diff -p -u -r1.24 tcp_syncache.c                                                
--- bsd/sys/netinet/tcp_syncache.c      29 Jul 2008 17:07:43 -0000      1.24    
+++ bsd/sys/netinet/tcp_syncache.c      16 Dec 2008 19:23:31 -0000              
@@ -1271,6 +1271,7 @@ syncache_respond(sc, m)                                   
        struct inpcb *inp;                                                      
 #ifdef INET6                                                                   
        struct ip6_hdr *ip6 = NULL;                                             
+       int inp_tclass;                                                         
 #endif                                                                         
        struct rt_nexthop *minmtu_nh;                                           
        struct route_table *rtb = NULL;                                         
@@ -1387,6 +1388,12 @@ syncache_respond(sc, m)                                  
                /* ip6_hlim is set after checksum */                            
                ip6->ip6_flow &= ~IPV6_FLOWLABEL_MASK;                          
                ip6->ip6_flow |= sc->sc_flowlabel;                              
+               /* Set the TC for IPv6 just like TOS for IPv4 */                
+               ip6->ip6_flow &= ~IPV6_CLASS_MASK;                              
+               if (inp) {                                                      
+                   inp_tclass = IPV6_GET_CLASS(inp->in6p_flowinfo);            
+                   ip6->ip6_flow |= IPV6_SET_CLASS(inp_tclass);                
+               }                                                               
                                                                                
                th = (struct tcphdr *)(ip6 + 1);                                
        } else