngx_http_run_posted_requests() calls to
ngx_http_process_request_line() and ngx_http_process_request_headers()
functions, and to ngx_http_v2_run_request() and ngx_http_v2_push_stream()
functions in HTTP/2.
Since the ngx_http_process_request() function is now only called via
other functions which call ngx_http_run_posted_requests(), the call
there is no longer needed and was removed.
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There are clients which cannot handle HPACK's dynamic table size updates
as added in 12cadc4669a7 (1.13.6). Notably, old versions of OkHttp library
are known to fail on it (ticket #1397).
This change makes it possible to work with such clients by only sending
dynamic table size updates in response to SETTINGS_HEADER_TABLE_SIZE. As
a downside, clients which do not use SETTINGS_HEADER_TABLE_SIZE will
continue to maintain default 4k table.
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Instead of the connection scheme, use scheme from the original request.
This fixes pushes when SSL is terminated by a proxy server in front of
nginx.
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For HTTP/1, it keeps scheme from the absolute form of URI.
For HTTP/2, the :scheme request pseudo-header field value.
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The scheme is validated as per RFC 3986, Section 3.1.
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The gRPC protocol makes a distinction between HEADERS frame with
the END_STREAM flag set, and a HEADERS frame followed by an empty
DATA frame with the END_STREAM flag. The latter is not permitted,
and results in errors not being propagated through nginx. Instead,
gRPC clients complain that "server closed the stream without sending
trailers" (seen in grpc-go) or "13: Received RST_STREAM with error
code 2" (seen in grpc-c).
To fix this, nginx now returns HEADERS with the END_STREAM flag if
the response length is known to be 0, and we are not expecting
any trailer headers to be added. And the response length is
explicitly set to 0 in the gRPC proxy if we see initial HEADERS frame
with the END_STREAM flag set.
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Unified the style of validity checks in ngx_http_v2_validate_header().
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There is no need to calculate hashes of static strings at runtime. The
ngx_hash() macro can be used to do it during compilation instead, similarly
to how it is done in ngx_http_proxy_module.c for "Server" and "Date" headers.
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In particular, if a stream object allocation failed, and a client sent
the PRIORITY frame for this stream, ngx_http_v2_set_dependency() could
dereference a null pointer while trying to re-parent a dependency node.
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