Function ng_snd_item

freebsd/netgraph/ng_base.c:2222–2352

 */

int
ng_snd_item(item_p item, int flags)
{
	hook_p hook;
	node_p node;
	int queue, rw;
	struct ng_queue *ngq;
	int error = 0;

	/* We are sending item, so it must be present! */
	KASSERT(item != NULL, ("ng_snd_item: item is NULL"));

#ifdef	NETGRAPH_DEBUG
	_ngi_check(item, __FILE__, __LINE__);
#endif

	/* Item was sent once more, postpone apply() call. */
	if (item->apply)
		refcount_acquire(&item->apply->refs);

	node = NGI_NODE(item);
	/* Node is never optional. */
	KASSERT(node != NULL, ("ng_snd_item: node is NULL"));

	hook = NGI_HOOK(item);
	/* Valid hook and mbuf are mandatory for data. */
	if ((item->el_flags & NGQF_TYPE) == NGQF_DATA) {
		KASSERT(hook != NULL, ("ng_snd_item: hook for data is NULL"));
		if (NGI_M(item) == NULL)
			ERROUT(EINVAL);
		CHECK_DATA_MBUF(NGI_M(item));
	}

	/*
	 * If the item or the node specifies single threading, force
	 * writer semantics. Similarly, the node may say one hook always
	 * produces writers. These are overrides.
	 */
	if (((item->el_flags & NGQF_RW) == NGQF_WRITER) ||
	    (node->nd_flags & NGF_FORCE_WRITER) ||
	    (hook && (hook->hk_flags & HK_FORCE_WRITER))) {
		rw = NGQRW_W;
	} else {
		rw = NGQRW_R;
	}

	/*
	 * If sender or receiver requests queued delivery, or call graph
	 * loops back from outbound to inbound path, or stack usage
	 * level is dangerous - enqueue message.
	 */
	if ((flags & NG_QUEUE) || (hook && (hook->hk_flags & HK_QUEUE))) {
		queue = 1;
	} else if (hook && (hook->hk_flags & HK_TO_INBOUND) &&
	    curthread->td_ng_outbound) {
		queue = 1;
	} else {
		queue = 0;