Since application most likely allocates the stream object in
nghttp2_on_begin_headers_callback, it is desirable to handle its
failure as stream error. But previously it only signals success or
fatal error. Submitting RST_STREAM does not prevent
nghttp2_on_header_callback from being invoked. This commit improves
this situation by allowing NGHTTP2_ERR_TEMPORAL_CALLBACK_FAILURE from
nghttp2_on_begin_headers_callback. If that value is returned, library
submits RST_STREAM with error code INTERNAL_ERROR, and
nghttp2_on_header_callback and nghttp2_on_frame_recv_callback for that
frame are not invoked. Note that for PUSH_PROMISE frame, the stream
to be reset is promised stream.
We rewrite static header table handling in nghttp2_hd.c. We expand
nghttp2_token to include all static header table entries, and fully
use them in header compression and decompression. The lookup function
is now located in nghttp2_hd.c. We add new nghttp2_hd_inflate_hd2()
function to export token value for header name, then we pass it to
nghttp2_http_on_header function, so that we don't have to look up
token there. We carefully set enum value of token to static table
index, so looking up static table is now O(1), assuming we have token.
The existing nghttp2_session_consume() affects both connection and
stream level flow control windows. The new functions only affects
either connection or stream. There is some interesting use cases.
For example, we may want to pause a stream by not sending
WINDOW_UPDATE, meanwhile we want to continue to process other streams.
In this case, we use nghttp2_session_consume_connection() to tell
library that only connection level window is recovered. The relevant
discussion: https://code.google.com/p/chromium/issues/detail?id=473259
Previously nghttp2_session_send() and nghttp2_session_mem_send() did
not send 24 bytes client magic byte string (MAGIC). We made
nghttp2_session_recv() and nghttp2_session_mem_recv() process MAGIC by
default, so it is natural to make library send MAGIC as well. This
commit makes nghttp2_session_send() and nghttp2_session_mem_send()
send MAGIC. This commit also replace "connection preface" with
"client magic", since we call MAGIC as "connection preface" but it is
just a part of connection preface. NGHTTP2_CLIENT_CONNECTION_PREFACE
macro was replaced with NGHTTP2_CLIENT_MAGIC. The already deprecated
NGHTTP2_CLIENT_CONNECTION_HEADER macro was removed permanently.
nghttp2_option_set_no_recv_client_preface() was renamed as
nghttp2_option_set_no_recv_client_magic(). NGHTTP2_ERR_BAD_PREFACE
was renamed as NGHTTP2_ERR_BAD_CLIENT_MAGIC.
Since HTTP/2 spec requires for client to send connection preface, it
is reasonable to make this option enabled by default. It is still a
use case to disable this, so replace this option with
nghttp2_option_set_no_recv_client_preface().
To avoid buffer copy in nghttp2_data_source_read_callback, this commit
introduces NGHTTP2_DATA_FLAG_NO_COPY and nghttp2_send_data_callback.
By using NGHTTP2_DATA_FLAG_NO_COPY in
nghttp2_data_source_read_callback, application can avoid to copy
application data to given buffer. Instead, application has to
implement nghttp2_send_data_callback to send complete DATA frame by
itself. We see noticeable performance increase in nghttpd and
tiny-nghttpd using this new feature. On the other hand, nghttpx does
not show such difference, probably because buffer copy is not
bottleneck. Using nghttp2_send_data_callback adds complexity, so it
is recommended to measure the performance to see whether this extra
complexity worth it.
nghttp2_submit_request and nghttp2_submit_response will set
NGHTTP2_FLAG_END_STREAM after all given data is sent (data could be
0). This means we have no way to send trailers. In this commit, we
added NGHTTP2_DATA_FLAG_NO_END_STREAM flag. The application can set
this flag in *data_flags inside nghttp2_data_source_read_callback. If
NGHTTP2_DATA_FLAG_EOF is set, library automatically set
NGHTTP2_FLAG_END_STREAM. But if both NGHTTP2_DATA_FLAG_EOF and
NGHTTP2_DATA_FLAG_NO_END_STREAM are set, NGHTTP2_FLAG_END_STREAM will
not set by library. Then application can use new
nghttp2_submit_trailer() to send trailers. nghttp2_submit_trailer()
will set NGHTTP2_FLAG_END_STREAM and it is actually thing wrapper of
nghttp2_submit_headers().
After we sent SETTINGS including ENABLE_PUSH = 0, peer may already
issue PUSH_PROMISE before receiving our SETTINGS and react it to
SETTINGS ACK. Previously we accept this PUSH_PROMISE. In this
commit, we check the pending ENABLE_PUSH value and if it means
disabling push, we refuse PUSH_PROMISE with RST_STREAM of error
REFUSED_STREAM.
This commit only affects the library behaviour unless
nghttp2_option_set_no_http_messaging() is used.
We like strict validation against header field name and value against
RFC 7230, but we have already so much web sites and libraries in
public internet which do not obey these rules. Simply just
terminating stream because of this may break web sites and it is too
disruptive. So we decided that we should be conservative here so
those header fields containing illegal characters are just ignored.
But we are conservative only for regular headers. We are strict for
pseudo headers since it is new to HTTP/2 and new implementations
should know the rules better.
This API function with nonzero |val| parameter disables HTTP Messaging
validation in nghttp2 library, so that application can use nghttp2
library for non-HTTP use.
Previously we did not check HTTP semantics and it is left out for
application. Although checking is relatively easy, but they are
scattered and error prone. We have implemented these checks in our
applications and also feel they are tedious. To make application
development a bit easier, this commit adds basic HTTP semantics
validation to library code. We do following checks:
server:
* HEADERS is either request header or trailer header. Other type of
header is disallowed.
client:
* HEADERS is either zero or more non-final response header or final
response header or trailer header. Other type of header is
disallowed.
For both:
* Check mandatory pseudo header fields.
* Make sure that content-length matches the amount of DATA we
received.
If validation fails, RST_STREAM of type PROTOCOL_ERROR is issued.
Previously we did not handle the situation where RST_STREAM is
submitted against a stream while requet HEADERS which opens that
stream is still in queue. Due to max concurrent streams limit,
RST_STREAM is sent first, and then request HEADERS, which effectively
voids RST_STREAM.
In this commit, we checks RST_STREAM against currently pending request
HEADERS in queue and if stream ID matches, we mark that HEADERS as
canceled and RST_STREAM is not sent in this case. The library will
call on_frame_not_sent_callback for the canceled HEADERS with error
code from RST_STREAM.
Previously we treat stream in NGHTTP2_STREAM_RESERVED state specially,
that is we don't increment or decrement streams counts if stream is in
that state. Because of this, we don't change the stream state to
NGHTTP2_STREAM_CLOSING if stream is in NGHTTP2_STREAM_RESERVED. But
it turns out that it causes a problem. If client canceled pushed
stream before push response HEADERS, stream is still in
NGHTTP2_STREAM_RESERVED state. If push response HEADERS arrived in
this state, library happily accepts it and passed to application.
With this commit, this bug was corrected. We now change stream state
to NGHTTP2_STREAM_CLOSING even if it was in NGHTTP2_STREAM_RESERVED
state. We now use NGHTTP2_STREAM_FLAG_PUSH to determine whether we
have to increase/decrase stream count.
nghttp2_submit_shutdown_notice() is used to notify the client that
graceful shutdown is started. We expect that after this call, the
server application should send another GOAWAY using
nghttp2_submit_goaway() with appropriate last_stream_id. In this
commit, we also added nghttp2_session_get_last_proc_stream_id(), which
can be used as last_stream_id parameter.
This commit implements graceful shutdown in nghttpx. The integration
test for graceful shutdown is also added.
This change makes sure that GOAWAY which terminates session is
immediately sent without blocked by other frames.
NGHTTP2_ERR_SESSION_CLOSING library error code was added to indicate
this situation to callback.
Initially, we use nghttp2_stream.data_item to refer only item with
DATA frame. But recently we use it to refer HEADERS frame as well.
So it is better to call just item rather than data_item. This applies
to all related functions.
Previously session_after_frame_sent is called after we detected all
data is sent. In nghttp2_session_mem_send, we only detect it in the
next call of the function. It means that if a frame data bearing
END_STREAM is on flight to the peer as a result of
nghttp2_session_mem_send, peer may get that data and knows the stream
closure and issues new stream. We may receive this new stream before
the next nghttp2_session_mem_send call, which means that we may
incorrectly assumes that peer violates maximum concurrent stream
limit. To fix this issue, we separate session_after_frame_sent into 2
functions: session_after_frame_sent1 and session_after_frame_sent2.
session_after_frame_sent1 handles on_frame_send_callback and stream
closure and we call this early in nghttp2_session_mem_send. This
makes number of streams are synchronized correctly with peer.
Previously we handle idle streams as closed streams. We only keeps
sum of closed streams and active streams under max concurrent streams
limit, idle streams gets deleted earlier than client expects.
In this change, idle streams are kept in separate list and not handled
as closed streams. To mitigate possible attack vector to make
unlimited idle streams, we cap the number of idle streams in a half of
max concurrent streams. This is arbitrary choice. It may be adjusted
in the future when we have interop experience.
Tatsuhiro Tsujikawa
Alexis La Goutte