see sys/net/if_fwsubr.c::firewire_input().
Why does it perform htonl() at the time of input of a packet?
An input packet is a network-byte-order. We should use ntohl().

Fix: 

sys/net/if_fwsubr.c::firewire_input()
-------------------------------------
void
firewire_input(struct ifnet *ifp, struct mbuf *m, uint16_t src)
{

      ... snip ...

	/*
	 * Byte swap the encapsulation header manually.
	 */
-	enc->ul[0] = htonl(enc->ul[0]);
+	enc->ul[0] = ntohl(enc->ul[0]);

	if (enc->unfrag.lf != 0) {
		m = m_pullup(m, 2*sizeof(uint32_t));
		if (!m)
			return;
		enc = mtod(m, union fw_encap *);
-		enc->ul[1] = htonl(enc->ul[1]);
+		enc->ul[1] = ntohl(enc->ul[1]);
		m = firewire_input_fragment(fc, m, src);