--- sys/netinet/ip_output.c.orig	2012-02-25 19:19:15.000000000 +0700
+++ sys/netinet/ip_output.c	2012-02-25 19:32:00.000000000 +0700
@@ -825,6 +825,10 @@
 		}
 		m->m_pkthdr.len = mhlen + len;
 		m->m_pkthdr.rcvif = NULL;
+		if (m0->m_flags & M_FLOWID) {
+			m->m_pkthdr.flowid = m0->m_pkthdr.flowid;
+			m->m_flags |= M_FLOWID;
+		}
 #ifdef MAC
 		mac_netinet_fragment(m0, m);
 #endif