Function pf_pull_hdr

freebsd/netpfil/pf/pf.c:5379–5424

* ipoff and off are measured from the start of the mbuf chain. * h must be at "ipoff" on the mbuf chain. */

 * h must be at "ipoff" on the mbuf chain.
 */
void *
pf_pull_hdr(struct mbuf *m, int off, void *p, int len,
    u_short *actionp, u_short *reasonp, sa_family_t af)
{
	switch (af) {
#ifdef INET
	case AF_INET: {
		struct ip	*h = mtod(m, struct ip *);
		u_int16_t	 fragoff = (ntohs(h->ip_off) & IP_OFFMASK) << 3;

		if (fragoff) {
			if (fragoff >= len)
				ACTION_SET(actionp, PF_PASS);
			else {
				ACTION_SET(actionp, PF_DROP);
				REASON_SET(reasonp, PFRES_FRAG);
			}
			return (NULL);
		}
		if (m->m_pkthdr.len < off + len ||
		    ntohs(h->ip_len) < off + len) {
			ACTION_SET(actionp, PF_DROP);
			REASON_SET(reasonp, PFRES_SHORT);
			return (NULL);
		}
		break;
	}
#endif /* INET */
#ifdef INET6
	case AF_INET6: {
		struct ip6_hdr	*h = mtod(m, struct ip6_hdr *);

		if (m->m_pkthdr.len < off + len ||
		    (ntohs(h->ip6_plen) + sizeof(struct ip6_hdr)) <
		    (unsigned)(off + len)) {
			ACTION_SET(actionp, PF_DROP);
			REASON_SET(reasonp, PFRES_SHORT);
			return (NULL);
		}
		break;
	}
#endif /* INET6 */
	}
	m_copydata(m, off, len, p);
	return (p);
}

int
pf_routable(struct pf_addr *addr, sa_family_t af, struct pfi_kkif *kif,