# nghttp2_submit_extension

## Synopsis

#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_error.NGHTTP2_ERR_INVALID_ARGUMENT`.

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

  `nghttp2_error.NGHTTP2_ERR_INVALID_STATE`

    If `nghttp2_pack_extension_callback` is not set.

  `nghttp2_error.NGHTTP2_ERR_INVALID_ARGUMENT`

    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.

  `nghttp2_error.NGHTTP2_ERR_NOMEM`

    Out of memory