#include <nghttp2/nghttp2.h>

void nghttp2_option_set_max_send_header_block_length(nghttp2_option *option, size_t val)

This option sets the maximum length of header block (a set of header fields per one HEADERS frame) to send. The length of a given set of header fields is calculated using nghttp2_hd_deflate_bound(). The default value is 64KiB. If application attempts to send header fields larger than this limit, the transmission of the frame fails with error code NGHTTP2_ERR_FRAME_SIZE_ERROR.