Function pim6_input

freebsd/netinet6/ip6_mroute.c:1705–1887

* PIM sparse mode hook * Receives the pim control messages, and passes them up to the listening * socket, using rip6_input. * The only message processed is the REGISTER pim message; the pim header * is stripped off, and the inner packet is passed to register_mforward. */

 * is stripped off, and the inner packet is passed to register_mforward.
 */
static int
pim6_input(struct mbuf *m, int off, int proto, void *arg __unused)
{
	struct pim *pim; /* pointer to a pim struct */
	struct ip6_hdr *ip6;
	int pimlen;
	int minlen;

	PIM6STAT_INC(pim6s_rcv_total);

	/*
	 * Validate lengths
	 */
	pimlen = m->m_pkthdr.len - off;
	if (pimlen < PIM_MINLEN) {
		PIM6STAT_INC(pim6s_rcv_tooshort);
		MRT6_DLOG(DEBUG_PIM, "PIM packet too short");
		m_freem(m);
		return (IPPROTO_DONE);
	}

	/*
	 * if the packet is at least as big as a REGISTER, go ahead
	 * and grab the PIM REGISTER header size, to avoid another
	 * possible m_pullup() later.
	 *
	 * PIM_MINLEN       == pimhdr + u_int32 == 8
	 * PIM6_REG_MINLEN   == pimhdr + reghdr + eip6hdr == 4 + 4 + 40
	 */
	minlen = (pimlen >= PIM6_REG_MINLEN) ? PIM6_REG_MINLEN : PIM_MINLEN;

	/*
	 * Make sure that the IP6 and PIM headers in contiguous memory, and
	 * possibly the PIM REGISTER header
	 */
	if (m->m_len < off + minlen) {
		m = m_pullup(m, off + minlen);
		if (m == NULL) {
			IP6STAT_INC(ip6s_exthdrtoolong);
			return (IPPROTO_DONE);
		}
	}
	ip6 = mtod(m, struct ip6_hdr *);
	pim = (struct pim *)((caddr_t)ip6 + off);

#define PIM6_CHECKSUM
#ifdef PIM6_CHECKSUM
	{
		int cksumlen;

		/*
		 * Validate checksum.
		 * If PIM REGISTER, exclude the data packet
		 */
		if (pim->pim_type == PIM_REGISTER)
			cksumlen = PIM_MINLEN;
		else
			cksumlen = pimlen;