e of the pbuf. New space is on the front. (Using a negative value decreases the header size.) If header_size_increment is 0, this function does nothing and returns successful.</td></tr>
  </table>
  </dd>
</dl>
<p>PBUF_ROM and PBUF_REF type buffers cannot have their sizes increased, so the call will fail. A check is made that the increase in header size does not move the payload pointer in front of the start of the buffer. </p><dl class="section return"><dt>Returns</dt><dd>non-zero on failure, zero on succe