diff --git a/sys/netinet/udp_usrreq.c b/sys/netinet/udp_usrreq.c
--- a/sys/netinet/udp_usrreq.c
+++ b/sys/netinet/udp_usrreq.c
@@ -1208,6 +1208,23 @@
 			error = udp_v4mapped_pktinfo(cm, &src, inp, flags);
 			if (error != 0)
 				break;
+			if (((flags & PRUS_IPV6) != 0) &&
+			    (cm->cmsg_level == IPPROTO_IPV6) &&
+			    (cm->cmsg_type == IPV6_TCLASS)) {
+				int tclass;
+
+				if (cm->cmsg_len != CMSG_LEN(sizeof(int))) {
+					error = EINVAL;
+					break;
+				}
+				tclass = *(int *)CMSG_DATA(cm);
+				if (tclass < -1 || tclass > 255) {
+					error = EINVAL;
+					break;
+				}
+				if (tclass != -1)
+					tos = (u_char)tclass;
+			}
 #endif
 			if (cm->cmsg_level != IPPROTO_IP)
 				continue;