Function tunoutput

freebsd/net/if_tuntap.c:1367–1451

* tunoutput - queue packets from higher level ready to put out. */

 * tunoutput - queue packets from higher level ready to put out.
 */
static int
tunoutput(struct ifnet *ifp, struct mbuf *m0, const struct sockaddr *dst,
    struct route *ro)
{
	struct tuntap_softc *tp = ifp->if_softc;
	u_short cached_tun_flags;
	int error;
	u_int32_t af;

	TUNDEBUG (ifp, "tunoutput\n");

#ifdef MAC
	error = mac_ifnet_check_transmit(ifp, m0);
	if (error) {
		m_freem(m0);
		return (error);
	}
#endif

	/* Could be unlocked read? */
	TUN_LOCK(tp);
	cached_tun_flags = tp->tun_flags;
	TUN_UNLOCK(tp);
	if ((cached_tun_flags & TUN_READY) != TUN_READY) {
		TUNDEBUG (ifp, "not ready 0%o\n", tp->tun_flags);
		m_freem (m0);
		return (EHOSTDOWN);
	}

	if ((ifp->if_flags & IFF_UP) != IFF_UP) {
		m_freem (m0);
		return (EHOSTDOWN);
	}

	/* BPF writes need to be handled specially. */
	if (dst->sa_family == AF_UNSPEC)
		bcopy(dst->sa_data, &af, sizeof(af));
	else
		af = dst->sa_family;

	if (bpf_peers_present(ifp->if_bpf))
		bpf_mtap2(ifp->if_bpf, &af, sizeof(af), m0);

	/* prepend sockaddr? this may abort if the mbuf allocation fails */
	if (cached_tun_flags & TUN_LMODE) {
		/* allocate space for sockaddr */
		M_PREPEND(m0, dst->sa_len, M_NOWAIT);

		/* if allocation failed drop packet */
		if (m0 == NULL) {
			if_inc_counter(ifp, IFCOUNTER_IQDROPS, 1);
			if_inc_counter(ifp, IFCOUNTER_OERRORS, 1);
			return (ENOBUFS);
		} else {
			bcopy(dst, m0->m_data, dst->sa_len);
		}
	}