Function vxlan_encap4

freebsd/net/if_vxlan.c:2464–2574

}

static int
vxlan_encap4(struct vxlan_softc *sc, const union vxlan_sockaddr *fvxlsa,
    struct mbuf *m)
{
#ifdef INET
	struct ifnet *ifp;
	struct ip *ip;
	struct in_addr srcaddr, dstaddr;
	uint16_t srcport, dstport;
	int len, mcast, error;
	struct route route, *ro;
	struct sockaddr_in *sin;
	uint32_t csum_flags;

	NET_EPOCH_ASSERT();

	ifp = sc->vxl_ifp;
	srcaddr = sc->vxl_src_addr.in4.sin_addr;
	srcport = vxlan_pick_source_port(sc, m);
	dstaddr = fvxlsa->in4.sin_addr;
	dstport = fvxlsa->in4.sin_port;

	M_PREPEND(m, sizeof(struct ip) + sizeof(struct vxlanudphdr),
	    M_NOWAIT);
	if (m == NULL) {
		if_inc_counter(ifp, IFCOUNTER_OERRORS, 1);
		return (ENOBUFS);
	}

	len = m->m_pkthdr.len;

	ip = mtod(m, struct ip *);
	ip->ip_tos = 0;
	ip->ip_len = htons(len);
	ip->ip_off = 0;
	ip->ip_ttl = sc->vxl_ttl;
	ip->ip_p = IPPROTO_UDP;
	ip->ip_sum = 0;
	ip->ip_src = srcaddr;
	ip->ip_dst = dstaddr;

	vxlan_encap_header(sc, m, sizeof(struct ip), srcport, dstport);

	mcast = (m->m_flags & (M_MCAST | M_BCAST)) ? 1 : 0;
	m->m_flags &= ~(M_MCAST | M_BCAST);

	m->m_pkthdr.csum_flags &= CSUM_FLAGS_TX;
	if (m->m_pkthdr.csum_flags != 0) {
		/*
		 * HW checksum (L3 and/or L4) or TSO has been requested.  Look
		 * up the ifnet for the outbound route and verify that the
		 * outbound ifnet can perform the requested operation on the
		 * inner frame.
		 */
		bzero(&route, sizeof(route));
		ro = &route;
		sin = (struct sockaddr_in *)&ro->ro_dst;
		sin->sin_family = AF_INET;