#include <nghttp2/nghttp2.h>

int nghttp2_submit_extension(nghttp2_session *session, uint8_t type, uint8_t flags, int32_t stream_id, void *payload)

Submits extension frame.

Application can pass arbitrary frame flags and stream ID in flags and stream_id respectively. The payload is opaque pointer, and it can be accessible though frame->ext.payload in nghttp2_pack_extension_callback. The library will not own passed payload pointer.

The application must set nghttp2_pack_extension_callback using nghttp2_session_callbacks_set_pack_extension_callback().

The application should retain the memory pointed by payload until the transmission of extension frame is done (which is indicated by nghttp2_on_frame_send_callback), or transmission fails (which is indicated by nghttp2_on_frame_not_send_callback). If application does not touch this memory region after packing it into a wire format, application can free it inside nghttp2_pack_extension_callback.

The standard HTTP/2 frame cannot be sent with this function, so type must be strictly grater than 0x9. Otherwise, this function will fail with error code NGHTTP2_ERR_INVALID_ARGUMENT.

This function returns 0 if it succeeds, or one of the following negative error codes:

If nghttp2_pack_extension_callback is not set.
If type specifies standard HTTP/2 frame type. The frame types in the rage [0x0, 0x9], both inclusive, are standard HTTP/2 frame type, and cannot be sent using this function.
Out of memory