Index: if.c
===================================================================
RCS file: /cvs/src/sys/net/if.c,v
retrieving revision 1.620
diff -u -p -r1.620 if.c
--- if.c	3 Oct 2020 00:23:55 -0000	1.620
+++ if.c	12 Dec 2020 00:24:28 -0000
@@ -682,6 +682,8 @@ if_qstart_compat(struct ifqueue *ifq)
 int
 if_enqueue(struct ifnet *ifp, struct mbuf *m)
 {
+	CLR(m->m_pkthdr.csum_flags, M_TIMESTAMP);
+
 #if NPF > 0
 	if (m->m_pkthdr.pf.delay > 0)
 		return (pf_delay_pkt(m, ifp->if_index));