Function pim_register_send_rp

freebsd/netinet/ip_mroute.c:2465–2531

* Encapsulate the data packet in PIM Register message and send it to the RP. */

 * Encapsulate the data packet in PIM Register message and send it to the RP.
 */
static int
pim_register_send_rp(struct ip *ip, struct vif *vifp, struct mbuf *mb_copy,
    struct mfc *rt)
{
    struct mbuf *mb_first;
    struct ip *ip_outer;
    struct pim_encap_pimhdr *pimhdr;
    int len = ntohs(ip->ip_len);
    vifi_t vifi = rt->mfc_parent;

    VIF_LOCK_ASSERT();

    if ((vifi >= V_numvifs) || in_nullhost(V_viftable[vifi].v_lcl_addr)) {
	m_freem(mb_copy);
	return EADDRNOTAVAIL;		/* The iif vif is invalid */
    }

    /*
     * Add a new mbuf with the encapsulating header
     */
    mb_first = m_gethdr(M_NOWAIT, MT_DATA);
    if (mb_first == NULL) {
	m_freem(mb_copy);
	return ENOBUFS;
    }
    mb_first->m_data += max_linkhdr;
    mb_first->m_len = sizeof(pim_encap_iphdr) + sizeof(pim_encap_pimhdr);
    mb_first->m_next = mb_copy;

    mb_first->m_pkthdr.len = len + mb_first->m_len;

    /*
     * Fill in the encapsulating IP and PIM header
     */
    ip_outer = mtod(mb_first, struct ip *);
    *ip_outer = pim_encap_iphdr;
    ip_outer->ip_len = htons(len + sizeof(pim_encap_iphdr) +
	sizeof(pim_encap_pimhdr));
    ip_outer->ip_src = V_viftable[vifi].v_lcl_addr;
    ip_outer->ip_dst = rt->mfc_rp;
    /*
     * Copy the inner header TOS to the outer header, and take care of the
     * IP_DF bit.
     */
    ip_outer->ip_tos = ip->ip_tos;
    if (ip->ip_off & htons(IP_DF))
	ip_outer->ip_off |= htons(IP_DF);
    ip_fillid(ip_outer);
    pimhdr = (struct pim_encap_pimhdr *)((caddr_t)ip_outer
					 + sizeof(pim_encap_iphdr));
    *pimhdr = pim_encap_pimhdr;
    /* If the iif crosses a border, set the Border-bit */
    if (rt->mfc_flags[vifi] & MRT_MFC_FLAGS_BORDER_VIF & V_mrt_api_config)
	pimhdr->flags |= htonl(PIM_BORDER_REGISTER);

    mb_first->m_data += sizeof(pim_encap_iphdr);
    pimhdr->pim.pim_cksum = in_cksum(mb_first, sizeof(pim_encap_pimhdr));
    mb_first->m_data -= sizeof(pim_encap_iphdr);