Function ng_ppp_link_xmit

freebsd/netgraph/ng_ppp.c:1318–1399

 */

static int
ng_ppp_link_xmit(node_p node, item_p item, uint16_t proto, uint16_t linkNum, int plen)
{
	const priv_p priv = NG_NODE_PRIVATE(node);
	struct ng_ppp_link *link;
	int len, error;
	struct mbuf *m;
	uint16_t mru;

	/* Check if link correct. */
	if (linkNum >= NG_PPP_MAX_LINKS) {
		ERROUT(ENETDOWN);
	}

	/* Get link pointer (optimization). */
	link = &priv->links[linkNum];

	/* Check link status (if real). */
	if (link->hook == NULL) {
		ERROUT(ENETDOWN);
	}

	/* Extract mbuf. */
	NGI_GET_M(item, m);

	/* Check peer's MRU for this link. */
	mru = link->conf.mru;
	if (mru != 0 && m->m_pkthdr.len > mru) {
		NG_FREE_M(m);
		ERROUT(EMSGSIZE);
	}

	/* Prepend protocol number, possibly compressed. */
	if ((m = ng_ppp_addproto(m, proto, link->conf.enableProtoComp)) ==
	    NULL) {
		ERROUT(ENOBUFS);
	}

	/* Prepend address and control field (unless compressed). */
	if (proto == PROT_LCP || !link->conf.enableACFComp) {
		if ((m = ng_ppp_prepend(m, &ng_ppp_acf, 2)) == NULL)
			ERROUT(ENOBUFS);
	}

	/* Deliver frame. */
	len = m->m_pkthdr.len;
	NG_FWD_NEW_DATA(error, item, link->hook, m);

	mtx_lock(&priv->xmtx);

	/* Update link stats. */
	link->stats.xmitFrames++;
	link->stats.xmitOctets += len;

	/* Update bundle stats. */
	if (plen > 0) {
	    priv->bundleStats.xmitFrames++;
	    priv->bundleStats.xmitOctets += plen;