1 files changed, 13 insertions, 0 deletions

diff --git a/sys/net/if_ethersubr.c b/sys/net/if_ethersubr.c
index 399f0658b92d..d743187d6a35 100644
--- a/sys/net/if_ethersubr.c
+++ b/sys/net/if_ethersubr.c
@@ -325,12 +325,25 @@ ether_output(ifp, m, dst, rt0)
 	 * reasons and compatibility with the original behavior.
 	 */
 	if ((ifp->if_flags & IFF_SIMPLEX) && (loop_copy != -1)) {
+		int csum_flags = 0;
+
+		if (m->m_pkthdr.csum_flags & CSUM_IP)
+			csum_flags |= (CSUM_IP_CHECKED|CSUM_IP_VALID);
+		if (m->m_pkthdr.csum_flags & CSUM_DELAY_DATA)
+			csum_flags |= (CSUM_DATA_VALID|CSUM_PSEUDO_HDR);
 		if ((m->m_flags & M_BCAST) || (loop_copy > 0)) {
 			struct mbuf *n = m_copy(m, 0, (int)M_COPYALL);
 
+			n->m_pkthdr.csum_flags |= csum_flags;
+			if (csum_flags & CSUM_DATA_VALID)
+				n->m_pkthdr.csum_data = 0xffff;
+
 			(void) if_simloop(ifp, n, dst->sa_family, hlen);
 		} else if (bcmp(eh->ether_dhost,
 		    eh->ether_shost, ETHER_ADDR_LEN) == 0) {
+			m->m_pkthdr.csum_flags |= csum_flags;
+			if (csum_flags & CSUM_DATA_VALID)
+				m->m_pkthdr.csum_data = 0xffff;
 			(void) if_simloop(ifp, m, dst->sa_family, hlen);
 			return (0);	/* XXX */
 		}