Index: head/share/man/man4/dtrace_udp.4
===================================================================
--- head/share/man/man4/dtrace_udp.4
+++ head/share/man/man4/dtrace_udp.4
@@ -24,7 +24,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd April 18, 2015
+.Dd July 20, 2018
 .Dt DTRACE_UDP 4
 .Os
 .Sh NAME
@@ -45,7 +45,11 @@
 .Fn udp:::send
 probe fires whenever the kernel prepares to transmit a UDP packet, and the
 .Fn udp:::receive
-probe fires whenever the kernel receives a UDP packet.
+probe fires whenever the kernel receives a UDP packet, unless
+the UDP header is incomplete,
+the destination port is 0,
+the length field is invalid,
+or the checksum is wrong.
 The arguments to these probes can be used to obtain detailed information about
 the IP and UDP headers of the corresponding packet.
 .Sh ARGUMENTS
Index: head/sys/netinet/udp_usrreq.c
===================================================================
--- head/sys/netinet/udp_usrreq.c
+++ head/sys/netinet/udp_usrreq.c
@@ -685,6 +685,7 @@
 			    inet_ntoa_r(ip->ip_dst, dst), ntohs(uh->uh_dport),
 			    inet_ntoa_r(ip->ip_src, src), ntohs(uh->uh_sport));
 		}
+		UDP_PROBE(receive, NULL, NULL, ip, NULL, uh);
 		UDPSTAT_INC(udps_noport);
 		if (m->m_flags & (M_BCAST | M_MCAST)) {
 			UDPSTAT_INC(udps_noportbcast);
@@ -704,6 +705,7 @@
 	 */
 	INP_RLOCK_ASSERT(inp);
 	if (inp->inp_ip_minttl && inp->inp_ip_minttl > ip->ip_ttl) {
+		UDP_PROBE(receive, NULL, inp, ip, inp, uh);
 		INP_RUNLOCK(inp);
 		m_freem(m);
 		return (IPPROTO_DONE);
Index: head/sys/netinet6/udp6_usrreq.c
===================================================================
--- head/sys/netinet6/udp6_usrreq.c
+++ head/sys/netinet6/udp6_usrreq.c
@@ -483,6 +483,7 @@
 			    ip6_sprintf(ip6bufs, &ip6->ip6_src),
 			    ntohs(uh->uh_sport));
 		}
+		UDP_PROBE(receive, NULL, NULL, ip6, NULL, uh);
 		UDPSTAT_INC(udps_noport);
 		if (m->m_flags & M_MCAST) {
 			printf("UDP6: M_MCAST is set in a unicast packet.\n");