check if IPV6_TCLASS is defined

diff --git a/lib/isc/unix/socket.c b/lib/isc/unix/socket.c
index d38d6e3cdf2c317333725dea0ae73032e8841c83..77c06fd80c996d027b24101b99ba94f9334ed88a 100644 (file)
--- a/lib/isc/unix/socket.c
+++ b/lib/isc/unix/socket.c
@@ -1526,7 +1526,7 @@ build_msghdr_send(isc__socket_t *sock, isc_socketevent_t *dev,
                        }
                }
 #endif
-#ifdef IPPROTO_IPV6
+#if defined(IPPROTO_IPV6) && defined(IPV6_TCLASS)
                if (sock->pf == AF_INET6 &&
                    ((isc_net_probedscp() & ISC_NET_DSCPPKTV6) != 0))
                {