diff --git a/sys/netinet/udp_var.h b/sys/netinet/udp_var.h
index 5d04a9da9c1..37bc0c846d9 100644
--- a/sys/netinet/udp_var.h
+++ b/sys/netinet/udp_var.h
@@ -154,6 +154,9 @@ VNET_DECLARE(int, udp_log_in_vain);
 #define	V_udp_blackhole		VNET(udp_blackhole)
 #define	V_udp_log_in_vain	VNET(udp_log_in_vain)
 
+VNET_DECLARE(int, zero_checksum_port);
+#define	V_zero_checksum_port	VNET(zero_checksum_port)
+
 static __inline struct inpcbinfo *
 udp_get_inpcbinfo(int protocol)
 {
diff --git a/sys/netinet6/udp6_usrreq.c b/sys/netinet6/udp6_usrreq.c
index 535ebcd4530..32aa21cb24a 100644
--- a/sys/netinet6/udp6_usrreq.c
+++ b/sys/netinet6/udp6_usrreq.c
@@ -124,6 +124,11 @@ __FBSDID("$FreeBSD$");
 
 #include <security/mac/mac_framework.h>
 
+VNET_DEFINE(int, zero_checksum_port) = 0;
+#define	V_zero_checksum_port	VNET(zero_checksum_port)
+SYSCTL_INT(_net_inet6_udp6, OID_AUTO, rfc6935_port, CTLFLAG_VNET | CTLFLAG_RW,
+    &VNET_NAME(zero_checksum_port), 0,
+    "Zero UDP checksum allowed for traffic to/from this port.");
 /*
  * UDP protocol implementation.
  * Per RFC 768, August, 1980.
@@ -267,7 +272,14 @@ udp6_input(struct mbuf **mp, int *offp, int proto)
 		}
 		if (uh->uh_sum == 0) {
 			UDPSTAT_INC(udps_nosum);
-			goto badunlocked;
+			/*
+			 * dport 0 was rejected earlier so this is OK even if
+			 * zero_checksum_port is 0 (which is its default value).
+			 */
+			if (ntohs(uh->uh_dport) == V_zero_checksum_port)
+				goto skip_checksum;
+			else
+				goto badunlocked;
 		}
 	}
 
@@ -287,6 +299,7 @@ udp6_input(struct mbuf **mp, int *offp, int proto)
 		goto badunlocked;
 	}
 
+skip_checksum:
 	/*
 	 * Construct sockaddr format source address.
 	 */