Function igmp_intr

freebsd/netinet/igmp.c:3439–3522

* Transmit the next pending IGMP message in the output queue. * * We get called from netisr_processqueue(). A mutex private to igmpoq * will be acquired and released around this routine. * * VIMAGE: Needs to store/restore vnet pointer on a per-mbuf-chain basis. * MRT: Nothing needs to be done, as IGMP traffic is always local to * a link and uses a link-scope multicast address. */

 * a link and uses a link-scope multicast address.
 */
static void
igmp_intr(struct mbuf *m)
{
	struct ip_moptions	 imo;
	struct ifnet		*ifp;
	struct mbuf		*ipopts, *m0;
	int			 error;
	uint32_t		 ifindex;

	CTR2(KTR_IGMPV3, "%s: transmit %p", __func__, m);

	/*
	 * Set VNET image pointer from enqueued mbuf chain
	 * before doing anything else. Whilst we use interface
	 * indexes to guard against interface detach, they are
	 * unique to each VIMAGE and must be retrieved.
	 */
	CURVNET_SET((struct vnet *)(m->m_pkthdr.PH_loc.ptr));
	ifindex = igmp_restore_context(m);

	/*
	 * Check if the ifnet still exists. This limits the scope of
	 * any race in the absence of a global ifp lock for low cost
	 * (an array lookup).
	 */
	ifp = ifnet_byindex(ifindex);
	if (ifp == NULL) {
		CTR3(KTR_IGMPV3, "%s: dropped %p as ifindex %u went away.",
		    __func__, m, ifindex);
		m_freem(m);
		IPSTAT_INC(ips_noroute);
		goto out;
	}

	ipopts = V_igmp_sendra ? m_raopt : NULL;

	imo.imo_multicast_ttl  = 1;
	imo.imo_multicast_vif  = -1;
	imo.imo_multicast_loop = (V_ip_mrouter != NULL);

	/*
	 * If the user requested that IGMP traffic be explicitly
	 * redirected to the loopback interface (e.g. they are running a
	 * MANET interface and the routing protocol needs to see the
	 * updates), handle this now.
	 */
	if (m->m_flags & M_IGMP_LOOP)
		imo.imo_multicast_ifp = V_loif;
	else
		imo.imo_multicast_ifp = ifp;

	if (m->m_flags & M_IGMPV2) {
		m0 = m;
	} else {
		m0 = igmp_v3_encap_report(ifp, m);
		if (m0 == NULL) {
			CTR2(KTR_IGMPV3, "%s: dropped %p", __func__, m);
			m_freem(m);