agr_m_extract
ip = agr_m_extract(m, off, sizeof(*ip), &ip_store);
ip6 = agr_m_extract(m, off, sizeof(*ip6), &ip6_store);
static const void *agr_m_extract(struct mbuf *, int, int, void *);
eh = agr_m_extract(m, off, sizeof(*eh), &eh_store);
vlanhdr = agr_m_extract(m, off, sizeof(*vlanhdr),