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.
Allowing PRIORITY frame at anytime so that PRIORITY frame to idle
stream can create anchor node in dependency tree. In this change, we
open stream with new NGHTTP2_STREAM_IDLE state, which is linked in
session->closed_stream_head and is treated as if it is closed stream.
One difference is that if the stream is opened, we remove it from
linked list and change the state to the appropriate one. To O(1)
removal from linked list, we change session->closed_stream_head to
doubly linked list.
This change fixes the bug that stream is out of dependency tree if the
number of nodes in a dependency tree which we add new node to is
already maximum (NGHTTP2_MAX_DEP_TREE_LENGTH) and the number of
maximum concurrent streams is more than more than
NGHTTP2_MAX_DEP_TREE_LENGTH.
Previously we missed the case where stream->data_item is not deleted
and it caused leak. Now stream->data_item is properly deleted when
session is deleted. We decided not to delete data_item in
nghttp2_stream_free() since we need nghttp2_session to decide whether
data_item should be deleted or not there.
By default, nghttp2 library only handles HTTP/2 frames and does not
recognize first 24 bytes of client connection preface. This design
choice is done due to the fact that server may want to detect the
application protocol based on first few bytes on clear text
communication. But for simple servers which only speak HTTP/2, it is
easier for developers if nghttp2 library takes care of client
connection preface.
If this option is used with nonzero val, nghttp2 library checks first
24 bytes client connection preface. If it is not a valid one,
nghttp2_session_recv() and nghttp2_session_mem_recv() will return
error NGHTTP2_ERR_BAD_PREFACE, which is fatal error.
Motivation:
The send window size is currently fixed by a macro at compile time.
In order for users of the library to impact the send window size they
would have to change a macro at compile time. The window size may be dynamic
depending on the environment and deployment scheme. The library users
currently have no way to change this parameter.
Modifications:
Add a new optional callback method which is called before data is sent to
obtain the desired send window size. The callback return value will be
subject to a range check for the current session, stream, and settings
limits defined by flow control.
Result:
Library users have control over their send sizes.
Previously returning NGHTTP2_ERR_TEMPORAL_CALLBACK_FAILURE from
on_header_callback moves input offset badly and it causes header
decompression error on the subsequent frames. This commit fix this
bug.
Previously we just assumed that if same settings ID is found in
SETTINGS, it is enough to process last seen entry. But it turns out
it is not enough for SETTINGS_HEADER_TABLE_SIZE. If we have 0 and
4096 for SETTINGS_HEADER_TABLE_SIZE in one SETTINGS, we must first
shrink dynamic table to 0 and then enlarge it to 4096. This means
that we have to remember the minimum value and last value.
Previously in inflater we reserve new ringbuffer when table size is
changed. This may be potentially a problem if new table size is very
large number. When inflater is not used directly by application, this
is not a problem because application can choose the buffer size. On
the other hand, if application uses inflater directly and it does not
have control of new buffer size (e.g., protocol dissector), then we
just fail to allocate large buffer in
nghttp2_hd_inflate_change_table_size() without actually use such huge
buffer. This change defers the actual allocation of buffer when it is
actually needed so that we will fail when it is absolutely needed.
We inherited gzip compression API from spdylay codebase. In spdylay,
the cost of having such API is almost free because spdylay requires
zlib for header compression. nghttp2 no longer uses gzip to header
compression. zlib dependency exists just for gzip compression API,
which is not an essential. So we decided to move gzip code to under
src and remove zlib dependency from libnghttp2 itself. As nghttp2
package, we depend on zlib to compile tools under src.
If stream with dpri value of no_data, we check any its descendant has
stream with dpri value of top. If so, we have to distribute of its
portion of weight to its descendants.
We need paddings regardless of payload and frame boundary to mitigate
certain attacks.
Since we handles CONTINUATION internally, we don't show FLAG_PAD_HIGH
and PAD_LOW flags of HEADERS in nghttp/nghttpd. We just show the
total paddings in HEADERS + CONTINUATION.
* Use 1 Huffman code table for both request and response
* Remove complicated deflater side table size management
* Add encoding context update
* Fix memory leak in inflater
Now previous padding options are removed and instead we added
select_padding_callback to select padding length for each frame
by application. If this callback is not implemented by application,
no padding is added.
This change also fixes the broken session_detect_idle_stream()
if stream_id is our side.
Tatsuhiro Tsujikawa
Alexis La Goutte
Scott Mitchell