MFC r238871:

  Hardcode the loopback rx/tx checkum options for IPv6 to on without
  checking. This allows the FreeBSD 9.1 release process to move forward.
  Work around the problem that loopback connections to local addresses 
  not on loopback interfaces and not on interfaces w/ IPv6 checksum offloading 
  enabled would not work.
  A proper fix to allow us to disable the "checksum offload" on loopback
  for testing, measurements, ... as we allow for IPv4 needs to put in
  place later.

PR:		kern/170070

Index: sys
===================================================================
--- sys	(revision 238871)
+++ sys	(working copy)

Property changes on: sys
___________________________________________________________________
Modified: svn:mergeinfo
   Merged /head/sys:r238871
Index: sys/net/if_loop.c
===================================================================
--- sys/net/if_loop.c	(revision 238871)
+++ sys/net/if_loop.c	(working copy)
@@ -257,10 +257,20 @@ looutput(struct ifnet *ifp, struct mbuf *m, struct
 		m->m_pkthdr.csum_flags &= ~LO_CSUM_FEATURES;
 		break;
 	case AF_INET6:
+#if 0
+		/*
+		 * XXX-BZ for now always claim the checksum is good despite
+		 * any interface flags.   This is a workaround for 9.1-R and
+		 * a proper solution ought to be sought later.
+		 */
 		if (ifp->if_capenable & IFCAP_RXCSUM_IPV6) {
 			m->m_pkthdr.csum_data = 0xffff;
 			m->m_pkthdr.csum_flags = LO_CSUM_SET;
 		}
+#else
+		m->m_pkthdr.csum_data = 0xffff;
+		m->m_pkthdr.csum_flags = LO_CSUM_SET;
+#endif
 		m->m_pkthdr.csum_flags &= ~LO_CSUM_FEATURES6;
 		break;
 	case AF_IPX:
@@ -446,15 +456,29 @@ loioctl(struct ifnet *ifp, u_long cmd, caddr_t dat
 			ifp->if_capenable ^= IFCAP_RXCSUM;
 		if ((mask & IFCAP_TXCSUM) != 0)
 			ifp->if_capenable ^= IFCAP_TXCSUM;
-		if ((mask & IFCAP_RXCSUM_IPV6) != 0)
+		if ((mask & IFCAP_RXCSUM_IPV6) != 0) {
+#if 0
 			ifp->if_capenable ^= IFCAP_RXCSUM_IPV6;
-		if ((mask & IFCAP_TXCSUM_IPV6) != 0)
+#else
+			error = EOPNOTSUPP;
+			break;
+#endif
+		}
+		if ((mask & IFCAP_TXCSUM_IPV6) != 0) {
+#if 0
 			ifp->if_capenable ^= IFCAP_TXCSUM_IPV6;
+#else
+			error = EOPNOTSUPP;
+			break;
+#endif
+		}
 		ifp->if_hwassist = 0;
 		if (ifp->if_capenable & IFCAP_TXCSUM)
 			ifp->if_hwassist = LO_CSUM_FEATURES;
+#if 0
 		if (ifp->if_capenable & IFCAP_TXCSUM_IPV6)
 			ifp->if_hwassist |= LO_CSUM_FEATURES6;
+#endif
 		break;
 
 	default: