From 5e5c0e798021b4f52519e6bc6976b763efbe749c Mon Sep 17 00:00:00 2001
From: "Bjoern A. Zeeb" <bz@FreeBSD.org>
Date: Sat, 28 Jul 2012 20:31:39 +0000
Subject: [PATCH] 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.

Reported by:	tuexen, Matthew Seaman (m.seaman infracaninophile.co.uk)
Reported by:	Mike Andrews (mandrews bit0.com), kib, ...
PR:		kern/170070
MFC after:	1 day
X-MFC after:	re approval
---
 sys/net/if_loop.c | 28 ++++++++++++++++++++++++++--
 1 file changed, 26 insertions(+), 2 deletions(-)

diff --git a/sys/net/if_loop.c b/sys/net/if_loop.c
index 8d371eb172e1..2850b3848a58 100644
--- a/sys/net/if_loop.c
+++ b/sys/net/if_loop.c
@@ -257,10 +257,20 @@ looutput(struct ifnet *ifp, struct mbuf *m, struct sockaddr *dst,
 		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 data)
 			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: