Source

File: wp-includes/comment-template.php

function pings_open( $post_id = null ) {

	$_post = get_post( $post_id );

	$post_id = $_post ? $_post->ID : 0;
	$open    = ( 'open' === $_post->ping_status );

	/**
	 * Filters whether the current post is open for pings.
	 *
	 * @since 2.5.0
	 *
	 * @param bool $open    Whether the current post is open for pings.
	 * @param int  $post_id The post ID.
	 */
	return apply_filters( 'pings_open', $open, $post_id );
}