Function ng_add_hook

freebsd/netgraph/ng_base.c:1063–1115

* Add an unconnected hook to a node. Only used internally. * Assumes node is locked. (XXX not yet true ) */

 * Assumes node is locked. (XXX not yet true )
 */
static int
ng_add_hook(node_p node, const char *name, hook_p *hookp)
{
	hook_p hook;
	int error = 0;

	/* Check that the given name is good */
	if (name == NULL) {
		TRAP_ERROR();
		return (EINVAL);
	}
	if (ng_findhook(node, name) != NULL) {
		TRAP_ERROR();
		return (EEXIST);
	}

	/* Allocate the hook and link it up */
	NG_ALLOC_HOOK(hook);
	if (hook == NULL) {
		TRAP_ERROR();
		return (ENOMEM);
	}
	hook->hk_refs = 1;		/* add a reference for us to return */
	hook->hk_flags = HK_INVALID;
	hook->hk_peer = &ng_deadhook;	/* start off this way */
	hook->hk_node = node;
	NG_NODE_REF(node);		/* each hook counts as a reference */

	/* Set hook name */
	strlcpy(NG_HOOK_NAME(hook), name, NG_HOOKSIZ);

	/*
	 * Check if the node type code has something to say about it
	 * If it fails, the unref of the hook will also unref the node.
	 */
	if (node->nd_type->newhook != NULL) {
		if ((error = (*node->nd_type->newhook)(node, hook, name))) {
			NG_HOOK_UNREF(hook);	/* this frees the hook */
			return (error);
		}
	}
	/*
	 * The 'type' agrees so far, so go ahead and link it in.
	 * We'll ask again later when we actually connect the hooks.
	 */
	LIST_INSERT_HEAD(&node->nd_hooks, hook, hk_hooks);
	node->nd_numhooks++;
	NG_HOOK_REF(hook);	/* one for the node */

	if (hookp)
		*hookp = hook;
	return (0);
}

/*
 * Find a hook