When preserving the IP header in extra mbuf in the IP forwarding

case, also preserve the MAC label.  Note that this mbuf allocation
is fairly non-optimal, but not my fault.

Obtained from:	TrustedBSD Project
Sponsored by:	DARPA, NAI Labs

sys/netinet/ip_input.c

@@ -1690,6 +1690,13 @@ ip_forward(struct mbuf *m, int srcrt, struct sockaddr_in *next_hop)
 		mcopy->m_len = imin((IP_VHL_HL(ip->ip_vhl) << 2) + 8,
 		    (int)ip->ip_len);
 		m_copydata(m, 0, mcopy->m_len, mtod(mcopy, caddr_t));
+#ifdef MAC
+		/*
+		 * XXXMAC: This will eventually become an explicit
+		 * labeling point.
+		 */
+		mac_create_mbuf_from_mbuf(m, mcopy);
+#endif
 	}
 
 #ifdef IPSTEALTH