Types (structs, unions and typedefs)
====================================
.. type:: nghttp2_session
The primary structure to hold the resources needed for a HTTP/2
session. The details of this structure are intentionally hidden
from the public API.
.. type:: nghttp2_info
This struct is what `nghttp2_version()` returns. It holds
information about the particular nghttp2 version.
.. member:: int age
Age of this struct. This instance of nghttp2 sets it to
:macro:`NGHTTP2_VERSION_AGE` but a future version may bump it and
add more struct fields at the bottom
.. member:: int version_num
the :macro:`NGHTTP2_VERSION_NUM` number (since age ==1)
.. member:: const char *version_str
points to the :macro:`NGHTTP2_VERSION` string (since age ==1)
.. member:: const char *proto_str
points to the :macro:`NGHTTP2_PROTO_VERSION_ID` string this
instance implements (since age ==1)
.. type:: nghttp2_vec
The object representing single contiguous buffer.
.. member:: uint8_t *base
The pointer to the buffer.
.. member:: size_t len
The length of the buffer.
.. type:: nghttp2_rcbuf
The object representing reference counted buffer. The details of
this structure are intentionally hidden from the public API.
.. type:: nghttp2_nv
The name/value pair, which mainly used to represent header fields.
.. member:: uint8_t *name
The *name* byte string. If this struct is presented from library
(e.g., :type:`nghttp2_on_frame_recv_callback`), *name* is
guaranteed to be NULL-terminated. For some callbacks
(:type:`nghttp2_before_frame_send_callback`,
:type:`nghttp2_on_frame_send_callback`, and
:type:`nghttp2_on_frame_not_send_callback`), it may not be
NULL-terminated if header field is passed from application with
the flag :macro:`NGHTTP2_NV_FLAG_NO_COPY_NAME`). When application
is constructing this struct, *name* is not required to be
NULL-terminated.
.. member:: uint8_t *value
The *value* byte string. If this struct is presented from
library (e.g., :type:`nghttp2_on_frame_recv_callback`), *value*
is guaranteed to be NULL-terminated. For some callbacks
(:type:`nghttp2_before_frame_send_callback`,
:type:`nghttp2_on_frame_send_callback`, and
:type:`nghttp2_on_frame_not_send_callback`), it may not be
NULL-terminated if header field is passed from application with
the flag :macro:`NGHTTP2_NV_FLAG_NO_COPY_VALUE`). When
application is constructing this struct, *value* is not required
to be NULL-terminated.
.. member:: size_t namelen
The length of the *name*, excluding terminating NULL.
.. member:: size_t valuelen
The length of the *value*, excluding terminating NULL.
.. member:: uint8_t flags
Bitwise OR of one or more of :type:`nghttp2_nv_flag`.
.. type:: nghttp2_frame_hd
The frame header.
.. member:: size_t length
The length field of this frame, excluding frame header.
.. member:: int32_t stream_id
The stream identifier (aka, stream ID)
.. member:: uint8_t type
The type of this frame. See `nghttp2_frame_type`.
.. member:: uint8_t flags
The flags.
.. member:: uint8_t reserved
Reserved bit in frame header. Currently, this is always set to 0
and application should not expect something useful in here.
.. type:: nghttp2_data_source
This union represents the some kind of data source passed to
:type:`nghttp2_data_source_read_callback`.
.. member:: int fd
The integer field, suitable for a file descriptor.
.. member:: void *ptr
The pointer to an arbitrary object.
.. type:: typedef ssize_t (*nghttp2_data_source_read_callback)( nghttp2_session *session, int32_t stream_id, uint8_t *buf, size_t length, uint32_t *data_flags, nghttp2_data_source *source, void *user_data)
Callback function invoked when the library wants to read data from
the *source*. The read data is sent in the stream *stream_id*.
The implementation of this function must read at most *length*
bytes of data from *source* (or possibly other places) and store
them in *buf* and return number of data stored in *buf*. If EOF is
reached, set :macro:`NGHTTP2_DATA_FLAG_EOF` flag in *\*data_flags*.
Sometime it is desirable to avoid copying data into *buf* and let
application to send data directly. To achieve this, set
:macro:`NGHTTP2_DATA_FLAG_NO_COPY` to *\*data_flags* (and possibly
other flags, just like when we do copy), and return the number of
bytes to send without copying data into *buf*. The library, seeing
:macro:`NGHTTP2_DATA_FLAG_NO_COPY`, will invoke
:type:`nghttp2_send_data_callback`. The application must send
complete DATA frame in that callback.
If this callback is set by `nghttp2_submit_request()`,
`nghttp2_submit_response()` or `nghttp2_submit_headers()` and
`nghttp2_submit_data()` with flag parameter
:macro:`NGHTTP2_FLAG_END_STREAM` set, and
:macro:`NGHTTP2_DATA_FLAG_EOF` flag is set to *\*data_flags*, DATA
frame will have END_STREAM flag set. Usually, this is expected
behaviour and all are fine. One exception is send trailer fields.
You cannot send trailer fields after sending frame with END_STREAM
set. To avoid this problem, one can set
:macro:`NGHTTP2_DATA_FLAG_NO_END_STREAM` along with
:macro:`NGHTTP2_DATA_FLAG_EOF` to signal the library not to set
END_STREAM in DATA frame. Then application can use
`nghttp2_submit_trailer()` to send trailer fields.
`nghttp2_submit_trailer()` can be called inside this callback.
If the application wants to postpone DATA frames (e.g.,
asynchronous I/O, or reading data blocks for long time), it is
achieved by returning :macro:`NGHTTP2_ERR_DEFERRED` without reading
any data in this invocation. The library removes DATA frame from
the outgoing queue temporarily. To move back deferred DATA frame
to outgoing queue, call `nghttp2_session_resume_data()`.
By default, *length* is limited to 16KiB at maximum. If peer
allows larger frames, application can enlarge transmission buffer
size. See :type:`nghttp2_data_source_read_length_callback` for
more details.
If the application just wants to return from
`nghttp2_session_send()` or `nghttp2_session_mem_send()` without
sending anything, return :macro:`NGHTTP2_ERR_PAUSE`.
In case of error, there are 2 choices. Returning
:macro:`NGHTTP2_ERR_TEMPORAL_CALLBACK_FAILURE` will close the stream
by issuing RST_STREAM with :macro:`NGHTTP2_INTERNAL_ERROR`. If a
different error code is desirable, use
`nghttp2_submit_rst_stream()` with a desired error code and then
return :macro:`NGHTTP2_ERR_TEMPORAL_CALLBACK_FAILURE`. Returning
:macro:`NGHTTP2_ERR_CALLBACK_FAILURE` will signal the entire session
failure.
.. type:: nghttp2_data_provider
This struct represents the data source and the way to read a chunk
of data from it.
.. member:: nghttp2_data_source source
The data source.
.. member:: nghttp2_data_source_read_callback read_callback
The callback function to read a chunk of data from the *source*.
.. type:: nghttp2_data
The DATA frame. The received data is delivered via
:type:`nghttp2_on_data_chunk_recv_callback`.
.. member:: size_t padlen
The length of the padding in this frame. This includes PAD_HIGH
and PAD_LOW.
.. type:: nghttp2_priority_spec
The structure to specify stream dependency.
.. member:: int32_t stream_id
The stream ID of the stream to depend on. Specifying 0 makes
stream not depend any other stream.
.. member:: int32_t weight
The weight of this dependency.
.. member:: uint8_t exclusive
nonzero means exclusive dependency
.. type:: nghttp2_headers
The HEADERS frame. It has the following members:
.. member:: nghttp2_frame_hd hd
The frame header.
.. member:: size_t padlen
The length of the padding in this frame. This includes PAD_HIGH
and PAD_LOW.
.. member:: nghttp2_priority_spec pri_spec
The priority specification
.. member:: nghttp2_nv *nva
The name/value pairs.
.. member:: size_t nvlen
The number of name/value pairs in *nva*.
.. member:: nghttp2_headers_category cat
The category of this HEADERS frame.
.. type:: nghttp2_priority
The PRIORITY frame. It has the following members:
.. member:: nghttp2_frame_hd hd
The frame header.
.. member:: nghttp2_priority_spec pri_spec
The priority specification.
.. type:: nghttp2_rst_stream
The RST_STREAM frame. It has the following members:
.. member:: nghttp2_frame_hd hd
The frame header.
.. member:: uint32_t error_code
The error code. See :type:`nghttp2_error_code`.
.. type:: nghttp2_settings_entry
The SETTINGS ID/Value pair. It has the following members:
.. member:: int32_t settings_id
The SETTINGS ID. See :type:`nghttp2_settings_id`.
.. member:: uint32_t value
The value of this entry.
.. type:: nghttp2_settings
The SETTINGS frame. It has the following members:
.. member:: nghttp2_frame_hd hd
The frame header.
.. member:: size_t niv
The number of SETTINGS ID/Value pairs in *iv*.
.. member:: nghttp2_settings_entry *iv
The pointer to the array of SETTINGS ID/Value pair.
.. type:: nghttp2_push_promise
The PUSH_PROMISE frame. It has the following members:
.. member:: nghttp2_frame_hd hd
The frame header.
.. member:: size_t padlen
The length of the padding in this frame. This includes PAD_HIGH
and PAD_LOW.
.. member:: nghttp2_nv *nva
The name/value pairs.
.. member:: size_t nvlen
The number of name/value pairs in *nva*.
.. member:: int32_t promised_stream_id
The promised stream ID
.. member:: uint8_t reserved
Reserved bit. Currently this is always set to 0 and application
should not expect something useful in here.
.. type:: nghttp2_ping
The PING frame. It has the following members:
.. member:: nghttp2_frame_hd hd
The frame header.
.. member:: uint8_t opaque_data[8]
The opaque data
.. type:: nghttp2_goaway
The GOAWAY frame. It has the following members:
.. member:: nghttp2_frame_hd hd
The frame header.
.. member:: int32_t last_stream_id
The last stream stream ID.
.. member:: uint32_t error_code
The error code. See :type:`nghttp2_error_code`.
.. member:: uint8_t *opaque_data
The additional debug data
.. member:: size_t opaque_data_len
The length of *opaque_data* member.
.. member:: uint8_t reserved
Reserved bit. Currently this is always set to 0 and application
should not expect something useful in here.
.. type:: nghttp2_window_update
The WINDOW_UPDATE frame. It has the following members:
.. member:: nghttp2_frame_hd hd
The frame header.
.. member:: int32_t window_size_increment
The window size increment.
.. member:: uint8_t reserved
Reserved bit. Currently this is always set to 0 and application
should not expect something useful in here.
.. type:: nghttp2_extension
The extension frame. It has following members:
.. member:: nghttp2_frame_hd hd
The frame header.
.. member:: void *payload
The pointer to extension payload. The exact pointer type is
determined by hd.type.
Currently, no extension is supported. This is a place holder for
the future extensions.
.. type:: nghttp2_frame
This union includes all frames to pass them to various function
calls as nghttp2_frame type. The CONTINUATION frame is omitted
from here because the library deals with it internally.
.. member:: nghttp2_frame_hd hd
The frame header, which is convenient to inspect frame header.
.. member:: nghttp2_data data
The DATA frame.
.. member:: nghttp2_headers headers
The HEADERS frame.
.. member:: nghttp2_priority priority
The PRIORITY frame.
.. member:: nghttp2_rst_stream rst_stream
The RST_STREAM frame.
.. member:: nghttp2_settings settings
The SETTINGS frame.
.. member:: nghttp2_push_promise push_promise
The PUSH_PROMISE frame.
.. member:: nghttp2_ping ping
The PING frame.
.. member:: nghttp2_goaway goaway
The GOAWAY frame.
.. member:: nghttp2_window_update window_update
The WINDOW_UPDATE frame.
.. member:: nghttp2_extension ext
The extension frame.
.. type:: typedef ssize_t (*nghttp2_send_callback)(nghttp2_session *session, const uint8_t *data, size_t length, int flags, void *user_data)
Callback function invoked when *session* wants to send data to the
remote peer. The implementation of this function must send at most
*length* bytes of data stored in *data*. The *flags* is currently
not used and always 0. It must return the number of bytes sent if
it succeeds. If it cannot send any single byte without blocking,
it must return :macro:`NGHTTP2_ERR_WOULDBLOCK`. For other errors,
it must return :macro:`NGHTTP2_ERR_CALLBACK_FAILURE`. The
*user_data* pointer is the third argument passed in to the call to
`nghttp2_session_client_new()` or `nghttp2_session_server_new()`.
This callback is required if the application uses
`nghttp2_session_send()` to send data to the remote endpoint. If
the application uses solely `nghttp2_session_mem_send()` instead,
this callback function is unnecessary.
To set this callback to :type:`nghttp2_session_callbacks`, use
`nghttp2_session_callbacks_set_send_callback()`.
.. note::
The *length* may be very small. If that is the case, and
application disables Nagle algorithm (``TCP_NODELAY``), then just
writing *data* to the network stack leads to very small packet,
and it is very inefficient. An application should be responsible
to buffer up small chunks of data as necessary to avoid this
situation.
.. type:: typedef int (*nghttp2_send_data_callback)(nghttp2_session *session, nghttp2_frame *frame, const uint8_t *framehd, size_t length, nghttp2_data_source *source, void *user_data)
Callback function invoked when :macro:`NGHTTP2_DATA_FLAG_NO_COPY` is
used in :type:`nghttp2_data_source_read_callback` to send complete
DATA frame.
The *frame* is a DATA frame to send. The *framehd* is the
serialized frame header (9 bytes). The *length* is the length of
application data to send (this does not include padding). The
*source* is the same pointer passed to
:type:`nghttp2_data_source_read_callback`.
The application first must send frame header *framehd* of length 9
bytes. If ``frame->data.padlen > 0``, send 1 byte of value
``frame->data.padlen - 1``. Then send exactly *length* bytes of
application data. Finally, if ``frame->data.padlen > 1``, send
``frame->data.padlen - 1`` bytes of zero as padding.
The application has to send complete DATA frame in this callback.
If all data were written successfully, return 0.
If it cannot send any data at all, just return
:macro:`NGHTTP2_ERR_WOULDBLOCK`; the library will call this callback
with the same parameters later (It is recommended to send complete
DATA frame at once in this function to deal with error; if partial
frame data has already sent, it is impossible to send another data
in that state, and all we can do is tear down connection). When
data is fully processed, but application wants to make
`nghttp2_session_mem_send()` or `nghttp2_session_send()` return
immediately without processing next frames, return
:macro:`NGHTTP2_ERR_PAUSE`. If application decided to reset this
stream, return :macro:`NGHTTP2_ERR_TEMPORAL_CALLBACK_FAILURE`, then
the library will send RST_STREAM with INTERNAL_ERROR as error code.
The application can also return
:macro:`NGHTTP2_ERR_CALLBACK_FAILURE`, which will result in
connection closure. Returning any other value is treated as
:macro:`NGHTTP2_ERR_CALLBACK_FAILURE` is returned.
.. type:: typedef ssize_t (*nghttp2_recv_callback)(nghttp2_session *session, uint8_t *buf, size_t length, int flags, void *user_data)
Callback function invoked when *session* wants to receive data from
the remote peer. The implementation of this function must read at
most *length* bytes of data and store it in *buf*. The *flags* is
currently not used and always 0. It must return the number of
bytes written in *buf* if it succeeds. If it cannot read any
single byte without blocking, it must return
:macro:`NGHTTP2_ERR_WOULDBLOCK`. If it gets EOF before it reads any
single byte, it must return :macro:`NGHTTP2_ERR_EOF`. For other
errors, it must return :macro:`NGHTTP2_ERR_CALLBACK_FAILURE`.
Returning 0 is treated as :macro:`NGHTTP2_ERR_WOULDBLOCK`. The
*user_data* pointer is the third argument passed in to the call to
`nghttp2_session_client_new()` or `nghttp2_session_server_new()`.
This callback is required if the application uses
`nghttp2_session_recv()` to receive data from the remote endpoint.
If the application uses solely `nghttp2_session_mem_recv()`
instead, this callback function is unnecessary.
To set this callback to :type:`nghttp2_session_callbacks`, use
`nghttp2_session_callbacks_set_recv_callback()`.
.. type:: typedef int (*nghttp2_on_frame_recv_callback)(nghttp2_session *session, const nghttp2_frame *frame, void *user_data)
Callback function invoked by `nghttp2_session_recv()` and
`nghttp2_session_mem_recv()` when a frame is received. The
*user_data* pointer is the third argument passed in to the call to
`nghttp2_session_client_new()` or `nghttp2_session_server_new()`.
If frame is HEADERS or PUSH_PROMISE, the ``nva`` and ``nvlen``
member of their data structure are always ``NULL`` and 0
respectively. The header name/value pairs are emitted via
:type:`nghttp2_on_header_callback`.
For HEADERS, PUSH_PROMISE and DATA frames, this callback may be
called after stream is closed (see
:type:`nghttp2_on_stream_close_callback`). The application should
check that stream is still alive using its own stream management or
:func:`nghttp2_session_get_stream_user_data()`.
Only HEADERS and DATA frame can signal the end of incoming data.
If ``frame->hd.flags & NGHTTP2_FLAG_END_STREAM`` is nonzero, the
*frame* is the last frame from the remote peer in this stream.
This callback won't be called for CONTINUATION frames.
HEADERS/PUSH_PROMISE + CONTINUATIONs are treated as single frame.
The implementation of this function must return 0 if it succeeds.
If nonzero value is returned, it is treated as fatal error and
`nghttp2_session_recv()` and `nghttp2_session_mem_recv()` functions
immediately return :macro:`NGHTTP2_ERR_CALLBACK_FAILURE`.
To set this callback to :type:`nghttp2_session_callbacks`, use
`nghttp2_session_callbacks_set_on_frame_recv_callback()`.
.. type:: typedef int (*nghttp2_on_invalid_frame_recv_callback)( nghttp2_session *session, const nghttp2_frame *frame, int lib_error_code, void *user_data)
Callback function invoked by `nghttp2_session_recv()` and
`nghttp2_session_mem_recv()` when an invalid non-DATA frame is
received. The error is indicated by the *lib_error_code*, which is
one of the values defined in :type:`nghttp2_error`. When this
callback function is invoked, the library automatically submits
either RST_STREAM or GOAWAY frame. The *user_data* pointer is the
third argument passed in to the call to
`nghttp2_session_client_new()` or `nghttp2_session_server_new()`.
If frame is HEADERS or PUSH_PROMISE, the ``nva`` and ``nvlen``
member of their data structure are always ``NULL`` and 0
respectively.
The implementation of this function must return 0 if it succeeds.
If nonzero is returned, it is treated as fatal error and
`nghttp2_session_recv()` and `nghttp2_session_mem_recv()` functions
immediately return :macro:`NGHTTP2_ERR_CALLBACK_FAILURE`.
To set this callback to :type:`nghttp2_session_callbacks`, use
`nghttp2_session_callbacks_set_on_invalid_frame_recv_callback()`.
.. type:: typedef int (*nghttp2_on_data_chunk_recv_callback)(nghttp2_session *session, uint8_t flags, int32_t stream_id, const uint8_t *data, size_t len, void *user_data)
Callback function invoked when a chunk of data in DATA frame is
received. The *stream_id* is the stream ID this DATA frame belongs
to. The *flags* is the flags of DATA frame which this data chunk
is contained. ``(flags & NGHTTP2_FLAG_END_STREAM) != 0`` does not
necessarily mean this chunk of data is the last one in the stream.
You should use :type:`nghttp2_on_frame_recv_callback` to know all
data frames are received. The *user_data* pointer is the third
argument passed in to the call to `nghttp2_session_client_new()` or
`nghttp2_session_server_new()`.
If the application uses `nghttp2_session_mem_recv()`, it can return
:macro:`NGHTTP2_ERR_PAUSE` to make `nghttp2_session_mem_recv()`
return without processing further input bytes. The memory by
pointed by the *data* is retained until
`nghttp2_session_mem_recv()` or `nghttp2_session_recv()` is called.
The application must retain the input bytes which was used to
produce the *data* parameter, because it may refer to the memory
region included in the input bytes.
The implementation of this function must return 0 if it succeeds.
If nonzero is returned, it is treated as fatal error, and
`nghttp2_session_recv()` and `nghttp2_session_mem_recv()` functions
immediately return :macro:`NGHTTP2_ERR_CALLBACK_FAILURE`.
To set this callback to :type:`nghttp2_session_callbacks`, use
`nghttp2_session_callbacks_set_on_data_chunk_recv_callback()`.
.. type:: typedef int (*nghttp2_before_frame_send_callback)(nghttp2_session *session, const nghttp2_frame *frame, void *user_data)
Callback function invoked just before the non-DATA frame *frame* is
sent. The *user_data* pointer is the third argument passed in to
the call to `nghttp2_session_client_new()` or
`nghttp2_session_server_new()`.
The implementation of this function must return 0 if it succeeds.
It can also return :macro:`NGHTTP2_ERR_CANCEL` to cancel the
transmission of the given frame.
If there is a fatal error while executing this callback, the
implementation should return :macro:`NGHTTP2_ERR_CALLBACK_FAILURE`,
which makes `nghttp2_session_send()` and
`nghttp2_session_mem_send()` functions immediately return
:macro:`NGHTTP2_ERR_CALLBACK_FAILURE`.
If the other value is returned, it is treated as if
:macro:`NGHTTP2_ERR_CALLBACK_FAILURE` is returned. But the
implementation should not rely on this since the library may define
new return value to extend its capability.
To set this callback to :type:`nghttp2_session_callbacks`, use
`nghttp2_session_callbacks_set_before_frame_send_callback()`.
.. type:: typedef int (*nghttp2_on_frame_send_callback)(nghttp2_session *session, const nghttp2_frame *frame, void *user_data)
Callback function invoked after the frame *frame* is sent. The
*user_data* pointer is the third argument passed in to the call to
`nghttp2_session_client_new()` or `nghttp2_session_server_new()`.
The implementation of this function must return 0 if it succeeds.
If nonzero is returned, it is treated as fatal error and
`nghttp2_session_send()` and `nghttp2_session_mem_send()` functions
immediately return :macro:`NGHTTP2_ERR_CALLBACK_FAILURE`.
To set this callback to :type:`nghttp2_session_callbacks`, use
`nghttp2_session_callbacks_set_on_frame_send_callback()`.
.. type:: typedef int (*nghttp2_on_frame_not_send_callback)(nghttp2_session *session, const nghttp2_frame *frame, int lib_error_code, void *user_data)
Callback function invoked after the non-DATA frame *frame* is not
sent because of the error. The error is indicated by the
*lib_error_code*, which is one of the values defined in
:type:`nghttp2_error`. The *user_data* pointer is the third
argument passed in to the call to `nghttp2_session_client_new()` or
`nghttp2_session_server_new()`.
The implementation of this function must return 0 if it succeeds.
If nonzero is returned, it is treated as fatal error and
`nghttp2_session_send()` and `nghttp2_session_mem_send()` functions
immediately return :macro:`NGHTTP2_ERR_CALLBACK_FAILURE`.
`nghttp2_session_get_stream_user_data()` can be used to get
associated data.
To set this callback to :type:`nghttp2_session_callbacks`, use
`nghttp2_session_callbacks_set_on_frame_not_send_callback()`.
.. type:: typedef int (*nghttp2_on_stream_close_callback)(nghttp2_session *session, int32_t stream_id, uint32_t error_code, void *user_data)
Callback function invoked when the stream *stream_id* is closed.
The reason of closure is indicated by the *error_code*. The
*error_code* is usually one of :macro:`nghttp2_error_code`, but that
is not guaranteed. The stream_user_data, which was specified in
`nghttp2_submit_request()` or `nghttp2_submit_headers()`, is still
available in this function. The *user_data* pointer is the third
argument passed in to the call to `nghttp2_session_client_new()` or
`nghttp2_session_server_new()`.
This function is also called for a stream in reserved state.
The implementation of this function must return 0 if it succeeds.
If nonzero is returned, it is treated as fatal error and
`nghttp2_session_recv()`, `nghttp2_session_mem_recv()`,
`nghttp2_session_send()`, and `nghttp2_session_mem_send()`
functions immediately return :macro:`NGHTTP2_ERR_CALLBACK_FAILURE`.
To set this callback to :type:`nghttp2_session_callbacks`, use
`nghttp2_session_callbacks_set_on_stream_close_callback()`.
.. type:: typedef int (*nghttp2_on_begin_headers_callback)(nghttp2_session *session, const nghttp2_frame *frame, void *user_data)
Callback function invoked when the reception of header block in
HEADERS or PUSH_PROMISE is started. Each header name/value pair
will be emitted by :type:`nghttp2_on_header_callback`.
The ``frame->hd.flags`` may not have
:macro:`NGHTTP2_FLAG_END_HEADERS` flag set, which indicates that one
or more CONTINUATION frames are involved. But the application does
not need to care about that because the header name/value pairs are
emitted transparently regardless of CONTINUATION frames.
The server applications probably create an object to store
information about new stream if ``frame->hd.type ==
NGHTTP2_HEADERS`` and ``frame->headers.cat ==
NGHTTP2_HCAT_REQUEST``. If *session* is configured as server side,
``frame->headers.cat`` is either ``NGHTTP2_HCAT_REQUEST``
containing request headers or ``NGHTTP2_HCAT_HEADERS`` containing
trailer fields and never get PUSH_PROMISE in this callback.
For the client applications, ``frame->hd.type`` is either
``NGHTTP2_HEADERS`` or ``NGHTTP2_PUSH_PROMISE``. In case of
``NGHTTP2_HEADERS``, ``frame->headers.cat ==
NGHTTP2_HCAT_RESPONSE`` means that it is the first response
headers, but it may be non-final response which is indicated by 1xx
status code. In this case, there may be zero or more HEADERS frame
with ``frame->headers.cat == NGHTTP2_HCAT_HEADERS`` which has
non-final response code and finally client gets exactly one HEADERS
frame with ``frame->headers.cat == NGHTTP2_HCAT_HEADERS``
containing final response headers (non-1xx status code). The
trailer fields also has ``frame->headers.cat ==
NGHTTP2_HCAT_HEADERS`` which does not contain any status code.
Returning :macro:`NGHTTP2_ERR_TEMPORAL_CALLBACK_FAILURE` will close
the stream (promised stream if frame is PUSH_PROMISE) by issuing
RST_STREAM with :macro:`NGHTTP2_INTERNAL_ERROR`. In this case,
:type:`nghttp2_on_header_callback` and
:type:`nghttp2_on_frame_recv_callback` will not be invoked. If a
different error code is desirable, use
`nghttp2_submit_rst_stream()` with a desired error code and then
return :macro:`NGHTTP2_ERR_TEMPORAL_CALLBACK_FAILURE`. Again, use
``frame->push_promise.promised_stream_id`` as stream_id parameter
in `nghttp2_submit_rst_stream()` if frame is PUSH_PROMISE.
The implementation of this function must return 0 if it succeeds.
It can return :macro:`NGHTTP2_ERR_TEMPORAL_CALLBACK_FAILURE` to
reset the stream (promised stream if frame is PUSH_PROMISE). For
critical errors, it must return
:macro:`NGHTTP2_ERR_CALLBACK_FAILURE`. If the other value is
returned, it is treated as if :macro:`NGHTTP2_ERR_CALLBACK_FAILURE`
is returned. If :macro:`NGHTTP2_ERR_CALLBACK_FAILURE` is returned,
`nghttp2_session_mem_recv()` function will immediately return
:macro:`NGHTTP2_ERR_CALLBACK_FAILURE`.
To set this callback to :type:`nghttp2_session_callbacks`, use
`nghttp2_session_callbacks_set_on_begin_headers_callback()`.
.. type:: typedef int (*nghttp2_on_header_callback)(nghttp2_session *session, const nghttp2_frame *frame, const uint8_t *name, size_t namelen, const uint8_t *value, size_t valuelen, uint8_t flags, void *user_data)
Callback function invoked when a header name/value pair is received
for the *frame*. The *name* of length *namelen* is header name.
The *value* of length *valuelen* is header value. The *flags* is
bitwise OR of one or more of :type:`nghttp2_nv_flag`.
If :macro:`NGHTTP2_NV_FLAG_NO_INDEX` is set in *flags*, the receiver
must not index this name/value pair when forwarding it to the next
hop. More specifically, "Literal Header Field never Indexed"
representation must be used in HPACK encoding.
When this callback is invoked, ``frame->hd.type`` is either
:macro:`NGHTTP2_HEADERS` or :macro:`NGHTTP2_PUSH_PROMISE`. After all
header name/value pairs are processed with this callback, and no
error has been detected, :type:`nghttp2_on_frame_recv_callback`
will be invoked. If there is an error in decompression,
:type:`nghttp2_on_frame_recv_callback` for the *frame* will not be
invoked.
Both *name* and *value* are guaranteed to be NULL-terminated. The
*namelen* and *valuelen* do not include terminal NULL. If
`nghttp2_option_set_no_http_messaging()` is used with nonzero
value, NULL character may be included in *name* or *value* before
terminating NULL.
Please note that unless `nghttp2_option_set_no_http_messaging()` is
used, nghttp2 library does perform validation against the *name*
and the *value* using `nghttp2_check_header_name()` and
`nghttp2_check_header_value()`. In addition to this, nghttp2
performs validation based on HTTP Messaging rule, which is briefly
explained in :ref:`http-messaging` section.
If the application uses `nghttp2_session_mem_recv()`, it can return
:macro:`NGHTTP2_ERR_PAUSE` to make `nghttp2_session_mem_recv()`
return without processing further input bytes. The memory pointed
by *frame*, *name* and *value* parameters are retained until
`nghttp2_session_mem_recv()` or `nghttp2_session_recv()` is called.
The application must retain the input bytes which was used to
produce these parameters, because it may refer to the memory region
included in the input bytes.
Returning :macro:`NGHTTP2_ERR_TEMPORAL_CALLBACK_FAILURE` will close
the stream (promised stream if frame is PUSH_PROMISE) by issuing
RST_STREAM with :macro:`NGHTTP2_INTERNAL_ERROR`. In this case,
:type:`nghttp2_on_header_callback` and
:type:`nghttp2_on_frame_recv_callback` will not be invoked. If a
different error code is desirable, use
`nghttp2_submit_rst_stream()` with a desired error code and then
return :macro:`NGHTTP2_ERR_TEMPORAL_CALLBACK_FAILURE`. Again, use
``frame->push_promise.promised_stream_id`` as stream_id parameter
in `nghttp2_submit_rst_stream()` if frame is PUSH_PROMISE.
The implementation of this function must return 0 if it succeeds.
It may return :macro:`NGHTTP2_ERR_PAUSE` or
:macro:`NGHTTP2_ERR_TEMPORAL_CALLBACK_FAILURE`. For other critical
failures, it must return :macro:`NGHTTP2_ERR_CALLBACK_FAILURE`. If
the other nonzero value is returned, it is treated as
:macro:`NGHTTP2_ERR_CALLBACK_FAILURE`. If
:macro:`NGHTTP2_ERR_CALLBACK_FAILURE` is returned,
`nghttp2_session_recv()` and `nghttp2_session_mem_recv()` functions
immediately return :macro:`NGHTTP2_ERR_CALLBACK_FAILURE`.
To set this callback to :type:`nghttp2_session_callbacks`, use
`nghttp2_session_callbacks_set_on_header_callback()`.
.. warning::
Application should properly limit the total buffer size to store
incoming header fields. Without it, peer may send large number
of header fields or large header fields to cause out of memory in
local endpoint. Due to how HPACK works, peer can do this
effectively without using much memory on their own.
.. type:: typedef int (*nghttp2_on_header_callback2)(nghttp2_session *session, const nghttp2_frame *frame, nghttp2_rcbuf *name, nghttp2_rcbuf *value, uint8_t flags, void *user_data)
Callback function invoked when a header name/value pair is received
for the *frame*. The *name* is header name. The *value* is header
value. The *flags* is bitwise OR of one or more of
:type:`nghttp2_nv_flag`.
This callback behaves like :type:`nghttp2_on_header_callback`,
except that *name* and *value* are stored in reference counted
buffer. If application wishes to keep these references without
copying them, use `nghttp2_rcbuf_incref()` to increment their
reference count. It is the application's responsibility to call
`nghttp2_rcbuf_decref()` if they called `nghttp2_rcbuf_incref()` so
as not to leak memory. If the *session* is created by
`nghttp2_session_server_new3()` or `nghttp2_session_client_new3()`,
the function to free memory is the one belongs to the mem
parameter. As long as this free function alives, *name* and
*value* can live after *session* was destroyed.
.. type:: typedef int (*nghttp2_on_invalid_header_callback)( nghttp2_session *session, const nghttp2_frame *frame, const uint8_t *name, size_t namelen, const uint8_t *value, size_t valuelen, uint8_t flags, void *user_data)
Callback function invoked when a invalid header name/value pair is
received for the *frame*.
The parameter and behaviour are similar to
:type:`nghttp2_on_header_callback`. The difference is that this
callback is only invoked when a invalid header name/value pair is
received which is treated as stream error if this callback is not
set. Only invalid regular header field are passed to this
callback. In other words, invalid pseudo header field is not
passed to this callback. Also header fields which includes upper
cased latter are also treated as error without passing them to this
callback.
This callback is only considered if HTTP messaging validation is
turned on (which is on by default, see
`nghttp2_option_set_no_http_messaging()`).
With this callback, application inspects the incoming invalid
field, and it also can reset stream from this callback by returning
:macro:`NGHTTP2_ERR_TEMPORAL_CALLBACK_FAILURE`. By default, the
error code is :macro:`NGHTTP2_PROTOCOL_ERROR`. To change the error
code, call `nghttp2_submit_rst_stream()` with the error code of
choice in addition to returning
:macro:`NGHTTP2_ERR_TEMPORAL_CALLBACK_FAILURE`.
If 0 is returned, the header field is ignored, and the stream is
not reset.
.. type:: typedef int (*nghttp2_on_invalid_header_callback2)( nghttp2_session *session, const nghttp2_frame *frame, nghttp2_rcbuf *name, nghttp2_rcbuf *value, uint8_t flags, void *user_data)
Callback function invoked when a invalid header name/value pair is
received for the *frame*.
The parameter and behaviour are similar to
:type:`nghttp2_on_header_callback2`. The difference is that this
callback is only invoked when a invalid header name/value pair is
received which is silently ignored if this callback is not set.
Only invalid regular header field are passed to this callback. In
other words, invalid pseudo header field is not passed to this
callback. Also header fields which includes upper cased latter are
also treated as error without passing them to this callback.
This callback is only considered if HTTP messaging validation is
turned on (which is on by default, see
`nghttp2_option_set_no_http_messaging()`).
With this callback, application inspects the incoming invalid
field, and it also can reset stream from this callback by returning
:macro:`NGHTTP2_ERR_TEMPORAL_CALLBACK_FAILURE`. By default, the
error code is :macro:`NGHTTP2_INTERNAL_ERROR`. To change the error
code, call `nghttp2_submit_rst_stream()` with the error code of
choice in addition to returning
:macro:`NGHTTP2_ERR_TEMPORAL_CALLBACK_FAILURE`.
.. type:: typedef ssize_t (*nghttp2_select_padding_callback)(nghttp2_session *session, const nghttp2_frame *frame, size_t max_payloadlen, void *user_data)
Callback function invoked when the library asks application how
many padding bytes are required for the transmission of the
*frame*. The application must choose the total length of payload
including padded bytes in range [frame->hd.length, max_payloadlen],
inclusive. Choosing number not in this range will be treated as
:macro:`NGHTTP2_ERR_CALLBACK_FAILURE`. Returning
``frame->hd.length`` means no padding is added. Returning
:macro:`NGHTTP2_ERR_CALLBACK_FAILURE` will make
`nghttp2_session_send()` and `nghttp2_session_mem_send()` functions
immediately return :macro:`NGHTTP2_ERR_CALLBACK_FAILURE`.
To set this callback to :type:`nghttp2_session_callbacks`, use
`nghttp2_session_callbacks_set_select_padding_callback()`.
.. type:: typedef ssize_t (*nghttp2_data_source_read_length_callback)( nghttp2_session *session, uint8_t frame_type, int32_t stream_id, int32_t session_remote_window_size, int32_t stream_remote_window_size, uint32_t remote_max_frame_size, void *user_data)
Callback function invoked when library wants to get max length of
data to send data to the remote peer. The implementation of this
function should return a value in the following range. [1,
min(*session_remote_window_size*, *stream_remote_window_size*,
*remote_max_frame_size*)]. If a value greater than this range is
returned than the max allow value will be used. Returning a value
smaller than this range is treated as
:macro:`NGHTTP2_ERR_CALLBACK_FAILURE`. The *frame_type* is provided
for future extensibility and identifies the type of frame (see
:type:`nghttp2_frame_type`) for which to get the length for.
Currently supported frame types are: :macro:`NGHTTP2_DATA`.
This callback can be used to control the length in bytes for which
:type:`nghttp2_data_source_read_callback` is allowed to send to the
remote endpoint. This callback is optional. Returning
:macro:`NGHTTP2_ERR_CALLBACK_FAILURE` will signal the entire session
failure.
To set this callback to :type:`nghttp2_session_callbacks`, use
`nghttp2_session_callbacks_set_data_source_read_length_callback()`.
.. type:: typedef int (*nghttp2_on_begin_frame_callback)(nghttp2_session *session, const nghttp2_frame_hd *hd, void *user_data)
Callback function invoked when a frame header is received. The
*hd* points to received frame header.
Unlike :type:`nghttp2_on_frame_recv_callback`, this callback will
also be called when frame header of CONTINUATION frame is received.
If both :type:`nghttp2_on_begin_frame_callback` and
:type:`nghttp2_on_begin_headers_callback` are set and HEADERS or
PUSH_PROMISE is received, :type:`nghttp2_on_begin_frame_callback`
will be called first.
The implementation of this function must return 0 if it succeeds.
If nonzero value is returned, it is treated as fatal error and
`nghttp2_session_recv()` and `nghttp2_session_mem_recv()` functions
immediately return :macro:`NGHTTP2_ERR_CALLBACK_FAILURE`.
To set this callback to :type:`nghttp2_session_callbacks`, use
`nghttp2_session_callbacks_set_on_begin_frame_callback()`.
.. type:: typedef int (*nghttp2_on_extension_chunk_recv_callback)( nghttp2_session *session, const nghttp2_frame_hd *hd, const uint8_t *data, size_t len, void *user_data)
Callback function invoked when chunk of extension frame payload is
received. The *hd* points to frame header. The received
chunk is *data* of length *len*.
The implementation of this function must return 0 if it succeeds.
To abort processing this extension frame, return
:macro:`NGHTTP2_ERR_CANCEL`.
If fatal error occurred, application should return
:macro:`NGHTTP2_ERR_CALLBACK_FAILURE`. In this case,
`nghttp2_session_recv()` and `nghttp2_session_mem_recv()` functions
immediately return :macro:`NGHTTP2_ERR_CALLBACK_FAILURE`. If the
other values are returned, currently they are treated as
:macro:`NGHTTP2_ERR_CALLBACK_FAILURE`.
.. type:: typedef int (*nghttp2_unpack_extension_callback)(nghttp2_session *session, void **payload, const nghttp2_frame_hd *hd, void *user_data)
Callback function invoked when library asks the application to
unpack extension payload from its wire format. The extension
payload has been passed to the application using
:type:`nghttp2_on_extension_chunk_recv_callback`. The frame header
is already unpacked by the library and provided as *hd*.
To receive extension frames, the application must tell desired
extension frame type to the library using
`nghttp2_option_set_user_recv_extension_type()`.
The implementation of this function may store the pointer to the
created object as a result of unpacking in *\*payload*, and returns
0. The pointer stored in *\*payload* is opaque to the library, and
the library does not own its pointer. *\*payload* is initialized as
``NULL``. The *\*payload* is available as ``frame->ext.payload`` in
:type:`nghttp2_on_frame_recv_callback`. Therefore if application
can free that memory inside :type:`nghttp2_on_frame_recv_callback`
callback. Of course, application has a liberty not ot use
*\*payload*, and do its own mechanism to process extension frames.
To abort processing this extension frame, return
:macro:`NGHTTP2_ERR_CANCEL`.
If fatal error occurred, application should return
:macro:`NGHTTP2_ERR_CALLBACK_FAILURE`. In this case,
`nghttp2_session_recv()` and `nghttp2_session_mem_recv()` functions
immediately return :macro:`NGHTTP2_ERR_CALLBACK_FAILURE`. If the
other values are returned, currently they are treated as
:macro:`NGHTTP2_ERR_CALLBACK_FAILURE`.
.. type:: typedef ssize_t (*nghttp2_pack_extension_callback)(nghttp2_session *session, uint8_t *buf, size_t len, const nghttp2_frame *frame, void *user_data)
Callback function invoked when library asks the application to pack
extension payload in its wire format. The frame header will be
packed by library. Application must pack payload only.
``frame->ext.payload`` is the object passed to
`nghttp2_submit_extension()` as payload parameter. Application
must pack extension payload to the *buf* of its capacity *len*
bytes. The *len* is at least 16KiB.
The implementation of this function should return the number of
bytes written into *buf* when it succeeds.
To abort processing this extension frame, return
:macro:`NGHTTP2_ERR_CANCEL`, and
:type:`nghttp2_on_frame_not_send_callback` will be invoked.
If fatal error occurred, application should return
:macro:`NGHTTP2_ERR_CALLBACK_FAILURE`. In this case,
`nghttp2_session_send()` and `nghttp2_session_mem_send()` functions
immediately return :macro:`NGHTTP2_ERR_CALLBACK_FAILURE`. If the
other values are returned, currently they are treated as
:macro:`NGHTTP2_ERR_CALLBACK_FAILURE`. If the return value is
strictly larger than *len*, it is treated as
:macro:`NGHTTP2_ERR_CALLBACK_FAILURE`.
.. type:: typedef int (*nghttp2_error_callback)(nghttp2_session *session, const char *msg, size_t len, void *user_data)
Callback function invoked when library provides the error message
intended for human consumption. This callback is solely for
debugging purpose. The *msg* is typically NULL-terminated string
of length *len*. *len* does not include the sentinel NULL
character.
This function is deprecated. The new application should use
:type:`nghttp2_error_callback2`.
The format of error message may change between nghttp2 library
versions. The application should not depend on the particular
format.
Normally, application should return 0 from this callback. If fatal
error occurred while doing something in this callback, application
should return :macro:`NGHTTP2_ERR_CALLBACK_FAILURE`. In this case,
library will return immediately with return value
:macro:`NGHTTP2_ERR_CALLBACK_FAILURE`. Currently, if nonzero value
is returned from this callback, they are treated as
:macro:`NGHTTP2_ERR_CALLBACK_FAILURE`, but application should not
rely on this details.
.. type:: typedef int (*nghttp2_error_callback2)(nghttp2_session *session, int lib_error_code, const char *msg, size_t len, void *user_data)
Callback function invoked when library provides the error code, and
message. This callback is solely for debugging purpose.
*lib_error_code* is one of error code defined in
:macro:`nghttp2_error`. The *msg* is typically NULL-terminated
string of length *len*, and intended for human consumption. *len*
does not include the sentinel NULL character.
The format of error message may change between nghttp2 library
versions. The application should not depend on the particular
format.
Normally, application should return 0 from this callback. If fatal
error occurred while doing something in this callback, application
should return :macro:`NGHTTP2_ERR_CALLBACK_FAILURE`. In this case,
library will return immediately with return value
:macro:`NGHTTP2_ERR_CALLBACK_FAILURE`. Currently, if nonzero value
is returned from this callback, they are treated as
:macro:`NGHTTP2_ERR_CALLBACK_FAILURE`, but application should not
rely on this details.
.. type:: nghttp2_session_callbacks
Callback functions for :type:`nghttp2_session`. The details of
this structure are intentionally hidden from the public API.
.. type:: typedef void *(*nghttp2_malloc)(size_t size, void *mem_user_data)
Custom memory allocator to replace malloc(). The *mem_user_data*
is the mem_user_data member of :type:`nghttp2_mem` structure.
.. type:: typedef void (*nghttp2_free)(void *ptr, void *mem_user_data)
Custom memory allocator to replace free(). The *mem_user_data* is
the mem_user_data member of :type:`nghttp2_mem` structure.
.. type:: typedef void *(*nghttp2_calloc)(size_t nmemb, size_t size, void *mem_user_data)
Custom memory allocator to replace calloc(). The *mem_user_data*
is the mem_user_data member of :type:`nghttp2_mem` structure.
.. type:: typedef void *(*nghttp2_realloc)(void *ptr, size_t size, void *mem_user_data)
Custom memory allocator to replace realloc(). The *mem_user_data*
is the mem_user_data member of :type:`nghttp2_mem` structure.
.. type:: nghttp2_mem
Custom memory allocator functions and user defined pointer. The
*mem_user_data* member is passed to each allocator function. This
can be used, for example, to achieve per-session memory pool.
In the following example code, ``my_malloc``, ``my_free``,
``my_calloc`` and ``my_realloc`` are the replacement of the
standard allocators ``malloc``, ``free``, ``calloc`` and
``realloc`` respectively::
void *my_malloc_cb(size_t size, void *mem_user_data) {
return my_malloc(size);
}
void my_free_cb(void *ptr, void *mem_user_data) { my_free(ptr); }
void *my_calloc_cb(size_t nmemb, size_t size, void *mem_user_data) {
return my_calloc(nmemb, size);
}
void *my_realloc_cb(void *ptr, size_t size, void *mem_user_data) {
return my_realloc(ptr, size);
}
void session_new() {
nghttp2_session *session;
nghttp2_session_callbacks *callbacks;
nghttp2_mem mem = {NULL, my_malloc_cb, my_free_cb, my_calloc_cb,
my_realloc_cb};
...
nghttp2_session_client_new3(&session, callbacks, NULL, NULL, &mem);
...
}
.. member:: void *mem_user_data
An arbitrary user supplied data. This is passed to each
allocator function.
.. member:: nghttp2_malloc malloc
Custom allocator function to replace malloc().
.. member:: nghttp2_free free
Custom allocator function to replace free().
.. member:: nghttp2_calloc calloc
Custom allocator function to replace calloc().
.. member:: nghttp2_realloc realloc
Custom allocator function to replace realloc().
.. type:: nghttp2_option
Configuration options for :type:`nghttp2_session`. The details of
this structure are intentionally hidden from the public API.
.. type:: nghttp2_ext_altsvc
The payload of ALTSVC frame. ALTSVC frame is a non-critical
extension to HTTP/2. If this frame is received, and
`nghttp2_option_set_user_recv_extension_type()` is not set, and
`nghttp2_option_set_builtin_recv_extension_type()` is set for
:macro:`NGHTTP2_ALTSVC`, ``nghttp2_extension.payload`` will point to
this struct.
It has the following members:
.. member:: uint8_t *origin
The pointer to origin which this alternative service is
associated with. This is not necessarily NULL-terminated.
.. member:: size_t origin_len
The length of the *origin*.
.. member:: uint8_t *field_value
The pointer to Alt-Svc field value contained in ALTSVC frame.
This is not necessarily NULL-terminated.
.. member:: size_t field_value_len
The length of the *field_value*.
.. type:: nghttp2_origin_entry
The single entry of an origin.
.. member:: uint8_t *origin
The pointer to origin. No validation is made against this field
by the library. This is not necessarily NULL-terminated.
.. member:: size_t origin_len
The length of the *origin*.
.. type:: nghttp2_ext_origin
The payload of ORIGIN frame. ORIGIN frame is a non-critical
extension to HTTP/2 and defined by `RFC 8336
<https://tools.ietf.org/html/rfc8336>`_.
If this frame is received, and
`nghttp2_option_set_user_recv_extension_type()` is not set, and
`nghttp2_option_set_builtin_recv_extension_type()` is set for
:macro:`NGHTTP2_ORIGIN`, ``nghttp2_extension.payload`` will point to
this struct.
It has the following members:
.. member:: size_t nov
The number of origins contained in *ov*.
.. member:: nghttp2_origin_entry *ov
The pointer to the array of origins contained in ORIGIN frame.
.. type:: nghttp2_hd_deflater
HPACK deflater object.
.. type:: nghttp2_hd_inflater
HPACK inflater object.
.. type:: nghttp2_stream
The structure to represent HTTP/2 stream. The details of this
structure are intentionally hidden from the public API.
.. type:: typedef void (*nghttp2_debug_vprintf_callback)(const char *format, va_list args)
Callback function invoked when the library outputs debug logging.
The function is called with arguments suitable for ``vfprintf(3)``
The debug output is only enabled if the library is built with
``DEBUGBUILD`` macro defined.