Function igmp_input

freebsd/netinet/igmp.c:1468–1657

}

int
igmp_input(struct mbuf **mp, int *offp, int proto)
{
	int iphlen;
	struct ifnet *ifp;
	struct igmp *igmp;
	struct ip *ip;
	struct mbuf *m;
	int igmplen;
	int minlen;
	int queryver;

	CTR3(KTR_IGMPV3, "%s: called w/mbuf (%p,%d)", __func__, *mp, *offp);

	m = *mp;
	ifp = m->m_pkthdr.rcvif;
	*mp = NULL;

	IGMPSTAT_INC(igps_rcv_total);

	ip = mtod(m, struct ip *);
	iphlen = *offp;
	igmplen = ntohs(ip->ip_len) - iphlen;

	/*
	 * Validate lengths.
	 */
	if (igmplen < IGMP_MINLEN) {
		IGMPSTAT_INC(igps_rcv_tooshort);
		m_freem(m);
		return (IPPROTO_DONE);
	}

	/*
	 * Always pullup to the minimum size for v1/v2 or v3
	 * to amortize calls to m_pullup().
	 */
	minlen = iphlen;
	if (igmplen >= IGMP_V3_QUERY_MINLEN)
		minlen += IGMP_V3_QUERY_MINLEN;
	else
		minlen += IGMP_MINLEN;
	if ((!M_WRITABLE(m) || m->m_len < minlen) &&
	    (m = m_pullup(m, minlen)) == NULL) {
		IGMPSTAT_INC(igps_rcv_tooshort);
		return (IPPROTO_DONE);
	}
	ip = mtod(m, struct ip *);

	/*
	 * Validate checksum.
	 */
	m->m_data += iphlen;
	m->m_len -= iphlen;
	igmp = mtod(m, struct igmp *);
	if (in_cksum(m, igmplen)) {
		IGMPSTAT_INC(igps_rcv_badsum);
		m_freem(m);